netdev - Re: [RFC net-next 2/7] net: bridge: switchdev: Include local flag in FDB notifications

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Message-ID: <20210118192842.GA2396253@shredder.lan>
Date:   Mon, 18 Jan 2021 21:28:42 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Tobias Waldekranz <tobias@...dekranz.com>, davem@...emloft.net,
        kuba@...nel.org, andrew@...n.ch, vivien.didelot@...il.com,
        f.fainelli@...il.com, roopa@...dia.com, nikolay@...dia.com,
        netdev@...r.kernel.org, jiri@...nulli.us,
        stephen@...workplumber.org
Subject: Re: [RFC net-next 2/7] net: bridge: switchdev: Include local flag in
 FDB notifications

On Sun, Jan 17, 2021 at 09:30:09PM +0200, Vladimir Oltean wrote:
> Hi Tobias,
> 
> On Sat, Jan 16, 2021 at 02:25:10AM +0100, Tobias Waldekranz wrote:
> > Some switchdev drivers, notably DSA, ignore all dynamically learned
> > address notifications (!added_by_user) as these are autonomously added
> > by the switch. Previously, such a notification was indistinguishable
> > from a local address notification. Include a local bit in the
> > notification so that the two classes can be discriminated.
> >
> > This allows DSA-like devices to add local addresses to the hardware
> > FDB (with the CPU as the destination), thereby avoiding flows towards
> > the CPU being flooded by the switch as unknown unicast.
> >
> > Signed-off-by: Tobias Waldekranz <tobias@...dekranz.com>
> > ---
> 
> In an ideal world, the BR_FDB_LOCAL bit of an FDB entry is what you
> would probably want to use as an indication that the packet must be
> delivered upstream by the hardware, considering that this is what the
> software data path does:
> 
> br_handle_frame_finish:
> 		if (test_bit(BR_FDB_LOCAL, &dst->flags))
> 			return br_pass_frame_up(skb);
> 
> However, we are not in an ideal world, but in a cacophony of nonsensical
> flags that must be passed to the 'bridge fdb add' command. For example,
> I noticed this usage pattern in your patch 6/7:

Thanks for adding me. Reflecting FDB flags is a very much needed change.
I will take a look tomorrow or the day after.