Re: [PATCH bpf-next v3 8/8] samples/bpf: Add xdp_trafficgen sample

From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	Network Development <netdev@vger.kernel.org>,
	bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf-next v3 8/8] samples/bpf: Add xdp_trafficgen sample
Date: Mon, 13 Dec 2021 16:05:56 -0800	[thread overview]
Message-ID: <CAADnVQL6yL6hVGWL0cni-t+Lvpe91ST8moF69u5CwOLBKZT-GQ@mail.gmail.com> (raw)
In-Reply-To: <87r1ageafo.fsf@toke.dk>

On Mon, Dec 13, 2021 at 8:28 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:
>
> > On Sat, Dec 11, 2021 at 10:43 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
> >>
> >> This adds an XDP-based traffic generator sample which uses the DO_REDIRECT
> >> flag of bpf_prog_run(). It works by building the initial packet in
> >> userspace and passing it to the kernel where an XDP program redirects the
> >> packet to the target interface. The traffic generator supports two modes of
> >> operation: one that just sends copies of the same packet as fast as it can
> >> without touching the packet data at all, and one that rewrites the
> >> destination port number of each packet, making the generated traffic span a
> >> range of port numbers.
> >>
> >> The dynamic mode is included to demonstrate how the bpf_prog_run() facility
> >> enables building a completely programmable packet generator using XDP.
> >> Using the dynamic mode has about a 10% overhead compared to the static
> >> mode, because the latter completely avoids touching the page data.
> >>
> >> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> >> ---
> >>  samples/bpf/.gitignore            |   1 +
> >>  samples/bpf/Makefile              |   4 +
> >>  samples/bpf/xdp_redirect.bpf.c    |  34 +++
> >>  samples/bpf/xdp_trafficgen_user.c | 421 ++++++++++++++++++++++++++++++
> >>  4 files changed, 460 insertions(+)
> >>  create mode 100644 samples/bpf/xdp_trafficgen_user.c
> >
> > I think it deserves to be in tools/bpf/
> > samples/bpf/ bit rots too often now.
> > imo everything in there either needs to be converted to selftests/bpf
> > or deleted.
>
> I think there's value in having a separate set of utilities that are
> more user-facing than the selftests. But I do agree that it's annoying
> they bit rot. So how about we fix that instead? Andrii suggested just
> integrating the build of samples/bpf into selftests[0], so I'll look
> into that after the holidays. But in the meantime I don't think there's
> any harm in adding this utility here?

I think samples/bpf building would help to stabilize bitroting,
but the question of the right home for this trafficgen tool remains.
I think it's best to keep it outside of the kernel tree.
It's not any more special than all other libbpf and bcc tools.
I think xdp-tools repo or bcc could be a home for it.