Adding Dandelion++ support to public networks:

- New flag in NOTIFY_NEW_TRANSACTION to indicate stem mode
  - Stem loops detected in tx_pool.cpp
  - Embargo timeout for a blackhole attack during stem phase

src/cryptonote_basic/verification_context.h

@@ -29,6 +29,9 @@
 // Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
 
 #pragma once
+
+#include "cryptonote_protocol/enums.h"
+
 namespace cryptonote
 {
   /************************************************************************/
@@ -36,7 +39,9 @@ namespace cryptonote
   /************************************************************************/
   struct tx_verification_context
   {
-    bool m_should_be_relayed;
+    static_assert(unsigned(relay_method::none) == 0, "default m_relay initialization is not to relay_method::none");
+
+    relay_method m_relay; // gives indication on how tx should be relayed (if at all)
     bool m_verifivation_failed; //bad tx, should drop connection
     bool m_verifivation_impossible; //the transaction is related with an alternative blockchain
     bool m_added_to_pool;