[libvirt] error: server response too large

[Daniel P. Berrange]

On Mon, Sep 30, 2013 at 04:24:49PM +0100, Daniel P. Berrange wrote:
> On Mon, Sep 30, 2013 at 05:23:33PM +0200, Michal Privoznik wrote:
> > On 30.09.2013 17:02, Claudio Bley wrote:
> > > Hi.
> > > 
> > > When trying to do a screenshot of a remote domain connected via
> > > qemu+tcp (for testing purposes only), I receive this error:
> > > 
> > > ----------------------------------------------------------------------
> > > virsh -c qemu+tcp://dev/system
> > > Welcome to virsh, the virtualization interactive terminal.
> > > 
> > > Type:  'help' for help with commands
> > >        'quit' to quit
> > > 
> > > virsh # version
> > > Compiled against library: libvir 0.9.8
> > > Using library: libvir 0.9.8
> > > Using API: QEMU 0.9.8
> > > Running hypervisor: QEMU 1.5.1
> > > 
> > > virsh # screenshot 2 /tmp/screendump
> > > error: could not receive data from domain 2
> > > error: packet 1048600 bytes received from server too large, want 262144
> > > 
> > > virsh # 2013-09-30 14:47:05.158+0000: 21646: info : libvirt version: 0.9.8
> > > 2013-09-30 14:47:05.158+0000: 21646: warning : virNetClientIncomingEvent:1660 : Something went wrong during async message processing
> > > ----------------------------------------------------------------------
> > > 
> > > I'm using Ubuntu LTS 12.04.3, latest version in the repo which is
> > > 0.9.8-2ubuntu17.13.
> > 
> > This works as expected. 0.9.8 still had a small buffer for RPC messages.
> > It's since 0.9.13 release that we've switched to dynamically allocated
> > buffer and hence could size up the limit for incoming data. Update the
> > client and problem will just go away.
> 
> Actually that is not working as expected. The old client should *always*
> be able to talk to a new server. If the new server is unconditionally
> sending back data that is too large for the client, this is a bug.

This problem was fixed in

commit 27e81517a876dcb738dd8a9bb2e0e68d71c3b7e3
Author: Daniel P. Berrange <berrange at redhat.com>
Date:   Mon Sep 30 17:27:51 2013 +0100

    Fix max stream packet size for old clients
    
    The libvirtd server pushes data out to clients. It does not
    know what protocol version the client might have, so must be
    conservative and use the old payload limits. ie send no more
    than 256kb of data per packet.


And backported to stable branches.

Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|