Merge ~alexsander-souza/maas:lp2043970_to_34 into maas:3.4

[Alexsander de Souza]

fix(metadataserver): leave discovered interfaces disconnected

don't create a default VLAN for interfaces discovered by hardware sync
when MAAS cannot figure out the correct one.

fixes LP#2043970

(cherry picked from commit 253fdfa645f5596ff824f01f5cea6f2f5d316f13)

[MAAS Lander (maas-lander)]

UNIT TESTS
-b lp2043970_to_34 lp:~alexsander-souza/maas/+git/maas into -b 3.4 lp:~maas-committers/maas

STATUS: SUCCESS
COMMIT: 94f692cb5c4f7feb1ef356700b01c20e21eeaf19

review: Approve

[Alexsander de Souza (alexsander-souza)]

self-approving back-port

review: Approve

diff --git a/src/maasserver/forms/settings.py b/src/maasserver/forms/settings.py
index 3c77516..69415de 100644
--- a/src/maasserver/forms/settings.py
+++ b/src/maasserver/forms/settings.py
@@ -1068,6 +1068,20 @@ CONFIG_ITEMS = {
             "max_value": 1209600,
         },
     },
+    "auto_vlan_creation": {
+        "default": True,
+        "form": forms.BooleanField,
+        "form_kwargs": {
+            "label": "Automatically create VLANs and Fabrics for interfaces",
+            "required": False,
+            "help_text": (
+                "Enables the creation of a default VLAN and Fabric for "
+                "discovered network interfaces when MAAS cannot connect it "
+                "to an existing one. When disabled, the interface is left "
+                "disconnected in these cases."
+            ),
+        },
+    },
 }
 
 
diff --git a/src/maasserver/models/config.py b/src/maasserver/models/config.py
index 4c06aae..e4bca20 100644
--- a/src/maasserver/models/config.py
+++ b/src/maasserver/models/config.py
@@ -147,6 +147,7 @@ def get_default_config():
         "windows_kms_host": None,
         # Session timeout length (s)
         "session_length": 1209600,
+        "auto_vlan_creation": True,
     }
 
 
diff --git a/src/metadataserver/builtin_scripts/network.py b/src/metadataserver/builtin_scripts/network.py
index 3479c09..9282986 100644
--- a/src/metadataserver/builtin_scripts/network.py
+++ b/src/metadataserver/builtin_scripts/network.py
@@ -1,7 +1,7 @@
 from django.db.models.expressions import RawSQL
 from netaddr import IPAddress, IPNetwork
 
-from maasserver.enum import INTERFACE_TYPE, IPADDRESS_TYPE
+from maasserver.enum import INTERFACE_TYPE, IPADDRESS_TYPE, NODE_STATUS
 from maasserver.models.config import Config
 from maasserver.models.fabric import Fabric
 from maasserver.models.interface import (
@@ -506,13 +506,26 @@ def update_parent_vlans(node, interface, parent_nics, update_ip_addresses):
                 parent_nic.save()
 
 
+def auto_vlan_creation(node) -> bool:
+    if node.is_controller:
+        # Always create controller's vlans
+        return True
+
+    if node.status == NODE_STATUS.DEPLOYED:
+        # don't create empty vlan/fabric for interfaces discovered by HW sync,
+        # they cannot be used.
+        return False
+
+    return Config.objects.get_config("auto_vlan_creation", True)
+
+
 def guess_vlan_for_interface(node, links):
     # Make sure that the VLAN on the interface is correct. When
     # links exists on this interface we place it into the correct
     # VLAN. If it cannot be determined and its a new interface it
     # gets placed on its own fabric.
     new_vlan = get_interface_vlan_from_links(links)
-    if new_vlan is None:
+    if new_vlan is None and auto_vlan_creation(node):
         # If the default VLAN on the default fabric has no interfaces
         # associated with it, the first interface will be placed there
         # (rather than creating a new fabric).
diff --git a/src/metadataserver/builtin_scripts/tests/test_network.py b/src/metadataserver/builtin_scripts/tests/test_network.py
index a1853b4..214df73 100644
--- a/src/metadataserver/builtin_scripts/tests/test_network.py
+++ b/src/metadataserver/builtin_scripts/tests/test_network.py
@@ -10,6 +10,7 @@ from maasserver.enum import (
     NODE_TYPE,
 )
 from maasserver.models import Event, EventType
+from maasserver.models.config import Config
 from maasserver.models.fabric import Fabric
 from maasserver.models.interface import (
     BondInterface,
@@ -86,6 +87,35 @@ class TestUpdateInterfaces(MAASServerTestCase, UpdateInterfacesMixin):
         eth0 = node.current_config.interface_set.get(name="eth0")
         self.assertEqual(eth0.numa_node, node.default_numanode)
 
+    def test_dont_create_default_vlan_for_deployed_machines(self):
+        node = factory.make_Machine(status=NODE_STATUS.DEPLOYED)
+        data = FakeCommissioningData()
+        data_eth0 = data.create_physical_network(
+            "eth0",
+            mac_address="11:11:11:11:11:11",
+        )
+        data_eth0.state = "up"
+        self.update_interfaces(node, data)
+        eth0 = PhysicalInterface.objects.get(
+            name="eth0", node_config=node.current_config
+        )
+        self.assertIsNone(eth0.vlan)
+
+    def test_dont_create_default_vlan_if_disabled(self):
+        Config.objects.set_config(name="auto_vlan_creation", value=False)
+        node = factory.make_Machine(status=NODE_STATUS.NEW)
+        data = FakeCommissioningData()
+        data_eth0 = data.create_physical_network(
+            "eth0",
+            mac_address="11:11:11:11:11:11",
+        )
+        data_eth0.state = "up"
+        self.update_interfaces(node, data)
+        eth0 = PhysicalInterface.objects.get(
+            name="eth0", node_config=node.current_config
+        )
+        self.assertIsNone(eth0.vlan)
+
     def test_all_new_physical_interfaces_no_links(self):
         controller = self.create_empty_controller()
         data = FakeCommissioningData()