linux-kernel - Re: [PATCH v4 net-next 3/6] drivers: net: dsa: add locked fdb entry flag to drivers

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Message-ID: <YsqPWK67U0+Iw2Ru@shredder>
Date:   Sun, 10 Jul 2022 11:35:36 +0300
From:   Ido Schimmel <idosch@...dia.com>
To:     netdev@...io-technology.com
Cc:     Vladimir Oltean <olteanv@...il.com>, davem@...emloft.net,
        kuba@...nel.org, netdev@...r.kernel.org,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.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>,
        Daniel Borkmann <daniel@...earbox.net>,
        linux-kernel@...r.kernel.org, bridge@...ts.linux-foundation.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v4 net-next 3/6] drivers: net: dsa: add locked fdb entry
 flag to drivers

On Fri, Jul 08, 2022 at 02:34:25PM +0200, netdev@...io-technology.com wrote:
> On 2022-07-08 13:56, Vladimir Oltean wrote:
> > On Fri, Jul 08, 2022 at 11:50:33AM +0200, netdev@...io-technology.com
> > wrote:
> > > On 2022-07-08 11:15, Vladimir Oltean wrote:
> > > > When the possibility for it to be true will exist, _all_ switchdev
> > > > drivers will need to be updated to ignore that (mlxsw, cpss, ocelot,
> > > > rocker, prestera, etc etc), not just DSA. And you don't need to
> > > > propagate the is_locked flag to all individual DSA sub-drivers when none
> > > > care about is_locked in the ADD_TO_DEVICE direction, you can just ignore
> > > > within DSA until needed otherwise.
> > > >
> > > 
> > > Maybe I have it wrong, but I think that Ido requested me to send it
> > > to all
> > > the drivers, and have them ignore entries with is_locked=true ...
> > 
> > I don't think Ido requested you to ignore is_locked from all DSA
> > drivers, but instead from all switchdev drivers maybe. Quite different.
> 
> So without changing the signature on port_fdb_add(). If that is to avoid
> changing that signature, which needs to be changed anyhow for any switchcore
> driver to act on it, then my next patch set will change the signarure also
> as it is needed for creating dynamic ATU entries from userspace, which is
> needed to make the whole thing complete.
> 
> As it is already done (with the is_locked to the drivers) and needed for
> future application, I would like Ido to comment on it before I take action.

It's related to my reply here [1]. AFAICT, we have two classes of device
drivers:

1. Drivers like mv88e6xxx that report locked entries to the bridge
driver via 'SWITCHDEV_FDB_ADD_TO_BRIDGE'.

2. Drivers like mlxsw that trap packets that incurred an FDB miss to the
bridge driver. These packets will cause the bridge driver to emit
'SWITCHDEV_FDB_ADD_TO_DEVICE' notifications with the locked flag.

If we can agree that locked entries are only meant to signal to user
space that a certain MAC tried to gain authorization and that the bridge
should ignore them while forwarding, then there is no point in
generating the 'SWITCHDEV_FDB_ADD_TO_DEVICE' notifications. We should
teach the bridge driver to suppress these so that there is no need to
patch all the device drivers.

[1] https://lore.kernel.org/netdev/YsqLyxTRtUjzDj6D@shredder/

> 
> > 
> > In any case I'm going to take a look at this patch set more closely and
> > run the selftest on my Marvell switch, but I can't do this today
> > unfortunately. I'll return with more comments.
> 
> Yes :-)