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

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('/')
    netaddr = struct.unpack('!L',socket.inet_aton(netaddr))[0]
    netmask = ((1<<(32-int(bits))) - 1)^0xffffffff
    return ipaddr & netmask == netaddr & netmask
print addressInNetwork('10.10.10.110','10.10.10.128/25')
print addressInNetwork('10.10.10.110','10.10.10.0/25')
print addressInNetwork('10.10.10.110','10.20.10.128/25')

$ python check-subnet.py
False
True
False

Answer 2

Here is my code

# -*- coding: utf-8 -*-
import socket


class SubnetTest(object):
    def __init__(self, network):
        self.network, self.netmask = network.split('/')
        self._network_int = int(socket.inet_aton(self.network).encode('hex'), 16)
        self._mask = ((1L << int(self.netmask)) - 1) << (32 - int(self.netmask))
        self._net_prefix = self._network_int & self._mask

    def match(self, ip):
        '''
        判断传入的 IP 是不是本 Network 内的 IP
        '''
        ip_int = int(socket.inet_aton(ip).encode('hex'), 16)
        return (ip_int & self._mask) == self._net_prefix

st = SubnetTest('100.98.21.0/24')
print st.match('100.98.23.32')

Answer 3

For python3

In [64]: ipaddress.IPv4Address('192.168.1.1') in ipaddress.IPv4Network('192.168.0.0/24')
Out[64]: False

Answer 4

I tried Dave Webb's solution but hit some problems:

Most fundamentally - a match should be checked by ANDing the IP address with the mask, then checking the result matched the Network address exactly. Not ANDing the IP address with the Network address as was done.

I also noticed that just ignoring the Endian behaviour assuming that consistency will save you will only work for masks on octet boundaries (/24, /16). In order to get other masks (/23, /21) working correctly I added a "greater than" to the struct commands and changed the code for creating the binary mask to start with all "1" and shift left by (32-mask).

Finally, I added a simple check that the network address is valid for the mask and just print a warning if it is not.

Here's the result:

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]
    ipaddr_masked = ipaddr & (4294967295<<(32-int(bits)))   # Logical AND of IP address and mask will equal the network address if it matches
    if netmask == netmask & (4294967295<<(32-int(bits))):   # Validate network address is valid for mask
            return ipaddr_masked == netmask
    else:
            print "***WARNING*** Network",netaddr,"not valid with mask /"+bits
            return ipaddr_masked == netmask

Answer 5

There is an API that's called SubnetTree available in python that do this job very well. This is a simple example :

import SubnetTree
t = SubnetTree.SubnetTree()
t.insert("10.0.1.3/32")
print("10.0.1.3" in t)

This is the link

Answer 6

previous solution have a bug in ip & net == net. Correct ip lookup is ip & netmask = net

bugfixed code:

import socket
import 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 addressInNetwork(ip,net,netmask):
   "Is an address in a network"
   print "IP "+str(ip) + " NET "+str(net) + " MASK "+str(netmask)+" AND "+str(ip & netmask)
   return ip & netmask == net

def humannetcheck(ip,net):
        address=dottedQuadToNum(ip)
        netaddr=dottedQuadToNum(net.split("/")[0])
        netmask=makeMask(long(net.split("/")[1]))
        return addressInNetwork(address,netaddr,netmask)


print humannetcheck("192.168.0.1","192.168.0.0/24");
print humannetcheck("192.169.0.1","192.168.0.0/24");