Re: [PATCH bpf-next 3/3] selftests/bpf: Add test for xdp_md context in BPF_PROG_TEST_RUN

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Zvi Effron <zeffron@riotgames.com>
Cc: bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	Cody Haas <chaas@riotgames.com>,
	Lisa Watanabe <lwatanabe@riotgames.com>
Subject: Re: [PATCH bpf-next 3/3] selftests/bpf: Add test for xdp_md context in BPF_PROG_TEST_RUN
Date: Wed, 26 May 2021 14:05:39 -0700	[thread overview]
Message-ID: <CAEf4BzZqi_PcYXKgXr=t62z2K05rMxB7vYtAkW68ucwu1mdHqg@mail.gmail.com> (raw)
In-Reply-To: <20210524220555.251473-4-zeffron@riotgames.com>

On Mon, May 24, 2021 at 3:08 PM Zvi Effron <zeffron@riotgames.com> wrote:
>
> Add a test for using xdp_md as a context to BPF_PROG_TEST_RUN for XDP
> programs.
>
> The test uses a BPF program that takes in a return value from XDP
> metadata, then reduces the size of the XDP metadata by 4 bytes.
>
> Test cases validate the possible failure cases for passing in invalid
> xdp_md contexts, that the return value is successfully passed
> in, and that the adjusted metadata is successfully copied out.
>
> Co-developed-by: Cody Haas <chaas@riotgames.com>
> Signed-off-by: Cody Haas <chaas@riotgames.com>
> Co-developed-by: Lisa Watanabe <lwatanabe@riotgames.com>
> Signed-off-by: Lisa Watanabe <lwatanabe@riotgames.com>
> Signed-off-by: Zvi Effron <zeffron@riotgames.com>
> ---
>  .../bpf/prog_tests/xdp_context_test_run.c     | 117 ++++++++++++++++++
>  .../bpf/progs/test_xdp_context_test_run.c     |  22 ++++
>  2 files changed, 139 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_context_test_run.c
>
> 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
> new file mode 100644
> index 000000000000..92ce2e4a5c30
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
> @@ -0,0 +1,117 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <test_progs.h>
> +#include <network_helpers.h>
> +
> +void test_xdp_context_test_run(void)
> +{
> +       const char *file = "./test_xdp_context_test_run.o";

please use BPF skeleton for new tests

> +       struct bpf_object *obj;
> +       char data[sizeof(pkt_v4) + sizeof(__u32)];
> +       char buf[128];
> +       char bad_ctx[sizeof(struct xdp_md)];
> +       struct xdp_md ctx_in, ctx_out;
> +       struct bpf_test_run_opts tattr = {
> +               .sz = sizeof(struct bpf_test_run_opts),
> +               .data_in = &data,
> +               .data_out = buf,
> +               .data_size_in = sizeof(data),
> +               .data_size_out = sizeof(buf),
> +               .ctx_out = &ctx_out,
> +               .ctx_size_out = sizeof(ctx_out),
> +               .repeat = 1,
> +       };
> +       int err, prog_fd;
> +
> +       err = bpf_prog_load(file, BPF_PROG_TYPE_XDP, &obj, &prog_fd);
> +       if (CHECK_FAIL(err))
> +               return;
> +
> +       *(__u32 *)data = XDP_PASS;
> +       *(struct ipv4_packet *)(data + sizeof(__u32)) = pkt_v4;
> +
> +       memset(&ctx_in, 0, sizeof(ctx_in));
> +       tattr.ctx_in = &ctx_in;
> +       tattr.ctx_size_in = sizeof(ctx_in);
> +
> +       tattr.ctx_in = &ctx_in;
> +       tattr.ctx_size_in = sizeof(ctx_in);
> +       ctx_in.data_meta = 0;
> +       ctx_in.data = sizeof(__u32);
> +       ctx_in.data_end = ctx_in.data + sizeof(pkt_v4);
> +       err = bpf_prog_test_run_opts(prog_fd, &tattr);
> +       CHECK_ATTR(err || tattr.retval != XDP_PASS ||

please use ASSERT_xxx() macros instead of CHECK() variants

> +                  tattr.data_size_out != sizeof(pkt_v4) ||
> +                  tattr.ctx_size_out != tattr.ctx_size_in ||
> +                  ctx_out.data_meta != 0 ||
> +                  ctx_out.data != ctx_out.data_meta ||
> +                  ctx_out.data_end != sizeof(pkt_v4), "xdp_md context",
> +                  "err %d errno %d retval %d data size out %d context size out %d data_meta %d data %d data_end %d\n",
> +                  err, errno, tattr.retval, tattr.data_size_out,
> +                  tattr.ctx_size_out, ctx_out.data_meta, ctx_out.data,
> +                  ctx_out.data_end);
> +

[...]

> diff --git a/tools/testing/selftests/bpf/progs/test_xdp_context_test_run.c b/tools/testing/selftests/bpf/progs/test_xdp_context_test_run.c
> new file mode 100644
> index 000000000000..c66a756b238e
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_xdp_context_test_run.c
> @@ -0,0 +1,22 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +int _version SEC("version") = 1;

this is obsolete, you can drop this variable completely

> +
> +SEC("xdp_context")

SEC("xdp") is a standard way for XDP programs, please use that

> +int _xdp_context(struct xdp_md *xdp)
> +{
> +       void *data = (void *)(unsigned long)xdp->data;
> +       __u32 *metadata = (void *)(unsigned long)xdp->data_meta;
> +       __u32 ret;
> +
> +       if (metadata + 1 > data)
> +               return XDP_ABORTED;
> +       ret = *metadata;
> +       if (bpf_xdp_adjust_meta(xdp, 4))
> +               return XDP_ABORTED;
> +       return ret;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.31.1
>