Subject: Re: [PATCH] SCTP: Fix Protocol violation when receiving a error length INIT ACK

From: Gui Jianfeng <[email-masked]>
Date: Tue, 25 Mar 2008 15:10:30 +0800

Wei Yongjun wrote:
> Hi Gui:
> 
> I looked the source code and found that only in the state *COOKIE_WAIT*
> received INIT-ACK need to do this, not all of the states. The other
> states we should have known the init-tag of peer.
  yes, it's the only possibility.

> 
> Gui Jianfeng wrote:
>> Wei Yongjun wrote:
>>  
>>> NACK.
>>>
>>> If the INIT-ACK chunk is too short to contain the init-tag, get the
>>> init-tag of peer may get a unexpected value.
>>> Such as this:
>>>  CHUNK_INIT_ACK
>>>   Type                             = 2
>>>   Flags                            = 0
>>>   Length                           = 4
>>>
>>> So I think the better way is to set T bit of ABORT chunk and used the
>>> own's Tag.
>>>     
>>
>>   Seems reasonable. Please ignore the previous one, here is a new patch.
>>
>> Signed-off-by: Gui Jianfeng <[email-masked]>
>> ---
>>  net/sctp/outqueue.c     |    3 +++
>>  net/sctp/sm_statefuns.c |    5 +++++
>>  2 files changed, 8 insertions(+), 0 deletions(-)
>>
>> diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
>> index 1bb3c5c..c071446 100644
>> --- a/net/sctp/outqueue.c
>> +++ b/net/sctp/outqueue.c
>> @@ -793,6 +793,9 @@ int sctp_outq_flush(struct sctp_outq *q, int
>> rtx_timeout)
>>              break;
>>  
>>          case SCTP_CID_ABORT:
>> +            if (sctp_test_T_bit(chunk)) {
>> +                packet->vtag = asoc->c.my_vtag;
>> +            }
>>          case SCTP_CID_SACK:
>>          case SCTP_CID_HEARTBEAT:
>>          case SCTP_CID_HEARTBEAT_ACK:
>>   
> 
>> diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
>> index f2ed647..85e1d63 100644
>> --- a/net/sctp/sm_statefuns.c
>> +++ b/net/sctp/sm_statefuns.c
>> @@ -4144,6 +4144,11 @@ static sctp_disposition_t sctp_sf_abort_violation(
>>          goto nomem;
>>  
>>      if (asoc) {
>> +        /* Treat INIT-ACK as a special case. */
>> +        if (chunk->chunk_hdr->type == SCTP_CID_INIT_ACK) {
>> +            abort->chunk_hdr->flags |= SCTP_CHUNK_FLAG_T;
>> +        }
>> +
>>          sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
>>          SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
>>  
>>   
> Those code should be move to sctp_make_abort() for
> common using. And may be need check whether we need the T flags.
  This rarely happens, so i think it's sufficient to place this block of code here.
  Moving it into sctp_make_abort() will waste much cpu time when generating each abort chunk .

-- 
Regards
Gui Jianfeng