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

[Lennart Poettering]

On Wed, 18.01.06 03:23, Anand Kumria (wildfire at progsoc.org) wrote:

> > 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.

I don't know how kdnssd works internally, but it might *require*
libnss-mdns to work sensibly. Better ask Jakub Stachowski about
that. I'll forward this Email to him.

> > 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.

I don't think kdednssd should depend on "zeroconf". If it all, a
Suggest or Recommend should suffice. 

In addition I don't think that kdednssd should depend even on
avahi-daemon. The avahi client libraries return a proper error code
when no running daemon is found, so in case kdednssd becomes a hard
dependency of the KDE desktop and people don't like DNS-SD, they don't
need to install the daemon.

> > Any other packages we should Depend/Suggest/Recommend? avahi-dnsconfd, etc.? 
> > Any advice would be much appreciated.

My suggestion is to depend on avahi-client. And suggest/recommend
avahi-daemon and libnss-mdns. However, since avahi-client recommends
avahi-daemon, and avahi-daemon in turn recommends libnss-mdns you may
even omit those suggest/recommend lines entirely.

Hence i would suggest to just add a dependency to avahi-client and
that's it. 

(Unless Jakub says that libnss-mdns is required for avahi-kdnssd to
work properly, in which case you should add another hard dep on that.)

> > 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

I think it should be "file mdns4 dns". Someone should file a bug about this.

> 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).

By default, nss-mdns will only lookup services in the ".local"
zone. Hence this would not result in any significant delay for normal
(unicast DNS) name lookups.

Lennart

-- 
Lennart Poettering; lennart [at] poettering [dot] net
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