Re: [p4tc-discussions] Re: [PATCH RFC v2 net-next 03/28] net/sched: act_api: increase TCA_ID_MAX

[Jamal Hadi Salim <hadi@mojatatu.com>]

On Mon, Jun 5, 2023 at 5:19 PM Jakub Kicinski via p4tc-discussions
<p4tc-discussions@netdevconf.info> wrote:
>
> On Wed, 17 May 2023 07:02:07 -0400 Jamal Hadi Salim wrote:
> > Increase TCA_ID_MAX from 255 to 1023
> >
> > Given P4TC dynamic actions required new IDs (dynamically) and 30 of those are
> > already taken by the standard actions (such as gact, mirred and ife) we are left
> > with 225 actions to create, which seems like a small number.
>
> > diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
> > index 5b66df3ec332..337411949ad0 100644
> > --- a/include/uapi/linux/pkt_cls.h
> > +++ b/include/uapi/linux/pkt_cls.h
> > @@ -140,9 +140,9 @@ enum tca_id {
> >       TCA_ID_MPLS,
> >       TCA_ID_CT,
> >       TCA_ID_GATE,
> > -     TCA_ID_DYN,
> > +     TCA_ID_DYN = 256,
> >       /* other actions go here */
> > -     __TCA_ID_MAX = 255
> > +     __TCA_ID_MAX = 1023
> >  };
> >
> >  #define TCA_ID_MAX __TCA_ID_MAX
>
> I haven't look at any of the patches but this stands out as bad idea
> on the surface.

The idea is to reserve a range of the IDs for dynamic use in this case
from 256-1023. The kernel will issue an action id from that range when
we request it. The assumption is someone adding a "static" action ID
will populate the above enum and is able to move the range boundaries.
P4TC continues to work with old and new kernels and with old and new
tc.
Did i miss something you were alluding to?

cheers,
jamal