func get_serial(zone_name, query_dest string) (uint32, error) {
	var in *dns.Msg
	m := new(dns.Msg)
	m.SetQuestion(zone_name, dns.TypeSOA)

	if conf.Transfer_source != nil {
		d := net.Dialer{LocalAddr: conf.Transfer_source}
		c, err := d.Dial("tcp", query_dest)
		if err != nil {
			logger.Error(fmt.Sprintf("QUERY ERROR : problem dialing query_dest %s", query_dest))
			return 0, err
		}
		co := &dns.Conn{Conn: c}
		co.WriteMsg(m)
		in, err = co.ReadMsg()
		if err != nil {
			logger.Error(fmt.Sprintf("QUERY ERROR : problem querying query_dest %s", query_dest))
			return 0, err
		}
		co.Close()
	} else {
		c := &dns.Client{DialTimeout: conf.Query_timeout, ReadTimeout: conf.Query_timeout}
		if conf.All_tcp == true {
			c.Net = "tcp"
		}
		// _ is query time, might be useful later
		var err error
		in, _, err = c.Exchange(m, query_dest)
		if err != nil {
			logger.Error(fmt.Sprintf("QUERY ERROR : problem querying query_dest %s", query_dest))
			return 0, err
		}
	}
	return serial_query_parse(in), nil
}

func (res *Resolver) handleSRV(rs *records.RecordGenerator, name string, m, r *dns.Msg) error {
	var errs multiError
	added := map[string]struct{}{} // track the A RR's we've already added, avoid dups
	for srv := range rs.SRVs[name] {
		srvRR, err := res.formatSRV(r.Question[0].Name, srv)
		if err != nil {
			errs.Add(err)
			continue
		}

		m.Answer = append(m.Answer, srvRR)
		host := strings.Split(srv, ":")[0]
		if _, found := added[host]; found {
			// avoid dups
			continue
		}
		if len(rs.As[host]) == 0 {
			continue
		}

		if a, ok := rs.As.First(host); ok {
			aRR, err := res.formatA(host, a)
			if err != nil {
				errs.Add(err)
				continue
			}
			m.Extra = append(m.Extra, aRR)
			added[host] = struct{}{}
		}
	}
	return errs
}

func (r *resolver) handlePTRQuery(ptr string, query *dns.Msg) (*dns.Msg, error) {
	parts := []string{}

	if strings.HasSuffix(ptr, ptrIPv4domain) {
		parts = strings.Split(ptr, ptrIPv4domain)
	} else if strings.HasSuffix(ptr, ptrIPv6domain) {
		parts = strings.Split(ptr, ptrIPv6domain)
	} else {
		return nil, fmt.Errorf("invalid PTR query, %v", ptr)
	}

	host := r.backend.ResolveIP(parts[0])

	if len(host) == 0 {
		return nil, nil
	}

	logrus.Debugf("Lookup for IP %s: name %s", parts[0], host)
	fqdn := dns.Fqdn(host)

	resp := new(dns.Msg)
	resp.SetReply(query)
	setCommonFlags(resp)

	rr := new(dns.PTR)
	rr.Hdr = dns.RR_Header{Name: ptr, Rrtype: dns.TypePTR, Class: dns.ClassINET, Ttl: respTTL}
	rr.Ptr = fqdn
	resp.Answer = append(resp.Answer, rr)
	return resp, nil
}

// handleDNS is a handler function to actualy perform the dns querey response
func (c *CatchAll) handleDNS(w dns.ResponseWriter, r *dns.Msg) {
	defer w.Close()
	var rr dns.RR

	domainSpoof := r.Question[0].Name

	msgResp := new(dns.Msg)
	msgResp.SetReply(r)
	msgResp.Compress = false

	rr = new(dns.A)

	if c.SpoofDomain {
		rr.(*dns.A).Hdr = dns.RR_Header{Name: domainSpoof, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 0}
	} else {
		rr.(*dns.A).Hdr = dns.RR_Header{Name: c.Domain, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 0}
	}

	rr.(*dns.A).A = c.IP

	switch r.Question[0].Qtype {
	case dns.TypeA:
		msgResp.Answer = append(msgResp.Answer, rr)
	default:
		log.Warnf("Unknown dns type %T", r.Question[0].Qtype)
		return
	}

	w.WriteMsg(msgResp)
}

// Perform DNS resolution
func resolve(w http.ResponseWriter, r *http.Request, server string, domain string, querytype uint16) {
	m := new(dns.Msg)
	m.SetQuestion(domain, querytype)
	m.MsgHdr.RecursionDesired = true

