"copy-pasting only 500 lines of code"

.gitignore

@@ -70,6 +70,11 @@ cmake_install.cmake
 install_manifest.txt
 cmake-build-debug/
 
+### Clangd ###
+.cache/
+.clangd
+compile_commands.json
+
 ### Linux ###
 *~
 

src/CMakeLists.txt

@@ -2,86 +2,83 @@
 #
 # All rights reserved.
 #
-# Redistribution and use in source and binary forms, with or without modification, are
-# permitted provided that the following conditions are met:
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
 #
-# 1. Redistributions of source code must retain the above copyright notice, this list of
-#    conditions and the following disclaimer.
+# 1. Redistributions of source code must retain the above copyright notice, this
+#   list of conditions and the following disclaimer.
 #
-# 2. Redistributions in binary form must reproduce the above copyright notice, this list
-#    of conditions and the following disclaimer in the documentation and/or other
-#    materials provided with the distribution.
+# 1. Redistributions in binary form must reproduce the above copyright notice,
+#   this list of conditions and the following disclaimer in the documentation
+#   and/or other materials provided with the distribution.
 #
-# 3. Neither the name of the copyright holder nor the names of its contributors may be
-#    used to endorse or promote products derived from this software without specific
-#    prior written permission.
+# 1. Neither the name of the copyright holder nor the names of its contributors
+#   may be used to endorse or promote products derived from this software
+#   without specific prior written permission.
 #
-# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
-# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
-# MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
-# THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
-# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
-# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
-# STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
-# THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
-# Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
+# Parts of this file are originally copyright (c) 2012-2013 The Cryptonote
+# developers
 
-if (WIN32 OR STATIC)
+if(WIN32 OR STATIC)
   add_definitions(-DSTATICLIB)
   # miniupnp changed their static define
   add_definitions(-DMINIUPNP_STATICLIB)
-endif ()
+endif()
 
-function (monero_private_headers group)
-  source_group("${group}\\Private"
-    FILES
-      ${ARGN})
-endfunction ()
+function(monero_private_headers group)
+  source_group("${group}\\Private" FILES ${ARGN})
+endfunction()
 
-function (monero_install_headers subdir)
+function(monero_install_headers subdir)
   install(
     FILES ${ARGN}
     DESTINATION "include/${subdir}"
     COMPONENT development)
-endfunction ()
+endfunction()
 
-function (enable_stack_trace target)
+function(enable_stack_trace target)
   if(STACK_TRACE)
-    set_property(TARGET ${target}
-      APPEND PROPERTY COMPILE_DEFINITIONS "STACK_TRACE")
-    if (STATIC)
-      set_property(TARGET "${target}"
-        APPEND PROPERTY LINK_FLAGS "-Wl,--wrap=__cxa_throw")
+    set_property(
+      TARGET ${target}
+      APPEND
+      PROPERTY COMPILE_DEFINITIONS "STACK_TRACE")
+    if(STATIC)
+      set_property(
+        TARGET "${target}"
+        APPEND
+        PROPERTY LINK_FLAGS "-Wl,--wrap=__cxa_throw")
     endif()
   endif()
 endfunction()
 
-function (monero_add_executable name)
-  source_group("${name}"
-    FILES
-      ${ARGN})
+function(monero_add_executable name)
+  source_group("${name}" FILES ${ARGN})
 
-  add_executable("${name}"
-    ${ARGN})
-  target_link_libraries("${name}"
-    PRIVATE
-      ${EXTRA_LIBRARIES})
-  set_property(TARGET "${name}"
-    PROPERTY
-      FOLDER "prog")
-  set_property(TARGET "${name}"
-    PROPERTY
-      RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin")
+  add_executable("${name}" ${ARGN})
+  target_link_libraries("${name}" PRIVATE ${EXTRA_LIBRARIES})
+  set_property(TARGET "${name}" PROPERTY FOLDER "prog")
+  set_property(TARGET "${name}" PROPERTY RUNTIME_OUTPUT_DIRECTORY
+                                         "${CMAKE_BINARY_DIR}/bin")
   enable_stack_trace("${name}")
 
   monero_set_target_no_relink("${name}")
-  monero_set_target_strip    ("${name}")
-endfunction ()
+  monero_set_target_strip("${name}")
+endfunction()
 
 include(Version)
-monero_add_library(version SOURCES ${CMAKE_BINARY_DIR}/version.cpp DEPENDS genversion)
+monero_add_library(version SOURCES ${CMAKE_BINARY_DIR}/version.cpp DEPENDS
+                   genversion)
 
 add_subdirectory(common)
 add_subdirectory(crypto)
@@ -92,6 +89,7 @@ add_subdirectory(cryptonote_core)
 add_subdirectory(lmdb)
 add_subdirectory(multisig)
 add_subdirectory(net)
+add_subdirectory(i2p)
 add_subdirectory(hardforks)
 add_subdirectory(blockchain_db)
 add_subdirectory(mnemonics)

src/i2p/.logging.h

@@ -0,0 +1,282 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_LOGGING_H
+#define BITCOIN_LOGGING_H
+
+#include "threadsafety.h"
+#include "tinyformat.h"
+#include "util/fs.h"
+#include "util/string.h"
+
+#include <atomic>
+#include <cstdint>
+#include <functional>
+#include <list>
+#include <mutex>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+static const bool DEFAULT_LOGTIMEMICROS = false;
+static const bool DEFAULT_LOGIPS = false;
+static const bool DEFAULT_LOGTIMESTAMPS = true;
+static const bool DEFAULT_LOGTHREADNAMES = false;
+static const bool DEFAULT_LOGSOURCELOCATIONS = false;
+static constexpr bool DEFAULT_LOGLEVELALWAYS = false;
+extern const char *const DEFAULT_DEBUGLOGFILE;
+
+extern bool fLogIPs;
+
+struct LogCategory {
+  std::string category;
+  bool active;
+};
+
+namespace BCLog {
+enum LogFlags : uint32_t {
+  NONE = 0,
+  NET = (1 << 0),
+  TOR = (1 << 1),
+  MEMPOOL = (1 << 2),
+  HTTP = (1 << 3),
+  BENCH = (1 << 4),
+  ZMQ = (1 << 5),
+  WALLETDB = (1 << 6),
+  RPC = (1 << 7),
+  ESTIMATEFEE = (1 << 8),
+  ADDRMAN = (1 << 9),
+  SELECTCOINS = (1 << 10),
+  REINDEX = (1 << 11),
+  CMPCTBLOCK = (1 << 12),
+  RAND = (1 << 13),
+  PRUNE = (1 << 14),
+  PROXY = (1 << 15),
+  MEMPOOLREJ = (1 << 16),
+  LIBEVENT = (1 << 17),
+  COINDB = (1 << 18),
+  QT = (1 << 19),
+  LEVELDB = (1 << 20),
+  VALIDATION = (1 << 21),
+  I2P = (1 << 22),
+  IPC = (1 << 23),
+#ifdef DEBUG_LOCKCONTENTION
+  LOCK = (1 << 24),
+#endif
+  UTIL = (1 << 25),
+  BLOCKSTORAGE = (1 << 26),
+  TXRECONCILIATION = (1 << 27),
+  SCAN = (1 << 28),
+  TXPACKAGES = (1 << 29),
+  ALL = ~(uint32_t)0,
+};
+enum class Level {
+  Trace = 0, // High-volume or detailed logging for development/debugging
+  Debug,     // Reasonably noisy logging, but still usable in production
+  Info,      // Default
+  Warning,
+  Error,
+};
+constexpr auto DEFAULT_LOG_LEVEL{Level::Debug};
+
+class Logger {
+private:
+  mutable StdMutex
+      m_cs; // Can not use Mutex from sync.h because in debug mode it would
+            // cause a deadlock when a potential deadlock was detected
+
+  FILE *m_fileout GUARDED_BY(m_cs) = nullptr;
+  std::list<std::string> m_msgs_before_open GUARDED_BY(m_cs);
+  bool m_buffering GUARDED_BY(m_cs) =
+      true; //!< Buffer messages before logging can be started.
+
+  /**
+   * m_started_new_line is a state variable that will suppress printing of
+   * the timestamp when multiple calls are made that don't end in a
+   * newline.
+   */
+  std::atomic_bool m_started_new_line{true};
+
+  //! Category-specific log level. Overrides `m_log_level`.
+  std::unordered_map<LogFlags, Level> m_category_log_levels GUARDED_BY(m_cs);
+
+  //! If there is no category-specific log level, all logs with a severity
+  //! level lower than `m_log_level` will be ignored.
+  std::atomic<Level> m_log_level{DEFAULT_LOG_LEVEL};
+
+  /** Log categories bitfield. */
+  std::atomic<uint32_t> m_categories{0};
+
+  std::string LogTimestampStr(const std::string &str);
+
+  /** Slots that connect to the print signal */
+  std::list<std::function<void(const std::string &)>>
+      m_print_callbacks GUARDED_BY(m_cs){};
+
+public:
+  bool m_print_to_console = false;
+  bool m_print_to_file = false;
+
+  bool m_log_timestamps = DEFAULT_LOGTIMESTAMPS;
+  bool m_log_time_micros = DEFAULT_LOGTIMEMICROS;
+  bool m_log_threadnames = DEFAULT_LOGTHREADNAMES;
+  bool m_log_sourcelocations = DEFAULT_LOGSOURCELOCATIONS;
+  bool m_always_print_category_level = DEFAULT_LOGLEVELALWAYS;
+
+  fs::path m_file_path;
+  std::atomic<bool> m_reopen_file{false};
+
+  std::string GetLogPrefix(LogFlags category, Level level) const;
+
+  /** Send a string to the log output */
+  void LogPrintStr(const std::string &str, const std::string &logging_function,
+                   const std::string &source_file, int source_line,
+                   BCLog::LogFlags category, BCLog::Level level);
+
+  /** Returns whether logs will be written to any output */
+  bool Enabled() const {
+    StdLockGuard scoped_lock(m_cs);
+    return m_buffering || m_print_to_console || m_print_to_file ||
+           !m_print_callbacks.empty();
+  }
+
+  /** Connect a slot to the print signal and return the connection */
+  std::list<std::function<void(const std::string &)>>::iterator
+  PushBackCallback(std::function<void(const std::string &)> fun) {
+    StdLockGuard scoped_lock(m_cs);
+    m_print_callbacks.push_back(std::move(fun));
+    return --m_print_callbacks.end();
+  }
+
+  /** Delete a connection */
+  void DeleteCallback(
+      std::list<std::function<void(const std::string &)>>::iterator it) {
+    StdLockGuard scoped_lock(m_cs);
+    m_print_callbacks.erase(it);
+  }
+
+  /** Start logging (and flush all buffered messages) */
+  bool StartLogging();
+  /** Only for testing */
+  void DisconnectTestLogger();
+
+  void ShrinkDebugFile();
+
+  std::unordered_map<LogFlags, Level> CategoryLevels() const {
+    StdLockGuard scoped_lock(m_cs);
+    return m_category_log_levels;
+  }
+  void SetCategoryLogLevel(const std::unordered_map<LogFlags, Level> &levels) {
+    StdLockGuard scoped_lock(m_cs);
+    m_category_log_levels = levels;
+  }
+  bool SetCategoryLogLevel(const std::string &category_str,
+                           const std::string &level_str);
+
+  Level LogLevel() const { return m_log_level.load(); }
+  void SetLogLevel(Level level) { m_log_level = level; }
+  bool SetLogLevel(const std::string &level);
+
+  uint32_t GetCategoryMask() const { return m_categories.load(); }
+
+  void EnableCategory(LogFlags flag);
+  bool EnableCategory(const std::string &str);
+  void DisableCategory(LogFlags flag);
+  bool DisableCategory(const std::string &str);
+
+  bool WillLogCategory(LogFlags category) const;
+  bool WillLogCategoryLevel(LogFlags category, Level level) const;
+
+  /** Returns a vector of the log categories in alphabetical order. */
+  std::vector<LogCategory> LogCategoriesList() const;
+  /** Returns a string with the log categories in alphabetical order. */
+  std::string LogCategoriesString() const {
+    return Join(LogCategoriesList(), ", ",
+                [&](const LogCategory &i) { return i.category; });
+  };
+
+  //! Returns a string with all user-selectable log levels.
+  std::string LogLevelsString() const;
+
+  //! Returns the string representation of a log level.
+  static std::string LogLevelToStr(BCLog::Level level);
+
+  bool DefaultShrinkDebugFile() const;
+};
+
+} // namespace BCLog
+
+BCLog::Logger &LogInstance();
+
+/** Return true if log accepts specified category, at the specified level. */
+static inline bool LogAcceptCategory(BCLog::LogFlags category,
+                                     BCLog::Level level) {
+  return LogInstance().WillLogCategoryLevel(category, level);
+}
+
+/** Return true if str parses as a log category and set the flag */
+bool GetLogCategory(BCLog::LogFlags &flag, const std::string &str);
+
+// Be conservative when using functions that
+// unconditionally log to debug.log! It should not be the case that an inbound
+// peer can fill up a user's disk with debug.log entries.
+
+template <typename... Args>
+static inline void
+LogPrintf_(const std::string &logging_function, const std::string &source_file,
+           const int source_line, const BCLog::LogFlags flag,
+           const BCLog::Level level, const char *fmt, const Args &...args) {
+  if (LogInstance().Enabled()) {
+    std::string log_msg;
+    try {
+      log_msg = tfm::format(fmt, args...);
+    } catch (tinyformat::format_error &fmterr) {
+      /* Original format string will have newline so don't add one here */
+      log_msg = "Error \"" + std::string(fmterr.what()) +
+                "\" while formatting log message: " + fmt;
+    }
+    LogInstance().LogPrintStr(log_msg, logging_function, source_file,
+                              source_line, flag, level);
+  }
+}
+
+#define LogPrintLevel_(category, level, ...)                                   \
+  LogPrintf_(__func__, __FILE__, __LINE__, category, level, __VA_ARGS__)
+
+// Log unconditionally.
+#define LogInfo(...)                                                           \
+  LogPrintLevel_(BCLog::LogFlags::ALL, BCLog::Level::Info, __VA_ARGS__)
+#define LogWarning(...)                                                        \
+  LogPrintLevel_(BCLog::LogFlags::ALL, BCLog::Level::Warning, __VA_ARGS__)
+#define LogError(...)                                                          \
+  LogPrintLevel_(BCLog::LogFlags::ALL, BCLog::Level::Error, __VA_ARGS__)
+
+// Deprecated unconditional logging.
+#define LogPrintf(...) LogInfo(__VA_ARGS__)
+#define LogPrintfCategory(category, ...)                                       \
+  LogPrintLevel_(category, BCLog::Level::Info, __VA_ARGS__)
+
+// Use a macro instead of a function for conditional logging to prevent
+// evaluating arguments when logging for the category is not enabled.
+
+// Log conditionally, prefixing the output with the passed category name and
+// severity level.
+#define LogPrintLevel(category, level, ...)                                    \
+  do {                                                                         \
+    if (LogAcceptCategory((category), (level))) {                              \
+      LogPrintLevel_(category, level, __VA_ARGS__);                            \
+    }                                                                          \
+  } while (0)
+
+// Log conditionally, prefixing the output with the passed category name.
+#define LogDebug(category, ...)                                                \
+  LogPrintLevel(category, BCLog::Level::Debug, __VA_ARGS__)
+#define LogTrace(category, ...)                                                \
+  LogPrintLevel(category, BCLog::Level::Trace, __VA_ARGS__)
+
+// Deprecated conditional logging
+#define LogPrint(category, ...) LogDebug(category, __VA_ARGS__)
+
+#endif // BITCOIN_LOGGING_H

src/i2p/CMakeLists.txt

@@ -0,0 +1,45 @@
+# conditions and the following disclaimer.
+#
+# 1. Redistributions in binary form must reproduce the above copyright notice,
+#   this list of conditions and the following disclaimer in the documentation
+#   and/or other materials provided with the distribution.
+#
+# 1. Neither the name of the copyright holder nor the names of its contributors
+#   may be used to endorse or promote products derived from this software
+#   without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+set(CMAKE_CXX_STANDARD 20)
+set(i2p_sources i2p.cpp)
+monero_find_all_headers(i2p_headers "${CMAKE_CURRENT_SOURCE_DIR}")
+
+monero_add_library(i2p ${i2p_sources} ${i2p_headers})
+
+# target_include_directories(i2p PUBLIC
+# ${CMAKE_CURRENT_SOURCE_DIR}/contrib/epee/include )
+
+target_link_libraries(
+  i2p
+  common
+  epee
+  ${I2P_LIB}
+  ${EPEE_READLINE}
+  ${Boost_CHRONO_LIBRARY}
+  ${Boost_FILESYSTEM_LIBRARY}
+  ${Boost_PROGRAM_OPTIONS_LIBRARY}
+  ${Boost_REGEX_LIBRARY}
+  ${Boost_SYSTEM_LIBRARY}
+  ${CMAKE_THREAD_LIBS_INIT}
+  ${ZMQ_LIB}
+  ${GNU_READLINE_LIBRARY}
+  ${EXTRA_LIBRARIES}
+  ${Blocks})

src/i2p/attributes.h

@@ -0,0 +1,27 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_ATTRIBUTES_H
+#define BITCOIN_ATTRIBUTES_H
+
+#if defined(__clang__)
+#  if __has_attribute(lifetimebound)
+#    define LIFETIMEBOUND [[clang::lifetimebound]]
+#  else
+#    define LIFETIMEBOUND
+#  endif
+#else
+#  define LIFETIMEBOUND
+#endif
+
+#if defined(__GNUC__)
+#  define ALWAYS_INLINE inline __attribute__((always_inline))
+#elif defined(_MSC_VER)
+#  define ALWAYS_INLINE __forceinline
+#else
+#  error No known always_inline attribute for this platform.
+#endif
+
+#endif // BITCOIN_ATTRIBUTES_H

src/i2p/chainparams.h

@@ -0,0 +1,31 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CHAINPARAMS_H
+#define BITCOIN_CHAINPARAMS_H
+
+#include "kernel/chainparams.h" // IWYU pragma: export
+
+#include <memory>
+
+class ArgsManager;
+
+/**
+ * Creates and returns a std::unique_ptr<CChainParams> of the chosen chain.
+ */
+std::unique_ptr<const CChainParams> CreateChainParams(const ArgsManager& args, const ChainType chain);
+
+/**
+ * Return the currently selected parameters. This won't change after app
+ * startup, except for unit tests.
+ */
+const CChainParams &Params();
+
+/**
+ * Sets the params returned by Params() to those for the given chain type.
+ */
+void SelectParams(const ChainType chain);
+
+#endif // BITCOIN_CHAINPARAMS_H

src/i2p/common/args.h

@@ -0,0 +1,510 @@
+// Copyright (c) 2023 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_COMMON_ARGS_H
+#define BITCOIN_COMMON_ARGS_H
+
+#include "../common/settings.h"
+#include "../compat/compat.h"
+#include "../sync.h"
+#include "../util/chaintype.h"
+#include "../util/fs.h"
+
+#include <iosfwd>
+#include <list>
+#include <map>
+#include <optional>
+#include <set>
+#include <stdint.h>
+#include <string>
+#include <variant>
+#include <vector>
+
+class ArgsManager;
+
+extern const char *const BITCOIN_CONF_FILENAME;
+extern const char *const BITCOIN_SETTINGS_FILENAME;
+
+// Return true if -datadir option points to a valid directory or is not
+// specified.
+bool CheckDataDirOption(const ArgsManager &args);
+
+/**
+ * Most paths passed as configuration arguments are treated as relative to
+ * the datadir if they are not absolute.
+ *
+ * @param args Parsed arguments and settings.
+ * @param path The path to be conditionally prefixed with datadir.
+ * @param net_specific Use network specific datadir variant
+ * @return The normalized path.
+ */
+fs::path AbsPathForConfigVal(const ArgsManager &args, const fs::path &path,
+                             bool net_specific = true);
+
+inline bool IsSwitchChar(char c) {
+#ifdef WIN32
+  return c == '-' || c == '/';
+#else
+  return c == '-';
+#endif
+}
+
+enum class OptionsCategory {
+  OPTIONS,
+  CONNECTION,
+  WALLET,
+  WALLET_DEBUG_TEST,
+  ZMQ,
+  DEBUG_TEST,
+  CHAINPARAMS,
+  NODE_RELAY,
+  BLOCK_CREATION,
+  RPC,
+  GUI,
+  COMMANDS,
+  REGISTER_COMMANDS,
+
+  HIDDEN // Always the last option to avoid printing these in the help
+};
+
+struct KeyInfo {
+  std::string name;
+  std::string section;
+  bool negated{false};
+};
+
+KeyInfo InterpretKey(std::string key);
+
+std::optional<common::SettingsValue> InterpretValue(const KeyInfo &key,
+                                                    const std::string *value,
+                                                    unsigned int flags,
+                                                    std::string &error);
+
+struct SectionInfo {
+  std::string m_name;
+  std::string m_file;
+  int m_line;
+};
+
+std::string SettingToString(const common::SettingsValue &, const std::string &);
+std::optional<std::string> SettingToString(const common::SettingsValue &);
+
+int64_t SettingToInt(const common::SettingsValue &, int64_t);
+std::optional<int64_t> SettingToInt(const common::SettingsValue &);
+
+bool SettingToBool(const common::SettingsValue &, bool);
+std::optional<bool> SettingToBool(const common::SettingsValue &);
+
+class ArgsManager {
+public:
+  /**
+   * Flags controlling how config and command line arguments are validated and
+   * interpreted.
+   */
+  enum Flags : uint32_t {
+    ALLOW_ANY = 0x01, //!< disable validation
+    // ALLOW_BOOL = 0x02,     //!< unimplemented, draft implementation in #16545
+    // ALLOW_INT = 0x04,      //!< unimplemented, draft implementation in #16545
+    // ALLOW_STRING = 0x08,   //!< unimplemented, draft implementation in #16545
+    // ALLOW_LIST = 0x10,     //!< unimplemented, draft implementation in #16545
+    DISALLOW_NEGATION = 0x20, //!< disallow -nofoo syntax
+    DISALLOW_ELISION =
+        0x40, //!< disallow -foo syntax that doesn't assign any value
+
+    DEBUG_ONLY = 0x100,
+    /* Some options would cause cross-contamination if values for
+     * mainnet were used while running on regtest/testnet (or vice-versa).
+     * Setting them as NETWORK_ONLY ensures that sharing a config file
+     * between mainnet and regtest/testnet won't cause problems due to these
+     * parameters by accident. */
+    NETWORK_ONLY = 0x200,
+    // This argument's value is sensitive (such as a password).
+    SENSITIVE = 0x400,
+    COMMAND = 0x800,
+  };
+
+protected:
+  struct Arg {
+    std::string m_help_param;
+    std::string m_help_text;
+    unsigned int m_flags;
+  };
+
+  mutable RecursiveMutex cs_args;
+  common::Settings m_settings GUARDED_BY(cs_args);
+  std::vector<std::string> m_command GUARDED_BY(cs_args);
+  std::string m_network GUARDED_BY(cs_args);
+  std::set<std::string> m_network_only_args GUARDED_BY(cs_args);
+  std::map<OptionsCategory, std::map<std::string, Arg>>
+      m_available_args GUARDED_BY(cs_args);
+  bool m_accept_any_command GUARDED_BY(cs_args){true};
+  std::list<SectionInfo> m_config_sections GUARDED_BY(cs_args);
+  std::optional<fs::path> m_config_path GUARDED_BY(cs_args);
+  mutable fs::path m_cached_blocks_path GUARDED_BY(cs_args);
+  mutable fs::path m_cached_datadir_path GUARDED_BY(cs_args);
+  mutable fs::path m_cached_network_datadir_path GUARDED_BY(cs_args);
+
+  [[nodiscard]] bool ReadConfigStream(std::istream &stream,
+                                      const std::string &filepath,
+                                      std::string &error,
+                                      bool ignore_invalid_keys = false);
+
+  /**
+   * Returns true if settings values from the default section should be used,
+   * depending on the current network and whether the setting is
+   * network-specific.
+   */
+  bool UseDefaultSection(const std::string &arg) const
+      EXCLUSIVE_LOCKS_REQUIRED(cs_args);
+
+public:
+  /**
+   * Get setting value.
+   *
+   * Result will be null if setting was unset, true if "-setting" argument was
+   * passed false if "-nosetting" argument was passed, and a string if a
+   * "-setting=value" argument was passed.
+   */
+  common::SettingsValue GetSetting(const std::string &arg) const;
+
+  /**
+   * Get list of setting values.
+   */
+  std::vector<common::SettingsValue>
+  GetSettingsList(const std::string &arg) const;
+
+  ArgsManager();
+  ~ArgsManager();
+
+  /**
+   * Select the network in use
+   */
+  void SelectConfigNetwork(const std::string &network);
+
+  [[nodiscard]] bool ParseParameters(int argc, const char *const argv[],
+                                     std::string &error);
+
+  /**
+   * Return config file path (read-only)
+   */
+  fs::path GetConfigFilePath() const;
+  void SetConfigFilePath(fs::path);
+  [[nodiscard]] bool ReadConfigFiles(std::string &error,
+                                     bool ignore_invalid_keys = false);
+
+  /**
+   * Log warnings for options in m_section_only_args when
+   * they are specified in the default section but not overridden
+   * on the command line or in a network-specific section in the
+   * config file.
+   */
+  std::set<std::string> GetUnsuitableSectionOnlyArgs() const;
+
+  /**
+   * Log warnings for unrecognized section names in the config file.
+   */
+  std::list<SectionInfo> GetUnrecognizedSections() const;
+
+  struct Command {
+    /** The command (if one has been registered with AddCommand), or empty */
+    std::string command;
+    /**
+     * If command is non-empty: Any args that followed it
+     * If command is empty: The unregistered command and any args that followed
+     * it
+     */
+    std::vector<std::string> args;
+  };
+  /**
+   * Get the command and command args (returns std::nullopt if no command
+   * provided)
+   */
+  std::optional<const Command> GetCommand() const;
+
+  /**
+   * Get blocks directory path
+   *
+   * @return Blocks path which is network specific
+   */
+  fs::path GetBlocksDirPath() const;
+
+  /**
+   * Get data directory path
+   *
+   * @return Absolute path on success, otherwise an empty path when a
+   * non-directory path would be returned
+   */
+  fs::path GetDataDirBase() const { return GetDataDir(false); }
+
+  /**
+   * Get data directory path with appended network identifier
+   *
+   * @return Absolute path on success, otherwise an empty path when a
+   * non-directory path would be returned
+   */
+  fs::path GetDataDirNet() const { return GetDataDir(true); }
+
+  /**
+   * Clear cached directory paths
+   */
+  void ClearPathCache();
+
+  /**
+   * Return a vector of strings of the given argument
+   *
+   * @param strArg Argument to get (e.g. "-foo")
+   * @return command-line arguments
+   */
+  std::vector<std::string> GetArgs(const std::string &strArg) const;
+
+  /**
+   * Return true if the given argument has been manually set
+   *
+   * @param strArg Argument to get (e.g. "-foo")
+   * @return true if the argument has been set
+   */
+  bool IsArgSet(const std::string &strArg) const;
+
+  /**
+   * Return true if the argument was originally passed as a negated option,
+   * i.e. -nofoo.
+   *
+   * @param strArg Argument to get (e.g. "-foo")
+   * @return true if the argument was passed negated
+   */
+  bool IsArgNegated(const std::string &strArg) const;
+
+  /**
+   * Return string argument or default value
+   *
+   * @param strArg Argument to get (e.g. "-foo")
+   * @param strDefault (e.g. "1")
+   * @return command-line argument or default value
+   */
+  std::string GetArg(const std::string &strArg,
+                     const std::string &strDefault) const;
+  std::optional<std::string> GetArg(const std::string &strArg) const;
+
+  /**
+   * Return path argument or default value
+   *
+   * @param arg Argument to get a path from (e.g., "-datadir", "-blocksdir" or
+   * "-walletdir")
+   * @param default_value Optional default value to return instead of the empty
+   * path.
+   * @return normalized path if argument is set, with redundant "." and ".."
+   * path components and trailing separators removed (see patharg unit test
+   * for examples or implementation for details). If argument is empty or not
+   * set, default_value is returned unchanged.
+   */
+  fs::path GetPathArg(std::string arg,
+                      const fs::path &default_value = {}) const;
+
+  /**
+   * Return integer argument or default value
+   *
+   * @param strArg Argument to get (e.g. "-foo")
+   * @param nDefault (e.g. 1)
+   * @return command-line argument (0 if invalid number) or default value
+   */
+  int64_t GetIntArg(const std::string &strArg, int64_t nDefault) const;
+  std::optional<int64_t> GetIntArg(const std::string &strArg) const;
+
+  /**
+   * Return boolean argument or default value
+   *
+   * @param strArg Argument to get (e.g. "-foo")
+   * @param fDefault (true or false)
+   * @return command-line argument or default value
+   */
+  bool GetBoolArg(const std::string &strArg, bool fDefault) const;
+  std::optional<bool> GetBoolArg(const std::string &strArg) const;
+
+  /**
+   * Set an argument if it doesn't already have a value
+   *
+   * @param strArg Argument to set (e.g. "-foo")
+   * @param strValue Value (e.g. "1")
+   * @return true if argument gets set, false if it already had a value
+   */
+  bool SoftSetArg(const std::string &strArg, const std::string &strValue);
+
+  /**
+   * Set a boolean argument if it doesn't already have a value
+   *
+   * @param strArg Argument to set (e.g. "-foo")
+   * @param fValue Value (e.g. false)
+   * @return true if argument gets set, false if it already had a value
+   */
+  bool SoftSetBoolArg(const std::string &strArg, bool fValue);
+
+  // Forces an arg setting. Called by SoftSetArg() if the arg hasn't already
+  // been set. Also called directly in testing.
+  void ForceSetArg(const std::string &strArg, const std::string &strValue);
+
+  /**
+   * Returns the appropriate chain type from the program arguments.
+   * @return ChainType::MAIN by default; raises runtime error if an invalid
+   * combination, or unknown chain is given.
+   */
+  ChainType GetChainType() const;
+
+  /**
+   * Returns the appropriate chain type string from the program arguments.
+   * @return ChainType::MAIN string by default; raises runtime error if an
+   * invalid combination is given.
+   */
+  std::string GetChainTypeString() const;
+
+  /**
+   * Add argument
+   */
+  void AddArg(const std::string &name, const std::string &help,
+              unsigned int flags, const OptionsCategory &cat);
+
+  /**
+   * Add subcommand
+   */
+  void AddCommand(const std::string &cmd, const std::string &help);
+
+  /**
+   * Add many hidden arguments
+   */
+  void AddHiddenArgs(const std::vector<std::string> &args);
+
+  /**
+   * Clear available arguments
+   */
+  void ClearArgs() {
+    LOCK(cs_args);
+    m_available_args.clear();
+    m_network_only_args.clear();
+  }
+
+  /**
+   * Get the help string
+   */
+  std::string GetHelpMessage() const;
+
+  /**
+   * Return Flags for known arg.
+   * Return nullopt for unknown arg.
+   */
+  std::optional<unsigned int> GetArgFlags(const std::string &name) const;
+
+  /**
+   * Get settings file path, or return false if read-write settings were
+   * disabled with -nosettings.
+   */
+  bool GetSettingsPath(fs::path *filepath = nullptr, bool temp = false,
+                       bool backup = false) const;
+
+  /**
+   * Read settings file. Push errors to vector, or log them if null.
+   */
+  bool ReadSettingsFile(std::vector<std::string> *errors = nullptr);
+
+  /**
+   * Write settings file or backup settings file. Push errors to vector, or
+   * log them if null.
+   */
+  bool WriteSettingsFile(std::vector<std::string> *errors = nullptr,
+                         bool backup = false) const;
+
+  /**
+   * Get current setting from config file or read/write settings file,
+   * ignoring nonpersistent command line or forced settings values.
+   */
+  common::SettingsValue GetPersistentSetting(const std::string &name) const;
+
+  /**
+   * Access settings with lock held.
+   */
+  template <typename Fn> void LockSettings(Fn &&fn) {
+    LOCK(cs_args);
+    fn(m_settings);
+  }
+
+  /**
+   * Log the config file options and the command line arguments,
+   * useful for troubleshooting.
+   */
+  void LogArgs() const;
+
+private:
+  /**
+   * Get data directory path
+   *
+   * @param net_specific Append network identifier to the returned path
+   * @return Absolute path on success, otherwise an empty path when a
+   * non-directory path would be returned
+   */
+  fs::path GetDataDir(bool net_specific) const;
+
+  /**
+   * Return -regtest/-signet/-testnet/-chain= setting as a ChainType enum if a
+   * recognized chain type was set, or as a string if an unrecognized chain
+   * name was set. Raise an exception if an invalid combination of flags was
+   * provided.
+   */
+  std::variant<ChainType, std::string> GetChainArg() const;
+
+  // Helper function for LogArgs().
+  void
+  logArgsPrefix(const std::string &prefix, const std::string &section,
+                const std::map<std::string, std::vector<common::SettingsValue>>
+                    &args) const;
+};
+
+extern ArgsManager gArgs;
+
+/**
+ * @return true if help has been requested via a command-line arg
+ */
+bool HelpRequested(const ArgsManager &args);
+
+/** Add help options to the args manager */
+void SetupHelpOptions(ArgsManager &args);
+
+extern const std::vector<std::string> TEST_OPTIONS_DOC;
+
+/** Checks if a particular test option is present in -test command-line arg
+ * options */
+bool HasTestOption(const ArgsManager &args, const std::string &test_option);
+
+/**
+ * Format a string to be used as group of options in help messages
+ *
+ * @param message Group name (e.g. "RPC server options:")
+ * @return the formatted string
+ */
+std::string HelpMessageGroup(const std::string &message);
+
+/**
+ * Format a string to be used as option description in help messages
+ *
+ * @param option Option message (e.g. "-rpcuser=<user>")
+ * @param message Option description (e.g. "Username for JSON-RPC connections")
+ * @return the formatted string
+ */
+std::string HelpMessageOpt(const std::string &option,
+                           const std::string &message);
+
+namespace common {
+#ifdef WIN32
+class WinCmdLineArgs {
+public:
+  WinCmdLineArgs();
+  ~WinCmdLineArgs();
+  std::pair<int, char **> get();
+
+private:
+  int argc;
+  char **argv;
+  std::vector<std::string> args;
+};
+#endif
+} // namespace common
+
+#endif // BITCOIN_COMMON_ARGS_H

src/i2p/common/settings.h

@@ -0,0 +1,117 @@
+// Copyright (c) 2019-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_COMMON_SETTINGS_H
+#define BITCOIN_COMMON_SETTINGS_H
+
+#include "../util/fs.h"
+
+#include <cstddef>
+#include <map>
+#include <string>
+#include <vector>
+
+class UniValue;
+
+namespace common {
+
+//! Settings value type (string/integer/boolean/null variant).
+//!
+//! @note UniValue is used here for convenience and because it can be easily
+//!       serialized in a readable format. But any other variant type that can
+//!       be assigned strings, int64_t, and bool values and has get_str(),
+//!       getInt<int64_t>(), get_bool(), isNum(), isBool(), isFalse(), isTrue()
+//!       and isNull() methods can be substituted if there's a need to move away
+//!       from UniValue. (An implementation with boost::variant was posted at
+//!       https://github.com/bitcoin/bitcoin/pull/15934/files#r337691812)
+using SettingsValue = UniValue;
+
+//! Stored settings. This struct combines settings from the command line, a
+//! read-only configuration file, and a read-write runtime settings file.
+struct Settings {
+  //! Map of setting name to forced setting value.
+  std::map<std::string, SettingsValue> forced_settings;
+  //! Map of setting name to list of command line values.
+  std::map<std::string, std::vector<SettingsValue>> command_line_options;
+  //! Map of setting name to read-write file setting value.
+  std::map<std::string, SettingsValue> rw_settings;
+  //! Map of config section name and setting name to list of config file values.
+  std::map<std::string, std::map<std::string, std::vector<SettingsValue>>>
+      ro_config;
+};
+
+//! Read settings file.
+bool ReadSettings(const fs::path &path,
+                  std::map<std::string, SettingsValue> &values,
+                  std::vector<std::string> &errors);
+
+//! Write settings file.
+bool WriteSettings(const fs::path &path,
+                   const std::map<std::string, SettingsValue> &values,
+                   std::vector<std::string> &errors);
+
+//! Get settings value from combined sources: forced settings, command line
+//! arguments, runtime read-write settings, and the read-only config file.
+//!
+//! @param ignore_default_section_config - ignore values in the default section
+//!                                        of the config file (part before any
+//!                                        [section] keywords)
+//! @param ignore_nonpersistent - ignore non-persistent settings values (forced
+//!                               settings values and values specified on the
+//!                               command line). Only return settings in the
+//!                               read-only config and read-write settings
+//!                               files.
+//! @param get_chain_type - enable special backwards compatible behavior
+//!                         for GetChainType
+SettingsValue GetSetting(const Settings &settings, const std::string &section,
+                         const std::string &name,
+                         bool ignore_default_section_config,
+                         bool ignore_nonpersistent, bool get_chain_type);
+
+//! Get combined setting value similar to GetSetting(), except if setting was
+//! specified multiple times, return a list of all the values specified.
+std::vector<SettingsValue> GetSettingsList(const Settings &settings,
+                                           const std::string &section,
+                                           const std::string &name,
+                                           bool ignore_default_section_config);
+
+//! Return true if a setting is set in the default config file section, and not
+//! overridden by a higher priority command-line or network section value.
+//!
+//! This is used to provide user warnings about values that might be getting
+//! ignored unintentionally.
+bool OnlyHasDefaultSectionSetting(const Settings &settings,
+                                  const std::string &section,
+                                  const std::string &name);
+
+//! Accessor for list of settings that skips negated values when iterated over.
+//! The last boolean `false` value in the list and all earlier values are
+//! considered negated.
+struct SettingsSpan {
+  explicit SettingsSpan() = default;
+  explicit SettingsSpan(const SettingsValue &value) noexcept
+      : SettingsSpan(&value, 1) {}
+  explicit SettingsSpan(const SettingsValue *data, size_t size) noexcept
+      : data(data), size(size) {}
+  explicit SettingsSpan(const std::vector<SettingsValue> &vec) noexcept;
+  const SettingsValue *begin() const; //!< Pointer to first non-negated value.
+  const SettingsValue *end() const;   //!< Pointer to end of values.
+  bool empty() const;        //!< True if there are any non-negated values.
+  bool last_negated() const; //!< True if the last value is negated.
+  size_t negated() const;    //!< Number of negated values.
+
+  const SettingsValue *data = nullptr;
+  size_t size = 0;
+};
+
+//! Map lookup helper.
+template <typename Map, typename Key>
+auto FindKey(Map &&map, Key &&key) -> decltype(&map.at(key)) {
+  auto it = map.find(key);
+  return it == map.end() ? nullptr : &it->second;
+}
+
+} // namespace common
+
+#endif // BITCOIN_COMMON_SETTINGS_H

src/i2p/compat/assumptions.h

@@ -0,0 +1,44 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+// Compile-time verification of assumptions we make.
+
+#ifndef BITCOIN_COMPAT_ASSUMPTIONS_H
+#define BITCOIN_COMPAT_ASSUMPTIONS_H
+
+#include <cstddef>
+#include <limits>
+
+// Assumption: We assume the floating-point types to fulfill the requirements of
+//             IEC 559 (IEEE 754) standard.
+// Example(s): Floating-point division by zero in ConnectBlock, CreateTransaction
+//             and EstimateMedianVal.
+static_assert(std::numeric_limits<float>::is_iec559, "IEEE 754 float assumed");
+static_assert(std::numeric_limits<double>::is_iec559, "IEEE 754 double assumed");
+
+// Assumption: We assume eight bits per byte (obviously, but remember: don't
+//             trust -- verify!).
+// Example(s): Everywhere :-)
+static_assert(std::numeric_limits<unsigned char>::digits == 8, "8-bit byte assumed");
+
+// Assumption: We assume integer widths.
+// Example(s): GetSizeOfCompactSize and WriteCompactSize in the serialization
+//             code.
+static_assert(sizeof(short) == 2, "16-bit short assumed");
+static_assert(sizeof(int) == 4, "32-bit int assumed");
+static_assert(sizeof(unsigned) == 4, "32-bit unsigned assumed");
+
+// Assumption: We assume size_t to be 32-bit or 64-bit.
+// Example(s): size_t assumed to be at least 32-bit in ecdsa_signature_parse_der_lax(...).
+//             size_t assumed to be 32-bit or 64-bit in MallocUsage(...).
+static_assert(sizeof(size_t) == 4 || sizeof(size_t) == 8, "size_t assumed to be 32-bit or 64-bit");
+static_assert(sizeof(size_t) == sizeof(void*), "Sizes of size_t and void* assumed to be equal");
+
+// Some important things we are NOT assuming (non-exhaustive list):
+// * We are NOT assuming a specific value for std::endian::native.
+// * We are NOT assuming a specific value for std::locale("").name().
+// * We are NOT assuming a specific value for std::numeric_limits<char>::is_signed.
+
+#endif // BITCOIN_COMPAT_ASSUMPTIONS_H

src/i2p/compat/byteswap.h

@@ -0,0 +1,79 @@
+// Copyright (c) 2014-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_COMPAT_BYTESWAP_H
+#define BITCOIN_COMPAT_BYTESWAP_H
+
+#include <cstdint>
+#ifdef _MSC_VER
+#include <cstdlib>
+#endif
+
+
+// All internal_bswap_* functions can be replaced with std::byteswap once we
+// require c++23. Both libstdc++ and libc++ implement std::byteswap via these
+// builtins.
+
+#ifndef DISABLE_BUILTIN_BSWAPS
+#  if defined __has_builtin
+#    if __has_builtin(__builtin_bswap16)
+#      define bitcoin_builtin_bswap16(x) __builtin_bswap16(x)
+#    endif
+#    if __has_builtin(__builtin_bswap32)
+#      define bitcoin_builtin_bswap32(x) __builtin_bswap32(x)
+#    endif
+#    if __has_builtin(__builtin_bswap64)
+#      define bitcoin_builtin_bswap64(x) __builtin_bswap64(x)
+#    endif
+#  elif defined(_MSC_VER)
+#      define bitcoin_builtin_bswap16(x) _byteswap_ushort(x)
+#      define bitcoin_builtin_bswap32(x) _byteswap_ulong(x)
+#      define bitcoin_builtin_bswap64(x) _byteswap_uint64(x)
+#  endif
+#endif
+
+// MSVC's _byteswap_* functions are not constexpr
+
+#ifndef _MSC_VER
+#define BSWAP_CONSTEXPR constexpr
+#else
+#define BSWAP_CONSTEXPR
+#endif
+
+inline BSWAP_CONSTEXPR uint16_t internal_bswap_16(uint16_t x)
+{
+#ifdef bitcoin_builtin_bswap16
+    return bitcoin_builtin_bswap16(x);
+#else
+    return (x >> 8) | (x << 8);
+#endif
+}
+
+inline BSWAP_CONSTEXPR uint32_t internal_bswap_32(uint32_t x)
+{
+#ifdef bitcoin_builtin_bswap32
+    return bitcoin_builtin_bswap32(x);
+#else
+    return (((x & 0xff000000U) >> 24) | ((x & 0x00ff0000U) >>  8) |
+            ((x & 0x0000ff00U) <<  8) | ((x & 0x000000ffU) << 24));
+#endif
+}
+
+inline BSWAP_CONSTEXPR uint64_t internal_bswap_64(uint64_t x)
+{
+#ifdef bitcoin_builtin_bswap64
+    return bitcoin_builtin_bswap64(x);
+#else
+     return (((x & 0xff00000000000000ull) >> 56)
+          | ((x & 0x00ff000000000000ull) >> 40)
+          | ((x & 0x0000ff0000000000ull) >> 24)
+          | ((x & 0x000000ff00000000ull) >> 8)
+          | ((x & 0x00000000ff000000ull) << 8)
+          | ((x & 0x0000000000ff0000ull) << 24)
+          | ((x & 0x000000000000ff00ull) << 40)
+          | ((x & 0x00000000000000ffull) << 56));
+#endif
+}
+
+#endif // BITCOIN_COMPAT_BYTESWAP_H

src/i2p/compat/compat.h

@@ -0,0 +1,115 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_COMPAT_COMPAT_H
+#define BITCOIN_COMPAT_COMPAT_H
+
+// Windows defines FD_SETSIZE to 64 (see _fd_types.h in mingw-w64),
+// which is too small for our usage, but allows us to redefine it safely.
+// We redefine it to be 1024, to match glibc, see typesizes.h.
+#ifdef WIN32
+#ifdef FD_SETSIZE
+#undef FD_SETSIZE
+#endif
+#define FD_SETSIZE 1024
+#include <winsock2.h>
+#include <ws2tcpip.h>
+#include <cstdint>
+#else
+#include <arpa/inet.h>   // IWYU pragma: export
+#include <fcntl.h>       // IWYU pragma: export
+#include <ifaddrs.h>     // IWYU pragma: export
+#include <net/if.h>      // IWYU pragma: export
+#include <netdb.h>       // IWYU pragma: export
+#include <netinet/in.h>  // IWYU pragma: export
+#include <netinet/tcp.h> // IWYU pragma: export
+#include <sys/mman.h>    // IWYU pragma: export
+#include <sys/select.h>  // IWYU pragma: export
+#include <sys/socket.h>  // IWYU pragma: export
+#include <sys/types.h>   // IWYU pragma: export
+#include <unistd.h>      // IWYU pragma: export
+#endif
+
+// Windows does not have `sa_family_t` - it defines `sockaddr::sa_family` as `u_short`.
+// Thus define `sa_family_t` on Windows too so that the rest of the code can use `sa_family_t`.
+// See https://learn.microsoft.com/en-us/windows/win32/api/winsock/ns-winsock-sockaddr#syntax
+#ifdef WIN32
+typedef u_short sa_family_t;
+#endif
+
+// We map Linux / BSD error functions and codes, to the equivalent
+// Windows definitions, and use the WSA* names throughout our code.
+// Note that glibc defines EWOULDBLOCK as EAGAIN (see errno.h).
+#ifndef WIN32
+typedef unsigned int SOCKET;
+#include <cerrno>
+#define WSAGetLastError()   errno
+#define WSAEINVAL           EINVAL
+#define WSAEWOULDBLOCK      EWOULDBLOCK
+#define WSAEAGAIN           EAGAIN
+#define WSAEMSGSIZE         EMSGSIZE
+#define WSAEINTR            EINTR
+#define WSAEINPROGRESS      EINPROGRESS
+#define WSAEADDRINUSE       EADDRINUSE
+#define INVALID_SOCKET      (SOCKET)(~0)
+#define SOCKET_ERROR        -1
+#else
+// WSAEAGAIN doesn't exist on Windows
+#ifdef EAGAIN
+#define WSAEAGAIN EAGAIN
+#else
+#define WSAEAGAIN WSAEWOULDBLOCK
+#endif
+#endif
+
+// Windows defines MAX_PATH as it's maximum path length.
+// We define MAX_PATH for use on non-Windows systems.
+#ifndef WIN32
+#define MAX_PATH            1024
+#endif
+
+// ssize_t is POSIX, and not present when using MSVC.
+#ifdef _MSC_VER
+#include <BaseTsd.h>
+typedef SSIZE_T ssize_t;
+#endif
+
+// The type of the option value passed to getsockopt & setsockopt
+// differs between Windows and non-Windows.
+#ifndef WIN32
+typedef void* sockopt_arg_type;
+#else
+typedef char* sockopt_arg_type;
+#endif
+
+#ifdef WIN32
+// Export main() and ensure working ASLR when using mingw-w64.
+// Exporting a symbol will prevent the linker from stripping
+// the .reloc section from the binary, which is a requirement
+// for ASLR. While release builds are not affected, anyone
+// building with a binutils < 2.36 is subject to this ld bug.
+#define MAIN_FUNCTION __declspec(dllexport) int main(int argc, char* argv[])
+#else
+#define MAIN_FUNCTION int main(int argc, char* argv[])
+#endif
+
+// Note these both should work with the current usage of poll, but best to be safe
+// WIN32 poll is broken https://daniel.haxx.se/blog/2012/10/10/wsapoll-is-broken/
+// __APPLE__ poll is broke https://github.com/bitcoin/bitcoin/pull/14336#issuecomment-437384408
+#if defined(__linux__)
+#define USE_POLL
+#endif
+
+// MSG_NOSIGNAL is not available on some platforms, if it doesn't exist define it as 0
+#if !defined(MSG_NOSIGNAL)
+#define MSG_NOSIGNAL 0
+#endif
+
+// MSG_DONTWAIT is not available on some platforms, if it doesn't exist define it as 0
+#if !defined(MSG_DONTWAIT)
+#define MSG_DONTWAIT 0
+#endif
+
+#endif // BITCOIN_COMPAT_COMPAT_H

src/i2p/compat/endian.h

@@ -0,0 +1,74 @@
+// Copyright (c) 2014-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_COMPAT_ENDIAN_H
+#define BITCOIN_COMPAT_ENDIAN_H
+
+#include "byteswap.h"
+
+#include <bit>
+#include <cstdint>
+
+inline BSWAP_CONSTEXPR uint16_t htobe16_internal(uint16_t host_16bits)
+{
+    if constexpr (std::endian::native == std::endian::little) return internal_bswap_16(host_16bits);
+        else return host_16bits;
+}
+inline BSWAP_CONSTEXPR uint16_t htole16_internal(uint16_t host_16bits)
+{
+    if constexpr (std::endian::native == std::endian::big) return internal_bswap_16(host_16bits);
+        else return host_16bits;
+}
+inline BSWAP_CONSTEXPR uint16_t be16toh_internal(uint16_t big_endian_16bits)
+{
+    if constexpr (std::endian::native == std::endian::little) return internal_bswap_16(big_endian_16bits);
+        else return big_endian_16bits;
+}
+inline BSWAP_CONSTEXPR uint16_t le16toh_internal(uint16_t little_endian_16bits)
+{
+    if constexpr (std::endian::native == std::endian::big) return internal_bswap_16(little_endian_16bits);
+        else return little_endian_16bits;
+}
+inline BSWAP_CONSTEXPR uint32_t htobe32_internal(uint32_t host_32bits)
+{
+    if constexpr (std::endian::native == std::endian::little) return internal_bswap_32(host_32bits);
+        else return host_32bits;
+}
+inline BSWAP_CONSTEXPR uint32_t htole32_internal(uint32_t host_32bits)
+{
+    if constexpr (std::endian::native == std::endian::big) return internal_bswap_32(host_32bits);
+        else return host_32bits;
+}
+inline BSWAP_CONSTEXPR uint32_t be32toh_internal(uint32_t big_endian_32bits)
+{
+    if constexpr (std::endian::native == std::endian::little) return internal_bswap_32(big_endian_32bits);
+        else return big_endian_32bits;
+}
+inline BSWAP_CONSTEXPR uint32_t le32toh_internal(uint32_t little_endian_32bits)
+{
+    if constexpr (std::endian::native == std::endian::big) return internal_bswap_32(little_endian_32bits);
+        else return little_endian_32bits;
+}
+inline BSWAP_CONSTEXPR uint64_t htobe64_internal(uint64_t host_64bits)
+{
+    if constexpr (std::endian::native == std::endian::little) return internal_bswap_64(host_64bits);
+        else return host_64bits;
+}
+inline BSWAP_CONSTEXPR uint64_t htole64_internal(uint64_t host_64bits)
+{
+    if constexpr (std::endian::native == std::endian::big) return internal_bswap_64(host_64bits);
+        else return host_64bits;
+}
+inline BSWAP_CONSTEXPR uint64_t be64toh_internal(uint64_t big_endian_64bits)
+{
+    if constexpr (std::endian::native == std::endian::little) return internal_bswap_64(big_endian_64bits);
+        else return big_endian_64bits;
+}
+inline BSWAP_CONSTEXPR uint64_t le64toh_internal(uint64_t little_endian_64bits)
+{
+    if constexpr (std::endian::native == std::endian::big) return internal_bswap_64(little_endian_64bits);
+        else return little_endian_64bits;
+}
+
+#endif // BITCOIN_COMPAT_ENDIAN_H

