bring_interface()
{
    local INTERFACE="$2"
    case "$1" in
        up)
            if ! ( eval $IFACE_UP ); then
                return 1
            fi
            ip link set dev "$INTERFACE" up &>/dev/null
            sleep "${UP_SLEEP:-2}"
        ;;
        flush|down)
            if ! ( eval $IFACE_DOWN ); then
                return 1
            fi
            ip addr flush dev "$INTERFACE" &>/dev/null
        ;;&
        down)
            ip link set dev "$INTERFACE" down &>/dev/null
        ;;
    esac
}