Launch

2026-05-16 00:18:06 -03:00
commit 92941e68a2
66 changed files with 10352 additions and 0 deletions
--- a/internal/dnsttcore/dns/dns.go
+++ b/internal/dnsttcore/dns/dns.go
@@ -0,0 +1,575 @@
+// Package dns deals with encoding and decoding DNS wire format.
+package dns
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+)
+
+// The maximum number of DNS name compression pointers we are willing to follow.
+// Without something like this, infinite loops are possible.
+const compressionPointerLimit = 10
+
+var (
+	// ErrZeroLengthLabel is the error returned for names that contain a
+	// zero-length label, like "example..com".
+	ErrZeroLengthLabel = errors.New("name contains a zero-length label")
+
+	// ErrLabelTooLong is the error returned for labels that are longer than
+	// 63 octets.
+	ErrLabelTooLong = errors.New("name contains a label longer than 63 octets")
+
+	// ErrNameTooLong is the error returned for names whose encoded
+	// representation is longer than 255 octets.
+	ErrNameTooLong = errors.New("name is longer than 255 octets")
+
+	// ErrReservedLabelType is the error returned when reading a label type
+	// prefix whose two most significant bits are not 00 or 11.
+	ErrReservedLabelType = errors.New("reserved label type")
+
+	// ErrTooManyPointers is the error returned when reading a compressed
+	// name that has too many compression pointers.
+	ErrTooManyPointers = errors.New("too many compression pointers")
+
+	// ErrTrailingBytes is the error returned when bytes remain in the parse
+	// buffer after parsing a message.
+	ErrTrailingBytes = errors.New("trailing bytes after message")
+
+	// ErrIntegerOverflow is the error returned when trying to encode an
+	// integer greater than 65535 into a 16-bit field.
+	ErrIntegerOverflow = errors.New("integer overflow")
+)
+
+const (
+	// https://tools.ietf.org/html/rfc1035#section-3.2.2
+	RRTypeTXT = 16
+	// https://tools.ietf.org/html/rfc6891#section-6.1.1
+	RRTypeOPT = 41
+
+	// https://tools.ietf.org/html/rfc1035#section-3.2.4
+	ClassIN = 1
+
+	// https://tools.ietf.org/html/rfc1035#section-4.1.1
+	RcodeNoError        = 0 // a.k.a. NOERROR
+	RcodeFormatError    = 1 // a.k.a. FORMERR
+	RcodeNameError      = 3 // a.k.a. NXDOMAIN
+	RcodeNotImplemented = 4 // a.k.a. NOTIMPL
+	// https://tools.ietf.org/html/rfc6891#section-9
+	ExtendedRcodeBadVers = 16 // a.k.a. BADVERS
+)
+
+// Name represents a domain name, a sequence of labels each of which is 63
+// octets or less in length.
+//
+// https://tools.ietf.org/html/rfc1035#section-3.1
+type Name [][]byte
+
+// NewName returns a Name from a slice of labels, after checking the labels for
+// validity. Does not include a zero-length label at the end of the slice.
+func NewName(labels [][]byte) (Name, error) {
+	name := Name(labels)
+	// https://tools.ietf.org/html/rfc1035#section-2.3.4
+	// Various objects and parameters in the DNS have size limits.
+	//   labels          63 octets or less
+	//   names           255 octets or less
+	for _, label := range labels {
+		if len(label) == 0 {
+			return nil, ErrZeroLengthLabel
+		}
+		if len(label) > 63 {
+			return nil, ErrLabelTooLong
+		}
+	}
+	// Check the total length.
+	builder := newMessageBuilder()
+	builder.WriteName(name)
+	if len(builder.Bytes()) > 255 {
+		return nil, ErrNameTooLong
+	}
+	return name, nil
+}
+
+// ParseName returns a new Name from a string of labels separated by dots, after
+// checking the name for validity. A single dot at the end of the string is
+// ignored.
+func ParseName(s string) (Name, error) {
+	b := bytes.TrimSuffix([]byte(s), []byte("."))
+	if len(b) == 0 {
+		// bytes.Split(b, ".") would return [""] in this case
+		return NewName([][]byte{})
+	} else {
+		return NewName(bytes.Split(b, []byte(".")))
+	}
+}
+
+// String returns a reversible string representation of name. Labels are
+// separated by dots, and any bytes in a label that are outside the set
+// [0-9A-Za-z-] are replaced with a \xXX hex escape sequence.
+func (name Name) String() string {
+	if len(name) == 0 {
+		return "."
+	}
+
+	var buf strings.Builder
+	for i, label := range name {
+		if i > 0 {
+			buf.WriteByte('.')
+		}
+		for _, b := range label {
+			if b == '-' ||
+				('0' <= b && b <= '9') ||
+				('A' <= b && b <= 'Z') ||
+				('a' <= b && b <= 'z') {
+				buf.WriteByte(b)
+			} else {
+				fmt.Fprintf(&buf, "\\x%02x", b)
+			}
+		}
+	}
+	return buf.String()
+}
+
+// TrimSuffix returns a Name with the given suffix removed, if it was present.
+// The second return value indicates whether the suffix was present. If the
+// suffix was not present, the first return value is nil.
+func (name Name) TrimSuffix(suffix Name) (Name, bool) {
+	if len(name) < len(suffix) {
+		return nil, false
+	}
+	split := len(name) - len(suffix)
+	fore, aft := name[:split], name[split:]
+	for i := 0; i < len(aft); i++ {
+		if !bytes.Equal(bytes.ToLower(aft[i]), bytes.ToLower(suffix[i])) {
+			return nil, false
+		}
+	}
+	return fore, true
+}
+
+// Message represents a DNS message.
+//
+// https://tools.ietf.org/html/rfc1035#section-4.1
+type Message struct {
+	ID    uint16
+	Flags uint16
+
+	Question   []Question
+	Answer     []RR
+	Authority  []RR
+	Additional []RR
+}
+
+// Opcode extracts the OPCODE part of the Flags field.
+//
+// https://tools.ietf.org/html/rfc1035#section-4.1.1
+func (message *Message) Opcode() uint16 {
+	return (message.Flags >> 11) & 0xf
+}
+
+// Rcode extracts the RCODE part of the Flags field.
+//
+// https://tools.ietf.org/html/rfc1035#section-4.1.1
+func (message *Message) Rcode() uint16 {
+	return message.Flags & 0x000f
+}
+
+// Question represents an entry in the question section of a message.
+//
+// https://tools.ietf.org/html/rfc1035#section-4.1.2
+type Question struct {
+	Name  Name
+	Type  uint16
+	Class uint16
+}
+
+// RR represents a resource record.
+//
+// https://tools.ietf.org/html/rfc1035#section-4.1.3
+type RR struct {
+	Name  Name
+	Type  uint16
+	Class uint16
+	TTL   uint32
+	Data  []byte
+}
+
+// readName parses a DNS name from r. It leaves r positioned just after the
+// parsed name.
+func readName(r io.ReadSeeker) (Name, error) {
+	var labels [][]byte
+	// We limit the number of compression pointers we are willing to follow.
+	numPointers := 0
+	// If we followed any compression pointers, we must finally seek to just
+	// past the first pointer.
+	var seekTo int64
+loop:
+	for {
+		var labelType byte
+		err := binary.Read(r, binary.BigEndian, &labelType)
+		if err != nil {
+			return nil, err
+		}
+
+		switch labelType & 0xc0 {
+		case 0x00:
+			// This is an ordinary label.
+			// https://tools.ietf.org/html/rfc1035#section-3.1
+			length := int(labelType & 0x3f)
+			if length == 0 {
+				break loop
+			}
+			label := make([]byte, length)
+			_, err := io.ReadFull(r, label)
+			if err != nil {
+				return nil, err
+			}
+			labels = append(labels, label)
+		case 0xc0:
+			// This is a compression pointer.
+			// https://tools.ietf.org/html/rfc1035#section-4.1.4
+			upper := labelType & 0x3f
+			var lower byte
+			err := binary.Read(r, binary.BigEndian, &lower)
+			if err != nil {
+				return nil, err
+			}
+			offset := (uint16(upper) << 8) | uint16(lower)
+
+			if numPointers == 0 {
+				// The first time we encounter a pointer,
+				// remember our position so we can seek back to
+				// it when done.
+				seekTo, err = r.Seek(0, io.SeekCurrent)
+				if err != nil {
+					return nil, err
+				}
+			}
+			numPointers++
+			if numPointers > compressionPointerLimit {
+				return nil, ErrTooManyPointers
+			}
+
+			// Follow the pointer and continue.
+			_, err = r.Seek(int64(offset), io.SeekStart)
+			if err != nil {
+				return nil, err
+			}
+		default:
+			// "The 10 and 01 combinations are reserved for future
+			// use."
+			return nil, ErrReservedLabelType
+		}
+	}
+	// If we followed any pointers, then seek back to just after the first
+	// one.
+	if numPointers > 0 {
+		_, err := r.Seek(seekTo, io.SeekStart)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return NewName(labels)
+}
+
+// readQuestion parses one entry from the Question section. It leaves r
+// positioned just after the parsed entry.
