Add ip_to_reverse function

This function calculate the reverse for an IPv4 or IPv6 address

Fixes: #228

REFERENCE.md

@@ -19,6 +19,7 @@
 * [`extlib::file_separator`](#extlib--file_separator): Returns the os specific file path separator.
 * [`extlib::has_module`](#extlib--has_module): A function that lets you know whether a specific module is on your modulepath.
 * [`extlib::ip_to_cron`](#extlib--ip_to_cron): Provides a "random" value to cron based on the last bit of the machine IP address. used to avoid starting a certain cron job at the same time
+* [`extlib::ip_to_reverse`](#extlib--ip_to_reverse): Returns the reverse of an IP address
 * [`extlib::is_in_cidr`](#extlib--is_in_cidr): Returns a boolean indicating whether an IP address is part of a network CIDR
 * [`extlib::last_in_cidr`](#extlib--last_in_cidr): Converts an IPv4 or IPv6 CIDR address of the form 192.0.2.1/24 or 2001:db8::1/64 into the last address in the network
 * [`extlib::mkdir_p`](#extlib--mkdir_p): Like the unix command mkdir_p except with puppet code.
@@ -636,6 +637,42 @@ Data type: `Optional[Integer[1]]`
 
 The number of seconds to use as the run interval
 
+### <a name="extlib--ip_to_reverse"></a>`extlib::ip_to_reverse`
+
+Type: Ruby 4.x API
+
+Not actual query is done to the DNS server, it only calculate the record
+that could be added to a DNS zone file.
+
+#### Examples
+
+##### Calling the function
+
+```puppet
+extlib::ip_to_reverse('192.0.2.0')
+```
+
+#### `extlib::ip_to_reverse(Stdlib::IP::Address::Nosubnet $ip)`
+
+Not actual query is done to the DNS server, it only calculate the record
+that could be added to a DNS zone file.
+
+Returns: `String`
+
+##### Examples
+
+###### Calling the function
+
+```puppet
+extlib::ip_to_reverse('192.0.2.0')
+```
+
+##### `ip`
+
+Data type: `Stdlib::IP::Address::Nosubnet`
+
+IPv4 or IPv6 address
+
 ### <a name="extlib--is_in_cidr"></a>`extlib::is_in_cidr`
 
 Type: Ruby 4.x API

lib/puppet/functions/extlib/ip_to_reverse.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require 'ipaddr'
+
+# @summary Returns the reverse of an IP address
+#
+# Not actual query is done to the DNS server, it only calculate the record
+# that could be added to a DNS zone file.
+Puppet::Functions.create_function(:'extlib::ip_to_reverse') do
+  # @param ip
+  #   IPv4 or IPv6 address
+  #
+  # @example Calling the function
+  #   extlib::ip_to_reverse('192.0.2.0')
+  dispatch :ip_to_reverse? do
+    param 'Stdlib::IP::Address::Nosubnet', :ip
+    return_type 'String'
+  end
+
+  def ip_to_reverse?(ip)
+    IPAddr(ip).reverse
+  end
+end