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

Jakub Kicinski <[email protected]> writes:

> 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)

I'm not sure why it would be helpful to keep them separate. You would
still need to dump them presumably? Or maybe there's a way to request
skipping specifically local entries, but then you don't need to keep
them separate? I find it better to not create them in the first place,
because then you have faster iteration in all for-each-fdb contexts,
faster marshalling, less memory taken.

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