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-rw-r--r--vendor/golang.org/x/net/dns/dnsmessage/message.go1418
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diff --git a/vendor/golang.org/x/net/dns/dnsmessage/message.go b/vendor/golang.org/x/net/dns/dnsmessage/message.go
new file mode 100644
index 000000000..da43b0ba4
--- /dev/null
+++ b/vendor/golang.org/x/net/dns/dnsmessage/message.go
@@ -0,0 +1,1418 @@
+// 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.
+
+// Package dnsmessage provides a mostly RFC 1035 compliant implementation of
+// DNS message packing and unpacking.
+//
+// This implementation is designed to minimize heap allocations and avoid
+// unnecessary packing and unpacking as much as possible.
+package dnsmessage
+
+import (
+ "errors"
+)
+
+// Packet formats
+
+// A Type is a type of DNS request and response.
+type Type uint16
+
+// A Class is a type of network.
+type Class uint16
+
+// An OpCode is a DNS operation code.
+type OpCode uint16
+
+// An RCode is a DNS response status code.
+type RCode uint16
+
+// Wire constants.
+const (
+ // ResourceHeader.Type and Question.Type
+ TypeA Type = 1
+ TypeNS Type = 2
+ TypeCNAME Type = 5
+ TypeSOA Type = 6
+ TypePTR Type = 12
+ TypeMX Type = 15
+ TypeTXT Type = 16
+ TypeAAAA Type = 28
+ TypeSRV Type = 33
+
+ // Question.Type
+ TypeWKS Type = 11
+ TypeHINFO Type = 13
+ TypeMINFO Type = 14
+ TypeAXFR Type = 252
+ TypeALL Type = 255
+
+ // ResourceHeader.Class and Question.Class
+ ClassINET Class = 1
+ ClassCSNET Class = 2
+ ClassCHAOS Class = 3
+ ClassHESIOD Class = 4
+
+ // Question.Class
+ ClassANY Class = 255
+
+ // Message.Rcode
+ RCodeSuccess RCode = 0
+ RCodeFormatError RCode = 1
+ RCodeServerFailure RCode = 2
+ RCodeNameError RCode = 3
+ RCodeNotImplemented RCode = 4
+ RCodeRefused RCode = 5
+)
+
+var (
+ // ErrNotStarted indicates that the prerequisite information isn't
+ // available yet because the previous records haven't been appropriately
+ // parsed or skipped.
+ ErrNotStarted = errors.New("parsing of this type isn't available yet")
+
+ // ErrSectionDone indicated that all records in the section have been
+ // parsed.
+ ErrSectionDone = errors.New("parsing of this section has completed")
+
+ errBaseLen = errors.New("insufficient data for base length type")
+ errCalcLen = errors.New("insufficient data for calculated length type")
+ errReserved = errors.New("segment prefix is reserved")
+ errTooManyPtr = errors.New("too many pointers (>10)")
+ errInvalidPtr = errors.New("invalid pointer")
+ errResourceLen = errors.New("insufficient data for resource body length")
+ errSegTooLong = errors.New("segment length too long")
+ errZeroSegLen = errors.New("zero length segment")
+ errResTooLong = errors.New("resource length too long")
+ errTooManyQuestions = errors.New("too many Questions to pack (>65535)")
+ errTooManyAnswers = errors.New("too many Answers to pack (>65535)")
+ errTooManyAuthorities = errors.New("too many Authorities to pack (>65535)")
+ errTooManyAdditionals = errors.New("too many Additionals to pack (>65535)")
+)
+
+type nestedError struct {
+ // s is the current level's error message.
+ s string
+
+ // err is the nested error.
+ err error
+}
+
+// nestedError implements error.Error.
+func (e *nestedError) Error() string {
+ return e.s + ": " + e.err.Error()
+}
+
+// Header is a representation of a DNS message header.
+type Header struct {
+ ID uint16
+ Response bool
+ OpCode OpCode
+ Authoritative bool
+ Truncated bool
+ RecursionDesired bool
+ RecursionAvailable bool
+ RCode RCode
+}
+
+func (m *Header) pack() (id uint16, bits uint16) {
+ id = m.ID
+ bits = uint16(m.OpCode)<<11 | uint16(m.RCode)
+ if m.RecursionAvailable {
+ bits |= headerBitRA
+ }
+ if m.RecursionDesired {
+ bits |= headerBitRD
+ }
+ if m.Truncated {
+ bits |= headerBitTC
+ }
+ if m.Authoritative {
+ bits |= headerBitAA
+ }
+ if m.Response {
+ bits |= headerBitQR
+ }
+ return
+}
+
+// Message is a representation of a DNS message.
+type Message struct {
+ Header
+ Questions []Question
+ Answers []Resource
+ Authorities []Resource
+ Additionals []Resource
+}
+
+type section uint8
+
+const (
+ sectionHeader section = iota
+ sectionQuestions
+ sectionAnswers
+ sectionAuthorities
+ sectionAdditionals
+ sectionDone
+
+ headerBitQR = 1 << 15 // query/response (response=1)
+ headerBitAA = 1 << 10 // authoritative
+ headerBitTC = 1 << 9 // truncated
+ headerBitRD = 1 << 8 // recursion desired
+ headerBitRA = 1 << 7 // recursion available
+)
+
+var sectionNames = map[section]string{
+ sectionHeader: "header",
+ sectionQuestions: "Question",
+ sectionAnswers: "Answer",
+ sectionAuthorities: "Authority",
+ sectionAdditionals: "Additional",
+}
+
+// header is the wire format for a DNS message header.
