NAME
Net::IP::Match::Regexp - Efficiently match IP addresses against ranges
LICENSE
Copyright 2005-2006 Clotho Advanced Media, Inc., <cpan@clotho.com>
Copyright 2007-2008 Chris Dolan, <cdolan@cpan.org>
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
SYNOPSIS
use Net::IP::Match::Regexp qw( create_iprange_regexp match_ip );
my $regexp = create_iprange_regexp(
qw( 10.0.0.0/8 87.134.66.128 87.134.87.0/24 145.97.0.0/16 )
);
if (match_ip('209.249.163.62', $regexp)) {
...
}
DESCRIPTION
This module allows you to check an IP address against one or more IP
ranges. It employs Perl's highly optimized regular expression engine to
do the hard work, so it is very fast. It is optimized for speed by doing
the match against a regexp which implicitly checks the broadest IP
ranges first. An advantage is that the regexp can be computed and stored
in advance (in source code, in a database table, etc) and reused, saving
much time if the IP ranges don't change too often. The match can
optionally report a value (e.g. a network name) instead of just a
boolean, which makes module useful for mapping IP ranges to names or
codes or anything else.
LIMITATIONS
This module does not yet support IPv6 addresses, although that feature
should not be hard to implement as long as the regexps start with a 4
vs. 6 flag. Patches welcome. :-)
This module only accepts IP ranges in `a.b.c.d/x' (aka CIDR) notation.
To work around that limitation, I recommend Net::CIDR::Lite to
conveniently convert collections of IP address ranges into CIDR format.
This module makes no effort to validate the IP addresses or ranges
passed as arguments. If you pass address ranges like `1000.0.0.0/300',
you will probably get weird regexps out.
FUNCTIONS
create_iprange_regexp($iprange | $hashref | $arrayref, ...)
This function digests IP ranges into a regular expression that can
subsequently be used to efficiently test single IP addresses. It
returns a regular expression string that can be passed to
match_ip().
The simple way to use this is to pass a list of IP ranges as
`aaa.bbb.ccc.ddd/n'. When used this way, the return value of the
match_ip() function will be simply `1' or `undef'.
The more complex way is to pass a hash reference of IP range =>
return value pairs. When used this way, the return value of the
match_ip() function will be the specified return value or `undef'
for no match.
For example:
my $re1 = create_iprange_regexp('209.249.163.0/25', '127.0.0.1/32');
print match_ip('209.249.163.62', $re1); # prints '1'
my $re2 = create_iprange_regexp({'209.249.163.0/25' => 'clotho.com',
'127.0.0.1/32' => 'localhost'});
print match_ip('209.249.163.62', $re2); # prints 'clotho.com'
Be aware that the value string will be wrapped in single quotes in
the regexp. Therefore, you must double-escape any single quotes in
that value. For example:
create_iprange_regexp({'208.201.239.36/31' => 'O\\'Reilly publishing'});
Note that the scalar and hash styles can be mixed (a rarely used
feature). These two examples are equivalent:
create_iprange_regexp('127.0.0.1/32',
{'209.249.163.0/25' => 'clotho.com'},
'10.0.0.0/8',
{'192.168.0.0/16' => 'LAN'});
create_iprange_regexp({'127.0.0.1/32' => 1,
'209.249.163.0/25' => 'clotho.com',
'10.0.0.0/8' => 1,
'192.168.0.0/16' => 'LAN'});
If any of the IP ranges are overlapping, the broadest one is used.
If they are equivalent, then the first one passed is used. If you
have some data that might be ambiguous, you pass an arrayref instead
of a hashref, but it's better to clean up your data instead! For
example:
my $re = create_iprange_regexp(['1.1.1.0/31' => 'zero', '1.1.1.1/31' => 'one']);
print match_ip('1.1.1.1', $re)); # prints 'zero', since both match
WARNING: This function does no checking for validity of IP ranges.
It happily accepts `1000.0.0.0/-38' and makes a garbage regexp.
Hopefully a future version will validate the ranges, perhaps via
Net::CIDR or Net::IP.
create_iprange_regexp_depthfirst($iprange | $hashref | $arrayref, ...)
Returns a regexp in matches the most specific IP range instead of
the broadest range. Example:
my $re = create_iprange_regexp_depthfirst({'192.168.0.0/16' => 'LAN',
'192.168.0.1' => 'router'});
match_ip('192.168.0.1', $re);
returns 'router' instead of 'LAN'.
match_ip($ipaddr, $regexp)
Given a single IP address as a string of the form `aaa.bbb.ccc.ddd'
and a regular expression string (typically the output of
create_iprange_regexp()), this function returns a specified value
(typically `1') if the IP is in one of the ranges, or `undef' if no
ranges match.
See create_ipranges_regexp() for more details about the return value
of this function.
WARNING: This function does no checking for validity of the IP
address.
SEE ALSO
There are several other CPAN modules that perform a similar function.
