rpc: new function and RPC to get alternative chain info

src/cryptonote_core/blockchain.cpp

@@ -3880,6 +3880,38 @@ std::map<uint64_t, std::tuple<uint64_t, uint64_t, uint64_t>> Blockchain:: get_ou
   return m_db->get_output_histogram(amounts, unlocked, recent_cutoff);
 }
 
+std::list<std::pair<Blockchain::block_extended_info,uint64_t>> Blockchain::get_alternative_chains() const
+{
+  std::list<std::pair<Blockchain::block_extended_info,uint64_t>> chains;
+
+  for (const auto &i: m_alternative_chains)
+  {
+    const crypto::hash &top = i.first;
+    bool found = false;
+    for (const auto &j: m_alternative_chains)
+    {
+      if (j.second.bl.prev_id == top)
+      {
+        found = true;
+        break;
+      }
+    }
+    if (!found)
+    {
+      uint64_t length = 1;
+      auto h = i.second.bl.prev_id;
+      blocks_ext_by_hash::const_iterator prev;
+      while ((prev = m_alternative_chains.find(h)) != m_alternative_chains.end())
+      {
+        h = prev->second.bl.prev_id;
+        ++length;
+      }
+      chains.push_back(std::make_pair(i.second, length));
+    }
+  }
+  return chains;
+}
+
 void Blockchain::cancel()
 {
   m_cancel = true;

src/cryptonote_core/blockchain.h

@@ -844,6 +844,13 @@ namespace cryptonote
     void block_longhash_worker(const uint64_t height, const std::vector<block> &blocks,
         std::unordered_map<crypto::hash, crypto::hash> &map) const;
 
+    /**
+     * @brief returns a set of known alternate chains
+     *
+     * @return a list of chains
+     */
+    std::list<std::pair<block_extended_info,uint64_t>> get_alternative_chains() const;
+
     void cancel();
 
   private:

src/daemon/command_parser_executor.cpp

@@ -482,4 +482,15 @@ bool t_command_parser_executor::print_coinbase_tx_sum(const std::vector<std::str
   return m_executor.print_coinbase_tx_sum(height, count);
 }
 
+bool t_command_parser_executor::alt_chain_info(const std::vector<std::string>& args)
+{
+  if(args.size())
+  {
+    std::cout << "No parameters allowed" << std::endl;
+    return false;
+  }
+
+  return m_executor.alt_chain_info();
+}
+
 } // namespace daemonize

src/daemon/command_parser_executor.h

@@ -119,6 +119,8 @@ public:
   bool output_histogram(const std::vector<std::string>& args);
 
   bool print_coinbase_tx_sum(const std::vector<std::string>& args);
+
+  bool alt_chain_info(const std::vector<std::string>& args);
 };
 
 } // namespace daemonize

src/daemon/command_server.cpp

@@ -225,6 +225,11 @@ t_command_server::t_command_server(
     , std::bind(&t_command_parser_executor::print_coinbase_tx_sum, &m_parser, p::_1)
     , "Print sum of coinbase transactions (start height, block count)"
     );
+    m_command_lookup.set_handler(
+      "alt_chain_info"
+    , std::bind(&t_command_parser_executor::alt_chain_info, &m_parser, p::_1)
+    , "Print information about alternative chains"
+    );
 }
 
 bool t_command_server::process_command_str(const std::string& cmd)

src/daemon/rpc_command_executor.cpp

@@ -1367,5 +1367,38 @@ bool t_rpc_command_executor::print_coinbase_tx_sum(uint64_t height, uint64_t cou
   return true;
 }
 
+bool t_rpc_command_executor::alt_chain_info()
+{
+  cryptonote::COMMAND_RPC_GET_ALTERNATE_CHAINS::request req;
+  cryptonote::COMMAND_RPC_GET_ALTERNATE_CHAINS::response res;
+  epee::json_rpc::error error_resp;
+
+  std::string fail_message = "Unsuccessful";
+
+  if (m_is_rpc)
+  {
+    if (!m_rpc_client->json_rpc_request(req, res, "get_alternate_chains", fail_message.c_str()))
+    {
+      return true;
+    }
+  }
+  else
+  {
+    if (!m_rpc_server->on_get_alternate_chains(req, res, error_resp))
+    {
+      tools::fail_msg_writer() << fail_message.c_str();
+      return true;
+    }
+  }
+
+  tools::msg_writer() << boost::lexical_cast<std::string>(res.chains.size()) << " alternate chains found:";
+  for (const auto chain: res.chains)
+  {
+    tools::msg_writer() << chain.length << " blocks long, branching at height " << (chain.height - chain.length + 1)
+        << ", difficulty " << chain.difficulty << ": " << chain.block_hash;
+  }
+  return true;
+}
+
 
