On Tue, Apr 18, 2023 at 5:37 PM Kui-Feng Lee <thinker.li@xxxxxxxxx> wrote:
>
> A new link type, BPF_LINK_TYPE_STRUCT_OPS, was added to attach
> struct_ops to links. (226bc6ae6405) It would be helpful for users to
> know which map is associated with the link.
>
> The assumption was that every link is associated with a BPF program, but
> this does not hold true for struct_ops. It would be better to display
> map_id instead of prog_id for struct_ops links. However, some tools may
> rely on the old assumption and need a prog_id. The discussion on the
> mailing list suggests that tools should parse JSON format. We will maintain
> the existing JSON format by adding a map_id without removing prog_id. As
> for plain text format, we will remove prog_id from the header line and add
> a map_id for struct_ops links.
>
> Signed-off-by: Kui-Feng Lee <kuifeng@xxxxxxxx>
> Reviewed-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
> ---
> tools/bpf/bpftool/link.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
> index f985b79cca27..8eb8520bd7b4 100644
> --- a/tools/bpf/bpftool/link.c
> +++ b/tools/bpf/bpftool/link.c
> @@ -195,6 +195,10 @@ static int show_link_close_json(int fd, struct bpf_link_info *info)
> info->netns.netns_ino);
> show_link_attach_type_json(info->netns.attach_type, json_wtr);
> break;
> + case BPF_LINK_TYPE_STRUCT_OPS:
> + jsonw_uint_field(json_wtr, "map_id",
> + info->struct_ops.map_id);
> + break;
> default:
> break;
> }
> @@ -227,7 +231,10 @@ static void show_link_header_plain(struct bpf_link_info *info)
> else
> printf("type %u ", info->type);
>
> - printf("prog %u ", info->prog_id);
> + if (info->type == BPF_LINK_TYPE_STRUCT_OPS)
> + printf("map_id %u ", info->struct_ops.map_id);
> + else
> + printf("prog %u ", info->prog_id);
if we output "prog %u" for prog_id, shouldn't we just output "map %u"
for map_id?
> }
>
> static void show_link_attach_type_plain(__u32 attach_type)
> --
> 2.34.1
>
