keepaliveinterval for UDP client tunnel

libi2pd_client/ClientContext.cpp

@@ -680,6 +680,13 @@ namespace client
 						auto clientTunnel = std::make_shared<I2PUDPClientTunnel> (name, dest, end,
 							localDestination, destinationPort, gzip, (i2p::datagram::DatagramVersion)datagramVersion);
 
+						uint32_t keepAlive = section.second.get<uint32_t>(I2P_CLIENT_TUNNEL_KEEP_ALIVE_INTERVAL, 0);
+						if (keepAlive)
+						{
+							clientTunnel->SetKeepAliveInterval (keepAlive);
+							LogPrint(eLogInfo, "Clients: UDP Client tunnel keep alive interval set to ", keepAlive);
+						}
+
 						auto ins = m_ClientForwards.insert (std::make_pair (end, clientTunnel));
 						if (ins.second)
 						{

libi2pd_client/UDPTunnel.cpp

@@ -424,10 +424,15 @@ namespace client
 		if (m_ResolveThread == nullptr)
 			m_ResolveThread = new std::thread (std::bind (&I2PUDPClientTunnel::TryResolving, this));
 		RecvFromLocal ();
+
+		if (m_KeepAliveInterval)
+			ScheduleKeepAliveTimer ();
 	}
 
 	void I2PUDPClientTunnel::Stop ()
 	{
+		if (m_KeepAliveTimer) m_KeepAliveTimer->cancel ();
+
 		auto dgram = m_LocalDest->GetDatagramDestination ();
 		if (dgram)
 		{
@@ -670,5 +675,32 @@ namespace client
 		else
 			LogPrint (eLogWarning, "UDP Client: Not tracking udp session using port ", (int) toPort);
 	}
+
+	void I2PUDPClientTunnel::SetKeepAliveInterval (uint32_t keepAliveInterval)
+	{
+		m_KeepAliveInterval = keepAliveInterval;
+		if (m_KeepAliveInterval)
+			m_KeepAliveTimer.reset (new boost::asio::steady_timer (m_LocalDest->GetService ()));
+	}
+
+	void I2PUDPClientTunnel::ScheduleKeepAliveTimer ()
+	{
+		if (m_KeepAliveTimer)
+		{
+			m_KeepAliveTimer->expires_after (std::chrono::seconds (m_KeepAliveInterval));
+			m_KeepAliveTimer->async_wait (std::bind (&I2PUDPClientTunnel::HandleKeepAliveTimer,
+				this, std::placeholders::_1));
+		}
+	}
+
+	void I2PUDPClientTunnel::HandleKeepAliveTimer (const boost::system::error_code& ecode)
+	{
+		if (ecode != boost::asio::error::operation_aborted)
+		{
+			if (i2p::util::GetMillisecondsSinceEpoch () > m_LastRepliableDatagramTime + m_KeepAliveInterval*1000)
+				HandleRecvFromLocal (boost::system::error_code(), 0); // send empty packet like it was received from local
+			ScheduleKeepAliveTimer ();
+		}
+	}
 }
 }

libi2pd_client/UDPTunnel.h

@@ -183,6 +183,7 @@ namespace client
 			const boost::asio::ip::udp::endpoint& GetLocalEndpoint () const { return m_LocalEndpoint; };
 
 			void ExpireStale (const uint64_t delta=I2P_UDP_SESSION_TIMEOUT);
+			void SetKeepAliveInterval (uint32_t keepAliveInterval);
 
 		private:
 
@@ -194,6 +195,9 @@ namespace client
 			void HandleRecvFromI2PRaw (uint16_t fromPort, uint16_t toPort, const uint8_t * buf, size_t len);
 			void TryResolving ();
 
+			void ScheduleKeepAliveTimer ();
+			void HandleKeepAliveTimer (const boost::system::error_code& ecode);
+
 		private:
 
 			const std::string m_Name;
@@ -211,6 +215,8 @@ namespace client
 			bool m_Gzip;
 			i2p::datagram::DatagramVersion m_DatagramVersion;
 			std::shared_ptr<UDPConvo> m_LastSession;
+			uint32_t m_KeepAliveInterval;
+			std::unique_ptr<boost::asio::steady_timer> m_KeepAliveTimer;
 
 		public: