netdev - Re: [PATCH bpf-next v3 8/8] samples/bpf: Add xdp

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Date:   Mon, 13 Dec 2021 16:05:56 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v3 8/8] samples/bpf: Add xdp_trafficgen sample

On Mon, Dec 13, 2021 at 8:28 AM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> Alexei Starovoitov <alexei.starovoitov@...il.com> writes:
>
> > On Sat, Dec 11, 2021 at 10:43 AM Toke Høiland-Jørgensen <toke@...hat.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@...hat.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.