def vm_netstats(vm_=None, **kwargs):
    '''
    Return combined network counters used by the vms on this hyper in a
    list of dicts:

    :param vm_: domain name
    :param connection: libvirt connection URI, overriding defaults

        .. versionadded:: 2019.2.0
    :param username: username to connect with, overriding defaults

        .. versionadded:: 2019.2.0
    :param password: password to connect with, overriding defaults

        .. versionadded:: 2019.2.0

    .. code-block:: python

        [
            'your-vm': {
                'rx_bytes'   : 0,
                'rx_packets' : 0,
                'rx_errs'    : 0,
                'rx_drop'    : 0,
                'tx_bytes'   : 0,
                'tx_packets' : 0,
                'tx_errs'    : 0,
                'tx_drop'    : 0
                },
            ...
            ]

    If you pass a VM name in as an argument then it will return info
    for just the named VM, otherwise it will return all VMs.

    CLI Example:

    .. code-block:: bash

        salt '*' virt.vm_netstats
    '''
    def _info(dom):
        '''
        Compute network stats of a domain
        '''
        nics = _get_nics(dom)
        ret = {
                'rx_bytes': 0,
                'rx_packets': 0,
                'rx_errs': 0,
                'rx_drop': 0,
                'tx_bytes': 0,
                'tx_packets': 0,
                'tx_errs': 0,
                'tx_drop': 0
               }
        for attrs in six.itervalues(nics):
            if 'target' in attrs:
                dev = attrs['target']
                stats = dom.interfaceStats(dev)
                ret['rx_bytes'] += stats[0]
                ret['rx_packets'] += stats[1]
                ret['rx_errs'] += stats[2]
                ret['rx_drop'] += stats[3]
                ret['tx_bytes'] += stats[4]
                ret['tx_packets'] += stats[5]
                ret['tx_errs'] += stats[6]
                ret['tx_drop'] += stats[7]

        return ret
    info = {}
    conn = __get_conn(**kwargs)
    if vm_:
        info[vm_] = _info(_get_domain(conn, vm_))
    else:
        for domain in _get_domain(conn, iterable=True):
            info[domain.name()] = _info(domain)
    conn.close()
    return info