netdev - Re: [RFC net-next v2 2/5] net: psample: add multicast filtering on group

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Message-ID: <bc05f7f9-79d2-40a5-bede-d9ad9d1b0825@redhat.com>
Date: Wed, 10 Apr 2024 15:42:45 +0200
From: Adrian Moreno <amorenoz@...hat.com>
To: Ido Schimmel <idosch@...sch.org>
Cc: netdev@...r.kernel.org, jiri@...nulli.us, xiyou.wangcong@...il.com,
 cmi@...dia.com, yotam.gi@...il.com, i.maximets@....org, aconole@...hat.com,
 echaudro@...hat.com, horms@...nel.org
Subject: Re: [RFC net-next v2 2/5] net: psample: add multicast filtering on
 group_id



On 4/10/24 15:06, Ido Schimmel wrote:
> On Mon, Apr 08, 2024 at 02:57:41PM +0200, Adrian Moreno wrote:
>> Packet samples can come from several places (e.g: different tc sample
>> actions), typically using the sample group (PSAMPLE_ATTR_SAMPLE_GROUP)
>> to differentiate them.
>>
>> Likewise, sample consumers that listen on the multicast group may only
>> be interested on a single group. However, they are currently forced to
>> receive all samples and discard the ones that are not relevant, causing
>> unnecessary overhead.
>>
>> Allow users to filter on the desired group_id by adding a new command
>> SAMPLE_FILTER_SET that can be used to pass the desired group id.
>> Store this filter on the per-socket private pointer and use it for
>> filtering multicasted samples.
> 
> Did you consider using BPF for this type of filtering instead of new
> uAPI?
>

Yes. I ended up going for a uAPI change because, since the group_id is part of 
the psample uAPI semantics, requiring users to load ebpf programs for that 
seemed a bit excessive. Given devlink already uses this mechanism [1], I thought 
it would make things easier for users that already just use netlink.

[1] https://lore.kernel.org/netdev/20231214181549.1270696-9-jiri@resnulli.us/

> See example here:
> https://github.com/Mellanox/libpsample/blob/master/src/psample.c#L290
>