def convert_iface(iface):
    """Convert iface string like 'any', 'eth', 'eth0' to iptables iface naming like *, eth+, eth0. 
    """
    if iface == 'any':
        return '*'
    else:
        # append '+' quantifier to iface
        if not iface[-1].isdigit():
            iface += '+'
        return iface