send and receive sequence number in UDP tunnels

libi2pd/Datagram.cpp

@@ -226,10 +226,10 @@ namespace datagram
 				}	
 			}	
 		}
-		uint16_t flags = bufbe16toh (buf + identityLen);
+		const uint8_t * flags = buf + identityLen;
 		size_t offset = identityLen + 2;
 		bool isOptions = false;
-		if (flags & DATAGRAM2_FLAG_OPTIONS)
+		if (flags[1] & DATAGRAM2_FLAG_OPTIONS)
 		{	
 			isOptions = true;
 			m_Options.CleanUp ();
@@ -250,7 +250,7 @@ namespace datagram
 		if (!verified)
 		{
 			std::shared_ptr<i2p::crypto::Verifier> transientVerifier;
-			if (flags & DATAGRAM2_FLAG_OFFLINE_SIGNATURE)
+			if (flags[1] & DATAGRAM2_FLAG_OFFLINE_SIGNATURE)
 			{	
 				transientVerifier = i2p::data::ProcessOfflineSignature (&identity, buf, len, offset);
 				if (!transientVerifier)
@@ -308,10 +308,10 @@ namespace datagram
 					auto r = FindReceiver(toPort);
 					if (r)
 					{
-						uint16_t flags = bufbe16toh (buf + 32);
+						const uint8_t * flags = buf + 32;
 						size_t offset = 34;
 						bool isOptions = false;
-						if (flags & DATAGRAM3_FLAG_OPTIONS)
+						if (flags[1] & DATAGRAM3_FLAG_OPTIONS)
 						{	
 							isOptions = true;
 							m_Options.CleanUp ();

libi2pd/Datagram.h

@@ -53,9 +53,9 @@ namespace datagram
 		eDatagramV3 = 3,
 	};	
 
-	constexpr uint16_t DATAGRAM2_FLAG_OPTIONS = 0x10;
-	constexpr uint16_t DATAGRAM2_FLAG_OFFLINE_SIGNATURE = 0x20;
-	constexpr uint16_t DATAGRAM3_FLAG_OPTIONS = 0x10;
+	constexpr uint8_t DATAGRAM2_FLAG_OPTIONS = 0x10;
+	constexpr uint8_t DATAGRAM2_FLAG_OFFLINE_SIGNATURE = 0x20;
+	constexpr uint8_t DATAGRAM3_FLAG_OPTIONS = 0x10;
 	
 	class DatagramSession : public std::enable_shared_from_this<DatagramSession>
 	{

libi2pd/util.h

@@ -247,12 +247,12 @@ namespace util
 			static size_t WriteOption (std::string_view param, std::string_view value, uint8_t * buf, size_t len);
 
 			template<typename T>
-			bool Get(std::string_view param, T& value)
+			bool Get(std::string_view param, T& value) const
 			{
 				auto s = (*this)[param];
 				if (s.empty ()) return false;
 				auto res = std::from_chars(s.data(), s.data() + s.size(), value);
-				return res.ec != std::errc();
+				return res.ec == std::errc();
 			}	
 			template<typename T>
 			bool Put (std::string_view param, T value)

libi2pd_client/UDPTunnel.cpp

@@ -6,6 +6,7 @@
 * See full license text in LICENSE file at top of project tree
 */
 
+#include <string_view>
 #include "Log.h"
 #include "util.h"
 #include "ClientContext.h"
@@ -16,6 +17,9 @@ namespace i2p
 {
 namespace client
 {
+	constexpr std::string_view UDP_SESSION_SEQN { "seqn" };
+	constexpr std::string_view UDP_SESSION_ACKED { "acked" };
+	
 	void I2PUDPServerTunnel::HandleRecvFromI2P(const i2p::data::IdentityEx& from, uint16_t fromPort, uint16_t toPort, 
 		const uint8_t * buf, size_t len, const i2p::util::Mapping * options)
 	{
@@ -27,6 +31,15 @@ namespace client
 			m_LastSession->LastActivity = i2p::util::GetMillisecondsSinceEpoch();
 		else
 			LogPrint (eLogInfo, "UDP Server: Send exception: ", ec.message (), " to ", m_RemoteEndpoint);
+		if (options)
+		{
+			uint32_t seqn = 0;
+			if (options->Get (UDP_SESSION_SEQN, seqn) && seqn > m_LastSession->m_LastReceivedPacketNum)
+			{	
+				m_LastSession->m_LastReceivedPacketNum = seqn;
+				LogPrint (eLogDebug, "UDP Server: Received packet with seqn ", seqn);
+			}	
+		}		
 	}
 
