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

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Date:   Mon, 13 Dec 2021 17:28:27 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.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

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?

-Toke

[0] https://lore.kernel.org/r/CAEf4BzYv3ONhy-JnQUtknzgBSK0gpm9GBJYtbAiJQe50_eX7Uw@mail.gmail.com