[bpf-next,3/3] selftests/bpf: add tests for bpf_dynptr_copy

Commit Message

Mykyta Yatsenko Feb. 18, 2025, 7 p.m. UTC

From: Mykyta Yatsenko <[e-mail]>

Add XDP setup type for dynptr tests, enabling testing for
non-contiguous buffer.
Add 2 tests:
 - test_dynptr_copy - verify correctness for the fast (contiguous
 buffer) code path.
 - test_dynptr_copy_xdp - verifies code paths that handle
 non-contiguous buffer.

Signed-off-by: Mykyta Yatsenko <[e-mail]>
---
 tools/testing/selftests/bpf/bpf_kfuncs.h      |  8 ++
 .../testing/selftests/bpf/prog_tests/dynptr.c | 25 ++++++
 .../selftests/bpf/progs/dynptr_success.c      | 77 +++++++++++++++++++
 3 files changed, 110 insertions(+)

Comments

Eduard Zingerman Feb. 19, 2025, 1:04 a.m. UTC | #1

On Tue, 2025-02-18 at 19:00 +0000, Mykyta Yatsenko wrote:
> From: Mykyta Yatsenko <[e-mail]>
> 
> Add XDP setup type for dynptr tests, enabling testing for
> non-contiguous buffer.
> Add 2 tests:
>  - test_dynptr_copy - verify correctness for the fast (contiguous
>  buffer) code path.
>  - test_dynptr_copy_xdp - verifies code paths that handle
>  non-contiguous buffer.
> 
> Signed-off-by: Mykyta Yatsenko <[e-mail]>
> ---

Acked-by: Eduard Zingerman <[e-mail]>

[...]

> +SEC("xdp")
> +int test_dynptr_copy_xdp(struct xdp_md *xdp)
> +{

Nit: it would be helpful if there were a few comments
     explaining which special cases are tested at each step.

> +	struct bpf_dynptr ptr_buf, ptr_xdp;
> +	char *data = "qwertyuiopasdfghjkl;";
> +	char buf[32] = {'\0'};
> +	__u32 len = strlen(data);
> +	int i, chunks = 200;
> +
> +	bpf_dynptr_from_xdp(xdp, 0, &ptr_xdp);
> +	bpf_ringbuf_reserve_dynptr(&ringbuf, len * chunks, 0, &ptr_buf);
> +
> +	bpf_for(i, 0, chunks) {
> +		err =  err ?: bpf_dynptr_write(&ptr_buf, i * len, data, len, 0);
> +	}
> +
> +	err = err ?: bpf_dynptr_copy(&ptr_xdp, 0, &ptr_buf, 0, len * chunks);
> +
> +	bpf_for(i, 0, chunks) {
> +		memset(buf, 0, sizeof(buf));
> +		err = err ?: bpf_dynptr_read(&buf, len, &ptr_xdp, i * len, 0);
> +		err = err ?: memcmp(data, buf, len);
> +	}
> +
> +	memset(buf, 0, sizeof(buf));
> +	bpf_for(i, 0, chunks) {
> +		err = err ?: bpf_dynptr_write(&ptr_buf, i * len, buf, len, 0);
> +	}
> +
> +	err = err ?: bpf_dynptr_copy(&ptr_buf, 0, &ptr_xdp, 0, len * chunks);
> +
> +	bpf_for(i, 0, chunks) {
> +		memset(buf, 0, sizeof(buf));
> +		err = err ?: bpf_dynptr_read(&buf, len, &ptr_buf, i * len, 0);
> +		err = err ?: memcmp(data, buf, len);
> +	}
> +
> +	bpf_ringbuf_discard_dynptr(&ptr_buf, 0);
> +
> +	err = err ?: bpf_dynptr_copy(&ptr_xdp, 2, &ptr_xdp, len, len * (chunks - 1));
> +
> +	bpf_for(i, 0, chunks - 1) {
> +		memset(buf, 0, sizeof(buf));
> +		err = err ?: bpf_dynptr_read(&buf, len, &ptr_xdp, 2 + i * len, 0);
> +		err = err ?: memcmp(data, buf, len);
> +	}
> +
> +	err = err ?: (bpf_dynptr_copy(&ptr_xdp, 2000, &ptr_xdp, 0, len * chunks) == -E2BIG ? 0 : 1);
> +
> +	return XDP_DROP;
> +}

