[Dnsmasq-discuss] dnsmasq listening on 0.0.0.0

[Simon Kelley]

Robert Diamond wrote:
> I know that dnsmasq likes to do it's ip filtering in the user-space,
> but I'd rather be able to specify ip's for it to bind to, that show up
> in netstat. Maybe I'm just a little anal about that stuff, but it just
> doesn't look right to me :) (Yahp, I've even added iptables rules in my
> never ending effort to be crazy ^.~)
> 
> http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2007q2/001322.html
> 
> Shows some options to get the dns server part binding to an ip via the
> kernel. The dhcp server will still look like it's listening on all ip's
> (as will the dns forwarder; and possibly tftp server?).
> 
> $ netstat -anlpA inet
> <snip>
> udp  0  0  127.0.0.1:53      0.0.0.0:*  30768/dnsmasq
> udp  0  0  192.168.1.1:53    0.0.0.0:*  30768/dnsmasq
> udp  0  0  0.0.0.0:67        0.0.0.0:*  30768/dnsmasq
> udp  0  0  0.0.0.0:5353      0.0.0.0:*  30768/dnsmasq
> 
> [Internet interface ip]:5353 is where forwarded dns queries get sent
> back to. I'd like "0.0.0.0:67" to show 192.168.1.1:67 and 0.0.0.0:5353
> to show a.x.y.z:5353 (a.x.y.z being my internet/external ip). There was
> a patch somewhere in this list, that has been added to the code a few
> versions back that allowed multiple instances of dnsmasq to bind to
> 0.0.0.0. I'd just prefer if there was a 'listen-dns; listen-dnsforward;
> listen-dhcp' (and maybe a 'listen-tftp') option that couples with
> 'bind-interface' to give my desired results.
> 
> I'm going to be doing some looking over the code in an effort to
> include this functionality in a patch, but if someone else has done the
> work already, or if I've somehow missed an available option in my conf
> file please let me know :)
> 

Splitting up the question:

DNS listening port - you've already solved that, with "bind-interfaces"
DNS upstream port  - That's possible, if you specify the servers via a
"server=" line in /etc/dnsmasq.conf then you can specify the local
address (and port) too.

server=1.2.3.4 at 192.168.1.1#5353

tftp: "bind-interfaces" works for that too.

DHCP that always binds the wildcard - doing otherwise _may_ be possible,
but be prepared for much testing and strange behaviour. For instance,
you need to be able to receive packets whose destination address in
255.255.255.255.


Cheers,

Simon.