[Dnsmasq-discuss] setting up dynamic DNS?

Simon Kelley simon at thekelleys.org.uk
Tue Sep 11 12:18:06 BST 2007


Adam Hardy wrote:
> It's the fqdn.fqdn line that causes the problem! I took that out of the
> dhclient.conf on the clients and now have just
> 
> send host-name gondor;
> 
> which works (massive grin!) - thanks!


FQDN overrides hostname (this makes some sense since FQDN is a newer
facility, so one can assume that a FQDN is authoritative, with hostname
left only for servers which don't implement FQDN).


It would help me if you could just check that FQDN works with the
correct domain. The last logs you posted seemed to indicate that the
problem was just a mismatch between the domain part of the FQDN and the
domain configured in dnsmasq. If the FQDN was indeed correct, then there
might be a bug in FQDN handling in dnsmasq. If so, let me know and give
me the version of dnsmasq you're using and I'll take a look.


Cheers,

Simon.


> 
> But there is one more niggle: it looks as though dnsmasq on isengard is
> asking the internet name-server where isengard is when another machine
> asks it to resolve its hostname.
> 
> isengard dnsmasq[2716]: query[AAAA] isengard.localdomain.net from
> 192.168.0.234
> isengard dnsmasq[2716]: forwarded isengard.localdomain.net to 194.74.65.69
> isengard dnsmasq[2716]: forwarded isengard.localdomain.net to 194.74.65.69
> isengard dnsmasq[2716]: query[AAAA] isengard.localdomain.net from
> 192.168.0.234
> isengard dnsmasq[2716]: forwarded isengard.localdomain.net to 194.74.65.69
> isengard dnsmasq[2716]: query[A] isengard.localdomain.net from
> 192.168.0.234
> isengard dnsmasq[2716]: /etc/hosts isengard.localdomain.net is 192.168.0.2
> isengard dnsmasq[2716]: query[A] isengard.localdomain.net from
> 192.168.0.234
> isengard dnsmasq[2716]: /etc/hosts isengard.localdomain.net is 192.168.0.2
> isengard dnsmasq[2716]: query[PTR] 2.0.168.192.in-addr.arpa from
> 192.168.0.234
> isengard dnsmasq[2716]: /etc/hosts 192.168.0.2 is isengard.localdomain.net
> isengard dnsmasq[2716]: query[A] isengard.localdomain.net from
> 192.168.0.234
> isengard dnsmasq[2716]: /etc/hosts isengard.localdomain.net is 192.168.0.2
> isengard dnsmasq[2716]: query[PTR] 2.0.168.192.in-addr.arpa from
> 192.168.0.234
> isengard dnsmasq[2716]: /etc/hosts 192.168.0.2 is isengard.localdomain.net
> isengard dnsmasq[2716]: query[PTR] 234.0.168.192.in-addr.arpa from
> 127.0.0.1
> isengard dnsmasq[2716]: DHCP 192.168.0.234 is gondor.localdomain.net
> isengard dnsmasq[2716]: query[A] gondor.localdomain.net from 127.0.0.1
> isengard dnsmasq[2716]: DHCP gondor.localdomain.net is 192.168.0.234
> 
> 
> 
> Jan 'RedBully' Seiffert on 10/09/07 21:54, wrote:
>> Adam Hardy wrote:
>>> Thanks again for the help. Config files appended at bottom for
>>> reference.
>>>
>>> Jan 'RedBully' Seiffert on 10/09/07 16:45, wrote:
>>>> Adam Hardy wrote:
>>> adam at gondor:~$ cat /etc/resolv.conf
>>> search localdomain.net
>>> nameserver 192.168.0.2
>>
>> Ok, looks good.
>>
>>
>>>> Is their default gateway set to isengard? (route -n should say so)
>>> Yes
>>>
>>
>> Ok, so this works.
>>
>>>> What's printed to isengards system logs when a client gets an IP?
>>> isengard dnsmasq[26803]: reading /etc/resolv.conf
>>> isengard dnsmasq[26803]: using nameserver 194.74.65.69#53
>>> isengard dnsmasq[26803]: ignoring nameserver 127.0.0.1 - local interface
>>> isengard dnsmasq[26803]: Ignoring DHCP host name arnor.localdomain
>>> because it has an illegal domain part
>>
>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>
>> here is the problem
>>
>> [snip]
>>> /var/lib/misc/dnsmasq.leases has no hostnames in it.
>>>
>>> Hmmm. Doesn't look good does it? :(
>>
>> No no, all working within it's spec IMHO ;)
>>
>>> What do you think could be wrong
>>> with it? There seems to be something wrong with the hostname I'm sending
>>> it ('illegal domain name part')
>>
>> dnsmasq is basicaly fine with the hostname, it does not like the domain
>> you're client is sending.
>> It tries to protect you from forgery.
>> If a client would record itself as www.google.com, and dnsmasq would
>> believe this, it would forward all your LAN machines for www.google.com
>> to this machine.
>>
>> Somehow the "domain=localdomain.net" doesn't do the trick.
>>
>> But when looking again, arnor (and maybe the other machines) is sending
>> "$HOSTNAME.localdomain" as hostname?
>>
>> the final ".net" seems to get eaten...
>>
>> May you can remove all the references to your domain from your
>> dhclient.conf, for a test.
>>
>>> adam at gondor:~$ cat /etc/dhcp3/dhclient.conf |grep -v ^#
>>>
>>> send host-name "gondor.localdomain.net";
>>
>> This should be the hostname only, or?
>>
>>> send dhcp-lease-time 3600;
>>> supersede domain-name "localdomain.net";
>>
>> drop this, dnsmasq should give out the right domain
>>
>>> request subnet-mask, broadcast-address, time-offset, routers,
>>>         domain-name, domain-name-servers, host-name,
>>>         netbios-name-servers, netbios-scope, interface-mtu;
>>
>>> send fqdn.fqdn "gondor.localdomain.net";
>>> send fqdn.encoded on;
>>> send fqdn.server-update off;
>>>
>>
>> drop all this fqdn stuff for a test
>>
>> Which version of dnsmasq is this?
>>
>>> and it also seems to be forwarding the
>>> query for arnor.localdomain.net up to the internet nameserver.
>>>
>>
>> Thats because dnsmasq could not find an entry in it's own db, and thinks
>> maybe the upstream server know something about it.
>>
>> To tell dnsmasq that localdomain.net is local, and it should not ask
>> upstream about it, you may want to add:
>> local=/localdomain.net/
>> to your dnsmasq.conf
>>
>>
>>> Adam
>>>
>>
>> Grettings
>>     Jan
>>
>>> PS here are the files for reference if they help:
>>>
>> [snip]
>>> isengard:~# cat /etc/dnsmasq.conf |grep -v ^# |grep -e ^[[:alnum:]]
>>> domain-needed
>>> bogus-priv
>>> filterwin2k
>>> domain=localdomain.net
>>> dhcp-range=192.168.0.3,192.168.0.254,12h
>>> dhcp-option=1,255.255.255.0
>>
>>
>>> dhcp-option=3,192.168.0.2
>>> dhcp-option=6,192.168.0.2
>> normally you should be able to put 0.0.0.0 in here, so dnsmasq will
>> automatically fill in the right value for your interface
>>
>>> log-queries
>>
> 
> 
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