vendor.github.com.miekg.dns.msg_helpers.go Maven / Gradle / Ivy
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package dns
import (
"encoding/base32"
"encoding/base64"
"encoding/binary"
"encoding/hex"
"net"
"sort"
"strings"
)
// helper functions called from the generated zmsg.go
// These function are named after the tag to help pack/unpack, if there is no tag it is the name
// of the type they pack/unpack (string, int, etc). We prefix all with unpackData or packData, so packDataA or
// packDataDomainName.
func unpackDataA(msg []byte, off int) (net.IP, int, error) {
if off+net.IPv4len > len(msg) {
return nil, len(msg), &Error{err: "overflow unpacking a"}
}
return cloneSlice(msg[off : off+net.IPv4len]), off + net.IPv4len, nil
}
func packDataA(a net.IP, msg []byte, off int) (int, error) {
switch len(a) {
case net.IPv4len, net.IPv6len:
// It must be a slice of 4, even if it is 16, we encode only the first 4
if off+net.IPv4len > len(msg) {
return len(msg), &Error{err: "overflow packing a"}
}
copy(msg[off:], a.To4())
off += net.IPv4len
case 0:
// Allowed, for dynamic updates.
default:
return len(msg), &Error{err: "overflow packing a"}
}
return off, nil
}
func unpackDataAAAA(msg []byte, off int) (net.IP, int, error) {
if off+net.IPv6len > len(msg) {
return nil, len(msg), &Error{err: "overflow unpacking aaaa"}
}
return cloneSlice(msg[off : off+net.IPv6len]), off + net.IPv6len, nil
}
func packDataAAAA(aaaa net.IP, msg []byte, off int) (int, error) {
switch len(aaaa) {
case net.IPv6len:
if off+net.IPv6len > len(msg) {
return len(msg), &Error{err: "overflow packing aaaa"}
}
copy(msg[off:], aaaa)
off += net.IPv6len
case 0:
// Allowed, dynamic updates.
default:
return len(msg), &Error{err: "overflow packing aaaa"}
}
return off, nil
}
// unpackHeader unpacks an RR header, returning the offset to the end of the header and a
// re-sliced msg according to the expected length of the RR.
func unpackHeader(msg []byte, off int) (rr RR_Header, off1 int, truncmsg []byte, err error) {
hdr := RR_Header{}
if off == len(msg) {
return hdr, off, msg, nil
}
hdr.Name, off, err = UnpackDomainName(msg, off)
if err != nil {
return hdr, len(msg), msg, err
}
hdr.Rrtype, off, err = unpackUint16(msg, off)
if err != nil {
return hdr, len(msg), msg, err
}
hdr.Class, off, err = unpackUint16(msg, off)
if err != nil {
return hdr, len(msg), msg, err
}
hdr.Ttl, off, err = unpackUint32(msg, off)
if err != nil {
return hdr, len(msg), msg, err
}
hdr.Rdlength, off, err = unpackUint16(msg, off)
if err != nil {
return hdr, len(msg), msg, err
}
msg, err = truncateMsgFromRdlength(msg, off, hdr.Rdlength)
return hdr, off, msg, err
}
// packHeader packs an RR header, returning the offset to the end of the header.
// See PackDomainName for documentation about the compression.
func (hdr RR_Header) packHeader(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
if off == len(msg) {
return off, nil
}
off, err := packDomainName(hdr.Name, msg, off, compression, compress)
if err != nil {
return len(msg), err
}
off, err = packUint16(hdr.Rrtype, msg, off)
if err != nil {
return len(msg), err
}
off, err = packUint16(hdr.Class, msg, off)
if err != nil {
return len(msg), err
}
off, err = packUint32(hdr.Ttl, msg, off)
if err != nil {
return len(msg), err
}
off, err = packUint16(0, msg, off) // The RDLENGTH field will be set later in packRR.
if err != nil {
return len(msg), err
}
return off, nil
}
// helper helper functions.
// truncateMsgFromRdLength truncates msg to match the expected length of the RR.
