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

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Message-ID: <CADvbK_cb84dyjpnCQqgdryM7XcJ+GjBr1DmqFAgPEBX7d9aKvA@mail.gmail.com>
Date:	Fri, 28 Aug 2015 00:40:21 +0800
From:	lucien xin <lucien.xin@...il.com>
To:	Vlad Yasevich <vyasevic@...hat.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

>>>
>>> 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.
>
I find this one *addip_disabled_mask*, but it's really bad to use it.
we should put a extensible mask or point there before.

as to a_rwnd, it's a good idea, but if we just use it here, it may not be worth
doing that. if there are a lot places need it, we can add it.
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