Merge tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

Martin KaFai Lau says:

====================
pull-request: bpf-next 2025-08-21

We've added 9 non-merge commits during the last 3 day(s) which contain
a total of 13 files changed, 1027 insertions(+), 27 deletions(-).

The main changes are:

1) Added bpf dynptr support for accessing the metadata of a skb,
from Jakub Sitnicki.
The patches are merged from a stable branch bpf-next/skb-meta-dynptr.
The same patches have also been merged into bpf-next/master.

* tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next:
selftests/bpf: Cover metadata access from a modified skb clone
selftests/bpf: Cover read/write to skb metadata at an offset
selftests/bpf: Cover write access to skb metadata via dynptr
selftests/bpf: Cover read access to skb metadata via dynptr
selftests/bpf: Parametrize test_xdp_context_tuntap
selftests/bpf: Pass just bpf_map to xdp_context_test helper
selftests/bpf: Cover verifier checks for skb_meta dynptr type
bpf: Enable read/write access to skb metadata through a dynptr
bpf: Add dynptr type for skb metadata
====================

Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

include/linux/bpf.h

···
 	 */
 	MEM_WRITE		= BIT(18 + BPF_BASE_TYPE_BITS),
 
+	/* DYNPTR points to skb_metadata_end()-skb_metadata_len() */
+	DYNPTR_TYPE_SKB_META	= BIT(19 + BPF_BASE_TYPE_BITS),
+
 	__BPF_TYPE_FLAG_MAX,
 	__BPF_TYPE_LAST_FLAG	= __BPF_TYPE_FLAG_MAX - 1,
 };
 
 #define DYNPTR_TYPE_FLAG_MASK	(DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF | DYNPTR_TYPE_SKB \
-				 | DYNPTR_TYPE_XDP)
+				 | DYNPTR_TYPE_XDP | DYNPTR_TYPE_SKB_META)
 
 /* Max number of base types. */
 #define BPF_BASE_TYPE_LIMIT	(1UL << BPF_BASE_TYPE_BITS)
···
 	BPF_DYNPTR_TYPE_SKB,
 	/* Underlying data is a xdp_buff */
 	BPF_DYNPTR_TYPE_XDP,
+	/* Points to skb_metadata_end()-skb_metadata_len() */
+	BPF_DYNPTR_TYPE_SKB_META,
 };
 
 int bpf_dynptr_check_size(u32 size);

include/linux/filter.h

···
 void *bpf_xdp_pointer(struct xdp_buff *xdp, u32 offset, u32 len);
 void bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off,
 		      void *buf, unsigned long len, bool flush);
+void *bpf_skb_meta_pointer(struct sk_buff *skb, u32 offset);
 #else /* CONFIG_NET */
 static inline int __bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset,
 				       void *to, u32 len)
···
 static inline void bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off, void *buf,
 				    unsigned long len, bool flush)
 {
+}
+
+static inline void *bpf_skb_meta_pointer(struct sk_buff *skb, u32 offset)
+{
+	return NULL;
 }
 #endif /* CONFIG_NET */
 

kernel/bpf/helpers.c

···
 		return __bpf_skb_load_bytes(src->data, src->offset + offset, dst, len);
 	case BPF_DYNPTR_TYPE_XDP:
 		return __bpf_xdp_load_bytes(src->data, src->offset + offset, dst, len);
+	case BPF_DYNPTR_TYPE_SKB_META:
+		memmove(dst, bpf_skb_meta_pointer(src->data, src->offset + offset), len);
+		return 0;
 	default:
 		WARN_ONCE(true, "bpf_dynptr_read: unknown dynptr type %d\n", type);
 		return -EFAULT;
···
 		if (flags)
 			return -EINVAL;
 		return __bpf_xdp_store_bytes(dst->data, dst->offset + offset, src, len);
+	case BPF_DYNPTR_TYPE_SKB_META:
+		if (flags)
+			return -EINVAL;
+		memmove(bpf_skb_meta_pointer(dst->data, dst->offset + offset), src, len);
+		return 0;
 	default:
 		WARN_ONCE(true, "bpf_dynptr_write: unknown dynptr type %d\n", type);
 		return -EFAULT;
···
 		return (unsigned long)(ptr->data + ptr->offset + offset);
 	case BPF_DYNPTR_TYPE_SKB:
 	case BPF_DYNPTR_TYPE_XDP:
+	case BPF_DYNPTR_TYPE_SKB_META:
 		/* skb and xdp dynptrs should use bpf_dynptr_slice / bpf_dynptr_slice_rdwr */
 		return 0;
 	default:
···
 		bpf_xdp_copy_buf(ptr->data, ptr->offset + offset, buffer__opt, len, false);
 		return buffer__opt;
 	}
+	case BPF_DYNPTR_TYPE_SKB_META:
+		return bpf_skb_meta_pointer(ptr->data, ptr->offset + offset);
 	default:
 		WARN_ONCE(true, "unknown dynptr type %d\n", type);
 		return NULL;

kernel/bpf/log.c

···
 		return "skb";
 	case BPF_DYNPTR_TYPE_XDP:
 		return "xdp";
+	case BPF_DYNPTR_TYPE_SKB_META:
+		return "skb_meta";
 	case BPF_DYNPTR_TYPE_INVALID:
 		return "<invalid>";
 	default:

kernel/bpf/verifier.c

···
 		return BPF_DYNPTR_TYPE_SKB;
 	case DYNPTR_TYPE_XDP:
 		return BPF_DYNPTR_TYPE_XDP;
+	case DYNPTR_TYPE_SKB_META:
+		return BPF_DYNPTR_TYPE_SKB_META;
 	default:
 		return BPF_DYNPTR_TYPE_INVALID;
 	}
···
 		return DYNPTR_TYPE_SKB;
 	case BPF_DYNPTR_TYPE_XDP:
 		return DYNPTR_TYPE_XDP;
+	case BPF_DYNPTR_TYPE_SKB_META:
+		return DYNPTR_TYPE_SKB_META;
 	default:
 		return 0;
 	}
···
 static bool reg_is_dynptr_slice_pkt(const struct bpf_reg_state *reg)
 {
 	return base_type(reg->type) == PTR_TO_MEM &&
-		(reg->type & DYNPTR_TYPE_SKB || reg->type & DYNPTR_TYPE_XDP);
+	       (reg->type &
+		(DYNPTR_TYPE_SKB | DYNPTR_TYPE_XDP | DYNPTR_TYPE_SKB_META));
 }
 
