Return the current policy for the specified table/chain

    CLI Example:

    .. code-block:: bash

        salt '*' iptables.get_policy filter INPUT

        IPv6:
        salt '*' iptables.get_policy filter INPUT family=ipv6

def get_policy(table='filter', chain=None, family='ipv4'):
    '''
    Return the current policy for the specified table/chain

    CLI Example:

    .. code-block:: bash

        salt '*' iptables.get_policy filter INPUT

        IPv6:
        salt '*' iptables.get_policy filter INPUT family=ipv6
    '''
    if not chain:
        return 'Error: Chain needs to be specified'

    rules = _parse_conf(in_mem=True, family=family)
    try:
        return rules[table][chain]['policy']
    except KeyError:
        return None