Don't change Yddrasil address if router becomes unreachable through ipv6

libi2pd/RouterContext.cpp

@@ -250,9 +250,17 @@ namespace i2p
 		bool updated = false;
 		for (auto& address : m_RouterInfo.GetAddresses ())
 		{
-			if (address->IsNTCP2 () && (address->port != port || address->ntcp2->isPublished != publish) 
-			    && ((v4 && address->IsV4 ()) || (v6 && address->IsV6 ()) || 
-			    (ygg && i2p::util::net::IsYggdrasilAddress (address->host))))
+			if (address->IsNTCP2 () && (address->port != port || address->ntcp2->isPublished != publish)) 
+			{
+				bool isAddr = v4 && address->IsV4 ();
+				if (!isAddr && (v6 || ygg))
+				{	
+					if (i2p::util::net::IsYggdrasilAddress (address->host))
+						isAddr = ygg;
+					else
+						isAddr = v6 && address->IsV6 ();
+				}
+				if (isAddr)
 				{	
 					if (!port && !address->port)
 					{
@@ -267,6 +275,7 @@ namespace i2p
 					updated = true;
 				}	
 			}
+		}
 		if (updated)
 			UpdateRouterInfo ();
 	}