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

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Date:	Sat, 4 Jun 2016 09:22:06 -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 <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCHv2 net-next] sctp: sctp should change socket state when
 shutdown is received

Em 04-06-2016 06:45, Xin Long escreveu:
> On Sat, Jun 4, 2016 at 1:49 AM, Marcelo Ricardo Leitner
> <marcelo.leitner@...il.com> wrote:
>> 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.
> agreed, but it's another problem
> there, we'd better free newsk and assoc after sctp_sock_migrate,
> and let sctp_accept return err. I will think more about it and see if
> I cook another patch for it.

Return error? Please don't. Adam Endrodi asked in May (linux-sctp@) a 
way to return the addresses used on such attempts and currently this 
address returned by accept() is the only one we can get.

   Marcelo