Retro68/gcc/libgo/go/net/dnsmsg.go
2017-04-10 13:32:00 +02:00

907 lines
21 KiB
Go
Raw Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// DNS packet assembly. See RFC 1035.
//
// This is intended to support name resolution during Dial.
// It doesn't have to be blazing fast.
//
// Each message structure has a Walk method that is used by
// a generic pack/unpack routine. Thus, if in the future we need
// to define new message structs, no new pack/unpack/printing code
// needs to be written.
//
// The first half of this file defines the DNS message formats.
// The second half implements the conversion to and from wire format.
// A few of the structure elements have string tags to aid the
// generic pack/unpack routines.
//
// TODO(rsc): There are enough names defined in this file that they're all
// prefixed with dns. Perhaps put this in its own package later.
package net
// Packet formats
// Wire constants.
const (
// valid dnsRR_Header.Rrtype and dnsQuestion.qtype
dnsTypeA = 1
dnsTypeNS = 2
dnsTypeMD = 3
dnsTypeMF = 4
dnsTypeCNAME = 5
dnsTypeSOA = 6
dnsTypeMB = 7
dnsTypeMG = 8
dnsTypeMR = 9
dnsTypeNULL = 10
dnsTypeWKS = 11
dnsTypePTR = 12
dnsTypeHINFO = 13
dnsTypeMINFO = 14
dnsTypeMX = 15
dnsTypeTXT = 16
dnsTypeAAAA = 28
dnsTypeSRV = 33
// valid dnsQuestion.qtype only
dnsTypeAXFR = 252
dnsTypeMAILB = 253
dnsTypeMAILA = 254
dnsTypeALL = 255
// valid dnsQuestion.qclass
dnsClassINET = 1
dnsClassCSNET = 2
dnsClassCHAOS = 3
dnsClassHESIOD = 4
dnsClassANY = 255
// dnsMsg.rcode
dnsRcodeSuccess = 0
dnsRcodeFormatError = 1
dnsRcodeServerFailure = 2
dnsRcodeNameError = 3
dnsRcodeNotImplemented = 4
dnsRcodeRefused = 5
)
// A dnsStruct describes how to iterate over its fields to emulate
// reflective marshalling.
type dnsStruct interface {
// Walk iterates over fields of a structure and calls f
// with a reference to that field, the name of the field
// and a tag ("", "domain", "ipv4", "ipv6") specifying
// particular encodings. Possible concrete types
// for v are *uint16, *uint32, *string, or []byte, and
// *int, *bool in the case of dnsMsgHdr.
// Whenever f returns false, Walk must stop and return
// false, and otherwise return true.
Walk(f func(v interface{}, name, tag string) (ok bool)) (ok bool)
}
// The wire format for the DNS packet header.
type dnsHeader struct {
Id uint16
Bits uint16
Qdcount, Ancount, Nscount, Arcount uint16
}
func (h *dnsHeader) Walk(f func(v interface{}, name, tag string) bool) bool {
return f(&h.Id, "Id", "") &&
f(&h.Bits, "Bits", "") &&
f(&h.Qdcount, "Qdcount", "") &&
f(&h.Ancount, "Ancount", "") &&
f(&h.Nscount, "Nscount", "") &&
f(&h.Arcount, "Arcount", "")
}
const (
// dnsHeader.Bits
_QR = 1 << 15 // query/response (response=1)
_AA = 1 << 10 // authoritative
_TC = 1 << 9 // truncated
_RD = 1 << 8 // recursion desired
_RA = 1 << 7 // recursion available
)
// DNS queries.
type dnsQuestion struct {
Name string `net:"domain-name"` // `net:"domain-name"` specifies encoding; see packers below
Qtype uint16
Qclass uint16
}
func (q *dnsQuestion) Walk(f func(v interface{}, name, tag string) bool) bool {
return f(&q.Name, "Name", "domain") &&
f(&q.Qtype, "Qtype", "") &&
f(&q.Qclass, "Qclass", "")
}
// DNS responses (resource records).
