[Dnsmasq-discuss] rereading configuration files

[Simon Kelley]

On 23/10/12 20:21, Gene Czarcinski wrote:
> It would be useful to libvirt if dnsmasq would reread the configuration
> file and/or the files in the configuration directory upon demand (via
> SIG<something>) as is done for some other files.
>
> Right now, when minor changes are made to a network configuration, it is
> necessary to restart dnsmasq to get those changes adopted.
>
> Is this a possibility this could be done or is this one of those things
> that yes, it could be done, but it would require rewriting most of
> dnsmasq. What types of changes might be accommodated? What if these
> changeable definitions were put into a special configuration file?
>
> Example: v6 or v6 dhcp-range.
>
> Example of something that would unlikely be possible: interface=
>

The most difficult problem is that dnsmasq throws away root permissions 
after start-up, so re-reading the configuration is impossible if acting 
on the new configuration involves anything that needs root (for 
instance, binding sockets to ports <1024 or opening the lease file.)

The philosophy is that things that would be really useful to change, 
without restarting dnsmasq, and certainly don't need root, are re-read 
on SIGHUP. That's dhcp-host information and dhcp-option information in 
special configuration files, /etc/hosts and /etc/ethers, and possibly 
/etc/resolv.conf, if it's not being polled anyway.

For anything else, restarting dnsmasq is a pain-free operation anyway: 
there's very little state and nothing important is lost over a reboot.


Cheers,

Simon.