[avahi] Strange MDNS response from Axis cameras

Lennart Poettering lennart at poettering.net
Thu Feb 9 17:17:50 PST 2006

On Tue, 07.02.06 20:26, Iván Sánchez Ortega (i.sanchez at mirame.net) wrote:
> El Martes 07 de Febrero de 2006 19:03, Marc Krochmal escribió:
> > [...] there's still many poor customers in the world that don't have the 
> > benefits of Zeroconf, [...] This doesn't work when you have two cameras on 
> > the network that both use the same IP [...]
> I can see your point. If Avahi returned the 192.168.x.x IPs for the cameras, 
> I'd be running into that problem. So the right way for Avahi to do this is, 
> as you say, to use the 169.254.x.x addresses...

Actually, Avahi uses the first address record it gets from the device, so this
is somewhat dependant of the device logic, though this is not fully
deterministic, due to cache management and stuff.

BTW: Avahi itself doesn't publish link local addresses if an
interface has both a public and an ipv4ll address assigned. So, if the
the Axis camera would run Avahi, the problem would go away. ;-)

I wonder if we should add some logic to always prefer real addresses
over ipv4ll if we recieve both when browsing for them. Would make some
sense, I guess.

> However, the default network configuration for most Linux boxes is to have 
> just one IP, and not be aware of the network. I guess that making 
> Avahi aware of the routing table to decide whether to get the 169.154.x.x or 
> the 192.168.x.x IP would be a real mess.

Actually, we already have code like that for choosing the outgoing local IP
address for our MDNS traffic.


Lennart Poettering; lennart [at] poettering [dot] net
ICQ# 11060553; GPG 0x1A015CC4; http://0pointer.net/lennart/

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