+type header struct {
+ id uint16
+ bits uint16
+ questions uint16
+ answers uint16
+ authorities uint16
+ additionals uint16
+}
+
+func (h *header) count(sec section) uint16 {
+ switch sec {
+ case sectionQuestions:
+ return h.questions
+ case sectionAnswers:
+ return h.answers
+ case sectionAuthorities:
+ return h.authorities
+ case sectionAdditionals:
+ return h.additionals
+ }
+ return 0
+}
+
+func (h *header) pack(msg []byte) []byte {
+ msg = packUint16(msg, h.id)
+ msg = packUint16(msg, h.bits)
+ msg = packUint16(msg, h.questions)
+ msg = packUint16(msg, h.answers)
+ msg = packUint16(msg, h.authorities)
+ return packUint16(msg, h.additionals)
+}
+
+func (h *header) unpack(msg []byte, off int) (int, error) {
+ newOff := off
+ var err error
+ if h.id, newOff, err = unpackUint16(msg, newOff); err != nil {
+ return off, &nestedError{"id", err}
+ }
+ if h.bits, newOff, err = unpackUint16(msg, newOff); err != nil {
+ return off, &nestedError{"bits", err}
+ }
+ if h.questions, newOff, err = unpackUint16(msg, newOff); err != nil {
+ return off, &nestedError{"questions", err}
+ }
+ if h.answers, newOff, err = unpackUint16(msg, newOff); err != nil {
+ return off, &nestedError{"answers", err}
+ }
+ if h.authorities, newOff, err = unpackUint16(msg, newOff); err != nil {
+ return off, &nestedError{"authorities", err}
+ }
+ if h.additionals, newOff, err = unpackUint16(msg, newOff); err != nil {
+ return off, &nestedError{"additionals", err}
+ }
+ return newOff, nil
+}
+
+func (h *header) header() Header {
+ return Header{
+ ID: h.id,
+ Response: (h.bits & headerBitQR) != 0,
+ OpCode: OpCode(h.bits>>11) & 0xF,
+ Authoritative: (h.bits & headerBitAA) != 0,
+ Truncated: (h.bits & headerBitTC) != 0,
+ RecursionDesired: (h.bits & headerBitRD) != 0,
+ RecursionAvailable: (h.bits & headerBitRA) != 0,
+ RCode: RCode(h.bits & 0xF),
+ }
+}
+
+// A Resource is a DNS resource record.
+type Resource interface {
+ // Header return's the Resource's ResourceHeader.
+ Header() *ResourceHeader
+
+ // pack packs a Resource except for its header.
+ pack(msg []byte, compression map[string]int) ([]byte, error)
+
+ // realType returns the actual type of the Resource. This is used to
+ // fill in the header Type field.
+ realType() Type
+}
+
+func packResource(msg []byte, resource Resource, compression map[string]int) ([]byte, error) {
+ oldMsg := msg
+ resource.Header().Type = resource.realType()
+ msg, length, err := resource.Header().pack(msg, compression)
+ if err != nil {
+ return msg, &nestedError{"ResourceHeader", err}
+ }
+ preLen := len(msg)
+ msg, err = resource.pack(msg, compression)
+ if err != nil {
+ return msg, &nestedError{"content", err}
+ }
+ conLen := len(msg) - preLen
+ if conLen > int(^uint16(0)) {
+ return oldMsg, errResTooLong
+ }
+ // Fill in the length now that we know how long the content is.
+ packUint16(length[:0], uint16(conLen))
+ resource.Header().Length = uint16(conLen)
+ return msg, nil
+}
+
+// A Parser allows incrementally parsing a DNS message.
+//
+// When parsing is started, the Header is parsed. Next, each Question can be
+// either parsed or skipped. Alternatively, all Questions can be skipped at
+// once. When all Questions have been parsed, attempting to parse Questions
+// will return (nil, nil) and attempting to skip Questions will return
+// (true, nil). After all Questions have been either parsed or skipped, all
+// Answers, Authorities and Additionals can be either parsed or skipped in the
+// same way, and each type of Resource must be fully parsed or skipped before
+// proceeding to the next type of Resource.
+//
+// Note that there is no requirement to fully skip or parse the message.
+type Parser struct {
+ msg []byte
+ header header
+
+ section section
+ off int
+ index int
+ resHeaderValid bool
+ resHeader ResourceHeader
+}
+
+// Start parses the header and enables the parsing of Questions.
