[Libvir] RFC: Broadcast our presence with avahi

[Daniel P. Berrange]

On Fri, Sep 14, 2007 at 10:20:53AM +0200, Gerd Hoffmann wrote:
>   Hi,
> 
> >  - I arbitrarily picked a service type of '_libvirtd._tcp'. The docs on
> >    picking service types seem non-existant on Avahi website, but it seems
> >    to be common to use service name from /etc/services and protocol both
> >    prefixed with _.
> 
> Cool.
> 
> >  - I want to advertise whether the server is configured with TLS certs or
> >    not, so remote clients can automatically choose to use SSH urls with
> >    the remote driver if neccessary.
> 
> Hmm.  Shouldn't work that simply by port number?  The tls and non-tls
> connections use different port numbers, right?  The ssh tunneling case
> is a bit icky though ...

Yes, actually the port number should be sufficient, even for the SSH case.
In the latter we just advertise _libvirtd._tcp with port 22. Though I think
we might still want to include the info about whether it requires TLS or
not, since as Rich mentions the user can override the default port number

> And while you are at it, how about announcing the vm vnc screens too
> (assuming they are not bound to the loopback interface only) as _rfb._tcp?

I thought about that too. It is easy for VNC provided by the regular
QEMU driver, since libvirtd manages all the QEMU instances, so knows when
they are running. Its harder for Xen since we don't know when they're
running currently.  We'd have to add in the APIs in the driver for getting
notifications back - which would let us use xenstore watches to discover
when Xen instances come & go. To be honest I want this now anyway for 
virt-manager so we can reduce the amount of polling we have todo to monitor
VMs on a remote connection, so its probably worth trying this now (at least
for the internal API to start off with).

Dan.
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