 /* Unmodified PTR_TO_PACKET[_META,_END] register from ctx access. */
···
 		if (dynptr_type == BPF_DYNPTR_TYPE_INVALID)
 			return -EFAULT;
 
-		if (dynptr_type == BPF_DYNPTR_TYPE_SKB)
+		if (dynptr_type == BPF_DYNPTR_TYPE_SKB ||
+		    dynptr_type == BPF_DYNPTR_TYPE_SKB_META)
 			/* this will trigger clear_all_pkt_pointers(), which will
 			 * invalidate all dynptr slices associated with the skb
 			 */
···
 	KF_bpf_rbtree_right,
 	KF_bpf_dynptr_from_skb,
 	KF_bpf_dynptr_from_xdp,
+	KF_bpf_dynptr_from_skb_meta,
 	KF_bpf_dynptr_slice,
 	KF_bpf_dynptr_slice_rdwr,
 	KF_bpf_dynptr_clone,
···
 #ifdef CONFIG_NET
 BTF_ID(func, bpf_dynptr_from_skb)
 BTF_ID(func, bpf_dynptr_from_xdp)
+BTF_ID(func, bpf_dynptr_from_skb_meta)
 #else
+BTF_ID_UNUSED
 BTF_ID_UNUSED
 BTF_ID_UNUSED
 #endif
···
 				dynptr_arg_type |= DYNPTR_TYPE_SKB;
 			} else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_xdp]) {
 				dynptr_arg_type |= DYNPTR_TYPE_XDP;
+			} else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_from_skb_meta]) {
+				dynptr_arg_type |= DYNPTR_TYPE_SKB_META;
 			} else if (meta->func_id == special_kfunc_list[KF_bpf_dynptr_clone] &&
 				   (dynptr_arg_type & MEM_UNINIT)) {
 				enum bpf_dynptr_type parent_type = meta->initialized_dynptr.type;

net/core/filter.c

···
 	return func;
 }
 
+/**
+ * bpf_skb_meta_pointer() - Gets a mutable pointer within the skb metadata area.
+ * @skb: socket buffer carrying the metadata
+ * @offset: offset into the metadata area, must be <= skb_metadata_len()
+ */
+void *bpf_skb_meta_pointer(struct sk_buff *skb, u32 offset)
+{
+	return skb_metadata_end(skb) - skb_metadata_len(skb) + offset;
+}
+
 __bpf_kfunc_start_defs();
 __bpf_kfunc int bpf_dynptr_from_skb(struct __sk_buff *s, u64 flags,
 				    struct bpf_dynptr *ptr__uninit)
···
 	}
 
 	bpf_dynptr_init(ptr, skb, BPF_DYNPTR_TYPE_SKB, 0, skb->len);
+
+	return 0;
+}
+
+/**
+ * bpf_dynptr_from_skb_meta() - Initialize a dynptr to the skb metadata area.
+ * @skb_: socket buffer carrying the metadata
+ * @flags: future use, must be zero
+ * @ptr__uninit: dynptr to initialize
+ *
+ * Set up a dynptr for access to the metadata area earlier allocated from the
+ * XDP context with bpf_xdp_adjust_meta(). Serves as an alternative to
+ * &__sk_buff->data_meta.
+ *
+ * If passed @skb_ is a clone which shares the data with the original, the
+ * dynptr will be read-only. This limitation may be lifted in the future.
+ *
+ * Return:
+ * * %0         - dynptr ready to use
+ * * %-EINVAL   - invalid flags, dynptr set to null
+ */
+__bpf_kfunc int bpf_dynptr_from_skb_meta(struct __sk_buff *skb_, u64 flags,
+					 struct bpf_dynptr *ptr__uninit)
+{
+	struct bpf_dynptr_kern *ptr = (struct bpf_dynptr_kern *)ptr__uninit;
+	struct sk_buff *skb = (struct sk_buff *)skb_;
+
+	if (flags) {
+		bpf_dynptr_set_null(ptr);
+		return -EINVAL;
+	}
+
+	bpf_dynptr_init(ptr, skb, BPF_DYNPTR_TYPE_SKB_META, 0, skb_metadata_len(skb));
+
+	if (skb_cloned(skb))
+		bpf_dynptr_set_rdonly(ptr);
 
 	return 0;
 }
···
 BTF_ID_FLAGS(func, bpf_dynptr_from_skb, KF_TRUSTED_ARGS)
 BTF_KFUNCS_END(bpf_kfunc_check_set_skb)
 
+BTF_KFUNCS_START(bpf_kfunc_check_set_skb_meta)
+BTF_ID_FLAGS(func, bpf_dynptr_from_skb_meta, KF_TRUSTED_ARGS)
+BTF_KFUNCS_END(bpf_kfunc_check_set_skb_meta)
+
 BTF_KFUNCS_START(bpf_kfunc_check_set_xdp)
 BTF_ID_FLAGS(func, bpf_dynptr_from_xdp)
 BTF_KFUNCS_END(bpf_kfunc_check_set_xdp)
···
 static const struct btf_kfunc_id_set bpf_kfunc_set_skb = {
 	.owner = THIS_MODULE,
 	.set = &bpf_kfunc_check_set_skb,
+};
+
+static const struct btf_kfunc_id_set bpf_kfunc_set_skb_meta = {
+	.owner = THIS_MODULE,
+	.set = &bpf_kfunc_check_set_skb_meta,
 };
 
 static const struct btf_kfunc_id_set bpf_kfunc_set_xdp = {
···
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_LWT_SEG6LOCAL, &bpf_kfunc_set_skb);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_NETFILTER, &bpf_kfunc_set_skb);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_kfunc_set_skb);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_kfunc_set_skb_meta);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_ACT, &bpf_kfunc_set_skb_meta);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &bpf_kfunc_set_xdp);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
 					       &bpf_kfunc_set_sock_addr);

tools/testing/selftests/bpf/bpf_kfuncs.h

···
 extern int bpf_dynptr_from_xdp(struct xdp_md *xdp, __u64 flags,
 			       struct bpf_dynptr *ptr__uninit) __ksym __weak;
 