+//
+// https://tools.ietf.org/html/rfc1035#section-4.1.2
+func readQuestion(r io.ReadSeeker) (Question, error) {
+	var question Question
+	var err error
+	question.Name, err = readName(r)
+	if err != nil {
+		return question, err
+	}
+	for _, ptr := range []*uint16{&question.Type, &question.Class} {
+		err := binary.Read(r, binary.BigEndian, ptr)
+		if err != nil {
+			return question, err
+		}
+	}
+
+	return question, nil
+}
+
+// readRR parses one resource record. It leaves r positioned just after the
+// parsed resource record.
+//
+// https://tools.ietf.org/html/rfc1035#section-4.1.3
+func readRR(r io.ReadSeeker) (RR, error) {
+	var rr RR
+	var err error
+	rr.Name, err = readName(r)
+	if err != nil {
+		return rr, err
+	}
+	for _, ptr := range []*uint16{&rr.Type, &rr.Class} {
+		err := binary.Read(r, binary.BigEndian, ptr)
+		if err != nil {
+			return rr, err
+		}
+	}
+	err = binary.Read(r, binary.BigEndian, &rr.TTL)
+	if err != nil {
+		return rr, err
+	}
+	var rdLength uint16
+	err = binary.Read(r, binary.BigEndian, &rdLength)
+	if err != nil {
+		return rr, err
+	}
+	rr.Data = make([]byte, rdLength)
+	_, err = io.ReadFull(r, rr.Data)
+	if err != nil {
+		return rr, err
+	}
+
+	return rr, nil
+}
+
+// readMessage parses a complete DNS message. It leaves r positioned just after
+// the parsed message.
+func readMessage(r io.ReadSeeker) (Message, error) {
+	var message Message
+
+	// Header section
+	// https://tools.ietf.org/html/rfc1035#section-4.1.1
+	var qdCount, anCount, nsCount, arCount uint16
+	for _, ptr := range []*uint16{
+		&message.ID, &message.Flags,
+		&qdCount, &anCount, &nsCount, &arCount,
+	} {
+		err := binary.Read(r, binary.BigEndian, ptr)
+		if err != nil {
+			return message, err
+		}
+	}
+
+	// Question section
+	// https://tools.ietf.org/html/rfc1035#section-4.1.2
+	for i := 0; i < int(qdCount); i++ {
+		question, err := readQuestion(r)
+		if err != nil {
+			return message, err
+		}
+		message.Question = append(message.Question, question)
+	}
+
+	// Answer, Authority, and Additional sections
+	// https://tools.ietf.org/html/rfc1035#section-4.1.3
+	for _, rec := range []struct {
+		ptr   *[]RR
+		count uint16
+	}{
+		{&message.Answer, anCount},
+		{&message.Authority, nsCount},
+		{&message.Additional, arCount},
+	} {
+		for i := 0; i < int(rec.count); i++ {
+			rr, err := readRR(r)
+			if err != nil {
+				return message, err
+			}
+			*rec.ptr = append(*rec.ptr, rr)
+		}
+	}
+
+	return message, nil
+}
+
+// MessageFromWireFormat parses a message from buf and returns a Message object.
+// It returns ErrTrailingBytes if there are bytes remaining in buf after parsing
+// is done.
+func MessageFromWireFormat(buf []byte) (Message, error) {
+	r := bytes.NewReader(buf)
+	message, err := readMessage(r)
+	if err == io.EOF {
+		err = io.ErrUnexpectedEOF
+	} else if err == nil {
+		// Check for trailing bytes.
+		_, err = r.ReadByte()
+		if err == io.EOF {
+			err = nil
+		} else if err == nil {
+			err = ErrTrailingBytes
+		}
+	}
+	return message, err
+}
+
+// messageBuilder manages the state of serializing a DNS message. Its main
+// function is to keep track of names already written for the purpose of name
+// compression.
+type messageBuilder struct {
+	w         bytes.Buffer
+	nameCache map[string]int
+}
+
+// newMessageBuilder creates a new messageBuilder with an empty name cache.
+func newMessageBuilder() *messageBuilder {
+	return &messageBuilder{
+		nameCache: make(map[string]int),
+	}
+}
+
+// Bytes returns the serialized DNS message as a slice of bytes.
+func (builder *messageBuilder) Bytes() []byte {
+	return builder.w.Bytes()
+}
+
+// WriteName appends name to the in-progress messageBuilder, employing
+// compression pointers to previously written names if possible.
+func (builder *messageBuilder) WriteName(name Name) {
+	// https://tools.ietf.org/html/rfc1035#section-3.1
+	for i := range name {
+		// Has this suffix already been encoded in the message?
+		if ptr, ok := builder.nameCache[name[i:].String()]; ok && ptr&0x3fff == ptr {
+			// If so, we can write a compression pointer.
+			binary.Write(&builder.w, binary.BigEndian, uint16(0xc000|ptr))
+			return
+		}
+		// Not cached; we must encode this label verbatim. Store a cache
+		// entry pointing to the beginning of it.
+		builder.nameCache[name[i:].String()] = builder.w.Len()
+		length := len(name[i])
+		if length == 0 || length > 63 {
+			panic(length)
+		}
+		builder.w.WriteByte(byte(length))
+		builder.w.Write(name[i])
+	}
+	builder.w.WriteByte(0)
+}
+
+// WriteQuestion appends a Question section entry to the in-progress
+// messageBuilder.
+func (builder *messageBuilder) WriteQuestion(question *Question) {
+	// https://tools.ietf.org/html/rfc1035#section-4.1.2
+	builder.WriteName(question.Name)
+	binary.Write(&builder.w, binary.BigEndian, question.Type)
+	binary.Write(&builder.w, binary.BigEndian, question.Class)
+}
+
+// WriteRR appends a resource record to the in-progress messageBuilder. It
+// returns ErrIntegerOverflow if the length of rr.Data does not fit in 16 bits.
+func (builder *messageBuilder) WriteRR(rr *RR) error {
+	// https://tools.ietf.org/html/rfc1035#section-4.1.3
+	builder.WriteName(rr.Name)
+	binary.Write(&builder.w, binary.BigEndian, rr.Type)
+	binary.Write(&builder.w, binary.BigEndian, rr.Class)
+	binary.Write(&builder.w, binary.BigEndian, rr.TTL)
+	rdLength := uint16(len(rr.Data))
+	if int(rdLength) != len(rr.Data) {
+		return ErrIntegerOverflow
+	}
+	binary.Write(&builder.w, binary.BigEndian, rdLength)
+	builder.w.Write(rr.Data)
+	return nil
+}
+
+// WriteMessage appends a complete DNS message to the in-progress
+// messageBuilder. It returns ErrIntegerOverflow if the number of entries in any
+// section, or the length of the data in any resource record, does not fit in 16
+// bits.
+func (builder *messageBuilder) WriteMessage(message *Message) error {
+	// Header section
+	// https://tools.ietf.org/html/rfc1035#section-4.1.1
+	binary.Write(&builder.w, binary.BigEndian, message.ID)
+	binary.Write(&builder.w, binary.BigEndian, message.Flags)
+	for _, count := range []int{
+		len(message.Question),
+		len(message.Answer),
+		len(message.Authority),
+		len(message.Additional),
+	} {
+		count16 := uint16(count)
+		if int(count16) != count {
+			return ErrIntegerOverflow
+		}
+		binary.Write(&builder.w, binary.BigEndian, count16)
+	}
+
+	// Question section
+	// https://tools.ietf.org/html/rfc1035#section-4.1.2
+	for _, question := range message.Question {
+		builder.WriteQuestion(&question)
+	}
+
+	// Answer, Authority, and Additional sections
+	// https://tools.ietf.org/html/rfc1035#section-4.1.3
+	for _, rrs := range [][]RR{message.Answer, message.Authority, message.Additional} {
+		for _, rr := range rrs {
+			err := builder.WriteRR(&rr)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+// WireFormat encodes a Message as a slice of bytes in DNS wire format. It
+// returns ErrIntegerOverflow if the number of entries in any section, or the
+// length of the data in any resource record, does not fit in 16 bits.
+func (message *Message) WireFormat() ([]byte, error) {
+	builder := newMessageBuilder()
+	err := builder.WriteMessage(message)
+	if err != nil {
+		return nil, err
+	}
+	return builder.Bytes(), nil
+}
+
+// DecodeRDataTXT decodes TXT-DATA (as found in the RDATA for a resource record
+// with TYPE=TXT) as a raw byte slice, by concatenating all the
+// <character-string>s it contains.
+//
+// https://tools.ietf.org/html/rfc1035#section-3.3.14
+func DecodeRDataTXT(p []byte) ([]byte, error) {
+	var buf bytes.Buffer
+	for {
+		if len(p) == 0 {
+			return nil, io.ErrUnexpectedEOF
+		}
+		n := int(p[0])
+		p = p[1:]
+		if len(p) < n {
+			return nil, io.ErrUnexpectedEOF
+		}
+		buf.Write(p[:n])
+		p = p[n:]
+		if len(p) == 0 {
+			break
+		}
+	}
+	return buf.Bytes(), nil
+}
+
+// EncodeRDataTXT encodes a slice of bytes as TXT-DATA, as appropriate for the
+// RDATA of a resource record with TYPE=TXT. No length restriction is enforced
+// here; that must be checked at a higher level.
