selftests/bpf: Expect unclone to preserve skb metadata

Since pskb_expand_head() no longer clears metadata on unclone, update tests
for cloned packets to expect metadata to remain intact.

Also simplify the clone_dynptr_kept_on_{data,meta}_slice_write tests.
Creating an r/w dynptr slice is sufficient to trigger an unclone in the
prologue, so remove the extraneous writes to the data/meta slice.

Signed-off-by: Jakub Sitnicki <[email protected]>

Author: jsitnicki

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

@@ -454,29 +454,29 @@ void test_xdp_context_tuntap(void)
 			    skel->progs.ing_cls_dynptr_offset_oob,
 			    skel->progs.ing_cls,
 			    &skel->bss->test_pass);
-	if (test__start_subtest("clone_data_meta_empty_on_data_write"))
+	if (test__start_subtest("clone_data_meta_survives_data_write"))
 		test_tuntap_mirred(skel->progs.ing_xdp,
-				   skel->progs.clone_data_meta_empty_on_data_write,
+				   skel->progs.clone_data_meta_survives_data_write,
 				   &skel->bss->test_pass);
-	if (test__start_subtest("clone_data_meta_empty_on_meta_write"))
+	if (test__start_subtest("clone_data_meta_survives_meta_write"))
 		test_tuntap_mirred(skel->progs.ing_xdp,
-				   skel->progs.clone_data_meta_empty_on_meta_write,
+				   skel->progs.clone_data_meta_survives_meta_write,
 				   &skel->bss->test_pass);
-	if (test__start_subtest("clone_dynptr_empty_on_data_slice_write"))
+	if (test__start_subtest("clone_meta_dynptr_survives_data_slice_write"))
 		test_tuntap_mirred(skel->progs.ing_xdp,
-				   skel->progs.clone_dynptr_empty_on_data_slice_write,
+				   skel->progs.clone_meta_dynptr_survives_data_slice_write,
 				   &skel->bss->test_pass);
-	if (test__start_subtest("clone_dynptr_empty_on_meta_slice_write"))
+	if (test__start_subtest("clone_meta_dynptr_survives_meta_slice_write"))
 		test_tuntap_mirred(skel->progs.ing_xdp,
-				   skel->progs.clone_dynptr_empty_on_meta_slice_write,
+				   skel->progs.clone_meta_dynptr_survives_meta_slice_write,
 				   &skel->bss->test_pass);
-	if (test__start_subtest("clone_dynptr_rdonly_before_data_dynptr_write"))
+	if (test__start_subtest("clone_meta_dynptr_rw_before_data_dynptr_write"))
 		test_tuntap_mirred(skel->progs.ing_xdp,
-				   skel->progs.clone_dynptr_rdonly_before_data_dynptr_write,
+				   skel->progs.clone_meta_dynptr_rw_before_data_dynptr_write,
 				   &skel->bss->test_pass);
-	if (test__start_subtest("clone_dynptr_rdonly_before_meta_dynptr_write"))
+	if (test__start_subtest("clone_meta_dynptr_rw_before_meta_dynptr_write"))
 		test_tuntap_mirred(skel->progs.ing_xdp,
-				   skel->progs.clone_dynptr_rdonly_before_meta_dynptr_write,
+				   skel->progs.clone_meta_dynptr_rw_before_meta_dynptr_write,
 				   &skel->bss->test_pass);
 
 	test_xdp_meta__destroy(skel);

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

@@ -321,12 +321,13 @@ int ing_xdp(struct xdp_md *ctx)
 }
 
 /*
- * Check that skb->data_meta..skb->data is empty if prog writes to packet
- * _payload_ using packet pointers. Applies only to cloned skbs.
+ * Check that, when operating on a cloned packet, skb->data_meta..skb->data is
+ * kept intact if prog writes to packet _payload_ using packet pointers.
  */
 SEC("tc")
-int clone_data_meta_empty_on_data_write(struct __sk_buff *ctx)
+int clone_data_meta_survives_data_write(struct __sk_buff *ctx)
 {
+	__u8 *meta_have = ctx_ptr(ctx, data_meta);
 	struct ethhdr *eth = ctx_ptr(ctx, data);
 
 	if (eth + 1 > ctx_ptr(ctx, data_end))
@@ -335,8 +336,10 @@ int clone_data_meta_empty_on_data_write(struct __sk_buff *ctx)
 	if (eth->h_proto != 0)
 		goto out;
 
-	/* Expect no metadata */
-	if (ctx->data_meta != ctx->data)
+	if (meta_have + META_SIZE > eth)
+		goto out;
+
+	if (!check_metadata(meta_have))
 		goto out;
 
 	/* Packet write to trigger unclone in prologue */
@@ -348,40 +351,44 @@ int clone_data_meta_empty_on_data_write(struct __sk_buff *ctx)
 }
 
