[pkg-kde-talk] Re: kdnssd and avahi/libnss-mdns

[Anand Kumria]

Hi Christopher,

On Sat, Jan 14, 2006 at 01:10:05PM -0500, Christopher Martin wrote:
> Hello,
> 
> With avahi's arrival in Sid, the KDE team is enabling zeroconf support in 
> our packages. The new KDE zeroconf-related package, kdnssd, allows users to 
> browse zeroconf-accessible resources, and so should probably depend on (or 
> at least Recommend/Suggest) enough packages to create a reasonable default 
> zeroconf setup for users. Not being too knowledgeable about zeroconf (and 
> not able to test it very well, at the moment), I was hoping you could 
> advise us on what to depend/recommend/suggest for kdnssd.

No problem, I've also CC'd Lennart Poettering who can no doubt also
provide some guidance.

> kdnssd needs avahi-daemon to function at all. avahi-daemon recommends your 
> libnss-mdns; 

avahi doesn't need libnss-mdns, and nor does libnss-mdns but if both are
installed libnss-mdns will use avahi for caching purposes.

You want to have libnss-mdns installed for applications which may not
(indeed ever) link directly to avahi, e.g. telnet; that way things like
'telnet foo.local' will work.

> presumably these two packages would be a sensible core 
> zeroconf setup for kdnssd to depend on (right?). libnss-mdns recommends the 
> package 'zeroconf' as well. It runs in the background, which is something 
> I'd rather not have too many packages do, if they're not critical; but 
> libnss-mdns does recommend it... what do you suggest?

well 'zeroconf' performs the link-local address allocation, which you
definately need.  I have a 0.7 version that I'm testing that
should address most of the current bugs against it.  I hope to have it 
ready to upload later this week.

> Any other packages we should Depend/Suggest/Recommend? avahi-dnsconfd, etc.? 
> Any advice would be much appreciated.
> 
> One last thing you might know about. 
> http://wiki.kde.org/tiki-index.php?page=Zeroconf+in+KDE states 
> that /etc/nsswitch.conf should have 'mdns' on the hosts line _before_ 
> 'dns'. Yet on my system, mdns comes _after_ by default (this was added due 
> to bug #324954. Is this a problem?

Well, I think it should be:

hosts: file mdns dns

because this prevents the local DNS from seeing queries to the '.local'
zone; however it could slow things done as the NSS sub-system waits for
mdns to return a response (which, from memory can take 3 seconds).

I myself have things set to:

hosts: files dns mdns

but I defer to Lennart's opinion on this (perhaps worth following up
to bug#324954 as well).

Anand

-- 
 `When any government, or any church for that matter, undertakes to say to
  its subjects, "This you may not read, this you must not see, this you are
  forbidden to know," the end result is tyranny and oppression no matter how
  holy the motives' -- Robert A Heinlein, "If this goes on --"
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