session to introducer

SSU.cpp

@@ -18,8 +18,8 @@ namespace ssu
 	SSUSession::SSUSession (SSUServer& server, boost::asio::ip::udp::endpoint& remoteEndpoint,
 		const i2p::data::RouterInfo * router, bool peerTest ): 
 		m_Server (server), m_RemoteEndpoint (remoteEndpoint), m_RemoteRouter (router), 
-		m_Timer (m_Server.GetService ()), m_PeerTest (peerTest), m_State (eSessionStateUnknown),
-		m_IsSessionKey (false), m_RelayTag (0), m_Data (*this),
+		m_Timer (m_Server.GetService ()), m_PeerTest (peerTest), m_ToIntroducer (false),
+		m_State (eSessionStateUnknown), m_IsSessionKey (false), m_RelayTag (0), m_Data (*this),
 		m_NumSentBytes (0), m_NumReceivedBytes (0)
 	{
 		m_DHKeysPair = i2p::transports.GetNextDHKeysPair ();
@@ -87,10 +87,10 @@ namespace ssu
 		}
 		else
 		{
-			if (m_State == eSessionStateEstablished)
+			if (!len) return; // ignore zero-length packets	
+			if (m_State == eSessionStateEstablished && !m_ToIntroducer)
 				ScheduleTermination ();		
 			
-			if (!len) return; // ignore zero-length packets	
 			if (m_IsSessionKey && Validate (buf, len, m_MacKey)) // try session key first
 				DecryptSessionKey (buf, len);	
 			else 
@@ -416,10 +416,8 @@ namespace ssu
 		payload += 2; // port
 		*(uint32_t *)payload = htobe32 (nonce);		
 
-		uint8_t iv[16];
-		CryptoPP::RandomNumberGenerator& rnd = i2p::context.GetRandomNumberGenerator ();
-		rnd.GenerateBlock (iv, 16); // random iv
-		FillHeaderAndEncrypt (PAYLOAD_TYPE_RELAY_RESPONSE, buf, 64, m_SessionKey, iv, m_MacKey);
+		// encrypt with session key
+		FillHeaderAndEncrypt (PAYLOAD_TYPE_RELAY_RESPONSE, buf, 64);
 		Send (buf, 64);
 	}	
 
@@ -673,6 +671,21 @@ namespace ssu
 		}	
 	}	
 	
+	void SSUSession::ScheduleKeepAlive ()
+	{
+		m_Timer.cancel ();
+		m_Timer.expires_from_now (boost::posix_time::seconds(SSU_KEEP_ALIVE_INETRVAL));
+		m_Timer.async_wait (boost::bind (&SSUSession::HandleKeepAliveTimer,
+			this, boost::asio::placeholders::error));
+	}
+
+	void SSUSession::HandleKeepAliveTimer (const boost::system::error_code& ecode)
+	{
+		if (ecode != boost::asio::error::operation_aborted)
+			SendKeepAlive ();
+	}
+
+	
 	const uint8_t * SSUSession::GetIntroKey () const
 	{
 		if (m_RemoteRouter)
@@ -765,7 +778,7 @@ namespace ssu
 			else
 			{
 				LogPrint ("SSU peer test from Alice. We are Bob");
-				auto session = m_Server.GetRandomEstablishedSession (); // charlie
+				auto session = m_Server.GetRandomEstablishedSession (this); // charlie
 				if (session)
 					session->SendPeerTest (nonce, senderEndpoint.address ().to_v4 ().to_ulong (),
 						senderEndpoint.port (), introKey, false); 		
@@ -821,6 +834,18 @@ namespace ssu
 		SendPeerTest (nonce, 0, 0, address->key, false); // address and port always zero for Alice
 	}	
 
+	void SSUSession::SendKeepAlive ()
+	{
+		uint8_t buf[48 + 18];	
+		uint8_t	* payload = buf + sizeof (SSUHeader);
+		*payload = 0; // flags
+		payload++;
+		*payload = 0; // num fragments  
+		// encrypt message with session key
+		FillHeaderAndEncrypt (PAYLOAD_TYPE_SESSION_DESTROYED, buf, 48);
+		Send (buf, 48);
+		LogPrint ("SSU keep-alive sent");
+	}
 
 	void SSUSession::SendSesionDestroyed ()
 	{
@@ -855,6 +880,24 @@ namespace ssu
 		m_Server.Send (buf, size, m_RemoteEndpoint);
 	}	
 
