Golang State.Clear方法代碼示例

func (e Etcd) NS(zone string, state middleware.State) (records, extra []dns.RR, debug []msg.Service, err error) {
	// NS record for this zone live in a special place, ns.dns.<zone>. Fake our lookup.
	// only a tad bit fishy...
	old := state.QName()

	state.Clear()
	state.Req.Question[0].Name = "ns.dns." + zone
	services, debug, err := e.records(state, false)
	if err != nil {
		return nil, nil, debug, err
	}
	// ... and reset
	state.Req.Question[0].Name = old

	for _, serv := range services {
		ip := net.ParseIP(serv.Host)
		switch {
		case ip == nil:
			return nil, nil, debug, fmt.Errorf("NS record must be an IP address: %s", serv.Host)
		case ip.To4() != nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewNS(state.QName()))
			extra = append(extra, serv.NewA(serv.Host, ip.To4()))
		case ip.To4() == nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewNS(state.QName()))
			extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
		}
	}
	return records, extra, debug, nil
}

func (e Etcd) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
	state := middleware.State{W: w, Req: r}
	if state.QClass() != dns.ClassINET {
		return dns.RcodeServerFailure, fmt.Errorf("can only deal with ClassINET")
	}
	name := state.Name()
	if e.Debug {
		if debug := isDebug(name); debug != "" {
			e.debug = r.Question[0].Name
			state.Clear()
			state.Req.Question[0].Name = debug
		}
	}

	// We need to check stubzones first, because we may get a request for a zone we
	// are not auth. for *but* do have a stubzone forward for. If we do the stubzone
	// handler will handle the request.
	if e.Stubmap != nil && len(*e.Stubmap) > 0 {
		for zone := range *e.Stubmap {
			if middleware.Name(zone).Matches(name) {
				stub := Stub{Etcd: e, Zone: zone}
				return stub.ServeDNS(ctx, w, r)
			}
		}
	}

	zone := middleware.Zones(e.Zones).Matches(state.Name())
	if zone == "" {
		if e.Next == nil {
			return dns.RcodeServerFailure, nil
		}
		return e.Next.ServeDNS(ctx, w, r)
	}

	var (
		records, extra []dns.RR
		debug          []msg.Service
		err            error
	)
	switch state.Type() {
	case "A":
		records, debug, err = e.A(zone, state, nil)
	case "AAAA":
		records, debug, err = e.AAAA(zone, state, nil)
	case "TXT":
		records, debug, err = e.TXT(zone, state)
	case "CNAME":
		records, debug, err = e.CNAME(zone, state)
	case "PTR":
		records, debug, err = e.PTR(zone, state)
	case "MX":
		records, extra, debug, err = e.MX(zone, state)
	case "SRV":
		records, extra, debug, err = e.SRV(zone, state)
	case "SOA":
		records, debug, err = e.SOA(zone, state)
	case "NS":
		if state.Name() == zone {
			records, extra, debug, err = e.NS(zone, state)
			break
		}
		fallthrough
	default:
		// Do a fake A lookup, so we can distinguish between NODATA and NXDOMAIN
		_, debug, err = e.A(zone, state, nil)
	}

	if e.debug != "" {
		// Substitute this name with the original when we return the request.
		state.Clear()
		state.Req.Question[0].Name = e.debug
	}

	if isEtcdNameError(err) {
		return e.Err(zone, dns.RcodeNameError, state, debug, err)
	}
	if err != nil {
		return e.Err(zone, dns.RcodeServerFailure, state, debug, err)
	}

	if len(records) == 0 {
		return e.Err(zone, dns.RcodeSuccess, state, debug, err)
	}

	m := new(dns.Msg)
	m.SetReply(r)
	m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true
	m.Answer = append(m.Answer, records...)
	m.Extra = append(m.Extra, extra...)
	if e.debug != "" {
		m.Extra = append(m.Extra, servicesToTxt(debug)...)
	}

	m = dedup(m)
	state.SizeAndDo(m)
	m, _ = state.Scrub(m)
	w.WriteMsg(m)
	return dns.RcodeSuccess, nil
}