add support for setting the network adapter MAC address (macaddr) and…

… default it to 'repeatable'

- this is to work around an issue where duplicate addresses are generated

README.md

@@ -168,6 +168,10 @@ As of November 2023, the following limitations and residuals have been observed:
    configuration. Markdown is used in the description to try and make clear which
    bit is configuration. 
 
+10. The Terraform provider Telmate/Proxmox can generate duplicate MAC addresses when
+   provisioning multiple VMs. IPv6 notices the duplicate/collision and doesn't complete
+   SLAAC, thus the VM doesn't get IPv6 addresses.
+
 # Links
 
 - https://austinsnerdythings.com/2021/09/01/how-to-deploy-vms-in-proxmox-with-terraform/

main.tf

@@ -228,13 +228,19 @@ EOT
   scsihw  = "virtio-scsi-single"
 
   // Support an array of virtio network adapters.
+  //
+  // If multiple VMs are created at the same time then the macaddr may be
+  // duplicated due to the time epoch being used to initialise the random
+  // seed (seen on Windows). Default to using the Telmate provider 'repeatable'
+  // option to generate a non-time based MAC address.
   dynamic "network" {
     for_each = var.networks
     content {
-      model  = "virtio"
-      bridge = lookup(network.value, "bridge", "vmbr0")
-      tag    = lookup(network.value, "tag", null)
-      mtu    = lookup(network.value, "mtu", null)
+      model   = "virtio"
+      bridge  = lookup(network.value, "bridge", "vmbr0")
+      tag     = lookup(network.value, "tag", null)
+      mtu     = lookup(network.value, "mtu", null)
+      macaddr = lookup(network.value, "macaddr", "repeatable")
     }
   }
 

variables.tf

@@ -131,9 +131,10 @@ variable "memory" {
 variable "networks" {
   description = "An ordered list of network interfaces"
   type        = list(object({
-    bridge = optional(string, "vmbr0")
-    tag    = optional(number)
-    mtu    = optional(number)
+    bridge  = optional(string, "vmbr0")
+    tag     = optional(number)
+    mtu     = optional(number)
+    macaddr = optional(string, "repeatable")
   }))
   default = [
     {