+extern int bpf_dynptr_from_skb_meta(struct __sk_buff *skb, __u64 flags,
+				    struct bpf_dynptr *ptr__uninit) __ksym __weak;
+
 /* Description
  *  Obtain a read-only pointer to the dynptr's data
  * Returns

tools/testing/selftests/bpf/config

···
 CONFIG_MPLS_ROUTING=y
 CONFIG_MPTCP=y
 CONFIG_NET_ACT_GACT=y
+CONFIG_NET_ACT_MIRRED=y
 CONFIG_NET_ACT_SKBMOD=y
 CONFIG_NET_CLS=y
 CONFIG_NET_CLS_ACT=y

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

···
 	{"test_ringbuf", SETUP_SYSCALL_SLEEP},
 	{"test_skb_readonly", SETUP_SKB_PROG},
 	{"test_dynptr_skb_data", SETUP_SKB_PROG},
+	{"test_dynptr_skb_meta_data", SETUP_SKB_PROG},
+	{"test_dynptr_skb_meta_flags", SETUP_SKB_PROG},
 	{"test_adjust", SETUP_SYSCALL_SLEEP},
 	{"test_adjust_err", SETUP_SYSCALL_SLEEP},
 	{"test_zero_size_dynptr", SETUP_SYSCALL_SLEEP},

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

···
 #define TX_NETNS "xdp_context_tx"
 #define RX_NETNS "xdp_context_rx"
 #define TAP_NAME "tap0"
+#define DUMMY_NAME "dum0"
 #define TAP_NETNS "xdp_context_tuntap"
 
 #define TEST_PAYLOAD_LEN 32
···
 	return -1;
 }
 
-static void assert_test_result(struct test_xdp_meta *skel)
+static int write_test_packet(int tap_fd)
+{
+	__u8 packet[sizeof(struct ethhdr) + TEST_PAYLOAD_LEN];
+	int n;
+
+	/* The ethernet header doesn't need to be valid for this test */
+	memset(packet, 0, sizeof(struct ethhdr));
+	memcpy(packet + sizeof(struct ethhdr), test_payload, TEST_PAYLOAD_LEN);
+
+	n = write(tap_fd, packet, sizeof(packet));
+	if (!ASSERT_EQ(n, sizeof(packet), "write packet"))
+		return -1;
+
+	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(skel->maps.test_result, &map_key,
-				   sizeof(map_key), &map_value,
-				   TEST_PAYLOAD_LEN, BPF_ANY);
+	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)
···
 	if (!ASSERT_OK(ret, "send_test_packet"))
 		goto close;
 
-	assert_test_result(skel);
+	assert_test_result(skel->maps.test_result);
 
 close:
 	close_netns(nstoken);
···
 	netns_free(tx_ns);
 }
 
-void test_xdp_context_tuntap(void)
+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)
 {
 	LIBBPF_OPTS(bpf_tc_hook, tc_hook, .attach_point = BPF_TC_INGRESS);
 	LIBBPF_OPTS(bpf_tc_opts, tc_opts, .handle = 1, .priority = 1);
 	struct netns_obj *ns = NULL;
-	struct test_xdp_meta *skel = NULL;
-	__u8 packet[sizeof(struct ethhdr) + TEST_PAYLOAD_LEN];
 	int tap_fd = -1;
 	int tap_ifindex;
 	int ret;
+
+	if (!clear_test_result(result_map))
+		return;
 
 	ns = netns_new(TAP_NETNS, true);
 	if (!ASSERT_OK_PTR(ns, "create and open ns"))
···
 
 	SYS(close, "ip link set dev " TAP_NAME " up");
 
-	skel = test_xdp_meta__open_and_load();
-	if (!ASSERT_OK_PTR(skel, "open and load skeleton"))
-		goto close;
-
 	tap_ifindex = if_nametoindex(TAP_NAME);
 	if (!ASSERT_GE(tap_ifindex, 0, "if_nametoindex"))
 		goto close;
···
 	if (!ASSERT_OK(ret, "bpf_tc_hook_create"))
 		goto close;
 
-	tc_opts.prog_fd = bpf_program__fd(skel->progs.ing_cls);
+	tc_opts.prog_fd = bpf_program__fd(tc_prio_1_prog);
 	ret = bpf_tc_attach(&tc_hook, &tc_opts);
 	if (!ASSERT_OK(ret, "bpf_tc_attach"))
 		goto close;
 
-	ret = bpf_xdp_attach(tap_ifindex, bpf_program__fd(skel->progs.ing_xdp),
+	if (tc_prio_2_prog) {
+		LIBBPF_OPTS(bpf_tc_opts, tc_opts, .handle = 1, .priority = 2,
+			    .prog_fd = bpf_program__fd(tc_prio_2_prog));
+
+		ret = bpf_tc_attach(&tc_hook, &tc_opts);
+		if (!ASSERT_OK(ret, "bpf_tc_attach"))
+			goto close;
+	}
+
+	ret = bpf_xdp_attach(tap_ifindex, bpf_program__fd(xdp_prog),
 			     0, NULL);
 	if (!ASSERT_GE(ret, 0, "bpf_xdp_attach"))
 		goto close;
 
-	/* The ethernet header is not relevant for this test and doesn't need to
-	 * be meaningful.
-	 */
-	struct ethhdr eth = { 0 };
-
-	memcpy(packet, &eth, sizeof(eth));
-	memcpy(packet + sizeof(eth), test_payload, TEST_PAYLOAD_LEN);
-
-	ret = write(tap_fd, packet, sizeof(packet));
-	if (!ASSERT_EQ(ret, sizeof(packet), "write packet"))
+	ret = write_test_packet(tap_fd);
+	if (!ASSERT_OK(ret, "write_test_packet"))
 		goto close;
 
