wgengine/router: split out from wgengine.

The router implementations are logically separate, with their own API.

Signed-off-by: David Anderson <danderson@tailscale.com>

wgengine/router/router_windows.go

@@ -0,0 +1,62 @@
+// Copyright (c) 2020 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 router
+
+import (
+	"log"
+
+	winipcfg "github.com/tailscale/winipcfg-go"
+	"github.com/tailscale/wireguard-go/device"
+	"github.com/tailscale/wireguard-go/tun"
+	"tailscale.com/types/logger"
+)
+
+type winRouter struct {
+	logf                func(fmt string, args ...interface{})
+	tunname             string
+	nativeTun           *tun.NativeTun
+	wgdev               *device.Device
+	routeChangeCallback *winipcfg.RouteChangeCallback
+}
+
+func newUserspaceRouter(logf logger.Logf, wgdev *device.Device, tundev tun.Device) (Router, error) {
+	tunname, err := tundev.Name()
+	if err != nil {
+		return nil, err
+	}
+	return &winRouter{
+		logf:      logf,
+		wgdev:     wgdev,
+		tunname:   tunname,
+		nativeTun: tundev.(*tun.NativeTun),
+	}, nil
+}
+
+func (r *winRouter) Up() error {
+	// MonitorDefaultRoutes handles making sure our wireguard UDP
+	// traffic goes through the old route, not recursively through the VPN.
+	var err error
+	r.routeChangeCallback, err = monitorDefaultRoutes(r.wgdev, true, r.nativeTun)
+	if err != nil {
+		log.Fatalf("MonitorDefaultRoutes: %v\n", err)
+	}
+	return nil
+}
+
+func (r *winRouter) SetRoutes(rs RouteSettings) error {
+	err := configureInterface(rs.Cfg, r.nativeTun, rs.DNS, rs.DNSDomains)
+	if err != nil {
+		r.logf("ConfigureInterface: %v\n", err)
+		return err
+	}
+	return nil
+}
+
+func (r *winRouter) Close() error {
+	if r.routeChangeCallback != nil {
+		r.routeChangeCallback.Unregister()
+	}
+	return nil
+}