Public bug reported: [ Impact ]
Cloud-init recently added policy based routing for multi-nic setups in EC2. The added code assumed that "subnet-ipv4-cidr-block" would be present in the metadata obtained from EC2's IMDS. However, on ipv6-only instances, this is not true. The assumption leads to a traceback when attempting to access the key, resulting in cloud-init failing to properly render the network configuration and leaving the instance unaccessable. The fix is to check for required keys before configuring policy based routing, and if the keys do not exist, skip configuration. [ Test Plan ] Launch an EC2 instance with at least two NICs in an ipv6-only subnet. Verify that the instance can be accessed via SSH. Verify that there are no warnings of tracebacks in the logs related to network configuration. Verify that /etc/netplan/50-cloud-init.yaml contains the relevant routing information and that `ip route` shows the routes as active. [ Where problems could occur ] Since we've added a guard to the policy-based routing rendering, any error in this code would result in the same functionality as now, or result in rendering all of the network except for the policy based routing for secondary NICs. [ Other Info ] Upstream bug: https://github.com/canonical/cloud-init/issues/5283 Upstream fix: https://github.com/canonical/cloud-init/pull/5287 Upstream change causing issue: https://github.com/canonical/cloud-init/pull/4799/files#diff-66c4d0c34e626a49273eda62819c3068f5501520b86f28e89e0f998cf4cf2027R1058 ** Affects: cloud-init (Ubuntu) Importance: Undecided Status: New ** Affects: cloud-init (Ubuntu Noble) Importance: Undecided Status: New ** Affects: cloud-init (Ubuntu Oracular) Importance: Undecided Status: New ** Also affects: cloud-init (Ubuntu Noble) Importance: Undecided Status: New ** Also affects: cloud-init (Ubuntu Oracular) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2066979 Title: cloud-init network fails in ipv6-only subnet with multi-NICs To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/cloud-init/+bug/2066979/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
