[Bug 612671] [NEW] Live Migration Guest Network Stops Responding

[Moshe Ortov]

Public bug reported:

After configuring 2 identical servers with KVM and then trying to
migrate an image using bridged networking from one to the other, the
guest loses network connectivity after the migration completes.

A tcpdump shows the bridged network is passing packets /from/ the guest
(a test ping run in the guest via the VNC console) and reply packets are
received and bridged back onto the guest network interface without the
guest seeing the packet (i.e. packets come from vnet0, sent out on br0,
reply comes back from br0, is forwarded onto vnet0 but the guest never
sees the reply).

tcpdump -n -i vnet0
18:19:47.072378 IP 192.168.35.49 > 192.168.35.4: ICMP echo request, id 512, seq 2816, length 40
This is the echo packet sent by the guest

18:19:47.073119 IP 192.168.35.4 > 192.168.35.49: ICMP echo reply, id 512, seq 2816, length 40
This is the reply coming back except the actual guest does not ever see the reply.

# lsb_release -rd
Description:	Ubuntu 10.04.1 LTS
Release:	10.04

The packet forwarding seems to go amiss on the bridge or in qemu or
libvirt - there are a number of posts online with people finding similar
problems but nothing ever seems to answer why or how to fix it that I've
found.

brctl show
# brctl show
bridge name	bridge id		STP enabled	interfaces
br0		8000.001517c8ef5e	no		eth1
							eth2
							vnet0

brctl showstp br0
br0
 bridge id		8000.001517c8ef5e
 designated root	8000.001517c8ef5e
 root port		   0			path cost		   0
 max age		  20.00			bridge max age		  20.00
 hello time		   2.00			bridge hello time	   2.00
 forward delay		   0.00			bridge forward delay	   0.00
 ageing time		 300.00
 hello timer		   1.64			tcn timer		   0.00
 topology change timer	   0.00			gc timer		   0.64
 flags			


eth1 (1)
 port id		8001			state		       disabled
 designated root	8000.001517c8ef5e	path cost		 100
 designated bridge	8000.001517c8ef5e	message age timer	   0.00
 designated port	8001			forward delay timer	   0.00
 designated cost	   0			hold timer		   0.00
 flags			

eth2 (2)
 port id		8002			state		     forwarding
 designated root	8000.001517c8ef5e	path cost		   4
 designated bridge	8000.001517c8ef5e	message age timer	   0.00
 designated port	8002			forward delay timer	   0.00
 designated cost	   0			hold timer		   0.64
 flags			

vnet0 (3)   <-- the guest nic
 port id		8003			state		     forwarding
 designated root	8000.001517c8ef5e	path cost		 100
 designated bridge	8000.001517c8ef5e	message age timer	   0.00
 designated port	8003			forward delay timer	   0.00
 designated cost	   0			hold timer		   0.64
 flags

** Affects: libvirt (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: bridge libvirt migrate

-- 
Live Migration Guest Network Stops Responding
https://bugs.launchpad.net/bugs/612671
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