 /*
- * Check that skb->data_meta..skb->data is empty if prog writes to packet
- * _metadata_ using packet pointers. Applies only to cloned skbs.
+ * Check that, when operating on a cloned packet, skb->data_meta..skb->data is
+ * kept intact if prog writes to packet _metadata_ using packet pointers.
  */
 SEC("tc")
-int clone_data_meta_empty_on_meta_write(struct __sk_buff *ctx)
+int clone_data_meta_survives_meta_write(struct __sk_buff *ctx)
 {
+	__u8 *meta_have = ctx_ptr(ctx, data_meta);
 	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;
-	}
+	if (meta_have + META_SIZE > eth)
+		goto out;
+
+	if (!check_metadata(meta_have))
+		goto out;
+
+	/* Metadata write to trigger unclone in prologue */
+	*meta_have = 42;
+
+	test_pass = true;
 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.
+ * Check that, when operating on a cloned packet, metadata remains intact if
+ * prog creates a r/w slice to packet _payload_.
  */
 SEC("tc")
-int clone_dynptr_empty_on_data_slice_write(struct __sk_buff *ctx)
+int clone_meta_dynptr_survives_data_slice_write(struct __sk_buff *ctx)
 {
 	struct bpf_dynptr data, meta;
+	__u8 meta_have[META_SIZE];
 	struct ethhdr *eth;
 
 	bpf_dynptr_from_skb(ctx, 0, &data);
@@ -392,29 +399,26 @@ int clone_dynptr_empty_on_data_slice_write(struct __sk_buff *ctx)
 	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)
+	bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0);
+	if (!check_metadata(meta_have))
 		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.
+ * Check that, when operating on a cloned packet, metadata remains intact if
+ * prog creates an r/w slice to packet _metadata_.
  */
 SEC("tc")
-int clone_dynptr_empty_on_meta_slice_write(struct __sk_buff *ctx)
+int clone_meta_dynptr_survives_meta_slice_write(struct __sk_buff *ctx)
 {
 	struct bpf_dynptr data, meta;
 	const struct ethhdr *eth;
-	__u8 *md;
+	__u8 *meta_have;
 
 	bpf_dynptr_from_skb(ctx, 0, &data);
 	eth = bpf_dynptr_slice(&data, 0, NULL, sizeof(*eth));
@@ -424,31 +428,31 @@ int clone_dynptr_empty_on_meta_slice_write(struct __sk_buff *ctx)
 	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)
+	meta_have = bpf_dynptr_slice_rdwr(&meta, 0, NULL, META_SIZE);
+	if (!meta_have)
 		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;
+	if (!check_metadata(meta_have))
+		goto out;
 
 	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.
+ * Check that, when operating on a cloned packet, skb_meta dynptr is read-write
+ * before prog writes to packet _payload_ using dynptr_write helper and metadata
+ * remains intact before and after the write.
  */
 SEC("tc")
-int clone_dynptr_rdonly_before_data_dynptr_write(struct __sk_buff *ctx)
+int clone_meta_dynptr_rw_before_data_dynptr_write(struct __sk_buff *ctx)
 {
 	struct bpf_dynptr data, meta;
+	__u8 meta_have[META_SIZE];
 	const struct ethhdr *eth;
+	int err;
 
 	bpf_dynptr_from_skb(ctx, 0, &data);
 	eth = bpf_dynptr_slice(&data, 0, NULL, sizeof(*eth));
@@ -458,17 +462,20 @@ int clone_dynptr_rdonly_before_data_dynptr_write(struct __sk_buff *ctx)
 	if (eth->h_proto != 0)
 		goto out;
 
-	/* Expect read-only metadata before unclone */
+	/* Expect read-write metadata before unclone */
 	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
-	if (!bpf_dynptr_is_rdonly(&meta) || bpf_dynptr_size(&meta) != META_SIZE)
+	if (bpf_dynptr_is_rdonly(&meta))
+		goto out;
+
+	err = bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0);
+	if (err || !check_metadata(meta_have))
 		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)
+	err = bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0);
+	if (err || !check_metadata(meta_have))
 		goto out;
 
 	test_pass = true;
@@ -477,14 +484,17 @@ int clone_dynptr_rdonly_before_data_dynptr_write(struct __sk_buff *ctx)
 }
 
 /*
- * Check that skb_meta dynptr is read-only if prog writes to packet
- * metadata using dynptr_write helper. Applies only to cloned skbs.
+ * Check that, when operating on a cloned packet, skb_meta dynptr is read-write
+ * before prog writes to packet _metadata_ using dynptr_write helper and
+ * metadata remains intact before and after the write.
  */
 SEC("tc")
-int clone_dynptr_rdonly_before_meta_dynptr_write(struct __sk_buff *ctx)
+int clone_meta_dynptr_rw_before_meta_dynptr_write(struct __sk_buff *ctx)
 {
 	struct bpf_dynptr data, meta;
+	__u8 meta_have[META_SIZE];
 	const struct ethhdr *eth;
+	int err;
 
 	bpf_dynptr_from_skb(ctx, 0, &data);
 	eth = bpf_dynptr_slice(&data, 0, NULL, sizeof(*eth));
@@ -494,14 +504,20 @@ int clone_dynptr_rdonly_before_meta_dynptr_write(struct __sk_buff *ctx)
 	if (eth->h_proto != 0)
 		goto out;
 
-	/* Expect read-only metadata */
+	/* Expect read-write metadata before unclone */
 	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
-	if (!bpf_dynptr_is_rdonly(&meta) || bpf_dynptr_size(&meta) != META_SIZE)
+	if (bpf_dynptr_is_rdonly(&meta))
 		goto out;
 
-	/* Metadata write. Expect failure. */
-	bpf_dynptr_from_skb_meta(ctx, 0, &meta);
-	if (bpf_dynptr_write(&meta, 0, "x", 1, 0) != -EINVAL)
+	err = bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0);
+	if (err || !check_metadata(meta_have))
+		goto out;
+
+	/* Helper write to metadata will unclone the packet */
+	bpf_dynptr_write(&meta, 0, &meta_have[0], 1, 0);
+
+	err = bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0);
+	if (err || !check_metadata(meta_have))
 		goto out;
 
 	test_pass = true;