Trying to fix issue #6312 (API GET "/api/dcim/interfaces?device=XXX" yields too many interfaces for VC members)

[cs-1]

Dear all,

I'm currently trying to figure out how to fix issue #6312. The issue is this: from v2.11.1 to v2.11.2 there was a commit 9a58823 to fix a problem with assigning interfaces of virtual chassis members to a LAG. This fix introduced a new parameter "if_master" to https://github.com/netbox-community/netbox/blob/develop/netbox/dcim/models/devices.py. If you have a VC "myname" with two members "myname/1" and "myname/2" (none of which is a master!), the web UI correctly shows the interfaces of just the device that you're currently viewing in the UI (as expected), however, querying the API via GET https://<netbox-server>/api/dcim/interfaces/?device=myname%2F1, the result will always include all interfaces of all VC members not matter which VC member you query (in v2.11.1 it would work as expected and only show the interfaces of the VC member being queried -- remember that none of the VC members is a master). You can easily verify this behaviour by using the Swagger API browser.

Please note that I'm not a coder and I'm a novice regarding NetBox code so please be patient with me. :) From what I understand it all boils down to how the function "vc_interfaces()" in netbox/dcim/models/devices.py is called. The default for the newly introduced variable "if_master" is "False":

netbox/netbox/dcim/models/devices.py

Line 869 in 67945f2

def vc_interfaces(self, if_master=False):

The following code in "vc_interfaces()" adds a filter that shows all interfaces of all VC members when called if the condition in the if-clause is met:

netbox/netbox/dcim/models/devices.py

Lines 877 to 878 in 67945f2

	if self.virtual_chassis and (not if_master or self.virtual_chassis.master == self):
	filter |= Q(device__virtual_chassis=self.virtual_chassis, mgmt_only=False)

This used to only be the case if the device queried was master of the VC it's part of (self.virtual_chassis.master == self). However, since if_master=False is the default, this if-clause will by default evaluate to "True" unless you call vc_interfaces(if_master=True). So the default is that all interfaces of all VC members are shown. As far as I can tell, when viewing a device that's part of a VC in the web UI, vc_interfaces(if_master=True) is called:

netbox/netbox/dcim/views.py

Line 1408 in 9a58823

interfaces = instance.vc_interfaces(if_master=True).restrict(request.user, 'view').prefetch_related(

(Please correct my if this assumption is wrong.)

However, since an API call yields more than the interfaces seen in the web UI, I suspect that whatever part of the code calls vc_interfaces() when using the API GET, it doesn't set if_master=True. (I verified this by changing the default to if_master=True in "vc_interfaces"; as soon as I made this change, the API GET would only show the interfaces of the chassis that I queried.) The trouble is that I have no idea where to look in the code to fix this.

Sorry for the lengthy post. This issue is quite critical for us because we use VCs extensively and currently our Ansible playbooks which use the API query to get information from NetBox are broken. Any help is therefore highly appreciated. Thanks!

Cheers,
CS

[cs-1]

This issue was resolved in v2.11.3. Thanks to @jeremystretch for fixing it.