[PATCH bpf-next v4 4/7] bpftool: Implement link show support for netkit

[Daniel Borkmann <daniel@xxxxxxxxxxxxx>]

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

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: netkit  prog 35
        ifindex nk1(18)  attach_type netkit_primary
  [...]

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": "netkit",
    "prog_id": 61,
    "devname": "nk1",
    "ifindex": 21,
    "attach_type": "netkit_primary"
  }
  [...]

Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Reviewed-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
---
 tools/bpf/bpftool/link.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
index 4b1407b05056..a1528cde81ab 100644
--- a/tools/bpf/bpftool/link.c
+++ b/tools/bpf/bpftool/link.c
@@ -451,6 +451,10 @@ 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_NETKIT:
+		show_link_ifindex_json(info->netkit.ifindex, json_wtr);
+		show_link_attach_type_json(info->netkit.attach_type, json_wtr);
+		break;
 	case BPF_LINK_TYPE_XDP:
 		show_link_ifindex_json(info->xdp.ifindex, json_wtr);
 		break;
@@ -791,6 +795,11 @@ 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_NETKIT:
+		printf("\n\t");
+		show_link_ifindex_plain(info->netkit.ifindex);
+		show_link_attach_type_plain(info->netkit.attach_type);
+		break;
 	case BPF_LINK_TYPE_XDP:
 		printf("\n\t");
 		show_link_ifindex_plain(info->xdp.ifindex);
-- 
2.34.1