netdev - Re: [PATCH bpf 2/2] selftests/bpf: Update xdp_context_test

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Message-ID: <CAMB2axPO7VENB-XUSUb5eU1ae7h0NBjbVukzxaObBDMMmkGYAw@mail.gmail.com>
Date: Mon, 5 Jan 2026 10:44:58 -0800
From: Amery Hung <ameryhung@...il.com>
To: Toke Høiland-Jørgensen <toke@...hat.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	"David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, 
	Stanislav Fomichev <sdf@...ichev.me>, Andrii Nakryiko <andrii@...nel.org>, 
	Eduard Zingerman <eddyz87@...il.com>, Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
	Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, Shuah Khan <shuah@...nel.org>, 
	netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH bpf 2/2] selftests/bpf: Update xdp_context_test_run test
 to check maximum metadata size

On Mon, Jan 5, 2026 at 3:48 AM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> Update the selftest to check that the metadata size check takes the
> xdp_frame size into account in bpf_prog_test_run. The original
> check (for meta size 256) was broken because the data frame supplied was
> smaller than this, triggering a different EINVAL return. So supply a
> larger data frame for this test to make sure we actually exercise the
> check we think we are.
>
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
> ---
>  .../bpf/prog_tests/xdp_context_test_run.c          | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
> index ee94c281888a..24d7d6d8fea1 100644
> --- a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
> @@ -47,6 +47,7 @@ void test_xdp_context_test_run(void)
>         struct test_xdp_context_test_run *skel = NULL;
>         char data[sizeof(pkt_v4) + sizeof(__u32)];
>         char bad_ctx[sizeof(struct xdp_md) + 1];
> +       char large_data[256];
>         struct xdp_md ctx_in, ctx_out;
>         DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts,
>                             .data_in = &data,
> @@ -94,9 +95,6 @@ void test_xdp_context_test_run(void)
>         test_xdp_context_error(prog_fd, opts, 4, sizeof(__u32), sizeof(data),
>                                0, 0, 0);
>
> -       /* Meta data must be 255 bytes or smaller */
> -       test_xdp_context_error(prog_fd, opts, 0, 256, sizeof(data), 0, 0, 0);
> -
>         /* Total size of data must be data_end - data_meta or larger */
>         test_xdp_context_error(prog_fd, opts, 0, sizeof(__u32),
>                                sizeof(data) + 1, 0, 0, 0);
> @@ -116,6 +114,16 @@ void test_xdp_context_test_run(void)
>         test_xdp_context_error(prog_fd, opts, 0, sizeof(__u32), sizeof(data),
>                                0, 0, 1);
>
> +       /* Meta data must be 216 bytes or smaller (256 - sizeof(struct
> +        * xdp_frame)). Test both nearest invalid size and nearest invalid
> +        * 4-byte-aligned size, and make sure data_in is large enough that we
> +        * actually hit the cheeck on metadata length

nit: a typo here: cheeck -> check

> +        */
> +       opts.data_in = large_data;
> +       opts.data_size_in = sizeof(large_data);
> +       test_xdp_context_error(prog_fd, opts, 0, 217, sizeof(large_data), 0, 0, 0);
> +       test_xdp_context_error(prog_fd, opts, 0, 220, sizeof(large_data), 0, 0, 0);
> +
>         test_xdp_context_test_run__destroy(skel);
>  }

Reviewed-by: Amery Hung <ameryhung@...il.com>

>
> --
> 2.52.0
>
>