// There are many types of messages,
// but they all share the same header.
type dnsRR_Header struct {
Name string `net:"domain-name"`
Rrtype uint16
Class uint16
Ttl uint32
Rdlength uint16 // length of data after header
}
func (h *dnsRR_Header) Header() *dnsRR_Header {
return h
}
func (h *dnsRR_Header) Walk(f func(v interface{}, name, tag string) bool) bool {
return f(&h.Name, "Name", "domain") &&
f(&h.Rrtype, "Rrtype", "") &&
f(&h.Class, "Class", "") &&
f(&h.Ttl, "Ttl", "") &&
f(&h.Rdlength, "Rdlength", "")
}
type dnsRR interface {
dnsStruct
Header() *dnsRR_Header
}
// Specific DNS RR formats for each query type.
type dnsRR_CNAME struct {
Hdr dnsRR_Header
Cname string `net:"domain-name"`
}
func (rr *dnsRR_CNAME) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_CNAME) Walk(f func(v interface{}, name, tag string) bool) bool {
return rr.Hdr.Walk(f) && f(&rr.Cname, "Cname", "domain")
}
type dnsRR_HINFO struct {
Hdr dnsRR_Header
Cpu string
Os string
}
func (rr *dnsRR_HINFO) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_HINFO) Walk(f func(v interface{}, name, tag string) bool) bool {
return rr.Hdr.Walk(f) && f(&rr.Cpu, "Cpu", "") && f(&rr.Os, "Os", "")
}
type dnsRR_MB struct {
Hdr dnsRR_Header
Mb string `net:"domain-name"`
}
func (rr *dnsRR_MB) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_MB) Walk(f func(v interface{}, name, tag string) bool) bool {
return rr.Hdr.Walk(f) && f(&rr.Mb, "Mb", "domain")
}
type dnsRR_MG struct {
Hdr dnsRR_Header
Mg string `net:"domain-name"`
}
func (rr *dnsRR_MG) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_MG) Walk(f func(v interface{}, name, tag string) bool) bool {
return rr.Hdr.Walk(f) && f(&rr.Mg, "Mg", "domain")
}
type dnsRR_MINFO struct {
Hdr dnsRR_Header
Rmail string `net:"domain-name"`
Email string `net:"domain-name"`
}
func (rr *dnsRR_MINFO) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_MINFO) Walk(f func(v interface{}, name, tag string) bool) bool {
return rr.Hdr.Walk(f) && f(&rr.Rmail, "Rmail", "domain") && f(&rr.Email, "Email", "domain")
}
type dnsRR_MR struct {
Hdr dnsRR_Header
Mr string `net:"domain-name"`
}
func (rr *dnsRR_MR) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_MR) Walk(f func(v interface{}, name, tag string) bool) bool {
return rr.Hdr.Walk(f) && f(&rr.Mr, "Mr", "domain")
}
type dnsRR_MX struct {
Hdr dnsRR_Header
Pref uint16
Mx string `net:"domain-name"`
}
func (rr *dnsRR_MX) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_MX) Walk(f func(v interface{}, name, tag string) bool) bool {
return rr.Hdr.Walk(f) && f(&rr.Pref, "Pref", "") && f(&rr.Mx, "Mx", "domain")
}
type dnsRR_NS struct {
Hdr dnsRR_Header
Ns string `net:"domain-name"`
}
func (rr *dnsRR_NS) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_NS) Walk(f func(v interface{}, name, tag string) bool) bool {
return rr.Hdr.Walk(f) && f(&rr.Ns, "Ns", "domain")
}
type dnsRR_PTR struct {
Hdr dnsRR_Header
Ptr string `net:"domain-name"`
}
func (rr *dnsRR_PTR) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_PTR) Walk(f func(v interface{}, name, tag string) bool) bool {
return rr.Hdr.Walk(f) && f(&rr.Ptr, "Ptr", "domain")
}
type dnsRR_SOA struct {
Hdr dnsRR_Header
Ns string `net:"domain-name"`
Mbox string `net:"domain-name"`
Serial uint32
Refresh uint32
Retry uint32
Expire uint32
Minttl uint32
}
