limit number of incoming ECIES sessions. Don't try to create ECIES session for incoming stream

libi2pd/Garlic.cpp

@@ -426,7 +426,8 @@ namespace garlic
 	}
 
 	GarlicDestination::GarlicDestination (): m_NumTags (32), // 32 tags by default
-		m_PayloadBuffer (nullptr), m_NumRatchetInboundTags (0) // 0 means standard
+		m_PayloadBuffer (nullptr), m_LastIncomingSessionTimestamp (0), 
+		m_NumRatchetInboundTags (0) // 0 means standard
 	{
 	}
 
@@ -539,10 +540,18 @@ namespace garlic
 				else if (SupportsEncryptionType (i2p::data::CRYPTO_KEY_TYPE_ECIES_X25519_AEAD))
 				{
 					// otherwise ECIESx25519
+					auto ts = i2p::util::GetMillisecondsSinceEpoch ();
+					if (ts > m_LastIncomingSessionTimestamp + INCOMING_SESSIONS_MINIMAL_INTERVAL) 
+					{	
 						auto session = std::make_shared<ECIESX25519AEADRatchetSession> (this, false); // incoming
-					if (!session->HandleNextMessage (buf, length, nullptr, 0))
+						if (session->HandleNextMessage (buf, length, nullptr, 0))
+							m_LastIncomingSessionTimestamp = ts;
+						else
 							LogPrint (eLogError, "Garlic: Can't handle ECIES-X25519-AEAD-Ratchet message");
 					}
+					else
+						LogPrint (eLogWarning, "Garlic: Incoming sessions come too ofter");
+				}
 				else
 					LogPrint (eLogError, "Garlic: Failed to decrypt message");
 			}
@@ -737,7 +746,8 @@ namespace garlic
 	}
 
 	std::shared_ptr<GarlicRoutingSession> GarlicDestination::GetRoutingSession (
-		std::shared_ptr<const i2p::data::RoutingDestination> destination, bool attachLeaseSet)
+		std::shared_ptr<const i2p::data::RoutingDestination> destination, bool attachLeaseSet,
+	    bool requestNewIfNotFound)
 	{
 		if (destination->GetEncryptionType () == i2p::data::CRYPTO_KEY_TYPE_ECIES_X25519_AEAD &&
 			SupportsEncryptionType (i2p::data::CRYPTO_KEY_TYPE_ECIES_X25519_AEAD))
@@ -752,15 +762,16 @@ namespace garlic
 				if (session->IsInactive (i2p::util::GetSecondsSinceEpoch ()))
 				{
 					LogPrint (eLogDebug, "Garlic: Session restarted");
+					requestNewIfNotFound = true; // it's not a new session
 					session = nullptr;
 				}
 			}
-			if (!session)
+			if (!session && requestNewIfNotFound)
 			{
 				session = std::make_shared<ECIESX25519AEADRatchetSession> (this, true);
 				session->SetRemoteStaticKey (staticKey);
 			}
-			if (destination->IsDestination ())
+			if (session && destination->IsDestination ())
 				session->SetDestination (destination->GetIdentHash ()); // NS or NSR
 			return session;
 		}

libi2pd/Garlic.h

@@ -52,6 +52,7 @@ namespace garlic
 	const int OUTGOING_TAGS_CONFIRMATION_TIMEOUT = 10; // 10 seconds
 	const int LEASESET_CONFIRMATION_TIMEOUT = 4000; // in milliseconds
 	const int ROUTING_PATH_EXPIRATION_TIMEOUT = 120; // in seconds
+	const int INCOMING_SESSIONS_MINIMAL_INTERVAL = 200; // in milliseconds
 
