netdev - Re: [PATCH net 1/2] net: sched: drop ct for the packets toward ingress only in act

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Message-ID: <CAM_iQpULkRxRjMBWKn+7V51PZXLWW17iQBLr1N5vdJmFVZtJ4A@mail.gmail.com>
Date:   Tue, 21 Sep 2021 20:43:18 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Davide Caratti <dcaratti@...hat.com>,
        Hangbin Liu <liuhangbin@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [PATCH net 1/2] net: sched: drop ct for the packets toward
 ingress only in act_mirred

On Tue, Sep 21, 2021 at 12:02 AM Xin Long <lucien.xin@...il.com> wrote:
>
> On Tue, Sep 21, 2021 at 2:31 AM Cong Wang <xiyou.wangcong@...il.com> wrote:
> >
> > On Mon, Sep 20, 2021 at 7:12 AM Xin Long <lucien.xin@...il.com> wrote:
> > >
> > > nf_reset_ct() called in tcf_mirred_act() is supposed to drop ct for
> > > those packets that are mirred or redirected to only ingress, not
> > > ingress and egress.
> >
> > Any reason behind this? I think we at least need to reset it when
> > redirecting from ingress to egress as well? That is, when changing
> > directions?
> For the reason why ct should be reset, it's said in
> d09c548dbf3b ("net: sched: act_mirred: Reset ct info when mirror").
> The user case is OVS HWOL using TC to do NAT and then redirecting
> the NATed skb back to the ingress of one local dev, it's ingress only, this
> patch is more like to minimize the side effect of d09c548dbf3b IF there is.

What is the side effect here? Or what is wrong with resetting CT on
egress side?

>
> Not sure if it's too much to do for that from ingress to egress.
> What I was thinking is this should happen on rx path(ingress), like it
> does in internal_dev_recv() in the OVS kernel module. But IF there is
> any user case needing doing this for ingress to egress, I would add it.

If that is the case, then this patch is completely unnecessary. So
instead of going back and forth, please elaborate on why resetting
CT for egress is a problem here.

Thanks.