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    SubjectRe: [PATCH] sctp: Make "Invalid Stream Identifier" ERROR follows SACK when bundling
    On 07/19/2012 01:57 PM, xufengzhang.main@gmail.com 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<xufeng.zhang@windriver.com>
    > ---
    > 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;
    >
    >



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