+//
+// https://tools.ietf.org/html/rfc1035#section-3.3.14
+func EncodeRDataTXT(p []byte) []byte {
+	// https://tools.ietf.org/html/rfc1035#section-3.3
+	// https://tools.ietf.org/html/rfc1035#section-3.3.14
+	// TXT data is a sequence of one or more <character-string>s, where
+	// <character-string> is a length octet followed by that number of
+	// octets.
+	var buf bytes.Buffer
+	for len(p) > 255 {
+		buf.WriteByte(255)
+		buf.Write(p[:255])
+		p = p[255:]
+	}
+	// Must write here, even if len(p) == 0, because it's "*one or more*
+	// <character-string>s".
+	buf.WriteByte(byte(len(p)))
+	buf.Write(p)
+	return buf.Bytes()
+}
--- a/internal/dnsttcore/dns/dns_test.go
+++ b/internal/dnsttcore/dns/dns_test.go
@@ -0,0 +1,592 @@
+package dns
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+func namesEqual(a, b Name) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := 0; i < len(a); i++ {
+		if !bytes.Equal(a[i], b[i]) {
+			return false
+		}
+	}
+	return true
+}
+
+func TestName(t *testing.T) {
+	for _, test := range []struct {
+		labels [][]byte
+		err    error
+		s      string
+	}{
+		{[][]byte{}, nil, "."},
+		{[][]byte{[]byte("test")}, nil, "test"},
+		{[][]byte{[]byte("a"), []byte("b"), []byte("c")}, nil, "a.b.c"},
+
+		{[][]byte{{}}, ErrZeroLengthLabel, ""},
+		{[][]byte{[]byte("a"), {}, []byte("c")}, ErrZeroLengthLabel, ""},
+
+		// 63 octets.
+		{[][]byte{[]byte("0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABCDE")}, nil,
+			"0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABCDE"},
+		// 64 octets.
+		{[][]byte{[]byte("0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABCDEF")}, ErrLabelTooLong, ""},
+
+		// 64+64+64+62 octets.
+		{[][]byte{
+			[]byte("0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABCDE"),
+			[]byte("0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABCDE"),
+			[]byte("0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABCDE"),
+			[]byte("0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABC"),
+		}, nil,
+			"0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABCDE.0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABCDE.0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABCDE.0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABC"},
+		// 64+64+64+63 octets.
+		{[][]byte{
+			[]byte("0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABCDE"),
+			[]byte("0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABCDE"),
+			[]byte("0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABCDE"),
+			[]byte("0123456789abcdef0123456789ABCDEF0123456789abcdef0123456789ABCD"),
+		}, ErrNameTooLong, ""},
+		// 127 one-octet labels.
+		{[][]byte{
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'a'}, {'b'}, {'c'}, {'d'}, {'e'}, {'f'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'A'}, {'B'}, {'C'}, {'D'}, {'E'}, {'F'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'a'}, {'b'}, {'c'}, {'d'}, {'e'}, {'f'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'A'}, {'B'}, {'C'}, {'D'}, {'E'}, {'F'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'a'}, {'b'}, {'c'}, {'d'}, {'e'}, {'f'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'A'}, {'B'}, {'C'}, {'D'}, {'E'}, {'F'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'a'}, {'b'}, {'c'}, {'d'}, {'e'}, {'f'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'A'}, {'B'}, {'C'}, {'D'}, {'E'},
+		}, nil,
+			"0.1.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.1.2.3.4.5.6.7.8.9.A.B.C.D.E.F.0.1.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.1.2.3.4.5.6.7.8.9.A.B.C.D.E.F.0.1.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.1.2.3.4.5.6.7.8.9.A.B.C.D.E.F.0.1.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.1.2.3.4.5.6.7.8.9.A.B.C.D.E"},
+		// 128 one-octet labels.
+		{[][]byte{
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'a'}, {'b'}, {'c'}, {'d'}, {'e'}, {'f'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'A'}, {'B'}, {'C'}, {'D'}, {'E'}, {'F'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'a'}, {'b'}, {'c'}, {'d'}, {'e'}, {'f'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'A'}, {'B'}, {'C'}, {'D'}, {'E'}, {'F'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'a'}, {'b'}, {'c'}, {'d'}, {'e'}, {'f'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'A'}, {'B'}, {'C'}, {'D'}, {'E'}, {'F'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'a'}, {'b'}, {'c'}, {'d'}, {'e'}, {'f'},
+			{'0'}, {'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}, {'7'}, {'8'}, {'9'}, {'A'}, {'B'}, {'C'}, {'D'}, {'E'}, {'F'},
+		}, ErrNameTooLong, ""},
+	} {
+		// Test that NewName returns proper error codes, and otherwise
+		// returns an equal slice of labels.
+		name, err := NewName(test.labels)
+		if err != test.err || (err == nil && !namesEqual(name, test.labels)) {
+			t.Errorf("%+q returned (%+q, %v), expected (%+q, %v)",
+				test.labels, name, err, test.labels, test.err)
+			continue
+		}
+		if test.err != nil {
+			continue
+		}
+
+		// Test that the string version of the name comes out as
+		// expected.
+		s := name.String()
+		if s != test.s {
+			t.Errorf("%+q became string %+q, expected %+q", test.labels, s, test.s)
+			continue
+		}
+
+		// Test that parsing from a string back to a Name results in the
+		// original slice of labels.
+		name, err = ParseName(s)
+		if err != nil || !namesEqual(name, test.labels) {
+			t.Errorf("%+q parsing %+q returned (%+q, %v), expected (%+q, %v)",
+				test.labels, s, name, err, test.labels, nil)
+			continue
+		}
+		// A trailing dot should be ignored.
+		if !strings.HasSuffix(s, ".") {
+			dotName, dotErr := ParseName(s + ".")
+			if dotErr != err || !namesEqual(dotName, name) {
+				t.Errorf("%+q parsing %+q returned (%+q, %v), expected (%+q, %v)",
+					test.labels, s+".", dotName, dotErr, name, err)
+				continue
+			}
+		}
+	}
+}
+
+func TestParseName(t *testing.T) {
+	for _, test := range []struct {
+		s    string
+		name Name
+		err  error
+	}{
+		// This case can't be tested by TestName above because String
+		// will never produce "" (it produces "." instead).
+		{"", [][]byte{}, nil},
+	} {
+		name, err := ParseName(test.s)
+		if err != test.err || (err == nil && !namesEqual(name, test.name)) {
+			t.Errorf("%+q returned (%+q, %v), expected (%+q, %v)",
+				test.s, name, err, test.name, test.err)
+			continue
+		}
+	}
+}
+
+func unescapeString(s string) ([][]byte, error) {
+	if s == "." {
