Update deps

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

@@ -0,0 +1,773 @@
+package dns
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"net"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+type SVCBKey uint16
+
+// Keys defined in draft-ietf-dnsop-svcb-https-02 Section 11.1.2
+const (
+	SVCB_MANDATORY       SVCBKey = 0
+	SVCB_ALPN            SVCBKey = 1
+	SVCB_NO_DEFAULT_ALPN SVCBKey = 2
+	SVCB_PORT            SVCBKey = 3
+	SVCB_IPV4HINT        SVCBKey = 4
+	SVCB_ECHCONFIG       SVCBKey = 5
+	SVCB_IPV6HINT        SVCBKey = 6
+	svcb_RESERVED        SVCBKey = 65535
+)
+
+var svcbKeyToStringMap = map[SVCBKey]string{
+	SVCB_MANDATORY:       "mandatory",
+	SVCB_ALPN:            "alpn",
+	SVCB_NO_DEFAULT_ALPN: "no-default-alpn",
+	SVCB_PORT:            "port",
+	SVCB_IPV4HINT:        "ipv4hint",
+	SVCB_ECHCONFIG:       "echconfig",
+	SVCB_IPV6HINT:        "ipv6hint",
+}
+
+var svcbStringToKeyMap = reverseSVCBKeyMap(svcbKeyToStringMap)
+
+func reverseSVCBKeyMap(m map[SVCBKey]string) map[string]SVCBKey {
+	n := make(map[string]SVCBKey, len(m))
+	for u, s := range m {
+		n[s] = u
+	}
+	return n
+}
+
+// String takes the numerical code of an SVCB key and returns its name.
+// Returns an empty string for reserved keys.
+// Accepts unassigned keys as well as experimental/private keys.
+func (key SVCBKey) String() string {
+	if x := svcbKeyToStringMap[key]; x != "" {
+		return x
+	}
+	if key == svcb_RESERVED {
+		return ""
+	}
+	return "key" + strconv.FormatUint(uint64(key), 10)
+}
+
+// svcbStringToKey returns the numerical code of an SVCB key.
+// Returns svcb_RESERVED for reserved/invalid keys.
+// Accepts unassigned keys as well as experimental/private keys.
+func svcbStringToKey(s string) SVCBKey {
+	if strings.HasPrefix(s, "key") {
+		a, err := strconv.ParseUint(s[3:], 10, 16)
+		// no leading zeros
+		// key shouldn't be registered
+		if err != nil || a == 65535 || s[3] == '0' || svcbKeyToStringMap[SVCBKey(a)] != "" {
+			return svcb_RESERVED
+		}
+		return SVCBKey(a)
+	}
+	if key, ok := svcbStringToKeyMap[s]; ok {
+		return key
+	}
+	return svcb_RESERVED
+}
+
+func (rr *SVCB) parse(c *zlexer, o string) *ParseError {
+	l, _ := c.Next()
+	i, e := strconv.ParseUint(l.token, 10, 16)
+	if e != nil || l.err {
+		return &ParseError{l.token, "bad SVCB priority", l}
+	}
+	rr.Priority = uint16(i)
+
+	c.Next()        // zBlank
+	l, _ = c.Next() // zString
+	rr.Target = l.token
+
+	name, nameOk := toAbsoluteName(l.token, o)
+	if l.err || !nameOk {
+		return &ParseError{l.token, "bad SVCB Target", l}
+	}
+	rr.Target = name
+
+	// Values (if any)
+	l, _ = c.Next()
+	var xs []SVCBKeyValue
+	// Helps require whitespace between pairs.
+	// Prevents key1000="a"key1001=...
+	canHaveNextKey := true
+	for l.value != zNewline && l.value != zEOF {
+		switch l.value {
+		case zString:
+			if !canHaveNextKey {
+				// The key we can now read was probably meant to be
+				// a part of the last value.
+				return &ParseError{l.token, "bad SVCB value quotation", l}
+			}
+
+			// In key=value pairs, value does not have to be quoted unless value
+			// contains whitespace. And keys don't need to have values.
