If the MAC80211_HWSIM netlink family disappears, exit hwsim. This can
happen already at startup, for example if MAC80211_HWSIM functionality is
not compiled in the kernel or respective module loaded.
Kernel sends HWSIM_CMD_NEW_RADIO and HWSIM_CMD_DEL_RADIO multicast
events when new radio have been created and when existing one has
been deleted. The events are sent to "config" netlink multicast group.
The hwsim catches these events and uses the information to monitor
what simulated radios are created and deleted in the system.
The new attribute causes the radio to be removed if the hwsim process
dies. This is the default behaviour. If user calls the binary with -k
option, then the radio is kept after hwsim quits.
This requires kernel support for HWSIM_ATTR_DESTROY_RADIO_ON_CLOSE
attribute.
When a new radio is created, the kernel returns the new radio id
in the error code. If the error < 0, then that means a real error
and other values are used as a radio id.
When a radio is destroyed, the error code 0 means a success and
other values indicate an error.