src/i2p/consensus/amount.h

@@ -0,0 +1,29 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CONSENSUS_AMOUNT_H
+#define BITCOIN_CONSENSUS_AMOUNT_H
+
+#include <cstdint>
+
+/** Amount in satoshis (Can be negative) */
+typedef int64_t CAmount;
+
+/** The amount of satoshis in one BTC. */
+static constexpr CAmount COIN = 100000000;
+
+/** No amount larger than this (in satoshi) is valid.
+ *
+ * Note that this constant is *not* the total money supply, which in Bitcoin
+ * currently happens to be less than 21,000,000 BTC for various reasons, but
+ * rather a sanity check. As this sanity check is used by consensus-critical
+ * validation code, the exact value of the MAX_MONEY constant is consensus
+ * critical; in unusual circumstances like a(nother) overflow bug that allowed
+ * for the creation of coins out of thin air modification could lead to a fork.
+ * */
+static constexpr CAmount MAX_MONEY = 21000000 * COIN;
+inline bool MoneyRange(const CAmount& nValue) { return (nValue >= 0 && nValue <= MAX_MONEY); }
+
+#endif // BITCOIN_CONSENSUS_AMOUNT_H

src/i2p/consensus/params.h

@@ -0,0 +1,151 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CONSENSUS_PARAMS_H
+#define BITCOIN_CONSENSUS_PARAMS_H
+
+#include "../uint256.h"
+
+#include <chrono>
+#include <limits>
+#include <map>
+#include <vector>
+
+namespace Consensus {
+
+/**
+ * A buried deployment is one where the height of the activation has been hardcoded into
+ * the client implementation long after the consensus change has activated. See BIP 90.
+ */
+enum BuriedDeployment : int16_t {
+    // buried deployments get negative values to avoid overlap with DeploymentPos
+    DEPLOYMENT_HEIGHTINCB = std::numeric_limits<int16_t>::min(),
+    DEPLOYMENT_CLTV,
+    DEPLOYMENT_DERSIG,
+    DEPLOYMENT_CSV,
+    DEPLOYMENT_SEGWIT,
+};
+constexpr bool ValidDeployment(BuriedDeployment dep) { return dep <= DEPLOYMENT_SEGWIT; }
+
+enum DeploymentPos : uint16_t {
+    DEPLOYMENT_TESTDUMMY,
+    DEPLOYMENT_TAPROOT, // Deployment of Schnorr/Taproot (BIPs 340-342)
+    // NOTE: Also add new deployments to VersionBitsDeploymentInfo in deploymentinfo.cpp
+    MAX_VERSION_BITS_DEPLOYMENTS
+};
+constexpr bool ValidDeployment(DeploymentPos dep) { return dep < MAX_VERSION_BITS_DEPLOYMENTS; }
+
+/**
+ * Struct for each individual consensus rule change using BIP9.
+ */
+struct BIP9Deployment {
+    /** Bit position to select the particular bit in nVersion. */
+    int bit{28};
+    /** Start MedianTime for version bits miner confirmation. Can be a date in the past */
+    int64_t nStartTime{NEVER_ACTIVE};
+    /** Timeout/expiry MedianTime for the deployment attempt. */
+    int64_t nTimeout{NEVER_ACTIVE};
+    /** If lock in occurs, delay activation until at least this block
+     *  height.  Note that activation will only occur on a retarget
+     *  boundary.
+     */
+    int min_activation_height{0};
+
+    /** Constant for nTimeout very far in the future. */
+    static constexpr int64_t NO_TIMEOUT = std::numeric_limits<int64_t>::max();
+
+    /** Special value for nStartTime indicating that the deployment is always active.
+     *  This is useful for testing, as it means tests don't need to deal with the activation
+     *  process (which takes at least 3 BIP9 intervals). Only tests that specifically test the
+     *  behaviour during activation cannot use this. */
+    static constexpr int64_t ALWAYS_ACTIVE = -1;
+
+    /** Special value for nStartTime indicating that the deployment is never active.
+     *  This is useful for integrating the code changes for a new feature
+     *  prior to deploying it on some or all networks. */
+    static constexpr int64_t NEVER_ACTIVE = -2;
+};
+
+/**
+ * Parameters that influence chain consensus.
+ */
+struct Params {
+    uint256 hashGenesisBlock;
+    int nSubsidyHalvingInterval;
+    /**
+     * Hashes of blocks that
+     * - are known to be consensus valid, and
+     * - buried in the chain, and
+     * - fail if the default script verify flags are applied.
+     */
+    std::map<uint256, uint32_t> script_flag_exceptions;
+    /** Block height and hash at which BIP34 becomes active */
+    int BIP34Height;
+    uint256 BIP34Hash;
+    /** Block height at which BIP65 becomes active */
+    int BIP65Height;
+    /** Block height at which BIP66 becomes active */
+    int BIP66Height;
+    /** Block height at which CSV (BIP68, BIP112 and BIP113) becomes active */
+    int CSVHeight;
+    /** Block height at which Segwit (BIP141, BIP143 and BIP147) becomes active.
+     * Note that segwit v0 script rules are enforced on all blocks except the
+     * BIP 16 exception blocks. */
+    int SegwitHeight;
+    /** Don't warn about unknown BIP 9 activations below this height.
+     * This prevents us from warning about the CSV and segwit activations. */
+    int MinBIP9WarningHeight;
+    /**
+     * Minimum blocks including miner confirmation of the total of 2016 blocks in a retargeting period,
+     * (nPowTargetTimespan / nPowTargetSpacing) which is also used for BIP9 deployments.
+     * Examples: 1916 for 95%, 1512 for testchains.
+     */
+    uint32_t nRuleChangeActivationThreshold;
+    uint32_t nMinerConfirmationWindow;
+    BIP9Deployment vDeployments[MAX_VERSION_BITS_DEPLOYMENTS];
+    /** Proof of work parameters */
+    uint256 powLimit;
+    bool fPowAllowMinDifficultyBlocks;
+    bool fPowNoRetargeting;
+    int64_t nPowTargetSpacing;
+    int64_t nPowTargetTimespan;
+    std::chrono::seconds PowTargetSpacing() const
+    {
+        return std::chrono::seconds{nPowTargetSpacing};
+    }
+    int64_t DifficultyAdjustmentInterval() const { return nPowTargetTimespan / nPowTargetSpacing; }
+    /** The best chain should have at least this much work */
+    uint256 nMinimumChainWork;
+    /** By default assume that the signatures in ancestors of this block are valid */
+    uint256 defaultAssumeValid;
+
+    /**
+     * If true, witness commitments contain a payload equal to a Bitcoin Script solution
+     * to the signet challenge. See BIP325.
+     */
+    bool signet_blocks{false};
+    std::vector<uint8_t> signet_challenge;
+
+    int DeploymentHeight(BuriedDeployment dep) const
+    {
+        switch (dep) {
+        case DEPLOYMENT_HEIGHTINCB:
+            return BIP34Height;
+        case DEPLOYMENT_CLTV:
+            return BIP65Height;
+        case DEPLOYMENT_DERSIG:
+            return BIP66Height;
+        case DEPLOYMENT_CSV:
+            return CSVHeight;
+        case DEPLOYMENT_SEGWIT:
+            return SegwitHeight;
+        } // no default case, so the compiler can warn about missing cases
+        return std::numeric_limits<int>::max();
+    }
+};
+
+} // namespace Consensus
+
+#endif // BITCOIN_CONSENSUS_PARAMS_H

src/i2p/crypto/chacha20.h

@@ -0,0 +1,159 @@
+// Copyright (c) 2017-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CRYPTO_CHACHA20_H
+#define BITCOIN_CRYPTO_CHACHA20_H
+
+#include "../span.h"
+
+#include <array>
+#include <cstddef>
+#include <cstdlib>
+#include <stdint.h>
+#include <utility>
+
+// classes for ChaCha20 256-bit stream cipher developed by Daniel J. Bernstein
+// https://cr.yp.to/chacha/chacha-20080128.pdf.
+//
+// The 128-bit input is here implemented as a 96-bit nonce and a 32-bit block
+// counter, as in RFC8439 Section 2.3. When the 32-bit block counter overflows
+// the first 32-bit part of the nonce is automatically incremented, making it
+// conceptually compatible with variants that use a 64/64 split instead.
+
+/** ChaCha20 cipher that only operates on multiples of 64 bytes. */
+class ChaCha20Aligned
+{
+private:
+    uint32_t input[12];
+
+public:
+    /** Expected key length in constructor and SetKey. */
+    static constexpr unsigned KEYLEN{32};
+
+    /** Block size (inputs/outputs to Keystream / Crypt should be multiples of this). */
+    static constexpr unsigned BLOCKLEN{64};
+
+    /** For safety, disallow initialization without key. */
+    ChaCha20Aligned() noexcept = delete;
+
+    /** Initialize a cipher with specified 32-byte key. */
+    ChaCha20Aligned(Span<const std::byte> key) noexcept;
+
+    /** Destructor to clean up private memory. */
+    ~ChaCha20Aligned();
+
+    /** Set 32-byte key, and seek to nonce 0 and block position 0. */
+    void SetKey(Span<const std::byte> key) noexcept;
+
+    /** Type for 96-bit nonces used by the Set function below.
+     *
+     * The first field corresponds to the LE32-encoded first 4 bytes of the nonce, also referred
+     * to as the '32-bit fixed-common part' in Example 2.8.2 of RFC8439.
+     *
+     * The second field corresponds to the LE64-encoded last 8 bytes of the nonce.
+     *
+     */
+    using Nonce96 = std::pair<uint32_t, uint64_t>;
+
+    /** Set the 96-bit nonce and 32-bit block counter.
+     *
+     * Block_counter selects a position to seek to (to byte BLOCKLEN*block_counter). After 256 GiB,
+     * the block counter overflows, and nonce.first is incremented.
+     */
+    void Seek(Nonce96 nonce, uint32_t block_counter) noexcept;
+
+    /** outputs the keystream into out, whose length must be a multiple of BLOCKLEN. */
+    void Keystream(Span<std::byte> out) noexcept;
+
+    /** en/deciphers the message <input> and write the result into <output>
+     *
+     * The size of input and output must be equal, and be a multiple of BLOCKLEN.
+     */
+    void Crypt(Span<const std::byte> input, Span<std::byte> output) noexcept;
+};
+
+/** Unrestricted ChaCha20 cipher. */
+class ChaCha20
+{
+private:
+    ChaCha20Aligned m_aligned;
+    std::array<std::byte, ChaCha20Aligned::BLOCKLEN> m_buffer;
+    unsigned m_bufleft{0};
+
+public:
+    /** Expected key length in constructor and SetKey. */
+    static constexpr unsigned KEYLEN = ChaCha20Aligned::KEYLEN;
+
+    /** For safety, disallow initialization without key. */
+    ChaCha20() noexcept = delete;
+
+    /** Initialize a cipher with specified 32-byte key. */
+    ChaCha20(Span<const std::byte> key) noexcept : m_aligned(key) {}
+
+    /** Destructor to clean up private memory. */
+    ~ChaCha20();
+
+    /** Set 32-byte key, and seek to nonce 0 and block position 0. */
+    void SetKey(Span<const std::byte> key) noexcept;
+
+    /** 96-bit nonce type. */
+    using Nonce96 = ChaCha20Aligned::Nonce96;
+
+    /** Set the 96-bit nonce and 32-bit block counter. See ChaCha20Aligned::Seek. */
+    void Seek(Nonce96 nonce, uint32_t block_counter) noexcept
+    {
+        m_aligned.Seek(nonce, block_counter);
+        m_bufleft = 0;
+    }
+
+    /** en/deciphers the message <in_bytes> and write the result into <out_bytes>
+     *
+     * The size of in_bytes and out_bytes must be equal.
+     */
+    void Crypt(Span<const std::byte> in_bytes, Span<std::byte> out_bytes) noexcept;
+
+    /** outputs the keystream to out. */
+    void Keystream(Span<std::byte> out) noexcept;
+};
+
+/** Forward-secure ChaCha20
+ *
+ * This implements a stream cipher that automatically transitions to a new stream with a new key
+ * and new nonce after a predefined number of encryptions or decryptions.
+ *
+ * See BIP324 for details.
+ */
+class FSChaCha20
+{
+private:
+    /** Internal stream cipher. */
+    ChaCha20 m_chacha20;
+
+    /** The number of encryptions/decryptions before a rekey happens. */
+    const uint32_t m_rekey_interval;
+
+    /** The number of encryptions/decryptions since the last rekey. */
+    uint32_t m_chunk_counter{0};
+
+    /** The number of rekey operations that have happened. */
+    uint64_t m_rekey_counter{0};
+
+public:
+    /** Length of keys expected by the constructor. */
+    static constexpr unsigned KEYLEN = 32;
+
+    // No copy or move to protect the secret.
+    FSChaCha20(const FSChaCha20&) = delete;
+    FSChaCha20(FSChaCha20&&) = delete;
+    FSChaCha20& operator=(const FSChaCha20&) = delete;
+    FSChaCha20& operator=(FSChaCha20&&) = delete;
+
+    /** Construct an FSChaCha20 cipher that rekeys every rekey_interval Crypt() calls. */
+    FSChaCha20(Span<const std::byte> key, uint32_t rekey_interval) noexcept;
+
+    /** Encrypt or decrypt a chunk. */
+    void Crypt(Span<const std::byte> input, Span<std::byte> output) noexcept;
+};
+
+#endif // BITCOIN_CRYPTO_CHACHA20_H

src/i2p/crypto/common.h

@@ -0,0 +1,85 @@
+// Copyright (c) 2014-2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CRYPTO_COMMON_H
+#define BITCOIN_CRYPTO_COMMON_H
+
+#include "../compat/endian.h"
+
+#include <cstdint>
+#include <cstring>
+
+uint16_t static inline ReadLE16(const unsigned char* ptr)
+{
+    uint16_t x;
+    memcpy(&x, ptr, 2);
+    return le16toh_internal(x);
+}
+
+uint32_t static inline ReadLE32(const unsigned char* ptr)
+{
+    uint32_t x;
+    memcpy(&x, ptr, 4);
+    return le32toh_internal(x);
+}
+
+uint64_t static inline ReadLE64(const unsigned char* ptr)
+{
+    uint64_t x;
+    memcpy(&x, ptr, 8);
+    return le64toh_internal(x);
+}
+
+void static inline WriteLE16(unsigned char* ptr, uint16_t x)
+{
+    uint16_t v = htole16_internal(x);
+    memcpy(ptr, &v, 2);
+}
+
+void static inline WriteLE32(unsigned char* ptr, uint32_t x)
+{
+    uint32_t v = htole32_internal(x);
+    memcpy(ptr, &v, 4);
+}
+
+void static inline WriteLE64(unsigned char* ptr, uint64_t x)
+{
+    uint64_t v = htole64_internal(x);
+    memcpy(ptr, &v, 8);
+}
+
+uint16_t static inline ReadBE16(const unsigned char* ptr)
+{
+    uint16_t x;
+    memcpy(&x, ptr, 2);
+    return be16toh_internal(x);
+}
+
+uint32_t static inline ReadBE32(const unsigned char* ptr)
+{
+    uint32_t x;
+    memcpy(&x, ptr, 4);
+    return be32toh_internal(x);
+}
+
+uint64_t static inline ReadBE64(const unsigned char* ptr)
+{
+    uint64_t x;
+    memcpy(&x, ptr, 8);
+    return be64toh_internal(x);
+}
+
+void static inline WriteBE32(unsigned char* ptr, uint32_t x)
+{
+    uint32_t v = htobe32_internal(x);
+    memcpy(ptr, &v, 4);
+}
+
+void static inline WriteBE64(unsigned char* ptr, uint64_t x)
+{
+    uint64_t v = htobe64_internal(x);
+    memcpy(ptr, &v, 8);
+}
+
+#endif // BITCOIN_CRYPTO_COMMON_H

src/i2p/crypto/hmac_sha512.cpp

@@ -0,0 +1,32 @@
+// Copyright (c) 2014-2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "hmac_sha512.h"
+
+#include <string.h>
+
+CHMAC_SHA512::CHMAC_SHA512(const unsigned char *key, size_t keylen) {
+  unsigned char rkey[128];
+  if (keylen <= 128) {
+    memcpy(rkey, key, keylen);
+    memset(rkey + keylen, 0, 128 - keylen);
+  } else {
+    CSHA512().Write(key, keylen).Finalize(rkey);
+    memset(rkey + 64, 0, 64);
+  }
+
+  for (int n = 0; n < 128; n++)
+    rkey[n] ^= 0x5c;
+  outer.Write(rkey, 128);
+
+  for (int n = 0; n < 128; n++)
+    rkey[n] ^= 0x5c ^ 0x36;
+  inner.Write(rkey, 128);
+}
+
+void CHMAC_SHA512::Finalize(unsigned char hash[OUTPUT_SIZE]) {
+  unsigned char temp[64];
+  inner.Finalize(temp);
+  outer.Write(temp, 64).Finalize(hash);
+}

src/i2p/crypto/hmac_sha512.h

@@ -0,0 +1,30 @@
+// Copyright (c) 2014-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CRYPTO_HMAC_SHA512_H
+#define BITCOIN_CRYPTO_HMAC_SHA512_H
+
+#include "sha512.h"
+
+#include <cstdlib>
+#include <stdint.h>
+
+/** A hasher class for HMAC-SHA-512. */
+class CHMAC_SHA512 {
+private:
+  CSHA512 outer;
+  CSHA512 inner;
+
+public:
+  static const size_t OUTPUT_SIZE = 64;
+
+  CHMAC_SHA512(const unsigned char *key, size_t keylen);
+  CHMAC_SHA512 &Write(const unsigned char *data, size_t len) {
+    inner.Write(data, len);
+    return *this;
+  }
+  void Finalize(unsigned char hash[OUTPUT_SIZE]);
+};
+
+#endif // BITCOIN_CRYPTO_HMAC_SHA512_H

src/i2p/crypto/ripemd160.cpp

@@ -0,0 +1,320 @@
+// Copyright (c) 2014-2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "ripemd160.h"
+
+#include "common.h"
+
+#include <string.h>
+
+// Internal implementation code.
+namespace {
+/// Internal RIPEMD-160 implementation.
+namespace ripemd160 {
+uint32_t inline f1(uint32_t x, uint32_t y, uint32_t z) { return x ^ y ^ z; }
+uint32_t inline f2(uint32_t x, uint32_t y, uint32_t z) {
+  return (x & y) | (~x & z);
+}
+uint32_t inline f3(uint32_t x, uint32_t y, uint32_t z) { return (x | ~y) ^ z; }
+uint32_t inline f4(uint32_t x, uint32_t y, uint32_t z) {
+  return (x & z) | (y & ~z);
+}
+uint32_t inline f5(uint32_t x, uint32_t y, uint32_t z) { return x ^ (y | ~z); }
+
+/** Initialize RIPEMD-160 state. */
+void inline Initialize(uint32_t *s) {
+  s[0] = 0x67452301ul;
+  s[1] = 0xEFCDAB89ul;
+  s[2] = 0x98BADCFEul;
+  s[3] = 0x10325476ul;
+  s[4] = 0xC3D2E1F0ul;
+}
+
+uint32_t inline rol(uint32_t x, int i) { return (x << i) | (x >> (32 - i)); }
+
+void inline Round(uint32_t &a, uint32_t b, uint32_t &c, uint32_t d, uint32_t e,
+                  uint32_t f, uint32_t x, uint32_t k, int r) {
+  a = rol(a + f + x + k, r) + e;
+  c = rol(c, 10);
+}
+
+void inline R11(uint32_t &a, uint32_t b, uint32_t &c, uint32_t d, uint32_t e,
+                uint32_t x, int r) {
+  Round(a, b, c, d, e, f1(b, c, d), x, 0, r);
+}
+void inline R21(uint32_t &a, uint32_t b, uint32_t &c, uint32_t d, uint32_t e,
+                uint32_t x, int r) {
+  Round(a, b, c, d, e, f2(b, c, d), x, 0x5A827999ul, r);
+}
+void inline R31(uint32_t &a, uint32_t b, uint32_t &c, uint32_t d, uint32_t e,
+                uint32_t x, int r) {
+  Round(a, b, c, d, e, f3(b, c, d), x, 0x6ED9EBA1ul, r);
+}
+void inline R41(uint32_t &a, uint32_t b, uint32_t &c, uint32_t d, uint32_t e,
+                uint32_t x, int r) {
+  Round(a, b, c, d, e, f4(b, c, d), x, 0x8F1BBCDCul, r);
+}
+void inline R51(uint32_t &a, uint32_t b, uint32_t &c, uint32_t d, uint32_t e,
+                uint32_t x, int r) {
+  Round(a, b, c, d, e, f5(b, c, d), x, 0xA953FD4Eul, r);
+}
+
+void inline R12(uint32_t &a, uint32_t b, uint32_t &c, uint32_t d, uint32_t e,
+                uint32_t x, int r) {
+  Round(a, b, c, d, e, f5(b, c, d), x, 0x50A28BE6ul, r);
+}
+void inline R22(uint32_t &a, uint32_t b, uint32_t &c, uint32_t d, uint32_t e,
+                uint32_t x, int r) {
+  Round(a, b, c, d, e, f4(b, c, d), x, 0x5C4DD124ul, r);
+}
+void inline R32(uint32_t &a, uint32_t b, uint32_t &c, uint32_t d, uint32_t e,
+                uint32_t x, int r) {
+  Round(a, b, c, d, e, f3(b, c, d), x, 0x6D703EF3ul, r);
+}
+void inline R42(uint32_t &a, uint32_t b, uint32_t &c, uint32_t d, uint32_t e,
+                uint32_t x, int r) {
+  Round(a, b, c, d, e, f2(b, c, d), x, 0x7A6D76E9ul, r);
+}
+void inline R52(uint32_t &a, uint32_t b, uint32_t &c, uint32_t d, uint32_t e,
+                uint32_t x, int r) {
+  Round(a, b, c, d, e, f1(b, c, d), x, 0, r);
+}
+
+/** Perform a RIPEMD-160 transformation, processing a 64-byte chunk. */
+void Transform(uint32_t *s, const unsigned char *chunk) {
+  uint32_t a1 = s[0], b1 = s[1], c1 = s[2], d1 = s[3], e1 = s[4];
+  uint32_t a2 = a1, b2 = b1, c2 = c1, d2 = d1, e2 = e1;
+  uint32_t w0 = ReadLE32(chunk + 0), w1 = ReadLE32(chunk + 4),
+           w2 = ReadLE32(chunk + 8), w3 = ReadLE32(chunk + 12);
+  uint32_t w4 = ReadLE32(chunk + 16), w5 = ReadLE32(chunk + 20),
+           w6 = ReadLE32(chunk + 24), w7 = ReadLE32(chunk + 28);
+  uint32_t w8 = ReadLE32(chunk + 32), w9 = ReadLE32(chunk + 36),
+           w10 = ReadLE32(chunk + 40), w11 = ReadLE32(chunk + 44);
+  uint32_t w12 = ReadLE32(chunk + 48), w13 = ReadLE32(chunk + 52),
+           w14 = ReadLE32(chunk + 56), w15 = ReadLE32(chunk + 60);
+
+  R11(a1, b1, c1, d1, e1, w0, 11);
+  R12(a2, b2, c2, d2, e2, w5, 8);
+  R11(e1, a1, b1, c1, d1, w1, 14);
+  R12(e2, a2, b2, c2, d2, w14, 9);
+  R11(d1, e1, a1, b1, c1, w2, 15);
+  R12(d2, e2, a2, b2, c2, w7, 9);
+  R11(c1, d1, e1, a1, b1, w3, 12);
+  R12(c2, d2, e2, a2, b2, w0, 11);
+  R11(b1, c1, d1, e1, a1, w4, 5);
+  R12(b2, c2, d2, e2, a2, w9, 13);
+  R11(a1, b1, c1, d1, e1, w5, 8);
+  R12(a2, b2, c2, d2, e2, w2, 15);
+  R11(e1, a1, b1, c1, d1, w6, 7);
+  R12(e2, a2, b2, c2, d2, w11, 15);
+  R11(d1, e1, a1, b1, c1, w7, 9);
+  R12(d2, e2, a2, b2, c2, w4, 5);
+  R11(c1, d1, e1, a1, b1, w8, 11);
+  R12(c2, d2, e2, a2, b2, w13, 7);
+  R11(b1, c1, d1, e1, a1, w9, 13);
+  R12(b2, c2, d2, e2, a2, w6, 7);
+  R11(a1, b1, c1, d1, e1, w10, 14);
+  R12(a2, b2, c2, d2, e2, w15, 8);
+  R11(e1, a1, b1, c1, d1, w11, 15);
+  R12(e2, a2, b2, c2, d2, w8, 11);
+  R11(d1, e1, a1, b1, c1, w12, 6);
+  R12(d2, e2, a2, b2, c2, w1, 14);
+  R11(c1, d1, e1, a1, b1, w13, 7);
+  R12(c2, d2, e2, a2, b2, w10, 14);
+  R11(b1, c1, d1, e1, a1, w14, 9);
+  R12(b2, c2, d2, e2, a2, w3, 12);
+  R11(a1, b1, c1, d1, e1, w15, 8);
+  R12(a2, b2, c2, d2, e2, w12, 6);
+
+  R21(e1, a1, b1, c1, d1, w7, 7);
+  R22(e2, a2, b2, c2, d2, w6, 9);
+  R21(d1, e1, a1, b1, c1, w4, 6);
+  R22(d2, e2, a2, b2, c2, w11, 13);
+  R21(c1, d1, e1, a1, b1, w13, 8);
+  R22(c2, d2, e2, a2, b2, w3, 15);
+  R21(b1, c1, d1, e1, a1, w1, 13);
+  R22(b2, c2, d2, e2, a2, w7, 7);
+  R21(a1, b1, c1, d1, e1, w10, 11);
+  R22(a2, b2, c2, d2, e2, w0, 12);
+  R21(e1, a1, b1, c1, d1, w6, 9);
+  R22(e2, a2, b2, c2, d2, w13, 8);
+  R21(d1, e1, a1, b1, c1, w15, 7);
+  R22(d2, e2, a2, b2, c2, w5, 9);
+  R21(c1, d1, e1, a1, b1, w3, 15);
+  R22(c2, d2, e2, a2, b2, w10, 11);
+  R21(b1, c1, d1, e1, a1, w12, 7);
+  R22(b2, c2, d2, e2, a2, w14, 7);
+  R21(a1, b1, c1, d1, e1, w0, 12);
+  R22(a2, b2, c2, d2, e2, w15, 7);
+  R21(e1, a1, b1, c1, d1, w9, 15);
+  R22(e2, a2, b2, c2, d2, w8, 12);
+  R21(d1, e1, a1, b1, c1, w5, 9);
+  R22(d2, e2, a2, b2, c2, w12, 7);
+  R21(c1, d1, e1, a1, b1, w2, 11);
+  R22(c2, d2, e2, a2, b2, w4, 6);
+  R21(b1, c1, d1, e1, a1, w14, 7);
+  R22(b2, c2, d2, e2, a2, w9, 15);
+  R21(a1, b1, c1, d1, e1, w11, 13);
+  R22(a2, b2, c2, d2, e2, w1, 13);
+  R21(e1, a1, b1, c1, d1, w8, 12);
+  R22(e2, a2, b2, c2, d2, w2, 11);
+
+  R31(d1, e1, a1, b1, c1, w3, 11);
+  R32(d2, e2, a2, b2, c2, w15, 9);
+  R31(c1, d1, e1, a1, b1, w10, 13);
+  R32(c2, d2, e2, a2, b2, w5, 7);
+  R31(b1, c1, d1, e1, a1, w14, 6);
+  R32(b2, c2, d2, e2, a2, w1, 15);
+  R31(a1, b1, c1, d1, e1, w4, 7);
+  R32(a2, b2, c2, d2, e2, w3, 11);
+  R31(e1, a1, b1, c1, d1, w9, 14);
+  R32(e2, a2, b2, c2, d2, w7, 8);
+  R31(d1, e1, a1, b1, c1, w15, 9);
+  R32(d2, e2, a2, b2, c2, w14, 6);
+  R31(c1, d1, e1, a1, b1, w8, 13);
+  R32(c2, d2, e2, a2, b2, w6, 6);
+  R31(b1, c1, d1, e1, a1, w1, 15);
+  R32(b2, c2, d2, e2, a2, w9, 14);
+  R31(a1, b1, c1, d1, e1, w2, 14);
+  R32(a2, b2, c2, d2, e2, w11, 12);
+  R31(e1, a1, b1, c1, d1, w7, 8);
+  R32(e2, a2, b2, c2, d2, w8, 13);
+  R31(d1, e1, a1, b1, c1, w0, 13);
+  R32(d2, e2, a2, b2, c2, w12, 5);
+  R31(c1, d1, e1, a1, b1, w6, 6);
+  R32(c2, d2, e2, a2, b2, w2, 14);
+  R31(b1, c1, d1, e1, a1, w13, 5);
+  R32(b2, c2, d2, e2, a2, w10, 13);
+  R31(a1, b1, c1, d1, e1, w11, 12);
+  R32(a2, b2, c2, d2, e2, w0, 13);
+  R31(e1, a1, b1, c1, d1, w5, 7);
+  R32(e2, a2, b2, c2, d2, w4, 7);
+  R31(d1, e1, a1, b1, c1, w12, 5);
+  R32(d2, e2, a2, b2, c2, w13, 5);
+
+  R41(c1, d1, e1, a1, b1, w1, 11);
+  R42(c2, d2, e2, a2, b2, w8, 15);
+  R41(b1, c1, d1, e1, a1, w9, 12);
+  R42(b2, c2, d2, e2, a2, w6, 5);
+  R41(a1, b1, c1, d1, e1, w11, 14);
+  R42(a2, b2, c2, d2, e2, w4, 8);
+  R41(e1, a1, b1, c1, d1, w10, 15);
+  R42(e2, a2, b2, c2, d2, w1, 11);
+  R41(d1, e1, a1, b1, c1, w0, 14);
+  R42(d2, e2, a2, b2, c2, w3, 14);
+  R41(c1, d1, e1, a1, b1, w8, 15);
+  R42(c2, d2, e2, a2, b2, w11, 14);
+  R41(b1, c1, d1, e1, a1, w12, 9);
+  R42(b2, c2, d2, e2, a2, w15, 6);
+  R41(a1, b1, c1, d1, e1, w4, 8);
+  R42(a2, b2, c2, d2, e2, w0, 14);
+  R41(e1, a1, b1, c1, d1, w13, 9);
+  R42(e2, a2, b2, c2, d2, w5, 6);
+  R41(d1, e1, a1, b1, c1, w3, 14);
+  R42(d2, e2, a2, b2, c2, w12, 9);
+  R41(c1, d1, e1, a1, b1, w7, 5);
+  R42(c2, d2, e2, a2, b2, w2, 12);
+  R41(b1, c1, d1, e1, a1, w15, 6);
+  R42(b2, c2, d2, e2, a2, w13, 9);
+  R41(a1, b1, c1, d1, e1, w14, 8);
+  R42(a2, b2, c2, d2, e2, w9, 12);
+  R41(e1, a1, b1, c1, d1, w5, 6);
+  R42(e2, a2, b2, c2, d2, w7, 5);
+  R41(d1, e1, a1, b1, c1, w6, 5);
+  R42(d2, e2, a2, b2, c2, w10, 15);
+  R41(c1, d1, e1, a1, b1, w2, 12);
+  R42(c2, d2, e2, a2, b2, w14, 8);
+
+  R51(b1, c1, d1, e1, a1, w4, 9);
+  R52(b2, c2, d2, e2, a2, w12, 8);
+  R51(a1, b1, c1, d1, e1, w0, 15);
+  R52(a2, b2, c2, d2, e2, w15, 5);
+  R51(e1, a1, b1, c1, d1, w5, 5);
+  R52(e2, a2, b2, c2, d2, w10, 12);
+  R51(d1, e1, a1, b1, c1, w9, 11);
+  R52(d2, e2, a2, b2, c2, w4, 9);
+  R51(c1, d1, e1, a1, b1, w7, 6);
+  R52(c2, d2, e2, a2, b2, w1, 12);
+  R51(b1, c1, d1, e1, a1, w12, 8);
+  R52(b2, c2, d2, e2, a2, w5, 5);
+  R51(a1, b1, c1, d1, e1, w2, 13);
+  R52(a2, b2, c2, d2, e2, w8, 14);
+  R51(e1, a1, b1, c1, d1, w10, 12);
+  R52(e2, a2, b2, c2, d2, w7, 6);
+  R51(d1, e1, a1, b1, c1, w14, 5);
+  R52(d2, e2, a2, b2, c2, w6, 8);
+  R51(c1, d1, e1, a1, b1, w1, 12);
+  R52(c2, d2, e2, a2, b2, w2, 13);
+  R51(b1, c1, d1, e1, a1, w3, 13);
+  R52(b2, c2, d2, e2, a2, w13, 6);
+  R51(a1, b1, c1, d1, e1, w8, 14);
+  R52(a2, b2, c2, d2, e2, w14, 5);
+  R51(e1, a1, b1, c1, d1, w11, 11);
+  R52(e2, a2, b2, c2, d2, w0, 15);
+  R51(d1, e1, a1, b1, c1, w6, 8);
+  R52(d2, e2, a2, b2, c2, w3, 13);
+  R51(c1, d1, e1, a1, b1, w15, 5);
+  R52(c2, d2, e2, a2, b2, w9, 11);
+  R51(b1, c1, d1, e1, a1, w13, 6);
+  R52(b2, c2, d2, e2, a2, w11, 11);
+
+  uint32_t t = s[0];
+  s[0] = s[1] + c1 + d2;
+  s[1] = s[2] + d1 + e2;
+  s[2] = s[3] + e1 + a2;
+  s[3] = s[4] + a1 + b2;
+  s[4] = t + b1 + c2;
+}
+
+} // namespace ripemd160
+
+} // namespace
+
+////// RIPEMD160
+
+CRIPEMD160::CRIPEMD160() { ripemd160::Initialize(s); }
+
+CRIPEMD160 &CRIPEMD160::Write(const unsigned char *data, size_t len) {
+  const unsigned char *end = data + len;
+  size_t bufsize = bytes % 64;
+  if (bufsize && bufsize + len >= 64) {
+    // Fill the buffer, and process it.
+    memcpy(buf + bufsize, data, 64 - bufsize);
+    bytes += 64 - bufsize;
+    data += 64 - bufsize;
+    ripemd160::Transform(s, buf);
+    bufsize = 0;
+  }
+  while (end - data >= 64) {
+    // Process full chunks directly from the source.
+    ripemd160::Transform(s, data);
+    bytes += 64;
+    data += 64;
+  }
+  if (end > data) {
+    // Fill the buffer with what remains.
+    memcpy(buf + bufsize, data, end - data);
+    bytes += end - data;
+  }
+  return *this;
+}
+
+void CRIPEMD160::Finalize(unsigned char hash[OUTPUT_SIZE]) {
+  static const unsigned char pad[64] = {0x80};
+  unsigned char sizedesc[8];
+  WriteLE64(sizedesc, bytes << 3);
+  Write(pad, 1 + ((119 - (bytes % 64)) % 64));
+  Write(sizedesc, 8);
+  WriteLE32(hash, s[0]);
+  WriteLE32(hash + 4, s[1]);
+  WriteLE32(hash + 8, s[2]);
+  WriteLE32(hash + 12, s[3]);
+  WriteLE32(hash + 16, s[4]);
+}
+
+CRIPEMD160 &CRIPEMD160::Reset() {
+  bytes = 0;
+  ripemd160::Initialize(s);
+  return *this;
+}

src/i2p/crypto/ripemd160.h

@@ -0,0 +1,27 @@
+// Copyright (c) 2014-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CRYPTO_RIPEMD160_H
+#define BITCOIN_CRYPTO_RIPEMD160_H
+
+#include <cstdlib>
+#include <stdint.h>
+
+/** A hasher class for RIPEMD-160. */
+class CRIPEMD160 {
+private:
+  uint32_t s[5];
+  unsigned char buf[64];
+  uint64_t bytes{0};
+
+public:
+  static const size_t OUTPUT_SIZE = 20;
+
+  CRIPEMD160();
+  CRIPEMD160 &Write(const unsigned char *data, size_t len);
+  void Finalize(unsigned char hash[OUTPUT_SIZE]);
+  CRIPEMD160 &Reset();
+};
+
+#endif // BITCOIN_CRYPTO_RIPEMD160_H

src/i2p/crypto/sha256.h

@@ -0,0 +1,55 @@
+// Copyright (c) 2014-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CRYPTO_SHA256_H
+#define BITCOIN_CRYPTO_SHA256_H
+
+#include <cstdlib>
+#include <stdint.h>
+#include <string>
+
+/** A hasher class for SHA-256. */
+class CSHA256 {
+private:
+  uint32_t s[8];
+  unsigned char buf[64];
+  uint64_t bytes{0};
+
+public:
+  static const size_t OUTPUT_SIZE = 32;
+
+  CSHA256();
+  CSHA256 &Write(const unsigned char *data, size_t len);
+  void Finalize(unsigned char hash[OUTPUT_SIZE]);
+  CSHA256 &Reset();
+};
+
+namespace sha256_implementation {
+enum UseImplementation : uint8_t {
+  STANDARD = 0,
+  USE_SSE4 = 1 << 0,
+  USE_AVX2 = 1 << 1,
+  USE_SHANI = 1 << 2,
+  USE_SSE4_AND_AVX2 = USE_SSE4 | USE_AVX2,
+  USE_SSE4_AND_SHANI = USE_SSE4 | USE_SHANI,
+  USE_ALL = USE_SSE4 | USE_AVX2 | USE_SHANI,
+};
+}
+
+/** Autodetect the best available SHA256 implementation.
+ *  Returns the name of the implementation.
+ */
+std::string
+SHA256AutoDetect(sha256_implementation::UseImplementation use_implementation =
+                     sha256_implementation::USE_ALL);
+
+/** Compute multiple double-SHA256's of 64-byte blobs.
+ *  output:  pointer to a blocks*32 byte output buffer
+ *  input:   pointer to a blocks*64 byte input buffer
+ *  blocks:  the number of hashes to compute.
+ */
+void SHA256D64(unsigned char *output, const unsigned char *input,
+               size_t blocks);
+
+#endif // BITCOIN_CRYPTO_SHA256_H

src/i2p/crypto/sha3.cpp

@@ -0,0 +1,245 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+// Based on https://github.com/mjosaarinen/tiny_sha3/blob/master/sha3.c
+// by Markku-Juhani O. Saarinen <mjos@iki.fi>
+
+#include "../crypto/sha3.h"
+#include "../crypto/common.h"
+#include "../span.h"
+
+#include <algorithm>
+#include <array> // For std::begin and std::end.
+#include <bit>
+
+#include <stdint.h>
+
+void KeccakF(uint64_t (&st)[25]) {
+  static constexpr uint64_t RNDC[24] = {
+      0x0000000000000001, 0x0000000000008082, 0x800000000000808a,
+      0x8000000080008000, 0x000000000000808b, 0x0000000080000001,
+      0x8000000080008081, 0x8000000000008009, 0x000000000000008a,
+      0x0000000000000088, 0x0000000080008009, 0x000000008000000a,
+      0x000000008000808b, 0x800000000000008b, 0x8000000000008089,
+      0x8000000000008003, 0x8000000000008002, 0x8000000000000080,
+      0x000000000000800a, 0x800000008000000a, 0x8000000080008081,
+      0x8000000000008080, 0x0000000080000001, 0x8000000080008008};
+  static constexpr int ROUNDS = 24;
+
+  for (int round = 0; round < ROUNDS; ++round) {
+    uint64_t bc0, bc1, bc2, bc3, bc4, t;
+
+    // Theta
+    bc0 = st[0] ^ st[5] ^ st[10] ^ st[15] ^ st[20];
+    bc1 = st[1] ^ st[6] ^ st[11] ^ st[16] ^ st[21];
+    bc2 = st[2] ^ st[7] ^ st[12] ^ st[17] ^ st[22];
+    bc3 = st[3] ^ st[8] ^ st[13] ^ st[18] ^ st[23];
+    bc4 = st[4] ^ st[9] ^ st[14] ^ st[19] ^ st[24];
+    t = bc4 ^ std::rotl(bc1, 1);
+    st[0] ^= t;
+    st[5] ^= t;
+    st[10] ^= t;
+    st[15] ^= t;
+    st[20] ^= t;
+    t = bc0 ^ std::rotl(bc2, 1);
+    st[1] ^= t;
+    st[6] ^= t;
+    st[11] ^= t;
+    st[16] ^= t;
+    st[21] ^= t;
+    t = bc1 ^ std::rotl(bc3, 1);
+    st[2] ^= t;
+    st[7] ^= t;
+    st[12] ^= t;
+    st[17] ^= t;
+    st[22] ^= t;
+    t = bc2 ^ std::rotl(bc4, 1);
+    st[3] ^= t;
+    st[8] ^= t;
+    st[13] ^= t;
+    st[18] ^= t;
+    st[23] ^= t;
+    t = bc3 ^ std::rotl(bc0, 1);
+    st[4] ^= t;
+    st[9] ^= t;
+    st[14] ^= t;
+    st[19] ^= t;
+    st[24] ^= t;
+
+    // Rho Pi
+    t = st[1];
+    bc0 = st[10];
+    st[10] = std::rotl(t, 1);
+    t = bc0;
+    bc0 = st[7];
+    st[7] = std::rotl(t, 3);
+    t = bc0;
+    bc0 = st[11];
+    st[11] = std::rotl(t, 6);
+    t = bc0;
+    bc0 = st[17];
+    st[17] = std::rotl(t, 10);
+    t = bc0;
+    bc0 = st[18];
+    st[18] = std::rotl(t, 15);
+    t = bc0;
+    bc0 = st[3];
+    st[3] = std::rotl(t, 21);
+    t = bc0;
+    bc0 = st[5];
+    st[5] = std::rotl(t, 28);
+    t = bc0;
+    bc0 = st[16];
+    st[16] = std::rotl(t, 36);
+    t = bc0;
+    bc0 = st[8];
+    st[8] = std::rotl(t, 45);
+    t = bc0;
+    bc0 = st[21];
+    st[21] = std::rotl(t, 55);
+    t = bc0;
+    bc0 = st[24];
+    st[24] = std::rotl(t, 2);
+    t = bc0;
+    bc0 = st[4];
+    st[4] = std::rotl(t, 14);
+    t = bc0;
+    bc0 = st[15];
+    st[15] = std::rotl(t, 27);
+    t = bc0;
+    bc0 = st[23];
+    st[23] = std::rotl(t, 41);
+    t = bc0;
+    bc0 = st[19];
+    st[19] = std::rotl(t, 56);
+    t = bc0;
+    bc0 = st[13];
+    st[13] = std::rotl(t, 8);
+    t = bc0;
+    bc0 = st[12];
+    st[12] = std::rotl(t, 25);
+    t = bc0;
+    bc0 = st[2];
+    st[2] = std::rotl(t, 43);
+    t = bc0;
+    bc0 = st[20];
+    st[20] = std::rotl(t, 62);
+    t = bc0;
+    bc0 = st[14];
+    st[14] = std::rotl(t, 18);
+    t = bc0;
+    bc0 = st[22];
+    st[22] = std::rotl(t, 39);
+    t = bc0;
+    bc0 = st[9];
+    st[9] = std::rotl(t, 61);
+    t = bc0;
+    bc0 = st[6];
+    st[6] = std::rotl(t, 20);
+    t = bc0;
+    st[1] = std::rotl(t, 44);
+
+    // Chi Iota
+    bc0 = st[0];
+    bc1 = st[1];
+    bc2 = st[2];
+    bc3 = st[3];
+    bc4 = st[4];
+    st[0] = bc0 ^ (~bc1 & bc2) ^ RNDC[round];
+    st[1] = bc1 ^ (~bc2 & bc3);
+    st[2] = bc2 ^ (~bc3 & bc4);
+    st[3] = bc3 ^ (~bc4 & bc0);
+    st[4] = bc4 ^ (~bc0 & bc1);
+    bc0 = st[5];
+    bc1 = st[6];
+    bc2 = st[7];
+    bc3 = st[8];
+    bc4 = st[9];
+    st[5] = bc0 ^ (~bc1 & bc2);
+    st[6] = bc1 ^ (~bc2 & bc3);
+    st[7] = bc2 ^ (~bc3 & bc4);
+    st[8] = bc3 ^ (~bc4 & bc0);
+    st[9] = bc4 ^ (~bc0 & bc1);
+    bc0 = st[10];
+    bc1 = st[11];
+    bc2 = st[12];
+    bc3 = st[13];
+    bc4 = st[14];
+    st[10] = bc0 ^ (~bc1 & bc2);
+    st[11] = bc1 ^ (~bc2 & bc3);
+    st[12] = bc2 ^ (~bc3 & bc4);
+    st[13] = bc3 ^ (~bc4 & bc0);
+    st[14] = bc4 ^ (~bc0 & bc1);
+    bc0 = st[15];
+    bc1 = st[16];
+    bc2 = st[17];
+    bc3 = st[18];
+    bc4 = st[19];
+    st[15] = bc0 ^ (~bc1 & bc2);
+    st[16] = bc1 ^ (~bc2 & bc3);
+    st[17] = bc2 ^ (~bc3 & bc4);
+    st[18] = bc3 ^ (~bc4 & bc0);
+    st[19] = bc4 ^ (~bc0 & bc1);
+    bc0 = st[20];
+    bc1 = st[21];
+    bc2 = st[22];
+    bc3 = st[23];
+    bc4 = st[24];
+    st[20] = bc0 ^ (~bc1 & bc2);
+    st[21] = bc1 ^ (~bc2 & bc3);
+    st[22] = bc2 ^ (~bc3 & bc4);
+    st[23] = bc3 ^ (~bc4 & bc0);
+    st[24] = bc4 ^ (~bc0 & bc1);
+  }
+}
+
+SHA3_256 &SHA3_256::Write(Span<const unsigned char> data) {
+  if (m_bufsize && m_bufsize + data.size() >= sizeof(m_buffer)) {
+    // Fill the buffer and process it.
+    std::copy(data.begin(), data.begin() + sizeof(m_buffer) - m_bufsize,
+              m_buffer + m_bufsize);
+    data = data.subspan(sizeof(m_buffer) - m_bufsize);
+    m_state[m_pos++] ^= ReadLE64(m_buffer);
+    m_bufsize = 0;
+    if (m_pos == RATE_BUFFERS) {
+      KeccakF(m_state);
+      m_pos = 0;
+    }
+  }
+  while (data.size() >= sizeof(m_buffer)) {
+    // Process chunks directly from the buffer.
+    m_state[m_pos++] ^= ReadLE64(data.data());
+    data = data.subspan(8);
+    if (m_pos == RATE_BUFFERS) {
+      KeccakF(m_state);
+      m_pos = 0;
+    }
+  }
+  if (data.size()) {
+    // Keep the remainder in the buffer.
+    std::copy(data.begin(), data.end(), m_buffer + m_bufsize);
+    m_bufsize += data.size();
+  }
+  return *this;
+}
+
+SHA3_256 &SHA3_256::Finalize(Span<unsigned char> output) {
+  assert(output.size() == OUTPUT_SIZE);
+  std::fill(m_buffer + m_bufsize, m_buffer + sizeof(m_buffer), 0);
+  m_buffer[m_bufsize] ^= 0x06;
+  m_state[m_pos] ^= ReadLE64(m_buffer);
+  m_state[RATE_BUFFERS - 1] ^= 0x8000000000000000;
+  KeccakF(m_state);
+  for (unsigned i = 0; i < 4; ++i) {
+    WriteLE64(output.data() + 8 * i, m_state[i]);
+  }
+  return *this;
+}
+
+SHA3_256 &SHA3_256::Reset() {
+  m_bufsize = 0;
+  m_pos = 0;
+  std::fill(std::begin(m_state), std::end(m_state), 0);
+  return *this;
+}

src/i2p/crypto/sha3.h

@@ -0,0 +1,41 @@
+// Copyright (c) 2020-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CRYPTO_SHA3_H
+#define BITCOIN_CRYPTO_SHA3_H
+
+#include "../span.h"
+
+#include <cstdlib>
+#include <stdint.h>
+
+//! The Keccak-f[1600] transform.
+void KeccakF(uint64_t (&st)[25]);
+
+class SHA3_256 {
+private:
+  uint64_t m_state[25] = {0};
+  unsigned char m_buffer[8];
+  unsigned m_bufsize = 0;
+  unsigned m_pos = 0;
+
+  //! Sponge rate in bits.
+  static constexpr unsigned RATE_BITS = 1088;
+
+  //! Sponge rate expressed as a multiple of the buffer size.
+  static constexpr unsigned RATE_BUFFERS = RATE_BITS / (8 * sizeof(m_buffer));
+
+  static_assert(RATE_BITS % (8 * sizeof(m_buffer)) == 0,
+                "Rate must be a multiple of 8 bytes");
+
+public:
+  static constexpr size_t OUTPUT_SIZE = 32;
+
+  SHA3_256() {}
+  SHA3_256 &Write(Span<const unsigned char> data);
+  SHA3_256 &Finalize(Span<unsigned char> output);
+  SHA3_256 &Reset();
+};
+
+#endif // BITCOIN_CRYPTO_SHA3_H

