Reconfigure mangle postrouting for both v4 and v6.

bug.py

import iptc
import time

class Iptables(object):
    tablecls = iptc.Table
    rulecls = iptc.Rule

    @classmethod
    def get_ttl_rule(cls):
        rule = cls.rulecls()
        rule.create_match("comment").comment = "change ttl"
        rule.create_target("TTL").ttl_set = str(2)
        rule.create_match("devgroup").dst_group = "!0"
        return rule

    @classmethod
    def get_dscp_rule(cls):
        rule = cls.rulecls()
        rule.create_match("comment").comment = "add dscp mark"
        rule.create_target("DSCP").set_dscp = str(0x20)
        rule.create_match("devgroup").dst_group = "!0"
        return rule

    @classmethod
    def reconfigure(cls):
        table = cls.tablecls(cls.tablecls.MANGLE)
        table.autocommit = False
        table.refresh()

        rules = [cls.get_ttl_rule(), cls.get_dscp_rule()]
        chain = iptc.Chain(table, 'POSTROUTING')

        if chain.rules != rules:
            if chain.rules:
                chain.flush()
            for rule in rules:
                chain.append_rule(rule)

        table.commit()
        
class Ip6tables(Iptables):
    tablecls = iptc.Table6
    rulecls = iptc.Rule6

    @classmethod
    def get_ttl_rule(cls):
        rule = cls.rulecls()
        rule.create_match("comment").comment = "change ttl"
        rule.create_target("HL").hl_set = str(2)
        rule.create_match("devgroup").dst_group = "!0"
        return rule

if __name__ == "__main__":
    while True:
        print "Configuring.."
        Iptables.reconfigure()
        Ip6tables.reconfigure()
        time.sleep(5)