func main() {
	// Open device
	handle, err = pcap.OpenLive(device, snapshot_len, promiscuous, timeout)
	if err != nil {
		log.Fatal(err)
	}
	defer handle.Close()

	// Send raw bytes over wire
	rawBytes := []byte{10, 20, 30}
	err = handle.WritePacketData(rawBytes)
	if err != nil {
		log.Fatal(err)
	}

	// Create a properly formed packet, just with
	// empty details. Should fill out MAC addresses,
	// IP addresses, etc.
	buffer = gopacket.NewSerializeBuffer()
	gopacket.SerializeLayers(buffer, options,
		&layers.Ethernet{},
		&layers.IPv4{},
		&layers.TCP{},
		gopacket.Payload(rawBytes),
	)
	outgoingPacket := buffer.Bytes()
	// Send our packet
	err = handle.WritePacketData(outgoingPacket)
	if err != nil {
		log.Fatal(err)
	}

	// This time lets fill out some information
	ipLayer := &layers.IPv4{
		SrcIP: net.IP{127, 0, 0, 1},
		DstIP: net.IP{8, 8, 8, 8},
	}
	ethernetLayer := &layers.Ethernet{
		SrcMAC: net.HardwareAddr{0xFF, 0xAA, 0xFA, 0xAA, 0xFF, 0xAA, 0xFA, 0xAA},
		DstMAC: net.HardwareAddr{0xBD, 0xBD, 0xBD, 0xBD, 0xBD, 0xBD, 0xBD, 0xBD},
	}
	tcpLayer := &layers.TCP{
		SrcPort: layers.TCPPort(4321),
		DstPort: layers.TCPPort(80),
	}
	// And create the packet with the layers
	buffer = gopacket.NewSerializeBuffer()
	gopacket.SerializeLayers(buffer, options,
		ethernetLayer,
		ipLayer,
		tcpLayer,
		gopacket.Payload(rawBytes),
	)
	outgoingPacket = buffer.Bytes()
}

func (sender *RawUDPSender) Send(msg []byte) error {
	payload := gopacket.Payload(msg)
	sender.udpHeader.DstPort = layers.UDPPort(sender.conn.RemoteUDPAddr().Port)

	err := gopacket.SerializeLayers(sender.ipBuf, sender.opts, sender.udpHeader, &payload)
	if err != nil {
		return err
	}
	packet := sender.ipBuf.Bytes()
	_, err = sender.socket.Write(packet)
	if err == nil || PosixError(err) != syscall.EMSGSIZE {
		return err
	}
	f, err := sender.socket.File()
	if err != nil {
		return err
	}
	defer f.Close()
	fd := int(f.Fd())
	log.Println("EMSGSIZE on send, expecting PMTU update (IP packet was",
		len(packet), "bytes, payload was", len(msg), "bytes)")
	pmtu, err := syscall.GetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_MTU)
	if err != nil {
		return err
	}
	return MsgTooBigError{PMTU: pmtu}
}

func newIcmpData(src, dest *net.IPAddr, typeCode, offSet, ttl int) (data []byte) {
	ip := &layers.IPv4{}
	ip.Version = 4
	ip.Protocol = layers.IPProtocolICMPv4
	ip.SrcIP = src.IP
	ip.DstIP = dest.IP
	ip.Length = 20
	ip.TTL = uint8(ttl)

	icmp := &layers.ICMPv4{}
	icmp.TypeCode = layers.ICMPv4TypeCode(uint16(typeCode) << 8)
	icmp.Id = pid
	icmp.Seq = 1
	icmp.Checksum = 0

	opts := gopacket.SerializeOptions{}
	opts.ComputeChecksums = true
	opts.FixLengths = true

	now := time.Now().UnixNano()
	var payload = make([]byte, 8)
	binary.LittleEndian.PutUint64(payload, uint64(now))

	buf := gopacket.NewSerializeBuffer()
	gopacket.SerializeLayers(buf, opts, ip, icmp, gopacket.Payload(payload))

	return buf.Bytes()
}

func TestSetupPan(t *testing.T) {
	/*
		packetManifest := types.PacketManifest{
			Timestamp: time.Now(),
			Flow:      nil,
			RawPacket: nil,
			IP:        ip,
			TCP:       tcp,
			Payload:   payload,
		}
	*/

