qemu-ifup and qemu-ifdown

#!/bin/sh
set -x

switch=br0

if [ -n " $1 " ]; then
/usr/sbin/tunctl -t $1
/sbin/ip link set $1 up
sleep 0.5s
/usr/sbin/brctl addif $switch $1
exit 0
else
echo " Error : no interface specified "
exit 1
fi