Fixes: 17292 - Detect infinite loop condition while iterating terminations in CablePath.from_origin

netbox/dcim/models/cables.py

@@ -1,6 +1,8 @@
 import itertools
+import logging
 from collections import defaultdict
 
+from django.conf import settings
 from django.contrib.contenttypes.fields import GenericForeignKey
 from django.core.exceptions import ValidationError
 from django.db import models
@@ -27,6 +29,8 @@
     'CableTermination',
 )
 
+logger = logging.getLogger('netbox.dcim.cable')
+
 
 trace_paths = Signal()
 
@@ -521,7 +525,7 @@ def segment_count(self):
         return int(len(self.path) / 3)
 
     @classmethod
-    def from_origin(cls, terminations):
+    def from_origin(cls, terminations, max_length=settings.CABLE_TRACE_MAX_LENGTH):
         """
         Create a new CablePath instance as traced from the given termination objects. These can be any object to which a
         Cable or WirelessLink connects (interfaces, console ports, circuit termination, etc.). All terminations must be
@@ -585,9 +589,13 @@ def from_origin(cls, terminations):
             # Step 4: Record the links, keeping cables in order to allow for SVG rendering
             cables = []
             for link in links:
-                if object_to_path_node(link) not in cables:
-                    cables.append(object_to_path_node(link))
+                cable = object_to_path_node(link)
+                if cable not in cables:
+                    cables.append(cable)
             path.append(cables)
+            if len(path) >= max_length:
+                logger.warning('Infinite loop detected while updating cable path trace')
+                break
 
             # Step 5: Update the path status if a link is not connected
             links_status = [link.status for link in links if link.status != LinkStatusChoices.STATUS_CONNECTED]

netbox/dcim/tests/test_cablepaths.py

@@ -1,10 +1,12 @@
 from django.test import TestCase
+from django.contrib.contenttypes.models import ContentType
 
 from circuits.models import *
 from dcim.choices import LinkStatusChoices
 from dcim.models import *
 from dcim.svg import CableTraceSVG
 from dcim.utils import object_to_path_node
+from dcim.choices import CableEndChoices
 
 
 class CablePathTestCase(TestCase):
@@ -2343,3 +2345,54 @@ def test_401_exclude_midspan_devices(self):
             is_active=True
         )
         self.assertEqual(CablePath.objects.count(), 0)
+
+    def test_detect_infinite_loop(self):
+        """
+        Tests the ability to detect a non-resolving path and break out with a logged warning.
+        Assertion will fail if max_length is exceeded (meaning infinite loop detection failed), or not reached
+        (meaning this test is no longer valid as existing synthetic path no longer creates an infinite loop).
+        [IF1] --C1-- [FP1][Test Device][Rear Splice]
+                     [FP2]   --C2--    [ Rear Splice
+        """
+        manufacturer = Manufacturer.objects.create(name='Infinite Loop Co', slug='infinite-loop-co')
+        role = DeviceRole.objects.create(name='Infinite Loop Device Role', slug='infinite-loop-device-role')
+        device_type = DeviceType.objects.create(manufacturer=manufacturer, model='Infinite Loop Device Type', slug='infinite-loop-device-type')
+        device = Device.objects.create(site=self.site, device_type=device_type, role=role, name='Infinite Loop Device')
+        interface = Interface.objects.create(device=device, name='Interface 1')
+
+        patch_panel_device_type = DeviceType.objects.create(
+            manufacturer=manufacturer,
+            front_port_template_count=48,
+            rear_port_template_count=48,
+        )
+        patch_panel = Device.objects.create(site=self.site, device_type=patch_panel_device_type, role=role)
+        rear_splice = RearPort.objects.create(device=patch_panel, positions=48, name='Rear Splice')
+        front_port_1 = FrontPort.objects.create(device=patch_panel, rear_port=rear_splice, rear_port_position=1, name='Front Port 1')
+        front_port_2 = FrontPort.objects.create(device=patch_panel, rear_port=rear_splice, rear_port_position=2, name='Front Port 2')
+
+        ct_interface = ContentType.objects.get(app_label='dcim', model='interface')
+        ct_frontport = ContentType.objects.get(app_label='dcim', model='frontport')
+        ct_rearport = ContentType.objects.get(app_label='dcim', model='rearport')
+
+        cable_1 = Cable.objects.create()
+        CableTermination.objects.create(cable=cable_1, cable_end='A', termination_type=ct_interface, termination_id=interface.id)
+        CableTermination.objects.create(cable=cable_1, cable_end='B', termination_type=ct_frontport, termination_id=front_port_1.id)
+
+        cable_2 = Cable.objects.create()
+        CableTermination.objects.create(cable=cable_2, cable_end='A', termination_type=ct_frontport, termination_id=front_port_2.id)
+        CableTermination.objects.create(cable=cable_2, cable_end='B', termination_type=ct_rearport, termination_id=rear_splice.id)
+
+        cable_1.save()
+
+        max_length = 50
+        a_terminations = []
+        b_terminations = []
+        for t in cable_1.terminations.all():
+            if t.cable_end == CableEndChoices.SIDE_A:
+                a_terminations.append(t.termination)
+            else:
+                b_terminations.append(t.termination)
+        cp = CablePath.from_origin(a_terminations, max_length=max_length)
+        self.assertEqual(len(cp.path), max_length)
+        cp = CablePath.from_origin(b_terminations, max_length=max_length)
+        self.assertLess(len(cp.path), max_length)

netbox/netbox/settings.py

@@ -72,6 +72,7 @@
     },
 ])
 BASE_PATH = trailing_slash(getattr(configuration, 'BASE_PATH', ''))
+CABLE_TRACE_MAX_LENGTH = getattr(configuration, 'CABLE_TRACE_MAX_LENGTH', 99999)
 CHANGELOG_SKIP_EMPTY_CHANGES = getattr(configuration, 'CHANGELOG_SKIP_EMPTY_CHANGES', True)
 CENSUS_REPORTING_ENABLED = getattr(configuration, 'CENSUS_REPORTING_ENABLED', True)
 CORS_ORIGIN_ALLOW_ALL = getattr(configuration, 'CORS_ORIGIN_ALLOW_ALL', False)