net: tcp: move sk_rx_dst_set call after tcp_create_openreq_child()

This commit removes the sk_rx_dst_set calls from
tcp_create_openreq_child(), because at that point the icsk_af_ops
field of ipv6_mapped TCP sockets has not been set to its proper final
value.

Instead, to make sure we get the right sk_rx_dst_set variant
appropriate for the address family of the new connection, we have
tcp_v{4,6}_syn_recv_sock() directly call the appropriate function
shortly after the call to tcp_create_openreq_child() returns.

This also moves inet6_sk_rx_dst_set() to avoid a forward declaration
with the new approach.

Signed-off-by: Neal Cardwell <[e-mail]>
Reported-by: Artem Savkov <[e-mail]>
Cc: Eric Dumazet <[e-mail]>
Acked-by: Eric Dumazet <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/tcp_ipv4.c

···
 		goto exit_nonewsk;
 
 	newsk->sk_gso_type = SKB_GSO_TCPV4;
+	inet_sk_rx_dst_set(newsk, skb);
 
 	newtp		      = tcp_sk(newsk);
 	newinet		      = inet_sk(newsk);

net/ipv4/tcp_minisocks.c

···
 		struct tcp_sock *oldtp = tcp_sk(sk);
 		struct tcp_cookie_values *oldcvp = oldtp->cookie_values;
 
-		newicsk->icsk_af_ops->sk_rx_dst_set(newsk, skb);
-
 		/* TCP Cookie Transactions require space for the cookie pair,
 		 * as it differs for each connection.  There is no need to
 		 * copy any s_data_payload stored at the original socket.

net/ipv6/tcp_ipv6.c

···
 }
 #endif
 
+static void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
+{
+	struct dst_entry *dst = skb_dst(skb);
+	const struct rt6_info *rt = (const struct rt6_info *)dst;
+
+	dst_hold(dst);
+	sk->sk_rx_dst = dst;
+	inet_sk(sk)->rx_dst_ifindex = skb->skb_iif;
+	if (rt->rt6i_node)
+		inet6_sk(sk)->rx_dst_cookie = rt->rt6i_node->fn_sernum;
+}
+
 static void tcp_v6_hash(struct sock *sk)
 {
 	if (sk->sk_state != TCP_CLOSE) {
···
 
 	newsk->sk_gso_type = SKB_GSO_TCPV6;
 	__ip6_dst_store(newsk, dst, NULL, NULL);
+	inet6_sk_rx_dst_set(newsk, skb);
 
 	newtcp6sk = (struct tcp6_sock *)newsk;
 	inet_sk(newsk)->pinet6 = &newtcp6sk->inet6;
···
 	.twsk_unique	= tcp_twsk_unique,
 	.twsk_destructor= tcp_twsk_destructor,
 };
-
-static void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
-{
-	struct dst_entry *dst = skb_dst(skb);
-	const struct rt6_info *rt = (const struct rt6_info *)dst;
-
-	dst_hold(dst);
-	sk->sk_rx_dst = dst;
-	inet_sk(sk)->rx_dst_ifindex = skb->skb_iif;
-	if (rt->rt6i_node)
-		inet6_sk(sk)->rx_dst_cookie = rt->rt6i_node->fn_sernum;
-}
 
 static const struct inet_connection_sock_af_ops ipv6_specific = {
 	.queue_xmit	   = inet6_csk_xmit,