Re: [PATCH net 3/5] net: dsa: b53: clear stale state when creating an ARL entry

[Jonas Gorski]

On Tue, Oct 27, 2026 at 9:22 PM Florian Fainelli
<florian.fainelli@xxxxxxxxxxxx> wrote:
>
> When an ARL lookup does not find the requested MAC and VID, b53_arl_read()
> returns the first free bin index but leaves the entry populated with the
> last bin examined. The multicast add path then ORs the requested port into
> that unrelated entry's forwarding bitmap, potentially forwarding packets
> to ports which are not members of the multicast group.
>
> Clear the entry before creating a new one. Also return without writing
> anything when deleting an entry which is not present, instead of making
> a new entry from stale bin contents.
>
> Fixes: 5d65b64a3d97 ("net: dsa: b53: Add support for MDB")
> Signed-off-by: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>
> ---
>  drivers/net/dsa/b53/b53_common.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
> index 559d4b360c82..0871a10d8cbc 100644
> --- a/drivers/net/dsa/b53/b53_common.c
> +++ b/drivers/net/dsa/b53/b53_common.c
> @@ -1992,6 +1992,10 @@ static int b53_arl_op(struct b53_device *dev, int op, int port,
>                         addr, vid);
>                 return is_valid ? ret : 0;
>         case -ENOENT:
> +               if (!is_valid)
> +                       return 0;

Should we return 0, or should we pass on the -ENOENT? We failed to
remove the entry, so implies there was a desync between hardware state
and software state.

If we don't, we should at least report the issue. If we do, we don't
need to, as dsa will do that. Though we then should also report
-ENOSPC && !is_valid as -ENOENT.

Likewise when trying to add an entry that already exists.

> +
> +               memset(&ent, 0, sizeof(ent));

Just bikeshedding, but semantically it feels the memset should be
below the comment/dev_dbg().

>                 /* We could not find a matching MAC, so reset to a new entry */
>                 dev_dbg(dev->dev, "{%pM,%.4d} not found, using idx: %d\n",
>                         addr, vid, idx);
> --
> 2.53.0
>

Best regards,
Jonas