netdev - Re: Something hitting my total number of connections to the server

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Message-ID: <CADVnQy=57_rc8A93zAcqr9hz1WtWniSoZdtx+-aTiZ6AyjZmQg@mail.gmail.com>
Date:   Tue, 22 Aug 2017 08:28:14 -0400
From:   Neal Cardwell <ncardwell@...gle.com>
To:     Akshat Kakkar <akshat.1984@...il.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        David Laight <David.Laight@...lab.com>,
        netdev <netdev@...r.kernel.org>
Subject: Re: Something hitting my total number of connections to the server

On Tue, Aug 22, 2017 at 1:42 AM, Akshat Kakkar <akshat.1984@...il.com> wrote:
> There are multiple hosts/clients. All are mainly windows based.
>
> Timestamp is not used as my clients mainly are windows based and in
> that it tcp timestamp is by defauly disabled.
...
> net.ipv4.tcp_tw_reuse=1
> net.ipv4.tcp_tw_recycle=1

I suspect the problem is there. The net.ipv4.tcp_tw_recycle setting
should be 0. Running with the value 1 is known to cause buggy behavior
related to TCP timestamps, and that feature has been removed in kernel
v4.12.

Can you please re-run your tests with net.ipv4.tcp_tw_recycle=0 or a
newer kernel?

neal