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| package main
import ( "context" "errors" "flag" "fmt" "github.com/google/gopacket" "github.com/google/gopacket/layers" "github.com/google/gopacket/pcap" "log" "net" "os" "os/signal" "strings" )
var packetChan chan *Packet
type UDP struct { SrcIP net.IP DstIP net.IP SrcPort int DstPort int Content []byte }
func (u *UDP) Send() error { laddr := &net.UDPAddr{IP: u.SrcIP, Port: u.SrcPort} raddr := &net.UDPAddr{IP: u.DstIP, Port: u.DstPort}
if conn, err := net.DialUDP("udp", laddr, raddr); err != nil { return err } else { defer conn.Close() if _, err := conn.Write(u.Content); err != nil { return err } else { return nil } } }
type Packet struct { Ethernet layers.Ethernet IP4 layers.IPv4 TCP layers.TCP UDP layers.UDP Payload gopacket.Payload
Decoded []gopacket.LayerType }
func NewPacket(packetData []byte) (*Packet, error) { var p Packet parser := gopacket.NewDecodingLayerParser(layers.LayerTypeEthernet, &p.Ethernet, &p.IP4, &p.TCP, &p.UDP, &p.Payload) if err := parser.DecodeLayers(packetData, &p.Decoded); err != nil { return nil, err } else { return &p, nil } }
func (p *Packet) String() string { var info []string for _, layerType := range p.Decoded { switch layerType { case layers.LayerTypeEthernet: info = append(info, p.Ethernet.SrcMAC.String()+" > "+p.Ethernet.DstMAC.String(), "Ethernet Type: "+p.Ethernet.EthernetType.String(), ) case layers.LayerTypeIPv4: info = append(info, p.IP4.SrcIP.String()+" > "+p.IP4.DstIP.String(), "Protocol: "+p.IP4.Protocol.String(), ) case layers.LayerTypeTCP: info = append(info, p.TCP.SrcPort.String()+" > "+p.TCP.DstPort.String(), ) case layers.LayerTypeUDP: info = append(info, p.UDP.SrcPort.String()+" > "+p.UDP.DstPort.String(), ) case gopacket.LayerTypePayload: info = append(info, "Content: "+string(p.Payload.LayerContents()), ) } } return strings.Join(info, " | ") }
func findDevByIp(ip net.IP) (*pcap.Interface, error) { devices, err := pcap.FindAllDevs() if err != nil { return nil, err } for _, device := range devices { for _, address := range device.Addresses { if address.IP.Equal(ip) { return &device, nil } } } return nil, errors.New("find device failed by ip") }
func capture(dev *pcap.Interface, filter string) { if h, err := pcap.OpenLive(dev.Name, 4096, true, -1); err != nil { log.Panicln(err) } else if err := h.SetBPFFilter(filter); err != nil { log.Panicln(err) } else { defer h.Close() for { if packetData, _, err := h.ReadPacketData(); err != nil { log.Panicln(err) } else if p, err := NewPacket(packetData); err != nil { log.Panicln(err) } else { fmt.Println(p.String()) packetChan <- p } } } }
func redirect(ctx context.Context, srcIP, dstIP net.IP) { for { select { case <-ctx.Done(): return case p := <-packetChan: u := UDP{ SrcIP: srcIP, DstIP: dstIP, SrcPort: int(p.UDP.SrcPort), DstPort: int(p.UDP.DstPort), Content: p.Payload.LayerContents(), } if err := u.Send(); err != nil { log.Printf("send p failed: %+v", u) } } } }
func Run(ctx context.Context, devIp, filter, srcIp, dstIp string) { dev, err := findDevByIp(net.ParseIP(devIp)) if err != nil { log.Panicf("find device by ip failed: ip=%s, err=%s", devIp, err) }
packetChan = make(chan *Packet, 64) go capture(dev, filter) redirect(ctx, net.ParseIP(srcIp), net.ParseIP(dstIp)) }
func main() { var ( devIP = flag.String("d", "192.168.1.106", "Device IP.") filter = flag.String("f", "port 14001", "BPF filter expression.") srcIP = flag.String("src-ip", "10.0.1.3", "Redirect src IP.") dstIP = flag.String("dst-ip", "10.0.1.2", "Redirect dst IP.") ) flag.Parse()
ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt) defer stop() Run(ctx, *devIP, *filter, *srcIP, *dstIP) }
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