tun: add Windows support

tun_linux.go

-// +build linux
-
 package gost
 
 import (

tun_win.go

-// +build windows
-
-package gost
-
-import (
-	"errors"
-	"net"
-)
-
-//TODO: wintun for Windows: https://www.wintun.net/
-// https://godoc.org/golang.zx2c4.com/wireguard/tun/wintun
-func createTun(cfg TunConfig) (conn net.Conn, ipNet *net.IPNet, err error) {
-	err = errors.New("tun is not supported on Windows")
-	return
-}

tun_windows.go

+package gost
+
+import (
+	"fmt"
+	"net"
+	"os/exec"
+
+	"github.com/go-log/log"
+	"github.com/songgao/water"
+)
+
+func createTun(cfg TunConfig) (conn net.Conn, ipNet *net.IPNet, err error) {
+	ip, ipNet, err := net.ParseCIDR(cfg.Addr)
+	if err != nil {
+		return
+	}
+
+	ifce, err := water.New(water.Config{
+		DeviceType: water.TUN,
+		PlatformSpecificParams: water.PlatformSpecificParams{
+			ComponentID:   "tap0901",
+			InterfaceName: cfg.Name,
+			Network:       cfg.Addr,
+		},
+	})
+	if err != nil {
+		return
+	}
+
+	cmd := fmt.Sprintf("netsh interface ip set address name=%s "+
+		"source=static addr=%s mask=%s gateway=none",
+		ifce.Name(), ip.String(), ipMask(ipNet.Mask))
+	log.Log("[tun]", cmd)
+	if er := exec.Command("netsh",
+		"interface", "ip", "set", "address",
+		"name="+ifce.Name(), "source=static",
+		"addr="+ip.String(), "mask="+ipMask(ipNet.Mask), "gateway=none").Run(); er != nil {
+		err = fmt.Errorf("%s: %v", cmd, er)
+		return
+	}
+
+	conn = &tunConn{
+		ifce: ifce,
+		addr: &net.IPAddr{IP: ip},
+	}
+	return
+}
+
+func ipMask(mask net.IPMask) string {
+	return fmt.Sprintf("%d.%d.%d.%d", mask[0], mask[1], mask[2], mask[3])
+}