Script to help in operating ovs on ubuntu

ovs-connect.py

'''
Author : Vikas Yadav

DISCLAIMER:
Running this script requires root privileges
You can loose internet connectivity after using this script. So proceed with
caution.
This should not be used on systems which have two physical interfaces connected
to internet.
This should not be used on system which already has a ovs bridge up and running.
'''

import os
import sys

def gatewayIP():
    cmd = """route -n | grep UG | awk '{split($0,a," "); print a[2]}'"""
    result = os.popen(cmd).read()
    return result[:-1]

def gatewayInterface():
    cmd = """route -n | grep UG | awk '{split($0,a," "); print a[8]}'"""
    result = os.popen(cmd).read()
    return result[:-1]

'''
Please make sure that "interface" passed in this argument is connected to the
"bridge" otherwise this will make no difference.
'''
def reset(bridge, interface):
    cmd = "ovs-vsctl del-port %s %s" % (bridge, interface)
    os.system(cmd)
    os.system("ifconfig %s down" % (bridge))

'''
Please make sure that "interface" passed in this argument is connected to Internet
'''
def connect(bridge, interface):
    # Connect interface to bridge
    cmd = "ovs-vsctl add-port %s %s" % (bridge, interface)
    os.system(cmd)
    # Change the default gateway
    cmd = """ifconfig %s | grep "inet addr" """ % (interface)
    try:
        current_ip = os.popen(cmd).read().split(":")[1].split(" ")[0]
        print current_ip
        netmask = os.popen(cmd).read().split(":")[-1][:-1]
        print netmask
        gateway = gatewayIP()
    except:
        print "Error occured. Cannot proceed further"
        return 0

    # Bring up the bridge interface in case it is down
    os.system("ifconfig %s up" % (bridge))
    # Set the ip of current interface as 0
    os.system("ifconfig %s 0" %(interface))
    # change the ip of bridged interface
    os.system("ifconfig %s %s && ifconfig %s netmask %s" % (bridge, current_ip, bridge, netmask))
    os.system("route add default gw %s %s" % (gateway, bridge))
    print "OVS Switch Enabled. Now create a tuntap interface and enjoy"

'''
from ovs-connect import *
'''

# Enter name of the Interface which is connected to Internet or the interface
# which you want to bridge to the Internet.
INTERFACE = "wlp3s0"
# Enter the name of OVS Bridge which you created
BRIDGE = "br0"

if sys.argv[1] == "reset":
    reset(BRIDGE, INTERFACE)

if sys.argv[1] == "connect":
    connect(BRIDGE, INTERFACE)


#print gatewayIP()
#print gatewayInterface()
#refresh("br0", "wlp3s0")
#connect("br0", gatewayInterface())