netdev - Re: [PATCHv2 bpf-next 2/4] xdp: extend xdp_redirect

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Message-ID: <875z1oczng.fsf@toke.dk>
Date:   Thu, 18 Mar 2021 15:19:47 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Hangbin Liu <liuhangbin@...il.com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        Jiri Benc <jbenc@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>, ast@...nel.org,
        Daniel Borkmann <daniel@...earbox.net>,
        Lorenzo Bianconi <lorenzo.bianconi@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        John Fastabend <john.fastabend@...il.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        bjorn@...nel.org
Subject: Re: [PATCHv2 bpf-next 2/4] xdp: extend xdp_redirect_map with
 broadcast support

Hangbin Liu <liuhangbin@...il.com> writes:

> On Wed, Mar 17, 2021 at 01:03:02PM +0100, Toke Høiland-Jørgensen wrote:
>> FYI, this no longer applies to bpf-next due to Björn's refactor in
>> commit: ee75aef23afe ("bpf, xdp: Restructure redirect actions")
>
> Thanks Toke, I need to see how to get the map via map_id, does
> bpf_map_get_curr_or_next() works? Should I call bpf_map_put() after
> using?

I would expect that to be terrible for performance; I think it would be
better to just add back the map pointer into struct bpf_redirect_info.
If you only set the map pointer when the multicast flag is set, you can
just check that pointer to disambiguate between when you need to call
dev_map_enqueue() and dev_map_enqueue_multi(), in which case you don't
need to add back the flags member...

-Toke