From 88cee39bdbbeb0cfa558ddb62b8ce0e03bd7b9b1 Mon Sep 17 00:00:00 2001
From: EZForever <34133756+EZForever@users.noreply.github.com>
Date: Fri, 6 Jun 2025 00:10:23 +0800
Subject: [PATCH] vnet: initial Windows support

---
 pkg/vnet/tun_unsupported.go |   2 +-
 pkg/vnet/tun_windows.go     | 124 ++++++++++++++++++++++++++++++++++++
 2 files changed, 125 insertions(+), 1 deletion(-)
 create mode 100644 pkg/vnet/tun_windows.go

diff --git a/pkg/vnet/tun_unsupported.go b/pkg/vnet/tun_unsupported.go
index 731a06cd..08f3ee05 100644
--- a/pkg/vnet/tun_unsupported.go
+++ b/pkg/vnet/tun_unsupported.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build !darwin && !linux
+//go:build !darwin && !linux && !windows
 
 package vnet
 
diff --git a/pkg/vnet/tun_windows.go b/pkg/vnet/tun_windows.go
new file mode 100644
index 00000000..f10da6b1
--- /dev/null
+++ b/pkg/vnet/tun_windows.go
@@ -0,0 +1,124 @@
+// Copyright 2025 The frp Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package vnet
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"net"
+	"os/exec"
+	"strconv"
+	"strings"
+
+	"github.com/google/uuid"
+	"golang.org/x/sys/windows"
+	"golang.zx2c4.com/wireguard/tun"
+)
+
+const (
+	baseTunName = "utun"
+	defaultMTU  = 1420
+)
+
+func openTun(_ context.Context, addr string) (tun.Device, error) {
+	name, err := findNextTunName(baseTunName)
+	if err != nil {
+		name = getFallbackTunName(baseTunName, addr)
+	}
+
+	// This is for not creating a new entry in Windows device history on each usage
+	guid := uuid.NewSHA1(uuid.Nil, []byte(name))
+	winGuid, err := windows.GUIDFromString("{" + guid.String() + "}")
+	if err != nil {
+		return nil, err
+	}
+
+	tun.WintunTunnelType = "frpc VirtualNet"
+	tunDevice, err := tun.CreateTUNWithRequestedGUID(name, &winGuid, defaultMTU)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create TUN device '%s': %w", name, err)
+	}
+
+	actualName, err := tunDevice.Name()
+	if err != nil {
+		return nil, err
+	}
+
+	ip, ipNet, err := net.ParseCIDR(addr)
+	if err != nil {
+		return nil, err
+	}
+
+	if err = exec.Command("netsh", "interface", "ipv4", "add", "address", actualName, ip.String(), net.IP(ipNet.Mask).String(), "store=active").Run(); err != nil {
+		return nil, err
+	}
+
+	routes := []net.IPNet{*ipNet}
+	if err = addRoutes(actualName, routes); err != nil {
+		return nil, err
+	}
+
+	return tunDevice, nil
+}
+
+func findNextTunName(basename string) (string, error) {
+	interfaces, err := net.Interfaces()
+	if err != nil {
+		return "", fmt.Errorf("failed to get network interfaces: %w", err)
+	}
+	maxSuffix := -1
+
+	for _, iface := range interfaces {
+		name := iface.Name
+		if strings.HasPrefix(name, basename) {
+			suffix := name[len(basename):]
+			if suffix == "" {
+				continue
+			}
+
+			numSuffix, err := strconv.Atoi(suffix)
+			if err == nil && numSuffix > maxSuffix {
+				maxSuffix = numSuffix
+			}
+		}
+	}
+
+	nextSuffix := maxSuffix + 1
+	name := fmt.Sprintf("%s%d", basename, nextSuffix)
+	return name, nil
+}
+
+// getFallbackTunName generates a deterministic fallback TUN device name
+// based on the base name and the provided address string using a hash.
+func getFallbackTunName(baseName, addr string) string {
+	hasher := sha256.New()
+	hasher.Write([]byte(addr))
+	hashBytes := hasher.Sum(nil)
+	// Use first 4 bytes -> 8 hex chars for brevity, respecting IFNAMSIZ limit.
+	shortHash := hex.EncodeToString(hashBytes[:4])
+	return fmt.Sprintf("%s%s", baseName, shortHash)
+}
+
+func addRoutes(ifName string, routes []net.IPNet) error {
+	for _, route := range routes {
+		routeStr := route.String()
+		if err := exec.Command("netsh", "interface", "ipv4", "add", "route", routeStr, ifName, "store=active").Run(); err != nil {
+			return err
+		}
+	}
+	return nil
+}