NAME¶
Net::Patricia - Patricia Trie perl module for fast IP address lookups
SYNOPSIS¶
use Net::Patricia;
my $pt = new Net::Patricia;
$pt->add_string('127.0.0.0/8', \$user_data);
$pt->match_string('127.0.0.1');
$pt->match_exact_string('127.0.0.0');
$pt->match_integer(2130706433); # 127.0.0.1
$pt->match_exact_integer(2130706432, 8); # 127.0.0.0
$pt->remove_string('127.0.0.0/8');
$pt->climb(sub { print "climbing at node $_[0]\n" });
undef $pt; # automatically destroys the Patricia Trie
DESCRIPTION¶
This module uses a Patricia Trie data structure to quickly perform IP address
prefix matching for applications such as IP subnet, network or routing table
lookups. The data structure is based on a radix tree using a radix of two, so
sometimes you see patricia implementations called "radix" as well.
The term "Trie" is derived from the word "retrieval" but
is pronounced like "try". Patricia stands for "Practical
Algorithm to Retrieve Information Coded as Alphanumeric", and was first
suggested for routing table lookups by Van Jacobsen. Patricia Trie performance
characteristics are well-known as it has been employed for routing table
lookups within the BSD kernel since the 4.3 Reno release.
The BSD radix code is thoroughly described in "TCP/IP Illustrated, Volume
2" by Wright and Stevens and in the paper ``A Tree-Based Packet Routing
Table for Berkeley Unix'' by Keith Sklower.
METHODS¶
- new - create a new Net::Patricia object
-
$pt = new Net::Patricia;
This is the class' constructor - it returns a "Net::Patricia"
object upon success or undef on failure. The constructor takes an optional
argument (of AF_INET or AF_INET6, defaulting to the former), and creates a
tree with address and mask values of that type as keys.
The "Net::Patricia" object will be destroyed automatically when
there are no longer any references to it.
- add_string
-
$pt->add_string(key_string[,user_data]);
The first argument, key_string, is a network or subnet specification in
canonical form, e.g. "10.0.0.0/8", where the number after the
slash represents the number of bits in the netmask. If no mask width is
specified, the longest possible mask is assumed, i.e. 32 bits for AF_INET
addresses.
The second argument, user_data, is optional. If supplied, it should be a
SCALAR value (which may be a perl reference) specifying the user data that
will be stored in the Patricia Trie node. Subsequently, this value will be
returned by the match methods described below to indicate a successful
search. Remember that perl references and objects are represented as
SCALAR values and therefore the user data can be complicated data objects.
If no second argument is passed, the key_string will be stored as the user
data and therfore will likewise be returned by the match functions.
On success, this method returns the user_data passed as the second argument
or key_string if no user data was specified. It returns undef on
failure.
- match_string
-
$pt->match_string(key_string);
This method searches the Patricia Trie to find a matching node, according to
normal subnetting rules for the address and mask specified.
The key_string argument is a network or subnet specification in canonical
form, e.g. "10.0.0.0/8", where the number after the slash
represents the number of bits in the netmask. If no mask width value is
specified, the longest mask is assumed, i.e. 32 bits for AF_INET
addresses.
If a matching node is found in the Patricia Trie, this method returns the
user data for the node. This method returns undef on failure.
- match_exact_string
-
$pt->match_exact_string(key_string);
This method searches the Patricia Trie to find a matching node. Its
semantics are exactly the same as those described for
"match_string" except that the key must match a node exactly.
I.e. it is not sufficient that the address and mask specified merely falls
within the subnet specified by a particular node.
- match_integer
-
$pt->match_integer(integer[,mask_bits]);
This method searches the Patricia Trie to find a matching node, according to
normal subnetting rules for the address and mask specified. Its semantics
are similar to those described for "match_string" except that
the key is specified using an integer (i.e. SCALAR), such as that returned
by perl's "unpack" function for values converted using the
"N" (network-ordered long). Note that this argument is not a
packed network-ordered long.
