vi /etc/qemu-ifup

#!/bin/sh

ME=$(basename $0)

ifext=${ME#qemu-ifup-}

case $ifext in
qemu-ifup)
ifname=eth0;;
*)
ifname=$ifext;;
esac

echo "Executing /etc/$ME"
echo "Bringing up $1 for bridged mode..."
/sbin/ifconfig $1 0.0.0.0 promisc up
echo "Adding $1 to ${ifname}..."
/usr/sbin/brctl addif $ifname $1
sleep 2

vi /etc/qemu-ifdown

#!/bin/sh

set_ifname () {
[ -e /sys/class/net/$1 ] || return

ifname=$(cat /sys/class/net/$1/brport/bridge/uevent \
|grep ^INTERFACE |cut -d '=' -f 2)
}

ME=$(basename $0)

set_ifname $1

echo "Executing /etc/$ME"
if [ -z "$ifname" ]; then
echo "Can not detect target bridge name"
exit 1
fi
echo "Removing $1 from ${ifname}..."
/usr/sbin/brctl delif $ifname $1
echo "Shutting down $1 ..."
/sbin/ifconfig $1 down
sleep 2

chmod 755 /etc/qemu-*

ln -s /etc/qemu-ifup /var/kvm/qemu-ifup-br0

ln -s /etc/qemu-ifdown /var/kvm/qemu-ifdown-br0