networkd: add basic dbus API Only the very basics, more to come. For now: $ busctl tree org.freedesktop.network1 └─/org/freedesktop/network1 └─/org/freedesktop/network1/link ├─/org/freedesktop/network1/link/1 ├─/org/freedesktop/network1/link/2 ├─/org/freedesktop/network1/link/3 ├─/org/freedesktop/network1/link/4 ├─/org/freedesktop/network1/link/5 ├─/org/freedesktop/network1/link/6 ├─/org/freedesktop/network1/link/7 ├─/org/freedesktop/network1/link/8 └─/org/freedesktop/network1/link/9 $ busctl introspect org.freedesktop.network1 /org/freedesktop/network1 NAME TYPE SIGNATURE RESULT/VALUE FLAGS org.freedesktop.network1.Manager interface - - - .OperationalState property s "carrier" emits-change $ busctl introspect org.freedesktop.network1 /org/freedesktop/network1/link/1 NAME TYPE SIGNATURE RESULT/VALUE FLAGS org.freedesktop.network1.Link interface - - - .AdministrativeState property s "unmanaged" emits-change .OperationalState property s "carrier" emits-change