[change] Ensure subnet can have multiple subnet division rules

The "rule" field of SubnetDivisionIndex will be set to "None" if
the rule is deleted. Subnets related to indexes with rule "None"
will be deleted.

openwisp_controller/subnet_division/base/models.py

@@ -192,15 +192,18 @@ def update_related_objects(self):
                 )
 
     def delete_provisioned_subnets(self):
-        # Deleting an object of SubnetDivisionRule will automatically delete
-        # it's related SubnetDivisionIndex objects due to "on_delete=CASCADE".
-        # Similarly, deleting a Subnet object will automatically delete IpAddress
-        # objects related to it.
-        # Hence, this method only executes query of deleting Subnets provisioned by
-        # this corresponding SubnetDivisionRule.
+        # Deleting an object of SubnetDivisionRule will set the rule field
+        # of related SubnetDivisionIndex to "None" due to "on_delete=SET_NULL".
+        # These indexes are used delete subnets that were provisioned by the
+        # deleted rule. Deleting a Subnet object will automatically delete
+        # related IpAddress objects.
         Subnet = swapper.load_model('openwisp_ipam', 'Subnet')
+        SubnetDivisionIndex = swapper.load_model(
+            'subnet_division', 'SubnetDivisionIndex'
+        )
+
         Subnet.objects.filter(
-            organization_id=self.organization_id, name__startswith=self.label
+            id__in=SubnetDivisionIndex.objects.filter(rule_id=None).values('subnet_id')
         ).delete()
 
     @classmethod
@@ -241,7 +244,8 @@ class AbstractSubnetDivisionIndex(models.Model):
     )
     rule = models.ForeignKey(
         swapper.get_model_name('subnet_division', 'SubnetDivisionRule'),
-        on_delete=models.CASCADE,
+        null=True,
+        on_delete=models.SET_NULL,
     )
     config = models.ForeignKey(
         swapper.get_model_name('config', 'Config'),

openwisp_controller/subnet_division/migrations/0004_index_rule_on_delete.py

@@ -0,0 +1,24 @@
+# Generated by Django 3.1.13 on 2021-09-27 19:25
+
+import django.db.models.deletion
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('subnet_division', '0003_related_field_allow_blank'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='subnetdivisionindex',
+            name='rule',
+            field=models.ForeignKey(
+                null=True,
+                on_delete=django.db.models.deletion.SET_NULL,
+                to=settings.SUBNET_DIVISION_SUBNETDIVISIONRULE_MODEL,
+            ),
+        ),
+    ]

openwisp_controller/subnet_division/rule_types/base.py

@@ -53,13 +53,25 @@ def provision_receiver(cls, instance, **kwargs):
         def _provision_receiver():
             # If any of following operations fail, the database transaction
             # should fail/rollback.
-            provisioned = cls.create_subnets_ips(instance, rule_type, **kwargs)
-            cls.post_provision_handler(instance, provisioned, **kwargs)
-            cls.subnet_provisioned_signal_emitter(instance, provisioned)
 
-        if kwargs['created'] is False:
+            # This method is also called by "provision_for_existing_objects"
+            # which passes the "rule" keyword argument. In such case,
+            # provisioning should be only triggered for received rule.
+            if 'rule' in kwargs:
+                rules = [kwargs['rule']]
+            else:
+                try:
+                    rules = cls.get_subnet_division_rules(instance)
+                except (AttributeError, ObjectDoesNotExist):
+                    return
+            for rule in rules:
+                provisioned = cls.create_subnets_ips(instance, rule, **kwargs)
+                cls.post_provision_handler(instance, provisioned, **kwargs)
+                cls.subnet_provisioned_signal_emitter(instance, provisioned)
+
+        if not cls.should_create_subnets_ips(instance, **kwargs):
             return
-        rule_type = f'{cls.__module__}.{cls.__name__}'
+
         transaction.on_commit(_provision_receiver)
 
     @classmethod
@@ -99,16 +111,9 @@ def provision_for_existing_objects(cls, rule_obj):
         raise NotImplementedError()
 
     @classmethod
-    def create_subnets_ips(cls, instance, rule_type, **kwargs):
-        if not cls.should_create_subnets_ips(instance, **kwargs):
-            return
+    def create_subnets_ips(cls, instance, division_rule, **kwargs):
         try:
-            organization_id = cls.get_organization(instance)
             config = cls.get_config(instance)
-            subnet = cls.get_subnet(instance)
-            division_rule = subnet.subnetdivisionrule_set.get(
-                organization_id__in=(organization_id, None), type=rule_type,
-            )
         except (AttributeError, ObjectDoesNotExist):
             return
 
@@ -132,6 +137,15 @@ def get_organization(cls, instance):
     def get_subnet(cls, instance):
         return attrgetter(cls.subnet_path)(instance)
 