Andrii Nakryiko Feb. 21, 2025, 12:52 a.m. UTC | #2

On Tue, Feb 18, 2025 at 11:01 AM Mykyta Yatsenko
<[e-mail]> wrote:
>
> From: Mykyta Yatsenko <[e-mail]>
>
> Add XDP setup type for dynptr tests, enabling testing for
> non-contiguous buffer.
> Add 2 tests:
>  - test_dynptr_copy - verify correctness for the fast (contiguous
>  buffer) code path.
>  - test_dynptr_copy_xdp - verifies code paths that handle
>  non-contiguous buffer.
>
> Signed-off-by: Mykyta Yatsenko <[e-mail]>
> ---
>  tools/testing/selftests/bpf/bpf_kfuncs.h      |  8 ++
>  .../testing/selftests/bpf/prog_tests/dynptr.c | 25 ++++++
>  .../selftests/bpf/progs/dynptr_success.c      | 77 +++++++++++++++++++
>  3 files changed, 110 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/bpf_kfuncs.h b/tools/testing/selftests/bpf/bpf_kfuncs.h
> index 8215c9b3115e..e9c193036c82 100644
> --- a/tools/testing/selftests/bpf/bpf_kfuncs.h
> +++ b/tools/testing/selftests/bpf/bpf_kfuncs.h
> @@ -43,6 +43,14 @@ extern bool bpf_dynptr_is_rdonly(const struct bpf_dynptr *ptr) __ksym __weak;
>  extern __u32 bpf_dynptr_size(const struct bpf_dynptr *ptr) __ksym __weak;
>  extern int bpf_dynptr_clone(const struct bpf_dynptr *ptr, struct bpf_dynptr *clone__init) __ksym __weak;
>
> +/* Description
> + *  Copy data from one dynptr to another
> + * Returns
> + *  Error code
> + */
> +extern int bpf_dynptr_copy(struct bpf_dynptr *dst, __u32 dst_off,
> +                          struct bpf_dynptr *src, __u32 src_off, __u32 size) __ksym __weak;
> +

Do we *need* this? Doesn't all this come from vmlinux.h nowadays?

>  /* Description
>   *  Modify the address of a AF_UNIX sockaddr.
>   * Returns
> diff --git a/tools/testing/selftests/bpf/prog_tests/dynptr.c b/tools/testing/selftests/bpf/prog_tests/dynptr.c
> index b614a5272dfd..247618958155 100644
> --- a/tools/testing/selftests/bpf/prog_tests/dynptr.c
> +++ b/tools/testing/selftests/bpf/prog_tests/dynptr.c
> @@ -10,6 +10,7 @@ enum test_setup_type {
>         SETUP_SYSCALL_SLEEP,
>         SETUP_SKB_PROG,
>         SETUP_SKB_PROG_TP,
> +       SETUP_XDP_PROG,
>  };
>
>  static struct {
> @@ -18,6 +19,8 @@ static struct {
>  } success_tests[] = {
>         {"test_read_write", SETUP_SYSCALL_SLEEP},
>         {"test_dynptr_data", SETUP_SYSCALL_SLEEP},
> +       {"test_dynptr_copy", SETUP_SYSCALL_SLEEP},
> +       {"test_dynptr_copy_xdp", SETUP_XDP_PROG},
>         {"test_ringbuf", SETUP_SYSCALL_SLEEP},
>         {"test_skb_readonly", SETUP_SKB_PROG},
>         {"test_dynptr_skb_data", SETUP_SKB_PROG},
> @@ -120,6 +123,28 @@ static void verify_success(const char *prog_name, enum test_setup_type setup_typ
>
>                 break;
>         }
> +       case SETUP_XDP_PROG:
> +       {
> +               char data[5000];
> +               int err, prog_fd;
> +

no empty line here, opts is a variable

> +               LIBBPF_OPTS(bpf_test_run_opts, opts,
> +                           .data_in = &data,
> +                           .data_size_in = sizeof(data),
> +                           .repeat = 1,
> +               );
> +
> +               prog_fd = bpf_program__fd(prog);
> +               if (!ASSERT_GE(prog_fd, 0, "prog_fd"))
> +                       goto cleanup;


we shouldn't check this, if program loaded successfully this will
always be true (and yeah, I know that existing code does that, we
should remove or at least not duplicate this)

