netdev - Re: [PATCH net v2] sctp: start t5 timer only when peer.rwnd is 0 and local.state is SHUTDOWN

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Date:	Thu, 27 Aug 2015 11:14:57 -0400
From:	Vlad Yasevich <vyasevic@...hat.com>
To:	lucien xin <lucien.xin@...il.com>
CC:	Marcelo Ricardo Leitner <mleitner@...hat.com>,
	network dev <netdev@...r.kernel.org>,
	Thomas Graf <tgraf@...radead.org>, davem <davem@...emloft.net>
Subject: Re: [PATCH net v2] sctp: start t5 timer only when peer.rwnd is 0
 and local.state is SHUTDOWN_PENDING

On 08/27/2015 10:49 AM, lucien xin wrote:
>>
>> So one potential way is to have peer.rwnd and peer.a_rwnd, where peer.a_rwnd is
>> the window advertised by peer and peer.rwnd and our estimation based on peer.a_rwnd.
>> This way we will always know where we stand.
>>
>> Although I am not sure yet if we want to grow the peer structure any more.
>>
>> Another way is to have an estimate or 0-window probe bit/flags one the send side
>> and set it when we do 0-window probe.  This way we'd know that when 0-window probe
>> bit is set, peer returned 0 window.
>>
> I think updating 0-window may happen in sctp_process_init() and
> sctp_outq_sack(),
> I don't think 0-window can be probed, cause unreachable and closing
> window both has
> no reply from peer. but we can update the 0-window bit in those two
> functions. I just do
> not know where there is a available bit we can use if won't change the
> peer structure.

You can ignore INIT as the window will never be 0 (not allowed).

The updates could happen at the end of sctp_outq_sack().   There some spare
bits in peer if you want to go that way.

-vlad


> 
>> Just some thoughts.
>> -vlad

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