+func (p *Parser) Start(msg []byte) (Header, error) {
+ if p.msg != nil {
+ *p = Parser{}
+ }
+ p.msg = msg
+ var err error
+ if p.off, err = p.header.unpack(msg, 0); err != nil {
+ return Header{}, &nestedError{"unpacking header", err}
+ }
+ p.section = sectionQuestions
+ return p.header.header(), nil
+}
+
+func (p *Parser) checkAdvance(sec section) error {
+ if p.section < sec {
+ return ErrNotStarted
+ }
+ if p.section > sec {
+ return ErrSectionDone
+ }
+ p.resHeaderValid = false
+ if p.index == int(p.header.count(sec)) {
+ p.index = 0
+ p.section++
+ return ErrSectionDone
+ }
+ return nil
+}
+
+func (p *Parser) resource(sec section) (Resource, error) {
+ var r Resource
+ hdr, err := p.resourceHeader(sec)
+ if err != nil {
+ return r, err
+ }
+ p.resHeaderValid = false
+ r, p.off, err = unpackResource(p.msg, p.off, hdr)
+ if err != nil {
+ return nil, &nestedError{"unpacking " + sectionNames[sec], err}
+ }
+ p.index++
+ return r, nil
+}
+
+func (p *Parser) resourceHeader(sec section) (ResourceHeader, error) {
+ if p.resHeaderValid {
+ return p.resHeader, nil
+ }
+ if err := p.checkAdvance(sec); err != nil {
+ return ResourceHeader{}, err
+ }
+ var hdr ResourceHeader
+ off, err := hdr.unpack(p.msg, p.off)
+ if err != nil {
+ return ResourceHeader{}, err
+ }
+ p.resHeaderValid = true
+ p.resHeader = hdr
+ p.off = off
+ return hdr, nil
+}
+
+func (p *Parser) skipResource(sec section) error {
+ if p.resHeaderValid {
+ newOff := p.off + int(p.resHeader.Length)
+ if newOff > len(p.msg) {
+ return errResourceLen
+ }
+ p.off = newOff
+ p.resHeaderValid = false
+ p.index++
+ return nil
+ }
+ if err := p.checkAdvance(sec); err != nil {
+ return err
+ }
+ var err error
+ p.off, err = skipResource(p.msg, p.off)
+ if err != nil {
+ return &nestedError{"skipping: " + sectionNames[sec], err}
+ }
+ p.index++
+ return nil
+}
+
+// Question parses a single Question.
+func (p *Parser) Question() (Question, error) {
+ if err := p.checkAdvance(sectionQuestions); err != nil {
+ return Question{}, err
+ }
+ name, off, err := unpackName(p.msg, p.off)
+ if err != nil {
+ return Question{}, &nestedError{"unpacking Question.Name", err}
+ }
+ typ, off, err := unpackType(p.msg, off)
+ if err != nil {
+ return Question{}, &nestedError{"unpacking Question.Type", err}
+ }
+ class, off, err := unpackClass(p.msg, off)
+ if err != nil {
+ return Question{}, &nestedError{"unpacking Question.Class", err}
+ }
+ p.off = off
+ p.index++
+ return Question{name, typ, class}, nil
+}
+
+// AllQuestions parses all Questions.
+func (p *Parser) AllQuestions() ([]Question, error) {
+ qs := make([]Question, 0, p.header.questions)
+ for {
+ q, err := p.Question()
+ if err == ErrSectionDone {
+ return qs, nil
+ }
+ if err != nil {
+ return nil, err
+ }
+ qs = append(qs, q)
+ }
+}
+
+// SkipQuestion skips a single Question.
+func (p *Parser) SkipQuestion() error {
+ if err := p.checkAdvance(sectionQuestions); err != nil {
+ return err
+ }
+ off, err := skipName(p.msg, p.off)
+ if err != nil {
+ return &nestedError{"skipping Question Name", err}
+ }
+ if off, err = skipType(p.msg, off); err != nil {
+ return &nestedError{"skipping Question Type", err}
+ }
+ if off, err = skipClass(p.msg, off); err != nil {
+ return &nestedError{"skipping Question Class", err}
+ }
+ p.off = off
+ p.index++
+ return nil
+}
+
+// SkipAllQuestions skips all Questions.
+func (p *Parser) SkipAllQuestions() error {
+ for {
+ if err := p.SkipQuestion(); err == ErrSectionDone {
+ return nil
+ } else if err != nil {
+ return err
+ }
+ }
+}
+
+// AnswerHeader parses a single Answer ResourceHeader.
+func (p *Parser) AnswerHeader() (ResourceHeader, error) {
+ return p.resourceHeader(sectionAnswers)
+}
+
+// Answer parses a single Answer Resource.
+func (p *Parser) Answer() (Resource, error) {
+ return p.resource(sectionAnswers)
+}
+
+// AllAnswers parses all Answer Resources.
+func (p *Parser) AllAnswers() ([]Resource, error) {
+ as := make([]Resource, 0, p.header.answers)
+ for {
+ a, err := p.Answer()
+ if err == ErrSectionDone {
+ return as, nil
+ }
+ if err != nil {
+ return nil, err
+ }
+ as = append(as, a)
+ }
+}
+
+// SkipAnswer skips a single Answer Resource.
+func (p *Parser) SkipAnswer() error {
+ return p.skipResource(sectionAnswers)
+}
+
+// SkipAllAnswers skips all Answer Resources.
+func (p *Parser) SkipAllAnswers() error {
+ for {
+ if err := p.SkipAnswer(); err == ErrSectionDone {
+ return nil
+ } else if err != nil {
+ return err
+ }
+ }
+}
+
+// AuthorityHeader parses a single Authority ResourceHeader.
+func (p *Parser) AuthorityHeader() (ResourceHeader, error) {
+ return p.resourceHeader(sectionAuthorities)
+}
+
+// Authority parses a single Authority Resource.
+func (p *Parser) Authority() (Resource, error) {
+ return p.resource(sectionAuthorities)
+}
+
+// AllAuthorities parses all Authority Resources.
+func (p *Parser) AllAuthorities() ([]Resource, error) {
+ as := make([]Resource, 0, p.header.authorities)
+ for {
+ a, err := p.Authority()
+ if err == ErrSectionDone {
+ return as, nil
+ }
+ if err != nil {
+ return nil, err
+ }
+ as = append(as, a)
+ }
+}
+
+// SkipAuthority skips a single Authority Resource.
+func (p *Parser) SkipAuthority() error {
+ return p.skipResource(sectionAuthorities)
+}
+
+// SkipAllAuthorities skips all Authority Resources.
