virtual-net: initial (#4751)

pkg/vnet/tun.go

@@ -0,0 +1,77 @@
+// 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"
+	"io"
+
+	"github.com/fatedier/golib/pool"
+	"golang.zx2c4.com/wireguard/tun"
+)
+
+const (
+	offset = 16
+)
+
+type TunDevice interface {
+	io.ReadWriteCloser
+}
+
+func OpenTun(ctx context.Context, addr string) (TunDevice, error) {
+	td, err := openTun(ctx, addr)
+	if err != nil {
+		return nil, err
+	}
+	return &tunDeviceWrapper{dev: td}, nil
+}
+
+type tunDeviceWrapper struct {
+	dev tun.Device
+}
+
+func (d *tunDeviceWrapper) Read(p []byte) (int, error) {
+	buf := pool.GetBuf(len(p) + offset)
+	defer pool.PutBuf(buf)
+
+	sz := make([]int, 1)
+
+	n, err := d.dev.Read([][]byte{buf}, sz, offset)
+	if err != nil {
+		return 0, err
+	}
+	if n == 0 {
+		return 0, io.EOF
+	}
+
+	dataSize := sz[0]
+	if dataSize > len(p) {
+		dataSize = len(p)
+	}
+	copy(p, buf[offset:offset+dataSize])
+	return dataSize, nil
+}
+
+func (d *tunDeviceWrapper) Write(p []byte) (int, error) {
+	buf := pool.GetBuf(len(p) + offset)
+	defer pool.PutBuf(buf)
+
+	copy(buf[offset:], p)
+	return d.dev.Write([][]byte{buf}, offset)
+}
+
+func (d *tunDeviceWrapper) Close() error {
+	return d.dev.Close()
+}