terraform-openstack: Added possibility to enable dhcp flag critical o…

…n one interface (kubernetes-sigs#10446)

* terraform-openstack: Updated extra partitions to use empty list by default

* terraform-openstack: Added possibility to enable dhcp flag critical on one interface

contrib/terraform/openstack/README.md

@@ -318,6 +318,7 @@ k8s_nodes:
         mount_path: string # Path to where the partition should be mounted
         partition_start: string # Where the partition should start (e.g. 10GB ). Note, if you set the partition_start to 0 there will be no space left for the root partition
         partition_end: string # Where the partition should end (e.g. 10GB or -1 for end of volume)
+      netplan_critical_dhcp_interface: string # Name of interface to set the dhcp flag critical = true, to circumvent [this issue](https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1776013).
 ```
 
 For example:

contrib/terraform/openstack/modules/compute/main.tf

@@ -19,8 +19,8 @@ data "cloudinit_config" "cloudinit" {
   part {
     content_type =  "text/cloud-config"
     content = templatefile("${path.module}/templates/cloudinit.yaml.tmpl", {
-      # template_file doesn't support lists
-      extra_partitions = ""
+      extra_partitions = [],
+      netplan_critical_dhcp_interface = ""
     })
   }
 }
@@ -821,7 +821,8 @@ resource "openstack_compute_instance_v2" "k8s_nodes" {
   flavor_id         = each.value.flavor
   key_pair          = openstack_compute_keypair_v2.k8s.name
   user_data         = each.value.cloudinit != null ? templatefile("${path.module}/templates/cloudinit.yaml.tmpl", {
-    extra_partitions = each.value.cloudinit.extra_partitions
+    extra_partitions = each.value.cloudinit.extra_partitions,
+    netplan_critical_dhcp_interface = each.value.cloudinit.netplan_critical_dhcp_interface,
   }) : data.cloudinit_config.cloudinit.rendered
 
   dynamic "block_device" {

contrib/terraform/openstack/modules/compute/templates/cloudinit.yaml.tmpl

@@ -1,4 +1,4 @@
-%{~ if length(extra_partitions) > 0 }
+%{~ if length(extra_partitions) > 0 || netplan_critical_dhcp_interface != "" }
 #cloud-config
 bootcmd:
 %{~ for idx, partition in extra_partitions }
@@ -8,11 +8,26 @@ bootcmd:
 %{~ endfor }
 
 runcmd:
+%{~ if netplan_critical_dhcp_interface != "" }
+  - netplan apply
+%{~ endif }
 %{~ for idx, partition in extra_partitions }
   - mkdir -p ${partition.mount_path}
   - chown nobody:nogroup ${partition.mount_path}
   - mount ${partition.partition_path} ${partition.mount_path}
-%{~ endfor }
+%{~ endfor ~}
+
+%{~ if netplan_critical_dhcp_interface != "" }
+write_files:
+  - path: /etc/netplan/90-critical-dhcp.yaml
+    content: |
+      network:
+        version: 2
+        ethernets:
+          ${ netplan_critical_dhcp_interface }:
+            dhcp4: true
+            critical: true
+%{~ endif }
 
 mounts:
 %{~ for idx, partition in extra_partitions }

contrib/terraform/openstack/modules/compute/variables.tf

@@ -142,13 +142,14 @@ variable "k8s_nodes" {
     additional_server_groups = optional(list(string))
     server_group           = optional(string)
     cloudinit              = optional(object({
-      extra_partitions = list(object({
+      extra_partitions = optional(list(object({
         volume_path     = string
         partition_path  = string
         partition_start = string
         partition_end   = string
         mount_path      = string
-      }))
+      })), [])
+      netplan_critical_dhcp_interface = optional(string, "")
     }))
   }))
 }