+		return [][]byte{}, nil
+	}
+
+	var result [][]byte
+	for _, label := range strings.Split(s, ".") {
+		var buf bytes.Buffer
+		i := 0
+		for i < len(label) {
+			switch label[i] {
+			case '\\':
+				if i+3 >= len(label) {
+					return nil, fmt.Errorf("truncated escape sequence at index %v", i)
+				}
+				if label[i+1] != 'x' {
+					return nil, fmt.Errorf("malformed escape sequence at index %v", i)
+				}
+				b, err := strconv.ParseUint(string(label[i+2:i+4]), 16, 8)
+				if err != nil {
+					return nil, fmt.Errorf("malformed hex sequence at index %v", i+2)
+				}
+				buf.WriteByte(byte(b))
+				i += 4
+			default:
+				buf.WriteByte(label[i])
+				i++
+			}
+		}
+		result = append(result, buf.Bytes())
+	}
+	return result, nil
+}
+
+func TestNameString(t *testing.T) {
+	for _, test := range []struct {
+		name Name
+		s    string
+	}{
+		{[][]byte{}, "."},
+		{[][]byte{[]byte("\x00"), []byte("a.b"), []byte("c\nd\\")}, "\\x00.a\\x2eb.c\\x0ad\\x5c"},
+		{[][]byte{
+			[]byte("\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !\"#$%&'()*+,-./0123456789:;<=>"),
+			[]byte("?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}"),
+			[]byte("~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc"),
+			[]byte("\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb"),
+			[]byte("\xfc\xfd\xfe\xff"),
+		}, "\\x00\\x01\\x02\\x03\\x04\\x05\\x06\\x07\\x08\\x09\\x0a\\x0b\\x0c\\x0d\\x0e\\x0f\\x10\\x11\\x12\\x13\\x14\\x15\\x16\\x17\\x18\\x19\\x1a\\x1b\\x1c\\x1d\\x1e\\x1f\\x20\\x21\\x22\\x23\\x24\\x25\\x26\\x27\\x28\\x29\\x2a\\x2b\\x2c-\\x2e\\x2f0123456789\\x3a\\x3b\\x3c\\x3d\\x3e.\\x3f\\x40ABCDEFGHIJKLMNOPQRSTUVWXYZ\\x5b\\x5c\\x5d\\x5e\\x5f\\x60abcdefghijklmnopqrstuvwxyz\\x7b\\x7c\\x7d.\\x7e\\x7f\\x80\\x81\\x82\\x83\\x84\\x85\\x86\\x87\\x88\\x89\\x8a\\x8b\\x8c\\x8d\\x8e\\x8f\\x90\\x91\\x92\\x93\\x94\\x95\\x96\\x97\\x98\\x99\\x9a\\x9b\\x9c\\x9d\\x9e\\x9f\\xa0\\xa1\\xa2\\xa3\\xa4\\xa5\\xa6\\xa7\\xa8\\xa9\\xaa\\xab\\xac\\xad\\xae\\xaf\\xb0\\xb1\\xb2\\xb3\\xb4\\xb5\\xb6\\xb7\\xb8\\xb9\\xba\\xbb\\xbc.\\xbd\\xbe\\xbf\\xc0\\xc1\\xc2\\xc3\\xc4\\xc5\\xc6\\xc7\\xc8\\xc9\\xca\\xcb\\xcc\\xcd\\xce\\xcf\\xd0\\xd1\\xd2\\xd3\\xd4\\xd5\\xd6\\xd7\\xd8\\xd9\\xda\\xdb\\xdc\\xdd\\xde\\xdf\\xe0\\xe1\\xe2\\xe3\\xe4\\xe5\\xe6\\xe7\\xe8\\xe9\\xea\\xeb\\xec\\xed\\xee\\xef\\xf0\\xf1\\xf2\\xf3\\xf4\\xf5\\xf6\\xf7\\xf8\\xf9\\xfa\\xfb.\\xfc\\xfd\\xfe\\xff"},
+	} {
+		s := test.name.String()
+		if s != test.s {
+			t.Errorf("%+q escaped to %+q, expected %+q", test.name, s, test.s)
+			continue
+		}
+		unescaped, err := unescapeString(s)
+		if err != nil {
+			t.Errorf("%+q unescaping %+q resulted in error %v", test.name, s, err)
+			continue
+		}
+		if !namesEqual(Name(unescaped), test.name) {
+			t.Errorf("%+q roundtripped through %+q to %+q", test.name, s, unescaped)
+			continue
+		}
+	}
+}
+
+func TestNameTrimSuffix(t *testing.T) {
+	for _, test := range []struct {
+		name, suffix string
+		trimmed      string
+		ok           bool
+	}{
+		{"", "", ".", true},
+		{".", ".", ".", true},
+		{"abc", "", "abc", true},
+		{"abc", ".", "abc", true},
+		{"", "abc", ".", false},
+		{".", "abc", ".", false},
+		{"example.com", "com", "example", true},
+		{"example.com", "net", ".", false},
+		{"example.com", "example.com", ".", true},
+		{"example.com", "test.com", ".", false},
+		{"example.com", "xample.com", ".", false},
+		{"example.com", "example", ".", false},
+		{"example.com", "COM", "example", true},
+		{"EXAMPLE.COM", "com", "EXAMPLE", true},
+	} {
+		tmp, ok := mustParseName(test.name).TrimSuffix(mustParseName(test.suffix))
+		trimmed := tmp.String()
+		if ok != test.ok || trimmed != test.trimmed {
+			t.Errorf("TrimSuffix %+q %+q returned (%+q, %v), expected (%+q, %v)",
+				test.name, test.suffix, trimmed, ok, test.trimmed, test.ok)
+			continue
+		}
+	}
+}
+
+func TestReadName(t *testing.T) {
+	// Good tests.
+	for _, test := range []struct {
+		start int64
+		end   int64
+		input string
+		s     string
+	}{
+		// Empty name.
+		{0, 1, "\x00abcd", "."},
+		// No pointers.
+		{12, 25, "AAAABBBBCCCC\x07example\x03com\x00", "example.com"},
+		// Backward pointer.
+		{25, 31, "AAAABBBBCCCC\x07example\x03com\x00\x03sub\xc0\x0c", "sub.example.com"},
+		// Forward pointer.
+		{0, 4, "\x01a\xc0\x04\x03bcd\x00", "a.bcd"},
+		// Two backwards pointers.
+		{31, 38, "AAAABBBBCCCC\x07example\x03com\x00\x03sub\xc0\x0c\x04sub2\xc0\x19", "sub2.sub.example.com"},
+		// Forward then backward pointer.
+		{25, 31, "AAAABBBBCCCC\x07example\x03com\x00\x03sub\xc0\x1f\x04sub2\xc0\x0c", "sub.sub2.example.com"},
+		// Overlapping codons.
+		{0, 4, "\x01a\xc0\x03bcd\x00", "a.bcd"},
+		// Pointer to empty label.
+		{0, 10, "\x07example\xc0\x0a\x00", "example"},
+		{1, 11, "\x00\x07example\xc0\x00", "example"},
+		// Pointer to pointer to empty label.
+		{0, 10, "\x07example\xc0\x0a\xc0\x0c\x00", "example"},
+		{1, 11, "\x00\x07example\xc0\x0c\xc0\x00", "example"},
+	} {
+		r := bytes.NewReader([]byte(test.input))
+		_, err := r.Seek(test.start, io.SeekStart)
+		if err != nil {
+			panic(err)
+		}
+		name, err := readName(r)
+		if err != nil {
+			t.Errorf("%+q returned error %s", test.input, err)
+			continue
+		}
+		s := name.String()
+		if s != test.s {
+			t.Errorf("%+q returned %+q, expected %+q", test.input, s, test.s)
+			continue
+		}
+		cur, _ := r.Seek(0, io.SeekCurrent)
+		if cur != test.end {
+			t.Errorf("%+q left offset %d, expected %d", test.input, cur, test.end)
+			continue
+		}
+	}
+
+	// Bad tests.
+	for _, test := range []struct {
+		start int64
+		input string
+		err   error
+	}{
+		{0, "", io.ErrUnexpectedEOF},
+		// Reserved label type.
+		{0, "\x80example", ErrReservedLabelType},
+		// Reserved label type.
+		{0, "\x40example", ErrReservedLabelType},
+		// No Terminating empty label.
+		{0, "\x07example\x03com", io.ErrUnexpectedEOF},
+		// Pointer past end of buffer.
+		{0, "\x07example\xc0\xff", io.ErrUnexpectedEOF},
+		// Pointer to self.
+		{0, "\x07example\x03com\xc0\x0c", ErrTooManyPointers},
+		// Pointer to self with intermediate label.
+		{0, "\x07example\x03com\xc0\x08", ErrTooManyPointers},
+		// Two pointers that point to each other.
+		{0, "\xc0\x02\xc0\x00", ErrTooManyPointers},
+		// Two pointers that point to each other, with intermediate labels.
+		{0, "\x01a\xc0\x04\x01b\xc0\x00", ErrTooManyPointers},
+		// EOF while reading label.
+		{0, "\x0aexample", io.ErrUnexpectedEOF},
+		// EOF before second byte of pointer.
