[PATCH net-next v3 0/6] netlink: support reporting missing attributes

[Jakub Kicinski <kuba@kernel.org>]

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.

v3:
 - update cover letter
 - minor (non-functional) adjustments to patches 1, 2, 6
v2:
 - add patch 1
 - remove the nest attr if the attr is missing in the root

Jakub Kicinski (6):
  netlink: factor out extack composition
  netlink: add support for ext_ack missing attributes
  netlink: add helpers for extack attr presence checking
  devlink: use missing attribute ext_ack
  ethtool: strset: report missing ETHTOOL_A_STRINGSET_ID via ext_ack
  ethtool: report missing header via ext_ack in the default handler

 Documentation/userspace-api/netlink/intro.rst |  7 +-
 include/linux/netlink.h                       | 24 +++++
 include/net/genetlink.h                       |  7 ++
 include/uapi/linux/netlink.h                  |  6 ++
 net/core/devlink.c                            | 41 ++++----
 net/ethtool/netlink.c                         |  3 +
 net/ethtool/strset.c                          |  2 +-
 net/netlink/af_netlink.c                      | 97 +++++++++++++------
 8 files changed, 133 insertions(+), 54 deletions(-)

-- 
2.37.2