Add windows support

monitor_windows.go

@@ -0,0 +1,98 @@
+package tun
+
+import (
+	"github.com/sagernet/sing-tun/internal/winipcfg"
+
+	"golang.org/x/sys/windows"
+)
+
+var _ InterfaceMonitor = (*NativeMonitor)(nil)
+
+type NativeMonitor struct {
+	listener              *winipcfg.RouteChangeCallback
+	callback              InterfaceMonitorCallback
+	defaultInterfaceName  string
+	defaultInterfaceIndex int
+}
+
+func NewMonitor(callback InterfaceMonitorCallback) (InterfaceMonitor, error) {
+	return &NativeMonitor{callback: callback}, nil
+}
+
+func (m *NativeMonitor) Start() error {
+	err := m.checkUpdate()
+	if err != nil {
+		return err
+	}
+	listener, err := winipcfg.RegisterRouteChangeCallback(func(notificationType winipcfg.MibNotificationType, route *winipcfg.MibIPforwardRow2) {
+		m.checkUpdate()
+	})
+	if err != nil {
+		return err
+	}
+	m.listener = listener
+	return nil
+}
+
+func (m *NativeMonitor) checkUpdate() error {
+	rows, err := winipcfg.GetIPForwardTable2(windows.AF_INET)
+	if err != nil {
+		return err
+	}
+
+	lowestMetric := ^uint32(0)
+	alias := ""
+	var index int
+
+	for _, row := range rows {
+		ifrow, err := row.InterfaceLUID.Interface()
+		if err != nil || ifrow.OperStatus != winipcfg.IfOperStatusUp {
+			continue
+		}
+
+		iface, err := row.InterfaceLUID.IPInterface(windows.AF_INET)
+		if err != nil {
+			continue
+		}
+
+		if ifrow.Type == winipcfg.IfTypePropVirtual || ifrow.Type == winipcfg.IfTypeSoftwareLoopback {
+			continue
+		}
+
+		metric := row.Metric + iface.Metric
+		if metric < lowestMetric {
+			lowestMetric = metric
+			alias = ifrow.Alias()
+			index = int(ifrow.InterfaceIndex)
+		}
+	}
+
+	if alias == "" {
+		return ErrNoRoute
+	}
+
+	oldInterface := m.defaultInterfaceName
+	oldIndex := m.defaultInterfaceIndex
+
+	m.defaultInterfaceName = alias
+	m.defaultInterfaceIndex = index
+
+	if oldInterface == m.defaultInterfaceName && oldIndex == m.defaultInterfaceIndex {
+		return nil
+	}
+
+	m.callback()
+	return nil
+}
+
+func (m *NativeMonitor) Close() error {
+	return m.listener.Unregister()
+}
+
+func (m *NativeMonitor) DefaultInterfaceName() string {
+	return m.defaultInterfaceName
+}
+
+func (m *NativeMonitor) DefaultInterfaceIndex() int {
+	return m.defaultInterfaceIndex
+}