limit received SSU2 packets queue

libi2pd/SSU2.cpp

@@ -457,13 +457,20 @@ namespace transport
 	void SSU2Server::InsertToReceivedPacketsQueue (std::list<Packet *>& packets)
 	{
 		if (packets.empty ()) return;
-		bool empty = false;
+		size_t queueSize = 0;
 		{
 			std::lock_guard<std::mutex> l(m_ReceivedPacketsQueueMutex);
-			empty = m_ReceivedPacketsQueue.empty ();
+			queueSize = m_ReceivedPacketsQueue.size ();
+			if (queueSize < SSU2_MAX_RECEIVED_QUEUE_SIZE)
 				m_ReceivedPacketsQueue.splice (m_ReceivedPacketsQueue.end (), packets);
+			else
+			{
+				LogPrint (eLogError, "SSU2: Received queue size ", queueSize, " exceeds max size", SSU2_MAX_RECEIVED_QUEUE_SIZE);
+				m_PacketsPool.ReleaseMt (packets);
+				queueSize = 0; // invoke processing just in case
 			}		
-		if (empty)
+		}
+		if (!queueSize)
 			GetService ().post([this]() { HandleReceivedPacketsQueue (); });
 	}	
 		

libi2pd/SSU2.h

@@ -37,6 +37,7 @@ namespace transport
 	const uint64_t SSU2_SOCKET_MAX_BUFFER_SIZE = 4 * 1024 * 1024;
 	const size_t SSU2_MAX_NUM_INTRODUCERS = 3;
 	const size_t SSU2_MIN_RECEIVED_PACKET_SIZE = 40; // 16 byte short header + 8 byte minimum payload + 16 byte MAC
+	const size_t SSU2_MAX_RECEIVED_QUEUE_SIZE = 2500; // in packets
 	const int SSU2_TO_INTRODUCER_SESSION_DURATION = 3600; // 1 hour
 	const int SSU2_TO_INTRODUCER_SESSION_EXPIRATION = 4800; // 80 minutes
 	const int SSU2_KEEP_ALIVE_INTERVAL = 15; // in seconds