ipv6: Early TCP socket demux

This is the IPv6 missing bits for infrastructure added in commit
41063e9d (ipv4: Early TCP socket demux.)
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/inet6_hashtables.h

@@ -96,14 +96,15 @@ static inline struct sock *__inet6_lookup_skb(struct inet_hashinfo *hashinfo,
 					      const __be16 sport,
 					      const __be16 dport)
 {
-	struct sock *sk;
+	struct sock *sk = skb_steal_sock(skb);
 
-	if (unlikely(sk = skb_steal_sock(skb)))
+	if (sk)
 		return sk;
-	else return __inet6_lookup(dev_net(skb_dst(skb)->dev), hashinfo,
-				   &ipv6_hdr(skb)->saddr, sport,
-				   &ipv6_hdr(skb)->daddr, ntohs(dport),
-				   inet6_iif(skb));
+
+	return __inet6_lookup(dev_net(skb_dst(skb)->dev), hashinfo,
+			      &ipv6_hdr(skb)->saddr, sport,
+			      &ipv6_hdr(skb)->daddr, ntohs(dport),
+			      inet6_iif(skb));
 }
 
 extern struct sock *inet6_lookup(struct net *net, struct inet_hashinfo *hashinfo,

include/net/protocol.h

@@ -52,6 +52,8 @@ struct net_protocol {
 
 #if IS_ENABLED(CONFIG_IPV6)
 struct inet6_protocol {
+	void	(*early_demux)(struct sk_buff *skb);
+
 	int	(*handler)(struct sk_buff *skb);
 
 	void	(*err_handler)(struct sk_buff *skb,

net/ipv4/ip_input.c

@@ -314,6 +314,7 @@ static inline bool ip_rcv_options(struct sk_buff *skb)
 }
 
 int sysctl_ip_early_demux __read_mostly = 1;
+EXPORT_SYMBOL(sysctl_ip_early_demux);
 
 static int ip_rcv_finish(struct sk_buff *skb)
 {

net/ipv6/ip6_input.c

@@ -47,9 +47,18 @@
 
 
 
-inline int ip6_rcv_finish( struct sk_buff *skb)
+int ip6_rcv_finish(struct sk_buff *skb)
 {
-	if (skb_dst(skb) == NULL)
+	if (sysctl_ip_early_demux && !skb_dst(skb)) {
+		const struct inet6_protocol *ipprot;
+
+		rcu_read_lock();
+		ipprot = rcu_dereference(inet6_protos[ipv6_hdr(skb)->nexthdr]);
+		if (ipprot && ipprot->early_demux)
+			ipprot->early_demux(skb);
+		rcu_read_unlock();
+	}
+	if (!skb_dst(skb))
 		ip6_route_input(skb);
 
 	return dst_input(skb);

net/ipv6/tcp_ipv6.c

@@ -1674,6 +1674,43 @@ static int tcp_v6_rcv(struct sk_buff *skb)
 	goto discard_it;
 }
 
+static void tcp_v6_early_demux(struct sk_buff *skb)
+{
+	const struct ipv6hdr *hdr;
+	const struct tcphdr *th;
+	struct sock *sk;
+
+	if (skb->pkt_type != PACKET_HOST)
+		return;
+
+	if (!pskb_may_pull(skb, skb_transport_offset(skb) + sizeof(struct tcphdr)))
+		return;
+
+	hdr = ipv6_hdr(skb);
+	th = tcp_hdr(skb);
+
+	if (th->doff < sizeof(struct tcphdr) / 4)
+		return;
+
+	sk = __inet6_lookup_established(dev_net(skb->dev), &tcp_hashinfo,
+					&hdr->saddr, th->source,
+					&hdr->daddr, ntohs(th->dest),
+					inet6_iif(skb));
+	if (sk) {
+		skb->sk = sk;
+		skb->destructor = sock_edemux;
+		if (sk->sk_state != TCP_TIME_WAIT) {
+			struct dst_entry *dst = sk->sk_rx_dst;
+			struct inet_sock *icsk = inet_sk(sk);
+			if (dst)
+				dst = dst_check(dst, 0);
+			if (dst &&
+			    icsk->rx_dst_ifindex == inet6_iif(skb))
+				skb_dst_set_noref(skb, dst);
+		}
+	}
+}
+
 static struct timewait_sock_ops tcp6_timewait_sock_ops = {
 	.twsk_obj_size	= sizeof(struct tcp6_timewait_sock),
 	.twsk_unique	= tcp_twsk_unique,
@@ -1984,6 +2021,7 @@ struct proto tcpv6_prot = {
 };
 
 static const struct inet6_protocol tcpv6_protocol = {
+	.early_demux	=	tcp_v6_early_demux,
 	.handler	=	tcp_v6_rcv,
 	.err_handler	=	tcp_v6_err,
 	.gso_send_check	=	tcp_v6_gso_send_check,