+			// Similarly, keys with an equality signs after them don't need values.
+			// l.token includes at least up to the first equality sign.
+			idx := strings.IndexByte(l.token, '=')
+			var key, value string
+			if idx < 0 {
+				// Key with no value and no equality sign
+				key = l.token
+			} else if idx == 0 {
+				return &ParseError{l.token, "bad SVCB key", l}
+			} else {
+				key, value = l.token[:idx], l.token[idx+1:]
+
+				if value == "" {
+					// We have a key and an equality sign. Maybe we have nothing
+					// after "=" or we have a double quote.
+					l, _ = c.Next()
+					if l.value == zQuote {
+						// Only needed when value ends with double quotes.
+						// Any value starting with zQuote ends with it.
+						canHaveNextKey = false
+
+						l, _ = c.Next()
+						switch l.value {
+						case zString:
+							// We have a value in double quotes.
+							value = l.token
+							l, _ = c.Next()
+							if l.value != zQuote {
+								return &ParseError{l.token, "SVCB unterminated value", l}
+							}
+						case zQuote:
+							// There's nothing in double quotes.
+						default:
+							return &ParseError{l.token, "bad SVCB value", l}
+						}
+					}
+				}
+			}
+			kv := makeSVCBKeyValue(svcbStringToKey(key))
+			if kv == nil {
+				return &ParseError{l.token, "bad SVCB key", l}
+			}
+			if err := kv.parse(value); err != nil {
+				return &ParseError{l.token, err.Error(), l}
+			}
+			xs = append(xs, kv)
+		case zQuote:
+			return &ParseError{l.token, "SVCB key can't contain double quotes", l}
+		case zBlank:
+			canHaveNextKey = true
+		default:
+			return &ParseError{l.token, "bad SVCB values", l}
+		}
+		l, _ = c.Next()
+	}
+	rr.Value = xs
+	if rr.Priority == 0 && len(xs) > 0 {
+		return &ParseError{l.token, "SVCB aliasform can't have values", l}
+	}
+	return nil
+}
+
+// makeSVCBKeyValue returns an SVCBKeyValue struct with the key
+// or nil for reserved keys.
+func makeSVCBKeyValue(key SVCBKey) SVCBKeyValue {
+	switch key {
+	case SVCB_MANDATORY:
+		return new(SVCBMandatory)
+	case SVCB_ALPN:
+		return new(SVCBAlpn)
+	case SVCB_NO_DEFAULT_ALPN:
+		return new(SVCBNoDefaultAlpn)
+	case SVCB_PORT:
+		return new(SVCBPort)
+	case SVCB_IPV4HINT:
+		return new(SVCBIPv4Hint)
+	case SVCB_ECHCONFIG:
+		return new(SVCBECHConfig)
+	case SVCB_IPV6HINT:
+		return new(SVCBIPv6Hint)
+	case svcb_RESERVED:
+		return nil
+	default:
+		e := new(SVCBLocal)
+		e.KeyCode = key
+		return e
+	}
+}
+
+// SVCB RR. See RFC xxxx (https://tools.ietf.org/html/draft-ietf-dnsop-svcb-https-00)
+
+// The one with the smallest priority should be given preference. Of those with
+// equal priority, a random one should be preferred for load balancing.
+type SVCB struct {
+	Hdr      RR_Header
+	Priority uint16
+	Target   string         `dns:"domain-name"`
+	Value    []SVCBKeyValue `dns:"pairs"` // This must be empty if Priority is non-zero
+}
+
+// HTTPS RR. Everything valid for SVCB applies to HTTPS as well
+// except that the HTTPS record is intended for use with the HTTP and HTTPS protocols.
+type HTTPS struct {
+	SVCB
+}
+
+func (rr *HTTPS) String() string {
+	return rr.SVCB.String()
+}
+
+func (rr *HTTPS) parse(c *zlexer, o string) *ParseError {
+	return rr.SVCB.parse(c, o)
+}
+
+// SVCBKeyValue defines a key=value pair for the SVCB RR type.
+// An SVCB RR can have multiple SVCBKeyValues appended to it.
