(FACT-3172) Fix filtering of Unique Local Unicast addresses

We do not want these addresses to be reported as the default IPv6
address in `networking.ip6`.  Quoting RFC4193:

> This document defines an IPv6 unicast address format that is globally
> unique and is intended for local communications, usually inside of a
> site.  These addresses are not expected to be routable on the global
> Internet.

Author: smortex

lib/facter/util/resolvers/networking/networking.rb

@@ -66,6 +66,7 @@ def find_valid_binding(bindings)
 
           IPV4_LINK_LOCAL_ADDR = IPAddr.new('169.254.0.0/16').freeze # RFC5735
           IPV6_LINK_LOCAL_ADDR = IPAddr.new('fe80::/10').freeze # RFC4291
+          IPV6_UNIQUE_LOCAL_ADDR = IPAddr.new('fc00::/7').freeze # RFC4193
 
           def ignored_ip_address(addr)
             return true if addr.empty?
@@ -75,7 +76,8 @@ def ignored_ip_address(addr)
 
             [
               IPV4_LINK_LOCAL_ADDR,
-              IPV6_LINK_LOCAL_ADDR
+              IPV6_LINK_LOCAL_ADDR,
+              IPV6_UNIQUE_LOCAL_ADDR
             ].each do |range|
               return true if range.include?(ip)
             end

spec/facter/util/resolvers/networking/networking_spec.rb

@@ -263,6 +263,36 @@
       end
     end
 
+    context 'when there is a unique local ip address' do
+      let(:networking_facts) do
+        {
+          interfaces:
+            { 'lo0' =>
+              { mtu: 16_384,
+                bindings6:
+                  [{ address: '::1',
+                     netmask: 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff',
+                     network: '::1' },
+                   { address: 'fdfc:f496:4c6f:0:b0e3:7bff:fe3a:6baf',
+                     netmask: 'ffff:ffff:ffff:ffff::',
+                     network: 'fdfc:f496:4c6f:0::' }] } }
+        }
+      end
+
+      it 'expands the correct binding' do
+        expected = {
+          ip6: '::1',
+          netmask6: 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff',
+          network6: '::1',
+          scope6: 'host'
+        }
+
+        networking_helper.expand_main_bindings(networking_facts)
+
+        expect(networking_facts[:interfaces]['lo0']).to include(expected)
+      end
+    end
+
     context 'when there is a global ip address' do
       let(:networking_facts) do
         {