+find_active_interface() {
+ [[ ! -d /sys/class/net ]] && { log_error "find_active_interface: /sys/class/net doesn't exist"; return 2; }
+ local iface
+ for x in $(ls -d /sys/class/net/* 2>/dev/null); do
+ iface=$(basename $x)
+ # find interfaces with:
+ # - type == 1 (ethernet)
+ # - not wireless
+ # - with state up
+
+ [[ $(cat $x/type) != 1 ]] && continue
+ [[ -d $x/wireless ]] && continue
+ [[ $(cat $x/operstate) != "up" ]] && continue
+
+ log_info "find_active_interface: first active interface is $iface"
+ echo $iface
+ return 0
+ done
+
+ log_error "Unable to find any active network interface."
+ return 1
+}
+