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_fake.go

@@ -0,0 +1,36 @@
+// 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 (
+	"github.com/tailscale/wireguard-go/device"
+	"github.com/tailscale/wireguard-go/tun"
+	"tailscale.com/types/logger"
+)
+
+// NewFakeRouter returns a Router that does nothing when called and
+// always returns nil errors.
+func NewFake(logf logger.Logf, _ *device.Device, _ tun.Device) (Router, error) {
+	return fakeRouter{logf: logf}, nil
+}
+
+type fakeRouter struct {
+	logf logger.Logf
+}
+
+func (r fakeRouter) Up() error {
+	r.logf("Warning: fakeRouter.Up: not implemented.")
+	return nil
+}
+
+func (r fakeRouter) SetRoutes(rs RouteSettings) error {
+	r.logf("Warning: fakeRouter.SetRoutes: not implemented.")
+	return nil
+}
+
+func (r fakeRouter) Close() error {
+	r.logf("Warning: fakeRouter.Close: not implemented.")
+	return nil
+}