cryptonote core/protocol: don't drop peers for soft offenses

src/cryptonote_basic/verification_context.h

@@ -42,7 +42,12 @@ namespace cryptonote
     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_failed; //bad tx, tx should not enter mempool and connection should be dropped unless m_no_drop_offense
+    // Do not add to mempool, do not relay, but also do not punish the peer for sending or drop
+    // connections to them. Used for low fees, tx_extra too big, "relay-only rules". Not to be
+    // confused with breaking soft fork rules, because tx could be later added to the chain if mined
+    // because it does not violate consensus rules.
+    bool m_no_drop_offense;
     bool m_verifivation_impossible; //the transaction is related with an alternative blockchain
     bool m_added_to_pool; 
     bool m_low_mixin;

src/cryptonote_core/cryptonote_core.cpp

@@ -1099,7 +1099,7 @@ namespace cryptonote
       else if(tvc[i].m_verifivation_impossible)
       {MERROR_VER("Transaction verification impossible: " << results[i].hash);}
 
-      if(tvc[i].m_added_to_pool)
+      if(tvc[i].m_added_to_pool && results[i].tx.extra.size() <= MAX_TX_EXTRA_SIZE)
       {
         MDEBUG("tx added: " << results[i].hash);
         valid_events = true;

src/cryptonote_core/tx_pool.cpp

@@ -212,6 +212,7 @@ namespace cryptonote
     {
       tvc.m_verifivation_failed = true;
       tvc.m_fee_too_low = true;
+      tvc.m_no_drop_offense = true;
       return false;
     }
 
@@ -230,6 +231,7 @@ namespace cryptonote
       LOG_PRINT_L1("transaction tx-extra is too big: " << tx_extra_size << " bytes, the limit is: " << MAX_TX_EXTRA_SIZE);
       tvc.m_verifivation_failed = true;
       tvc.m_tx_extra_too_big = true;
+      tvc.m_no_drop_offense = true;
       return false;
     }
 

src/cryptonote_protocol/cryptonote_protocol_handler.inl

@@ -1020,7 +1020,7 @@ namespace cryptonote
     for (auto& tx : arg.txs)
     {
       tx_verification_context tvc{};
-      if (!m_core.handle_incoming_tx({tx, crypto::null_hash}, tvc, tx_relay, true))
+      if (!m_core.handle_incoming_tx({tx, crypto::null_hash}, tvc, tx_relay, true) && !tvc.m_no_drop_offense)
       {
         LOG_PRINT_CCONTEXT_L1("Tx verification failed, dropping connection");
         drop_connection(context, false, false);