148 lines
3.3 KiB
Go
148 lines
3.3 KiB
Go
package main
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import (
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"encoding/json"
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"fmt"
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"log"
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"net"
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"os"
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"strconv"
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"strings"
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"github.com/google/gopacket"
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"github.com/google/gopacket/layers"
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)
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// Forwarder 流量转发器
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type Forwarder struct {
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enabled bool
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natTable map[string]string // 简单的NAT映射表，key: 原始地址:端口, value: 转发后地址:端口
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}
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// NewForwarder 创建新的流量转发器
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func NewForwarder() *Forwarder {
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return &Forwarder{
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enabled: false,
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natTable: make(map[string]string),
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}
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}
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// Start 启动转发服务
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func (f *Forwarder) Start() error {
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f.enabled = true
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log.Println("Forwarding service started")
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return nil
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}
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// Stop 停止转发服务
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func (f *Forwarder) Stop() {
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f.enabled = false
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log.Println("Forwarding service stopped")
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}
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func (f *Forwarder) LoadRulesFromFile(ruleFile string) error {
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content, err := os.ReadFile(ruleFile)
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if err != nil {
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return err
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}
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decoder := json.NewDecoder(strings.NewReader(string(content)))
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for decoder.More() {
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var rule ForwardRule
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err := decoder.Decode(&rule)
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if err != nil {
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return err
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}
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f.AddForwardRule(rule)
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}
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return nil
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}
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// ForwardRule 定义转发规则结构
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type ForwardRule struct {
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SrcIP string // 源IP
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SrcPort int // 源端口
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DstIP string // 目标IP
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DstPort int // 目标端口
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}
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// AddForwardRule 添加转发规则
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func (f *Forwarder) AddForwardRule(rule ForwardRule) {
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key := fmt.Sprintf("%s:%d", rule.SrcIP, rule.SrcPort)
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value := fmt.Sprintf("%s:%d", rule.DstIP, rule.DstPort)
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f.natTable[key] = value
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}
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// RemoveForwardRule 移除转发规则
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func (f *Forwarder) RemoveForwardRule(rule ForwardRule) {
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key := fmt.Sprintf("%s:%d", rule.SrcIP, rule.SrcPort)
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delete(f.natTable, key)
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}
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// ForwardPacket 转发数据包
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func (f *Forwarder) ForwardPacket(ipLayer *layers.IPv4, transportLayer gopacket.TransportLayer, packetData []byte) error {
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if !f.enabled {
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return nil
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}
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// 获取源IP和端口
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srcIP := ipLayer.SrcIP.String()
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var srcPort, dstPort int
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// 根据传输层协议获取端口
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switch t := transportLayer.(type) {
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case *layers.TCP:
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srcPort = int(t.SrcPort)
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dstPort = int(t.DstPort)
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case *layers.UDP:
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srcPort = int(t.SrcPort)
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dstPort = int(t.DstPort)
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default:
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// 不支持的传输层协议
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return nil
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}
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// 查找转发规则, 按照目标端口查找并转发。
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// 相当于做了一个端口映射。
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key := fmt.Sprintf(":%d", dstPort) // srcIP, srcPort)
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if forwardAddr, exists := f.natTable[key]; exists {
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// 解析转发目标地址
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addr, port, err := net.SplitHostPort(forwardAddr)
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if err != nil {
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return err
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}
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// 更新IP层目标地址
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newDstIP := net.ParseIP(addr)
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if newDstIP == nil {
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return fmt.Errorf("invalid forward IP address: %s", addr)
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}
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ipLayer.DstIP = newDstIP
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// 更新传输层目标端口
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newDstPort, err := strconv.Atoi(port)
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if err != nil {
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return err
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}
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switch t := transportLayer.(type) {
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case *layers.TCP:
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t.DstPort = layers.TCPPort(newDstPort)
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case *layers.UDP:
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t.DstPort = layers.UDPPort(newDstPort)
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}
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// 重新计算校验和
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switch t := transportLayer.(type) {
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case *layers.TCP:
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t.SetNetworkLayerForChecksum(ipLayer)
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case *layers.UDP:
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t.SetNetworkLayerForChecksum(ipLayer)
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}
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log.Printf("Forwarding packet: %s:%d -> %s:%d", srcIP, srcPort, addr, newDstPort)
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}
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return nil
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}
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