Add support for API servers on IPv6 addresses (#48)

* Remove duplicate file for deletion

* Add support for IPv6 clusters

To correctly escape IPv6 addresses when ports are used, they must be
wrapped in square brackets [1]. This patch adds support for that,
using Ansible's ipwrap filter [2].

[1]: https://datatracker.ietf.org/doc/html/rfc4038#section-5.1
[2]: http://docs.ansible.com/ansible/latest/collections/ansible/utils/docsite/filters_ipaddr.html#wrapping-ipv6-addresses-in-brackets

* Do not abort other molecule jobs on failure

* Fix cache keys for Vagrant boxes

* Molecule: Derive overrides.yml location from scenario dir

# Conflicts:
#	molecule/default/molecule.yml
#	molecule/ipv6/molecule.yml

molecule/ipv6/README.md

@@ -0,0 +1,35 @@
+# Sample IPv6 configuration for `k3s-ansible`
+
+This scenario contains a cluster configuration which is _IPv6 first_, but still supports dual-stack networking with IPv4 for most things.
+This means:
+
+- The API server VIP is an IPv6 address.
+- The MetalLB pool consists of both IPv4 and IPv4 addresses.
+- Nodes as well as cluster-internal resources (pods and services) are accessible via IPv4 as well as IPv6.
+
+## Network design
+
+All IPv6 addresses used in this scenario share a single `/48` prefix: `fdad:bad:ba55`.
+The following subnets are used:
+
+- `fdad:bad:ba55:`**`0`**`::/64` is the subnet which contains the cluster components meant for external access.
+  That includes:
+
+  - The VIP for the Kubernetes API server: `fdad:bad:ba55::333`
+  - Services load-balanced by MetalLB: `fdad:bad:ba55::1b:0/112`
+  - Cluster nodes: `fdad:bad:ba55::de:0/112`
+  - The host executing Vagrant: `fdad:bad:ba55::1`
+
+  In a home lab setup, this might be your LAN.
+
+- `fdad:bad:ba55:`**`4200`**`::/56` is used internally by the cluster for pods.
+
+- `fdad:bad:ba55:`**`4300`**`::/108` is used internally by the cluster for services.
+
+IPv4 networking is also available:
+
+- The nodes have addresses inside `192.168.123.0/24`.
+  MetalLB also has a bit of address space in this range: `192.168.123.80-192.168.123.90`
+- For pods and services, the k3s defaults (`10.42.0.0/16` and `10.43.0.0/16)` are used.
+
+Note that the host running Vagrant is not part any of these IPv4 networks.

molecule/ipv6/host_vars/control1.yml

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+---
+node_ipv4: 192.168.123.11
+node_ipv6: fdad:bad:ba55::de:11

molecule/ipv6/host_vars/node1.yml

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+---
+node_ipv4: 192.168.123.21
+node_ipv6: fdad:bad:ba55::de:21

molecule/ipv6/molecule.yml

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+---
+dependency:
+  name: galaxy
+driver:
+  name: vagrant
+platforms:
+  - &control
+    name: control1
+    box: generic/ubuntu2204
+    memory: 2048
+    cpus: 2
+    config_options:
+      # We currently can not use public-key based authentication on Ubuntu 22.04,
+      # see: https://github.com/chef/bento/issues/1405
+      ssh.username: "vagrant"
+      ssh.password: "vagrant"
+    groups:
+      - k3s_cluster
+      - master
+    interfaces:
+      - network_name: private_network
+        ip: fdad:bad:ba55::de:11
+  - <<: *control
+    name: node1
+    groups:
+      - k3s_cluster
+      - node
+    interfaces:
+      - network_name: private_network
+        ip: fdad:bad:ba55::de:21
+provisioner:
+  name: ansible
+  playbooks:
+    converge: ../resources/converge.yml
+    side_effect: ../resources/reset.yml
+    verify: ../resources/verify.yml
+  inventory:
+    links:
+      group_vars: ../../inventory/sample/group_vars
+scenario:
+  test_sequence:
+    - dependency
+    - lint
+    - cleanup
+    - destroy
+    - syntax
+    - create
+    - prepare
+    - converge
+    # idempotence is not possible with the playbook in its current form.
+    - verify
+    # We are repurposing side_effect here to test the reset playbook.
+    # This is why we do not run it before verify (which tests the cluster),
+    # but after the verify step.
+    - side_effect
+    - cleanup
+    - destroy