src/i2p/crypto/sha512.cpp

@@ -0,0 +1,289 @@
+// Copyright (c) 2014-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "sha512.h"
+
+#include "common.h"
+
+#include <string.h>
+
+// Internal implementation code.
+namespace {
+/// Internal SHA-512 implementation.
+namespace sha512 {
+uint64_t inline Ch(uint64_t x, uint64_t y, uint64_t z) {
+  return z ^ (x & (y ^ z));
+}
+uint64_t inline Maj(uint64_t x, uint64_t y, uint64_t z) {
+  return (x & y) | (z & (x | y));
+}
+uint64_t inline Sigma0(uint64_t x) {
+  return (x >> 28 | x << 36) ^ (x >> 34 | x << 30) ^ (x >> 39 | x << 25);
+}
+uint64_t inline Sigma1(uint64_t x) {
+  return (x >> 14 | x << 50) ^ (x >> 18 | x << 46) ^ (x >> 41 | x << 23);
+}
+uint64_t inline sigma0(uint64_t x) {
+  return (x >> 1 | x << 63) ^ (x >> 8 | x << 56) ^ (x >> 7);
+}
+uint64_t inline sigma1(uint64_t x) {
+  return (x >> 19 | x << 45) ^ (x >> 61 | x << 3) ^ (x >> 6);
+}
+
+/** One round of SHA-512. */
+void inline Round(uint64_t a, uint64_t b, uint64_t c, uint64_t &d, uint64_t e,
+                  uint64_t f, uint64_t g, uint64_t &h, uint64_t k, uint64_t w) {
+  uint64_t t1 = h + Sigma1(e) + Ch(e, f, g) + k + w;
+  uint64_t t2 = Sigma0(a) + Maj(a, b, c);
+  d += t1;
+  h = t1 + t2;
+}
+
+/** Initialize SHA-512 state. */
+void inline Initialize(uint64_t *s) {
+  s[0] = 0x6a09e667f3bcc908ull;
+  s[1] = 0xbb67ae8584caa73bull;
+  s[2] = 0x3c6ef372fe94f82bull;
+  s[3] = 0xa54ff53a5f1d36f1ull;
+  s[4] = 0x510e527fade682d1ull;
+  s[5] = 0x9b05688c2b3e6c1full;
+  s[6] = 0x1f83d9abfb41bd6bull;
+  s[7] = 0x5be0cd19137e2179ull;
+}
+
+/** Perform one SHA-512 transformation, processing a 128-byte chunk. */
+void Transform(uint64_t *s, const unsigned char *chunk) {
+  uint64_t a = s[0], b = s[1], c = s[2], d = s[3], e = s[4], f = s[5], g = s[6],
+           h = s[7];
+  uint64_t w0, w1, w2, w3, w4, w5, w6, w7, w8, w9, w10, w11, w12, w13, w14, w15;
+
+  Round(a, b, c, d, e, f, g, h, 0x428a2f98d728ae22ull,
+        w0 = ReadBE64(chunk + 0));
+  Round(h, a, b, c, d, e, f, g, 0x7137449123ef65cdull,
+        w1 = ReadBE64(chunk + 8));
+  Round(g, h, a, b, c, d, e, f, 0xb5c0fbcfec4d3b2full,
+        w2 = ReadBE64(chunk + 16));
+  Round(f, g, h, a, b, c, d, e, 0xe9b5dba58189dbbcull,
+        w3 = ReadBE64(chunk + 24));
+  Round(e, f, g, h, a, b, c, d, 0x3956c25bf348b538ull,
+        w4 = ReadBE64(chunk + 32));
+  Round(d, e, f, g, h, a, b, c, 0x59f111f1b605d019ull,
+        w5 = ReadBE64(chunk + 40));
+  Round(c, d, e, f, g, h, a, b, 0x923f82a4af194f9bull,
+        w6 = ReadBE64(chunk + 48));
+  Round(b, c, d, e, f, g, h, a, 0xab1c5ed5da6d8118ull,
+        w7 = ReadBE64(chunk + 56));
+  Round(a, b, c, d, e, f, g, h, 0xd807aa98a3030242ull,
+        w8 = ReadBE64(chunk + 64));
+  Round(h, a, b, c, d, e, f, g, 0x12835b0145706fbeull,
+        w9 = ReadBE64(chunk + 72));
+  Round(g, h, a, b, c, d, e, f, 0x243185be4ee4b28cull,
+        w10 = ReadBE64(chunk + 80));
+  Round(f, g, h, a, b, c, d, e, 0x550c7dc3d5ffb4e2ull,
+        w11 = ReadBE64(chunk + 88));
+  Round(e, f, g, h, a, b, c, d, 0x72be5d74f27b896full,
+        w12 = ReadBE64(chunk + 96));
+  Round(d, e, f, g, h, a, b, c, 0x80deb1fe3b1696b1ull,
+        w13 = ReadBE64(chunk + 104));
+  Round(c, d, e, f, g, h, a, b, 0x9bdc06a725c71235ull,
+        w14 = ReadBE64(chunk + 112));
+  Round(b, c, d, e, f, g, h, a, 0xc19bf174cf692694ull,
+        w15 = ReadBE64(chunk + 120));
+
+  Round(a, b, c, d, e, f, g, h, 0xe49b69c19ef14ad2ull,
+        w0 += sigma1(w14) + w9 + sigma0(w1));
+  Round(h, a, b, c, d, e, f, g, 0xefbe4786384f25e3ull,
+        w1 += sigma1(w15) + w10 + sigma0(w2));
+  Round(g, h, a, b, c, d, e, f, 0x0fc19dc68b8cd5b5ull,
+        w2 += sigma1(w0) + w11 + sigma0(w3));
+  Round(f, g, h, a, b, c, d, e, 0x240ca1cc77ac9c65ull,
+        w3 += sigma1(w1) + w12 + sigma0(w4));
+  Round(e, f, g, h, a, b, c, d, 0x2de92c6f592b0275ull,
+        w4 += sigma1(w2) + w13 + sigma0(w5));
+  Round(d, e, f, g, h, a, b, c, 0x4a7484aa6ea6e483ull,
+        w5 += sigma1(w3) + w14 + sigma0(w6));
+  Round(c, d, e, f, g, h, a, b, 0x5cb0a9dcbd41fbd4ull,
+        w6 += sigma1(w4) + w15 + sigma0(w7));
+  Round(b, c, d, e, f, g, h, a, 0x76f988da831153b5ull,
+        w7 += sigma1(w5) + w0 + sigma0(w8));
+  Round(a, b, c, d, e, f, g, h, 0x983e5152ee66dfabull,
+        w8 += sigma1(w6) + w1 + sigma0(w9));
+  Round(h, a, b, c, d, e, f, g, 0xa831c66d2db43210ull,
+        w9 += sigma1(w7) + w2 + sigma0(w10));
+  Round(g, h, a, b, c, d, e, f, 0xb00327c898fb213full,
+        w10 += sigma1(w8) + w3 + sigma0(w11));
+  Round(f, g, h, a, b, c, d, e, 0xbf597fc7beef0ee4ull,
+        w11 += sigma1(w9) + w4 + sigma0(w12));
+  Round(e, f, g, h, a, b, c, d, 0xc6e00bf33da88fc2ull,
+        w12 += sigma1(w10) + w5 + sigma0(w13));
+  Round(d, e, f, g, h, a, b, c, 0xd5a79147930aa725ull,
+        w13 += sigma1(w11) + w6 + sigma0(w14));
+  Round(c, d, e, f, g, h, a, b, 0x06ca6351e003826full,
+        w14 += sigma1(w12) + w7 + sigma0(w15));
+  Round(b, c, d, e, f, g, h, a, 0x142929670a0e6e70ull,
+        w15 += sigma1(w13) + w8 + sigma0(w0));
+
+  Round(a, b, c, d, e, f, g, h, 0x27b70a8546d22ffcull,
+        w0 += sigma1(w14) + w9 + sigma0(w1));
+  Round(h, a, b, c, d, e, f, g, 0x2e1b21385c26c926ull,
+        w1 += sigma1(w15) + w10 + sigma0(w2));
+  Round(g, h, a, b, c, d, e, f, 0x4d2c6dfc5ac42aedull,
+        w2 += sigma1(w0) + w11 + sigma0(w3));
+  Round(f, g, h, a, b, c, d, e, 0x53380d139d95b3dfull,
+        w3 += sigma1(w1) + w12 + sigma0(w4));
+  Round(e, f, g, h, a, b, c, d, 0x650a73548baf63deull,
+        w4 += sigma1(w2) + w13 + sigma0(w5));
+  Round(d, e, f, g, h, a, b, c, 0x766a0abb3c77b2a8ull,
+        w5 += sigma1(w3) + w14 + sigma0(w6));
+  Round(c, d, e, f, g, h, a, b, 0x81c2c92e47edaee6ull,
+        w6 += sigma1(w4) + w15 + sigma0(w7));
+  Round(b, c, d, e, f, g, h, a, 0x92722c851482353bull,
+        w7 += sigma1(w5) + w0 + sigma0(w8));
+  Round(a, b, c, d, e, f, g, h, 0xa2bfe8a14cf10364ull,
+        w8 += sigma1(w6) + w1 + sigma0(w9));
+  Round(h, a, b, c, d, e, f, g, 0xa81a664bbc423001ull,
+        w9 += sigma1(w7) + w2 + sigma0(w10));
+  Round(g, h, a, b, c, d, e, f, 0xc24b8b70d0f89791ull,
+        w10 += sigma1(w8) + w3 + sigma0(w11));
+  Round(f, g, h, a, b, c, d, e, 0xc76c51a30654be30ull,
+        w11 += sigma1(w9) + w4 + sigma0(w12));
+  Round(e, f, g, h, a, b, c, d, 0xd192e819d6ef5218ull,
+        w12 += sigma1(w10) + w5 + sigma0(w13));
+  Round(d, e, f, g, h, a, b, c, 0xd69906245565a910ull,
+        w13 += sigma1(w11) + w6 + sigma0(w14));
+  Round(c, d, e, f, g, h, a, b, 0xf40e35855771202aull,
+        w14 += sigma1(w12) + w7 + sigma0(w15));
+  Round(b, c, d, e, f, g, h, a, 0x106aa07032bbd1b8ull,
+        w15 += sigma1(w13) + w8 + sigma0(w0));
+
+  Round(a, b, c, d, e, f, g, h, 0x19a4c116b8d2d0c8ull,
+        w0 += sigma1(w14) + w9 + sigma0(w1));
+  Round(h, a, b, c, d, e, f, g, 0x1e376c085141ab53ull,
+        w1 += sigma1(w15) + w10 + sigma0(w2));
+  Round(g, h, a, b, c, d, e, f, 0x2748774cdf8eeb99ull,
+        w2 += sigma1(w0) + w11 + sigma0(w3));
+  Round(f, g, h, a, b, c, d, e, 0x34b0bcb5e19b48a8ull,
+        w3 += sigma1(w1) + w12 + sigma0(w4));
+  Round(e, f, g, h, a, b, c, d, 0x391c0cb3c5c95a63ull,
+        w4 += sigma1(w2) + w13 + sigma0(w5));
+  Round(d, e, f, g, h, a, b, c, 0x4ed8aa4ae3418acbull,
+        w5 += sigma1(w3) + w14 + sigma0(w6));
+  Round(c, d, e, f, g, h, a, b, 0x5b9cca4f7763e373ull,
+        w6 += sigma1(w4) + w15 + sigma0(w7));
+  Round(b, c, d, e, f, g, h, a, 0x682e6ff3d6b2b8a3ull,
+        w7 += sigma1(w5) + w0 + sigma0(w8));
+  Round(a, b, c, d, e, f, g, h, 0x748f82ee5defb2fcull,
+        w8 += sigma1(w6) + w1 + sigma0(w9));
+  Round(h, a, b, c, d, e, f, g, 0x78a5636f43172f60ull,
+        w9 += sigma1(w7) + w2 + sigma0(w10));
+  Round(g, h, a, b, c, d, e, f, 0x84c87814a1f0ab72ull,
+        w10 += sigma1(w8) + w3 + sigma0(w11));
+  Round(f, g, h, a, b, c, d, e, 0x8cc702081a6439ecull,
+        w11 += sigma1(w9) + w4 + sigma0(w12));
+  Round(e, f, g, h, a, b, c, d, 0x90befffa23631e28ull,
+        w12 += sigma1(w10) + w5 + sigma0(w13));
+  Round(d, e, f, g, h, a, b, c, 0xa4506cebde82bde9ull,
+        w13 += sigma1(w11) + w6 + sigma0(w14));
+  Round(c, d, e, f, g, h, a, b, 0xbef9a3f7b2c67915ull,
+        w14 += sigma1(w12) + w7 + sigma0(w15));
+  Round(b, c, d, e, f, g, h, a, 0xc67178f2e372532bull,
+        w15 += sigma1(w13) + w8 + sigma0(w0));
+
+  Round(a, b, c, d, e, f, g, h, 0xca273eceea26619cull,
+        w0 += sigma1(w14) + w9 + sigma0(w1));
+  Round(h, a, b, c, d, e, f, g, 0xd186b8c721c0c207ull,
+        w1 += sigma1(w15) + w10 + sigma0(w2));
+  Round(g, h, a, b, c, d, e, f, 0xeada7dd6cde0eb1eull,
+        w2 += sigma1(w0) + w11 + sigma0(w3));
+  Round(f, g, h, a, b, c, d, e, 0xf57d4f7fee6ed178ull,
+        w3 += sigma1(w1) + w12 + sigma0(w4));
+  Round(e, f, g, h, a, b, c, d, 0x06f067aa72176fbaull,
+        w4 += sigma1(w2) + w13 + sigma0(w5));
+  Round(d, e, f, g, h, a, b, c, 0x0a637dc5a2c898a6ull,
+        w5 += sigma1(w3) + w14 + sigma0(w6));
+  Round(c, d, e, f, g, h, a, b, 0x113f9804bef90daeull,
+        w6 += sigma1(w4) + w15 + sigma0(w7));
+  Round(b, c, d, e, f, g, h, a, 0x1b710b35131c471bull,
+        w7 += sigma1(w5) + w0 + sigma0(w8));
+  Round(a, b, c, d, e, f, g, h, 0x28db77f523047d84ull,
+        w8 += sigma1(w6) + w1 + sigma0(w9));
+  Round(h, a, b, c, d, e, f, g, 0x32caab7b40c72493ull,
+        w9 += sigma1(w7) + w2 + sigma0(w10));
+  Round(g, h, a, b, c, d, e, f, 0x3c9ebe0a15c9bebcull,
+        w10 += sigma1(w8) + w3 + sigma0(w11));
+  Round(f, g, h, a, b, c, d, e, 0x431d67c49c100d4cull,
+        w11 += sigma1(w9) + w4 + sigma0(w12));
+  Round(e, f, g, h, a, b, c, d, 0x4cc5d4becb3e42b6ull,
+        w12 += sigma1(w10) + w5 + sigma0(w13));
+  Round(d, e, f, g, h, a, b, c, 0x597f299cfc657e2aull,
+        w13 += sigma1(w11) + w6 + sigma0(w14));
+  Round(c, d, e, f, g, h, a, b, 0x5fcb6fab3ad6faecull,
+        w14 + sigma1(w12) + w7 + sigma0(w15));
+  Round(b, c, d, e, f, g, h, a, 0x6c44198c4a475817ull,
+        w15 + sigma1(w13) + w8 + sigma0(w0));
+
+  s[0] += a;
+  s[1] += b;
+  s[2] += c;
+  s[3] += d;
+  s[4] += e;
+  s[5] += f;
+  s[6] += g;
+  s[7] += h;
+}
+
+} // namespace sha512
+
+} // namespace
+
+////// SHA-512
+
+CSHA512::CSHA512() { sha512::Initialize(s); }
+
+CSHA512 &CSHA512::Write(const unsigned char *data, size_t len) {
+  const unsigned char *end = data + len;
+  size_t bufsize = bytes % 128;
+  if (bufsize && bufsize + len >= 128) {
+    // Fill the buffer, and process it.
+    memcpy(buf + bufsize, data, 128 - bufsize);
+    bytes += 128 - bufsize;
+    data += 128 - bufsize;
+    sha512::Transform(s, buf);
+    bufsize = 0;
+  }
+  while (end - data >= 128) {
+    // Process full chunks directly from the source.
+    sha512::Transform(s, data);
+    data += 128;
+    bytes += 128;
+  }
+  if (end > data) {
+    // Fill the buffer with what remains.
+    memcpy(buf + bufsize, data, end - data);
+    bytes += end - data;
+  }
+  return *this;
+}
+
+void CSHA512::Finalize(unsigned char hash[OUTPUT_SIZE]) {
+  static const unsigned char pad[128] = {0x80};
+  unsigned char sizedesc[16] = {0x00};
+  WriteBE64(sizedesc + 8, bytes << 3);
+  Write(pad, 1 + ((239 - (bytes % 128)) % 128));
+  Write(sizedesc, 16);
+  WriteBE64(hash, s[0]);
+  WriteBE64(hash + 8, s[1]);
+  WriteBE64(hash + 16, s[2]);
+  WriteBE64(hash + 24, s[3]);
+  WriteBE64(hash + 32, s[4]);
+  WriteBE64(hash + 40, s[5]);
+  WriteBE64(hash + 48, s[6]);
+  WriteBE64(hash + 56, s[7]);
+}
+
+CSHA512 &CSHA512::Reset() {
+  bytes = 0;
+  sha512::Initialize(s);
+  return *this;
+}

src/i2p/crypto/sha512.h

@@ -0,0 +1,28 @@
+// Copyright (c) 2014-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CRYPTO_SHA512_H
+#define BITCOIN_CRYPTO_SHA512_H
+
+#include <cstdlib>
+#include <stdint.h>
+
+/** A hasher class for SHA-512. */
+class CSHA512 {
+private:
+  uint64_t s[8];
+  unsigned char buf[128];
+  uint64_t bytes{0};
+
+public:
+  static constexpr size_t OUTPUT_SIZE = 64;
+
+  CSHA512();
+  CSHA512 &Write(const unsigned char *data, size_t len);
+  void Finalize(unsigned char hash[OUTPUT_SIZE]);
+  CSHA512 &Reset();
+  uint64_t Size() const { return bytes; }
+};
+
+#endif // BITCOIN_CRYPTO_SHA512_H

src/i2p/crypto/siphash.h

@@ -0,0 +1,48 @@
+// Copyright (c) 2016-2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CRYPTO_SIPHASH_H
+#define BITCOIN_CRYPTO_SIPHASH_H
+
+#include <stdint.h>
+
+#include "../span.h"
+#include "../uint256.h"
+
+/** SipHash-2-4 */
+class CSipHasher
+{
+private:
+    uint64_t v[4];
+    uint64_t tmp;
+    uint8_t count; // Only the low 8 bits of the input size matter.
+
+public:
+    /** Construct a SipHash calculator initialized with 128-bit key (k0, k1) */
+    CSipHasher(uint64_t k0, uint64_t k1);
+    /** Hash a 64-bit integer worth of data
+     *  It is treated as if this was the little-endian interpretation of 8 bytes.
+     *  This function can only be used when a multiple of 8 bytes have been written so far.
+     */
+    CSipHasher& Write(uint64_t data);
+    /** Hash arbitrary bytes. */
+    CSipHasher& Write(Span<const unsigned char> data);
+    /** Compute the 64-bit SipHash-2-4 of the data written so far. The object remains untouched. */
+    uint64_t Finalize() const;
+};
+
+/** Optimized SipHash-2-4 implementation for uint256.
+ *
+ *  It is identical to:
+ *    SipHasher(k0, k1)
+ *      .Write(val.GetUint64(0))
+ *      .Write(val.GetUint64(1))
+ *      .Write(val.GetUint64(2))
+ *      .Write(val.GetUint64(3))
+ *      .Finalize()
+ */
+uint64_t SipHashUint256(uint64_t k0, uint64_t k1, const uint256& val);
+uint64_t SipHashUint256Extra(uint64_t k0, uint64_t k1, const uint256& val, uint32_t extra);
+
+#endif // BITCOIN_CRYPTO_SIPHASH_H

src/i2p/hash.cpp

@@ -0,0 +1,98 @@
+// Copyright (c) 2013-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "hash.h"
+#include "crypto/common.h"
+#include "crypto/hmac_sha512.h"
+#include "span.h"
+
+#include <bit>
+#include <string>
+
+unsigned int MurmurHash3(unsigned int nHashSeed,
+                         Span<const unsigned char> vDataToHash) {
+  // The following is MurmurHash3 (x86_32), see
+  // https://github.com/aappleby/smhasher/blob/master/src/MurmurHash3.cpp
+  uint32_t h1 = nHashSeed;
+  const uint32_t c1 = 0xcc9e2d51;
+  const uint32_t c2 = 0x1b873593;
+
+  const int nblocks = vDataToHash.size() / 4;
+
+  //----------
+  // body
+  const uint8_t *blocks = vDataToHash.data();
+
+  for (int i = 0; i < nblocks; ++i) {
+    uint32_t k1 = ReadLE32(blocks + i * 4);
+
+    k1 *= c1;
+    k1 = std::rotl(k1, 15);
+    k1 *= c2;
+
+    h1 ^= k1;
+    h1 = std::rotl(h1, 13);
+    h1 = h1 * 5 + 0xe6546b64;
+  }
+
+  //----------
+  // tail
+  const uint8_t *tail = vDataToHash.data() + nblocks * 4;
+
+  uint32_t k1 = 0;
+
+  switch (vDataToHash.size() & 3) {
+  case 3:
+    k1 ^= tail[2] << 16;
+    [[fallthrough]];
+  case 2:
+    k1 ^= tail[1] << 8;
+    [[fallthrough]];
+  case 1:
+    k1 ^= tail[0];
+    k1 *= c1;
+    k1 = std::rotl(k1, 15);
+    k1 *= c2;
+    h1 ^= k1;
+  }
+
+  //----------
+  // finalization
+  h1 ^= vDataToHash.size();
+  h1 ^= h1 >> 16;
+  h1 *= 0x85ebca6b;
+  h1 ^= h1 >> 13;
+  h1 *= 0xc2b2ae35;
+  h1 ^= h1 >> 16;
+
+  return h1;
+}
+
+void BIP32Hash(const ChainCode &chainCode, unsigned int nChild,
+               unsigned char header, const unsigned char data[32],
+               unsigned char output[64]) {
+  unsigned char num[4];
+  WriteBE32(num, nChild);
+  CHMAC_SHA512(chainCode.begin(), chainCode.size())
+      .Write(&header, 1)
+      .Write(data, 32)
+      .Write(num, 4)
+      .Finalize(output);
+}
+
+uint256 SHA256Uint256(const uint256 &input) {
+  uint256 result;
+  CSHA256().Write(input.begin(), 32).Finalize(result.begin());
+  return result;
+}
+
+HashWriter TaggedHash(const std::string &tag) {
+  HashWriter writer{};
+  uint256 taghash;
+  CSHA256()
+      .Write((const unsigned char *)tag.data(), tag.size())
+      .Finalize(taghash.begin());
+  writer << taghash << taghash;
+  return writer;
+}

src/i2p/hash.h

@@ -0,0 +1,221 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_HASH_H
+#define BITCOIN_HASH_H
+
+#include "attributes.h"
+#include "crypto/common.h"
+#include "crypto/ripemd160.h"
+#include "crypto/sha256.h"
+#include "prevector.h"
+#include "serialize.h"
+#include "span.h"
+#include "uint256.h"
+
+#include <string>
+#include <vector>
+
+typedef uint256 ChainCode;
+
+/** A hasher class for Bitcoin's 256-bit hash (double SHA-256). */
+class CHash256 {
+private:
+  CSHA256 sha;
+
+public:
+  static const size_t OUTPUT_SIZE = CSHA256::OUTPUT_SIZE;
+
+  void Finalize(Span<unsigned char> output) {
+    assert(output.size() == OUTPUT_SIZE);
+    unsigned char buf[CSHA256::OUTPUT_SIZE];
+    sha.Finalize(buf);
+    sha.Reset().Write(buf, CSHA256::OUTPUT_SIZE).Finalize(output.data());
+  }
+
+  CHash256 &Write(Span<const unsigned char> input) {
+    sha.Write(input.data(), input.size());
+    return *this;
+  }
+
+  CHash256 &Reset() {
+    sha.Reset();
+    return *this;
+  }
+};
+
+/** A hasher class for Bitcoin's 160-bit hash (SHA-256 + RIPEMD-160). */
+class CHash160 {
+private:
+  CSHA256 sha;
+
+public:
+  static const size_t OUTPUT_SIZE = CRIPEMD160::OUTPUT_SIZE;
+
+  void Finalize(Span<unsigned char> output) {
+    assert(output.size() == OUTPUT_SIZE);
+    unsigned char buf[CSHA256::OUTPUT_SIZE];
+    sha.Finalize(buf);
+    CRIPEMD160().Write(buf, CSHA256::OUTPUT_SIZE).Finalize(output.data());
+  }
+
+  CHash160 &Write(Span<const unsigned char> input) {
+    sha.Write(input.data(), input.size());
+    return *this;
+  }
+
+  CHash160 &Reset() {
+    sha.Reset();
+    return *this;
+  }
+};
+
+/** Compute the 256-bit hash of an object. */
+template <typename T> inline uint256 Hash(const T &in1) {
+  uint256 result;
+  CHash256().Write(MakeUCharSpan(in1)).Finalize(result);
+  return result;
+}
+
+/** Compute the 256-bit hash of the concatenation of two objects. */
+template <typename T1, typename T2>
+inline uint256 Hash(const T1 &in1, const T2 &in2) {
+  uint256 result;
+  CHash256()
+      .Write(MakeUCharSpan(in1))
+      .Write(MakeUCharSpan(in2))
+      .Finalize(result);
+  return result;
+}
+
+/** Compute the 160-bit hash an object. */
+template <typename T1> inline uint160 Hash160(const T1 &in1) {
+  uint160 result;
+  CHash160().Write(MakeUCharSpan(in1)).Finalize(result);
+  return result;
+}
+
+/** A writer stream (for serialization) that computes a 256-bit hash. */
+class HashWriter {
+private:
+  CSHA256 ctx;
+
+public:
+  void write(Span<const std::byte> src) {
+    ctx.Write(UCharCast(src.data()), src.size());
+  }
+
+  /** Compute the double-SHA256 hash of all data written to this object.
+   *
+   * Invalidates this object.
+   */
+  uint256 GetHash() {
+    uint256 result;
+    ctx.Finalize(result.begin());
+    ctx.Reset()
+        .Write(result.begin(), CSHA256::OUTPUT_SIZE)
+        .Finalize(result.begin());
+    return result;
+  }
+
+  /** Compute the SHA256 hash of all data written to this object.
+   *
+   * Invalidates this object.
+   */
+  uint256 GetSHA256() {
+    uint256 result;
+    ctx.Finalize(result.begin());
+    return result;
+  }
+
+  /**
+   * Returns the first 64 bits from the resulting hash.
+   */
+  inline uint64_t GetCheapHash() {
+    uint256 result = GetHash();
+    return ReadLE64(result.begin());
+  }
+
+  template <typename T> HashWriter &operator<<(const T &obj) {
+    ::Serialize(*this, obj);
+    return *this;
+  }
+};
+
+/** Reads data from an underlying stream, while hashing the read data. */
+template <typename Source> class HashVerifier : public HashWriter {
+private:
+  Source &m_source;
+
+public:
+  explicit HashVerifier(Source &source LIFETIMEBOUND) : m_source{source} {}
+
+  void read(Span<std::byte> dst) {
+    m_source.read(dst);
+    this->write(dst);
+  }
+
+  void ignore(size_t num_bytes) {
+    std::byte data[1024];
+    while (num_bytes > 0) {
+      size_t now = std::min<size_t>(num_bytes, 1024);
+      read({data, now});
+      num_bytes -= now;
+    }
+  }
+
+  template <typename T> HashVerifier<Source> &operator>>(T &&obj) {
+    ::Unserialize(*this, obj);
+    return *this;
+  }
+};
+
+/** Writes data to an underlying source stream, while hashing the written data.
+ */
+template <typename Source> class HashedSourceWriter : public HashWriter {
+private:
+  Source &m_source;
+
+public:
+  explicit HashedSourceWriter(Source &source LIFETIMEBOUND)
+      : HashWriter{}, m_source{source} {}
+
+  void write(Span<const std::byte> src) {
+    m_source.write(src);
+    HashWriter::write(src);
+  }
+
+  template <typename T> HashedSourceWriter &operator<<(const T &obj) {
+    ::Serialize(*this, obj);
+    return *this;
+  }
+};
+
+/** Single-SHA256 a 32-byte input (represented as uint256). */
+[[nodiscard]] uint256 SHA256Uint256(const uint256 &input);
+
+unsigned int MurmurHash3(unsigned int nHashSeed,
+                         Span<const unsigned char> vDataToHash);
+
+void BIP32Hash(const ChainCode &chainCode, unsigned int nChild,
+               unsigned char header, const unsigned char data[32],
+               unsigned char output[64]);
+
+/** Return a HashWriter primed for tagged hashes (as specified in BIP 340).
+ *
+ * The returned object will have SHA256(tag) written to it twice (= 64 bytes).
+ * A tagged hash can be computed by feeding the message into this object, and
+ * then calling HashWriter::GetSHA256().
+ */
+HashWriter TaggedHash(const std::string &tag);
+
+/** Compute the 160-bit RIPEMD-160 hash of an array. */
+inline uint160 RIPEMD160(Span<const unsigned char> data) {
+  uint160 result;
+  CRIPEMD160().Write(data.data(), data.size()).Finalize(result.begin());
+  return result;
+}
+
+#endif // BITCOIN_HASH_H

src/i2p/i2p.cpp

@@ -0,0 +1,529 @@
+// Copyright (c) 2020-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "i2p.h"
+// #include "chainparams.h"
+// #include "common/args.h"
+// #include "compat/compat.h"
+#include "compat/endian.h"
+#include "crypto/sha256.h"
+#include "easylogging++.h"
+#include "misc_log_ex.h"
+#include "netaddress.h"
+#include "netbase.h"
+#include "random.h"
+#include "sync.h"
+#include "tinyformat.h"
+#include "util/fs.h"
+#include "util/readwritefile.h"
+#include "util/sock.h"
+#include "util/spanparsing.h"
+#include "util/strencodings.h"
+#include "util/threadinterrupt.h"
+
+#include <chrono>
+#include <memory>
+#include <stdexcept>
+#include <string>
+
+namespace i2p {
+
+/**
+ * Swap Standard Base64 <-> I2P Base64.
+ * Standard Base64 uses `+` and `/` as last two characters of its alphabet.
+ * I2P Base64 uses `-` and `~` respectively.
+ * So it is easy to detect in which one is the input and convert to the other.
+ * @param[in] from Input to convert.
+ * @return converted `from`
+ */
+/* quik notes area
+ * required classes:
+ * DecodeBase64(util/strencodings.h)
+ * tfm::format(tinyformat.h)v
+ * CNetAddr(netaddress.h)
+ * CSHA256(crypto/sha256.h")v
+ * EncodeBase32(util/strencodings.h)
+ * Proxy(netbase.h)
+ * CThreadInterrupt(util/threadinterrupt.h)
+ * LOCK(sync.h)
+ * AssertLockNotHeld(sync.h)
+ * Sock(util/sock.h)
+ * MAX_WAIT_FOR_IO(util/sock.h)
+ * CService(netaddress.h)
+ * Split(util/spanparsing.h)
+ * Span(span.h)
+ * WriteBinaryFile(util/readwritefile.h)
+ * quoted(fs.h)
+ * PathToString(fs.h)
+ * be16toh_internal(compat/endian.h)
+ * ReadBinaryFile(util/readwritefile.h)
+ * EncodeBase64(util/strencodings.h)
+ * I2P_SAM31_PORT(netaddress.h)
+ * Capitalize(util/strencodings.h)
+ * ToStringAddrPort(netaddress.h)
+ * LogPrint(logging.h)x
+ */
+// preland: this is my "checked line". nothing below this is checked.
+static std::string SwapBase64(const std::string &from) {
+  std::string to;
+  to.resize(from.size());
+  for (size_t i = 0; i < from.size(); ++i) {
+    switch (from[i]) {
+    case '-':
+      to[i] = '+';
+      break;
+    case '~':
+      to[i] = '/';
+      break;
+    case '+':
+      to[i] = '-';
+      break;
+    case '/':
+      to[i] = '~';
+      break;
+    default:
+      to[i] = from[i];
+      break;
+    }
+  }
+  return to;
+}
+
+/**
+ * Decode an I2P-style Base64 string.
+ * @param[in] i2p_b64 I2P-style Base64 string.
+ * @return decoded `i2p_b64`
+ * @throw std::runtime_error if decoding fails
+ */
+static Binary DecodeI2PBase64(const std::string &i2p_b64) {
+  const std::string &std_b64 = SwapBase64(i2p_b64);
+  auto decoded = DecodeBase64(std_b64);
+  if (!decoded) {
+    throw std::runtime_error(
+        tfm::format("Cannot decode Base64: \"%s\"", i2p_b64));
+  }
+  return std::move(*decoded);
+}
+
+/**
+ * Derive the .b32.i2p address of an I2P destination (binary).
+ * @param[in] dest I2P destination.
+ * @return the address that corresponds to `dest`
+ * @throw std::runtime_error if conversion fails
+ */
+static CNetAddr DestBinToAddr(const Binary &dest) {
+  CSHA256 hasher;
+  hasher.Write(dest.data(), dest.size());
+  unsigned char hash[CSHA256::OUTPUT_SIZE];
+  hasher.Finalize(hash);
+
+  CNetAddr addr;
+  const std::string addr_str = EncodeBase32(hash, false) + ".b32.i2p";
+  if (!addr.SetSpecial(addr_str)) {
+    throw std::runtime_error(
+        tfm::format("Cannot parse I2P address: \"%s\"", addr_str));
+  }
+
+  return addr;
+}
+
+/**
+ * Derive the .b32.i2p address of an I2P destination (I2P-style Base64).
+ * @param[in] dest I2P destination.
+ * @return the address that corresponds to `dest`
+ * @throw std::runtime_error if conversion fails
+ */
+static CNetAddr DestB64ToAddr(const std::string &dest) {
+  const Binary &decoded = DecodeI2PBase64(dest);
+  return DestBinToAddr(decoded);
+}
+
+namespace sam {
+
+Session::Session(const fs::path &private_key_file, const Proxy &control_host,
+                 CThreadInterrupt *interrupt)
+    : m_private_key_file{private_key_file}, m_control_host{control_host},
+      m_interrupt{interrupt}, m_transient{false} {}
+
+Session::Session(const Proxy &control_host, CThreadInterrupt *interrupt)
+    : m_control_host{control_host}, m_interrupt{interrupt}, m_transient{true} {}
+
+Session::~Session() {
+  LOCK(m_mutex);
+  Disconnect();
+}
+
+bool Session::Listen(Connection &conn) {
+  try {
+    LOCK(m_mutex);
+    CreateIfNotCreatedAlready();
+    conn.me = m_my_addr;
+    conn.sock = StreamAccept();
+    return true;
+  } catch (const std::runtime_error &e) {
+    Log("Error listening: %s", e.what());
+    CheckControlSock();
+  }
+  return false;
+}
+
+bool Session::Accept(Connection &conn) {
+  AssertLockNotHeld(m_mutex);
+
+  std::string errmsg;
+  bool disconnect{false};
+
+  while (!*m_interrupt) {
+    Sock::Event occurred;
+    if (!conn.sock->Wait(MAX_WAIT_FOR_IO, Sock::RECV, &occurred)) {
+      errmsg = "wait on socket failed";
+      break;
+    }
+
+    if (occurred == 0) {
+      // Timeout, no incoming connections or errors within MAX_WAIT_FOR_IO.
+      continue;
+    }
+
+    std::string peer_dest;
+    try {
+      peer_dest = conn.sock->RecvUntilTerminator('\n', MAX_WAIT_FOR_IO,
+                                                 *m_interrupt, MAX_MSG_SIZE);
+    } catch (const std::runtime_error &e) {
+      errmsg = e.what();
+      break;
+    }
+
+    CNetAddr peer_addr;
+    try {
+      peer_addr = DestB64ToAddr(peer_dest);
+    } catch (const std::runtime_error &e) {
+      // The I2P router is expected to send the Base64 of the connecting peer,
+      // but it may happen that something like this is sent instead:
+      // STREAM STATUS RESULT=I2P_ERROR MESSAGE="Session was closed"
+      // In that case consider the session damaged and close it right away,
+      // even if the control socket is alive.
+      if (peer_dest.find("RESULT=I2P_ERROR") != std::string::npos) {
+        errmsg = tfm::format(
+            "unexpected reply that hints the session is unusable: %s",
+            peer_dest);
+        disconnect = true;
+      } else {
+        errmsg = e.what();
+      }
+      break;
+    }
+
+    conn.peer = CService(peer_addr, I2P_SAM31_PORT);
+
+    return true;
+  }
+
+  Log("Error accepting%s: %s", disconnect ? " (will close the session)" : "",
+      errmsg);
+  if (disconnect) {
+    LOCK(m_mutex);
+    Disconnect();
+  } else {
+    CheckControlSock();
+  }
+  return false;
+}
+
+bool Session::Connect(const CService &to, Connection &conn, bool &proxy_error) {
+  // Refuse connecting to arbitrary ports. We don't specify any destination
+  // port to the SAM proxy
+  // when connecting (SAM 3.1 does not use ports) and it forces/defaults it
+  // to I2P_SAM31_PORT.
+  if (to.GetPort() != I2P_SAM31_PORT) {
+    Log("Error connecting to % s, connection refused due to arbitrary port % "
+        "s ",
+        to.ToStringAddrPort(), to.GetPort());
+    proxy_error = false;
+    return false;
+  }
+
+  proxy_error = true;
+
+  std::string session_id;
+  std::unique_ptr<Sock> sock;
+  conn.peer = to;
+
+  try {
+    {
+      LOCK(m_mutex);
+      CreateIfNotCreatedAlready();
+      session_id = m_session_id;
+      conn.me = m_my_addr;
+      sock = Hello();
+    }
+
+    const Reply &lookup_reply = SendRequestAndGetReply(
+        *sock, tfm::format("NAMING LOOKUP NAME=%s", to.ToStringAddr()));
+
+    const std::string &dest = lookup_reply.Get("VALUE");
+
+    const Reply &connect_reply = SendRequestAndGetReply(
+        *sock,
+        tfm::format("STREAM CONNECT ID=%s DESTINATION=%s SILENT=false",
+                    session_id, dest),
+        false);
+
+    const std::string &result = connect_reply.Get("RESULT");
+
+    if (result == "OK") {
+      conn.sock = std::move(sock);
+      return true;
+    }
+
+    if (result == "INVALID_ID") {
+      LOCK(m_mutex);
+      Disconnect();
+      throw std::runtime_error("Invalid session id");
+    }
+
+    if (result == "CANT_REACH_PEER" || result == "TIMEOUT") {
+      proxy_error = false;
+    }
+
+    throw std::runtime_error(tfm::format("\"%s\"", connect_reply.full));
+  } catch (const std::runtime_error &e) {
+    Log("Error connecting to %s: %s", to.ToStringAddrPort(), e.what());
+    CheckControlSock();
+    return false;
+  }
+}
+
+// Private methods
+
+std::string Session::Reply::Get(const std::string &key) const {
+  const auto &pos = keys.find(key);
+  if (pos == keys.end() || !pos->second.has_value()) {
+    throw std::runtime_error(tfm::format(
+        "Missing %s= in the reply to \"%s\": \"%s\"", key, request, full));
+  }
+  return pos->second.value();
+}
+
+template <typename... Args>
+void Session::Log(const std::string &fmt, const Args &...args) const {
+  // LogPrint(BCLog::I2P, "%s\n", tfm::format(fmt, args...));
+  MLOG_GREEN(el::Level::Info, tfm::format(fmt, args...));
+}
+
+Session::Reply Session::SendRequestAndGetReply(const Sock &sock,
+                                               const std::string &request,
+                                               bool check_result_ok) const {
+  sock.SendComplete(request + "\n", MAX_WAIT_FOR_IO, *m_interrupt);
+
+  Reply reply;
+
+  // Don't log the full "SESSION CREATE ..." because it contains our private
+  // key.
+  reply.request = request.substr(0, 14) == "SESSION CREATE"
+                      ? "SESSION CREATE ... "
+                      : request;
+
+  // It could take a few minutes for the I2P router to reply as it is
+  // querying
+  // the I2P network
+  // (when doing name lookup, for example). Notice:
+  // `RecvUntilTerminator()` is
+  // checking
+  // `m_interrupt` more often, so we would not be stuck here for long if
+  // `m_interrupt` is
+  // signaled.
+  static constexpr auto recv_timeout = 3min;
+
+  reply.full =
+      sock.RecvUntilTerminator('\n', recv_timeout, *m_interrupt, MAX_MSG_SIZE);
+
+  for (const auto &kv : spanparsing::Split(reply.full, ' ')) {
+    const auto &pos = std::find(kv.begin(), kv.end(), '=');
+    if (pos != kv.end()) {
+      reply.keys.emplace(std::string{kv.begin(), pos},
+                         std::string{pos + 1, kv.end()});
+    } else {
+      reply.keys.emplace(std::string{kv.begin(), kv.end()}, std::nullopt);
+    }
+  }
+
+  if (check_result_ok && reply.Get("RESULT") != "OK") {
+    throw std::runtime_error(
+        tfm::format("Unexpected reply to \"%s\": \"%s\"", request, reply.full));
+  }
+
+  return reply;
+}
+
+std::unique_ptr<Sock> Session::Hello() const {
+  auto sock = m_control_host.Connect();
+
+  if (!sock) {
+    throw std::runtime_error(
+        tfm::format("Cannot connect to %s", m_control_host.ToString()));
+  }
+
+  SendRequestAndGetReply(*sock, "HELLO VERSION MIN=3.1 MAX=3.1");
+
+  return sock;
+}
+
+void Session::CheckControlSock() {
+  LOCK(m_mutex);
+
+  std::string errmsg;
+  if (m_control_sock && !m_control_sock->IsConnected(errmsg)) {
+    Log("Control socket error: %s", errmsg);
+    Disconnect();
+  }
+}
+
+void Session::DestGenerate(const Sock &sock) {
+  // https://geti2p.net/spec/common-structures#key-certificates
+  // "7" or "EdDSA_SHA512_Ed25519" - "Recent Router Identities and
+  // Destinations".
+  // Use "7" because i2pd <2.24.0 does not recognize the textual form.
+  // If SIGNATURE_TYPE is not specified, then the default one is DSA_SHA1.
+  const Reply &reply =
+      SendRequestAndGetReply(sock, "DEST GENERATE SIGNATURE_TYPE=7", false);
+
+  m_private_key = DecodeI2PBase64(reply.Get("PRIV"));
+}
+
+void Session::GenerateAndSavePrivateKey(const Sock &sock) {
+  DestGenerate(sock);
+
+  // umask is set to 0077 in common/system.cpp, which is ok.
+  if (!WriteBinaryFile(m_private_key_file, std::string(m_private_key.begin(),
+                                                       m_private_key.end()))) {
+    throw std::runtime_error(
+        tfm::format("Cannot save I2P private key to %s",
+                    fs::quoted(fs::PathToString(m_private_key_file))));
+  }
+}
+
+Binary Session::MyDestination() const {
+  // From https://geti2p.net/spec/common-structures#destination:
+  // "They are 387 bytes plus the certificate length specified at bytes
+  // 385 - 386, which may be
+  // non-zero"
+  static constexpr size_t DEST_LEN_BASE = 387;
+  static constexpr size_t CERT_LEN_POS = 385;
+
+  uint16_t cert_len;
+
+  if (m_private_key.size() < CERT_LEN_POS + sizeof(cert_len)) {
+    throw std::runtime_error(
+        tfm::format("The private key is too short (%d < %d)",
+                    m_private_key.size(), CERT_LEN_POS + sizeof(cert_len)));
+  }
+
+  memcpy(&cert_len, &m_private_key.at(CERT_LEN_POS), sizeof(cert_len));
+  cert_len = be16toh_internal(cert_len);
+
+  const size_t dest_len = DEST_LEN_BASE + cert_len;
+
+  if (dest_len > m_private_key.size()) {
+    throw std::runtime_error(tfm::format(
+        "Certificate length (%d) designates that the private key should "
+        " be % d bytes, but it is only % d bytes ",
+        cert_len, dest_len, m_private_key.size()));
+  }
+
+  return Binary{m_private_key.begin(), m_private_key.begin() + dest_len};
+}
+
+void Session::CreateIfNotCreatedAlready() {
+  std::string errmsg;
+  if (m_control_sock && m_control_sock->IsConnected(errmsg)) {
+    return;
+  }
+
+  const auto session_type = m_transient ? "transient" : "persistent";
+  const auto session_id = GetRandHash().GetHex().substr(
+      0, 10); // full is overkill, too verbose in the logs
+
+  Log("Creating %s SAM session %s with %s", session_type, session_id,
+      m_control_host.ToString());
+
+  auto sock = Hello();
+
+  if (m_transient) {
+    // The destination (private key) is generated upon session creation and
+    // returned
+    // in the reply in DESTINATION=.
+    const Reply &reply = SendRequestAndGetReply(
+        *sock,
+        tfm::format(
+            "SESSION CREATE STYLE=STREAM ID=%s DESTINATION=TRANSIENT "
+            "SIGNATURE_TYPE=7 "
+            "i2cp.leaseSetEncType=4,0 inbound.quantity=1 outbound.quantity=1",
+            session_id));
+
+    m_private_key = DecodeI2PBase64(reply.Get("DESTINATION"));
+  } else {
+    // Read our persistent destination (private key) from disk or generate
+    // one and save it to disk. Then use it when creating the session.
+    const auto &[read_ok, data] = ReadBinaryFile(m_private_key_file);
+    if (read_ok) {
+      m_private_key.assign(data.begin(), data.end());
+    } else {
+      GenerateAndSavePrivateKey(*sock);
+    }
+
+    const std::string &private_key_b64 =
+        SwapBase64(EncodeBase64(m_private_key));
+
+    SendRequestAndGetReply(
+        *sock,
+        tfm::format(
+            "SESSION CREATE STYLE=STREAM ID=%s DESTINATION=%s "
+            "i2cp.leaseSetEncType=4,0 inbound.quantity=3 outbound.quantity=3",
+            session_id, private_key_b64));
+  }
+
+  m_my_addr = CService(DestBinToAddr(MyDestination()), I2P_SAM31_PORT);
+  m_session_id = session_id;
+  m_control_sock = std::move(sock);
+
+  Log("%s SAM session %s created, my address=%s", Capitalize(session_type),
+      m_session_id, m_my_addr.ToStringAddrPort());
+}
+
+std::unique_ptr<Sock> Session::StreamAccept() {
+  auto sock = Hello();
+
+  const Reply &reply = SendRequestAndGetReply(
+      *sock, tfm::format("STREAM ACCEPT ID=%s SILENT=false", m_session_id),
+      false);
+
+  const std::string &result = reply.Get("RESULT");
+
+  if (result == "OK") {
+    return sock;
+  }
+
+  if (result == "INVALID_ID") {
+    // If our session id is invalid, then force session re-creation on next
+    // usage.
+    Disconnect();
+  }
+
+  throw std::runtime_error(tfm::format("\"%s\"", reply.full));
+}
+
+void Session::Disconnect() {
+  if (m_control_sock) {
+    if (m_session_id.empty()) {
+      Log("Destroying incomplete SAM session");
+    } else {
+      Log("Destroying SAM session %s", m_session_id);
+    }
+    m_control_sock.reset();
+  }
+  m_session_id.clear();
+}
+} // namespace sam
+} // namespace i2p

