[azure] Ephemeral networking interface shows `None` in cloud-init.log

[cadejacobson]

Bug report

When creating an Ubuntu VM on Azure, Cloud-init creates an ephemeral networking session to query IMDS metadata. The logs output which interface will be used for this process, but in most cases this outputs iface=None. In reality, when the interface is None, Cloud-init determines an interface and attempts to bring up the ephemeral session on the determined interface.

This None log makes navigating provisioning issues slightly more difficult, and it should instead output the correct interface, MAC address, and driver for ease of debugging.

Steps to reproduce the problem

1. Create an Ubuntu 24.04 or 22.04 VM on Azure.
2. SSH into the VM.
3. Check the logs with cat /var/log/cloud-init.log | grep "ephemeral networking"

Environment details

• Cloud-init version: cloud-init 25.2-0ubuntu1~24.04.1, cloud-init 25.2-0ubuntu1~22.04.1
• Operating System Distribution: Ubuntu 24.04.3 LTS, Ubuntu 22.04.5 LTS
• Cloud provider, platform or installer type: Azure

cloud-init logs

2025-11-04 18:09:26,334 - azure.py[DEBUG]: Bringing up ephemeral networking with iface=None: [('lo', '00:00:00:00:00:00', None, None), ('eth0', '60:45:bd:b8:a9:ef', 'hv_netvsc', '0x3')]

or

2025-11-04 21:47:15,765 - azure.py[DEBUG]: Bringing up ephemeral networking with iface=None: [('lo', '00:00:00:00:00:00', None, None), ('eth1', '7c:1e:52:e8:5e:80', 'hv_netvsc', '0x3'), ('eth0', '7c:1e:52:e8:55:f9', 'hv_netvsc', '0x3')]