[PATCH bpf-next v2 12/15] selftests/bpf: Cover skb metadata access after vlan push/pop helper
From: Jakub Sitnicki <jakub@cloudflare.com>
Date: 2025-10-19 12:46:03
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
Add a test to verify that skb metadata remains accessible after calling bpf_skb_vlan_push() and bpf_skb_vlan_pop(), which modify the packet headroom. Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com> --- .../bpf/prog_tests/xdp_context_test_run.c | 6 +++ tools/testing/selftests/bpf/progs/test_xdp_meta.c | 43 ++++++++++++++++++++++ 2 files changed, 49 insertions(+)
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 df6248dbaae8..e83b33526595 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@@ -482,6 +482,12 @@ void test_xdp_context_tuntap(void) test_tuntap_mirred(skel->progs.ing_xdp, skel->progs.clone_dynptr_rdonly_before_meta_dynptr_write, &skel->bss->test_pass); + /* Tests for BPF helpers which touch headroom */ + if (test__start_subtest("helper_skb_vlan_push_pop")) + test_tuntap(skel->progs.ing_xdp, + skel->progs.helper_skb_vlan_push_pop, + NULL, /* tc prio 2 */ + &skel->bss->test_pass); test_xdp_meta__destroy(skel); }
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_meta.c b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
index dba76f84c0c5..8d2b0512f8d3 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_meta.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_meta.c@@ -49,6 +49,16 @@ static bool check_metadata(const char *file, int line, __u8 *meta_have) #define check_metadata(meta_have) check_metadata(__FILE__, __LINE__, meta_have) +static bool check_skb_metadata(const char *file, int line, struct __sk_buff *skb) +{ + __u8 *data_meta = ctx_ptr(skb, data_meta); + __u8 *data = ctx_ptr(skb, data); + + return data_meta + META_SIZE <= data && (check_metadata)(file, line, data_meta); +} + +#define check_skb_metadata(skb) check_skb_metadata(__FILE__, __LINE__, skb) + SEC("tc") int ing_cls(struct __sk_buff *ctx) {
@@ -525,4 +535,37 @@ int clone_dynptr_rdonly_before_meta_dynptr_write(struct __sk_buff *ctx) return TC_ACT_SHOT; } +SEC("tc") +int helper_skb_vlan_push_pop(struct __sk_buff *ctx) +{ + int err; + + /* bpf_skb_vlan_push assumes HW offload for primary VLAN tag. Only + * secondary tag push triggers an actual MAC header modification. + */ + err = bpf_skb_vlan_push(ctx, 0, 42); + if (err) + goto out; + err = bpf_skb_vlan_push(ctx, 0, 207); + if (err) + goto out; + + if (!check_skb_metadata(ctx)) + goto out; + + err = bpf_skb_vlan_pop(ctx); + if (err) + goto out; + err = bpf_skb_vlan_pop(ctx); + if (err) + goto out; + + if (!check_skb_metadata(ctx)) + goto out; + + test_pass = true; +out: + return TC_ACT_SHOT; +} + char _license[] SEC("license") = "GPL";
--
2.43.0