279 lines
7.5 KiB
Go
279 lines
7.5 KiB
Go
package dns
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import (
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"net"
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"strconv"
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"strings"
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)
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const hexDigit = "0123456789abcdef"
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// Everything is assumed in the ClassINET class. If
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// you need other classes you are on your own.
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// SetReply creates a reply packet from a request message.
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func (dns *Msg) SetReply(request *Msg) *Msg {
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dns.Id = request.Id
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dns.RecursionDesired = request.RecursionDesired // Copy rd bit
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dns.Response = true
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dns.Opcode = OpcodeQuery
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dns.Rcode = RcodeSuccess
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if len(request.Question) > 0 {
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dns.Question = make([]Question, 1)
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dns.Question[0] = request.Question[0]
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}
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return dns
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}
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// SetQuestion creates a question packet.
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func (dns *Msg) SetQuestion(z string, t uint16) *Msg {
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dns.Id = Id()
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dns.RecursionDesired = true
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dns.Question = make([]Question, 1)
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dns.Question[0] = Question{z, t, ClassINET}
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return dns
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}
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// SetNotify creates a notify packet.
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func (dns *Msg) SetNotify(z string) *Msg {
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dns.Opcode = OpcodeNotify
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dns.Authoritative = true
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dns.Id = Id()
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dns.Question = make([]Question, 1)
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dns.Question[0] = Question{z, TypeSOA, ClassINET}
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return dns
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}
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// SetRcode creates an error packet suitable for the request.
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func (dns *Msg) SetRcode(request *Msg, rcode int) *Msg {
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dns.Rcode = rcode
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dns.Opcode = OpcodeQuery
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dns.Response = true
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dns.Id = request.Id
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// Note that this is actually a FORMERR
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if len(request.Question) > 0 {
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dns.Question = make([]Question, 1)
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dns.Question[0] = request.Question[0]
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}
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return dns
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}
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// SetRcodeFormatError creates a packet with FormError set.
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func (dns *Msg) SetRcodeFormatError(request *Msg) *Msg {
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dns.Rcode = RcodeFormatError
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dns.Opcode = OpcodeQuery
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dns.Response = true
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dns.Authoritative = false
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dns.Id = request.Id
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return dns
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}
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// SetUpdate makes the message a dynamic update packet. It
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// sets the ZONE section to: z, TypeSOA, ClassINET.
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func (dns *Msg) SetUpdate(z string) *Msg {
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dns.Id = Id()
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dns.Response = false
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dns.Opcode = OpcodeUpdate
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dns.Compress = false // BIND9 cannot handle compression
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dns.Question = make([]Question, 1)
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dns.Question[0] = Question{z, TypeSOA, ClassINET}
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return dns
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}
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// SetIxfr creates dns msg suitable for requesting an ixfr.
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func (dns *Msg) SetIxfr(z string, serial uint32) *Msg {
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dns.Id = Id()
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dns.Question = make([]Question, 1)
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dns.Ns = make([]RR, 1)
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s := new(RR_SOA)
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s.Hdr = RR_Header{z, TypeSOA, ClassINET, defaultTtl, 0}
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s.Serial = serial
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dns.Question[0] = Question{z, TypeIXFR, ClassINET}
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dns.Ns[0] = s
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return dns
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}
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// SetAxfr creates dns msg suitable for requesting an axfr.
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func (dns *Msg) SetAxfr(z string) *Msg {
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dns.Id = Id()
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dns.Question = make([]Question, 1)
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dns.Question[0] = Question{z, TypeAXFR, ClassINET}
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return dns
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}
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// SetTsig appends a TSIG RR to the message.
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// This is only a skeleton TSIG RR that is added as the last RR in the
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// additional section. The Tsig is calculated when the message is being send.
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func (dns *Msg) SetTsig(z, algo string, fudge, timesigned int64) *Msg {
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t := new(RR_TSIG)
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t.Hdr = RR_Header{z, TypeTSIG, ClassANY, 0, 0}
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t.Algorithm = algo
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t.Fudge = 300
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t.TimeSigned = uint64(timesigned)
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t.OrigId = dns.Id
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dns.Extra = append(dns.Extra, t)
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return dns
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}
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// SetEdns0 appends a EDNS0 OPT RR to the message.
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// TSIG should always the last RR in a message.
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func (dns *Msg) SetEdns0(udpsize uint16, do bool) *Msg {
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e := new(RR_OPT)
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e.Hdr.Name = "."
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e.Hdr.Rrtype = TypeOPT
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e.SetUDPSize(udpsize)
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if do {
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e.SetDo()
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}
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dns.Extra = append(dns.Extra, e)
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return dns
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}
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// IsTsig checks if the message has a TSIG record as the last record
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// in the additional section. It returns the TSIG record found or nil.
