--- /dev/null
+package dns
+
+import (
+ "fmt"
+ "time"
+)
+
+// Envelope is used when doing a zone transfer with a remote server.
+type Envelope struct {
+ RR []RR // The set of RRs in the answer section of the xfr reply message.
+ Error error // If something went wrong, this contains the error.
+}
+
+// A Transfer defines parameters that are used during a zone transfer.
+type Transfer struct {
+ *Conn
+ DialTimeout time.Duration // net.DialTimeout, defaults to 2 seconds
+ ReadTimeout time.Duration // net.Conn.SetReadTimeout value for connections, defaults to 2 seconds
+ WriteTimeout time.Duration // net.Conn.SetWriteTimeout value for connections, defaults to 2 seconds
+ TsigSecret map[string]string // Secret(s) for Tsig map[<zonename>]<base64 secret>, zonename must be in canonical form (lowercase, fqdn, see RFC 4034 Section 6.2)
+ tsigTimersOnly bool
+}
+
+// Think we need to away to stop the transfer
+
+// In performs an incoming transfer with the server in a.
+// If you would like to set the source IP, or some other attribute
+// of a Dialer for a Transfer, you can do so by specifying the attributes
+// in the Transfer.Conn:
+//
+// d := net.Dialer{LocalAddr: transfer_source}
+// con, err := d.Dial("tcp", master)
+// dnscon := &dns.Conn{Conn:con}
+// transfer = &dns.Transfer{Conn: dnscon}
+// channel, err := transfer.In(message, master)
+//
+func (t *Transfer) In(q *Msg, a string) (env chan *Envelope, err error) {
+ switch q.Question[0].Qtype {
+ case TypeAXFR, TypeIXFR:
+ default:
+ return nil, &Error{"unsupported question type"}
+ }
+
+ timeout := dnsTimeout
+ if t.DialTimeout != 0 {
+ timeout = t.DialTimeout
+ }
+
+ if t.Conn == nil {
+ t.Conn, err = DialTimeout("tcp", a, timeout)
+ if err != nil {
+ return nil, err
+ }
+ }
+
+ if err := t.WriteMsg(q); err != nil {
+ return nil, err
+ }
+
+ env = make(chan *Envelope)
+ switch q.Question[0].Qtype {
+ case TypeAXFR:
+ go t.inAxfr(q, env)
+ case TypeIXFR:
+ go t.inIxfr(q, env)
+ }
+
+ return env, nil
+}
+
+func (t *Transfer) inAxfr(q *Msg, c chan *Envelope) {
+ first := true
+ defer t.Close()
+ defer close(c)
+ timeout := dnsTimeout
+ if t.ReadTimeout != 0 {
+ timeout = t.ReadTimeout
+ }
+ for {
+ t.Conn.SetReadDeadline(time.Now().Add(timeout))
+ in, err := t.ReadMsg()
+ if err != nil {
+ c <- &Envelope{nil, err}
+ return
+ }
+ if q.Id != in.Id {
+ c <- &Envelope{in.Answer, ErrId}
+ return
+ }
+ if first {
+ if in.Rcode != RcodeSuccess {
+ c <- &Envelope{in.Answer, &Error{err: fmt.Sprintf(errXFR, in.Rcode)}}
+ return
+ }
+ if !isSOAFirst(in) {
+ c <- &Envelope{in.Answer, ErrSoa}
+ return
+ }
+ first = !first
+ // only one answer that is SOA, receive more
+ if len(in.Answer) == 1 {
+ t.tsigTimersOnly = true
+ c <- &Envelope{in.Answer, nil}
+ continue
+ }
+ }
+
+ if !first {
+ t.tsigTimersOnly = true // Subsequent envelopes use this.