-	assert_test_result(skel);
+	assert_test_result(result_map);
 
 close:
 	if (tap_fd >= 0)
 		close(tap_fd);
-	test_xdp_meta__destroy(skel);
 	netns_free(ns);
+}
+
+/* Write a packet to a tap dev and copy it to ingress of a dummy dev */
+static void test_tuntap_mirred(struct bpf_program *xdp_prog,
+			       struct bpf_program *tc_prog,
+			       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);
+	struct netns_obj *ns = NULL;
+	int dummy_ifindex;
+	int tap_fd = -1;
+	int tap_ifindex;
+	int ret;
+
+	*test_pass = false;
+
+	ns = netns_new(TAP_NETNS, true);
+	if (!ASSERT_OK_PTR(ns, "netns_new"))
+		return;
+
+	/* Setup dummy interface */
+	SYS(close, "ip link add name " DUMMY_NAME " type dummy");
+	SYS(close, "ip link set dev " DUMMY_NAME " up");
+
+	dummy_ifindex = if_nametoindex(DUMMY_NAME);
+	if (!ASSERT_GE(dummy_ifindex, 0, "if_nametoindex"))
+		goto close;
+
+	tc_hook.ifindex = dummy_ifindex;
+	ret = bpf_tc_hook_create(&tc_hook);
+	if (!ASSERT_OK(ret, "bpf_tc_hook_create"))
+		goto close;
+
+	tc_opts.prog_fd = bpf_program__fd(tc_prog);
+	ret = bpf_tc_attach(&tc_hook, &tc_opts);
+	if (!ASSERT_OK(ret, "bpf_tc_attach"))
+		goto close;
+
+	/* Setup TAP interface */
+	tap_fd = open_tuntap(TAP_NAME, true);
+	if (!ASSERT_GE(tap_fd, 0, "open_tuntap"))
+		goto close;
+
+	SYS(close, "ip link set dev " TAP_NAME " up");
+
+	tap_ifindex = if_nametoindex(TAP_NAME);
+	if (!ASSERT_GE(tap_ifindex, 0, "if_nametoindex"))
+		goto close;
+
+	ret = bpf_xdp_attach(tap_ifindex, bpf_program__fd(xdp_prog), 0, NULL);
+	if (!ASSERT_GE(ret, 0, "bpf_xdp_attach"))
+		goto close;
+
+	/* Copy all packets received from TAP to dummy ingress */
+	SYS(close, "tc qdisc add dev " TAP_NAME " clsact");
+	SYS(close, "tc filter add dev " TAP_NAME " ingress "
+		   "protocol all matchall "
+		   "action mirred ingress mirror dev " DUMMY_NAME);
+
+	/* Receive a packet on TAP */
+	ret = write_test_packet(tap_fd);
+	if (!ASSERT_OK(ret, "write_test_packet"))
+		goto close;
+
+	ASSERT_TRUE(*test_pass, "test_pass");
+
+close:
+	if (tap_fd >= 0)
+		close(tap_fd);
+	netns_free(ns);
+}
+
+void test_xdp_context_tuntap(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("data_meta"))
+		test_tuntap(skel->progs.ing_xdp,
+			    skel->progs.ing_cls,
+			    NULL, /* tc prio 2 */
+			    skel->maps.test_result);
+	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);
+	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);
+	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);
+	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);
+	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);
+	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);
+	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,
+				   &skel->bss->test_pass);
+	if (test__start_subtest("clone_data_meta_empty_on_meta_write"))
+		test_tuntap_mirred(skel->progs.ing_xdp,
+				   skel->progs.clone_data_meta_empty_on_meta_write,
+				   &skel->bss->test_pass);
+	if (test__start_subtest("clone_dynptr_empty_on_data_slice_write"))
+		test_tuntap_mirred(skel->progs.ing_xdp,
+				   skel->progs.clone_dynptr_empty_on_data_slice_write,
+				   &skel->bss->test_pass);
+	if (test__start_subtest("clone_dynptr_empty_on_meta_slice_write"))
+		test_tuntap_mirred(skel->progs.ing_xdp,
+				   skel->progs.clone_dynptr_empty_on_meta_slice_write,
+				   &skel->bss->test_pass);
+	if (test__start_subtest("clone_dynptr_rdonly_before_data_dynptr_write"))
+		test_tuntap_mirred(skel->progs.ing_xdp,
+				   skel->progs.clone_dynptr_rdonly_before_data_dynptr_write,
+				   &skel->bss->test_pass);
+	if (test__start_subtest("clone_dynptr_rdonly_before_meta_dynptr_write"))
+		test_tuntap_mirred(skel->progs.ing_xdp,
+				   skel->progs.clone_dynptr_rdonly_before_meta_dynptr_write,
+				   &skel->bss->test_pass);
+
+	test_xdp_meta__destroy(skel);
 }

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

···
 	return SK_PASS;
 }
 
+/* A metadata slice can't be accessed out of bounds */
+SEC("?tc")
+__failure __msg("value is outside of the allowed memory range")
+int data_slice_out_of_bounds_skb_meta(struct __sk_buff *skb)
+{
+	struct bpf_dynptr meta;
+	__u8 *md;
+
+	bpf_dynptr_from_skb_meta(skb, 0, &meta);
+
+	md = bpf_dynptr_slice_rdwr(&meta, 0, NULL, sizeof(*md));
+	if (!md)
+		return SK_DROP;
+
+	/* this should fail */
+	*(md + 1) = 42;
+
+	return SK_PASS;
+}
+
 SEC("?raw_tp")
 __failure __msg("value is outside of the allowed memory range")
 int data_slice_out_of_bounds_map_value(void *ctx)
···
 	return SK_PASS;
 }
 