+func (p *Parser) SkipAllAuthorities() error {
+ for {
+ if err := p.SkipAuthority(); err == ErrSectionDone {
+ return nil
+ } else if err != nil {
+ return err
+ }
+ }
+}
+
+// AdditionalHeader parses a single Additional ResourceHeader.
+func (p *Parser) AdditionalHeader() (ResourceHeader, error) {
+ return p.resourceHeader(sectionAdditionals)
+}
+
+// Additional parses a single Additional Resource.
+func (p *Parser) Additional() (Resource, error) {
+ return p.resource(sectionAdditionals)
+}
+
+// AllAdditionals parses all Additional Resources.
+func (p *Parser) AllAdditionals() ([]Resource, error) {
+ as := make([]Resource, 0, p.header.additionals)
+ for {
+ a, err := p.Additional()
+ if err == ErrSectionDone {
+ return as, nil
+ }
+ if err != nil {
+ return nil, err
+ }
+ as = append(as, a)
+ }
+}
+
+// SkipAdditional skips a single Additional Resource.
+func (p *Parser) SkipAdditional() error {
+ return p.skipResource(sectionAdditionals)
+}
+
+// SkipAllAdditionals skips all Additional Resources.
+func (p *Parser) SkipAllAdditionals() error {
+ for {
+ if err := p.SkipAdditional(); err == ErrSectionDone {
+ return nil
+ } else if err != nil {
+ return err
+ }
+ }
+}
+
+// Unpack parses a full Message.
+func (m *Message) Unpack(msg []byte) error {
+ var p Parser
+ var err error
+ if m.Header, err = p.Start(msg); err != nil {
+ return err
+ }
+ if m.Questions, err = p.AllQuestions(); err != nil {
+ return err
+ }
+ if m.Answers, err = p.AllAnswers(); err != nil {
+ return err
+ }
+ if m.Authorities, err = p.AllAuthorities(); err != nil {
+ return err
+ }
+ if m.Additionals, err = p.AllAdditionals(); err != nil {
+ return err
+ }
+ return nil
+}
+
+// Pack packs a full Message.
+func (m *Message) Pack() ([]byte, error) {
+ // Validate the lengths. It is very unlikely that anyone will try to
+ // pack more than 65535 of any particular type, but it is possible and
+ // we should fail gracefully.
+ if len(m.Questions) > int(^uint16(0)) {
+ return nil, errTooManyQuestions
+ }
+ if len(m.Answers) > int(^uint16(0)) {
+ return nil, errTooManyAnswers
+ }
+ if len(m.Authorities) > int(^uint16(0)) {
+ return nil, errTooManyAuthorities
+ }
+ if len(m.Additionals) > int(^uint16(0)) {
+ return nil, errTooManyAdditionals
+ }
+
+ var h header
+ h.id, h.bits = m.Header.pack()
+
+ h.questions = uint16(len(m.Questions))
+ h.answers = uint16(len(m.Answers))
+ h.authorities = uint16(len(m.Authorities))
+ h.additionals = uint16(len(m.Additionals))
+
+ // The starting capacity doesn't matter too much, but most DNS responses
+ // Will be <= 512 bytes as it is the limit for DNS over UDP.
+ msg := make([]byte, 0, 512)
+
+ msg = h.pack(msg)
+
+ // RFC 1035 allows (but does not require) compression for packing. RFC
+ // 1035 requires unpacking implementations to support compression, so
+ // unconditionally enabling it is fine.
+ //
+ // DNS lookups are typically done over UDP, and RFC 1035 states that UDP
+ // DNS packets can be a maximum of 512 bytes long. Without compression,
+ // many DNS response packets are over this limit, so enabling
+ // compression will help ensure compliance.
+ compression := map[string]int{}
+
+ for _, q := range m.Questions {
+ var err error
+ msg, err = q.pack(msg, compression)
+ if err != nil {
+ return nil, &nestedError{"packing Question", err}
+ }
+ }
+ for _, a := range m.Answers {
+ var err error
+ msg, err = packResource(msg, a, compression)
+ if err != nil {
+ return nil, &nestedError{"packing Answer", err}
+ }
+ }
+ for _, a := range m.Authorities {
+ var err error
+ msg, err = packResource(msg, a, compression)
+ if err != nil {
+ return nil, &nestedError{"packing Authority", err}
+ }
+ }
+ for _, a := range m.Additionals {
+ var err error
+ msg, err = packResource(msg, a, compression)
+ if err != nil {
+ return nil, &nestedError{"packing Additional", err}
+ }
+ }
+
+ return msg, nil
+}
+
+// An ResourceHeader is the header of a DNS resource record. There are
+// many types of DNS resource records, but they all share the same header.
+type ResourceHeader struct {
+ // Name is the domain name for which this resource record pertains.
+ Name string
+
+ // Type is the type of DNS resource record.
+ //
+ // This field will be set automatically during packing.
+ Type Type
+
+ // Class is the class of network to which this DNS resource record
+ // pertains.
+ Class Class
+
+ // TTL is the length of time (measured in seconds) which this resource
+ // record is valid for (time to live). All Resources in a set should
+ // have the same TTL (RFC 2181 Section 5.2).
+ TTL uint32
+
+ // Length is the length of data in the resource record after the header.
+ //
+ // This field will be set automatically during packing.
+ Length uint16
+}
+
+// Header implements Resource.Header.
+func (h *ResourceHeader) Header() *ResourceHeader {
+ return h
+}
+
+// pack packs all of the fields in a ResourceHeader except for the length. The
+// length bytes are returned as a slice so they can be filled in after the rest
+// of the Resource has been packed.
