introducer expiration time variance

libi2pd/SSU2.cpp

@@ -1267,9 +1267,7 @@ namespace transport
 					ts < session->GetCreationTime () + SSU2_TO_INTRODUCER_SESSION_EXPIRATION)
 				{	
 					session->SendKeepAlive ();
-					if (ts < session->GetCreationTime () + SSU2_TO_INTRODUCER_SESSION_DURATION ||
-					    ts < session->GetCreationTime () + SSU2_TO_INTRODUCER_SESSION_DURATION +
-					    m_Rng () % SSU2_TO_INTRODUCER_SESSION_DURATION_VARIANCE)	
+					if (ts < session->GetCreationTime () + SSU2_TO_INTRODUCER_SESSION_DURATION)	
 					{	
 						newList.push_back ({ident, session->GetRelayTag ()});
 						if (tag != session->GetRelayTag ())
@@ -1316,6 +1314,9 @@ namespace transport
 			for (const auto& it : sessions)
 			{
 				uint32_t tag = it->GetRelayTag ();
+				auto extraTime = std::min ((int)(ts - it->GetCreationTime ()), SSU2_TO_INTRODUCER_SESSION_EXPIRATION_VARIANCE);
+				if( extraTime > 1)
+					it->SetCreationTime (it->GetCreationTime () + m_Rng () % extraTime); 
 				uint32_t exp = it->GetCreationTime () + SSU2_TO_INTRODUCER_SESSION_EXPIRATION;
 				if (!tag || ts + SSU2_TO_INTRODUCER_SESSION_DURATION/2 > exp)
 					continue; // don't pick too old session for introducer	

libi2pd/SSU2.h

@@ -35,9 +35,9 @@ 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 int SSU2_TO_INTRODUCER_SESSION_DURATION = 3480; // 58 minutes
-	const int SSU2_TO_INTRODUCER_SESSION_DURATION_VARIANCE = 330; // 5 minutes
+	const int SSU2_TO_INTRODUCER_SESSION_DURATION = 3680; // 1 hour
 	const int SSU2_TO_INTRODUCER_SESSION_EXPIRATION = 4800; // 80 minutes
+	const int SSU2_TO_INTRODUCER_SESSION_EXPIRATION_VARIANCE = 120; // 2 minutes
 	const int SSU2_KEEP_ALIVE_INTERVAL = 15; // in seconds
 	const int SSU2_KEEP_ALIVE_INTERVAL_VARIANCE = 4; // in seconds
 	const int SSU2_PROXY_CONNECT_RETRY_TIMEOUT = 30; // in seconds