> +
> +               err = bpf_prog_test_run_opts(prog_fd, &opts);
> +
> +               if (!ASSERT_OK(err, "test_run"))
> +                       goto cleanup;
> +
> +               break;
> +       }
>         }
>
>         ASSERT_EQ(skel->bss->err, 0, "err");
> diff --git a/tools/testing/selftests/bpf/progs/dynptr_success.c b/tools/testing/selftests/bpf/progs/dynptr_success.c
> index bfcc85686cf0..8a6b35418e39 100644
> --- a/tools/testing/selftests/bpf/progs/dynptr_success.c
> +++ b/tools/testing/selftests/bpf/progs/dynptr_success.c
> @@ -567,3 +567,80 @@ int BPF_PROG(test_dynptr_skb_tp_btf, void *skb, void *location)
>
>         return 1;
>  }
> +
> +SEC("?tp/syscalls/sys_enter_nanosleep")
> +int test_dynptr_copy(void *ctx)
> +{
> +       char *data = "hello there, world!!";
> +       char buf[32] = {'\0'};
> +       __u32 sz = strlen(data);

this is fragile, this is not guaranteed to work (only if compiler just
substituted a constant value). maybe just use data[] = "hello
there..." and use sizeof(data) then?

> +       struct bpf_dynptr src, dst;
> +
> +       bpf_ringbuf_reserve_dynptr(&ringbuf, sz, 0, &src);
> +       bpf_ringbuf_reserve_dynptr(&ringbuf, sz, 0, &dst);
> +
> +       err = bpf_dynptr_write(&src, 0, data, sz, 0);
> +       err = err ?: bpf_dynptr_copy(&dst, 0, &src, 0, sz);
> +       err = err ?: bpf_dynptr_read(buf, sz, &dst, 0, 0);
> +       err = err ?: __builtin_memcmp(data, buf, sz);
> +
> +       err = err ?: bpf_dynptr_copy(&dst, 3, &src, 5, sz - 5);
> +       err = err ?: bpf_dynptr_read(buf, sz - 5, &dst, 3, 0);
> +       err = err ?: __builtin_memcmp(data + 5, buf, sz - 5);
> +
> +       bpf_ringbuf_discard_dynptr(&src, 0);
> +       bpf_ringbuf_discard_dynptr(&dst, 0);
> +       return 0;
> +}
> +
> +SEC("xdp")
> +int test_dynptr_copy_xdp(struct xdp_md *xdp)
> +{
> +       struct bpf_dynptr ptr_buf, ptr_xdp;
> +       char *data = "qwertyuiopasdfghjkl;";
> +       char buf[32] = {'\0'};
> +       __u32 len = strlen(data);

ditto

> +       int i, chunks = 200;
> +
> +       bpf_dynptr_from_xdp(xdp, 0, &ptr_xdp);
> +       bpf_ringbuf_reserve_dynptr(&ringbuf, len * chunks, 0, &ptr_buf);
> +
> +       bpf_for(i, 0, chunks) {
> +               err =  err ?: bpf_dynptr_write(&ptr_buf, i * len, data, len, 0);
> +       }
> +
> +       err = err ?: bpf_dynptr_copy(&ptr_xdp, 0, &ptr_buf, 0, len * chunks);
> +
> +       bpf_for(i, 0, chunks) {
> +               memset(buf, 0, sizeof(buf));

__builtin_memset(), memset() works only because compiler optimizes it
to built-in, but let's not rely on that

> +               err = err ?: bpf_dynptr_read(&buf, len, &ptr_xdp, i * len, 0);
> +               err = err ?: memcmp(data, buf, len);

__builtin_memcmp() and all the other cases below, please

> +       }
> +
> +       memset(buf, 0, sizeof(buf));
> +       bpf_for(i, 0, chunks) {
> +               err = err ?: bpf_dynptr_write(&ptr_buf, i * len, buf, len, 0);
> +       }
> +
> +       err = err ?: bpf_dynptr_copy(&ptr_buf, 0, &ptr_xdp, 0, len * chunks);
> +
> +       bpf_for(i, 0, chunks) {
> +               memset(buf, 0, sizeof(buf));
> +               err = err ?: bpf_dynptr_read(&buf, len, &ptr_buf, i * len, 0);
> +               err = err ?: memcmp(data, buf, len);
> +       }
> +
> +       bpf_ringbuf_discard_dynptr(&ptr_buf, 0);
> +
> +       err = err ?: bpf_dynptr_copy(&ptr_xdp, 2, &ptr_xdp, len, len * (chunks - 1));
> +
> +       bpf_for(i, 0, chunks - 1) {
> +               memset(buf, 0, sizeof(buf));
> +               err = err ?: bpf_dynptr_read(&buf, len, &ptr_xdp, 2 + i * len, 0);
> +               err = err ?: memcmp(data, buf, len);
> +       }
> +
> +       err = err ?: (bpf_dynptr_copy(&ptr_xdp, 2000, &ptr_xdp, 0, len * chunks) == -E2BIG ? 0 : 1);

overdoing it a bit with the whole `err ?: ` pattern, IMO


BTW, more questions to networking folks (maybe Martin knows). Is there
a way to setup SKB or XDP packet with a non-linear region for testing?

