netdev - Re: [PATCHv10 bpf-next 2/4] xdp: extend xdp_redirect

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Date:   Mon, 26 Apr 2021 15:00:27 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Hangbin Liu <liuhangbin@...il.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        Jiri Benc <jbenc@...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>,
        Björn Töpel 
        <bjorn.topel@...il.com>, Martin KaFai Lau <kafai@...com>
Subject: Re: [PATCHv10 bpf-next 2/4] xdp: extend xdp_redirect_map with
 broadcast support

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

> On Mon, Apr 26, 2021 at 07:40:28PM +0800, Hangbin Liu wrote:
>> On Mon, Apr 26, 2021 at 11:53:50AM +0200, Jesper Dangaard Brouer wrote:
>> > Decode: perf_trace_xdp_redirect_template+0xba
>> >  ./scripts/faddr2line vmlinux perf_trace_xdp_redirect_template+0xba
>> > perf_trace_xdp_redirect_template+0xba/0x130:
>> > perf_trace_xdp_redirect_template at include/trace/events/xdp.h:89 (discriminator 13)
>> > 
>> > less -N net/core/filter.c
>> >  [...]
>> >    3993         if (unlikely(err))
>> >    3994                 goto err;
>> >    3995 
>> > -> 3996         _trace_xdp_redirect_map(dev, xdp_prog, fwd, map_type, map_id, ri->tgt_index);
>> 
>> Oh, the fwd in xdp xdp_redirect_map broadcast is NULL...
>> 
>> I will see how to fix it. Maybe assign the ingress interface to fwd?
>
> Er, sorry for the flood message. I just checked the trace point code, fwd
> in xdp trace event means to_ifindex. So we can't assign the ingress interface
> to fwd.
>
> In xdp_redirect_map broadcast case, there is no specific to_ifindex.
> So how about just ignore it... e.g.

Yeah, just leaving the ifindex as 0 when tgt is unset is fine :)

-Toke