[fix] Ensure VpnClient.post_delete fires on VPN template removal openwisp#1221

Replaced QuerySet.delete() with per-instance deletion in all three
locations where VpnClient objects are bulk-deleted so that post_delete
signals fire for every instance, ensuring:
- VPN peer cache is invalidated on the affected VPN server
- Client certificates are revoked (OpenVPN, auto_cert=True)
- IP addresses are released (Wireguard)

Also fixed the serializers.py cleanup logic: vpn_list was built from
the old templates so .exclude(vpn__in=vpn_list) never matched the
client being removed. Now uses new_vpn_ids from config_templates (the
incoming new set) so PATCH with an empty templates list also works.

Added select_related("vpn", "cert", "ip") to all deletion querysets
to avoid N+1 queries triggered by the post_delete signal handler.
Wrapped deletion loops in transaction.atomic() to prevent partial
deletions on failure.

Fixes openwisp#1221
[backport 1.2]

Author: mn-ram

CHANGES.rst

@@ -4,7 +4,14 @@ Changelog
 Version 1.3.0 [unreleased]
 --------------------------
 
-Work in progress.
+Bugfixes
+~~~~~~~~
+
+- Fixed VPN peer cache desync when a VPN template is removed from a
+  device: replaced bulk ``QuerySet.delete()`` with per-instance deletion
+  so that ``post_delete`` signals fire, ensuring peer cache invalidation,
+  certificate revocation and IP address release `#1221
+  <https://github.com/openwisp/openwisp-controller/issues/1221>`_
 
 Version 1.2.2 [2026-03-06]
 --------------------------

openwisp_controller/config/api/serializers.py

@@ -200,16 +200,17 @@ def _update_config(self, device, config_data):
             old_templates = list(config.templates.values_list("id", flat=True))
             if config_templates != old_templates:
                 with transaction.atomic():
-                    vpn_list = config.templates.filter(type="vpn").values_list("vpn")
-                    if vpn_list:
-                        # Per-instance delete ensures post_delete signals fire
-                        # (cache invalidation, cert revocation, IP release).
-                        for vpnclient in (
-                            config.vpnclient_set.exclude(vpn__in=vpn_list)
-                            .select_related("vpn", "cert", "ip")
-                            .iterator()
-                        ):
-                            vpnclient.delete()
+                    # Per-instance delete ensures post_delete signals fire
+                    # (cache invalidation, cert revocation, IP release).
+                    new_vpn_ids = Template.objects.filter(
+                        pk__in=config_templates, type="vpn"
+                    ).values_list("vpn", flat=True)
+                    for vpnclient in (
+                        config.vpnclient_set.select_related("vpn", "cert", "ip")
+                        .exclude(vpn__in=new_vpn_ids)
+                        .iterator()
+                    ):
+                        vpnclient.delete()
                     config.templates.set(config_templates, clear=True)
             config.save()
         except ValidationError as error:

openwisp_controller/config/tests/test_api.py

@@ -26,6 +26,7 @@
 Template = load_model("config", "Template")
 Vpn = load_model("config", "Vpn")
 VpnClient = load_model("config", "VpnClient")
+Cert = load_model("django_x509", "Cert")
 Device = load_model("config", "Device")
 Config = load_model("config", "Config")
 DeviceGroup = load_model("config", "DeviceGroup")
@@ -518,6 +519,50 @@ def test_device_patch_with_templates_of_different_org(self):
             f" do not match the organization of this configuration: {t3}",
         )
 
+    def test_device_patch_vpn_template_removal_triggers_post_delete(self):
+        """Regression test for #1221: removing VPN template via PATCH API must
+        trigger VpnClient.post_delete so peer cache is invalidated and the
+        certificate is revoked. Tests both empty and non-empty replacement."""
+        org = self._get_org()
+        vpn = self._create_vpn(organization=org)
+        t_vpn = self._create_template(
+            name="vpn-test", type="vpn", vpn=vpn, auto_cert=True, organization=org
+        )
+        t_generic = self._create_template(name="generic-test", organization=org)
+        device = self._create_device(organization=org)
+        config = self._create_config(device=device)
+        path = reverse("config_api:device_detail", args=[device.pk])
+
+        with self.subTest("replace VPN template with generic template"):
+            config.templates.set([t_vpn])
+            vpnclient = config.vpnclient_set.first()
+            self.assertIsNotNone(vpnclient)
+            cert_pk = vpnclient.cert.pk
+            data = {"config": {"templates": [str(t_generic.pk)]}}
+            with patch.object(Vpn, "_invalidate_peer_cache") as mock_invalidate:
+                response = self.client.patch(
+                    path, data, content_type="application/json"
+                )
+                mock_invalidate.assert_called_once()
+            self.assertEqual(response.status_code, 200)
+            self.assertFalse(VpnClient.objects.filter(pk=vpnclient.pk).exists())
+            self.assertTrue(Cert.objects.get(pk=cert_pk).revoked)
+
+        with self.subTest("remove all templates (empty list)"):
+            config.templates.set([t_vpn])
+            vpnclient = config.vpnclient_set.first()
+            self.assertIsNotNone(vpnclient)
+            cert_pk = vpnclient.cert.pk
+            data = {"config": {"templates": []}}
+            with patch.object(Vpn, "_invalidate_peer_cache") as mock_invalidate:
+                response = self.client.patch(
+                    path, data, content_type="application/json"
+                )
+                mock_invalidate.assert_called_once()
+            self.assertEqual(response.status_code, 200)
+            self.assertFalse(VpnClient.objects.filter(pk=vpnclient.pk).exists())
+            self.assertTrue(Cert.objects.get(pk=cert_pk).revoked)
+
     def test_device_change_organization_required_templates(self):
         org1 = self._create_org(name="org1")
         org2 = self._create_org(name="org2")

openwisp_controller/config/tests/test_vpn.py

@@ -286,6 +286,70 @@ def _assert_vpn_client_cert(cert, vpn_client, cert_ct, vpn_client_ct):
             vpnclient.save()
             _assert_vpn_client_cert(cert, vpnclient, 1, 0)
 
