check if we connected recently to an endpoint before sending peer test

libi2pd/SSU2.cpp

@@ -210,6 +210,22 @@ namespace transport
 		return ep.port ();
 	}
 
+	bool SSU2Server::IsConnectedRecently (const boost::asio::ip::udp::endpoint& ep) const
+	{
+		if (!ep.port () || ep.address ().is_unspecified ()) return false;
+		auto it = m_ConnectedRecently.find (ep);
+		if (it != m_ConnectedRecently.end ())
+			return i2p::util::GetSecondsSinceEpoch () <= it->second + SSU2_HOLE_PUNCH_EXPIRATION;
+		return false;
+	}	
+
+	void SSU2Server::AddConnectedRecently (const boost::asio::ip::udp::endpoint& ep, uint64_t ts)
+	{
+		if (!ep.port () || ep.address ().is_unspecified () || 
+		    i2p::util::GetSecondsSinceEpoch () > ts + SSU2_HOLE_PUNCH_EXPIRATION) return;
+		m_ConnectedRecently.try_emplace (ep, ts);
+	}	
+		
 	void SSU2Server::AdjustTimeOffset (int64_t offset, std::shared_ptr<const i2p::data::IdentityEx> from)
 	{
 		if (offset)
@@ -1001,6 +1017,14 @@ namespace transport
 					it++;
 			}
 
+			for (auto it = m_ConnectedRecently.begin (); it != m_ConnectedRecently.end (); )
+			{
+				if (ts > it->second + SSU2_HOLE_PUNCH_EXPIRATION)
+					it = m_ConnectedRecently.erase (it);
+				else
+					it++;
+			}	
+			
 			m_PacketsPool.CleanUpMt ();
 			m_SentPacketsPool.CleanUp ();
 			m_IncompleteMessagesPool.CleanUp ();

libi2pd/SSU2.h

@@ -39,6 +39,7 @@ namespace transport
 	const int SSU2_KEEP_ALIVE_INTERVAL = 15; // in seconds
 	const int SSU2_KEEP_ALIVE_INTERVAL_VARIANCE = 4; // in seconds
 	const int SSU2_PROXY_CONNECT_RETRY_TIMEOUT = 30; // in seconds
+	const int SSU2_HOLE_PUNCH_EXPIRATION = 20; // in seconds
 
 	class SSU2Server: private i2p::util::RunnableServiceWithWork
 	{
@@ -72,6 +73,8 @@ namespace transport
 			bool UsesProxy () const { return m_IsThroughProxy; };
 			bool IsSupported (const boost::asio::ip::address& addr) const;
 			uint16_t GetPort (bool v4) const;
+			bool IsConnectedRecently (const boost::asio::ip::udp::endpoint& ep) const;
+			void AddConnectedRecently (const boost::asio::ip::udp::endpoint& ep, uint64_t ts);
 			std::mt19937& GetRng () { return m_Rng; }
 			bool IsMaxNumIntroducers (bool v4) const { return (v4 ? m_Introducers.size () : m_IntroducersV6.size ()) >= SSU2_MAX_NUM_INTRODUCERS; }
 			bool IsSyncClockFromPeers () const { return m_IsSyncClockFromPeers; };
@@ -160,7 +163,7 @@ namespace transport
 			std::map<boost::asio::ip::udp::endpoint, std::shared_ptr<SSU2Session> > m_PendingOutgoingSessions;
 			mutable std::mutex m_PendingOutgoingSessionsMutex;
 			std::map<boost::asio::ip::udp::endpoint, std::pair<uint64_t, uint32_t> > m_IncomingTokens, m_OutgoingTokens; // remote endpoint -> (token, expires in seconds)
-			std::map<uint32_t, std::shared_ptr<SSU2Session> > m_Relays; // we are introducer, relay tag -> session
+			std::unordered_map<uint32_t, std::shared_ptr<SSU2Session> > m_Relays; // we are introducer, relay tag -> session
 			std::list<i2p::data::IdentHash> m_Introducers, m_IntroducersV6; // introducers we are connected to
 			i2p::util::MemoryPoolMt<Packet> m_PacketsPool;
 			i2p::util::MemoryPool<SSU2SentPacket> m_SentPacketsPool;
@@ -174,6 +177,7 @@ namespace transport
 			int64_t m_PendingTimeOffset; // during peer test
 			std::shared_ptr<const i2p::data::IdentityEx> m_PendingTimeOffsetFrom;
 			std::mt19937 m_Rng;
+			std::map<boost::asio::ip::udp::endpoint, uint64_t> m_ConnectedRecently; // endpoint -> last activity time in seconds
 		
