IFLA_CARRIER allows to know when a cable is plugged to the Ethernet
card or when the WiFi is connected. If there's no carrier, the
interface will be considered disconnected.
Last part of the rework of handleEvents(), this time we take the
getExternalInterface() function and add it to the handleEvents()
function. That way, waybar can react immediately when a new "external
interface" is available and doesn't need to probe. Also that avoid to
have two different functions consuming from the same socket and we
don't need to recode some of the functions that are already available
via libnl (to send and receive messages).
In order to get the IP address of an interface, we can get the
information out of NEWADDR events without needed to call getifaddrs().
And when now events are expected, we can requests a dump of all
addresses and handle addresses changes the same way via handleEvents()
only.
Instead of using an alternative way to list all links in order to
choose one when an "interface" is in the configuration, we can ask for
a dump of all interface an reuse the handleEvents() function.
This patch also start to rework the handleEvents() function to grab
more information out of each event, like the interface name.
Open rfkill device only once per module.
Remove rfkill threads and use `Glib::signal_io` as a more efficient way
to poll the rfkill device.
Handle runtime errors from rfkill and stop polling of the device instead
of crashing waybar.
