linux-kernel - 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: <CAKUejP6g3HxS=Scj-2yhsQRJApxnq1e31Nkcc995s7gzfMJOew@mail.gmail.com>
Date:   Sun, 17 Jul 2022 18:22:57 +0200
From:   Hans S <schultz.hans@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Ido Schimmel <idosch@...dia.com>,
        "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>,
        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 Sun, Jul 17, 2022 at 4:03 PM Vladimir Oltean <olteanv@...il.com> wrote:
>
> On Sun, Jul 17, 2022 at 04:46:10PM +0300, Vladimir Oltean wrote:
> > Here, what happens is that a locked port learns the MAC SA from the
> > traffic it didn't drop, i.e. link-local. In other words, the bridge
> > behaves as expected and instructed: +locked +learning will cause just
> > that. It's the administrator's fault for not disabling learning.
> > It's also the mv88e6xxx driver's fault for not validating the "locked" +
> > "learning" brport flag *combination* until it properly supports "+locked
> > +learning" (the feature you are currently working on).
> >
> > I'm still confused why we don't just say that "+locked -learning" means
> > plain 802.1X, "+locked +learning" means MAB where we learn locked FDB entries.
>
> Or is it the problem that a "+locked +learning" bridge port will learn
> MAC SA from link-local traffic, but it will create FDB entries without
> the locked flag while doing so? The mv88e6xxx driver should react to the
> 'locked' flag from both directions (ADD_TO_DEVICE too, not just ADD_TO_BRIDGE).

Yes, it creates an FDB entry in the bridge without the locked flag
set, and sends an ADD_TO_DEVICE notice with it.
And furthermore link-local packets include of course EAPOL packets, so
that's why +learning is a problem.