skip resent recently sessions during resend

libi2pd/SSU2.cpp

@@ -987,7 +987,8 @@ namespace transport
 			auto ts = i2p::util::GetMillisecondsSinceEpoch ();
 			for (auto it: m_Sessions)
 			{
-				resentPacketsNum += it.second->Resend (ts);
+				if (ts >= it.second->GetLastResendTime () + SSU2_RESEND_CHECK_TIMEOUT)
+					resentPacketsNum += it.second->Resend (ts);
 				if (resentPacketsNum > SSU2_MAX_RESEND_PACKETS) break;
 			}
 			for (auto it: m_PendingOutgoingSessions)

libi2pd/SSU2Session.cpp

@@ -90,7 +90,8 @@ namespace transport
 		m_WindowSize (SSU2_MIN_WINDOW_SIZE),
 		m_RTO (SSU2_INITIAL_RTO), m_RelayTag (0),m_ConnectTimer (server.GetService ()), 
 		m_TerminationReason (eSSU2TerminationReasonNormalClose),
-		m_MaxPayloadSize (SSU2_MIN_PACKET_SIZE - IPV6_HEADER_SIZE - UDP_HEADER_SIZE - 32) // min size
+		m_MaxPayloadSize (SSU2_MIN_PACKET_SIZE - IPV6_HEADER_SIZE - UDP_HEADER_SIZE - 32), // min size
+		m_LastResendTime (0)
 	{
 		m_NoiseState.reset (new i2p::crypto::NoiseSymmetricState);
 		if (in_RemoteRouter && m_Address)
@@ -565,6 +566,7 @@ namespace transport
 				it++;
 		if (!resentPackets.empty ())
 		{
+			m_LastResendTime = ts;
 #if (__cplusplus >= 201703L) // C++ 17 or higher
 			m_SentPackets.merge (resentPackets);
 #else

libi2pd/SSU2Session.h

@@ -256,7 +256,8 @@ namespace transport
 			void SendLocalRouterInfo (bool update) override;
 			void SendI2NPMessages (const std::vector<std::shared_ptr<I2NPMessage> >& msgs) override;
 			uint32_t GetRelayTag () const override { return m_RelayTag; };
-			size_t Resend (uint64_t ts); // return number or resent packets
+			size_t Resend (uint64_t ts); // return number of resent packets
+			uint64_t GetLastResendTime () const { return m_LastResendTime; };
 			bool IsEstablished () const override { return m_State == eSSU2SessionStateEstablished; };
 			uint64_t GetConnID () const { return m_SourceConnID; };
 			SSU2SessionState GetState () const { return m_State; };
@@ -369,6 +370,7 @@ namespace transport
 			size_t m_MaxPayloadSize;
 			std::unique_ptr<i2p::data::IdentHash> m_PathChallenge;
 			std::unordered_map<uint32_t, uint32_t> m_ReceivedI2NPMsgIDs; // msgID -> timestamp in seconds
+			uint64_t m_LastResendTime; // in milliseconds
 	};
 
 	inline uint64_t CreateHeaderMask (const uint8_t * kh, const uint8_t * nonce)