// Returns an error if msg is smaller than the expected size.
func truncateMsgFromRdlength(msg []byte, off int, rdlength uint16) (truncmsg []byte, err error) {
lenrd := off + int(rdlength)
if lenrd > len(msg) {
return msg, &Error{err: "overflowing header size"}
}
return msg[:lenrd], nil
}
var base32HexNoPadEncoding = base32.HexEncoding.WithPadding(base32.NoPadding)
func fromBase32(s []byte) (buf []byte, err error) {
for i, b := range s {
if b >= 'a' && b <= 'z' {
s[i] = b - 32
}
}
buflen := base32HexNoPadEncoding.DecodedLen(len(s))
buf = make([]byte, buflen)
n, err := base32HexNoPadEncoding.Decode(buf, s)
buf = buf[:n]
return
}
func toBase32(b []byte) string {
return base32HexNoPadEncoding.EncodeToString(b)
}
func fromBase64(s []byte) (buf []byte, err error) {
buflen := base64.StdEncoding.DecodedLen(len(s))
buf = make([]byte, buflen)
n, err := base64.StdEncoding.Decode(buf, s)
buf = buf[:n]
return
}
func toBase64(b []byte) string { return base64.StdEncoding.EncodeToString(b) }
// dynamicUpdate returns true if the Rdlength is zero.
func noRdata(h RR_Header) bool { return h.Rdlength == 0 }
func unpackUint8(msg []byte, off int) (i uint8, off1 int, err error) {
if off+1 > len(msg) {
return 0, len(msg), &Error{err: "overflow unpacking uint8"}
}
return msg[off], off + 1, nil
}
func packUint8(i uint8, msg []byte, off int) (off1 int, err error) {
if off+1 > len(msg) {
return len(msg), &Error{err: "overflow packing uint8"}
}
msg[off] = i
return off + 1, nil
}
func unpackUint16(msg []byte, off int) (i uint16, off1 int, err error) {
if off+2 > len(msg) {
return 0, len(msg), &Error{err: "overflow unpacking uint16"}
}
return binary.BigEndian.Uint16(msg[off:]), off + 2, nil
}
func packUint16(i uint16, msg []byte, off int) (off1 int, err error) {
if off+2 > len(msg) {
return len(msg), &Error{err: "overflow packing uint16"}
}
binary.BigEndian.PutUint16(msg[off:], i)
return off + 2, nil
}
func unpackUint32(msg []byte, off int) (i uint32, off1 int, err error) {
if off+4 > len(msg) {
return 0, len(msg), &Error{err: "overflow unpacking uint32"}
}
return binary.BigEndian.Uint32(msg[off:]), off + 4, nil
}
func packUint32(i uint32, msg []byte, off int) (off1 int, err error) {
if off+4 > len(msg) {
return len(msg), &Error{err: "overflow packing uint32"}
}
binary.BigEndian.PutUint32(msg[off:], i)
return off + 4, nil
}
func unpackUint48(msg []byte, off int) (i uint64, off1 int, err error) {
if off+6 > len(msg) {
return 0, len(msg), &Error{err: "overflow unpacking uint64 as uint48"}
}
// Used in TSIG where the last 48 bits are occupied, so for now, assume a uint48 (6 bytes)
i = uint64(msg[off])<<40 | uint64(msg[off+1])<<32 | uint64(msg[off+2])<<24 | uint64(msg[off+3])<<16 |
uint64(msg[off+4])<<8 | uint64(msg[off+5])
off += 6
return i, off, nil
}
func packUint48(i uint64, msg []byte, off int) (off1 int, err error) {
if off+6 > len(msg) {
return len(msg), &Error{err: "overflow packing uint64 as uint48"}
}
msg[off] = byte(i >> 40)
msg[off+1] = byte(i >> 32)
msg[off+2] = byte(i >> 24)
msg[off+3] = byte(i >> 16)
msg[off+4] = byte(i >> 8)
msg[off+5] = byte(i)
off += 6
return off, nil
}
func unpackUint64(msg []byte, off int) (i uint64, off1 int, err error) {
if off+8 > len(msg) {
return 0, len(msg), &Error{err: "overflow unpacking uint64"}
}
return binary.BigEndian.Uint64(msg[off:]), off + 8, nil
}
func packUint64(i uint64, msg []byte, off int) (off1 int, err error) {
if off+8 > len(msg) {
return len(msg), &Error{err: "overflow packing uint64"}
}
binary.BigEndian.PutUint64(msg[off:], i)
off += 8
return off, nil
}
