netdev - Re: [PATCH net-next v4 0/3] net/sched: Introduce tc block ports tracking and use

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Date: Sat, 7 Oct 2023 07:06:43 -0400
From: Jamal Hadi Salim <jhs@...atatu.com>
To: Jiri Pirko <jiri@...nulli.us>
Cc: Jakub Kicinski <kuba@...nel.org>, Victor Nogueira <victor@...atatu.com>, xiyou.wangcong@...il.com, 
	davem@...emloft.net, pabeni@...hat.com, edumazet@...gle.com, 
	mleitner@...hat.com, vladbu@...dia.com, simon.horman@...igine.com, 
	pctammela@...atatu.com, netdev@...r.kernel.org, kernel@...atatu.com
Subject: Re: [PATCH net-next v4 0/3] net/sched: Introduce tc block ports
 tracking and use

On Sat, Oct 7, 2023 at 6:20 AM Jiri Pirko <jiri@...nulli.us> wrote:
>
> Sat, Oct 07, 2023 at 01:00:00AM CEST, jhs@...atatu.com wrote:
> >On Fri, Oct 6, 2023 at 6:25 PM Jakub Kicinski <kuba@...nel.org> wrote:
> >>
> >> On Fri, 6 Oct 2023 15:06:45 -0400 Jamal Hadi Salim wrote:
> >> > > I don't understand the need for configuration less here. You don't have
> >> > > it for the rest of the actions. Why this is special?
> >>
> >> +1, FWIW
> >
> >We dont have any rule that says all actions MUST have parameters ;->
> >There is nothing speacial about any action that doesnt have a
> >parameter.
>
> You are getting the configuration from the block/device the action is
> attached to. Can you point me to another action doing that?

We are entering a pedantic road i am afraid. If there is no existing
action that has zero config then consider this one the first one. We
use skb->metadata all the time as a source of information for actions,
classifiers, qdiscs. If i dont need config i dont need to invent one
just because, well, all other actions are using one or more config;->
Your suggestion to specify an extra config to select a block - which
may be different than the one the one packet on - is a useful
feature(it just adds more code) but really should be optional. i.e if
you dont specify a block id configuration then we pick the metadata
one.

> >If we can adequately cleanup mirred,  then we can put it there but
> >certainly now we are adding more buttons to click on mirred. It may
> >make sense to refactor the mirred code then reuse the refactored code
> >in a new action.
>
> I don't understand why you need any new action. mirred redirect to block
> instead of dev is exactly what you need. Isn't it?

The actions have different meanings and lumping them together then
selecting via a knob is not the right approach.
There's shared code for sure. Infact the sending code was ripped from
mirred so as not to touch the rest because like i said mirred has
since grown a couple of horns and tails. In retrospect mirred should
have been two actions with shared code - but it is too late to change
now because it is very widely used. If someone like me was afraid of
touching it is because there's a maintainance challenge. I consider it
in the same zone as trying to restructure something in the skb.
I agree mirroring to a group of ports with a simple config is a useful
feature. Mirroring to a group via a tc block is simpler but adding a
list of ports instead is more powerful. So this feature is useful to
have in mirred - just the adding of yet one more button to say "skip
this port" is my concern.
Lets see how the refactoring goes first then it will be clearer - it
is a lot of delicate work - but you are right lets give it some love
now.

cheers,
jamal

>