[Dnsmasq-discuss] Announce: dnsmasq-2.66
Jim Bos
jim876 at xs4all.nl
Thu Apr 18 16:04:13 BST 2013
On 04/18/2013 10:41 AM, Simon Kelley wrote:
> On 17/04/13 16:56, Jim Bos wrote:
>> On 04/17/2013 03:08 PM, Simon Kelley wrote:
>>> Add "constructed DHCP ranges" for DHCPv6. This is intended
>>> for IPv6 routers which get prefixes dynamically via prefix
>>> delegation. With suitable configuration, stateful DHCPv6
>>> and RA can happen automatically as prefixes are delegated
>>> and then deprecated, without having to re-write the
>>> dnsmasq configuration file or restart the daemon. Thanks to
>>> Steven Barth for extensive testing and development work on
>>> this idea.
>>
>> Simon,
>>
>> Excited about this new feature as I now have a hardcoded prefix (which
>> fortunately my ISP doesn't change very often).
>>
>> However, either I'm doing something wrong or there is something not
>> working:
>>
>> I changed
>> dhcp-range=2001:XXX:YYYY:ZZ::, ra-stateless, ra-names
>> enable-ra
>>
>> to
>>
>> dhcp-range=::,constructor:eth0, ra-stateless, ra-names
>> enable-ra
>>
>> And in the log I see this:
>>
>> Apr 17 17:11:24 dnsmasq[8972]: compile time options: IPv6 GNU-getopt
>> no-DBus i18n IDN DHCP DHCPv6 no-Lua TFTP no-conntrack ipset auth
>>
>> Apr 17 17:11:24 dnsmasq-dhcp[8972]: DHCPv6 stateless on ::, template for
>> eth0
>> Apr 17 17:11:24 dnsmasq-dhcp[8972]: DHCPv4-derived IPv6 names on ::,
>> template for eth0
>> Apr 17 17:11:24 dnsmasq-dhcp[8972]: router advertisement on ::, template
>> for eth0
>> Apr 17 17:11:24 dnsmasq-dhcp[8972]: IPv6 router advertisement enabled
>>
>> However, NO RA's are being sent on eth0 :-(
>>
>>
>> For reference, changing back the line I get
>>
>> Apr 17 17:34:25 dnsmasq[9198]: compile time options: IPv6 GNU-getopt
>> no-DBus i18n IDN DHCP DHCPv6 no-Lua TFTP no-conntrack ipset auth
>>
>> Apr 17 17:34:25 dnsmasq-dhcp[9198]: DHCPv6 stateless on
>> 2001:XXXX:YYYY:ZZ::
>> Apr 17 17:34:25 dnsmasq-dhcp[9198]: DHCPv4-derived IPv6 names on
>> 2001:XXXX:YYYY:ZZ::
>> Apr 17 17:34:25 dnsmasq-dhcp[9198]: router advertisement on
>> 2001:XXXX:YYYY:ZZ::
>> Apr 17 17:34:25 dnsmasq-dhcp[9198]: IPv6 router advertisement enabled
>>
>> Apr 17 17:34:39 dnsmasq-dhcp[9198]: RTR-ADVERT(eth0) 2001:XXXX:YYYY:ZZ::
>> Apr 17 17:34:45 dnsmasq-dhcp[9198]: RTR-ADVERT(eth0) 2001:XXXX:YYYY:ZZ::
>>
>>
>> Jim
>>
>>
>
> You need the host-identifier part of the address in the dhcp-range to
> match the host identifier part of the address on the local interface. So
> if your prefix is 2001:XXX:YYYY:ZZ:: and the address of eth0 is
> consequently set to, say
>
> 2001:XXX:YYYY:ZZ::1
>
> then you need a dhcp-range statement of
>
> dhcp-range=::1 ,constructor:eth0, ra-stateless, ra-names
>
>
> The reason for this is that once advertisements are being sent for
> 2001:XXX:YYYY:ZZ:: then eth0 can easily end up with SLAAC address on
> that prefix as well as its hard-coded one. If any address in the prefix
> was ok to trigger RAs, then you could never get rid of a prefix simply
> deleting the original address from the interface.
>
>
> Cheers,
>
> Simon.
>
Ah, ok. That does indeed work.
However, having a known address isn't as trivial as you might expect, I
get the network via prefix delegation on eth1 and that automatically set
on eth0.
Using wide-dhcp6c with config simular to this:
==
interface eth1 {
send ia-pd 0;
send rapid-commit;
script "/usr/bin/dhcp6c-state";
request domain-name-servers;
};
id-assoc pd 0 {
prefix-interface eth0 {
sla-id 1;
sla-len 2;
};
};
==
I.e. I actually don't manually set an IPv6 IP on eth0. But specifying in
the dhcp-range command the SLAAC interface-id part from the eth0
interface does seem to work, and that's a fixed (mac based) identifier.
BTW:
Having above prefix delegation integrated in dnsmasq would really be a
cool feature ! More and more people get native IPv6, and PD seems the
way this is usually done, but integrating some sort of dhcp-client on an
upstream interface with dnsmasq serving the downstream interface is
confusing many people.
Jim
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