readd ip-allocation-threshold

c7n/resources/vpc.py

@@ -2885,3 +2885,59 @@ def process(self, resources, event=None):
                 results.append(resource)
 
         return results
+
+@Subnet.filter_registry.register('ip-allocation-threshold')
+class SubnetIpAllocationFilter(Filter):
+    """Filters subnets based on ip allocation percentage
+    :example:
+    .. code-block:: yaml
+            policies:
+              - name: subnet-ip-threshold-policy
+                resource: subnet
+                filters:
+                  - type: ip-allocation-threshold
+                    percentage: 80
+                    op: gte
+    """
+    schema = type_schema(
+        'ip-allocation-threshold',
+        percentage={'type': 'number'},
+        op={'enum': ['eq', 'ne', 'lt', 'gt', 'lte', 'gte']}
+    )
+
+    permissions = ("ec2:DescribeSubnets",)
+
+    def calculate_ip_allocation(self, subnet):
+        subnetMask = subnet.get('CidrBlock').split('/')[1]
+        hostBits = 32 - int(subnetMask)
+        totalHost = ((2 ** hostBits) - 2)
+        availableHost = subnet.get('AvailableIpAddressCount')
+        ipsUsed = totalHost - availableHost
+        percentageOfIpsUsed = (ipsUsed / totalHost) * 100
+        return percentageOfIpsUsed
+
+    def process(self, resources, event=None):
+        results = []
+        threshold_percentage = self.data.get('percentage')
+        op = self.data.get('op')
+        for subnet in resources:
+            percentage_used = self.calculate_ip_allocation(subnet)
+            if op == 'eq':
+                if threshold_percentage == percentage_used:
+                    results.append(subnet)
+            elif op == 'ne':
+                if threshold_percentage != percentage_used:
+                    results.append(subnet)
+            elif op == 'lt':
+                if percentage_used < threshold_percentage:
+                    results.append(subnet)
+            elif op == 'gt':
+                if percentage_used > threshold_percentage:
+                    results.append(subnet)
+            elif op == 'lte':
+                if (percentage_used < threshold_percentage) or (percentage_used == threshold_percentage):
+                    results.append(subnet)
+            elif op == 'gte':
+                if (percentage_used > threshold_percentage) or (percentage_used == threshold_percentage):
+                    results.append(subnet)
+        return results