+    def test_vpn_client_post_delete_on_template_removal(self):
+        """Regression test for #1221: VpnClient.post_delete must fire
+        when a VPN template is removed so that peer cache is invalidated
+        and certificates are properly revoked."""
+        org = self._get_org()
+        vpn = self._create_vpn()
+        t = self._create_template(name="vpn-test", type="vpn", vpn=vpn, auto_cert=True)
+        c = self._create_config(organization=org)
+        c.templates.add(t)
+        vpnclient = c.vpnclient_set.first()
+        self.assertIsNotNone(vpnclient)
+        cert_pk = vpnclient.cert.pk
+        with mock.patch.object(Vpn, "_invalidate_peer_cache") as mock_invalidate:
+            c.templates.remove(t)
+            mock_invalidate.assert_called_once()
+        self.assertFalse(VpnClient.objects.filter(pk=vpnclient.pk).exists())
+        # Certificate should be revoked (auto_cert=True)
+        self.assertTrue(Cert.objects.get(pk=cert_pk).revoked)
+
+    def test_vpn_client_post_delete_on_device_deactivation(self):
+        """Regression test for #1221: VpnClient.post_delete must fire
+        when a device is deactivated so that peer cache is invalidated
+        and certificates are properly revoked."""
+        org = self._get_org()
+        vpn = self._create_vpn()
+        t = self._create_template(name="vpn-test", type="vpn", vpn=vpn, auto_cert=True)
+        d = self._create_device(organization=org)
+        c = self._create_config(device=d)
+        c.templates.add(t)
+        vpnclient = c.vpnclient_set.first()
+        self.assertIsNotNone(vpnclient)
+        cert_pk = vpnclient.cert.pk
+        with mock.patch.object(Vpn, "_invalidate_peer_cache") as mock_invalidate:
+            d.deactivate()
+            mock_invalidate.assert_called_once()
+        self.assertFalse(VpnClient.objects.filter(pk=vpnclient.pk).exists())
+        # Certificate should be revoked (auto_cert=True)
+        self.assertTrue(Cert.objects.get(pk=cert_pk).revoked)
+
+    def test_vpn_client_post_delete_multiple_clients(self):
+        """Regression test for #1221: when a device has multiple VPN templates,
+        removing all of them must delete every VpnClient, invalidate peer cache
+        for each VPN, and revoke all auto-created certificates."""
+        org = self._get_org()
+        vpn1 = self._create_vpn(name="vpn1")
+        vpn2 = self._create_vpn(name="vpn2", ca=vpn1.ca)
+        t1 = self._create_template(name="vpn-t1", type="vpn", vpn=vpn1, auto_cert=True)
+        t2 = self._create_template(name="vpn-t2", type="vpn", vpn=vpn2, auto_cert=True)
+        d = self._create_device(organization=org)
+        c = self._create_config(device=d)
+        c.templates.add(t1, t2)
+        self.assertEqual(c.vpnclient_set.count(), 2)
+        vpnclient1 = c.vpnclient_set.get(vpn=vpn1)
+        vpnclient2 = c.vpnclient_set.get(vpn=vpn2)
+        cert_pk1 = vpnclient1.cert.pk
+        cert_pk2 = vpnclient2.cert.pk
+        with mock.patch.object(Vpn, "_invalidate_peer_cache") as mock_invalidate:
+            d.deactivate()
+            self.assertEqual(mock_invalidate.call_count, 2)
+        self.assertFalse(VpnClient.objects.filter(pk=vpnclient1.pk).exists())
+        self.assertFalse(VpnClient.objects.filter(pk=vpnclient2.pk).exists())
+        self.assertTrue(Cert.objects.get(pk=cert_pk1).revoked)
+        self.assertTrue(Cert.objects.get(pk=cert_pk2).revoked)
+
     def test_vpn_client_get_common_name(self):
         vpn = self._create_vpn()
         d = self._create_device()
@@ -728,6 +792,18 @@ def test_trigger_vpn_server_endpoint_invalid_vpn_id(self):
                 f"VPN Server UUID: {vpn_id} does not exist."
             )
 
+    def test_wireguard_vpnclient_ip_released_on_template_removal(self):
+        """Regression test for #1221: when a Wireguard VPN template is removed,
+        the allocated IP address must be released (deleted)."""
+        device, vpn, template = self._create_wireguard_vpn_template()
+        vpnclient = device.config.vpnclient_set.first()
+        self.assertIsNotNone(vpnclient)
+        self.assertIsNotNone(vpnclient.ip)
+        ip_pk = vpnclient.ip.pk
+        device.config.templates.remove(template)
+        self.assertFalse(VpnClient.objects.filter(pk=vpnclient.pk).exists())
+        self.assertFalse(IpAddress.objects.filter(pk=ip_pk).exists())
+
 
 class TestWireguardTransaction(BaseTestVpn, TestWireguardVpnMixin, TransactionTestCase):
     mock_response = mock.Mock(spec=requests.Response)