[Bug 668042] Re: If Libvirtd is restarted, libvirt drops active domains lose network interface info.

[Dave Walker]

** Description changed:

- Missing target device info makes it impossible to retrieve network usage
- information about a guest from libvirt.
+ IMPACT:  If libvirt daemon is restarted, it forgets about domain interfaces (breaking domifstat)
+ RESOLUTION: Check that the domain is inactive before wiping knowledge of it.
+ PATCH: Based on upstream commit, attached comment #6.
+ TEST CASE: (Based on Fedora bug report)
  
- Reproduce:
- Trigger of issue unknown. 
+ {{{
+ 1. Start QEMU/KVM guest with: sudo virsh start vm01
+ 2. restart libvirtd: sudo restart libvrtd
+ 3. Get statistics with sudo virsh domifstat vm01 vnet0
  
- Workaround:
- Restart the guest, and the network device info reappears again.
+ Actual results:
+ $ sudo virsh domifstat vm01 vnet0
+ error: Failed to get interface stats vm01 vnet0
+ error: invalid argument in invalid path, 'vnet0' is not a known interface
  
- Detect:
- Use virsh with the dumpxml command to view information about a running guest.
+ Expected results:
+ $ sudo virsh domifstat vm01 vnet0
+ vnet0 rx_bytes 83980
+ vnet0 rx_packets 1612
+ vnet0 rx_errs 0
+ vnet0 rx_drop 0
+ vnet0 tx_bytes 3546
+ vnet0 tx_packets 15
+ vnet0 tx_errs 0
+ vnet0 tx_drop 0
  
- Good result:
- virsh # dumpxml myhost1
-     ...
-     <interface type='bridge'>
-       <mac address='52:54:00:11:a6:2c'/>
-       <source bridge='br0'/>
-       <target dev='vnet0'/>
-       <model type='virtio'/>
-     </interface>
-     ...
+ }}}
  
- Bad result:
- virsh # dumpxml myhost2
-     ...
-     <interface type='bridge'>
-       <mac address='52:54:14:79:32:6d'/>
-       <source bridge='br0'/>
-       <model type='virtio'/>
-     </interface>
-     ...
- 
- I am attaching an image of my munin graphs to illustrate the effects of
- the bug.
+ REGRESSION POTENTIAL:  This would seem to be low, the patch adds an
+ extra conditional statement before wiping the domain network interface
+ knowledge.  The patch has been in upstream Git since 4/05/2010, and has
+ had at least one upstream release and is also in Maverick.
  
  ProblemType: Bug
  DistroRelease: Ubuntu 10.04
  Package: libvirt-bin 0.7.5-5ubuntu27.6
  ProcVersionSignature: Ubuntu 2.6.32-23.37-server 2.6.32.15+drm33.5
  Uname: Linux 2.6.32-23-server x86_64
  Architecture: amd64
  Date: Thu Oct 28 13:40:36 2010
  InstallationMedia: Ubuntu-Server 10.04 LTS "Lucid Lynx" - Release amd64 (20100427)
  ProcEnviron:
-  LANG=en_US.UTF-8
-  SHELL=/bin/bash
+  LANG=en_US.UTF-8
+  SHELL=/bin/bash
  SourcePackage: libvirt

-- 
If Libvirtd is restarted, libvirt drops active domains lose network interface info.
https://bugs.launchpad.net/bugs/668042
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