[Dnsmasq-discuss] dnsmasq lease file not updating properly

Sachin Garg s.garg.computer at gmail.com
Fri Jun 17 04:37:11 BST 2016


Hi,

My dnsmasq.conf contains the following. Even though SLAAC is enabled,
the hosts that are supposed to get static DHCPv6 leases get them as
configured. I also do not have the IPv6 line that you have. I am using
the "constructor:<interface>" for it to pick up the prefix.

> # IPv6
> dhcp-range=lan,::F000:0000,::FFFF:FFFF, constructor:br-lan, slaac, 64, 12h
> enable-ra
> 
> # Static DHCPv6 IP addresses
> dhcp-host=<MAC address>,<IPv4 address>,<hostname>,[::dead:beef]

>From the manual
(http://www.thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html):

> slaac tells dnsmasq to offer Router Advertisement on this subnet and 
> to set the A bit in the router advertisement, so that the client
> will use SLAAC addresses. When used with a DHCP range or static DHCP 
> address this results in the client having both a DHCP-assigned and a 
> SLAAC address.

Further down:

> ra-names enables a mode which gives DNS names to dual-stack hosts
> which do SLAAC for IPv6. Dnsmasq uses the host's IPv4 lease to derive
> the name, network segment and MAC address and assumes that the host
> will also have an IPv6 address calculated using the SLAAC algorithm,
> on the same network segment. The address is pinged, and if a reply is
> received, an AAAA record is added to the DNS for this IPv6 address.
> Note that this is only happens for directly-connected networks, (not
> one doing DHCP via a relay) and it will not work if a host is using
> privacy extensions. ra-names can be combined with ra-stateless and
> slaac.

(I will be testing this now and will report back)

However, it works only when MAC id is provided, not with DUID. (I think
this is because I was unable to get a cross-platform way to get the DUIDs).

Another thing to note is that *not* all devices are capable of
requesting and accepting an IPv6 address via DHCPv6. Most notably
Android. See the following:

https://code.google.com/p/android/issues/detail?id=32621

A workaround that is this:
https://play.google.com/store/apps/details?id=org.daduke.realmar.dhcpv6client


However, sadly that seems to work (for me) only when manually initialised.

So, is it a possibility that you are only testing your config with
Android machines?

Hope this helps. Off-topic: I am assuming that you are in India.
Wondering how you are getting IPv6 connectivity?

Best,
Sachin

On Wednesday 25 May 2016 09:47 AM, Gopi Krishna M wrote:
> Hi All,
> 
> I have been using dnsmasq 2.70 vesrion as dhcp server for ipv4 and 
> ipv6. My lease file is not getting updated properly when running 
> dnsmasq. It is updating properly for ipv4  but not correct for ipv6.
> 
> #cat /etc/dnsmasq_new.leases 2082886681 00:80:48:4b:83:12 
> 192.168.10.161 host-mysy * duid 
> 00:01:00:01:43:b8:34:78:00:80:a3:a0:bb:38 2082843195 1212908306 
> *18:2001:2002:2003:: ** 00:01:00:01:00:80:10:7e:ea:09
> 
> It is marked as above and its actual lease ip is 
> *2001:2002:2003::10a* but its not showing. Meanwhile even if we 
> connect multiple clients then the same *18:2001:2002:2003:: *is 
> getting repeated. Meanwhile it is not showing the proper mac also.
> 
> for your kind ref:
> 
> config file # cat /etc/dnsmasq_gateway.conf interface=lan0 
> except-interface=lo bind-interfaces dhcp-range=192.168.10.20, 
> 192.168.10.254, 14h dhcp-range=2001:2002:2003::105, 
> 2001:2002:2003::110, 64, 14h enable-ra
> 
> Interface IP: 192.168.10.1 IPv6: 2001:2002:2003::100
> 
> running as *dnsmasq -C /etc/dnsmasq_gateway.conf -l 
> /etc/dnsmasq_new.leases
> 
> 
> * Please tell your suggestions.
> 
> Note: Clients are getting IPv4 and IPv6 properly. Everything is fine
>  apart from updating the lease file. Compiled for ARM(linux 3.10)
> 
> Thanks in advance.
> 
> Regards, Gopi krishna M 
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