introducer duration variance

libi2pd/SSU2.cpp

@@ -1267,7 +1267,9 @@ namespace transport
 					ts < session->GetCreationTime () + SSU2_TO_INTRODUCER_SESSION_EXPIRATION)
 				{	
 					session->SendKeepAlive ();
-					if (ts < session->GetCreationTime () + SSU2_TO_INTRODUCER_SESSION_DURATION)	
+					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)	
 					{	
 						newList.push_back ({ident, session->GetRelayTag ()});
 						if (tag != session->GetRelayTag ())

libi2pd/SSU2.h

@@ -35,7 +35,8 @@ 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 = 3600; // 1 hour
+	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_EXPIRATION = 4800; // 80 minutes
 	const int SSU2_KEEP_ALIVE_INTERVAL = 15; // in seconds
 	const int SSU2_KEEP_ALIVE_INTERVAL_VARIANCE = 4; // in seconds