+/* bpf_dynptr_slice()s are read-only and cannot be written to */
+SEC("?tc")
+__failure __msg("R{{[0-9]+}} cannot write into rdonly_mem")
+int skb_meta_invalid_slice_write(struct __sk_buff *skb)
+{
+	struct bpf_dynptr meta;
+	__u8 *md;
+
+	bpf_dynptr_from_skb_meta(skb, 0, &meta);
+
+	md = bpf_dynptr_slice(&meta, 0, NULL, sizeof(*md));
+	if (!md)
+		return SK_DROP;
+
+	/* this should fail */
+	*md = 42;
+
+	return SK_PASS;
+}
+
 /* The read-only data slice is invalidated whenever a helper changes packet data */
 SEC("?tc")
 __failure __msg("invalid mem access 'scalar'")
···
 	return SK_PASS;
 }
 
+/* Read-only skb data slice is invalidated on write to skb metadata */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int ro_skb_slice_invalid_after_metadata_write(struct __sk_buff *skb)
+{
+	struct bpf_dynptr data, meta;
+	__u8 *d;
+
+	bpf_dynptr_from_skb(skb, 0, &data);
+	bpf_dynptr_from_skb_meta(skb, 0, &meta);
+
+	d = bpf_dynptr_slice(&data, 0, NULL, sizeof(*d));
+	if (!d)
+		return SK_DROP;
+
+	bpf_dynptr_write(&meta, 0, "x", 1, 0);
+
+	/* this should fail */
+	val = *d;
+
+	return SK_PASS;
+}
+
+/* Read-write skb data slice is invalidated on write to skb metadata */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int rw_skb_slice_invalid_after_metadata_write(struct __sk_buff *skb)
+{
+	struct bpf_dynptr data, meta;
+	__u8 *d;
+
+	bpf_dynptr_from_skb(skb, 0, &data);
+	bpf_dynptr_from_skb_meta(skb, 0, &meta);
+
+	d = bpf_dynptr_slice_rdwr(&data, 0, NULL, sizeof(*d));
+	if (!d)
+		return SK_DROP;
+
+	bpf_dynptr_write(&meta, 0, "x", 1, 0);
+
+	/* this should fail */
+	*d = 42;
+
+	return SK_PASS;
+}
+
+/* Read-only skb metadata slice is invalidated on write to skb data */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int ro_skb_meta_slice_invalid_after_payload_write(struct __sk_buff *skb)
+{
+	struct bpf_dynptr data, meta;
+	__u8 *md;
+
+	bpf_dynptr_from_skb(skb, 0, &data);
+	bpf_dynptr_from_skb_meta(skb, 0, &meta);
+
+	md = bpf_dynptr_slice(&meta, 0, NULL, sizeof(*md));
+	if (!md)
+		return SK_DROP;
+
+	bpf_dynptr_write(&data, 0, "x", 1, 0);
+
+	/* this should fail */
+	val = *md;
+
+	return SK_PASS;
+}
+
+/* Read-write skb metadata slice is invalidated on write to skb data slice */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int rw_skb_meta_slice_invalid_after_payload_write(struct __sk_buff *skb)
+{
+	struct bpf_dynptr data, meta;
+	__u8 *md;
+
+	bpf_dynptr_from_skb(skb, 0, &data);
+	bpf_dynptr_from_skb_meta(skb, 0, &meta);
+
+	md = bpf_dynptr_slice_rdwr(&meta, 0, NULL, sizeof(*md));
+	if (!md)
+		return SK_DROP;
+
+	bpf_dynptr_write(&data, 0, "x", 1, 0);
+
+	/* this should fail */
+	*md = 42;
+
+	return SK_PASS;
+}
+
+/* Read-only skb metadata slice is invalidated whenever a helper changes packet data */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int ro_skb_meta_slice_invalid_after_payload_helper(struct __sk_buff *skb)
+{
+	struct bpf_dynptr meta;
+	__u8 *md;
+
+	bpf_dynptr_from_skb_meta(skb, 0, &meta);
+
+	md = bpf_dynptr_slice(&meta, 0, NULL, sizeof(*md));
+	if (!md)
+		return SK_DROP;
+
+	if (bpf_skb_pull_data(skb, skb->len))
+		return SK_DROP;
+
+	/* this should fail */
+	val = *md;
+
+	return SK_PASS;
+}
+
+/* Read-write skb metadata slice is invalidated whenever a helper changes packet data */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int rw_skb_meta_slice_invalid_after_payload_helper(struct __sk_buff *skb)
+{
+	struct bpf_dynptr meta;
+	__u8 *md;
+
+	bpf_dynptr_from_skb_meta(skb, 0, &meta);
+
+	md = bpf_dynptr_slice_rdwr(&meta, 0, NULL, sizeof(*md));
+	if (!md)
+		return SK_DROP;
+
+	if (bpf_skb_pull_data(skb, skb->len))
+		return SK_DROP;
+
+	/* this should fail */
+	*md = 42;
+
+	return SK_PASS;
+}
+
+/* Read-only skb metadata slice is invalidated on write to skb metadata */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int ro_skb_meta_slice_invalid_after_metadata_write(struct __sk_buff *skb)
+{
+	struct bpf_dynptr meta;
+	__u8 *md;
+
+	bpf_dynptr_from_skb_meta(skb, 0, &meta);
+
+	md = bpf_dynptr_slice(&meta, 0, NULL, sizeof(*md));
+	if (!md)
+		return SK_DROP;
+
+	bpf_dynptr_write(&meta, 0, "x", 1, 0);
+
+	/* this should fail */
+	val = *md;
+
+	return SK_PASS;
+}
+
+/* Read-write skb metadata slice is invalidated on write to skb metadata */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int rw_skb_meta_slice_invalid_after_metadata_write(struct __sk_buff *skb)
+{
+	struct bpf_dynptr meta;
+	__u8 *md;
+
+	bpf_dynptr_from_skb_meta(skb, 0, &meta);
+
+	md = bpf_dynptr_slice_rdwr(&meta, 0, NULL, sizeof(*md));
+	if (!md)
+		return SK_DROP;
+
+	bpf_dynptr_write(&meta, 0, "x", 1, 0);
+
+	/* this should fail */
+	*md = 42;
+
+	return SK_PASS;
+}
+
 /* The read-only data slice is invalidated whenever a helper changes packet data */
 SEC("?xdp")
 __failure __msg("invalid mem access 'scalar'")
···
 
