netdev - Re: [PATCH net-next RFC v5 4/4] net/sched: act_blockcast: Introduce blockcast tc action

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Date: Thu, 23 Nov 2023 08:37:13 -0500
From: Jamal Hadi Salim <jhs@...atatu.com>
To: Jiri Pirko <jiri@...nulli.us>
Cc: Victor Nogueira <victor@...atatu.com>, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, xiyou.wangcong@...il.com, 
	mleitner@...hat.com, vladbu@...dia.com, paulb@...dia.com, 
	pctammela@...atatu.com, netdev@...r.kernel.org, kernel@...atatu.com
Subject: Re: [PATCH net-next RFC v5 4/4] net/sched: act_blockcast: Introduce
 blockcast tc action

On Thu, Nov 23, 2023 at 3:51 AM Jiri Pirko <jiri@...nulli.us> wrote:
>
> Fri, Nov 10, 2023 at 10:46:18PM CET, victor@...atatu.com wrote:
> >This action takes advantage of the presence of tc block ports set in the
> >datapath and multicasts a packet to ports on a block. By default, it will
> >broadcast the packet to a block, that is send to all members of the block except
> >the port in which the packet arrived on. However, the user may specify
> >the option "tx_type all", which will send the packet to all members of the
> >block indiscriminately.
> >
> >Example usage:
> >    $ tc qdisc add dev ens7 ingress_block 22
> >    $ tc qdisc add dev ens8 ingress_block 22
> >
> >Now we can add a filter to broadcast packets to ports on ingress block id 22:
> >$ tc filter add block 22 protocol ip pref 25 \
> >  flower dst_ip 192.168.0.0/16 action blockcast blockid 22
>
> Name the arg "block" so it is consistent with "filter add block". Make
> sure this is aligned netlink-wise as well.
>
>
> >
> >Or if we wish to send to all ports in the block:
> >$ tc filter add block 22 protocol ip pref 25 \
> >  flower dst_ip 192.168.0.0/16 action blockcast blockid 22 tx_type all
>
> I read the discussion the the previous version again. I suggested this
> to be part of mirred. Why exactly that was not addressed?
>

I am the one who pushed back (in that discussion). Actions should be
small and specific. Like i had said in that earlier discussion it was
a mistake to make mirred do both mirror and redirect - they should
have been two actions. So i feel like adding a block to mirred is
adding more knobs. We are also going to add dev->group as a way to
select what devices to mirror to. Should that be in mirred as well?

cheers,
jamal

> Instead of:
> $ tc filter add block 22 protocol ip pref 25 \
>   flower dst_ip 192.168.0.0/16 action blockcast blockid 22
> You'd have:
> $ tc filter add block 22 protocol ip pref 25 \
>   flower dst_ip 192.168.0.0/16 action mirred egress redirect block 22
>
> I don't see why we need special action for this.
>
> Regarding "tx_type all":
> Do you expect to have another "tx_type"? Seems to me a bit odd. Why not
> to have this as "no_src_skip" or some other similar arg, without value
> acting as a bool (flag) on netlink level.
>
>