Add NAT64 to enable IPv6 provision in v4 only host #1567

nuhakala · 2025-09-04T09:53:26Z

This adds

Tayga as NAT64 service
Bind9 and configure it as local DNS server with DNS64
IPv6 specific addresses and logic to cluster, controlplane, and worker templates
Updates vars.md with new variables
Updates CNI configuration for IPv6

Why we need this? Previously IPv6 support was added so that the dev env could create bare metal hosts over IPv6. This PR extends that so that we can also provision the bare metal hosts over IPv6 and the provisioned images will be IPv6 only. The tricky part is that our CI environment does not support IPv6 natively, so the VMs cannot access internet over IPv6 and hence also cannot download Kubernetes images and other needed images to set up cluster.

Introducing NAT64/DNS64 solves that issue. It essentially allows the dev env to be deployed with IPv6 only scenario on IPv4 host. Furthermore, this PR introduces required changes to the templates so that they are configured to use IPv6.

NOTE! Running make test does not pass yet. However, these changes should allow IPv6 only BMH to be provisioned with operating system and creating a K8s cluster in those BMHs. Only working with centos node images.

Other not directly related changes that could actually be in their own PR:

Moving the docker daemon template in vm-setup/roles/packages_installation/files/daemon.json to vm-setup/roles/packages_installation/templates/daemon.json to better reflect the purpose of the file.
Fixing kubernetes yum repository address in template.

Other considerations

Currently tests failed after pivoting the control plane components to target cluster. In this step the target cluster needs to create pods for capm3 and other metal3 related components, but this failed because crio inside the target VM was not able to resolve IPv6 address in the registry address. So pulling images failed with cannot parse input: [fd55::1]:5000/localimages/cluster-api-provider-metal3:main. I manually tested this and crio was able to pull images after creating a hostname in /etc/hosts and specifying that hostname instead of bare IPv6 address.
I had to change CLUSTER_APIENDPOINT_HOST into CLUSTER_APIENDPOINT_IP in some templates, because having brackets around the IPv6 address caused errors.
Introducing domain names would solve both these problems, but do we want to spend time on that. Though as this PR introduces proper DNS server, and configures the environment to use that, using local domain names could be feasible.

metal3-io-bot · 2025-09-04T09:53:32Z

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nuhakala · 2025-09-04T10:01:26Z

/cc @Rozzii @tuminoid

This PR is quite big so I can also split it into smaller PRs.

The IPv6 is not ready in dev env after this, but I just want to have some feedback and discussion on how to do the DNS stuff.

The bot already pinged @elfosardo but you might also want to test this on your tests, because this is quite big and introduces new moving parts.

nuhakala · 2025-09-04T10:02:47Z

/test metal3-centos-e2e-integration-test-release-1-10 metal3-dev-env-integration-test-ubuntu-main

tests/roles/run_tests/templates/main/metal3datatemplate-template.yaml

nuhakala · 2025-09-04T11:09:51Z

/test metal3-centos-e2e-integration-test-release-1-10 metal3-dev-env-integration-test-ubuntu-main

tuminoid · 2025-09-04T12:04:20Z

/cc @terror96

metal3-io-bot · 2025-09-04T12:04:22Z

@tuminoid: GitHub didn't allow me to request PR reviews from the following users: terror96.

Note that only metal3-io members and repo collaborators can review this PR, and authors cannot review their own PRs.

In response to this:

/cc @terror96

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tuminoid · 2025-09-15T05:53:37Z

/cc @terror96

terror96 · 2025-09-15T13:36:49Z

/cc @terror96

Not much to comment at this point. Need to have a longer look. I just told @nuhakala that it would most likely be beneficial to support cases where NAT64 and DNS64 are deployed separately, because there could be scenarios where one uses a shared DNS64.

terror96

Minor comments & suggestions

tests/roles/run_tests/templates/main/cluster-template-workers-kubeadm-config-centos.yaml

tests/roles/run_tests/templates/main/cluster-template-controlplane-kubeadm-config-centos.yaml

terror96 · 2025-09-16T07:40:55Z

tests/roles/run_tests/templates/main/cluster-template-cluster.yaml

 spec:
  controlPlaneEndpoint:
-    host: ${ CLUSTER_APIENDPOINT_HOST }
+    host: ${ CLUSTER_APIENDPOINT_IP }


Is there an original setup where we would prefer using CLUSTER_APIENDPOINT_HOST?

This is rather annoying. Using host would be usually the way to go, but in this case if we add the brackets around IPv6 address to make it look like host, kubeadm errors and the cluster does not get connection.

Also, host names are not used anywhere, so it should not be a problem to use ATM, but of course moving to use host names later would be annoying.

tests/roles/run_tests/vars/main.yml

vm-setup/roles/nat64/defaults/main.yml

terror96 · 2025-09-16T08:16:21Z

vm-setup/roles/nat64/tasks/teardown_nat.yml

+  shell:
+    cmd: "ip addr del {{ LOCAL_DNS_V6 }}/128 dev lo"
+  become: yes
+  ignore_errors: true


We could also add IPv4 and IPv6 addresses to the tunnel device in order to enable sending of ICMP(v6) messages. It is a stupid that the need to be added manually, because they also need to be specified in the tayga configuration file. Well, life is.

Yeah, that would be good, but again, I feel that introducing any extra complexity at this point is not really needed.

terror96 · 2025-09-16T08:16:52Z

vm-setup/roles/nat64/templates/tayga.conf

+ipv4-addr 192.168.255.1
+prefix {{ DNS64_PREFIX }}
+dynamic-pool 192.168.255.0/24
+data-dir /var/spool/tayga


Maybe also IPv6 address for ICMPv6 traffic.

vm-setup/roles/packages_installation/templates/daemon.json

- Install Tayga as NAT64 service - Install Bind9 and configure it as local DNS server with DNS64 - Add IPv6 specific addresses and logic to cluster, controlplane, and worker templates - Update vars.md with new variables - Update CNI configuration for IPv6 Signed-off-by: Nuutti Hakala <[email protected]>

metal3-io-bot requested a review from dtantsur September 4, 2025 09:53

metal3-io-bot requested a review from elfosardo September 4, 2025 09:53

metal3-io-bot added the size/L Denotes a PR that changes 100-499 lines, ignoring generated files. label Sep 4, 2025

nuhakala force-pushed the nuhakala/ipv6_nat64_and_provision_support branch from 1abf0ce to 6122b0f Compare September 4, 2025 09:55

metal3-io-bot requested review from Rozzii and tuminoid September 4, 2025 10:01

nuhakala commented Sep 4, 2025

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tests/roles/run_tests/templates/main/metal3datatemplate-template.yaml Show resolved Hide resolved

nuhakala force-pushed the nuhakala/ipv6_nat64_and_provision_support branch from 6122b0f to cfafbd0 Compare September 4, 2025 11:09

metal3-io-bot requested a review from terror96 September 15, 2025 05:53

terror96 reviewed Sep 16, 2025

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metal3-io-bot added the needs-rebase Indicates that a PR cannot be merged because it has merge conflicts with HEAD. label Sep 17, 2025

nuhakala force-pushed the nuhakala/ipv6_nat64_and_provision_support branch from cfafbd0 to 222275a Compare November 20, 2025 11:46

metal3-io-bot removed the needs-rebase Indicates that a PR cannot be merged because it has merge conflicts with HEAD. label Nov 20, 2025

Add NAT64 to enable IPv6 provision in v4 only host #1567

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