src/i2p/i2p.h

@@ -0,0 +1,314 @@
+// Copyright (c) 2020-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_I2P_H
+#define BITCOIN_I2P_H
+
+// #include "compat/compat.h"
+#include "netaddress.h"
+#include "netbase.h"
+#include "sync.h"
+#include "util/fs.h"
+#include "util/sock.h"
+#include "util/threadinterrupt.h"
+
+#include <memory>
+#include <optional>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+// #include "misc_log_ex.h"
+/*
+ * quik notes area:
+ *
+ * required classes:
+ * Sock(util/sock.h)
+ * CService(netaddress.h)
+ * path(fs.h)
+ * Proxy(netbase.h)
+ * CThreadInterrupt(util/threadinterrupt.h)
+ * EXCLUSIVE_LOCKS_REQUIRED(sync.h)
+ * GUARDED_BY(sync.h)
+ * Mutex(sync.h)
+ */
+
+namespace i2p {
+
+/**
+ * Binary data.
+ */
+// preland: this is my "checked line". nothing below this is checked.
+using Binary = std::vector<uint8_t>;
+
+/**
+ * An established connection with another peer.
+ */
+struct Connection {
+  /** Connected socket. */
+  std::unique_ptr<Sock> sock;
+
+  /** Our I2P address. */
+  CService me;
+
+  /** The peer's I2P address. */
+  CService peer;
+};
+
+namespace sam {
+
+/**
+ * The maximum size of an incoming message from the I2P SAM proxy (in bytes).
+ * Used to avoid a runaway proxy from sending us an "unlimited" amount of data
+ * without a terminator. The longest known message is ~1400 bytes, so this is
+ * high enough not to be triggered during normal operation, yet low enough to
+ * avoid a malicious proxy from filling our memory.
+ */
+static constexpr size_t MAX_MSG_SIZE{65536};
+
+/**
+ * I2P SAM session.
+ */
+class Session {
+public:
+  /**
+   * Construct a session. This will not initiate any IO, the session will be
+   * lazily created later when first used.
+   * @param[in] private_key_file Path to a private key file. If the file does
+   * not exist then the private key will be generated and saved into the file.
+   * @param[in] control_host Location of the SAM proxy.
+   * @param[in,out] interrupt If this is signaled then all operations are
+   * canceled as soon as possible and executing methods throw an exception.
+   * Notice: only a pointer to the `CThreadInterrupt` object is saved, so it
+   * must not be destroyed earlier than this `Session` object.
+   */
+  Session(const fs::path &private_key_file, const Proxy &control_host,
+          CThreadInterrupt *interrupt);
+
+  /**
+   * Construct a transient session which will generate its own I2P private key
+   * rather than read the one from disk (it will not be saved on disk either and
+   * will be lost once this object is destroyed). This will not initiate any IO,
+   * the session will be lazily created later when first used.
+   * @param[in] control_host Location of the SAM proxy.
+   * @param[in,out] interrupt If this is signaled then all operations are
+   * canceled as soon as possible and executing methods throw an exception.
+   * Notice: only a pointer to the `CThreadInterrupt` object is saved, so it
+   * must not be destroyed earlier than this `Session` object.
+   */
+  Session(const Proxy &control_host, CThreadInterrupt *interrupt);
+
+  /**
+   * Destroy the session, closing the internally used sockets. The sockets that
+   * have been returned by `Accept()` or `Connect()` will not be closed, but
+   * they will be closed by the SAM proxy because the session is destroyed. So
+   * they will return an error next time we try to read or write to them.
+   */
+  ~Session();
+
+  /**
+   * Start listening for an incoming connection.
+   * @param[out] conn Upon successful completion the `sock` and `me` members
+   * will be set to the listening socket and address.
+   * @return true on success
+   */
+  bool Listen(Connection &conn) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+
+  /**
+   * Wait for and accept a new incoming connection.
+   * @param[in,out] conn The `sock` member is used for waiting and accepting.
+   * Upon successful completion the `peer` member will be set to the address of
+   * the incoming peer.
+   * @return true on success
+   */
+  bool Accept(Connection &conn) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+
+  /**
+   * Connect to an I2P peer.
+   * @param[in] to Peer to connect to.
+   * @param[out] conn Established connection. Only set if `true` is returned.
+   * @param[out] proxy_error If an error occurs due to proxy or general network
+   * failure, then this is set to `true`. If an error occurs due to unreachable
+   * peer (likely peer is down), then it is set to `false`. Only set if `false`
+   * is returned.
+   * @return true on success
+   */
+  bool Connect(const CService &to, Connection &conn, bool &proxy_error)
+      EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+
+private:
+  /**
+   * A reply from the SAM proxy.
+   */
+  struct Reply {
+    /**
+     * Full, unparsed reply.
+     */
+    std::string full;
+
+    /**
+     * Request, used for detailed error reporting.
+     */
+    std::string request;
+
+    /**
+     * A map of keywords from the parsed reply.
+     * For example, if the reply is "A=X B C=YZ", then the map will be
+     * keys["A"] == "X"
+     * keys["B"] == (empty std::optional)
+     * keys["C"] == "YZ"
+     */
+    std::unordered_map<std::string, std::optional<std::string>> keys;
+
+    /**
+     * Get the value of a given key.
+     * For example if the reply is "A=X B" then:
+     * Value("A") -> "X"
+     * Value("B") -> throws
+     * Value("C") -> throws
+     * @param[in] key Key whose value to retrieve
+     * @returns the key's value
+     * @throws std::runtime_error if the key is not present or if it has no
+     * value
+     */
+    std::string Get(const std::string &key) const;
+  };
+
+  /**
+   * Log a message in the `BCLog::I2P` category.
+   * @param[in] fmt printf(3)-like format string.
+   * @param[in] args printf(3)-like arguments that correspond to `fmt`.
+   */
+  template <typename... Args>
+  void Log(const std::string &fmt, const Args &...args) const;
+
+  /**
+   * Send request and get a reply from the SAM proxy.
+   * @param[in] sock A socket that is connected to the SAM proxy.
+   * @param[in] request Raw request to send, a newline terminator is appended to
+   * it.
+   * @param[in] check_result_ok If true then after receiving the reply a check
+   * is made whether it contains "RESULT=OK" and an exception is thrown if it
+   * does not.
+   * @throws std::runtime_error if an error occurs
+   */
+  Reply SendRequestAndGetReply(const Sock &sock, const std::string &request,
+                               bool check_result_ok = true) const;
+
+  /**
+   * Open a new connection to the SAM proxy.
+   * @return a connected socket
+   * @throws std::runtime_error if an error occurs
+   */
+  std::unique_ptr<Sock> Hello() const EXCLUSIVE_LOCKS_REQUIRED(m_mutex);
+
+  /**
+   * Check the control socket for errors and possibly disconnect.
+   */
+  void CheckControlSock() EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+
+  /**
+   * Generate a new destination with the SAM proxy and set `m_private_key` to
+   * it.
+   * @param[in] sock Socket to use for talking to the SAM proxy.
+   * @throws std::runtime_error if an error occurs
+   */
+  void DestGenerate(const Sock &sock) EXCLUSIVE_LOCKS_REQUIRED(m_mutex);
+
+  /**
+   * Generate a new destination with the SAM proxy, set `m_private_key` to it
+   * and save it on disk to `m_private_key_file`.
+   * @param[in] sock Socket to use for talking to the SAM proxy.
+   * @throws std::runtime_error if an error occurs
+   */
+  void GenerateAndSavePrivateKey(const Sock &sock)
+      EXCLUSIVE_LOCKS_REQUIRED(m_mutex);
+
+  /**
+   * Derive own destination from `m_private_key`.
+   * @see https://geti2p.net/spec/common-structures#destination
+   * @return an I2P destination
+   */
+  Binary MyDestination() const EXCLUSIVE_LOCKS_REQUIRED(m_mutex);
+
+  /**
+   * Create the session if not already created. Reads the private key file and
+   * connects to the SAM proxy.
+   * @throws std::runtime_error if an error occurs
+   */
+  void CreateIfNotCreatedAlready() EXCLUSIVE_LOCKS_REQUIRED(m_mutex);
+
+  /**
+   * Open a new connection to the SAM proxy and issue "STREAM ACCEPT" request
+   * using the existing session id.
+   * @return the idle socket that is waiting for a peer to connect to us
+   * @throws std::runtime_error if an error occurs
+   */
+  std::unique_ptr<Sock> StreamAccept() EXCLUSIVE_LOCKS_REQUIRED(m_mutex);
+
+  /**
+   * Destroy the session, closing the internally used sockets.
+   */
+  void Disconnect() EXCLUSIVE_LOCKS_REQUIRED(m_mutex);
+
+  /**
+   * The name of the file where this peer's private key is stored (in binary).
+   */
+  const fs::path m_private_key_file;
+
+  /**
+   * The SAM control service proxy.
+   */
+  const Proxy m_control_host;
+
+  /**
+   * Cease network activity when this is signaled.
+   */
+  CThreadInterrupt *const m_interrupt;
+
+  /**
+   * Mutex protecting the members that can be concurrently accessed.
+   */
+  mutable Mutex m_mutex;
+
+  /**
+   * The private key of this peer.
+   * @see The reply to the "DEST GENERATE" command in
+   * https://geti2p.net/en/docs/api/samv3
+   */
+  Binary m_private_key GUARDED_BY(m_mutex);
+
+  /**
+   * SAM control socket.
+   * Used to connect to the I2P SAM service and create a session
+   * ("SESSION CREATE"). With the established session id we later open
+   * other connections to the SAM service to accept incoming I2P
+   * connections and make outgoing ones.
+   * If not connected then this unique_ptr will be empty.
+   * See https://geti2p.net/en/docs/api/samv3
+   */
+  std::unique_ptr<Sock> m_control_sock GUARDED_BY(m_mutex);
+
+  /**
+   * Our .b32.i2p address.
+   * Derived from `m_private_key`.
+   */
+  CService m_my_addr GUARDED_BY(m_mutex);
+
+  /**
+   * SAM session id.
+   */
+  std::string m_session_id GUARDED_BY(m_mutex);
+
+  /**
+   * Whether this is a transient session (the I2P private key will not be
+   * read or written to disk).
+   */
+  const bool m_transient;
+};
+
+} // namespace sam
+} // namespace i2p
+
+#endif // BITCOIN_I2P_H

src/i2p/kernel/chain.h

@@ -0,0 +1,43 @@
+// Copyright (c) 2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_KERNEL_CHAIN_H
+#define BITCOIN_KERNEL_CHAIN_H
+
+#include <iostream>
+
+class CBlock;
+class CBlockIndex;
+namespace interfaces {
+struct BlockInfo;
+} // namespace interfaces
+
+namespace kernel {
+//! Return data from block index.
+interfaces::BlockInfo MakeBlockInfo(const CBlockIndex *block_index,
+                                    const CBlock *data = nullptr);
+
+} // namespace kernel
+
+//! This enum describes the various roles a specific Chainstate instance can
+//! take. Other parts of the system sometimes need to vary in behavior depending
+//! on the existence of a background validation chainstate, e.g. when building
+//! indexes.
+enum class ChainstateRole {
+  // Single chainstate in use, "normal" IBD mode.
+  NORMAL,
+
+  // Doing IBD-style validation in the background. Implies use of an
+  // assumed-valid
+  // chainstate.
+  BACKGROUND,
+
+  // Active assumed-valid chainstate. Implies use of a background IBD
+  // chainstate.
+  ASSUMEDVALID,
+};
+
+std::ostream &operator<<(std::ostream &os, const ChainstateRole &role);
+
+#endif // BITCOIN_KERNEL_CHAIN_H

src/i2p/kernel/chainparams.h

@@ -0,0 +1,198 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_KERNEL_CHAINPARAMS_H
+#define BITCOIN_KERNEL_CHAINPARAMS_H
+
+#include "../consensus/params.h"
+#include "../primitives/block.h"
+#include "../uint256.h"
+#include "../util/chaintype.h"
+#include "../util/hash_type.h"
+#include "../util/vector.h"
+#include "messagestartchars.h"
+
+#include <cstdint>
+#include <iterator>
+#include <map>
+#include <memory>
+#include <optional>
+#include <string>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+
+typedef std::map<int, uint256> MapCheckpoints;
+
+struct CCheckpointData {
+  MapCheckpoints mapCheckpoints;
+
+  int GetHeight() const {
+    const auto &final_checkpoint = mapCheckpoints.rbegin();
+    return final_checkpoint->first /* height */;
+  }
+};
+
+struct AssumeutxoHash : public BaseHash<uint256> {
+  explicit AssumeutxoHash(const uint256 &hash) : BaseHash(hash) {}
+};
+
+/**
+ * Holds configuration for use during UTXO snapshot load and validation. The
+ * contents here are security critical, since they dictate which UTXO snapshots
+ * are recognized as valid.
+ */
+struct AssumeutxoData {
+  int height;
+
+  //! The expected hash of the deserialized UTXO set.
+  AssumeutxoHash hash_serialized;
+
+  //! Used to populate the nChainTx value, which is used during
+  //! BlockManager::LoadBlockIndex().
+  //!
+  //! We need to hardcode the value here because this is computed cumulatively
+  //! using block data, which we do not necessarily have at the time of snapshot
+  //! load.
+  unsigned int nChainTx;
+
+  //! The hash of the base block for this snapshot. Used to refer to assumeutxo
+  //! data prior to having a loaded blockindex.
+  uint256 blockhash;
+};
+
+/**
+ * Holds various statistics on transactions within a chain. Used to estimate
+ * verification progress during chain sync.
+ *
+ * See also: CChainParams::TxData, GuessVerificationProgress.
+ */
+struct ChainTxData {
+  int64_t nTime;    //!< UNIX timestamp of last known number of transactions
+  int64_t nTxCount; //!< total number of transactions between genesis and that
+                    //!< timestamp
+  double dTxRate;   //!< estimated number of transactions per second after that
+                    //!< timestamp
+};
+
+/**
+ * CChainParams defines various tweakable parameters of a given instance of the
+ * Bitcoin system.
+ */
+class CChainParams {
+public:
+  enum Base58Type {
+    PUBKEY_ADDRESS,
+    SCRIPT_ADDRESS,
+    SECRET_KEY,
+    EXT_PUBLIC_KEY,
+    EXT_SECRET_KEY,
+
+    MAX_BASE58_TYPES
+  };
+
+  const Consensus::Params &GetConsensus() const { return consensus; }
+  const MessageStartChars &MessageStart() const { return pchMessageStart; }
+  uint16_t GetDefaultPort() const { return nDefaultPort; }
+
+  const CBlock &GenesisBlock() const { return genesis; }
+  /** Default value for -checkmempool and -checkblockindex argument */
+  bool DefaultConsistencyChecks() const { return fDefaultConsistencyChecks; }
+  /** If this chain is exclusively used for testing */
+  bool IsTestChain() const { return m_chain_type != ChainType::MAIN; }
+  /** If this chain allows time to be mocked */
+  bool IsMockableChain() const { return m_is_mockable_chain; }
+  uint64_t PruneAfterHeight() const { return nPruneAfterHeight; }
+  /** Minimum free space (in GB) needed for data directory */
+  uint64_t AssumedBlockchainSize() const { return m_assumed_blockchain_size; }
+  /** Minimum free space (in GB) needed for data directory when pruned; Does not
+   * include prune target*/
+  uint64_t AssumedChainStateSize() const { return m_assumed_chain_state_size; }
+  /** Whether it is possible to mine blocks on demand (no retargeting) */
+  bool MineBlocksOnDemand() const { return consensus.fPowNoRetargeting; }
+  /** Return the chain type string */
+  std::string GetChainTypeString() const {
+    return ChainTypeToString(m_chain_type);
+  }
+  /** Return the chain type */
+  ChainType GetChainType() const { return m_chain_type; }
+  /** Return the list of hostnames to look up for DNS seeds */
+  const std::vector<std::string> &DNSSeeds() const { return vSeeds; }
+  const std::vector<unsigned char> &Base58Prefix(Base58Type type) const {
+    return base58Prefixes[type];
+  }
+  const std::string &Bech32HRP() const { return bech32_hrp; }
+  const std::vector<uint8_t> &FixedSeeds() const { return vFixedSeeds; }
+  const CCheckpointData &Checkpoints() const { return checkpointData; }
+
+  std::optional<AssumeutxoData> AssumeutxoForHeight(int height) const {
+    return FindFirst(m_assumeutxo_data,
+                     [&](const auto &d) { return d.height == height; });
+  }
+  std::optional<AssumeutxoData>
+  AssumeutxoForBlockhash(const uint256 &blockhash) const {
+    return FindFirst(m_assumeutxo_data,
+                     [&](const auto &d) { return d.blockhash == blockhash; });
+  }
+
+  const ChainTxData &TxData() const { return chainTxData; }
+
+  /**
+   * SigNetOptions holds configurations for creating a signet CChainParams.
+   */
+  struct SigNetOptions {
+    std::optional<std::vector<uint8_t>> challenge{};
+    std::optional<std::vector<std::string>> seeds{};
+  };
+
+  /**
+   * VersionBitsParameters holds activation parameters
+   */
+  struct VersionBitsParameters {
+    int64_t start_time;
+    int64_t timeout;
+    int min_activation_height;
+  };
+
+  /**
+   * RegTestOptions holds configurations for creating a regtest CChainParams.
+   */
+  struct RegTestOptions {
+    std::unordered_map<Consensus::DeploymentPos, VersionBitsParameters>
+        version_bits_parameters{};
+    std::unordered_map<Consensus::BuriedDeployment, int> activation_heights{};
+    bool fastprune{false};
+  };
+
+  static std::unique_ptr<const CChainParams>
+  RegTest(const RegTestOptions &options);
+  static std::unique_ptr<const CChainParams>
+  SigNet(const SigNetOptions &options);
+  static std::unique_ptr<const CChainParams> Main();
+  static std::unique_ptr<const CChainParams> TestNet();
+
+protected:
+  CChainParams() {}
+
+  Consensus::Params consensus;
+  MessageStartChars pchMessageStart;
+  uint16_t nDefaultPort;
+  uint64_t nPruneAfterHeight;
+  uint64_t m_assumed_blockchain_size;
+  uint64_t m_assumed_chain_state_size;
+  std::vector<std::string> vSeeds;
+  std::vector<unsigned char> base58Prefixes[MAX_BASE58_TYPES];
+  std::string bech32_hrp;
+  ChainType m_chain_type;
+  CBlock genesis;
+  std::vector<uint8_t> vFixedSeeds;
+  bool fDefaultConsistencyChecks;
+  bool m_is_mockable_chain;
+  CCheckpointData checkpointData;
+  std::vector<AssumeutxoData> m_assumeutxo_data;
+  ChainTxData chainTxData;
+};
+
+#endif // BITCOIN_KERNEL_CHAINPARAMS_H

src/i2p/kernel/messagestartchars.h

@@ -0,0 +1,13 @@
+// Copyright (c) 2023 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_KERNEL_MESSAGESTARTCHARS_H
+#define BITCOIN_KERNEL_MESSAGESTARTCHARS_H
+
+#include <array>
+#include <cstdint>
+
+using MessageStartChars = std::array<uint8_t, 4>;
+
+#endif // BITCOIN_KERNEL_MESSAGESTARTCHARS_H

src/i2p/netbase.cpp

@@ -0,0 +1,942 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#if defined(HAVE_CONFIG_H)
+#include <config/bitcoin-config.h>
+#endif
+
+#include "netbase.h"
+
+#include "compat/compat.h"
+#include "logging.h"
+#include "sync.h"
+#include "tinyformat.h"
+#include "util/sock.h"
+#include "util/strencodings.h"
+#include "util/string.h"
+#include "util/time.h"
+
+#include <atomic>
+#include <chrono>
+#include <cstdint>
+#include <functional>
+#include <limits>
+#include <memory>
+
+#if HAVE_SOCKADDR_UN
+#include <sys/un.h>
+#endif
+
+// Settings
+static GlobalMutex g_proxyinfo_mutex;
+static Proxy proxyInfo[NET_MAX] GUARDED_BY(g_proxyinfo_mutex);
+static Proxy nameProxy GUARDED_BY(g_proxyinfo_mutex);
+int nConnectTimeout = DEFAULT_CONNECT_TIMEOUT;
+bool fNameLookup = DEFAULT_NAME_LOOKUP;
+
+// Need ample time for negotiation for very slow proxies such as Tor
+std::chrono::milliseconds g_socks5_recv_timeout = 20s;
+CThreadInterrupt g_socks5_interrupt;
+
+ReachableNets g_reachable_nets;
+
+std::vector<CNetAddr> WrappedGetAddrInfo(const std::string &name,
+                                         bool allow_lookup) {
+  addrinfo ai_hint{};
+  // We want a TCP port, which is a streaming socket type
+  ai_hint.ai_socktype = SOCK_STREAM;
+  ai_hint.ai_protocol = IPPROTO_TCP;
+  // We don't care which address family (IPv4 or IPv6) is returned
+  ai_hint.ai_family = AF_UNSPEC;
+  // If we allow lookups of hostnames, use the AI_ADDRCONFIG flag to only
+  // return addresses whose family we have an address configured for.
+  //
+  // If we don't allow lookups, then use the AI_NUMERICHOST flag for
+  // getaddrinfo to only decode numerical network addresses and suppress
+  // hostname lookups.
+  ai_hint.ai_flags = allow_lookup ? AI_ADDRCONFIG : AI_NUMERICHOST;
+
+  addrinfo *ai_res{nullptr};
+  const int n_err{getaddrinfo(name.c_str(), nullptr, &ai_hint, &ai_res)};
+  if (n_err != 0) {
+    return {};
+  }
+
+  // Traverse the linked list starting with ai_trav.
+  addrinfo *ai_trav{ai_res};
+  std::vector<CNetAddr> resolved_addresses;
+  while (ai_trav != nullptr) {
+    if (ai_trav->ai_family == AF_INET) {
+      assert(ai_trav->ai_addrlen >= sizeof(sockaddr_in));
+      resolved_addresses.emplace_back(
+          reinterpret_cast<sockaddr_in *>(ai_trav->ai_addr)->sin_addr);
+    }
+    if (ai_trav->ai_family == AF_INET6) {
+      assert(ai_trav->ai_addrlen >= sizeof(sockaddr_in6));
+      const sockaddr_in6 *s6{
+          reinterpret_cast<sockaddr_in6 *>(ai_trav->ai_addr)};
+      resolved_addresses.emplace_back(s6->sin6_addr, s6->sin6_scope_id);
+    }
+    ai_trav = ai_trav->ai_next;
+  }
+  freeaddrinfo(ai_res);
+
+  return resolved_addresses;
+}
+
+DNSLookupFn g_dns_lookup{WrappedGetAddrInfo};
+
+enum Network ParseNetwork(const std::string &net_in) {
+  std::string net = ToLower(net_in);
+  if (net == "ipv4")
+    return NET_IPV4;
+  if (net == "ipv6")
+    return NET_IPV6;
+  if (net == "onion")
+    return NET_ONION;
+  if (net == "tor") {
+    LogPrintf("Warning: net name 'tor' is deprecated and will be removed in "
+              "the future. You should use 'onion' instead.\n");
+    return NET_ONION;
+  }
+  if (net == "i2p") {
+    return NET_I2P;
+  }
+  if (net == "cjdns") {
+    return NET_CJDNS;
+  }
+  return NET_UNROUTABLE;
+}
+
+std::string GetNetworkName(enum Network net) {
+  switch (net) {
+  case NET_UNROUTABLE:
+    return "not_publicly_routable";
+  case NET_IPV4:
+    return "ipv4";
+  case NET_IPV6:
+    return "ipv6";
+  case NET_ONION:
+    return "onion";
+  case NET_I2P:
+    return "i2p";
+  case NET_CJDNS:
+    return "cjdns";
+  case NET_INTERNAL:
+    return "internal";
+  case NET_MAX:
+    assert(false);
+  } // no default case, so the compiler can warn about missing cases
+
+  assert(false);
+}
+
+std::vector<std::string> GetNetworkNames(bool append_unroutable) {
+  std::vector<std::string> names;
+  for (int n = 0; n < NET_MAX; ++n) {
+    const enum Network network { static_cast<Network>(n) };
+    if (network == NET_UNROUTABLE || network == NET_INTERNAL)
+      continue;
+    names.emplace_back(GetNetworkName(network));
+  }
+  if (append_unroutable) {
+    names.emplace_back(GetNetworkName(NET_UNROUTABLE));
+  }
+  return names;
+}
+
+static std::vector<CNetAddr> LookupIntern(const std::string &name,
+                                          unsigned int nMaxSolutions,
+                                          bool fAllowLookup,
+                                          DNSLookupFn dns_lookup_function) {
+  if (!ContainsNoNUL(name))
+    return {};
+  {
+    CNetAddr addr;
+    // From our perspective, onion addresses are not hostnames but rather
+    // direct encodings of CNetAddr much like IPv4 dotted-decimal notation
+    // or IPv6 colon-separated hextet notation. Since we can't use
+    // getaddrinfo to decode them and it wouldn't make sense to resolve
+    // them, we return a network address representing it instead. See
+    // CNetAddr::SetSpecial(const std::string&) for more details.
+    if (addr.SetSpecial(name))
+      return {addr};
+  }
+
+  std::vector<CNetAddr> addresses;
+
+  for (const CNetAddr &resolved : dns_lookup_function(name, fAllowLookup)) {
+    if (nMaxSolutions > 0 && addresses.size() >= nMaxSolutions) {
+      break;
+    }
+    /* Never allow resolving to an internal address. Consider any such result
+     * invalid */
+    if (!resolved.IsInternal()) {
+      addresses.push_back(resolved);
+    }
+  }
+
+  return addresses;
+}
+
+std::vector<CNetAddr> LookupHost(const std::string &name,
+                                 unsigned int nMaxSolutions, bool fAllowLookup,
+                                 DNSLookupFn dns_lookup_function) {
+  if (!ContainsNoNUL(name))
+    return {};
+  std::string strHost = name;
+  if (strHost.empty())
+    return {};
+  if (strHost.front() == '[' && strHost.back() == ']') {
+    strHost = strHost.substr(1, strHost.size() - 2);
+  }
+
+  return LookupIntern(strHost, nMaxSolutions, fAllowLookup,
+                      dns_lookup_function);
+}
+
+std::optional<CNetAddr> LookupHost(const std::string &name, bool fAllowLookup,
+                                   DNSLookupFn dns_lookup_function) {
+  const std::vector<CNetAddr> addresses{
+      LookupHost(name, 1, fAllowLookup, dns_lookup_function)};
+  return addresses.empty() ? std::nullopt
+                           : std::make_optional(addresses.front());
+}
+
+std::vector<CService> Lookup(const std::string &name, uint16_t portDefault,
+                             bool fAllowLookup, unsigned int nMaxSolutions,
+                             DNSLookupFn dns_lookup_function) {
+  if (name.empty() || !ContainsNoNUL(name)) {
+    return {};
+  }
+  uint16_t port{portDefault};
+  std::string hostname;
+  SplitHostPort(name, port, hostname);
+
+  const std::vector<CNetAddr> addresses{
+      LookupIntern(hostname, nMaxSolutions, fAllowLookup, dns_lookup_function)};
+  if (addresses.empty())
+    return {};
+  std::vector<CService> services;
+  services.reserve(addresses.size());
+  for (const auto &addr : addresses)
+    services.emplace_back(addr, port);
+  return services;
+}
+
+std::optional<CService> Lookup(const std::string &name, uint16_t portDefault,
+                               bool fAllowLookup,
+                               DNSLookupFn dns_lookup_function) {
+  const std::vector<CService> services{
+      Lookup(name, portDefault, fAllowLookup, 1, dns_lookup_function)};
+
+  return services.empty() ? std::nullopt : std::make_optional(services.front());
+}
+
+CService LookupNumeric(const std::string &name, uint16_t portDefault,
+                       DNSLookupFn dns_lookup_function) {
+  if (!ContainsNoNUL(name)) {
+    return {};
+  }
+  // "1.2:345" will fail to resolve the ip, but will still set the port.
+  // If the ip fails to resolve, re-init the result.
+  return Lookup(name, portDefault, /*fAllowLookup=*/false, dns_lookup_function)
+      .value_or(CService{});
+}
+
+bool IsUnixSocketPath(const std::string &name) {
+#if HAVE_SOCKADDR_UN
+  if (name.find(ADDR_PREFIX_UNIX) != 0)
+    return false;
+
+  // Split off "unix:" prefix
+  std::string str{name.substr(ADDR_PREFIX_UNIX.length())};
+
+  // Path size limit is platform-dependent
+  // see https://manpages.ubuntu.com/manpages/xenial/en/man7/unix.7.html
+  if (str.size() + 1 > sizeof(((sockaddr_un *)nullptr)->sun_path))
+    return false;
+
+  return true;
+#else
+  return false;
+#endif
+}
+
+/** SOCKS version */
+enum SOCKSVersion : uint8_t { SOCKS4 = 0x04, SOCKS5 = 0x05 };
+
+/** Values defined for METHOD in RFC1928 */
+enum SOCKS5Method : uint8_t {
+  NOAUTH = 0x00,        //!< No authentication required
+  GSSAPI = 0x01,        //!< GSSAPI
+  USER_PASS = 0x02,     //!< Username/password
+  NO_ACCEPTABLE = 0xff, //!< No acceptable methods
+};
+
+/** Values defined for CMD in RFC1928 */
+enum SOCKS5Command : uint8_t {
+  CONNECT = 0x01,
+  BIND = 0x02,
+  UDP_ASSOCIATE = 0x03
+};
+
+/** Values defined for REP in RFC1928 */
+enum SOCKS5Reply : uint8_t {
+  SUCCEEDED = 0x00,        //!< Succeeded
+  GENFAILURE = 0x01,       //!< General failure
+  NOTALLOWED = 0x02,       //!< Connection not allowed by ruleset
+  NETUNREACHABLE = 0x03,   //!< Network unreachable
+  HOSTUNREACHABLE = 0x04,  //!< Network unreachable
+  CONNREFUSED = 0x05,      //!< Connection refused
+  TTLEXPIRED = 0x06,       //!< TTL expired
+  CMDUNSUPPORTED = 0x07,   //!< Command not supported
+  ATYPEUNSUPPORTED = 0x08, //!< Address type not supported
+};
+
+/** Values defined for ATYPE in RFC1928 */
+enum SOCKS5Atyp : uint8_t {
+  IPV4 = 0x01,
+  DOMAINNAME = 0x03,
+  IPV6 = 0x04,
+};
+
+/** Status codes that can be returned by InterruptibleRecv */
+enum class IntrRecvError {
+  OK,
+  Timeout,
+  Disconnected,
+  NetworkError,
+  Interrupted
+};
+
+/**
+ * Try to read a specified number of bytes from a socket. Please read the "see
+ * also" section for more detail.
+ *
+ * @param data The buffer where the read bytes should be stored.
+ * @param len The number of bytes to read into the specified buffer.
+ * @param timeout The total timeout for this read.
+ * @param sock The socket (has to be in non-blocking mode) from which to read
+ * bytes.
+ *
+ * @returns An IntrRecvError indicating the resulting status of this read.
+ *          IntrRecvError::OK only if all of the specified number of bytes were
+ *          read.
+ *
+ * @see This function can be interrupted by calling g_socks5_interrupt().
+ *      Sockets can be made non-blocking with Sock::SetNonBlocking().
+ */
+static IntrRecvError InterruptibleRecv(uint8_t *data, size_t len,
+                                       std::chrono::milliseconds timeout,
+                                       const Sock &sock) {
+  auto curTime{Now<SteadyMilliseconds>()};
+  const auto endTime{curTime + timeout};
+  while (len > 0 && curTime < endTime) {
+    ssize_t ret = sock.Recv(data, len, 0); // Optimistically try the recv first
+    if (ret > 0) {
+      len -= ret;
+      data += ret;
+    } else if (ret == 0) { // Unexpected disconnection
+      return IntrRecvError::Disconnected;
+    } else { // Other error or blocking
+      int nErr = WSAGetLastError();
+      if (nErr == WSAEINPROGRESS || nErr == WSAEWOULDBLOCK ||
+          nErr == WSAEINVAL) {
+        // Only wait at most MAX_WAIT_FOR_IO at a time, unless
+        // we're approaching the end of the specified total timeout
+        const auto remaining = std::chrono::milliseconds{endTime - curTime};
+        const auto timeout =
+            std::min(remaining, std::chrono::milliseconds{MAX_WAIT_FOR_IO});
+        if (!sock.Wait(timeout, Sock::RECV)) {
+          return IntrRecvError::NetworkError;
+        }
+      } else {
+        return IntrRecvError::NetworkError;
+      }
+    }
+    if (g_socks5_interrupt) {
+      return IntrRecvError::Interrupted;
+    }
+    curTime = Now<SteadyMilliseconds>();
+  }
+  return len == 0 ? IntrRecvError::OK : IntrRecvError::Timeout;
+}
+
+/** Convert SOCKS5 reply to an error message */
+static std::string Socks5ErrorString(uint8_t err) {
+  switch (err) {
+  case SOCKS5Reply::GENFAILURE:
+    return "general failure";
+  case SOCKS5Reply::NOTALLOWED:
+    return "connection not allowed";
+  case SOCKS5Reply::NETUNREACHABLE:
+    return "network unreachable";
+  case SOCKS5Reply::HOSTUNREACHABLE:
+    return "host unreachable";
+  case SOCKS5Reply::CONNREFUSED:
+    return "connection refused";
+  case SOCKS5Reply::TTLEXPIRED:
+    return "TTL expired";
+  case SOCKS5Reply::CMDUNSUPPORTED:
+    return "protocol error";
+  case SOCKS5Reply::ATYPEUNSUPPORTED:
+    return "address type not supported";
+  default:
+    return "unknown";
+  }
+}
+
+bool Socks5(const std::string &strDest, uint16_t port,
+            const ProxyCredentials *auth, const Sock &sock) {
+  try {
+    IntrRecvError recvr;
+    LogPrint(BCLog::NET, "SOCKS5 connecting %s\n", strDest);
+    if (strDest.size() > 255) {
+      LogError("Hostname too long\n");
+      return false;
+    }
+    // Construct the version identifier/method selection message
+    std::vector<uint8_t> vSocks5Init;
+    vSocks5Init.push_back(SOCKSVersion::SOCKS5); // We want the SOCK5 protocol
+    if (auth) {
+      vSocks5Init.push_back(0x02); // 2 method identifiers follow...
+      vSocks5Init.push_back(SOCKS5Method::NOAUTH);
+      vSocks5Init.push_back(SOCKS5Method::USER_PASS);
+    } else {
+      vSocks5Init.push_back(0x01); // 1 method identifier follows...
+      vSocks5Init.push_back(SOCKS5Method::NOAUTH);
+    }
+    sock.SendComplete(vSocks5Init, g_socks5_recv_timeout, g_socks5_interrupt);
+    uint8_t pchRet1[2];
+    if (InterruptibleRecv(pchRet1, 2, g_socks5_recv_timeout, sock) !=
+        IntrRecvError::OK) {
+      LogPrintf("Socks5() connect to %s:%d failed: InterruptibleRecv() timeout "
+                "or other failure\n",
+                strDest, port);
+      return false;
+    }
+    if (pchRet1[0] != SOCKSVersion::SOCKS5) {
+      LogError("Proxy failed to initialize\n");
+      return false;
+    }
+    if (pchRet1[1] == SOCKS5Method::USER_PASS && auth) {
+      // Perform username/password authentication (as described in RFC1929)
+      std::vector<uint8_t> vAuth;
+      vAuth.push_back(
+          0x01); // Current (and only) version of user/pass subnegotiation
+      if (auth->username.size() > 255 || auth->password.size() > 255) {
+        LogError("Proxy username or password too long\n");
+        return false;
+      }
+      vAuth.push_back(auth->username.size());
+      vAuth.insert(vAuth.end(), auth->username.begin(), auth->username.end());
+      vAuth.push_back(auth->password.size());
+      vAuth.insert(vAuth.end(), auth->password.begin(), auth->password.end());
+      sock.SendComplete(vAuth, g_socks5_recv_timeout, g_socks5_interrupt);
+      LogPrint(BCLog::PROXY, "SOCKS5 sending proxy authentication %s:%s\n",
+               auth->username, auth->password);
+      uint8_t pchRetA[2];
+      if (InterruptibleRecv(pchRetA, 2, g_socks5_recv_timeout, sock) !=
+          IntrRecvError::OK) {
+        LogError("Error reading proxy authentication response\n");
+        return false;
+      }
+      if (pchRetA[0] != 0x01 || pchRetA[1] != 0x00) {
+        LogError("Proxy authentication unsuccessful\n");
+        return false;
+      }
+    } else if (pchRet1[1] == SOCKS5Method::NOAUTH) {
+      // Perform no authentication
+    } else {
+      LogError("Proxy requested wrong authentication method %02x\n",
+               pchRet1[1]);
+      return false;
+    }
+    std::vector<uint8_t> vSocks5;
+    vSocks5.push_back(SOCKSVersion::SOCKS5);   // VER protocol version
+    vSocks5.push_back(SOCKS5Command::CONNECT); // CMD CONNECT
+    vSocks5.push_back(0x00);                   // RSV Reserved must be 0
+    vSocks5.push_back(SOCKS5Atyp::DOMAINNAME); // ATYP DOMAINNAME
+    vSocks5.push_back(
+        strDest.size()); // Length<=255 is checked at beginning of function
+    vSocks5.insert(vSocks5.end(), strDest.begin(), strDest.end());
+    vSocks5.push_back((port >> 8) & 0xFF);
+    vSocks5.push_back((port >> 0) & 0xFF);
+    sock.SendComplete(vSocks5, g_socks5_recv_timeout, g_socks5_interrupt);
+    uint8_t pchRet2[4];
+    if ((recvr = InterruptibleRecv(pchRet2, 4, g_socks5_recv_timeout, sock)) !=
+        IntrRecvError::OK) {
+      if (recvr == IntrRecvError::Timeout) {
+        /* If a timeout happens here, this effectively means we timed out while
+         * connecting to the remote node. This is very common for Tor, so do not
+         * print an error message. */
+        return false;
+      } else {
+        LogError("Error while reading proxy response\n");
+        return false;
+      }
+    }
+    if (pchRet2[0] != SOCKSVersion::SOCKS5) {
+      LogError("Proxy failed to accept request\n");
+      return false;
+    }
+    if (pchRet2[1] != SOCKS5Reply::SUCCEEDED) {
+      // Failures to connect to a peer that are not proxy errors
+      LogPrintf("Socks5() connect to %s:%d failed: %s\n", strDest, port,
+                Socks5ErrorString(pchRet2[1]));
+      return false;
+    }
+    if (pchRet2[2] != 0x00) { // Reserved field must be 0
+      LogError("Error: malformed proxy response\n");
+      return false;
+    }
+    uint8_t pchRet3[256];
+    switch (pchRet2[3]) {
+    case SOCKS5Atyp::IPV4:
+      recvr = InterruptibleRecv(pchRet3, 4, g_socks5_recv_timeout, sock);
+      break;
+    case SOCKS5Atyp::IPV6:
+      recvr = InterruptibleRecv(pchRet3, 16, g_socks5_recv_timeout, sock);
+      break;
+    case SOCKS5Atyp::DOMAINNAME: {
+      recvr = InterruptibleRecv(pchRet3, 1, g_socks5_recv_timeout, sock);
+      if (recvr != IntrRecvError::OK) {
+        LogError("Error reading from proxy\n");
+        return false;
+      }
+      int nRecv = pchRet3[0];
+      recvr = InterruptibleRecv(pchRet3, nRecv, g_socks5_recv_timeout, sock);
+      break;
+    }
+    default: {
+      LogError("Error: malformed proxy response\n");
+      return false;
+    }
+    }
+    if (recvr != IntrRecvError::OK) {
+      LogError("Error reading from proxy\n");
+      return false;
+    }
+    if (InterruptibleRecv(pchRet3, 2, g_socks5_recv_timeout, sock) !=
+        IntrRecvError::OK) {
+      LogError("Error reading from proxy\n");
+      return false;
+    }
+    LogPrint(BCLog::NET, "SOCKS5 connected %s\n", strDest);
+    return true;
+  } catch (const std::runtime_error &e) {
+    LogError("Error during SOCKS5 proxy handshake: %s\n", e.what());
+    return false;
+  }
+}
+
+std::unique_ptr<Sock> CreateSockOS(sa_family_t address_family) {
+  // Not IPv4, IPv6 or UNIX
+  if (address_family == AF_UNSPEC)
+    return nullptr;
+
+  int protocol{IPPROTO_TCP};
+#if HAVE_SOCKADDR_UN
+  if (address_family == AF_UNIX)
+    protocol = 0;
+#endif
+
+  // Create a socket in the specified address family.
+  SOCKET hSocket = socket(address_family, SOCK_STREAM, protocol);
+  if (hSocket == INVALID_SOCKET) {
+    return nullptr;
+  }
+
+  auto sock = std::make_unique<Sock>(hSocket);
+
+  // Ensure that waiting for I/O on this socket won't result in undefined
+  // behavior.
+  if (!sock->IsSelectable()) {
+    LogPrintf("Cannot create connection: non-selectable socket created (fd >= "
+              "FD_SETSIZE ?)\n");
+    return nullptr;
+  }
+
+#ifdef SO_NOSIGPIPE
+  int set = 1;
+  // Set the no-sigpipe option on the socket for BSD systems, other UNIXes
+  // should use the MSG_NOSIGNAL flag for every send.
+  if (sock->SetSockOpt(SOL_SOCKET, SO_NOSIGPIPE, (void *)&set, sizeof(int)) ==
+      SOCKET_ERROR) {
+    LogPrintf("Error setting SO_NOSIGPIPE on socket: %s, continuing anyway\n",
+              NetworkErrorString(WSAGetLastError()));
+  }
+#endif
+
+  // Set the non-blocking option on the socket.
+  if (!sock->SetNonBlocking()) {
+    LogPrintf("Error setting socket to non-blocking: %s\n",
+              NetworkErrorString(WSAGetLastError()));
+    return nullptr;
+  }
+
+#if HAVE_SOCKADDR_UN
+  if (address_family == AF_UNIX)
+    return sock;
+#endif
+
+  // Set the no-delay option (disable Nagle's algorithm) on the TCP socket.
+  const int on{1};
+  if (sock->SetSockOpt(IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on)) ==
+      SOCKET_ERROR) {
+    LogPrint(BCLog::NET, "Unable to set TCP_NODELAY on a newly created socket, "
+                         "continuing anyway\n");
+  }
+  return sock;
+}
+
+std::function<std::unique_ptr<Sock>(const sa_family_t &)> CreateSock =
+    CreateSockOS;
+
+template <typename... Args>
+static void LogConnectFailure(bool manual_connection, const char *fmt,
+                              const Args &...args) {
+  std::string error_message = tfm::format(fmt, args...);
+  if (manual_connection) {
+    LogPrintf("%s\n", error_message);
+  } else {
+    LogPrint(BCLog::NET, "%s\n", error_message);
+  }
+}
+
+static bool ConnectToSocket(const Sock &sock, struct sockaddr *sockaddr,
+                            socklen_t len, const std::string &dest_str,
+                            bool manual_connection) {
+  // Connect to `sockaddr` using `sock`.
+  if (sock.Connect(sockaddr, len) == SOCKET_ERROR) {
+    int nErr = WSAGetLastError();
+    // WSAEINVAL is here because some legacy version of winsock uses it
+    if (nErr == WSAEINPROGRESS || nErr == WSAEWOULDBLOCK || nErr == WSAEINVAL) {
+      // Connection didn't actually fail, but is being established
+      // asynchronously. Thus, use async I/O api (select/poll)
+      // synchronously to check for successful connection with a timeout.
+      const Sock::Event requested = Sock::RECV | Sock::SEND;
+      Sock::Event occurred;
+      if (!sock.Wait(std::chrono::milliseconds{nConnectTimeout}, requested,
+                     &occurred)) {
+        LogPrintf("wait for connect to %s failed: %s\n", dest_str,
+                  NetworkErrorString(WSAGetLastError()));
+        return false;
+      } else if (occurred == 0) {
+        LogPrint(BCLog::NET, "connection attempt to %s timed out\n", dest_str);
+        return false;
+      }
+
+      // Even if the wait was successful, the connect might not
+      // have been successful. The reason for this failure is hidden away
+      // in the SO_ERROR for the socket in modern systems. We read it into
+      // sockerr here.
+      int sockerr;
+      socklen_t sockerr_len = sizeof(sockerr);
+      if (sock.GetSockOpt(SOL_SOCKET, SO_ERROR, (sockopt_arg_type)&sockerr,
+                          &sockerr_len) == SOCKET_ERROR) {
+        LogPrintf("getsockopt() for %s failed: %s\n", dest_str,
+                  NetworkErrorString(WSAGetLastError()));
+        return false;
+      }
+      if (sockerr != 0) {
+        LogConnectFailure(manual_connection,
+                          "connect() to %s failed after wait: %s", dest_str,
+                          NetworkErrorString(sockerr));
+        return false;
+      }
+    }
+#ifdef WIN32
+    else if (WSAGetLastError() != WSAEISCONN)
+#else
+    else
+#endif
+    {
+      LogConnectFailure(manual_connection, "connect() to %s failed: %s",
+                        dest_str, NetworkErrorString(WSAGetLastError()));
+      return false;
+    }
+  }
+  return true;
+}
+
+std::unique_ptr<Sock> ConnectDirectly(const CService &dest,
+                                      bool manual_connection) {
+  auto sock = CreateSock(dest.GetSAFamily());
+  if (!sock) {
+    LogPrintLevel(BCLog::NET, BCLog::Level::Error,
+                  "Cannot create a socket for connecting to %s\n",
+                  dest.ToStringAddrPort());
+    return {};
+  }
+
+  // Create a sockaddr from the specified service.
+  struct sockaddr_storage sockaddr;
+  socklen_t len = sizeof(sockaddr);
+  if (!dest.GetSockAddr((struct sockaddr *)&sockaddr, &len)) {
+    LogPrintf("Cannot get sockaddr for %s: unsupported network\n",
+              dest.ToStringAddrPort());
+    return {};
+  }
+
+  if (!ConnectToSocket(*sock, (struct sockaddr *)&sockaddr, len,
+                       dest.ToStringAddrPort(), manual_connection)) {
+    return {};
+  }
+
+  return sock;
+}
+
+std::unique_ptr<Sock> Proxy::Connect() const {
+  if (!IsValid()) {
+    LogPrintf("Cannot connect to invalid Proxy\n");
+    return {};
+  }
+
+  if (!m_is_unix_socket)
+    return ConnectDirectly(proxy, /*manual_connection=*/true);
+
+#if HAVE_SOCKADDR_UN
+  auto sock = CreateSock(AF_UNIX);
+  if (!sock) {
+    LogPrintLevel(BCLog::NET, BCLog::Level::Error,
+                  "Cannot create a socket for connecting to %s\n",
+                  m_unix_socket_path);
+    return {};
+  }
+
+  const std::string path{m_unix_socket_path.substr(ADDR_PREFIX_UNIX.length())};
+
+  struct sockaddr_un addrun;
+  memset(&addrun, 0, sizeof(addrun));
+  addrun.sun_family = AF_UNIX;
+  // leave the last char in addrun.sun_path[] to be always '\0'
+  memcpy(addrun.sun_path, path.c_str(),
+         std::min(sizeof(addrun.sun_path) - 1, path.length()));
+  socklen_t len = sizeof(addrun);
+
+  if (!ConnectToSocket(*sock, (struct sockaddr *)&addrun, len, path,
+                       /*manual_connection=*/true)) {
+    LogPrintf("Cannot connect to socket for %s\n", path);
+    return {};
+  }
+
+  return sock;
+#else
+  return {};
+#endif
+}
+
+bool SetProxy(enum Network net, const Proxy &addrProxy) {
+  assert(net >= 0 && net < NET_MAX);
+  if (!addrProxy.IsValid())
+    return false;
+  LOCK(g_proxyinfo_mutex);
+  proxyInfo[net] = addrProxy;
+  return true;
+}
+
+bool GetProxy(enum Network net, Proxy &proxyInfoOut) {
+  assert(net >= 0 && net < NET_MAX);
+  LOCK(g_proxyinfo_mutex);
+  if (!proxyInfo[net].IsValid())
+    return false;
+  proxyInfoOut = proxyInfo[net];
+  return true;
+}
+
+bool SetNameProxy(const Proxy &addrProxy) {
+  if (!addrProxy.IsValid())
+    return false;
+  LOCK(g_proxyinfo_mutex);
+  nameProxy = addrProxy;
+  return true;
+}
+
+bool GetNameProxy(Proxy &nameProxyOut) {
+  LOCK(g_proxyinfo_mutex);
+  if (!nameProxy.IsValid())
+    return false;
+  nameProxyOut = nameProxy;
+  return true;
+}
+
+bool HaveNameProxy() {
+  LOCK(g_proxyinfo_mutex);
+  return nameProxy.IsValid();
+}
+
+bool IsProxy(const CNetAddr &addr) {
+  LOCK(g_proxyinfo_mutex);
+  for (int i = 0; i < NET_MAX; i++) {
+    if (addr == static_cast<CNetAddr>(proxyInfo[i].proxy))
+      return true;
+  }
+  return false;
+}
+
+std::unique_ptr<Sock> ConnectThroughProxy(const Proxy &proxy,
+                                          const std::string &dest,
+                                          uint16_t port,
+                                          bool &proxy_connection_failed) {
+  // first connect to proxy server
+  auto sock = proxy.Connect();
+  if (!sock) {
+    proxy_connection_failed = true;
+    return {};
+  }
+
+  // do socks negotiation
+  if (proxy.m_randomize_credentials) {
+    ProxyCredentials random_auth;
+    static std::atomic_int counter(0);
+    random_auth.username = random_auth.password = strprintf("%i", counter++);
+    if (!Socks5(dest, port, &random_auth, *sock)) {
+      return {};
+    }
+  } else {
+    if (!Socks5(dest, port, nullptr, *sock)) {
+      return {};
+    }
+  }
+  return sock;
+}
+
+CSubNet LookupSubNet(const std::string &subnet_str) {
+  CSubNet subnet;
+  assert(!subnet.IsValid());
+  if (!ContainsNoNUL(subnet_str)) {
+    return subnet;
+  }
+
+  const size_t slash_pos{subnet_str.find_last_of('/')};
+  const std::string str_addr{subnet_str.substr(0, slash_pos)};
+  std::optional<CNetAddr> addr{LookupHost(str_addr, /*fAllowLookup=*/false)};
+
+  if (addr.has_value()) {
+    addr = static_cast<CNetAddr>(
+        MaybeFlipIPv6toCJDNS(CService{addr.value(), /*port=*/0}));
+    if (slash_pos != subnet_str.npos) {
+      const std::string netmask_str{subnet_str.substr(slash_pos + 1)};
+      uint8_t netmask;
+      if (ParseUInt8(netmask_str, &netmask)) {
+        // Valid number; assume CIDR variable-length subnet masking.
+        subnet = CSubNet{addr.value(), netmask};
+      } else {
+        // Invalid number; try full netmask syntax. Never allow lookup for
+        // netmask.
+        const std::optional<CNetAddr> full_netmask{
+            LookupHost(netmask_str, /*fAllowLookup=*/false)};
+        if (full_netmask.has_value()) {
+          subnet = CSubNet{addr.value(), full_netmask.value()};
+        }
+      }
+    } else {
+      // Single IP subnet (<ipv4>/32 or <ipv6>/128).
+      subnet = CSubNet{addr.value()};
+    }
+  }
+
+  return subnet;
+}
+
+bool IsBadPort(uint16_t port) {
+  /* Don't forget to update doc/p2p-bad-ports.md if you change this list. */
+
+  switch (port) {
+  case 1:     // tcpmux
+  case 7:     // echo
+  case 9:     // discard
+  case 11:    // systat
+  case 13:    // daytime
+  case 15:    // netstat
+  case 17:    // qotd
+  case 19:    // chargen
+  case 20:    // ftp data
+  case 21:    // ftp access
+  case 22:    // ssh
+  case 23:    // telnet
+  case 25:    // smtp
+  case 37:    // time
+  case 42:    // name
+  case 43:    // nicname
+  case 53:    // domain
+  case 69:    // tftp
+  case 77:    // priv-rjs
+  case 79:    // finger
+  case 87:    // ttylink
+  case 95:    // supdup
+  case 101:   // hostname
+  case 102:   // iso-tsap
+  case 103:   // gppitnp
+  case 104:   // acr-nema
+  case 109:   // pop2
+  case 110:   // pop3
+  case 111:   // sunrpc
+  case 113:   // auth
+  case 115:   // sftp
+  case 117:   // uucp-path
+  case 119:   // nntp
+  case 123:   // NTP
+  case 135:   // loc-srv /epmap
+  case 137:   // netbios
+  case 139:   // netbios
+  case 143:   // imap2
+  case 161:   // snmp
+  case 179:   // BGP
+  case 389:   // ldap
+  case 427:   // SLP (Also used by Apple Filing Protocol)
+  case 465:   // smtp+ssl
+  case 512:   // print / exec
+  case 513:   // login
+  case 514:   // shell
+  case 515:   // printer
+  case 526:   // tempo
+  case 530:   // courier
+  case 531:   // chat
+  case 532:   // netnews
+  case 540:   // uucp
+  case 548:   // AFP (Apple Filing Protocol)
+  case 554:   // rtsp
+  case 556:   // remotefs
+  case 563:   // nntp+ssl
+  case 587:   // smtp (rfc6409)
+  case 601:   // syslog-conn (rfc3195)
+  case 636:   // ldap+ssl
+  case 989:   // ftps-data
+  case 990:   // ftps
+  case 993:   // ldap+ssl
+  case 995:   // pop3+ssl
+  case 1719:  // h323gatestat
+  case 1720:  // h323hostcall
+  case 1723:  // pptp
+  case 2049:  // nfs
+  case 3659:  // apple-sasl / PasswordServer
+  case 4045:  // lockd
+  case 5060:  // sip
+  case 5061:  // sips
+  case 6000:  // X11
+  case 6566:  // sane-port
+  case 6665:  // Alternate IRC
+  case 6666:  // Alternate IRC
+  case 6667:  // Standard IRC
+  case 6668:  // Alternate IRC
+  case 6669:  // Alternate IRC
+  case 6697:  // IRC + TLS
+  case 10080: // Amanda
+    return true;
+  }
+  return false;
+}
+
+CService MaybeFlipIPv6toCJDNS(const CService &service) {
+  CService ret{service};
+  if (ret.IsIPv6() && ret.HasCJDNSPrefix() &&
+      g_reachable_nets.Contains(NET_CJDNS)) {
+    ret.m_net = NET_CJDNS;
+  }
+  return ret;
+}

