Support unsafe_routes on Darwin (#139)

* Support unsafe_routes on darwin

* fix formatting in tun_darwin.go (spaces to tabs)

tun_darwin.go

@@ -13,6 +13,7 @@ type Tun struct {
 	Device       string
 	Cidr         *net.IPNet
 	MTU          int
+	UnsafeRoutes []route
 
 	*water.Interface
 }
@@ -21,13 +22,11 @@ func newTun(deviceName string, cidr *net.IPNet, defaultMTU int, routes []route,
 	if len(routes) > 0 {
 		return nil, fmt.Errorf("Route MTU not supported in Darwin")
 	}
-	if len(unsafeRoutes) > 0 {
-		return nil, fmt.Errorf("unsafeRoutes not supported in Darwin")
-	}
 	// NOTE: You cannot set the deviceName under Darwin, so you must check tun.Device after calling .Activate()
 	return &Tun{
 		Cidr:         cidr,
 		MTU:          defaultMTU,
+		UnsafeRoutes: unsafeRoutes,
 	}, nil
 }
 
@@ -52,6 +51,12 @@ func (c *Tun) Activate() error {
 	if err = exec.Command("ifconfig", c.Device, "mtu", strconv.Itoa(c.MTU)).Run(); err != nil {
 		return fmt.Errorf("failed to run 'ifconfig': %s", err)
 	}
+	// Unsafe path routes
+	for _, r := range c.UnsafeRoutes {
+		if err = exec.Command("route", "-n", "add", "-net", r.route.String(), "-interface", c.Device).Run(); err != nil {
+			return fmt.Errorf("failed to run 'route add' for unsafe_route %s: %s", r.route.String(), err)
+		}
+	}
 
 	return nil
 }