Re: [PATCH net-next 00/10] bridge: Allow keeping local FDB entries only on VLAN 0

[Jakub Kicinski <kuba@kernel.org>]

On Thu, 4 Sep 2025 19:07:17 +0200 Petr Machata wrote:
> Yet another option might be to use in-kernel FDB filtering, and to filter
> the local entries when dumping. Unfortunately, this does not help all that
> much either, because the linked-list walk still needs to happen. Also, with
> the obvious filtering interface built around ndm_flags / ndm_state
> filtering, one can't just exclude pure local entries in one query. One
> needs to dump all non-local entries first, and then to get permanent
> entries in another run filter local & added_by_user. I.e. one needs to pay
> the iteration overhead twice, and then integrate the result in userspace.
> To get significant savings, one would need a very specific knob like "dump,
> but skip/only include local entries". But if we are adding a local-specific
> knobs, maybe let's have an option to just not duplicate them in the first
> place.

Local-specific knob for dump seems like the most direct way to address
your concern, if I'm reading the cover letter right. Also, is it normal
to special case vlan 0 the way this series does? Wouldn't it be cleaner
to store local entries in a separate hash table? Perhaps if they lived
in a separate hash table it'd be odd to dump them for VLAN 0 (so the
series also conflates the kernel internals and control path/dump output)

Given that Nik has authored the previous version a third opinion would
be great... adding a handful of people to CC.