linux-kernel - Re: [PATCH v8 net-next 10/12] net: dsa: mv88e6xxx: mac-auth/MAB implementation

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Message-ID: <20221022133937.hfrr7sxaq2zlbnoq@skbuf>
Date:   Sat, 22 Oct 2022 16:39:37 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Oleksandr Mazur <oleksandr.mazur@...ision.eu>
Cc:     "netdev@...io-technology.com" <netdev@...io-technology.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
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        Florian Fainelli <f.fainelli@...il.com>,
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        Kurt Kanzenbach <kurt@...utronix.de>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Woojung Huh <woojung.huh@...rochip.com>,
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        Yuwei Wang <wangyuweihx@...il.com>,
        Petr Machata <petrm@...dia.com>,
        Ido Schimmel <idosch@...dia.com>,
        Florent Fourcot <florent.fourcot@...irst.fr>,
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        Amit Cohen <amcohen@...dia.com>,
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        <linux-mediatek@...ts.infradead.org>,
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        <bridge@...ts.linux-foundation.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH v8 net-next 10/12] net: dsa: mv88e6xxx: mac-auth/MAB
 implementation

On Sat, Oct 22, 2022 at 12:55:14PM +0000, Oleksandr Mazur wrote:
> 
> > I hope the following script will exemplify what I mean.
> ..
> Oh, i get it now.
> 
> Frankly speaking we haven't stumbled across such scenario / issue
> before. But i can tell it does indeed seems a bit broken;
> 
> I think there are 2 options here:
>   1. The setup itself seems insecure, and user should be aware of such behavior / issue;

Be aware, and do what? Port locking is unfit for use if learning is left
enabled (in the way learning is currently done).

>   2. Bridge indeed should not learn MACs if BR_PORT_LOCKED is set.
>   E.g. learning condition should be something like: not BR_PORT_locked
>   and learning is on; 

Rather than violate the BR_LEARNING flag (have it set but do nothing,
which would require even more checks in the fast path), I was proposing
to not allow the BR_PORT_LOCKED | BR_LEARNING configuration at all.
My question to you was if you're aware of any regression in prestera
with such a change.

> > I don't understand the last step. Why is the BR_PORT_LOCKED flag disabled?
> > If disabled, the port will receive frames with any unknown MAC SA,
> > not just the authorized ones.
> 
> Sorry for the confusion. Basically, what i described what i would
> expect from a daemon (e.g. daemon would disable LOCKED); So just
> ignore that part.

But still, why would the daemon disable BR_PORT_LOCKED once a station is
authorized? You're describing a sample/test application, not a port
security solution...