+		{0, "\xc0", io.ErrUnexpectedEOF},
+		{0, "\x07example\xc0", io.ErrUnexpectedEOF},
+	} {
+		r := bytes.NewReader([]byte(test.input))
+		_, err := r.Seek(test.start, io.SeekStart)
+		if err != nil {
+			panic(err)
+		}
+		name, err := readName(r)
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		}
+		if err != test.err {
+			t.Errorf("%+q returned (%+q, %v), expected %v", test.input, name, err, test.err)
+			continue
+		}
+	}
+}
+
+func mustParseName(s string) Name {
+	name, err := ParseName(s)
+	if err != nil {
+		panic(err)
+	}
+	return name
+}
+
+func questionsEqual(a, b *Question) bool {
+	if !namesEqual(a.Name, b.Name) {
+		return false
+	}
+	if a.Type != b.Type || a.Class != b.Class {
+		return false
+	}
+	return true
+}
+
+func rrsEqual(a, b *RR) bool {
+	if !namesEqual(a.Name, b.Name) {
+		return false
+	}
+	if a.Type != b.Type || a.Class != b.Class || a.TTL != b.TTL {
+		return false
+	}
+	if !bytes.Equal(a.Data, b.Data) {
+		return false
+	}
+	return true
+}
+
+func messagesEqual(a, b *Message) bool {
+	if a.ID != b.ID || a.Flags != b.Flags {
+		return false
+	}
+	if len(a.Question) != len(b.Question) {
+		return false
+	}
+	for i := 0; i < len(a.Question); i++ {
+		if !questionsEqual(&a.Question[i], &b.Question[i]) {
+			return false
+		}
+	}
+	for _, rec := range []struct{ rrA, rrB []RR }{
+		{a.Answer, b.Answer},
+		{a.Authority, b.Authority},
+		{a.Additional, b.Additional},
+	} {
+		if len(rec.rrA) != len(rec.rrB) {
+			return false
+		}
+		for i := 0; i < len(rec.rrA); i++ {
+			if !rrsEqual(&rec.rrA[i], &rec.rrB[i]) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+func TestMessageFromWireFormat(t *testing.T) {
+	for _, test := range []struct {
+		buf      string
+		expected Message
+		err      error
+	}{
+		{
+			"\x12\x34",
+			Message{},
+			io.ErrUnexpectedEOF,
+		},
+		{
+			"\x12\x34\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00\x03www\x07example\x03com\x00\x00\x01\x00\x01",
+			Message{
+				ID:    0x1234,
+				Flags: 0x0100,
+				Question: []Question{
+					{
+						Name:  mustParseName("www.example.com"),
+						Type:  1,
+						Class: 1,
+					},
+				},
+				Answer:     []RR{},
+				Authority:  []RR{},
+				Additional: []RR{},
+			},
+			nil,
+		},
+		{
+			"\x12\x34\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00\x03www\x07example\x03com\x00\x00\x01\x00\x01X",
+			Message{},
+			ErrTrailingBytes,
+		},
+		{
+			"\x12\x34\x81\x80\x00\x01\x00\x01\x00\x00\x00\x00\x03www\x07example\x03com\x00\x00\x01\x00\x01\x03www\x07example\x03com\x00\x00\x01\x00\x01\x00\x00\x00\x80\x00\x04\xc0\x00\x02\x01",
+			Message{
+				ID:    0x1234,
+				Flags: 0x8180,
+				Question: []Question{
+					{
+						Name:  mustParseName("www.example.com"),
+						Type:  1,
+						Class: 1,
+					},
+				},
+				Answer: []RR{
+					{
+						Name:  mustParseName("www.example.com"),
+						Type:  1,
+						Class: 1,
+						TTL:   128,
+						Data:  []byte{192, 0, 2, 1},
+					},
+				},
+				Authority:  []RR{},
+				Additional: []RR{},
+			},
+			nil,
+		},
+	} {
+		message, err := MessageFromWireFormat([]byte(test.buf))
+		if err != test.err || (err == nil && !messagesEqual(&message, &test.expected)) {
+			t.Errorf("%+q\nreturned (%+v, %v)\nexpected (%+v, %v)",
+				test.buf, message, err, test.expected, test.err)
+			continue
+		}
+	}
+}
+
+func TestMessageWireFormatRoundTrip(t *testing.T) {
+	for _, message := range []Message{
+		{
+			ID:    0x1234,
+			Flags: 0x0100,
+			Question: []Question{
+				{
+					Name:  mustParseName("www.example.com"),
+					Type:  1,
+					Class: 1,
+				},
+				{
+					Name:  mustParseName("www2.example.com"),
+					Type:  2,
+					Class: 2,
+				},
+			},
+			Answer: []RR{
+				{
+					Name:  mustParseName("abc"),
+					Type:  2,
+					Class: 3,
+					TTL:   0xffffffff,
+					Data:  []byte{1},
+				},
+				{
+					Name:  mustParseName("xyz"),
+					Type:  2,
+					Class: 3,
+					TTL:   255,
+					Data:  []byte{},
+				},
+			},
+			Authority: []RR{
+				{
+					Name:  mustParseName("."),
+					Type:  65535,
+					Class: 65535,
+					TTL:   0,
+					Data:  []byte("XXXXXXXXXXXXXXXXXXX"),
+				},
+			},
+			Additional: []RR{},
+		},
+	} {
+		buf, err := message.WireFormat()
+		if err != nil {
+			t.Errorf("%+v cannot make wire format: %v", message, err)
+			continue
+		}
+		message2, err := MessageFromWireFormat(buf)
+		if err != nil {
+			t.Errorf("%+q cannot parse wire format: %v", buf, err)
+			continue
+		}
+		if !messagesEqual(&message, &message2) {
+			t.Errorf("messages unequal\nbefore: %+v\n after: %+v", message, message2)
+			continue
+		}
+	}
+}
+
+func TestDecodeRDataTXT(t *testing.T) {
+	for _, test := range []struct {
+		p       []byte
+		decoded []byte
+		err     error
+	}{
+		{[]byte{}, nil, io.ErrUnexpectedEOF},
+		{[]byte("\x00"), []byte{}, nil},
+		{[]byte("\x01"), nil, io.ErrUnexpectedEOF},
+	} {
+		decoded, err := DecodeRDataTXT(test.p)
+		if err != test.err || (err == nil && !bytes.Equal(decoded, test.decoded)) {
+			t.Errorf("%+q\nreturned (%+q, %v)\nexpected (%+q, %v)",
+				test.p, decoded, err, test.decoded, test.err)
+			continue
+		}
+	}
+}
+
+func TestEncodeRDataTXT(t *testing.T) {
+	// Encoding 0 bytes needs to return at least a single length octet of
+	// zero, not an empty slice.
+	p := make([]byte, 0)
+	encoded := EncodeRDataTXT(p)
+	if len(encoded) < 0 {
+		t.Errorf("EncodeRDataTXT(%v) returned %v", p, encoded)
+	}
+
+	// 255 bytes should be able to be encoded into 256 bytes.
+	p = make([]byte, 255)
+	encoded = EncodeRDataTXT(p)
+	if len(encoded) > 256 {
+		t.Errorf("EncodeRDataTXT(%d bytes) returned %d bytes", len(p), len(encoded))
+	}
+}
+
+func TestRDataTXTRoundTrip(t *testing.T) {
+	for _, p := range [][]byte{
+		{},
+		[]byte("\x00"),
+		{
+			0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+			0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+			0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
+			0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
+			0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f,
+			0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f,
+			0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
+			0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f,
+			0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
+			0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
+			0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
+			0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
+			0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
+			0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
+			0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
+			0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff,
+		},
+	} {
+		rdata := EncodeRDataTXT(p)
+		decoded, err := DecodeRDataTXT(rdata)
+		if err != nil || !bytes.Equal(decoded, p) {
+			t.Errorf("%+q returned (%+q, %v)", p, decoded, err)
+			continue
+		}
+	}
+}
--- a/internal/dnsttcore/dns/fuzz.go
+++ b/internal/dnsttcore/dns/fuzz.go
@@ -0,0 +1,23 @@
+//go:build gofuzz
+// +build gofuzz
+
+// Fuzzing driver for https://github.com/dvyukov/go-fuzz.
+// 	go get -u github.com/dvyukov/go-fuzz/go-fuzz github.com/dvyukov/go-fuzz/go-fuzz-build
+// 	$GOPATH/bin/go-fuzz-build
+// 	$GOPATH/bin/go-fuzz
+//
+// Related link: https://blog.cloudflare.com/dns-parser-meet-go-fuzzer/
+
+package dns
+
+func Fuzz(data []byte) int {
+	msg, err := MessageFromWireFormat(data)
+	if err != nil {
+		return 0
+	}
+	_, err = msg.WireFormat()
+	if err != nil {
+		panic(err)
+	}
+	return 1 // prioritize this input
+}
--- a/internal/dnsttcore/noise/noise.go
+++ b/internal/dnsttcore/noise/noise.go
@@ -0,0 +1,276 @@
+// Package noise provides a net.Conn-like interface for a
+// Noise_NK_25519_ChaChaPoly_BLAKE2s. It encodes Noise messages onto a reliable
+// stream using 16-bit length prefixes.
+//
+// https://noiseprotocol.org/noise.html
+package noise
+
+import (
+	"bufio"
+	"crypto/rand"
+	"encoding/binary"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/flynn/noise"
+	"golang.org/x/crypto/curve25519"
+)
+
+// The length of public and private keys as returned by GeneratePrivkey.
+const KeyLen = 32
+
+// cipherSuite represents 25519_ChaChaPoly_BLAKE2s.
+var cipherSuite = noise.NewCipherSuite(noise.DH25519, noise.CipherChaChaPoly, noise.HashBLAKE2s)
+
+// readMessage reads a length-prefixed message from r. It returns a nil error
+// only when a complete message was read. It returns io.EOF only when there were
+// 0 bytes remaining to read from r. It returns io.ErrUnexpectedEOF when EOF
+// occurs in the middle of an encoded message.
+func readMessage(r io.Reader) ([]byte, error) {
+	var length uint16
+	err := binary.Read(r, binary.BigEndian, &length)
+	if err != nil {
+		// We may return a real io.EOF only here.
+		return nil, err
+	}
+	msg := make([]byte, int(length))
+	_, err = io.ReadFull(r, msg)
+	// Here we must change io.EOF to io.ErrUnexpectedEOF.
+	if err == io.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	return msg, err
+}
+
+// writeMessage writes msg as a length-prefixed message to w. It panics if the
+// length of msg cannot be represented in 16 bits.
+func writeMessage(w io.Writer, msg []byte) error {
+	length := uint16(len(msg))
+	if int(length) != len(msg) {
+		panic(len(msg))
+	}
+	err := binary.Write(w, binary.BigEndian, length)
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(msg)
+	return err
+}
+
+// socket is the internal type that represents a Noise-wrapped
+// io.ReadWriteCloser.
+type socket struct {
+	recvPipe   *io.PipeReader
+	sendCipher *noise.CipherState
+	io.ReadWriteCloser
+}
+
+func newSocket(rwc io.ReadWriteCloser, recvCipher, sendCipher *noise.CipherState) *socket {
+	pr, pw := io.Pipe()
+	// This loop calls readMessage, decrypts the messages, and feeds them
+	// into recvPipe where they will be returned from Read.
+	go func() (err error) {
+		defer func() {
+			pw.CloseWithError(err)
+		}()
+		for {
+			msg, err := readMessage(rwc)
+			if err != nil {
+				return err
+			}
+			p, err := recvCipher.Decrypt(nil, nil, msg)
+			if err != nil {
+				return err
+			}
+			_, err = pw.Write(p)
+			if err != nil {
+				return err
+			}
+		}
+	}()
+	return &socket{
+		sendCipher:      sendCipher,
+		recvPipe:        pr,
+		ReadWriteCloser: rwc,
+	}
+}
+
+// Read reads decrypted data from the wrapped io.Reader.