	buf := gopacket.NewSerializeBuffer()
	opts := gopacket.SerializeOptions{}
	ip0 := net.ParseIP("127.0.0.100")
	ip1 := net.ParseIP("127.0.0.1")
	gopacket.SerializeLayers(buf, opts,
		&layers.Ethernet{},
		&layers.IPv4{SrcIP: ip0, DstIP: ip1},
		&layers.TCP{},
		gopacket.Payload([]byte{1, 2, 3, 4, 5}))
	packetData := buf.Bytes()
	assert.NotEqual(t, packetData, nil)

}

func forgeEthIPTCP(t *testing.T, seed int64) *gopacket.Packet {
	var options gopacket.SerializeOptions
	rnd := rand.New(rand.NewSource(seed))

	rawBytes := []byte{10, 20, 30}
	ethernetLayer := &layers.Ethernet{
		SrcMAC: net.HardwareAddr{0x00, 0x0F, 0xAA, 0xFA, 0xAA, byte(rnd.Intn(0x100))},
		DstMAC: net.HardwareAddr{0x00, 0x0D, 0xBD, 0xBD, byte(rnd.Intn(0x100)), 0xBD},
	}
	ipLayer := &layers.IPv4{
		SrcIP: net.IP{127, 0, 0, byte(rnd.Intn(0x100))},
		DstIP: net.IP{byte(rnd.Intn(0x100)), 8, 8, 8},
	}
	tcpLayer := &layers.TCP{
		SrcPort: layers.TCPPort(byte(rnd.Intn(0x10000))),
		DstPort: layers.TCPPort(byte(rnd.Intn(0x10000))),
	}
	// And create the packet with the layers
	buffer := gopacket.NewSerializeBuffer()
	err := gopacket.SerializeLayers(buffer, options,
		ethernetLayer,
		ipLayer,
		tcpLayer,
		gopacket.Payload(rawBytes),
	)
	if err != nil {
		t.Fail()
	}

	gpacket := gopacket.NewPacket(buffer.Bytes(), layers.LayerTypeEthernet, gopacket.Default)
	return &gpacket

}

func (dec *EthernetDecoder) sendICMPFragNeeded(mtu int, sendFrame func([]byte) error) error {
	buf := gopacket.NewSerializeBuffer()
	opts := gopacket.SerializeOptions{
		FixLengths:       true,
		ComputeChecksums: true}
	ipHeaderSize := int(dec.IP.IHL) * 4 // IHL is the number of 32-byte words in the header
	payload := gopacket.Payload(dec.IP.BaseLayer.Contents[:ipHeaderSize+8])
	err := gopacket.SerializeLayers(buf, opts,
		&layers.Ethernet{
			SrcMAC:       dec.Eth.DstMAC,
			DstMAC:       dec.Eth.SrcMAC,
			EthernetType: dec.Eth.EthernetType},
		&layers.IPv4{
			Version:    4,
			TOS:        dec.IP.TOS,
			Id:         0,
			Flags:      0,
			FragOffset: 0,
			TTL:        64,
			Protocol:   layers.IPProtocolICMPv4,
			DstIP:      dec.IP.SrcIP,
			SrcIP:      dec.IP.DstIP},
		&layers.ICMPv4{
			TypeCode: 0x304,
			Id:       0,
			Seq:      uint16(mtu)},
		&payload)
	if err != nil {
		return err
	}

	Log.Printf("Sending ICMP 3,4 (%v -> %v): PMTU= %v\n", dec.IP.DstIP, dec.IP.SrcIP, mtu)
	return sendFrame(buf.Bytes())
}

func main() {
	// If we don't have a handle to a device or a file, but we have a bunch
	// of raw bytes, we can try to decode them in to packet information

	// NewPacket() takes the raw bytes that make up the packet as the first parameter
	// The second parameter is the lowest level layer you want to decode. It will
	// decode that layer and all layers on top of it. The third layer
	// is the type of decoding: default(all at once), lazy(on demand), and NoCopy
	// which will not create a copy of the buffer

