netdev - Re: commit 4c7ea3c0791e (net: dsa: mv88e6xxx: disable SA learning for DSA and CPU ports)

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Date:   Mon, 18 Jan 2021 20:01:12 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Tobias Waldekranz <tobias@...dekranz.com>
Cc:     Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
        Network Development <netdev@...r.kernel.org>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        Vladimir Oltean <olteanv@...il.com>
Subject: Re: commit 4c7ea3c0791e (net: dsa: mv88e6xxx: disable SA learning
 for DSA and CPU ports)

On Mon, Jan 18, 2021 at 07:30:49PM +0100, Tobias Waldekranz wrote:
> On Mon, Jan 18, 2021 at 18:50, Andrew Lunn <andrew@...n.ch> wrote:
> >> I suppose the real solution is having userspace do some "bridge mdb add"
> >> yoga, but since no code currently uses
> >> MV88E6XXX_G1_ATU_DATA_STATE_MC_STATIC_DA_MGMT, I don't think there's any
> >> way to actually achieve this. And I have no idea how to represent the
> >> requirement that "frames with this multicast DA are only to be directed
> >> at the CPU" in a hardware-agnostic way.
> >
> > The switchdev interface for this exists, because there can be
> > multicast listeners on the bridge. When they join a group, they ask
> > the switch to put in a HOST MDB, which should cause the traffic for
> 
> That is not quite the same thing as "management" though. Adding the
> group to the host MDB will not allow it to pass through blocked (in the
> STP sense) ports for example. With a management entry, the switch will
> trap the packet with a TO_CPU tag, which means no ingress policy can get
> in the way of it reaching the CPU.

Ah, yes. I don't suppose the DA is part of the special group which the
switch will recognise as management and pass it on?

01:80:c2:00:00:00 - 01:80:c2:00:00:07
01:80:c2:00:00:08 - 01:80:c2:00:00:0f
01:80:c2:00:00:20 - 01:80:c2:00:00:27
01:80:c2:00:00:28 - 01:80:c2:00:00:2f

	Andrew