droplet: Document and warn that enabling IPv6 requires OS-level confi…

…g changes. (#1111)

digitalocean/droplet/resource_droplet.go

@@ -471,6 +471,7 @@ func FindIPv4AddrByType(d *godo.Droplet, addrType string) string {
 
 func resourceDigitalOceanDropletUpdate(ctx context.Context, d *schema.ResourceData, meta interface{}) diag.Diagnostics {
 	client := meta.(*config.CombinedConfig).GodoClient()
+	var warnings []diag.Diagnostic
 
 	id, err := strconv.Atoi(d.Id())
 	if err != nil {
@@ -602,7 +603,6 @@ func resourceDigitalOceanDropletUpdate(ctx context.Context, d *schema.ResourceDa
 	// As there is no way to disable IPv6, we only check if it needs to be enabled
 	if d.HasChange("ipv6") && d.Get("ipv6").(bool) {
 		_, _, err = client.DropletActions.EnableIPv6(context.Background(), id)
-
 		if err != nil {
 			return diag.Errorf(
 				"Error turning on ipv6 for droplet (%s): %s", d.Id(), err)
@@ -616,6 +616,12 @@ func resourceDigitalOceanDropletUpdate(ctx context.Context, d *schema.ResourceDa
 			return diag.Errorf(
 				"Error waiting for ipv6 to be turned on for droplet (%s): %s", d.Id(), err)
 		}
+
+		warnings = append(warnings, diag.Diagnostic{
+			Severity: diag.Warning,
+			Summary:  "Enabling IPv6 requires additional OS-level configuration",
+			Detail:   "When enabling IPv6 on an existing Droplet, additional OS-level configuration is required. For more info, see: \nhttps://docs.digitalocean.com/products/networking/ipv6/how-to/enable/#on-existing-droplets",
+		})
 	}
 
 	if d.HasChange("tags") {
@@ -661,7 +667,12 @@ func resourceDigitalOceanDropletUpdate(ctx context.Context, d *schema.ResourceDa
 		}
 	}
 
-	return resourceDigitalOceanDropletRead(ctx, d, meta)
+	readErr := resourceDigitalOceanDropletRead(ctx, d, meta)
+	if readErr != nil {
+		readErr = append(warnings, readErr...)
+	}
+
+	return warnings
 }
 
 func resourceDigitalOceanDropletDelete(ctx context.Context, d *schema.ResourceData, meta interface{}) diag.Diagnostics {

docs/resources/droplet.md

@@ -34,10 +34,12 @@ The following arguments are supported:
    Defaults to false. If set to `true`, you can configure monitor alert policies
    [monitor alert resource](/providers/digitalocean/digitalocean/latest/docs/resources/monitor_alert)
 * `ipv6` - (Optional) Boolean controlling if IPv6 is enabled. Defaults to false.
+   Once enabled for a Droplet, IPv6 can not be disabled. When enabling IPv6 on
+   an existing Droplet, [additional OS-level configuration](https://docs.digitalocean.com/products/networking/ipv6/how-to/enable/#on-existing-droplets)
+   is required.
 * `vpc_uuid` - (Optional) The ID of the VPC where the Droplet will be located.
 * `private_networking` - (Optional) **Deprecated** Boolean controlling if private networking
   is enabled. This parameter has been deprecated. Use `vpc_uuid` instead to specify a VPC network for the Droplet. If no `vpc_uuid` is provided, the Droplet will be placed in your account's default VPC for the region.
-
 * `ssh_keys` - (Optional) A list of SSH key IDs or fingerprints to enable in
    the format `[12345, 123456]`. To retrieve this info, use the
    [DigitalOcean API](https://docs.digitalocean.com/reference/api/api-reference/#tag/SSH-Keys)