	// Create an packet with ethernet, IP, TCP, and payload layers
	// We are creating one we know will be decoded properly but
	// your byte source could be anything. If any of the packets
	// come back as nil, that means it could not decode it in to
	// the proper layer (malformed or incorrect packet type)
	payload := []byte{2, 4, 6}
	options := gopacket.SerializeOptions{}
	buffer := gopacket.NewSerializeBuffer()
	gopacket.SerializeLayers(buffer, options,
		&layers.Ethernet{},
		&layers.IPv4{},
		&layers.TCP{},
		gopacket.Payload(payload),
	)
	rawBytes := buffer.Bytes()

	// Decode an ethernet packet
	ethPacket :=
		gopacket.NewPacket(
			rawBytes,
			layers.LayerTypeEthernet,
			gopacket.Default,
		)

	// with Lazy decoding it will only decode what it needs when it needs it
	// This is not concurrency safe. If using concurrency, use default
	ipPacket :=
		gopacket.NewPacket(
			rawBytes,
			layers.LayerTypeIPv4,
			gopacket.Lazy,
		)

	// With the NoCopy option, the underlying slices are referenced
	// directly and not copied. If the underlying bytes change so will
	// the packet
	tcpPacket :=
		gopacket.NewPacket(
			rawBytes,
			layers.LayerTypeTCP,
			gopacket.NoCopy,
		)

	fmt.Println(ethPacket)
	fmt.Println(ipPacket)
	fmt.Println(tcpPacket)
}

/* protos must contain a UDP or TCP layer on top of IPv4 */
func forgeTestPacket(t *testing.T, seed int64, protos ...ProtocolType) *gopacket.Packet {
	rnd := rand.New(rand.NewSource(seed))

	rawBytes := []byte{10, 20, 30}
	var protoStack []gopacket.SerializableLayer

	for i, proto := range protos {
		switch proto {
		case ETH:
			ethernetLayer := &layers.Ethernet{
				SrcMAC:       net.HardwareAddr{0x00, 0x0F, 0xAA, 0xFA, 0xAA, byte(rnd.Intn(0x100))},
				DstMAC:       net.HardwareAddr{0x00, 0x0D, 0xBD, 0xBD, byte(rnd.Intn(0x100)), 0xBD},
				EthernetType: layers.EthernetTypeIPv4,
			}
			protoStack = append(protoStack, ethernetLayer)
		case IPv4:
			ipv4Layer := &layers.IPv4{
				SrcIP: net.IP{127, 0, 0, byte(rnd.Intn(0x100))},
				DstIP: net.IP{byte(rnd.Intn(0x100)), 8, 8, 8},
			}
			switch protos[i+1] {
			case TCP:
				ipv4Layer.Protocol = layers.IPProtocolTCP
			case UDP:
				ipv4Layer.Protocol = layers.IPProtocolUDP
			}
			protoStack = append(protoStack, ipv4Layer)
		case TCP:
			tcpLayer := &layers.TCP{
				SrcPort: layers.TCPPort(byte(rnd.Intn(0x10000))),
				DstPort: layers.TCPPort(byte(rnd.Intn(0x10000))),
			}
			protoStack = append(protoStack, tcpLayer)
		case UDP:
			udpLayer := &layers.UDP{
				SrcPort: layers.UDPPort(byte(rnd.Intn(0x10000))),
				DstPort: layers.UDPPort(byte(rnd.Intn(0x10000))),
			}
			protoStack = append(protoStack, udpLayer)
		default:
			t.Log("forgeTestPacket : Unsupported protocol ", proto)
		}
	}
	protoStack = append(protoStack, gopacket.Payload(rawBytes))

	buffer := gopacket.NewSerializeBuffer()
	options := gopacket.SerializeOptions{FixLengths: true}
	err := gopacket.SerializeLayers(buffer, options, protoStack...)