func (rr *dnsRR_SOA) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_SOA) Walk(f func(v interface{}, name, tag string) bool) bool {
return rr.Hdr.Walk(f) &&
f(&rr.Ns, "Ns", "domain") &&
f(&rr.Mbox, "Mbox", "domain") &&
f(&rr.Serial, "Serial", "") &&
f(&rr.Refresh, "Refresh", "") &&
f(&rr.Retry, "Retry", "") &&
f(&rr.Expire, "Expire", "") &&
f(&rr.Minttl, "Minttl", "")
}
type dnsRR_TXT struct {
Hdr dnsRR_Header
Txt string // not domain name
}
func (rr *dnsRR_TXT) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_TXT) Walk(f func(v interface{}, name, tag string) bool) bool {
if !rr.Hdr.Walk(f) {
return false
}
var n uint16 = 0
for n < rr.Hdr.Rdlength {
var txt string
if !f(&txt, "Txt", "") {
return false
}
// more bytes than rr.Hdr.Rdlength said there woudld be
if rr.Hdr.Rdlength-n < uint16(len(txt))+1 {
return false
}
n += uint16(len(txt)) + 1
rr.Txt += txt
}
return true
}
type dnsRR_SRV struct {
Hdr dnsRR_Header
Priority uint16
Weight uint16
Port uint16
Target string `net:"domain-name"`
}
func (rr *dnsRR_SRV) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_SRV) Walk(f func(v interface{}, name, tag string) bool) bool {
return rr.Hdr.Walk(f) &&
f(&rr.Priority, "Priority", "") &&
f(&rr.Weight, "Weight", "") &&
f(&rr.Port, "Port", "") &&
f(&rr.Target, "Target", "domain")
}
type dnsRR_A struct {
Hdr dnsRR_Header
A uint32 `net:"ipv4"`
}
func (rr *dnsRR_A) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_A) Walk(f func(v interface{}, name, tag string) bool) bool {
return rr.Hdr.Walk(f) && f(&rr.A, "A", "ipv4")
}
type dnsRR_AAAA struct {
Hdr dnsRR_Header
AAAA [16]byte `net:"ipv6"`
}
func (rr *dnsRR_AAAA) Header() *dnsRR_Header {
return &rr.Hdr
}
func (rr *dnsRR_AAAA) Walk(f func(v interface{}, name, tag string) bool) bool {
return rr.Hdr.Walk(f) && f(rr.AAAA[:], "AAAA", "ipv6")
}
// Packing and unpacking.
//
// All the packers and unpackers take a (msg []byte, off int)
// and return (off1 int, ok bool). If they return ok==false, they
// also return off1==len(msg), so that the next unpacker will
// also fail. This lets us avoid checks of ok until the end of a
// packing sequence.
// Map of constructors for each RR wire type.
var rr_mk = map[int]func() dnsRR{
dnsTypeCNAME: func() dnsRR { return new(dnsRR_CNAME) },
dnsTypeHINFO: func() dnsRR { return new(dnsRR_HINFO) },
dnsTypeMB: func() dnsRR { return new(dnsRR_MB) },
dnsTypeMG: func() dnsRR { return new(dnsRR_MG) },
dnsTypeMINFO: func() dnsRR { return new(dnsRR_MINFO) },
dnsTypeMR: func() dnsRR { return new(dnsRR_MR) },
dnsTypeMX: func() dnsRR { return new(dnsRR_MX) },
dnsTypeNS: func() dnsRR { return new(dnsRR_NS) },
dnsTypePTR: func() dnsRR { return new(dnsRR_PTR) },
dnsTypeSOA: func() dnsRR { return new(dnsRR_SOA) },
dnsTypeTXT: func() dnsRR { return new(dnsRR_TXT) },
dnsTypeSRV: func() dnsRR { return new(dnsRR_SRV) },
dnsTypeA: func() dnsRR { return new(dnsRR_A) },
dnsTypeAAAA: func() dnsRR { return new(dnsRR_AAAA) },
}
// Pack a domain name s into msg[off:].
// Domain names are a sequence of counted strings
// split at the dots. They end with a zero-length string.
func packDomainName(s string, msg []byte, off int) (off1 int, ok bool) {
// Add trailing dot to canonicalize name.
if n := len(s); n == 0 || s[n-1] != '.' {
s += "."
}
// Each dot ends a segment of the name.
// We trade each dot byte for a length byte.
// There is also a trailing zero.
