adding vendor folder

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

@@ -0,0 +1,894 @@
+// Copyright 2014 Google, Inc. 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"
+	"errors"
+	"fmt"
+	"net"
+
+	"github.com/google/gopacket"
+)
+
+// DNSClass defines the class associated with a request/response.  Different DNS
+// classes can be thought of as an array of parallel namespace trees.
+type DNSClass uint16
+
+// DNSClass known values.
+const (
+	DNSClassIN  DNSClass = 1   // Internet
+	DNSClassCS  DNSClass = 2   // the CSNET class (Obsolete)
+	DNSClassCH  DNSClass = 3   // the CHAOS class
+	DNSClassHS  DNSClass = 4   // Hesiod [Dyer 87]
+	DNSClassAny DNSClass = 255 // AnyClass
+)
+
+func (dc DNSClass) String() string {
+	switch dc {
+	default:
+		return "Unknown"
+	case DNSClassIN:
+		return "IN"
+	case DNSClassCS:
+		return "CS"
+	case DNSClassCH:
+		return "CH"
+	case DNSClassHS:
+		return "HS"
+	case DNSClassAny:
+		return "Any"
+	}
+}
+
+// DNSType defines the type of data being requested/returned in a
+// question/answer.
+type DNSType uint16
+
+// DNSType known values.
+const (
+	DNSTypeA     DNSType = 1  // a host address
+	DNSTypeNS    DNSType = 2  // an authoritative name server
+	DNSTypeMD    DNSType = 3  // a mail destination (Obsolete - use MX)
+	DNSTypeMF    DNSType = 4  // a mail forwarder (Obsolete - use MX)
+	DNSTypeCNAME DNSType = 5  // the canonical name for an alias
+	DNSTypeSOA   DNSType = 6  // marks the start of a zone of authority
+	DNSTypeMB    DNSType = 7  // a mailbox domain name (EXPERIMENTAL)
+	DNSTypeMG    DNSType = 8  // a mail group member (EXPERIMENTAL)
+	DNSTypeMR    DNSType = 9  // a mail rename domain name (EXPERIMENTAL)
+	DNSTypeNULL  DNSType = 10 // a null RR (EXPERIMENTAL)
+	DNSTypeWKS   DNSType = 11 // a well known service description
+	DNSTypePTR   DNSType = 12 // a domain name pointer
+	DNSTypeHINFO DNSType = 13 // host information
+	DNSTypeMINFO DNSType = 14 // mailbox or mail list information
+	DNSTypeMX    DNSType = 15 // mail exchange
+	DNSTypeTXT   DNSType = 16 // text strings
+	DNSTypeAAAA  DNSType = 28 // a IPv6 host address [RFC3596]
+	DNSTypeSRV   DNSType = 33 // server discovery [RFC2782] [RFC6195]
+)
+
+func (dt DNSType) String() string {
+	switch dt {
+	default:
+		return "Unknown"
+	case DNSTypeA:
+		return "A"
+	case DNSTypeNS:
+		return "NS"
+	case DNSTypeMD:
+		return "MD"
+	case DNSTypeMF:
+		return "MF"
+	case DNSTypeCNAME:
+		return "CNAME"
+	case DNSTypeSOA:
+		return "SOA"
+	case DNSTypeMB:
+		return "MB"
+	case DNSTypeMG:
+		return "MG"
+	case DNSTypeMR:
+		return "MR"
+	case DNSTypeNULL:
+		return "NULL"
+	case DNSTypeWKS:
+		return "WKS"
+	case DNSTypePTR:
+		return "PTR"
+	case DNSTypeHINFO:
+		return "HINFO"
+	case DNSTypeMINFO:
+		return "MINFO"
+	case DNSTypeMX:
+		return "MX"
+	case DNSTypeTXT:
+		return "TXT"
+	case DNSTypeAAAA:
+		return "AAAA"
+	case DNSTypeSRV:
+		return "SRV"
+	}
+}
+
+// DNSResponseCode provides response codes for question answers.
+type DNSResponseCode uint8
+
+// DNSResponseCode known values.