src/i2p/netbase.h

@@ -0,0 +1,345 @@
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_NETBASE_H
+#define BITCOIN_NETBASE_H
+
+#include "compat/compat.h"
+#include "netaddress.h"
+#include "serialize.h"
+#include "util/sock.h"
+#include "util/threadinterrupt.h"
+
+#include <functional>
+#include <memory>
+#include <stdint.h>
+#include <string>
+#include <type_traits>
+#include <unordered_set>
+#include <vector>
+
+extern int nConnectTimeout;
+extern bool fNameLookup;
+
+//! -timeout default
+static const int DEFAULT_CONNECT_TIMEOUT = 5000;
+//! -dns default
+static const int DEFAULT_NAME_LOOKUP = true;
+
+/** Prefix for unix domain socket addresses (which are local filesystem paths) */
+const std::string ADDR_PREFIX_UNIX = "unix:";
+
+enum class ConnectionDirection {
+    None = 0,
+    In = (1U << 0),
+    Out = (1U << 1),
+    Both = (In | Out),
+};
+static inline ConnectionDirection& operator|=(ConnectionDirection& a, ConnectionDirection b) {
+    using underlying = typename std::underlying_type<ConnectionDirection>::type;
+    a = ConnectionDirection(underlying(a) | underlying(b));
+    return a;
+}
+static inline bool operator&(ConnectionDirection a, ConnectionDirection b) {
+    using underlying = typename std::underlying_type<ConnectionDirection>::type;
+    return (underlying(a) & underlying(b));
+}
+
+/**
+ * Check if a string is a valid UNIX domain socket path
+ *
+ * @param      name     The string provided by the user representing a local path
+ *
+ * @returns Whether the string has proper format, length, and points to an existing file path
+ */
+bool IsUnixSocketPath(const std::string& name);
+
+class Proxy
+{
+public:
+    Proxy() : m_is_unix_socket(false), m_randomize_credentials(false) {}
+    explicit Proxy(const CService& _proxy, bool _randomize_credentials = false) : proxy(_proxy), m_is_unix_socket(false), m_randomize_credentials(_randomize_credentials) {}
+    explicit Proxy(const std::string path, bool _randomize_credentials = false) : m_unix_socket_path(path), m_is_unix_socket(true), m_randomize_credentials(_randomize_credentials) {}
+
+    CService proxy;
+    std::string m_unix_socket_path;
+    bool m_is_unix_socket;
+    bool m_randomize_credentials;
+
+    bool IsValid() const
+    {
+        if (m_is_unix_socket) return IsUnixSocketPath(m_unix_socket_path);
+        return proxy.IsValid();
+    }
+
+    sa_family_t GetFamily() const
+    {
+        if (m_is_unix_socket) return AF_UNIX;
+        return proxy.GetSAFamily();
+    }
+
+    std::string ToString() const
+    {
+        if (m_is_unix_socket) return m_unix_socket_path;
+        return proxy.ToStringAddrPort();
+    }
+
+    std::unique_ptr<Sock> Connect() const;
+};
+
+/** Credentials for proxy authentication */
+struct ProxyCredentials
+{
+    std::string username;
+    std::string password;
+};
+
+/**
+ * List of reachable networks. Everything is reachable by default.
+ */
+class ReachableNets {
+public:
+    void Add(Network net) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)
+    {
+        AssertLockNotHeld(m_mutex);
+        LOCK(m_mutex);
+        m_reachable.insert(net);
+    }
+
+    void Remove(Network net) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)
+    {
+        AssertLockNotHeld(m_mutex);
+        LOCK(m_mutex);
+        m_reachable.erase(net);
+    }
+
+    void RemoveAll() EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)
+    {
+        AssertLockNotHeld(m_mutex);
+        LOCK(m_mutex);
+        m_reachable.clear();
+    }
+
+    [[nodiscard]] bool Contains(Network net) const EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)
+    {
+        AssertLockNotHeld(m_mutex);
+        LOCK(m_mutex);
+        return m_reachable.count(net) > 0;
+    }
+
+    [[nodiscard]] bool Contains(const CNetAddr& addr) const EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)
+    {
+        AssertLockNotHeld(m_mutex);
+        return Contains(addr.GetNetwork());
+    }
+
+private:
+    mutable Mutex m_mutex;
+
+    std::unordered_set<Network> m_reachable GUARDED_BY(m_mutex){
+        NET_UNROUTABLE,
+        NET_IPV4,
+        NET_IPV6,
+        NET_ONION,
+        NET_I2P,
+        NET_CJDNS,
+        NET_INTERNAL
+    };
+};
+
+extern ReachableNets g_reachable_nets;
+
+/**
+ * Wrapper for getaddrinfo(3). Do not use directly: call Lookup/LookupHost/LookupNumeric/LookupSubNet.
+ */
+std::vector<CNetAddr> WrappedGetAddrInfo(const std::string& name, bool allow_lookup);
+
+enum Network ParseNetwork(const std::string& net);
+std::string GetNetworkName(enum Network net);
+/** Return a vector of publicly routable Network names; optionally append NET_UNROUTABLE. */
+std::vector<std::string> GetNetworkNames(bool append_unroutable = false);
+bool SetProxy(enum Network net, const Proxy &addrProxy);
+bool GetProxy(enum Network net, Proxy &proxyInfoOut);
+bool IsProxy(const CNetAddr &addr);
+/**
+ * Set the name proxy to use for all connections to nodes specified by a
+ * hostname. After setting this proxy, connecting to a node specified by a
+ * hostname won't result in a local lookup of said hostname, rather, connect to
+ * the node by asking the name proxy for a proxy connection to the hostname,
+ * effectively delegating the hostname lookup to the specified proxy.
+ *
+ * This delegation increases privacy for those who set the name proxy as they no
+ * longer leak their external hostname queries to their DNS servers.
+ *
+ * @returns Whether or not the operation succeeded.
+ *
+ * @note SOCKS5's support for UDP-over-SOCKS5 has been considered, but no SOCK5
+ *       server in common use (most notably Tor) actually implements UDP
+ *       support, and a DNS resolver is beyond the scope of this project.
+ */
+bool SetNameProxy(const Proxy &addrProxy);
+bool HaveNameProxy();
+bool GetNameProxy(Proxy &nameProxyOut);
+
+using DNSLookupFn = std::function<std::vector<CNetAddr>(const std::string&, bool)>;
+extern DNSLookupFn g_dns_lookup;
+
+/**
+ * Resolve a host string to its corresponding network addresses.
+ *
+ * @param name    The string representing a host. Could be a name or a numerical
+ *                IP address (IPv6 addresses in their bracketed form are
+ *                allowed).
+ *
+ * @returns The resulting network addresses to which the specified host
+ *          string resolved.
+ *
+ * @see Lookup(const std::string&, uint16_t, bool, unsigned int, DNSLookupFn)
+ *      for additional parameter descriptions.
+ */
+std::vector<CNetAddr> LookupHost(const std::string& name, unsigned int nMaxSolutions, bool fAllowLookup, DNSLookupFn dns_lookup_function = g_dns_lookup);
+
+/**
+ * Resolve a host string to its first corresponding network address.
+ *
+ * @returns The resulting network address to which the specified host
+ *          string resolved or std::nullopt if host does not resolve to an address.
+ *
+ * @see LookupHost(const std::string&, unsigned int, bool, DNSLookupFn)
+ *      for additional parameter descriptions.
+ */
+std::optional<CNetAddr> LookupHost(const std::string& name, bool fAllowLookup, DNSLookupFn dns_lookup_function = g_dns_lookup);
+
+/**
+ * Resolve a service string to its corresponding service.
+ *
+ * @param name    The string representing a service. Could be a name or a
+ *                numerical IP address (IPv6 addresses should be in their
+ *                disambiguated bracketed form), optionally followed by a uint16_t port
+ *                number. (e.g. example.com:8333 or
+ *                [2001:db8:85a3:8d3:1319:8a2e:370:7348]:420)
+ * @param portDefault The default port for resulting services if not specified
+ *                    by the service string.
+ * @param fAllowLookup Whether or not hostname lookups are permitted. If yes,
+ *                     external queries may be performed.
+ * @param nMaxSolutions The maximum number of results we want, specifying 0
+ *                      means "as many solutions as we get."
+ *
+ * @returns The resulting services to which the specified service string
+ *          resolved.
+ */
+std::vector<CService> Lookup(const std::string& name, uint16_t portDefault, bool fAllowLookup, unsigned int nMaxSolutions, DNSLookupFn dns_lookup_function = g_dns_lookup);
+
+/**
+ * Resolve a service string to its first corresponding service.
+ *
+ * @see Lookup(const std::string&, uint16_t, bool, unsigned int, DNSLookupFn)
+ *      for additional parameter descriptions.
+ */
+std::optional<CService> Lookup(const std::string& name, uint16_t portDefault, bool fAllowLookup, DNSLookupFn dns_lookup_function = g_dns_lookup);
+
+/**
+ * Resolve a service string with a numeric IP to its first corresponding
+ * service.
+ *
+ * @returns The resulting CService if the resolution was successful, [::]:0 otherwise.
+ *
+ * @see Lookup(const std::string&, uint16_t, bool, unsigned int, DNSLookupFn)
+ *      for additional parameter descriptions.
+ */
+CService LookupNumeric(const std::string& name, uint16_t portDefault = 0, DNSLookupFn dns_lookup_function = g_dns_lookup);
+
+/**
+ * Parse and resolve a specified subnet string into the appropriate internal
+ * representation.
+ *
+ * @param[in]  subnet_str  A string representation of a subnet of the form
+ *                         `network address [ "/", ( CIDR-style suffix | netmask ) ]`
+ *                         e.g. "2001:db8::/32", "192.0.2.0/255.255.255.0" or "8.8.8.8".
+ * @returns a CSubNet object (that may or may not be valid).
+ */
+CSubNet LookupSubNet(const std::string& subnet_str);
+
+/**
+ * Create a TCP or UNIX socket in the given address family.
+ * @param[in] address_family to use for the socket.
+ * @return pointer to the created Sock object or unique_ptr that owns nothing in case of failure
+ */
+std::unique_ptr<Sock> CreateSockOS(sa_family_t address_family);
+
+/**
+ * Socket factory. Defaults to `CreateSockOS()`, but can be overridden by unit tests.
+ */
+extern std::function<std::unique_ptr<Sock>(const sa_family_t&)> CreateSock;
+
+/**
+ * Create a socket and try to connect to the specified service.
+ *
+ * @param[in] dest The service to which to connect.
+ * @param[in] manual_connection Whether or not the connection was manually requested (e.g. through the addnode RPC)
+ *
+ * @returns the connected socket if the operation succeeded, empty unique_ptr otherwise
+ */
+std::unique_ptr<Sock> ConnectDirectly(const CService& dest, bool manual_connection);
+
+/**
+ * Connect to a specified destination service through a SOCKS5 proxy by first
+ * connecting to the SOCKS5 proxy.
+ *
+ * @param[in] proxy The SOCKS5 proxy.
+ * @param[in] dest The destination service to which to connect.
+ * @param[in] port The destination port.
+ * @param[out] proxy_connection_failed Whether or not the connection to the SOCKS5 proxy failed.
+ *
+ * @returns the connected socket if the operation succeeded. Otherwise an empty unique_ptr.
+ */
+std::unique_ptr<Sock> ConnectThroughProxy(const Proxy& proxy,
+                                          const std::string& dest,
+                                          uint16_t port,
+                                          bool& proxy_connection_failed);
+
+/**
+ * Interrupt SOCKS5 reads or writes.
+ */
+extern CThreadInterrupt g_socks5_interrupt;
+
+/**
+ * Connect to a specified destination service through an already connected
+ * SOCKS5 proxy.
+ *
+ * @param strDest The destination fully-qualified domain name.
+ * @param port The destination port.
+ * @param auth The credentials with which to authenticate with the specified
+ *             SOCKS5 proxy.
+ * @param socket The SOCKS5 proxy socket.
+ *
+ * @returns Whether or not the operation succeeded.
+ *
+ * @note The specified SOCKS5 proxy socket must already be connected to the
+ *       SOCKS5 proxy.
+ *
+ * @see <a href="https://www.ietf.org/rfc/rfc1928.txt">RFC1928: SOCKS Protocol
+ *      Version 5</a>
+ */
+bool Socks5(const std::string& strDest, uint16_t port, const ProxyCredentials* auth, const Sock& socket);
+
+/**
+ * Determine if a port is "bad" from the perspective of attempting to connect
+ * to a node on that port.
+ * @see doc/p2p-bad-ports.md
+ * @param[in] port Port to check.
+ * @returns whether the port is bad
+ */
+bool IsBadPort(uint16_t port);
+
+/**
+ * If an IPv6 address belongs to the address range used by the CJDNS network and
+ * the CJDNS network is reachable (-cjdnsreachable config is set), then change
+ * the type from NET_IPV6 to NET_CJDNS.
+ * @param[in] service Address to potentially convert.
+ * @return a copy of `service` either unmodified or changed to CJDNS.
+ */
+CService MaybeFlipIPv6toCJDNS(const CService& service);
+
+#endif // BITCOIN_NETBASE_H

src/i2p/prevector.h

@@ -0,0 +1,541 @@
+// Copyright (c) 2015-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_PREVECTOR_H
+#define BITCOIN_PREVECTOR_H
+
+#include <assert.h>
+#include <cstdlib>
+#include <stdint.h>
+#include <string.h>
+
+#include <algorithm>
+#include <cstddef>
+#include <type_traits>
+#include <utility>
+
+/** Implements a drop-in replacement for std::vector<T> which stores up to N
+ *  elements directly (without heap allocation). The types Size and Diff are
+ *  used to store element counts, and can be any unsigned + signed type.
+ *
+ *  Storage layout is either:
+ *  - Direct allocation:
+ *    - Size _size: the number of used elements (between 0 and N)
+ *    - T direct[N]: an array of N elements of type T
+ *      (only the first _size are initialized).
+ *  - Indirect allocation:
+ *    - Size _size: the number of used elements plus N + 1
+ *    - Size capacity: the number of allocated elements
+ *    - T* indirect: a pointer to an array of capacity elements of type T
+ *      (only the first _size are initialized).
+ *
+ *  The data type T must be movable by memmove/realloc(). Once we switch to C++,
+ *  move constructors can be used instead.
+ */
+template<unsigned int N, typename T, typename Size = uint32_t, typename Diff = int32_t>
+class prevector {
+    static_assert(std::is_trivially_copyable_v<T>);
+
+public:
+    typedef Size size_type;
+    typedef Diff difference_type;
+    typedef T value_type;
+    typedef value_type& reference;
+    typedef const value_type& const_reference;
+    typedef value_type* pointer;
+    typedef const value_type* const_pointer;
+
+    class iterator {
+        T* ptr{};
+    public:
+        typedef Diff difference_type;
+        typedef T value_type;
+        typedef T* pointer;
+        typedef T& reference;
+        using element_type = T;
+        using iterator_category = std::contiguous_iterator_tag;
+        iterator() = default;
+        iterator(T* ptr_) : ptr(ptr_) {}
+        T& operator*() const { return *ptr; }
+        T* operator->() const { return ptr; }
+        T& operator[](size_type pos) const { return ptr[pos]; }
+        iterator& operator++() { ptr++; return *this; }
+        iterator& operator--() { ptr--; return *this; }
+        iterator operator++(int) { iterator copy(*this); ++(*this); return copy; }
+        iterator operator--(int) { iterator copy(*this); --(*this); return copy; }
+        difference_type friend operator-(iterator a, iterator b) { return (&(*a) - &(*b)); }
+        iterator operator+(size_type n) const { return iterator(ptr + n); }
+        iterator friend operator+(size_type n, iterator x) { return x + n; }
+        iterator& operator+=(size_type n) { ptr += n; return *this; }
+        iterator operator-(size_type n) const { return iterator(ptr - n); }
+        iterator& operator-=(size_type n) { ptr -= n; return *this; }
+        bool operator==(iterator x) const { return ptr == x.ptr; }
+        bool operator!=(iterator x) const { return ptr != x.ptr; }
+        bool operator>=(iterator x) const { return ptr >= x.ptr; }
+        bool operator<=(iterator x) const { return ptr <= x.ptr; }
+        bool operator>(iterator x) const { return ptr > x.ptr; }
+        bool operator<(iterator x) const { return ptr < x.ptr; }
+    };
+
+    class reverse_iterator {
+        T* ptr{};
+    public:
+        typedef Diff difference_type;
+        typedef T value_type;
+        typedef T* pointer;
+        typedef T& reference;
+        typedef std::bidirectional_iterator_tag iterator_category;
+        reverse_iterator() = default;
+        reverse_iterator(T* ptr_) : ptr(ptr_) {}
+        T& operator*() const { return *ptr; }
+        T* operator->() const { return ptr; }
+        reverse_iterator& operator--() { ptr++; return *this; }
+        reverse_iterator& operator++() { ptr--; return *this; }
+        reverse_iterator operator++(int) { reverse_iterator copy(*this); ++(*this); return copy; }
+        reverse_iterator operator--(int) { reverse_iterator copy(*this); --(*this); return copy; }
+        bool operator==(reverse_iterator x) const { return ptr == x.ptr; }
+        bool operator!=(reverse_iterator x) const { return ptr != x.ptr; }
+    };
+
+    class const_iterator {
+        const T* ptr{};
+    public:
+        typedef Diff difference_type;
+        typedef const T value_type;
+        typedef const T* pointer;
+        typedef const T& reference;
+        using element_type = const T;
+        using iterator_category = std::contiguous_iterator_tag;
+        const_iterator() = default;
+        const_iterator(const T* ptr_) : ptr(ptr_) {}
+        const_iterator(iterator x) : ptr(&(*x)) {}
+        const T& operator*() const { return *ptr; }
+        const T* operator->() const { return ptr; }
+        const T& operator[](size_type pos) const { return ptr[pos]; }
+        const_iterator& operator++() { ptr++; return *this; }
+        const_iterator& operator--() { ptr--; return *this; }
+        const_iterator operator++(int) { const_iterator copy(*this); ++(*this); return copy; }
+        const_iterator operator--(int) { const_iterator copy(*this); --(*this); return copy; }
+        difference_type friend operator-(const_iterator a, const_iterator b) { return (&(*a) - &(*b)); }
+        const_iterator operator+(size_type n) const { return const_iterator(ptr + n); }
+        const_iterator friend operator+(size_type n, const_iterator x) { return x + n; }
+        const_iterator& operator+=(size_type n) { ptr += n; return *this; }
+        const_iterator operator-(size_type n) const { return const_iterator(ptr - n); }
+        const_iterator& operator-=(size_type n) { ptr -= n; return *this; }
+        bool operator==(const_iterator x) const { return ptr == x.ptr; }
+        bool operator!=(const_iterator x) const { return ptr != x.ptr; }
+        bool operator>=(const_iterator x) const { return ptr >= x.ptr; }
+        bool operator<=(const_iterator x) const { return ptr <= x.ptr; }
+        bool operator>(const_iterator x) const { return ptr > x.ptr; }
+        bool operator<(const_iterator x) const { return ptr < x.ptr; }
+    };
+
+    class const_reverse_iterator {
+        const T* ptr{};
+    public:
+        typedef Diff difference_type;
+        typedef const T value_type;
+        typedef const T* pointer;
+        typedef const T& reference;
+        typedef std::bidirectional_iterator_tag iterator_category;
+        const_reverse_iterator() = default;
+        const_reverse_iterator(const T* ptr_) : ptr(ptr_) {}
+        const_reverse_iterator(reverse_iterator x) : ptr(&(*x)) {}
+        const T& operator*() const { return *ptr; }
+        const T* operator->() const { return ptr; }
+        const_reverse_iterator& operator--() { ptr++; return *this; }
+        const_reverse_iterator& operator++() { ptr--; return *this; }
+        const_reverse_iterator operator++(int) { const_reverse_iterator copy(*this); ++(*this); return copy; }
+        const_reverse_iterator operator--(int) { const_reverse_iterator copy(*this); --(*this); return copy; }
+        bool operator==(const_reverse_iterator x) const { return ptr == x.ptr; }
+        bool operator!=(const_reverse_iterator x) const { return ptr != x.ptr; }
+    };
+
+private:
+#pragma pack(push, 1)
+    union direct_or_indirect {
+        char direct[sizeof(T) * N];
+        struct {
+            char* indirect;
+            size_type capacity;
+        } indirect_contents;
+    };
+#pragma pack(pop)
+    alignas(char*) direct_or_indirect _union = {};
+    size_type _size = 0;
+
+    static_assert(alignof(char*) % alignof(size_type) == 0 && sizeof(char*) % alignof(size_type) == 0, "size_type cannot have more restrictive alignment requirement than pointer");
+    static_assert(alignof(char*) % alignof(T) == 0, "value_type T cannot have more restrictive alignment requirement than pointer");
+
+    T* direct_ptr(difference_type pos) { return reinterpret_cast<T*>(_union.direct) + pos; }
+    const T* direct_ptr(difference_type pos) const { return reinterpret_cast<const T*>(_union.direct) + pos; }
+    T* indirect_ptr(difference_type pos) { return reinterpret_cast<T*>(_union.indirect_contents.indirect) + pos; }
+    const T* indirect_ptr(difference_type pos) const { return reinterpret_cast<const T*>(_union.indirect_contents.indirect) + pos; }
+    bool is_direct() const { return _size <= N; }
+
+    void change_capacity(size_type new_capacity) {
+        if (new_capacity <= N) {
+            if (!is_direct()) {
+                T* indirect = indirect_ptr(0);
+                T* src = indirect;
+                T* dst = direct_ptr(0);
+                memcpy(dst, src, size() * sizeof(T));
+                free(indirect);
+                _size -= N + 1;
+            }
+        } else {
+            if (!is_direct()) {
+                /* FIXME: Because malloc/realloc here won't call new_handler if allocation fails, assert
+                    success. These should instead use an allocator or new/delete so that handlers
+                    are called as necessary, but performance would be slightly degraded by doing so. */
+                _union.indirect_contents.indirect = static_cast<char*>(realloc(_union.indirect_contents.indirect, ((size_t)sizeof(T)) * new_capacity));
+                assert(_union.indirect_contents.indirect);
+                _union.indirect_contents.capacity = new_capacity;
+            } else {
+                char* new_indirect = static_cast<char*>(malloc(((size_t)sizeof(T)) * new_capacity));
+                assert(new_indirect);
+                T* src = direct_ptr(0);
+                T* dst = reinterpret_cast<T*>(new_indirect);
+                memcpy(dst, src, size() * sizeof(T));
+                _union.indirect_contents.indirect = new_indirect;
+                _union.indirect_contents.capacity = new_capacity;
+                _size += N + 1;
+            }
+        }
+    }
+
+    T* item_ptr(difference_type pos) { return is_direct() ? direct_ptr(pos) : indirect_ptr(pos); }
+    const T* item_ptr(difference_type pos) const { return is_direct() ? direct_ptr(pos) : indirect_ptr(pos); }
+
+    void fill(T* dst, ptrdiff_t count, const T& value = T{}) {
+        std::fill_n(dst, count, value);
+    }
+
+    template<typename InputIterator>
+    void fill(T* dst, InputIterator first, InputIterator last) {
+        while (first != last) {
+            new(static_cast<void*>(dst)) T(*first);
+            ++dst;
+            ++first;
+        }
+    }
+
+public:
+    void assign(size_type n, const T& val) {
+        clear();
+        if (capacity() < n) {
+            change_capacity(n);
+        }
+        _size += n;
+        fill(item_ptr(0), n, val);
+    }
+
+    template<typename InputIterator>
+    void assign(InputIterator first, InputIterator last) {
+        size_type n = last - first;
+        clear();
+        if (capacity() < n) {
+            change_capacity(n);
+        }
+        _size += n;
+        fill(item_ptr(0), first, last);
+    }
+
+    prevector() {}
+
+    explicit prevector(size_type n) {
+        resize(n);
+    }
+
+    explicit prevector(size_type n, const T& val) {
+        change_capacity(n);
+        _size += n;
+        fill(item_ptr(0), n, val);
+    }
+
+    template<typename InputIterator>
+    prevector(InputIterator first, InputIterator last) {
+        size_type n = last - first;
+        change_capacity(n);
+        _size += n;
+        fill(item_ptr(0), first, last);
+    }
+
+    prevector(const prevector<N, T, Size, Diff>& other) {
+        size_type n = other.size();
+        change_capacity(n);
+        _size += n;
+        fill(item_ptr(0), other.begin(),  other.end());
+    }
+
+    prevector(prevector<N, T, Size, Diff>&& other) noexcept
+        : _union(std::move(other._union)), _size(other._size)
+    {
+        other._size = 0;
+    }
+
+    prevector& operator=(const prevector<N, T, Size, Diff>& other) {
+        if (&other == this) {
+            return *this;
+        }
+        assign(other.begin(), other.end());
+        return *this;
+    }
+
+    prevector& operator=(prevector<N, T, Size, Diff>&& other) noexcept {
+        if (!is_direct()) {
+            free(_union.indirect_contents.indirect);
+        }
+        _union = std::move(other._union);
+        _size = other._size;
+        other._size = 0;
+        return *this;
+    }
+
+    size_type size() const {
+        return is_direct() ? _size : _size - N - 1;
+    }
+
+    bool empty() const {
+        return size() == 0;
+    }
+
+    iterator begin() { return iterator(item_ptr(0)); }
+    const_iterator begin() const { return const_iterator(item_ptr(0)); }
+    iterator end() { return iterator(item_ptr(size())); }
+    const_iterator end() const { return const_iterator(item_ptr(size())); }
+
+    reverse_iterator rbegin() { return reverse_iterator(item_ptr(size() - 1)); }
+    const_reverse_iterator rbegin() const { return const_reverse_iterator(item_ptr(size() - 1)); }
+    reverse_iterator rend() { return reverse_iterator(item_ptr(-1)); }
+    const_reverse_iterator rend() const { return const_reverse_iterator(item_ptr(-1)); }
+
+    size_t capacity() const {
+        if (is_direct()) {
+            return N;
+        } else {
+            return _union.indirect_contents.capacity;
+        }
+    }
+
+    T& operator[](size_type pos) {
+        return *item_ptr(pos);
+    }
+
+    const T& operator[](size_type pos) const {
+        return *item_ptr(pos);
+    }
+
+    void resize(size_type new_size) {
+        size_type cur_size = size();
+        if (cur_size == new_size) {
+            return;
+        }
+        if (cur_size > new_size) {
+            erase(item_ptr(new_size), end());
+            return;
+        }
+        if (new_size > capacity()) {
+            change_capacity(new_size);
+        }
+        ptrdiff_t increase = new_size - cur_size;
+        fill(item_ptr(cur_size), increase);
+        _size += increase;
+    }
+
+    void reserve(size_type new_capacity) {
+        if (new_capacity > capacity()) {
+            change_capacity(new_capacity);
+        }
+    }
+
+    void shrink_to_fit() {
+        change_capacity(size());
+    }
+
+    void clear() {
+        resize(0);
+    }
+
+    iterator insert(iterator pos, const T& value) {
+        size_type p = pos - begin();
+        size_type new_size = size() + 1;
+        if (capacity() < new_size) {
+            change_capacity(new_size + (new_size >> 1));
+        }
+        T* ptr = item_ptr(p);
+        memmove(ptr + 1, ptr, (size() - p) * sizeof(T));
+        _size++;
+        new(static_cast<void*>(ptr)) T(value);
+        return iterator(ptr);
+    }
+
+    void insert(iterator pos, size_type count, const T& value) {
+        size_type p = pos - begin();
+        size_type new_size = size() + count;
+        if (capacity() < new_size) {
+            change_capacity(new_size + (new_size >> 1));
+        }
+        T* ptr = item_ptr(p);
+        memmove(ptr + count, ptr, (size() - p) * sizeof(T));
+        _size += count;
+        fill(item_ptr(p), count, value);
+    }
+
+    template<typename InputIterator>
+    void insert(iterator pos, InputIterator first, InputIterator last) {
+        size_type p = pos - begin();
+        difference_type count = last - first;
+        size_type new_size = size() + count;
+        if (capacity() < new_size) {
+            change_capacity(new_size + (new_size >> 1));
+        }
+        T* ptr = item_ptr(p);
+        memmove(ptr + count, ptr, (size() - p) * sizeof(T));
+        _size += count;
+        fill(ptr, first, last);
+    }
+
+    inline void resize_uninitialized(size_type new_size) {
+        // resize_uninitialized changes the size of the prevector but does not initialize it.
+        // If size < new_size, the added elements must be initialized explicitly.
+        if (capacity() < new_size) {
+            change_capacity(new_size);
+            _size += new_size - size();
+            return;
+        }
+        if (new_size < size()) {
+            erase(item_ptr(new_size), end());
+        } else {
+            _size += new_size - size();
+        }
+    }
+
+    iterator erase(iterator pos) {
+        return erase(pos, pos + 1);
+    }
+
+    iterator erase(iterator first, iterator last) {
+        // Erase is not allowed to the change the object's capacity. That means
+        // that when starting with an indirectly allocated prevector with
+        // size and capacity > N, the result may be a still indirectly allocated
+        // prevector with size <= N and capacity > N. A shrink_to_fit() call is
+        // necessary to switch to the (more efficient) directly allocated
+        // representation (with capacity N and size <= N).
+        iterator p = first;
+        char* endp = (char*)&(*end());
+        _size -= last - p;
+        memmove(&(*first), &(*last), endp - ((char*)(&(*last))));
+        return first;
+    }
+
+    template<typename... Args>
+    void emplace_back(Args&&... args) {
+        size_type new_size = size() + 1;
+        if (capacity() < new_size) {
+            change_capacity(new_size + (new_size >> 1));
+        }
+        new(item_ptr(size())) T(std::forward<Args>(args)...);
+        _size++;
+    }
+
+    void push_back(const T& value) {
+        emplace_back(value);
+    }
+
+    void pop_back() {
+        erase(end() - 1, end());
+    }
+
+    T& front() {
+        return *item_ptr(0);
+    }
+
+    const T& front() const {
+        return *item_ptr(0);
+    }
+
+    T& back() {
+        return *item_ptr(size() - 1);
+    }
+
+    const T& back() const {
+        return *item_ptr(size() - 1);
+    }
+
+    void swap(prevector<N, T, Size, Diff>& other) noexcept
+    {
+        std::swap(_union, other._union);
+        std::swap(_size, other._size);
+    }
+
+    ~prevector() {
+        if (!is_direct()) {
+            free(_union.indirect_contents.indirect);
+            _union.indirect_contents.indirect = nullptr;
+        }
+    }
+
+    bool operator==(const prevector<N, T, Size, Diff>& other) const {
+        if (other.size() != size()) {
+            return false;
+        }
+        const_iterator b1 = begin();
+        const_iterator b2 = other.begin();
+        const_iterator e1 = end();
+        while (b1 != e1) {
+            if ((*b1) != (*b2)) {
+                return false;
+            }
+            ++b1;
+            ++b2;
+        }
+        return true;
+    }
+
+    bool operator!=(const prevector<N, T, Size, Diff>& other) const {
+        return !(*this == other);
+    }
+
+    bool operator<(const prevector<N, T, Size, Diff>& other) const {
+        if (size() < other.size()) {
+            return true;
+        }
+        if (size() > other.size()) {
+            return false;
+        }
+        const_iterator b1 = begin();
+        const_iterator b2 = other.begin();
+        const_iterator e1 = end();
+        while (b1 != e1) {
+            if ((*b1) < (*b2)) {
+                return true;
+            }
+            if ((*b2) < (*b1)) {
+                return false;
+            }
+            ++b1;
+            ++b2;
+        }
+        return false;
+    }
+
+    size_t allocated_memory() const {
+        if (is_direct()) {
+            return 0;
+        } else {
+            return ((size_t)(sizeof(T))) * _union.indirect_contents.capacity;
+        }
+    }
+
+    value_type* data() {
+        return item_ptr(0);
+    }
+
+    const value_type* data() const {
+        return item_ptr(0);
+    }
+};
+
+#endif // BITCOIN_PREVECTOR_H

src/i2p/primitives/block.h

@@ -0,0 +1,158 @@
+// // Copyright (c) 2009-2010 Satoshi Nakamoto
+// // Copyright (c) 2009-2022 The Bitcoin Core developers
+// // Distributed under the MIT software license, see the accompanying
+// // file COPYING or http://www.opensource.org/licenses/mit-license.php.
+// *
+// #ifndef BITCOIN_PRIMITIVES_BLOCK_H
+// #define BITCOIN_PRIMITIVES_BLOCK_H
+//
+// #include "transaction.h"
+// #include "serialize.h"
+// #include "uint256.h"
+// #include "util/time.h"
+//
+// /** Nodes collect new transactions into a block, hash them into a hash tree,
+//  * and scan through nonce values to make the block's hash satisfy proof-of-work
+//  * requirements.  When they solve the proof-of-work, they broadcast the block
+//  * to everyone and the block is added to the block chain.  The first transaction
+//  * in the block is a special one that creates a new coin owned by the creator
+//  * of the block.
+//  */
+// class CBlockHeader
+// {
+// public:
+//     // header
+//     int32_t nVersion;
+//     uint256 hashPrevBlock;
+//     uint256 hashMerkleRoot;
+//     uint32_t nTime;
+//     uint32_t nBits;
+//     uint32_t nNonce;
+//
+//     CBlockHeader()
+//     {
+//         SetNull();
+//     }
+//
+//     SERIALIZE_METHODS(CBlockHeader, obj) { READWRITE(obj.nVersion, obj.hashPrevBlock, obj.hashMerkleRoot, obj.nTime, obj.nBits, obj.nNonce); }
+//
+//     void SetNull()
+//     {
+//         nVersion = 0;
+//         hashPrevBlock.SetNull();
+//         hashMerkleRoot.SetNull();
+//         nTime = 0;
+//         nBits = 0;
+//         nNonce = 0;
+//     }
+//
+//     bool IsNull() const
+//     {
+//         return (nBits == 0);
+//     }
+//
+//     uint256 GetHash() const;
+//
+//     NodeSeconds Time() const
+//     {
+//         return NodeSeconds{std::chrono::seconds{nTime}};
+//     }
+//
+//     int64_t GetBlockTime() const
+//     {
+//         return (int64_t)nTime;
+//     }
+// };
+//
+//
+// class CBlock : public CBlockHeader
+// {
+// public:
+//     // network and disk
+//     std::vector<CTransactionRef> vtx;
+//
+//     // Memory-only flags for caching expensive checks
+//     mutable bool fChecked;                            // CheckBlock()
+//     mutable bool m_checked_witness_commitment{false}; // CheckWitnessCommitment()
+//     mutable bool m_checked_merkle_root{false};        // CheckMerkleRoot()
+//
+//     CBlock()
+//     {
+//         SetNull();
+//     }
+//
+//     CBlock(const CBlockHeader &header)
+//     {
+//         SetNull();
+//         *(static_cast<CBlockHeader*>(this)) = header;
+//     }
+//
+//     SERIALIZE_METHODS(CBlock, obj)
+//     {
+//         READWRITE(AsBase<CBlockHeader>(obj), obj.vtx);
+//     }
+//
+//     void SetNull()
+//     {
+//         CBlockHeader::SetNull();
+//         vtx.clear();
+//         fChecked = false;
+//         m_checked_witness_commitment = false;
+//         m_checked_merkle_root = false;
+//     }
+//
+//     CBlockHeader GetBlockHeader() const
+//     {
+//         CBlockHeader block;
+//         block.nVersion       = nVersion;
+//         block.hashPrevBlock  = hashPrevBlock;
+//         block.hashMerkleRoot = hashMerkleRoot;
+//         block.nTime          = nTime;
+//         block.nBits          = nBits;
+//         block.nNonce         = nNonce;
+//         return block;
+//     }
+//
+//     std::string ToString() const;
+// };
+//
+// /** Describes a place in the block chain to another node such that if the
+//  * other node doesn't have the same branch, it can find a recent common trunk.
+//  * The further back it is, the further before the fork it may be.
+//  */
+// struct CBlockLocator
+// {
+//     /** Historically CBlockLocator's version field has been written to network
+//      * streams as the negotiated protocol version and to disk streams as the
+//      * client version, but the value has never been used.
+//      *
+//      * Hard-code to the highest protocol version ever written to a network stream.
+//      * SerParams can be used if the field requires any meaning in the future,
+//      **/
+//     static constexpr int DUMMY_VERSION = 70016;
+//
+//     std::vector<uint256> vHave;
+//
+//     CBlockLocator() {}
+//
+//     explicit CBlockLocator(std::vector<uint256>&& have) : vHave(std::move(have)) {}
+//
+//     SERIALIZE_METHODS(CBlockLocator, obj)
+//     {
+//         int nVersion = DUMMY_VERSION;
+//         READWRITE(nVersion);
+//         READWRITE(obj.vHave);
+//     }
+//
+//     void SetNull()
+//     {
+//         vHave.clear();
+//     }
+//
+//     bool IsNull() const
+//     {
+//         return vHave.empty();
+//     }
+// };
+//
+// #endif */ // BITCOIN_PRIMITIVES_BLOCK_H

src/i2p/primitives/transaction.h

@@ -0,0 +1,442 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_PRIMITIVES_TRANSACTION_H
+#define BITCOIN_PRIMITIVES_TRANSACTION_H
+
+#include "../attributes.h"
+#include "../consensus/amount.h"
+#include "../script/script.h"
+#include "../serialize.h"
+#include "../uint256.h"
+#include "../util/transaction_identifier.h" // IWYU pragma: export
+
+#include <cstddef>
+#include <cstdint>
+#include <ios>
+#include <limits>
+#include <memory>
+#include <numeric>
+#include <string>
+#include <tuple>
+#include <utility>
+#include <vector>
+
+/** An outpoint - a combination of a transaction hash and an index n into its vout */
+class COutPoint
+{
+public:
+    Txid hash;
+    uint32_t n;
+
+    static constexpr uint32_t NULL_INDEX = std::numeric_limits<uint32_t>::max();
+
+    COutPoint(): n(NULL_INDEX) { }
+    COutPoint(const Txid& hashIn, uint32_t nIn): hash(hashIn), n(nIn) { }
+
+    SERIALIZE_METHODS(COutPoint, obj) { READWRITE(obj.hash, obj.n); }
+
+    void SetNull() { hash.SetNull(); n = NULL_INDEX; }
+    bool IsNull() const { return (hash.IsNull() && n == NULL_INDEX); }
+
+    friend bool operator<(const COutPoint& a, const COutPoint& b)
+    {
+        return std::tie(a.hash, a.n) < std::tie(b.hash, b.n);
+    }
+
+    friend bool operator==(const COutPoint& a, const COutPoint& b)
+    {
+        return (a.hash == b.hash && a.n == b.n);
+    }
+
+    friend bool operator!=(const COutPoint& a, const COutPoint& b)
+    {
+        return !(a == b);
+    }
+
+    std::string ToString() const;
+};
+
+/** An input of a transaction.  It contains the location of the previous
+ * transaction's output that it claims and a signature that matches the
+ * output's public key.
+ */
+class CTxIn
+{
+public:
+    COutPoint prevout;
+    CScript scriptSig;
+    uint32_t nSequence;
+    CScriptWitness scriptWitness; //!< Only serialized through CTransaction
+
+    /**
+     * Setting nSequence to this value for every input in a transaction
+     * disables nLockTime/IsFinalTx().
+     * It fails OP_CHECKLOCKTIMEVERIFY/CheckLockTime() for any input that has
+     * it set (BIP 65).
+     * It has SEQUENCE_LOCKTIME_DISABLE_FLAG set (BIP 68/112).
+     */
+    static const uint32_t SEQUENCE_FINAL = 0xffffffff;
+    /**
+     * This is the maximum sequence number that enables both nLockTime and
+     * OP_CHECKLOCKTIMEVERIFY (BIP 65).
+     * It has SEQUENCE_LOCKTIME_DISABLE_FLAG set (BIP 68/112).
+     */
+    static const uint32_t MAX_SEQUENCE_NONFINAL{SEQUENCE_FINAL - 1};
+
+    // Below flags apply in the context of BIP 68. BIP 68 requires the tx
+    // version to be set to 2, or higher.
+    /**
+     * If this flag is set, CTxIn::nSequence is NOT interpreted as a
+     * relative lock-time.
+     * It skips SequenceLocks() for any input that has it set (BIP 68).
+     * It fails OP_CHECKSEQUENCEVERIFY/CheckSequence() for any input that has
+     * it set (BIP 112).
+     */
+    static const uint32_t SEQUENCE_LOCKTIME_DISABLE_FLAG = (1U << 31);
+
+    /**
+     * If CTxIn::nSequence encodes a relative lock-time and this flag
+     * is set, the relative lock-time has units of 512 seconds,
+     * otherwise it specifies blocks with a granularity of 1. */
+    static const uint32_t SEQUENCE_LOCKTIME_TYPE_FLAG = (1 << 22);
+
+    /**
+     * If CTxIn::nSequence encodes a relative lock-time, this mask is
+     * applied to extract that lock-time from the sequence field. */
+    static const uint32_t SEQUENCE_LOCKTIME_MASK = 0x0000ffff;
+
+    /**
+     * In order to use the same number of bits to encode roughly the
+     * same wall-clock duration, and because blocks are naturally
+     * limited to occur every 600s on average, the minimum granularity
+     * for time-based relative lock-time is fixed at 512 seconds.
+     * Converting from CTxIn::nSequence to seconds is performed by
+     * multiplying by 512 = 2^9, or equivalently shifting up by
+     * 9 bits. */
+    static const int SEQUENCE_LOCKTIME_GRANULARITY = 9;
+
+    CTxIn()
+    {
+        nSequence = SEQUENCE_FINAL;
+    }
+
+    explicit CTxIn(COutPoint prevoutIn, CScript scriptSigIn=CScript(), uint32_t nSequenceIn=SEQUENCE_FINAL);
+    CTxIn(Txid hashPrevTx, uint32_t nOut, CScript scriptSigIn=CScript(), uint32_t nSequenceIn=SEQUENCE_FINAL);
+
+    SERIALIZE_METHODS(CTxIn, obj) { READWRITE(obj.prevout, obj.scriptSig, obj.nSequence); }
+
+    friend bool operator==(const CTxIn& a, const CTxIn& b)
+    {
+        return (a.prevout   == b.prevout &&
+                a.scriptSig == b.scriptSig &&
+                a.nSequence == b.nSequence);
+    }
+
+    friend bool operator!=(const CTxIn& a, const CTxIn& b)
+    {
+        return !(a == b);
+    }
+
+    std::string ToString() const;
+};
+
+/** An output of a transaction.  It contains the public key that the next input
+ * must be able to sign with to claim it.
+ */
+class CTxOut
+{
+public:
+    CAmount nValue;
+    CScript scriptPubKey;
+
+    CTxOut()
+    {
+        SetNull();
+    }
+
+    CTxOut(const CAmount& nValueIn, CScript scriptPubKeyIn);
+
+    SERIALIZE_METHODS(CTxOut, obj) { READWRITE(obj.nValue, obj.scriptPubKey); }
+
+    void SetNull()
+    {
+        nValue = -1;
+        scriptPubKey.clear();
+    }
+
+    bool IsNull() const
+    {
+        return (nValue == -1);
+    }
+
+    friend bool operator==(const CTxOut& a, const CTxOut& b)
+    {
+        return (a.nValue       == b.nValue &&
+                a.scriptPubKey == b.scriptPubKey);
+    }
+
+    friend bool operator!=(const CTxOut& a, const CTxOut& b)
+    {
+        return !(a == b);
+    }
+
+    std::string ToString() const;
+};
+
+struct CMutableTransaction;
+
+struct TransactionSerParams {
+    const bool allow_witness;
+    SER_PARAMS_OPFUNC
+};
+static constexpr TransactionSerParams TX_WITH_WITNESS{.allow_witness = true};
+static constexpr TransactionSerParams TX_NO_WITNESS{.allow_witness = false};
+
+/**
+ * Basic transaction serialization format:
+ * - int32_t nVersion
+ * - std::vector<CTxIn> vin
+ * - std::vector<CTxOut> vout
+ * - uint32_t nLockTime
+ *
+ * Extended transaction serialization format:
+ * - int32_t nVersion
+ * - unsigned char dummy = 0x00
+ * - unsigned char flags (!= 0)
+ * - std::vector<CTxIn> vin
+ * - std::vector<CTxOut> vout
+ * - if (flags & 1):
+ *   - CScriptWitness scriptWitness; (deserialized into CTxIn)
+ * - uint32_t nLockTime
+ */
+template<typename Stream, typename TxType>
+void UnserializeTransaction(TxType& tx, Stream& s, const TransactionSerParams& params)
+{
+    const bool fAllowWitness = params.allow_witness;
+
+    s >> tx.nVersion;
+    unsigned char flags = 0;
+    tx.vin.clear();
+    tx.vout.clear();
+    /* Try to read the vin. In case the dummy is there, this will be read as an empty vector. */
+    s >> tx.vin;
+    if (tx.vin.size() == 0 && fAllowWitness) {
+        /* We read a dummy or an empty vin. */
+        s >> flags;
+        if (flags != 0) {
+            s >> tx.vin;
+            s >> tx.vout;
+        }
+    } else {
+        /* We read a non-empty vin. Assume a normal vout follows. */
+        s >> tx.vout;
+    }
+    if ((flags & 1) && fAllowWitness) {
+        /* The witness flag is present, and we support witnesses. */
+        flags ^= 1;
+        for (size_t i = 0; i < tx.vin.size(); i++) {
+            s >> tx.vin[i].scriptWitness.stack;
+        }
+        if (!tx.HasWitness()) {
+            /* It's illegal to encode witnesses when all witness stacks are empty. */
+            throw std::ios_base::failure("Superfluous witness record");
+        }
+    }
+    if (flags) {
+        /* Unknown flag in the serialization */
+        throw std::ios_base::failure("Unknown transaction optional data");
+    }
+    s >> tx.nLockTime;
+}
+
+template<typename Stream, typename TxType>
+void SerializeTransaction(const TxType& tx, Stream& s, const TransactionSerParams& params)
+{
+    const bool fAllowWitness = params.allow_witness;
+
+    s << tx.nVersion;
+    unsigned char flags = 0;
+    // Consistency check
+    if (fAllowWitness) {
+        /* Check whether witnesses need to be serialized. */
+        if (tx.HasWitness()) {
+            flags |= 1;
+        }
+    }
+    if (flags) {
+        /* Use extended format in case witnesses are to be serialized. */
+        std::vector<CTxIn> vinDummy;
+        s << vinDummy;
+        s << flags;
+    }
+    s << tx.vin;
+    s << tx.vout;
+    if (flags & 1) {
+        for (size_t i = 0; i < tx.vin.size(); i++) {
+            s << tx.vin[i].scriptWitness.stack;
+        }
+    }
+    s << tx.nLockTime;
+}
+
+template<typename TxType>
+inline CAmount CalculateOutputValue(const TxType& tx)
+{
+    return std::accumulate(tx.vout.cbegin(), tx.vout.cend(), CAmount{0}, [](CAmount sum, const auto& txout) { return sum + txout.nValue; });
+}
+
+
+/** The basic transaction that is broadcasted on the network and contained in
+ * blocks.  A transaction can contain multiple inputs and outputs.
+ */
+class CTransaction
+{
+public:
+    // Default transaction version.
+    static const int32_t CURRENT_VERSION=2;
+
+    // The local variables are made const to prevent unintended modification
+    // without updating the cached hash value. However, CTransaction is not
+    // actually immutable; deserialization and assignment are implemented,
+    // and bypass the constness. This is safe, as they update the entire
+    // structure, including the hash.
+    const std::vector<CTxIn> vin;
+    const std::vector<CTxOut> vout;
+    const int32_t nVersion;
+    const uint32_t nLockTime;
+
+private:
+    /** Memory only. */
+    const bool m_has_witness;
+    const Txid hash;
+    const Wtxid m_witness_hash;
+
+    Txid ComputeHash() const;
+    Wtxid ComputeWitnessHash() const;
+
+    bool ComputeHasWitness() const;
+
+public:
+    /** Convert a CMutableTransaction into a CTransaction. */
+    explicit CTransaction(const CMutableTransaction& tx);
+    explicit CTransaction(CMutableTransaction&& tx);
+
+    template <typename Stream>
+    inline void Serialize(Stream& s) const {
+        SerializeTransaction(*this, s, s.GetParams());
+    }
+
+    /** This deserializing constructor is provided instead of an Unserialize method.
+     *  Unserialize is not possible, since it would require overwriting const fields. */
+    template <typename Stream>
+    CTransaction(deserialize_type, const TransactionSerParams& params, Stream& s) : CTransaction(CMutableTransaction(deserialize, params, s)) {}
+    template <typename Stream>
+    CTransaction(deserialize_type, ParamsStream<TransactionSerParams,Stream>& s) : CTransaction(CMutableTransaction(deserialize, s)) {}
+
+    bool IsNull() const {
+        return vin.empty() && vout.empty();
+    }
+
+    const Txid& GetHash() const LIFETIMEBOUND { return hash; }
+    const Wtxid& GetWitnessHash() const LIFETIMEBOUND { return m_witness_hash; };
+
+    // Return sum of txouts.
+    CAmount GetValueOut() const;
+
+    /**
+     * Get the total transaction size in bytes, including witness data.
+     * "Total Size" defined in BIP141 and BIP144.
+     * @return Total transaction size in bytes
+     */
+    unsigned int GetTotalSize() const;
+
+    bool IsCoinBase() const
+    {
+        return (vin.size() == 1 && vin[0].prevout.IsNull());
+    }
+
+    friend bool operator==(const CTransaction& a, const CTransaction& b)
+    {
+        return a.hash == b.hash;
+    }
+
+    friend bool operator!=(const CTransaction& a, const CTransaction& b)
+    {
+        return a.hash != b.hash;
+    }
+
+    std::string ToString() const;
+
+    bool HasWitness() const { return m_has_witness; }
+};
+
+/** A mutable version of CTransaction. */
+struct CMutableTransaction
+{
+    std::vector<CTxIn> vin;
+    std::vector<CTxOut> vout;
+    int32_t nVersion;
+    uint32_t nLockTime;
+
+    explicit CMutableTransaction();
+    explicit CMutableTransaction(const CTransaction& tx);
+
+    template <typename Stream>
+    inline void Serialize(Stream& s) const {
+        SerializeTransaction(*this, s, s.GetParams());
+    }
+
+    template <typename Stream>
+    inline void Unserialize(Stream& s) {
+        UnserializeTransaction(*this, s, s.GetParams());
+    }
+
+    template <typename Stream>
+    CMutableTransaction(deserialize_type, const TransactionSerParams& params, Stream& s) {
+        UnserializeTransaction(*this, s, params);
+    }
+
+    template <typename Stream>
+    CMutableTransaction(deserialize_type, ParamsStream<TransactionSerParams,Stream>& s) {
+        Unserialize(s);
+    }
+
+    /** Compute the hash of this CMutableTransaction. This is computed on the
+     * fly, as opposed to GetHash() in CTransaction, which uses a cached result.
+     */
+    Txid GetHash() const;
+
+    bool HasWitness() const
+    {
+        for (size_t i = 0; i < vin.size(); i++) {
+            if (!vin[i].scriptWitness.IsNull()) {
+                return true;
+            }
+        }
+        return false;
+    }
+};
+
+typedef std::shared_ptr<const CTransaction> CTransactionRef;
+template <typename Tx> static inline CTransactionRef MakeTransactionRef(Tx&& txIn) { return std::make_shared<const CTransaction>(std::forward<Tx>(txIn)); }
+
+/** A generic txid reference (txid or wtxid). */
+class GenTxid
+{
+    bool m_is_wtxid;
+    uint256 m_hash;
+    GenTxid(bool is_wtxid, const uint256& hash) : m_is_wtxid(is_wtxid), m_hash(hash) {}
+
+public:
+    static GenTxid Txid(const uint256& hash) { return GenTxid{false, hash}; }
+    static GenTxid Wtxid(const uint256& hash) { return GenTxid{true, hash}; }
+    bool IsWtxid() const { return m_is_wtxid; }
+    const uint256& GetHash() const LIFETIMEBOUND { return m_hash; }
+    friend bool operator==(const GenTxid& a, const GenTxid& b) { return a.m_is_wtxid == b.m_is_wtxid && a.m_hash == b.m_hash; }
+    friend bool operator<(const GenTxid& a, const GenTxid& b) { return std::tie(a.m_is_wtxid, a.m_hash) < std::tie(b.m_is_wtxid, b.m_hash); }
+};
+
+#endif // BITCOIN_PRIMITIVES_TRANSACTION_H

