netdev - Re: [PATCH net-next v1 1/1] net: bridge: ensure that link-local traffic cannot unlock a locked port

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Message-ID: <CAKUejP5=eNyAso=MW2nb2o=OKMaysmWUJ-zqLcerPg6EzsQVYQ@mail.gmail.com>
Date:   Mon, 4 Jul 2022 16:36:12 +0200
From:   Hans S <schultz.hans@...il.com>
To:     Ido Schimmel <idosch@...dia.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>, Jiri Pirko <jiri@...nulli.us>,
        Ivan Vecera <ivecera@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Shuah Khan <shuah@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Hans Schultz <schultz.hans+netdev@...il.com>,
        linux-kernel@...r.kernel.org, bridge@...ts.linux-foundation.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next v1 1/1] net: bridge: ensure that link-local
 traffic cannot unlock a locked port

On Mon, Jul 4, 2022 at 1:00 PM Ido Schimmel <idosch@...dia.com> wrote:
>
> On Mon, Jul 04, 2022 at 09:54:31AM +0200, Hans S wrote:
> > >
> > > IIUC, with mv88e6xxx, when the port is locked and learning is disabled:
> > >
> > > 1. You do not get miss violation interrupts. Meaning, you can't report
> > > 'locked' entries to the bridge driver.
> > >
> > > 2. You do not get aged-out interrupts. Meaning, you can't tell the
> > > bridge driver to remove aged-out entries.
> > >
> > > My point is that this should happen regardless if learning is enabled on
> > > the bridge driver or not. Just make sure it is always enabled in
> > > mv88e6xxx when the port is locked. Learning in the bridge driver itself
> > > can be off, thereby eliminating the need to disable learning from
> > > link-local packets.
> >
> > So you suggest that we enable learning in the driver when locking the
> > port and document that learning should be turned off from user space
> > before locking the port?
>
> Yes. Ideally, the bridge driver would reject configurations where
> learning is enabled and the port is locked, but it might be too late for
> that. It would be good to add a note in the man page that learning
> should be disabled when the port is locked to avoid "unlocking" the port
> by accident.

Well you cannot unlock the port by either enabling or disabling
learning after the port is locked, but Mac-Auth and refreshing might
not work. I clarify just so that no-one gets confused.

I can do so that the driver returns -EINVAL if learning is on when
locking the port, but that would of course only be for mv88e6xxx...