make single front/rear port work when between panels

netbox/dcim/models/device_components.py

@@ -115,26 +115,32 @@ class CableTermination(models.Model):
 
             # Map a front port to its corresponding rear port
             if isinstance(termination, FrontPort):
-                position_stack.append(termination.rear_port_position)
                 # Retrieve the corresponding RearPort from database to ensure we have an up-to-date instance
                 peer_port = RearPort.objects.get(pk=termination.rear_port.pk)
+
+                # Don't use the stack for 1-on-1 ports, they don't have to come in pairs
+                if peer_port.positions > 1:
+                    position_stack.append(termination.rear_port_position)
+
                 return peer_port
 
             # Map a rear port/position to its corresponding front port
             elif isinstance(termination, RearPort):
-
-                # Can't map to a FrontPort without a position if there are multiple options
-                if termination.positions > 1 and not position_stack:
-                    raise CableTraceSplit(termination)
-
-                # We can assume position 1 if the RearPort has only one position
-                position = position_stack.pop() if position_stack else 1
-
-                # Validate the position
-                if position not in range(1, termination.positions + 1):
-                    raise Exception("Invalid position for {} ({} positions): {})".format(
-                        termination, termination.positions, position
-                    ))
+                if termination.positions > 1:
+                    # Can't map to a FrontPort without a position if there are multiple options
+                    if not position_stack:
+                        raise CableTraceSplit(termination)
+
+                    position = position_stack.pop()
+
+                    # Validate the position
+                    if position not in range(1, termination.positions + 1):
+                        raise Exception("Invalid position for {} ({} positions): {})".format(
+                            termination, termination.positions, position
+                        ))
+                else:
+                    # Don't use the stack for 1-on-1 ports, they don't have to come in pairs
+                    position = 1
 
                 try:
                     peer_port = FrontPort.objects.get(

netbox/dcim/tests/test_models.py

@@ -512,6 +512,11 @@ class CablePathTestCase(TestCase):
                 FrontPort(device=patch_panel, name='Front Port 4', rear_port=rearport, rear_port_position=4, type=PortTypeChoices.TYPE_8P8C),
             ))
 
+        # Create a 1-on-1 patch panel
+        patch_panel = Device.objects.create(device_type=devicetype, device_role=devicerole, name='Panel 5', site=site)
+        rearport = RearPort.objects.create(device=patch_panel, name='Rear Port 1', positions=1, type=PortTypeChoices.TYPE_8P8C)
+        FrontPort.objects.create(device=patch_panel, name='Front Port 1', rear_port=rearport, rear_port_position=1, type=PortTypeChoices.TYPE_8P8C)
+
     def test_direct_connection(self):
         """
         Test a direct connection between two interfaces.
@@ -554,17 +559,17 @@ class CablePathTestCase(TestCase):
         Test a connection which passes through a single front/rear port pair.
 
                      1               2
-        [Device 1] ----- [Panel 1] ----- [Device 2]
+        [Device 1] ----- [Panel 5] ----- [Device 2]
              Iface1     FP1     RP1     Iface1
         """
-        # Create cables
+        # Create cables (FP first, RP second)
         cable1 = Cable(
             termination_a=Interface.objects.get(device__name='Device 1', name='Interface 1'),
-            termination_b=FrontPort.objects.get(device__name='Panel 1', name='Front Port 1')
+            termination_b=FrontPort.objects.get(device__name='Panel 5', name='Front Port 1')
         )
         cable1.save()
         cable2 = Cable(
-            termination_b=RearPort.objects.get(device__name='Panel 1', name='Rear Port 1'),
+            termination_b=RearPort.objects.get(device__name='Panel 5', name='Rear Port 1'),
             termination_a=Interface.objects.get(device__name='Device 2', name='Interface 1')
         )
         cable2.save()
@@ -592,6 +597,155 @@ class CablePathTestCase(TestCase):
         self.assertIsNone(endpoint_a.connection_status)
         self.assertIsNone(endpoint_b.connection_status)
 
