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Re: finding netmask for "arbitrary" ip address

by Khen1950fx (Canon)
on Nov 29, 2011 at 02:35 UTC ( #940508=note: print w/ replies, xml ) Need Help??


in reply to finding netmask for "arbitrary" ip address

In the original, Net::Subnet, there were a couple of typos at lines 41 and 52. Heres the fixed source:

package Net::Subnet; use strict; use Socket; use Socket6; use base 'Exporter'; our @EXPORT = qw(subnet_matcher subnet_classifier sort_subnets); our $VERSION = '1.02'; sub cidr2mask_v4 { my ($length) = @_; return pack "N", 0xffffffff << (32 - $length); } sub cidr2mask_v6 { my ($length) = @_; my $mask = "\x00" x 16; vec($mask, $_, 1) = 1 for 0 .. ($length - 1); return $mask; } sub subnet_matcher { @_ > 1 and goto &multi_matcher; my ($net, $mask) = split m[/], shift; return $net =~ /:/ ? ipv6_matcher($net, $mask) : ipv4_matcher($net, $mask); } sub ipv4_matcher { my ($net, $mask) = @_; $net = inet_aton($net); $mask = $mask =~ /\./ ? inet_aton($mask) : cidr2mask_v4($mask); my $masked_net = $net & $mask; return sub { ((inet_aton(shift) || return !1) & $mask) eq $masked_ +net }; } sub ipv6_matcher { my ($net, $mask) = @_; $net = inet_pton(AF_INET6, $net); $mask = $mask =~ /:/ ? inet_pton(AF_INET6, $mask) : cidr2mask_v6($ +mask); my $masked_net = $net & $mask; return sub { ((inet_pton(AF_INET6,shift) || return!1) & $mask) eq +$masked_net} } sub multi_matcher { my @v4 = map subnet_matcher($_), grep !/:/, @_; my @v6 = map subnet_matcher($_), grep /:/, @_; return sub { $_->($_[0]) and return 1 for $_[0] =~ /:/ ? @v6 : @v4; return !!0; } } use constant MATCHER => 0; use constant SUBNET => 1; sub subnet_classifier { # MATCHER, SUBNET my @v4 = map [ subnet_matcher($_), $_ ], grep !/:/, @_; my @v6 = map [ subnet_matcher($_), $_ ], grep /:/, @_; return sub { $_->[MATCHER]->($_[0]) and return $_->[SUBNET] for $_[0] =~ /:/ ? @v6 : @v4; return undef; } } sub sort_subnets { my @unsorted; for (@_) { my ($net, $mask) = split m[/]; $mask = $net =~ /:/ ? ($mask =~ /:/ ? inet_pton(AF_INET6, $mask) : cidr2mask_v +6($mask)) : ($mask =~ /\./ ? inet_aton($mask) : cidr2mask_v4($mask)) +; $net = $net =~ /:/ ? inet_pton(AF_INET6, $net) : inet_aton($net); push @unsorted, sprintf "%-16s%-16s%s", ($net & $mask), $mask, + $_; } return map substr($_, 32), reverse sort @unsorted; } 1; __END__ =head1 NAME Net::Subnet - Fast IP-in-subnet matcher for IPv4 and IPv6, CIDR or mas +k. =head1 SYNOPSIS use Net::Subnet; # CIDR notation my $is_rfc1918 = subnet_matcher qw( 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 ); # Subnet mask notation my $is_rfc1918 = subnet_matcher qw( 10.0.0.0/255.0.0.0 172.16.0.0/255.240.0.0 192.168.0.0/255.255.0.0 ); print $is_rfc1918->('192.168.1.1') ? 'yes' : 'no'; # prints "yes" print $is_rfc1918->('8.8.8.8') ? 'yes' : 'no'; # prints "no" # Mixed IPv4 and IPv6 my $in_office_network = subnet_matcher qw( 192.168.1.0/24 2001:db8:1337::/48 ); $x = $in_office_network->('192.168.1.1'); # $x is true $x = $in_office_network->('2001:db8:dead:beef::5'); # $x is false my $classifier = subnet_classifier qw( 192.168.1.0/24 2001:db8:1337::/48 10.0.0.0/255.0.0.0 ); $x = $classifier->('192.168.1.250'); # $x is '192.168.1.0/2 +4' $x = $classifier->('2001:db8:1337::babe'); # $x is '2001:db8:1337 +::/48' $x = $classifier->('10.2.127.1'); # $x is '10.0.0.0/255. +0.0.0' $x = $classifier->('8.8.8.8'); # $x is undef # More specific subnets (smaller subnets) must be listed first my @subnets = sort_subnets( '192.168.0.0/24', # second '192.168.0.1/32', # first '192.168.0.0/16', # third ); my $classifier = subnet_classifier @subnets; =head1 DESCRIPTION This is a simple but fast pure Perl module for determining whether a g +iven IP address is in a given set of IP subnets. It's iterative, and it doesn' +t use any fancy tries, but because it uses simple bitwise operations on strings +it's still very fast. All documented functions are exported by default. Subnets have to be given in "address/mask" or "address/length" (CIDR) +format. The Socket and Socket6 modules are used to normalise addresses, which +means that any of the address formats supported by inet_aton and inet_pton c +an be used with Net::Subnet. =head1 FUNCTIONS =head2 subnet_matcher(@subnets) Returns a reference to a function that returns true if the given IP ad +dress is in @subnets, false it it's not. =head2 subnet_classifier(@subnets) Returns a reference to a function that returns the element from @subne +ts that matches the given IP address, or undef if none matched. =head2 sort_subnets(@subnets) Returns @subnets in reverse order of prefix length and prefix; use thi +s with subnet_matcher or subnet_classifier if your subnet list has overlappin +g ranges and it's not already sorted most-specific-first. =head1 TRICKS =head2 Generating PTR records for IPv6 If you need to classify an IP address, but want some other value than +the original subnet string, just use a hash. You could even use code refer +ences; here's an example of how to generate dynamic reverse DNS records for I +Pv6 addresses: my %ptr = ( '2001:db8:1337:d00d::/64' => sub { my $hostname = get_machine_name(shift); return $hostname =~ /\.$/ ? $hostname : "$hostname.example +.org."; }, '2001:db8:1337:babe::/64' => sub { my $hostname = get_machine_name(shift); return $hostname =~ /\.$/ ? $hostname : "$hostname.example +.net."; }, '::/0' => sub { (my $ip = shift) =~ s/:/x/g; return "$ip.unknown.example.com."; }, ); my $classifier = subnet_classifier sort_subnets keys %ptr; while (my $ip = readline) { # We get IP adresses from STDIN and return the hostnames on ST +DOUT print $ptr{ $classifier->($ip) }->($ip), "\n"; } =head2 Matching ::ffff:192.168.1.200 IPv4 subnets only match IPv4 addresses. If you need to match IPv4-mapp +ed IPv6 addresses, i.e. IPv4 addresses with C<::ffff:> stuck in front of them, + simply remove that part before matching: my $matcher = subnet_matcher qw(192.168.1.0/22); $ip =~ s/^::ffff://; my $boolean = $matcher->($ip); Alternatively, translate the subnet definition to IPv6 notation: C<1.2 +.3.0/24> becomes C<::ffff:1.2.3.0/120>. If you do this, hexadecimal addresses s +uch as C<::ffff:102:304> will also match, but IPv4 addresses without C<::ffff +:> will no longer match unless you include C<1.2.3.0/24> as well. my $matcher = subnet_matcher qw(::ffff:192.168.1.0/118 192.168.1.0 +/22); my $boolean = $matcher->($ip); =head1 CAVEATS No argument verification is done; garbage in, garbage out. If you give + it hostnames, DNS may be used to resolve them, courtesy of the Socket and + Socket6 modules. =head1 AUTHOR Juerd Waalboer <juerd#@tnx.nl> =head1 LICENSE This library is free software; you can redistribute it and/or modify i +t under the same terms as Perl itself.
========================================================
Now, after manually installing with the new source:
!/usr/bin/perl -slw use strict; use warnings; use Net::Subnet; my $is_rfc1918 = subnet_matcher qw( 10.96.2.0/255.255.254.0 10.123.50.0/255.255.255.0 72.24.196.0/255.255.255.0 72.24.137.192/255.255.255.192 10.122.50.0/255.255.255.0 ); print $is_rfc1918->('10.96.2.0') ? 'yes' : 'no';
Outputs:
yes


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