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bpftool: Show map IDs along with struct_ops links.

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A new link type, BPF_LINK_TYPE_STRUCT_OPS, was added to attach
struct_ops to links. (226bc6ae64) 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@meta.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20230421214131.352662-1-kuifeng@meta.com
This commit is contained in:
Kui-Feng Lee 2023-04-21 14:41:31 -07:00 • committed by Daniel Borkmann
parent 1a986518b8
commit 74fc8801ed
1 changed files with 8 additions and 2 deletions
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8
tools/bpf/bpftool/link.c
View file

@ -212,7 +212,10 @@ static int show_link_close_json(int fd, struct bpf_link_info *info)
case BPF_LINK_TYPE_NETFILTER:
netfilter_dump_json(info, json_wtr);
break;
case BPF_LINK_TYPE_STRUCT_OPS:
jsonw_uint_field(json_wtr, "map_id",
info->struct_ops.map_id);
break;
default:
break;
}
@ -245,6 +248,9 @@ static void show_link_header_plain(struct bpf_link_info *info)
else
printf("type %u ", info->type);
if (info->type == BPF_LINK_TYPE_STRUCT_OPS)
printf("map %u ", info->struct_ops.map_id);
else
printf("prog %u ", info->prog_id);
}