Odd DNS requests

[Ian Smith]

On Sat, 28 Feb 2009, George Davidovich wrote:
 > On Sat, Feb 28, 2009 at 04:32:47PM +1100, Ian Smith wrote:
 > > Recently we've had a Mac notebook of some sort on our LAN, that likes
 > > to make these DNS queries from time to time, to no avail, as noticed
 > > on a filtering bridge between the LAN and the router+DNS at
 > > 192.168.0.1:
 > > 
 > > 16:13:05.020397 192.168.0.59.53207 > 192.168.0.1.53:  63162+ PTR? b._dns-sd._udp.0.0.168.192.in-addr.arpa. (57) [tos 0x18]
 > > 16:13:05.021093 192.168.0.1.53 > 192.168.0.59.53207:  63162 NXDomain* 0/1/0 (128) (DF)
 > > 16:13:05.215790 192.168.0.59.64633 > 192.168.0.1.53:  61059+ PTR? db._dns-sd._udp.0.0.168.192.in-addr.arpa. (58) [tos 0x18]
 > > 16:13:05.216469 192.168.0.1.53 > 192.168.0.59.64633:  61059 NXDomain* 0/1/0 (129) (DF)
 > > 16:13:05.226242 192.168.0.59.61635 > 192.168.0.1.53:  6749+ PTR? r._dns-sd._udp.0.0.168.192.in-addr.arpa. (57) [tos 0x18]
 > > 16:13:05.226789 192.168.0.1.53 > 192.168.0.59.61635:  6749 NXDomain* 0/1/0 (128) (DF)
 > > 16:13:05.237319 192.168.0.59.56300 > 192.168.0.1.53:  21450+ PTR? dr._dns-sd._udp.0.0.168.192.in-addr.arpa. (58) [tos 0x18]
 > > 16:13:05.237842 192.168.0.1.53 > 192.168.0.59.56300:  21450 NXDomain* 0/1/0 (129) (DF)
 > > 16:13:05.248440 192.168.0.59.60806 > 192.168.0.1.53:  10032+ PTR? lb._dns-sd._udp.0.0.168.192.in-addr.arpa. (58) [tos 0x18]
 > > 16:13:05.249252 192.168.0.1.53 > 192.168.0.59.60806:  10032 NXDomain* 0/1/0 (129) (DF)
 > > 
 > > What exactly are these hoping to discover, and what needs turning off
 > > in the Mac's setup (OSX, most likely a recent version) to quell them?
 > 
 > DNS-Based Service Discovery:
 > <http://files.dns-sd.org/draft-cheshire-dnsext-dns-sd.txt>
 > 
 > Skip to the section titled: 
 > 
 > 	12. Discovery of Browsing and Registration Domains (Domain
 > 	Enumeration)'
 > 
 > when it gets boring.  There may be something more recent or more
 > authoritative, but that's what I have bookmarked.  

Thankyou George.  Not tonight's bedtime reading but I'll get through it.

 > As for configuring the notebook, etc., perhaps someone else can chime
 > in.

On the face of it, it seems not a bad idea.  I'm not averse to using DNS 
in ways that some may consider impure, being more bothered by things I 
don't understand :)  I'll check the Mac's mDNS setup though, there's no 
sense it banging away forever on NXDOMAIN responses, that often anyway.

cheers, Ian