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[Mark McLoughlin <markmc@xxxxxxxxxx>]

** Changed in: nova/folsom
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1029430

Title:
  KVM guests networking issues with no virbr0 and with vhost_net kernel
  modules loaded

Status in OpenStack Compute (Nova):
  Fix Released
Status in OpenStack Compute (nova) folsom series:
  Fix Released
Status in “libvirt” package in Ubuntu:
  Triaged
Status in “nova” package in Ubuntu:
  Confirmed

Bug description:
  We've found that having vhost_net module and using bridged networking
  breaks DHCP and (some?) guests do not get an IP address.

  The issue has been properly described in the following RH doc:

  http://docs.redhat.com/docs/en-
  US/Red_Hat_Enterprise_Linux/6/html/Virtualization_Host_Configuration_and_Guest_Installation_Guide/ch11s02.html

  "11.2.1. Checksum correction for older DHCP clients"

  Their workaround works in Precise too in fact.

  Another workaround is to disable/unload the vhost_net module so new
  guests do not make use of it.

  RH has fixed this stuff in libvirt apparently:

  "This iptables rule is programmed automatically on the host when the
  server is started by libvirt, so no further action is required"

  My apologies if this stuff does not belong to libvirt.

  Some info from our environment:

  compute-002:~# lsb_release -rd
  Description:	Ubuntu 12.04 LTS
  Release:	12.04

  compute-002:~# uname -a
  Linux compute-002 3.2.0-27-generic #43-Ubuntu SMP Fri Jul 6 14:25:57 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

  compute-002:~# dpkg -l|egrep "kvm|libvirt|dhcp|dns"
  ii  dnsmasq-base                       2.59-4                                    Small caching DNS proxy and DHCP/TFTP server
  ii  dnsmasq-utils                      2.59-4                                    Utilities for manipulating DHCP leases
  ii  dnsutils                           1:9.8.1.dfsg.P1-4ubuntu0.1                Clients provided with BIND
  ii  isc-dhcp-client                    4.1.ESV-R4-0ubuntu5.1                     ISC DHCP client
  ii  isc-dhcp-common                    4.1.ESV-R4-0ubuntu5.1                     common files used by all the isc-dhcp* packages
  ii  kvm-ipxe                           1.0.0+git-3.55f6c88-0ubuntu1              PXE ROM's for KVM
  ii  libdns81                           1:9.8.1.dfsg.P1-4ubuntu0.1                DNS Shared Library used by BIND
  ii  libnet-dns-perl                    0.66-2ubuntu3                             Perform DNS queries from a Perl script
  ii  libvirt-bin                        0.9.8-2ubuntu17.2                         programs for the libvirt library
  ii  libvirt0                           0.9.8-2ubuntu17.2                         library for interfacing with different virtualization systems
  ii  munin-libvirt-plugins              0.0.6-1                                   Munin plugins using libvirt
  ii  nova-compute-kvm                   2012.1+stable~20120612-3ee026e-0ubuntu1.2 OpenStack Compute - compute node (KVM)
  ii  python-libvirt                     0.9.8-2ubuntu17.2                         libvirt Python bindings
  ii  qemu-kvm                           1.0+noroms-0ubuntu14                      Full virtualization on i386 and amd64 hardware

  We've also tested this with kernel 3.5 backport from Quantal:

  Linux compute-002 3.5.0-6-generic #6~precise1-Ubuntu SMP Tue Jul 24
  14:45:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

  The guest is running Debian Squeeze:

  debian-squeeze-amd64-ext3:~$ uname -a
  Linux debian-squeeze-amd64-ext3 2.6.32-5-amd64 #1 SMP Mon Jan 16 16:22:28 UTC 2012 x86_64 GNU/Linux

  debian-squeeze-amd64-ext3:~$ dpkg -l|grep dhcp
  ii  isc-dhcp-client                     4.1.1-P1-15+squeeze3         ISC DHCP client
  ii  isc-dhcp-common                     4.1.1-P1-15+squeeze3         common files used by all the isc-dhcp* packages

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