+func (h *ResourceHeader) pack(oldMsg []byte, compression map[string]int) (msg []byte, length []byte, err error) {
+ msg = oldMsg
+ if msg, err = packName(msg, h.Name, compression); err != nil {
+ return oldMsg, nil, &nestedError{"Name", err}
+ }
+ msg = packType(msg, h.Type)
+ msg = packClass(msg, h.Class)
+ msg = packUint32(msg, h.TTL)
+ lenBegin := len(msg)
+ msg = packUint16(msg, h.Length)
+ return msg, msg[lenBegin:], nil
+}
+
+func (h *ResourceHeader) unpack(msg []byte, off int) (int, error) {
+ newOff := off
+ var err error
+ if h.Name, newOff, err = unpackName(msg, newOff); err != nil {
+ return off, &nestedError{"Name", err}
+ }
+ if h.Type, newOff, err = unpackType(msg, newOff); err != nil {
+ return off, &nestedError{"Type", err}
+ }
+ if h.Class, newOff, err = unpackClass(msg, newOff); err != nil {
+ return off, &nestedError{"Class", err}
+ }
+ if h.TTL, newOff, err = unpackUint32(msg, newOff); err != nil {
+ return off, &nestedError{"TTL", err}
+ }
+ if h.Length, newOff, err = unpackUint16(msg, newOff); err != nil {
+ return off, &nestedError{"Length", err}
+ }
+ return newOff, nil
+}
+
+func skipResource(msg []byte, off int) (int, error) {
+ newOff, err := skipName(msg, off)
+ if err != nil {
+ return off, &nestedError{"Name", err}
+ }
+ if newOff, err = skipType(msg, newOff); err != nil {
+ return off, &nestedError{"Type", err}
+ }
+ if newOff, err = skipClass(msg, newOff); err != nil {
+ return off, &nestedError{"Class", err}
+ }
+ if newOff, err = skipUint32(msg, newOff); err != nil {
+ return off, &nestedError{"TTL", err}
+ }
+ length, newOff, err := unpackUint16(msg, newOff)
+ if err != nil {
+ return off, &nestedError{"Length", err}
+ }
+ if newOff += int(length); newOff > len(msg) {
+ return off, errResourceLen
+ }
+ return newOff, nil
+}
+
+func packUint16(msg []byte, field uint16) []byte {
+ return append(msg, byte(field>>8), byte(field))
+}
+
+func unpackUint16(msg []byte, off int) (uint16, int, error) {
+ if off+2 > len(msg) {
+ return 0, off, errBaseLen
+ }
+ return uint16(msg[off])<<8 | uint16(msg[off+1]), off + 2, nil
+}
+
+func skipUint16(msg []byte, off int) (int, error) {
+ if off+2 > len(msg) {
+ return off, errBaseLen
+ }
+ return off + 2, nil
+}
+
+func packType(msg []byte, field Type) []byte {
+ return packUint16(msg, uint16(field))
+}
+
+func unpackType(msg []byte, off int) (Type, int, error) {
+ t, o, err := unpackUint16(msg, off)
+ return Type(t), o, err
+}
+
+func skipType(msg []byte, off int) (int, error) {
+ return skipUint16(msg, off)
+}
+
+func packClass(msg []byte, field Class) []byte {
+ return packUint16(msg, uint16(field))
+}
+
+func unpackClass(msg []byte, off int) (Class, int, error) {
+ c, o, err := unpackUint16(msg, off)
+ return Class(c), o, err
+}
+
+func skipClass(msg []byte, off int) (int, error) {
+ return skipUint16(msg, off)
+}
+
+func packUint32(msg []byte, field uint32) []byte {
+ return append(
+ msg,
+ byte(field>>24),
+ byte(field>>16),
+ byte(field>>8),
+ byte(field),
+ )
+}
+
+func unpackUint32(msg []byte, off int) (uint32, int, error) {
+ if off+4 > len(msg) {
+ return 0, off, errBaseLen
+ }
+ v := uint32(msg[off])<<24 | uint32(msg[off+1])<<16 | uint32(msg[off+2])<<8 | uint32(msg[off+3])
+ return v, off + 4, nil
+}
+
+func skipUint32(msg []byte, off int) (int, error) {
+ if off+4 > len(msg) {
+ return off, errBaseLen
+ }
+ return off + 4, nil
+}
+
+func packText(msg []byte, field string) []byte {
+ for len(field) > 0 {
+ l := len(field)
+ if l > 255 {
+ l = 255
+ }
+ msg = append(msg, byte(l))
+ msg = append(msg, field[:l]...)
+ field = field[l:]
+ }
+ return msg
+}
+
+func unpackText(msg []byte, off int) (string, int, error) {
+ if off >= len(msg) {
+ return "", off, errBaseLen
+ }
+ beginOff := off + 1
+ endOff := beginOff + int(msg[off])
+ if endOff > len(msg) {
+ return "", off, errCalcLen
+ }
+ return string(msg[beginOff:endOff]), endOff, nil
+}
+
+func skipText(msg []byte, off int) (int, error) {
+ if off >= len(msg) {
+ return off, errBaseLen
+ }
+ endOff := off + 1 + int(msg[off])
+ if endOff > len(msg) {
+ return off, errCalcLen
+ }
+ return endOff, nil
+}
+
+func packBytes(msg []byte, field []byte) []byte {
+ return append(msg, field...)