// Check that we have all the space we need.
tot := len(s) + 1
if off+tot > len(msg) {
return len(msg), false
}
// Emit sequence of counted strings, chopping at dots.
begin := 0
for i := 0; i < len(s); i++ {
if s[i] == '.' {
if i-begin >= 1<<6 { // top two bits of length must be clear
return len(msg), false
}
msg[off] = byte(i - begin)
off++
for j := begin; j < i; j++ {
msg[off] = s[j]
off++
}
begin = i + 1
}
}
msg[off] = 0
off++
return off, true
}
// Unpack a domain name.
// In addition to the simple sequences of counted strings above,
// domain names are allowed to refer to strings elsewhere in the
// packet, to avoid repeating common suffixes when returning
// many entries in a single domain. The pointers are marked
// by a length byte with the top two bits set. Ignoring those
// two bits, that byte and the next give a 14 bit offset from msg[0]
// where we should pick up the trail.
// Note that if we jump elsewhere in the packet,
// we return off1 == the offset after the first pointer we found,
// which is where the next record will start.
// In theory, the pointers are only allowed to jump backward.
// We let them jump anywhere and stop jumping after a while.
func unpackDomainName(msg []byte, off int) (s string, off1 int, ok bool) {
s = ""
ptr := 0 // number of pointers followed
Loop:
for {
if off >= len(msg) {
return "", len(msg), false
}
c := int(msg[off])
off++
switch c & 0xC0 {
case 0x00:
if c == 0x00 {
// end of name
break Loop
}
// literal string
if off+c > len(msg) {
return "", len(msg), false
}
s += string(msg[off:off+c]) + "."
off += c
case 0xC0:
// pointer to somewhere else in msg.
// remember location after first ptr,
// since that's how many bytes we consumed.
// also, don't follow too many pointers --
// maybe there's a loop.
if off >= len(msg) {
return "", len(msg), false
}
c1 := msg[off]
off++
if ptr == 0 {
off1 = off
}
if ptr++; ptr > 10 {
return "", len(msg), false
}
off = (c^0xC0)<<8 | int(c1)
default:
// 0x80 and 0x40 are reserved
return "", len(msg), false
}
}
if ptr == 0 {
off1 = off
}
return s, off1, true
}
// packStruct packs a structure into msg at specified offset off, and
// returns off1 such that msg[off:off1] is the encoded data.
func packStruct(any dnsStruct, msg []byte, off int) (off1 int, ok bool) {
ok = any.Walk(func(field interface{}, name, tag string) bool {
switch fv := field.(type) {
default:
println("net: dns: unknown packing type")
return false
case *uint16:
i := *fv
if off+2 > len(msg) {
return false
}
msg[off] = byte(i >> 8)
msg[off+1] = byte(i)
off += 2
case *uint32:
i := *fv
msg[off] = byte(i >> 24)
msg[off+1] = byte(i >> 16)
msg[off+2] = byte(i >> 8)
msg[off+3] = byte(i)
off += 4
case []byte:
n := len(fv)
if off+n > len(msg) {
return false
}
copy(msg[off:off+n], fv)
off += n
case *string:
s := *fv
switch tag {
default:
println("net: dns: unknown string tag", tag)
return false
case "domain":
off, ok = packDomainName(s, msg, off)
if !ok {
return false
}
case "":
// Counted string: 1 byte length.
if len(s) > 255 || off+1+len(s) > len(msg) {
return false
}
msg[off] = byte(len(s))
off++
off += copy(msg[off:], s)
}
}
return true
})
if !ok {
return len(msg), false
}
return off, true
}
// unpackStruct decodes msg[off:] into the given structure, and
// returns off1 such that msg[off:off1] is the encoded data.
