[Bug 1172091] [NEW] KVM guests with bridged network drops out intermittently

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This appears to be the same bug as this:
https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/997978

Issue
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Guest networking will randomly drop out and then work again. This is easiest to be seen by sshing into a guest and running top. After 10-20 minutes I get a broken pipe. Sometimes I can ssh back in to the guest right away, other times it gives me an incorrect fingerprint and ssh will refuse as it doesn't match the know_hosts figerprint. I don't believe this is the vm hosts fingerprint either but might be mistaken.  If I continue to wait I can eventually ssh back in.

Set up
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I have a fresh install of ubuntu 12.10 x86_64 server with everything updated

I selected OpenSSH and Virtual Machine Host during installation.

I removed the default virbr0 and set up br0 and br1 manually.

$ cat /etc/network/interfaces 
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
# 10.10.0.x network
auto eth0
iface eth0 inet manual

auto br0
iface br0 inet static
	address 10.10.0.201
	netmask 255.255.240.0
	network 10.10.0.0
	broadcast 10.10.15.255
	gateway 10.10.0.1
	# dns-* options are implemented by the resolvconf package, if installed
	dns-nameservers 10.10.0.1
	dns-search burnet-int.edu.au
	bridge_ports eth0
	bridge_fd 0
	bridge_stp off

# 203.0.141.x network
auto eth1
iface eth1 inet manual

auto br1
iface br1 inet manual
        bridge_ports eth1
        bridge_fd 0
        bridge_stp off


$ brctl show

bridge name	bridge id		STP enabled	interfaces
br0		8000.001e4f42aa69	no		eth0
br1		8000.001e4f42aa6b	no		eth1
							vnet0

$ virsh net-list
Name                 State      Autostart
-----------------------------------------


I created a new user to manage the VMs and added them to the kvm and libvirtd groups. They don't have access to sudo and the VMs aren't started with sudo.

Created a virtual machine.

$ virt-install --connect qemu:///system \
--name proxy01 --ram 4096 --vcpus 4 \
--disk path=/srv/nfs01/disks/proxy01.raw,format=raw,bus=virtio,cache=none \
--cdrom=/srv/nfs01/images/ubuntu-12.10-server-i386.iso \
--network bridge=br1,model=virtio \
--os-type=linux --os-variant=ubuntuquantal \
--graphics vnc,password=password \
--noautoconsole \
--virt-type=kvm \
--autostart

I only install OpenSSH on the guest and configure the network as:

$ cat /etc/network/interfaces 
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
	address 203.0.141.2
	netmask 255.255.255.0
	network 203.0.141.0
	broadcast 203.0.141.255
	gateway 203.0.141.1
	# dns-* options are implemented by the resolvconf package, if installed
	dns-nameservers 203.0.141.99 203.0.141.66
	dns-search burnet.edu.au

I then start the VM with

$ virsh start proxy01

SSH into proxy01 and run top and I get a broken pipe after 10 or 20
minutes. It's not consistent.

Packages Version
------
$ apt-cache policy qemu-kvm
qemu-kvm:
  Installed: 1.2.0+noroms-0ubuntu2.12.10.3
  Candidate: 1.2.0+noroms-0ubuntu2.12.10.3
  Version table:
 *** 1.2.0+noroms-0ubuntu2.12.10.3 0
        500 http://au.archive.ubuntu.com/ubuntu/ quantal-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     1.2.0+noroms-0ubuntu2.12.10.2 0
        500 http://security.ubuntu.com/ubuntu/ quantal-security/main amd64 Packages
     1.2.0+noroms-0ubuntu2 0
        500 http://au.archive.ubuntu.com/ubuntu/ quantal/main amd64 Packages

** Affects: qemu-kvm (Ubuntu)
     Importance: Undecided
         Status: New

-- 
KVM guests with bridged network drops out intermittently
https://bugs.launchpad.net/bugs/1172091
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