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

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Message-ID: <20200804224430.qt4zc2vihz7zeks6@skbuf>
Date:   Wed, 5 Aug 2020 01:44:30 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>,
        "Steinar H. Gunderson" <steinar+kernel@...derson.no>
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 Wed, Aug 05, 2020 at 01:39:52AM +0300, Vladimir Oltean wrote:
> On Tue, Aug 04, 2020 at 03:29:05PM -0700, Eric Dumazet wrote:
> > On Tue, Aug 4, 2020 at 2:24 PM Vladimir Oltean <olteanv@...il.com> wrote:
> > >
> > > On Tue, Aug 04, 2020 at 01:36:56PM -0700, Eric Dumazet wrote:
> > > > On Tue, Aug 4, 2020 at 12:43 PM Vladimir Oltean <olteanv@...il.com> wrote:
> > > > >
> > > > > On Tue, Aug 04, 2020 at 12:40:24PM -0700, Eric Dumazet wrote:
> > > > > > 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.
> > > > >
> > > > > Do you mind if I respectfully revert then? It's clear that the patch has
> > > > > loopholes already (it clears the vlan if it's hwaccel, but leaves it
> > > > > alone if it isn't) and that the proper solution should be different
> > > > > anyway.
> > > >
> > > > Clearly the situation before the patch was not good, it seems well
> > > > explained in the changelog.
> > > >
> > > > If you want to revert, you will need to convince the bug has been
> > > > solved in another way.
> > > >
> > > > So it seems you might have to repro the initial problem.
> > >
> > > What bug? What repro? You just said you don't have any.
> > 
> > Ask Steinar ?
> > 
> 
> Hi Steinar, do you have a reproducer for the bug that Eric fixed in
> commit d4b812dea4a2 ("vlan: mask vlan prio bits")?
> 
> Thanks,
> -Vladimir

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