providers/virtualbox: some validation around internal networks

plugins/providers/virtualbox/config.rb

@@ -120,6 +120,14 @@ module VagrantPlugins
           end
         end
 
+        # Verify that internal networks are only on private networks.
+        machine.config.vm.networks.each do |type, data|
+          if data[:virtualbox__intnet] && type != :private_network
+            errors << I18n.t("vagrant.virtualbox.config.intnet_on_bad_type")
+            break
+          end
+        end
+
         { "VirtualBox Provider" => errors }
       end
 

templates/locales/en.yml

@@ -61,6 +61,8 @@ en:
       config:
         id_in_pre_import: |-
           The ':id' parameter is not available in "pre-import" customizations.
+        intnet_on_bad_type: |-
+          VirtualBox internal networks can only be enabled on "private_networks"
         invalid_event: |-
           %{event} is not a valid event for customization. Valid events
           are: %{valid_events}