How can I check if an ip is in a network in python

Question

Given an ip address (say 192.168.0.1), how do I check if it's in a network (say 192.168.0.0/24) in Python?

Are there general tools in Python for ip address manipulation? Stuff like host lookups, ip adddress to int, network address with netmask to int and so on? Hopefully in the standard Python library for 2.5.

Answer 1

I don't know of anything in the standard library, but PySubnetTree is a Python library that will do subnet matching.

Answer 2

This article shows you can do it with socket and struct modules without too much extra effort. I added a little to the article as follows:

import socket,struct

def makeMask(n):
    "return a mask of n bits as a long integer"
    return (2L<<n-1) - 1

def dottedQuadToNum(ip):
    "convert decimal dotted quad string to long integer"
    return struct.unpack('L',socket.inet_aton(ip))[0]

def networkMask(ip,bits):
    "Convert a network address to a long integer" 
    return dottedQuadToNum(ip) & makeMask(bits)

def addressInNetwork(ip,net):
   "Is an address in a network"
   return ip & net == net

address = dottedQuadToNum("192.168.1.1")
networka = networkMask("10.0.0.0",24)
networkb = networkMask("192.168.0.0",24)
print (address,networka,networkb)
print addressInNetwork(address,networka)
print addressInNetwork(address,networkb)

This outputs:

False
True

If you just want a single function that takes strings it would look like this:

import socket,struct

def addressInNetwork(ip,net):
   "Is an address in a network"
   ipaddr = struct.unpack('L',socket.inet_aton(ip))[0]
   netaddr,bits = net.split('/')
   netmask = struct.unpack('L',socket.inet_aton(netaddr))[0] & ((2L<<int(bits)-1) - 1)
   return ipaddr & netmask == netmask

Answer 3

I like to use netaddr for that:

from netaddr import CIDR, IP

if IP("192.168.0.1") in CIDR("192.168.0.0/24"):
    print "Yay!"

Answer 4

ipaddr is a nice library as well.

Answer 5

Using ipaddr (in the Python stdlib since Python2.7/3.1):

>>> from ipaddr import IP
>>> IP('192.168.0.1') in IP('192.168.0.0/24')
True