netdev - Re: resend: tcp: performance issue with fastopen connections (mss

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Date:   Wed, 18 Jan 2017 10:16:45 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Yuchung Cheng <ycheng@...gle.com>
Cc:     Alexey Kodanev <alexey.kodanev@...cle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Vasily Isaenko <vasily.isaenko@...cle.com>,
        Neal Cardwell <ncardwell@...gle.com>
Subject: Re: resend: tcp: performance issue with fastopen connections (mss > window)

On Wed, Jan 18, 2017 at 10:13 AM, Yuchung Cheng <ycheng@...gle.com> wrote:
> On Wed, Jan 18, 2017 at 9:35 AM, Eric Dumazet <edumazet@...gle.com> wrote:
>>
>> On Wed, Jan 18, 2017 at 9:32 AM, Alexey Kodanev
>> <alexey.kodanev@...cle.com> wrote:
>> > Hi Eric,
>> >
>> > On 01/13/2017 08:07 PM, Alexey Kodanev wrote:
>> >
>>
>> > Looks like max_window not correctly initialized for tfo sockets.
>> > On my test machine it has set to '5592320' in tcp_fastopen_create_child().
>> >
>> > This diff fixes the issue, the question: is this the right place to do it?
>> >
>> > diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
>> > index 4e777a3..33ed508 100644
>> > --- a/net/ipv4/tcp_fastopen.c
>> > +++ b/net/ipv4/tcp_fastopen.c
>> > @@ -206,6 +206,8 @@ static struct sock *tcp_fastopen_create_child(struct
>> > sock *sk,
>> >          */
>> >         tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
>> >
>> > +       tp->max_window = tp->snd_wnd;
>> > +
>>
>> Excellent catch. Let me test our regression tests with this.
> Indeed nice catch. Thanks for the investigative work!
>

We do have 2 failures, but tests might have depended on undocumented behavior

(For googlers :
Ran 211 tests: 209 passing, 0 flaky 2 failing
Sponge: http://sponge/f1575065-6e1c-4514-bced-9167ce56d2ee
)

Please Alexey submit an official patch, thanks a lot !