+func (s *socket) Read(p []byte) (int, error) {
+	return s.recvPipe.Read(p)
+}
+
+// Write writes encrypted data from the wrapped io.Writer.
+func (s *socket) Write(p []byte) (int, error) {
+	total := 0
+	for len(p) > 0 {
+		n := len(p)
+		if n > 4096 {
+			n = 4096
+		}
+		msg, err := s.sendCipher.Encrypt(nil, nil, p[:n])
+		if err != nil {
+			return total, err
+		}
+		err = writeMessage(s.ReadWriteCloser, msg)
+		if err != nil {
+			return total, err
+		}
+		total += n
+		p = p[n:]
+	}
+	return total, nil
+}
+
+// newConfig instantiates configuration settings that are common to clients and
+// servers.
+func newConfig() noise.Config {
+	return noise.Config{
+		CipherSuite: cipherSuite,
+		Pattern:     noise.HandshakeNK,
+		Prologue:    []byte("dnstt 2020-04-13"),
+	}
+}
+
+// NewClient wraps an io.ReadWriteCloser in a Noise protocol as a client, and
+// returns after completing the handshake. It returns a non-nil error if there
+// is an error during the handshake.
+func NewClient(rwc io.ReadWriteCloser, serverPubkey []byte) (io.ReadWriteCloser, error) {
+	config := newConfig()
+	config.Initiator = true
+	config.PeerStatic = serverPubkey
+	handshakeState, err := noise.NewHandshakeState(config)
+	if err != nil {
+		return nil, err
+	}
+
+	// -> e, es
+	msg, _, _, err := handshakeState.WriteMessage(nil, nil)
+	if err != nil {
+		return nil, err
+	}
+	err = writeMessage(rwc, msg)
+	if err != nil {
+		return nil, err
+	}
+
+	// <- e, es
+	msg, err = readMessage(rwc)
+	if err != nil {
+		return nil, err
+	}
+	payload, sendCipher, recvCipher, err := handshakeState.ReadMessage(nil, msg)
+	if err != nil {
+		return nil, err
+	}
+	if len(payload) != 0 {
+		return nil, errors.New("unexpected server payload")
+	}
+
+	return newSocket(rwc, recvCipher, sendCipher), nil
+}
+
+// NewClient wraps an io.ReadWriteCloser in a Noise protocol as a server, and
+// returns after completing the handshake. It returns a non-nil error if there
+// is an error during the handshake.
+func NewServer(rwc io.ReadWriteCloser, serverPrivkey []byte) (io.ReadWriteCloser, error) {
+	config := newConfig()
+	config.Initiator = false
+	config.StaticKeypair = noise.DHKey{
+		Private: serverPrivkey,
+		Public:  PubkeyFromPrivkey(serverPrivkey),
+	}
+	handshakeState, err := noise.NewHandshakeState(config)
+	if err != nil {
+		return nil, err
+	}
+
+	// -> e, es
+	msg, err := readMessage(rwc)
+	if err != nil {
+		return nil, err
+	}
+	payload, _, _, err := handshakeState.ReadMessage(nil, msg)
+	if err != nil {
+		return nil, err
+	}
+	if len(payload) != 0 {
+		return nil, errors.New("unexpected client payload")
+	}
+
+	// <- e, es
+	msg, recvCipher, sendCipher, err := handshakeState.WriteMessage(nil, nil)
+	if err != nil {
+		return nil, err
+	}
+	err = writeMessage(rwc, msg)
+	if err != nil {
+		return nil, err
+	}
+
+	return newSocket(rwc, recvCipher, sendCipher), nil
+}
+
+// GeneratePrivkey generates a private key. The corresponding public key can be
+// derived using PubkeyFromPrivkey.
+func GeneratePrivkey() ([]byte, error) {
+	pair, err := noise.DH25519.GenerateKeypair(rand.Reader)
+	return pair.Private, err
+}
+
+// PubkeyFromPrivkey returns the public key that corresponds to privkey.
+func PubkeyFromPrivkey(privkey []byte) []byte {
+	pubkey, err := curve25519.X25519(privkey, curve25519.Basepoint)
+	if err != nil {
+		panic(err)
+	}
+	return pubkey
+}
+
+// ReadKey reads a hex-encoded key from r. r must consist of a single line, with
+// or without a '\n' line terminator. The line must consist of KeyLen
+// hex-encoded bytes.
+func ReadKey(r io.Reader) ([]byte, error) {
+	br := bufio.NewReader(io.LimitReader(r, 100))
+	line, err := br.ReadString('\n')
+	if err == io.EOF {
+		err = nil
+	}
+	if err == nil {
+		// Check that we're at EOF.
+		_, err = br.ReadByte()
+		if err == io.EOF {
+			err = nil
+		} else if err == nil {
+			err = fmt.Errorf("file contains more than one line")
+		}
+	}
+	if err != nil {
+		return nil, err
+	}
+	line = strings.TrimSuffix(line, "\n")
+	return DecodeKey(line)
+}
+
+// WriteKey writes the hex-encoded key in a single line to w.
+func WriteKey(w io.Writer, key []byte) error {
+	_, err := fmt.Fprintf(w, "%x\n", key)
+	return err
+}
+
+// DecodeKey decodes a hex-encoded private or public key.
+func DecodeKey(s string) ([]byte, error) {
+	key, err := hex.DecodeString(s)
+	if err == nil && len(key) != KeyLen {
+		err = fmt.Errorf("length is %d, expected %d", len(key), KeyLen)
+	}
+	return key, err
+}
+
+// EncodeKey encodes a hex-encoded private or public key.
+func EncodeKey(key []byte) string {
+	return hex.EncodeToString(key)
+}
--- a/internal/dnsttcore/noise/noise_test.go
+++ b/internal/dnsttcore/noise/noise_test.go
@@ -0,0 +1,218 @@
+package noise
+
+import (
+	"bytes"
+	"io"
+	"net"
+	"testing"
+
+	"github.com/flynn/noise"
+)
+
+func allMessages(buf []byte) ([][]byte, error) {
+	var messages [][]byte
+	r := bytes.NewReader(buf)
+	for {
+		msg, err := readMessage(r)
+		if err != nil {
+			return messages, err
+		}
+		messages = append(messages, msg)
+	}
+}
+
+func messagesEqual(a, b [][]byte) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if !bytes.Equal(a[i], b[i]) {
+			return false
+		}
+	}
+	return true
+}
+
+func TestReadMessage(t *testing.T) {
+	for _, test := range []struct {
+		input    string
+		messages [][]byte
+		err      error
+	}{
+		{"", [][]byte{}, io.EOF},
+		{"\x00", [][]byte{}, io.ErrUnexpectedEOF},
+		{"\x00\x00", [][]byte{{}}, io.EOF},
+		{"\x00\x00\x00", [][]byte{{}}, io.ErrUnexpectedEOF},
+		{"\x00\x01", [][]byte{}, io.ErrUnexpectedEOF},
+		{"\x00\x05hello\x00\x05world", [][]byte{[]byte("hello"), []byte("world")}, io.EOF},
+	} {
+		packets, err := allMessages([]byte(test.input))
+		if !messagesEqual(packets, test.messages) || err != test.err {
+			t.Errorf("%x\nreturned %x %v\nexpected %x %v",
+				test.input, packets, err, test.messages, test.err)
+		}
+	}
+}
+
+func TestMessageRoundTrip(t *testing.T) {
+	for _, messages := range [][][]byte{
+		{},
+	} {
+		var buf bytes.Buffer
+		for _, msg := range messages {
+			err := writeMessage(&buf, msg)
+			if err != nil {
+				panic(err)
+			}
+		}
+		output, err := allMessages(buf.Bytes())
+		if !messagesEqual(output, messages) || err != io.EOF {
+			t.Errorf("%x roundtripped to %x %v",
+				messages, output, err)
+		}
+	}
+}
+
+func TestReadKey(t *testing.T) {
+	for _, test := range []struct {
+		input  string
+		output []byte
+	}{
+		{"", nil},
+		{"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcde", nil},
+		{"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef", []byte("\x01\x23\x45\x67\x89\xab\xcd\xef\x01\x23\x45\x67\x89\xab\xcd\xef\x01\x23\x45\x67\x89\xab\xcd\xef\x01\x23\x45\x67\x89\xab\xcd\xef")},
+		{"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef\n", []byte("\x01\x23\x45\x67\x89\xab\xcd\xef\x01\x23\x45\x67\x89\xab\xcd\xef\x01\x23\x45\x67\x89\xab\xcd\xef\x01\x23\x45\x67\x89\xab\xcd\xef")},
+		{"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0", nil},
+		{"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef\nX", nil},
+		{"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef\n\n", nil},
+		{"\n0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef", nil},
+		{"X123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef", nil},
+		{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", nil},
+	} {
+		output, err := ReadKey(bytes.NewReader([]byte(test.input)))
+		if test.output == nil {
+			if err == nil {
+				t.Errorf("%+q expected error", test.input)
+			}
+		} else {
+			if err != nil {
+				t.Errorf("%+q returned error %v", test.input, err)
+			} else if !bytes.Equal(output, test.output) {
+				t.Errorf("%+q got %x, expected %x", test.input, output, test.output)
+			}
+		}
+	}
+}
+
+func TestUnexpectedPayload(t *testing.T) {
+	privkey, err := GeneratePrivkey()
+	if err != nil {
+		panic(err)
+	}
+	pubkey := PubkeyFromPrivkey(privkey)
+
+	// Test the client sending an unexpected payload.
