Merge branch 'netlink-formatted-extacks'

Edward Cree says:

====================
netlink: formatted extacks

Currently, netlink extacks can only carry fixed string messages, which
 is limiting when reporting failures in complex systems.  This series
 adds the ability to return printf-formatted messages, and uses it in
 the sfc driver's TC offload code.
Formatted extack messages are limited in length to a fixed buffer size,
 currently 80 characters.  If the message exceeds this, the full message
 will be logged (ratelimited) to the console and a truncated version
 returned over netlink.
There is no change to the netlink uAPI; only internal kernel changes
 are needed.
====================

Link: https://lore.kernel.org/r/cover.1666102698.git.ecree.xilinx@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>