+type SVCBKeyValue interface {
+	// Key returns the numerical key code.
+	Key() SVCBKey
+	// pack returns the encoded value.
+	pack() ([]byte, error)
+	// unpack sets the value.
+	unpack([]byte) error
+	// String returns the string representation of the value.
+	String() string
+	// parse sets the value to the given string representation of the value.
+	parse(string) error
+	// copy returns a deep-copy of the pair.
+	copy() SVCBKeyValue
+	// len returns the length of value in the wire format.
+	len() int
+}
+
+// SVCBMandatory pair adds to required keys that must be interpreted for the RR
+// to be functional.
+// Basic use pattern for creating a mandatory option:
+//
+//	o := new(dns.SVCB)
+//	o.Hdr.Name = "."
+//	o.Hdr.Rrtype = dns.TypeSVCB
+//	e := new(dns.SVCBMandatory)
+//	e.Code = []uint16{65403}
+//	o.Value = append(o.Value, e)
+//  // Then add key-value pair for key65403
+type SVCBMandatory struct {
+	Code []SVCBKey // Must not include mandatory
+}
+
+func (*SVCBMandatory) Key() SVCBKey { return SVCB_MANDATORY }
+
+func (s *SVCBMandatory) String() string {
+	str := make([]string, len(s.Code))
+	for i, e := range s.Code {
+		str[i] = e.String()
+	}
+	return strings.Join(str, ",")
+}
+
+func (s *SVCBMandatory) pack() ([]byte, error) {
+	codes := append([]SVCBKey(nil), s.Code...)
+	sort.Slice(codes, func(i, j int) bool {
+		return codes[i] < codes[j]
+	})
+	b := make([]byte, 2*len(codes))
+	for i, e := range codes {
+		binary.BigEndian.PutUint16(b[2*i:], uint16(e))
+	}
+	return b, nil
+}
+
+func (s *SVCBMandatory) unpack(b []byte) error {
+	if len(b)%2 != 0 {
+		return errors.New("dns: svcbmandatory: value length is not a multiple of 2")
+	}
+	codes := make([]SVCBKey, 0, len(b)/2)
+	for i := 0; i < len(b); i += 2 {
+		// We assume strictly increasing order.
+		codes = append(codes, SVCBKey(binary.BigEndian.Uint16(b[i:])))
+	}
+	s.Code = codes
+	return nil
+}
+
+func (s *SVCBMandatory) parse(b string) error {
+	str := strings.Split(b, ",")
+	codes := make([]SVCBKey, 0, len(str))
+	for _, e := range str {
+		codes = append(codes, svcbStringToKey(e))
+	}
+	s.Code = codes
+	return nil
+}
+
+func (s *SVCBMandatory) len() int {
+	return 2 * len(s.Code)
+}
+
+func (s *SVCBMandatory) copy() SVCBKeyValue {
+	return &SVCBMandatory{
+		append([]SVCBKey(nil), s.Code...),
+	}
+}
+
+// SVCBAlpn pair is used to list supported connection protocols.
+// Protocol ids can be found at:
+// https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml#alpn-protocol-ids
+// Basic use pattern for creating an alpn option:
+//
+//	o := new(dns.HTTPS)
+//	o.Hdr.Name = "."
+//	o.Hdr.Rrtype = dns.TypeHTTPS
+//	e := new(dns.SVCBAlpn)
+//	e.Alpn = []string{"h2", "http/1.1"}
+//	o.Value = append(o.Value, e)
+type SVCBAlpn struct {
+	Alpn []string
+}
+
+func (*SVCBAlpn) Key() SVCBKey     { return SVCB_ALPN }
+func (s *SVCBAlpn) String() string { return strings.Join(s.Alpn, ",") }
+
+// The spec requires the alpn keys including \ or , to be escaped.
+// In practice, no standard key including those exists.
+// Therefore those characters are not escaped.
