[PATCH net-next 07/14] selftests/bpf: Test skb_ext read from cgroup_skb and sk_filter hooks

@@ -992,3 +992,124 @@ void test_skb_ext_basic(void)
 
 	test_xdp_meta__destroy(skel);
 }
+
+/* Send test_payload over loopback UDP to recv_fd */
+static int send_loopback_udp(int recv_fd)
+{
+	struct sockaddr_in addr = {
+		.sin_family = AF_INET,
+		.sin_addr.s_addr = htonl(INADDR_LOOPBACK),
+	};
+	char buf[TEST_PAYLOAD_LEN];
+	int ret = -1;
+	int fd = -1;
+	__be16 port;
+
+	port = get_socket_local_port(recv_fd);
+	if (!ASSERT_GE(port, 0, "get_port"))
+		goto out;
+
+	fd = socket(AF_INET, SOCK_DGRAM, 0);
+	if (!ASSERT_GE(fd, 0, "socket"))
+		goto out;
+
+	addr.sin_port = port;
+	sendto(fd, test_payload, TEST_PAYLOAD_LEN, 0,
+	       (void *)&addr, sizeof(addr));
+	recvfrom(recv_fd, buf, sizeof(buf), 0, NULL, NULL);
+	ret = 0;
+out:
+	if (fd >= 0)
+		close(fd);
+	return ret;
+}
+
+enum udp_reader_type {
+	READER_CGRP_SKB,
+	READER_SK_FILTER,
+};
+
+/* Test skb_ext survival across TC ingress -> UDP reader hook */
+static void test_skb_ext_udp(struct test_xdp_meta *skel, const char *name,
+			     enum udp_reader_type reader)
+{
+	LIBBPF_OPTS(bpf_tc_hook, tc_hook,
+		    .ifindex = 1 /* IFINDEX_LO */,
+		    .attach_point = BPF_TC_INGRESS);
+	LIBBPF_OPTS(bpf_tc_opts, tc_opts, .handle = 1, .priority = 1);
+	struct bpf_link *reader_link = NULL;
+	struct netns_obj *ns = NULL;
+	int server_fd = -1;
+	int cgroup_fd = -1;
+	int filter_fd;
+	int ret;
+
+	ns = netns_new(name, true);
+	if (!ASSERT_OK_PTR(ns, "netns_new"))
+		return;
+
+	cgroup_fd = test__join_cgroup(name);
+	if (!ASSERT_GE(cgroup_fd, 0, "join_cgroup"))
+		goto cleanup;
+
+	server_fd = start_server(AF_INET, SOCK_DGRAM, "127.0.0.1", 0, 0);
+	if (!ASSERT_GE(server_fd, 0, "start_server"))
+		goto cleanup;
+
+	skel->bss->test_pass = false;
+
+	ret = bpf_tc_hook_create(&tc_hook);
+	if (!ASSERT_OK(ret, "bpf_tc_hook_create"))
+		goto cleanup;
+
+	tc_opts.prog_fd = bpf_program__fd(skel->progs.tc_skb_ext_write);
+	ret = bpf_tc_attach(&tc_hook, &tc_opts);
+	if (!ASSERT_OK(ret, "bpf_tc_attach"))
+		goto cleanup;
+
+	switch (reader) {
+	case READER_CGRP_SKB:
+		reader_link = bpf_program__attach_cgroup(skel->progs.cgrp_skb_ext_read,
+							 cgroup_fd);
+		if (!ASSERT_OK_PTR(reader_link, "attach_cgroup"))
+			goto cleanup;
+		break;
+	case READER_SK_FILTER:
+		filter_fd = bpf_program__fd(skel->progs.sk_filter_skb_ext_read);
+		ret = setsockopt(server_fd, SOL_SOCKET, SO_ATTACH_BPF,
+				 &filter_fd, sizeof(filter_fd));
+		if (!ASSERT_OK(ret, "attach_socket_filter"))
+			goto cleanup;
+		break;
+	}
+
+	if (send_loopback_udp(server_fd))
+		goto cleanup;
+
+	ASSERT_TRUE(skel->bss->test_pass, "test_pass");
+
+cleanup:
+	bpf_link__destroy(reader_link);
+	bpf_tc_hook_destroy(&tc_hook);
+	if (server_fd >= 0)
+		close(server_fd);
+	if (cgroup_fd >= 0)
+		close(cgroup_fd);
+	netns_free(ns);
+}
+
+void test_skb_ext_cross_hook(void)
+{
+	struct test_xdp_meta *skel = NULL;
+
+	skel = test_xdp_meta__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "open and load skeleton"))
+		return;
+
+	if (test__start_subtest("tc_to_cgrp_ingress"))
+		test_skb_ext_udp(skel, "tc_to_cgrp_ingress", READER_CGRP_SKB);
+	if (test__start_subtest("tc_to_sk_filter"))
+		test_skb_ext_udp(skel, "tc_to_sk_filter", READER_SK_FILTER);
+
+	test_xdp_meta__destroy(skel);
+}

@@ -920,4 +920,41 @@ int BPF_PROG(tp_kfree_skb_cow_check, struct sk_buff *skb)
 	return 0;
 }
 
+/* Read skb_ext from cgroup/skb ingress -- tests cross-hook survival */
+SEC("cgroup_skb/ingress")
+int cgrp_skb_ext_read(struct __sk_buff *ctx)
+{
+	__u8 meta_have[META_SIZE];
+	struct bpf_dynptr meta;
+
+	if (bpf_dynptr_from_skb_ext(ctx, 0, 0, &meta))
+		return 1;
+	if (bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0))
+		return 1;
+	if (!check_metadata(meta_have))
+		return 1;
+
+	test_pass = true;
+	return 1;
+}
+
+/* Read skb_ext from socket filter -- tests TC -> sk_filter path */
+SEC("socket")
+int sk_filter_skb_ext_read(struct __sk_buff *ctx)
+{
+	__u8 meta_have[META_SIZE];
+	struct bpf_dynptr meta;
+
+	if (bpf_dynptr_from_skb_ext(ctx, 0, 0, &meta))
+		goto out;
+	if (bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0))
+		goto out;
+	if (!check_metadata(meta_have))
+		goto out;
+
+	test_pass = true;
+out:
+	return ctx->len;
+}
+
 char _license[] SEC("license") = "GPL";