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

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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: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20251105-skb-meta-rx-path-v4-15-5ceb08a9b37b@cloudflare.com
This commit is contained in:
Jakub Sitnicki
2025-11-05 21:19:52 +01:00
committed by Martin KaFai Lau
parent 29960e635b
commit 85d454afef
2 changed files with 39 additions and 0 deletions
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tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
+5
View File
@@ -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
View File
@@ -611,4 +611,38 @@ out:
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";