[libvirt] error: server response too large

[Viktor Mihajlovski]

On 10/01/2013 03:02 PM, Daniel P. Berrange wrote:
> 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
>
I tried libvirt 1.1.3 containing the commit on the server and
Ubuntu libvirt 0.9.8 as the client and still have the issue
if the message is greater than 256KB. The problem is that
the old client checks the message size during decode (which is
greater than the client's max message size).

Not sure how to get out of this ...

-- 

Mit freundlichen Grüßen/Kind Regards
    Viktor Mihajlovski

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