From: Jakub Sitnicki <jakub@cloudflare.com>
To: bpf@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>,
Paolo Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Daniel Borkmann <daniel@iogearbox.net>,
John Fastabend <john.fastabend@gmail.com>,
Stanislav Fomichev <sdf@fomichev.me>,
Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
KP Singh <kpsingh@kernel.org>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Arthur Fabre <arthur@arthurfabre.com>,
Jesper Dangaard Brouer <hawk@kernel.org>,
netdev@vger.kernel.org, kernel-team@cloudflare.com
Subject: [PATCH bpf-next v3 11/16] selftests/bpf: Dump skb metadata on verification failure
Date: Sun, 26 Oct 2025 15:18:31 +0100 [thread overview]
Message-ID: <20251026-skb-meta-rx-path-v3-11-37cceebb95d3@cloudflare.com> (raw)
In-Reply-To: <20251026-skb-meta-rx-path-v3-0-37cceebb95d3@cloudflare.com>
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: Jakub Sitnicki <jakub@cloudflare.com>
---
.../bpf/prog_tests/xdp_context_test_run.c | 24 ++++++++++++++++++---
tools/testing/selftests/bpf/progs/test_xdp_meta.c | 25 ++++++++++++++++++----
2 files changed, 42 insertions(+), 7 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 93a1fbe6a4fd..db3027564261 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
@@ -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)
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_meta.c b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
index 11288b20f56c..74d7e2aab2ef 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_meta.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
@@ -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_have[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;
--
2.43.0
next prev parent reply other threads:[~2025-10-26 14:18 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-26 14:18 [PATCH bpf-next v3 00/16] Make TC BPF helpers preserve skb metadata Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 01/16] net: Helper to move packet data and metadata after skb_push/pull Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 02/16] net: Preserve metadata on pskb_expand_head Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 03/16] bpf: Unclone skb head on bpf_dynptr_write to skb metadata Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 04/16] vlan: Make vlan_remove_tag return nothing Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 05/16] bpf: Make bpf_skb_vlan_pop helper metadata-safe Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 06/16] bpf: Make bpf_skb_vlan_push " Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 07/16] bpf: Make bpf_skb_adjust_room metadata-safe Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 08/16] bpf: Make bpf_skb_change_proto helper metadata-safe Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 09/16] bpf: Make bpf_skb_change_head " Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 10/16] selftests/bpf: Verify skb metadata in BPF instead of userspace Jakub Sitnicki
2025-10-26 14:18 ` Jakub Sitnicki [this message]
2025-10-27 12:29 ` [PATCH bpf-next v3 11/16] selftests/bpf: Dump skb metadata on verification failure Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 12/16] selftests/bpf: Expect unclone to preserve skb metadata Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 13/16] selftests/bpf: Cover skb metadata access after vlan push/pop helper Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 14/16] selftests/bpf: Cover skb metadata access after bpf_skb_adjust_room Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 15/16] selftests/bpf: Cover skb metadata access after change_head/tail helper Jakub Sitnicki
2025-10-26 14:18 ` [PATCH bpf-next v3 16/16] selftests/bpf: Cover skb metadata access after bpf_skb_change_proto Jakub Sitnicki
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