[libvirt] Turning off libvirtd mdns by default

Dave Allan dallan at redhat.com
Tue Mar 27 14:21:49 UTC 2012


On Tue, Mar 27, 2012 at 10:17:02AM +0100, Daniel P. Berrange wrote:
> On Mon, Mar 26, 2012 at 09:31:44PM +0200, Stef Walter wrote:
> > In the GNOME UI we'd like to make use of Avahi discovery and name
> > resolution "out of the box". A typical use case is for discovery of
> > printers that are advertised using MDNS. This should work even on
> > potentially 'hostile' networks such as a wireless access point in a
> > print shop or airport. It should work without user configuration.
> > 
> > https://fedoraproject.org/wiki/Desktop/Whiteboards/AvahiDefault
> > 
> > In order to turn on Avahi by default, and make it work by default,
> > we'd like to make it possible to use Avahi without advertising any
> > information to the network by default. Advertising information to
> > the network (even the host name) without the user's configuration or
> > consent is a privacy issue.
> > 
> > libvirtd advertises itself via MDNS on the network by default. I
> > understand that MDNS discovery of libvirtd is really handy in many
> > cases.
> > 
> > However since one has to configure network access in libvirtd anyway
> > -- none of the access methods work "out of the box" to my
> > understanding -- I'd like to suggest turning off libvirtd's MDNS
> > publishing by default. As part of setting up libvirtd for network
> > access, the user would turn on mdns_adv.
> 
> Actually, it is possible to remotely connect to any libvirtd instance
> using an SSH tunnel, which works out of the box. Only the direct,
> non-tunnelled TLS/SASL based connections require manual setup.
> 
> But since, IIUC, the default Fedora firewall setup blocks mDNS,
> it still wouldn't work out of the box.
> 
> > I hope that makes sense. Let me know if I've gotten something wrong.
> > 
> > Would you accept a patch to do this? Or would you suggest that we
> > try and do this downstream in the Fedora/RHEL packages instead?
> 
> Our policy for Fedora / RHEL is to not change upstream behaviour, so this
> kind of policy decision should be resolved here.
> 
> 
> While apps like virt-manager do have the ability to use mDNS to locate
> remote libvirtd servers, my gut feeling is that it is probably rarely
> used. So given the need to tradeoff off out of the box usability against
> privacy concerns, I think we could probably say turning off mDNS by
> default is acceptable.
> 
> What do others think ?

I agree with you that turning off mDNS by default is probably ok.

Dave

> Daniel
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