linux-kernel - Re: Question on SCTP ABORT chunk is generated when the association_max

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Date:	Mon, 26 Jan 2015 21:17:02 +0800
From:	Sun Paul <paulrbk@...il.com>
To:	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:	Daniel Borkmann <dborkman@...hat.com>,
	Michael Tuexen <tuexen@...muenster.de>,
	Vlad Yasevich <vyasevich@...il.com>,
	linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Question on SCTP ABORT chunk is generated when the
 association_max_retrans is reached

When an ABORT is sent to side-A, side-A INIT a new connection again.

On Mon, Jan 26, 2015 at 7:46 PM, Marcelo Ricardo Leitner
<marcelo.leitner@...il.com> wrote:
> Hi,
>
> On 25-01-2015 23:27, Sun Paul wrote:
>>
>> Hi
>>
>> sorry for the late reply. I am a bit confused. when side-A sends a
>> request to side-B, and side-B return the response, but side-A keep
>> re-transmit the same request to side-B, why side-B needed to send a
>> ABORT to side-A?
>
>
> That happens on data transfers. When A pushes data to B, A has to retry it
> until B finally acknowledges it and A receive this signal. If the ack from B
> gets dropped, A has no way to know if a) the ack was lost or b) its initial
> message never actually made it to A, thus it retransmits. If it reaches a
> limit, it gives up..
>
>> If it is used in order to reestablish the connection, shoudn't it
>> should be side-A to send ABORT instead?
>
>
> Meant to reestablish it? Not really.. just to keep both sides in sync, as A
> has given up by then.
>
>   Marcelo
>
>> - PS
>>
>> On Sat, Jan 24, 2015 at 3:05 AM, Daniel Borkmann <dborkman@...hat.com>
>> wrote:
>>>
>>> On 01/23/2015 07:36 PM, Michael Tuexen wrote:
>>> ...
>>>>
>>>>
>>>> Yepp. It might not reach the peer or it might. If it does it helps
>>>> to keep the states in sync. If it doesn't it sometimes helps in
>>>> analysing tracefiles. In BSD, we also send it. It is not required,
>>>> doesn't harm and is useful in some cases...
>>>
>>>
>>>
>>> Ok, as the TCB is destroyed in any case, should be fine then.
>>>
>>> Thanks,
>>> Daniel
>>
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>
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