selftests/bpf: Verify skb metadata in BPF instead of userspace

Move metadata verification into the BPF TC programs. Previously,
userspace read metadata from a map and verified it once at test end.

Now TC programs compare metadata directly using __builtin_memcmp() and
set a test_pass flag. This enables verification at multiple points during
test execution rather than a single final check.

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-v4-10-5ceb08a9b37b@cloudflare.com

1 files changed, 13 insertions, 39 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 178292d1251a..93a1fbe6a4fd 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
@@ -171,33 +171,6 @@ static int write_test_packet(int tap_fd)
 	return 0;
 }
 
-static void assert_test_result(const struct bpf_map *result_map)
-{
-	int err;
-	__u32 map_key = 0;
-	__u8 map_value[TEST_PAYLOAD_LEN];
-
-	err = bpf_map__lookup_elem(result_map, &map_key, sizeof(map_key),
-				   &map_value, TEST_PAYLOAD_LEN, BPF_ANY);
-	if (!ASSERT_OK(err, "lookup test_result"))
-		return;
-
-	ASSERT_MEMEQ(&map_value, &test_payload, TEST_PAYLOAD_LEN,
-		     "test_result map contains test payload");
-}
-
-static bool clear_test_result(struct bpf_map *result_map)
-{
-	const __u8 v[sizeof(test_payload)] = {};
-	const __u32 k = 0;
-	int err;
-
-	err = bpf_map__update_elem(result_map, &k, sizeof(k), v, sizeof(v), BPF_ANY);
-	ASSERT_OK(err, "update test_result");
-
-	return err == 0;
-}
-
 void test_xdp_context_veth(void)
 {
 	LIBBPF_OPTS(bpf_tc_hook, tc_hook, .attach_point = BPF_TC_INGRESS);
@@ -270,11 +243,13 @@ void test_xdp_context_veth(void)
 	if (!ASSERT_GE(tx_ifindex, 0, "if_nametoindex tx"))
 		goto close;
 
+	skel->bss->test_pass = false;
+
 	ret = send_test_packet(tx_ifindex);
 	if (!ASSERT_OK(ret, "send_test_packet"))
 		goto close;
 
-	assert_test_result(skel->maps.test_result);
+	ASSERT_TRUE(skel->bss->test_pass, "test_pass");
 
 close:
 	close_netns(nstoken);
@@ -286,7 +261,7 @@ close:
 static void test_tuntap(struct bpf_program *xdp_prog,
 			struct bpf_program *tc_prio_1_prog,
 			struct bpf_program *tc_prio_2_prog,
-			struct bpf_map *result_map)
+			bool *test_pass)
 {
 	LIBBPF_OPTS(bpf_tc_hook, tc_hook, .attach_point = BPF_TC_INGRESS);
 	LIBBPF_OPTS(bpf_tc_opts, tc_opts, .handle = 1, .priority = 1);
@@ -295,8 +270,7 @@ static void test_tuntap(struct bpf_program *xdp_prog,
 	int tap_ifindex;
 	int ret;
 
-	if (!clear_test_result(result_map))
-		return;
+	*test_pass = false;
 
 	ns = netns_new(TAP_NETNS, true);
 	if (!ASSERT_OK_PTR(ns, "create and open ns"))
@@ -340,7 +314,7 @@ static void test_tuntap(struct bpf_program *xdp_prog,
 	if (!ASSERT_OK(ret, "write_test_packet"))
 		goto close;
 
-	assert_test_result(result_map);
+	ASSERT_TRUE(*test_pass, "test_pass");
 
 close:
 	if (tap_fd >= 0)
@@ -431,37 +405,37 @@ void test_xdp_context_tuntap(void)
 		test_tuntap(skel->progs.ing_xdp,
 			    skel->progs.ing_cls,
 			    NULL, /* tc prio 2 */
-			    skel->maps.test_result);
+			    &skel->bss->test_pass);
 	if (test__start_subtest("dynptr_read"))
 		test_tuntap(skel->progs.ing_xdp,
 			    skel->progs.ing_cls_dynptr_read,
 			    NULL, /* tc prio 2 */
-			    skel->maps.test_result);
+			    &skel->bss->test_pass);
 	if (test__start_subtest("dynptr_slice"))
 		test_tuntap(skel->progs.ing_xdp,
 			    skel->progs.ing_cls_dynptr_slice,
 			    NULL, /* tc prio 2 */
-			    skel->maps.test_result);
+			    &skel->bss->test_pass);
 	if (test__start_subtest("dynptr_write"))
 		test_tuntap(skel->progs.ing_xdp_zalloc_meta,
 			    skel->progs.ing_cls_dynptr_write,
 			    skel->progs.ing_cls_dynptr_read,
-			    skel->maps.test_result);
+			    &skel->bss->test_pass);
 	if (test__start_subtest("dynptr_slice_rdwr"))
 		test_tuntap(skel->progs.ing_xdp_zalloc_meta,
 			    skel->progs.ing_cls_dynptr_slice_rdwr,
 			    skel->progs.ing_cls_dynptr_slice,
-			    skel->maps.test_result);
+			    &skel->bss->test_pass);
 	if (test__start_subtest("dynptr_offset"))
 		test_tuntap(skel->progs.ing_xdp_zalloc_meta,
 			    skel->progs.ing_cls_dynptr_offset_wr,
 			    skel->progs.ing_cls_dynptr_offset_rd,
-			    skel->maps.test_result);
+			    &skel->bss->test_pass);
 	if (test__start_subtest("dynptr_offset_oob"))
 		test_tuntap(skel->progs.ing_xdp,
 			    skel->progs.ing_cls_dynptr_offset_oob,
 			    skel->progs.ing_cls,
-			    skel->maps.test_result);
+			    &skel->bss->test_pass);
 	if (test__start_subtest("clone_data_meta_empty_on_data_write"))
 		test_tuntap_mirred(skel->progs.ing_xdp,
 				   skel->progs.clone_data_meta_empty_on_data_write,