dns/xfr.go

package dns

// Outgoing AXFR and IXFR implementations
// error handling??

// Msg tells use what to do
func (d *Conn) XfrRead(q *Msg, m chan Xfr) {
        switch q.Question[0].Qtype {
        case TypeAXFR:
                d.axfrRead(q, m)
        case TypeIXFR:
                d.ixfrRead(q, m)
        }
}

func (d *Conn) XfrWrite(q *Msg, m chan Xfr) {
        switch q.Question[0].Qtype {
        case TypeAXFR:
                d.axfrWrite(q, m)
        case TypeIXFR:
//                d.ixfrWrite(q, m)
        }
}

func (d *Conn) axfrRead(q *Msg, m chan Xfr) {
	defer close(m)
	first := true
	in := new(Msg)
	for {
		inb := make([]byte, MaxMsgSize)
		n, err := d.Read(inb)
		if err != nil {
			return
		}
		inb = inb[:n]

		if !in.Unpack(inb) {
			return
		}
		if in.Id != q.Id {
			return
		}

		if first {
			if !checkXfrSOA(in, true) {
				return
			}
			first = !first
		}

		if !first {
			if !checkXfrSOA(in, false) {
				// Soa record not the last one
				sendMsg(in, m, false)
				continue
			} else {
				sendMsg(in, m, true)
				return
			}
			d.Tsig.TimersOnly = true // Subsequent envelopes use this
		}
	}
	panic("not reached")
	return
}

// Just send the zone
func (d *Conn) axfrWrite(q *Msg, m chan Xfr) {
	out := new(Msg)
        out.Id = q.Id
        out.Question = q.Question
        out.Answer = make([]RR, 1000)
        var soa *RR_SOA;
        i := 0
        for r := range m  {
                out.Answer[i] = r.RR
                if soa == nil {
                        if r.RR.Header().Rrtype != TypeSOA {
                                return
                        } else {
                                soa = r.RR.(*RR_SOA)
                        }
                }
                i++
                if i > 1000 {
                        // Send it
                        send, _ := out.Pack()
                        _, err := d.Write(send)
                        if err != nil {
                                /* ... */
                        }
                        i = 0
                        out.Answer = out.Answer[:0]
                }
        }
        // Everything is send, only the closing soa is left.
        out.Answer[i] = soa
        send, _ := out.Pack()
        _, err := d.Write(send)
        if err != nil {
                /* ... */
        }
}

func (d *Conn) ixfrRead(q *Msg, m chan Xfr) {
	defer close(m)
	var serial uint32 // The first serial seen is the current server serial
	var x Xfr
	first := true
	in := new(Msg)
	for {
		var inb []byte
		if d.TCP != nil {
			inb = make([]byte, MaxMsgSize)
		} else {
			inb = make([]byte, DefaultMsgSize)
		}
		n, err := d.Read(inb)
		if err != nil {
			return
		}
		inb = inb[:n]

		if !in.Unpack(inb) {
			return
		}
		if in.Id != q.Id {
			return
		}

		if first {
			// A single SOA RR signals "no changes"
			if len(in.Answer) == 1 && checkXfrSOA(in, true) {
				return
			}

			// But still check if the returned answer is ok
			if !checkXfrSOA(in, true) {
				return
			}
			// This serial is important
			serial = in.Answer[0].(*RR_SOA).Serial
			first = !first
		}

		// Now we need to check each message for SOA records, to see what we need to do
		x.Add = true
		if !first {
			d.Tsig.TimersOnly = true
			for k, r := range in.Answer {
				// If the last record in the IXFR contains the servers' SOA,  we should quit
				if r.Header().Rrtype == TypeSOA {
					switch {
					case r.(*RR_SOA).Serial == serial:
						if k == len(in.Answer)-1 {
							// last rr is SOA with correct serial
							//m <- r dont' send it
							return
						}
						x.Add = true
						if k != 0 {
							// Intermediate SOA
							continue
						}
					case r.(*RR_SOA).Serial != serial:
						x.Add = false
						continue // Don't need to see this SOA
					}
				}
				x.RR = r
				m <- x
			}
		}
	}
	panic("not reached")
	return
}