 	/* this should fail */
 	bpf_dynptr_from_skb(ctx, 0, &ptr);
+
+	return 0;
+}
+
+/* Only supported prog type can create skb_meta-type dynptrs */
+SEC("?raw_tp")
+__failure __msg("calling kernel function bpf_dynptr_from_skb_meta is not allowed")
+int skb_meta_invalid_ctx(void *ctx)
+{
+	struct bpf_dynptr meta;
+
+	/* this should fail */
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
 
 	return 0;
 }
···
 
 	/* this should fail */
 	*data = 123;
+
+	return 0;
+}
+
+/* A skb clone's metadata slice becomes invalid anytime packet data changes */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int clone_skb_packet_meta(struct __sk_buff *skb)
+{
+	struct bpf_dynptr clone, meta;
+	__u8 *md;
+
+	bpf_dynptr_from_skb_meta(skb, 0, &meta);
+	bpf_dynptr_clone(&meta, &clone);
+	md = bpf_dynptr_slice_rdwr(&clone, 0, NULL, sizeof(*md));
+	if (!md)
+		return SK_DROP;
+
+	if (bpf_skb_pull_data(skb, skb->len))
+		return SK_DROP;
+
+	/* this should fail */
+	*md = 42;
 
 	return 0;
 }

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

···
 	return 1;
 }
 
+SEC("?tc")
+int test_dynptr_skb_meta_data(struct __sk_buff *skb)
+{
+	struct bpf_dynptr meta;
+	__u8 *md;
+	int ret;
+
+	err = 1;
+	ret = bpf_dynptr_from_skb_meta(skb, 0, &meta);
+	if (ret)
+		return 1;
+
+	/* This should return NULL. Must use bpf_dynptr_slice API */
+	err = 2;
+	md = bpf_dynptr_data(&meta, 0, sizeof(*md));
+	if (md)
+		return 1;
+
+	err = 0;
+	return 1;
+}
+
+/* Check that skb metadata dynptr ops don't accept any flags. */
+SEC("?tc")
+int test_dynptr_skb_meta_flags(struct __sk_buff *skb)
+{
+	const __u64 INVALID_FLAGS = ~0ULL;
+	struct bpf_dynptr meta;
+	__u8 buf;
+	int ret;
+
+	err = 1;
+	ret = bpf_dynptr_from_skb_meta(skb, INVALID_FLAGS, &meta);
+	if (ret != -EINVAL)
+		return 1;
+
+	err = 2;
+	ret = bpf_dynptr_from_skb_meta(skb, 0, &meta);
+	if (ret)
+		return 1;
+
+	err = 3;
+	ret = bpf_dynptr_read(&buf, 0, &meta, 0, INVALID_FLAGS);
+	if (ret != -EINVAL)
+		return 1;
+
+	err = 4;
+	ret = bpf_dynptr_write(&meta, 0, &buf, 0, INVALID_FLAGS);
+	if (ret != -EINVAL)
+		return 1;
+
+	err = 0;
+	return 1;
+}
+
 SEC("tp/syscalls/sys_enter_nanosleep")
 int test_adjust(void *ctx)
 {

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

···
+#include <stdbool.h>
 #include <linux/bpf.h>
+#include <linux/errno.h>
 #include <linux/if_ether.h>
 #include <linux/pkt_cls.h>
 
 #include <bpf/bpf_helpers.h>
+#include "bpf_kfuncs.h"
 
 #define META_SIZE 32
 
···
 	__uint(value_size, META_SIZE);
 } test_result SEC(".maps");
 
+bool test_pass;
+
 SEC("tc")
 int ing_cls(struct __sk_buff *ctx)
 {
···
 	bpf_map_update_elem(&test_result, &key, data_meta, BPF_ANY);
 
