[PATCH bpf-next v2 09/15] selftests/bpf: Verify skb metadata in BPF instead of userspace
From: Jakub Sitnicki <jakub@cloudflare.com>
Date: 2025-10-19 12:45:57
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest, xdp (express data path) · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Shuah Khan, Linus Torvalds, David S. Miller, Jakub Kicinski, Jesper Dangaard Brouer, John Fastabend
Move metadata verification into the BPF TC programs. Previously, userspace read metadata from a map and verified it once at test end. Now TC programs compare metadata directly using __builtin_memcmp() and set a test_pass flag. This enables verification at multiple points during test execution rather than a single final check. Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com> --- .../bpf/prog_tests/xdp_context_test_run.c | 52 ++++--------- tools/testing/selftests/bpf/progs/test_xdp_meta.c | 88 +++++++++++----------- 2 files changed, 57 insertions(+), 83 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 178292d1251a..93a1fbe6a4fd 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@@ -171,33 +171,6 @@ static int write_test_packet(int tap_fd) 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(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) { LIBBPF_OPTS(bpf_tc_hook, tc_hook, .attach_point = BPF_TC_INGRESS);
@@ -270,11 +243,13 @@ void test_xdp_context_veth(void) if (!ASSERT_GE(tx_ifindex, 0, "if_nametoindex tx")) goto close; + skel->bss->test_pass = false; + ret = send_test_packet(tx_ifindex); if (!ASSERT_OK(ret, "send_test_packet")) goto close; - assert_test_result(skel->maps.test_result); + ASSERT_TRUE(skel->bss->test_pass, "test_pass"); close: close_netns(nstoken);
@@ -286,7 +261,7 @@ void test_xdp_context_veth(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) + 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);
@@ -295,8 +270,7 @@ static void test_tuntap(struct bpf_program *xdp_prog, int tap_ifindex; int ret; - if (!clear_test_result(result_map)) - return; + *test_pass = false; ns = netns_new(TAP_NETNS, true); if (!ASSERT_OK_PTR(ns, "create and open ns"))
@@ -340,7 +314,7 @@ static void test_tuntap(struct bpf_program *xdp_prog, if (!ASSERT_OK(ret, "write_test_packet")) goto close; - assert_test_result(result_map); + ASSERT_TRUE(*test_pass, "test_pass"); close: if (tap_fd >= 0)
@@ -431,37 +405,37 @@ void test_xdp_context_tuntap(void) test_tuntap(skel->progs.ing_xdp, skel->progs.ing_cls, NULL, /* tc prio 2 */ - skel->maps.test_result); + &skel->bss->test_pass); 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); + &skel->bss->test_pass); 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); + &skel->bss->test_pass); 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); + &skel->bss->test_pass); 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); + &skel->bss->test_pass); 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); + &skel->bss->test_pass); 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); + &skel->bss->test_pass); 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,
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_meta.c b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
index d79cb74b571e..11288b20f56c 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_meta.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_meta.c@@ -11,37 +11,36 @@ #define ctx_ptr(ctx, mem) (void *)(unsigned long)ctx->mem -/* Demonstrates how metadata can be passed from an XDP program to a TC program - * using bpf_xdp_adjust_meta. - * For the sake of testing the metadata support in drivers, the XDP program uses - * a fixed-size payload after the Ethernet header as metadata. The TC program - * copies the metadata it receives into a map so it can be checked from - * userspace. +/* Demonstrate passing metadata from XDP to TC using bpf_xdp_adjust_meta. + * + * The XDP program extracts a fixed-size payload following the Ethernet header + * and stores it as packet metadata to test the driver's metadata support. The + * TC program then verifies if the passed metadata is correct. */ -struct { - __uint(type, BPF_MAP_TYPE_ARRAY); - __uint(max_entries, 1); - __type(key, __u32); - __uint(value_size, META_SIZE); -} test_result SEC(".maps"); - bool test_pass; +static const __u8 meta_want[META_SIZE] = { + 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, + 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, + 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, + 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, +}; + SEC("tc") int ing_cls(struct __sk_buff *ctx) { - __u8 *data, *data_meta; - __u32 key = 0; - - data_meta = ctx_ptr(ctx, data_meta); - data = ctx_ptr(ctx, data); + __u8 *meta_have = ctx_ptr(ctx, data_meta); + __u8 *data = ctx_ptr(ctx, data); - if (data_meta + META_SIZE > data) - return TC_ACT_SHOT; + if (meta_have + META_SIZE > data) + goto out; - bpf_map_update_elem(&test_result, &key, data_meta, BPF_ANY); + if (__builtin_memcmp(meta_want, meta_have, META_SIZE)) + goto out; + test_pass = true; +out: return TC_ACT_SHOT; }
@@ -49,17 +48,17 @@ int ing_cls(struct __sk_buff *ctx) SEC("tc") int ing_cls_dynptr_read(struct __sk_buff *ctx) { + __u8 meta_have[META_SIZE]; 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); + bpf_dynptr_read(meta_have, META_SIZE, &meta, 0, 0); + + if (__builtin_memcmp(meta_want, meta_have, META_SIZE)) + goto out; + test_pass = true; +out: return TC_ACT_SHOT; }
@@ -86,20 +85,18 @@ 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; + __u8 *meta_have; bpf_dynptr_from_skb_meta(ctx, 0, &meta); - src = bpf_dynptr_slice(&meta, 0, NULL, META_SIZE); - if (!src) - return TC_ACT_SHOT; + meta_have = bpf_dynptr_slice(&meta, 0, NULL, META_SIZE); + if (!meta_have) + goto out; - __builtin_memcpy(dst, src, META_SIZE); + if (__builtin_memcmp(meta_want, meta_have, META_SIZE)) + goto out; + test_pass = true; +out: return TC_ACT_SHOT; }
@@ -129,14 +126,12 @@ int ing_cls_dynptr_slice_rdwr(struct __sk_buff *ctx) 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 meta_have[META_SIZE]; + struct bpf_dynptr meta; __u8 *dst, *src; - dst = bpf_map_lookup_elem(&test_result, &zero); - if (!dst) - return TC_ACT_SHOT; + dst = meta_have; /* 1. Regular read */ bpf_dynptr_from_skb_meta(ctx, 0, &meta);
@@ -155,9 +150,14 @@ int ing_cls_dynptr_offset_rd(struct __sk_buff *ctx) /* 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; + goto out; __builtin_memcpy(dst, src, chunk_len); + if (__builtin_memcmp(meta_want, meta_have, META_SIZE)) + goto out; + + test_pass = true; +out: return TC_ACT_SHOT; }
--
2.43.0