 }// namespace daemonize

src/daemon/rpc_command_executor.h

@@ -137,6 +137,8 @@ public:
   bool output_histogram(uint64_t min_count, uint64_t max_count);
 
   bool print_coinbase_tx_sum(uint64_t height, uint64_t count);
+
+  bool alt_chain_info();
 };
 
 } // namespace daemonize

src/rpc/core_rpc_server.cpp

@@ -1337,6 +1337,24 @@ namespace cryptonote
     return true;
   }
   //------------------------------------------------------------------------------------------------------------------------------
+  bool core_rpc_server::on_get_alternate_chains(const COMMAND_RPC_GET_ALTERNATE_CHAINS::request& req, COMMAND_RPC_GET_ALTERNATE_CHAINS::response& res, epee::json_rpc::error& error_resp)
+  {
+    try
+    {
+      std::list<std::pair<Blockchain::block_extended_info, uint64_t>> chains = m_core.get_blockchain_storage().get_alternative_chains();
+      for (const auto &i: chains)
+      {
+        res.chains.push_back(COMMAND_RPC_GET_ALTERNATE_CHAINS::chain_info{epee::string_tools::pod_to_hex(get_block_hash(i.first.bl)), i.first.height, i.second, i.first.cumulative_difficulty});
+      }
+      res.status = CORE_RPC_STATUS_OK;
+    }
+    catch (...)
+    {
+      res.status = "Error retrieving alternate chains";
+    }
+    return true;
+  }
+  //------------------------------------------------------------------------------------------------------------------------------
   bool core_rpc_server::on_out_peers(const COMMAND_RPC_OUT_PEERS::request& req, COMMAND_RPC_OUT_PEERS::response& res)
   {
 	  // TODO

src/rpc/core_rpc_server.h

@@ -118,6 +118,7 @@ namespace cryptonote
         MAP_JON_RPC_WE("get_version",            on_get_version,                COMMAND_RPC_GET_VERSION)
         MAP_JON_RPC_WE("get_coinbase_tx_sum",    on_get_coinbase_tx_sum,        COMMAND_RPC_GET_COINBASE_TX_SUM)
         MAP_JON_RPC_WE("get_fee_estimate",       on_get_per_kb_fee_estimate,    COMMAND_RPC_GET_PER_KB_FEE_ESTIMATE)
+        MAP_JON_RPC_WE_IF("get_alternate_chains",on_get_alternate_chains,       COMMAND_RPC_GET_ALTERNATE_CHAINS, !m_restricted)
       END_JSON_RPC_MAP()
     END_URI_MAP2()
 
@@ -166,6 +167,7 @@ namespace cryptonote
     bool on_get_version(const COMMAND_RPC_GET_VERSION::request& req, COMMAND_RPC_GET_VERSION::response& res, epee::json_rpc::error& error_resp);
     bool on_get_coinbase_tx_sum(const COMMAND_RPC_GET_COINBASE_TX_SUM::request& req, COMMAND_RPC_GET_COINBASE_TX_SUM::response& res, epee::json_rpc::error& error_resp);
     bool on_get_per_kb_fee_estimate(const COMMAND_RPC_GET_PER_KB_FEE_ESTIMATE::request& req, COMMAND_RPC_GET_PER_KB_FEE_ESTIMATE::response& res, epee::json_rpc::error& error_resp);
+    bool on_get_alternate_chains(const COMMAND_RPC_GET_ALTERNATE_CHAINS::request& req, COMMAND_RPC_GET_ALTERNATE_CHAINS::response& res, epee::json_rpc::error& error_resp);
     //-----------------------
 
 private:

src/rpc/core_rpc_server_commands_defs.h

@@ -1336,4 +1336,39 @@ namespace cryptonote
       END_KV_SERIALIZE_MAP()
     };
   };
+
+  struct COMMAND_RPC_GET_ALTERNATE_CHAINS
+  {
+    struct request
+    {
+      BEGIN_KV_SERIALIZE_MAP()
+      END_KV_SERIALIZE_MAP()
+    };
+
+    struct chain_info
+    {
+      std::string block_hash;
+      uint64_t height;
+      uint64_t length;
+      uint64_t difficulty;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(block_hash)
+        KV_SERIALIZE(height)
+        KV_SERIALIZE(length)
+        KV_SERIALIZE(difficulty)
+      END_KV_SERIALIZE_MAP()
+    };
+
+    struct response
+    {
+      std::string status;
+      std::list<chain_info> chains;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(status)
+        KV_SERIALIZE(chains)
+      END_KV_SERIALIZE_MAP()
+    };
+  };
 }