func unpackString(msg []byte, off int) (string, int, error) {
if off+1 > len(msg) {
return "", off, &Error{err: "overflow unpacking txt"}
}
l := int(msg[off])
off++
if off+l > len(msg) {
return "", off, &Error{err: "overflow unpacking txt"}
}
var s strings.Builder
consumed := 0
for i, b := range msg[off : off+l] {
switch {
case b == '"' || b == '\\':
if consumed == 0 {
s.Grow(l * 2)
}
s.Write(msg[off+consumed : off+i])
s.WriteByte('\\')
s.WriteByte(b)
consumed = i + 1
case b < ' ' || b > '~': // unprintable
if consumed == 0 {
s.Grow(l * 2)
}
s.Write(msg[off+consumed : off+i])
s.WriteString(escapeByte(b))
consumed = i + 1
}
}
if consumed == 0 { // no escaping needed
return string(msg[off : off+l]), off + l, nil
}
s.Write(msg[off+consumed : off+l])
return s.String(), off + l, nil
}
func packString(s string, msg []byte, off int) (int, error) {
off, err := packTxtString(s, msg, off)
if err != nil {
return len(msg), err
}
return off, nil
}
func unpackStringBase32(msg []byte, off, end int) (string, int, error) {
if end > len(msg) {
return "", len(msg), &Error{err: "overflow unpacking base32"}
}
s := toBase32(msg[off:end])
return s, end, nil
}
func packStringBase32(s string, msg []byte, off int) (int, error) {
b32, err := fromBase32([]byte(s))
if err != nil {
return len(msg), err
}
if off+len(b32) > len(msg) {
return len(msg), &Error{err: "overflow packing base32"}
}
copy(msg[off:off+len(b32)], b32)
off += len(b32)
return off, nil
}
func unpackStringBase64(msg []byte, off, end int) (string, int, error) {
// Rest of the RR is base64 encoded value, so we don't need an explicit length
// to be set. Thus far all RR's that have base64 encoded fields have those as their
// last one. What we do need is the end of the RR!
if end > len(msg) {
return "", len(msg), &Error{err: "overflow unpacking base64"}
}
s := toBase64(msg[off:end])
return s, end, nil
}
func packStringBase64(s string, msg []byte, off int) (int, error) {
b64, err := fromBase64([]byte(s))
if err != nil {
return len(msg), err
}
if off+len(b64) > len(msg) {
return len(msg), &Error{err: "overflow packing base64"}
}
copy(msg[off:off+len(b64)], b64)
off += len(b64)
return off, nil
}
func unpackStringHex(msg []byte, off, end int) (string, int, error) {
// Rest of the RR is hex encoded value, so we don't need an explicit length
// to be set. NSEC and TSIG have hex fields with a length field.
// What we do need is the end of the RR!
if end > len(msg) {
return "", len(msg), &Error{err: "overflow unpacking hex"}
}
s := hex.EncodeToString(msg[off:end])
return s, end, nil
}
func packStringHex(s string, msg []byte, off int) (int, error) {
h, err := hex.DecodeString(s)
if err != nil {
return len(msg), err
}
if off+len(h) > len(msg) {
return len(msg), &Error{err: "overflow packing hex"}
}
copy(msg[off:off+len(h)], h)
off += len(h)
return off, nil
}
func unpackStringAny(msg []byte, off, end int) (string, int, error) {
if end > len(msg) {
return "", len(msg), &Error{err: "overflow unpacking anything"}
}
return string(msg[off:end]), end, nil
}
func packStringAny(s string, msg []byte, off int) (int, error) {
if off+len(s) > len(msg) {
return len(msg), &Error{err: "overflow packing anything"}
}
copy(msg[off:off+len(s)], s)
off += len(s)
return off, nil
}
func unpackStringTxt(msg []byte, off int) ([]string, int, error) {
txt, off, err := unpackTxt(msg, off)
if err != nil {
return nil, len(msg), err
}
return txt, off, nil
}
func packStringTxt(s []string, msg []byte, off int) (int, error) {
off, err := packTxt(s, msg, off)
if err != nil {
return len(msg), err