func unpackStruct(any dnsStruct, msg []byte, off int) (off1 int, ok bool) {
ok = any.Walk(func(field interface{}, name, tag string) bool {
switch fv := field.(type) {
default:
println("net: dns: unknown packing type")
return false
case *uint16:
if off+2 > len(msg) {
return false
}
*fv = uint16(msg[off])<<8 | uint16(msg[off+1])
off += 2
case *uint32:
if off+4 > len(msg) {
return false
}
*fv = uint32(msg[off])<<24 | uint32(msg[off+1])<<16 |
uint32(msg[off+2])<<8 | uint32(msg[off+3])
off += 4
case []byte:
n := len(fv)
if off+n > len(msg) {
return false
}
copy(fv, msg[off:off+n])
off += n
case *string:
var s string
switch tag {
default:
println("net: dns: unknown string tag", tag)
return false
case "domain":
s, off, ok = unpackDomainName(msg, off)
if !ok {
return false
}
case "":
if off >= len(msg) || off+1+int(msg[off]) > len(msg) {
return false
}
n := int(msg[off])
off++
b := make([]byte, n)
for i := 0; i < n; i++ {
b[i] = msg[off+i]
}
off += n
s = string(b)
}
*fv = s
}
return true
})
if !ok {
return len(msg), false
}
return off, true
}
// Generic struct printer. Prints fields with tag "ipv4" or "ipv6"
// as IP addresses.
func printStruct(any dnsStruct) string {
s := "{"
i := 0
any.Walk(func(val interface{}, name, tag string) bool {
i++
if i > 1 {
s += ", "
}
s += name + "="
switch tag {
case "ipv4":
i := *val.(*uint32)
s += IPv4(byte(i>>24), byte(i>>16), byte(i>>8), byte(i)).String()
case "ipv6":
i := val.([]byte)
s += IP(i).String()
default:
var i int64
switch v := val.(type) {
default:
// can't really happen.
s += "<unknown type>"
return true
case *string:
s += *v
return true
case []byte:
s += string(v)
return true
case *bool:
if *v {
s += "true"
} else {
s += "false"
}
return true
case *int:
i = int64(*v)
case *uint:
i = int64(*v)
case *uint8:
i = int64(*v)
case *uint16:
i = int64(*v)
case *uint32:
i = int64(*v)
case *uint64:
i = int64(*v)
case *uintptr:
i = int64(*v)
}
s += itoa(int(i))
}
return true
})
s += "}"
return s
}
// Resource record packer.
func packRR(rr dnsRR, msg []byte, off int) (off2 int, ok bool) {
var off1 int
// pack twice, once to find end of header
// and again to find end of packet.
// a bit inefficient but this doesn't need to be fast.
// off1 is end of header
// off2 is end of rr
off1, ok = packStruct(rr.Header(), msg, off)
if !ok {
return len(msg), false
}
off2, ok = packStruct(rr, msg, off)
if !ok {
return len(msg), false
}
// pack a third time; redo header with correct data length
rr.Header().Rdlength = uint16(off2 - off1)
packStruct(rr.Header(), msg, off)
return off2, true
}
// Resource record unpacker.
func unpackRR(msg []byte, off int) (rr dnsRR, off1 int, ok bool) {
// unpack just the header, to find the rr type and length
var h dnsRR_Header
off0 := off
if off, ok = unpackStruct(&h, msg, off); !ok {
return nil, len(msg), false
}
end := off + int(h.Rdlength)
// make an rr of that type and re-unpack.
// again inefficient but doesn't need to be fast.
mk, known := rr_mk[int(h.Rrtype)]
if !known {
return &h, end, true
}
rr = mk()
off, ok = unpackStruct(rr, msg, off0)
if off != end {
return &h, end, true
}
return rr, off, ok
}
// Usable representation of a DNS packet.
// A manually-unpacked version of (id, bits).
// This is in its own struct for easy printing.
type dnsMsgHdr struct {
id uint16
response bool
opcode int
authoritative bool
truncated bool
recursion_desired bool
recursion_available bool
rcode int
}
func (h *dnsMsgHdr) Walk(f func(v interface{}, name, tag string) bool) bool {
return f(&h.id, "id", "") &&
f(&h.response, "response", "") &&
f(&h.opcode, "opcode", "") &&
f(&h.authoritative, "authoritative", "") &&
f(&h.truncated, "truncated", "") &&
f(&h.recursion_desired, "recursion_desired", "") &&
f(&h.recursion_available, "recursion_available", "") &&
f(&h.rcode, "rcode", "")
}
type dnsMsg struct {
dnsMsgHdr
question []dnsQuestion
answer []dnsRR
ns []dnsRR
extra []dnsRR
}
func (dns *dnsMsg) Pack() (msg []byte, ok bool) {
var dh dnsHeader
// Convert convenient dnsMsg into wire-like dnsHeader.