src/i2p/random.h

@@ -0,0 +1,302 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_RANDOM_H
+#define BITCOIN_RANDOM_H
+
+#include "crypto/chacha20.h"
+#include "crypto/common.h"
+#include "span.h"
+#include "uint256.h"
+
+#include <bit>
+#include <cassert>
+#include <chrono>
+#include <cstdint>
+#include <limits>
+#include <vector>
+
+/**
+ * Overall design of the RNG and entropy sources.
+ *
+ * We maintain a single global 256-bit RNG state for all high-quality randomness.
+ * The following (classes of) functions interact with that state by mixing in new
+ * entropy, and optionally extracting random output from it:
+ *
+ * - The GetRand*() class of functions, as well as construction of FastRandomContext objects,
+ *   perform 'fast' seeding, consisting of mixing in:
+ *   - A stack pointer (indirectly committing to calling thread and call stack)
+ *   - A high-precision timestamp (rdtsc when available, c++ high_resolution_clock otherwise)
+ *   - 64 bits from the hardware RNG (rdrand) when available.
+ *   These entropy sources are very fast, and only designed to protect against situations
+ *   where a VM state restore/copy results in multiple systems with the same randomness.
+ *   FastRandomContext on the other hand does not protect against this once created, but
+ *   is even faster (and acceptable to use inside tight loops).
+ *
+ * - The GetStrongRand*() class of function perform 'slow' seeding, including everything
+ *   that fast seeding includes, but additionally:
+ *   - OS entropy (/dev/urandom, getrandom(), ...). The application will terminate if
+ *     this entropy source fails.
+ *   - Another high-precision timestamp (indirectly committing to a benchmark of all the
+ *     previous sources).
+ *   These entropy sources are slower, but designed to make sure the RNG state contains
+ *   fresh data that is unpredictable to attackers.
+ *
+ * - RandAddPeriodic() seeds everything that fast seeding includes, but additionally:
+ *   - A high-precision timestamp
+ *   - Dynamic environment data (performance monitoring, ...)
+ *   - Strengthen the entropy for 10 ms using repeated SHA512.
+ *   This is run once every minute.
+ *
+ * On first use of the RNG (regardless of what function is called first), all entropy
+ * sources used in the 'slow' seeder are included, but also:
+ * - 256 bits from the hardware RNG (rdseed or rdrand) when available.
+ * - Dynamic environment data (performance monitoring, ...)
+ * - Static environment data
+ * - Strengthen the entropy for 100 ms using repeated SHA512.
+ *
+ * When mixing in new entropy, H = SHA512(entropy || old_rng_state) is computed, and
+ * (up to) the first 32 bytes of H are produced as output, while the last 32 bytes
+ * become the new RNG state.
+*/
+
+/**
+ * Generate random data via the internal PRNG.
+ *
+ * These functions are designed to be fast (sub microsecond), but do not necessarily
+ * meaningfully add entropy to the PRNG state.
+ *
+ * Thread-safe.
+ */
+void GetRandBytes(Span<unsigned char> bytes) noexcept;
+/** Generate a uniform random integer in the range [0..range). Precondition: range > 0 */
+uint64_t GetRandInternal(uint64_t nMax) noexcept;
+/** Generate a uniform random integer of type T in the range [0..nMax)
+ *  nMax defaults to std::numeric_limits<T>::max()
+ *  Precondition: nMax > 0, T is an integral type, no larger than uint64_t
+ */
+template<typename T>
+T GetRand(T nMax=std::numeric_limits<T>::max()) noexcept {
+    static_assert(std::is_integral<T>(), "T must be integral");
+    static_assert(std::numeric_limits<T>::max() <= std::numeric_limits<uint64_t>::max(), "GetRand only supports up to uint64_t");
+    return T(GetRandInternal(nMax));
+}
+/** Generate a uniform random duration in the range [0..max). Precondition: max.count() > 0 */
+template <typename D>
+D GetRandomDuration(typename std::common_type<D>::type max) noexcept
+// Having the compiler infer the template argument from the function argument
+// is dangerous, because the desired return value generally has a different
+// type than the function argument. So std::common_type is used to force the
+// call site to specify the type of the return value.
+{
+    assert(max.count() > 0);
+    return D{GetRand(max.count())};
+};
+constexpr auto GetRandMicros = GetRandomDuration<std::chrono::microseconds>;
+constexpr auto GetRandMillis = GetRandomDuration<std::chrono::milliseconds>;
+
+/**
+ * Return a timestamp in the future sampled from an exponential distribution
+ * (https://en.wikipedia.org/wiki/Exponential_distribution). This distribution
+ * is memoryless and should be used for repeated network events (e.g. sending a
+ * certain type of message) to minimize leaking information to observers.
+ *
+ * The probability of an event occurring before time x is 1 - e^-(x/a) where a
+ * is the average interval between events.
+ * */
+std::chrono::microseconds GetExponentialRand(std::chrono::microseconds now, std::chrono::seconds average_interval);
+
+uint256 GetRandHash() noexcept;
+
+/**
+ * Gather entropy from various sources, feed it into the internal PRNG, and
+ * generate random data using it.
+ *
+ * This function will cause failure whenever the OS RNG fails.
+ *
+ * Thread-safe.
+ */
+void GetStrongRandBytes(Span<unsigned char> bytes) noexcept;
+
+/**
+ * Gather entropy from various expensive sources, and feed them to the PRNG state.
+ *
+ * Thread-safe.
+ */
+void RandAddPeriodic() noexcept;
+
+/**
+ * Gathers entropy from the low bits of the time at which events occur. Should
+ * be called with a uint32_t describing the event at the time an event occurs.
+ *
+ * Thread-safe.
+ */
+void RandAddEvent(const uint32_t event_info) noexcept;
+
+/**
+ * Fast randomness source. This is seeded once with secure random data, but
+ * is completely deterministic and does not gather more entropy after that.
+ *
+ * This class is not thread-safe.
+ */
+class FastRandomContext
+{
+private:
+    bool requires_seed;
+    ChaCha20 rng;
+
+    uint64_t bitbuf;
+    int bitbuf_size;
+
+    void RandomSeed();
+
+    void FillBitBuffer()
+    {
+        bitbuf = rand64();
+        bitbuf_size = 64;
+    }
+
+public:
+    explicit FastRandomContext(bool fDeterministic = false) noexcept;
+
+    /** Initialize with explicit seed (only for testing) */
+    explicit FastRandomContext(const uint256& seed) noexcept;
+
+    // Do not permit copying a FastRandomContext (move it, or create a new one to get reseeded).
+    FastRandomContext(const FastRandomContext&) = delete;
+    FastRandomContext(FastRandomContext&&) = delete;
+    FastRandomContext& operator=(const FastRandomContext&) = delete;
+
+    /** Move a FastRandomContext. If the original one is used again, it will be reseeded. */
+    FastRandomContext& operator=(FastRandomContext&& from) noexcept;
+
+    /** Generate a random 64-bit integer. */
+    uint64_t rand64() noexcept
+    {
+        if (requires_seed) RandomSeed();
+        std::array<std::byte, 8> buf;
+        rng.Keystream(buf);
+        return ReadLE64(UCharCast(buf.data()));
+    }
+
+    /** Generate a random (bits)-bit integer. */
+    uint64_t randbits(int bits) noexcept
+    {
+        if (bits == 0) {
+            return 0;
+        } else if (bits > 32) {
+            return rand64() >> (64 - bits);
+        } else {
+            if (bitbuf_size < bits) FillBitBuffer();
+            uint64_t ret = bitbuf & (~uint64_t{0} >> (64 - bits));
+            bitbuf >>= bits;
+            bitbuf_size -= bits;
+            return ret;
+        }
+    }
+
+    /** Generate a random integer in the range [0..range).
+     * Precondition: range > 0.
+     */
+    uint64_t randrange(uint64_t range) noexcept
+    {
+        assert(range);
+        --range;
+        int bits = std::bit_width(range);
+        while (true) {
+            uint64_t ret = randbits(bits);
+            if (ret <= range) return ret;
+        }
+    }
+
+    /** Generate random bytes. */
+    template <typename B = unsigned char>
+    std::vector<B> randbytes(size_t len);
+
+    /** Fill a byte Span with random bytes. */
+    void fillrand(Span<std::byte> output);
+
+    /** Generate a random 32-bit integer. */
+    uint32_t rand32() noexcept { return randbits(32); }
+
+    /** generate a random uint256. */
+    uint256 rand256() noexcept;
+
+    /** Generate a random boolean. */
+    bool randbool() noexcept { return randbits(1); }
+
+    /** Return the time point advanced by a uniform random duration. */
+    template <typename Tp>
+    Tp rand_uniform_delay(const Tp& time, typename Tp::duration range)
+    {
+        return time + rand_uniform_duration<Tp>(range);
+    }
+
+    /** Generate a uniform random duration in the range from 0 (inclusive) to range (exclusive). */
+    template <typename Chrono>
+    typename Chrono::duration rand_uniform_duration(typename Chrono::duration range) noexcept
+    {
+        using Dur = typename Chrono::duration;
+        return range.count() > 0 ? /* interval [0..range) */ Dur{randrange(range.count())} :
+               range.count() < 0 ? /* interval (range..0] */ -Dur{randrange(-range.count())} :
+                                   /* interval [0..0] */ Dur{0};
+    };
+
+    // Compatibility with the UniformRandomBitGenerator concept
+    typedef uint64_t result_type;
+    static constexpr uint64_t min() { return 0; }
+    static constexpr uint64_t max() { return std::numeric_limits<uint64_t>::max(); }
+    inline uint64_t operator()() noexcept { return rand64(); }
+};
+
+/** More efficient than using std::shuffle on a FastRandomContext.
+ *
+ * This is more efficient as std::shuffle will consume entropy in groups of
+ * 64 bits at the time and throw away most.
+ *
+ * This also works around a bug in libstdc++ std::shuffle that may cause
+ * type::operator=(type&&) to be invoked on itself, which the library's
+ * debug mode detects and panics on. This is a known issue, see
+ * https://stackoverflow.com/questions/22915325/avoiding-self-assignment-in-stdshuffle
+ */
+template <typename I, typename R>
+void Shuffle(I first, I last, R&& rng)
+{
+    while (first != last) {
+        size_t j = rng.randrange(last - first);
+        if (j) {
+            using std::swap;
+            swap(*first, *(first + j));
+        }
+        ++first;
+    }
+}
+
+/* Number of random bytes returned by GetOSRand.
+ * When changing this constant make sure to change all call sites, and make
+ * sure that the underlying OS APIs for all platforms support the number.
+ * (many cap out at 256 bytes).
+ */
+static const int NUM_OS_RANDOM_BYTES = 32;
+
+/** Get 32 bytes of system entropy. Do not use this in application code: use
+ * GetStrongRandBytes instead.
+ */
+void GetOSRand(unsigned char* ent32);
+
+/** Check that OS randomness is available and returning the requested number
+ * of bytes.
+ */
+bool Random_SanityCheck();
+
+/**
+ * Initialize global RNG state and log any CPU features that are used.
+ *
+ * Calling this function is optional. RNG state will be initialized when first
+ * needed if it is not called.
+ */
+void RandomInit();
+
+#endif // BITCOIN_RANDOM_H

src/i2p/span.h

@@ -0,0 +1,354 @@
+// Copyright (c) 2018-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_SPAN_H
+#define BITCOIN_SPAN_H
+
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <span>
+#include <type_traits>
+
+#ifdef DEBUG
+#define CONSTEXPR_IF_NOT_DEBUG
+#define ASSERT_IF_DEBUG(x) assert((x))
+#else
+#define CONSTEXPR_IF_NOT_DEBUG constexpr
+#define ASSERT_IF_DEBUG(x)
+#endif
+
+#if defined(__clang__)
+#if __has_attribute(lifetimebound)
+#define SPAN_ATTR_LIFETIMEBOUND [[clang::lifetimebound]]
+#else
+#define SPAN_ATTR_LIFETIMEBOUND
+#endif
+#else
+#define SPAN_ATTR_LIFETIMEBOUND
+#endif
+
+/** A Span is an object that can refer to a contiguous sequence of objects.
+ *
+ * This file implements a subset of C++20's std::span.  It can be considered
+ * temporary compatibility code until C++20 and is designed to be a
+ * self-contained abstraction without depending on other project files. For this
+ * reason, Clang lifetimebound is defined here instead of including
+ * <attributes.h>, which also defines it.
+ *
+ * Things to be aware of when writing code that deals with Spans:
+ *
+ * - Similar to references themselves, Spans are subject to reference lifetime
+ *   issues. The user is responsible for making sure the objects pointed to by
+ *   a Span live as long as the Span is used. For example:
+ *
+ *       std::vector<int> vec{1,2,3,4};
+ *       Span<int> sp(vec);
+ *       vec.push_back(5);
+ *       printf("%i\n", sp.front()); // UB!
+ *
+ *   may exhibit undefined behavior, as increasing the size of a vector may
+ *   invalidate references.
+ *
+ * - One particular pitfall is that Spans can be constructed from temporaries,
+ *   but this is unsafe when the Span is stored in a variable, outliving the
+ *   temporary. For example, this will compile, but exhibits undefined behavior:
+ *
+ *       Span<const int> sp(std::vector<int>{1, 2, 3});
+ *       printf("%i\n", sp.front()); // UB!
+ *
+ *   The lifetime of the vector ends when the statement it is created in ends.
+ *   Thus the Span is left with a dangling reference, and using it is undefined.
+ *
+ * - Due to Span's automatic creation from range-like objects (arrays, and data
+ *   types that expose a data() and size() member function), functions that
+ *   accept a Span as input parameter can be called with any compatible
+ *   range-like object. For example, this works:
+ *
+ *       void Foo(Span<const int> arg);
+ *
+ *       Foo(std::vector<int>{1, 2, 3}); // Works
+ *
+ *   This is very useful in cases where a function truly does not care about the
+ *   container, and only about having exactly a range of elements. However it
+ *   may also be surprising to see automatic conversions in this case.
+ *
+ *   When a function accepts a Span with a mutable element type, it will not
+ *   accept temporaries; only variables or other references. For example:
+ *
+ *       void FooMut(Span<int> arg);
+ *
+ *       FooMut(std::vector<int>{1, 2, 3}); // Does not compile
+ *       std::vector<int> baz{1, 2, 3};
+ *       FooMut(baz); // Works
+ *
+ *   This is similar to how functions that take (non-const) lvalue references
+ *   as input cannot accept temporaries. This does not work either:
+ *
+ *       void FooVec(std::vector<int>& arg);
+ *       FooVec(std::vector<int>{1, 2, 3}); // Does not compile
+ *
+ *   The idea is that if a function accepts a mutable reference, a meaningful
+ *   result will be present in that variable after the call. Passing a temporary
+ *   is useless in that context.
+ */
+template <typename C> class Span {
+  C *m_data;
+  std::size_t m_size{0};
+
+  template <class T> struct is_Span_int : public std::false_type {};
+  template <class T> struct is_Span_int<Span<T>> : public std::true_type {};
+  template <class T>
+  struct is_Span : public is_Span_int<typename std::remove_cv<T>::type> {};
+
+public:
+  constexpr Span() noexcept : m_data(nullptr) {}
+
+  /** Construct a span from a begin pointer and a size.
+   *
+   * This implements a subset of the iterator-based std::span constructor in
+   * C++20, which is hard to implement without std::address_of.
+   */
+  template <typename T,
+            typename std::enable_if<
+                std::is_convertible<T (*)[], C (*)[]>::value, int>::type = 0>
+  constexpr Span(T *begin, std::size_t size) noexcept
+      : m_data(begin), m_size(size) {}
+
+  /** Construct a span from a begin and end pointer.
+   *
+   * This implements a subset of the iterator-based std::span constructor in
+   * C++20, which is hard to implement without std::address_of.
+   */
+  template <typename T,
+            typename std::enable_if<
+                std::is_convertible<T (*)[], C (*)[]>::value, int>::type = 0>
+  CONSTEXPR_IF_NOT_DEBUG Span(T *begin, T *end) noexcept
+      : m_data(begin), m_size(end - begin) {
+    ASSERT_IF_DEBUG(end >= begin);
+  }
+
+  /** Implicit conversion of spans between compatible types.
+   *
+   *  Specifically, if a pointer to an array of type O can be implicitly
+   * converted to a pointer to an array of type C, then permit implicit
+   * conversion of Span<O> to Span<C>. This matches the behavior of the
+   * corresponding C++20 std::span constructor.
+   *
+   *  For example this means that a Span<T> can be converted into a Span<const
+   * T>.
+   */
+  template <typename O,
+            typename std::enable_if<
+                std::is_convertible<O (*)[], C (*)[]>::value, int>::type = 0>
+  constexpr Span(const Span<O> &other) noexcept
+      : m_data(other.m_data), m_size(other.m_size) {}
+
+  /** Default copy constructor. */
+  constexpr Span(const Span &) noexcept = default;
+
+  /** Default assignment operator. */
+  Span &operator=(const Span &other) noexcept = default;
+
+  /** Construct a Span from an array. This matches the corresponding C++20
+   * std::span constructor. */
+  template <int N> constexpr Span(C (&a)[N]) noexcept : m_data(a), m_size(N) {}
+
+  /** Construct a Span for objects with .data() and .size() (std::string,
+   * std::array, std::vector, ...).
+   *
+   * This implements a subset of the functionality provided by the C++20
+   * std::span range-based constructor.
+   *
+   * To prevent surprises, only Spans for constant value types are supported
+   * when passing in temporaries. Note that this restriction does not exist when
+   * converting arrays or other Spans (see above).
+   */
+  template <typename V>
+  constexpr Span(
+      V &other SPAN_ATTR_LIFETIMEBOUND,
+      typename std::enable_if<
+          !is_Span<V>::value &&
+              std::is_convertible<
+                  typename std::remove_pointer<
+                      decltype(std::declval<V &>().data())>::type (*)[],
+                  C (*)[]>::value &&
+              std::is_convertible<decltype(std::declval<V &>().size()),
+                                  std::size_t>::value,
+          std::nullptr_t>::type = nullptr)
+      : m_data(other.data()), m_size(other.size()) {}
+
+  template <typename V>
+  constexpr Span(
+      const V &other SPAN_ATTR_LIFETIMEBOUND,
+      typename std::enable_if<
+          !is_Span<V>::value &&
+              std::is_convertible<
+                  typename std::remove_pointer<
+                      decltype(std::declval<const V &>().data())>::type (*)[],
+                  C (*)[]>::value &&
+              std::is_convertible<decltype(std::declval<const V &>().size()),
+                                  std::size_t>::value,
+          std::nullptr_t>::type = nullptr)
+      : m_data(other.data()), m_size(other.size()) {}
+
+  constexpr C *data() const noexcept { return m_data; }
+  constexpr C *begin() const noexcept { return m_data; }
+  constexpr C *end() const noexcept { return m_data + m_size; }
+  CONSTEXPR_IF_NOT_DEBUG C &front() const noexcept {
+    ASSERT_IF_DEBUG(size() > 0);
+    return m_data[0];
+  }
+  CONSTEXPR_IF_NOT_DEBUG C &back() const noexcept {
+    ASSERT_IF_DEBUG(size() > 0);
+    return m_data[m_size - 1];
+  }
+  constexpr std::size_t size() const noexcept { return m_size; }
+  constexpr std::size_t size_bytes() const noexcept {
+    return sizeof(C) * m_size;
+  }
+  constexpr bool empty() const noexcept { return size() == 0; }
+  CONSTEXPR_IF_NOT_DEBUG C &operator[](std::size_t pos) const noexcept {
+    ASSERT_IF_DEBUG(size() > pos);
+    return m_data[pos];
+  }
+  CONSTEXPR_IF_NOT_DEBUG Span<C> subspan(std::size_t offset) const noexcept {
+    ASSERT_IF_DEBUG(size() >= offset);
+    return Span<C>(m_data + offset, m_size - offset);
+  }
+  CONSTEXPR_IF_NOT_DEBUG Span<C> subspan(std::size_t offset,
+                                         std::size_t count) const noexcept {
+    ASSERT_IF_DEBUG(size() >= offset + count);
+    return Span<C>(m_data + offset, count);
+  }
+  CONSTEXPR_IF_NOT_DEBUG Span<C> first(std::size_t count) const noexcept {
+    ASSERT_IF_DEBUG(size() >= count);
+    return Span<C>(m_data, count);
+  }
+  CONSTEXPR_IF_NOT_DEBUG Span<C> last(std::size_t count) const noexcept {
+    ASSERT_IF_DEBUG(size() >= count);
+    return Span<C>(m_data + m_size - count, count);
+  }
+
+  friend constexpr bool operator==(const Span &a, const Span &b) noexcept {
+    return a.size() == b.size() && std::equal(a.begin(), a.end(), b.begin());
+  }
+  friend constexpr bool operator!=(const Span &a, const Span &b) noexcept {
+    return !(a == b);
+  }
+  friend constexpr bool operator<(const Span &a, const Span &b) noexcept {
+    return std::lexicographical_compare(a.begin(), a.end(), b.begin(), b.end());
+  }
+  friend constexpr bool operator<=(const Span &a, const Span &b) noexcept {
+    return !(b < a);
+  }
+  friend constexpr bool operator>(const Span &a, const Span &b) noexcept {
+    return (b < a);
+  }
+  friend constexpr bool operator>=(const Span &a, const Span &b) noexcept {
+    return !(a < b);
+  }
+
+  template <typename O> friend class Span;
+};
+
+// Return result of calling .data() method on type T. This is used to be able to
+// write template deduction guides for the single-parameter Span constructor
+// below that will work if the value that is passed has a .data() method, and if
+// the data method does not return a void pointer.
+//
+// It is important to check for the void type specifically below, so the
+// deduction guides can be used in SFINAE contexts to check whether objects can
+// be converted to spans. If the deduction guides did not explicitly check for
+// void, and an object was passed that returned void* from data (like
+// std::vector<bool>), the template deduction would succeed, but the Span<void>
+// object instantiation would fail, resulting in a hard error, rather than a
+// SFINAE error.
+// https://stackoverflow.com/questions/68759148/sfinae-to-detect-the-explicitness-of-a-ctad-deduction-guide
+// https://stackoverflow.com/questions/16568986/what-happens-when-you-call-data-on-a-stdvectorbool
+template <typename T>
+using DataResult = std::remove_pointer_t<decltype(std::declval<T &>().data())>;
+
+// Deduction guides for Span
+// For the pointer/size based and iterator based constructor:
+template <typename T, typename EndOrSize> Span(T *, EndOrSize) -> Span<T>;
+// For the array constructor:
+template <typename T, std::size_t N> Span(T (&)[N]) -> Span<T>;
+// For the temporaries/rvalue references constructor, only supporting const
+// output.
+template <typename T>
+Span(T &&) -> Span<std::enable_if_t<!std::is_lvalue_reference_v<T> &&
+                                        !std::is_void_v<DataResult<T &&>>,
+                                    const DataResult<T &&>>>;
+// For (lvalue) references, supporting mutable output.
+template <typename T>
+Span(T &) -> Span<
+    std::enable_if_t<!std::is_void_v<DataResult<T &>>, DataResult<T &>>>;
+
+/** Pop the last element off a span, and return a reference to that element. */
+template <typename T> T &SpanPopBack(Span<T> &span) {
+  size_t size = span.size();
+  ASSERT_IF_DEBUG(size > 0);
+  T &back = span[size - 1];
+  span = Span<T>(span.data(), size - 1);
+  return back;
+}
+
+// From C++20 as_bytes and as_writeable_bytes
+template <typename T> Span<const std::byte> AsBytes(Span<T> s) noexcept {
+  return {reinterpret_cast<const std::byte *>(s.data()), s.size_bytes()};
+}
+template <typename T> Span<std::byte> AsWritableBytes(Span<T> s) noexcept {
+  return {reinterpret_cast<std::byte *>(s.data()), s.size_bytes()};
+}
+
+template <typename V> Span<const std::byte> MakeByteSpan(V &&v) noexcept {
+  return AsBytes(Span{std::forward<V>(v)});
+}
+template <typename V> Span<std::byte> MakeWritableByteSpan(V &&v) noexcept {
+  return AsWritableBytes(Span{std::forward<V>(v)});
+}
+
+// Helper functions to safely cast basic byte pointers to unsigned char
+// pointers.
+inline unsigned char *UCharCast(char *c) {
+  return reinterpret_cast<unsigned char *>(c);
+}
+inline unsigned char *UCharCast(unsigned char *c) { return c; }
+inline unsigned char *UCharCast(signed char *c) {
+  return reinterpret_cast<unsigned char *>(c);
+}
+inline unsigned char *UCharCast(std::byte *c) {
+  return reinterpret_cast<unsigned char *>(c);
+}
+inline const unsigned char *UCharCast(const char *c) {
+  return reinterpret_cast<const unsigned char *>(c);
+}
+inline const unsigned char *UCharCast(const unsigned char *c) { return c; }
+inline const unsigned char *UCharCast(const signed char *c) {
+  return reinterpret_cast<const unsigned char *>(c);
+}
+inline const unsigned char *UCharCast(const std::byte *c) {
+  return reinterpret_cast<const unsigned char *>(c);
+}
+// Helper concept for the basic byte types.
+template <typename B>
+concept BasicByte = requires { UCharCast(std::span<B>{}.data()); };
+
+// Helper function to safely convert a Span to a Span<[const] unsigned char>.
+template <typename T>
+constexpr auto UCharSpanCast(Span<T> s)
+    -> Span<typename std::remove_pointer<decltype(UCharCast(s.data()))>::type> {
+  return {UCharCast(s.data()), s.size()};
+}
+
+/** Like the Span constructor, but for (const) unsigned char member types only.
+ * Only works for (un)signed char containers. */
+template <typename V>
+constexpr auto MakeUCharSpan(V &&v)
+    -> decltype(UCharSpanCast(Span{std::forward<V>(v)})) {
+  return UCharSpanCast(Span{std::forward<V>(v)});
+}
+
+#endif // BITCOIN_SPAN_H

src/i2p/sync.cpp

@@ -0,0 +1,331 @@
+// Copyright (c) 2011-2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "sync.h"
+
+#include "logging.h"
+#include "tinyformat.h"
+#include "util/strencodings.h"
+// #include "util/threadnames.h"
+
+#include <map>
+#include <mutex>
+#include <set>
+#include <system_error>
+#include <thread>
+#include <type_traits>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+
+#ifdef DEBUG_LOCKORDER
+//
+// Early deadlock detection.
+// Problem being solved:
+//    Thread 1 locks A, then B, then C
+//    Thread 2 locks D, then C, then A
+//     --> may result in deadlock between the two threads, depending on when
+//     they run.
+// Solution implemented here:
+// Keep track of pairs of locks: (A before B), (A before C), etc.
+// Complain if any thread tries to lock in a different order.
+//
+
+struct CLockLocation {
+  CLockLocation(const char *pszName, const char *pszFile, int nLine,
+                bool fTryIn, const std::string &thread_name)
+      : fTry(fTryIn), mutexName(pszName), sourceFile(pszFile),
+        m_thread_name(thread_name), sourceLine(nLine) {}
+
+  std::string ToString() const {
+    return strprintf("'%s' in %s:%s%s (in thread '%s')", mutexName, sourceFile,
+                     sourceLine, (fTry ? " (TRY)" : ""), m_thread_name);
+  }
+
+  std::string Name() const { return mutexName; }
+
+private:
+  bool fTry;
+  std::string mutexName;
+  std::string sourceFile;
+  const std::string &m_thread_name;
+  int sourceLine;
+};
+
+using LockStackItem = std::pair<void *, CLockLocation>;
+using LockStack = std::vector<LockStackItem>;
+using LockStacks = std::unordered_map<std::thread::id, LockStack>;
+
+using LockPair = std::pair<void *, void *>;
+using LockOrders = std::map<LockPair, LockStack>;
+using InvLockOrders = std::set<LockPair>;
+
+struct LockData {
+  LockStacks m_lock_stacks;
+  LockOrders lockorders;
+  InvLockOrders invlockorders;
+  std::mutex dd_mutex;
+};
+
+LockData &GetLockData() {
+  // This approach guarantees that the object is not destroyed until after its
+  // last use. The operating system automatically reclaims all the memory in a
+  // program's heap when that program exits. Since the ~LockData() destructor is
+  // never called, the LockData class and all its subclasses must have
+  // implicitly-defined destructors.
+  static LockData &lock_data = *new LockData();
+  return lock_data;
+}
+
+static void potential_deadlock_detected(const LockPair &mismatch,
+                                        const LockStack &s1,
+                                        const LockStack &s2) {
+  LogPrintf("POTENTIAL DEADLOCK DETECTED\n");
+  LogPrintf("Previous lock order was:\n");
+  for (const LockStackItem &i : s1) {
+    std::string prefix{};
+    if (i.first == mismatch.first) {
+      prefix = " (1)";
+    }
+    if (i.first == mismatch.second) {
+      prefix = " (2)";
+    }
+    LogPrintf("%s %s\n", prefix, i.second.ToString());
+  }
+
+  std::string mutex_a, mutex_b;
+  LogPrintf("Current lock order is:\n");
+  for (const LockStackItem &i : s2) {
+    std::string prefix{};
+    if (i.first == mismatch.first) {
+      prefix = " (1)";
+      mutex_a = i.second.Name();
+    }
+    if (i.first == mismatch.second) {
+      prefix = " (2)";
+      mutex_b = i.second.Name();
+    }
+    LogPrintf("%s %s\n", prefix, i.second.ToString());
+  }
+  if (g_debug_lockorder_abort) {
+    tfm::format(std::cerr,
+                "Assertion failed: detected inconsistent lock order for %s, "
+                "details in debug log.\n",
+                s2.back().second.ToString());
+    abort();
+  }
+  throw std::logic_error(
+      strprintf("potential deadlock detected: %s -> %s -> %s", mutex_b, mutex_a,
+                mutex_b));
+}
+
+static void double_lock_detected(const void *mutex,
+                                 const LockStack &lock_stack) {
+  LogPrintf("DOUBLE LOCK DETECTED\n");
+  LogPrintf("Lock order:\n");
+  for (const LockStackItem &i : lock_stack) {
+    std::string prefix{};
+    if (i.first == mutex) {
+      prefix = " (*)";
+    }
+    LogPrintf("%s %s\n", prefix, i.second.ToString());
+  }
+  if (g_debug_lockorder_abort) {
+    tfm::format(std::cerr,
+                "Assertion failed: detected double lock for %s, details in "
+                "debug log.\n",
+                lock_stack.back().second.ToString());
+    abort();
+  }
+  throw std::logic_error("double lock detected");
+}
+
+template <typename MutexType>
+static void push_lock(MutexType *c, const CLockLocation &locklocation) {
+  constexpr bool is_recursive_mutex =
+      std::is_base_of<RecursiveMutex, MutexType>::value ||
+      std::is_base_of<std::recursive_mutex, MutexType>::value;
+
+  LockData &lockdata = GetLockData();
+  std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
+
+  LockStack &lock_stack = lockdata.m_lock_stacks[std::this_thread::get_id()];
+  lock_stack.emplace_back(c, locklocation);
+  for (size_t j = 0; j < lock_stack.size() - 1; ++j) {
+    const LockStackItem &i = lock_stack[j];
+    if (i.first == c) {
+      if (is_recursive_mutex) {
+        break;
+      }
+      // It is not a recursive mutex and it appears in the stack two times:
+      // at position `j` and at the end (which we added just before this loop).
+      // Can't allow locking the same (non-recursive) mutex two times from the
+      // same thread as that results in an undefined behavior.
+      auto lock_stack_copy = lock_stack;
+      lock_stack.pop_back();
+      double_lock_detected(c, lock_stack_copy);
+      // double_lock_detected() does not return.
+    }
+
+    const LockPair p1 = std::make_pair(i.first, c);
+    if (lockdata.lockorders.count(p1))
+      continue;
+
+    const LockPair p2 = std::make_pair(c, i.first);
+    if (lockdata.lockorders.count(p2)) {
+      auto lock_stack_copy = lock_stack;
+      lock_stack.pop_back();
+      potential_deadlock_detected(p1, lockdata.lockorders[p2], lock_stack_copy);
+      // potential_deadlock_detected() does not return.
+    }
+
+    lockdata.lockorders.emplace(p1, lock_stack);
+    lockdata.invlockorders.insert(p2);
+  }
+}
+
+static void pop_lock() {
+  LockData &lockdata = GetLockData();
+  std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
+
+  LockStack &lock_stack = lockdata.m_lock_stacks[std::this_thread::get_id()];
+  lock_stack.pop_back();
+  if (lock_stack.empty()) {
+    lockdata.m_lock_stacks.erase(std::this_thread::get_id());
+  }
+}
+
+template <typename MutexType>
+void EnterCritical(const char *pszName, const char *pszFile, int nLine,
+                   MutexType *cs, bool fTry) {
+  push_lock(cs, CLockLocation(pszName, pszFile, nLine, fTry,
+                              util::ThreadGetInternalName()));
+}
+template void EnterCritical(const char *, const char *, int, Mutex *, bool);
+template void EnterCritical(const char *, const char *, int, RecursiveMutex *,
+                            bool);
+template void EnterCritical(const char *, const char *, int, std::mutex *,
+                            bool);
+template void EnterCritical(const char *, const char *, int,
+                            std::recursive_mutex *, bool);
+
+void CheckLastCritical(void *cs, std::string &lockname, const char *guardname,
+                       const char *file, int line) {
+  LockData &lockdata = GetLockData();
+  std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
+
+  const LockStack &lock_stack =
+      lockdata.m_lock_stacks[std::this_thread::get_id()];
+  if (!lock_stack.empty()) {
+    const auto &lastlock = lock_stack.back();
+    if (lastlock.first == cs) {
+      lockname = lastlock.second.Name();
+      return;
+    }
+  }
+
+  LogPrintf("INCONSISTENT LOCK ORDER DETECTED\n");
+  LogPrintf("Current lock order (least recent first) is:\n");
+  for (const LockStackItem &i : lock_stack) {
+    LogPrintf(" %s\n", i.second.ToString());
+  }
+  if (g_debug_lockorder_abort) {
+    tfm::format(std::cerr,
+                "%s:%s %s was not most recent critical section locked, details "
+                "in debug log.\n",
+                file, line, guardname);
+    abort();
+  }
+  throw std::logic_error(
+      strprintf("%s was not most recent critical section locked", guardname));
+}
+
+void LeaveCritical() { pop_lock(); }
+
+static std::string LocksHeld() {
+  LockData &lockdata = GetLockData();
+  std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
+
+  const LockStack &lock_stack =
+      lockdata.m_lock_stacks[std::this_thread::get_id()];
+  std::string result;
+  for (const LockStackItem &i : lock_stack)
+    result += i.second.ToString() + std::string("\n");
+  return result;
+}
+
+static bool LockHeld(void *mutex) {
+  LockData &lockdata = GetLockData();
+  std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
+
+  const LockStack &lock_stack =
+      lockdata.m_lock_stacks[std::this_thread::get_id()];
+  for (const LockStackItem &i : lock_stack) {
+    if (i.first == mutex)
+      return true;
+  }
+
+  return false;
+}
+
+template <typename MutexType>
+void AssertLockHeldInternal(const char *pszName, const char *pszFile, int nLine,
+                            MutexType *cs) {
+  if (LockHeld(cs))
+    return;
+  tfm::format(std::cerr,
+              "Assertion failed: lock %s not held in %s:%i; locks held:\n%s",
+              pszName, pszFile, nLine, LocksHeld());
+  abort();
+}
+template void AssertLockHeldInternal(const char *, const char *, int, Mutex *);
+template void AssertLockHeldInternal(const char *, const char *, int,
+                                     RecursiveMutex *);
+
+template <typename MutexType>
+void AssertLockNotHeldInternal(const char *pszName, const char *pszFile,
+                               int nLine, MutexType *cs) {
+  if (!LockHeld(cs))
+    return;
+  tfm::format(std::cerr,
+              "Assertion failed: lock %s held in %s:%i; locks held:\n%s",
+              pszName, pszFile, nLine, LocksHeld());
+  abort();
+}
+template void AssertLockNotHeldInternal(const char *, const char *, int,
+                                        Mutex *);
+template void AssertLockNotHeldInternal(const char *, const char *, int,
+                                        RecursiveMutex *);
+
+void DeleteLock(void *cs) {
+  LockData &lockdata = GetLockData();
+  std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
+  const LockPair item = std::make_pair(cs, nullptr);
+  LockOrders::iterator it = lockdata.lockorders.lower_bound(item);
+  while (it != lockdata.lockorders.end() && it->first.first == cs) {
+    const LockPair invitem = std::make_pair(it->first.second, it->first.first);
+    lockdata.invlockorders.erase(invitem);
+    lockdata.lockorders.erase(it++);
+  }
+  InvLockOrders::iterator invit = lockdata.invlockorders.lower_bound(item);
+  while (invit != lockdata.invlockorders.end() && invit->first == cs) {
+    const LockPair invinvitem = std::make_pair(invit->second, invit->first);
+    lockdata.lockorders.erase(invinvitem);
+    lockdata.invlockorders.erase(invit++);
+  }
+}
+
+bool LockStackEmpty() {
+  LockData &lockdata = GetLockData();
+  std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
+  const auto it = lockdata.m_lock_stacks.find(std::this_thread::get_id());
+  if (it == lockdata.m_lock_stacks.end()) {
+    return true;
+  }
+  return it->second.empty();
+}
+
+bool g_debug_lockorder_abort = true;
+
+#endif /* DEBUG_LOCKORDER */

src/i2p/sync.h

@@ -0,0 +1,430 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_SYNC_H
+#define BITCOIN_SYNC_H
+
+#ifdef DEBUG_LOCKCONTENTION
+//#include <logging.h>
+//#include <logging/timer.h>
+#endif
+
+#include "threadsafety.h" // IWYU pragma: export
+#include "util/macros.h"
+
+#include <condition_variable>
+#include <mutex>
+#include <string>
+#include <thread>
+
+////////////////////////////////////////////////
+//                                            //
+// THE SIMPLE DEFINITION, EXCLUDING DEBUG CODE //
+//                                            //
+////////////////////////////////////////////////
+
+/*
+RecursiveMutex mutex;
+    std::recursive_mutex mutex;
+
+LOCK(mutex);
+    std::unique_lock<std::recursive_mutex> criticalblock(mutex);
+
+LOCK2(mutex1, mutex2);
+    std::unique_lock<std::recursive_mutex> criticalblock1(mutex1);
+    std::unique_lock<std::recursive_mutex> criticalblock2(mutex2);
+
+TRY_LOCK(mutex, name);
+    std::unique_lock<std::recursive_mutex> name(mutex, std::try_to_lock_t);
+
+ENTER_CRITICAL_SECTION(mutex); // no RAII
+    mutex.lock();
+
+LEAVE_CRITICAL_SECTION(mutex); // no RAII
+    mutex.unlock();
+ */
+
+///////////////////////////////
+//                           //
+// THE ACTUAL IMPLEMENTATION //
+//                           //
+///////////////////////////////
+
+#ifdef DEBUG_LOCKORDER
+template <typename MutexType>
+void EnterCritical(const char* pszName, const char* pszFile, int nLine, MutexType* cs, bool fTry = false);
+void LeaveCritical();
+void CheckLastCritical(void* cs, std::string& lockname, const char* guardname, const char* file, int line);
+template <typename MutexType>
+void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, MutexType* cs) EXCLUSIVE_LOCKS_REQUIRED(cs);
+template <typename MutexType>
+void AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, MutexType* cs) LOCKS_EXCLUDED(cs);
+void DeleteLock(void* cs);
+bool LockStackEmpty();
+
+/**
+ * Call abort() if a potential lock order deadlock bug is detected, instead of
+ * just logging information and throwing a logic_error. Defaults to true, and
+ * set to false in DEBUG_LOCKORDER unit tests.
+ */
+extern bool g_debug_lockorder_abort;
+#else
+template <typename MutexType>
+inline void EnterCritical(const char* pszName, const char* pszFile, int nLine, MutexType* cs, bool fTry = false) {}
+inline void LeaveCritical() {}
+inline void CheckLastCritical(void* cs, std::string& lockname, const char* guardname, const char* file, int line) {}
+template <typename MutexType>
+inline void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, MutexType* cs) EXCLUSIVE_LOCKS_REQUIRED(cs) {}
+template <typename MutexType>
+void AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, MutexType* cs) LOCKS_EXCLUDED(cs) {}
+inline void DeleteLock(void* cs) {}
+inline bool LockStackEmpty() { return true; }
+#endif
+
+/**
+ * Template mixin that adds -Wthread-safety locking annotations and lock order
+ * checking to a subset of the mutex API.
+ */
+template <typename PARENT>
+class LOCKABLE AnnotatedMixin : public PARENT
+{
+public:
+    ~AnnotatedMixin() {
+        DeleteLock((void*)this);
+    }
+
+    void lock() EXCLUSIVE_LOCK_FUNCTION()
+    {
+        PARENT::lock();
+    }
+
+    void unlock() UNLOCK_FUNCTION()
+    {
+        PARENT::unlock();
+    }
+
+    bool try_lock() EXCLUSIVE_TRYLOCK_FUNCTION(true)
+    {
+        return PARENT::try_lock();
+    }
+
+    using unique_lock = std::unique_lock<PARENT>;
+#ifdef __clang__
+    //! For negative capabilities in the Clang Thread Safety Analysis.
+    //! A negative requirement uses the EXCLUSIVE_LOCKS_REQUIRED attribute, in conjunction
+    //! with the ! operator, to indicate that a mutex should not be held.
+    const AnnotatedMixin& operator!() const { return *this; }
+#endif // __clang__
+};
+
+/**
+ * Wrapped mutex: supports recursive locking, but no waiting
+ * TODO: We should move away from using the recursive lock by default.
+ */
+using RecursiveMutex = AnnotatedMixin<std::recursive_mutex>;
+
+/** Wrapped mutex: supports waiting but not recursive locking */
+using Mutex = AnnotatedMixin<std::mutex>;
+
+/** Different type to mark Mutex at global scope
+ *
+ * Thread safety analysis can't handle negative assertions about mutexes
+ * with global scope well, so mark them with a separate type, and
+ * eventually move all the mutexes into classes so they are not globally
+ * visible.
+ *
+ * See: https://github.com/bitcoin/bitcoin/pull/20272#issuecomment-720755781
+ */
+class GlobalMutex : public Mutex { };
+
+#define AssertLockHeld(cs) AssertLockHeldInternal(#cs, __FILE__, __LINE__, &cs)
+
+inline void AssertLockNotHeldInline(const char* name, const char* file, int line, Mutex* cs) EXCLUSIVE_LOCKS_REQUIRED(!cs) { AssertLockNotHeldInternal(name, file, line, cs); }
+inline void AssertLockNotHeldInline(const char* name, const char* file, int line, RecursiveMutex* cs) LOCKS_EXCLUDED(cs) { AssertLockNotHeldInternal(name, file, line, cs); }
+inline void AssertLockNotHeldInline(const char* name, const char* file, int line, GlobalMutex* cs) LOCKS_EXCLUDED(cs) { AssertLockNotHeldInternal(name, file, line, cs); }
+#define AssertLockNotHeld(cs) AssertLockNotHeldInline(#cs, __FILE__, __LINE__, &cs)
+
+/** Wrapper around std::unique_lock style lock for MutexType. */
+template <typename MutexType>
+class SCOPED_LOCKABLE UniqueLock : public MutexType::unique_lock
+{
+private:
+    using Base = typename MutexType::unique_lock;
+
+    void Enter(const char* pszName, const char* pszFile, int nLine)
+    {
+        EnterCritical(pszName, pszFile, nLine, Base::mutex());
+#ifdef DEBUG_LOCKCONTENTION
+        if (Base::try_lock()) return;
+        LOG_TIME_MICROS_WITH_CATEGORY(strprintf("lock contention %s, %s:%d", pszName, pszFile, nLine), BCLog::LOCK);
+#endif
+        Base::lock();
+    }
+
+    bool TryEnter(const char* pszName, const char* pszFile, int nLine)
+    {
+        EnterCritical(pszName, pszFile, nLine, Base::mutex(), true);
+        if (Base::try_lock()) {
+            return true;
+        }
+        LeaveCritical();
+        return false;
+    }
+
+public:
+    UniqueLock(MutexType& mutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(mutexIn) : Base(mutexIn, std::defer_lock)
+    {
+        if (fTry)
+            TryEnter(pszName, pszFile, nLine);
+        else
+            Enter(pszName, pszFile, nLine);
+    }
+
+    UniqueLock(MutexType* pmutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(pmutexIn)
+    {
+        if (!pmutexIn) return;
+
+        *static_cast<Base*>(this) = Base(*pmutexIn, std::defer_lock);
+        if (fTry)
+            TryEnter(pszName, pszFile, nLine);
+        else
+            Enter(pszName, pszFile, nLine);
+    }
+
+    ~UniqueLock() UNLOCK_FUNCTION()
+    {
+        if (Base::owns_lock())
+            LeaveCritical();
+    }
+
+    operator bool()
+    {
+        return Base::owns_lock();
+    }
+
+protected:
+    // needed for reverse_lock
+    UniqueLock() { }
+
+public:
+    /**
+     * An RAII-style reverse lock. Unlocks on construction and locks on destruction.
+     */
+    class reverse_lock {
+    public:
+        explicit reverse_lock(UniqueLock& _lock, const char* _guardname, const char* _file, int _line) : lock(_lock), file(_file), line(_line) {
+            CheckLastCritical((void*)lock.mutex(), lockname, _guardname, _file, _line);
+            lock.unlock();
+            LeaveCritical();
+            lock.swap(templock);
+        }
+
+        ~reverse_lock() {
+            templock.swap(lock);
+            EnterCritical(lockname.c_str(), file.c_str(), line, lock.mutex());
+            lock.lock();
+        }
+
+     private:
+        reverse_lock(reverse_lock const&);
+        reverse_lock& operator=(reverse_lock const&);
+
+        UniqueLock& lock;
+        UniqueLock templock;
+        std::string lockname;
+        const std::string file;
+        const int line;
+     };
+     friend class reverse_lock;
+};
+
+#define REVERSE_LOCK(g) typename std::decay<decltype(g)>::type::reverse_lock UNIQUE_NAME(revlock)(g, #g, __FILE__, __LINE__)
+
+// When locking a Mutex, require negative capability to ensure the lock
+// is not already held
+inline Mutex& MaybeCheckNotHeld(Mutex& cs) EXCLUSIVE_LOCKS_REQUIRED(!cs) LOCK_RETURNED(cs) { return cs; }
+inline Mutex* MaybeCheckNotHeld(Mutex* cs) EXCLUSIVE_LOCKS_REQUIRED(!cs) LOCK_RETURNED(cs) { return cs; }
+
+// When locking a GlobalMutex or RecursiveMutex, just check it is not
+// locked in the surrounding scope.
+template <typename MutexType>
+inline MutexType& MaybeCheckNotHeld(MutexType& m) LOCKS_EXCLUDED(m) LOCK_RETURNED(m) { return m; }
+template <typename MutexType>
+inline MutexType* MaybeCheckNotHeld(MutexType* m) LOCKS_EXCLUDED(m) LOCK_RETURNED(m) { return m; }
+
+#define LOCK(cs) UniqueLock UNIQUE_NAME(criticalblock)(MaybeCheckNotHeld(cs), #cs, __FILE__, __LINE__)
+#define LOCK2(cs1, cs2)                                               \
+    UniqueLock criticalblock1(MaybeCheckNotHeld(cs1), #cs1, __FILE__, __LINE__); \
+    UniqueLock criticalblock2(MaybeCheckNotHeld(cs2), #cs2, __FILE__, __LINE__)
+#define TRY_LOCK(cs, name) UniqueLock name(MaybeCheckNotHeld(cs), #cs, __FILE__, __LINE__, true)
+#define WAIT_LOCK(cs, name) UniqueLock name(MaybeCheckNotHeld(cs), #cs, __FILE__, __LINE__)
+
+#define ENTER_CRITICAL_SECTION(cs)                            \
+    {                                                         \
+        EnterCritical(#cs, __FILE__, __LINE__, &cs); \
+        (cs).lock();                                          \
+    }
+
+#define LEAVE_CRITICAL_SECTION(cs)                                          \
+    {                                                                       \
+        std::string lockname;                                               \
+        CheckLastCritical((void*)(&cs), lockname, #cs, __FILE__, __LINE__); \
+        (cs).unlock();                                                      \
+        LeaveCritical();                                                    \
+    }
+
+//! Run code while locking a mutex.
+//!
+//! Examples:
+//!
+//!   WITH_LOCK(cs, shared_val = shared_val + 1);
+//!
+//!   int val = WITH_LOCK(cs, return shared_val);
+//!
+//! Note:
+//!
+//! Since the return type deduction follows that of decltype(auto), while the
+//! deduced type of:
+//!
+//!   WITH_LOCK(cs, return {int i = 1; return i;});
+//!
+//! is int, the deduced type of:
+//!
+//!   WITH_LOCK(cs, return {int j = 1; return (j);});
+//!
+//! is &int, a reference to a local variable
+//!
+//! The above is detectable at compile-time with the -Wreturn-local-addr flag in
+//! gcc and the -Wreturn-stack-address flag in clang, both enabled by default.
+#define WITH_LOCK(cs, code) (MaybeCheckNotHeld(cs), [&]() -> decltype(auto) { LOCK(cs); code; }())
+
+/** An implementation of a semaphore.
+ *
+ * See https://en.wikipedia.org/wiki/Semaphore_(programming)
+ */
+class CSemaphore
+{
+private:
+    std::condition_variable condition;
+    std::mutex mutex;
+    int value;
+
+public:
+    explicit CSemaphore(int init) noexcept : value(init) {}
+
+    // Disallow default construct, copy, move.
+    CSemaphore() = delete;
+    CSemaphore(const CSemaphore&) = delete;
+    CSemaphore(CSemaphore&&) = delete;
+    CSemaphore& operator=(const CSemaphore&) = delete;
+    CSemaphore& operator=(CSemaphore&&) = delete;
+
+    void wait() noexcept
+    {
+        std::unique_lock<std::mutex> lock(mutex);
+        condition.wait(lock, [&]() { return value >= 1; });
+        value--;
+    }
+
+    bool try_wait() noexcept
+    {
+        std::lock_guard<std::mutex> lock(mutex);
+        if (value < 1) {
+            return false;
+        }
+        value--;
+        return true;
+    }
+
+    void post() noexcept
+    {
+        {
+            std::lock_guard<std::mutex> lock(mutex);
+            value++;
+        }
+        condition.notify_one();
+    }
+};
+
+/** RAII-style semaphore lock */
+class CSemaphoreGrant
+{
+private:
+    CSemaphore* sem;
+    bool fHaveGrant;
+
+public:
+    void Acquire() noexcept
+    {
+        if (fHaveGrant) {
+            return;
+        }
+        sem->wait();
+        fHaveGrant = true;
+    }
+
+    void Release() noexcept
+    {
+        if (!fHaveGrant) {
+            return;
+        }
+        sem->post();
+        fHaveGrant = false;
+    }
+
+    bool TryAcquire() noexcept
+    {
+        if (!fHaveGrant && sem->try_wait()) {
+            fHaveGrant = true;
+        }
+        return fHaveGrant;
+    }
+
+    // Disallow copy.
+    CSemaphoreGrant(const CSemaphoreGrant&) = delete;
+    CSemaphoreGrant& operator=(const CSemaphoreGrant&) = delete;
+
+    // Allow move.
+    CSemaphoreGrant(CSemaphoreGrant&& other) noexcept
+    {
+        sem = other.sem;
+        fHaveGrant = other.fHaveGrant;
+        other.fHaveGrant = false;
+        other.sem = nullptr;
+    }
+
+    CSemaphoreGrant& operator=(CSemaphoreGrant&& other) noexcept
+    {
+        Release();
+        sem = other.sem;
+        fHaveGrant = other.fHaveGrant;
+        other.fHaveGrant = false;
+        other.sem = nullptr;
+        return *this;
+    }
+
+    CSemaphoreGrant() noexcept : sem(nullptr), fHaveGrant(false) {}
+
+    explicit CSemaphoreGrant(CSemaphore& sema, bool fTry = false) noexcept : sem(&sema), fHaveGrant(false)
+    {
+        if (fTry) {
+            TryAcquire();
+        } else {
+            Acquire();
+        }
+    }
+
+    ~CSemaphoreGrant()
+    {
+        Release();
+    }
+
+    explicit operator bool() const noexcept
+    {
+        return fHaveGrant;
+    }
+};
+
+#endif // BITCOIN_SYNC_H

