- consistently check for success/failure of _ethtool_call_handle()
with "< 0" / ">= 0".
- drop unnecessary memset(). In the past, I argued to add this because
there were obscure cases with valgrind where this made a difference.
As it's not clear when/how that is necessary, drop it again.
Also, we want to prefer explicit struct initialization over memset(),
so if memset() would be necessary, those places would be problematic
as well.
- inline unnecessary helper functions. They had only one caller and
only make the code more verbose.
- use _ethtool_call_once() instead of _ethtool_call_handle() at places
where we use the handle only once. The handle and _ethtool_call_handle()
are useful to cache and reuse the file descriptor and the interface
name. If we only make one call with the handle, we can use
_ethtool_call_once() instead.
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/830
