eth="eth0"
eth_ip="192.168.1.99"
eth_netmask="255.255.255.0"
eth_broadcast="192.168.0.255"

openvpn --mktun --dev tap0

brctl addbr br0
brctl addif br0 eth0
brctl addif br0 tap0

ifconfig tap0 0.0.0.0 promisc up
ifconfig $eth 0.0.0.0 promisc up
ifconfig br0 $eth_ip netmask $eth_netmask broadcast $eth_broadcast

iptables -A INPUT -i tap0 -j ACCEPT
iptables -A INPUT -i br0 -j ACCEPT
iptables -A FORWARD -i br0 -j ACCEPT