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

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Date:   Mon, 13 Dec 2021 19:28:57 -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 4:37 PM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> Alexei Starovoitov <alexei.starovoitov@...il.com> writes:
>
> > 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.
>
> Alright, I'll drop it from the next version and put it into xdp-tools.
> I've been contemplating doing the same for some of the other tools
> (xdp_redirect* and xdp_monitor, for instance). Any opinion on that?

Please move them too if you don't mind.
samples/ just doesn't have the right production quality vibe.
Everything in there is a sample code. In other words a toy application.
I hope xdp_trafficgen aims to be a solid maintained tool with
a man page that distros will ship eventually.
So starting with a good home is important.