netdev - Re: [PATCH v4 net-next 3/6] drivers: net: dsa: add locked fdb entry flag to drivers

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Date:   Sun, 17 Jul 2022 18:08:21 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     netdev@...io-technology.com
Cc:     Ido Schimmel <idosch@...dia.com>, davem@...emloft.net,
        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>,
        linux-kernel@...r.kernel.org, bridge@...ts.linux-foundation.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v4 net-next 3/6] drivers: net: dsa: add locked fdb entry
 flag to drivers

On Sun, Jul 17, 2022 at 04:57:50PM +0200, netdev@...io-technology.com wrote:
> 
> Maybe I am just trying to understand the problem you are posing, so afaics
> MAC addresses should be unique and having the same MAC address behind a
> locked port and a not-locked port seems like a mis-configuration regardless
> of vlan setup? As the zero-DPV entry only blocks the specific SA MAC on a
> specific vlan, which is behind a locked port, there shouldn't be any
> problem...?
> 
> If the host behind a locked port starts sending on another vlan than where
> it got the first locked entry, another locked entry will occur, as the
> locked entries are MAC + vlan.

I don't think it's an invalid configuration, I have a 17-port Marvell
switch which I use as infrastructure to connect my PC with my board farm
and to the Internet. I've cropped 4 out of those 17 ports for use in
selftests, effectively now having 2 bridges (br0 used by the selftests
and br-lan for systemd-networkd).

Currently all the traffic sent and received by the selftests is done
through lan1-lan4, but if I wanted to run some bridge locked port tests
with traffic from my PC, what I'd do is I'd connect a (locked) port from br0
to a port from br-lan, and my PC would thus gain indirect connectivity to the
locked port.

Then I'd send a packet and the switch would create a locked FDB entry
for my PC's MAC address, but that FDB entry would span across the entire
MV88E6XXX_FID_BRIDGED, so practically speaking, it would block my PC's
MAC address from doing anything, including accessing the Internet, i.e.
traffic that has nothing at all to do with the locked port in br0.
That isn't quite ok.