<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def update_iptables(self):
 """Update iptables based on information in the rule_info."""


        # Read the iptables
        iptables_cmds = ['iptables-save', '-c']
        all_rules = dsl.execute(iptables_cmds, root_helper=self._root_helper,
                                log_output=False)

        # For each rule in rule_info update the rule if necessary.
        new_rules = []
        is_modified = False
        for line in all_rules.split('\n'):
            new_line = line
            line_content = line.split()
            # The spoofing rule which includes mac and ip should have
            # -s cidr/32  option for ip address. Otherwise no rule
            # will be modified.
            if '-s' in line_content:
                tmp_rule_info = list(self.rule_info)
                for rule in tmp_rule_info:
                    if (rule.mac in line.lower() and
                        rule.chain.lower() in line.lower() and
                            not self._is_ip_in_rule(rule.ip, line_content)):
                        ip_loc = line_content.index('-s') + 1
                        line_content[ip_loc] = rule.ip + '/32'
                        new_line = ' '.join(line_content)
                        LOG.debug('Modified %(old_rule)s. '
                                  'New rule is %(new_rule)s.' % (
                                      {'old_rule': line,
                                       'new_rule': new_line}))
                        is_modified = True
            new_rules.append(new_line)

        if is_modified and new_rules:
            # Updated all the rules. Now commit the new rules.
            iptables_cmds = ['iptables-restore', '-c']
            dsl.execute(iptables_cmds, process_input='\n'.join(new_rules),
                        root_helper=self._root_helper, log_output=False)