[PATCH net-next 04/14] selftests/bpf: Add tests for bpf_dynptr_from_skb_ext

Cover the bpf_dynptr_from_skb_ext() kfunc and the dynptr interface
to skb_ext with TC-to-TC tests on a tuntap device:

- write/read via bpf_dynptr_read and bpf_dynptr_write
- write/read via bpf_dynptr_slice and bpf_dynptr_slice_rdwr
- clone read via bpf_dynptr_clone
- error paths: no allocation without F_CREATE, invalid flags, read-only
  enforcement without F_CREATE
- double allocation: data from first alloc survives second skb_ext_add

Signed-off-by: Jakub Sitnicki <[email protected]>
---
 tools/testing/selftests/bpf/config                 |   1 +
 .../bpf/prog_tests/xdp_context_test_run.c          |  52 ++++++
 tools/testing/selftests/bpf/progs/test_xdp_meta.c  | 185 +++++++++++++++++++++
 3 files changed, 238 insertions(+)

diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
index ea7044f30adc..502f4504bdba 100644
--- a/tools/testing/selftests/bpf/config
+++ b/tools/testing/selftests/bpf/config
@@ -7,6 +7,7 @@ CONFIG_BPF_JIT=y
 CONFIG_BPF_KPROBE_OVERRIDE=y
 CONFIG_BPF_LIRC_MODE2=y
 CONFIG_BPF_LSM=y
+CONFIG_BPF_SKB_EXT=y
 CONFIG_BPF_STREAM_PARSER=y
 CONFIG_BPF_SYSCALL=y
 # CONFIG_BPF_UNPRIV_DEFAULT_OFF is not set
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 448807676176..fd340e5538a3 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
@@ -693,3 +693,55 @@ void test_xdp_context_lwt_encap(void)
 
 	test_xdp_meta__destroy(skel);
 }
+
+void test_skb_ext_basic(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_write_read"))
+		test_tuntap(NULL, /* xdp */
+			    skel->progs.tc_skb_ext_write,
+			    skel->progs.tc_skb_ext_read,
+			    &skel->bss->test_pass);
+	if (test__start_subtest("tc_write_clone_read"))
+		test_tuntap(NULL, /* xdp */
+			    skel->progs.tc_skb_ext_write,
+			    skel->progs.tc_skb_ext_clone_read,
+			    &skel->bss->test_pass);
+	if (test__start_subtest("tc_write_slice_read"))
+		test_tuntap(NULL, /* xdp */
+			    skel->progs.tc_skb_ext_write,
+			    skel->progs.tc_skb_ext_slice_read,
+			    &skel->bss->test_pass);
+	if (test__start_subtest("tc_slice_write_read"))
+		test_tuntap(NULL, /* xdp */
+			    skel->progs.tc_skb_ext_slice_write,
+			    skel->progs.tc_skb_ext_read,
+			    &skel->bss->test_pass);
+	if (test__start_subtest("tc_no_alloc"))
+		test_tuntap(NULL, /* xdp */
+			    skel->progs.tc_skb_ext_no_alloc,
+			    NULL, /* tc prio 2 */
+			    &skel->bss->test_pass);
+	if (test__start_subtest("tc_invalid_flags"))
+		test_tuntap(NULL, /* xdp */
+			    skel->progs.tc_skb_ext_invalid_flags,
+			    NULL, /* tc prio 2 */
+			    &skel->bss->test_pass);
+	if (test__start_subtest("tc_rdonly"))
+		test_tuntap(NULL, /* xdp */
+			    skel->progs.tc_skb_ext_rdonly,
+			    NULL, /* tc prio 2 */
+			    &skel->bss->test_pass);
+	if (test__start_subtest("tc_double_alloc"))
+		test_tuntap(NULL, /* xdp */
+			    skel->progs.tc_skb_ext_double_alloc,
+			    NULL, /* tc prio 2 */
+			    &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 08b03be0b891..43840ee32d35 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_meta.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
@@ -6,6 +6,7 @@
 #include <errno.h>
 
 #include "bpf_kfuncs.h"
+#include "bpf_misc.h"
 #include "bpf_tracing_net.h"
 
 #define META_SIZE 32
@@ -689,4 +690,188 @@ int helper_skb_change_proto(struct __sk_buff *ctx)
 	return TC_ACT_SHOT;
 }
 
