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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def update_ip_rule(self, ip, mac):
 """Update a rule associated with given ip and mac."""


        rule_no = self._find_rule_no(mac)
        chain = self._find_chain_name(mac)
        if not rule_no or not chain:
            LOG.error('Failed to update ip rule for %(ip)s %(mac)s',
                      {'ip': ip, 'mac': mac})
            return

        update_cmd = ['iptables', '-R', '%s' % chain, '%s' % rule_no,
                      '-s', '%s/32' % ip, '-m', 'mac', '--mac-source',
                      '%s' % mac, '-j', 'RETURN']
        LOG.debug('Execute command: %s', update_cmd)
        dsl.execute(update_cmd, self._root_helper, log_output=False)