Example #1
0
func (h *dnsStream) creatPacket(msg_buf []byte, nomalPack chan gopacket.Packet) {
	var sourcePort, DesPort int16
	//read the port from tranport flow
	b_buf := bytes.NewBuffer(h.transport.Src().Raw())
	binary.Read(b_buf, binary.BigEndian, &sourcePort)
	b_buf = bytes.NewBuffer(h.transport.Dst().Raw())
	binary.Read(b_buf, binary.BigEndian, &DesPort)
	//new a UDP layer
	udpLayer := layers.UDP{
		BaseLayer: layers.BaseLayer{
			Contents: []byte{},
			Payload:  msg_buf,
		},
		SrcPort:  layers.UDPPort(sourcePort),
		DstPort:  layers.UDPPort(DesPort),
		Length:   1024,
		Checksum: 30026,
	}
	UDPNewSerializBuffer := gopacket.NewSerializeBuffer() // this buffer could be used as a payload of IP layer
	udpBuffer, _ := UDPNewSerializBuffer.PrependBytes(len(msg_buf))

	copy(udpBuffer, msg_buf)

	ops := gopacket.SerializeOptions{
		FixLengths:       true,
		ComputeChecksums: true,
	}

	if h.net.EndpointType() == layers.EndpointIPv4 {
		ip_checksum := layers.IPv4{}
		ip_checksum.Version = 4
		ip_checksum.TTL = 0
		ip_checksum.SrcIP = h.net.Src().Raw()
		ip_checksum.DstIP = h.net.Dst().Raw()
		udpLayer.SetNetworkLayerForChecksum(&ip_checksum)
	} else {
		ip6_checksum := layers.IPv6{}
		ip6_checksum.Version = 6
		ip6_checksum.NextHeader = layers.IPProtocolNoNextHeader
		ip6_checksum.HopLimit = 0
		ip6_checksum.SrcIP = h.net.Src().Raw()
		ip6_checksum.DstIP = h.net.Dst().Raw()
		udpLayer.SetNetworkLayerForChecksum(&ip6_checksum)
	}
	err := udpLayer.SerializeTo(UDPNewSerializBuffer, ops)
	if err != nil {
		fmt.Print("error in create udp Layer")
		return
		//err = nil
		//	need err handle there
	}

	fmt.Println("finished creat udplayer, the length is ", udpLayer.Length)
	if h.net.EndpointType() == layers.EndpointIPv4 { // if it is from ipv4, construct a ipv4 layer
		ip := layers.IPv4{
			BaseLayer: layers.BaseLayer{
				Contents: []byte{},
				Payload:  UDPNewSerializBuffer.Bytes(),
			},
			Version:    4,
			IHL:        0,
			TOS:        0,
			Length:     0,
			Id:         0,
			Flags:      0,
			FragOffset: 0,
			TTL:        0,
			Protocol:   layers.IPProtocolUDP,
			Checksum:   0,
			SrcIP:      h.net.Src().Raw(),
			DstIP:      h.net.Dst().Raw(),
			Options:    []layers.IPv4Option{},
			Padding:    []byte{},
		}
		//serialize it and use the serilize buffer to new packet
		IPserializeBuffer := gopacket.NewSerializeBuffer()

		ipBuffer, _ := IPserializeBuffer.PrependBytes(len(UDPNewSerializBuffer.Bytes()))
		copy(ipBuffer, UDPNewSerializBuffer.Bytes())
		err = ip.SerializeTo(IPserializeBuffer, ops)
		if err != nil {
			fmt.Print("error in create ipv4 Layer")
			return
			//err = nil
			//	need err handle there
		}

		fmt.Println("finished creat ip, the length is ", ip.Length)
		resultPack := gopacket.NewPacket(IPserializeBuffer.Bytes(), layers.LayerTypeIPv4, gopacket.Default)
		resultPack.Metadata().CaptureLength = len(resultPack.Data())
		resultPack.Metadata().Length = len(resultPack.Data())
		//seems the capture length is 0 so the pcapwrite cannot write it, try to give them a write value
		nomalPack <- resultPack
		return

	} else if h.net.EndpointType() == layers.EndpointIPv6 {
		// if it is in IPV6 contruct ipv6 packet
		ip := layers.IPv6{
			BaseLayer: layers.BaseLayer{
				Contents: []byte{},
				Payload:  UDPNewSerializBuffer.Bytes(),
			},
			Version:      6,
			TrafficClass: 0,
			FlowLabel:    0,
			Length:       0,
			NextHeader:   layers.IPProtocolNoNextHeader, //no sure what next header should be used there
			HopLimit:     0,
			SrcIP:        h.net.Src().Raw(),
			DstIP:        h.net.Dst().Raw(),
			HopByHop:     nil,
			// hbh will be pointed to by HopByHop if that layer exists.
		}
		IPserializeBuffer := gopacket.NewSerializeBuffer()
		err := ip.SerializeTo(IPserializeBuffer, ops)
		if err != nil {
			fmt.Printf("error in creat IPV6 Layer")
			return
		}
		fmt.Println("finished creat ip, the length is ", ip.Length)
		resultPack := gopacket.NewPacket(IPserializeBuffer.Bytes(), layers.LayerTypeIPv6, gopacket.Default)
		resultPack.Metadata().CaptureLength = len(resultPack.Data())
		resultPack.Metadata().Length = len(resultPack.Data())
		//seems the capture length is 0 so the pcapwrite cannot write it, try to give them a write value
		nomalPack <- resultPack
		return
	} else {
		return //unknown network just return?
	}
}