 	struct SessionTag: public i2p::data::Tag<32>
 	{
@@ -234,7 +235,8 @@ namespace garlic
 			int GetNumTags () const { return m_NumTags; };
 			void SetNumRatchetInboundTags (int numTags) { m_NumRatchetInboundTags = numTags; };
 			int GetNumRatchetInboundTags () const { return m_NumRatchetInboundTags; };
-			std::shared_ptr<GarlicRoutingSession> GetRoutingSession (std::shared_ptr<const i2p::data::RoutingDestination> destination, bool attachLeaseSet);
+			std::shared_ptr<GarlicRoutingSession> GetRoutingSession (std::shared_ptr<const i2p::data::RoutingDestination> destination,
+				bool attachLeaseSet, bool requestNewIfNotFound = true);
 			void CleanupExpiredTags ();
 			void RemoveDeliveryStatusSession (uint32_t msgID);
 			std::shared_ptr<I2NPMessage> WrapMessageForRouter (std::shared_ptr<const i2p::data::RouterInfo> router,
@@ -284,6 +286,7 @@ namespace garlic
 			std::unordered_map<i2p::data::IdentHash, ElGamalAESSessionPtr> m_Sessions;
 			std::unordered_map<i2p::data::Tag<32>, ECIESX25519AEADRatchetSessionPtr> m_ECIESx25519Sessions; // static key -> session
 			uint8_t * m_PayloadBuffer; // for ECIESX25519AEADRatchet
+			uint64_t m_LastIncomingSessionTimestamp; // in millseconds
 			// incoming
 			int m_NumRatchetInboundTags;
 			std::unordered_map<SessionTag, std::shared_ptr<AESDecryption>, std::hash<i2p::data::Tag<32> > > m_Tags;

libi2pd/Streaming.cpp

@@ -757,8 +757,8 @@ namespace stream
 				if (!m_RemoteLeaseSet) m_RemoteLeaseSet = m_LocalDestination.GetOwner ()->FindLeaseSet (m_RemoteIdentity->GetIdentHash ());;
 				if (m_RemoteLeaseSet)
 				{
-					m_RoutingSession = m_LocalDestination.GetOwner ()->GetRoutingSession (m_RemoteLeaseSet, true);
+					m_RoutingSession = m_LocalDestination.GetOwner ()->GetRoutingSession (m_RemoteLeaseSet, true, !m_IsIncoming);
-					m_MTU = m_RoutingSession->IsRatchets () ? STREAMING_MTU_RATCHETS : STREAMING_MTU;
+					m_MTU = (m_RoutingSession && m_RoutingSession->IsRatchets ()) ? STREAMING_MTU_RATCHETS : STREAMING_MTU;
 				}
 				uint16_t flags = PACKET_FLAG_SYNCHRONIZE | PACKET_FLAG_FROM_INCLUDED |
 					PACKET_FLAG_SIGNATURE_INCLUDED | PACKET_FLAG_MAX_PACKET_SIZE_INCLUDED;
@@ -1115,7 +1115,15 @@ namespace stream
 			}
 		}
 		if (!m_RoutingSession || m_RoutingSession->IsTerminated () || !m_RoutingSession->IsReadyToSend ()) // expired and detached or new session sent
-			m_RoutingSession = m_LocalDestination.GetOwner ()->GetRoutingSession (m_RemoteLeaseSet, true);
+		{	
+			m_RoutingSession = m_LocalDestination.GetOwner ()->GetRoutingSession (m_RemoteLeaseSet, true, !m_IsIncoming);
+			if (!m_RoutingSession)
+			{
+				LogPrint (eLogError, "Streaming: Can't obtain routing session, sSID=", m_SendStreamID);
+				Terminate ();
+				return;
+			}	
+		}	
 		if (!m_CurrentOutboundTunnel && m_RoutingSession) // first message to send
 		{
 			// try to get shared path first
@@ -1416,7 +1424,13 @@ namespace stream
 				SendPackets (packets);
 				m_LastSendTime = ts;
 				m_IsSendTime = false;
-				if (m_IsNAcked || m_IsResendNeeded) ScheduleSend ();
+				if (m_IsNAcked || m_IsResendNeeded) 
+				{
+					if (m_SequenceNumber > 1) // doesn't resend agressively very first packet
+						ScheduleSend ();
+					else
+						ScheduleResend ();
+				}	
 			}
 			else
 				SendBuffer ();