Commit 85d454af authored by Jakub Sitnicki's avatar Jakub Sitnicki Committed by Martin KaFai Lau
Browse files

selftests/bpf: Cover skb metadata access after change_head/tail helper 



Add a test to verify that skb metadata remains accessible after calling
bpf_skb_change_head() and bpf_skb_change_tail(), which modify packet
headroom/tailroom and can trigger head reallocation.

Signed-off-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20251105-skb-meta-rx-path-v4-15-5ceb08a9b37b@cloudflare.com
parent 29960e63

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

+5 −0
Original line number Diff line number Diff line
@@ -497,6 +497,11 @@ void test_xdp_context_tuntap(void) 
			    skel->progs.helper_skb_adjust_room,

			    NULL, /* tc prio 2 */

			    &skel->bss->test_pass);

	if (test__start_subtest("helper_skb_change_head_tail"))

		test_tuntap(skel->progs.ing_xdp,

			    skel->progs.helper_skb_change_head_tail,

			    NULL, /* tc prio 2 */

			    &skel->bss->test_pass);



	test_xdp_meta__destroy(skel);

}

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

+34 −0
Original line number Diff line number Diff line
@@ -611,4 +611,38 @@ int helper_skb_adjust_room(struct __sk_buff *ctx) 
	return TC_ACT_SHOT;

}



SEC("tc")

int helper_skb_change_head_tail(struct __sk_buff *ctx)

{

	int err;



	/* Reserve 1 extra in the front for packet data */

	err = bpf_skb_change_head(ctx, 1, 0);

	if (err)

		goto out;



	if (!check_skb_metadata(ctx))

		goto out;



	/* Reserve 256 extra bytes in the front to trigger head reallocation */

	err = bpf_skb_change_head(ctx, 256, 0);

	if (err)

		goto out;



	if (!check_skb_metadata(ctx))

		goto out;



	/* Reserve 4k extra bytes in the back to trigger head reallocation */

	err = bpf_skb_change_tail(ctx, ctx->len + 4096, 0);

	if (err)

		goto out;



	if (!check_skb_metadata(ctx))

		goto out;



	test_pass = true;

out:

	return TC_ACT_SHOT;

}



char _license[] SEC("license") = "GPL";