From: Jakub Sitnicki <jakub@cloudflare.com>
Date: Wed, 5 Nov 2025 20:19:50 +0000 (+0100)
Subject: selftests/bpf: Cover skb metadata access after vlan push/pop helper
X-Git-Tag: v6.19-rc1~170^2~199^2~1^2~3
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=354d020c29f72513dce4f3902890158d99b67b67;p=thirdparty%2Fkernel%2Flinux.git

selftests/bpf: Cover skb metadata access after vlan push/pop helper

Add a test to verify that skb metadata remains accessible after calling
bpf_skb_vlan_push() and bpf_skb_vlan_pop(), which modify the packet
headroom.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20251105-skb-meta-rx-path-v4-13-5ceb08a9b37b@cloudflare.com
---

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 a129c3057202b..97c8f876f673b 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
@@ -478,6 +478,12 @@ void test_xdp_context_tuntap(void)
 		test_tuntap_mirred(skel->progs.ing_xdp,
 				   skel->progs.clone_meta_dynptr_rw_before_meta_dynptr_write,
 				   &skel->bss->test_pass);
+	/* Tests for BPF helpers which touch headroom */
+	if (test__start_subtest("helper_skb_vlan_push_pop"))
+		test_tuntap(skel->progs.ing_xdp,
+			    skel->progs.helper_skb_vlan_push_pop,
+			    NULL, /* tc prio 2 */
+			    &skel->bss->test_pass);
 
 	test_xdp_meta__destroy(skel);
 }
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_meta.c b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
index a70de55c6997f..04c7487bb350e 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_meta.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
@@ -44,6 +44,16 @@ static bool check_metadata(const char *file, int line, __u8 *meta_have)
 
 #define check_metadata(meta_have) check_metadata(__FILE__, __LINE__, meta_have)
 
+static bool check_skb_metadata(const char *file, int line, struct __sk_buff *skb)
+{
+	__u8 *data_meta = ctx_ptr(skb, data_meta);
+	__u8 *data = ctx_ptr(skb, data);
+
+	return data_meta + META_SIZE <= data && (check_metadata)(file, line, data_meta);
+}
+
+#define check_skb_metadata(skb) check_skb_metadata(__FILE__, __LINE__, skb)
+
 SEC("tc")
 int ing_cls(struct __sk_buff *ctx)
 {
@@ -525,4 +535,37 @@ out:
 	return TC_ACT_SHOT;
 }
 
+SEC("tc")
+int helper_skb_vlan_push_pop(struct __sk_buff *ctx)
+{
+	int err;
+
+	/* bpf_skb_vlan_push assumes HW offload for primary VLAN tag. Only
+	 * secondary tag push triggers an actual MAC header modification.
+	 */
+	err = bpf_skb_vlan_push(ctx, 0, 42);
+	if (err)
+		goto out;
+	err = bpf_skb_vlan_push(ctx, 0, 207);
+	if (err)
+		goto out;
+
+	if (!check_skb_metadata(ctx))
+		goto out;
+
+	err = bpf_skb_vlan_pop(ctx);
+	if (err)
+		goto out;
+	err = bpf_skb_vlan_pop(ctx);
+	if (err)
+		goto out;
+
+	if (!check_skb_metadata(ctx))
+		goto out;
+
+	test_pass = true;
+out:
+	return TC_ACT_SHOT;
+}
+
 char _license[] SEC("license") = "GPL";