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

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Date:   Fri, 08 Jul 2022 11:06:24 +0200
From:   netdev@...io-technology.com
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     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>,
        Ido Schimmel <idosch@...dia.com>, 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 2022-07-08 10:49, Vladimir Oltean wrote:
> Hi Hans,
> 
> On Thu, Jul 07, 2022 at 05:29:27PM +0200, Hans Schultz wrote:
>> Ignore locked fdb entries coming in on all drivers.
>> 
>> Signed-off-by: Hans Schultz <netdev@...io-technology.com>
>> ---
> 
> A good patch should have a reason for the change in the commit message.
> This has no reason because there is no reason.
> 
> Think about it, you've said it yourself in patch 1:
> 
> | Only the kernel can set this FDB entry flag, while userspace can read
> | the flag and remove it by replacing or deleting the FDB entry.
> 
> So if user space will never add locked FDB entries to the bridge,
> then FDB entries with is_locked=true are never transported using
> SWITCHDEV_FDB_ADD_TO_DEVICE to drivers, and so, there is no reason at
> all to pass is_locked to drivers, just for them to ignore something 
> that
> won't appear.

Correct me if I am wrong, but since the bridge can add locked entries, 
and
the ensuring fdb update will create a SWITCHDEV_FDB_ADD_TO_DEVICE, those 
entries
should reach the driver. The policy to ignore those in the driver can be
seen as either the right thing to do, or not yet implemented.

I remember Ido wrote at a point that the scheme they use is to trap 
various
packets to the CPU and let the bridge add the locked entry, which I then
understand is sent to the driver with a SWITCHDEV_FDB_ADD_TO_DEVICE 
event.

> 
> You just need this for SWITCHDEV_FDB_ADD_TO_BRIDGE, so please keep it
> only in those code paths, and remove it from net/dsa/slave.c as well.
> 
>>  drivers/net/dsa/b53/b53_common.c       | 5 +++++
>>  drivers/net/dsa/b53/b53_priv.h         | 1 +
>>  drivers/net/dsa/hirschmann/hellcreek.c | 5 +++++
>>  drivers/net/dsa/lan9303-core.c         | 5 +++++
>>  drivers/net/dsa/lantiq_gswip.c         | 5 +++++
>>  drivers/net/dsa/microchip/ksz9477.c    | 5 +++++
>>  drivers/net/dsa/mt7530.c               | 5 +++++
>>  drivers/net/dsa/mv88e6xxx/chip.c       | 5 +++++
>>  drivers/net/dsa/ocelot/felix.c         | 5 +++++
>>  drivers/net/dsa/qca8k.c                | 5 +++++
>>  drivers/net/dsa/sja1105/sja1105_main.c | 5 +++++
>>  include/net/dsa.h                      | 1 +
>>  net/dsa/switch.c                       | 4 ++--
>>  13 files changed, 54 insertions(+), 2 deletions(-)