Salut and Suspend/Resume issues
ypod at mit.edu
Tue Feb 19 13:10:22 EST 2008
If the time between a resume and a suspend is shorter than the time
period between consecutive presence updates (which is several minutes),
then the presence service should not even know that a suspend happened
in between. Then why are icons disappearing?
Sjoerd Simons wrote:
> It's avahi that's giving you problems. Or more precisely, it can't cope with
> the fact that during suspend it's essentially deaf.
> If we want to make presence on the local lan work in a way to allow the host
> CPU to sleep most of the time we need both a different presence protocol (some
> people are already working on this). And we need some assistence from the
> wireless card to keep track of presence while the host cpu is asleep.. But i
> don't see this happening soon.
>> Should we be setting the wireless module to wake on multicast, so that we can
>> respond to whatever traffic the presence service is using to see who's
> Yes please do. And if possible only to the multicast traffic the host is
> actually interested in.
> I'm pretty sure i mentioned this before, if you don't wake up on multicast
> traffic your completely breaking the way mdns works. And thus the notions of
> presence in a link-local network. Also if you don't wake up on multicast then
> activities in a local lan will break as they won't receive data and other
> metainformation from other participants.
>> Should it be using unicast traffic instead?
>> What is it in Avahi's code path that causes its peer list to be emptied on
> Given that it's long suspends that have this problem. It's probably the fact
> that the TTL for all contacts has run out, that is causing avahi to flush the
> peer list. After which it needs to rediscover all of them. Which is a valid
> thing to do, if you've been away for quite some time you have no idea who is
> still around.
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