Remove dependency on Data::Validate::IP

This module is not available by default on many systems, and not
available at all on lightweight embedded systems.

ChangeLog.md

@@ -8,6 +8,7 @@ repository history](https://github.com/ddclient/ddclient/commits/master).
 ### New features
 
   * Added support for OVH DynHost.
+  * Removed dependency on Data::Validate::IP.
 
 ### Compatibility changes
 

README.md

@@ -46,7 +46,6 @@ through github.com. Please check out http://ddclient.net
 - one or more accounts from one of the dynamic DNS services
 
 - Perl v5.10.1 or later
-  - `Data::Validate::IP` perl library
   - `IO::Socket::SSL` perl library for ssl-support
   - `JSON::PP` perl library for JSON support
   - `IO::Socket:INET6` perl library for ipv6-support

ddclient

@@ -24,7 +24,6 @@ use warnings;
 use Getopt::Long;
 use Sys::Hostname;
 use IO::Socket;
-use Data::Validate::IP;
 
 my $version  = "3.9.1";
 my $programd = $0;
@@ -2306,6 +2305,15 @@ sub get_ip {
     return $ip;
 }
 
+######################################################################
+## is_ipv6() validates if string is valid IPv6 address
+######################################################################
+sub is_ipv6 {
+    my ($value) = @_;
+    # This little gem from http://home.deds.nl/~aeron/regex/
+    return $value =~ /^(((?=.*(::))(?!.*\3.+\3))\3?|([\dA-F]{1,4}(\3|:\b|$)|\2))(?4){5}((?4){2}|(((2[0-4]|1\d|[1-9])?\d|25[0-5])\.?\b){4})\z/ai;
+}
+
 ######################################################################
 ## ipv6_match determine ipv6 address from given string and return them
 ######################################################################