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

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Message-ID: <87lfae6urp.fsf@toke.dk>
Date:   Tue, 23 Mar 2021 11:15:22 +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 Thu, Mar 18, 2021 at 03:19:47PM +0100, Toke Høiland-Jørgensen wrote:
>> 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...
>
> There are 2 flags, BROADCAST and EXCLUDE_INGRESS. There is no way
> to only check the map pointer and ignore flags..

Ah, right, of course, my bad :)

Well, in that case adding both members back is probably the right thing
to do...

-Toke