}
return off, nil
}
func unpackDataOpt(msg []byte, off int) ([]EDNS0, int, error) {
var edns []EDNS0
for off < len(msg) {
if off+4 > len(msg) {
return nil, len(msg), &Error{err: "overflow unpacking opt"}
}
code := binary.BigEndian.Uint16(msg[off:])
off += 2
optlen := binary.BigEndian.Uint16(msg[off:])
off += 2
if off+int(optlen) > len(msg) {
return nil, len(msg), &Error{err: "overflow unpacking opt"}
}
opt := makeDataOpt(code)
if err := opt.unpack(msg[off : off+int(optlen)]); err != nil {
return nil, len(msg), err
}
edns = append(edns, opt)
off += int(optlen)
}
return edns, off, nil
}
func packDataOpt(options []EDNS0, msg []byte, off int) (int, error) {
for _, el := range options {
b, err := el.pack()
if err != nil || off+4 > len(msg) {
return len(msg), &Error{err: "overflow packing opt"}
}
binary.BigEndian.PutUint16(msg[off:], el.Option()) // Option code
binary.BigEndian.PutUint16(msg[off+2:], uint16(len(b))) // Length
off += 4
if off+len(b) > len(msg) {
return len(msg), &Error{err: "overflow packing opt"}
}
// Actual data
copy(msg[off:off+len(b)], b)
off += len(b)
}
return off, nil
}
func unpackStringOctet(msg []byte, off int) (string, int, error) {
s := string(msg[off:])
return s, len(msg), nil
}
func packStringOctet(s string, msg []byte, off int) (int, error) {
off, err := packOctetString(s, msg, off)
if err != nil {
return len(msg), err
}
return off, nil
}
func unpackDataNsec(msg []byte, off int) ([]uint16, int, error) {
var nsec []uint16
length, window, lastwindow := 0, 0, -1
for off < len(msg) {
if off+2 > len(msg) {
return nsec, len(msg), &Error{err: "overflow unpacking NSEC(3)"}
}
window = int(msg[off])
length = int(msg[off+1])
off += 2
if window <= lastwindow {
// RFC 4034: Blocks are present in the NSEC RR RDATA in
// increasing numerical order.
return nsec, len(msg), &Error{err: "out of order NSEC(3) block in type bitmap"}
}
if length == 0 {
// RFC 4034: Blocks with no types present MUST NOT be included.
return nsec, len(msg), &Error{err: "empty NSEC(3) block in type bitmap"}
}
if length > 32 {
return nsec, len(msg), &Error{err: "NSEC(3) block too long in type bitmap"}
}
if off+length > len(msg) {
return nsec, len(msg), &Error{err: "overflowing NSEC(3) block in type bitmap"}
}
// Walk the bytes in the window and extract the type bits
for j, b := range msg[off : off+length] {
// Check the bits one by one, and set the type
if b&0x80 == 0x80 {
nsec = append(nsec, uint16(window*256+j*8+0))
}
if b&0x40 == 0x40 {
nsec = append(nsec, uint16(window*256+j*8+1))
}
if b&0x20 == 0x20 {
nsec = append(nsec, uint16(window*256+j*8+2))
}
if b&0x10 == 0x10 {
nsec = append(nsec, uint16(window*256+j*8+3))
}
if b&0x8 == 0x8 {
nsec = append(nsec, uint16(window*256+j*8+4))
}
if b&0x4 == 0x4 {
nsec = append(nsec, uint16(window*256+j*8+5))
}
if b&0x2 == 0x2 {
nsec = append(nsec, uint16(window*256+j*8+6))
}
if b&0x1 == 0x1 {
nsec = append(nsec, uint16(window*256+j*8+7))
}
}
off += length
lastwindow = window
}
return nsec, off, nil
}
// typeBitMapLen is a helper function which computes the "maximum" length of
// a the NSEC Type BitMap field.
func typeBitMapLen(bitmap []uint16) int {
var l int
var lastwindow, lastlength uint16
for _, t := range bitmap {
window := t / 256
length := (t-window*256)/8 + 1
if window > lastwindow && lastlength != 0 { // New window, jump to the new offset
l += int(lastlength) + 2
lastlength = 0
}
if window < lastwindow || length < lastlength {
// packDataNsec would return Error{err: "nsec bits out of order"} here, but
// when computing the length, we want do be liberal.