dh.Id = dns.id
dh.Bits = uint16(dns.opcode)<<11 | uint16(dns.rcode)
if dns.recursion_available {
dh.Bits |= _RA
}
if dns.recursion_desired {
dh.Bits |= _RD
}
if dns.truncated {
dh.Bits |= _TC
}
if dns.authoritative {
dh.Bits |= _AA
}
if dns.response {
dh.Bits |= _QR
}
// Prepare variable sized arrays.
question := dns.question
answer := dns.answer
ns := dns.ns
extra := dns.extra
dh.Qdcount = uint16(len(question))
dh.Ancount = uint16(len(answer))
dh.Nscount = uint16(len(ns))
dh.Arcount = uint16(len(extra))
// Could work harder to calculate message size,
// but this is far more than we need and not
// big enough to hurt the allocator.
msg = make([]byte, 2000)
// Pack it in: header and then the pieces.
off := 0
off, ok = packStruct(&dh, msg, off)
for i := 0; i < len(question); i++ {
off, ok = packStruct(&question[i], msg, off)
}
for i := 0; i < len(answer); i++ {
off, ok = packRR(answer[i], msg, off)
}
for i := 0; i < len(ns); i++ {
off, ok = packRR(ns[i], msg, off)
}
for i := 0; i < len(extra); i++ {
off, ok = packRR(extra[i], msg, off)
}
if !ok {
return nil, false
}
return msg[0:off], true
}
func (dns *dnsMsg) Unpack(msg []byte) bool {
// Header.
var dh dnsHeader
off := 0
var ok bool
if off, ok = unpackStruct(&dh, msg, off); !ok {
return false
}
dns.id = dh.Id
dns.response = (dh.Bits & _QR) != 0
dns.opcode = int(dh.Bits>>11) & 0xF
dns.authoritative = (dh.Bits & _AA) != 0
dns.truncated = (dh.Bits & _TC) != 0
dns.recursion_desired = (dh.Bits & _RD) != 0
dns.recursion_available = (dh.Bits & _RA) != 0
dns.rcode = int(dh.Bits & 0xF)
// Arrays.
dns.question = make([]dnsQuestion, dh.Qdcount)
dns.answer = make([]dnsRR, 0, dh.Ancount)
dns.ns = make([]dnsRR, 0, dh.Nscount)
dns.extra = make([]dnsRR, 0, dh.Arcount)
var rec dnsRR
for i := 0; i < len(dns.question); i++ {
off, ok = unpackStruct(&dns.question[i], msg, off)
}
for i := 0; i < int(dh.Ancount); i++ {
rec, off, ok = unpackRR(msg, off)
if !ok {
return false
}
dns.answer = append(dns.answer, rec)
}
for i := 0; i < int(dh.Nscount); i++ {
rec, off, ok = unpackRR(msg, off)
if !ok {
return false
}
dns.ns = append(dns.ns, rec)
}
for i := 0; i < int(dh.Arcount); i++ {
rec, off, ok = unpackRR(msg, off)
if !ok {
return false
}
dns.extra = append(dns.extra, rec)
}
// if off != len(msg) {
// println("extra bytes in dns packet", off, "<", len(msg));
// }
return true
}
func (dns *dnsMsg) String() string {
s := "DNS: " + printStruct(&dns.dnsMsgHdr) + "\n"
if len(dns.question) > 0 {
s += "-- Questions\n"
for i := 0; i < len(dns.question); i++ {
s += printStruct(&dns.question[i]) + "\n"
}
}
if len(dns.answer) > 0 {
s += "-- Answers\n"
for i := 0; i < len(dns.answer); i++ {
s += printStruct(dns.answer[i]) + "\n"
}
}
if len(dns.ns) > 0 {
s += "-- Name servers\n"
for i := 0; i < len(dns.ns); i++ {
s += printStruct(dns.ns[i]) + "\n"
}
}
if len(dns.extra) > 0 {
s += "-- Extra\n"
for i := 0; i < len(dns.extra); i++ {
s += printStruct(dns.extra[i]) + "\n"
}
}
return s
}