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

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Message-ID: <ZV9tCT9d7dm7dOeA@nanopsycho>
Date: Thu, 23 Nov 2023 16:17:29 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Jamal Hadi Salim <jhs@...atatu.com>
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

Thu, Nov 23, 2023 at 03:38:35PM CET, jhs@...atatu.com wrote:
>On Thu, Nov 23, 2023 at 9:04 AM Jiri Pirko <jiri@...nulli.us> wrote:
>>
>> Thu, Nov 23, 2023 at 02:37:13PM CET, jhs@...atatu.com wrote:
>> >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
>>
>> For mirror and redirect, I agree. For redirect and redirect, does not
>> make much sense. It's just confusing for the user.
>>
>
>Blockcast only emulates the mirror part. I agree redirect doesnt make
>any sense because once you redirect the packet is gone.

How is it mirror? It is redirect to multiple, isn't it?


>
>> >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?
>>
>> I need more details.
>>
>
>You set any port you want to be mirrored to using ip link, example:
>ip link set dev $DEV1 group 2
>ip link set dev $DEV2 group 2

That does not looks correct at all. Do tc stuff in tc, no?


>...
>
>Then you can blockcast:
>tc filter add devx protocol ip pref 25 \
>  flower dst_ip 192.168.0.0/16 action blockcast group 2

"blockcasting" to something that is not a block anymore. Not nice.

>
>cheers,
>jamal
>
>>
>> >
>> >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.
>> >>
>> >>