+}
+
+func unpackBytes(msg []byte, off int, field []byte) (int, error) {
+ newOff := off + len(field)
+ if newOff > len(msg) {
+ return off, errBaseLen
+ }
+ copy(field, msg[off:newOff])
+ return newOff, nil
+}
+
+func skipBytes(msg []byte, off int, field []byte) (int, error) {
+ newOff := off + len(field)
+ if newOff > len(msg) {
+ return off, errBaseLen
+ }
+ return newOff, nil
+}
+
+// packName packs a domain name.
+//
+// Domain names are a sequence of counted strings split at the dots. They end
+// with a zero-length string. Compression can be used to reuse domain suffixes.
+//
+// The compression map will be updated with new domain suffixes. If compression
+// is nil, compression will not be used.
+func packName(msg []byte, name string, compression map[string]int) ([]byte, error) {
+ oldMsg := msg
+
+ // Add a trailing dot to canonicalize name.
+ if n := len(name); n == 0 || name[n-1] != '.' {
+ name += "."
+ }
+
+ // Allow root domain.
+ if name == "." {
+ return append(msg, 0), nil
+ }
+
+ // Emit sequence of counted strings, chopping at dots.
+ for i, begin := 0, 0; i < len(name); i++ {
+ // Check for the end of the segment.
+ if name[i] == '.' {
+ // The two most significant bits have special meaning.
+ // It isn't allowed for segments to be long enough to
+ // need them.
+ if i-begin >= 1<<6 {
+ return oldMsg, errSegTooLong
+ }
+
+ // Segments must have a non-zero length.
+ if i-begin == 0 {
+ return oldMsg, errZeroSegLen
+ }
+
+ msg = append(msg, byte(i-begin))
+
+ for j := begin; j < i; j++ {
+ msg = append(msg, name[j])
+ }
+
+ begin = i + 1
+ continue
+ }
+
+ // We can only compress domain suffixes starting with a new
+ // segment. A pointer is two bytes with the two most significant
+ // bits set to 1 to indicate that it is a pointer.
+ if (i == 0 || name[i-1] == '.') && compression != nil {
+ if ptr, ok := compression[name[i:]]; ok {
+ // Hit. Emit a pointer instead of the rest of
+ // the domain.
+ return append(msg, byte(ptr>>8|0xC0), byte(ptr)), nil
+ }
+
+ // Miss. Add the suffix to the compression table if the
+ // offset can be stored in the available 14 bytes.
+ if len(msg) <= int(^uint16(0)>>2) {
+ compression[name[i:]] = len(msg)
+ }
+ }
+ }
+ return append(msg, 0), nil
+}
+
+// unpackName unpacks a domain name.
+func unpackName(msg []byte, off int) (string, int, error) {
+ // currOff is the current working offset.
+ currOff := off
+
+ // newOff is the offset where the next record will start. Pointers lead
+ // to data that belongs to other names and thus doesn't count towards to
+ // the usage of this name.
+ newOff := off
+
+ // name is the domain name being unpacked.
+ name := make([]byte, 0, 255)
+
+ // ptr is the number of pointers followed.
+ var ptr int
+Loop:
+ for {
+ if currOff >= len(msg) {
+ return "", off, errBaseLen
+ }
+ c := int(msg[currOff])
+ currOff++
+ switch c & 0xC0 {
+ case 0x00: // String segment
+ if c == 0x00 {
+ // A zero length signals the end of the name.
+ break Loop
+ }
+ endOff := currOff + c
+ if endOff > len(msg) {
+ return "", off, errCalcLen
+ }
+ name = append(name, msg[currOff:endOff]...)
+ name = append(name, '.')
+ currOff = endOff
+ case 0xC0: // Pointer
+ if currOff >= len(msg) {
+ return "", off, errInvalidPtr
+ }
+ c1 := msg[currOff]
+ currOff++
+ if ptr == 0 {
+ newOff = currOff
+ }
+ // Don't follow too many pointers, maybe there's a loop.
+ if ptr++; ptr > 10 {
+ return "", off, errTooManyPtr
+ }
+ currOff = (c^0xC0)<<8 | int(c1)
+ default:
+ // Prefixes 0x80 and 0x40 are reserved.
+ return "", off, errReserved
+ }
+ }
+ if len(name) == 0 {
+ name = append(name, '.')
+ }
+ if ptr == 0 {
+ newOff = currOff
+ }
+ return string(name), newOff, nil
+}
+
+func skipName(msg []byte, off int) (int, error) {
+ // newOff is the offset where the next record will start. Pointers lead
+ // to data that belongs to other names and thus doesn't count towards to
+ // the usage of this name.
+ newOff := off
+
+Loop:
+ for {
+ if newOff >= len(msg) {
+ return off, errBaseLen
+ }
+ c := int(msg[newOff])
+ newOff++
+ switch c & 0xC0 {
+ case 0x00:
+ if c == 0x00 {
+ // A zero length signals the end of the name.
+ break Loop
+ }
+ // literal string
+ newOff += c
+ if newOff > len(msg) {
+ return off, errCalcLen
+ }
+ case 0xC0:
+ // Pointer to somewhere else in msg.
+
+ // Pointers are two bytes.
+ newOff++
+
+ // Don't follow the pointer as the data here has ended.
+ break Loop
+ default:
+ // Prefixes 0x80 and 0x40 are reserved.
+ return off, errReserved
+ }
+ }
+
+ return newOff, nil
+}
+
+// A Question is a DNS query.
