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

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Date:   Thu, 21 Apr 2022 09:38:03 +0200
From:   Clément Léger <clement.leger@...tlin.com>
To:     Vladimir Oltean <olteanv@...il.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>,
        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>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 08/12] net: dsa: rzn1-a5psw: add FDB support

Le Wed, 20 Apr 2022 22:52:14 +0300,
Vladimir Oltean <olteanv@...il.com> a écrit :

> > > 
> > > Shouldn't this contain something along the lines of a VID, FID, something?  
> > 
> > This is extracted directly from the datasheet [1]. The switch FDB table
> > does not seems to store the VID with the entries (See page 300).
> > 
> > [1]
> > https://www.renesas.com/us/en/document/mah/rzn1d-group-rzn1s-group-rzn1l-group-users-manual-r-engine-and-ethernet-peripherals  
> 
> Thanks for the link. I see that the switch has a non-partitionable
> lookup table, not even by VLAN. A shame.
> 
> This is also in contrast with the software bridge driver, where FDB and
> MDB entries can have independent destinations per VID.
> 
> So there's nothing you can do beyond limiting to a single offloaded
> bridge and hoping for the best w.r.t. per-VLAN forwarding destinations.
> 
> Note that if you limit to a single bridge does not mean that you can
> declare ds->fdb_isolation = true. Declaring that would opt you into
> unicast and multicast filtering towards the CPU, i.o.w. a method for
> software to only receive the addresses it has expressed an interest in,
> rather than all packets received on standalone ports. The way that is
> implemented in DSA is by adding FDB and MDB entries on the management
> port, and it would break a lot of things without a partitioning scheme
> for the lookup table.

Thanks Vladimir, it confirms what I thought.

-- 
Clément Léger,
Embedded Linux and Kernel engineer at Bootlin
https://bootlin.com