+const (
+	DNSResponseCodeNoErr    DNSResponseCode = 0  // No error
+	DNSResponseCodeFormErr  DNSResponseCode = 1  // Format Error                       [RFC1035]
+	DNSResponseCodeServFail DNSResponseCode = 2  // Server Failure                     [RFC1035]
+	DNSResponseCodeNXDomain DNSResponseCode = 3  // Non-Existent Domain                [RFC1035]
+	DNSResponseCodeNotImp   DNSResponseCode = 4  // Not Implemented                    [RFC1035]
+	DNSResponseCodeRefused  DNSResponseCode = 5  // Query Refused                      [RFC1035]
+	DNSResponseCodeYXDomain DNSResponseCode = 6  // Name Exists when it should not     [RFC2136]
+	DNSResponseCodeYXRRSet  DNSResponseCode = 7  // RR Set Exists when it should not   [RFC2136]
+	DNSResponseCodeNXRRSet  DNSResponseCode = 8  // RR Set that should exist does not  [RFC2136]
+	DNSResponseCodeNotAuth  DNSResponseCode = 9  // Server Not Authoritative for zone  [RFC2136]
+	DNSResponseCodeNotZone  DNSResponseCode = 10 // Name not contained in zone         [RFC2136]
+	DNSResponseCodeBadVers  DNSResponseCode = 16 // Bad OPT Version                    [RFC2671]
+	DNSResponseCodeBadSig   DNSResponseCode = 16 // TSIG Signature Failure             [RFC2845]
+	DNSResponseCodeBadKey   DNSResponseCode = 17 // Key not recognized                 [RFC2845]
+	DNSResponseCodeBadTime  DNSResponseCode = 18 // Signature out of time window       [RFC2845]
+	DNSResponseCodeBadMode  DNSResponseCode = 19 // Bad TKEY Mode                      [RFC2930]
+	DNSResponseCodeBadName  DNSResponseCode = 20 // Duplicate key name                 [RFC2930]
+	DNSResponseCodeBadAlg   DNSResponseCode = 21 // Algorithm not supported            [RFC2930]
+	DNSResponseCodeBadTruc  DNSResponseCode = 22 // Bad Truncation                     [RFC4635]
+)
+
+func (drc DNSResponseCode) String() string {
+	switch drc {
+	default:
+		return "Unknown"
+	case DNSResponseCodeNoErr:
+		return "No Error"
+	case DNSResponseCodeFormErr:
+		return "Format Error"
+	case DNSResponseCodeServFail:
+		return "Server Failure "
+	case DNSResponseCodeNXDomain:
+		return "Non-Existent Domain"
+	case DNSResponseCodeNotImp:
+		return "Not Implemented"
+	case DNSResponseCodeRefused:
+		return "Query Refused"
+	case DNSResponseCodeYXDomain:
+		return "Name Exists when it should not"
+	case DNSResponseCodeYXRRSet:
+		return "RR Set Exists when it should not"
+	case DNSResponseCodeNXRRSet:
+		return "RR Set that should exist does not"
+	case DNSResponseCodeNotAuth:
+		return "Server Not Authoritative for zone"
+	case DNSResponseCodeNotZone:
+		return "Name not contained in zone"
+	case DNSResponseCodeBadVers:
+		return "Bad OPT Version"
+	case DNSResponseCodeBadKey:
+		return "Key not recognized"
+	case DNSResponseCodeBadTime:
+		return "Signature out of time window"
+	case DNSResponseCodeBadMode:
+		return "Bad TKEY Mode"
+	case DNSResponseCodeBadName:
+		return "Duplicate key name"
+	case DNSResponseCodeBadAlg:
+		return "Algorithm not supported"
+	case DNSResponseCodeBadTruc:
+		return "Bad Truncation"
+	}
+}
+
+// DNSOpCode defines a set of different operation types.
+type DNSOpCode uint8
+
+// DNSOpCode known values.