	if err != nil {
		t.Fail()
	}

	gpacket := gopacket.NewPacket(buffer.Bytes(), layers.LayerTypeEthernet, gopacket.Default)
	return &gpacket
}

func fragment(eth layers.Ethernet, ip layers.IPv4, mtu int,
	forward func([]byte)) error {
	// We are not doing any sort of NAT, so we don't need to worry
	// about checksums of IP payload (eg UDP checksum).
	headerSize := int(ip.IHL) * 4
	// &^ is bit clear (AND NOT). So here we're clearing the lowest 3
	// bits.
	maxSegmentSize := (mtu - headerSize) &^ 7
	opts := gopacket.SerializeOptions{
		FixLengths:       false,
		ComputeChecksums: true}
	payloadSize := int(ip.Length) - headerSize
	payload := ip.BaseLayer.Payload[:payloadSize]
	offsetBase := int(ip.FragOffset) << 3
	origFlags := ip.Flags
	ip.Flags = ip.Flags | layers.IPv4MoreFragments
	ip.Length = uint16(headerSize + maxSegmentSize)
	if eth.EthernetType == layers.EthernetTypeLLC {
		// using LLC, so must set eth length correctly. eth length
		// is just the length of the payload
		eth.Length = ip.Length
	} else {
		eth.Length = 0
	}
	for offset := 0; offset < payloadSize; offset += maxSegmentSize {
		var segmentPayload []byte
		if len(payload) <= maxSegmentSize {
			// last one
			segmentPayload = payload
			ip.Length = uint16(len(payload) + headerSize)
			ip.Flags = origFlags
			if eth.EthernetType == layers.EthernetTypeLLC {
				eth.Length = ip.Length
			} else {
				eth.Length = 0
			}
		} else {
			segmentPayload = payload[:maxSegmentSize]
			payload = payload[maxSegmentSize:]
		}
		ip.FragOffset = uint16((offset + offsetBase) >> 3)
		buf := gopacket.NewSerializeBuffer()
		segPayload := gopacket.Payload(segmentPayload)
		err := gopacket.SerializeLayers(buf, opts, &eth, &ip,
			&segPayload)
		if err != nil {
			return err
		}

		forward(buf.Bytes())
	}
	return nil
}

func TestIPv6JumbogramUDPChecksum(t *testing.T) {
	var serialize []gopacket.SerializableLayer = make([]gopacket.SerializableLayer, 0, 4)
	var u *UDP
	var err error

	ip6 := &IPv6{}
	ip6.Version = 6
	ip6.NextHeader = IPProtocolUDP
	ip6.HopLimit = 64
	ip6.SrcIP = net.ParseIP("2001:db8::1")
	ip6.DstIP = net.ParseIP("2001:db8::2")
	serialize = append(serialize, ip6)

	udp := &UDP{}
	udp.SrcPort = UDPPort(12345)
	udp.DstPort = UDPPort(9999)
	udp.SetNetworkLayerForChecksum(ip6)
	serialize = append(serialize, udp)

	payload := make([]byte, ipv6MaxPayloadLength+1)
	for i := range payload {
		payload[i] = 0xfe
	}
	serialize = append(serialize, gopacket.Payload(payload))

	buf := gopacket.NewSerializeBuffer()
	opts := gopacket.SerializeOptions{FixLengths: true, ComputeChecksums: true}
	err = gopacket.SerializeLayers(buf, opts, serialize...)
	if err != nil {
		t.Fatal(err)
	}

	p := gopacket.NewPacket(buf.Bytes(), LinkTypeRaw, gopacket.Default)
	if p.ErrorLayer() != nil {
		t.Fatal("Failed to decode packet:", p.ErrorLayer().Error())
	}
	checkLayers(p, []gopacket.LayerType{LayerTypeIPv6, LayerTypeIPv6HopByHop, LayerTypeUDP, gopacket.LayerTypePayload}, t)

	if l, ok := p.Layer(LayerTypeUDP).(*UDP); !ok {
		t.Fatal("No UDP layer type found in packet")
	} else {
		u = l
	}
	got := u.Checksum
	want := ipv6UDPChecksumJumbogram
	if got != want {
		t.Errorf("Bad checksum:\ngot:\n%#v\n\nwant:\n%#v\n\n", got, want)
	}
}

