netfilter: flowtable: call dst_check() to fall back to classic forwarding

In case the route is stale, pass up the packet to the classic forwarding
path for re-evaluation and schedule this flow entry for removal.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Author: ummakynes

net/netfilter/nf_flow_table_ip.c

@@ -197,14 +197,6 @@ static bool nf_flow_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
 	return true;
 }
 
-static int nf_flow_offload_dst_check(struct dst_entry *dst)
-{
-	if (unlikely(dst_xfrm(dst)))
-		return dst_check(dst, 0) ? 0 : -1;
-
-	return 0;
-}
-
 static unsigned int nf_flow_xmit_xfrm(struct sk_buff *skb,
 				      const struct nf_hook_state *state,
 				      struct dst_entry *dst)
@@ -256,7 +248,7 @@ nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
 
 	flow_offload_refresh(flow_table, flow);
 
-	if (nf_flow_offload_dst_check(&rt->dst)) {
+	if (!dst_check(&rt->dst, 0)) {
 		flow_offload_teardown(flow);
 		return NF_ACCEPT;
 	}
@@ -476,7 +468,7 @@ nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 
 	flow_offload_refresh(flow_table, flow);
 
-	if (nf_flow_offload_dst_check(&rt->dst)) {
+	if (!dst_check(&rt->dst, 0)) {
 		flow_offload_teardown(flow);
 		return NF_ACCEPT;
 	}