netdev - Re: [PATCH net-next] tcp/dccp: drop SYN packets if accept queue is full

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Message-ID: <CADVnQy=f==Ffk_=xPN7hOHyu5sHqhgi3rUw89rTYn1fxF7HdqQ@mail.gmail.com>
Date:   Wed, 26 Oct 2016 14:39:47 -0400
From:   Neal Cardwell <ncardwell@...gle.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Yuchung Cheng <ycheng@...gle.com>
Subject: Re: [PATCH net-next] tcp/dccp: drop SYN packets if accept queue is full

On Wed, Oct 26, 2016 at 12:27 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> From: Eric Dumazet <edumazet@...gle.com>
>
> Per listen(fd, backlog) rules, there is really no point accepting a SYN,
> sending a SYNACK, and dropping the following ACK packet if accept queue
> is full, because application is not draining accept queue fast enough.
>
> This behavior is fooling TCP clients that believe they established a
> flow, while there is nothing at server side. They might then send about
> 10 MSS (if using IW10) that will be dropped anyway while server is under
> stress.
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---

Acked-by: Neal Cardwell <ncardwell@...gle.com>

Great. Thanks, Eric!

neal