linux-kernel - Re: [PATCH v2 net-next 2/6] net: dsa: propagate flags down towards drivers

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Date:   Mon, 27 Mar 2023 23:49:58 +0200
From:   Hans Schultz <netdev@...io-technology.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Woojung Huh <woojung.huh@...rochip.com>,
        "maintainer:MICROCHIP KSZ SERIES ETHERNET SWITCH DRIVER" 
        <UNGLinuxDriver@...rochip.com>, Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Clément Léger <clement.leger@...tlin.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>,
        Christian Marangi <ansuelsmth@...il.com>,
        Ido Schimmel <idosch@...dia.com>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        "open list:RENESAS RZ/N1 A5PSW SWITCH DRIVER" 
        <linux-renesas-soc@...r.kernel.org>,
        "moderated list:ETHERNET BRIDGE" <bridge@...ts.linux-foundation.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH v2 net-next 2/6] net: dsa: propagate flags down towards
 drivers

On Mon, Mar 27, 2023 at 19:00, Vladimir Oltean <olteanv@...il.com> wrote:
> A reasonable question you could ask yourself is: why do my BR_FDB_OFFLOADED
> entries have this flag in the software bridge in the first place?
> Did I add code for it? Is it because there is some difference between
> mv88e6xxx and ocelot/felix, or is it because dsa_fdb_offload_notify()
> gets called in both cases from generic code just the same?
>
> And if dsa_fdb_offload_notify() gets called in both cases just the same,
> but no other driver except for mv88e6xxx emits the SWITCHDEV_FDB_DEL_TO_BRIDGE
> which you've patched the bridge to expect in this series, then what exactly
> is surprising in the fact that offloaded and dynamic FDB entries now become
> stale, but are not removed from the software bridge as they were before?

Yes, I see I have missed that the dsa layer already adds the offloaded
flag in dsa_slave_switchdev_event_work() in slave.c.

My first approach was to use the SWITCHDEV_FDB_ADD_TO_BRIDGE event
and not the SWITCHDEV_FDB_OFFLOADED event as the first would set the
external learned flag which is not aged out by the bridge.
I have at some point earlier asked why there would be two quite
equivalent flags and what the difference between them are, but I didn't
get a response.

Now I see the difference and that I cannot use the offloaded flag
without changing the behaviour of the system as I actually change the
behaviour of the offloaded flag in this version of the patch-set.

So if the idea of a 'synthetically' learned fdb entry from the driver
using the SWITCHDEV_FDB_ADD_TO_BRIDGE event from the driver towards the
bridge instead is accepted, I can go with that?
(thus removing all the changes in the patch-set regarding the offloaded
flag ofcourse)