netdev - Re: PROBLEM: (DSA/Microchip): 802.1Q-Header lost on KSZ9477-DSA ingress without bridge

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Date:   Tue, 4 Aug 2020 12:40:24 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     "Gaube, Marvin (THSE-TL1)" <Marvin.Gaube@...at.de>,
        Florian Fainelli <f.fainelli@...il.com>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: PROBLEM: (DSA/Microchip): 802.1Q-Header lost on KSZ9477-DSA
 ingress without bridge

On Tue, Aug 4, 2020 at 12:29 PM Vladimir Oltean <olteanv@...il.com> wrote:
>
> On Tue, Aug 04, 2020 at 07:54:18AM -0700, Eric Dumazet wrote:
> >
> > My 2013 commit was a bug fix, and hinted that in the future (eg in
> > net-next tree) the stop-the-bleed could be refined.
> >
> > +               /* Note: we might in the future use prio bits
> > +                * and set skb->priority like in vlan_do_receive()
> > +                * For the time being, just ignore Priority Code Point
> > +                */
> > +               skb->vlan_tci = 0;
> >
> > If you believe this can be done, this is great.
>
> Do you have a reproducer for that bug? I am willing to spend some time
> understand what is going on. This has nothing to do with priority. You
> vaguely described a problem with 802.1p (VLAN 0) and used that as an
> excuse to clear the entire vlan hwaccel tag regardless of VLAN ID. I'm
> curious because we also now have commit 36b2f61a42c2 ("net: handle
> 802.1P vlan 0 packets properly") in that general area, and I simply want
> to know if your patch still serves a valid purpose or not.
>

I do not have a repro, the patch seemed to help at that time,
according to the reporter.