Net::CIDR - Manipulate IPv4/IPv6 netblocks in CIDR notation use Net::CIDR; use Net::CIDR ':all'; print join("\n", Net::CIDR::range2cidr("192.68.0.0-192.68.255.255", "10.0.0.0-10.3.255.255")) . "\n"; # # Output from above: # # 192.68.0.0/16 # 10.0.0.0/14 print join("\n", Net::CIDR::range2cidr( "dead:beef::-dead:beef:ffff:ffff:ffff:ffff:ffff:ffff")) . "\n"; # # Output from above: # # dead:beef::/32 print join("\n", Net::CIDR::range2cidr("192.68.1.0-192.68.2.255")) . "\n"; # # Output from above: # # 192.68.1.0/24 # 192.68.2.0/24 print join("\n", Net::CIDR::cidr2range("192.68.0.0/16")) . "\n"; # # Output from above: # # 192.68.0.0-192.68.255.255 print join("\n", Net::CIDR::cidr2range("dead::beef::/46")) . "\n"; # # Output from above: # # dead:beef::-dead:beef:3:ffff:ffff:ffff:ffff:ffff @list=("192.68.0.0/24"); @list=Net::CIDR::cidradd("192.68.1.0-192.68.1.255", @list); print join("\n", @list) . "\n"; # # Output from above: # # 192.68.0.0/23 print join("\n", Net::CIDR::cidr2octets("192.68.0.0/22")) . "\n"; # # Output from above: # # 192.68.0 # 192.68.1 # 192.68.2 # 192.68.3 print join("\n", Net::CIDR::cidr2octets("dead::beef::/46")) . "\n"; # # Output from above: # # dead:beef:0000 # dead:beef:0001 # dead:beef:0002 # dead:beef:0003 @list=("192.68.0.0/24"); print Net::CIDR::cidrlookup("192.68.0.12", @list); # # Output from above: # # 1 @list = Net::CIDR::addr2cidr("192.68.0.31"); print join("\n", @list); # # Output from above: # # 192.68.0.31/32 # 192.68.0.30/31 # 192.68.0.28/30 # 192.68.0.24/29 # 192.68.0.16/28 # 192.68.0.0/27 # 192.68.0.0/26 # 192.68.0.0/25 # 192.68.0.0/24 # 192.68.0.0/23 # [and so on] The Net::CIDR package contains functions that manipulate lists of IP netblocks expressed in CIDR notation. The Net::CIDR functions handle both IPv4 and IPv6 addresses.

@cidr_list=Net::CIDR::range2cidr(@range_list);
Each element in the @range_list is a string "start-finish", where "start" is the first IP address and "finish" is the last IP address. range2cidr() converts each range into an equivalent CIDR netblock. It returns a list of netblocks except in the case where it is given only one parameter and is called in scalar context. For example: @a=Net::CIDR::range2cidr("192.68.0.0-192.68.255.255"); The result is a one-element array, with $a[0] being "192.68.0.0/16". range2cidr() processes each "start-finish" element in @range_list separately. But if invoked like so: $a=Net::CIDR::range2cidr("192.68.0.0-192.68.255.255"); The result is a scalar "192.68.0.0/16". Where each element cannot be expressed as a single CIDR netblock range2cidr() will generate as many CIDR netblocks as are necessary to cover the full range of IP addresses. Example: @a=Net::CIDR::range2cidr("192.68.1.0-192.68.2.255"); The result is a two element array: ("192.68.1.0/24","192.68.2.0/24"); @a=Net::CIDR::range2cidr( "d08c:43::-d08c:43:ffff:ffff:ffff:ffff:ffff:ffff"); The result is an one element array: ("d08c:43::/32") that reflects this IPv6 netblock in CIDR notation. range2cidr() does not merge adjacent or overlapping netblocks in @range_list.

@range_list=Net::CIDR::cidr2range(@cidr_list);
The cidr2range() functions converts a netblock list in CIDR notation to a list of "start-finish" IP address ranges: @a=Net::CIDR::cidr2range("10.0.0.0/14", "192.68.0.0/24"); The result is a two-element array: ("10.0.0.0-10.3.255.255", "192.68.0.0-192.68.0.255"). @a=Net::CIDR::cidr2range("d08c:43::/32"); The result is a one-element array: ("d08c:43::-d08c:43:ffff:ffff:ffff:ffff:ffff:ffff"). cidr2range() does not merge adjacent or overlapping netblocks in @cidr_list.

@netblock_list = Net::CIDR::addr2cidr($address);
The addr2cidr function takes an IP address and returns a list of all the CIDR netblocks it might belong to: @a=Net::CIDR::addr2range('192.68.0.31'); The result is a thirtythree-element array: ('192.68.0.31/32', '192.68.0.30/31', '192.68.0.28/30', '192.68.0.24/29', [and so on]) consisting of all the possible subnets containing this address from 0.0.0.0/0 to address/32. Any addresses supplied to addr2range after the first will be ignored. It works similarly for IPv6 addresses, returning a list of one hundred and twenty nine elements.

@octet_list=Net::CIDR::cidr2octets(@cidr_list);
cidr2octets() takes @cidr_list and returns a list of leading octets representing those netblocks. Example: @octet_list=Net::CIDR::cidr2octets("10.0.0.0/14", "192.68.0.0/24"); The result is the following five-element array: ("10.0", "10.1", "10.2", "10.3", "192.68.0"). For IPv6 addresses, the hexadecimal words in the resulting list are zero-padded: @octet_list=Net::CIDR::cidr2octets("::dead:beef:0:0/110"); The result is a four-element array: ("0000:0000:0000:0000:dead:beef:0000", "0000:0000:0000:0000:dead:beef:0001", "0000:0000:0000:0000:dead:beef:0002", "0000:0000:0000:0000:dead:beef:0003"). Prefixes of IPv6 CIDR blocks should be even multiples of 16 bits, otherwise they can potentially expand out to a 32,768-element array, each!

@cidr_list=Net::CIDR::cidradd($block, @cidr_list);
The cidradd() functions allows a CIDR list to be built one CIDR netblock at a time, merging adjacent and overlapping ranges. $block is a single netblock, expressed as either "start-finish", or "address/prefix". Example: @cidr_list=Net::CIDR::range2cidr("192.68.0.0-192.68.0.255"); @cidr_list=Net::CIDR::cidradd("10.0.0.0/8", @cidr_list); @cidr_list=Net::CIDR::cidradd("192.68.1.0-192.68.1.255", @cidr_list); The result is a two-element array: ("10.0.0.0/8", "192.68.0.0/23"). IPv6 addresses are handled in an analogous fashion.

$found=Net::CIDR::cidrlookup($ip, @cidr_list);
Search for $ip in @cidr_list. $ip can be a single IP address, or a netblock in CIDR or start-finish notation. lookup() returns 1 if $ip overlaps any netblock in @cidr_list, 0 if not.

$ip=Net::CIDR::cidrvalidate($ip);
Validate whether $ip is a valid IPv4 or IPv6 address. Returns its argument or undef. Spaces are removed, and IPv6 hexadecimal address are converted to lowercase. Garbage in, garbage out. Always use validate() before doing anything with untrusted input. Otherwise, "slightly" invalid input will work (extraneous whitespace is generally OK), but the functions will croak if you're totally off the wall. Sam Varshavchik <sam@email-scan.com> With some contributions from David Cantrell <david@cantrell.org.uk>