Cloud-Init unable to bring interface up after interface-changes

[f0o]

Bug report

Cloud-Init retains some information of the previous interface's MAC and will fail bringing up the new interface if the interfaces have been swapped out, for instance to move the machine to a new subnet/network in OpenStack.

Steps to reproduce the problem

1. Setup NetworkA+SubnetA
2. Spin up Ubuntu 24.04 Cloud-Image
3. Observe Instance with correct first boot and accessible network
4. Shutdown Instance
5. Setup NetworkB+SubnetB
6. Add Interface to Instance to NetworkB+SubnetB
7. Remove NetworkA+SubnetA Interface from Instance
8. Start Instance
9. Observe errors in Cloud-Init and no network being set up at all

Environment details

• Cloud-init version: 24.3.1-0ubuntu0~24.04.2
• Operating System Distribution: 24.04 / Noble
• Cloud provider, platform or installer type: OpenStack+KVM / https://cloud-images.ubuntu.com/noble/current/noble-server-cloudimg-amd64.img

cloud-init logs

2024-10-11 07:57:37,423 - net[DEBUG]: Detected interfaces {'lo': {'downable': False, 'device_id': None, 'driver': None, 'mac': '00:00:00:00:00:00', 'name': 'lo', 'up': True}, 'ens3': {'downable': True, 'device_id': '0x0001', 'driver': 'virtio_net', 'mac': 'fa:16:3e:a9:e9:da', 'name': 'ens3', 'up': False}}
2024-10-11 07:57:37,423 - net[WARNING]: Unable to rename interfaces: [['fa:16:3e:f7:10:04', 'ens3', 'virtio_net', '0x0001']] due to errors: ['[nic not present] Cannot rename mac=fa:16:3e:f7:10:04 to ens3, not available.']
2024-10-11 07:57:37,423 - stages.py[WARNING]: Failed to rename devices: Failed to apply network config names: [nic not present] Cannot rename mac=fa:16:3e:f7:10:04 to ens3, not available.

Note the mismatch in MAC. e9:da is the new interface from NetworkB+SubnetB whereas 10:04 is the removed interface from NetworkA+SubnetA.