linux-kernel - Re: [PATCH] tcp: keepalive fixes

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Date:   Wed, 13 Jan 2021 12:06:27 -0800
From:   Enke Chen <enkechen2020@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Yuchung Cheng <ycheng@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Neal Cardwell <ncardwell@...gle.com>
Subject: Re: [PATCH] tcp: keepalive fixes

Hi, Eric:

Just to clarify: the issues for tcp keepalive and TCP_USER_TIMEOUT are
separate isues, and the fixes would not conflict afaik.

Thanks.  -- Enke

On Tue, Jan 12, 2021 at 11:52:43PM +0100, Eric Dumazet wrote:
> On Tue, Jan 12, 2021 at 11:48 PM Yuchung Cheng <ycheng@...gle.com> wrote:
> >
> > On Tue, Jan 12, 2021 at 2:31 PM Enke Chen <enkechen2020@...il.com> wrote:
> > >
> > > From: Enke Chen <enchen@...oaltonetworks.com>
> > >
> > > In this patch two issues with TCP keepalives are fixed:
> > >
> > > 1) TCP keepalive does not timeout when there are data waiting to be
> > >    delivered and then the connection got broken. The TCP keepalive
> > >    timeout is not evaluated in that condition.
> > hi enke
> > Do you have an example to demonstrate this issue -- in theory when
> > there is data inflight, an RTO timer should be pending (which
> > considers user-timeout setting). based on the user-timeout description
> > (man tcp), the user timeout should abort the socket per the specified
> > time after data commences. some data would help to understand the
> > issue.
> >
> 
> +1
> 
> A packetdrill test would be ideal.
> 
> Also, given that there is this ongoing issue with TCP_USER_TIMEOUT,
> lets not mix things
> or risk added work for backports to stable versions.