+const (
+	DNSOpCodeQuery  DNSOpCode = 0 // Query                  [RFC1035]
+	DNSOpCodeIQuery DNSOpCode = 1 // Inverse Query Obsolete [RFC3425]
+	DNSOpCodeStatus DNSOpCode = 2 // Status                 [RFC1035]
+	DNSOpCodeNotify DNSOpCode = 4 // Notify                 [RFC1996]
+	DNSOpCodeUpdate DNSOpCode = 5 // Update                 [RFC2136]
+)
+
+func (doc DNSOpCode) String() string {
+	switch doc {
+	default:
+		return "Unknown"
+	case DNSOpCodeQuery:
+		return "Query"
+	case DNSOpCodeIQuery:
+		return "Inverse Query"
+	case DNSOpCodeStatus:
+		return "Status"
+	case DNSOpCodeNotify:
+		return "Notify"
+	case DNSOpCodeUpdate:
+		return "Update"
+	}
+}
+
+// DNS is specified in RFC 1034 / RFC 1035
+// +---------------------+
+// |        Header       |
+// +---------------------+
+// |       Question      | the question for the name server
+// +---------------------+
+// |        Answer       | RRs answering the question
+// +---------------------+
+// |      Authority      | RRs pointing toward an authority
+// +---------------------+
+// |      Additional     | RRs holding additional information
+// +---------------------+
+//
+//  DNS Header
+//  0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                      ID                       |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |QR|   Opcode  |AA|TC|RD|RA|   Z    |   RCODE   |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                    QDCOUNT                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                    ANCOUNT                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                    NSCOUNT                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                    ARCOUNT                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+
+// DNS contains data from a single Domain Name Service packet.
+type DNS struct {
+	BaseLayer
+
+	// Header fields
+	ID     uint16
+	QR     bool
+	OpCode DNSOpCode
+
+	AA bool  // Authoritative answer
+	TC bool  // Truncated
+	RD bool  // Recursion desired
+	RA bool  // Recursion available
+	Z  uint8 // Resrved for future use
+
+	ResponseCode DNSResponseCode
+	QDCount      uint16 // Number of questions to expect
+	ANCount      uint16 // Number of answers to expect
+	NSCount      uint16 // Number of authorities to expect
+	ARCount      uint16 // Number of additional records to expect
+
+	// Entries
+	Questions   []DNSQuestion
+	Answers     []DNSResourceRecord
+	Authorities []DNSResourceRecord
+	Additionals []DNSResourceRecord
+
+	// buffer for doing name decoding.  We use a single reusable buffer to avoid
+	// name decoding on a single object via multiple DecodeFromBytes calls
+	// requiring constant allocation of small byte slices.
+	buffer []byte
+}
+
+// LayerType returns gopacket.LayerTypeDNS.
+func (d *DNS) LayerType() gopacket.LayerType { return LayerTypeDNS }
+
+// decodeDNS decodes the byte slice into a DNS type. It also
+// setups the application Layer in PacketBuilder.
+func decodeDNS(data []byte, p gopacket.PacketBuilder) error {
+	d := &DNS{}
+	err := d.DecodeFromBytes(data, p)
+	if err != nil {
+		return err
+	}
+	p.AddLayer(d)
+	p.SetApplicationLayer(d)
+	return nil
+}
+
+// DecodeFromBytes decodes the slice into the DNS struct.
+func (d *DNS) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
+	d.buffer = d.buffer[:0]
+
+	if len(data) < 12 {
+		df.SetTruncated()
+		return errors.New("DNS packet too short")
+	}
+
+	// since there are no further layers, the baselayer's content is
+	// pointing to this layer
+	d.BaseLayer = BaseLayer{Contents: data[:len(data)]}
+	d.ID = binary.BigEndian.Uint16(data[:2])
+	d.QR = data[2]&0x80 != 0
+	d.OpCode = DNSOpCode(data[2]>>3) & 0x0F
+	d.AA = data[2]&0x04 != 0
+	d.TC = data[2]&0x02 != 0
+	d.RD = data[2]&0x01 != 0
+	d.RA = data[3]&0x80 != 0
+	d.Z = uint8(data[3]>>4) & 0x7
+	d.ResponseCode = DNSResponseCode(data[3] & 0xF)
+	d.QDCount = binary.BigEndian.Uint16(data[4:6])
+	d.ANCount = binary.BigEndian.Uint16(data[6:8])
+	d.NSCount = binary.BigEndian.Uint16(data[8:10])
+	d.ARCount = binary.BigEndian.Uint16(data[10:12])
+
+	d.Questions = d.Questions[:0]
+	d.Answers = d.Answers[:0]
+	d.Authorities = d.Authorities[:0]
+	d.Additionals = d.Additionals[:0]
+
+	offset := 12
+	var err error
+	for i := 0; i < int(d.QDCount); i++ {
+		var q DNSQuestion
+		if offset, err = q.decode(data, offset, df, &d.buffer); err != nil {
+			return err
+		}
+		d.Questions = append(d.Questions, q)
+	}
+
+	// For some horrible reason, if we do the obvious thing in this loop:
+	//   var r DNSResourceRecord
+	//   if blah := r.decode(blah); err != nil {
+	//     return err
+	//   }
+	//   d.Foo = append(d.Foo, r)
+	// the Go compiler thinks that 'r' escapes to the heap, causing a malloc for
+	// every Answer, Authority, and Additional.  To get around this, we do
+	// something really silly:  we append an empty resource record to our slice,
+	// then use the last value in the slice to call decode.  Since the value is
+	// already in the slice, there's no WAY it can escape... on the other hand our
+	// code is MUCH uglier :(
+	for i := 0; i < int(d.ANCount); i++ {
+		d.Answers = append(d.Answers, DNSResourceRecord{})
+		if offset, err = d.Answers[i].decode(data, offset, df, &d.buffer); err != nil {
+			d.Answers = d.Answers[:i] // strip off erroneous value
+			return err
+		}
+	}
+	for i := 0; i < int(d.NSCount); i++ {
+		d.Authorities = append(d.Authorities, DNSResourceRecord{})
+		if offset, err = d.Authorities[i].decode(data, offset, df, &d.buffer); err != nil {
+			d.Authorities = d.Authorities[:i] // strip off erroneous value
+			return err
+		}
+	}
+	for i := 0; i < int(d.ARCount); i++ {
+		d.Additionals = append(d.Additionals, DNSResourceRecord{})
+		if offset, err = d.Additionals[i].decode(data, offset, df, &d.buffer); err != nil {
+			d.Additionals = d.Additionals[:i] // strip off erroneous value
+			return err
+		}
+	}
+
+	if uint16(len(d.Questions)) != d.QDCount {
+		return errors.New("Invalid query decoding, not the right number of questions")
+	} else if uint16(len(d.Answers)) != d.ANCount {
+		return errors.New("Invalid query decoding, not the right number of answers")
+	} else if uint16(len(d.Authorities)) != d.NSCount {
+		return errors.New("Invalid query decoding, not the right number of authorities")
+	} else if uint16(len(d.Additionals)) != d.ARCount {
+		return errors.New("Invalid query decoding, not the right number of additionals info")
+	}
+	return nil
+}
+
+// CanDecode implements gopacket.DecodingLayer.
+func (d *DNS) CanDecode() gopacket.LayerClass {
+	return LayerTypeDNS
+}
+
+// NextLayerType implements gopacket.DecodingLayer.
+func (d *DNS) NextLayerType() gopacket.LayerType {
+	return gopacket.LayerTypePayload
+}
+
+// Payload returns nil.
+func (d *DNS) Payload() []byte {
+	return nil
+}
+
+func b2i(b bool) int {
+	if b {
+		return 1
+	}
+	return 0
+}
+
+func recSize(rr *DNSResourceRecord) int {
+	switch rr.Type {
+	case DNSTypeA:
+		return 4
+	case DNSTypeAAAA:
+		return 16
+	case DNSTypeNS:
+		return len(rr.NS) + 2
+	case DNSTypeCNAME:
+		return len(rr.CNAME) + 2
+	case DNSTypePTR:
+		return len(rr.PTR) + 2
+	case DNSTypeSOA:
+		return len(rr.SOA.MName) + 2 + len(rr.SOA.RName) + 2 + 20
+	case DNSTypeMX:
+		return 2 + len(rr.MX.Name) + 2
+	case DNSTypeTXT:
+		l := len(rr.TXTs)
+		for _, txt := range rr.TXTs {
+			l += len(txt)
+		}
+		return l
+	case DNSTypeSRV:
+		return 6 + len(rr.SRV.Name) + 2
+	}
+
+	return 0
+}
+
+func computeSize(recs []DNSResourceRecord) int {
+	sz := 0
+	for _, rr := range recs {
+		sz += len(rr.Name) + 14
+		sz += recSize(&rr)
+	}
+	return sz
+}
+
+// SerializeTo writes the serialized form of this layer into the
+// SerializationBuffer, implementing gopacket.SerializableLayer.
+func (d *DNS) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
+	dsz := 0
+	for _, q := range d.Questions {
+		dsz += len(q.Name) + 6
+	}
+	dsz += computeSize(d.Answers)
+	dsz += computeSize(d.Authorities)
+	dsz += computeSize(d.Additionals)
+
+	bytes, err := b.PrependBytes(12 + dsz)
+	if err != nil {
+		return err
+	}
+	binary.BigEndian.PutUint16(bytes, d.ID)
+	bytes[2] = byte((b2i(d.QR) << 7) | (int(d.OpCode) << 3) | (b2i(d.AA) << 2) | (b2i(d.TC) << 1) | b2i(d.RD))
+	bytes[3] = byte((b2i(d.RA) << 7) | (int(d.Z) << 4) | int(d.ResponseCode))
+
+	if opts.FixLengths {
+		d.QDCount = uint16(len(d.Questions))
+		d.ANCount = uint16(len(d.Answers))
+		d.NSCount = uint16(len(d.Authorities))
+		d.ARCount = uint16(len(d.Additionals))
+	}
+	binary.BigEndian.PutUint16(bytes[4:], d.QDCount)
+	binary.BigEndian.PutUint16(bytes[6:], d.ANCount)
+	binary.BigEndian.PutUint16(bytes[8:], d.NSCount)
+	binary.BigEndian.PutUint16(bytes[10:], d.ARCount)
+
+	off := 12
+	for _, qd := range d.Questions {
+		n := qd.encode(bytes, off)
+		off += n
+	}
+
+	for i := range d.Answers {
+		// done this way so we can modify DNSResourceRecord to fix
+		// lengths if requested
+		qa := &d.Answers[i]
+		n, err := qa.encode(bytes, off, opts)
+		if err != nil {
+			return err
+		}
+		off += n
+	}
+
+	for i := range d.Authorities {
+		qa := &d.Authorities[i]
+		n, err := qa.encode(bytes, off, opts)
+		if err != nil {
+			return err
+		}
+		off += n
+	}
+	for i := range d.Additionals {
+		qa := &d.Additionals[i]
+		n, err := qa.encode(bytes, off, opts)
+		if err != nil {
+			return err
+		}
+		off += n
+	}
+
+	return nil
+}
+
+var errMaxRecursion = errors.New("max DNS recursion level hit")
+
+const maxRecursionLevel = 255
+
+func decodeName(data []byte, offset int, buffer *[]byte, level int) ([]byte, int, error) {
+	if level > maxRecursionLevel {
+		return nil, 0, errMaxRecursion
+	} else if offset >= len(data) {
+		return nil, 0, errors.New("dns name offset too high")
+	} else if offset < 0 {
+		return nil, 0, errors.New("dns name offset is negative")
+	}
+	start := len(*buffer)
+	index := offset
+	if data[index] == 0x00 {
+		return nil, index + 1, nil
+	}
+loop:
+	for data[index] != 0x00 {
+		switch data[index] & 0xc0 {
+		default:
+			/* RFC 1035
+			   A domain name represented as a sequence of labels, where
+			   each label consists of a length octet followed by that
+			   number of octets.  The domain name terminates with the
+			   zero length octet for the null label of the root.  Note
+			   that this field may be an odd number of octets; no
+			   padding is used.
+			*/
+			index2 := index + int(data[index]) + 1
+			if index2-offset > 255 {
+				return nil, 0, errors.New("dns name is too long")
+			} else if index2 < index+1 || index2 > len(data) {
+				return nil, 0, errors.New("dns name uncomputable: invalid index")
+			}
+			*buffer = append(*buffer, '.')
+			*buffer = append(*buffer, data[index+1:index2]...)
+			index = index2
+
+		case 0xc0:
+			/* RFC 1035
+			   The pointer takes the form of a two octet sequence.
+
+			   The first two bits are ones.  This allows a pointer to
+			   be distinguished from a label, since the label must
+			   begin with two zero bits because labels are restricted
+			   to 63 octets or less.  (The 10 and 01 combinations are
+			   reserved for future use.)  The OFFSET field specifies
+			   an offset from the start of the message (i.e., the
+			   first octet of the ID field in the domain header).  A
+			   zero offset specifies the first byte of the ID field,
+			   etc.
+
+			   The compression scheme allows a domain name in a message to be
+			   represented as either:
+			      - a sequence of labels ending in a zero octet
+			      - a pointer
+			      - a sequence of labels ending with a pointer
+			*/
+			if index+2 > len(data) {
+				return nil, 0, errors.New("dns offset pointer too high")
+			}
+			offsetp := int(binary.BigEndian.Uint16(data[index:index+2]) & 0x3fff)
+			if offsetp > len(data) {
+				return nil, 0, errors.New("dns offset pointer too high")
+			}
+			// This looks a little tricky, but actually isn't.  Because of how
+			// decodeName is written, calling it appends the decoded name to the
+			// current buffer.  We already have the start of the buffer, then, so
+			// once this call is done buffer[start:] will contain our full name.
+			_, _, err := decodeName(data, offsetp, buffer, level+1)
+			if err != nil {
+				return nil, 0, err
+			}
+			index++ // pointer is two bytes, so add an extra byte here.
+			break loop
+		/* EDNS, or other DNS option ? */
+		case 0x40: // RFC 2673
+			return nil, 0, fmt.Errorf("qname '0x40' - RFC 2673 unsupported yet (data=%x index=%d)",
+				data[index], index)
+
+		case 0x80:
+			return nil, 0, fmt.Errorf("qname '0x80' unsupported yet (data=%x index=%d)",
+				data[index], index)
+		}
+		if index >= len(data) {
+			return nil, 0, errors.New("dns index walked out of range")
+		}
+	}
+	if len(*buffer) <= start {
+		return nil, 0, errors.New("no dns data found for name")
+	}
+	return (*buffer)[start+1:], index + 1, nil
+}
+
+// DNSQuestion wraps a single request (question) within a DNS query.
+type DNSQuestion struct {
+	Name  []byte
+	Type  DNSType
+	Class DNSClass
+}
+
+func (q *DNSQuestion) decode(data []byte, offset int, df gopacket.DecodeFeedback, buffer *[]byte) (int, error) {
+	name, endq, err := decodeName(data, offset, buffer, 1)
+	if err != nil {
+		return 0, err
+	}
+
+	q.Name = name
+	q.Type = DNSType(binary.BigEndian.Uint16(data[endq : endq+2]))
+	q.Class = DNSClass(binary.BigEndian.Uint16(data[endq+2 : endq+4]))
+
+	return endq + 4, nil
+}
+
+func (q *DNSQuestion) encode(data []byte, offset int) int {
+	noff := encodeName(q.Name, data, offset)
+	binary.BigEndian.PutUint16(data[noff:], uint16(q.Type))
+	binary.BigEndian.PutUint16(data[noff+2:], uint16(q.Class))
+	return len(q.Name) + 6
+}
+
+//  DNSResourceRecord
+//  0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                                               |
+//  /                                               /
+//  /                      NAME                     /
+//  |                                               |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                      TYPE                     |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                     CLASS                     |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                      TTL                      |
+//  |                                               |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                   RDLENGTH                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
+//  /                     RDATA                     /
+//  /                                               /
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+
+// DNSResourceRecord wraps the data from a single DNS resource within a
+// response.
+type DNSResourceRecord struct {
+	// Header
+	Name  []byte
+	Type  DNSType
+	Class DNSClass
+	TTL   uint32
+
+	// RDATA Raw Values
+	DataLength uint16
+	Data       []byte
+
+	// RDATA Decoded Values
+	IP             net.IP
+	NS, CNAME, PTR []byte
+	TXTs           [][]byte
+	SOA            DNSSOA
+	SRV            DNSSRV
+	MX             DNSMX
+
+	// Undecoded TXT for backward compatibility
+	TXT []byte
+}
+
+// decode decodes the resource record, returning the total length of the record.
+func (rr *DNSResourceRecord) decode(data []byte, offset int, df gopacket.DecodeFeedback, buffer *[]byte) (int, error) {
+	name, endq, err := decodeName(data, offset, buffer, 1)
+	if err != nil {
+		return 0, err
+	}
+
+	rr.Name = name
+	rr.Type = DNSType(binary.BigEndian.Uint16(data[endq : endq+2]))
+	rr.Class = DNSClass(binary.BigEndian.Uint16(data[endq+2 : endq+4]))
+	rr.TTL = binary.BigEndian.Uint32(data[endq+4 : endq+8])
+	rr.DataLength = binary.BigEndian.Uint16(data[endq+8 : endq+10])
+	end := endq + 10 + int(rr.DataLength)
+	if end > len(data) {
+		return 0, fmt.Errorf("resource record length exceeds data")
+	}
+	rr.Data = data[endq+10 : end]
+
+	if err = rr.decodeRData(data, endq+10, buffer); err != nil {
+		return 0, err
+	}
+
+	return endq + 10 + int(rr.DataLength), nil
+}
+
+func encodeName(name []byte, data []byte, offset int) int {
+	l := 0
+	for i := range name {
+		if name[i] == '.' {
+			data[offset+i-l] = byte(l)
+			l = 0
+		} else {
+			// skip one to write the length
+			data[offset+i+1] = name[i]
+			l++
+		}
+	}
+	// length for final portion
+	data[offset+len(name)-l] = byte(l)
+	data[offset+len(name)+1] = 0x00 // terminal
+	return offset + len(name) + 2
+}
+
+func (rr *DNSResourceRecord) encode(data []byte, offset int, opts gopacket.SerializeOptions) (int, error) {
+
+	noff := encodeName(rr.Name, data, offset)
+
+	binary.BigEndian.PutUint16(data[noff:], uint16(rr.Type))
+	binary.BigEndian.PutUint16(data[noff+2:], uint16(rr.Class))
+	binary.BigEndian.PutUint32(data[noff+4:], uint32(rr.TTL))
+
+	switch rr.Type {
+	case DNSTypeA:
+		copy(data[noff+10:], rr.IP.To4())
+	case DNSTypeAAAA:
+		copy(data[noff+10:], rr.IP)
+	case DNSTypeNS:
+		encodeName(rr.NS, data, noff+10)
+	case DNSTypeCNAME:
+		encodeName(rr.CNAME, data, noff+10)
+	case DNSTypePTR:
+		encodeName(rr.PTR, data, noff+10)
+	case DNSTypeSOA:
+		noff2 := encodeName(rr.SOA.MName, data, noff+10)
+		noff2 = encodeName(rr.SOA.RName, data, noff2)
+		binary.BigEndian.PutUint32(data[noff2:], rr.SOA.Serial)
+		binary.BigEndian.PutUint32(data[noff2+4:], rr.SOA.Refresh)
+		binary.BigEndian.PutUint32(data[noff2+8:], rr.SOA.Retry)
+		binary.BigEndian.PutUint32(data[noff2+12:], rr.SOA.Expire)
+		binary.BigEndian.PutUint32(data[noff2+16:], rr.SOA.Minimum)
+	case DNSTypeMX:
+		binary.BigEndian.PutUint16(data[noff+10:], rr.MX.Preference)
+		encodeName(rr.MX.Name, data, noff+12)
+	case DNSTypeTXT:
+		noff2 := noff + 10
+		for _, txt := range rr.TXTs {
+			data[noff2] = byte(len(txt))
+			copy(data[noff2+1:], txt)
+			noff2 += 1 + len(txt)
+		}
+	case DNSTypeSRV:
+		binary.BigEndian.PutUint16(data[noff+10:], rr.SRV.Priority)
+		binary.BigEndian.PutUint16(data[noff+12:], rr.SRV.Weight)
+		binary.BigEndian.PutUint16(data[noff+14:], rr.SRV.Port)
+		encodeName(rr.SRV.Name, data, noff+16)
+	default:
+		return 0, fmt.Errorf("serializing resource record of type %v not supported", rr.Type)
+	}
+
+	// DataLength
+	dSz := recSize(rr)
+	binary.BigEndian.PutUint16(data[noff+8:], uint16(dSz))
+
+	if opts.FixLengths {
+		rr.DataLength = uint16(dSz)
+	}
+
+	return len(rr.Name) + 1 + 11 + dSz, nil
+}
+
+func (rr *DNSResourceRecord) String() string {
+
+	if rr.Class == DNSClassIN {
+		switch rr.Type {
+		case DNSTypeA, DNSTypeAAAA:
+			return rr.IP.String()
+		case DNSTypeNS:
+			return "NS " + string(rr.NS)
+		case DNSTypeCNAME:
+			return "CNAME " + string(rr.CNAME)
+		case DNSTypePTR:
+			return "PTR " + string(rr.PTR)
+		case DNSTypeTXT:
+			return "TXT " + string(rr.TXT)
+		}
+	}
+
+	return fmt.Sprintf("<%v, %v>", rr.Class, rr.Type)
+}
+
+func decodeCharacterStrings(data []byte) ([][]byte, error) {
+	strings := make([][]byte, 0, 1)
+	end := len(data)
+	for index, index2 := 0, 0; index != end; index = index2 {
+		index2 = index + 1 + int(data[index]) // index increases by 1..256 and does not overflow
+		if index2 > end {
+			return nil, errors.New("Insufficient data for a <character-string>")
+		}
+		strings = append(strings, data[index+1:index2])
+	}
+	return strings, nil
+}
+
+func (rr *DNSResourceRecord) decodeRData(data []byte, offset int, buffer *[]byte) error {
+	switch rr.Type {
+	case DNSTypeA:
+		rr.IP = rr.Data
+	case DNSTypeAAAA:
+		rr.IP = rr.Data
+	case DNSTypeTXT, DNSTypeHINFO:
+		rr.TXT = rr.Data
+		txts, err := decodeCharacterStrings(rr.Data)
+		if err != nil {
+			return err
+		}
+		rr.TXTs = txts
+	case DNSTypeNS:
+		name, _, err := decodeName(data, offset, buffer, 1)
+		if err != nil {
+			return err
+		}
+		rr.NS = name
+	case DNSTypeCNAME:
+		name, _, err := decodeName(data, offset, buffer, 1)
+		if err != nil {
+			return err
+		}
+		rr.CNAME = name
+	case DNSTypePTR:
+		name, _, err := decodeName(data, offset, buffer, 1)
+		if err != nil {
+			return err
+		}
+		rr.PTR = name
+	case DNSTypeSOA:
+		name, endq, err := decodeName(data, offset, buffer, 1)
+		if err != nil {
+			return err
+		}
+		rr.SOA.MName = name
+		name, endq, err = decodeName(data, endq, buffer, 1)
+		if err != nil {
+			return err
+		}
+		rr.SOA.RName = name
+		rr.SOA.Serial = binary.BigEndian.Uint32(data[endq : endq+4])
+		rr.SOA.Refresh = binary.BigEndian.Uint32(data[endq+4 : endq+8])
+		rr.SOA.Retry = binary.BigEndian.Uint32(data[endq+8 : endq+12])
+		rr.SOA.Expire = binary.BigEndian.Uint32(data[endq+12 : endq+16])
+		rr.SOA.Minimum = binary.BigEndian.Uint32(data[endq+16 : endq+20])
+	case DNSTypeMX:
+		rr.MX.Preference = binary.BigEndian.Uint16(data[offset : offset+2])
+		name, _, err := decodeName(data, offset+2, buffer, 1)
+		if err != nil {
+			return err
+		}
+		rr.MX.Name = name
+	case DNSTypeSRV:
+		rr.SRV.Priority = binary.BigEndian.Uint16(data[offset : offset+2])
+		rr.SRV.Weight = binary.BigEndian.Uint16(data[offset+2 : offset+4])
+		rr.SRV.Port = binary.BigEndian.Uint16(data[offset+4 : offset+6])
+		name, _, err := decodeName(data, offset+6, buffer, 1)
+		if err != nil {
+			return err
+		}
+		rr.SRV.Name = name
+	}
+	return nil
+}
+
+// DNSSOA is a Start of Authority record.  Each domain requires a SOA record at
+// the cutover where a domain is delegated from its parent.
+type DNSSOA struct {
+	MName, RName                            []byte
+	Serial, Refresh, Retry, Expire, Minimum uint32
+}
+
+// DNSSRV is a Service record, defining a location (hostname/port) of a
+// server/service.
+type DNSSRV struct {
+	Priority, Weight, Port uint16
+	Name                   []byte
+}
+
+// DNSMX is a mail exchange record, defining a mail server for a recipient's
+// domain.
+type DNSMX struct {
+	Preference uint16
+	Name       []byte
+}