+	void SSUSession::StartToIntroducer ()
+	{
+		if (m_State == eSessionStateEstablished)
+		{
+			m_ToIntroducer = true;
+			ScheduleKeepAlive ();
+		}
+	}
+
+	void SSUSession::StopToIntroducer ()
+	{
+		if (m_State == eSessionStateEstablished)
+		{
+			m_ToIntroducer = false;
+			ScheduleTermination ();
+		}
+	}	
+
 	SSUServer::SSUServer (int port): m_Thread (nullptr), m_Work (m_Service),
 		m_Endpoint (boost::asio::ip::udp::v4 (), port), m_Socket (m_Service, m_Endpoint)
 	{
@@ -1077,14 +1120,36 @@ namespace ssu
 		return nullptr;	
 	}
 
-	SSUSession * SSUServer::GetRandomEstablishedSession ()
+	SSUSession * SSUServer::GetRandomEstablishedSession (const SSUSession * excluded)
 	{
 		return GetRandomSession (
-				[](SSUSession * session)->bool 
+			[excluded](SSUSession * session)->bool 
+			{ 
+				return session->GetState () == eSessionStateEstablished &&
+					session != excluded; 
+			}
+								);
+	}
+
+	std::set<SSUSession *> SSUServer::GetIntroducers (int maxNumIntroducers)
+	{
+		std::set<SSUSession *> ret;
+		for (int i = 0; i < maxNumIntroducers; i++)
+		{
+			auto session = GetRandomSession (
+				[&ret](SSUSession * session)->bool 
 				{ 
-					return session->GetState () == eSessionStateEstablished; 
+					return session->GetRelayTag () && !ret.count (session) &&
+						session->GetState () == eSessionStateEstablished; 
 				}
-								);
+											);	
+			if (session)
+			{
+				ret.insert (session);
+				break;
+			}	
+		}
+		return ret;
 	}
 }
 }

SSU.h

@@ -33,6 +33,8 @@ namespace ssu
 
 	const int SSU_CONNECT_TIMEOUT = 5; // 5 seconds
 	const int SSU_TERMINATION_TIMEOUT = 330; // 5.5 minutes
+	const int SSU_KEEP_ALIVE_INETRVAL = 30; // 30 seconds	
+	const int SSU_TO_INTRODUCER_SESSION_DURATION = 3600; // 1 hour
 
 	// payload types (4 bits)
 	const uint8_t PAYLOAD_TYPE_SESSION_REQUEST = 0;
@@ -76,6 +78,9 @@ namespace ssu
 			size_t GetNumSentBytes () const { return m_NumSentBytes; };
 			size_t GetNumReceivedBytes () const { return m_NumReceivedBytes; };
 			
+			void StartToIntroducer ();
+			void StopToIntroducer ();	
+			uint32_t GetRelayTag () const { return m_RelayTag; };	
 
 		private:
 
@@ -103,6 +108,7 @@ namespace ssu
 			void SendPeerTest (uint32_t nonce, uint32_t address, uint16_t port, const uint8_t * introKey, bool toAddress = true); 
 			void ProcessData (uint8_t * buf, size_t len);		
 			void SendSesionDestroyed ();
+			void SendKeepAlive ();
 			void Send (uint8_t type, const uint8_t * payload, size_t len); // with session key
 			void Send (const uint8_t * buf, size_t size); 
 			
@@ -116,6 +122,9 @@ namespace ssu
 			void ScheduleTermination ();
 			void HandleTerminationTimer (const boost::system::error_code& ecode);
 			
+			void ScheduleKeepAlive ();
+			void HandleKeepAliveTimer (const boost::system::error_code& ecode);
+
 		private:
 	
 			friend class SSUData; // TODO: change in later
@@ -124,7 +133,7 @@ namespace ssu
 			const i2p::data::RouterInfo * m_RemoteRouter;
 			boost::asio::deadline_timer m_Timer;
 			i2p::data::DHKeysPair * m_DHKeysPair; // X - for client and Y - for server
-			bool m_PeerTest;
+			bool m_PeerTest, m_ToIntroducer;
 			SessionState m_State;
 			bool m_IsSessionKey;
 			uint32_t m_RelayTag;	
@@ -148,7 +157,7 @@ namespace ssu
 			SSUSession * GetSession (const i2p::data::RouterInfo * router, bool peerTest = false);
 			SSUSession * FindSession (const i2p::data::RouterInfo * router);
 			SSUSession * FindSession (const boost::asio::ip::udp::endpoint& e);
-			SSUSession * GetRandomEstablishedSession ();
+			SSUSession * GetRandomEstablishedSession (const SSUSession * excluded);
 			void DeleteSession (SSUSession * session);
 			void DeleteAllSessions ();			
 
@@ -164,6 +173,8 @@ namespace ssu
 			void Receive ();
 			void HandleReceivedFrom (const boost::system::error_code& ecode, std::size_t bytes_transferred);
 	
+			std::set<SSUSession *> GetIntroducers (int maxNumIntroducers);		
+
 			template<typename Filter>
 			SSUSession * GetRandomSession (Filter filter);