tcp: heed result of security_inet_conn_request() in tcp_v6_conn_request()

If security_inet_conn_request() returns non-zero then TCP/IPv6 should
drop the request, just as in TCP/IPv4 and DCCP in both IPv4 and IPv6.
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/tcp_ipv6.c

@@ -1212,7 +1212,8 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
 	tcp_rsk(req)->snt_isn = isn;
 	tcp_rsk(req)->snt_synack = tcp_time_stamp;
 
-	security_inet_conn_request(sk, skb, req);
+	if (security_inet_conn_request(sk, skb, req))
+		goto drop_and_release;
 
 	if (tcp_v6_send_synack(sk, req,
 			       (struct request_values *)&tmp_ext,