netdev - Re: [PATCH bpf v2 2/2] selftests: bpf: add test for skb_load

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Date:   Wed, 13 Apr 2022 21:11:16 +0000
From:   Song Liu <songliubraving@...com>
To:     Liu Jian <liujian56@...wei.com>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, Martin Lau <kafai@...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>,
        Stanislav Fomichev <sdf@...gle.com>,
        Networking <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf v2 2/2] selftests: bpf: add test for skb_load_bytes

I guess this should go via bpf-next instead? Please mark the patches with
prefix "PATCH bpf-next". 

> On Apr 12, 2022, at 11:21 PM, Liu Jian <liujian56@...wei.com> wrote:
> 
> Use bpf_prog_test_run_opts to test the skb_load_bytes function.
> Tests the behavior when offset is greater than INT_MAX or a normal value.
> 
> Signed-off-by: Liu Jian <liujian56@...wei.com>
> ---
> v1->v2: As Liu Song's review comments, use bpf skeleton and global variable.
> .../selftests/bpf/prog_tests/skb_load_bytes.c | 45 +++++++++++++++++++
> .../selftests/bpf/progs/skb_load_bytes.c      | 19 ++++++++
> 2 files changed, 64 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/skb_load_bytes.c
> create mode 100644 tools/testing/selftests/bpf/progs/skb_load_bytes.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/skb_load_bytes.c b/tools/testing/selftests/bpf/prog_tests/skb_load_bytes.c
> new file mode 100644
> index 000000000000..81cc224a0c69
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/skb_load_bytes.c
> @@ -0,0 +1,45 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <test_progs.h>
> +#include <network_helpers.h>
> +#include "skb_load_bytes.skel.h"
> +
> +void test_skb_load_bytes(void)
> +{
> +	struct skb_load_bytes *skel;
> +	int err, prog_fd, test_result;
> +	struct __sk_buff skb = { 0 };
> +
> +	LIBBPF_OPTS(bpf_test_run_opts, tattr,
> +		.data_in = &pkt_v4,
> +		.data_size_in = sizeof(pkt_v4),
> +		.ctx_in = &skb,
> +		.ctx_size_in = sizeof(skb),
> +	);
> +
> +	skel = skb_load_bytes__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
> +		return;
> +
> +	prog_fd = bpf_program__fd(skel->progs.skb_process);
> +	if (prog_fd < 0)
> +		goto out;

I guess we should report error here? like

	if (ASSERT_GE(prog_fd, 0, "prog_fd"))
		goto out;

> +
> +	skel->bss->load_offset = (uint32_t)(-1);
> +	tattr.data_out = NULL;
> +	tattr.data_size_out = 0;
> +	err = bpf_prog_test_run_opts(prog_fd, &tattr);
> +	CHECK_ATTR(err != 0, "offset -1", "err %d errno %d\n", err, errno);

We can use ASSERT_OK() here. 

> +	test_result = skel->bss->test_result;
> +	CHECK_ATTR(test_result != -EFAULT, "offset -1", "test error\n");
And ASSERT_NEQ

> +
> +	skel->bss->load_offset = (uint32_t)10;
> +	tattr.data_out = NULL;
> +	tattr.data_size_out = 0;

I guess = NULL and = 0 are not needed here. 

> +	err = bpf_prog_test_run_opts(prog_fd, &tattr);
> +	CHECK_ATTR(err != 0, "offset 10", "err %d errno %d\n", err, errno);
> +	test_result = skel->bss->test_result;
> +	CHECK_ATTR(test_result != 0, "offset 10", "test error\n");
> +
> +out:
> +	skb_load_bytes__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/skb_load_bytes.c b/tools/testing/selftests/bpf/progs/skb_load_bytes.c
> new file mode 100644
> index 000000000000..e4252fd973be
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/skb_load_bytes.c
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +__u32 load_offset = 0;
> +int test_result = 0;
> +
> +SEC("tc")
> +int skb_process(struct __sk_buff *skb)
> +{
> +	char buf[16];
> +
> +	test_result = bpf_skb_load_bytes(skb, load_offset, buf, 10);
> +
> +	return 0;
> +}
> -- 
> 2.17.1
>