+
+func (s *SVCBAlpn) pack() ([]byte, error) {
+	// Liberally estimate the size of an alpn as 10 octets
+	b := make([]byte, 0, 10*len(s.Alpn))
+	for _, e := range s.Alpn {
+		if len(e) == 0 {
+			return nil, errors.New("dns: svcbalpn: empty alpn-id")
+		}
+		if len(e) > 255 {
+			return nil, errors.New("dns: svcbalpn: alpn-id too long")
+		}
+		b = append(b, byte(len(e)))
+		b = append(b, e...)
+	}
+	return b, nil
+}
+
+func (s *SVCBAlpn) unpack(b []byte) error {
+	// Estimate the size of the smallest alpn as 4 bytes
+	alpn := make([]string, 0, len(b)/4)
+	for i := 0; i < len(b); {
+		length := int(b[i])
+		i++
+		if i+length > len(b) {
+			return errors.New("dns: svcbalpn: alpn array overflowing")
+		}
+		alpn = append(alpn, string(b[i:i+length]))
+		i += length
+	}
+	s.Alpn = alpn
+	return nil
+}
+
+func (s *SVCBAlpn) parse(b string) error {
+	s.Alpn = strings.Split(b, ",")
+	return nil
+}
+
+func (s *SVCBAlpn) len() int {
+	var l int
+	for _, e := range s.Alpn {
+		l += 1 + len(e)
+	}
+	return l
+}
+
+func (s *SVCBAlpn) copy() SVCBKeyValue {
+	return &SVCBAlpn{
+		append([]string(nil), s.Alpn...),
+	}
+}
+
+// SVCBNoDefaultAlpn pair signifies no support for default connection protocols.
+// Basic use pattern for creating a no-default-alpn option:
+//
+//	o := new(dns.SVCB)
+//	o.Hdr.Name = "."
+//	o.Hdr.Rrtype = dns.SVCB
+//	e := new(dns.SVCBNoDefaultAlpn)
+//	o.Value = append(o.Value, e)
+type SVCBNoDefaultAlpn struct {
+	// Empty
+}
+
+func (*SVCBNoDefaultAlpn) Key() SVCBKey          { return SVCB_NO_DEFAULT_ALPN }
+func (*SVCBNoDefaultAlpn) copy() SVCBKeyValue    { return &SVCBNoDefaultAlpn{} }
+func (*SVCBNoDefaultAlpn) pack() ([]byte, error) { return []byte{}, nil }
+func (*SVCBNoDefaultAlpn) String() string        { return "" }
+func (*SVCBNoDefaultAlpn) len() int              { return 0 }
+
+func (*SVCBNoDefaultAlpn) unpack(b []byte) error {
+	if len(b) != 0 {
+		return errors.New("dns: svcbnodefaultalpn: no_default_alpn must have no value")
+	}
+	return nil
+}
+
+func (*SVCBNoDefaultAlpn) parse(b string) error {
+	if len(b) != 0 {
+		return errors.New("dns: svcbnodefaultalpn: no_default_alpn must have no value")
+	}
+	return nil
+}
+
+// SVCBPort pair defines the port for connection.
+// Basic use pattern for creating a port option:
+//
+//	o := new(dns.SVCB)
+//	o.Hdr.Name = "."
+//	o.Hdr.Rrtype = dns.SVCB
+//	e := new(dns.SVCBPort)
+//	e.Port = 80
+//	o.Value = append(o.Value, e)
+type SVCBPort struct {
+	Port uint16
+}
+
+func (*SVCBPort) Key() SVCBKey         { return SVCB_PORT }
+func (*SVCBPort) len() int             { return 2 }
+func (s *SVCBPort) String() string     { return strconv.FormatUint(uint64(s.Port), 10) }
+func (s *SVCBPort) copy() SVCBKeyValue { return &SVCBPort{s.Port} }
+
+func (s *SVCBPort) unpack(b []byte) error {
+	if len(b) != 2 {
+		return errors.New("dns: svcbport: port length is not exactly 2 octets")
+	}
+	s.Port = binary.BigEndian.Uint16(b)
+	return nil
+}
+
+func (s *SVCBPort) pack() ([]byte, error) {
+	b := make([]byte, 2)
+	binary.BigEndian.PutUint16(b, s.Port)
+	return b, nil
+}
+
+func (s *SVCBPort) parse(b string) error {
+	port, err := strconv.ParseUint(b, 10, 16)
+	if err != nil {
+		return errors.New("dns: svcbport: port out of range")
+	}
+	s.Port = uint16(port)
+	return nil
+}
+
+// SVCBIPv4Hint pair suggests an IPv4 address which may be used to open connections
+// if A and AAAA record responses for SVCB's Target domain haven't been received.
