netdev - Re: [PATCH net] sctp: allow delivering notifications after receiving SHUTDOWN

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Date:	Sat, 30 Jul 2016 10:22:31 -0300
From:	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:	Xin Long <lucien.xin@...il.com>
Cc:	network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
	davem@...emloft.net, Vlad Yasevich <vyasevich@...il.com>,
	daniel@...earbox.net
Subject: Re: [PATCH net] sctp: allow delivering notifications after receiving
 SHUTDOWN

On Sat, Jul 30, 2016 at 02:09:09PM +0800, Xin Long wrote:
> Prior to this patch, once sctp received SHUTDOWN or shutdown with RD,
> sk->sk_shutdown would be set with RCV_SHUTDOWN, and all events would
> be dropped in sctp_ulpq_tail_event(). It would cause:
> 
> 1. some notifications couldn't be received by users. like
>    SCTP_SHUTDOWN_COMP generated by sctp_sf_do_4_C().
> 
> 2. sctp would also never trigger sk_data_ready when the association
>    was closed, making it harder to identify the end of the association
>    by calling recvmsg() and getting an EOF. It was not convenient for
>    kernel users.
> 
> The check here should be stopping delivering DATA chunks after receiving
> SHUTDOWN, and stopping delivering ANY chunks after sctp_close().
> 
> So this patch is to allow notifications to enqueue into receive queue
> even if sk->sk_shutdown is set to RCV_SHUTDOWN in sctp_ulpq_tail_event,
> but if sk->sk_shutdown == RCV_SHUTDOWN | SEND_SHUTDOWN, it drops all
> events.
> 
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>

> ---
>  net/sctp/ulpqueue.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/net/sctp/ulpqueue.c b/net/sctp/ulpqueue.c
> index ec166d2..877e550 100644
> --- a/net/sctp/ulpqueue.c
> +++ b/net/sctp/ulpqueue.c
> @@ -204,7 +204,9 @@ int sctp_ulpq_tail_event(struct sctp_ulpq *ulpq, struct sctp_ulpevent *event)
>  	/* If the socket is just going to throw this away, do not
>  	 * even try to deliver it.
>  	 */
> -	if (sock_flag(sk, SOCK_DEAD) || (sk->sk_shutdown & RCV_SHUTDOWN))
> +	if (sk->sk_shutdown & RCV_SHUTDOWN &&
> +	    (sk->sk_shutdown & SEND_SHUTDOWN ||
> +	     !sctp_ulpevent_is_notification(event)))
>  		goto out_free;
>  
>  	if (!sctp_ulpevent_is_notification(event)) {
> -- 
> 2.1.0
> 
> --
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