Merge ~cgrabowski/maas:fix_vlan_discovery_3.2 into maas:3.2

[Christian Grabowski]

update report_neighbours test
(cherry picked from commit 50f817870f78b6fadfe6f7c0e371d92ef7a93d0c)

ignore observed vlan if already exists
(cherry picked from commit 717044811f229360753ea10ff32f91ea897f16ec)

[MAAS Lander (maas-lander)]

UNIT TESTS
-b fix_vlan_discovery_3.2 lp:~cgrabowski/maas/+git/maas into -b 3.2 lp:~maas-committers/maas

STATUS: SUCCESS
COMMIT: 14202cb7119c1f7bc8c0ca02d04a2472ffb0e795

review: Approve

[Alberto Donato (ack)]

+1

review: Approve

diff --git a/src/maasserver/models/interface.py b/src/maasserver/models/interface.py
index 7945291..4fb826b 100644
--- a/src/maasserver/models/interface.py
+++ b/src/maasserver/models/interface.py
@@ -1547,16 +1547,8 @@ class Interface(CleanSave, TimestampedModel):
 
             if ip:
                 subnet = Subnet.objects.get_best_subnet_for_ip(ip)
-                if subnet:
-                    vlan = subnet.vlan
-                    vlan.fabric = fabric
-                    vlan.save()
-                    maaslog.info(
-                        "%s: Automatically updated VLAN %d (observed on %s).",
-                        self.get_log_string(),
-                        vid,
-                        vlan.fabric.get_name(),
-                    )
+                # VLAN already exists, don't update it
+                if subnet and subnet.vlan.vid == vid:
                     return
 
             vlan, created = VLAN.objects.get_or_create(
diff --git a/src/maasserver/models/tests/test_interface.py b/src/maasserver/models/tests/test_interface.py
index fcfdc85..8213518 100644
--- a/src/maasserver/models/tests/test_interface.py
+++ b/src/maasserver/models/tests/test_interface.py
@@ -4076,7 +4076,7 @@ class TestReportVID(MAASServerTestCase):
             new_vlan.description,
         )
 
-    def test_report_vid_handles_existing_vlan(self):
+    def test_report_vid_does_not_modify_existing_vlan(self):
         fabric1 = factory.make_Fabric()
         fabric2 = factory.make_Fabric()
         observing_vlan = fabric1.get_default_vlan()
@@ -4088,7 +4088,7 @@ class TestReportVID(MAASServerTestCase):
             neighbour_vlan.vid, ip=subnet2.get_next_ip_for_allocation()
         )
         neighbour_vlan.refresh_from_db()
-        self.assertEqual(observing_vlan.fabric, neighbour_vlan.fabric)
+        self.assertEqual(observing_vlan.fabric, fabric1)
 
 
 class TestInterfaceGetDefaultBridgeName(MAASServerTestCase):
diff --git a/src/maasserver/models/tests/test_node.py b/src/maasserver/models/tests/test_node.py
index f585f53..09fac42 100644
--- a/src/maasserver/models/tests/test_node.py
+++ b/src/maasserver/models/tests/test_node.py
@@ -10994,7 +10994,7 @@ class TestReportNeighbours(MAASServerTestCase):
             [call(3, ip=neighbours[0]["ip"]), call(7, ip=neighbours[1]["ip"])]
         )
 
-    def test_updates_fabric_of_existing_vlan(self):
+    def test_does_not_updates_fabric_of_existing_vlan(self):
         rack = factory.make_RackController()
         observing_fabric = factory.make_Fabric()
         other_fabric = factory.make_Fabric()
@@ -11015,10 +11015,10 @@ class TestReportNeighbours(MAASServerTestCase):
         ]
         rack.report_neighbours(neighbours)
         observed_vlan.refresh_from_db()
-        self.assertEqual(observing_fabric, observed_vlan.fabric)
+        self.assertEqual(other_fabric, observed_vlan.fabric)
         self.assertEqual(
             VLAN.objects.filter(
-                vid=observed_vlan.vid, fabric=observing_fabric
+                vid=observed_vlan.vid, fabric=other_fabric
             ).count(),
             1,
         )