[Dnsmasq-discuss] Re: Mac client constant reverse query on itself

[Eddy Geez]

Bob Davis wrote:
> Every 10-15 seconds the Mac performs a reverse DNS query on it's own address.  As far as I can tell, DNSMASQ seems to reply correctly with the host name but then 15 seconds later it queries again.  Not sure if this has to to with Bonjour or not.  IPV6 is turned off on the Mac.

It's not just you.

We're running dnsmasq and *ALL* of the Macs do this -- MacBooks,
iMacs, MacPros and yes, even the iPhone!

As a DNS admin, it is extremely annoying. DNS query logging provides
valuable insights, but logs full of PTR queries on the local LAN from
all the Mac OS X boxen, well, sucks. :)

I was actually going to send a feature request to Simon to address this issue:

First, would be a new option akin to
"dont-log-ptr-queries-for-local-addresses". (I was hoping that there
would be something that could be tweaked on the Mac side to prevent
these constant PTR queries, but even if there was some "hack", there'd
be no way to apply it to the iPhones on the network.)

Second, I'd like to see an option to log only the queries themselves,
but not the replies (something like "dont-log-query-replies"). This is
how BIND does query logging.

But...

Rune Kock wrote:
> Setting the local-ttl option might help.

seems to have resolved the problem! I set this to 3600 (one hour) and
the persistent queries from the Macs and iPhones stopped once dnsmasq
was restarted. Woo-hoo!

Since the default is apparently zero for some reason, what are the
implications of having this set to a non-zero value? Is a 3600 TTL any
worse than it would be if you had all local host information in a
regular (as opposed to an /etc/hosts file) DNS-supplied zone?

>  In any case, I don't think
> you need to be concerned about this behaviour, unless the bandwidth
> between the mac and the dnsmasq-machine is critically low.

True, but the logs are not pretty when you have a bunch of Macs doing
PTR queries every 10-15 seconds!

Anyway, I don't think my first enhancement request is necessary any
more, but I'd still like to see an option to log queries without
logging the reply.

Thanks and regards,
Eddy