This one is comparable to or faster than the other ones that I've found
and tried. Here is a synopsis of those others:
Net::IP::Match
Optimized for speed by taking a "source filter" approach. That is, it
modifies your source code at run time, kind of like a C preprocessor. A
huge limitation is that the IP ranges must be hard-coded into your
program.
Net::IP::Match::XS
(Also released as Net::IP::CMatch)
Optimized for speed by doing the match in C instead of in Perl. This
module loses efficiency, however, because the IP ranges must be
re-parsed every invocation.
Net::IP::Resolver
Uses Net::IP::Match::XS to implement a range-to-name map.
PERFORMANCE
I ran a series of test on a Mac G5 with Perl 5.8.6 to compare this
module to Net::IP::Match::XS. The tests are intended to be a realistic
net filter case: 100,000 random IP addresses tested against a number of
semi-random IP ranges. Times are in seconds.
Networks: 1, IPs: 100000
Test name | Setup time | Run time | Total time
-----------------------+------------+----------+------------
Net::IP::Match::XS | 0.000 | 0.415 | 0.415
Net::IP::Match::Regexp | 0.001 | 1.141 | 1.141
Networks: 10, IPs: 100000
Test name | Setup time | Run time | Total time
-----------------------+------------+----------+------------
Net::IP::Match::XS | 0.000 | 0.613 | 0.613
Net::IP::Match::Regexp | 0.003 | 1.312 | 1.316
Networks: 100, IPs: 100000
Test name | Setup time | Run time | Total time
-----------------------+------------+----------+------------
Net::IP::Match::XS | 0.000 | 2.621 | 2.622
Net::IP::Match::Regexp | 0.024 | 1.381 | 1.405
Networks: 1000, IPs: 100000
Test name | Setup time | Run time | Total time
-----------------------+------------+----------+------------
Net::IP::Match::XS | 0.003 | 20.910 | 20.912
Net::IP::Match::Regexp | 0.203 | 1.514 | 1.717
This test indicates that ::Regexp is faster than ::XS when you have more
than about 50 IP ranges to test. The relative run time does not vary
significantly with the number of singe IP to match, but with a small
number of IP addresses to match, the setup time begins to dominate, so
::Regexp loses in that scenario.
To reproduce the above benchmarks, run the following command in the
distribution directory:
perl benchmark/speedtest.pl -s -n 1,10,100,1000 -i 100000
IMPLEMENTATION
The speed of this module comes from the short-circuit nature of regular
expressions. The setup function turns all of the IP ranges into binary
strings, and mixes them into a regexp with `|' choices between ones and
zeros. This regexp can then be passed to the match function. When an
unambiguous match is found, the regexp sets a variable (via the regexp
$LAST_REGEXP_CODE_RESULT, aka $^R, feature) and terminates. That
variable becomes the return value for the match, typically a true value.
Here's an example of the regexp for a single range, that of the
Clotho.com subnet:
print create_iprange_regexp('209.249.163.0/25')'
# ^41101000111111001101000110(?{'1'})
If we add another range, say a NAT LAN, we get:
print create_iprange_regexp('209.249.163.0/25', '192.168.0.0/16')'
# ^4110(?>0000010101000(?{'1'})|1000111111001101000110(?{'1'}))
Note that for a 192.168.x.x address, the regexp checks at most the first
16 bits (1100000010101000) whereas for a 209.249.163.x address, it goes
out to 25 bits (1101000111111001101000110). The cool part is that for an
IP address that starts in the lower half (say 127.0.0.1) only needs to
check the first bit (0) to see that the regexp won't match.
If mapped return values are specified for the ranges, they get embedded
into the regexp like so:
print create_iprange_regexp({'209.249.163.0/25' => 'clotho.com',
'192.168.0.0/16' => 'localhost'})'
# ^4110(?>0000010101000(?{'localhost'})|1000111111001101000110(?{'clotho.com'}))
This could be implemented in C to be even faster. In C, it would
probably be better to use a binary tree instead of a regexp. However, a
goal of this module is to create a serializable representation of the
range data, and the regexp is perfect for that. So, I'll probably never
do a C version.
COMPATIBILITY
Because this module relies on the `(?{ code })' feature of regexps, it
won't work on old Perl versions. I've successfully tested this module on
Perl 5.6.0, 5.8.1 and 5.8.6. In theory, the code regexp feature should
work in 5.005, but I've used `our' and the like, so it won't work there.
I don't have a 5.005 to test anyway...
Update from Oct 2008: I no longer keep a 5.6.0 around, so I rely on
cpantesters.org to tell me when this breaks for older Perls.
CODING
This module has 100% code coverage in its regression tests, as reported
by Devel::Cover via `perl Build testcover'.
This module passes Perl Best Practices guidelines, as enforced by
Perl::Critic v1.093.
AUTHOR
Chris Dolan
I originally developed this module at Clotho Advanced Media Inc. Now I
maintain it in my spare time.
ACKNOWLEDGMENTS
TeachingBooks.net inspired and subsidized development of the original
version of this module.
Chris Snyder contributed a valuable and well-written bug report about
handling missing mask values.
Michael Aronsen of cohaesio.com suggested the depth-first matching
feature.
