Linux Ethernet Bridging - Mar 2023 - [Bridge] [PATCH v2 net-next 2/6] net: dsa: propagate flags down towards drivers

On Mon, Mar 27, 2023 at 11:49:58PM +0200, Hans Schultz
wrote:
> 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.
Link to patch? I don't see any SWITCHDEV_FDB_ADD_TO_BRIDGE call in
either the v1:
https://lore.kernel.org/netdev/20230130173429.3577450-6-netdev at
kapio-technology.com/
or the RFC:
https://lore.kernel.org/netdev/20230117185714.3058453-6-netdev at
kapio-technology.com/
and the change log does not mention it either.
> 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.
Actually, the part which you are now posing as a question (what is the
difference?) was part of the premise of your earlier question (there is
no difference => why do we have both?).
https://lore.kernel.org/netdev/d972e76bed896b229d9df4da81ad8eb4 at
kapio-technology.com/

I believe that no one answered because the question was confused and it
wasn't really clear what you were asking.
> 
> 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)
which idea is that, again?

On Tue, Mar 28, 2023 at 01:59, Vladimir Oltean <olteanv at gmail.com>
wrote:
>
> which idea is that, again?
So I cannot us the offloaded flag as it is added by DSA in the common
case when using 'bridge fdb replace ... dynamic'.

The idea is then to use the ext_learn flag instead, which is not aged by
the bridge. To do this the driver (mv88e6xxx) will send a
SWITCHDEV_FDB_ADD_TO_BRIDGE switchdev event when the new dynamic flag is
true. The function sending this event will then be named
mv88e6xxx_add_fdb_synth_learned() in
drivers/net/dsa/mv88e6xxx/switchdev.c, replacing the
mv88e6xxx_set_fdb_offloaded() function but in most part the same
content, just another event type.