molecule/ipv6/overrides.yml

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+---
+- name: Apply overrides
+  hosts: all
+  tasks:
+    - name: Override host variables (1/2)
+      ansible.builtin.set_fact:
+        # See: https://github.com/flannel-io/flannel/blob/67d603aaf45ef80f5dd39f43714fc5e6f8a637eb/Documentation/troubleshooting.md#Vagrant  # noqa yaml[line-length]
+        flannel_iface: eth1
+
+        # The test VMs might be a bit slow, so we give them more time to join the cluster:
+        retry_count: 45
+
+        # IPv6 configuration
+        # ######################################################################
+
+        # The API server will be reachable on IPv6 only
+        apiserver_endpoint: fdad:bad:ba55::333
+
+        # We give MetalLB address space for both IPv4 and IPv6
+        metal_lb_ip_range:
+          - fdad:bad:ba55::1b:0/112
+          - 192.168.123.80-192.168.123.90
+
+        # k3s_node_ip is by default set to the IPv4 address of flannel_iface.
+        # We want IPv6 addresses here of course, so we just specify them
+        # manually below.
+        k3s_node_ip: "{{ node_ipv4 }},{{ node_ipv6 }}"
+
+    - name: Override host variables (2/2)
+      # Since "extra_args" depends on "k3s_node_ip" and "flannel_iface" we have
+      # to set this AFTER overriding the both of them.
+      ansible.builtin.set_fact:
+        # A few extra server args are necessary:
+        #  - the network policy needs to be disabled.
+        #  - we need to manually specify the subnets for services and pods, as
+        #    the default has IPv4 ranges only.
+        extra_server_args: >-
+          {{ extra_args }}
+          --disable servicelb
+          --disable traefik
+          --disable-network-policy
+          --cluster-cidr=10.42.0.0/16,fdad:bad:ba55:4200::/56
+          --service-cidr=10.43.0.0/16,fdad:bad:ba55:4300::/108

molecule/ipv6/prepare.yml

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+---
+- name: Apply overrides
+  ansible.builtin.import_playbook: >-
+    {{ lookup("ansible.builtin.env", "MOLECULE_SCENARIO_DIRECTORY") }}/overrides.yml
+
+- name: Configure dual-stack networking
+  hosts: all
+  become: true
+
+  # Unfortunately, as of 2022-09, Vagrant does not support the configuration
+  # of both IPv4 and IPv6 addresses for a single network adapter. So we have
+  # to configure that ourselves.
+  # Moreover, we have to explicitly enable IPv6 for the loopback interface.
+
+  tasks:
+    - name: Enable IPv6 for network interfaces
+      ansible.posix.sysctl:
+        name: net.ipv6.conf.{{ item }}.disable_ipv6
+        value: "0"
+      with_items:
+        - all
+        - default
+        - lo
+
+    - name: Disable duplicate address detection
+      # Duplicate address detection did repeatedly fail within the virtual
+      # network. But since this setup does not use SLAAC anyway, we can safely
+      # disable it.
+      ansible.posix.sysctl:
+        name: net.ipv6.conf.{{ item }}.accept_dad
+        value: "0"
+      with_items:
+        - "{{ flannel_iface }}"
+
+    - name: Write IPv4 configuration
+      ansible.builtin.template:
+        src: 55-flannel-ipv4.yaml.j2
+        dest: /etc/netplan/55-flannel-ipv4.yaml
+        owner: root
+        group: root
+        mode: 0644
+      register: netplan_template
+
+    - name: Apply netplan configuration
+      # Conceptually, this should be a handler rather than a task.
+      # However, we are currently not in a role context - creating
+      # one just for this seemed overkill.
+      when: netplan_template.changed
+      ansible.builtin.command:
+        cmd: netplan apply
+      changed_when: true

molecule/ipv6/templates/55-flannel-ipv4.yaml.j2

@@ -0,0 +1,8 @@
+---
+network:
+  version: 2
+  renderer: networkd
+  ethernets:
+    {{ flannel_iface }}:
+      addresses:
+      - {{ node_ipv4 }}/24