netdev - Re: [PATCH net-next 2/2] net: bridge: switchdev: include local flag in FDB notifications

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Message-ID: <YHcadT4XhBq7g61Y@lunn.ch>
Date:   Wed, 14 Apr 2021 18:38:13 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Ioana Ciornei <ioana.ciornei@....com>,
        Vadym Kochan <vkochan@...vell.com>,
        Taras Chornyi <tchornyi@...vell.com>,
        Jiri Pirko <jiri@...dia.com>, Ido Schimmel <idosch@...dia.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Ivan Vecera <ivecera@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <nikolay@...dia.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-omap@...r.kernel.org,
        Vladimir Oltean <vladimir.oltean@....com>,
        Tobias Waldekranz <tobias@...dekranz.com>
Subject: Re: [PATCH net-next 2/2] net: bridge: switchdev: include local flag
 in FDB notifications

On Wed, Apr 14, 2021 at 07:05:10PM +0300, Vladimir Oltean wrote:
> On Wed, Apr 14, 2021 at 05:58:44PM +0200, Andrew Lunn wrote:
> > > Let us now add the 'is_local' bit to bridge FDB entries, and make all
> > > drivers ignore these entries by their own choice.
> > 
> > Hi Vladimir
> > 
> > This goes to the question about the missing cover letter. Why should
> > drivers get to ignore them, rather than the core? It feels like there
> > should be another patch in the series, where a driver does not
> > actually ignore them, but does something?
> 
> Hi Andrew,
> 
> Bridge fdb entries with the is_local flag are entries which are
> terminated locally and not forwarded. Switchdev drivers might want to be
> notified of these addresses so they can trap them (otherwise, if they
> don't program these entries to hardware, there is no guarantee that they
> will do the right thing with these entries, and they won't be, let's
> say, flooded). Of course, ideally none of the switchdev drivers should
> ignore them, but having access to the is_local bit is the bare minimum
> change that should be done in the bridge layer, before this is even
> possible.
> 
> These 2 changes are actually part of a larger group of changes that
> together form the "RX filtering for DSA" series. I haven't had a lot of
> success with that, so I thought a better approach would be to take it
> step by step. DSA will need to be notified of local FDB entries. For
> now, it ignores them like everybody else. This is supposed to be a
> non-functional patch series because I don't want to spam every switchdev
> maintainer with 15+ DSA RX filtering patches.

This is the sort of information which goes into 0/2. It explains the
big picture 'Why' of the change.

    Andrew