Merge branch 'netlink-support-reporting-missing-attributes'

Jakub Kicinski says:

====================
netlink: support reporting missing attributes

This series adds support for reporting missing attributes
in a structured way. We communicate the type of the missing
attribute and if it was missing inside a nest the offset
of that nest.

Example of (YAML-based) user space reporting ethtool header
missing:

 Kernel error: missing attribute: .header

I was tempted to integrate the check with the policy
but it seems tricky without doing a full scan, and there
may be a ton of attrs in the policy. So leaving that
for later.
====================

Link: https://lore.kernel.org/r/20220826030935.2165661-1-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>