Re: [Lksctp-developers] [PATCH] sctp: Fix to handle SHUTDOWN in SHUTDOWN-PENDING

[Vlad Yasevich <vladislav.yasevich@hp.com>]

Hi Wei

If I can't take that without a patch that processes SHUTDOWN chunks in
SHUTDOWN_RECEIVED state.

The problem is that if B in your example has more data to send,
it will ignore subsequent SHUTDOWN chunks.  If A uses only SHUTDOWNS
to acknowledge data, then this would results us ignoring acks and
retransmitting and eventually ABORTING the association.

-vlad

Wei Yongjun wrote:
> If SHUTDOWN is received in SHUTDOWN-PENDING state, enpoint should enter
> the SHUTDOWN-RECEIVED state and check the Cumulative TSN Ack field of
> the SHUTDOWN chunk (RFC 4960 Section 9.2). If the SHUTDOWN chunk can
> acknowledge all of the send DATA chunks, SHUTDOWN-ACK should be sent.
> 
> But now endpoint just silently discarded the SHUTDOWN chunk.
> 
> SHUTDOWN received in SHUTDOWN-PENDING state can happend when the last
> SACK is lost by network, or the SHUTDOWN chunk can acknowledge all of
> the received DATA chunks. The packet sequence(SACK lost) is like this:
> 
> Endpoint A                       Endpoint B       ULP
> (ESTABLISHED)                    (ESTABLISHED)
> 
>                <-----------      DATA
>                                              <--- shutdown
>                                  Enter SHUTDOWN-PENDING state
>   SACK         ----lost---->
> 
>   SHUTDOWN(*1) ------------>
> 
>                <-----------      SHUTDOWN-ACK
> 
>  (*1) silently discarded now.
> 
> This patch fix to handle SHUTDOWN in SHUTDOWN-PENDING state as the same
> as ESTABLISHED state.
> 
> Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
> ---
>  net/sctp/sm_statetable.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/net/sctp/sm_statetable.c b/net/sctp/sm_statetable.c
> index dd4ddc4..a5b5590 100644
> --- a/net/sctp/sm_statetable.c
> +++ b/net/sctp/sm_statetable.c
> @@ -266,7 +266,7 @@ const sctp_sm_table_entry_t *sctp_sm_lookup_event(sctp_event_t event_type,
>  	/* SCTP_STATE_ESTABLISHED */ \
>  	TYPE_SCTP_FUNC(sctp_sf_do_9_2_shutdown), \
>  	/* SCTP_STATE_SHUTDOWN_PENDING */ \
> -	TYPE_SCTP_FUNC(sctp_sf_discard_chunk), \
> +	TYPE_SCTP_FUNC(sctp_sf_do_9_2_shutdown), \
>  	/* SCTP_STATE_SHUTDOWN_SENT */ \
>  	TYPE_SCTP_FUNC(sctp_sf_do_9_2_shutdown_ack), \
>  	/* SCTP_STATE_SHUTDOWN_RECEIVED */ \