jayeye/README.md

## README.md

      
    Raw
  

              README.md
            
          
    My ISP (Time Warner Cable) hands out IPv6 addresses with DHCPv6;
it will delegate a /56 if asked. So long as I keep refreshing the lease,
it won't renumber me. I have my cable modem set to bridge, and do all the
firewalling, NATing, etc., on a Debian box.
In what follows, eth0 is the internal interface.
The dhclient that ships with debian/ubuntu does not support asking
for a prefix delegation, so I had to build one from sources.

Get the ISC dhcp source.
Get patches.
Build, and install the client as /sbin/dhclient6 if you don't want to do an actual make install,
which would probably also require to figure out how to apply the Debian packaging changes.

Next, change the stanza for your external interface (in my case, eth1) in /etc/network/interfaces to this:
iface eth1 inet dhcp
    up /sbin/dhclient6 -v -6 -P -Pl 56  -pf /run/dhclient6.eth1.pid -lf /var/lib/dhcp/dhclient6.eth1.leases eth1
    down killall dhclient6
    down service radvd stop

(there are many other ways to skin this particular cat, I opted for the one that involved the least amount of blood!)
Install ipv6 in /etc/dhcp/dhclient-enter-hooks.d/, and
dhclient-ipv6-hook.py in /usr/local/sbin/.
Make sure the following sysctl variables are set correctly:
net.ipv6.conf.eth1.accept_ra=2
net.ipv6.conf.all.disable_ipv6=0
net.ipv6.conf.all.forwarding=1

(you need the first one so you can get the LL address of the default route from your ISP; at least I do).
ifdown eth1; ifup eth1 should do the trick.
In my case, I'm asking for a /56, I allocate a /64 to each of my interfaces, vlans, etc.
I'm only showing one interface here, of course.

  
## dhclient-ipv6-hook.py
#!/usr/bin/env python3

import ipaddress
import logging
import os
import sys
import textwrap

reason = os.getenv('reason')
if reason not in ['BOUND6', 'REBIND6']:
  logging.info('Reason was %s, exiting ip6 hook', reason)
  sys.exit(0)
new_prefix = os.getenv('new_ip6_prefix')
pfx, pfxlen = new_prefix.split('/')
if int(pfxlen) != 56:
  logging.fatal('Prefix length %s is not 56', pfxlen)
  sys.exit(1)
os.system('service radvd stop')
delegation = ipaddress.IPv6Network(new_prefix)
all_subnets = list(delegation.subnets(prefixlen_diff=8))
external_subnet = all_subnets[-1]
external_address = ipaddress.IPv6Address(int(external_subnet.network_address) + 1)
os.system('ip -6 addr add {}/64 dev {}'.format(external_address, os.getenv('interface')))
internal_subnet = all_subnets[0]
internal_address = ipaddress.IPv6Address(int(internal_subnet.network_address) + 1)
os.system('ip -6 addr add {}/64 dev {}'.format(internal_address, 'eth0'))
with open('/etc/radvd.conf', 'w') as fd:
  fd.write(textwrap.dedent('''
    interface eth0 {
      AdvSendAdvert on;
      RDNSS 2001:4860:4860::8888 2001:4860:4860::8844 {};
      DNSSL example.com {};
      prefix %s {
        AdvOnLink on;
        AdvAutonomous on;
      };
    };
    ''') % internal_subnet)
os.system('service radvd start')
sys.exit(0)

## ipv6
/usr/local/sbin/dhclient-ipv6-hook.py
	#!/usr/bin/env python3

	import ipaddress
	import logging
	import os
	import sys
	import textwrap

	reason = os.getenv('reason')
	if reason not in ['BOUND6', 'REBIND6']:
	logging.info('Reason was %s, exiting ip6 hook', reason)
	sys.exit(0)
	new_prefix = os.getenv('new_ip6_prefix')
	pfx, pfxlen = new_prefix.split('/')
	if int(pfxlen) != 56:
	logging.fatal('Prefix length %s is not 56', pfxlen)
	sys.exit(1)
	os.system('service radvd stop')
	delegation = ipaddress.IPv6Network(new_prefix)
	all_subnets = list(delegation.subnets(prefixlen_diff=8))
	external_subnet = all_subnets[-1]
	external_address = ipaddress.IPv6Address(int(external_subnet.network_address) + 1)
	os.system('ip -6 addr add {}/64 dev {}'.format(external_address, os.getenv('interface')))
	internal_subnet = all_subnets[0]
	internal_address = ipaddress.IPv6Address(int(internal_subnet.network_address) + 1)
	os.system('ip -6 addr add {}/64 dev {}'.format(internal_address, 'eth0'))
	with open('/etc/radvd.conf', 'w') as fd:
	fd.write(textwrap.dedent('''
	interface eth0 {
	AdvSendAdvert on;
	RDNSS 2001:4860:4860::8888 2001:4860:4860::8844 {};
	DNSSL example.com {};
	prefix %s {
	AdvOnLink on;
	AdvAutonomous on;
	};
	};
	''') % internal_subnet)
	os.system('service radvd start')
	sys.exit(0)