linux-kernel - Re: [PATCH net-next v3 08/12] net: dsa: rzn1-a5psw: add FDB support

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Date:   Thu, 5 May 2022 19:30:33 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Clément Léger <clement.leger@...tlin.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Herve Codina <herve.codina@...tlin.com>,
        Miquèl Raynal <miquel.raynal@...tlin.com>,
        Milan Stevanovic <milan.stevanovic@...com>,
        Jimmy Lalande <jimmy.lalande@...com>,
        Pascal Eberhard <pascal.eberhard@...com>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v3 08/12] net: dsa: rzn1-a5psw: add FDB support

On Thu, May 05, 2022 at 03:44:31PM +0200, Clément Léger wrote:
> Indeed, I'll simply remove these error message. Should I still return
> an error value however ? Seems like I should not to avoid triggering
> any error that might confuse the user.

The error code will not be propagated to the bridge driver anyway, but
will trigger prints in dsa_slave_switchdev_event_work() however.

You have to choose between 2 alternatives
(a) keep the FDB entry around until it gets removed from all VLANs
(b) delete the FDB entry as soon as it gets removed from the first VLAN

Both options are going to raise eyebrows. (a) will result in "huh, why
did my packet get delivered to this port when the address wasn't in the
FDB?", while (b) will result in "huh, why was my packet flooded when the
address was in the FDB?"

And since (b) is of lower complexity than (a), I'd just silently exit,
maybe add a comment explaining why, and hope for the best.