Commit 9ef9ac15 authored by Jakub Sitnicki's avatar Jakub Sitnicki Committed by Martin KaFai Lau
Browse files

selftests/bpf: Dump skb metadata on verification failure 



Add diagnostic output when metadata verification fails to help with
troubleshooting test failures. Introduce a check_metadata() helper that
prints both expected and received metadata to the BPF program's stderr
stream on mismatch. The userspace test reads and dumps this stream on
failure.

Signed-off-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20251105-skb-meta-rx-path-v4-11-5ceb08a9b37b@cloudflare.com
parent 967534e5

tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c

+21 −3
Original line number Diff line number Diff line
@@ -171,6 +171,21 @@ static int write_test_packet(int tap_fd) 
	return 0;

}



static void dump_err_stream(const struct bpf_program *prog)

{

	char buf[512];

	int ret;



	ret = 0;

	do {

		ret = bpf_prog_stream_read(bpf_program__fd(prog),

					   BPF_STREAM_STDERR, buf, sizeof(buf),

					   NULL);

		if (ret > 0)

			fwrite(buf, sizeof(buf[0]), ret, stderr);

	} while (ret > 0);

}



void test_xdp_context_veth(void)

{

	LIBBPF_OPTS(bpf_tc_hook, tc_hook, .attach_point = BPF_TC_INGRESS);
@@ -249,7 +264,8 @@ void test_xdp_context_veth(void) 
	if (!ASSERT_OK(ret, "send_test_packet"))

		goto close;



	ASSERT_TRUE(skel->bss->test_pass, "test_pass");

	if (!ASSERT_TRUE(skel->bss->test_pass, "test_pass"))

		dump_err_stream(tc_prog);



close:

	close_netns(nstoken);
@@ -314,7 +330,8 @@ static void test_tuntap(struct bpf_program *xdp_prog, 
	if (!ASSERT_OK(ret, "write_test_packet"))

		goto close;



	ASSERT_TRUE(*test_pass, "test_pass");

	if (!ASSERT_TRUE(*test_pass, "test_pass"))

		dump_err_stream(tc_prio_2_prog ? : tc_prio_1_prog);



close:

	if (tap_fd >= 0)
@@ -385,7 +402,8 @@ static void test_tuntap_mirred(struct bpf_program *xdp_prog, 
	if (!ASSERT_OK(ret, "write_test_packet"))

		goto close;



	ASSERT_TRUE(*test_pass, "test_pass");

	if (!ASSERT_TRUE(*test_pass, "test_pass"))

		dump_err_stream(tc_prog);



close:

	if (tap_fd >= 0)

tools/testing/selftests/bpf/progs/test_xdp_meta.c

+21 −4
Original line number Diff line number Diff line
@@ -27,6 +27,23 @@ static const __u8 meta_want[META_SIZE] = { 
	0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,

};



static bool check_metadata(const char *file, int line, __u8 *meta_have)

{

	if (!__builtin_memcmp(meta_have, meta_want, META_SIZE))

		return true;



	bpf_stream_printk(BPF_STREAM_STDERR,

			  "FAIL:%s:%d: metadata mismatch\n"

			  "  have:\n    %pI6\n    %pI6\n"

			  "  want:\n    %pI6\n    %pI6\n",

			  file, line,

			  &meta_have[0x00], &meta_have[0x10],

			  &meta_want[0x00], &meta_want[0x10]);

	return false;

}



#define check_metadata(meta_have) check_metadata(__FILE__, __LINE__, meta_have)



SEC("tc")

int ing_cls(struct __sk_buff *ctx)

{
@@ -36,7 +53,7 @@ int ing_cls(struct __sk_buff *ctx) 
	if (meta_have + META_SIZE > data)

		goto out;



	if (__builtin_memcmp(meta_want, meta_have, META_SIZE))

	if (!check_metadata(meta_have))

		goto out;



	test_pass = true;
@@ -54,7 +71,7 @@ int ing_cls_dynptr_read(struct __sk_buff *ctx) 
	bpf_dynptr_from_skb_meta(ctx, 0, &meta);

	bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0);



	if (__builtin_memcmp(meta_want, meta_have, META_SIZE))

	if (!check_metadata(meta_have))

		goto out;



	test_pass = true;
@@ -92,7 +109,7 @@ int ing_cls_dynptr_slice(struct __sk_buff *ctx) 
	if (!meta_have)

		goto out;



	if (__builtin_memcmp(meta_want, meta_have, META_SIZE))

	if (!check_metadata(meta_have))

		goto out;



	test_pass = true;
@@ -153,7 +170,7 @@ int ing_cls_dynptr_offset_rd(struct __sk_buff *ctx) 
		goto out;

	__builtin_memcpy(dst, src, chunk_len);



	if (__builtin_memcmp(meta_want, meta_have, META_SIZE))

	if (!check_metadata(meta_have))

		goto out;



	test_pass = true;