Re: [RFC PATCH bpf-next 3/5] libbpf: Add link support for BPF_PROG_TYPE_SK_MSG

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Tue, Mar 5, 2024 at 12:22 PM Yonghong Song <yonghong.song@linux.dev> wrote:
>
> Introduce a libbpf API bpf_program__attach_sk_msg() which allows
> user to get a bpf_link. The API makes auto-deletion easier and
> also allows user space application easier as link based APIs
> are used for all programs.
>
> Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
> ---
>  tools/lib/bpf/libbpf.c   | 8 ++++++++
>  tools/lib/bpf/libbpf.h   | 3 +++
>  tools/lib/bpf/libbpf.map | 1 +
>  3 files changed, 12 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 97b573516675..b3982bb3f979 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -149,6 +149,7 @@ static const char * const link_type_name[] = {
>         [BPF_LINK_TYPE_TCX]                     = "tcx",
>         [BPF_LINK_TYPE_UPROBE_MULTI]            = "uprobe_multi",
>         [BPF_LINK_TYPE_NETKIT]                  = "netkit",
> +       [BPF_LINK_TYPE_SK_MSG]                  = "sk_msg",
>  };
>
>  static const char * const map_type_name[] = {
> @@ -12280,6 +12281,13 @@ bpf_program__attach_netkit(const struct bpf_program *prog, int ifindex,
>         return bpf_program_attach_fd(prog, ifindex, "netkit", &link_create_opts);
>  }
>
> +struct bpf_link *
> +bpf_program__attach_sk_msg(const struct bpf_program *prog, int map_fd,
> +                          enum bpf_attach_type attach_type)

Why do we need to allow users to override attach_type? Why can't it
come from bpf_program's expected attach type?

> +{
> +       return __bpf_program_attach_fd(prog, map_fd, attach_type, "sk_msg", NULL);
> +}
> +
>  struct bpf_link *bpf_program__attach_freplace(const struct bpf_program *prog,
>                                               int target_fd,
>                                               const char *attach_func_name)
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 5723cbbfcc41..c8448f05e8d6 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -786,6 +786,9 @@ bpf_program__attach_netns(const struct bpf_program *prog, int netns_fd);
>  LIBBPF_API struct bpf_link *
>  bpf_program__attach_xdp(const struct bpf_program *prog, int ifindex);
>  LIBBPF_API struct bpf_link *
> +bpf_program__attach_sk_msg(const struct bpf_program *prog, int map_fd,
> +                          enum bpf_attach_type attach_type);
> +LIBBPF_API struct bpf_link *
>  bpf_program__attach_freplace(const struct bpf_program *prog,
>                              int target_fd, const char *attach_func_name);
>
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 86804fd90dd1..c59986c6dbc5 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -410,6 +410,7 @@ LIBBPF_1.3.0 {
>
>  LIBBPF_1.4.0 {
>         global:
> +               bpf_program__attach_sk_msg;
>                 bpf_token_create;
>                 btf__new_split;
>                 btf_ext__raw_data;
> --
> 2.43.0
>