src/i2p/threadsafety.h

@@ -0,0 +1,77 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_THREADSAFETY_H
+#define BITCOIN_THREADSAFETY_H
+
+#include <mutex>
+
+#ifdef __clang__
+// TL;DR Add GUARDED_BY(mutex) to member variables. The others are
+// rarely necessary. Ex: int nFoo GUARDED_BY(cs_foo);
+//
+// See https://clang.llvm.org/docs/ThreadSafetyAnalysis.html
+// for documentation.  The clang compiler can do advanced static analysis
+// of locking when given the -Wthread-safety option.
+#define LOCKABLE __attribute__((lockable))
+#define SCOPED_LOCKABLE __attribute__((scoped_lockable))
+#define GUARDED_BY(x) __attribute__((guarded_by(x)))
+#define PT_GUARDED_BY(x) __attribute__((pt_guarded_by(x)))
+#define ACQUIRED_AFTER(...) __attribute__((acquired_after(__VA_ARGS__)))
+#define ACQUIRED_BEFORE(...) __attribute__((acquired_before(__VA_ARGS__)))
+#define EXCLUSIVE_LOCK_FUNCTION(...) __attribute__((exclusive_lock_function(__VA_ARGS__)))
+#define SHARED_LOCK_FUNCTION(...) __attribute__((shared_lock_function(__VA_ARGS__)))
+#define EXCLUSIVE_TRYLOCK_FUNCTION(...) __attribute__((exclusive_trylock_function(__VA_ARGS__)))
+#define SHARED_TRYLOCK_FUNCTION(...) __attribute__((shared_trylock_function(__VA_ARGS__)))
+#define UNLOCK_FUNCTION(...) __attribute__((unlock_function(__VA_ARGS__)))
+#define LOCK_RETURNED(x) __attribute__((lock_returned(x)))
+#define LOCKS_EXCLUDED(...) __attribute__((locks_excluded(__VA_ARGS__)))
+#define EXCLUSIVE_LOCKS_REQUIRED(...) __attribute__((exclusive_locks_required(__VA_ARGS__)))
+#define SHARED_LOCKS_REQUIRED(...) __attribute__((shared_locks_required(__VA_ARGS__)))
+#define NO_THREAD_SAFETY_ANALYSIS __attribute__((no_thread_safety_analysis))
+#define ASSERT_EXCLUSIVE_LOCK(...) __attribute__((assert_exclusive_lock(__VA_ARGS__)))
+#else
+#define LOCKABLE
+#define SCOPED_LOCKABLE
+#define GUARDED_BY(x)
+#define PT_GUARDED_BY(x)
+#define ACQUIRED_AFTER(...)
+#define ACQUIRED_BEFORE(...)
+#define EXCLUSIVE_LOCK_FUNCTION(...)
+#define SHARED_LOCK_FUNCTION(...)
+#define EXCLUSIVE_TRYLOCK_FUNCTION(...)
+#define SHARED_TRYLOCK_FUNCTION(...)
+#define UNLOCK_FUNCTION(...)
+#define LOCK_RETURNED(x)
+#define LOCKS_EXCLUDED(...)
+#define EXCLUSIVE_LOCKS_REQUIRED(...)
+#define SHARED_LOCKS_REQUIRED(...)
+#define NO_THREAD_SAFETY_ANALYSIS
+#define ASSERT_EXCLUSIVE_LOCK(...)
+#endif // __GNUC__
+
+// StdMutex provides an annotated version of std::mutex for us,
+// and should only be used when sync.h Mutex/LOCK/etc are not usable.
+class LOCKABLE StdMutex : public std::mutex
+{
+public:
+#ifdef __clang__
+    //! For negative capabilities in the Clang Thread Safety Analysis.
+    //! A negative requirement uses the EXCLUSIVE_LOCKS_REQUIRED attribute, in conjunction
+    //! with the ! operator, to indicate that a mutex should not be held.
+    const StdMutex& operator!() const { return *this; }
+#endif // __clang__
+};
+
+// StdLockGuard provides an annotated version of std::lock_guard for us,
+// and should only be used when sync.h Mutex/LOCK/etc are not usable.
+class SCOPED_LOCKABLE StdLockGuard : public std::lock_guard<StdMutex>
+{
+public:
+    explicit StdLockGuard(StdMutex& cs) EXCLUSIVE_LOCK_FUNCTION(cs) : std::lock_guard<StdMutex>(cs) {}
+    ~StdLockGuard() UNLOCK_FUNCTION() {}
+};
+
+#endif // BITCOIN_THREADSAFETY_H

src/i2p/uint256.h

@@ -0,0 +1,136 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UINT256_H
+#define BITCOIN_UINT256_H
+
+#include "crypto/common.h"
+#include "span.h"
+
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <cstring>
+#include <stdint.h>
+#include <string>
+
+/** Template base class for fixed-sized opaque blobs. */
+template<unsigned int BITS>
+class base_blob
+{
+protected:
+    static constexpr int WIDTH = BITS / 8;
+    static_assert(BITS % 8 == 0, "base_blob currently only supports whole bytes.");
+    std::array<uint8_t, WIDTH> m_data;
+    static_assert(WIDTH == sizeof(m_data), "Sanity check");
+
+public:
+    /* construct 0 value by default */
+    constexpr base_blob() : m_data() {}
+
+    /* constructor for constants between 1 and 255 */
+    constexpr explicit base_blob(uint8_t v) : m_data{v} {}
+
+    constexpr explicit base_blob(Span<const unsigned char> vch)
+    {
+        assert(vch.size() == WIDTH);
+        std::copy(vch.begin(), vch.end(), m_data.begin());
+    }
+
+    constexpr bool IsNull() const
+    {
+        return std::all_of(m_data.begin(), m_data.end(), [](uint8_t val) {
+            return val == 0;
+        });
+    }
+
+    constexpr void SetNull()
+    {
+        std::fill(m_data.begin(), m_data.end(), 0);
+    }
+
+    constexpr int Compare(const base_blob& other) const { return std::memcmp(m_data.data(), other.m_data.data(), WIDTH); }
+
+    friend constexpr bool operator==(const base_blob& a, const base_blob& b) { return a.Compare(b) == 0; }
+    friend constexpr bool operator!=(const base_blob& a, const base_blob& b) { return a.Compare(b) != 0; }
+    friend constexpr bool operator<(const base_blob& a, const base_blob& b) { return a.Compare(b) < 0; }
+
+    std::string GetHex() const;
+    void SetHex(const char* psz);
+    void SetHex(const std::string& str);
+    std::string ToString() const;
+
+    constexpr const unsigned char* data() const { return m_data.data(); }
+    constexpr unsigned char* data() { return m_data.data(); }
+
+    constexpr unsigned char* begin() { return m_data.data(); }
+    constexpr unsigned char* end() { return m_data.data() + WIDTH; }
+
+    constexpr const unsigned char* begin() const { return m_data.data(); }
+    constexpr const unsigned char* end() const { return m_data.data() + WIDTH; }
+
+    static constexpr unsigned int size() { return WIDTH; }
+
+    constexpr uint64_t GetUint64(int pos) const { return ReadLE64(m_data.data() + pos * 8); }
+
+    template<typename Stream>
+    void Serialize(Stream& s) const
+    {
+        s << Span(m_data);
+    }
+
+    template<typename Stream>
+    void Unserialize(Stream& s)
+    {
+        s.read(MakeWritableByteSpan(m_data));
+    }
+};
+
+/** 160-bit opaque blob.
+ * @note This type is called uint160 for historical reasons only. It is an opaque
+ * blob of 160 bits and has no integer operations.
+ */
+class uint160 : public base_blob<160> {
+public:
+    constexpr uint160() = default;
+    constexpr explicit uint160(Span<const unsigned char> vch) : base_blob<160>(vch) {}
+};
+
+/** 256-bit opaque blob.
+ * @note This type is called uint256 for historical reasons only. It is an
+ * opaque blob of 256 bits and has no integer operations. Use arith_uint256 if
+ * those are required.
+ */
+class uint256 : public base_blob<256> {
+public:
+    constexpr uint256() = default;
+    constexpr explicit uint256(uint8_t v) : base_blob<256>(v) {}
+    constexpr explicit uint256(Span<const unsigned char> vch) : base_blob<256>(vch) {}
+    static const uint256 ZERO;
+    static const uint256 ONE;
+};
+
+/* uint256 from const char *.
+ * This is a separate function because the constructor uint256(const char*) can result
+ * in dangerously catching uint256(0).
+ */
+inline uint256 uint256S(const char *str)
+{
+    uint256 rv;
+    rv.SetHex(str);
+    return rv;
+}
+/* uint256 from std::string.
+ * This is a separate function because the constructor uint256(const std::string &str) can result
+ * in dangerously catching uint256(0) via std::string(const char*).
+ */
+inline uint256 uint256S(const std::string& str)
+{
+    uint256 rv;
+    rv.SetHex(str);
+    return rv;
+}
+
+#endif // BITCOIN_UINT256_H

src/i2p/util/chaintype.h

@@ -0,0 +1,22 @@
+// Copyright (c) 2023 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_CHAINTYPE_H
+#define BITCOIN_UTIL_CHAINTYPE_H
+
+#include <optional>
+#include <string>
+
+enum class ChainType {
+  MAIN,
+  TESTNET,
+  SIGNET,
+  REGTEST,
+};
+
+std::string ChainTypeToString(ChainType chain);
+
+std::optional<ChainType> ChainTypeFromString(std::string_view chain);
+
+#endif // BITCOIN_UTIL_CHAINTYPE_H

src/i2p/util/fs.cpp

@@ -0,0 +1,126 @@
+// Copyright (c) 2017-present The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "../util/fs.h"
+#include "../util/syserror.h"
+
+#ifndef WIN32
+#include <cstring>
+#include <fcntl.h>
+#include <sys/file.h>
+#include <sys/utsname.h>
+#include <unistd.h>
+#else
+#include <codecvt>
+#include <limits>
+#include <windows.h>
+#endif
+
+#include <cassert>
+#include <cerrno>
+#include <string>
+
+namespace fsbridge {
+
+FILE *fopen(const fs::path &p, const char *mode) {
+#ifndef WIN32
+  return ::fopen(p.c_str(), mode);
+#else
+  std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t> utf8_cvt;
+  return ::_wfopen(p.wstring().c_str(), utf8_cvt.from_bytes(mode).c_str());
+#endif
+}
+
+fs::path AbsPathJoin(const fs::path &base, const fs::path &path) {
+  assert(base.is_absolute());
+  return path.empty() ? base : fs::path(base / path);
+}
+
+#ifndef WIN32
+
+static std::string GetErrorReason() { return SysErrorString(errno); }
+
+FileLock::FileLock(const fs::path &file) {
+  fd = open(file.c_str(), O_RDWR);
+  if (fd == -1) {
+    reason = GetErrorReason();
+  }
+}
+
+FileLock::~FileLock() {
+  if (fd != -1) {
+    close(fd);
+  }
+}
+
+bool FileLock::TryLock() {
+  if (fd == -1) {
+    return false;
+  }
+
+  struct flock lock;
+  lock.l_type = F_WRLCK;
+  lock.l_whence = SEEK_SET;
+  lock.l_start = 0;
+  lock.l_len = 0;
+  if (fcntl(fd, F_SETLK, &lock) == -1) {
+    reason = GetErrorReason();
+    return false;
+  }
+
+  return true;
+}
+#else
+
+static std::string GetErrorReason() { return Win32ErrorString(GetLastError()); }
+
+FileLock::FileLock(const fs::path &file) {
+  hFile = CreateFileW(file.wstring().c_str(), GENERIC_READ | GENERIC_WRITE,
+                      FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+                      nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+  if (hFile == INVALID_HANDLE_VALUE) {
+    reason = GetErrorReason();
+  }
+}
+
+FileLock::~FileLock() {
+  if (hFile != INVALID_HANDLE_VALUE) {
+    CloseHandle(hFile);
+  }
+}
+
+bool FileLock::TryLock() {
+  if (hFile == INVALID_HANDLE_VALUE) {
+    return false;
+  }
+  _OVERLAPPED overlapped = {};
+  if (!LockFileEx(hFile, LOCKFILE_EXCLUSIVE_LOCK | LOCKFILE_FAIL_IMMEDIATELY, 0,
+                  std::numeric_limits<DWORD>::max(),
+                  std::numeric_limits<DWORD>::max(), &overlapped)) {
+    reason = GetErrorReason();
+    return false;
+  }
+  return true;
+}
+#endif
+
+std::string get_filesystem_error_message(const fs::filesystem_error &e) {
+#ifndef WIN32
+  return e.what();
+#else
+  // Convert from Multi Byte to utf-16
+  std::string mb_string(e.what());
+  int size = MultiByteToWideChar(CP_ACP, 0, mb_string.data(), mb_string.size(),
+                                 nullptr, 0);
+
+  std::wstring utf16_string(size, L'\0');
+  MultiByteToWideChar(CP_ACP, 0, mb_string.data(), mb_string.size(),
+                      &*utf16_string.begin(), size);
+  // Convert from utf-16 to utf-8
+  return std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t>()
+      .to_bytes(utf16_string);
+#endif
+}
+
+} // namespace fsbridge

src/i2p/util/fs.h

@@ -0,0 +1,253 @@
+// Copyright (c) 2017-present The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_FS_H
+#define BITCOIN_UTIL_FS_H
+
+#include "../tinyformat.h"
+
+#include <cstdio>
+#include <filesystem> // IWYU pragma: export
+#include <functional>
+#include <iomanip>
+#include <ios>
+#include <ostream>
+#include <string>
+#include <system_error>
+#include <type_traits>
+#include <utility>
+
+/** Filesystem operations and types */
+namespace fs {
+
+using namespace std::filesystem;
+
+/**
+ * Path class wrapper to block calls to the fs::path(std::string) implicit
+ * constructor and the fs::path::string() method, which have unsafe and
+ * unpredictable behavior on Windows (see implementation note in
+ * \ref PathToString for details)
+ */
+class path : public std::filesystem::path
+{
+public:
+    using std::filesystem::path::path;
+
+    // Allow path objects arguments for compatibility.
+    path(std::filesystem::path path) : std::filesystem::path::path(std::move(path)) {}
+    path& operator=(std::filesystem::path path) { std::filesystem::path::operator=(std::move(path)); return *this; }
+    path& operator/=(const std::filesystem::path& path) { std::filesystem::path::operator/=(path); return *this; }
+
+    // Allow literal string arguments, which are safe as long as the literals are ASCII.
+    path(const char* c) : std::filesystem::path(c) {}
+    path& operator=(const char* c) { std::filesystem::path::operator=(c); return *this; }
+    path& operator/=(const char* c) { std::filesystem::path::operator/=(c); return *this; }
+    path& append(const char* c) { std::filesystem::path::append(c); return *this; }
+
+    // Disallow std::string arguments to avoid locale-dependent decoding on windows.
+    path(std::string) = delete;
+    path& operator=(std::string) = delete;
+    path& operator/=(std::string) = delete;
+    path& append(std::string) = delete;
+
+    // Disallow std::string conversion method to avoid locale-dependent encoding on windows.
+    std::string string() const = delete;
+
+    /**
+     * Return a UTF-8 representation of the path as a std::string, for
+     * compatibility with code using std::string. For code using the newer
+     * std::u8string type, it is more efficient to call the inherited
+     * std::filesystem::path::u8string method instead.
+     */
+    std::string utf8string() const
+    {
+        const std::u8string& utf8_str{std::filesystem::path::u8string()};
+        return std::string{utf8_str.begin(), utf8_str.end()};
+    }
+
+    // Required for path overloads in <fstream>.
+    // See https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=96e0367ead5d8dcac3bec2865582e76e2fbab190
+    path& make_preferred() { std::filesystem::path::make_preferred(); return *this; }
+    path filename() const { return std::filesystem::path::filename(); }
+};
+
+static inline path u8path(const std::string& utf8_str)
+{
+    return std::filesystem::path(std::u8string{utf8_str.begin(), utf8_str.end()});
+}
+
+// Disallow implicit std::string conversion for absolute to avoid
+// locale-dependent encoding on windows.
+static inline path absolute(const path& p)
+{
+    return std::filesystem::absolute(p);
+}
+
+// Disallow implicit std::string conversion for exists to avoid
+// locale-dependent encoding on windows.
+static inline bool exists(const path& p)
+{
+    return std::filesystem::exists(p);
+}
+
+// Allow explicit quoted stream I/O.
+static inline auto quoted(const std::string& s)
+{
+    return std::quoted(s, '"', '&');
+}
+
+// Allow safe path append operations.
+static inline path operator/(path p1, const path& p2)
+{
+    p1 /= p2;
+    return p1;
+}
+static inline path operator/(path p1, const char* p2)
+{
+    p1 /= p2;
+    return p1;
+}
+static inline path operator+(path p1, const char* p2)
+{
+    p1 += p2;
+    return p1;
+}
+static inline path operator+(path p1, path::value_type p2)
+{
+    p1 += p2;
+    return p1;
+}
+
+// Disallow unsafe path append operations.
+template<typename T> static inline path operator/(path p1, T p2) = delete;
+template<typename T> static inline path operator+(path p1, T p2) = delete;
+
+// Disallow implicit std::string conversion for copy_file
+// to avoid locale-dependent encoding on Windows.
+static inline bool copy_file(const path& from, const path& to, copy_options options)
+{
+    return std::filesystem::copy_file(from, to, options);
+}
+
+/**
+ * Convert path object to a byte string. On POSIX, paths natively are byte
+ * strings, so this is trivial. On Windows, paths natively are Unicode, so an
+ * encoding step is necessary. The inverse of \ref PathToString is \ref
+ * PathFromString. The strings returned and parsed by these functions can be
+ * used to call POSIX APIs, and for roundtrip conversion, logging, and
+ * debugging.
+ *
+ * Because \ref PathToString and \ref PathFromString functions don't specify an
+ * encoding, they are meant to be used internally, not externally. They are not
+ * appropriate to use in applications requiring UTF-8, where
+ * fs::path::u8string() / fs::path::utf8string() and fs::u8path() methods should be used instead. Other
+ * applications could require still different encodings. For example, JSON, XML,
+ * or URI applications might prefer to use higher-level escapes (\uXXXX or
+ * &XXXX; or %XX) instead of multibyte encoding. Rust, Python, Java applications
+ * may require encoding paths with their respective UTF-8 derivatives WTF-8,
+ * PEP-383, and CESU-8 (see https://en.wikipedia.org/wiki/UTF-8#Derivatives).
+ */
+static inline std::string PathToString(const path& path)
+{
+    // Implementation note: On Windows, the std::filesystem::path(string)
+    // constructor and std::filesystem::path::string() method are not safe to
+    // use here, because these methods encode the path using C++'s narrow
+    // multibyte encoding, which on Windows corresponds to the current "code
+    // page", which is unpredictable and typically not able to represent all
+    // valid paths. So fs::path::utf8string() and
+    // fs::u8path() functions are used instead on Windows. On
+    // POSIX, u8string/utf8string/u8path functions are not safe to use because paths are
+    // not always valid UTF-8, so plain string methods which do not transform
+    // the path there are used.
+#ifdef WIN32
+    return path.utf8string();
+#else
+    static_assert(std::is_same<path::string_type, std::string>::value, "PathToString not implemented on this platform");
+    return path.std::filesystem::path::string();
+#endif
+}
+
+/**
+ * Convert byte string to path object. Inverse of \ref PathToString.
+ */
+static inline path PathFromString(const std::string& string)
+{
+#ifdef WIN32
+    return u8path(string);
+#else
+    return std::filesystem::path(string);
+#endif
+}
+
+/**
+ * Create directory (and if necessary its parents), unless the leaf directory
+ * already exists or is a symlink to an existing directory.
+ * This is a temporary workaround for an issue in libstdc++ that has been fixed
+ * upstream [PR101510].
+ * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101510
+ */
+static inline bool create_directories(const std::filesystem::path& p)
+{
+    if (std::filesystem::is_symlink(p) && std::filesystem::is_directory(p)) {
+        return false;
+    }
+    return std::filesystem::create_directories(p);
+}
+
+/**
+ * This variant is not used. Delete it to prevent it from accidentally working
+ * around the workaround. If it is needed, add a workaround in the same pattern
+ * as above.
+ */
+bool create_directories(const std::filesystem::path& p, std::error_code& ec) = delete;
+
+} // namespace fs
+
+/** Bridge operations to C stdio */
+namespace fsbridge {
+    using FopenFn = std::function<FILE*(const fs::path&, const char*)>;
+    FILE *fopen(const fs::path& p, const char *mode);
+
+    /**
+     * Helper function for joining two paths
+     *
+     * @param[in] base  Base path
+     * @param[in] path  Path to combine with base
+     * @returns path unchanged if it is an absolute path, otherwise returns base joined with path. Returns base unchanged if path is empty.
+     * @pre  Base path must be absolute
+     * @post Returned path will always be absolute
+     */
+    fs::path AbsPathJoin(const fs::path& base, const fs::path& path);
+
+    class FileLock
+    {
+    public:
+        FileLock() = delete;
+        FileLock(const FileLock&) = delete;
+        FileLock(FileLock&&) = delete;
+        explicit FileLock(const fs::path& file);
+        ~FileLock();
+        bool TryLock();
+        std::string GetReason() { return reason; }
+
+    private:
+        std::string reason;
+#ifndef WIN32
+        int fd = -1;
+#else
+        void* hFile = (void*)-1; // INVALID_HANDLE_VALUE
+#endif
+    };
+
+    std::string get_filesystem_error_message(const fs::filesystem_error& e);
+};
+
+// Disallow path operator<< formatting in tinyformat to avoid locale-dependent
+// encoding on windows.
+namespace tinyformat {
+template<> inline void formatValue(std::ostream&, const char*, const char*, int, const std::filesystem::path&) = delete;
+template<> inline void formatValue(std::ostream&, const char*, const char*, int, const fs::path&) = delete;
+} // namespace tinyformat
+
+#endif // BITCOIN_UTIL_FS_H

src/i2p/util/hash_type.h

@@ -0,0 +1,48 @@
+// Copyright (c) 2020-2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_HASH_TYPE_H
+#define BITCOIN_UTIL_HASH_TYPE_H
+
+template <typename HashType> class BaseHash {
+protected:
+  HashType m_hash;
+
+public:
+  BaseHash() : m_hash() {}
+  explicit BaseHash(const HashType &in) : m_hash(in) {}
+
+  unsigned char *begin() { return m_hash.begin(); }
+
+  const unsigned char *begin() const { return m_hash.begin(); }
+
+  unsigned char *end() { return m_hash.end(); }
+
+  const unsigned char *end() const { return m_hash.end(); }
+
+  operator std::vector<unsigned char>() const {
+    return std::vector<unsigned char>{m_hash.begin(), m_hash.end()};
+  }
+
+  std::string ToString() const { return m_hash.ToString(); }
+
+  bool operator==(const BaseHash<HashType> &other) const noexcept {
+    return m_hash == other.m_hash;
+  }
+
+  bool operator!=(const BaseHash<HashType> &other) const noexcept {
+    return !(m_hash == other.m_hash);
+  }
+
+  bool operator<(const BaseHash<HashType> &other) const noexcept {
+    return m_hash < other.m_hash;
+  }
+
+  size_t size() const { return m_hash.size(); }
+
+  unsigned char *data() { return m_hash.data(); }
+  const unsigned char *data() const { return m_hash.data(); }
+};
+
+#endif // BITCOIN_UTIL_HASH_TYPE_H

src/i2p/util/macros.h

@@ -0,0 +1,20 @@
+// Copyright (c) 2019-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_MACROS_H
+#define BITCOIN_UTIL_MACROS_H
+
+#define PASTE(x, y) x ## y
+#define PASTE2(x, y) PASTE(x, y)
+
+#define UNIQUE_NAME(name) PASTE2(name, __COUNTER__)
+
+/**
+ * Converts the parameter X to a string after macro replacement on X has been performed.
+ * Don't merge these into one macro!
+ */
+#define STRINGIZE(X) DO_STRINGIZE(X)
+#define DO_STRINGIZE(X) #X
+
+#endif // BITCOIN_UTIL_MACROS_H

src/i2p/util/readwritefile.h

@@ -0,0 +1,28 @@
+// Copyright (c) 2015-2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_READWRITEFILE_H
+#define BITCOIN_UTIL_READWRITEFILE_H
+
+#include "fs.h"
+
+#include <limits>
+#include <string>
+#include <utility>
+
+/** Read full contents of a file and return them in a std::string.
+ * Returns a pair <status, string>.
+ * If an error occurred, status will be false, otherwise status will be true and the data will be returned in string.
+ *
+ * @param maxsize Puts a maximum size limit on the file that is read. If the file is larger than this, truncated data
+ *         (with len > maxsize) will be returned.
+ */
+std::pair<bool,std::string> ReadBinaryFile(const fs::path &filename, size_t maxsize=std::numeric_limits<size_t>::max());
+
+/** Write contents of std::string to a file.
+ * @return true on success.
+ */
+bool WriteBinaryFile(const fs::path &filename, const std::string &data);
+
+#endif // BITCOIN_UTIL_READWRITEFILE_H

src/i2p/util/sock.cpp

@@ -0,0 +1,429 @@
+// Copyright (c) 2020-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "i2p/util/sock.h"
+// #include "../common/system.h"
+// #include "easylogging++.h"
+// #include "i2p/compat/compat.h"
+// #include "../logging.h"
+#include "i2p/tinyformat.h"
+#include "i2p/util/syserror.h"
+// #include "i2p/util/threadinterrupt.h"
+// #include "i2p/util/time.h"
+#include "misc_log_ex.h"
+
+#include <memory>
+#include <stdexcept>
+#include <string>
+
+#ifdef USE_POLL
+#include <poll.h>
+#endif
+
+static inline bool IOErrorIsPermanent(int err) {
+  return err != WSAEAGAIN && err != WSAEINTR && err != WSAEWOULDBLOCK &&
+         err != WSAEINPROGRESS;
+}
+
+Sock::Sock(SOCKET s) : m_socket(s) {}
+
+Sock::Sock(Sock &&other) {
+  m_socket = other.m_socket;
+  other.m_socket = INVALID_SOCKET;
+}
+
+Sock::~Sock() { Close(); }
+
+Sock &Sock::operator=(Sock &&other) {
+  Close();
+  m_socket = other.m_socket;
+  other.m_socket = INVALID_SOCKET;
+  return *this;
+}
+
+ssize_t Sock::Send(const void *data, size_t len, int flags) const {
+  return send(m_socket, static_cast<const char *>(data), len, flags);
+}
+
+ssize_t Sock::Recv(void *buf, size_t len, int flags) const {
+  return recv(m_socket, static_cast<char *>(buf), len, flags);
+}
+
+int Sock::Connect(const sockaddr *addr, socklen_t addr_len) const {
+  return connect(m_socket, addr, addr_len);
+}
+
+int Sock::Bind(const sockaddr *addr, socklen_t addr_len) const {
+  return bind(m_socket, addr, addr_len);
+}
+
+int Sock::Listen(int backlog) const { return listen(m_socket, backlog); }
+
+std::unique_ptr<Sock> Sock::Accept(sockaddr *addr, socklen_t *addr_len) const {
+#ifdef WIN32
+  static constexpr auto ERR = INVALID_SOCKET;
+#else
+  static constexpr auto ERR = SOCKET_ERROR;
+#endif
+
+  std::unique_ptr<Sock> sock;
+
+  const auto socket = accept(m_socket, addr, addr_len);
+  if (socket != ERR) {
+    try {
+      sock = std::make_unique<Sock>(socket);
+    } catch (const std::exception &) {
+#ifdef WIN32
+      closesocket(socket);
+#else
+      close(socket);
+#endif
+    }
+  }
+
+  return sock;
+}
+
+int Sock::GetSockOpt(int level, int opt_name, void *opt_val,
+                     socklen_t *opt_len) const {
+  return getsockopt(m_socket, level, opt_name, static_cast<char *>(opt_val),
+                    opt_len);
+}
+
+int Sock::SetSockOpt(int level, int opt_name, const void *opt_val,
+                     socklen_t opt_len) const {
+  return setsockopt(m_socket, level, opt_name,
+                    static_cast<const char *>(opt_val), opt_len);
+}
+
+int Sock::GetSockName(sockaddr *name, socklen_t *name_len) const {
+  return getsockname(m_socket, name, name_len);
+}
+
+bool Sock::SetNonBlocking() const {
+#ifdef WIN32
+  u_long on{1};
+  if (ioctlsocket(m_socket, FIONBIO, &on) == SOCKET_ERROR) {
+    return false;
+  }
+#else
+  const int flags{fcntl(m_socket, F_GETFL, 0)};
+  if (flags == SOCKET_ERROR) {
+    return false;
+  }
+  if (fcntl(m_socket, F_SETFL, flags | O_NONBLOCK) == SOCKET_ERROR) {
+    return false;
+  }
+#endif
+  return true;
+}
+
+bool Sock::IsSelectable() const {
+#if defined(USE_POLL) || defined(WIN32)
+  return true;
+#else
+  return m_socket < FD_SETSIZE;
+#endif
+}
+
+bool Sock::Wait(std::chrono::milliseconds timeout, Event requested,
+                Event *occurred) const {
+  // We need a `shared_ptr` owning `this` for `WaitMany()`, but don't want
+  // `this` to be destroyed when the `shared_ptr` goes out of scope at the
+  // end of this function. Create it with a custom noop deleter.
+  std::shared_ptr<const Sock> shared{this, [](const Sock *) {}};
+
+  EventsPerSock events_per_sock{std::make_pair(shared, Events{requested})};
+
+  if (!WaitMany(timeout, events_per_sock)) {
+    return false;
+  }
+
+  if (occurred != nullptr) {
+    *occurred = events_per_sock.begin()->second.occurred;
+  }
+
+  return true;
+}
+
+bool Sock::WaitMany(std::chrono::milliseconds timeout,
+                    EventsPerSock &events_per_sock) const {
+#ifdef USE_POLL
+  std::vector<pollfd> pfds;
+  for (const auto &[sock, events] : events_per_sock) {
+    pfds.emplace_back();
+    auto &pfd = pfds.back();
+    pfd.fd = sock->m_socket;
+    if (events.requested & RECV) {
+      pfd.events |= POLLIN;
+    }
+    if (events.requested & SEND) {
+      pfd.events |= POLLOUT;
+    }
+  }
+
+  if (poll(pfds.data(), pfds.size(), count_milliseconds(timeout)) ==
+      SOCKET_ERROR) {
+    return false;
+  }
+
+  assert(pfds.size() == events_per_sock.size());
+  size_t i{0};
+  for (auto &[sock, events] : events_per_sock) {
+    assert(sock->m_socket == static_cast<SOCKET>(pfds[i].fd));
+    events.occurred = 0;
+    if (pfds[i].revents & POLLIN) {
+      events.occurred |= RECV;
+    }
+    if (pfds[i].revents & POLLOUT) {
+      events.occurred |= SEND;
+    }
+    if (pfds[i].revents & (POLLERR | POLLHUP)) {
+      events.occurred |= ERR;
+    }
+    ++i;
+  }
+
+  return true;
+#else
+  fd_set recv;
+  fd_set send;
+  fd_set err;
+  FD_ZERO(&recv);
+  FD_ZERO(&send);
+  FD_ZERO(&err);
+  SOCKET socket_max{0};
+
+  for (const auto &[sock, events] : events_per_sock) {
+    if (!sock->IsSelectable()) {
+      return false;
+    }
+    const auto &s = sock->m_socket;
+    if (events.requested & RECV) {
+      FD_SET(s, &recv);
+    }
+    if (events.requested & SEND) {
+      FD_SET(s, &send);
+    }
+    FD_SET(s, &err);
+    socket_max = std::max(socket_max, s);
+  }
+
+  timeval tv = MillisToTimeval(timeout);
+
+  if (select(socket_max + 1, &recv, &send, &err, &tv) == SOCKET_ERROR) {
+    return false;
+  }
+
+  for (auto &[sock, events] : events_per_sock) {
+    const auto &s = sock->m_socket;
+    events.occurred = 0;
+    if (FD_ISSET(s, &recv)) {
+      events.occurred |= RECV;
+    }
+    if (FD_ISSET(s, &send)) {
+      events.occurred |= SEND;
+    }
+    if (FD_ISSET(s, &err)) {
+      events.occurred |= ERR;
+    }
+  }
+
+  return true;
+#endif /* USE_POLL */
+}
+
+void Sock::SendComplete(Span<const unsigned char> data,
+                        std::chrono::milliseconds timeout,
+                        CThreadInterrupt &interrupt) const {
+  const auto deadline = GetTime<std::chrono::milliseconds>() + timeout;
+  size_t sent{0};
+
+  for (;;) {
+    const ssize_t ret{
+        Send(data.data() + sent, data.size() - sent, MSG_NOSIGNAL)};
+
+    if (ret > 0) {
+      sent += static_cast<size_t>(ret);
+      if (sent == data.size()) {
+        break;
+      }
+    } else {
+      const int err{WSAGetLastError()};
+      if (IOErrorIsPermanent(err)) {
+        throw std::runtime_error(
+            tfm::format("send(): %s", NetworkErrorString(err)));
+      }
+    }
+
+    const auto now = GetTime<std::chrono::milliseconds>();
+
+    if (now >= deadline) {
+      throw std::runtime_error(
+          tfm::format("Send timeout (sent only %u of %u bytes before that)",
+                      sent, data.size()));
+    }
+
+    if (interrupt) {
+      throw std::runtime_error(
+          tfm::format("Send interrupted (sent only %u of %u bytes before that)",
+                      sent, data.size()));
+    }
+
+    // Wait for a short while (or the socket to become ready for sending) before
+    // retrying if nothing was sent.
+    const auto wait_time =
+        std::min(deadline - now, std::chrono::milliseconds{MAX_WAIT_FOR_IO});
+    (void)Wait(wait_time, SEND);
+  }
+}
+
+void Sock::SendComplete(Span<const char> data,
+                        std::chrono::milliseconds timeout,
+                        CThreadInterrupt &interrupt) const {
+  SendComplete(MakeUCharSpan(data), timeout, interrupt);
+}
+
+std::string Sock::RecvUntilTerminator(uint8_t terminator,
+                                      std::chrono::milliseconds timeout,
+                                      CThreadInterrupt &interrupt,
+                                      size_t max_data) const {
+  const auto deadline = GetTime<std::chrono::milliseconds>() + timeout;
+  std::string data;
+  bool terminator_found{false};
+
+  // We must not consume any bytes past the terminator from the socket.
+  // One option is to read one byte at a time and check if we have read a
+  // terminator. However that is very slow. Instead, we peek at what is in the
+  // socket and only read as many bytes as possible without crossing the
+  // terminator. Reading 64 MiB of random data with 262526 terminator chars
+  // takes 37 seconds to read one byte at a time VS 0.71 seconds with the "peek"
+  // solution below. Reading one byte at a time is about 50 times slower.
+
+  for (;;) {
+    if (data.size() >= max_data) {
+      throw std::runtime_error(tfm::format(
+          "Received too many bytes without a terminator (%u)", data.size()));
+    }
+
+    char buf[512];
+
+    const ssize_t peek_ret{
+        Recv(buf, std::min(sizeof(buf), max_data - data.size()), MSG_PEEK)};
+
+    switch (peek_ret) {
+    case -1: {
+      const int err{WSAGetLastError()};
+      if (IOErrorIsPermanent(err)) {
+        throw std::runtime_error(
+            tfm::format("recv(): %s", NetworkErrorString(err)));
+      }
+      break;
+    }
+    case 0:
+      throw std::runtime_error("Connection unexpectedly closed by peer");
+    default:
+      auto end = buf + peek_ret;
+      auto terminator_pos = std::find(buf, end, terminator);
+      terminator_found = terminator_pos != end;
+
+      const size_t try_len{terminator_found ? terminator_pos - buf + 1
+                                            : static_cast<size_t>(peek_ret)};
+
+      const ssize_t read_ret{Recv(buf, try_len, 0)};
+
+      if (read_ret < 0 || static_cast<size_t>(read_ret) != try_len) {
+        throw std::runtime_error(tfm::format(
+            "recv() returned %u bytes on attempt to read %u bytes but previous "
+            "peek claimed %u bytes are available",
+            read_ret, try_len, peek_ret));
+      }
+
+      // Don't include the terminator in the output.
+      const size_t append_len{terminator_found ? try_len - 1 : try_len};
+
+      data.append(buf, buf + append_len);
+
+      if (terminator_found) {
+        return data;
+      }
+    }
+
+    const auto now = GetTime<std::chrono::milliseconds>();
+
+    if (now >= deadline) {
+      throw std::runtime_error(tfm::format(
+          "Receive timeout (received %u bytes without terminator before that)",
+          data.size()));
+    }
+
+    if (interrupt) {
+      throw std::runtime_error(tfm::format(
+          "Receive interrupted (received %u bytes without terminator "
+          "before that)",
+          data.size()));
+    }
+
+    // Wait for a short while (or the socket to become ready for reading) before
+    // retrying.
+    const auto wait_time =
+        std::min(deadline - now, std::chrono::milliseconds{MAX_WAIT_FOR_IO});
+    (void)Wait(wait_time, RECV);
+  }
+}
+
+bool Sock::IsConnected(std::string &errmsg) const {
+  if (m_socket == INVALID_SOCKET) {
+    errmsg = "not connected";
+    return false;
+  }
+
+  char c;
+  switch (Recv(&c, sizeof(c), MSG_PEEK)) {
+  case -1: {
+    const int err = WSAGetLastError();
+    if (IOErrorIsPermanent(err)) {
+      errmsg = NetworkErrorString(err);
+      return false;
+    }
+    return true;
+  }
+  case 0:
+    errmsg = "closed";
+    return false;
+  default:
+    return true;
+  }
+}
+
+void Sock::Close() {
+  if (m_socket == INVALID_SOCKET) {
+    return;
+  }
+#ifdef WIN32
+  int ret = closesocket(m_socket);
+#else
+  int ret = close(m_socket);
+#endif
+  if (ret) {
+    // LogPrintf("Error closing socket %d: %s\n", m_socket,
+    //            NetworkErrorString(WSAGetLastError()));
+    MLOG_GREEN(el::Level::Error, "Error closing socket %d: %s\n"
+                                     << m_socket
+                                     << NetworkErrorString(WSAGetLastError()));
+  }
+  m_socket = INVALID_SOCKET;
+}
+
+bool Sock::operator==(SOCKET s) const { return m_socket == s; };
+
+std::string NetworkErrorString(int err) {
+#if defined(WIN32)
+  return Win32ErrorString(err);
+#else
+  // On BSD sockets implementations, NetworkErrorString is the same as
+  // SysErrorString.
+  return SysErrorString(err);
+#endif
+}

src/i2p/util/sock.h

@@ -0,0 +1,311 @@
+// Copyright (c) 2020-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_SOCK_H
+#define BITCOIN_UTIL_SOCK_H
+
+// #include "../compat/compat.h"
+#include "../span.h"
+#include "threadinterrupt.h"
+#include "time.h"
+#include <chrono>
+#include <memory>
+#include <string>
+#include <unordered_map>
+
+/**
+ * Maximum time to wait for I/O readiness.
+ * It will take up until this time to break off in case of an interruption.
+ */
+static constexpr auto MAX_WAIT_FOR_IO = 1s;
+
+/**
+ * RAII helper class that manages a socket and closes it automatically when it
+ * goes out of scope.
+ */
+class Sock {
+public:
+  Sock() = delete;
+
+  /**
+   * Take ownership of an existent socket.
+   */
+  explicit Sock(SOCKET s);
+
+  /**
+   * Copy constructor, disabled because closing the same socket twice is
+   * undesirable.
+   */
+  Sock(const Sock &) = delete;
+
+  /**
+   * Move constructor, grab the socket from another object and close ours (if
+   * set).
+   */
+  Sock(Sock &&other);
+
+  /**
+   * Destructor, close the socket or do nothing if empty.
+   */
+  virtual ~Sock();
+
+  /**
+   * Copy assignment operator, disabled because closing the same socket twice is
+   * undesirable.
+   */
+  Sock &operator=(const Sock &) = delete;
+
+  /**
+   * Move assignment operator, grab the socket from another object and close
+   * ours (if set).
+   */
+  virtual Sock &operator=(Sock &&other);
+
+  /**
+   * send(2) wrapper. Equivalent to `send(m_socket, data, len, flags);`. Code
+   * that uses this wrapper can be unit tested if this method is overridden by a
+   * mock Sock implementation.
+   */
+  [[nodiscard]] virtual ssize_t Send(const void *data, size_t len,
+                                     int flags) const;
+
+  /**
+   * recv(2) wrapper. Equivalent to `recv(m_socket, buf, len, flags);`. Code
+   * that uses this wrapper can be unit tested if this method is overridden by a
+   * mock Sock implementation.
+   */
+  [[nodiscard]] virtual ssize_t Recv(void *buf, size_t len, int flags) const;
+
+  /**
+   * connect(2) wrapper. Equivalent to `connect(m_socket, addr, addrlen)`. Code
+   * that uses this wrapper can be unit tested if this method is overridden by a
+   * mock Sock implementation.
+   */
+  [[nodiscard]] virtual int Connect(const sockaddr *addr,
+                                    socklen_t addr_len) const;
+
+  /**
+   * bind(2) wrapper. Equivalent to `bind(m_socket, addr, addr_len)`. Code that
+   * uses this wrapper can be unit tested if this method is overridden by a mock
+   * Sock implementation.
+   */
+  [[nodiscard]] virtual int Bind(const sockaddr *addr,
+                                 socklen_t addr_len) const;
+
+  /**
+   * listen(2) wrapper. Equivalent to `listen(m_socket, backlog)`. Code that
+   * uses this wrapper can be unit tested if this method is overridden by a mock
+   * Sock implementation.
+   */
+  [[nodiscard]] virtual int Listen(int backlog) const;
+
+  /**
+   * accept(2) wrapper. Equivalent to `std::make_unique<Sock>(accept(m_socket,
+   * addr, addr_len))`. Code that uses this wrapper can be unit tested if this
+   * method is overridden by a mock Sock implementation. The returned unique_ptr
+   * is empty if `accept()` failed in which case errno will be set.
+   */
+  [[nodiscard]] virtual std::unique_ptr<Sock> Accept(sockaddr *addr,
+                                                     socklen_t *addr_len) const;
+
+  /**
+   * getsockopt(2) wrapper. Equivalent to
+   * `getsockopt(m_socket, level, opt_name, opt_val, opt_len)`. Code that uses
+   * this wrapper can be unit tested if this method is overridden by a mock Sock
+   * implementation.
+   */
+  [[nodiscard]] virtual int GetSockOpt(int level, int opt_name, void *opt_val,
+                                       socklen_t *opt_len) const;
+
+  /**
+   * setsockopt(2) wrapper. Equivalent to
+   * `setsockopt(m_socket, level, opt_name, opt_val, opt_len)`. Code that uses
+   * this wrapper can be unit tested if this method is overridden by a mock Sock
+   * implementation.
+   */
+  [[nodiscard]] virtual int SetSockOpt(int level, int opt_name,
+                                       const void *opt_val,
+                                       socklen_t opt_len) const;
+
+  /**
+   * getsockname(2) wrapper. Equivalent to
+   * `getsockname(m_socket, name, name_len)`. Code that uses this
+   * wrapper can be unit tested if this method is overridden by a mock Sock
+   * implementation.
+   */
+  [[nodiscard]] virtual int GetSockName(sockaddr *name,
+                                        socklen_t *name_len) const;
+
+  /**
+   * Set the non-blocking option on the socket.
+   * @return true if set successfully
+   */
+  [[nodiscard]] virtual bool SetNonBlocking() const;
+
+  /**
+   * Check if the underlying socket can be used for `select(2)` (or the `Wait()`
+   * method).
+   * @return true if selectable
+   */
+  [[nodiscard]] virtual bool IsSelectable() const;
+
+  using Event = uint8_t;
+
+  /**
+   * If passed to `Wait()`, then it will wait for readiness to read from the
+   * socket.
+   */
+  static constexpr Event RECV = 0b001;
+
+  /**
+   * If passed to `Wait()`, then it will wait for readiness to send to the
+   * socket.
+   */
+  static constexpr Event SEND = 0b010;
+
+  /**
+   * Ignored if passed to `Wait()`, but could be set in the occurred events if
+   * an exceptional condition has occurred on the socket or if it has been
+   * disconnected.
+   */
+  static constexpr Event ERR = 0b100;
+
+  /**
+   * Wait for readiness for input (recv) or output (send).
+   * @param[in] timeout Wait this much for at least one of the requested events
+   * to occur.
+   * @param[in] requested Wait for those events, bitwise-or of `RECV` and
+   * `SEND`.
+   * @param[out] occurred If not nullptr and the function returns `true`, then
+   * this indicates which of the requested events occurred (`ERR` will be added,
+   * even if not requested, if an exceptional event occurs on the socket). A
+   * timeout is indicated by return value of `true` and `occurred` being set to
+   * 0.
+   * @return true on success (or timeout, if `occurred` of 0 is returned), false
+   * otherwise
+   */
+  [[nodiscard]] virtual bool Wait(std::chrono::milliseconds timeout,
+                                  Event requested,
+                                  Event *occurred = nullptr) const;
+
+  /**
+   * Auxiliary requested/occurred events to wait for in `WaitMany()`.
+   */
+  struct Events {
+    explicit Events(Event req) : requested{req} {}
+    Event requested;
+    Event occurred{0};
+  };
+
+  struct HashSharedPtrSock {
+    size_t operator()(const std::shared_ptr<const Sock> &s) const {
+      return s ? s->m_socket : std::numeric_limits<SOCKET>::max();
+    }
+  };
+
+  struct EqualSharedPtrSock {
+    bool operator()(const std::shared_ptr<const Sock> &lhs,
+                    const std::shared_ptr<const Sock> &rhs) const {
+      if (lhs && rhs) {
+        return lhs->m_socket == rhs->m_socket;
+      }
+      if (!lhs && !rhs) {
+        return true;
+      }
+      return false;
+    }
+  };
+
+  /**
+   * On which socket to wait for what events in `WaitMany()`.
+   * The `shared_ptr` is copied into the map to ensure that the `Sock` object
+   * is not destroyed (its destructor would close the underlying socket).
+   * If this happens shortly before or after we call `poll(2)` and a new
+   * socket gets created under the same file descriptor number then the report
+   * from `WaitMany()` will be bogus.
+   */
+  using EventsPerSock =
+      std::unordered_map<std::shared_ptr<const Sock>, Events, HashSharedPtrSock,
+                         EqualSharedPtrSock>;
+
+  /**
+   * Same as `Wait()`, but wait on many sockets within the same timeout.
+   * @param[in] timeout Wait this long for at least one of the requested events
+   * to occur.
+   * @param[in,out] events_per_sock Wait for the requested events on these
+   * sockets and set `occurred` for the events that actually occurred.
+   * @return true on success (or timeout, if all `what[].occurred` are returned
+   * as 0), false otherwise
+   */
+  [[nodiscard]] virtual bool WaitMany(std::chrono::milliseconds timeout,
+                                      EventsPerSock &events_per_sock) const;
+
+  /* Higher level, convenience, methods. These may throw. */
+
+  /**
+   * Send the given data, retrying on transient errors.
+   * @param[in] data Data to send.
+   * @param[in] timeout Timeout for the entire operation.
+   * @param[in] interrupt If this is signaled then the operation is canceled.
+   * @throws std::runtime_error if the operation cannot be completed. In this
+   * case only some of the data will be written to the socket.
+   */
+  virtual void SendComplete(Span<const unsigned char> data,
+                            std::chrono::milliseconds timeout,
+                            CThreadInterrupt &interrupt) const;
+
+  /**
+   * Convenience method, equivalent to `SendComplete(MakeUCharSpan(data),
+   * timeout, interrupt)`.
+   */
+  virtual void SendComplete(Span<const char> data,
+                            std::chrono::milliseconds timeout,
+                            CThreadInterrupt &interrupt) const;
+
+  /**
+   * Read from socket until a terminator character is encountered. Will never
+   * consume bytes past the terminator from the socket.
+   * @param[in] terminator Character up to which to read from the socket.
+   * @param[in] timeout Timeout for the entire operation.
+   * @param[in] interrupt If this is signaled then the operation is canceled.
+   * @param[in] max_data The maximum amount of data (in bytes) to receive. If
+   * this many bytes are received and there is still no terminator, then this
+   * method will throw an exception.
+   * @return The data that has been read, without the terminating character.
+   * @throws std::runtime_error if the operation cannot be completed. In this
+   * case some bytes may have been consumed from the socket.
+   */
+  [[nodiscard]] virtual std::string
+  RecvUntilTerminator(uint8_t terminator, std::chrono::milliseconds timeout,
+                      CThreadInterrupt &interrupt, size_t max_data) const;
+
+  /**
+   * Check if still connected.
+   * @param[out] errmsg The error string, if the socket has been disconnected.
+   * @return true if connected
+   */
+  [[nodiscard]] virtual bool IsConnected(std::string &errmsg) const;
+
+  /**
+   * Check if the internal socket is equal to `s`. Use only in tests.
+   */
+  bool operator==(SOCKET s) const;
+
+protected:
+  /**
+   * Contained socket. `INVALID_SOCKET` designates the object is empty.
+   */
+  SOCKET m_socket;
+
+private:
+  /**
+   * Close `m_socket` if it is not `INVALID_SOCKET`.
+   */
+  void Close();
+};
+
+/** Return readable error string for a network error code */
+std::string NetworkErrorString(int err);
+
+#endif // BITCOIN_UTIL_SOCK_H

