Merge branch 'map-pinning'

Toke Høiland-Jørgensen says:

====================
This series fixes a few bugs in libbpf that I discovered while playing around
with the new auto-pinning code, and writing the first utility in xdp-tools[0]:

- If object loading fails, libbpf does not clean up the pinnings created by the
  auto-pinning mechanism.
- EPERM is not propagated to the caller on program load
- Netlink functions write error messages directly to stderr

In addition, libbpf currently only has a somewhat limited getter function for
XDP link info, which makes it impossible to discover whether an attached program
is in SKB mode or not. So the last patch in the series adds a new getter for XDP
link info which returns all the information returned via netlink (and which can
be extended later).

Finally, add a getter for BPF program size, which can be used by the caller to
estimate the amount of locked memory needed to load a program.

A selftest is added for the pinning change, while the other features were tested
in the xdp-filter tool from the xdp-tools repo. The 'new-libbpf-features' branch
contains the commits that make use of the new XDP getter and the corrected EPERM
error code.

[0] https://github.com/xdp-project/xdp-tools

Changelog:

v4:
  - Don't do any size checks on struct xdp_info, just copy (and/or zero)
    whatever size the caller supplied.

v3:
  - Pass through all kernel error codes on program load (instead of just EPERM).
  - No new bpf_object__unload() variant, just do the loop at the caller
  - Don't reject struct xdp_info sizes that are bigger than what we expect.
  - Add a comment noting that bpf_program__size() returns the size in bytes

v2:
  - Keep function names in libbpf.map sorted properly
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>