Add is_subnet filter to collection

Sometimes it's useful to know if a subnet belongs to another. For that
purpose we created `is_subnet` filter. It simply returns `true` if a
subnet belongs to another and `false` if not or if both subnets are
equal.

Author: cmeissner

plugins/filter/phpipam.py

@@ -0,0 +1,43 @@
+# Copyright (c) 2020 Christian Meißner
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+
+import ipaddress
+
+
+class FilterModule(object):
+    """Define useful filter in collection."""
+
+    def filters(self):
+        """Export filter for ansible.
+
+        :return: return a dictionary of filters
+        :rtype: dict
+        """
+        return {
+            'is_subnet': self.is_subnet,
+        }
+
+    def is_subnet(self, children, parent):
+        """Check if a subnet belongs to another.
+
+        First argument is a subnet  second another. If the first subnet belongs to second
+
+        :param children: [description]
+        :type children: [type]
+        :param parent: [description]
+        :type parent: [type]
+        :return: [description]
+        :rtype: [type]
+        """
+        c = ipaddress.ip_network(children)
+        p = ipaddress.ip_network(parent)
+
+        if not c.subnet_of(p) or c == p:
+            return False
+        else:
+            return c.subnet_of(p)