src/i2p/util/spanparsing.h

@@ -0,0 +1,79 @@
+// Copyright (c) 2018-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_SPANPARSING_H
+#define BITCOIN_UTIL_SPANPARSING_H
+
+#include "../span.h"
+
+#include <string>
+#include <string_view>
+#include <vector>
+
+namespace spanparsing {
+
+/** Parse a constant.
+ *
+ * If sp's initial part matches str, sp is updated to skip that part, and true is returned.
+ * Otherwise sp is unmodified and false is returned.
+ */
+bool Const(const std::string& str, Span<const char>& sp);
+
+/** Parse a function call.
+ *
+ * If sp's initial part matches str + "(", and sp ends with ")", sp is updated to be the
+ * section between the braces, and true is returned. Otherwise sp is unmodified and false
+ * is returned.
+ */
+bool Func(const std::string& str, Span<const char>& sp);
+
+/** Extract the expression that sp begins with.
+ *
+ * This function will return the initial part of sp, up to (but not including) the first
+ * comma or closing brace, skipping ones that are surrounded by braces. So for example,
+ * for "foo(bar(1),2),3" the initial part "foo(bar(1),2)" will be returned. sp will be
+ * updated to skip the initial part that is returned.
+ */
+Span<const char> Expr(Span<const char>& sp);
+
+/** Split a string on any char found in separators, returning a vector.
+ *
+ * If sep does not occur in sp, a singleton with the entirety of sp is returned.
+ *
+ * Note that this function does not care about braces, so splitting
+ * "foo(bar(1),2),3) on ',' will return {"foo(bar(1)", "2)", "3)"}.
+ */
+template <typename T = Span<const char>>
+std::vector<T> Split(const Span<const char>& sp, std::string_view separators)
+{
+    std::vector<T> ret;
+    auto it = sp.begin();
+    auto start = it;
+    while (it != sp.end()) {
+        if (separators.find(*it) != std::string::npos) {
+            ret.emplace_back(start, it);
+            start = it + 1;
+        }
+        ++it;
+    }
+    ret.emplace_back(start, it);
+    return ret;
+}
+
+/** Split a string on every instance of sep, returning a vector.
+ *
+ * If sep does not occur in sp, a singleton with the entirety of sp is returned.
+ *
+ * Note that this function does not care about braces, so splitting
+ * "foo(bar(1),2),3) on ',' will return {"foo(bar(1)", "2)", "3)"}.
+ */
+template <typename T = Span<const char>>
+std::vector<T> Split(const Span<const char>& sp, char sep)
+{
+    return Split<T>(sp, std::string_view{&sep, 1});
+}
+
+} // namespace spanparsing
+
+#endif // BITCOIN_UTIL_SPANPARSING_H

src/i2p/util/strencodings.cpp

@@ -0,0 +1,553 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "strencodings.h"
+#include "i2p/span.h"
+
+// #include <array>
+// #include <cassert>
+// #include <cstring>
+// #include <limits>
+#include <optional>
+// #include <ostream>
+#include <string>
+#include <vector>
+
+// static const std::string CHARS_ALPHA_NUM =
+//     "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+//
+// static const std::string SAFE_CHARS[] = {
+//     CHARS_ALPHA_NUM + " .,;-_/:?@()",            // SAFE_CHARS_DEFAULT
+//     CHARS_ALPHA_NUM + " .,;-_?@",                // SAFE_CHARS_UA_COMMENT
+//     CHARS_ALPHA_NUM + ".-_",                     // SAFE_CHARS_FILENAME
+//     CHARS_ALPHA_NUM + "!*'();:@&=+$,/?#[]-_.~%", // SAFE_CHARS_URI
+// };
+
+// std::string SanitizeString(std::string_view str, int rule) {
+//   std::string result;
+//   for (char c : str) {
+//     if (SAFE_CHARS[rule].find(c) != std::string::npos) {
+//       result.push_back(c);
+//     }
+//   }
+//   return result;
+// }
+
+// const signed char p_util_hexdigit[256] = {
+//     -1, -1,  -1,  -1,  -1,  -1,  -1,  -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     -1, -1,  -1,  -1,  -1,  -1,  -1,  -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     -1, -1,  -1,  -1,  -1,  -1,  -1,  -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     0,  1,   2,   3,   4,   5,   6,   7,  8,  9,  -1, -1, -1, -1, -1, -1,
+//     -1, 0xa, 0xb, 0xc, 0xd, 0xe, 0xf, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     -1, -1,  -1,  -1,  -1,  -1,  -1,  -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     -1, 0xa, 0xb, 0xc, 0xd, 0xe, 0xf, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     -1, -1,  -1,  -1,  -1,  -1,  -1,  -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     -1, -1,  -1,  -1,  -1,  -1,  -1,  -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     -1, -1,  -1,  -1,  -1,  -1,  -1,  -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     -1, -1,  -1,  -1,  -1,  -1,  -1,  -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     -1, -1,  -1,  -1,  -1,  -1,  -1,  -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     -1, -1,  -1,  -1,  -1,  -1,  -1,  -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     -1, -1,  -1,  -1,  -1,  -1,  -1,  -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     -1, -1,  -1,  -1,  -1,  -1,  -1,  -1, -1, -1, -1, -1, -1, -1, -1, -1,
+//     -1, -1,  -1,  -1,  -1,  -1,  -1,  -1, -1, -1, -1, -1, -1, -1, -1, -1,
+// };
+
+// signed char HexDigit(char c) { return p_util_hexdigit[(unsigned char)c]; }
+//
+// bool IsHex(std::string_view str) {
+//   for (char c : str) {
+//     if (HexDigit(c) < 0)
+//       return false;
+//   }
+//   return (str.size() > 0) && (str.size() % 2 == 0);
+// }
+//
+// bool IsHexNumber(std::string_view str) {
+//   if (str.substr(0, 2) == "0x")
+//     str.remove_prefix(2);
+//   for (char c : str) {
+//     if (HexDigit(c) < 0)
+//       return false;
+//   }
+//   // Return false for empty string or "0x".
+//   return str.size() > 0;
+// }
+
+// template <typename Byte>
+// std::optional<std::vector<Byte>> TryParseHex(std::string_view str) {
+//   std::vector<Byte> vch;
+//   vch.reserve(str.size() / 2); // two hex characters form a single byte
+//
+//   auto it = str.begin();
+//   while (it != str.end()) {
+//     if (IsSpace(*it)) {
+//       ++it;
+//       continue;
+//     }
+//     auto c1 = HexDigit(*(it++));
+//     if (it == str.end())
+//       return std::nullopt;
+//     auto c2 = HexDigit(*(it++));
+//     if (c1 < 0 || c2 < 0)
+//       return std::nullopt;
+//     vch.push_back(Byte(c1 << 4) | Byte(c2));
+//   }
+//   return vch;
+// }
+// template std::optional<std::vector<std::byte>> TryParseHex(std::string_view);
+// template std::optional<std::vector<uint8_t>> TryParseHex(std::string_view);
+//
+// bool SplitHostPort(std::string_view in, uint16_t &portOut,
+//                    std::string &hostOut) {
+//   bool valid = false;
+//   size_t colon = in.find_last_of(':');
+//   // if a : is found, and it either follows a [...], or no other : is in the
+//   // string, treat it as port separator
+//   bool fHaveColon = colon != in.npos;
+//   bool fBracketed =
+//       fHaveColon &&
+//       (in[0] == '[' &&
+//        in[colon - 1] == ']'); // if there is a colon, and in[0]=='[', colon
+//        is
+//                               // not 0, so in[colon-1] is safe
+//   bool fMultiColon{fHaveColon && colon != 0 &&
+//                    (in.find_last_of(':', colon - 1) != in.npos)};
+//   if (fHaveColon && (colon == 0 || fBracketed || !fMultiColon)) {
+//     uint16_t n;
+//     if (ParseUInt16(in.substr(colon + 1), &n)) {
+//       in = in.substr(0, colon);
+//       portOut = n;
+//       valid = (portOut != 0);
+//     }
+//   } else {
+//     valid = true;
+//   }
+//   if (in.size() > 0 && in[0] == '[' && in[in.size() - 1] == ']') {
+//     hostOut = in.substr(1, in.size() - 2);
+//   } else {
+//     hostOut = in;
+//   }
+//
+//   return valid;
+// }
+
+std::string EncodeBase64(Span<const unsigned char> input) {
+  static const char *pbase64 =
+      "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+  std::string str;
+  str.reserve(((input.size() + 2) / 3) * 4);
+  ConvertBits<8, 6, true>([&](int v) { str += pbase64[v]; }, input.begin(),
+                          input.end());
+  while (str.size() % 4)
+    str += '=';
+  return str;
+}
+
+std::optional<std::vector<unsigned char>> DecodeBase64(std::string_view str) {
+  static const int8_t decode64_table[256]{
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57,
+      58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0,  1,  2,  3,  4,  5,  6,
+      7,  8,  9,  10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
+      25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,
+      37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1};
+
+  if (str.size() % 4 != 0)
+    return {};
+  /* One or two = characters at the end are permitted. */
+  if (str.size() >= 1 && str.back() == '=')
+    str.remove_suffix(1);
+  if (str.size() >= 1 && str.back() == '=')
+    str.remove_suffix(1);
+
+  std::vector<unsigned char> ret;
+  ret.reserve((str.size() * 3) / 4);
+  bool valid = ConvertBits<6, 8, false>(
+      [&](unsigned char c) { ret.push_back(c); }, str.begin(), str.end(),
+      [](char c) { return decode64_table[uint8_t(c)]; });
+  if (!valid)
+    return {};
+
+  return ret;
+}
+
+std::string EncodeBase32(Span<const unsigned char> input, bool pad) {
+  static const char *pbase32 = "abcdefghijklmnopqrstuvwxyz234567";
+
+  std::string str;
+  str.reserve(((input.size() + 4) / 5) * 8);
+  ConvertBits<8, 5, true>([&](int v) { str += pbase32[v]; }, input.begin(),
+                          input.end());
+  if (pad) {
+    while (str.size() % 8) {
+      str += '=';
+    }
+  }
+  return str;
+}
+
+std::string EncodeBase32(std::string_view str, bool pad) {
+  return EncodeBase32(MakeUCharSpan(str), pad);
+}
+
+std::optional<std::vector<unsigned char>> DecodeBase32(std::string_view str) {
+  static const int8_t decode32_table[256]{
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29,
+      30, 31, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0,  1,  2,  3,  4,  5,  6,
+      7,  8,  9,  10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
+      25, -1, -1, -1, -1, -1, -1, 0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  10,
+      11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1};
+
+  if (str.size() % 8 != 0)
+    return {};
+  /* 1, 3, 4, or 6 padding '=' suffix characters are permitted. */
+  if (str.size() >= 1 && str.back() == '=')
+    str.remove_suffix(1);
+  if (str.size() >= 2 && str.substr(str.size() - 2) == "==")
+    str.remove_suffix(2);
+  if (str.size() >= 1 && str.back() == '=')
+    str.remove_suffix(1);
+  if (str.size() >= 2 && str.substr(str.size() - 2) == "==")
+    str.remove_suffix(2);
+
+  std::vector<unsigned char> ret;
+  ret.reserve((str.size() * 5) / 8);
+  bool valid = ConvertBits<5, 8, false>(
+      [&](unsigned char c) { ret.push_back(c); }, str.begin(), str.end(),
+      [](char c) { return decode32_table[uint8_t(c)]; });
+
+  if (!valid)
+    return {};
+
+  return ret;
+}
+
+// namespace {
+// template <typename T> bool ParseIntegral(std::string_view str, T *out) {
+//   static_assert(std::is_integral<T>::value);
+//   // Replicate the exact behavior of strtol/strtoll/strtoul/strtoull when
+//   // handling leading +/- for backwards compatibility.
+//   if (str.length() >= 2 && str[0] == '+' && str[1] == '-') {
+//     return false;
+//   }
+//   const std::optional<T> opt_int =
+//       ToIntegral<T>((!str.empty() && str[0] == '+') ? str.substr(1) : str);
+//   if (!opt_int) {
+//     return false;
+//   }
+//   if (out != nullptr) {
+//     *out = *opt_int;
+//   }
+//   return true;
+// }
+// }; // namespace
+
+// bool ParseInt32(std::string_view str, int32_t *out) {
+//   return ParseIntegral<int32_t>(str, out);
+// }
+//
+// bool ParseInt64(std::string_view str, int64_t *out) {
+//   return ParseIntegral<int64_t>(str, out);
+// }
+//
+// bool ParseUInt8(std::string_view str, uint8_t *out) {
+//   return ParseIntegral<uint8_t>(str, out);
+// }
+//
+// bool ParseUInt16(std::string_view str, uint16_t *out) {
+//   return ParseIntegral<uint16_t>(str, out);
+// }
+//
+// bool ParseUInt32(std::string_view str, uint32_t *out) {
+//   return ParseIntegral<uint32_t>(str, out);
+// }
+//
+// bool ParseUInt64(std::string_view str, uint64_t *out) {
+//   return ParseIntegral<uint64_t>(str, out);
+// }
+
+// std::string FormatParagraph(std::string_view in, size_t width, size_t indent)
+// {
+//   assert(width >= indent);
+//   std::stringstream out;
+//   size_t ptr = 0;
+//   size_t indented = 0;
+//   while (ptr < in.size()) {
+//     size_t lineend = in.find_first_of('\n', ptr);
+//     if (lineend == std::string::npos) {
+//       lineend = in.size();
+//     }
+//     const size_t linelen = lineend - ptr;
+//     const size_t rem_width = width - indented;
+//     if (linelen <= rem_width) {
+//       out << in.substr(ptr, linelen + 1);
+//       ptr = lineend + 1;
+//       indented = 0;
+//     } else {
+//       size_t finalspace = in.find_last_of(" \n", ptr + rem_width);
+//       if (finalspace == std::string::npos || finalspace < ptr) {
+//         // No place to break; just include the entire word and move on
+//         finalspace = in.find_first_of("\n ", ptr);
+//         if (finalspace == std::string::npos) {
+//           // End of the string, just add it and break
+//           out << in.substr(ptr);
+//           break;
+//         }
+//       }
+//       out << in.substr(ptr, finalspace - ptr) << "\n";
+//       if (in[finalspace] == '\n') {
+//         indented = 0;
+//       } else if (indent) {
+//         out << std::string(indent, ' ');
+//         indented = indent;
+//       }
+//       ptr = finalspace + 1;
+//     }
+//   }
+//   return out.str();
+// }
+
+/** Upper bound for mantissa.
+ * 10^18-1 is the largest arbitrary decimal that will fit in a signed 64-bit
+ * integer. Larger integers cannot consist of arbitrary combinations of 0-9:
+ *
+ *   999999999999999999  1^18-1
+ *  9223372036854775807  (1<<63)-1  (max int64_t)
+ *  9999999999999999999  1^19-1     (would overflow)
+ */
+// static const int64_t UPPER_BOUND = 1000000000000000000LL - 1LL;
+//
+// /** Helper function for ParseFixedPoint */
+// static inline bool ProcessMantissaDigit(char ch, int64_t &mantissa,
+//                                         int &mantissa_tzeros) {
+//   if (ch == '0')
+//     ++mantissa_tzeros;
+//   else {
+//     for (int i = 0; i <= mantissa_tzeros; ++i) {
+//       if (mantissa > (UPPER_BOUND / 10LL))
+//         return false; /* overflow */
+//       mantissa *= 10;
+//     }
+//     mantissa += ch - '0';
+//     mantissa_tzeros = 0;
+//   }
+//   return true;
+// }
+
+// bool ParseFixedPoint(std::string_view val, int decimals, int64_t *amount_out)
+// {
+//   int64_t mantissa = 0;
+//   int64_t exponent = 0;
+//   int mantissa_tzeros = 0;
+//   bool mantissa_sign = false;
+//   bool exponent_sign = false;
+//   int ptr = 0;
+//   int end = val.size();
+//   int point_ofs = 0;
+//
+//   if (ptr < end && val[ptr] == '-') {
+//     mantissa_sign = true;
+//     ++ptr;
+//   }
+//   if (ptr < end) {
+//     if (val[ptr] == '0') {
+//       /* pass single 0 */
+//       ++ptr;
+//     } else if (val[ptr] >= '1' && val[ptr] <= '9') {
+//       while (ptr < end && IsDigit(val[ptr])) {
+//         if (!ProcessMantissaDigit(val[ptr], mantissa, mantissa_tzeros))
+//           return false; /* overflow */
+//         ++ptr;
+//       }
+//     } else
+//       return false; /* missing expected digit */
+//   } else
+//     return false; /* empty string or loose '-' */
+//   if (ptr < end && val[ptr] == '.') {
+//     ++ptr;
+//     if (ptr < end && IsDigit(val[ptr])) {
+//       while (ptr < end && IsDigit(val[ptr])) {
+//         if (!ProcessMantissaDigit(val[ptr], mantissa, mantissa_tzeros))
+//           return false; /* overflow */
+//         ++ptr;
+//         ++point_ofs;
+//       }
+//     } else
+//       return false; /* missing expected digit */
+//   }
+//   if (ptr < end && (val[ptr] == 'e' || val[ptr] == 'E')) {
+//     ++ptr;
+//     if (ptr < end && val[ptr] == '+')
+//       ++ptr;
+//     else if (ptr < end && val[ptr] == '-') {
+//       exponent_sign = true;
+//       ++ptr;
+//     }
+//     if (ptr < end && IsDigit(val[ptr])) {
+//       while (ptr < end && IsDigit(val[ptr])) {
+//         if (exponent > (UPPER_BOUND / 10LL))
+//           return false; /* overflow */
+//         exponent = exponent * 10 + val[ptr] - '0';
+//         ++ptr;
+//       }
+//     } else
+//       return false; /* missing expected digit */
+//   }
+//   if (ptr != end)
+//     return false; /* trailing garbage */
+//
+//   /* finalize exponent */
+//   if (exponent_sign)
+//     exponent = -exponent;
+//   exponent = exponent - point_ofs + mantissa_tzeros;
+//
+//   /* finalize mantissa */
+//   if (mantissa_sign)
+//     mantissa = -mantissa;
+//
+//   /* convert to one 64-bit fixed-point value */
+//   exponent += decimals;
+//   if (exponent < 0)
+//     return false; /* cannot represent values smaller than 10^-decimals */
+//   if (exponent >= 18)
+//     return false; /* cannot represent values larger than or equal to
+//                      10^(18-decimals) */
+//
+//   for (int i = 0; i < exponent; ++i) {
+//     if (mantissa > (UPPER_BOUND / 10LL) || mantissa < -(UPPER_BOUND / 10LL))
+//       return false; /* overflow */
+//     mantissa *= 10;
+//   }
+//   if (mantissa > UPPER_BOUND || mantissa < -UPPER_BOUND)
+//     return false; /* overflow */
+//
+//   if (amount_out)
+//     *amount_out = mantissa;
+//
+//   return true;
+// }
+
+// std::string ToLower(std::string_view str) {
+//   std::string r;
+//   r.reserve(str.size());
+//   for (auto ch : str)
+//     r += ToLower(ch);
+//   return r;
+// }
+
+std::string ToUpper(std::string_view str) {
+  std::string r;
+  r.reserve(str.size());
+  for (auto ch : str)
+    r += ToUpper(ch);
+  return r;
+}
+
+std::string Capitalize(std::string str) {
+  if (str.empty())
+    return str;
+  str[0] = ToUpper(str.front());
+  return str;
+}
+
+// namespace {
+//
+// using ByteAsHex = std::array<char, 2>;
+//
+// constexpr std::array<ByteAsHex, 256> CreateByteToHexMap() {
+//   constexpr char hexmap[16] = {'0', '1', '2', '3', '4', '5', '6', '7',
+//                                '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+//
+//   std::array<ByteAsHex, 256> byte_to_hex{};
+//   for (size_t i = 0; i < byte_to_hex.size(); ++i) {
+//     byte_to_hex[i][0] = hexmap[i >> 4];
+//     byte_to_hex[i][1] = hexmap[i & 15];
+//   }
+//   return byte_to_hex;
+// }
+//
+// } // namespace
+
+// std::string HexStr(const Span<const uint8_t> s) {
+//   std::string rv(s.size() * 2, '\0');
+//   static constexpr auto byte_to_hex = CreateByteToHexMap();
+//   static_assert(sizeof(byte_to_hex) == 512);
+//
+//   char *it = rv.data();
+//   for (uint8_t v : s) {
+//     std::memcpy(it, byte_to_hex[v].data(), 2);
+//     it += 2;
+//   }
+//
+//   assert(it == rv.data() + rv.size());
+//   return rv;
+// }
+
+// std::optional<uint64_t> ParseByteUnits(std::string_view str,
+//                                        ByteUnit default_multiplier) {
+//   if (str.empty()) {
+//     return std::nullopt;
+//   }
+//   auto multiplier = default_multiplier;
+//   char unit = str.back();
+//   switch (unit) {
+//   case 'k':
+//     multiplier = ByteUnit::k;
+//     break;
+//   case 'K':
+//     multiplier = ByteUnit::K;
+//     break;
+//   case 'm':
+//     multiplier = ByteUnit::m;
+//     break;
+//   case 'M':
+//     multiplier = ByteUnit::M;
+//     break;
+//   case 'g':
+//     multiplier = ByteUnit::g;
+//     break;
+//   case 'G':
+//     multiplier = ByteUnit::G;
+//     break;
+//   case 't':
+//     multiplier = ByteUnit::t;
+//     break;
+//   case 'T':
+//     multiplier = ByteUnit::T;
+//     break;
+//   default:
+//     unit = 0;
+//     break;
+//   }
+//
+//   uint64_t unit_amount = static_cast<uint64_t>(multiplier);
+//   auto parsed_num =
+//       ToIntegral<uint64_t>(unit ? str.substr(0, str.size() - 1) : str);
+//   if (!parsed_num || parsed_num > std::numeric_limits<uint64_t>::max() /
+//                                       unit_amount) { // check overflow
+//     return std::nullopt;
+//   }
+//   return *parsed_num * unit_amount;
+// }

src/i2p/util/strencodings.h

@@ -0,0 +1,405 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+/**
+ * Utilities for converting data from/to strings.
+ */
+#ifndef BITCOIN_UTIL_STRENCODINGS_H
+#define BITCOIN_UTIL_STRENCODINGS_H
+
+#include "i2p/span.h"
+// #include "string.h"
+
+// #include <charconv>
+#include <cstddef>
+// #include <cstdint>
+//  #include <limits>
+#include <optional>
+#include <string>      // IWYU pragma: export
+#include <string_view> // IWYU pragma: export
+// #include <system_error>
+//  #include <type_traits>
+#include <vector>
+
+/** Used by SanitizeString() */
+// enum SafeChars {
+//   SAFE_CHARS_DEFAULT,    //!< The full set of allowed chars
+//   SAFE_CHARS_UA_COMMENT, //!< BIP-0014 subset
+//   SAFE_CHARS_FILENAME,   //!< Chars allowed in filenames
+//   SAFE_CHARS_URI,        //!< Chars allowed in URIs (RFC 3986)
+// };
+
+/**
+ * Used by ParseByteUnits()
+ * Lowercase base 1000
+ * Uppercase base 1024
+ */
+// enum class ByteUnit : uint64_t {
+//     NOOP = 1ULL,
+//     k = 1000ULL,
+//     K = 1024ULL,
+//     m = 1'000'000ULL,
+//     M = 1ULL << 20,
+//     g = 1'000'000'000ULL,
+//     G = 1ULL << 30,
+//     t = 1'000'000'000'000ULL,
+//     T = 1ULL << 40,
+// };
+
+/**
+ * Remove unsafe chars. Safe chars chosen to allow simple messages/URLs/email
+ * addresses, but avoid anything even possibly remotely dangerous like & or >
+ * @param[in] str    The string to sanitize
+ * @param[in] rule   The set of safe chars to choose (default: least
+ * restrictive)
+ * @return           A new string without unsafe chars
+ */
+// std::string SanitizeString(std::string_view str, int rule =
+// SAFE_CHARS_DEFAULT);
+// /** Parse the hex string into bytes (uint8_t or std::byte). Ignores
+// whitespace.
+//  * Returns nullopt on invalid input. */
+// template <typename Byte = std::byte>
+// std::optional<std::vector<Byte>> TryParseHex(std::string_view str);
+// /** Like TryParseHex, but returns an empty vector on invalid input. */
+// template <typename Byte = uint8_t>
+// std::vector<Byte> ParseHex(std::string_view hex_str) {
+//   return TryParseHex<Byte>(hex_str).value_or(std::vector<Byte>{});
+// }
+// signed char HexDigit(char c);
+// /* Returns true if each character in str is a hex character, and has an even
+//  * number of hex digits.*/
+// bool IsHex(std::string_view str);
+/**
+ * Return true if the string is a hex number, optionally prefixed with "0x"
+ */
+// bool IsHexNumber(std::string_view str);
+std::optional<std::vector<unsigned char>> DecodeBase64(std::string_view str);
+std::string EncodeBase64(Span<const unsigned char> input);
+inline std::string EncodeBase64(Span<const std::byte> input) {
+  return EncodeBase64(MakeUCharSpan(input));
+}
+inline std::string EncodeBase64(std::string_view str) {
+  return EncodeBase64(MakeUCharSpan(str));
+}
+std::optional<std::vector<unsigned char>> DecodeBase32(std::string_view str);
+
+/**
+ * Base32 encode.
+ * If `pad` is true, then the output will be padded with '=' so that its length
+ * is a multiple of 8.
+ */
+std::string EncodeBase32(Span<const unsigned char> input, bool pad = true);
+
+/**
+ * Base32 encode.
+ * If `pad` is true, then the output will be padded with '=' so that its length
+ * is a multiple of 8.
+ */
+std::string EncodeBase32(std::string_view str, bool pad = true);
+
+/**
+ * Splits socket address string into host string and port value.
+ * Validates port value.
+ *
+ * @param[in] in        The socket address string to split.
+ * @param[out] portOut  Port-portion of the input, if found and parsable.
+ * @param[out] hostOut  Host-portion of the input, if found.
+ * @return              true if port-portion is absent or within its allowed
+ * range, otherwise false
+ */
+// bool SplitHostPort(std::string_view in, uint16_t &portOut,
+//                    std::string &hostOut);
+
+// LocaleIndependentAtoi is provided for backwards compatibility reasons.
+//
+// New code should use ToIntegral or the ParseInt* functions
+// which provide parse error feedback.
+//
+// The goal of LocaleIndependentAtoi is to replicate the defined behaviour of
+// std::atoi as it behaves under the "C" locale, and remove some undefined
+// behavior. If the parsed value is bigger than the integer type's maximum
+// value, or smaller than the integer type's minimum value, std::atoi has
+// undefined behavior, while this function returns the maximum or minimum
+// values, respectively.
+// template <typename T> T LocaleIndependentAtoi(std::string_view str) {
+//   static_assert(std::is_integral<T>::value);
+//   T result;
+//   // Emulate atoi(...) handling of white space and leading +/-.
+//   std::string_view s = TrimStringView(str);
+//   if (!s.empty() && s[0] == '+') {
+//     if (s.length() >= 2 && s[1] == '-') {
+//       return 0;
+//     }
+//     s = s.substr(1);
+//   }
+//   auto [_, error_condition] =
+//       std::from_chars(s.data(), s.data() + s.size(), result);
+//   if (error_condition == std::errc::result_out_of_range) {
+//     if (s.length() >= 1 && s[0] == '-') {
+//       // Saturate underflow, per strtoll's behavior.
+//       return std::numeric_limits<T>::min();
+//     } else {
+//       // Saturate overflow, per strtoll's behavior.
+//       return std::numeric_limits<T>::max();
+//     }
+//   } else if (error_condition != std::errc{}) {
+//     return 0;
+//   }
+//   return result;
+// }
+
+/**
+ * Tests if the given character is a decimal digit.
+ * @param[in] c     character to test
+ * @return          true if the argument is a decimal digit; otherwise false.
+ */
+// constexpr bool IsDigit(char c) { return c >= '0' && c <= '9'; }
+
+/**
+ * Tests if the given character is a whitespace character. The whitespace
+ * characters are: space, form-feed ('\f'), newline ('\n'), carriage return
+ * ('\r'), horizontal tab ('\t'), and vertical tab ('\v').
+ *
+ * This function is locale independent. Under the C locale this function gives
+ * the same result as std::isspace.
+ *
+ * @param[in] c     character to test
+ * @return          true if the argument is a whitespace character; otherwise
+ * false
+ */
+// constexpr inline bool IsSpace(char c) noexcept {
+//   return c == ' ' || c == '\f' || c == '\n' || c == '\r' || c == '\t' ||
+//          c == '\v';
+// }
+
+/**
+ * Convert string to integral type T. Leading whitespace, a leading +, or any
+ * trailing character fail the parsing. The required format expressed as regex
+ * is `-?[0-9]+`. The minus sign is only permitted for signed integer types.
+ *
+ * @returns std::nullopt if the entire string could not be parsed, or if the
+ *   parsed value is not in the range representable by the type T.
+ */
+// template <typename T> std::optional<T> ToIntegral(std::string_view str) {
+//   static_assert(std::is_integral<T>::value);
+//   T result;
+//   const auto [first_nonmatching, error_condition] =
+//       std::from_chars(str.data(), str.data() + str.size(), result);
+//   if (first_nonmatching != str.data() + str.size() ||
+//       error_condition != std::errc{}) {
+//     return std::nullopt;
+//   }
+//   return result;
+// }
+
+/**
+ * Convert string to signed 32-bit integer with strict parse error feedback.
+ * @returns true if the entire string could be parsed as valid integer,
+ *   false if not the entire string could be parsed or when overflow or
+ * underflow occurred.
+ */
+/* [[nodiscard]] bool ParseInt32(std::string_view str, int32_t *out); */
+
+/**
+ * Convert string to signed 64-bit integer with strict parse error feedback.
+ * @returns true if the entire string could be parsed as valid integer,
+ *   false if not the entire string could be parsed or when overflow or
+ * underflow occurred.
+ */
+/* [[nodiscard]] bool ParseInt64(std::string_view str, int64_t *out); */
+
+/**
+ * Convert decimal string to unsigned 8-bit integer with strict parse error
+ * feedback.
+ * @returns true if the entire string could be parsed as valid integer,
+ *   false if not the entire string could be parsed or when overflow or
+ * underflow occurred.
+ */
+/* [[nodiscard]] bool ParseUInt8(std::string_view str, uint8_t *out); */
+
+/**
+ * Convert decimal string to unsigned 16-bit integer with strict parse error
+ * feedback.
+ * @returns true if the entire string could be parsed as valid integer,
+ *   false if the entire string could not be parsed or if overflow or underflow
+ * occurred.
+ */
+/* [[nodiscard]] bool ParseUInt16(std::string_view str, uint16_t *out); */
+
+/**
+ * Convert decimal string to unsigned 32-bit integer with strict parse error
+ * feedback.
+ * @returns true if the entire string could be parsed as valid integer,
+ *   false if not the entire string could be parsed or when overflow or
+ * underflow occurred.
+ */
+/* [[nodiscard]] bool ParseUInt32(std::string_view str, uint32_t *out); */
+
+/**
+ * Convert decimal string to unsigned 64-bit integer with strict parse error
+ * feedback.
+ * @returns true if the entire string could be parsed as valid integer,
+ *   false if not the entire string could be parsed or when overflow or
+ * underflow occurred.
+ */
+/* [[nodiscard]] bool ParseUInt64(std::string_view str, uint64_t *out); */
+
+/**
+ * Convert a span of bytes to a lower-case hexadecimal string.
+ */
+// std::string HexStr(const Span<const uint8_t> s);
+// inline std::string HexStr(const Span<const char> s) {
+//   return HexStr(MakeUCharSpan(s));
+// }
+// inline std::string HexStr(const Span<const std::byte> s) {
+//   return HexStr(MakeUCharSpan(s));
+// }
+
+/**
+ * Format a paragraph of text to a fixed width, adding spaces for
+ * indentation to any added line.
+ */
+// std::string FormatParagraph(std::string_view in, size_t width = 79,
+//                             size_t indent = 0);
+
+/**
+ * Timing-attack-resistant comparison.
+ * Takes time proportional to length
+ * of first argument.
+ */
+// template <typename T> bool TimingResistantEqual(const T &a, const T &b) {
+//   if (b.size() == 0)
+//     return a.size() == 0;
+//   size_t accumulator = a.size() ^ b.size();
+//   for (size_t i = 0; i < a.size(); i++)
+//     accumulator |= size_t(a[i] ^ b[i % b.size()]);
+//   return accumulator == 0;
+// }
+
+/** Parse number as fixed point according to JSON number syntax.
+ * @returns true on success, false on error.
+ * @note The result must be in the range (-10^18,10^18), otherwise an overflow
+ * error will trigger.
+ */
+// [[nodiscard]] bool ParseFixedPoint(std::string_view, int decimals,
+//                                    int64_t *amount_out);
+
+namespace {
+/** Helper class for the default infn argument to ConvertBits (just returns
+the
+ * input). */
+struct IntIdentity {
+  [[maybe_unused]] int operator()(int x) const { return x; }
+};
+
+} // namespace
+
+/** Convert from one power-of-2 number base to another. */
+template <int frombits, int tobits, bool pad, typename O, typename It,
+          typename I = IntIdentity>
+bool ConvertBits(O outfn, It it, It end, I infn = {}) {
+  size_t acc = 0;
+  size_t bits = 0;
+  constexpr size_t maxv = (1 << tobits) - 1;
+  constexpr size_t max_acc = (1 << (frombits + tobits - 1)) - 1;
+  while (it != end) {
+    int v = infn(*it);
+    if (v < 0)
+      return false;
+    acc = ((acc << frombits) | v) & max_acc;
+    bits += frombits;
+    while (bits >= tobits) {
+      bits -= tobits;
+      outfn((acc >> bits) & maxv);
+    }
+    ++it;
+  }
+  if (pad) {
+    if (bits)
+      outfn((acc << (tobits - bits)) & maxv);
+  } else if (bits >= frombits || ((acc << (tobits - bits)) & maxv)) {
+    return false;
+  }
+  return true;
+}
+
+/**
+ * Converts the given character to its lowercase equivalent.
+ * This function is locale independent. It only converts uppercase
+ * characters in the standard 7-bit ASCII range.
+ * This is a feature, not a limitation.
+ *
+ * @param[in] c     the character to convert to lowercase.
+ * @return          the lowercase equivalent of c; or the argument
+ *                  if no conversion is possible.
+ */
+// constexpr char ToLower(char c) {
+//   return (c >= 'A' && c <= 'Z' ? (c - 'A') + 'a' : c);
+// }
+
+/**
+ * Returns the lowercase equivalent of the given string.
+ * This function is locale independent. It only converts uppercase
+ * characters in the standard 7-bit ASCII range.
+ * This is a feature, not a limitation.
+ *
+ * @param[in] str   the string to convert to lowercase.
+ * @returns         lowercased equivalent of str
+ */
+// std::string ToLower(std::string_view str);
+//
+/**
+ * Converts the given character to its uppercase equivalent.
+ * This function is locale independent. It only converts lowercase
+ * characters in the standard 7-bit ASCII range.
+ * This is a feature, not a limitation.
+ *
+ * @param[in] c     the character to convert to uppercase.
+ * @return          the uppercase equivalent of c; or the argument
+ *                  if no conversion is possible.
+ */
+constexpr char ToUpper(char c) {
+  return (c >= 'a' && c <= 'z' ? (c - 'a') + 'A' : c);
+}
+
+/**
+ * Returns the uppercase equivalent of the given string.
+ * This function is locale independent. It only converts lowercase
+ * characters in the standard 7-bit ASCII range.
+ * This is a feature, not a limitation.
+ *
+ * @param[in] str   the string to convert to uppercase.
+ * @returns         UPPERCASED EQUIVALENT OF str
+ */
+// std::string ToUpper(std::string_view str);
+//
+/**
+ * Capitalizes the first character of the given string.
+ * This function is locale independent. It only converts lowercase
+ * characters in the standard 7-bit ASCII range.
+ * This is a feature, not a limitation.
+ *
+ * @param[in] str   the string to capitalize.
+ * @returns         string with the first letter capitalized.
+ */
+std::string Capitalize(std::string str);
+
+/**
+ * Parse a string with suffix unit [k|K|m|M|g|G|t|T].
+ * Must be a whole integer, fractions not allowed (0.5t), no whitespace or +-
+ * Lowercase units are 1000 base. Uppercase units are 1024 base.
+ * Examples: 2m,27M,19g,41T
+ *
+ * @param[in] str                  the string to convert into bytes
+ * @param[in] default_multiplier   if no unit is found in str use this unit
+ * @returns                        optional uint64_t bytes from str or nullopt
+ *                                 if ToIntegral is false, str is empty,
+ * trailing whitespace or overflow
+ */
+// std::optional<uint64_t> ParseByteUnits(std::string_view str,
+//                                        ByteUnit default_multiplier);
+
+#endif // BITCOIN_UTIL_STRENCODINGS_H

src/i2p/util/string.h

@@ -0,0 +1,128 @@
+// Copyright (c) 2019-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_STRING_H
+#define BITCOIN_UTIL_STRING_H
+
+#include "spanparsing.h"
+
+#include <array>
+#include <cstdint>
+#include <cstring>
+#include <locale>
+#include <sstream>
+#include <string>      // IWYU pragma: export
+#include <string_view> // IWYU pragma: export
+#include <vector>
+
+void ReplaceAll(std::string& in_out, const std::string& search, const std::string& substitute);
+
+[[nodiscard]] inline std::vector<std::string> SplitString(std::string_view str, char sep)
+{
+    return spanparsing::Split<std::string>(str, sep);
+}
+
+[[nodiscard]] inline std::vector<std::string> SplitString(std::string_view str, std::string_view separators)
+{
+    return spanparsing::Split<std::string>(str, separators);
+}
+
+[[nodiscard]] inline std::string_view TrimStringView(std::string_view str, std::string_view pattern = " \f\n\r\t\v")
+{
+    std::string::size_type front = str.find_first_not_of(pattern);
+    if (front == std::string::npos) {
+        return {};
+    }
+    std::string::size_type end = str.find_last_not_of(pattern);
+    return str.substr(front, end - front + 1);
+}
+
+[[nodiscard]] inline std::string TrimString(std::string_view str, std::string_view pattern = " \f\n\r\t\v")
+{
+    return std::string(TrimStringView(str, pattern));
+}
+
+[[nodiscard]] inline std::string_view RemovePrefixView(std::string_view str, std::string_view prefix)
+{
+    if (str.substr(0, prefix.size()) == prefix) {
+        return str.substr(prefix.size());
+    }
+    return str;
+}
+
+[[nodiscard]] inline std::string RemovePrefix(std::string_view str, std::string_view prefix)
+{
+    return std::string(RemovePrefixView(str, prefix));
+}
+
+/**
+ * Join all container items. Typically used to concatenate strings but accepts
+ * containers with elements of any type.
+ *
+ * @param container The items to join
+ * @param separator The separator
+ * @param unary_op  Apply this operator to each item
+ */
+template <typename C, typename S, typename UnaryOp>
+auto Join(const C& container, const S& separator, UnaryOp unary_op)
+{
+    decltype(unary_op(*container.begin())) ret;
+    bool first{true};
+    for (const auto& item : container) {
+        if (!first) ret += separator;
+        ret += unary_op(item);
+        first = false;
+    }
+    return ret;
+}
+
+template <typename C, typename S>
+auto Join(const C& container, const S& separator)
+{
+    return Join(container, separator, [](const auto& i) { return i; });
+}
+
+/**
+ * Create an unordered multi-line list of items.
+ */
+inline std::string MakeUnorderedList(const std::vector<std::string>& items)
+{
+    return Join(items, "\n", [](const std::string& item) { return "- " + item; });
+}
+
+/**
+ * Check if a string does not contain any embedded NUL (\0) characters
+ */
+[[nodiscard]] inline bool ContainsNoNUL(std::string_view str) noexcept
+{
+    for (auto c : str) {
+        if (c == 0) return false;
+    }
+    return true;
+}
+
+/**
+ * Locale-independent version of std::to_string
+ */
+template <typename T>
+std::string ToString(const T& t)
+{
+    std::ostringstream oss;
+    oss.imbue(std::locale::classic());
+    oss << t;
+    return oss.str();
+}
+
+/**
+ * Check whether a container begins with the given prefix.
+ */
+template <typename T1, size_t PREFIX_LEN>
+[[nodiscard]] inline bool HasPrefix(const T1& obj,
+                                const std::array<uint8_t, PREFIX_LEN>& prefix)
+{
+    return obj.size() >= PREFIX_LEN &&
+           std::equal(std::begin(prefix), std::end(prefix), std::begin(obj));
+}
+
+#endif // BITCOIN_UTIL_STRING_H

src/i2p/util/syserror.cpp

@@ -0,0 +1,63 @@
+// Copyright (c) 2020-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#if defined(HAVE_CONFIG_H)
+#include <config/bitcoin-config.h>
+#endif
+
+#include "../tinyformat.h"
+#include "../util/syserror.h"
+
+#include <cstring>
+#include <string>
+
+#if defined(WIN32)
+#include <codecvt>
+#include <locale>
+#include <windows.h>
+#endif
+
+std::string SysErrorString(int err) {
+  char buf[1024];
+  /* Too bad there are three incompatible implementations of the
+   * thread-safe strerror. */
+  const char *s = nullptr;
+#ifdef WIN32
+  if (strerror_s(buf, sizeof(buf), err) == 0)
+    s = buf;
+#else
+#ifdef STRERROR_R_CHAR_P /* GNU variant can return a pointer outside the       \
+                            passed buffer */
+  s = strerror_r(err, buf, sizeof(buf));
+#else                    /* POSIX variant always returns message in buffer */
+  if (strerror_r(err, buf, sizeof(buf)) == 0)
+    s = buf;
+#endif
+#endif
+  if (s != nullptr) {
+    return tfm::format("%s (%d)", s, err);
+  } else {
+    return tfm::format("Unknown error (%d)", err);
+  }
+}
+
+#if defined(WIN32)
+std::string Win32ErrorString(int err) {
+  wchar_t buf[256];
+  buf[0] = 0;
+  if (FormatMessageW(FORMAT_MESSAGE_FROM_SYSTEM |
+                         FORMAT_MESSAGE_IGNORE_INSERTS |
+                         FORMAT_MESSAGE_MAX_WIDTH_MASK,
+                     nullptr, err, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                     buf, ARRAYSIZE(buf), nullptr)) {
+    return strprintf(
+        "%s (%d)",
+        std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t>()
+            .to_bytes(buf),
+        err);
+  } else {
+    return strprintf("Unknown error (%d)", err);
+  }
+}
+#endif

src/i2p/util/syserror.h

@@ -0,0 +1,20 @@
+// Copyright (c) 2010-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_SYSERROR_H
+#define BITCOIN_UTIL_SYSERROR_H
+
+#include <string>
+
+/** Return system error string from errno value. Use this instead of
+ * std::strerror, which is not thread-safe. For network errors use
+ * NetworkErrorString from sock.h instead.
+ */
+std::string SysErrorString(int err);
+
+#if defined(WIN32)
+std::string Win32ErrorString(int err);
+#endif
+
+#endif // BITCOIN_UTIL_SYSERROR_H

src/i2p/util/threadinterrupt.cpp

@@ -0,0 +1,31 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "threadinterrupt.h"
+
+#include "../sync.h"
+
+CThreadInterrupt::CThreadInterrupt() : flag(false) {}
+
+CThreadInterrupt::operator bool() const {
+  return flag.load(std::memory_order_acquire);
+}
+
+void CThreadInterrupt::reset() { flag.store(false, std::memory_order_release); }
+
+void CThreadInterrupt::operator()() {
+  {
+    LOCK(mut);
+    flag.store(true, std::memory_order_release);
+  }
+  cond.notify_all();
+}
+
+bool CThreadInterrupt::sleep_for(Clock::duration rel_time) {
+  WAIT_LOCK(mut, lock);
+  return !cond.wait_for(lock, rel_time, [this]() {
+    return flag.load(std::memory_order_acquire);
+  });
+}

src/i2p/util/threadinterrupt.h

@@ -0,0 +1,42 @@
+// Copyright (c) 2016-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_THREADINTERRUPT_H
+#define BITCOIN_UTIL_THREADINTERRUPT_H
+
+#include "../sync.h"
+#include "../threadsafety.h"
+
+#include <atomic>
+#include <chrono>
+#include <condition_variable>
+
+/**
+ * A helper class for interruptible sleeps. Calling operator() will interrupt
+ * any current sleep, and after that point operator bool() will return true
+ * until reset.
+ *
+ * This class should not be used in a signal handler. It uses thread
+ * synchronization primitives that are not safe to use with signals. If sending
+ * an interrupt from a signal handler is necessary, the \ref SignalInterrupt
+ * class can be used instead.
+ */
+
+class CThreadInterrupt
+{
+public:
+    using Clock = std::chrono::steady_clock;
+    CThreadInterrupt();
+    explicit operator bool() const;
+    void operator()() EXCLUSIVE_LOCKS_REQUIRED(!mut);
+    void reset();
+    bool sleep_for(Clock::duration rel_time) EXCLUSIVE_LOCKS_REQUIRED(!mut);
+
+private:
+    std::condition_variable cond;
+    Mutex mut;
+    std::atomic<bool> flag;
+};
+
+#endif // BITCOIN_UTIL_THREADINTERRUPT_H

src/i2p/util/time.h

@@ -0,0 +1,122 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_TIME_H
+#define BITCOIN_UTIL_TIME_H
+
+#include <chrono> // IWYU pragma: export
+#include <cstdint>
+#include <string>
+
+using namespace std::chrono_literals;
+
+/** Mockable clock in the context of tests, otherwise the system clock */
+struct NodeClock : public std::chrono::system_clock {
+    using time_point = std::chrono::time_point<NodeClock>;
+    /** Return current system time or mocked time, if set */
+    static time_point now() noexcept;
+    static std::time_t to_time_t(const time_point&) = delete; // unused
+    static time_point from_time_t(std::time_t) = delete;      // unused
+};
+using NodeSeconds = std::chrono::time_point<NodeClock, std::chrono::seconds>;
+
+using SteadyClock = std::chrono::steady_clock;
+using SteadySeconds = std::chrono::time_point<std::chrono::steady_clock, std::chrono::seconds>;
+using SteadyMilliseconds = std::chrono::time_point<std::chrono::steady_clock, std::chrono::milliseconds>;
+using SteadyMicroseconds = std::chrono::time_point<std::chrono::steady_clock, std::chrono::microseconds>;
+
+using SystemClock = std::chrono::system_clock;
+
+void UninterruptibleSleep(const std::chrono::microseconds& n);
+
+/**
+ * Helper to count the seconds of a duration/time_point.
+ *
+ * All durations/time_points should be using std::chrono and calling this should generally
+ * be avoided in code. Though, it is still preferred to an inline t.count() to
+ * protect against a reliance on the exact type of t.
+ *
+ * This helper is used to convert durations/time_points before passing them over an
+ * interface that doesn't support std::chrono (e.g. RPC, debug log, or the GUI)
+ */
+template <typename Dur1, typename Dur2>
+constexpr auto Ticks(Dur2 d)
+{
+    return std::chrono::duration_cast<Dur1>(d).count();
+}
+template <typename Duration, typename Timepoint>
+constexpr auto TicksSinceEpoch(Timepoint t)
+{
+    return Ticks<Duration>(t.time_since_epoch());
+}
+constexpr int64_t count_seconds(std::chrono::seconds t) { return t.count(); }
+constexpr int64_t count_milliseconds(std::chrono::milliseconds t) { return t.count(); }
+constexpr int64_t count_microseconds(std::chrono::microseconds t) { return t.count(); }
+
+using HoursDouble = std::chrono::duration<double, std::chrono::hours::period>;
+using SecondsDouble = std::chrono::duration<double, std::chrono::seconds::period>;
+using MillisecondsDouble = std::chrono::duration<double, std::chrono::milliseconds::period>;
+
+/**
+ * DEPRECATED
+ * Use either ClockType::now() or Now<TimePointType>() if a cast is needed.
+ * ClockType is
+ * - SteadyClock/std::chrono::steady_clock for steady time
+ * - SystemClock/std::chrono::system_clock for system time
+ * - NodeClock                             for mockable system time
+ */
+int64_t GetTime();
+
+/**
+ * DEPRECATED
+ * Use SetMockTime with chrono type
+ *
+ * @param[in] nMockTimeIn Time in seconds.
+ */
+void SetMockTime(int64_t nMockTimeIn);
+
+/** For testing. Set e.g. with the setmocktime rpc, or -mocktime argument */
+void SetMockTime(std::chrono::seconds mock_time_in);
+
+/** For testing */
+std::chrono::seconds GetMockTime();
+
+/**
+ * Return the current time point cast to the given precision. Only use this
+ * when an exact precision is needed, otherwise use T::clock::now() directly.
+ */
+template <typename T>
+T Now()
+{
+    return std::chrono::time_point_cast<typename T::duration>(T::clock::now());
+}
+/** DEPRECATED, see GetTime */
+template <typename T>
+T GetTime()
+{
+    return Now<std::chrono::time_point<NodeClock, T>>().time_since_epoch();
+}
+
+/**
+ * ISO 8601 formatting is preferred. Use the FormatISO8601{DateTime,Date}
+ * helper functions if possible.
+ */
+std::string FormatISO8601DateTime(int64_t nTime);
+std::string FormatISO8601Date(int64_t nTime);
+
+/**
+ * Convert milliseconds to a struct timeval for e.g. select.
+ */
+struct timeval MillisToTimeval(int64_t nTimeout);
+
+/**
+ * Convert milliseconds to a struct timeval for e.g. select.
+ */
+struct timeval MillisToTimeval(std::chrono::milliseconds ms);
+
+/** Sanity check epoch match normal Unix epoch */
+bool ChronoSanityCheck();
+
+#endif // BITCOIN_UTIL_TIME_H

src/i2p/util/vector.h

@@ -0,0 +1,78 @@
+// Copyright (c) 2019-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_VECTOR_H
+#define BITCOIN_UTIL_VECTOR_H
+
+#include <functional>
+#include <initializer_list>
+#include <optional>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+/** Construct a vector with the specified elements.
+ *
+ * This is preferable over the list initializing constructor of std::vector:
+ * - It automatically infers the element type from its arguments.
+ * - If any arguments are rvalue references, they will be moved into the vector
+ *   (list initialization always copies).
+ */
+template <typename... Args>
+inline std::vector<typename std::common_type<Args...>::type>
+Vector(Args &&...args) {
+  std::vector<typename std::common_type<Args...>::type> ret;
+  ret.reserve(sizeof...(args));
+  // The line below uses the trick from
+  // https://www.experts-exchange.com/articles/32502/None-recursive-variadic-templates-with-std-initializer-list.html
+  (void)std::initializer_list<int>{
+      (ret.emplace_back(std::forward<Args>(args)), 0)...};
+  return ret;
+}
+
+/** Concatenate two vectors, moving elements. */
+template <typename V> inline V Cat(V v1, V &&v2) {
+  v1.reserve(v1.size() + v2.size());
+  for (auto &arg : v2) {
+    v1.push_back(std::move(arg));
+  }
+  return v1;
+}
+
+/** Concatenate two vectors. */
+template <typename V> inline V Cat(V v1, const V &v2) {
+  v1.reserve(v1.size() + v2.size());
+  for (const auto &arg : v2) {
+    v1.push_back(arg);
+  }
+  return v1;
+}
+
+/** Clear a vector (or std::deque) and release its allocated memory. */
+template <typename V> inline void ClearShrink(V &v) noexcept {
+  // There are various ways to clear a vector and release its memory:
+  //
+  // 1. V{}.swap(v)
+  // 2. v = V{}
+  // 3. v = {}; v.shrink_to_fit();
+  // 4. v.clear(); v.shrink_to_fit();
+  //
+  // (2) does not appear to release memory in glibc debug mode, even if
+  // v.shrink_to_fit() follows. (3) and (4) rely on std::vector::shrink_to_fit,
+  // which is only a non-binding request. Therefore, we use method (1).
+
+  V{}.swap(v);
+}
+
+template <typename V, typename L>
+inline std::optional<V> FindFirst(const std::vector<V> &vec, const L fnc) {
+  for (const auto &el : vec) {
+    if (fnc(el)) {
+      return el;
+    }
+  }
+  return std::nullopt;
+}
+
+#endif // BITCOIN_UTIL_VECTOR_H