netdev - Re: [PATCH net-next v1] net: dsa: mv88e6xxx: Trap PTP traffic

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Message-ID: <20211211153926.GA3357@hoboy.vegasvil.org>
Date:   Sat, 11 Dec 2021 07:39:26 -0800
From:   Richard Cochran <richardcochran@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Tobias Waldekranz <tobias@...dekranz.com>,
        Kurt Kanzenbach <kurt@...-computers.de>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v1] net: dsa: mv88e6xxx: Trap PTP traffic

On Fri, Dec 10, 2021 at 09:14:10PM -0800, Jakub Kicinski wrote:
> On Fri, 10 Dec 2021 01:07:59 +0100 Tobias Waldekranz wrote:
> > Do we know how PTP is supposed to work in relation to things like STP?
> > I.e should you be able to run PTP over a link that is currently in
> > blocking?
> 
> Not sure if I'm missing the real question but IIRC the standard
> calls out that PTP clock distribution tree can be different that
> the STP tree, ergo PTP ignores STP forwarding state.

That is correct.  The PTP will form its own spanning tree, and that
might be different than the STP.  In fact, the Layer2 PTP messages
have special MAC addresses that are supposed to be sent
unconditionally, even over blocked ports.

Thanks,
Richard