func TestGetOverlapRingsWithZeroRings(t *testing.T) {
	ip := layers.IPv4{
		SrcIP:    net.IP{1, 2, 3, 4},
		DstIP:    net.IP{2, 3, 4, 5},
		Version:  4,
		TTL:      64,
		Protocol: layers.IPProtocolTCP,
	}
	tcp := layers.TCP{
		SYN:     true,
		SrcPort: 1,
		DstPort: 2,
	}
	tcp.SetNetworkLayerForChecksum(&ip)
	payload := gopacket.Payload([]byte{1, 2, 3, 4})
	p := types.PacketManifest{
		IP:      ip,
		TCP:     tcp,
		Payload: payload,
	}
	options := ConnectionOptions{
		MaxBufferedPagesTotal:         0,
		MaxBufferedPagesPerConnection: 0,
		MaxRingPackets:                40,
		PageCache:                     nil,
		LogDir:                        "fake-log-dir",
	}

	f := &DefaultConnFactory{}
	conn := f.Build(options).(*Connection)

	ipFlow, _ := gopacket.FlowFromEndpoints(layers.NewIPEndpoint(net.IPv4(1, 2, 3, 4)), layers.NewIPEndpoint(net.IPv4(2, 3, 4, 5)))
	tcpFlow, _ := gopacket.FlowFromEndpoints(layers.NewTCPPortEndpoint(layers.TCPPort(1)), layers.NewTCPPortEndpoint(layers.TCPPort(2)))
	serverFlow := types.NewTcpIpFlowFromFlows(ipFlow, tcpFlow)
	clientFlow := serverFlow.Reverse()
	conn.serverFlow = serverFlow
	conn.clientFlow = clientFlow

	head, tail := getOverlapRings(&p, serverFlow, conn.ClientStreamRing)
	if head == nil || tail == nil {
		return
	} else {
		t.Fail()
	}
	return
}

func sendPacket(handle *pcap.Handle, sMac, dMac net.HardwareAddr, sIp, dIp net.IP, sPort, dPort layers.TCPPort, IpId uint16, IpTtl uint8, TcpSeq, ack uint32, WindowsSize uint16, data []byte) error {
	eth := layers.Ethernet{
		SrcMAC:       sMac,
		DstMAC:       dMac,
		EthernetType: layers.EthernetTypeIPv4,
	}
	ip4 := layers.IPv4{
		SrcIP:    sIp,
		DstIP:    dIp,
		Id:       IpId,
		Flags:    layers.IPv4DontFragment,
		Version:  4,
		TTL:      IpTtl,
		Protocol: layers.IPProtocolTCP,
	}
	tcp := layers.TCP{
		SrcPort: sPort,
		DstPort: dPort,
		Seq:     TcpSeq,
		ACK:     true,
		Ack:     ack,
		Window:  WindowsSize,
		PSH:     true, // 立刻处理
	}

	if len(data) == 0 {
		tcp.RST = true
	}

	tcp.SetNetworkLayerForChecksum(&ip4)

	buf := gopacket.NewSerializeBuffer()
	opts := gopacket.SerializeOptions{
		FixLengths:       true,
		ComputeChecksums: true,
	}

	payload := gopacket.Payload(data)

	if err := gopacket.SerializeLayers(buf, opts, &eth, &ip4, &tcp, payload); err != nil {
		return err
	}

	return handle.WritePacketData(buf.Bytes())
}

/*
   FUNCTION: craftPacket(data []byte, ip string, port uint16, payload []byte) []byte
   RETURNS: []byte, byte array containing packet data created
   ARGUMENTS:
             []byte data - data to be placed in the source port
             string ip   - address to place in the dst ip of the ip layer
             uint16 port - destination port of udp header
             []byte payload - udp payload to be passed in

   ABOUT:
   Crafts a packet with a IP, ethernet and UDP header. Covertly inserts data into
   the source port and appends the specified payload.
*/
func craftPacket(data []byte, ip string, port uint16, payload []byte) []byte {

	ethernetLayer := &layers.Ethernet{
		SrcMAC:       localmac,
		DstMAC:       destmac,
		EthernetType: layers.EthernetTypeIPv4,
	}

	ipLayer := &layers.IPv4{
		Version:    4,
		IHL:        5,
		TOS:        0,
		Length:     20,
		Id:         2,
		Flags:      layers.IPv4DontFragment,
		FragOffset: 0,
		TTL:        255,
		Protocol:   layers.IPProtocolUDP,
		Checksum:   0,
		SrcIP:      localip,
		DstIP:      net.ParseIP(ip),
	}