+type Question struct {
+ Name string
+ Type Type
+ Class Class
+}
+
+func (q *Question) pack(msg []byte, compression map[string]int) ([]byte, error) {
+ msg, err := packName(msg, q.Name, compression)
+ if err != nil {
+ return msg, &nestedError{"Name", err}
+ }
+ msg = packType(msg, q.Type)
+ return packClass(msg, q.Class), nil
+}
+
+func unpackResource(msg []byte, off int, hdr ResourceHeader) (Resource, int, error) {
+ var (
+ r Resource
+ err error
+ name string
+ )
+ switch hdr.Type {
+ case TypeA:
+ r, err = unpackAResource(hdr, msg, off)
+ name = "A"
+ case TypeNS:
+ r, err = unpackNSResource(hdr, msg, off)
+ name = "NS"
+ case TypeCNAME:
+ r, err = unpackCNAMEResource(hdr, msg, off)
+ name = "CNAME"
+ case TypeSOA:
+ r, err = unpackSOAResource(hdr, msg, off)
+ name = "SOA"
+ case TypePTR:
+ r, err = unpackPTRResource(hdr, msg, off)
+ name = "PTR"
+ case TypeMX:
+ r, err = unpackMXResource(hdr, msg, off)
+ name = "MX"
+ case TypeTXT:
+ r, err = unpackTXTResource(hdr, msg, off)
+ name = "TXT"
+ case TypeAAAA:
+ r, err = unpackAAAAResource(hdr, msg, off)
+ name = "AAAA"
+ case TypeSRV:
+ r, err = unpackSRVResource(hdr, msg, off)
+ name = "SRV"
+ }
+ if err != nil {
+ return nil, off, &nestedError{name + " record", err}
+ }
+ if r != nil {
+ return r, off + int(hdr.Length), nil
+ }
+ return nil, off, errors.New("invalid resource type: " + string(hdr.Type+'0'))
+}
+
+// A CNAMEResource is a CNAME Resource record.
+type CNAMEResource struct {
+ ResourceHeader
+
+ CNAME string
+}
+
+func (r *CNAMEResource) realType() Type {
+ return TypeCNAME
+}
+
+func (r *CNAMEResource) pack(msg []byte, compression map[string]int) ([]byte, error) {
+ return packName(msg, r.CNAME, compression)
+}
+
+func unpackCNAMEResource(hdr ResourceHeader, msg []byte, off int) (*CNAMEResource, error) {
+ cname, _, err := unpackName(msg, off)
+ if err != nil {
+ return nil, err
+ }
+ return &CNAMEResource{hdr, cname}, nil
+}
+
+// An MXResource is an MX Resource record.
+type MXResource struct {
+ ResourceHeader
+
+ Pref uint16
+ MX string
+}
+
+func (r *MXResource) realType() Type {
+ return TypeMX
+}
+
+func (r *MXResource) pack(msg []byte, compression map[string]int) ([]byte, error) {
+ oldMsg := msg
+ msg = packUint16(msg, r.Pref)
+ msg, err := packName(msg, r.MX, compression)
+ if err != nil {
+ return oldMsg, &nestedError{"MXResource.MX", err}
+ }
+ return msg, nil
+}
+
+func unpackMXResource(hdr ResourceHeader, msg []byte, off int) (*MXResource, error) {
+ pref, off, err := unpackUint16(msg, off)
+ if err != nil {
+ return nil, &nestedError{"Pref", err}
+ }
+ mx, _, err := unpackName(msg, off)
+ if err != nil {
+ return nil, &nestedError{"MX", err}
+ }
+ return &MXResource{hdr, pref, mx}, nil
+}
+
+// An NSResource is an NS Resource record.
+type NSResource struct {
+ ResourceHeader
+
+ NS string
+}
+
+func (r *NSResource) realType() Type {
+ return TypeNS
+}
+
+func (r *NSResource) pack(msg []byte, compression map[string]int) ([]byte, error) {
+ return packName(msg, r.NS, compression)
+}
+
+func unpackNSResource(hdr ResourceHeader, msg []byte, off int) (*NSResource, error) {
+ ns, _, err := unpackName(msg, off)
+ if err != nil {
+ return nil, err
+ }
+ return &NSResource{hdr, ns}, nil
+}
+
+// A PTRResource is a PTR Resource record.
+type PTRResource struct {
+ ResourceHeader
+
+ PTR string
+}
+
+func (r *PTRResource) realType() Type {
+ return TypePTR
+}
+
+func (r *PTRResource) pack(msg []byte, compression map[string]int) ([]byte, error) {
+ return packName(msg, r.PTR, compression)
+}
+
+func unpackPTRResource(hdr ResourceHeader, msg []byte, off int) (*PTRResource, error) {
+ ptr, _, err := unpackName(msg, off)
+ if err != nil {
+ return nil, err
+ }
+ return &PTRResource{hdr, ptr}, nil
+}
+
+// An SOAResource is an SOA Resource record.
