Subject: Re: [PATCH] sctp: send abort chunk when max_retrans exceeded

From: Vlad Yasevich <[email-masked]>
Date: Tue, 20 Nov 2012 13:44:23 -0500

On 11/20/2012 12:59 PM, Neil Horman wrote:
> In the event that an association exceeds its max_retrans attempts, we should
> send an ABORT chunk indicating that we are closing the assocation as a result.
> Because of the nature of the error, its unlikely to be received, but its a nice
> clean way to close the association if it does make it through, and it will give
> anyone watching via tcpdump a clue as to what happened.
>
> Signed-off-by: Neil Horman <[email-masked]>
> CC: Vlad Yasevich <[email-masked]>
> CC: "David S. Miller" <[email-masked]>
> CC: [email-masked]
> ---
>   include/net/sctp/sm.h    |  2 ++
>   net/sctp/sm_make_chunk.c | 26 +++++++++++++++++++++-----
>   net/sctp/sm_sideeffect.c |  9 ++++++++-
>   3 files changed, 31 insertions(+), 6 deletions(-)
>
> diff --git a/include/net/sctp/sm.h b/include/net/sctp/sm.h
> index b5887e1..2a82d13 100644
> --- a/include/net/sctp/sm.h
> +++ b/include/net/sctp/sm.h
> @@ -234,6 +234,8 @@ struct sctp_chunk *sctp_make_abort_violation(const struct sctp_association *,
>   struct sctp_chunk *sctp_make_violation_paramlen(const struct sctp_association *,
>   				   const struct sctp_chunk *,
>   				   struct sctp_paramhdr *);
> +struct sctp_chunk *sctp_make_violation_max_retrans(const struct sctp_association *,
> +						   const struct sctp_chunk *);
>   struct sctp_chunk *sctp_make_heartbeat(const struct sctp_association *,
>   				  const struct sctp_transport *);
>   struct sctp_chunk *sctp_make_heartbeat_ack(const struct sctp_association *,
> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> index fbe1636..d6a8c80 100644
> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -1074,17 +1074,33 @@ struct sctp_chunk *sctp_make_violation_paramlen(
>   {
>   	struct sctp_chunk *retval;
>   	static const char error[] = "The following parameter had invalid length:";
> -	size_t payload_len = sizeof(error) + sizeof(sctp_errhdr_t) +
> -				sizeof(sctp_paramhdr_t);
> +	size_t payload_len = sizeof(error) + sizeof(sctp_errhdr_t);
>
>   	retval = sctp_make_abort(asoc, chunk, payload_len);
>   	if (!retval)
>   		goto nodata;
>
> -	sctp_init_cause(retval, SCTP_ERROR_PROTO_VIOLATION,
> -			sizeof(error) + sizeof(sctp_paramhdr_t));
> +	sctp_init_cause(retval, SCTP_ERROR_PROTO_VIOLATION, sizeof(error));
> +	sctp_addto_chunk(retval, sizeof(error), error);
> +
> +nodata:
> +	return retval;
> +}

Neil

You ended dropping the parameter information of the parameter that 
caused the violation.  Was that intentional?

-vlad

> +
> +struct sctp_chunk *sctp_make_violation_max_retrans(
> +	const struct sctp_association *asoc,
> +	const struct sctp_chunk *chunk)
> +{
> +	struct sctp_chunk *retval;
> +	static const char error[] = "Association exceeded its max_retans count";
> +	size_t payload_len = sizeof(error) + sizeof(sctp_errhdr_t);
> +
> +	retval = sctp_make_abort(asoc, chunk, payload_len);
> +	if (!retval)
> +		goto nodata;
> +
> +	sctp_init_cause(retval, SCTP_ERROR_PROTO_VIOLATION, sizeof(error));
>   	sctp_addto_chunk(retval, sizeof(error), error);
> -	sctp_addto_param(retval, sizeof(sctp_paramhdr_t), param);
>
>   nodata:
>   	return retval;
> diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
> index 6eecf7e..c076956 100644
> --- a/net/sctp/sm_sideeffect.c
> +++ b/net/sctp/sm_sideeffect.c
> @@ -577,7 +577,7 @@ static void sctp_cmd_assoc_failed(sctp_cmd_seq_t *commands,
>   				  unsigned int error)
>   {
>   	struct sctp_ulpevent *event;
> -
> +	struct sctp_chunk *abort;
>   	/* Cancel any partial delivery in progress. */
>   	sctp_ulpq_abort_pd(&asoc->ulpq, GFP_ATOMIC);
>
> @@ -593,6 +593,13 @@ static void sctp_cmd_assoc_failed(sctp_cmd_seq_t *commands,
>   		sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
>   				SCTP_ULPEVENT(event));
>
> +	if (asoc->overall_error_count >= asoc->max_retrans) {
> +		abort = sctp_make_violation_max_retrans(asoc, chunk);
> +		if (abort)
> +			sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,
> +					SCTP_CHUNK(abort));
> +	}
> +
>   	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
>   			SCTP_STATE(SCTP_STATE_CLOSED));
>
>