continue
}
lastwindow, lastlength = window, length
}
l += int(lastlength) + 2
return l
}
func packDataNsec(bitmap []uint16, msg []byte, off int) (int, error) {
if len(bitmap) == 0 {
return off, nil
}
if off > len(msg) {
return off, &Error{err: "overflow packing nsec"}
}
toZero := msg[off:]
if maxLen := typeBitMapLen(bitmap); maxLen < len(toZero) {
toZero = toZero[:maxLen]
}
for i := range toZero {
toZero[i] = 0
}
var lastwindow, lastlength uint16
for _, t := range bitmap {
window := t / 256
length := (t-window*256)/8 + 1
if window > lastwindow && lastlength != 0 { // New window, jump to the new offset
off += int(lastlength) + 2
lastlength = 0
}
if window < lastwindow || length < lastlength {
return len(msg), &Error{err: "nsec bits out of order"}
}
if off+2+int(length) > len(msg) {
return len(msg), &Error{err: "overflow packing nsec"}
}
// Setting the window #
msg[off] = byte(window)
// Setting the octets length
msg[off+1] = byte(length)
// Setting the bit value for the type in the right octet
msg[off+1+int(length)] |= byte(1 << (7 - t%8))
lastwindow, lastlength = window, length
}
off += int(lastlength) + 2
return off, nil
}
func unpackDataSVCB(msg []byte, off int) ([]SVCBKeyValue, int, error) {
var xs []SVCBKeyValue
var code uint16
var length uint16
var err error
for off < len(msg) {
code, off, err = unpackUint16(msg, off)
if err != nil {
return nil, len(msg), &Error{err: "overflow unpacking SVCB"}
}
length, off, err = unpackUint16(msg, off)
if err != nil || off+int(length) > len(msg) {
return nil, len(msg), &Error{err: "overflow unpacking SVCB"}
}
e := makeSVCBKeyValue(SVCBKey(code))
if e == nil {
return nil, len(msg), &Error{err: "bad SVCB key"}
}
if err := e.unpack(msg[off : off+int(length)]); err != nil {
return nil, len(msg), err
}
if len(xs) > 0 && e.Key() <= xs[len(xs)-1].Key() {
return nil, len(msg), &Error{err: "SVCB keys not in strictly increasing order"}
}
xs = append(xs, e)
off += int(length)
}
return xs, off, nil
}
func packDataSVCB(pairs []SVCBKeyValue, msg []byte, off int) (int, error) {
pairs = cloneSlice(pairs)
sort.Slice(pairs, func(i, j int) bool {
return pairs[i].Key() < pairs[j].Key()
})
prev := svcb_RESERVED
for _, el := range pairs {
if el.Key() == prev {
return len(msg), &Error{err: "repeated SVCB keys are not allowed"}
}
prev = el.Key()
packed, err := el.pack()
if err != nil {
return len(msg), err
}
off, err = packUint16(uint16(el.Key()), msg, off)
if err != nil {
return len(msg), &Error{err: "overflow packing SVCB"}
}
off, err = packUint16(uint16(len(packed)), msg, off)
if err != nil || off+len(packed) > len(msg) {
return len(msg), &Error{err: "overflow packing SVCB"}
}
copy(msg[off:off+len(packed)], packed)
off += len(packed)
}
return off, nil
}
func unpackDataDomainNames(msg []byte, off, end int) ([]string, int, error) {
var (
servers []string
s string
err error
)
if end > len(msg) {
return nil, len(msg), &Error{err: "overflow unpacking domain names"}
}
for off < end {
s, off, err = UnpackDomainName(msg, off)
if err != nil {
return servers, len(msg), err
}
servers = append(servers, s)
}
return servers, off, nil
}
func packDataDomainNames(names []string, msg []byte, off int, compression compressionMap, compress bool) (int, error) {
var err error
for _, name := range names {
off, err = packDomainName(name, msg, off, compression, compress)
if err != nil {
return len(msg), err
}
}
return off, nil
}
func packDataApl(data []APLPrefix, msg []byte, off int) (int, error) {
var err error
for i := range data {
off, err = packDataAplPrefix(&data[i], msg, off)
if err != nil {
return len(msg), err
}
}
return off, nil
}
func packDataAplPrefix(p *APLPrefix, msg []byte, off int) (int, error) {
if len(p.Network.IP) != len(p.Network.Mask) {
return len(msg), &Error{err: "address and mask lengths don't match"}
}
var err error
prefix, _ := p.Network.Mask.Size()
addr := p.Network.IP.Mask(p.Network.Mask)[:(prefix+7)/8]
switch len(p.Network.IP) {
case net.IPv4len:
off, err = packUint16(1, msg, off)
case net.IPv6len:
off, err = packUint16(2, msg, off)
default:
err = &Error{err: "unrecognized address family"}
}
if err != nil {
return len(msg), err
}
off, err = packUint8(uint8(prefix), msg, off)
if err != nil {
return len(msg), err
}
var n uint8
if p.Negation {
n = 0x80
}
// trim trailing zero bytes as specified in RFC3123 Sections 4.1 and 4.2.
