don't pick too old session for introducer

libi2pd/SSU2.cpp

@@ -1035,10 +1035,13 @@ namespace transport
 
 			for (const auto& it : sessions)
 			{
+				uint32_t exp = it->GetCreationTime () + SSU2_TO_INTRODUCER_SESSION_EXPIRATION;
+				if (ts + SSU2_TO_INTRODUCER_SESSION_DURATION/2 > exp)
+					continue; // don't pick too old session for introducer	
 				i2p::data::RouterInfo::Introducer introducer;
 				introducer.iTag = it->GetRelayTag ();
 				introducer.iH = it->GetRemoteIdentity ()->GetIdentHash ();
-				introducer.iExp = it->GetCreationTime () + SSU2_TO_INTRODUCER_SESSION_EXPIRATION;
+				introducer.iExp = exp;
 				excluded.insert (it->GetRemoteIdentity ()->GetIdentHash ());
 				if (i2p::context.AddSSU2Introducer (introducer, v4))
 				{