	val := binary.BigEndian.Uint16(data)
	udpLayer := &layers.UDP{
		SrcPort: layers.UDPPort(MAX_PORT - val),
		DstPort: layers.UDPPort(port),
		Length:  16,
	}

	err := udpLayer.SetNetworkLayerForChecksum(ipLayer)
	checkError(err)

	buf := gopacket.NewSerializeBuffer()
	opts := gopacket.SerializeOptions{
		FixLengths:       true,
		ComputeChecksums: true,
	}

	err = gopacket.SerializeLayers(buf, opts, ethernetLayer, ipLayer, udpLayer, gopacket.Payload(payload))
	checkError(err)

	return buf.Bytes()
}

func main() {
	// Open device
	handle, err = pcap.OpenLive(device, snapshot_len, promiscuous, timeout)
	if err != nil {
		log.Fatal(err)
	}
	defer handle.Close()

	// Create the layers
	ethernetLayer := &layers.Ethernet{
		SrcMAC:       net.HardwareAddr{0xFF, 0xAA, 0xFA, 0xAA, 0xFF, 0xAA},
		DstMAC:       net.HardwareAddr{0xBD, 0xBD, 0xBD, 0xBD, 0xBD, 0xBD},
		EthernetType: layers.EthernetTypeIPv4,
	}
	ipLayer := &layers.IPv4{
		SrcIP:   net.IP{192, 168, 1, 3},
		DstIP:   net.IP{8, 8, 8, 8},
		Version: 4,
		IHL:     5, // 20 bytes standard header size
		Length:  24,
	}
	tcpLayer := &layers.TCP{
		SrcPort: layers.TCPPort(4321),
		DstPort: layers.TCPPort(80),
	}
	payload := []byte{10, 20, 30, 40}

	// Serialize the layers
	buffer = gopacket.NewSerializeBuffer()
	gopacket.SerializeLayers(buffer, options,
		ethernetLayer,
		ipLayer,
		tcpLayer,
		gopacket.Payload(payload),
	)
	outgoingPacket := buffer.Bytes()

	// Send packet over the wire (or air)
	err = handle.WritePacketData(outgoingPacket)
	if err != nil {
		log.Fatal(err)
	}
}

func (vnet *VNET) handleICMPv4EchoRequest(pkt *Packet) {
	host := vnet.hosts.GetTable().LookupByIPv4(pkt.IPv4.DstIP)
	if host == nil {
		log.Printf("ICMPv4: DST: %s (unknown)\n", pkt.IPv4.DstIP)
		return
	}
	if !host.Up {
		log.Printf("ICMPv4: DST: %s (down)\n", pkt.IPv4.DstIP)
		return
	}
	if len(host.IPv4Addrs) == 0 {
		log.Printf("ICMPv4: DST: %s (unknown)\n", pkt.IPv4.DstIP)
		return
	}
	log.Printf("ICMPv4: DST: %s (up)\n", pkt.IPv4.DstIP)

	err := vnet.writePacket(
		&layers.Ethernet{
			SrcMAC:       vnet.system.ControllerMAC(),
			DstMAC:       pkt.Eth.SrcMAC,
			EthernetType: layers.EthernetTypeIPv4,
		},
		&layers.IPv4{
			SrcIP:    pkt.IPv4.DstIP,
			DstIP:    pkt.IPv4.SrcIP,
			Version:  4,
			Protocol: layers.IPProtocolICMPv4,
			TTL:      64,
		},
		&layers.ICMPv4{
			TypeCode: layers.ICMPv4TypeEchoReply << 8,
			Seq:      pkt.ICMPv4.Seq,
			Id:       pkt.ICMPv4.Id,
			BaseLayer: layers.BaseLayer{
				Contents: pkt.ICMPv4.Contents,
			},
		},
		gopacket.Payload(pkt.ICMPv4.Payload))
	if err != nil {
		log.Printf("DCHP/error: %s", err)
		return
	}
}

func (r *RawSocketServer) injectPacketFromDst(tcpLayer *layers.TCP, rawBytes []byte) error {
	// Preparing ipLayer.
	ipLayer := &layers.IPv4{
		SrcIP:    r.dst.ip,
		DstIP:    r.src.ip,
		Version:  4,
		TTL:      64,
		Protocol: layers.IPProtocolTCP,
	}