 	void I2PUDPServerTunnel::HandleRecvFromI2PRaw (uint16_t fromPort, uint16_t toPort, const uint8_t * buf, size_t len)
@@ -123,11 +136,9 @@ namespace client
 		const boost::asio::ip::udp::endpoint& endpoint, const i2p::data::IdentHash& to,
 		uint16_t ourPort, uint16_t theirPort) :
 		m_Destination(localDestination->GetDatagramDestination()),
-		IPSocket(localDestination->GetService(), localEndpoint),
-		Identity (to), SendEndpoint(endpoint),
-		LastActivity(i2p::util::GetMillisecondsSinceEpoch()),
-		LocalPort(ourPort),
-		RemotePort(theirPort)
+		IPSocket(localDestination->GetService(), localEndpoint), Identity (to), 
+		SendEndpoint(endpoint), LastActivity(i2p::util::GetMillisecondsSinceEpoch()),
+		LocalPort(ourPort), RemotePort(theirPort), m_NextSendPacketNum (1), m_LastReceivedPacketNum (0)
 	{
 		IPSocket.set_option (boost::asio::socket_base::receive_buffer_size (I2P_UDP_MAX_MTU ));
 		IPSocket.non_blocking (true);
@@ -149,7 +160,13 @@ namespace client
 			auto ts = i2p::util::GetMillisecondsSinceEpoch();
 			auto session = m_Destination->GetSession (Identity);
 			if (ts > LastActivity + I2P_UDP_REPLIABLE_DATAGRAM_INTERVAL)
-				m_Destination->SendDatagram(session, m_Buffer, len, LocalPort, RemotePort);
+			{
+				i2p::util::Mapping options;
+				options.Put (UDP_SESSION_SEQN, m_NextSendPacketNum);
+				if (m_LastReceivedPacketNum > 0)
+					options.Put (UDP_SESSION_ACKED, m_LastReceivedPacketNum);
+				m_Destination->SendDatagram(session, m_Buffer, len, LocalPort, RemotePort, &options);
+			}	
 			else
 				m_Destination->SendRawDatagram(session, m_Buffer, len, LocalPort, RemotePort);
 			size_t numPackets = 0;
@@ -164,6 +181,7 @@ namespace client
 			}
 			if (numPackets > 0)
 				LogPrint(eLogDebug, "UDPSession: Forward more ", numPackets, "packets B from ", FromEndpoint);
+			m_NextSendPacketNum += numPackets + 1;
 			m_Destination->FlushSendQueue (session);
 			LastActivity = ts;
 			Receive();
@@ -238,7 +256,8 @@ namespace client
 		uint16_t remotePort, bool gzip, i2p::datagram::DatagramVersion datagramVersion) :
 		m_Name (name), m_RemoteDest (remoteDest), m_LocalDest (localDestination), m_LocalEndpoint (localEndpoint),
 		m_ResolveThread (nullptr), m_LocalSocket (nullptr), RemotePort (remotePort),
-		m_LastPort (0), m_cancel_resolve (false), m_Gzip (gzip), m_DatagramVersion (datagramVersion)
+		m_LastPort (0), m_cancel_resolve (false), m_Gzip (gzip), m_DatagramVersion (datagramVersion),
+		m_NextSendPacketNum (1), m_LastReceivedPacketNum (0)
 	{
 	}
 
@@ -339,7 +358,13 @@ namespace client
 		LogPrint (eLogDebug, "UDP Client: Send ", transferred, " to ", m_RemoteAddr->identHash.ToBase32 (), ":", RemotePort);
 		auto session = m_LocalDest->GetDatagramDestination ()->GetSession (m_RemoteAddr->identHash);
 		if (ts > m_LastSession->second + I2P_UDP_REPLIABLE_DATAGRAM_INTERVAL)
-			m_LocalDest->GetDatagramDestination ()->SendDatagram (session, m_RecvBuff, transferred, remotePort, RemotePort);
+		{	
+			i2p::util::Mapping options;
+			options.Put (UDP_SESSION_SEQN, m_NextSendPacketNum);
+			if (m_LastReceivedPacketNum > 0)
+				options.Put (UDP_SESSION_ACKED, m_LastReceivedPacketNum);
+			m_LocalDest->GetDatagramDestination ()->SendDatagram (session, m_RecvBuff, transferred, remotePort, RemotePort, &options);
+		}	
 		else
 			m_LocalDest->GetDatagramDestination ()->SendRawDatagram (session, m_RecvBuff, transferred, remotePort, RemotePort);
 		size_t numPackets = 0;
@@ -356,6 +381,7 @@ namespace client
 		}
 		if (numPackets)
 			LogPrint (eLogDebug, "UDP Client: Sent ", numPackets, " more packets to ", m_RemoteAddr->identHash.ToBase32 ());
+		m_NextSendPacketNum += numPackets + 1;
 		m_LocalDest->GetDatagramDestination ()->FlushSendQueue (session);
 
 		// mark convo as active

libi2pd_client/UDPTunnel.h

@@ -46,6 +46,7 @@ namespace client
 		uint16_t RemotePort;
 
 		uint8_t m_Buffer[I2P_UDP_MAX_MTU];
+		uint32_t m_NextSendPacketNum, m_LastReceivedPacketNum;
 
 		UDPSession(boost::asio::ip::udp::endpoint localEndpoint,
 			const std::shared_ptr<i2p::client::ClientDestination> & localDestination,
@@ -180,6 +181,7 @@ namespace client
 			bool m_Gzip;
 			i2p::datagram::DatagramVersion m_DatagramVersion;
 			std::shared_ptr<UDPConvo> m_LastSession;
+			uint32_t m_NextSendPacketNum, m_LastReceivedPacketNum;
 
 		public: