/ 
Net-IP-Match-1.101700
River stage zero No dependents
/ Net::IP::Match

NAME

Net::IP::Match - Efficiently match IP addresses against IP ranges

VERSION

version 1.101700

SYNOPSIS

use Net::IP::Match;

if(__MATCH_IP($_, qw{10.0.0.0/8 87.134.66.128
  87.134.87.0/24 145.97.0.0/16})) {
      # ...
}

DESCRIPTION

This module provides you with an efficient way to match an IP address against one or more IP ranges. Speed is the key issue here. If you have to check several million IP addresses, as can happen with big logs, every millisecond counts. If your way to check an address involves a method call and some temporary variables, a lot of time is burnt. In such a time-critical loop you don't want to make subroutine calls at all, as they involve stack operations.

So the approach we take here is that of a macro, preprocessed through Perl's source filter mechanism.

You get a function (or at least something that looks like a function) called __MATCH_IP that takes a string that is to be matched against one or more IP ranges which are specified as the remaining args. The first argument can be a literal string or a variable; the other args can only be literal strings.

The function returns a boolean value depending on whether there is a match.

For example, the following are legal:

__MATCH_IP('192.168.1.4', '192.168.0.0/16')
__MATCH_IP('192.168.1.4', '10.0.0.0/8', '202.175.29.0/24')
__MATCH_IP($some_ip, qw{ 10.0.0.0/8 202.175.29.0/24 })

The following won't work because the source filter doesn't handle nested parentheses:

__MATCH_IP('192.168.1.4', ('10.0.0.0/8', '202.175.29.0/24'))

The following won't work because the source filter is invoked at compile-time, so the ranges to be transformed need to be known at that time:

__MATCH_IP($some_ip, @ranges)

INTERNALS

The source filter turns this function into a series of bit shift and short-circuit logical OR operations. No subroutine calls are involved. For example, the following call:

__MATCH_IP('192.168.1.4', qw{ 10.0.0.0/8 192.168.0.0/16 })

would be turned into:

do {
  my $__tmp_match_ip = unpack("N", pack("C4", split(/\./, '192.168.1.4')));
  10 == $__tmp_match_ip >> 24 || 49320 == $__tmp_match_ip >> 16
}

As a special case, if you're matching against a specific IP address (as opposed to a range), no bit shifts are involved:

__MATCH_IP($some_ip, qw{ 10.0.0.0/8 192.168.1.4 })

becomes

do {
  my $__tmp_match_ip = unpack("N", pack("C4", split(/\./, $some_ip)));
  10 == $__tmp_match_ip >> 24 || 3232235780 == $__tmp_match_ip
}

Furthermore, if there is only one IP range to match against, the temporary variable and the do-block aren't necessary either:

__MATCH_IP($some_ip, '192.168.0.0/16')

becomes:

(49320 == unpack("N", pack("C4", split(/\./, $some_ip))) >> 16)

and that's about as efficient as it gets.

DEBUGGING

If you want to see the output of the source filter, set $::debug to a true value by the time the source filter runs. One way to achieve this is:

perl -s my_program.pl -debug

ALTERNATIVE APPROACHES

Of course, a C implementation would have been even faster, but you would have to call it as a function, which would add the stack overhead. Richard Clamp had the interesting idea of optimizing the generated opcode tree.

INSTALLATION

See perlmodinstall for information and options on installing Perl modules.

BUGS AND LIMITATIONS

No bugs have been reported.

Please report any bugs or feature requests through the web interface at http://rt.cpan.org.

AVAILABILITY

The latest version of this module is available from the Comprehensive Perl Archive Network (CPAN). Visit http://www.perl.com/CPAN/ to find a CPAN site near you, or see http://search.cpan.org/dist/Net-IP-Match/.

The development version lives at http://github.com/hanekomu/Net-IP-Match/. Instead of sending patches, please fork this project using the standard git and github infrastructure.

AUTHOR

Marcel Gruenauer <marcel@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2002 by Marcel Gruenauer.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.