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Message-Id: <20251026-skb-meta-rx-path-v3-12-37cceebb95d3@cloudflare.com>
Date: Sun, 26 Oct 2025 15:18:32 +0100
From: Jakub Sitnicki <jakub@...udflare.com>
To: bpf@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Daniel Borkmann <daniel@...earbox.net>,
John Fastabend <john.fastabend@...il.com>,
Stanislav Fomichev <sdf@...ichev.me>, Alexei Starovoitov <ast@...nel.org>,
Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman <eddyz87@...il.com>,
Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>,
KP Singh <kpsingh@...nel.org>, Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>, Arthur Fabre <arthur@...hurfabre.com>,
Jesper Dangaard Brouer <hawk@...nel.org>, netdev@...r.kernel.org,
kernel-team@...udflare.com
Subject: [PATCH bpf-next v3 12/16] 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 <jakub@...udflare.com>
---
.../bpf/prog_tests/xdp_context_test_run.c | 24 ++---
tools/testing/selftests/bpf/progs/test_xdp_meta.c | 118 ++++++++++++---------
2 files changed, 79 insertions(+), 63 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 db3027564261..a129c3057202 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
@@ -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);
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_meta.c b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
index 74d7e2aab2ef..ee89e1124cd8 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_meta.c
+++ b/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 */
@@ -348,14 +351,14 @@ 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;
@@ -363,25 +366,29 @@ int clone_data_meta_empty_on_meta_write(struct __sk_buff *ctx)
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));
@@ -424,16 +428,13 @@ 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:
@@ -441,14 +442,17 @@ int clone_dynptr_empty_on_meta_slice_write(struct __sk_buff *ctx)
}
/*
- * 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;
--
2.43.0
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