+        # Recreate cable 1 to test creating the cables in reverse order (RP first, FP second)
+        cable1.save()
+
+        # Refresh endpoints
+        endpoint_a.refresh_from_db()
+        endpoint_b.refresh_from_db()
+
+        # Validate connections
+        self.assertEqual(endpoint_a.connected_endpoint, endpoint_b)
+        self.assertEqual(endpoint_b.connected_endpoint, endpoint_a)
+        self.assertTrue(endpoint_a.connection_status)
+        self.assertTrue(endpoint_b.connection_status)
+
+        # Delete cable 2
+        cable2.delete()
+
+        # Refresh endpoints
+        endpoint_a.refresh_from_db()
+        endpoint_b.refresh_from_db()
+
+        # Check that connections have been nullified
+        self.assertIsNone(endpoint_a.connected_endpoint)
+        self.assertIsNone(endpoint_b.connected_endpoint)
+        self.assertIsNone(endpoint_a.connection_status)
+        self.assertIsNone(endpoint_b.connection_status)
+
+    def test_connection_via_nested_single_rear_port(self):
+        """
+        Test a connection which passes through a single front/rear port pair between two multi-port MUXes.
+
+        Test two connections via patched rear ports:
+            Device 1 <---> Device 2
+            Device 3 <---> Device 4
+
+                        1                                           2
+        [Device 1] -----------+                               +----------- [Device 2]
+              Iface1          |                               |          Iface1
+                          FP1 |       3               4       | FP1
+                          [Panel 1] ----- [Panel 5] ----- [Panel 2]
+                          FP2 |  RP1     RP1     FP1     RP1  | FP2
+              Iface1          |                               |          Iface1
+        [Device 3] -----------+                               +----------- [Device 4]
+                        5                                           6
+        """
+        # Create cables (Panel 5 RP first, FP second)
+        cable1 = Cable(
+            termination_a=Interface.objects.get(device__name='Device 1', name='Interface 1'),
+            termination_b=FrontPort.objects.get(device__name='Panel 1', name='Front Port 1')
+        )
+        cable1.save()
+        cable2 = Cable(
+            termination_b=FrontPort.objects.get(device__name='Panel 2', name='Front Port 1'),
+            termination_a=Interface.objects.get(device__name='Device 2', name='Interface 1')
+        )
+        cable2.save()
+        cable3 = Cable(
+            termination_b=RearPort.objects.get(device__name='Panel 1', name='Rear Port 1'),
+            termination_a=RearPort.objects.get(device__name='Panel 5', name='Rear Port 1')
+        )
+        cable3.save()
+        cable4 = Cable(
+            termination_b=FrontPort.objects.get(device__name='Panel 5', name='Front Port 1'),
+            termination_a=RearPort.objects.get(device__name='Panel 2', name='Rear Port 1')
+        )
+        cable4.save()
+        cable5 = Cable(
+            termination_b=FrontPort.objects.get(device__name='Panel 1', name='Front Port 2'),
+            termination_a=Interface.objects.get(device__name='Device 3', name='Interface 1')
+        )
+        cable5.save()
+        cable6 = Cable(
+            termination_b=FrontPort.objects.get(device__name='Panel 2', name='Front Port 2'),
+            termination_a=Interface.objects.get(device__name='Device 4', name='Interface 1')
+        )
+        cable6.save()
+
+        # Retrieve endpoints
+        endpoint_a = Interface.objects.get(device__name='Device 1', name='Interface 1')
+        endpoint_b = Interface.objects.get(device__name='Device 2', name='Interface 1')
+        endpoint_c = Interface.objects.get(device__name='Device 3', name='Interface 1')
+        endpoint_d = Interface.objects.get(device__name='Device 4', name='Interface 1')
+
+        # Validate connections
+        self.assertEqual(endpoint_a.connected_endpoint, endpoint_b)
+        self.assertEqual(endpoint_b.connected_endpoint, endpoint_a)
+        self.assertEqual(endpoint_c.connected_endpoint, endpoint_d)
+        self.assertEqual(endpoint_d.connected_endpoint, endpoint_c)
+        self.assertTrue(endpoint_a.connection_status)
+        self.assertTrue(endpoint_b.connection_status)
+        self.assertTrue(endpoint_c.connection_status)
+        self.assertTrue(endpoint_d.connection_status)
+
+        # Delete cable 3
+        cable3.delete()
+
+        # Refresh endpoints
+        endpoint_a.refresh_from_db()
+        endpoint_b.refresh_from_db()
+        endpoint_c.refresh_from_db()
+        endpoint_d.refresh_from_db()
+
+        # Check that connections have been nullified
+        self.assertIsNone(endpoint_a.connected_endpoint)
+        self.assertIsNone(endpoint_b.connected_endpoint)
+        self.assertIsNone(endpoint_c.connected_endpoint)
+        self.assertIsNone(endpoint_d.connected_endpoint)
+        self.assertIsNone(endpoint_a.connection_status)
+        self.assertIsNone(endpoint_b.connection_status)
+        self.assertIsNone(endpoint_c.connection_status)
+        self.assertIsNone(endpoint_d.connection_status)
+
+        # Recreate cable 3 to test reverse order (Panel 5 FP first, RP second)
+        cable3.save()
+
+        # Refresh endpoints
+        endpoint_a.refresh_from_db()
+        endpoint_b.refresh_from_db()
+        endpoint_c.refresh_from_db()
+        endpoint_d.refresh_from_db()
+
+        # Validate connections
+        self.assertEqual(endpoint_a.connected_endpoint, endpoint_b)
+        self.assertEqual(endpoint_b.connected_endpoint, endpoint_a)
+        self.assertEqual(endpoint_c.connected_endpoint, endpoint_d)
+        self.assertEqual(endpoint_d.connected_endpoint, endpoint_c)
+        self.assertTrue(endpoint_a.connection_status)
+        self.assertTrue(endpoint_b.connection_status)
+        self.assertTrue(endpoint_c.connection_status)
+        self.assertTrue(endpoint_d.connection_status)
+
+        # Delete cable 4
+        cable4.delete()
+
+        # Refresh endpoints
+        endpoint_a.refresh_from_db()
+        endpoint_b.refresh_from_db()
+        endpoint_c.refresh_from_db()
+        endpoint_d.refresh_from_db()
+
+        # Check that connections have been nullified
+        self.assertIsNone(endpoint_a.connected_endpoint)
+        self.assertIsNone(endpoint_b.connected_endpoint)
+        self.assertIsNone(endpoint_c.connected_endpoint)
+        self.assertIsNone(endpoint_d.connected_endpoint)
+        self.assertIsNone(endpoint_a.connection_status)
+        self.assertIsNone(endpoint_b.connection_status)
+        self.assertIsNone(endpoint_c.connection_status)
+        self.assertIsNone(endpoint_d.connection_status)
+
     def test_connections_via_patch(self):
         """
         Test two connections via patched rear ports: