+int tcp_v4_early_demux(struct sk_buff *skb)
+{
+ struct net *net = dev_net(skb->dev);
+ const struct iphdr *iph;
+ const struct tcphdr *th;
+ struct sock *sk;
+ int err;
+
+ err = -ENOENT;
+ if (skb->pkt_type != PACKET_HOST)
+ goto out_err;
+
+ if (!pskb_may_pull(skb, ip_hdrlen(skb) + sizeof(struct tcphdr)))
+ goto out_err;
+
+ iph = ip_hdr(skb);
+ th = (struct tcphdr *) ((char *)iph + ip_hdrlen(skb));
+
+ if (th->doff < sizeof(struct tcphdr) / 4)
+ goto out_err;
+
+ if (!pskb_may_pull(skb, ip_hdrlen(skb) + th->doff * 4))
+ goto out_err;
+
+ sk = __inet_lookup_established(net, &tcp_hashinfo,
+ iph->saddr, th->source,
+ iph->daddr, th->dest,
+ skb->dev->ifindex);
+ if (sk) {
+ skb->sk = sk;
+ skb->destructor = sock_edemux;
+ if (sk->sk_state != TCP_TIME_WAIT) {
+ struct dst_entry *dst = sk->sk_rx_dst;
+ if (dst)
+ dst = dst_check(dst, 0);
+ if (dst) {
+ skb_dst_set_noref(skb, dst);
+ err = 0;
+ }
+ }
+ }
+
+out_err:
+ return err;
+}
+