Re: Minimizing DNS-SD queries (was unescaped double quotes in TXT record)

On Tue, 25 May 2010, Daryl Tester wrote:

>> I later found out that the bulk of these DNS-SD queries were as a
>> result of MacOSX client misconfigurations, and fixing them seems to
>> quell some of the query storms.  Minimizing DNS-SD queries still
>> seem a worthwhile goal though.
>
> The problem here appears to be broken clients - how can you minimise
> what the clients are sending at the server end?  If they're not
> taking NXDOMAIN as a hint, then perhaps taking it up to a DoS level
> might be an appropriate solution?  (said in semi-jest).

You are right that fixing the client is the right solution.

(If anyone is interested, I think the client has 2 of our DNS servers
listed: one had the correct IP and the other one was wrong.  The DNS
server with the correct IP was the one receiving multiple queries per
second for DNS-SD records.  I am not sure whether correcting the IP
address, or removing all but one of the DNS servers calmed it down).

Even when it's working correctly, every MacOSX client polls the DNS
server for DNS-SD records.  I was hoping that by creating a placebo
DNS-SD record with a really long TTL, it would reduce the volume of
these useless queries.

I used to kill the Bonjour service, but with the later MacOSX (>=10.6),
the unicast and multicast DNS are now done by the same service daemon,
so disabling Bonjour disables DNS altogether.

MacOSX are noisy machines, broadcasting a plethora of
CUPS/SNMP/mDNS/DNS-SD/Microsoft-Office-Licensing/etc broadcasts.
They really need "Shut Up!" configuration button.

Matthew Dempsky <[email protected]> also contributes:

> &_dns-sd._udp.your.domain:127.0.0.1:a
> &_dns-sd._udp.d.c.b.a.in-addr.arpa:127.0.0.1:a

I'll give it a shot, although I'm not too hopeful since clients never
seem to ask for NS records.

Joseph Tam <[email protected]>