+    @classmethod
+    def get_subnet_division_rules(cls, instance):
+        rule_type = f'{cls.__module__}.{cls.__name__}'
+        organization_id = cls.get_organization(instance)
+        subnet = cls.get_subnet(instance)
+        return subnet.subnetdivisionrule_set.filter(
+            organization_id__in=(organization_id, None), type=rule_type,
+        ).iterator()
+
     @classmethod
     def get_config(cls, instance):
         if cls.config_path == 'self':
@@ -232,5 +246,8 @@ def destroy_provisioned_subnets_ips(cls, instance, **kwargs):
         # Deleting related subnets automatically deletes related IpAddress
         # and SubnetDivisionIndex objects
         config = cls.get_config(instance)
-        subnet_ids = config.subnetdivisionindex_set.values_list('subnet_id')
+        rule_type = f'{cls.__module__}.{cls.__name__}'
+        subnet_ids = config.subnetdivisionindex_set.filter(
+            rule__type=rule_type
+        ).values_list('subnet_id')
         Subnet.objects.filter(id__in=subnet_ids).delete()

openwisp_controller/subnet_division/rule_types/device.py

@@ -22,13 +22,18 @@ class DeviceSubnetDivisionRuleType(BaseSubnetDivisionRuleType):
 
     @classmethod
     def get_subnet(cls, instance):
-        return instance.device.organization.subnetdivisionrule_set.get(
-            type=f'{cls.__module__}.{cls.__name__}'
-        ).master_subnet
+        pass
+
+    @classmethod
+    def get_subnet_division_rules(cls, instance):
+        rule_type = f'{cls.__module__}.{cls.__name__}'
+        return instance.device.organization.subnetdivisionrule_set.filter(
+            type=rule_type
+        ).iterator()
 
     @classmethod
     def should_create_subnets_ips(cls, instance, **kwargs):
-        return 'created' in kwargs and kwargs['created']
+        return kwargs.get('created', False)
 
     @staticmethod
     def destroy_provisioned_subnets_ips(instance, **kwargs):
@@ -44,6 +49,4 @@ def provision_for_existing_objects(cls, rule_obj):
             .filter(device__organization_id=rule_obj.organization_id)
             .iterator()
         ):
-            cls.provision_receiver(
-                config, created=True,
-            )
+            cls.provision_receiver(config, created=True, rule=rule_obj)

openwisp_controller/subnet_division/rule_types/vpn.py

@@ -22,7 +22,7 @@ class VpnSubnetDivisionRuleType(BaseSubnetDivisionRuleType):
 
     @classmethod
     def should_create_subnets_ips(cls, instance, **kwargs):
-        return kwargs['created']
+        return kwargs.get('created', False)
 
     @classmethod
     def provision_for_existing_objects(cls, rule_obj):

openwisp_controller/subnet_division/tests/test_models.py

@@ -608,6 +608,47 @@ def test_subnet_division_index_validation(self):
             index.config = self.config
             index.full_clean()
 
+    def test_single_subnet_multiple_vpn_rule(self):
+        rule1 = self._get_vpn_subdivision_rule()
+        rule2 = self._get_vpn_subdivision_rule(label='VPN')
+        self.config.templates.add(self.template)
+        self.assertEqual(
+            self.subnet_query.exclude(id=self.master_subnet.id).count(),
+            rule1.number_of_subnets + rule2.number_of_subnets,
+        )
+        rule2.delete()
+        self.assertEqual(
+            self.subnet_query.exclude(id=self.master_subnet.id).count(),
+            rule1.number_of_subnets,
+        )
+
+    def test_single_subnet_multiple_device_rule(self):
+        rule1 = self._get_device_subdivision_rule(label='LAN1')
+        rule2 = self._get_device_subdivision_rule(label='LAN2')
+        self.assertEqual(
+            self.subnet_query.exclude(id=self.master_subnet.id).count(),
+            rule1.number_of_subnets + rule2.number_of_subnets,
+        )
+        rule2.delete()
+        self.assertEqual(
+            self.subnet_query.exclude(id=self.master_subnet.id).count(),
+            rule1.number_of_subnets,
+        )
+
+    def test_single_subnet_vpn_device_rule(self):
+        device_rule = self._get_device_subdivision_rule(label='LAN')
+        vpn_rule = self._get_vpn_subdivision_rule(label='VPN')
+        self.config.templates.add(self.template)
+        self.assertEqual(
+            self.subnet_query.exclude(id=self.master_subnet.id).count(),
+            device_rule.number_of_subnets + vpn_rule.number_of_subnets,
+        )
+        self.config.templates.remove(self.template)
+        self.assertEqual(
+            self.subnet_query.exclude(id=self.master_subnet.id).count(),
+            device_rule.number_of_subnets,
+        )
+
 
 class TestCeleryTasks(TestCase):
     def test_subnet_division_rule_does_not_exist(self):

tests/openwisp2/sample_subnet_division/migrations/0001_initial.py

@@ -144,7 +144,8 @@ class Migration(migrations.Migration):
                 (
                     'rule',
                     models.ForeignKey(
-                        on_delete=django.db.models.deletion.CASCADE,
+                        null=True,
+                        on_delete=django.db.models.deletion.SET_NULL,
                         to='sample_subnet_division.subnetdivisionrule',
                     ),
                 ),