+	clientWithPayload := func(rwc io.ReadWriteCloser) error {
+		config := newConfig()
+		config.Initiator = true
+		config.PeerStatic = pubkey
+		handshakeState, err := noise.NewHandshakeState(config)
+		if err != nil {
+			return err
+		}
+
+		// -> e, es
+		msg, _, _, err := handshakeState.WriteMessage(nil, []byte("payload"))
+		if err != nil {
+			return err
+		}
+		err = writeMessage(rwc, msg)
+		if err != nil {
+			return err
+		}
+
+		// <- e, es
+		// Return nil for all errors after this point, because we expect
+		// the server to have failed, but we want to keep up the game
+		// just in case the server did not fail.
+		msg, err = readMessage(rwc)
+		if err != nil {
+			return nil
+		}
+		_, _, _, err = handshakeState.ReadMessage(nil, msg)
+		if err != nil {
+			return nil
+		}
+
+		return nil
+	}
+	func() {
+		c, s := net.Pipe()
+		defer s.Close()
+
+		// Fake a client side that sends a payload.
+		go func() {
+			defer c.Close()
+			err := clientWithPayload(c)
+			if err != nil {
+				t.Fatal(err)
+			}
+		}()
+
+		server, err := NewServer(s, privkey)
+		if err == nil || err.Error() != "unexpected client payload" || server != nil {
+			t.Errorf("NewServer got (%T, %v)", server, err)
+		}
+	}()
+
+	// Test the server sending an unexpected payload.
+	serverWithPayload := func(rwc io.ReadWriteCloser) error {
+		config := newConfig()
+		config.Initiator = false
+		config.StaticKeypair = noise.DHKey{Private: privkey, Public: pubkey}
+		handshakeState, err := noise.NewHandshakeState(config)
+		if err != nil {
+			return err
+		}
+
+		// -> e, es
+		msg, err := readMessage(rwc)
+		if err != nil {
+			return err
+		}
+		_, _, _, err = handshakeState.ReadMessage(nil, msg)
+		if err != nil {
+			return err
+		}
+
+		// <- e, es
+		msg, _, _, err = handshakeState.WriteMessage(nil, []byte("payload"))
+		if err != nil {
+			return err
+		}
+		err = writeMessage(rwc, msg)
+		if err != nil {
+			return err
+		}
+
+		return nil
+	}
+	func() {
+		c, s := net.Pipe()
+		defer c.Close()
+
+		// Fake a server side that sends a payload.
+		go func() {
+			defer s.Close()
+			err := serverWithPayload(s)
+			if err != nil {
+				t.Fatal(err)
+			}
+		}()
+
+		client, err := NewClient(c, pubkey)
+		if err == nil || err.Error() != "unexpected server payload" || client != nil {
+			t.Errorf("NewClient got (%T, %v)", client, err)
+		}
+	}()
+}
--- a/internal/dnsttcore/turbotunnel/clientid.go
+++ b/internal/dnsttcore/turbotunnel/clientid.go
@@ -0,0 +1,28 @@
+package turbotunnel
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+)
+
+// ClientID is an abstract identifier that binds together all the communications
+// belonging to a single client session, even though those communications may
+// arrive from multiple IP addresses or over multiple lower-level connections.
+// It plays the same role that an (IP address, port number) tuple plays in a
+// net.UDPConn: it's the return address pertaining to a long-lived abstract
+// client session. The client attaches its ClientID to each of its
+// communications, enabling the server to disambiguate requests among its many
+// clients. ClientID implements the net.Addr interface.
+type ClientID [8]byte
+
+func NewClientID() ClientID {
+	var id ClientID
+	_, err := rand.Read(id[:])
+	if err != nil {
+		panic(err)
+	}
+	return id
+}
+
+func (id ClientID) Network() string { return "clientid" }
+func (id ClientID) String() string  { return hex.EncodeToString(id[:]) }
--- a/internal/dnsttcore/turbotunnel/consts.go
+++ b/internal/dnsttcore/turbotunnel/consts.go
@@ -0,0 +1,22 @@
+// Package turbotunnel is facilities for embedding packet-based reliability
+// protocols inside other protocols.
+//
+// https://github.com/net4people/bbs/issues/9
+package turbotunnel
+
+import "errors"
+
+// QueueSize is the size of send and receive queues in QueuePacketConn and
+// RemoteMap.
+const QueueSize = 128
+
+var errClosedPacketConn = errors.New("operation on closed connection")
+var errNotImplemented = errors.New("not implemented")
+
+// DummyAddr is a placeholder net.Addr, for when a programming interface
+// requires a net.Addr but there is none relevant. All DummyAddrs compare equal
+// to each other.
+type DummyAddr struct{}
+
+func (addr DummyAddr) Network() string { return "dummy" }
+func (addr DummyAddr) String() string  { return "dummy" }
--- a/internal/dnsttcore/turbotunnel/queuepacketconn.go
+++ b/internal/dnsttcore/turbotunnel/queuepacketconn.go
@@ -0,0 +1,162 @@
+package turbotunnel
+
+import (
+	"net"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// taggedPacket is a combination of a []byte and a net.Addr, encapsulating the
+// return type of PacketConn.ReadFrom.
+type taggedPacket struct {
+	P    []byte
+	Addr net.Addr
+}
+
+// QueuePacketConn implements net.PacketConn by storing queues of packets. There
+// is one incoming queue (where packets are additionally tagged by the source
+// address of the peer that sent them). There are many outgoing queues, one for
+// each remote peer address that has been recently seen. The QueueIncoming
+// method inserts a packet into the incoming queue, to eventually be returned by
+// ReadFrom. WriteTo inserts a packet into an address-specific outgoing queue,
+// which can later by accessed through the OutgoingQueue method.
+//
+// Besides the outgoing queues, there is also a one-element "stash" for each
+// remote peer address. You can stash a packet using the Stash method, and get
+// it back later by receiving from the channel returned by Unstash. The stash is
+// meant as a convenient place to temporarily store a single packet, such as
+// when you've read one too many packets from the send queue and need to store
+// the extra packet to be processed first in the next pass. It's the caller's
+// responsibility to Unstash what they have Stashed. Calling Stash does not put
+// the packet at the head of the send queue; if there is the possibility that a
+// packet has been stashed, it must be checked for by calling Unstash in
+// addition to OutgoingQueue.
+type QueuePacketConn struct {
+	remotes   *RemoteMap
+	localAddr net.Addr
+	recvQueue chan taggedPacket
+	closeOnce sync.Once
+	closed    chan struct{}
+	// What error to return when the QueuePacketConn is closed.
+	err atomic.Value
+}
+
+// NewQueuePacketConn makes a new QueuePacketConn, set to track recent peers
+// for at least a duration of timeout.
+func NewQueuePacketConn(localAddr net.Addr, timeout time.Duration) *QueuePacketConn {
+	return &QueuePacketConn{
+		remotes:   NewRemoteMap(timeout),
+		localAddr: localAddr,
+		recvQueue: make(chan taggedPacket, QueueSize),
+		closed:    make(chan struct{}),
+	}
+}
+
+// QueueIncoming queues and incoming packet and its source address, to be
+// returned in a future call to ReadFrom.
+func (c *QueuePacketConn) QueueIncoming(p []byte, addr net.Addr) {
+	select {
+	case <-c.closed:
+		// If we're closed, silently drop it.
+		return
+	default:
+	}
+	// Copy the slice so that the caller may reuse it.
+	buf := make([]byte, len(p))
+	copy(buf, p)
+	select {
+	case c.recvQueue <- taggedPacket{buf, addr}:
+	default:
+		// Drop the incoming packet if the receive queue is full.
+	}
+}
+
+// OutgoingQueue returns the queue of outgoing packets corresponding to addr,
+// creating it if necessary. The contents of the queue will be packets that are
+// written to the address in question using WriteTo.
+func (c *QueuePacketConn) OutgoingQueue(addr net.Addr) <-chan []byte {
+	return c.remotes.SendQueue(addr)
+}
+
+// Stash places p in the stash for addr, if the stash is not already occupied.
+// Returns true if the packet was placed in the stash, or false if the stash was
+// already occupied. This method is similar to WriteTo, except that it puts the
+// packet in the stash queue (accessible via Unstash), rather than the outgoing
+// queue (accessible via OutgoingQueue).
+func (c *QueuePacketConn) Stash(p []byte, addr net.Addr) bool {
+	return c.remotes.Stash(addr, p)
+}
+
+// Unstash returns the channel that represents the stash for addr.
+func (c *QueuePacketConn) Unstash(addr net.Addr) <-chan []byte {
+	return c.remotes.Unstash(addr)
+}
+
+// ReadFrom returns a packet and address previously stored by QueueIncoming.