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func (dns *Msg) IsTsig() *RR_TSIG {
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if len(dns.Extra) > 0 {
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if dns.Extra[len(dns.Extra)-1].Header().Rrtype == TypeTSIG {
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return dns.Extra[len(dns.Extra)-1].(*RR_TSIG)
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}
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}
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return nil
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}
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// IsEdns0 checks if the message has a EDNS0 (OPT) record, any EDNS0
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// record in the additional section will do. It returns the OPT record
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// found or nil.
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func (dns *Msg) IsEdns0() *RR_OPT {
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for _, r := range dns.Extra {
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if r.Header().Rrtype == TypeOPT {
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return r.(*RR_OPT)
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}
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}
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return nil
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}
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// IsDomainName checks if s is a valid domainname, it returns
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// the number of labels, total length and true, when a domain name is valid.
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// When false is returned the labelcount and length are not defined.
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// TODO(mg): checks for \DDD
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func IsDomainName(s string) (uint8, uint8, bool) { // copied from net package.
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// See RFC 1035, RFC 3696.
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l := len(s)
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if l == 0 || l > 255 {
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return 0, 0, false
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}
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longer := 0
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// Simplify checking loop: make the name end in a dot.
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// Don't call Fqdn() to save another len(s).
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// Keep in mind that if we do this, otherwise we report a length+1
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if s[l-1] != '.' {
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s += "."
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l++
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longer = 1
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}
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// Preloop check for root label
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if s == "." {
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return 0, 1, true
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}
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last := byte('.')
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ok := false // ok once we've seen a letter or digit
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partlen := 0
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labels := uint8(0)
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for i := 0; i < l; i++ {
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c := s[i]
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switch {
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default:
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return 0, uint8(l - longer), false
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case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || c == '_' || c == '*' || c == '/':
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ok = true
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partlen++
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case c == '\\':
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// Ok
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case c == '@':
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if last != '\\' {
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return 0, uint8(l - longer), false
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}
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partlen++
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case '0' <= c && c <= '9':
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ok = true
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partlen++
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case c == '-':
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// byte before dash cannot be dot
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if last == '.' {
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return 0, uint8(l - longer), false
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}
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partlen++
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case c == '.':
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// byte before dot cannot be dot
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if last == '.' {
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return 0, uint8(l - longer), false
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}
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if last == '\\' { // Ok, escaped dot.
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partlen++
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break
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}
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if partlen > 63 || partlen == 0 {
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return 0, uint8(l - longer), false
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}
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partlen = 0
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labels++
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}
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last = c
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}
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return labels, uint8(l - longer), ok
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}
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// IsSubDomain checks if child is indeed a child of the parent.
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func IsSubDomain(parent, child string) bool {
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// Entire child is contained in parent
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return CompareLabels(strings.ToLower(parent), strings.ToLower(child)) == LenLabels(parent)
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}
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// IsFqdn checks if a domain name is fully qualified.
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func IsFqdn(s string) bool {
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l := len(s)
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if l == 0 {
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return false // ?
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}
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return s[l-1] == '.'
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}
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// Fqdns return the fully qualified domain name from s.
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// If s is already fully qualified, it behaves as the identity function.
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func Fqdn(s string) string {
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if IsFqdn(s) {
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return s
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}
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return s + "."
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}
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// Copied from the official Go code
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// ReverseAddr returns the in-addr.arpa. or ip6.arpa. hostname of the IP
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// address addr suitable for rDNS (PTR) record lookup or an error if it fails
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// to parse the IP address.
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func ReverseAddr(addr string) (arpa string, err error) {
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ip := net.ParseIP(addr)
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if ip == nil {
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return "", &Error{Err: "unrecognized address", Name: addr}
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}
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if ip.To4() != nil {
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return strconv.Itoa(int(ip[15])) + "." + strconv.Itoa(int(ip[14])) + "." + strconv.Itoa(int(ip[13])) + "." +
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strconv.Itoa(int(ip[12])) + ".in-addr.arpa.", nil
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}
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// Must be IPv6
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buf := make([]byte, 0, len(ip)*4+len("ip6.arpa."))
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// Add it, in reverse, to the buffer
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for i := len(ip) - 1; i >= 0; i-- {
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v := ip[i]
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buf = append(buf, hexDigit[v&0xF])
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buf = append(buf, '.')
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buf = append(buf, hexDigit[v>>4])
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buf = append(buf, '.')
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}
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// Append "ip6.arpa." and return (buf already has the final .)
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buf = append(buf, "ip6.arpa."...)
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return string(buf), nil
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}
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