linux-kernel - Re: Flowtables ignore timeout settings in recent kernels

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Message-ID: <ZTglADWVBgKxKOIC@calendula>
Date:   Tue, 24 Oct 2023 22:11:44 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Bagas Sanjaya <bagasdotme@...il.com>
Cc:     Vladimir Smelhaus <vl.sm@...il.cz>,
        Linux Netfilter <netfilter@...r.kernel.org>,
        coreteam@...filter.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Regressions <regressions@...ts.linux.dev>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>
Subject: Re: Flowtables ignore timeout settings in recent kernels

On Mon, Oct 16, 2023 at 07:20:06AM +0700, Bagas Sanjaya wrote:
> On Sun, Oct 15, 2023 at 09:56:14PM +0200, Vladimir Smelhaus wrote:
> > Netfilter ignores the timeout settings for a flowtable
> > 
> > # sysctl -a -r flowtable
> > net.netfilter.nf_flowtable_tcp_timeout = 30
> > net.netfilter.nf_flowtable_udp_timeout = 30
> > 
> > Situation. A long udp connection (tunnel) with some data flowing through a
> > router. The connection is sent to a flowtable on the router. It's a few
> > packets per second, more here and there, a pause here and there, and so on
> > over and over. The pauses are minimal and are also limited by the tunnel
> > settings to be no longer than 25 seconds. Everything is satisfying to make
> > the connection last continuously in the flowtable and not reappear in
> > forward. However, the connection keeps dropping out of the flowtable. It
> > stays in the flowtable (offloaded) for a second at most and then it is
> > kicked out, back to forward.
> > 
> > In an attached test script you can see counters that should be zero but are not. If I watch the normal packet flow on a particular router, I can see packets in the conntrack table that should be OFFLOAD as ASSURED.
> > 
> > Tested in kernel 6.5.6. In an old(er) kernel 5.10 it works as expected.
> > 
> 
> Then please perform bisection to find a culprit that introduces your
> regression (see Documentation/admin-guide/bug-bisect.rst in the kernel
> sources for reference). Also, it'd been great if you also post the
> reproducer script inline (within your email) instead, as some MUAs
> (like mutt that I'm using now) may ignore the attachment.
> 
> Anyway, thanks for the regression report. I'm adding it to regzbot:
> 
> #regzbot ^introduced: v5.10..v6.5

Fix here:

https://patchwork.ozlabs.org/project/netfilter-devel/patch/20231024193815.1987-1-pablo@netfilter.org/

it is a bug from Jun 2023, regression was introduced in the v6.5
development cycle.

Thanks for reporting.