void IP_Widget::addTab()
{
    int i = ipSet->addTab(new _IP_Widget(this, &IPv4HasDHCP, &IPv6HasDHCP), "IP Element");
    _IP_Widget *wdg = static_cast<_IP_Widget*>(ipSet->widget(i));
    if ( NULL!=wdg ) {
        connect(wdg, SIGNAL(dhcpUsageChanged()),
                this, SLOT(updateDHCPUsage()));
    };
}
void IP_Widget::closeTab(int i)
{
    if ( ipSet->count()<2 ) return;
    _IP_Widget *wdg = static_cast<_IP_Widget*>(ipSet->widget(i));
    if ( nullptr!=wdg ) {
        wdg->ipv6->click();
        wdg->updateDHCPUsage();
        disconnect(wdg, SIGNAL(dhcpUsageChanged()),
                   this, SLOT(updateDHCPUsage()));
        ipSet->removeTab(i);
        wdg->deleteLater();
    };
}