Use -ENETUNREACH to mean "no reachable network device exists, don't bother

retrying".

src/net/ipv4.c

 	}
 	if ( ! netdev ) {
 		DBG ( "IPv4 has no route to %s\n", inet_ntoa ( iphdr->dest ) );
-		rc = -EHOSTUNREACH;
+		rc = -ENETUNREACH;
 		goto err;
 	}
 

src/net/ipv6.c

 	/* No network interface identified */
 	if ( !netdev ) {
 		DBG ( "No route to host %s\n", inet6_ntoa ( ip6hdr->dest ) );
-		rc = -EHOSTUNREACH;
+		rc = -ENETUNREACH;
 		goto err;
 	}