PySubnetTree - A Python Module for CIDR Lookups

The PySubnetTree package provides a Python data structure SubnetTree which maps subnets given in CIDR notation (incl. corresponding IPv6 versions) to Python objects. Lookups are performed by longest-prefix matching.

Download

You can find the latest PySubnetTree release for download at http://www.bro-ids.org/download.

PySubnetTree’s git repository is located at git://git.bro-ids.org/pysubnettree.git. You can browse the repository here.

This document describes PySubnetTree 0.17-8. See the CHANGES file for version history.

Example

A simple example which associates CIDR prefixes with strings:

>>> import SubnetTree
>>> t = SubnetTree.SubnetTree()
>>> t["10.1.0.0/16"] = "Network 1"
>>> t["10.1.42.0/24"] = "Network 1, Subnet 42"
>>> t["10.2.0.0/16"] = "Network 2"
>>> print t["10.1.42.1"]
Network 1, Subnet 42
>>> print t["10.1.43.1"]
Network 1
>>> print "10.1.42.1" in t
True
>>> print "10.1.43.1" in t
True
>>> print "10.20.1.1" in t
False
>>> print t["10.20.1.1"]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "SubnetTree.py", line 67, in __getitem__
    def __getitem__(*args): return _SubnetTree.SubnetTree___getitem__(*args)
KeyError: '10.20.1.1'

By default, CIDR prefixes and IP addresses are given as strings. Alternatively, a SubnetTree object can be switched into binary mode, in which single addresses are passed in the form of packed binary strings as, e.g., returned by socket.inet_aton:

>>> t.get_binary_lookup_mode()
False
>>> t.set_binary_lookup_mode(True)
>>> t.binary_lookup_mode()
True
>>> import socket
>>> print t[socket.inet_aton("10.1.42.1")]
Network 1, Subnet 42

A SubnetTree also provides methods insert(prefix,object=None) for insertion of prefixes (object can be skipped to use the tree like a set), and remove(prefix) for removing entries (remove performs an _exact_ match rather than longest-prefix).

Internally, the CIDR prefixes of a SubnetTree are managed by a Patricia tree data structure and lookups are therefore efficient even for large number of prefixes.

PySubnetTree comes with BSD license.

Prerequisites

This packages requires Python 2.4 or newer.

Installation

Installation is pretty simple:

> python setup.py install