netdev - Re: [PATCH net 1/2] tcp: disable Fast Open on timeouts after handshake

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Message-ID: <CAK6E8=eiL30svYbqSpRN=QKp4MEX7_ezmUNXm+b7api42QvPDg@mail.gmail.com>
Date:	Fri, 20 Nov 2015 09:40:53 -0800
From:	Yuchung Cheng <ycheng@...gle.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net 1/2] tcp: disable Fast Open on timeouts after handshake

On Fri, Nov 20, 2015 at 7:52 AM, David Miller <davem@...emloft.net> wrote:
> From: Yuchung Cheng <ycheng@...gle.com>
> Date: Wed, 18 Nov 2015 18:17:30 -0800
>
>> Some middle-boxes black-hole the data after the Fast Open handshake
>> (https://www.ietf.org/proceedings/94/slides/slides-94-tcpm-13.pdf).
>> The exact reason is unknown. The work-around is to disable Fast Open
>> temporarily after multiple recurring timeouts with few or no data
>> delivered in the established state.
>>
>> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
>> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>> Reported-by: Christoph Paasch <cpaasch@...le.com>
>
> Applied and queued up for -stable.
>
> Just out of curiosity, why isn't a test for zero data sufficient?
>
> Do these middle-boxes sometimes not black-hole all of the data?
Great question. I should be more clear in the commit message. The
answer is yes it should be sufficient. The tricky part is
tp->bytes_acked includes data acked in the SYN. Since we don't
remember data size sent in SYN, hence the heuristic.
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