From 3bdef5f58dad4237a9e6040583d256426452d2fb Mon Sep 17 00:00:00 2001
From: orignal <i2porignal@yandex.ru>
Date: Wed, 7 Sep 2022 19:11:33 -0400
Subject: [PATCH] update remote endpoint and send path challenge

---
 libi2pd/SSU2.cpp        |  4 ++--
 libi2pd/SSU2Session.cpp | 22 +++++++++++++++++++++-
 libi2pd/SSU2Session.h   |  3 ++-
 3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/libi2pd/SSU2.cpp b/libi2pd/SSU2.cpp
index 156bc2b0..245169d8 100644
--- a/libi2pd/SSU2.cpp
+++ b/libi2pd/SSU2.cpp
@@ -410,7 +410,7 @@ namespace transport
 			{
 				case eSSU2SessionStateEstablished:
 				case eSSU2SessionStateSessionConfirmedSent:	
-					m_LastSession->ProcessData (buf, len);
+					m_LastSession->ProcessData (buf, len, senderEndpoint);
 				break;
 				case eSSU2SessionStateSessionCreatedSent:
 					if (!m_LastSession->ProcessSessionConfirmed (buf, len))
@@ -437,7 +437,7 @@ namespace transport
 					m_LastSession->ProcessPeerTest (buf, len);
 				break;
 				case eSSU2SessionStateClosing:
-					m_LastSession->ProcessData (buf, len); // we might receive termintaion block
+					m_LastSession->ProcessData (buf, len, senderEndpoint); // we might receive termintaion block
 					if (m_LastSession && m_LastSession->GetState () != eSSU2SessionStateTerminated)
 						m_LastSession->RequestTermination (eSSU2TerminationReasonIdleTimeout); // send termination again
 				break;	
diff --git a/libi2pd/SSU2Session.cpp b/libi2pd/SSU2Session.cpp
index 4df9a076..e5430054 100644
--- a/libi2pd/SSU2Session.cpp
+++ b/libi2pd/SSU2Session.cpp
@@ -1301,7 +1301,7 @@ namespace transport
 		return m_SendPacketNum - 1;
 	}
 
-	void SSU2Session::ProcessData (uint8_t * buf, size_t len)
+	void SSU2Session::ProcessData (uint8_t * buf, size_t len, const boost::asio::ip::udp::endpoint& from)
 	{
 		Header header;
 		header.ll[0] = m_SourceConnID;
@@ -1316,6 +1316,12 @@ namespace transport
 				ResendHandshakePacket (); // assume we receive
 			return;
 		}
+		if (from != m_RemoteEndpoint)
+		{
+			LogPrint (eLogInfo, "SSU2: Remote endpoint update ", m_RemoteEndpoint, "->", from);
+			m_RemoteEndpoint = from;
+			SendPathChallenge ();
+		}	
 		uint8_t payload[SSU2_MAX_PACKET_SIZE];
 		size_t payloadSize = len - 32;
 		uint32_t packetNum = be32toh (header.h.packetNum);
@@ -2625,6 +2631,20 @@ namespace transport
 		memcpy (payload + 3, data, len);
 		SendData (payload, len + 3);
 	}	
+
+	void SSU2Session::SendPathChallenge ()
+	{
+		uint8_t payload[SSU2_MAX_PACKET_SIZE];
+		payload[0] = eSSU2BlkPathChallenge;
+		size_t len = rand () % (m_MaxPayloadSize - 3);
+		htobe16buf (payload + 1, len);
+		if (len > 0)
+			RAND_bytes (payload + 3, len);
+		len += 3;
+		if (len < m_MaxPayloadSize)
+			len += CreatePaddingBlock (payload + len, m_MaxPayloadSize - len);
+		SendData (payload, len);
+	}	
 		
 	void SSU2Session::CleanUp (uint64_t ts)
 	{
diff --git a/libi2pd/SSU2Session.h b/libi2pd/SSU2Session.h
index 72211bf6..a7aa5557 100644
--- a/libi2pd/SSU2Session.h
+++ b/libi2pd/SSU2Session.h
@@ -255,7 +255,7 @@ namespace transport
 			bool ProcessRetry (uint8_t * buf, size_t len);
 			bool ProcessHolePunch (uint8_t * buf, size_t len);
 			bool ProcessPeerTest (uint8_t * buf, size_t len);
-			void ProcessData (uint8_t * buf, size_t len);
+			void ProcessData (uint8_t * buf, size_t len, const boost::asio::ip::udp::endpoint& from);
 
 		private:
 
@@ -284,6 +284,7 @@ namespace transport
 			void SendHolePunch (uint32_t nonce, const boost::asio::ip::udp::endpoint& ep, const uint8_t * introKey, uint64_t token);
 			void SendPeerTest (uint8_t msg, const uint8_t * signedData, size_t signedDataLen, const uint8_t * introKey); // PeerTest message 
 			void SendPathResponse (const uint8_t * data, size_t len);
+			void SendPathChallenge ();
 			
 			void HandlePayload (const uint8_t * buf, size_t len);
 			void HandleDateTime (const uint8_t * buf, size_t len);