Re: [PATCHv10 bpf-next 2/4] xdp: extend xdp_redirect_map with broadcast support

From: Hangbin Liu <liuhangbin@gmail.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
	"Toke Høiland-Jørgensen" <toke@redhat.com>,
	"Jiri Benc" <jbenc@redhat.com>,
	"Eelco Chaudron" <echaudro@redhat.com>,
	ast@kernel.org, "Daniel Borkmann" <daniel@iogearbox.net>,
	"Lorenzo Bianconi" <lorenzo.bianconi@redhat.com>,
	"David Ahern" <dsahern@gmail.com>,
	"Andrii Nakryiko" <andrii.nakryiko@gmail.com>,
	"Alexei Starovoitov" <alexei.starovoitov@gmail.com>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"Maciej Fijalkowski" <maciej.fijalkowski@intel.com>,
	"Björn Töpel" <bjorn.topel@gmail.com>,
	"Martin KaFai Lau" <kafai@fb.com>
Subject: Re: [PATCHv10 bpf-next 2/4] xdp: extend xdp_redirect_map with broadcast support
Date: Mon, 26 Apr 2021 18:54:44 +0800	[thread overview]
Message-ID: <20210426105444.GS3465@Leo-laptop-t470s> (raw)
In-Reply-To: <20210426104704.GR3465@Leo-laptop-t470s>

On Mon, Apr 26, 2021 at 06:47:17PM +0800, Hangbin Liu wrote:
> On Mon, Apr 26, 2021 at 11:53:50AM +0200, Jesper Dangaard Brouer wrote:
> > On Fri, 23 Apr 2021 10:00:17 +0800
> > Hangbin Liu <liuhangbin@gmail.com> wrote:
> > 
> > > This patch adds two flags BPF_F_BROADCAST and BPF_F_EXCLUDE_INGRESS to
> > > extend xdp_redirect_map for broadcast support.
> > > 
> > > With BPF_F_BROADCAST the packet will be broadcasted to all the interfaces
> > > in the map. with BPF_F_EXCLUDE_INGRESS the ingress interface will be
> > > excluded when do broadcasting.
> > > 
> > > When getting the devices in dev hash map via dev_map_hash_get_next_key(),
> > > there is a possibility that we fall back to the first key when a device
> > > was removed. This will duplicate packets on some interfaces. So just walk
> > > the whole buckets to avoid this issue. For dev array map, we also walk the
> > > whole map to find valid interfaces.
> > > 
> > > Function bpf_clear_redirect_map() was removed in
> > > commit ee75aef23afe ("bpf, xdp: Restructure redirect actions").
> > > Add it back as we need to use ri->map again.
> > > 
> > > Here is the performance result by using 10Gb i40e NIC, do XDP_DROP on
> > > veth peer, run xdp_redirect_{map, map_multi} in sample/bpf and send pkts
> > > via pktgen cmd:
> > > ./pktgen_sample03_burst_single_flow.sh -i eno1 -d $dst_ip -m $dst_mac -t 10 -s 64
> > 
> > While running:
> >  $ sudo ./xdp_redirect_map_multi -F i40e2 i40e2
> >  Get interfaces 7 7
> >  libbpf: elf: skipping unrecognized data section(23) .eh_frame
> >  libbpf: elf: skipping relo section(24) .rel.eh_frame for section(23) .eh_frame
> >  Forwarding   10140845 pkt/s
> >  Forwarding   11767042 pkt/s
> >  Forwarding   11783437 pkt/s
> >  Forwarding   11767331 pkt/s
> > 
> > When starting:  sudo ./xdp_monitor --stats
> 
> That seems the same issue I reported previously in our meeting.
> https://bugzilla.redhat.com/show_bug.cgi?id=1906820#c4
> 
> I only saw it 3 times and can't reproduce it easily.
> 
> Do you have any idea where is the root cause?

OK, I just re-did the test and could reproduce it now.
Maybe because the code changed and it's easy to reproduce now.

I will check this issue.

Thanks
Hangbin