netdev - Re: [PATCHv2 net-next] sctp: sctp should change socket state when shutdown is received

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Message-ID: <20160603174918.GX22680@localhost.localdomain>
Date:	Fri, 3 Jun 2016 14:49:18 -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,
	Vlad Yasevich <vyasevich@...il.com>, daniel@...earbox.net,
	davem@...emloft.net, eric.dumazet@...il.com
Subject: Re: [PATCHv2 net-next] sctp: sctp should change socket state when
 shutdown is received

On Fri, Jun 03, 2016 at 10:42:45PM +0800, Xin Long wrote:
> Now sctp doesn't change socket state upon shutdown reception. It changes
> just the assoc state, even though it's a TCP-style socket.
> 
> For some cases, if we really need to check sk->sk_state, it's necessary to
> fix this issue, at least when we use ss or netstat to dump, we can get a
> more exact information.
> 
> As an improvement, we will change sk->sk_state when we change asoc->state
> to SHUTDOWN_RECEIVED, and also do it in sctp_shutdown to keep consistent with
> sctp_close.
> 
> Signed-off-by: Xin Long <lucien.xin@...il.com>
> ---
>  net/sctp/sm_sideeffect.c | 4 +++-
>  net/sctp/socket.c        | 1 +
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
> index aa37122..12d4519 100644
> --- a/net/sctp/sm_sideeffect.c
> +++ b/net/sctp/sm_sideeffect.c
> @@ -806,8 +806,10 @@ static void sctp_cmd_new_state(sctp_cmd_seq_t *cmds,
>  
>  		/* Set the RCV_SHUTDOWN flag when a SHUTDOWN is received. */
>  		if (sctp_state(asoc, SHUTDOWN_RECEIVED) &&
> -		    sctp_sstate(sk, ESTABLISHED))
> +		    sctp_sstate(sk, ESTABLISHED)) {
> +			sk->sk_state = SCTP_SS_CLOSING;
>  			sk->sk_shutdown |= RCV_SHUTDOWN;
> +		}
>  	}
>  
>  	if (sctp_state(asoc, COOKIE_WAIT)) {
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 67154b8..91a460d 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -4193,6 +4193,7 @@ static void sctp_shutdown(struct sock *sk, int how)
>  		return;
>  
>  	if (how & SEND_SHUTDOWN) {
> +		sk->sk_state = SCTP_SS_CLOSING;
>  		ep = sctp_sk(sk)->ep;
>  		if (!list_empty(&ep->asocs)) {
>  			asoc = list_entry(ep->asocs.next,

Oh but I think the removed chunk was important, it just needed fixing.

A comment in there said:
	/* If the association on the newsk is already closed before
	 * accept() is called, set RCV_SHUTDOWN flag.
	 */
Meaning that there is a way that it will create a socket in the state
you're trying to avoid here, which now is not handled.

  Marcelo