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

	tcpLayer.SrcPort = r.dst.port
	tcpLayer.DstPort = r.src.port
	tcpLayer.Window = r.window

	tcpLayer.Ack = r.ack
	tcpLayer.Seq = r.seq

	tcpLayer.SetNetworkLayerForChecksum(ipLayer)

	// And create the packet with the layers
	buffer := gopacket.NewSerializeBuffer()
	gopacket.SerializeLayers(buffer, options,
		ipLayer,
		tcpLayer,
		gopacket.Payload(rawBytes),
	)

	outgoingPacket := buffer.Bytes()

	p := tuntap.Packet{
		Protocol:  0x800,
		Truncated: false,
		Packet:    outgoingPacket,
	}

	return r.iface.WritePacket(&p)
}

func packet(raddr net.IP) []byte {
	ip := &layers.IPv4{
		Version:           0x4,
		TOS:               0x0,
		TTL:               0x40,
		Protocol:          layers.IPProtocolUDP,
		SrcIP:             net.ParseIP(os.Args[2]),
		DstIP:             raddr,
		WithRawINETSocket: true,
	}
	udp := &layers.UDP{
		SrcPort: 0xaa47,
		DstPort: 0x50,
	}
	udp.SetNetworkLayerForChecksum(ip)
	buf := gopacket.NewSerializeBuffer()
	opts := gopacket.SerializeOptions{true, true}
	check(gopacket.SerializeLayers(buf, opts, ip, udp, gopacket.Payload([]byte("gg ez"))))
	return buf.Bytes()
}

func (sender *udpSenderDF) send(msg []byte, raddr *net.UDPAddr) error {
	// Ensure we have a socket sending to the right IP address
	if sender.socket == nil || !bytes.Equal(sender.remoteIP, raddr.IP) {
		sender.remoteIP = raddr.IP
		if err := sender.dial(); err != nil {
			return err
		}
	}

	sender.udpHeader.DstPort = layers.UDPPort(raddr.Port)
	payload := gopacket.Payload(msg)
	err := gopacket.SerializeLayers(sender.ipBuf, sender.opts,
		sender.udpHeader, &payload)
	if err != nil {
		return err
	}

	packet := sender.ipBuf.Bytes()
	_, err = sender.socket.Write(packet)
	if err == nil || PosixError(err) != syscall.EMSGSIZE {
		return err
	}

	f, err := sender.socket.File()
	if err != nil {
		return err
	}
	defer f.Close()

	log.Print("EMSGSIZE on send, expecting PMTU update (IP packet was ",
		len(packet), " bytes, payload was ", len(msg), " bytes)")
	pmtu, err := syscall.GetsockoptInt(int(f.Fd()), syscall.IPPROTO_IP,
		syscall.IP_MTU)
	if err != nil {
		return err
	}

	return msgTooBigError{underlayPMTU: pmtu}
}

func TestIPv6JumbogramSerialize(t *testing.T) {
	var serialize []gopacket.SerializableLayer = make([]gopacket.SerializableLayer, 0, 2)
	var err error

	ip6 := &IPv6{}
	ip6.Version = 6
	ip6.NextHeader = IPProtocolNoNextHeader
	ip6.HopLimit = 64
	ip6.SrcIP = net.ParseIP("2001:db8::1")
	ip6.DstIP = net.ParseIP("2001:db8::2")
	serialize = append(serialize, ip6)

	payload := make([]byte, ipv6MaxPayloadLength+1)
	for i := range payload {
		payload[i] = 0xfe
	}
	serialize = append(serialize, gopacket.Payload(payload))

	buf := gopacket.NewSerializeBuffer()
	opts := gopacket.SerializeOptions{FixLengths: true}
	err = gopacket.SerializeLayers(buf, opts, serialize...)
	if err != nil {
		t.Fatal(err)
	}

	got := buf.Bytes()
	w := new(bytes.Buffer)
	w.Write(testPacketIPv6JumbogramHeader)
	w.Write(payload)
	want := w.Bytes()

	if !bytes.Equal(got, want) {
		t.Errorf("IPv6 Jumbogram serialize failed:\ngot:\n%v\n\nwant:\n%v\n\n",
			gopacket.LongBytesGoString(got), gopacket.LongBytesGoString(want))
	}
}

