Exception when modifying properties of an IP assigned to a VM

[abrahamvegh]

Environment

• Python version: 3.7.3
• NetBox version: 2.9.1

Steps to Reproduce

1. Create new IP e.g. 198.51.100.1/24
2. Create new VM
3. Create interface on VM
4. Edit IP and assign as primary to the VM interface
5. After the IP is assigned as primary, edit the IP and change the status to any other status
6. Exception

Expected Behavior

Modifications to the IP should be accepted.

Observed Behavior

Exception:

Traceback (most recent call last):
 File "/opt/netbox/venv/lib/python3.7/site-packages/django/core/handlers/exception.py", line 47, in inner
   response = get_response(request)
 File "/opt/netbox/venv/lib/python3.7/site-packages/django/core/handlers/base.py", line 179, in _get_response
   response = wrapped_callback(request, *callback_args, **callback_kwargs)
 File "/opt/netbox/venv/lib/python3.7/site-packages/django/views/generic/base.py", line 73, in view
   return self.dispatch(request, *args, **kwargs)
 File "/opt/netbox/netbox/utilities/views.py", line 392, in dispatch
   return super().dispatch(request, *args, **kwargs)
 File "/opt/netbox/netbox/utilities/views.py", line 123, in dispatch
   return super().dispatch(request, *args, **kwargs)
 File "/opt/netbox/venv/lib/python3.7/site-packages/django/views/generic/base.py", line 101, in dispatch
   return handler(request, *args, **kwargs)
 File "/opt/netbox/netbox/utilities/views.py", line 418, in post
   if form.is_valid():
 File "/opt/netbox/venv/lib/python3.7/site-packages/django/forms/forms.py", line 177, in is_valid
   return self.is_bound and not self.errors
 File "/opt/netbox/venv/lib/python3.7/site-packages/django/forms/forms.py", line 172, in errors
   self.full_clean()
 File "/opt/netbox/venv/lib/python3.7/site-packages/django/forms/forms.py", line 376, in full_clean
   self._post_clean()
 File "/opt/netbox/venv/lib/python3.7/site-packages/django/forms/models.py", line 405, in _post_clean
   self.instance.full_clean(exclude=exclude, validate_unique=False)
 File "/opt/netbox/venv/lib/python3.7/site-packages/django/db/models/base.py", line 1213, in full_clean
   self.clean()
 File "/opt/netbox/netbox/ipam/models.py", line 748, in clean
   elif self.interface.virtual_machine != vm:

Exception Type: AttributeError at /ipam/ip-addresses/4195/edit/
Exception Value: 'RelatedManager' object has no attribute 'virtual_machine'

This is presumably related to #4721. I bumped into it trying to update IPs relating to #4540.

[abrahamvegh]

This seems to be affecting any modification of an IP address assigned to a VM interface.

[jeremystretch]

Please detail the exact steps someone else can take to replicate this bug, beginning with the creation of the IP address.

[abrahamvegh]

Updated with full steps to reproduce. The hot path seems to be when an IP is marked as primary for the interface.