From 1419745a5d848ac283225230d1a76209253a4d61 Mon Sep 17 00:00:00 2001
From: orignal <i2porignal@yandex.ru>
Date: Thu, 17 Oct 2024 21:09:37 -0400
Subject: [PATCH] recognize symmetric NAT from peer test msg 7

---
 libi2pd/SSU2OutOfSession.cpp | 29 +++++++++++++++++++++++++++++
 libi2pd/SSU2OutOfSession.h   |  2 ++
 libi2pd/SSU2Session.h        |  5 +++--
 3 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/libi2pd/SSU2OutOfSession.cpp b/libi2pd/SSU2OutOfSession.cpp
index c337938e..262f93a9 100644
--- a/libi2pd/SSU2OutOfSession.cpp
+++ b/libi2pd/SSU2OutOfSession.cpp
@@ -65,6 +65,12 @@ namespace transport
 		return true;
 	}	
 
+	void SSU2PeerTestSession::HandleAddress (const uint8_t * buf, size_t len)
+	{
+		if (!ExtractEndpoint (buf, len, m_OurEndpoint))
+			LogPrint (eLogWarning, "SSU2: Can't hanlde address block from peer test message");
+	}	
+		
 	void SSU2PeerTestSession::HandlePeerTest (const uint8_t * buf, size_t len)
 	{
 		// msgs 5-7
@@ -112,6 +118,29 @@ namespace transport
 			case 7: // Alice from Charlie 2
 			{	
 				m_PeerTestResendTimer.cancel (); // no more msg 6 resends
+				if (m_MsgNumReceived < 5 && m_OurEndpoint.port ()) // msg 5 was not received
+				{
+					if (m_OurEndpoint.address ().is_v4 ()) // ipv4
+					{
+						if (i2p::context.GetStatus () == eRouterStatusFirewalled)
+						{	
+						    if (m_OurEndpoint.port () != GetServer ().GetPort (true))
+								i2p::context.SetError (eRouterErrorSymmetricNAT);
+							else if (i2p::context.GetError () == eRouterErrorSymmetricNAT)
+								i2p::context.SetError (eRouterErrorNone);
+						}
+					}	
+					else
+					{
+						if (i2p::context.GetStatusV6 () == eRouterStatusFirewalled)
+						{	
+						    if (m_OurEndpoint.port () != GetServer ().GetPort (false))
+								i2p::context.SetErrorV6 (eRouterErrorSymmetricNAT);
+							else if (i2p::context.GetErrorV6 () == eRouterErrorSymmetricNAT)
+								i2p::context.SetErrorV6 (eRouterErrorNone);
+						}
+					}	
+				}	
 				GetServer ().AddConnectedRecently (GetRemoteEndpoint (), i2p::util::GetSecondsSinceEpoch ());
 				GetServer ().RequestRemoveSession (GetConnID ());	
 				break;
diff --git a/libi2pd/SSU2OutOfSession.h b/libi2pd/SSU2OutOfSession.h
index 6f2a9fbd..e8c55c3c 100644
--- a/libi2pd/SSU2OutOfSession.h
+++ b/libi2pd/SSU2OutOfSession.h
@@ -41,6 +41,7 @@ namespace transport
 			void SendPeerTest (uint8_t msg, const uint8_t * signedData, size_t signedDataLen, bool delayed = false); // PeerTest message
 			void SendPeerTest (uint8_t msg); // send or resend m_SignedData
 			void HandlePeerTest (const uint8_t * buf, size_t len) override;
+			void HandleAddress (const uint8_t * buf, size_t len) override;
 
 			void ScheduleResend (uint8_t msg);
 			
@@ -50,6 +51,7 @@ namespace transport
 			bool m_IsConnectedRecently, m_IsStatusChanged;
 			std::vector<uint8_t> m_SignedData; // for resends
 			boost::asio::deadline_timer m_PeerTestResendTimer;
+			boost::asio::ip::udp::endpoint m_OurEndpoint; // as seen by peer
 	};	
 
 	const int SSU2_HOLE_PUNCH_RESEND_INTERVAL = 1000; // in milliseconds
diff --git a/libi2pd/SSU2Session.h b/libi2pd/SSU2Session.h
index ae0f18f4..e27671f8 100644
--- a/libi2pd/SSU2Session.h
+++ b/libi2pd/SSU2Session.h
@@ -296,6 +296,8 @@ namespace transport
 			size_t CreateAddressBlock (uint8_t * buf, size_t len, const boost::asio::ip::udp::endpoint& ep);
 			size_t CreatePaddingBlock (uint8_t * buf, size_t len, size_t minSize = 0);
 			size_t CreatePeerTestBlock (uint8_t * buf, size_t len, uint8_t msg, SSU2PeerTestCode code, const uint8_t * routerHash, const uint8_t * signedData, size_t signedDataLen);
+
+			bool ExtractEndpoint (const uint8_t * buf, size_t size, boost::asio::ip::udp::endpoint& ep);
 			
 		private:
 
@@ -328,8 +330,7 @@ namespace transport
 			void HandleRouterInfo (const uint8_t * buf, size_t len);
 			void HandleAck (const uint8_t * buf, size_t len);
 			void HandleAckRange (uint32_t firstPacketNum, uint32_t lastPacketNum, uint64_t ts);
-			void HandleAddress (const uint8_t * buf, size_t len);
-			bool ExtractEndpoint (const uint8_t * buf, size_t size, boost::asio::ip::udp::endpoint& ep);
+			virtual void HandleAddress (const uint8_t * buf, size_t len);
 			size_t CreateEndpoint (uint8_t * buf, size_t len, const boost::asio::ip::udp::endpoint& ep);
 			std::shared_ptr<const i2p::data::RouterInfo::Address> FindLocalAddress () const;
 			void AdjustMaxPayloadSize ();