MTU for ipv6

SSU.h

@@ -72,6 +72,7 @@ namespace transport
 			void WaitForIntroduction ();
 			void Close ();
 			boost::asio::ip::udp::endpoint& GetRemoteEndpoint () { return m_RemoteEndpoint; };
+			bool IsV6 () const { return m_RemoteEndpoint.address ().is_v6 (); };
 			void SendI2NPMessage (I2NPMessage * msg);
 			void SendPeerTest (); // Alice			
 
@@ -188,7 +189,7 @@ namespace transport
 			boost::asio::ip::udp::endpoint m_SenderEndpoint;
 			boost::asio::deadline_timer m_IntroducersUpdateTimer;
 			std::list<boost::asio::ip::udp::endpoint> m_Introducers; // introducers we are connected to
-			uint8_t m_ReceiveBuffer[2*SSU_MTU];
+			uint8_t m_ReceiveBuffer[2*SSU_MTU_V4]; 
 			std::map<boost::asio::ip::udp::endpoint, SSUSession *> m_Sessions;
 			std::map<uint32_t, boost::asio::ip::udp::endpoint> m_Relays; // we are introducer
 

SSUData.cpp

@@ -13,7 +13,8 @@ namespace transport
 	SSUData::SSUData (SSUSession& session):
 		m_Session (session), m_ResendTimer (session.m_Server.GetService ())
 	{
-		m_PacketSize = SSU_MAX_PACKET_SIZE;
+		m_MaxPacketSize = session.IsV6 () ? SSU_V6_MAX_PACKET_SIZE : SSU_V4_MAX_PACKET_SIZE;
+		m_PacketSize = m_MaxPacketSize;
 		auto remoteRouter = session.GetRemoteRouter ();
 		if (remoteRouter)
 			AdjustPacketSize (*remoteRouter);
@@ -36,19 +37,22 @@ namespace transport
 		auto ssuAddress = remoteRouter.GetSSUAddress ();
 		if (ssuAddress && ssuAddress->mtu)
 		{
-			m_PacketSize = ssuAddress->mtu - IPV4_HEADER_SIZE - UDP_HEADER_SIZE;
+			if (m_Session.IsV6 ())
+				m_PacketSize = ssuAddress->mtu - IPV6_HEADER_SIZE - UDP_HEADER_SIZE;
+			else
+				m_PacketSize = ssuAddress->mtu - IPV4_HEADER_SIZE - UDP_HEADER_SIZE;
 			if (m_PacketSize > 0)
 			{
 				// make sure packet size multiple of 16
 				m_PacketSize >>= 4;
 				m_PacketSize <<= 4;
-				if (m_PacketSize > (int)SSU_MAX_PACKET_SIZE) m_PacketSize = SSU_MAX_PACKET_SIZE;
+				if (m_PacketSize > m_MaxPacketSize) m_PacketSize = m_MaxPacketSize;
 				LogPrint ("MTU=", ssuAddress->mtu, " packet size=", m_PacketSize); 
 			}
 			else
 			{	
 				LogPrint (eLogWarning, "Unexpected MTU ", ssuAddress->mtu);
-				m_PacketSize = SSU_MAX_PACKET_SIZE;
+				m_PacketSize = m_MaxPacketSize;
 			}	
 		}		
 	}

SSUData.h

@@ -16,10 +16,13 @@ namespace i2p
 namespace transport
 {
 
-	const size_t SSU_MTU = 1484;
+	const size_t SSU_MTU_V4 = 1484;
+	const size_t SSU_MTU_V6 = 1472;
 	const size_t IPV4_HEADER_SIZE = 20;
+	const size_t IPV6_HEADER_SIZE = 40;	
 	const size_t UDP_HEADER_SIZE = 8;
-	const size_t SSU_MAX_PACKET_SIZE = SSU_MTU - IPV4_HEADER_SIZE - UDP_HEADER_SIZE; // 1456
+	const size_t SSU_V4_MAX_PACKET_SIZE = SSU_MTU_V4 - IPV4_HEADER_SIZE - UDP_HEADER_SIZE; // 1456
+	const size_t SSU_V6_MAX_PACKET_SIZE = SSU_MTU_V6 - IPV6_HEADER_SIZE - UDP_HEADER_SIZE; // 1424
 	const int RESEND_INTERVAL = 3; // in seconds
 	const int MAX_NUM_RESENDS = 5;
 	// data flags
@@ -35,7 +38,7 @@ namespace transport
 		int fragmentNum;
 		size_t len;
 		bool isLast;
-		uint8_t buf[SSU_MAX_PACKET_SIZE + 18];
+		uint8_t buf[SSU_V4_MAX_PACKET_SIZE + 18]; // use biggest
 
 		Fragment () = default;
 		Fragment (int n, const uint8_t * b, int l, bool last): 
@@ -102,7 +105,7 @@ namespace transport
 			std::map<uint32_t, SentMessage *> m_SentMessages;
 			std::set<uint32_t> m_ReceivedMessages;
 			boost::asio::deadline_timer m_ResendTimer;
-			int m_PacketSize;
+			int m_MaxPacketSize, m_PacketSize;
 	};	
 }
 }