+// In that case, optionally, A and AAAA requests can be made, after which the connection
+// to the hinted IP address may be terminated and a new connection may be opened.
+// Basic use pattern for creating an ipv4hint option:
+//
+//	o := new(dns.HTTPS)
+//	o.Hdr.Name = "."
+//	o.Hdr.Rrtype = dns.HTTPS
+//	e := new(dns.SVCBIPv4Hint)
+//	e.Hint = []net.IP{net.IPv4(1,1,1,1).To4()}
+//  // or
+//	e.Hint = []net.IP{net.ParseIP("1.1.1.1").To4()}
+//	o.Value = append(o.Value, e)
+type SVCBIPv4Hint struct {
+	Hint []net.IP
+}
+
+func (*SVCBIPv4Hint) Key() SVCBKey { return SVCB_IPV4HINT }
+func (s *SVCBIPv4Hint) len() int   { return 4 * len(s.Hint) }
+
+func (s *SVCBIPv4Hint) pack() ([]byte, error) {
+	b := make([]byte, 0, 4*len(s.Hint))
+	for _, e := range s.Hint {
+		x := e.To4()
+		if x == nil {
+			return nil, errors.New("dns: svcbipv4hint: expected ipv4, hint is ipv6")
+		}
+		b = append(b, x...)
+	}
+	return b, nil
+}
+
+func (s *SVCBIPv4Hint) unpack(b []byte) error {
+	if len(b) == 0 || len(b)%4 != 0 {
+		return errors.New("dns: svcbipv4hint: ipv4 address byte array length is not a multiple of 4")
+	}
+	x := make([]net.IP, 0, len(b)/4)
+	for i := 0; i < len(b); i += 4 {
+		x = append(x, net.IP(b[i:i+4]))
+	}
+	s.Hint = x
+	return nil
+}
+
+// String returns the string form of s, it returns "<nil>" if s is invalid.
+func (s *SVCBIPv4Hint) String() string {
+	str := make([]string, len(s.Hint))
+	for i, e := range s.Hint {
+		x := e.To4()
+		if x == nil {
+			return "<nil>"
+		}
+		str[i] = x.String()
+	}
+	return strings.Join(str, ",")
+}
+
+func (s *SVCBIPv4Hint) parse(b string) error {
+	if strings.Contains(b, ":") {
+		return errors.New("dns: svcbipv4hint: expected ipv4, got ipv6")
+	}
+	str := strings.Split(b, ",")
+	dst := make([]net.IP, len(str))
+	for i, e := range str {
+		ip := net.ParseIP(e).To4()
+		if ip == nil {
+			return errors.New("dns: svcbipv4hint: bad ip")
+		}
+		dst[i] = ip
+	}
+	s.Hint = dst
+	return nil
+}
+
+func (s *SVCBIPv4Hint) copy() SVCBKeyValue {
+	return &SVCBIPv4Hint{
+		append([]net.IP(nil), s.Hint...),
+	}
+}
+
+// SVCBECHConfig pair contains the ECHConfig structure defined in draft-ietf-tls-esni [RFC xxxx].
+// Basic use pattern for creating an echconfig option:
+//
+//	o := new(dns.HTTPS)
+//	o.Hdr.Name = "."
