selftests: net: add ctl_file_write() helper

Setting a sysctl or a sysfs attribute for the duration of a test and
putting the old value back has been open coded multiple times.

We generally avoid creating library helpers but this one is very
common, and the defer is a little tricky as using the same function
for defer as the initial write leads to an infinite loop (not that
I would ever make such mistake!)

Some of the conversions are not identical, but arguably ctl_file_write()
semantics are more correct.

Reviewed-by: Nimrod Oren <noren@nvidia.com>
Reviewed-by: Bobby Eshleman <bobbyeshleman@meta.com>
Link: https://patch.msgid.link/20260909180009.1894019-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2026-09-09 11:00:09 -07:00
commit 348ea4642f
8 changed files with 42 additions and 50 deletions