Use `getrandom(2)` system call
Using getrandom
system call is faster than reading from /dev/random
and doesn't require a
file descriptor.
Ubuntu also enables it: https://git.launchpad.net/ubuntu/+source/wpa/tree/debian/config/hostapd/linux?id=dd3cefa946a1fa14c957606bb016af801f7d6d44#n259