Middleware to destroy unused network interfaces

lib/vagrant/action/vm/destroy_unused_network_interfaces.rb

@@ -0,0 +1,33 @@
+module Vagrant
+  class Action
+    module VM
+      class DestroyUnusedNetworkInterfaces
+        def initialize(app, env)
+          @app = app
+        end
+
+        def call(env)
+          # We need to check if the host only network specified by any
+          # of the adapters would not have any more clients if it was
+          # destroyed. And if so, then destroy the host only network
+          # itself.
+          interfaces = env["vm"].vm.network_adapters.collect do |adapter|
+            adapter.host_interface_object
+          end
+
+          interfaces.compact.uniq.each do |interface|
+            # Destroy the network interface if there is only one
+            # attached VM (which must be this VM)
+            if interface.attached_vms.length == 1
+              env.logger.info "Destroying unused network interface..."
+              interface.destroy
+            end
+          end
+
+          # Continue along
+          @app.call(env)
+        end
+      end
+    end
+  end
+end

test/vagrant/action/vm/destroy_unused_network_interfaces_test.rb

@@ -0,0 +1,46 @@
+require File.join(File.dirname(__FILE__), '..', '..', '..', 'test_helper')
+
+class DestroyUnusedNetworkInterfacesVMActionTest < Test::Unit::TestCase
+  setup do
+    @klass = Vagrant::Action::VM::DestroyUnusedNetworkInterfaces
+    @app, @env = mock_action_data
+
+    @vm = mock("vm")
+    @env["vm"] = @vm
+
+    @internal_vm = mock("internal")
+    @vm.stubs(:vm).returns(@internal_vm)
+
+    @instance = @klass.new(@app, @env)
+  end
+
+  context "calling" do
+    setup do
+      @network_adapters = []
+      @internal_vm.stubs(:network_adapters).returns(@network_adapters)
+    end
+
+    def stub_interface(length=5)
+      interface = mock("interface")
+      adapter = mock("adapter")
+      adapter.stubs(:host_interface_object).returns(interface)
+      interface.stubs(:attached_vms).returns(Array.new(length))
+
+      @network_adapters << adapter
+      interface
+    end
+
+    should "destroy only the unused network interfaces" do
+      stub_interface(5)
+      stub_interface(7)
+      results = [stub_interface(1), stub_interface(1)]
+
+      results.each do |result|
+        result.expects(:destroy).once
+      end
+
+      @app.expects(:call).with(@env).once
+      @instance.call(@env)
+    end
+  end
+end