Description of problem:
Ping the bonding interface in the guest and use scirpt to ifconfig down/up to the slave interface would eventually cause the hang of guest.

Version-Release number of selected component (if applicable):
KVM version:
kvm-83-105.el5_4.10
kmod-kvm-83-105.el5_4.10
kvm-debuginfo-83-105.el5_4.10
kvm-tools-83-105.el5_4.10
etherboot-zroms-kvm-5.4.4-10.el5
kvm-qemu-img-83-105.el5_4.10
Kernel version:
2.6.18-164.2.1.el5

How reproducible:
100%

Steps to Reproduce:
1. start the virtual machine with two e1000 nic and smp 2
2. setup the bonding for the two interface in guest
3. in the guest run the following scripts:
while true; do ifconfig eth0 down; ifconfig eth0 up; ifconfig eth1 down; ifconfig eth1 up; done
4. ping the guest in the host: ping -i 0.001 $ip
  
Actual results:
1. Guest hang after seconds or minutes

Expected results:
1. Guest should works normally

Additional info:
When testing with two rtl8139s, the guest is not hung but the network connection is lost after seconds or minutes.
Could not test virtio nics because of bug #523915.

qemu command line:
qemu-kvm -drive file=RHEL-Server-5.4-64-virtio.qcow2,if=virtio,boot=on -net nic,model=rtl8139,macaddr=00:11:11:22:11:01,vlan=0 -net tap,vlan=0 -net nic,model=rtl8139,macaddr=00:11:11:22:11:02,vlan=1 -net tap,vlan=1 -m 1024 -vnc :10 -daemonize -smp 2

topology:
+-------------------------+
|   +----------------+    |
|   |     bond0      |    |
|   +----------------+    |
|       /        \        |
|   +------+  +------+    |
|   | eth0 |  | eth1 |    |
|   +------+  +------+    |
|      |         |  Guest |
+------|---------|--------+
       |         |
   +------+  +------+
   | tap0 |  | tap1 |
   +------+  +------+
       |         |
   +----------------+
   |     switch     |
   +----------------+
       |
   +------+
   | eth0 |
   +------+
       |
       +------------------------


bonding configuration of guest:
ifcfg-eth0:
DEVICE=eth0
USERCTL=no
ONBOOT=yes
MASTER=bond0
SLAVE=yes
BOOTPROTO=none

ifcfg-eth1:
DEVICE=eth1
USERCTL=no
ONBOOT=yes
MASTER=bond0
SLAVE=yes
BOOTPROTO=none

ifcfg-bond0:
DEVICE=bond0
BOOTPROTO=dhcp
ONBOOT=yes
USERCTL=no

switch configuration of host:
$brctl show
bridge name bridge id STP enabled interfaces
switch 8000.0023ae6ff63d no tap1
tap0
eth0
bridge configuration:
$cat /etc/sysconfig/network-scripts/ifcfg-br0
DEVICE=switch
BOOTPROTO=dhcp
ONBOOT=yes
DELAY=0
TYPE=Bridge