[avahi] network down does not remove services

[Lennart Poettering]

On Wed, 13.01.10 12:16, ecfu (ecforusers at gmail.com) wrote:

> When a node on my network goes down, I notice my avahi-browse keeps the
> services from the gone node.  Even if I kill the avahi-browse process and
> re-browse the services are still there.   The only way to know that those
> services are gone is to try to resolve them (or at least that is all I have
> found that I can do).  Am I just not waiting long enough?
> 
> Is there a way to know that the node has dropped off and the services have
> been removed?  Does this have to do with my network more than Avahi?  Or is
> there a timeout configuration setting I can set?

If a service becomes unavailable and no goodbye packet is sent for it
(for examnple, because the network went away before the mDNS daemon
that registered it could send out a msg), then the TTL of DNS RRs will
control how long the entry lingers in the other peer's caches.

To put it simply: in modern IP networks there is no way to notice if a
machine dropped off the network. And since for traffic reasons we
cannot continously ping the machine we hence can get notified about
that only after a certain delay. There is no way around it.

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4