+type SOAResource struct {
+ ResourceHeader
+
+ NS string
+ MBox string
+ Serial uint32
+ Refresh uint32
+ Retry uint32
+ Expire uint32
+
+ // MinTTL the is the default TTL of Resources records which did not
+ // contain a TTL value and the TTL of negative responses. (RFC 2308
+ // Section 4)
+ MinTTL uint32
+}
+
+func (r *SOAResource) realType() Type {
+ return TypeSOA
+}
+
+func (r *SOAResource) pack(msg []byte, compression map[string]int) ([]byte, error) {
+ oldMsg := msg
+ msg, err := packName(msg, r.NS, compression)
+ if err != nil {
+ return oldMsg, &nestedError{"SOAResource.NS", err}
+ }
+ msg, err = packName(msg, r.MBox, compression)
+ if err != nil {
+ return oldMsg, &nestedError{"SOAResource.MBox", err}
+ }
+ msg = packUint32(msg, r.Serial)
+ msg = packUint32(msg, r.Refresh)
+ msg = packUint32(msg, r.Retry)
+ msg = packUint32(msg, r.Expire)
+ return packUint32(msg, r.MinTTL), nil
+}
+
+func unpackSOAResource(hdr ResourceHeader, msg []byte, off int) (*SOAResource, error) {
+ ns, off, err := unpackName(msg, off)
+ if err != nil {
+ return nil, &nestedError{"NS", err}
+ }
+ mbox, off, err := unpackName(msg, off)
+ if err != nil {
+ return nil, &nestedError{"MBox", err}
+ }
+ serial, off, err := unpackUint32(msg, off)
+ if err != nil {
+ return nil, &nestedError{"Serial", err}
+ }
+ refresh, off, err := unpackUint32(msg, off)
+ if err != nil {
+ return nil, &nestedError{"Refresh", err}
+ }
+ retry, off, err := unpackUint32(msg, off)
+ if err != nil {
+ return nil, &nestedError{"Retry", err}
+ }
+ expire, off, err := unpackUint32(msg, off)
+ if err != nil {
+ return nil, &nestedError{"Expire", err}
+ }
+ minTTL, _, err := unpackUint32(msg, off)
+ if err != nil {
+ return nil, &nestedError{"MinTTL", err}
+ }
+ return &SOAResource{hdr, ns, mbox, serial, refresh, retry, expire, minTTL}, nil
+}
+
+// A TXTResource is a TXT Resource record.
+type TXTResource struct {
+ ResourceHeader
+
+ Txt string // Not a domain name.
+}
+
+func (r *TXTResource) realType() Type {
+ return TypeTXT
+}
+
+func (r *TXTResource) pack(msg []byte, compression map[string]int) ([]byte, error) {
+ return packText(msg, r.Txt), nil
+}
+
+func unpackTXTResource(hdr ResourceHeader, msg []byte, off int) (*TXTResource, error) {
+ var txt string
+ for n := uint16(0); n < hdr.Length; {
+ var t string
+ var err error
+ if t, off, err = unpackText(msg, off); err != nil {
+ return nil, &nestedError{"text", err}
+ }
+ // Check if we got too many bytes.
+ if hdr.Length-n < uint16(len(t))+1 {
+ return nil, errCalcLen
+ }
+ n += uint16(len(t)) + 1
+ txt += t
+ }
+ return &TXTResource{hdr, txt}, nil
+}
+
+// An SRVResource is an SRV Resource record.
+type SRVResource struct {
+ ResourceHeader
+
+ Priority uint16
+ Weight uint16
+ Port uint16
+ Target string // Not compressed as per RFC 2782.
+}
+
+func (r *SRVResource) realType() Type {
+ return TypeSRV
+}
+
+func (r *SRVResource) pack(msg []byte, compression map[string]int) ([]byte, error) {
+ oldMsg := msg
+ msg = packUint16(msg, r.Priority)
+ msg = packUint16(msg, r.Weight)
+ msg = packUint16(msg, r.Port)
+ msg, err := packName(msg, r.Target, nil)
+ if err != nil {
+ return oldMsg, &nestedError{"SRVResource.Target", err}
+ }
+ return msg, nil
+}
+
+func unpackSRVResource(hdr ResourceHeader, msg []byte, off int) (*SRVResource, error) {
+ priority, off, err := unpackUint16(msg, off)
+ if err != nil {
+ return nil, &nestedError{"Priority", err}
+ }
+ weight, off, err := unpackUint16(msg, off)
+ if err != nil {
+ return nil, &nestedError{"Weight", err}
+ }
+ port, off, err := unpackUint16(msg, off)
+ if err != nil {
+ return nil, &nestedError{"Port", err}
+ }
+ target, _, err := unpackName(msg, off)
+ if err != nil {
+ return nil, &nestedError{"Target", err}
+ }
+ return &SRVResource{hdr, priority, weight, port, target}, nil
+}
+
+// An AResource is an A Resource record.
+type AResource struct {
+ ResourceHeader
+
+ A [4]byte
+}
+
+func (r *AResource) realType() Type {
+ return TypeA
+}
+
+func (r *AResource) pack(msg []byte, compression map[string]int) ([]byte, error) {
+ return packBytes(msg, r.A[:]), nil
+}
+
+func unpackAResource(hdr ResourceHeader, msg []byte, off int) (*AResource, error) {
+ var a [4]byte
+ if _, err := unpackBytes(msg, off, a[:]); err != nil {
+ return nil, err
+ }
+ return &AResource{hdr, a}, nil
+}
+
+// An AAAAResource is an AAAA Resource record.
+type AAAAResource struct {
+ ResourceHeader
+
+ AAAA [16]byte
+}
+
+func (r *AAAAResource) realType() Type {
+ return TypeAAAA
+}
+
+func (r *AAAAResource) pack(msg []byte, compression map[string]int) ([]byte, error) {
+ return packBytes(msg, r.AAAA[:]), nil
+}
+
+func unpackAAAAResource(hdr ResourceHeader, msg []byte, off int) (*AAAAResource, error) {
+ var aaaa [16]byte
+ if _, err := unpackBytes(msg, off, aaaa[:]); err != nil {
+ return nil, err
+ }
+ return &AAAAResource{hdr, aaaa}, nil
+}
generated by cgit v1.2.3-1-g7c22 (git 2.25.1) at 2024-05-20 21:37:12 +0000