[avahi] Unicast Query Requests

Alastair Tse liquidx at gentoo.org
Wed Aug 2 10:07:16 PDT 2006

Hi All,

I was wondering if the developers were planning to implement the option
in the multicast-dns RFC section 6.5 to allow avahi-daemon to request
unicast responses rather than the default multicast responses.

The reason I ask this is because on my home network, I have a couple of
Macs and Linux machines that are all wireless through a Linksys WRT54G
wireless router. The problem is that multicast is broken on this router
over the wireless interface.[1] This means, my Linux machine can try to
make requests to the local network for DAAP shares through avahi, and
the Mac replies accordingly but the response never reaches the Linux
machine beacuse (a) multicast packets are not routed properly, and (b)
promiscious mode does not work on the linux ipw2100 drivers.

I notice that iTunes on Mac OS X will request multicast dns replies with
the unicast response flag set for it's query, so on my network there is
a weird asymmetry where my DAAP server is resolvable by the Mac, but my
Mac's iTunes DAAP server is not resolvable by the Linux machine.

I've had a quick run around the code and documentation and can see
possibly where the changes may be made. I'm just really asking whether
the developers were considering adding this feature, and if they were
willing to accept a patch that implements this feature, and if not, why
not. Or of course, maybe I'm missing something bleedingly obvious in my
home network setup that is causing this problems, and I'm just jumping
into the deep end to solve a simple problem.



[1] Sidenote: Multicast packets only get forwarded on the wired
interface even if it originates from the wireless interface by their
poorly implemented igmprt program. For some reason they've chosen a
simple incomplete implementation rather than mrouted.

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