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selftests/bpf: Cover write access to skb metadata via dynptr

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Add tests what exercise writes to skb metadata in two ways:
1. indirectly, using bpf_dynptr_write helper,
2. directly, using a read-write dynptr slice.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Jesse Brandeburg <jbrandeburg@cloudflare.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20250814-skb-metadata-thru-dynptr-v7-7-8a39e636e0fb@cloudflare.com
This commit is contained in:
Jakub Sitnicki 2025-08-14 11:59:33 +02:00 committed by Martin KaFai Lau
parent 153f6bfd48
commit ed93360807
2 changed files with 98 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
View File

@ -269,7 +269,8 @@ void test_xdp_context_veth(void)
}
static void test_tuntap(struct bpf_program *xdp_prog,
struct bpf_program *tc_prog,
struct bpf_program *tc_prio_1_prog,
struct bpf_program *tc_prio_2_prog,
struct bpf_map *result_map)
{
LIBBPF_OPTS(bpf_tc_hook, tc_hook, .attach_point = BPF_TC_INGRESS);
@ -302,11 +303,20 @@ static void test_tuntap(struct bpf_program *xdp_prog,
if (!ASSERT_OK(ret, "bpf_tc_hook_create"))
goto close;
tc_opts.prog_fd = bpf_program__fd(tc_prog);
tc_opts.prog_fd = bpf_program__fd(tc_prio_1_prog);
ret = bpf_tc_attach(&tc_hook, &tc_opts);
if (!ASSERT_OK(ret, "bpf_tc_attach"))
goto close;
if (tc_prio_2_prog) {
LIBBPF_OPTS(bpf_tc_opts, tc_opts, .handle = 1, .priority = 2,
.prog_fd = bpf_program__fd(tc_prio_2_prog));
ret = bpf_tc_attach(&tc_hook, &tc_opts);
if (!ASSERT_OK(ret, "bpf_tc_attach"))
goto close;
}
ret = bpf_xdp_attach(tap_ifindex, bpf_program__fd(xdp_prog),
0, NULL);
if (!ASSERT_GE(ret, 0, "bpf_xdp_attach"))
@ -341,13 +351,29 @@ void test_xdp_context_tuntap(void)
return;
if (test__start_subtest("data_meta"))
test_tuntap(skel->progs.ing_xdp, skel->progs.ing_cls,
test_tuntap(skel->progs.ing_xdp,
skel->progs.ing_cls,
NULL, /* tc prio 2 */
skel->maps.test_result);
if (test__start_subtest("dynptr_read"))
test_tuntap(skel->progs.ing_xdp, skel->progs.ing_cls_dynptr_read,
test_tuntap(skel->progs.ing_xdp,
skel->progs.ing_cls_dynptr_read,
NULL, /* tc prio 2 */
skel->maps.test_result);
if (test__start_subtest("dynptr_slice"))
test_tuntap(skel->progs.ing_xdp, skel->progs.ing_cls_dynptr_slice,
test_tuntap(skel->progs.ing_xdp,
skel->progs.ing_cls_dynptr_slice,
NULL, /* tc prio 2 */
skel->maps.test_result);
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);
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);
test_xdp_meta__destroy(skel);

67
tools/testing/selftests/bpf/progs/test_xdp_meta.c
View File

@ -60,6 +60,24 @@ int ing_cls_dynptr_read(struct __sk_buff *ctx)
return TC_ACT_SHOT;
}
/* Write to metadata using bpf_dynptr_write helper */
SEC("tc")
int ing_cls_dynptr_write(struct __sk_buff *ctx)
{
struct bpf_dynptr data, meta;
__u8 *src;
bpf_dynptr_from_skb(ctx, 0, &data);
src = bpf_dynptr_slice(&data, sizeof(struct ethhdr), NULL, META_SIZE);
if (!src)
return TC_ACT_SHOT;
bpf_dynptr_from_skb_meta(ctx, 0, &meta);
bpf_dynptr_write(&meta, 0, src, META_SIZE, 0);
return TC_ACT_UNSPEC; /* pass */
}
/* Read from metadata using read-only dynptr slice */
SEC("tc")
int ing_cls_dynptr_slice(struct __sk_buff *ctx)
@ -82,6 +100,55 @@ int ing_cls_dynptr_slice(struct __sk_buff *ctx)
return TC_ACT_SHOT;
}
/* Write to metadata using writeable dynptr slice */
SEC("tc")
int ing_cls_dynptr_slice_rdwr(struct __sk_buff *ctx)
{
struct bpf_dynptr data, meta;
__u8 *src, *dst;
bpf_dynptr_from_skb(ctx, 0, &data);
src = bpf_dynptr_slice(&data, sizeof(struct ethhdr), NULL, META_SIZE);
if (!src)
return TC_ACT_SHOT;
bpf_dynptr_from_skb_meta(ctx, 0, &meta);
dst = bpf_dynptr_slice_rdwr(&meta, 0, NULL, META_SIZE);
if (!dst)
return TC_ACT_SHOT;
__builtin_memcpy(dst, src, META_SIZE);
return TC_ACT_UNSPEC; /* pass */
}
/* Reserve and clear space for metadata but don't populate it */
SEC("xdp")
int ing_xdp_zalloc_meta(struct xdp_md *ctx)
{
struct ethhdr *eth = ctx_ptr(ctx, data);
__u8 *meta;
int ret;
/* Drop any non-test packets */
if (eth + 1 > ctx_ptr(ctx, data_end))
return XDP_DROP;
if (eth->h_proto != 0)
return XDP_DROP;
ret = bpf_xdp_adjust_meta(ctx, -META_SIZE);
if (ret < 0)
return XDP_DROP;
meta = ctx_ptr(ctx, data_meta);
if (meta + META_SIZE > ctx_ptr(ctx, data))
return XDP_DROP;
__builtin_memset(meta, 0, META_SIZE);
return XDP_PASS;
}
SEC("xdp")
int ing_xdp(struct xdp_md *ctx)
{