Commit ed933608 authored by Jakub Sitnicki's avatar Jakub Sitnicki Committed by Martin KaFai Lau
Browse files

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



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: default avatarJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: default avatarJesse Brandeburg <jbrandeburg@cloudflare.com>
Acked-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20250814-skb-metadata-thru-dynptr-v7-7-8a39e636e0fb@cloudflare.com
parent 153f6bfd

tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c

+31 −5
Original line number Diff line number Diff line
@@ -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);

tools/testing/selftests/bpf/progs/test_xdp_meta.c

+67 −0
Original line number Diff line number Diff line
@@ -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)

{