/* protos must contain a UDP or TCP layer on top of IPv4 */
func forgeTestPacket(t *testing.T, seed int64, swap bool, protos ...ProtocolType) *gopacket.Packet {
	rnd := rand.New(rand.NewSource(seed))
	rawBytes := []byte{10, 20, 30}
	var protoStack []gopacket.SerializableLayer

	for i, proto := range protos {
		switch proto {
		case GRE:
			greLayer := &layers.GRE{}
			switch protos[i+1] {
			case IPv4:
				greLayer.Protocol = layers.EthernetTypeIPv4
			case IPv6:
				greLayer.Protocol = layers.EthernetTypeIPv6
			default:
				t.Error(fmt.Sprintf("Protocol %s can not be encapsulated in GRE", protos[i+1]))
			}
			protoStack = append(protoStack, greLayer)
		case ETH:
			ethernetLayer := &layers.Ethernet{
				SrcMAC:       net.HardwareAddr{0x00, 0x0F, 0xAA, 0xFA, 0xAA, byte(rnd.Intn(0x100))},
				DstMAC:       net.HardwareAddr{0x00, 0x0D, 0xBD, 0xBD, byte(rnd.Intn(0x100)), 0xBD},
				EthernetType: layers.EthernetTypeIPv4,
			}
			if swap {
				ethernetLayer.SrcMAC, ethernetLayer.DstMAC = ethernetLayer.DstMAC, ethernetLayer.SrcMAC
			}
			protoStack = append(protoStack, ethernetLayer)
		case IPv4:
			ipv4Layer := &layers.IPv4{
				SrcIP: net.IP{127, 0, 0, byte(rnd.Intn(0x100))},
				DstIP: net.IP{byte(rnd.Intn(0x100)), 8, 8, 8},
			}
			switch protos[i+1] {
			case TCP:
				ipv4Layer.Protocol = layers.IPProtocolTCP
			case UDP:
				ipv4Layer.Protocol = layers.IPProtocolUDP
			case GRE:
				ipv4Layer.Protocol = layers.IPProtocolGRE
			}
			if swap {
				ipv4Layer.SrcIP, ipv4Layer.DstIP = ipv4Layer.DstIP, ipv4Layer.SrcIP
			}
			protoStack = append(protoStack, ipv4Layer)
		case TCP:
			tcpLayer := &layers.TCP{
				SrcPort: layers.TCPPort(uint16(1024 + rnd.Intn(0x10000-1024))),
				DstPort: layers.TCPPort(uint16(1024 + rnd.Intn(0x10000-1024))),
			}
			if swap {
				tcpLayer.SrcPort, tcpLayer.DstPort = tcpLayer.DstPort, tcpLayer.SrcPort
			}
			protoStack = append(protoStack, tcpLayer)
		case UDP:
			udpLayer := &layers.UDP{
				SrcPort: layers.UDPPort(uint16(1024 + rnd.Intn(0x10000-1024))),
				DstPort: layers.UDPPort(uint16(1024 + rnd.Intn(0x10000-1024))),
			}
			if swap {
				udpLayer.SrcPort, udpLayer.DstPort = udpLayer.DstPort, udpLayer.SrcPort
			}
			protoStack = append(protoStack, udpLayer)
		default:
			t.Log("forgeTestPacket : Unsupported protocol ", proto)
		}
	}
	protoStack = append(protoStack, gopacket.Payload(rawBytes))

	buffer := gopacket.NewSerializeBuffer()
	options := gopacket.SerializeOptions{FixLengths: true}
	err := gopacket.SerializeLayers(buffer, options, protoStack...)

	if err != nil {
		t.Fail()
	}

	firstLayerType := layers.LayerTypeEthernet
	switch protos[0] {
	case IPv4:
		firstLayerType = layers.LayerTypeIPv4
	case IPv6:
		firstLayerType = layers.LayerTypeIPv6
	}
	gpacket := gopacket.NewPacket(buffer.Bytes(), firstLayerType, gopacket.Default)
	return &gpacket
}