Re: [libvirt] error: server response too large

At Tue, 1 Oct 2013 17:19:56 +0100, Daniel P. Berrange wrote: > > On Tue, Oct 01, 2013 at 06:13:10PM +0200, Viktor Mihajlovski wrote: > > 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 problem was fixed in > > > > > >commit 27e81517a876dcb738dd8a9bb2e0e68d71c3b7e3 > > >Author: Daniel P. Berrange <berrange(a)redhat.com&gt; > > >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. > > > > > 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 ... > > What were you doing to get a message greater than 256KB ? This > patch did not attempt to fix all possible combinations. If a > API call such as virConnectListAllDomains has so much data that > it requires > 256KB to encode, this fix won't solve that. There > is nothing we can do for API calls which have a genuine need to > exceed the old size limit. > > I was only addressing the case of virStreamPtr data which was > mistakenly hardcoded in the server to try sending 16 MB of data > at once. I switched it to only try to send 256 KB of data per > stream packet. I've also tested your patch, and it seems 256 KB of data is still a bit too large: virsh # screenshot 2 /tmp/test error: could not receive data from domain 2 error: packet 262168 bytes received from server too large, want 262144 The max payload size is computed as: VIR_NET_MESSAGE_MAX = 16777216 VIR_NET_MESSAGE_HEADER_MAX = 24 VIR_NET_MESSAGE_PAYLOAD_MAX = (VIR_NET_MESSAGE_MAX - VIR_NET_MESSAGE_HEADER_MAX) = 16777192 So, it seems the legacy max payload size is actually 262120; I tested it and it works. ------------------- 8< ------ >8 --------------------------- Subject: [PATCH] Adjust legacy max payload size to account for header information Organization: AV-Test GmbH, Germany Commit 27e81517a87 set the payload size to 256 KB, which is actually the max packet size, including the size of the header. Reduce this by VIR_NET_MESSAGE_HEADER_MAX (24) and set VIR_NET_MESSAGE_LEGACY_PAYLOAD_MAX to 262120. Signed-off-by: Claudio Bley <cbley(a)av-test.de&gt; --- src/rpc/virnetprotocol.x | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/rpc/virnetprotocol.x b/src/rpc/virnetprotocol.x index 1eae7cb..7b6f753 100644 --- a/src/rpc/virnetprotocol.x +++ b/src/rpc/virnetprotocol.x @@ -55,7 +55,7 @@ const VIR_NET_MESSAGE_INITIAL = 65536; * payload size. We need to remember this for compat with * old clients. */ -const VIR_NET_MESSAGE_LEGACY_PAYLOAD_MAX = 262144; +const VIR_NET_MESSAGE_LEGACY_PAYLOAD_MAX = 262120; /* Maximum total message size (serialised). */ const VIR_NET_MESSAGE_MAX = 16777216;