TUN-6666: Define packet package

This package defines IP and ICMP packet, decoders, encoder and flow

vendor/github.com/google/gopacket/layers/udp.go

@@ -0,0 +1,133 @@
+// Copyright 2012 Google, Inc. All rights reserved.
+// Copyright 2009-2011 Andreas Krennmair. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the LICENSE file in the root of the source
+// tree.
+
+package layers
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	"github.com/google/gopacket"
+)
+
+// UDP is the layer for UDP headers.
+type UDP struct {
+	BaseLayer
+	SrcPort, DstPort UDPPort
+	Length           uint16
+	Checksum         uint16
+	sPort, dPort     []byte
+	tcpipchecksum
+}
+
+// LayerType returns gopacket.LayerTypeUDP
+func (u *UDP) LayerType() gopacket.LayerType { return LayerTypeUDP }
+
+func (udp *UDP) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
+	if len(data) < 8 {
+		df.SetTruncated()
+		return fmt.Errorf("Invalid UDP header. Length %d less than 8", len(data))
+	}
+	udp.SrcPort = UDPPort(binary.BigEndian.Uint16(data[0:2]))
+	udp.sPort = data[0:2]
+	udp.DstPort = UDPPort(binary.BigEndian.Uint16(data[2:4]))
+	udp.dPort = data[2:4]
+	udp.Length = binary.BigEndian.Uint16(data[4:6])
+	udp.Checksum = binary.BigEndian.Uint16(data[6:8])
+	udp.BaseLayer = BaseLayer{Contents: data[:8]}
+	switch {
+	case udp.Length >= 8:
+		hlen := int(udp.Length)
+		if hlen > len(data) {
+			df.SetTruncated()
+			hlen = len(data)
+		}
+		udp.Payload = data[8:hlen]
+	case udp.Length == 0: // Jumbogram, use entire rest of data
+		udp.Payload = data[8:]
+	default:
+		return fmt.Errorf("UDP packet too small: %d bytes", udp.Length)
+	}
+	return nil
+}
+
+// SerializeTo writes the serialized form of this layer into the
+// SerializationBuffer, implementing gopacket.SerializableLayer.
+// See the docs for gopacket.SerializableLayer for more info.
+func (u *UDP) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
+	var jumbo bool
+
+	payload := b.Bytes()
+	if _, ok := u.pseudoheader.(*IPv6); ok {
+		if len(payload)+8 > 65535 {
+			jumbo = true
+		}
+	}
+	bytes, err := b.PrependBytes(8)
+	if err != nil {
+		return err
+	}
+	binary.BigEndian.PutUint16(bytes, uint16(u.SrcPort))
+	binary.BigEndian.PutUint16(bytes[2:], uint16(u.DstPort))
+	if opts.FixLengths {
+		if jumbo {
+			u.Length = 0
+		} else {
+			u.Length = uint16(len(payload)) + 8
+		}
+	}
+	binary.BigEndian.PutUint16(bytes[4:], u.Length)
+	if opts.ComputeChecksums {
+		// zero out checksum bytes
+		bytes[6] = 0
+		bytes[7] = 0
+		csum, err := u.computeChecksum(b.Bytes(), IPProtocolUDP)
+		if err != nil {
+			return err
+		}
+		u.Checksum = csum
+	}
+	binary.BigEndian.PutUint16(bytes[6:], u.Checksum)
+	return nil
+}
+
+func (u *UDP) CanDecode() gopacket.LayerClass {
+	return LayerTypeUDP
+}
+
+// NextLayerType use the destination port to select the
+// right next decoder. It tries first to decode via the
+// destination port, then the source port.
+func (u *UDP) NextLayerType() gopacket.LayerType {
+	if lt := u.DstPort.LayerType(); lt != gopacket.LayerTypePayload {
+		return lt
+	}
+	return u.SrcPort.LayerType()
+}
+
+func decodeUDP(data []byte, p gopacket.PacketBuilder) error {
+	udp := &UDP{}
+	err := udp.DecodeFromBytes(data, p)
+	p.AddLayer(udp)
+	p.SetTransportLayer(udp)
+	if err != nil {
+		return err
+	}
+	return p.NextDecoder(udp.NextLayerType())
+}
+
+func (u *UDP) TransportFlow() gopacket.Flow {
+	return gopacket.NewFlow(EndpointUDPPort, u.sPort, u.dPort)
+}
+
+// For testing only
+func (u *UDP) SetInternalPortsForTesting() {
+	u.sPort = make([]byte, 2)
+	u.dPort = make([]byte, 2)
+	binary.BigEndian.PutUint16(u.sPort, uint16(u.SrcPort))
+	binary.BigEndian.PutUint16(u.dPort, uint16(u.DstPort))
+}