+//	o.Hdr.Rrtype = dns.HTTPS
+//	e := new(dns.SVCBECHConfig)
+//	e.ECH = "/wH...="
+//	o.Value = append(o.Value, e)
+type SVCBECHConfig struct {
+	ECH []byte
+}
+
+func (*SVCBECHConfig) Key() SVCBKey     { return SVCB_ECHCONFIG }
+func (s *SVCBECHConfig) String() string { return toBase64(s.ECH) }
+func (s *SVCBECHConfig) len() int       { return len(s.ECH) }
+
+func (s *SVCBECHConfig) pack() ([]byte, error) {
+	return append([]byte(nil), s.ECH...), nil
+}
+
+func (s *SVCBECHConfig) copy() SVCBKeyValue {
+	return &SVCBECHConfig{
+		append([]byte(nil), s.ECH...),
+	}
+}
+
+func (s *SVCBECHConfig) unpack(b []byte) error {
+	s.ECH = append([]byte(nil), b...)
+	return nil
+}
+func (s *SVCBECHConfig) parse(b string) error {
+	x, err := fromBase64([]byte(b))
+	if err != nil {
+		return errors.New("dns: svcbechconfig: bad base64 echconfig")
+	}
+	s.ECH = x
+	return nil
+}
+
+// SVCBIPv6Hint pair suggests an IPv6 address which may be used to open connections
+// if A and AAAA record responses for SVCB's Target domain haven't been received.
+// In that case, optionally, A and AAAA requests can be made, after which the
+// connection to the hinted IP address may be terminated and a new connection may be opened.
+// Basic use pattern for creating an ipv6hint option:
+//
+//	o := new(dns.HTTPS)
+//	o.Hdr.Name = "."
+//	o.Hdr.Rrtype = dns.HTTPS
+//	e := new(dns.SVCBIPv6Hint)
+//	e.Hint = []net.IP{net.ParseIP("2001:db8::1")}
+//	o.Value = append(o.Value, e)
+type SVCBIPv6Hint struct {
+	Hint []net.IP
+}
+
+func (*SVCBIPv6Hint) Key() SVCBKey { return SVCB_IPV6HINT }
+func (s *SVCBIPv6Hint) len() int   { return 16 * len(s.Hint) }
+
+func (s *SVCBIPv6Hint) pack() ([]byte, error) {
+	b := make([]byte, 0, 16*len(s.Hint))
+	for _, e := range s.Hint {
+		if len(e) != net.IPv6len || e.To4() != nil {
+			return nil, errors.New("dns: svcbipv6hint: expected ipv6, hint is ipv4")
+		}
+		b = append(b, e...)
+	}
+	return b, nil
+}
+
+func (s *SVCBIPv6Hint) unpack(b []byte) error {
+	if len(b) == 0 || len(b)%16 != 0 {
+		return errors.New("dns: svcbipv6hint: ipv6 address byte array length not a multiple of 16")
+	}
+	x := make([]net.IP, 0, len(b)/16)
+	for i := 0; i < len(b); i += 16 {
+		ip := net.IP(b[i : i+16])
+		if ip.To4() != nil {
+			return errors.New("dns: svcbipv6hint: expected ipv6, got ipv4")
+		}
+		x = append(x, ip)
+	}
+	s.Hint = x
+	return nil
+}
+
+// String returns the string form of s, it returns "<nil>" if s is invalid.
+func (s *SVCBIPv6Hint) String() string {
+	str := make([]string, len(s.Hint))
+	for i, e := range s.Hint {
+		if x := e.To4(); x != nil {
+			return "<nil>"
+		}
+		str[i] = e.String()
+	}
+	return strings.Join(str, ",")
+}
+
+func (s *SVCBIPv6Hint) parse(b string) error {
+	if strings.Contains(b, ".") {
+		return errors.New("dns: svcbipv6hint: expected ipv6, got ipv4")
+	}
+	str := strings.Split(b, ",")
+	dst := make([]net.IP, len(str))
+	for i, e := range str {
+		ip := net.ParseIP(e)
+		if ip == nil {
+			return errors.New("dns: svcbipv6hint: bad ip")
+		}
+		dst[i] = ip
+	}
+	s.Hint = dst
+	return nil
+}
+
+func (s *SVCBIPv6Hint) copy() SVCBKeyValue {
+	return &SVCBIPv6Hint{
+		append([]net.IP(nil), s.Hint...),
+	}
+}
+
+// SVCBLocal pair is intended for experimental/private use. The key is recommended
+// to be in the range [SVCB_PRIVATE_LOWER, SVCB_PRIVATE_UPPER].
