[PATCH bpf-next v4 0/3] bpf: implement link_query for bpf iterators

[Yonghong Song <yhs@fb.com>]

"link" has been an important concept for bpf ecosystem to connect
bpf program with other properties. Currently, the information related
information can be queried from userspace through bpf command
BPF_LINK_GET_NEXT_ID, BPF_LINK_GET_FD_BY_ID and BPF_OBJ_GET_INFO_BY_FD.
The information is also available by "cating" /proc/<pid>/fdinfo/<link_fd>.
Raw_tracepoint, tracing, cgroup, netns and xdp links are already
supported in the kernel and bpftool.

This patch added support for bpf iterator. Patch #1 added generic support
for link querying interface. Patch #2 implemented callback functions
for map element bpf iterators. Patch #3 added bpftool support.

Changelogs:
  v3 -> v4:
    . return target specific link_info even if target_name buffer
      is empty. (Andrii)
  v2 -> v3:
    . remove extra '\t' when fdinfo prints map_id to make parsing
      consistent. (Andrii)
  v1 -> v2:
    . fix checkpatch.pl warnings. (Jakub)

Yonghong Song (3):
  bpf: implement link_query for bpf iterators
  bpf: implement link_query callbacks in map element iterators
  bpftool: implement link_query for bpf iterators

 include/linux/bpf.h            | 10 ++++++
 include/uapi/linux/bpf.h       |  7 ++++
 kernel/bpf/bpf_iter.c          | 58 ++++++++++++++++++++++++++++++++++
 kernel/bpf/map_iter.c          | 15 +++++++++
 net/core/bpf_sk_storage.c      |  2 ++
 tools/bpf/bpftool/link.c       | 44 ++++++++++++++++++++++++--
 tools/include/uapi/linux/bpf.h |  7 ++++
 7 files changed, 140 insertions(+), 3 deletions(-)

-- 
2.24.1