feat(kube-vip): add endpoint override for the internal listening address

Add a kube_vip_endpoint variable so the address kube-vip binds and listens on
can differ from the announced apiserver_endpoint. This is useful for complex
routing and site-to-site tunnels where the VIP kube-vip advertises over ARP
differs from the address it listens on internally.

- roles/k3s_server/templates/vip.yaml.j2: use kube_vip_endpoint (defaulting to
  apiserver_endpoint) for the `address` env and for deriving `vip_subnet`
- roles/k3s_server/defaults/main.yml: add kube_vip_endpoint default (null)
- roles/k3s_server/meta/main.yml: add kube_vip_endpoint argument_spec
- inventory/sample/group_vars/all.yml: document the new sample variable
- README.md: document the kube_vip_endpoint option
- .github/scripts/test-kube-vip-manifest.py: extend regression test to cover the
  default (apiserver_endpoint) and the override case

Closes #221

.github/scripts/test-kube-vip-manifest.py

@@ -123,6 +123,35 @@ def main():
     if "name: bgp_peers" in output:
         fail("bgp_peers present even though the peer list is empty")
 
+    # kube_vip_endpoint unset (undefined default): the address and subnet use
+    # the apiserver endpoint, so the template always emits an address here.
+    output = render(
+        env,
+        {
+            "_kube_vip_bgp_peers": [],
+            "kube_vip_arp": True,
+            "kube_vip_bgp": False,
+        },
+    )
+    if "value: 192.168.30.222" not in output:
+        fail("default kube-vip address does not use apiserver_endpoint")
+
+    # kube_vip_endpoint set: overrides the internal listening address AND the
+    # subnet derivation while the advertised apiserver_endpoint stays separate.
+    output = render(
+        env,
+        {
+            "_kube_vip_bgp_peers": [],
+            "kube_vip_endpoint": "10.66.1.5",
+            "kube_vip_arp": True,
+            "kube_vip_bgp": False,
+        },
+    )
+    if "value: 10.66.1.5" not in output:
+        fail("kube_vip_endpoint did not override the address")
+    if "value: 192.168.30.222" in output:
+        fail("apiserver_endpoint leaked into address when kube_vip_endpoint set")
+
     print("kube-vip manifest regression test passed")
 
 

README.md

@@ -219,6 +219,7 @@ See the commands [here](https://technotim.com/posts/k3s-etcd-ansible/#testing-yo
 | `k3s_server` | `kube_vip_bgp_peers` | list | `[]` | Not required | List of BGP peer ASN & address pairs |
 | `k3s_server` | `kube_vip_bgp_peers_groups` | list | `['k3s_master']` | Not required | Inventory group in which to search for additional `kube_vip_bgp_peers` parameters to merge. |
 | `k3s_server` | `kube_vip_iface` | string | `~` | Not required | Explicitly define an interface that ALL control nodes should use to propagate the VIP, define it here. Otherwise, kube-vip will determine the right interface automatically at runtime. |
+| `k3s_server` | `kube_vip_endpoint` | string | `~` | Not required | Overrides the internal address kube-vip binds/listens on, which can differ from the announced apiserver_endpoint for complex routing/tunnels. Defaults to apiserver_endpoint. |
 | `k3s_server` | `kube_vip_tag_version` | string | `v1.2.2` | Not required | Image tag for kube-vip |
 | `k3s_server` | `kube_vip_cloud_provider_tag_version` | string | `v0.0.12` | Not required | Tag for kube-vip-cloud-provider manifest when enable |
 | `k3s_server`, `k3_server_post` | `kube_vip_lb_ip_range` | string | `~` | Not required | IP range for kube-vip load balancer |

inventory/sample/group_vars/all.yml

@@ -48,6 +48,11 @@ cilium_bgp_lb_cidr: 192.168.31.0/24 # cidr for cilium loadbalancer ipam
 # enable kube-vip ARP broadcasts
 kube_vip_arp: true
 
+# (optional) overrides the address kube-vip binds/listens on internally, which
+# can differ from the announced apiserver_endpoint for complex routing/tunnels.
+# Defaults to apiserver_endpoint. Also used to derive the kube-vip subnet.
+# kube_vip_endpoint: 10.66.1.5
+
 # enable kube-vip BGP peering
 kube_vip_bgp: false
 

roles/k3s_server/defaults/main.yml

@@ -7,6 +7,7 @@ group_name_master: master
 
 kube_vip_arp: true
 kube_vip_iface:
+kube_vip_endpoint:
 kube_vip_cloud_provider_tag_version: v0.0.12
 kube_vip_tag_version: v1.2.2
 

roles/k3s_server/meta/main.yml

@@ -78,6 +78,15 @@ argument_specs:
           - automatically at runtime.
         default: ~
 
+      kube_vip_endpoint:
+        description:
+          - Overrides the address kube-vip binds/listens on internally, which
+          - can differ from the announced apiserver_endpoint for complex
+          - routing and site-to-site tunnels.
+          - Defaults to apiserver_endpoint and is used to derive the kube-vip
+          - subnet.
+        default: ~
+
       kube_vip_tag_version:
         description: Image tag for kube-vip
         default: v1.2.2

roles/k3s_server/templates/vip.yaml.j2

@@ -37,7 +37,7 @@ spec:
           value: {{ kube_vip_iface }}
 {% endif %}
         - name: vip_subnet
-          value: "{{ apiserver_endpoint | ansible.utils.ipsubnet | ansible.utils.ipaddr('prefix') }}"
+          value: "{{ (kube_vip_endpoint | default(apiserver_endpoint)) | ansible.utils.ipsubnet | ansible.utils.ipaddr('prefix') }}"
         - name: cp_enable
           value: "true"
         - name: cp_namespace
@@ -55,7 +55,7 @@ spec:
         - name: vip_retryperiod
           value: "2"
         - name: address
-          value: {{ apiserver_endpoint }}
+          value: {{ kube_vip_endpoint | default(apiserver_endpoint) }}
 {% if kube_vip_bgp | default(false) | bool %}
 {% if kube_vip_bgp_routerid is defined %}
         - name: bgp_routerid