+// Basic use pattern for creating a keyNNNNN option:
+//
+//	o := new(dns.HTTPS)
+//	o.Hdr.Name = "."
+//	o.Hdr.Rrtype = dns.HTTPS
+//	e := new(dns.SVCBLocal)
+//	e.KeyCode = 65400
+//	e.Data = []byte("abc")
+//	o.Value = append(o.Value, e)
+type SVCBLocal struct {
+	KeyCode SVCBKey // Never 65535 or any assigned keys
+	Data    []byte  // All byte sequences are allowed
+}
+
+func (s *SVCBLocal) Key() SVCBKey          { return s.KeyCode }
+func (s *SVCBLocal) pack() ([]byte, error) { return append([]byte(nil), s.Data...), nil }
+func (s *SVCBLocal) len() int              { return len(s.Data) }
+
+func (s *SVCBLocal) unpack(b []byte) error {
+	s.Data = append([]byte(nil), b...)
+	return nil
+}
+
+func (s *SVCBLocal) String() string {
+	var str strings.Builder
+	str.Grow(4 * len(s.Data))
+	for _, e := range s.Data {
+		if ' ' <= e && e <= '~' {
+			switch e {
+			case '"', ';', ' ', '\\':
+				str.WriteByte('\\')
+				str.WriteByte(e)
+			default:
+				str.WriteByte(e)
+			}
+		} else {
+			str.WriteString(escapeByte(e))
+		}
+	}
+	return str.String()
+}
+
+func (s *SVCBLocal) parse(b string) error {
+	data := make([]byte, 0, len(b))
+	for i := 0; i < len(b); {
+		if b[i] != '\\' {
+			data = append(data, b[i])
+			i++
+			continue
+		}
+		if i+1 == len(b) {
+			return errors.New("dns: svcblocal: svcb private/experimental key escape unterminated")
+		}
+		if isDigit(b[i+1]) {
+			if i+3 < len(b) && isDigit(b[i+2]) && isDigit(b[i+3]) {
+				a, err := strconv.ParseUint(b[i+1:i+4], 10, 8)
+				if err == nil {
+					i += 4
+					data = append(data, byte(a))
+					continue
+				}
+			}
+			return errors.New("dns: svcblocal: svcb private/experimental key bad escaped octet")
+		} else {
+			data = append(data, b[i+1])
+			i += 2
+		}
+	}
+	s.Data = data
+	return nil
+}
+
+func (s *SVCBLocal) copy() SVCBKeyValue {
+	return &SVCBLocal{s.KeyCode,
+		append([]byte(nil), s.Data...),
+	}
+}
+
+func (rr *SVCB) String() string {
+	s := rr.Hdr.String() +
+		strconv.Itoa(int(rr.Priority)) + " " +
+		sprintName(rr.Target)
+	for _, e := range rr.Value {
+		s += " " + e.Key().String() + "=\"" + e.String() + "\""
+	}
+	return s
+}
+
+// areSVCBPairArraysEqual checks if SVCBKeyValue arrays are equal after sorting their
+// copies. arrA and arrB have equal lengths, otherwise zduplicate.go wouldn't call this function.
+func areSVCBPairArraysEqual(a []SVCBKeyValue, b []SVCBKeyValue) bool {
+	a = append([]SVCBKeyValue(nil), a...)
+	b = append([]SVCBKeyValue(nil), b...)
+	sort.Slice(a, func(i, j int) bool { return a[i].Key() < a[j].Key() })
+	sort.Slice(b, func(i, j int) bool { return b[i].Key() < b[j].Key() })
+	for i, e := range a {
+		if e.Key() != b[i].Key() {
+			return false
+		}
+		b1, err1 := e.pack()
+		b2, err2 := b[i].pack()
+		if err1 != nil || err2 != nil || !bytes.Equal(b1, b2) {
+			return false
+		}
+	}
+	return true
+}