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

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Message-ID: <CANn89iKuVa8-piOf424HyiFZqTHEjFEGa7C5KV4TMWNZyhJzvQ@mail.gmail.com>
Date:   Tue, 4 Aug 2020 15:29:05 -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 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 ?


>
> Maybe I'm dumb, but the changelog is vague to me. It isn't clear what
> kind of routing it is, what type of traffic was the router being
> subjected to, from what direction was the VLAN traffic coming, was it
> just VLAN 0 that was problematic, what drivers those were, what kernel
> was used, what has any of that have to do with the referenced commit
> 48cc32d38a52 ("vlan: don't deliver frames for unknown vlans to
> protocols") which is about macvlan returning RX_HANDLER_PASS instead of
> RX_HANDLER_ANOTHER, were there other sub-interfaces as well?

The kernel was the very kernel right before the change. git will tell
you that easily.

> And there are also obvious mistakes in the commit description: "if the
> vlan id is set and we could find a vlan device for this particular id."
> -> "couldn't" should be instead of "could".
>

Complaining about a change log seven years after the commit is rather useless.

> This is ridiculous.

Ok