 			// proxy
 			bool m_IsThroughProxy;

libi2pd/SSU2Session.cpp

@@ -265,6 +265,7 @@ namespace transport
 			m_OnEstablished = nullptr;
 			if (m_RelayTag)
 				m_Server.RemoveRelay (m_RelayTag);
+			m_Server.AddConnectedRecently (m_RemoteEndpoint, GetLastActivityTimestamp ());
 			m_SentHandshakePacket.reset (nullptr);
 			m_SessionConfirmedFragment.reset (nullptr);
 			m_PathChallenge.reset (nullptr);
@@ -281,14 +282,10 @@ namespace transport
 			transports.PeerDisconnected (shared_from_this ());
 			auto remoteIdentity = GetRemoteIdentity ();
 			if (remoteIdentity)
-			{
 				LogPrint (eLogDebug, "SSU2: Session with ", GetRemoteEndpoint (),
 					" (", i2p::data::GetIdentHashAbbreviation (remoteIdentity->GetIdentHash ()), ") terminated");
-			}
 			else
-			{
 				LogPrint (eLogDebug, "SSU2: Session with ", GetRemoteEndpoint (), " terminated");
-			}
 		}
 	}
 
@@ -1153,7 +1150,7 @@ namespace transport
 			if (profile) // older router?
 				profile->Duplicated (); // mark router as duplicated in profile
 			else	
-				LogPrint (eLogError, "SSU2: Host mismatch between published address ", m_Address->host,
+				LogPrint (eLogInfo, "SSU2: Host mismatch between published address ", m_Address->host,
 					" and actual endpoint ", m_RemoteEndpoint.address (), " from ", i2p::data::GetIdentHashAbbreviation (ri->GetIdentHash ()));
 			return false;
 		}
@@ -2276,14 +2273,19 @@ namespace transport
 								if (addr && m_Server.IsSupported (ep.address ()) && 
 								    i2p::context.GetRouterInfo ().IsSSU2PeerTesting (ep.address ().is_v4 ()))
 								{
-									// send msg 5 to Alice
-									auto session = std::make_shared<SSU2Session> (m_Server, r, addr);
-									session->SetState (eSSU2SessionStatePeerTest);
-									session->m_RemoteEndpoint = ep; // might be different
-									session->m_DestConnID = htobe64 (((uint64_t)nonce << 32) | nonce);
-									session->m_SourceConnID = ~session->m_DestConnID;
-									m_Server.AddSession (session);
-									session->SendPeerTest (5, newSignedData.data (), newSignedData.size (), addr->i);
+									if (!m_Server.IsConnectedRecently (ep)) // no alive hole punch
+									{	
+										// send msg 5 to Alice
+										auto session = std::make_shared<SSU2Session> (m_Server, r, addr);
+										session->SetState (eSSU2SessionStatePeerTest);
+										session->m_RemoteEndpoint = ep; // might be different
+										session->m_DestConnID = htobe64 (((uint64_t)nonce << 32) | nonce);
+										session->m_SourceConnID = ~session->m_DestConnID;
+										m_Server.AddSession (session);
+										session->SendPeerTest (5, newSignedData.data (), newSignedData.size (), addr->i);
+									}
+									else
+										code = eSSU2PeerTestCodeCharlieAliceIsAlreadyConnected;
 								}
 								else
 									code = eSSU2PeerTestCodeCharlieUnsupportedAddress;