From f96cf1892a26a1fe98970b6ef4d6c6aeb5f6f58f Mon Sep 17 00:00:00 2001
From: Aleksandar Pesic <peske.nis@gmail.com>
Date: Mon, 22 Feb 2021 15:50:45 +0100
Subject: [PATCH] Create ifacewatcher

---
 wgengine/ifacewatcher_other.go   | 25 +++++++++++++++++++++++++
 wgengine/ifacewatcher_windows.go | 28 ++++++++++++++++++++++++++++
 wgengine/userspace.go            |  9 +++++++++
 3 files changed, 62 insertions(+)
 create mode 100644 wgengine/ifacewatcher_other.go
 create mode 100644 wgengine/ifacewatcher_windows.go

diff --git a/wgengine/ifacewatcher_other.go b/wgengine/ifacewatcher_other.go
new file mode 100644
index 000000000..0c57d65e1
--- /dev/null
+++ b/wgengine/ifacewatcher_other.go
@@ -0,0 +1,25 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//+build !windows
+
+package wgengine
+
+import (
+	"tailscale.com/types/logger"
+)
+
+// Dummy implementation that does nothing.
+type ifaceWatcher struct {
+}
+
+func initWatcher(logf logger.Logf) (*ifaceWatcher, error) {
+	return &ifaceWatcher{}, nil
+}
+
+func (iw *ifaceWatcher) setTun(ifc interface{}) {
+}
+
+func (iw *ifaceWatcher) Destroy() {
+}
diff --git a/wgengine/ifacewatcher_windows.go b/wgengine/ifacewatcher_windows.go
new file mode 100644
index 000000000..f69434966
--- /dev/null
+++ b/wgengine/ifacewatcher_windows.go
@@ -0,0 +1,28 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package wgengine
+
+import (
+	"github.com/tailscale/wireguard-go/tun"
+	"tailscale.com/types/logger"
+)
+
+type ifaceWatcher struct {
+	logf logger.Logf
+	iface *tun.NativeTun
+}
+
+func initWatcher(logf logger.Logf) (*ifaceWatcher, error) {
+	return &ifaceWatcher{logf: logger.WithPrefix(logf, "ifaceWatcher: ")}, nil
+}
+
+func (iw *ifaceWatcher) setTun(ifc interface{}) {
+	iw.iface = ifc.(*tun.NativeTun)
+	iw.logf("setTun LUID=%v", iw.iface.LUID())
+}
+
+func (iw *ifaceWatcher) Destroy() {
+	iw.logf("Destroy")
+}
diff --git a/wgengine/userspace.go b/wgengine/userspace.go
index 352a490cd..3e0ef50ae 100644
--- a/wgengine/userspace.go
+++ b/wgengine/userspace.go
@@ -179,14 +179,22 @@ func NewUserspaceEngine(logf logger.Logf, tunName string, listenPort uint16) (En
 
 	logf("Starting userspace wireguard engine with tun device %q", tunName)
 
+	iw, err := initWatcher(logf)
+	if err != nil {
+		return nil, err
+	}
+
 	tun, err := tun.CreateTUN(tunName, minimalMTU)
 	if err != nil {
+		iw.Destroy()
 		diagnoseTUNFailure(tunName, logf)
 		logf("CreateTUN: %v", err)
 		return nil, err
 	}
 	logf("CreateTUN ok.")
 
+	iw.setTun(tun)
+
 	conf := EngineConfig{
 		Logf:       logf,
 		TUN:        tun,
@@ -196,6 +204,7 @@ func NewUserspaceEngine(logf logger.Logf, tunName string, listenPort uint16) (En
 
 	e, err := NewUserspaceEngineAdvanced(conf)
 	if err != nil {
+		iw.Destroy()
 		tun.Close()
 		return nil, err
 	}