Re: [PATCH net-next v2 3/6] net: bridge: add 802.1Qat stream reservation admission control

[Nikolay Aleksandrov <razor@blackwall.org>]

On Sun, Jun 07, 2026 at 07:49:26AM +1000, Luke Howard wrote:
> 
> 
> > On 6 Jun 2026, at 6:21 pm, Nikolay Aleksandrov <razor@blackwall.org> wrote:
> > 
> > On 06/06/2026 11:02, Luke Howard wrote:
> >> The definition of Dynamic Reservation Entries in 802.1Q (clause 8.8.7) might support the addition of a new MDB (or even FDB) entry state to the kernel:
> >> - add MDB_DYNAMIC_RESERVATION (a state, not a flag);
> >> - the software bridge only _classifies_ packets against  MDB_DYNAMIC_RESERVATION entries, and only when MDB is authoritative. Classification sets dynamic_reservation_hit on tc_skb_ext;
> >> - dynamic_reservation_hit is visible to the flow dissector so can be used for policy enforcement.
> > 
> > See, saying the bridge has to classify doesn't sound right. Why not do the
> > classification where such operations are usually done, e.g. tc?
> > You have to manually designate these entries anyway.
> 
> s/classify/mark, i.e. marking a forwarding bit for tc to match, a la l2_miss.
> 
> tc can’t see into the MDB to tell if a DA has a dynamic reservation entry so, without an explicit DRE bit, the SRP daemon would need to maintain a flower permit filter per DRE. Not needing this allows the user to set a single policy filter prior to starting SRP, e.g.:
> 
> tc filter add dev lan0 egress protocol 802.1Q pref 1 handle 1 flower vlan_prio 3 dynamic_reservation_hit 0 action drop
> 
> It also maps cleanly to chips that support 802.1Qav with priority regeneration or filtering, but which can’t support tc-flower.

Yeah, that was an expected answer and I've seen such claims multiple times.
Just because it is convenient to add it in the bridge, does not make it the
right software model. There are layers that do filtering, marking and manipulation
this must be done at such layer. If you have to create a new table with the entries
filled there then that is what your user-space software must do, or come up with a
better alternative. There're also bridge netfilter chains that can do packet
filtering and manipulation, that might be an option.

For the MDB to have a dynamic reservation entry means someone must've added it,
these are not dynamically learned, so you can just as well build the table
in a more appropriate place which can tag or filter the packet.