+/* Write to skb_ext using bpf_dynptr_write helper */
+SEC("tc")
+int tc_skb_ext_write(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr meta;
+
+	if (!is_test_packet_tc(ctx))
+		return TC_ACT_SHOT;
+	if (bpf_dynptr_from_skb_ext(ctx, 0, BPF_SKB_EXT_F_CREATE, &meta))
+		return TC_ACT_SHOT;
+	if (bpf_dynptr_write(&meta, 0, (void *)meta_want, ARRAY_SIZE(meta_want), 0))
+		return TC_ACT_SHOT;
+
+	return TC_ACT_UNSPEC;
+}
+
+/* Read from skb-ext metadata using bpf_dynptr_read helper */
+SEC("tc")
+int tc_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 TC_ACT_SHOT;
+	if (bpf_dynptr_read(meta_have, ARRAY_SIZE(meta_have), &meta, 0, 0))
+		return TC_ACT_SHOT;
+	if (!check_metadata(meta_have))
+		return TC_ACT_SHOT;
+
+	test_pass = true;
+	return TC_ACT_UNSPEC;
+}
+
+/* Read from a cloned skb_ext dynptr */
+SEC("tc")
+int tc_skb_ext_clone_read(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr meta, clone;
+	__u8 meta_have[META_SIZE];
+
+	if (bpf_dynptr_from_skb_ext(ctx, 0, 0, &meta))
+		return TC_ACT_SHOT;
+	if (bpf_dynptr_clone(&meta, &clone))
+		return TC_ACT_SHOT;
+	if (bpf_dynptr_read(meta_have, ARRAY_SIZE(meta_have), &clone, 0, 0))
+		return TC_ACT_SHOT;
+	if (!check_metadata(meta_have))
+		return TC_ACT_SHOT;
+
+	test_pass = true;
+	return TC_ACT_UNSPEC;
+}
+
+/* Read from skb_ext using bpf_dynptr_slice */
+SEC("tc")
+int tc_skb_ext_slice_read(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr meta;
+	__u8 *meta_have;
+
+	if (bpf_dynptr_from_skb_ext(ctx, 0, 0, &meta))
+		return TC_ACT_SHOT;
+	meta_have = bpf_dynptr_slice(&meta, 0, NULL, META_SIZE);
+	if (!meta_have)
+		return TC_ACT_SHOT;
+	if (!check_metadata(meta_have))
+		return TC_ACT_SHOT;
+
+	test_pass = true;
+	return TC_ACT_UNSPEC;
+}
+
+/* Write to skb_ext using bpf_dynptr_slice_rdwr */
+SEC("tc")
+int tc_skb_ext_slice_write(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr meta;
+	__u8 *dst;
+
+	if (!is_test_packet_tc(ctx))
+		return TC_ACT_SHOT;
+	if (bpf_dynptr_from_skb_ext(ctx, 0, BPF_SKB_EXT_F_CREATE, &meta))
+		return TC_ACT_SHOT;
+	dst = bpf_dynptr_slice_rdwr(&meta, 0, NULL, META_SIZE);
+	if (!dst)
+		return TC_ACT_SHOT;
+	__builtin_memcpy(dst, meta_want, META_SIZE);
+
+	return TC_ACT_UNSPEC;
+}
+
+/* Opening skb_ext without F_CREATE on a fresh skb should fail */
+SEC("tc")
+int tc_skb_ext_no_alloc(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr meta;
+
+	if (!is_test_packet_tc(ctx))
+		return TC_ACT_SHOT;
+	if (bpf_dynptr_from_skb_ext(ctx, 0, 0, &meta) != -ENOENT)
+		return TC_ACT_SHOT;
+
+	test_pass = true;
+	return TC_ACT_UNSPEC;
+}
+
+/* Invalid flags are rejected */
+SEC("tc")
+int tc_skb_ext_invalid_flags(struct __sk_buff *ctx)
+{
+	struct bpf_dynptr meta;
+
+	if (!is_test_packet_tc(ctx))
+		return TC_ACT_SHOT;
+	if (bpf_dynptr_from_skb_ext(ctx, 0, ~0ULL, &meta) != -EINVAL)
+		return TC_ACT_SHOT;
+
+	test_pass = true;
+	return TC_ACT_UNSPEC;
+}
+
+/* Without F_CREATE the dynptr is read-only */
+SEC("tc")
+int tc_skb_ext_rdonly(struct __sk_buff *ctx)
+{
+	__u8 meta_have[META_SIZE];
+	struct bpf_dynptr meta;
+
+	if (!is_test_packet_tc(ctx))
+		return TC_ACT_SHOT;
+
+	/* Create and populate the ext */
+	if (bpf_dynptr_from_skb_ext(ctx, 0, BPF_SKB_EXT_F_CREATE, &meta))
+		return TC_ACT_SHOT;
+	if (bpf_dynptr_write(&meta, 0, (void *)meta_want, META_SIZE, 0))
+		return TC_ACT_SHOT;
+
+	/* Reopen without F_CREATE -- should be read-only */
+	if (bpf_dynptr_from_skb_ext(ctx, 0, 0, &meta))
+		return TC_ACT_SHOT;
+
+	/* Verify read-only: writes must fail, reads must work */
+	if (!bpf_dynptr_is_rdonly(&meta))
+		return TC_ACT_SHOT;
+	if (!bpf_dynptr_write(&meta, 0, (void *)meta_want, META_SIZE, 0))
+		return TC_ACT_SHOT;
+	if (bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0))
+		return TC_ACT_SHOT;
+	if (!check_metadata(meta_have))
+		return TC_ACT_SHOT;
+
+	test_pass = true;
+	return TC_ACT_UNSPEC;
+}
+
+/* Double alloc: data from first alloc survives second skb_ext_add */
+SEC("tc")
+int tc_skb_ext_double_alloc(struct __sk_buff *ctx)
+{
+	__u8 meta_have[META_SIZE];
+	struct bpf_dynptr meta;
+
+	if (!is_test_packet_tc(ctx))
+		return TC_ACT_SHOT;
+
+	/* First alloc + write */
+	if (bpf_dynptr_from_skb_ext(ctx, 0, BPF_SKB_EXT_F_CREATE, &meta))
+		return TC_ACT_SHOT;
+	if (bpf_dynptr_write(&meta, 0, (void *)meta_want, META_SIZE, 0))
+		return TC_ACT_SHOT;
+
+	/* Second alloc -- skb_ext_add returns existing ext */
+	if (bpf_dynptr_from_skb_ext(ctx, 0, BPF_SKB_EXT_F_CREATE, &meta))
+		return TC_ACT_SHOT;
+	if (bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0))
+		return TC_ACT_SHOT;
+	if (!check_metadata(meta_have))
+		return TC_ACT_SHOT;
+
+	test_pass = true;
+	return TC_ACT_UNSPEC;
+}
+
 char _license[] SEC("license") = "GPL";

-- 
2.43.0