Package: cloud-init Subject: cloud-init fails to handle IPv6-only environments in Debian 12 generic-cloud
Dear Debian Development Team, I am writing to report an issue with the cloud-init package in the current version of Debian 12 (Bookworm). In an IPv6-only environment, cloud-init fails to properly detect and interact with the metadata service, which prevents the successful initialization of cloud instances, including login access via SSH or other remote methods. ### Issue Details: - **System:** Debian 12 (Bookworm) cloud image (2025-04-28 20:40) - **Problem:** Cloud-init fails to configure instances properly in an IPv6-only environment. - **Cause:** It appears the version of cloud-init included in Debian 12 (Bookworm) is outdated and does not fully support IPv6-only networking configurations. ### Steps to Reproduce: 1. Launch a cloud instance using the official Debian 12 cloud image (genericcloud) in an environment that has IPv6-only networking. 2. Ensure that the metadata service is accessible via IPv6 (e.g., `http:// [fe80::a9fe:a9fe%<interface>]/openstack`). 3. Observe that cloud-init attempts to fetch metadata but fails because it cannot handle the IPv6-only configuration properly. 4. Testing `curl -6` works correctly to retrieve metadata using the appropriate IPv6 address, confirming that the server and networking are configured correctly. 5. Cloud-init continues to default to IPv4 or fails to detect the IPv6 configuration. ### Observed Behavior: The root cause seems to be that the version of cloud-init shipped with Debian 12 does not properly handle IPv6-only networks, particularly when it comes to metadata fetching from an IPv6 address. Even though the metadata service is reachable via IPv6, cloud-init fails to detect and use this configuration due to its outdated handling of IPv6 routing and network settings. ### Proposed Solution: Upon investigation, it appears that updating the cloud-init package to the latest version would resolve this issue. The latest versions of cloud-init include improved support for IPv6-only environments and should handle the metadata service correctly when using IPv6 addressing. I kindly request that the cloud-init package be updated to the latest stable version that includes better IPv6-only support. This will ensure that Debian 12 instances function correctly in modern cloud environments where IPv6-only networking is the default. ### Additional Information: - The issue has been reproduced on multiple Debian 12 cloud images (genericcloud). - The metadata service is working correctly when accessed via `curl -6` on the host. - The problem is specific to cloud-init's interaction with IPv6-only environments and is not related to network misconfiguration or the metadata service itself. Thank you for your attention to this issue. Please feel free to contact me if you need additional information or further clarification. I look forward to your response and the resolution of this issue. Best regards
