1 files changed, 80 insertions, 0 deletions
diff --git a/tunnel/winipcfg/route_change_handler.go b/tunnel/winipcfg/route_change_handler.go
new file mode 100644
index 00000000..e43fa3c0
--- /dev/null
+++ b/tunnel/winipcfg/route_change_handler.go
@@ -0,0 +1,80 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package winipcfg
+
+import (
+	"sync"
+
+	"golang.org/x/sys/windows"
+)
+
+// RouteChangeCallback structure allows route change callback handling.
+type RouteChangeCallback struct {
+	cb func(notificationType MibNotificationType, route *MibIPforwardRow2)
+}
+
+var (
+	routeChangeAddRemoveMutex = sync.Mutex{}
+	routeChangeMutex          = sync.Mutex{}
+	routeChangeCallbacks      = make(map[*RouteChangeCallback]bool)
+	routeChangeHandle         = windows.Handle(0)
+)
+
+// RegisterRouteChangeCallback registers a new RouteChangeCallback. If this particular callback is already
+// registered, the function will silently return. Returned RouteChangeCallback.Unregister method should be used
+// to unregister.
+func RegisterRouteChangeCallback(callback func(notificationType MibNotificationType, route *MibIPforwardRow2)) (*RouteChangeCallback, error) {
+	s := &RouteChangeCallback{callback}
+
+	routeChangeAddRemoveMutex.Lock()
+	defer routeChangeAddRemoveMutex.Unlock()
+
+	routeChangeMutex.Lock()
+	defer routeChangeMutex.Unlock()
+
+	routeChangeCallbacks[s] = true
+
+	if routeChangeHandle == 0 {
+		err := notifyRouteChange2(windows.AF_UNSPEC, windows.NewCallback(routeChanged), 0, false, &routeChangeHandle)
+		if err != nil {
+			delete(routeChangeCallbacks, s)
+			routeChangeHandle = 0
+			return nil, err
+		}
+	}
+
+	return s, nil
+}
+
+// Unregister unregisters the callback.
+func (callback *RouteChangeCallback) Unregister() error {
+	routeChangeAddRemoveMutex.Lock()
+	defer routeChangeAddRemoveMutex.Unlock()
+
+	routeChangeMutex.Lock()
+	delete(routeChangeCallbacks, callback)
+	removeIt := len(routeChangeCallbacks) == 0 && routeChangeHandle != 0
+	routeChangeMutex.Unlock()
+
+	if removeIt {
+		err := cancelMibChangeNotify2(routeChangeHandle)
+		if err != nil {
+			return err
+		}
+		routeChangeHandle = 0
+	}
+
+	return nil
+}
+
+func routeChanged(callerContext uintptr, row *MibIPforwardRow2, notificationType MibNotificationType) uintptr {
+	routeChangeMutex.Lock()
+	for cb := range routeChangeCallbacks {
+		cb.cb(notificationType, row)
+	}
+	routeChangeMutex.Unlock()
+	return 0
+}