netdev - Re: [PATCH RFC net-next 2/5] net/sched: act

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Message-ID: <CANn89iLfM=sg4L16Fqj2o9VO59n_sn1u9acYr4Fe5P4bHBqE5Q@mail.gmail.com>
Date: Sun, 12 Oct 2025 11:34:51 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Jamal Hadi Salim <jhs@...atatu.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>, 
	Kuniyuki Iwashima <kuniyu@...gle.com>, Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com
Subject: Re: [PATCH RFC net-next 2/5] net/sched: act_mirred: add loop detection

On Sun, Oct 12, 2025 at 8:23 AM Jamal Hadi Salim <jhs@...atatu.com> wrote:
>
> On Mon, Oct 6, 2025 at 3:31 PM Eric Dumazet <edumazet@...gle.com> wrote:
> >
> > We want to revert commit 0f022d32c3ec ("net/sched: Fix mirred deadlock
> > on device recursion") because it adds code in the fast path, even when
> > act_mirred is not used.
> >
> > Use an additional device pointers array in struct netdev_xmit
> > and implement loop detection in tcf_mirred_is_act_redirect().
>
> Patch series looks good!
> This has the potential of (later on) fixing issue that are currently
> broken after the TTL bits were taken away.
> Small suggestion, the commit message was a bit confusing to me. How about:
>
> Commit 0f022d32c3ec ("net/sched: Fix mirred deadlock on device
> recursion") it adds code in the fast path, even when act_mirred is not
> used. We revert in the next patch.
>
> Prepare by adding an additional device pointers array in struct
> netdev_xmit and implement loop detection in
> tcf_mirred_is_act_redirect().
>
> Please give us time to run tests on this set!

SGTM, I will send when net-next reopens, with an amended changelog

    net/sched: act_mirred: add loop detection

     Commit 0f022d32c3ec ("net/sched: Fix mirred deadlock on device recursion")
    added code in the fast path, even when act_mirred is not used.

    Prepare its revert by implementing loop detection in act_mirred.

    Adds an array of device pointers in struct netdev_xmit.

    tcf_mirred_is_act_redirect() can detect if the array
    already contains the target device.