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

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Date:   Mon, 26 Apr 2021 19:47:42 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        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

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.

diff --git a/include/trace/events/xdp.h b/include/trace/events/xdp.h
index fcad3645a70b..1751da079330 100644
--- a/include/trace/events/xdp.h
+++ b/include/trace/events/xdp.h
@@ -110,7 +110,8 @@ DECLARE_EVENT_CLASS(xdp_redirect_template,
                u32 ifindex = 0, map_index = index;

                if (map_type == BPF_MAP_TYPE_DEVMAP || map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
-                       ifindex = ((struct _bpf_dtab_netdev *)tgt)->dev->ifindex;
+                       if (tgt)
+                               ifindex = ((struct _bpf_dtab_netdev *)tgt)->dev->ifindex;
                } else if (map_type == BPF_MAP_TYPE_UNSPEC && map_id == INT_MAX) {
                        ifindex = index;
                        map_index = 0;


Hangbin