From 1025c227ce8fbf16c352366e983d0eb21c241b7c Mon Sep 17 00:00:00 2001
From: Daniel Sheppard <dans@dansheps.com>
Date: Wed, 6 Aug 2025 21:16:19 -0500
Subject: [PATCH] Fixes: #19645 - Correct Interface selection for Cable add
 when VC master is the selected device

---
 netbox/dcim/filtersets.py        | 17 +++++++++++++++--
 netbox/dcim/forms/connections.py |  7 ++++++-
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/netbox/dcim/filtersets.py b/netbox/dcim/filtersets.py
index 814be356c..beecb7116 100644
--- a/netbox/dcim/filtersets.py
+++ b/netbox/dcim/filtersets.py
@@ -1885,6 +1885,16 @@ class InterfaceFilterSet(
     PathEndpointFilterSet,
     CommonInterfaceFilterSet
 ):
+    virtual_chassis_member_or_master = MultiValueCharFilter(
+        method='filter_virtual_chassis_member_or_master',
+        field_name='name',
+        label=_('Virtual Chassis Interfaces for Device')
+    )
+    virtual_chassis_member_or_master_id = MultiValueNumberFilter(
+        method='filter_virtual_chassis_member_or_master',
+        field_name='pk',
+        label=_('Virtual Chassis Interfaces for Device (ID)')
+    )
     virtual_chassis_member = MultiValueCharFilter(
         method='filter_virtual_chassis_member',
         field_name='name',
@@ -1995,11 +2005,14 @@ class InterfaceFilterSet(
             'cable_id', 'cable_end',
         )
 
-    def filter_virtual_chassis_member(self, queryset, name, value):
+    def filter_virtual_chassis_member_or_master(self, queryset, name, value):
+        return self.filter_virtual_chassis_member(queryset, name, value, if_master=True)
+
+    def filter_virtual_chassis_member(self, queryset, name, value, if_master=False):
         try:
             vc_interface_ids = []
             for device in Device.objects.filter(**{f'{name}__in': value}):
-                vc_interface_ids.extend(device.vc_interfaces(if_master=False).values_list('id', flat=True))
+                vc_interface_ids.extend(device.vc_interfaces(if_master=if_master).values_list('id', flat=True))
             return queryset.filter(pk__in=vc_interface_ids)
         except Device.DoesNotExist:
             return queryset.none()
diff --git a/netbox/dcim/forms/connections.py b/netbox/dcim/forms/connections.py
index 5e5d83b0b..d3588da39 100644
--- a/netbox/dcim/forms/connections.py
+++ b/netbox/dcim/forms/connections.py
@@ -19,6 +19,11 @@ def get_cable_form(a_type, b_type):
                 # Device component
                 if hasattr(term_cls, 'device'):
 
+                    # Dynamically change the param field for interfaces to use virtual_chassis filter
+                    query_param_device_field = 'device_id'
+                    if term_cls == Interface:
+                        query_param_device_field = 'virtual_chassis_member_or_master_id'
+
                     attrs[f'termination_{cable_end}_device'] = DynamicModelMultipleChoiceField(
                         queryset=Device.objects.all(),
                         label=_('Device'),
@@ -36,7 +41,7 @@ def get_cable_form(a_type, b_type):
                             'parent': 'device',
                         },
                         query_params={
-                            'device_id': f'$termination_{cable_end}_device',
+                            query_param_device_field: f'$termination_{cable_end}_device',
                             'kind': 'physical',  # Exclude virtual interfaces
                         }
                     )