使用gopacket更改目标端口

Question

我目前正在玩nfqueue的阅读软件包并修改它们。不幸的是，我有点卡在更改软件包的目标端口。请参阅下面的代码片段。想法是重写目标端口到。 我确实看到了修改后的软件包从队列中退出，但是如果我想通过连接到端口8888连接到监听端口8000的HTTP服务器，则连接超时。我认为这个软件包中有些东西是错误的。

package main 

import (
    "os" 
    "os/signal" 
    "syscall" 

    "github.com/chifflier/nfqueue-go/nfqueue" 
    "github.com/coreos/go-iptables/iptables" 

    "github.com/google/gopacket" 
    "github.com/google/gopacket/layers" 
) 

func sendNewPacket(payload *nfqueue.Payload, layers ...gopacket.SerializableLayer) { 
    buffer := gopacket.NewSerializeBuffer() 
    gopacket.SerializeLayers(buffer, gopacket.SerializeOptions{FixLengths: true, ComputeChecksums: true}, layers...) 
    outgoingPacket := buffer.Bytes() 
    payload.SetVerdictModified(nfqueue.NF_ACCEPT, outgoingPacket) 
} 

func realCallback(payload *nfqueue.Payload) int { 
    packet := gopacket.NewPacket(payload.Data, layers.LayerTypeIPv4, gopacket.Default) 
    ethLayer := packet.Layer(layers.LayerTypeEthernet) 
    eth, _ := ethLayer.(*layers.Ethernet) 
    if ipLayer := packet.Layer(layers.LayerTypeIPv4); ipLayer != nil { 
     ip, _ := ipLayer.(*layers.IPv4) 
     if tcpLayer := packet.Layer(layers.LayerTypeTCP); tcpLayer != nil { 
      tcp, _ := tcpLayer.(*layers.TCP) 
      if tcp.DstPort == 8888 { 
       tcp.DstPort = 8000 
       sendNewPacket(payload, eth, ip, tcp) 
       return 0 
      } 
      if tcp.SrcPort == 8000 { 
       tcp.SrcPort = 8888 
       sendNewPacket(payload, eth, ip, tcp) 
       return 0 
      } 
     } 
    } 
    payload.SetVerdict(nfqueue.NF_ACCEPT) 
    return 0 
} 

func main() { 
    ipt, err := iptables.New() 
    if err != nil { 
     panic(err) 
    } 
    ipt.Append("filter", "INPUT", "-p", "tcp", "-j", "NFQUEUE", "--queue-num", "0") 
    ipt.Append("filter", "OUTPUT", "-p", "tcp", "-j", "NFQUEUE", "--queue-num", "0") 
    q := new(nfqueue.Queue) 
    q.SetCallback(realCallback) 

    q.Init() 
    defer q.Close() 

    q.Unbind(syscall.AF_INET) 
    q.Bind(syscall.AF_INET) 
    q.CreateQueue(0) 

    c := make(chan os.Signal, 1) 
    signal.Notify(c, os.Interrupt) 
    go func() { 
     for sig := range c { 
      _ = sig 
      q.Close() 
      err = ipt.ClearChain("filter", "INPUT") 
      err = ipt.ClearChain("filter", "OUTPUT") 
      if err != nil { 
       panic(err) 
      } 
      os.Exit(0) 
     } 
    }() 
    q.TryRun() 
} 

Answer 1

如果你有兴趣的解决方案，代码可以在这里找到：https://github.com/kung-foo/freki