reuse current introducers if no more available

libi2pd/SSU.cpp

@@ -670,7 +670,7 @@ namespace transport
 		for (const auto& s : sessions)
 		{	
 			if (s.second->GetRelayTag () && s.second->GetState () == eSessionStateEstablished &&
-			    ts < s.second->GetCreationTime () + SSU_TO_INTRODUCER_SESSION_DURATION)
+			    ts < s.second->GetCreationTime () + SSU_TO_INTRODUCER_SESSION_EXPIRATION)
 				ret.push_back (s.second);
 		}	
 		if ((int)ret.size () > maxNumIntroducers)
@@ -762,13 +762,19 @@ namespace transport
 			for (const auto& it : introducers)
 			{
 				auto session = FindSession (it);
-				if (session && ts < session->GetCreationTime () + SSU_TO_INTRODUCER_SESSION_DURATION)
+				if (session)
 				{
+					if (ts < session->GetCreationTime () + SSU_TO_INTRODUCER_SESSION_EXPIRATION)
 						session->SendKeepAlive ();
+					if (ts < session->GetCreationTime () + SSU_TO_INTRODUCER_SESSION_DURATION)
+					{	
 						newList.push_back (it);
 						numIntroducers++;
 					}
 					else
+						session = nullptr;
+				}
+				if (!session)
 					i2p::context.RemoveIntroducer (it);
 			}
 
@@ -776,6 +782,19 @@ namespace transport
 			{
 				// create new
 				auto sessions = FindIntroducers (SSU_MAX_NUM_INTRODUCERS, v4); // try to find if duplicates
+				if (sessions.empty () && !introducers.empty ())
+				{
+					// bump creation time for previous introducers if no new sessions found
+					LogPrint (eLogDebug, "SSU: no new introducers found. Trying to reuse existing");
+					for (const auto& it : introducers)
+					{
+						auto session = FindSession (it);
+						if (session)
+							session->SetCreationTime (session->GetCreationTime () + SSU_TO_INTRODUCER_SESSION_DURATION);
+					}	
+					// try again
+					sessions = FindIntroducers (SSU_MAX_NUM_INTRODUCERS, v4);
+				}	
 				for (const auto& it1: sessions)
 				{
 					const auto& ep = it1->GetRemoteEndpoint ();
@@ -784,7 +803,7 @@ namespace transport
 					introducer.iPort = ep.port ();
 					introducer.iTag = it1->GetRelayTag ();
 					introducer.iKey = it1->GetIntroKey ();
-					introducer.iExp = it1->GetCreationTime () + SSU_TO_INTRODUCER_SESSION_DURATION;
+					introducer.iExp = it1->GetCreationTime () + SSU_TO_INTRODUCER_SESSION_EXPIRATION;
 					if (i2p::context.AddIntroducer (introducer))
 					{
 						newList.push_back (ep);

libi2pd/SSU.h

@@ -31,6 +31,7 @@ namespace transport
 	const int SSU_KEEP_ALIVE_INTERVAL = 30; // 30 seconds
 	const int SSU_PEER_TEST_TIMEOUT = 60; // 60 seconds
 	const int SSU_TO_INTRODUCER_SESSION_DURATION = 3600; // 1 hour
+	const int SSU_TO_INTRODUCER_SESSION_EXPIRATION = 4800; // 80 minutes
 	const int SSU_TERMINATION_CHECK_TIMEOUT = 30; // 30 seconds
 	const size_t SSU_MAX_NUM_INTRODUCERS = 3;
 	const size_t SSU_SOCKET_RECEIVE_BUFFER_SIZE = 0x1FFFF; // 128K

libi2pd/SSUSession.h

@@ -102,6 +102,7 @@ namespace transport
 			uint32_t GetRelayTag () const { return m_RelayTag; };
 			const i2p::data::RouterInfo::IntroKey& GetIntroKey () const { return m_IntroKey; };
 			uint32_t GetCreationTime () const { return m_CreationTime; };
+			void SetCreationTime (uint32_t ts) { m_CreationTime = ts; }; // for introducers
 			
 			void FlushData ();