> +
> +       return XDP_DROP;
> +}
> --
> 2.48.1
>

Eduard Zingerman Feb. 21, 2025, 12:56 a.m. UTC | #3

On Thu, 2025-02-20 at 16:52 -0800, Andrii Nakryiko wrote:
> On Tue, Feb 18, 2025 at 11:01 AM Mykyta Yatsenko
> <[e-mail]> wrote:
> > 
> > From: Mykyta Yatsenko <[e-mail]>
> > 
> > Add XDP setup type for dynptr tests, enabling testing for
> > non-contiguous buffer.
> > Add 2 tests:
> >  - test_dynptr_copy - verify correctness for the fast (contiguous
> >  buffer) code path.
> >  - test_dynptr_copy_xdp - verifies code paths that handle
> >  non-contiguous buffer.
> > 
> > Signed-off-by: Mykyta Yatsenko <[e-mail]>
> > ---
> >  tools/testing/selftests/bpf/bpf_kfuncs.h      |  8 ++
> >  .../testing/selftests/bpf/prog_tests/dynptr.c | 25 ++++++
> >  .../selftests/bpf/progs/dynptr_success.c      | 77 +++++++++++++++++++
> >  3 files changed, 110 insertions(+)
> > 
> > diff --git a/tools/testing/selftests/bpf/bpf_kfuncs.h b/tools/testing/selftests/bpf/bpf_kfuncs.h
> > index 8215c9b3115e..e9c193036c82 100644
> > --- a/tools/testing/selftests/bpf/bpf_kfuncs.h
> > +++ b/tools/testing/selftests/bpf/bpf_kfuncs.h
> > @@ -43,6 +43,14 @@ extern bool bpf_dynptr_is_rdonly(const struct bpf_dynptr *ptr) __ksym __weak;
> >  extern __u32 bpf_dynptr_size(const struct bpf_dynptr *ptr) __ksym __weak;
> >  extern int bpf_dynptr_clone(const struct bpf_dynptr *ptr, struct bpf_dynptr *clone__init) __ksym __weak;
> > 
> > +/* Description
> > + *  Copy data from one dynptr to another
> > + * Returns
> > + *  Error code
> > + */
> > +extern int bpf_dynptr_copy(struct bpf_dynptr *dst, __u32 dst_off,
> > +                          struct bpf_dynptr *src, __u32 src_off, __u32 size) __ksym __weak;
> > +
> 
> Do we *need* this? Doesn't all this come from vmlinux.h nowadays?

It does come from vmlinux.h, but this test does not include vmlinux.h
(and compiles a bit faster because of that).

[...]