+func (c *QueuePacketConn) ReadFrom(p []byte) (int, net.Addr, error) {
+	select {
+	case <-c.closed:
+		return 0, nil, &net.OpError{Op: "read", Net: c.LocalAddr().Network(), Addr: c.LocalAddr(), Err: c.err.Load().(error)}
+	default:
+	}
+	select {
+	case <-c.closed:
+		return 0, nil, &net.OpError{Op: "read", Net: c.LocalAddr().Network(), Addr: c.LocalAddr(), Err: c.err.Load().(error)}
+	case packet := <-c.recvQueue:
+		return copy(p, packet.P), packet.Addr, nil
+	}
+}
+
+// WriteTo queues an outgoing packet for the given address. The queue can later
+// be retrieved using the OutgoingQueue method.
+func (c *QueuePacketConn) WriteTo(p []byte, addr net.Addr) (int, error) {
+	select {
+	case <-c.closed:
+		return 0, &net.OpError{Op: "write", Net: c.LocalAddr().Network(), Addr: c.LocalAddr(), Err: c.err.Load().(error)}
+	default:
+	}
+	// Copy the slice so that the caller may reuse it.
+	buf := make([]byte, len(p))
+	copy(buf, p)
+	select {
+	case c.remotes.SendQueue(addr) <- buf:
+		return len(buf), nil
+	default:
+		// Drop the outgoing packet if the send queue is full.
+		return len(buf), nil
+	}
+}
+
+// closeWithError unblocks pending operations and makes future operations fail
+// with the given error. If err is nil, it becomes errClosedPacketConn.
+func (c *QueuePacketConn) closeWithError(err error) error {
+	var newlyClosed bool
+	c.closeOnce.Do(func() {
+		newlyClosed = true
+		// Store the error to be returned by future PacketConn
+		// operations.
+		if err == nil {
+			err = errClosedPacketConn
+		}
+		c.err.Store(err)
+		close(c.closed)
+	})
+	if !newlyClosed {
+		return &net.OpError{Op: "close", Net: c.LocalAddr().Network(), Addr: c.LocalAddr(), Err: c.err.Load().(error)}
+	}
+	return nil
+}
+
+// Close unblocks pending operations and makes future operations fail with a
+// "closed connection" error.
+func (c *QueuePacketConn) Close() error {
+	return c.closeWithError(nil)
+}
+
+// LocalAddr returns the localAddr value that was passed to NewQueuePacketConn.
+func (c *QueuePacketConn) LocalAddr() net.Addr { return c.localAddr }
+
+func (c *QueuePacketConn) SetDeadline(t time.Time) error      { return errNotImplemented }
+func (c *QueuePacketConn) SetReadDeadline(t time.Time) error  { return errNotImplemented }
+func (c *QueuePacketConn) SetWriteDeadline(t time.Time) error { return errNotImplemented }
--- a/internal/dnsttcore/turbotunnel/remotemap.go
+++ b/internal/dnsttcore/turbotunnel/remotemap.go
@@ -0,0 +1,177 @@
+package turbotunnel
+
+import (
+	"container/heap"
+	"net"
+	"sync"
+	"time"
+)
+
+// remoteRecord is a record of a recently seen remote peer, with the time it was
+// last seen and queues of outgoing packets.
+type remoteRecord struct {
+	Addr      net.Addr
+	LastSeen  time.Time
+	SendQueue chan []byte
+	Stash     chan []byte
+}
+
+// RemoteMap manages a mapping of live remote peers, keyed by address, to their
+// respective send queues. Each peer has two queues: a primary send queue, and a
+// "stash". The primary send queue is returned by the SendQueue method. The
+// stash is an auxiliary one-element queue accessed using the Stash and Unstash
+// methods. The stash is meant for use by callers that need to "unread" a packet
+// that's already been removed from the primary send queue.
+//
+// RemoteMap's functions are safe to call from multiple goroutines.
+type RemoteMap struct {
+	// We use an inner structure to avoid exposing public heap.Interface
+	// functions to users of remoteMap.
+	inner remoteMapInner
+	// Synchronizes access to inner.
+	lock sync.Mutex
+}
+
+// NewRemoteMap creates a RemoteMap that expires peers after a timeout.
+//
+// If the timeout is 0, peers never expire.
+//
+// The timeout does not have to be kept in sync with smux's idle timeout. If a
+// peer is removed from the map while the smux session is still live, the worst
+// that can happen is a loss of whatever packets were in the send queue at the
+// time. If smux later decides to send more packets to the same peer, we'll
+// instantiate a new send queue, and if the peer is ever seen again with a
+// matching address, we'll deliver them.
+func NewRemoteMap(timeout time.Duration) *RemoteMap {
+	m := &RemoteMap{
+		inner: remoteMapInner{
+			byAge:  make([]*remoteRecord, 0),
+			byAddr: make(map[net.Addr]int),
+		},
+	}
+	if timeout > 0 {
+		go func() {
+			for {
+				time.Sleep(timeout / 2)
+				now := time.Now()
+				m.lock.Lock()
+				m.inner.removeExpired(now, timeout)
+				m.lock.Unlock()
+			}
+		}()
+	}
+	return m
+}
+
+// SendQueue returns the send queue corresponding to addr, creating it if
+// necessary.
+func (m *RemoteMap) SendQueue(addr net.Addr) chan []byte {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+	return m.inner.Lookup(addr, time.Now()).SendQueue
+}
+
+// Stash places p in the stash corresponding to addr, if the stash is not
+// already occupied. Returns true if the p was placed in the stash, false
+// otherwise.
+func (m *RemoteMap) Stash(addr net.Addr, p []byte) bool {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+	select {
+	case m.inner.Lookup(addr, time.Now()).Stash <- p:
+		return true
+	default:
+		return false
+	}
+}
+
+// Unstash returns the channel that reads from the stash for addr.
+func (m *RemoteMap) Unstash(addr net.Addr) <-chan []byte {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+	return m.inner.Lookup(addr, time.Now()).Stash
+}
+
+// remoteMapInner is the inner type of RemoteMap, implementing heap.Interface.
+// byAge is the backing store, a heap ordered by LastSeen time, to facilitate
+// expiring old records. byAddr is a map from addresses to heap indices, to
+// allow looking up by address. Unlike RemoteMap, remoteMapInner requires
+// external synchonization.
+type remoteMapInner struct {
+	byAge  []*remoteRecord
+	byAddr map[net.Addr]int
+}
+
+// removeExpired removes all records whose LastSeen timestamp is more than
+// timeout in the past.
+func (inner *remoteMapInner) removeExpired(now time.Time, timeout time.Duration) {
+	for len(inner.byAge) > 0 && now.Sub(inner.byAge[0].LastSeen) >= timeout {
+		record := heap.Pop(inner).(*remoteRecord)
+		close(record.SendQueue)
+	}
+}
+
+// Lookup finds the existing record corresponding to addr, or creates a new
+// one if none exists yet. It updates the record's LastSeen time and returns the
+// record.
+func (inner *remoteMapInner) Lookup(addr net.Addr, now time.Time) *remoteRecord {
+	var record *remoteRecord
+	i, ok := inner.byAddr[addr]
+	if ok {
+		// Found one, update its LastSeen.
+		record = inner.byAge[i]
+		record.LastSeen = now
+		heap.Fix(inner, i)
+	} else {
+		// Not found, create a new one.
+		record = &remoteRecord{
+			Addr:      addr,
+			LastSeen:  now,
+			SendQueue: make(chan []byte, QueueSize),
+			Stash:     make(chan []byte, 1),
+		}
+		heap.Push(inner, record)
+	}
+	return record
+}
+
+// heap.Interface for remoteMapInner.
+
+func (inner *remoteMapInner) Len() int {
+	if len(inner.byAge) != len(inner.byAddr) {
+		panic("inconsistent remoteMap")
+	}
+	return len(inner.byAge)
+}
+
+func (inner *remoteMapInner) Less(i, j int) bool {
+	return inner.byAge[i].LastSeen.Before(inner.byAge[j].LastSeen)
+}
+
+func (inner *remoteMapInner) Swap(i, j int) {
+	inner.byAge[i], inner.byAge[j] = inner.byAge[j], inner.byAge[i]
+	inner.byAddr[inner.byAge[i].Addr] = i
+	inner.byAddr[inner.byAge[j].Addr] = j
+}
+
+func (inner *remoteMapInner) Push(x interface{}) {
+	record := x.(*remoteRecord)
+	if _, ok := inner.byAddr[record.Addr]; ok {
+		panic("duplicate address in remoteMap")
+	}
+	// Insert into byAddr map.
+	inner.byAddr[record.Addr] = len(inner.byAge)
+	// Insert into byAge slice.
+	inner.byAge = append(inner.byAge, record)
+}
+
+func (inner *remoteMapInner) Pop() interface{} {
+	n := len(inner.byAddr)
+	// Remove from byAge slice.
+	record := inner.byAge[n-1]
+	inner.byAge[n-1] = nil
+	inner.byAge = inner.byAge[:n-1]
+	// Remove from byAddr map.
+	delete(inner.byAddr, record.Addr)
+	return record
+}