sctp: check sk_bound_dev_if when matching ep in get_port

In sctp_get_port_local(), when binding to IP and PORT, it should
also check sk_bound_dev_if to match listening sk if it's set by
SO_BINDTOIFINDEX, so that multiple sockets with the same IP and
PORT, but different sk_bound_dev_if can be listened at the same
time.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/socket.c

@@ -8398,6 +8398,7 @@ static int sctp_get_port_local(struct sock *sk, union sctp_addr *addr)
 		 * in an endpoint.
 		 */
 		sk_for_each_bound(sk2, &pp->owner) {
+			int bound_dev_if2 = READ_ONCE(sk2->sk_bound_dev_if);
 			struct sctp_sock *sp2 = sctp_sk(sk2);
 			struct sctp_endpoint *ep2 = sp2->ep;
 
@@ -8408,7 +8409,9 @@ static int sctp_get_port_local(struct sock *sk, union sctp_addr *addr)
 			     uid_eq(uid, sock_i_uid(sk2))))
 				continue;
 
-			if (sctp_bind_addr_conflict(&ep2->base.bind_addr,
+			if ((!sk->sk_bound_dev_if || !bound_dev_if2 ||
+			     sk->sk_bound_dev_if == bound_dev_if2) &&
+			    sctp_bind_addr_conflict(&ep2->base.bind_addr,
 						    addr, sp2, sp)) {
 				ret = 1;
 				goto fail_unlock;