Andrii Nakryiko Feb. 21, 2025, 1:03 a.m. UTC | #4

On Thu, Feb 20, 2025 at 4:56 PM Eduard Zingerman <[e-mail]> wrote:
>
> On Thu, 2025-02-20 at 16:52 -0800, Andrii Nakryiko wrote:
> > On Tue, Feb 18, 2025 at 11:01 AM Mykyta Yatsenko
> > <[e-mail]> wrote:
> > >
> > > From: Mykyta Yatsenko <[e-mail]>
> > >
> > > Add XDP setup type for dynptr tests, enabling testing for
> > > non-contiguous buffer.
> > > Add 2 tests:
> > >  - test_dynptr_copy - verify correctness for the fast (contiguous
> > >  buffer) code path.
> > >  - test_dynptr_copy_xdp - verifies code paths that handle
> > >  non-contiguous buffer.
> > >
> > > Signed-off-by: Mykyta Yatsenko <[e-mail]>
> > > ---
> > >  tools/testing/selftests/bpf/bpf_kfuncs.h      |  8 ++
> > >  .../testing/selftests/bpf/prog_tests/dynptr.c | 25 ++++++
> > >  .../selftests/bpf/progs/dynptr_success.c      | 77 +++++++++++++++++++
> > >  3 files changed, 110 insertions(+)
> > >
> > > diff --git a/tools/testing/selftests/bpf/bpf_kfuncs.h b/tools/testing/selftests/bpf/bpf_kfuncs.h
> > > index 8215c9b3115e..e9c193036c82 100644
> > > --- a/tools/testing/selftests/bpf/bpf_kfuncs.h
> > > +++ b/tools/testing/selftests/bpf/bpf_kfuncs.h
> > > @@ -43,6 +43,14 @@ extern bool bpf_dynptr_is_rdonly(const struct bpf_dynptr *ptr) __ksym __weak;
> > >  extern __u32 bpf_dynptr_size(const struct bpf_dynptr *ptr) __ksym __weak;
> > >  extern int bpf_dynptr_clone(const struct bpf_dynptr *ptr, struct bpf_dynptr *clone__init) __ksym __weak;
> > >
> > > +/* Description
> > > + *  Copy data from one dynptr to another
> > > + * Returns
> > > + *  Error code
> > > + */
> > > +extern int bpf_dynptr_copy(struct bpf_dynptr *dst, __u32 dst_off,
> > > +                          struct bpf_dynptr *src, __u32 src_off, __u32 size) __ksym __weak;
> > > +
> >
> > Do we *need* this? Doesn't all this come from vmlinux.h nowadays?
>
> It does come from vmlinux.h, but this test does not include vmlinux.h
> (and compiles a bit faster because of that).

let's switch to vmlinux.h then instead of manually adding kfunc declarations?

>
> [...]
>

Patch

diff --git a/tools/testing/selftests/bpf/bpf_kfuncs.h b/tools/testing/selftests/bpf/bpf_kfuncs.h
index 8215c9b3115e..e9c193036c82 100644
--- a/tools/testing/selftests/bpf/bpf_kfuncs.h
+++ b/tools/testing/selftests/bpf/bpf_kfuncs.h
@@ -43,6 +43,14 @@  extern bool bpf_dynptr_is_rdonly(const struct bpf_dynptr *ptr) __ksym __weak;
 extern __u32 bpf_dynptr_size(const struct bpf_dynptr *ptr) __ksym __weak;
 extern int bpf_dynptr_clone(const struct bpf_dynptr *ptr, struct bpf_dynptr *clone__init) __ksym __weak;
 
+/* Description
+ *  Copy data from one dynptr to another
+ * Returns
+ *  Error code
+ */
+extern int bpf_dynptr_copy(struct bpf_dynptr *dst, __u32 dst_off,
+			   struct bpf_dynptr *src, __u32 src_off, __u32 size) __ksym __weak;
+
 /* Description
  *  Modify the address of a AF_UNIX sockaddr.
  * Returns
diff --git a/tools/testing/selftests/bpf/prog_tests/dynptr.c b/tools/testing/selftests/bpf/prog_tests/dynptr.c
index b614a5272dfd..247618958155 100644
--- a/tools/testing/selftests/bpf/prog_tests/dynptr.c
+++ b/tools/testing/selftests/bpf/prog_tests/dynptr.c
@@ -10,6 +10,7 @@  enum test_setup_type {
 	SETUP_SYSCALL_SLEEP,
 	SETUP_SKB_PROG,
 	SETUP_SKB_PROG_TP,
+	SETUP_XDP_PROG,
 };
 
 static struct {
@@ -18,6 +19,8 @@  static struct {
 } success_tests[] = {
 	{"test_read_write", SETUP_SYSCALL_SLEEP},
 	{"test_dynptr_data", SETUP_SYSCALL_SLEEP},
+	{"test_dynptr_copy", SETUP_SYSCALL_SLEEP},
+	{"test_dynptr_copy_xdp", SETUP_XDP_PROG},
 	{"test_ringbuf", SETUP_SYSCALL_SLEEP},
 	{"test_skb_readonly", SETUP_SKB_PROG},
 	{"test_dynptr_skb_data", SETUP_SKB_PROG},
@@ -120,6 +123,28 @@  static void verify_success(const char *prog_name, enum test_setup_type setup_typ
 
 		break;
 	}
+	case SETUP_XDP_PROG:
+	{
+		char data[5000];
+		int err, prog_fd;
+
+		LIBBPF_OPTS(bpf_test_run_opts, opts,
+			    .data_in = &data,
+			    .data_size_in = sizeof(data),
+			    .repeat = 1,
+		);
+
+		prog_fd = bpf_program__fd(prog);
+		if (!ASSERT_GE(prog_fd, 0, "prog_fd"))
+			goto cleanup;
+
+		err = bpf_prog_test_run_opts(prog_fd, &opts);
+
+		if (!ASSERT_OK(err, "test_run"))
+			goto cleanup;
+
+		break;
+	}
 	}
 
