fix: secondary IP blocks on "external" subnets (SVIs)

python/neutron-understack/neutron_understack/nautobot.py

@@ -188,21 +188,21 @@ def subnet_create(
         }
         return self.make_api_request("POST", "/api/ipam/prefixes/", payload)
 
-    def associate_subnet_with_network(
-        self, network_uuid: str, subnet_uuid: str, role: str
-    ):
+    def set_svi_role_on_network(self, network_uuid: str, role: str):
         url = f"/api/plugins/undercloud-vni/ucvnis/{network_uuid}/"
+        payload = {"role": {"name": role}}
+        self.make_api_request("PATCH", url, payload)
+
+    def associate_subnet_with_network(self, network_uuid: str, subnet_uuid: str):
+        url = "/api/extras/relationship-associations/"
         payload = {
-            "role": {"name": role},
-            "relationships": {
-                "ucvni_prefixes": {
-                    "destination": {
-                        "objects": [subnet_uuid],
-                    },
-                },
-            },
+            "relationship": {"key": "ucvni_prefixes"},
+            "source_type": "vni_custom_model.ucvni",
+            "source_id": network_uuid,
+            "destination_type": "ipam.prefix",
+            "destination_id": subnet_uuid,
         }
-        self.make_api_request("PATCH", url, payload)
+        self.make_api_request("POST", url, payload)
 
     def add_tenant_vlan_tag_to_ucvni(self, network_uuid: str, vlan_tag: int) -> dict:
         url = f"/api/plugins/undercloud-vni/ucvnis/{network_uuid}/"

python/neutron-understack/neutron_understack/neutron_understack_mech.py

@@ -176,10 +176,13 @@ def create_subnet_postcommit(self, context):
 
         if external:
             self.nb.associate_subnet_with_network(
-                role="svi_vxlan_anycast_gateway",
                 network_uuid=network_uuid,
                 subnet_uuid=subnet_uuid,
             )
+            self.nb.set_svi_role_on_network(
+                role="svi_vxlan_anycast_gateway",
+                network_uuid=network_uuid,
+            )
 
         LOG.info(
             "subnet with ID: %s and prefix %s has been "

python/neutron-understack/neutron_understack/tests/test_neutron_understack_mech.py

@@ -123,10 +123,13 @@ def test_create_public(self, understack_driver, subnet_context, subnet):
             tenant_uuid=ANY,
         )
         understack_driver.nb.associate_subnet_with_network.assert_called_once_with(
-            role="svi_vxlan_anycast_gateway",
             network_uuid=subnet.network_id,
             subnet_uuid=subnet.id,
         )
+        understack_driver.nb.set_svi_role_on_network.assert_called_once_with(
+            network_uuid=subnet.network_id,
+            role="svi_vxlan_anycast_gateway",
+        )
 
 
 class TestDeleteSubnetPostCommit: