Update deps

vendor/github.com/miekg/dns/msg.go

@@ -9,7 +9,6 @@
 package dns
 
 //go:generate go run msg_generate.go
-//go:generate go run compress_generate.go
 
 import (
 	crand "crypto/rand"
@@ -18,12 +17,35 @@ import (
 	"math/big"
 	"math/rand"
 	"strconv"
+	"strings"
 	"sync"
 )
 
 const (
 	maxCompressionOffset    = 2 << 13 // We have 14 bits for the compression pointer
 	maxDomainNameWireOctets = 255     // See RFC 1035 section 2.3.4
+
+	// This is the maximum number of compression pointers that should occur in a
+	// semantically valid message. Each label in a domain name must be at least one
+	// octet and is separated by a period. The root label won't be represented by a
+	// compression pointer to a compression pointer, hence the -2 to exclude the
+	// smallest valid root label.
+	//
+	// It is possible to construct a valid message that has more compression pointers
+	// than this, and still doesn't loop, by pointing to a previous pointer. This is
+	// not something a well written implementation should ever do, so we leave them
+	// to trip the maximum compression pointer check.
+	maxCompressionPointers = (maxDomainNameWireOctets+1)/2 - 2
+
+	// This is the maximum length of a domain name in presentation format. The
+	// maximum wire length of a domain name is 255 octets (see above), with the
+	// maximum label length being 63. The wire format requires one extra byte over
+	// the presentation format, reducing the number of octets by 1. Each label in
+	// the name will be separated by a single period, with each octet in the label
+	// expanding to at most 4 bytes (\DDD). If all other labels are of the maximum
+	// length, then the final label can only be 61 octets long to not exceed the
+	// maximum allowed wire length.
+	maxDomainNamePresentationLength = 61*4 + 1 + 63*4 + 1 + 63*4 + 1 + 63*4 + 1
 )
 
 // Errors defined in this package.
@@ -46,10 +68,9 @@ var (
 	ErrRRset         error = &Error{err: "bad rrset"}
 	ErrSecret        error = &Error{err: "no secrets defined"}
 	ErrShortRead     error = &Error{err: "short read"}
-	ErrSig           error = &Error{err: "bad signature"}                      // ErrSig indicates that a signature can not be cryptographically validated.
-	ErrSoa           error = &Error{err: "no SOA"}                             // ErrSOA indicates that no SOA RR was seen when doing zone transfers.
-	ErrTime          error = &Error{err: "bad time"}                           // ErrTime indicates a timing error in TSIG authentication.
-	ErrTruncated     error = &Error{err: "failed to unpack truncated message"} // ErrTruncated indicates that we failed to unpack a truncated message. We unpacked as much as we had so Msg can still be used, if desired.
+	ErrSig           error = &Error{err: "bad signature"} // ErrSig indicates that a signature can not be cryptographically validated.
+	ErrSoa           error = &Error{err: "no SOA"}        // ErrSOA indicates that no SOA RR was seen when doing zone transfers.
+	ErrTime          error = &Error{err: "bad time"}      // ErrTime indicates a timing error in TSIG authentication.
 )
 
 // Id by default, returns a 16 bits random number to be used as a
@@ -151,7 +172,7 @@ var RcodeToString = map[int]string{
 	RcodeFormatError:    "FORMERR",
 	RcodeServerFailure:  "SERVFAIL",
 	RcodeNameError:      "NXDOMAIN",
-	RcodeNotImplemented: "NOTIMPL",
+	RcodeNotImplemented: "NOTIMP",
 	RcodeRefused:        "REFUSED",
 	RcodeYXDomain:       "YXDOMAIN", // See RFC 2136
 	RcodeYXRrset:        "YXRRSET",
@@ -169,6 +190,39 @@ var RcodeToString = map[int]string{
 	RcodeBadCookie: "BADCOOKIE",
 }
 
+// compressionMap is used to allow a more efficient compression map
+// to be used for internal packDomainName calls without changing the
+// signature or functionality of public API.
+//
+// In particular, map[string]uint16 uses 25% less per-entry memory
+// than does map[string]int.
+type compressionMap struct {
+	ext map[string]int    // external callers
+	int map[string]uint16 // internal callers
+}
+
+func (m compressionMap) valid() bool {
+	return m.int != nil || m.ext != nil
+}
+
+func (m compressionMap) insert(s string, pos int) {
+	if m.ext != nil {
+		m.ext[s] = pos
+	} else {
+		m.int[s] = uint16(pos)
+	}
+}
+
+func (m compressionMap) find(s string) (int, bool) {
+	if m.ext != nil {
+		pos, ok := m.ext[s]
+		return pos, ok
+	}
+
+	pos, ok := m.int[s]
+	return int(pos), ok
+}
+
 // Domain names are a sequence of counted strings
 // split at the dots. They end with a zero-length string.
 
@@ -177,149 +231,156 @@ var RcodeToString = map[int]string{
 // map needs to hold a mapping between domain names and offsets
 // pointing into msg.
 func PackDomainName(s string, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error) {
-	off1, _, err = packDomainName(s, msg, off, compression, compress)
-	return
+	return packDomainName(s, msg, off, compressionMap{ext: compression}, compress)
 }
 
-func packDomainName(s string, msg []byte, off int, compression map[string]int, compress bool) (off1 int, labels int, err error) {
-	// special case if msg == nil
-	lenmsg := 256
-	if msg != nil {
-		lenmsg = len(msg)
-	}
+func packDomainName(s string, msg []byte, off int, compression compressionMap, compress bool) (off1 int, err error) {
+	// XXX: A logical copy of this function exists in IsDomainName and
+	// should be kept in sync with this function.
+
 	ls := len(s)
 	if ls == 0 { // Ok, for instance when dealing with update RR without any rdata.
-		return off, 0, nil
+		return off, nil
 	}
-	// If not fully qualified, error out, but only if msg == nil #ugly
-	switch {
-	case msg == nil:
-		if s[ls-1] != '.' {
-			s += "."
-			ls++
-		}
-	case msg != nil:
-		if s[ls-1] != '.' {
-			return lenmsg, 0, ErrFqdn
-		}
+
+	// If not fully qualified, error out.
+	if !IsFqdn(s) {
+		return len(msg), ErrFqdn
 	}
+
 	// Each dot ends a segment of the name.
 	// We trade each dot byte for a length byte.
 	// Except for escaped dots (\.), which are normal dots.
 	// There is also a trailing zero.
 
 	// Compression
-	nameoffset := -1
 	pointer := -1
+
 	// Emit sequence of counted strings, chopping at dots.
-	begin := 0
-	bs := []byte(s)
-	roBs, bsFresh, escapedDot := s, true, false
+	var (
+		begin     int
+		compBegin int
+		compOff   int
+		bs        []byte
+		wasDot    bool
+	)
+loop:
 	for i := 0; i < ls; i++ {
-		if bs[i] == '\\' {
-			for j := i; j < ls-1; j++ {
-				bs[j] = bs[j+1]
-			}
-			ls--
-			if off+1 > lenmsg {
-				return lenmsg, labels, ErrBuf
-			}
-			// check for \DDD
-			if i+2 < ls && isDigit(bs[i]) && isDigit(bs[i+1]) && isDigit(bs[i+2]) {
-				bs[i] = dddToByte(bs[i:])
-				for j := i + 1; j < ls-2; j++ {
-					bs[j] = bs[j+2]
-				}
-				ls -= 2
-			}
-			escapedDot = bs[i] == '.'
-			bsFresh = false
-			continue
+		var c byte
+		if bs == nil {
+			c = s[i]
+		} else {
+			c = bs[i]
 		}
 
-		if bs[i] == '.' {
-			if i > 0 && bs[i-1] == '.' && !escapedDot {
+		switch c {
+		case '\\':
+			if off+1 > len(msg) {
+				return len(msg), ErrBuf
+			}
+
+			if bs == nil {
+				bs = []byte(s)
+			}
+
+			// check for \DDD
+			if i+3 < ls && isDigit(bs[i+1]) && isDigit(bs[i+2]) && isDigit(bs[i+3]) {
+				bs[i] = dddToByte(bs[i+1:])
+				copy(bs[i+1:ls-3], bs[i+4:])
+				ls -= 3
+				compOff += 3
+			} else {
+				copy(bs[i:ls-1], bs[i+1:])
+				ls--
+				compOff++
+			}
+
+			wasDot = false
+		case '.':
+			if wasDot {
 				// two dots back to back is not legal
-				return lenmsg, labels, ErrRdata
+				return len(msg), ErrRdata
 			}
-			if i-begin >= 1<<6 { // top two bits of length must be clear
-				return lenmsg, labels, ErrRdata
+			wasDot = true
+
+			labelLen := i - begin
+			if labelLen >= 1<<6 { // top two bits of length must be clear
+				return len(msg), ErrRdata
 			}
+
 			// off can already (we're in a loop) be bigger than len(msg)
 			// this happens when a name isn't fully qualified
-			if off+1 > lenmsg {
-				return lenmsg, labels, ErrBuf
-			}
-			if msg != nil {
-				msg[off] = byte(i - begin)
-			}
-			offset := off
-			off++
-			for j := begin; j < i; j++ {
-				if off+1 > lenmsg {
-					return lenmsg, labels, ErrBuf
-				}
-				if msg != nil {
-					msg[off] = bs[j]
-				}
-				off++
-			}
-			if compress && !bsFresh {
-				roBs = string(bs)
-				bsFresh = true
+			if off+1+labelLen > len(msg) {
+				return len(msg), ErrBuf
 			}
+
 			// Don't try to compress '.'
-			// We should only compress when compress it true, but we should also still pick
+			// We should only compress when compress is true, but we should also still pick
 			// up names that can be used for *future* compression(s).
-			if compression != nil && roBs[begin:] != "." {
-				if p, ok := compression[roBs[begin:]]; !ok {
-					// Only offsets smaller than this can be used.
-					if offset < maxCompressionOffset {
-						compression[roBs[begin:]] = offset
-					}
-				} else {
+			if compression.valid() && !isRootLabel(s, bs, begin, ls) {
+				if p, ok := compression.find(s[compBegin:]); ok {
 					// The first hit is the longest matching dname
 					// keep the pointer offset we get back and store
 					// the offset of the current name, because that's
 					// where we need to insert the pointer later
 
 					// If compress is true, we're allowed to compress this dname
-					if pointer == -1 && compress {
-						pointer = p         // Where to point to
-						nameoffset = offset // Where to point from
-						break
+					if compress {
+						pointer = p // Where to point to
+						break loop
 					}
+				} else if off < maxCompressionOffset {
+					// Only offsets smaller than maxCompressionOffset can be used.
+					compression.insert(s[compBegin:], off)
 				}
 			}
-			labels++
+
+			// The following is covered by the length check above.
+			msg[off] = byte(labelLen)
+
+			if bs == nil {
+				copy(msg[off+1:], s[begin:i])
+			} else {
+				copy(msg[off+1:], bs[begin:i])
+			}
+			off += 1 + labelLen
+
 			begin = i + 1
+			compBegin = begin + compOff
+		default:
+			wasDot = false
 		}
-		escapedDot = false
 	}
+
 	// Root label is special
-	if len(bs) == 1 && bs[0] == '.' {
-		return off, labels, nil
+	if isRootLabel(s, bs, 0, ls) {
+		return off, nil
 	}
+
 	// If we did compression and we find something add the pointer here
 	if pointer != -1 {
-		// Clear the msg buffer after the pointer location, otherwise
-		// packDataNsec writes the wrong data to msg.
-		tainted := msg[nameoffset:off]
-		for i := range tainted {
-			tainted[i] = 0
-		}
 		// We have two bytes (14 bits) to put the pointer in
-		// if msg == nil, we will never do compression
-		binary.BigEndian.PutUint16(msg[nameoffset:], uint16(pointer^0xC000))
-		off = nameoffset + 1
-		goto End
+		binary.BigEndian.PutUint16(msg[off:], uint16(pointer^0xC000))
+		return off + 2, nil
 	}
-	if msg != nil && off < len(msg) {
+
+	if off < len(msg) {
 		msg[off] = 0
 	}
-End:
-	off++
-	return off, labels, nil
+
+	return off + 1, nil
+}
+
+// isRootLabel returns whether s or bs, from off to end, is the root
+// label ".".
+//
+// If bs is nil, s will be checked, otherwise bs will be checked.
+func isRootLabel(s string, bs []byte, off, end int) bool {
+	if bs == nil {
+		return s[off:end] == "."
+	}
+
+	return end-off == 1 && bs[off] == '.'
 }
 
 // Unpack a domain name.
@@ -336,12 +397,16 @@ End:
 // In theory, the pointers are only allowed to jump backward.
 // We let them jump anywhere and stop jumping after a while.
 
-// UnpackDomainName unpacks a domain name into a string.
+// UnpackDomainName unpacks a domain name into a string. It returns
+// the name, the new offset into msg and any error that occurred.
+//
+// When an error is encountered, the unpacked name will be discarded
+// and len(msg) will be returned as the offset.
 func UnpackDomainName(msg []byte, off int) (string, int, error) {
-	s := make([]byte, 0, 64)
+	s := make([]byte, 0, maxDomainNamePresentationLength)
 	off1 := 0
 	lenmsg := len(msg)
-	maxLen := maxDomainNameWireOctets
+	budget := maxDomainNameWireOctets
 	ptr := 0 // number of pointers followed
 Loop:
 	for {
@@ -360,25 +425,19 @@ Loop:
 			if off+c > lenmsg {
 				return "", lenmsg, ErrBuf
 			}
+			budget -= c + 1 // +1 for the label separator
+			if budget <= 0 {
+				return "", lenmsg, ErrLongDomain
+			}
 			for j := off; j < off+c; j++ {
 				switch b := msg[j]; b {
 				case '.', '(', ')', ';', ' ', '@':
 					fallthrough
 				case '"', '\\':
 					s = append(s, '\\', b)
-					// presentation-format \X escapes add an extra byte
-					maxLen++
 				default:
-					if b < 32 || b >= 127 { // unprintable, use \DDD
-						var buf [3]byte
-						bufs := strconv.AppendInt(buf[:0], int64(b), 10)
-						s = append(s, '\\')
-						for i := len(bufs); i < 3; i++ {
-							s = append(s, '0')
-						}
-						s = append(s, bufs...)
-						// presentation-format \DDD escapes add 3 extra bytes
-						maxLen += 3
+					if b < ' ' || b > '~' { // unprintable, use \DDD
+						s = append(s, escapeByte(b)...)
 					} else {
 						s = append(s, b)
 					}
@@ -400,7 +459,7 @@ Loop:
 			if ptr == 0 {
 				off1 = off
 			}
-			if ptr++; ptr > 10 {
+			if ptr++; ptr > maxCompressionPointers {
 				return "", lenmsg, &Error{err: "too many compression pointers"}
 			}
 			// pointer should guarantee that it advances and points forwards at least
@@ -416,10 +475,7 @@ Loop:
 		off1 = off
 	}
 	if len(s) == 0 {
-		s = []byte(".")
-	} else if len(s) >= maxLen {
-		// error if the name is too long, but don't throw it away
-		return string(s), lenmsg, ErrLongDomain
+		return ".", off1, nil
 	}
 	return string(s), off1, nil
 }
@@ -528,10 +584,12 @@ func unpackTxt(msg []byte, off0 int) (ss []string, off int, err error) {
 func isDigit(b byte) bool { return b >= '0' && b <= '9' }
 
 func dddToByte(s []byte) byte {
+	_ = s[2] // bounds check hint to compiler; see golang.org/issue/14808
 	return byte((s[0]-'0')*100 + (s[1]-'0')*10 + (s[2] - '0'))
 }
 
 func dddStringToByte(s string) byte {
+	_ = s[2] // bounds check hint to compiler; see golang.org/issue/14808
 	return byte((s[0]-'0')*100 + (s[1]-'0')*10 + (s[2] - '0'))
 }
 
@@ -549,19 +607,38 @@ func intToBytes(i *big.Int, length int) []byte {
 // PackRR packs a resource record rr into msg[off:].
 // See PackDomainName for documentation about the compression.
 func PackRR(rr RR, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error) {
+	headerEnd, off1, err := packRR(rr, msg, off, compressionMap{ext: compression}, compress)
+	if err == nil {
+		// packRR no longer sets the Rdlength field on the rr, but
+		// callers might be expecting it so we set it here.
+		rr.Header().Rdlength = uint16(off1 - headerEnd)
+	}
+	return off1, err
+}
+
+func packRR(rr RR, msg []byte, off int, compression compressionMap, compress bool) (headerEnd int, off1 int, err error) {
 	if rr == nil {
-		return len(msg), &Error{err: "nil rr"}
+		return len(msg), len(msg), &Error{err: "nil rr"}
 	}
 
-	off1, err = rr.pack(msg, off, compression, compress)
+	headerEnd, err = rr.Header().packHeader(msg, off, compression, compress)
 	if err != nil {
-		return len(msg), err
+		return headerEnd, len(msg), err
 	}
-	// TODO(miek): Not sure if this is needed? If removed we can remove rawmsg.go as well.
-	if rawSetRdlength(msg, off, off1) {
-		return off1, nil
+
+	off1, err = rr.pack(msg, headerEnd, compression, compress)
+	if err != nil {
+		return headerEnd, len(msg), err
 	}
-	return off, ErrRdata
+
+	rdlength := off1 - headerEnd
+	if int(uint16(rdlength)) != rdlength { // overflow
+		return headerEnd, len(msg), ErrRdata
+	}
+
+	// The RDLENGTH field is the last field in the header and we set it here.
+	binary.BigEndian.PutUint16(msg[headerEnd-2:], uint16(rdlength))
+	return headerEnd, off1, nil
 }
 
 // UnpackRR unpacks msg[off:] into an RR.
@@ -577,17 +654,28 @@ func UnpackRR(msg []byte, off int) (rr RR, off1 int, err error) {
 // UnpackRRWithHeader unpacks the record type specific payload given an existing
 // RR_Header.
 func UnpackRRWithHeader(h RR_Header, msg []byte, off int) (rr RR, off1 int, err error) {
+	if newFn, ok := TypeToRR[h.Rrtype]; ok {
+		rr = newFn()
+		*rr.Header() = h
+	} else {
+		rr = &RFC3597{Hdr: h}
+	}
+
+	if noRdata(h) {
+		return rr, off, nil
+	}
+
 	end := off + int(h.Rdlength)
 
-	if fn, known := typeToUnpack[h.Rrtype]; !known {
-		rr, off, err = unpackRFC3597(h, msg, off)
-	} else {
-		rr, off, err = fn(h, msg, off)
+	off, err = rr.unpack(msg, off)
+	if err != nil {
+		return nil, end, err
 	}
 	if off != end {
 		return &h, end, &Error{err: "bad rdlength"}
 	}
-	return rr, off, err
+
+	return rr, off, nil
 }
 
 // unpackRRslice unpacks msg[off:] into an []RR.
@@ -668,32 +756,33 @@ func (dns *Msg) Pack() (msg []byte, err error) {
 
 // PackBuffer packs a Msg, using the given buffer buf. If buf is too small a new buffer is allocated.
 func (dns *Msg) PackBuffer(buf []byte) (msg []byte, err error) {
-	var compression map[string]int
-	if dns.Compress {
-		compression = make(map[string]int) // Compression pointer mappings.
+	// If this message can't be compressed, avoid filling the
+	// compression map and creating garbage.
+	if dns.Compress && dns.isCompressible() {
+		compression := make(map[string]uint16) // Compression pointer mappings.
+		return dns.packBufferWithCompressionMap(buf, compressionMap{int: compression}, true)
 	}
-	return dns.packBufferWithCompressionMap(buf, compression)
+
+	return dns.packBufferWithCompressionMap(buf, compressionMap{}, false)
 }
 
 // packBufferWithCompressionMap packs a Msg, using the given buffer buf.
-func (dns *Msg) packBufferWithCompressionMap(buf []byte, compression map[string]int) (msg []byte, err error) {
-	// We use a similar function in tsig.go's stripTsig.
-
-	var dh Header
-
+func (dns *Msg) packBufferWithCompressionMap(buf []byte, compression compressionMap, compress bool) (msg []byte, err error) {
 	if dns.Rcode < 0 || dns.Rcode > 0xFFF {
 		return nil, ErrRcode
 	}
-	if dns.Rcode > 0xF {
-		// Regular RCODE field is 4 bits
-		opt := dns.IsEdns0()
-		if opt == nil {
-			return nil, ErrExtendedRcode
-		}
-		opt.SetExtendedRcode(uint8(dns.Rcode >> 4))
+
+	// Set extended rcode unconditionally if we have an opt, this will allow
+	// reseting the extended rcode bits if they need to.
+	if opt := dns.IsEdns0(); opt != nil {
+		opt.SetExtendedRcode(uint16(dns.Rcode))
+	} else if dns.Rcode > 0xF {
+		// If Rcode is an extended one and opt is nil, error out.
+		return nil, ErrExtendedRcode
 	}
 
 	// Convert convenient Msg into wire-like Header.
+	var dh Header
 	dh.Id = dns.Id
 	dh.Bits = uint16(dns.Opcode)<<11 | uint16(dns.Rcode&0xF)
 	if dns.Response {
@@ -721,50 +810,44 @@ func (dns *Msg) packBufferWithCompressionMap(buf []byte, compression map[string]
 		dh.Bits |= _CD
 	}
 
-	// Prepare variable sized arrays.
-	question := dns.Question
-	answer := dns.Answer
-	ns := dns.Ns
-	extra := dns.Extra
-
-	dh.Qdcount = uint16(len(question))
-	dh.Ancount = uint16(len(answer))
-	dh.Nscount = uint16(len(ns))
-	dh.Arcount = uint16(len(extra))
+	dh.Qdcount = uint16(len(dns.Question))
+	dh.Ancount = uint16(len(dns.Answer))
+	dh.Nscount = uint16(len(dns.Ns))
+	dh.Arcount = uint16(len(dns.Extra))
 
 	// We need the uncompressed length here, because we first pack it and then compress it.
 	msg = buf
-	uncompressedLen := compressedLen(dns, false)
+	uncompressedLen := msgLenWithCompressionMap(dns, nil)
 	if packLen := uncompressedLen + 1; len(msg) < packLen {
 		msg = make([]byte, packLen)
 	}
 
 	// Pack it in: header and then the pieces.
 	off := 0
-	off, err = dh.pack(msg, off, compression, dns.Compress)
+	off, err = dh.pack(msg, off, compression, compress)
 	if err != nil {
 		return nil, err
 	}
-	for i := 0; i < len(question); i++ {
-		off, err = question[i].pack(msg, off, compression, dns.Compress)
+	for _, r := range dns.Question {
+		off, err = r.pack(msg, off, compression, compress)
 		if err != nil {
 			return nil, err
 		}
 	}
-	for i := 0; i < len(answer); i++ {
-		off, err = PackRR(answer[i], msg, off, compression, dns.Compress)
+	for _, r := range dns.Answer {
+		_, off, err = packRR(r, msg, off, compression, compress)
 		if err != nil {
 			return nil, err
 		}
 	}
-	for i := 0; i < len(ns); i++ {
-		off, err = PackRR(ns[i], msg, off, compression, dns.Compress)
+	for _, r := range dns.Ns {
+		_, off, err = packRR(r, msg, off, compression, compress)
 		if err != nil {
 			return nil, err
 		}
 	}
-	for i := 0; i < len(extra); i++ {
-		off, err = PackRR(extra[i], msg, off, compression, dns.Compress)
+	for _, r := range dns.Extra {
+		_, off, err = packRR(r, msg, off, compression, compress)
 		if err != nil {
 			return nil, err
 		}
@@ -772,28 +855,7 @@ func (dns *Msg) packBufferWithCompressionMap(buf []byte, compression map[string]
 	return msg[:off], nil
 }
 
-// Unpack unpacks a binary message to a Msg structure.
-func (dns *Msg) Unpack(msg []byte) (err error) {
-	var (
-		dh  Header
-		off int
-	)
-	if dh, off, err = unpackMsgHdr(msg, off); err != nil {
-		return err
-	}
-
-	dns.Id = dh.Id
-	dns.Response = dh.Bits&_QR != 0
-	dns.Opcode = int(dh.Bits>>11) & 0xF
-	dns.Authoritative = dh.Bits&_AA != 0
-	dns.Truncated = dh.Bits&_TC != 0
-	dns.RecursionDesired = dh.Bits&_RD != 0
-	dns.RecursionAvailable = dh.Bits&_RA != 0
-	dns.Zero = dh.Bits&_Z != 0
-	dns.AuthenticatedData = dh.Bits&_AD != 0
-	dns.CheckingDisabled = dh.Bits&_CD != 0
-	dns.Rcode = int(dh.Bits & 0xF)
-
+func (dns *Msg) unpack(dh Header, msg []byte, off int) (err error) {
 	// If we are at the end of the message we should return *just* the
 	// header. This can still be useful to the caller. 9.9.9.9 sends these
 	// when responding with REFUSED for instance.
@@ -812,8 +874,6 @@ func (dns *Msg) Unpack(msg []byte) (err error) {
 		var q Question
 		q, off, err = unpackQuestion(msg, off)
 		if err != nil {
-			// Even if Truncated is set, we only will set ErrTruncated if we
-			// actually got the questions
 			return err
 		}
 		if off1 == off { // Offset does not increase anymore, dh.Qdcount is a lie!
@@ -837,16 +897,29 @@ func (dns *Msg) Unpack(msg []byte) (err error) {
 	// The header counts might have been wrong so we need to update it
 	dh.Arcount = uint16(len(dns.Extra))
 
+	// Set extended Rcode
+	if opt := dns.IsEdns0(); opt != nil {
+		dns.Rcode |= opt.ExtendedRcode()
+	}
+
 	if off != len(msg) {
 		// TODO(miek) make this an error?
 		// use PackOpt to let people tell how detailed the error reporting should be?
 		// println("dns: extra bytes in dns packet", off, "<", len(msg))
-	} else if dns.Truncated {
-		// Whether we ran into a an error or not, we want to return that it
-		// was truncated
-		err = ErrTruncated
 	}
 	return err
+
+}
+
+// Unpack unpacks a binary message to a Msg structure.
+func (dns *Msg) Unpack(msg []byte) (err error) {
+	dh, off, err := unpackMsgHdr(msg, 0)
+	if err != nil {
+		return err
+	}
+
+	dns.setHdr(dh)
+	return dns.unpack(dh, msg, off)
 }
 
 // Convert a complete message to a string with dig-like output.
@@ -892,151 +965,117 @@ func (dns *Msg) String() string {
 	return s
 }
 
+// isCompressible returns whether the msg may be compressible.
+func (dns *Msg) isCompressible() bool {
+	// If we only have one question, there is nothing we can ever compress.
+	return len(dns.Question) > 1 || len(dns.Answer) > 0 ||
+		len(dns.Ns) > 0 || len(dns.Extra) > 0
+}
+
 // Len returns the message length when in (un)compressed wire format.
 // If dns.Compress is true compression it is taken into account. Len()
 // is provided to be a faster way to get the size of the resulting packet,
 // than packing it, measuring the size and discarding the buffer.
-func (dns *Msg) Len() int { return compressedLen(dns, dns.Compress) }
-
-func compressedLenWithCompressionMap(dns *Msg, compression map[string]int) int {
-	l := 12 // Message header is always 12 bytes
-	for _, r := range dns.Question {
-		compressionLenHelper(compression, r.Name, l)
-		l += r.len()
+func (dns *Msg) Len() int {
+	// If this message can't be compressed, avoid filling the
+	// compression map and creating garbage.
+	if dns.Compress && dns.isCompressible() {
+		compression := make(map[string]struct{})
+		return msgLenWithCompressionMap(dns, compression)
 	}
-	l += compressionLenSlice(l, compression, dns.Answer)
-	l += compressionLenSlice(l, compression, dns.Ns)
-	l += compressionLenSlice(l, compression, dns.Extra)
-	return l
+
+	return msgLenWithCompressionMap(dns, nil)
 }
 
-// compressedLen returns the message length when in compressed wire format
-// when compress is true, otherwise the uncompressed length is returned.
-func compressedLen(dns *Msg, compress bool) int {
-	// We always return one more than needed.
-	if compress {
-		compression := map[string]int{}
-		return compressedLenWithCompressionMap(dns, compression)
-	}
-	l := 12 // Message header is always 12 bytes
+func msgLenWithCompressionMap(dns *Msg, compression map[string]struct{}) int {
+	l := headerSize
 
 	for _, r := range dns.Question {
-		l += r.len()
+		l += r.len(l, compression)
 	}
 	for _, r := range dns.Answer {
 		if r != nil {
-			l += r.len()
+			l += r.len(l, compression)
 		}
 	}
 	for _, r := range dns.Ns {
 		if r != nil {
-			l += r.len()
+			l += r.len(l, compression)
 		}
 	}
 	for _, r := range dns.Extra {
 		if r != nil {
-			l += r.len()
+			l += r.len(l, compression)
 		}
 	}
 
 	return l
 }
 
-func compressionLenSlice(lenp int, c map[string]int, rs []RR) int {
-	initLen := lenp
-	for _, r := range rs {
-		if r == nil {
+func domainNameLen(s string, off int, compression map[string]struct{}, compress bool) int {
+	if s == "" || s == "." {
+		return 1
+	}
+
+	escaped := strings.Contains(s, "\\")
+
+	if compression != nil && (compress || off < maxCompressionOffset) {
+		// compressionLenSearch will insert the entry into the compression
+		// map if it doesn't contain it.
+		if l, ok := compressionLenSearch(compression, s, off); ok && compress {
+			if escaped {
+				return escapedNameLen(s[:l]) + 2
+			}
+
+			return l + 2
+		}
+	}
+
+	if escaped {
+		return escapedNameLen(s) + 1
+	}
+
+	return len(s) + 1
+}
+
+func escapedNameLen(s string) int {
+	nameLen := len(s)
+	for i := 0; i < len(s); i++ {
+		if s[i] != '\\' {
 			continue
 		}
-		// TmpLen is to track len of record at 14bits boudaries
-		tmpLen := lenp
 
-		x := r.len()
-		// track this length, and the global length in len, while taking compression into account for both.
-		k, ok, _ := compressionLenSearch(c, r.Header().Name)
-		if ok {
-			// Size of x is reduced by k, but we add 1 since k includes the '.' and label descriptor take 2 bytes
-			// so, basically x:= x - k - 1 + 2
-			x += 1 - k
-		}
-
-		tmpLen += compressionLenHelper(c, r.Header().Name, tmpLen)
-		k, ok, _ = compressionLenSearchType(c, r)
-		if ok {
-			x += 1 - k
-		}
-		lenp += x
-		tmpLen = lenp
-		tmpLen += compressionLenHelperType(c, r, tmpLen)
-
-	}
-	return lenp - initLen
-}
-
-// Put the parts of the name in the compression map, return the size in bytes added in payload
-func compressionLenHelper(c map[string]int, s string, currentLen int) int {
-	if currentLen > maxCompressionOffset {
-		// We won't be able to add any label that could be re-used later anyway
-		return 0
-	}
-	if _, ok := c[s]; ok {
-		return 0
-	}
-	initLen := currentLen
-	pref := ""
-	prev := s
-	lbs := Split(s)
-	for j := 0; j < len(lbs); j++ {
-		pref = s[lbs[j]:]
-		currentLen += len(prev) - len(pref)
-		prev = pref
-		if _, ok := c[pref]; !ok {
-			// If first byte label is within the first 14bits, it might be re-used later
-			if currentLen < maxCompressionOffset {
-				c[pref] = currentLen
-			}
+		if i+3 < len(s) && isDigit(s[i+1]) && isDigit(s[i+2]) && isDigit(s[i+3]) {
+			nameLen -= 3
+			i += 3
 		} else {
-			added := currentLen - initLen
-			if j > 0 {
-				// We added a new PTR
-				added += 2
-			}
-			return added
+			nameLen--
+			i++
 		}
 	}
-	return currentLen - initLen
+
+	return nameLen
 }
 
-// Look for each part in the compression map and returns its length,
-// keep on searching so we get the longest match.
-// Will return the size of compression found, whether a match has been
-// found and the size of record if added in payload
-func compressionLenSearch(c map[string]int, s string) (int, bool, int) {
-	off := 0
-	end := false
-	if s == "" { // don't bork on bogus data
-		return 0, false, 0
-	}
-	fullSize := 0
-	for {
+func compressionLenSearch(c map[string]struct{}, s string, msgOff int) (int, bool) {
+	for off, end := 0, false; !end; off, end = NextLabel(s, off) {
 		if _, ok := c[s[off:]]; ok {
-			return len(s[off:]), true, fullSize + off
+			return off, true
 		}
-		if end {
-			break
+
+		if msgOff+off < maxCompressionOffset {
+			c[s[off:]] = struct{}{}
 		}
-		// Each label descriptor takes 2 bytes, add it
-		fullSize += 2
-		off, end = NextLabel(s, off)
 	}
-	return 0, false, fullSize + len(s)
+
+	return 0, false
 }
 
 // Copy returns a new RR which is a deep-copy of r.
-func Copy(r RR) RR { r1 := r.copy(); return r1 }
+func Copy(r RR) RR { return r.copy() }
 
 // Len returns the length (in octets) of the uncompressed RR in wire format.
-func Len(r RR) int { return r.len() }
+func Len(r RR) int { return r.len(0, nil) }
 
 // Copy returns a new *Msg which is a deep-copy of dns.
 func (dns *Msg) Copy() *Msg { return dns.CopyTo(new(Msg)) }
@@ -1084,8 +1123,8 @@ func (dns *Msg) CopyTo(r1 *Msg) *Msg {
 	return r1
 }
 
-func (q *Question) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
-	off, err := PackDomainName(q.Name, msg, off, compression, compress)
+func (q *Question) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
+	off, err := packDomainName(q.Name, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
@@ -1126,7 +1165,7 @@ func unpackQuestion(msg []byte, off int) (Question, int, error) {
 	return q, off, err
 }
 
-func (dh *Header) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (dh *Header) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := packUint16(dh.Id, msg, off)
 	if err != nil {
 		return off, err
@@ -1148,7 +1187,10 @@ func (dh *Header) pack(msg []byte, off int, compression map[string]int, compress
 		return off, err
 	}
 	off, err = packUint16(dh.Arcount, msg, off)
-	return off, err
+	if err != nil {
+		return off, err
+	}
+	return off, nil
 }
 
 func unpackMsgHdr(msg []byte, off int) (Header, int, error) {
@@ -1177,5 +1219,23 @@ func unpackMsgHdr(msg []byte, off int) (Header, int, error) {
 		return dh, off, err
 	}
 	dh.Arcount, off, err = unpackUint16(msg, off)
-	return dh, off, err
+	if err != nil {
+		return dh, off, err
+	}
+	return dh, off, nil
+}
+
+// setHdr set the header in the dns using the binary data in dh.
+func (dns *Msg) setHdr(dh Header) {
+	dns.Id = dh.Id
+	dns.Response = dh.Bits&_QR != 0
+	dns.Opcode = int(dh.Bits>>11) & 0xF
+	dns.Authoritative = dh.Bits&_AA != 0
+	dns.Truncated = dh.Bits&_TC != 0
+	dns.RecursionDesired = dh.Bits&_RD != 0
+	dns.RecursionAvailable = dh.Bits&_RA != 0
+	dns.Zero = dh.Bits&_Z != 0 // _Z covers the zero bit, which should be zero; not sure why we set it to the opposite.
+	dns.AuthenticatedData = dh.Bits&_AD != 0
+	dns.CheckingDisabled = dh.Bits&_CD != 0
+	dns.Rcode = int(dh.Bits & 0xF)
 }