From: Hui Zhu <zhuhui@kylinos.cn>

Building on the previous change that added flags to the kernel's link
creation path, this patch exposes this functionality through libbpf.

The `bpf_struct_ops_opts` struct is extended with a `flags` member,
which is then passed to the `bpf_link_create` syscall within
`bpf_map__attach_struct_ops_opts`.

This enables userspace applications to pass flags, such as
`BPF_F_ALLOW_OVERRIDE`, when attaching struct_ops to cgroups,
providing more control over the attachment behavior in nested
hierarchies.

Signed-off-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
---
 tools/lib/bpf/libbpf.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 70a00da54ff5..06c936bad211 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -13511,6 +13511,7 @@ struct bpf_link *bpf_map__attach_struct_ops_opts(const struct bpf_map *map,
 	}
 
 	link_opts.cgroup.relative_fd = OPTS_GET(opts, relative_fd, 0);
+	link_opts.flags = OPTS_GET(opts, flags, 0);
 
 	fd = bpf_link_create(map->fd, 0, BPF_STRUCT_OPS, &link_opts);
 	if (fd < 0) {
-- 
2.43.0

> The `bpf_struct_ops_opts` struct is extended with a `flags` member,
> which is then passed to the `bpf_link_create` syscall within
> `bpf_map__attach_struct_ops_opts`.

The commit message states the struct is "extended with a `flags` member", but
the flags field already exists in bpf_struct_ops_opts. It was added in commit
a09c73b18 ("libbpf: introduce bpf_map__attach_struct_ops_opts()"):

    struct bpf_struct_ops_opts {
        size_t sz;
        __u32 flags;
        __u32 relative_fd;
        __u64 expected_revision;
        size_t :0;
    };

This patch adds code to USE the existing flags field, not extend the struct.
Would a message like "Pass the existing flags field from bpf_struct_ops_opts
to bpf_link_create" be more accurate?


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/21665371660

AI-authorship-score: medium
AI-authorship-explanation: The commit message contains a factual inaccuracy about extending the struct when the field already existed, which could indicate AI-generated text that didn't fully analyze the prior commit in the series.
issues-found: 1
issue-severity-score: low
issue-severity-explanation: The only issue is an inaccurate commit message that claims to extend a struct with a field that already exists; this is a documentation issue, not a code bug.