i := len(addr) - 1
for ; i >= 0 && addr[i] == 0; i-- {
}
addr = addr[:i+1]
adflen := uint8(len(addr)) & 0x7f
off, err = packUint8(n|adflen, msg, off)
if err != nil {
return len(msg), err
}
if off+len(addr) > len(msg) {
return len(msg), &Error{err: "overflow packing APL prefix"}
}
off += copy(msg[off:], addr)
return off, nil
}
func unpackDataApl(msg []byte, off int) ([]APLPrefix, int, error) {
var result []APLPrefix
for off < len(msg) {
prefix, end, err := unpackDataAplPrefix(msg, off)
if err != nil {
return nil, len(msg), err
}
off = end
result = append(result, prefix)
}
return result, off, nil
}
func unpackDataAplPrefix(msg []byte, off int) (APLPrefix, int, error) {
family, off, err := unpackUint16(msg, off)
if err != nil {
return APLPrefix{}, len(msg), &Error{err: "overflow unpacking APL prefix"}
}
prefix, off, err := unpackUint8(msg, off)
if err != nil {
return APLPrefix{}, len(msg), &Error{err: "overflow unpacking APL prefix"}
}
nlen, off, err := unpackUint8(msg, off)
if err != nil {
return APLPrefix{}, len(msg), &Error{err: "overflow unpacking APL prefix"}
}
var ip []byte
switch family {
case 1:
ip = make([]byte, net.IPv4len)
case 2:
ip = make([]byte, net.IPv6len)
default:
return APLPrefix{}, len(msg), &Error{err: "unrecognized APL address family"}
}
if int(prefix) > 8*len(ip) {
return APLPrefix{}, len(msg), &Error{err: "APL prefix too long"}
}
afdlen := int(nlen & 0x7f)
if afdlen > len(ip) {
return APLPrefix{}, len(msg), &Error{err: "APL length too long"}
}
if off+afdlen > len(msg) {
return APLPrefix{}, len(msg), &Error{err: "overflow unpacking APL address"}
}
// Address MUST NOT contain trailing zero bytes per RFC3123 Sections 4.1 and 4.2.
off += copy(ip, msg[off:off+afdlen])
if afdlen > 0 {
last := ip[afdlen-1]
if last == 0 {
return APLPrefix{}, len(msg), &Error{err: "extra APL address bits"}
}
}
ipnet := net.IPNet{
IP: ip,
Mask: net.CIDRMask(int(prefix), 8*len(ip)),
}
return APLPrefix{
Negation: (nlen & 0x80) != 0,
Network: ipnet,
}, off, nil
}
func unpackIPSECGateway(msg []byte, off int, gatewayType uint8) (net.IP, string, int, error) {
var retAddr net.IP
var retString string
var err error
switch gatewayType {
case IPSECGatewayNone: // do nothing
case IPSECGatewayIPv4:
retAddr, off, err = unpackDataA(msg, off)
case IPSECGatewayIPv6:
retAddr, off, err = unpackDataAAAA(msg, off)
case IPSECGatewayHost:
retString, off, err = UnpackDomainName(msg, off)
}
return retAddr, retString, off, err
}
func packIPSECGateway(gatewayAddr net.IP, gatewayString string, msg []byte, off int, gatewayType uint8, compression compressionMap, compress bool) (int, error) {
var err error
switch gatewayType {
case IPSECGatewayNone: // do nothing
case IPSECGatewayIPv4:
off, err = packDataA(gatewayAddr, msg, off)
case IPSECGatewayIPv6:
off, err = packDataAAAA(gatewayAddr, msg, off)
case IPSECGatewayHost:
off, err = packDomainName(gatewayString, msg, off, compression, compress)
}
return off, err
}