ipvs: fix ip_vs_try_bind_dest to rebind app and transmitter

	Initially, when the synced connection is created we
use the forwarding method provided by master but once we
bind to destination it can be changed. As result, we must
update the application and the transmitter.

	As ip_vs_try_bind_dest is called always for connections
that require dest binding, there is no need to validate the
cp and dest pointers.
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>

net/netfilter/ipvs/ip_vs_conn.c

@@ -613,14 +613,33 @@ struct ip_vs_dest *ip_vs_try_bind_dest(struct ip_vs_conn *cp)
 {
 	struct ip_vs_dest *dest;
 
-	if ((cp) && (!cp->dest)) {
 	dest = ip_vs_find_dest(ip_vs_conn_net(cp), cp->af, &cp->daddr,
 			       cp->dport, &cp->vaddr, cp->vport,
 			       cp->protocol, cp->fwmark, cp->flags);
+	if (dest) {
+		struct ip_vs_proto_data *pd;
+
+		/* Applications work depending on the forwarding method
+		 * but better to reassign them always when binding dest */
+		if (cp->app)
+			ip_vs_unbind_app(cp);
+
 		ip_vs_bind_dest(cp, dest);
+
+		/* Update its packet transmitter */
+		cp->packet_xmit = NULL;
+#ifdef CONFIG_IP_VS_IPV6
+		if (cp->af == AF_INET6)
+			ip_vs_bind_xmit_v6(cp);
+		else
+#endif
+			ip_vs_bind_xmit(cp);
+
+		pd = ip_vs_proto_data_get(ip_vs_conn_net(cp), cp->protocol);
+		if (pd && atomic_read(&pd->appcnt))
+			ip_vs_bind_app(cp, pd->pp);
+	}
 	return dest;
-	} else
-		return NULL;
 }