 	return TC_ACT_SHOT;
+}
+
+/* Read from metadata using bpf_dynptr_read helper */
+SEC("tc")
+int ing_cls_dynptr_read(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr meta;
+	const __u32 zero = 0;
+	__u8 *dst;
+
+	dst = bpf_map_lookup_elem(&test_result, &zero);
+	if (!dst)
+		return TC_ACT_SHOT;
+
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	bpf_dynptr_read(dst, META_SIZE, &meta, 0, 0);
+
+	return TC_ACT_SHOT;
+}
+
+/* Write to metadata using bpf_dynptr_write helper */
+SEC("tc")
+int ing_cls_dynptr_write(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr data, meta;
+	__u8 *src;
+
+	bpf_dynptr_from_skb(ctx, 0, &data);
+	src = bpf_dynptr_slice(&data, sizeof(struct ethhdr), NULL, META_SIZE);
+	if (!src)
+		return TC_ACT_SHOT;
+
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	bpf_dynptr_write(&meta, 0, src, META_SIZE, 0);
+
+	return TC_ACT_UNSPEC; /* pass */
+}
+
+/* Read from metadata using read-only dynptr slice */
+SEC("tc")
+int ing_cls_dynptr_slice(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr meta;
+	const __u32 zero = 0;
+	__u8 *dst, *src;
+
+	dst = bpf_map_lookup_elem(&test_result, &zero);
+	if (!dst)
+		return TC_ACT_SHOT;
+
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	src = bpf_dynptr_slice(&meta, 0, NULL, META_SIZE);
+	if (!src)
+		return TC_ACT_SHOT;
+
+	__builtin_memcpy(dst, src, META_SIZE);
+
+	return TC_ACT_SHOT;
+}
+
+/* Write to metadata using writeable dynptr slice */
+SEC("tc")
+int ing_cls_dynptr_slice_rdwr(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr data, meta;
+	__u8 *src, *dst;
+
+	bpf_dynptr_from_skb(ctx, 0, &data);
+	src = bpf_dynptr_slice(&data, sizeof(struct ethhdr), NULL, META_SIZE);
+	if (!src)
+		return TC_ACT_SHOT;
+
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	dst = bpf_dynptr_slice_rdwr(&meta, 0, NULL, META_SIZE);
+	if (!dst)
+		return TC_ACT_SHOT;
+
+	__builtin_memcpy(dst, src, META_SIZE);
+
+	return TC_ACT_UNSPEC; /* pass */
+}
+
+/* Read skb metadata in chunks from various offsets in different ways. */
+SEC("tc")
+int ing_cls_dynptr_offset_rd(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr meta;
+	const __u32 chunk_len = META_SIZE / 4;
+	const __u32 zero = 0;
+	__u8 *dst, *src;
+
+	dst = bpf_map_lookup_elem(&test_result, &zero);
+	if (!dst)
+		return TC_ACT_SHOT;
+
+	/* 1. Regular read */
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	bpf_dynptr_read(dst, chunk_len, &meta, 0, 0);
+	dst += chunk_len;
+
+	/* 2. Read from an offset-adjusted dynptr */
+	bpf_dynptr_adjust(&meta, chunk_len, bpf_dynptr_size(&meta));
+	bpf_dynptr_read(dst, chunk_len, &meta, 0, 0);
+	dst += chunk_len;
+
+	/* 3. Read at an offset */
+	bpf_dynptr_read(dst, chunk_len, &meta, chunk_len, 0);
+	dst += chunk_len;
+
+	/* 4. Read from a slice starting at an offset */
+	src = bpf_dynptr_slice(&meta, 2 * chunk_len, NULL, chunk_len);
+	if (!src)
+		return TC_ACT_SHOT;
+	__builtin_memcpy(dst, src, chunk_len);
+
+	return TC_ACT_SHOT;
+}
+
+/* Write skb metadata in chunks at various offsets in different ways. */
+SEC("tc")
+int ing_cls_dynptr_offset_wr(struct __sk_buff *ctx)
+{
+	const __u32 chunk_len = META_SIZE / 4;
+	__u8 payload[META_SIZE];
+	struct bpf_dynptr meta;
+	__u8 *dst, *src;
+
+	bpf_skb_load_bytes(ctx, sizeof(struct ethhdr), payload, sizeof(payload));
+	src = payload;
+
+	/* 1. Regular write */
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	bpf_dynptr_write(&meta, 0, src, chunk_len, 0);
+	src += chunk_len;
+
+	/* 2. Write to an offset-adjusted dynptr */
+	bpf_dynptr_adjust(&meta, chunk_len, bpf_dynptr_size(&meta));
+	bpf_dynptr_write(&meta, 0, src, chunk_len, 0);
+	src += chunk_len;
+
+	/* 3. Write at an offset */
+	bpf_dynptr_write(&meta, chunk_len, src, chunk_len, 0);
+	src += chunk_len;
+
+	/* 4. Write to a slice starting at an offset */
+	dst = bpf_dynptr_slice_rdwr(&meta, 2 * chunk_len, NULL, chunk_len);
+	if (!dst)
+		return TC_ACT_SHOT;
+	__builtin_memcpy(dst, src, chunk_len);
+
+	return TC_ACT_UNSPEC; /* pass */
+}
+
+/* Pass an OOB offset to dynptr read, write, adjust, slice. */
+SEC("tc")
+int ing_cls_dynptr_offset_oob(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr meta;
+	__u8 md, *p;
+	int err;
+
+	err = bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	if (err)
+		goto fail;
+
+	/* read offset OOB */
+	err = bpf_dynptr_read(&md, sizeof(md), &meta, META_SIZE, 0);
+	if (err != -E2BIG)
+		goto fail;
+
+	/* write offset OOB */
+	err = bpf_dynptr_write(&meta, META_SIZE, &md, sizeof(md), 0);
+	if (err != -E2BIG)
+		goto fail;
+
+	/* adjust end offset OOB */
+	err = bpf_dynptr_adjust(&meta, 0, META_SIZE + 1);
+	if (err != -ERANGE)
+		goto fail;
+
+	/* adjust start offset OOB */
+	err = bpf_dynptr_adjust(&meta, META_SIZE + 1, META_SIZE + 1);
+	if (err != -ERANGE)
+		goto fail;
+
+	/* slice offset OOB */
+	p = bpf_dynptr_slice(&meta, META_SIZE, NULL, sizeof(*p));
+	if (p)
+		goto fail;
+
+	/* slice rdwr offset OOB */
+	p = bpf_dynptr_slice_rdwr(&meta, META_SIZE, NULL, sizeof(*p));
+	if (p)
+		goto fail;
+
+	return TC_ACT_UNSPEC;
+fail:
+	return TC_ACT_SHOT;
+}
+
+/* Reserve and clear space for metadata but don't populate it */
+SEC("xdp")
+int ing_xdp_zalloc_meta(struct xdp_md *ctx)
+{
+	struct ethhdr *eth = ctx_ptr(ctx, data);
+	__u8 *meta;
+	int ret;
+
+	/* Drop any non-test packets */
+	if (eth + 1 > ctx_ptr(ctx, data_end))
+		return XDP_DROP;
+	if (eth->h_proto != 0)
+		return XDP_DROP;
+
+	ret = bpf_xdp_adjust_meta(ctx, -META_SIZE);
+	if (ret < 0)
+		return XDP_DROP;
+
+	meta = ctx_ptr(ctx, data_meta);
+	if (meta + META_SIZE > ctx_ptr(ctx, data))
+		return XDP_DROP;
+
+	__builtin_memset(meta, 0, META_SIZE);
+
+	return XDP_PASS;
 }
 
