Subject: Re: [PATCH] sctp: Make "Invalid Stream Identifier" ERROR follows SACK when bundling

From: xufeng zhang <[email-masked]>
Date: Mon, 23 Jul 2012 13:16:37 +0800

On 07/19/2012 01:57 PM, [email-masked] wrote:
> When "Invalid Stream Identifier" ERROR happens after process the
> received DATA chunks, this ERROR chunk is enqueued into outqueue
> before SACK chunk, so when bundling ERROR chunk with SACK chunk,
> the ERROR chunk is always placed first in the packet because of
> the chunk's position in the outqueue.
> This violates sctp specification:
>      RFC 4960 6.5. Stream Identifier and Stream Sequence Number
>      ...The endpoint may bundle the ERROR chunk in the same
>      packet as the SACK as long as the ERROR follows the SACK.
> So we must place SACK first when bundling "Invalid Stream Identifier"
> ERROR and SACK in one packet.
> Although we can do that by enqueue SACK chunk into outqueue before
> ERROR chunk, it will violate the side-effect interpreter processing.
> It's easy to do this job when dequeue chunks from the outqueue,
> by this way, we introduce a flag 'has_isi_err' which indicate
> whether or not the "Invalid Stream Identifier" ERROR happens.
>
> Signed-off-by: Xufeng Zhang<[email-masked]>
> ---
>   include/net/sctp/structs.h |    2 ++
>   net/sctp/output.c          |   26 ++++++++++++++++++++++++++
>   2 files changed, 28 insertions(+), 0 deletions(-)
>
> diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
> index 88949a9..5adf4de 100644
> --- a/include/net/sctp/structs.h
> +++ b/include/net/sctp/structs.h
> @@ -842,6 +842,8 @@ struct sctp_packet {
>   	    has_sack:1,		/* This packet contains a SACK chunk. */
>   	    has_auth:1,		/* This packet contains an AUTH chunk */
>   	    has_data:1,		/* This packet contains at least 1 DATA chunk */
> +	    has_isi_err:1,	/* This packet contains a "Invalid Stream
> +				 * Identifier" ERROR chunk */
>   	    ipfragok:1,		/* So let ip fragment this packet */
>   	    malloced:1;		/* Is it malloced? */
>   };
> diff --git a/net/sctp/output.c b/net/sctp/output.c
> index 817174e..77fb1ae 100644
> --- a/net/sctp/output.c
> +++ b/net/sctp/output.c
> @@ -79,6 +79,7 @@ static void sctp_packet_reset(struct sctp_packet *packet)
>   	packet->has_sack = 0;
>   	packet->has_data = 0;
>   	packet->has_auth = 0;
> +	packet->has_isi_err = 0;
>   	packet->ipfragok = 0;
>   	packet->auth = NULL;
>   }
> @@ -267,6 +268,7 @@ static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt,
>   sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
>   				     struct sctp_chunk *chunk)
>   {
> +	struct sctp_chunk *lchunk;
>   	sctp_xmit_t retval = SCTP_XMIT_OK;
>   	__u16 chunk_len = WORD_ROUND(ntohs(chunk->chunk_hdr->length));
>
> @@ -316,7 +318,31 @@ sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
>   		packet->has_cookie_echo = 1;
>   		break;
>
> +	    case SCTP_CID_ERROR:
> +		if (chunk->subh.err_hdr->cause&  SCTP_ERROR_INV_STRM)
> +			packet->has_isi_err = 1;
> +		break;
> +
>   	    case SCTP_CID_SACK:
> +		/* RFC 4960
> +		 * 6.5 Stream Identifier and Stream Sequence Number
> +		 * The endpoint may bundle the ERROR chunk in the same
> +		 * packet as the SACK as long as the ERROR follows the SACK.
> +		 */
> +		if (packet->has_isi_err) {
> +			if (list_is_singular(&packet->chunk_list))
> +				list_add(&chunk->list,&packet->chunk_list);
> +			else {
> +				lchunk = list_first_entry(&packet->chunk_list,
> +						struct sctp_chunk, list);
> +				list_add(&chunk->list,&lchunk->list);
> +			}
>    
And I should clarify the above judgment code.
AFAIK, there should be two cases for the bundling when invalid stream 
identifier error happens:
1). COOKIE_ACK ERROR SACK
2). ERROR SACK
So I need to deal with the two cases differently.

Thanks,
Xufeng Zhang
> +			packet->size += chunk_len;
> +			chunk->transport = packet->transport;
> +			packet->has_sack = 1;
> +			goto finish;
> +		}
> +
>   		packet->has_sack = 1;
>   		break;
>
>