Re: [PATCH] sctp: set association state to established in dupcook_ahandler

[Vlad Yasevich]

On 01/23/2013 08:46 AM, Neil Horman wrote:
> On Wed, Jan 23, 2013 at 03:38:40PM +0800, xufengzhang.main@xxxxxxxxx wrote:
> > From: Xufeng Zhang <xufeng.zhang@xxxxxxxxxxxxx>
> >
> > While sctp handling a duplicate COOKIE-ECHO and the action is
> > 'Association restart', sctp_sf_do_dupcook_a() will processing
> > the unexpected COOKIE-ECHO for peer restart, but it does not set
> > the association state to SCTP_STATE_ESTABLISHED, so the association
> > could stuck in SCTP_STATE_SHUTDOWN_PENDING state forever.
> > This violates the sctp specification:
> >    RFC 4960 5.2.4. Handle a COOKIE ECHO when a TCB Exists
> >    Action
> >    A) In this case, the peer may have restarted. .....
> >       After this, the endpoint shall enter the ESTABLISHED state.
> >
> > Fix this problem by adding a SCTP_CMD_NEW_STATE cmd to the command
> > list so as to set the restart association to SCTP_STATE_ESTABLISHED
> > state properly.
> >
> > Signed-off-by: Xufeng Zhang <xufeng.zhang@xxxxxxxxxxxxx>
> > ---
> >   net/sctp/sm_statefuns.c |    2 ++
> >   1 files changed, 2 insertions(+), 0 deletions(-)
> >
> > diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
> > index 618ec7e..528f1c8 100644
> > --- a/net/sctp/sm_statefuns.c
> > +++ b/net/sctp/sm_statefuns.c
> > @@ -1779,6 +1779,8 @@ static sctp_disposition_t sctp_sf_do_dupcook_a(struct net *net,
> >
> >   	/* Update the content of current association. */
> >   	sctp_add_cmd_sf(commands, SCTP_CMD_UPDATE_ASSOC, SCTP_ASOC(new_asoc));
> > +	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
> > +			SCTP_STATE(SCTP_STATE_ESTABLISHED));
> >   	sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
> >   	sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));
> >   	return SCTP_DISPOSITION_CONSUME;
> > --
> > 1.7.0.2
>
> Looks reasonable to me, thanks
>
> nit: The RFC indicate the association should enter the ESTABLISHED state after
> preforming all other actions, so it seems that the state change should occur
> after the ULP event is sent

I have a slight concern here that if we change state last, then any data 
that may have been bundled with COOKIE-ACK as part of CMD_REPLY will get 
the SACK_IMMEDIATE flag set since we are still in the SHUTDOWN_PENDING 
state.

I would be more correct (and would match sctp_sf_do_5_1D_ce) to
do it in this order:
  UPDATE_ASSOC  - resets all the congestion/association variables
  EVENT_UP  - send RESTART to USER
  NEW_STATE  - set ESTABLISHED state (as per spec)
  REPLY	- Send cookie-ack along with any pending data.

-vlad
> Neil

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