Merge branch 'fix-unconnected-udp'

Daniel Borkmann says:

====================
Please refer to the patch 1/6 as the main patch with the details
on the current sendmsg hook API limitations and proposal to fix
it in order to work with basic applications like DNS. Remaining
patches are the usual uapi and tooling updates as well as test
cases. Thanks a lot!

v2 -> v3:
  - Add attach types to test_section_names.c and libbpf (Andrey)
  - Added given Acks, rest as-is
v1 -> v2:
  - Split off uapi header sync and bpftool bits (Martin, Alexei)
  - Added missing bpftool doc and bash completion as well
====================

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