 SEC("xdp")
···
 
 	__builtin_memcpy(data_meta, payload, META_SIZE);
 	return XDP_PASS;
+}
+
+/*
+ * Check that skb->data_meta..skb->data is empty if prog writes to packet
+ * _payload_ using packet pointers. Applies only to cloned skbs.
+ */
+SEC("tc")
+int clone_data_meta_empty_on_data_write(struct __sk_buff *ctx)
+{
+	struct ethhdr *eth = ctx_ptr(ctx, data);
+
+	if (eth + 1 > ctx_ptr(ctx, data_end))
+		goto out;
+	/* Ignore non-test packets */
+	if (eth->h_proto != 0)
+		goto out;
+
+	/* Expect no metadata */
+	if (ctx->data_meta != ctx->data)
+		goto out;
+
+	/* Packet write to trigger unclone in prologue */
+	eth->h_proto = 42;
+
+	test_pass = true;
+out:
+	return TC_ACT_SHOT;
+}
+
+/*
+ * Check that skb->data_meta..skb->data is empty if prog writes to packet
+ * _metadata_ using packet pointers. Applies only to cloned skbs.
+ */
+SEC("tc")
+int clone_data_meta_empty_on_meta_write(struct __sk_buff *ctx)
+{
+	struct ethhdr *eth = ctx_ptr(ctx, data);
+	__u8 *md = ctx_ptr(ctx, data_meta);
+
+	if (eth + 1 > ctx_ptr(ctx, data_end))
+		goto out;
+	/* Ignore non-test packets */
+	if (eth->h_proto != 0)
+		goto out;
+
+	if (md + 1 > ctx_ptr(ctx, data)) {
+		/* Expect no metadata */
+		test_pass = true;
+	} else {
+		/* Metadata write to trigger unclone in prologue */
+		*md = 42;
+	}
+out:
+	return TC_ACT_SHOT;
+}
+
+/*
+ * Check that skb_meta dynptr is writable but empty if prog writes to packet
+ * _payload_ using a dynptr slice. Applies only to cloned skbs.
+ */
+SEC("tc")
+int clone_dynptr_empty_on_data_slice_write(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr data, meta;
+	struct ethhdr *eth;
+
+	bpf_dynptr_from_skb(ctx, 0, &data);
+	eth = bpf_dynptr_slice_rdwr(&data, 0, NULL, sizeof(*eth));
+	if (!eth)
+		goto out;
+	/* Ignore non-test packets */
+	if (eth->h_proto != 0)
+		goto out;
+
+	/* Expect no metadata */
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	if (bpf_dynptr_is_rdonly(&meta) || bpf_dynptr_size(&meta) > 0)
+		goto out;
+
+	/* Packet write to trigger unclone in prologue */
+	eth->h_proto = 42;
+
+	test_pass = true;
+out:
+	return TC_ACT_SHOT;
+}
+
+/*
+ * Check that skb_meta dynptr is writable but empty if prog writes to packet
+ * _metadata_ using a dynptr slice. Applies only to cloned skbs.
+ */
+SEC("tc")
+int clone_dynptr_empty_on_meta_slice_write(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr data, meta;
+	const struct ethhdr *eth;
+	__u8 *md;
+
+	bpf_dynptr_from_skb(ctx, 0, &data);
+	eth = bpf_dynptr_slice(&data, 0, NULL, sizeof(*eth));
+	if (!eth)
+		goto out;
+	/* Ignore non-test packets */
+	if (eth->h_proto != 0)
+		goto out;
+
+	/* Expect no metadata */
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	if (bpf_dynptr_is_rdonly(&meta) || bpf_dynptr_size(&meta) > 0)
+		goto out;
+
+	/* Metadata write to trigger unclone in prologue */
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	md = bpf_dynptr_slice_rdwr(&meta, 0, NULL, sizeof(*md));
+	if (md)
+		*md = 42;
+
+	test_pass = true;
+out:
+	return TC_ACT_SHOT;
+}
+
+/*
+ * Check that skb_meta dynptr is read-only before prog writes to packet payload
+ * using dynptr_write helper. Applies only to cloned skbs.
+ */
+SEC("tc")
+int clone_dynptr_rdonly_before_data_dynptr_write(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr data, meta;
+	const struct ethhdr *eth;
+
+	bpf_dynptr_from_skb(ctx, 0, &data);
+	eth = bpf_dynptr_slice(&data, 0, NULL, sizeof(*eth));
+	if (!eth)
+		goto out;
+	/* Ignore non-test packets */
+	if (eth->h_proto != 0)
+		goto out;
+
+	/* Expect read-only metadata before unclone */
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	if (!bpf_dynptr_is_rdonly(&meta) || bpf_dynptr_size(&meta) != META_SIZE)
+		goto out;
+
+	/* Helper write to payload will unclone the packet */
+	bpf_dynptr_write(&data, offsetof(struct ethhdr, h_proto), "x", 1, 0);
+
+	/* Expect no metadata after unclone */
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	if (bpf_dynptr_is_rdonly(&meta) || bpf_dynptr_size(&meta) != 0)
+		goto out;
+
+	test_pass = true;
+out:
+	return TC_ACT_SHOT;
+}
+
+/*
+ * Check that skb_meta dynptr is read-only if prog writes to packet
+ * metadata using dynptr_write helper. Applies only to cloned skbs.
+ */
+SEC("tc")
+int clone_dynptr_rdonly_before_meta_dynptr_write(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr data, meta;
+	const struct ethhdr *eth;
+
+	bpf_dynptr_from_skb(ctx, 0, &data);
+	eth = bpf_dynptr_slice(&data, 0, NULL, sizeof(*eth));
+	if (!eth)
+		goto out;
+	/* Ignore non-test packets */
+	if (eth->h_proto != 0)
+		goto out;
+
+	/* Expect read-only metadata */
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	if (!bpf_dynptr_is_rdonly(&meta) || bpf_dynptr_size(&meta) != META_SIZE)
+		goto out;
+
+	/* Metadata write. Expect failure. */
+	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
+	if (bpf_dynptr_write(&meta, 0, "x", 1, 0) != -EINVAL)
+		goto out;
+
+	test_pass = true;
+out:
+	return TC_ACT_SHOT;
 }
 
 char _license[] SEC("license") = "GPL";