Re: [PATCH] sctp: Make "Invalid Stream Identifier" ERROR follows SACKwhen bundling

[Xufeng Zhang]

On 7/25/12, Neil Horman <nhorman@xxxxxxxxxxxxx> wrote:
> On Wed, Jul 25, 2012 at 05:22:19PM +0800, Xufeng Zhang wrote:
>> On 7/25/12, Xufeng Zhang <xufengzhang.main@xxxxxxxxx> wrote:
>> > On 7/25/12, Vlad Yasevich <vyasevich@xxxxxxxxx> wrote:
>> >>
>> >> Actually not true.  AUTH can be before SACK.  So can any addip chunks
>> >> that
>> >> aid in locating an association.
>> >>
>> >> Now AUTH isn't a big issue since its autogenerated to the packet but
>> >> ADDIP
>> >> is since it could be queued up for retransmission.
>> >>
>> >> There could be other extensions as well.  It really needs to be done
>> >> either
>> >> through side effects or making error chunks go at the end of other
>> >> control
>> >> chunks.  Need to audit the spec to see if that's ok.
>> > You are right, I just found SHUTDOWN chunks are also before SACK based
>> > on
>> > your commit "[SCTP]: Fix SACK sequence during shutdown".
>> > Maybe the only solution is to do some work on side effects just as you
>> > said.
>> > Thanks for your explanation!
>>
>> And after take a moment to look into the relative codes, I think we
>> can implement it
>> by below way:
>> 1). Add a flag(isi_err_needed) in the embedded struct peer of struct
>> struct sctp_association
>> just like sack_needed flag.
>> 2). When "invalid stream identifier" ERROR happens in sctp_eat_data()
>> function, we just
>> set isi_err_needed flag and don't create ERROR chunk and also don't
>> insert SCTP_CMD_REPLY command.
>> 3). In sctp_gen_sack() function, we create ERROR chunk and also insert
>> SCTP_CMD_REPLY command if isi_err_needed flag is set.
>>
>> Is this way proper?
>>
> That would probably work yes.  Another way might just be to do some
> re-ordering
> in sctp_outq_flush.  Before processing the control chunk list, scan it,
> and:
> 1) move all error chunks to the head of the list
> 2) move all sack chunks to the head of the list
> 3) move all shutdown chunks to the head of the list
>
> You can do that in a single iteration of the list if you use a few on-stack
> lists and list_splice

Thank you very much for your suggestion!
I'll compare it with side effects modification and make a decision.


Thanks,
Xufeng Zhang

>
> Neil
>
>>
>> Thanks,
>> Xufeng Zhang
>> >
>> >
>> >
>> > Thanks,
>> > Xufeng Zhang
>> >>
>> >> -vlad
>> >>>
>> >>>Thanks,
>> >>>Xufeng Zhang
>> >>>>
>> >>>> -vlad
>> >>
>> >>
>> >> --
>> >> Sent from my Android phone with SkitMail. Please excuse my brevity.
>> >>
>> >
>>
>
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