[virt-tools-list] virt-viewer over ssh

[Dave Allan]

On Wed, Nov 07, 2012 at 09:11:10AM +0100, Daniel P. Berrange wrote:
> On Tue, Nov 06, 2012 at 10:42:20PM -0500, Dave Allan wrote:
> > On Tue, Nov 06, 2012 at 04:14:43PM -0500, Dave Allan wrote:
> > > On Tue, Nov 06, 2012 at 08:11:07PM +0100, Guido Günther wrote:
> > > > On Tue, Nov 06, 2012 at 09:56:19AM -0500, Dave Allan wrote:
> > > > > I'm having trouble with virt-viewer not connecting to a VM on a remote
> > > > > host over SSH.  It connects, briefly gives me a black VM display, and
> > > > > then says that the remote disconnected.  I've noticed a few paches on
> > > > 
> > > > That was basically what I was seeing IIRC. I've roled my patches into
> > > > the Debian package:
> > > > 
> > > > 	http://packages.debian.org/experimental/virt-viewer
> > > > 
> > > > (in case you have a vm around to test). I didn't get around to dig
> > > > deeper into Christophe comments due to a lack of free time yet though.
> > > > Cheers, 
> > > >  -- Guido
> > > 
> > > I made some progress understanding what's happening, at least on my
> > > system.  Bisecting shows commit
> > > 56b0217c626349748c5cc6f2fbccfa6a905f75a4 to be the point at which
> > > virt-viewer stops connecting to my VM.  After looking at that commit,
> > > I was able to get virt-viewer to connect by adding listen='localhost'
> > > to my VM's graphics element.  I'm afraid I haven't had time today to
> > > dig into exactly what the effect of that patch is so I can't propose
> > > an alternative.
> > 
> > I think I see what's happening:
> > 
> > In the default qemu.conf VNC is configured to listen on 127.0.0.1.
> > When virt-viewer finds no listen address in the domain xml it
> > substitutes the hostname from the connect URI and tries to use nc to
> > connect to it, but in the default configuration the guest isn't
> > listening on that IP, it's only listening on 127.0.0.1 so the
> > connection fails.  Either specifying a listen address or changing
> > qemu.conf to allow the guest to listen on 0.0.0.0 will allow
> > connections to succeed.
> > 
> > The problem is tricky since I don't see how the client can determine,
> > in the absence of a listen tag in the graphics element, what IP the
> > guest is actually listening on.  However, the default qemu.conf
> > specifies localhost, so it seems to me that the behavior prior to the
> > change in 56b0217 was more likely to be correct as it matches the
> > server default.
> > 
> > At this point, I favor reverting 56b0217, but I'm curious to see
> > what other people think.
> 
> You're only considering the case where virt-viewer is using SSH and
> thus local to the VM. In the non-SSH case, virt-viewer is connecting
> to a remote host IP directly and thus 'localhost' is absolutely wrong.

That's a good point; in the SSH case, though, the default behavior
doesn't work.  Would you object to tying the behavior to the
transport?

Dave



> Daniel
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