+ if isSOALast(in) {
+ c <- &Envelope{in.Answer, nil}
+ return
+ }
+ c <- &Envelope{in.Answer, nil}
+ }
+ }
+}
+
+func (t *Transfer) inIxfr(q *Msg, c chan *Envelope) {
+ var serial uint32 // The first serial seen is the current server serial
+ axfr := true
+ n := 0
+ qser := q.Ns[0].(*SOA).Serial
+ defer t.Close()
+ defer close(c)
+ timeout := dnsTimeout
+ if t.ReadTimeout != 0 {
+ timeout = t.ReadTimeout
+ }
+ for {
+ t.SetReadDeadline(time.Now().Add(timeout))
+ in, err := t.ReadMsg()
+ if err != nil {
+ c <- &Envelope{nil, err}
+ return
+ }
+ if q.Id != in.Id {
+ c <- &Envelope{in.Answer, ErrId}
+ return
+ }
+ if in.Rcode != RcodeSuccess {
+ c <- &Envelope{in.Answer, &Error{err: fmt.Sprintf(errXFR, in.Rcode)}}
+ return
+ }
+ if n == 0 {
+ // Check if the returned answer is ok
+ if !isSOAFirst(in) {
+ c <- &Envelope{in.Answer, ErrSoa}
+ return
+ }
+ // This serial is important
+ serial = in.Answer[0].(*SOA).Serial
+ // Check if there are no changes in zone
+ if qser >= serial {
+ c <- &Envelope{in.Answer, nil}
+ return
+ }
+ }
+ // Now we need to check each message for SOA records, to see what we need to do
+ t.tsigTimersOnly = true
+ for _, rr := range in.Answer {
+ if v, ok := rr.(*SOA); ok {
+ if v.Serial == serial {
+ n++
+ // quit if it's a full axfr or the the servers' SOA is repeated the third time
+ if axfr && n == 2 || n == 3 {
+ c <- &Envelope{in.Answer, nil}
+ return
+ }
+ } else if axfr {
+ // it's an ixfr
+ axfr = false
+ }
+ }
+ }
+ c <- &Envelope{in.Answer, nil}
+ }
+}
+
+// Out performs an outgoing transfer with the client connecting in w.
+// Basic use pattern:
+//
+// ch := make(chan *dns.Envelope)
+// tr := new(dns.Transfer)
+// go tr.Out(w, r, ch)
+// ch <- &dns.Envelope{RR: []dns.RR{soa, rr1, rr2, rr3, soa}}
+// close(ch)
+// w.Hijack()
+// // w.Close() // Client closes connection
+//
+// The server is responsible for sending the correct sequence of RRs through the
+// channel ch.
+func (t *Transfer) Out(w ResponseWriter, q *Msg, ch chan *Envelope) error {
+ for x := range ch {
+ r := new(Msg)
+ // Compress?
+ r.SetReply(q)
+ r.Authoritative = true
+ // assume it fits TODO(miek): fix
+ r.Answer = append(r.Answer, x.RR...)
+ if err := w.WriteMsg(r); err != nil {
+ return err
+ }
+ }
+ w.TsigTimersOnly(true)
+ return nil
+}
+
+// ReadMsg reads a message from the transfer connection t.
+func (t *Transfer) ReadMsg() (*Msg, error) {
+ m := new(Msg)
+ p := make([]byte, MaxMsgSize)
+ n, err := t.Read(p)
+ if err != nil && n == 0 {
+ return nil, err
+ }
+ p = p[:n]
+ if err := m.Unpack(p); err != nil {
+ return nil, err
+ }
+ if ts := m.IsTsig(); ts != nil && t.TsigSecret != nil {
+ if _, ok := t.TsigSecret[ts.Hdr.Name]; !ok {
+ return m, ErrSecret
+ }
+ // Need to work on the original message p, as that was used to calculate the tsig.
+ err = TsigVerify(p, t.TsigSecret[ts.Hdr.Name], t.tsigRequestMAC, t.tsigTimersOnly)
+ t.tsigRequestMAC = ts.MAC
+ }
+ return m, err
+}
+
+// WriteMsg writes a message through the transfer connection t.
+func (t *Transfer) WriteMsg(m *Msg) (err error) {
+ var out []byte
+ if ts := m.IsTsig(); ts != nil && t.TsigSecret != nil {
+ if _, ok := t.TsigSecret[ts.Hdr.Name]; !ok {
+ return ErrSecret
+ }
+ out, t.tsigRequestMAC, err = TsigGenerate(m, t.TsigSecret[ts.Hdr.Name], t.tsigRequestMAC, t.tsigTimersOnly)
+ } else {
+ out, err = m.Pack()
+ }
+ if err != nil {
+ return err
+ }
+ _, err = t.Write(out)
+ return err
+}
+
+func isSOAFirst(in *Msg) bool {
+ return len(in.Answer) > 0 &&
+ in.Answer[0].Header().Rrtype == TypeSOA
+}
+
+func isSOALast(in *Msg) bool {
+ return len(in.Answer) > 0 &&
+ in.Answer[len(in.Answer)-1].Header().Rrtype == TypeSOA
+}
+
+const errXFR = "bad xfr rcode: %d"
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