mptcp: more accurate NL event generation

Currently the mptcp code generate a "new listener" event even
if the actual listen() syscall fails. Address the issue moving
the event generation call under the successful branch.

Cc: [email protected]
Fixes: f8c9dfb ("mptcp: add pm listener events")
Reviewed-by: Mat Martineau <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>
Signed-off-by: Mat Martineau <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Paolo Abeni

net/mptcp/protocol.c

@@ -3723,10 +3723,9 @@ static int mptcp_listen(struct socket *sock, int backlog)
 	if (!err) {
 		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
 		mptcp_copy_inaddrs(sk, ssock->sk);
+		mptcp_event_pm_listener(ssock->sk, MPTCP_EVENT_LISTENER_CREATED);
 	}
 
-	mptcp_event_pm_listener(ssock->sk, MPTCP_EVENT_LISTENER_CREATED);
-
 unlock:
 	release_sock(sk);
 	return err;