 	ASSERT_EQ(skel->bss->err, 0, "err");
diff --git a/tools/testing/selftests/bpf/progs/dynptr_success.c b/tools/testing/selftests/bpf/progs/dynptr_success.c
index bfcc85686cf0..8a6b35418e39 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_success.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_success.c
@@ -567,3 +567,80 @@  int BPF_PROG(test_dynptr_skb_tp_btf, void *skb, void *location)
 
 	return 1;
 }
+
+SEC("?tp/syscalls/sys_enter_nanosleep")
+int test_dynptr_copy(void *ctx)
+{
+	char *data = "hello there, world!!";
+	char buf[32] = {'\0'};
+	__u32 sz = strlen(data);
+	struct bpf_dynptr src, dst;
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, sz, 0, &src);
+	bpf_ringbuf_reserve_dynptr(&ringbuf, sz, 0, &dst);
+
+	err = bpf_dynptr_write(&src, 0, data, sz, 0);
+	err = err ?: bpf_dynptr_copy(&dst, 0, &src, 0, sz);
+	err = err ?: bpf_dynptr_read(buf, sz, &dst, 0, 0);
+	err = err ?: __builtin_memcmp(data, buf, sz);
+
+	err = err ?: bpf_dynptr_copy(&dst, 3, &src, 5, sz - 5);
+	err = err ?: bpf_dynptr_read(buf, sz - 5, &dst, 3, 0);
+	err = err ?: __builtin_memcmp(data + 5, buf, sz - 5);
+
+	bpf_ringbuf_discard_dynptr(&src, 0);
+	bpf_ringbuf_discard_dynptr(&dst, 0);
+	return 0;
+}
+
+SEC("xdp")
+int test_dynptr_copy_xdp(struct xdp_md *xdp)
+{
+	struct bpf_dynptr ptr_buf, ptr_xdp;
+	char *data = "qwertyuiopasdfghjkl;";
+	char buf[32] = {'\0'};
+	__u32 len = strlen(data);
+	int i, chunks = 200;
+
+	bpf_dynptr_from_xdp(xdp, 0, &ptr_xdp);
+	bpf_ringbuf_reserve_dynptr(&ringbuf, len * chunks, 0, &ptr_buf);
+
+	bpf_for(i, 0, chunks) {
+		err =  err ?: bpf_dynptr_write(&ptr_buf, i * len, data, len, 0);
+	}
+
+	err = err ?: bpf_dynptr_copy(&ptr_xdp, 0, &ptr_buf, 0, len * chunks);
+
+	bpf_for(i, 0, chunks) {
+		memset(buf, 0, sizeof(buf));
+		err = err ?: bpf_dynptr_read(&buf, len, &ptr_xdp, i * len, 0);
+		err = err ?: memcmp(data, buf, len);
+	}
+
+	memset(buf, 0, sizeof(buf));
+	bpf_for(i, 0, chunks) {
+		err = err ?: bpf_dynptr_write(&ptr_buf, i * len, buf, len, 0);
+	}
+
+	err = err ?: bpf_dynptr_copy(&ptr_buf, 0, &ptr_xdp, 0, len * chunks);
+
+	bpf_for(i, 0, chunks) {
+		memset(buf, 0, sizeof(buf));
+		err = err ?: bpf_dynptr_read(&buf, len, &ptr_buf, i * len, 0);
+		err = err ?: memcmp(data, buf, len);
+	}
+
+	bpf_ringbuf_discard_dynptr(&ptr_buf, 0);
+
+	err = err ?: bpf_dynptr_copy(&ptr_xdp, 2, &ptr_xdp, len, len * (chunks - 1));
+
+	bpf_for(i, 0, chunks - 1) {
+		memset(buf, 0, sizeof(buf));
+		err = err ?: bpf_dynptr_read(&buf, len, &ptr_xdp, 2 + i * len, 0);
+		err = err ?: memcmp(data, buf, len);
+	}
+
+	err = err ?: (bpf_dynptr_copy(&ptr_xdp, 2000, &ptr_xdp, 0, len * chunks) == -E2BIG ? 0 : 1);
+
+	return XDP_DROP;
+}