[PATCH bpf-next 5/8] bpftool: Implement link show support for meta

[Daniel Borkmann <daniel@xxxxxxxxxxxxx>]

Add support to dump meta link information to bpftool in similar way
as we have for XDP. The meta link info only exposes the ifindex.

Below shows an example link dump output, and a cgroup link is included
for comparison, too:

  # bpftool link
  [...]
  10: cgroup  prog 2466
        cgroup_id 1  attach_type cgroup_inet6_post_bind
  [...]
  8: meta  prog 35
        ifindex meta1(18)
  [...]

Equivalent json output:

  # bpftool link --json
  [...]
  {
    "id": 10,
    "type": "cgroup",
    "prog_id": 2466,
    "cgroup_id": 1,
    "attach_type": "cgroup_inet6_post_bind"
  },
  [...]
  {
    "id": 12,
    "type": "meta",
    "prog_id": 61,
    "devname": "meta1",
    "ifindex": 21
  }
  [...]

Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
---
 tools/bpf/bpftool/link.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
index 2e5c231e08ac..57fd3f1a7330 100644
--- a/tools/bpf/bpftool/link.c
+++ b/tools/bpf/bpftool/link.c
@@ -449,6 +449,9 @@ static int show_link_close_json(int fd, struct bpf_link_info *info)
 		show_link_ifindex_json(info->tcx.ifindex, json_wtr);
 		show_link_attach_type_json(info->tcx.attach_type, json_wtr);
 		break;
+	case BPF_LINK_TYPE_META:
+		show_link_ifindex_json(info->meta.ifindex, json_wtr);
+		break;
 	case BPF_LINK_TYPE_XDP:
 		show_link_ifindex_json(info->xdp.ifindex, json_wtr);
 		break;
@@ -785,6 +788,10 @@ static int show_link_close_plain(int fd, struct bpf_link_info *info)
 		show_link_ifindex_plain(info->tcx.ifindex);
 		show_link_attach_type_plain(info->tcx.attach_type);
 		break;
+	case BPF_LINK_TYPE_META:
+		printf("\n\t");
+		show_link_ifindex_plain(info->meta.ifindex);
+		break;
 	case BPF_LINK_TYPE_XDP:
 		printf("\n\t");
 		show_link_ifindex_plain(info->xdp.ifindex);
-- 
2.34.1