Just to be completely clear, the integer argument should be a value of the
sort produced by this code:
use Socket;
$integer = unpack("N", inet_aton("10.0.0.0"));
- match_exact_integer
-
$pt->match_exact_integer(integer[,mask_bits]);
This method searches the Patricia Trie to find a matching node. Its
semantics are exactly the same as "match_integer" except that
the key must match a node exactly. I.e. it is not sufficient that the
address and mask specified merely falls within the subnet specified by a
particular node.
- remove_string
-
$pt->remove_string(key_string);
This method removes the node which exactly matches the the address and mask
specified from the Patricia Trie.
If the matching node is found in the Patricia Trie, it is removed, and this
method returns the user data for the node. This method returns undef on
failure.
- climb
-
$pt->climb([CODEREF]);
This method climbs the Patricia Trie, visiting each node as it does so. It
performs a non-recursive, "preorder" traversal.
The CODEREF argument is optional. It is a perl code reference used to
specify a user-defined subroutine to be called when visiting each node.
The node's user data will be passed as the sole argument to that
subroutine.
This method returns the number of nodes successfully visited while climbing
the Trie. That is, without a CODEREF argument, it simply counts the number
of nodes in the Patricia Trie.
Note that currently the return value from your CODEREF subroutine is
ignored. In the future the climb method may return the number of times
your subroutine returned non-zero, as it is called once per node. So, if
you are currently relying on the climb return value to accurately report a
count of the number of nodes in the Patricia Trie, it would be prudent to
have your subroutine return a non-zero value.
This method is called climb() rather than walk() because
climbing trees (and therfore tries) is a more popular pass-time than
walking them.
- climb_inorder
-
$pt->climb_inorder([CODEREF]);
This method climbs the Patricia Trie, visiting each node in order as it does
so. That is, it performs an "inorder" traversal.
The CODEREF argument is optional. It is a perl code reference used to
specify a user-defined subroutine to be called when visiting each node.
The node's user data will be passed as the sole argument to that
subroutine.
This method returns the number of nodes successfully visited while climbing
the Trie. That is, without a CODEREF argument, it simply counts the number
of nodes in the Patricia Trie.
Note that currently the return value from your CODEREF subroutine is
ignored. In the future the climb method may return the number of times
your subroutine returned non-zero, as it is called once per node. So, if
you are currently relying on the climb return value to accurately report a
count of the number of nodes in the Patricia Trie, it would be prudent to
have your subroutine return a non-zero value.
This method is called climb() rather than walk() because
climbing trees (and therfore tries) is a more popular pass-time than
walking them.
BUGS¶
This modules does not yet support AF_INET6 (IP version 6) 128 bit addresses,
although the underlying patricialib C code does.
When passing a CODEREF argument to the climb method, the return value from your
CODEREF subroutine is currently ignored. In the future the climb method may
return the number of times your subroutine returned non-zero, as it is called
once per node. So, if you are currently relying on the climb return value to
accurately report a count of the number of nodes in the Patricia Trie, it
would be prudent to have your subroutine return a non-zero value.
AUTHOR¶
Dave Plonka <plonka@doit.wisc.edu> Philip Prindeville
<philipp@redfish-solutions.com>
Copyright (C) 2000-2005 Dave Plonka. Copyright (C) 2009 Dave Plonka & Philip
Prindeville. This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
This product includes software developed by the University of Michigan, Merit
Network, Inc., and their contributors. See the copyright file in the
patricialib sub-directory of the distribution for details.
patricialib, the C library used by this perl extension, is an extracted version
of MRT's patricia code from radix.[ch], which was worked on by Masaki Hirabaru
and Craig Labovitz. For more info on MRT see:
http://www.mrtd.net/
The MRT patricia code owes some heritage to GateD's radix code, which in turn
owes something to the BSD kernel.
SEE ALSO¶
perl(1), Socket, Net::Netmask, Text::Trie, Tree::Trie.
Tree::Radix and Net::RoutingTable are modules by Daniel Hagerty
<hag@linnaean.org> written entirely in perl, unlike this module. At the
time of this writing, they are works-in-progress but may be available at:
http://www.linnaean.org/~hag/