dhcp snippet create fails when dhcp subnet is relayed regression

[Patrick Hampson]

Behavior is similar to LP:1809939

If a DHCP subnet is relayed maas validation does not allow a node DHCP snippet to be created

"Unable to validate DHCP config, no available rack controller connected."

Contrary to original bug report, creating a DHCP snippet for the subnet works:
root@mtlctrl1pit1:/home/phampson# maas admin dhcpsnippets create name=cli_snippet_test value="authoritative;" description="" subnet="R402_A_V4"
Success.
Machine-readable output follows:
{
    "name": "cli_snippet_test",
    "description": "",
    "enabled": true,
    "node": null,
    "subnet": {
        "name": "R402_A_V4",
        "description": "",
        "vlan": {
            "vid": 0,
            "mtu": 1500,
            "dhcp_on": false,
            "external_dhcp": null,
            "relay_vlan": {
                "vid": 0,
                "mtu": 1500,
                "dhcp_on": true,
                "external_dhcp": null,
                "relay_vlan": null,
                "secondary_rack": null,
                "fabric_id": 0,
                "space": "undefined",
                "id": 5001,
                "name": "untagged",
                "fabric": "r211pit1",
                "primary_rack": "kqhmgc",
                "resource_uri": "/MAAS/api/2.0/vlans/5001/"
            },
            "secondary_rack": null,
            "fabric_id": 65,
            "space": "undefined",
            "id": 5067,
            "name": "untagged",
            "fabric": "R402_A",
            "primary_rack": null,
            "resource_uri": "/MAAS/api/2.0/vlans/5067/"
        },
        "cidr": "141.98.219.128/27",
        "rdns_mode": 2,
        "gateway_ip": "141.98.219.129",
        "dns_servers": [
            "1.1.1.1",
            "8.8.8.8"
        ],
        "allow_dns": false,
        "allow_proxy": false,
        "active_discovery": false,
        "managed": true,
        "disabled_boot_architectures": [],
        "id": 55,
        "space": "undefined",
        "resource_uri": "/MAAS/api/2.0/subnets/55/"
    },
    "value": "authoritative;",
    "global_snippet": false,
    "id": 1,
    "history": [
        {
            "id": 40,
            "value": "authoritative;",
            "created": "Thu, 01 Sep 2022 03:53:08 -0000"
        }
    ],
    "resource_uri": "/MAAS/api/2.0/dhcp-snippets/1/"
}

Creating a DHCP snippet for a machine fails
root@mtlctrl1pit1:/home/phampson# maas admin dhcpsnippets create name=cli_snippet_test value="authoritative;" description="" node="mtl2915"
Unable to validate DHCP config, no available rack controller connected.

This was tested on multiple versions of maas:
v3.0.0, v3.2.4

[Alberto Donato (ack)]

Could you please paste the output of `maas $profile subnet read $subnet_id` for the relevant subnets?

[Patrick Hampson (patrickhampson)]

Added additional details to the description. Creating a DHCP snippet attached to a subnet is successful but fails when attaching to a machine. Full output attached.

[Alberto Donato (ack)]

Thanks, could you please also attach the output from

 maas $profile machine read $machine_id

for the node you're trying to attach the snippet to

and from the following query:

 select boot_cluster_ip from maasserver_node where hostname = 'mtl2915'

[Patrick Hampson (patrickhampson)]

See attached. It looks like the get_boot_rack_controller method (https://git.launchpad.net/maas/tree/src/maasserver/models/node.py#n5351) is not aware of relay_vlan's for detecting the primary_rack.

[Björn Tillenius (bjornt)]

That seems to be the case, yes. I'm working on reproducing the issue now.