maas 3.1 creates alias when editing vlan instead of saving changes

[Tessa]

just doing some more setup of some new systems, and noticed some weird behaviour after cloning an initial system config onto other boxes. maas assigns some random new static IPs, so I've gone in and manually switched them to the IPs the systems should have. however, when editing the IP on a VLAN device, maas creates an alias to that device and adds the IP there, rather than editing it in place on the device itself. this isn't at all the behaviour I'd want or expect when editing a vlan, I'd create an alias manually if that's what I wanted.

[Christian Grabowski (cgrabowski)]

Hi there, could you please provide the output of `maas $PROFILE interfaces $SYSTEM_ID` of the machine with the original config, and the same command's output for the machine with the alias issue? Additionally, how are you cloning said config?

[Tessa (unit3)]

to be clear, this happens with all my systems, not just one. the bug seems universal. I'm using the "Clone from..." feature in the GUI to clone the systems storage and networking. here's the output from one of the affected systems:

```
# maas admin interfaces read 4smwte
Success.
Machine-readable output follows:
[
    {
        "parents": [],
        "sriov_max_vf": 128,
        "tags": [
            "sriov"
        ],
        "effective_mtu": 9000,
        "type": "physical",
        "link_connected": true,
        "name": "ens5f0",
        "enabled": true,
        "vlan": {
            "vid": 0,
            "mtu": 9000,
            "dhcp_on": true,
            "external_dhcp": null,
            "relay_vlan": null,
            "id": 5004,
            "primary_rack": "apcxt8",
            "secondary_rack": null,
            "name": "untagged",
            "fabric": "tr2_int",
            "space": "undefined",
            "fabric_id": 2,
            "resource_uri": "/MAAS/api/2.0/vlans/5004/"
        },
        "id": 50,
        "system_id": "4smwte",
        "mac_address": "b4:96:91:b9:0a:f8",
        "children": [
            "int"
        ],
        "firmware_version": "2.25 0x80007029 0.0.0",
        "params": {},
        "link_speed": 10000,
        "interface_speed": 10000,
        "vendor": "Intel Corporation",
        "product": null,
        "links": [],
        "numa_node": 0,
        "discovered": null,
        "resource_uri": "/MAAS/api/2.0/nodes/4smwte/interfaces/50/"
    },
    {
        "parents": [],
        "sriov_max_vf": 128,
        "tags": [
            "sriov"
        ],
        "effective_mtu": 9000,
        "type": "physical",
        "link_connected": true,
        "name": "ens5f1",
        "enabled": true,
        "vlan": {
            "vid": 0,
            "mtu": 9000,
            "dhcp_on": true,
            "external_dhcp": null,
            "relay_vlan": null,
            "id": 5004,
            "primary_rack": "apcxt8",
            "secondary_rack": null,
            "name": "untagged",
            "fabric": "tr2_int",
            "space": "undefined",
            "fabric_id": 2,
            "resource_uri": "/MAAS/api/2.0/vlans/5004/"
        },
        "id": 51,
        "system_id": "4smwte",
        "mac_address": "b4:96:91:b9:0a:f9",
        "children": [
            "int"
        ],
        "firmware_version": "2.25 0x80007029 0.0.0",
        "params": {},
        "link_speed": 10000,
        "interface_speed": 10000,
        "vendor": "Intel Corporation",
        "product": null,
        "links": [],
        "numa_node": 0,
        "discovered": [],
        "resource_uri": "/MAAS/api/2.0/nodes/4smwte/interfaces/51/"
    },
    {
        "parents": [
            "ens5f0",
            "ens5f1"
        ],
        "sriov_max_vf": 0,
        "tags": [],
        "effective_mtu": 9000,
        "type": "bond",
        "link_connected": false,
        "name": "int",
        "enabled": true,
        "vlan": {
            "vid": 0,
            "mtu": 9000,
            "dhcp_on": true,
            "external_dhcp": null,
            "relay_vlan": null,
            "id": 5004,
            "primary_rack": "apcxt8",
      ...

[Alberto Donato (ack)]

This seems to be a UI bug. When calling update_interface, "link_id" should be passed with the ID of the current StaticIPAddress. If that's not provided, MAAS interprets the request as adding a new IP to the interface (causing an alias to be added).