	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Access-Control-Allow-Origin", "*")

	c := new(dns.Client)

Redo:
	if in, _, err := c.Exchange(m, server); err == nil { // Second return value is RTT, not used for now
		if in.MsgHdr.Truncated {
			c.Net = "tcp"
			goto Redo
		}

		switch in.MsgHdr.Rcode {
		case dns.RcodeServerFailure:
			error(w, 500, 502, "The name server encountered an internal failure while processing this request (SERVFAIL)")
		case dns.RcodeNameError:
			error(w, 500, 503, "Some name that ought to exist, does not exist (NXDOMAIN)")
		case dns.RcodeRefused:
			error(w, 500, 505, "The name server refuses to perform the specified operation for policy or security reasons (REFUSED)")
		default:
			jsonify(w, r, in.Question, in.Answer, in.Ns, in.Extra)
		}
	} else {
		error(w, 500, 501, "DNS server could not be reached")
	}
}

func TestDNS_CaseInsensitiveNodeLookup(t *testing.T) {
	dir, srv := makeDNSServer(t)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	testutil.WaitForLeader(t, srv.agent.RPC, "dc1")

	// Register node
	args := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "Foo",
		Address:    "127.0.0.1",
	}

	var out struct{}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	m := new(dns.Msg)
	m.SetQuestion("fOO.node.dc1.consul.", dns.TypeANY)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) != 1 {
		t.Fatalf("empty lookup: %#v", in)
	}
}

func TestDNS_Recurse(t *testing.T) {
	recursor := makeRecursor(t, []dns.RR{dnsA("apple.com", "1.2.3.4")})
	defer recursor.Shutdown()

	dir, srv := makeDNSServerConfig(t, func(c *Config) {
		c.DNSRecursor = recursor.Addr
	}, nil)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	m := new(dns.Msg)
	m.SetQuestion("apple.com.", dns.TypeANY)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) == 0 {
		t.Fatalf("Bad: %#v", in)
	}
	if in.Rcode != dns.RcodeSuccess {
		t.Fatalf("Bad: %#v", in)
	}
}

func TestMsgOverflow(t *testing.T) {
	if testing.Short() {
		t.Skip("skipping test in short mode.")
	}

	s := newTestServer(t, false)
	defer s.Stop()

	c := new(dns.Client)
	m := new(dns.Msg)

	// TODO(miek): rethink how to enable metrics in tests.
	if !metricsDone {
		Metrics()
	}

	for i := 0; i < 2000; i++ {
		is := strconv.Itoa(i)
		m := &msg.Service{
			Host: "2001::" + is, Key: "machine" + is + ".machines.skydns.test.",
		}
		addService(t, s, m.Key, 0, m)
		defer delService(t, s, m.Key)
	}
	m.SetQuestion("machines.skydns.test.", dns.TypeSRV)
	resp, _, err := c.Exchange(m, "127.0.0.1:"+StrPort)
	if err != nil {
		t.Fatal(err)
	}
	t.Logf("%s", resp)

	if resp.Rcode != dns.RcodeServerFailure {
		t.Fatalf("expecting server failure, got %d", resp.Rcode)
	}
}

func (s *DNSServer) handlePTRRequest(r *dns.Msg, m *dns.Msg) {
	m.Answer = make([]dns.RR, 0, 2)
	query := r.Question[0].Name

	if query[len(query)-1] == '.' {
		query = query[:len(query)-1]
	}

	for service := range s.queryIp(query) {
		var ttl int
		if service.Ttl != -1 {
			ttl = service.Ttl
		} else {
			ttl = s.config.ttl
		}

		for domain := range s.listDomains(service) {
			rr := new(dns.PTR)
			rr.Hdr = dns.RR_Header{
				Name:   r.Question[0].Name,
				Rrtype: dns.TypePTR,
				Class:  dns.ClassINET,
				Ttl:    uint32(ttl),
			}
			rr.Ptr = domain

			m.Answer = append(m.Answer, rr)
		}
	}
}

func ParseDnsFrame(f Frame, req *dns.Msg) (addrs []net.IP, err error) {
	ft, ok := f.(*FrameDns)
	if !ok {
		return nil, ErrDnsMsgIllegal
	}

	res := new(dns.Msg)
	err = res.Unpack(ft.Data)
	if err != nil || !res.Response || res.Id != req.Id {
		return nil, ErrDnsMsgIllegal
	}

	if DEBUGDNS {
		DebugDNS(res, req.Question[0].Name)
	}
	for _, a := range res.Answer {
		switch ta := a.(type) {
		case *dns.A:
			addrs = append(addrs, ta.A)
		case *dns.AAAA:
			addrs = append(addrs, ta.AAAA)
		}
	}
	return
}

func TestShuffleAnswers(t *testing.T) {
	var res Resolver

	m := new(dns.Msg)

	for i := 0; i < 10; i++ {
		name := "10.0.0." + strconv.Itoa(i)
		rr, err := res.formatA("blah.com", name)
		if err != nil {
			t.Error(err)
		}
		m.Answer = append(m.Answer, rr)
	}

	n := new(dns.Msg)
	c := make([]dns.RR, len(m.Answer))
	copy(c, m.Answer)
	n.Answer = c

	_ = shuffleAnswers(m.Answer)

	sflag := false
	// 10! chance of failing here
	for i := 0; i < 10; i++ {
		if n.Answer[i] != m.Answer[i] {
			sflag = true
			break
		}
	}

	if !sflag {
		t.Error("not shuffling")
	}
}

func handle(writer dns.ResponseWriter, request *dns.Msg) {
	message := new(dns.Msg)
	message.SetReply(request)
	message.SetRcode(message, dns.RcodeSuccess)
	question := request.Question[0]

	switch request.Opcode {
	case dns.OpcodeNotify:
		log.Println(fmt.Sprintf("Recieved NOTIFY for %s", question.Name))
		message = handle_notify(question, message, writer)
	case dns.OpcodeQuery:
		log.Println(fmt.Sprintf("Recieved QUERY for %s", question.Name))
		message = handle_query(question, message, writer)
	default:
		message = handle_error(message, writer, "REFUSED")
	}

	// Apparently this dns library takes the question out on
	// certain RCodes, like REFUSED, which is not right. So we reinsert it.
	message.Question[0].Name = question.Name
	message.Question[0].Qtype = question.Qtype
	message.Question[0].Qclass = question.Qclass
	message.MsgHdr.Opcode = request.Opcode

	// Send an authoritative answer
	message.MsgHdr.Authoritative = true

	writer.WriteMsg(message)
}

// Create DNS packet with the config in line with the meta zone
// paper from Vixie
func metazone(w dns.ResponseWriter, req *dns.Msg, c *Config) {
	logPrintf("metazone command")

	// Only called when the class is CHAOS
	// PTR zone.	-> get a list of zone names

	// Top level zone stuff -- list them
	if strings.ToUpper(req.Question[0].Name) == "ZONE." {
		m := new(dns.Msg)
		m.SetReply(req)
		for _, z := range c.Zones {
			ptr, _ := dns.NewRR("zone. 0 CH PTR " + z.Origin)
			m.Answer = append(m.Answer, ptr)
		}
		w.WriteMsg(m)
		return
	}

	// Top level user stuff -- list them
	if strings.ToUpper(req.Question[0].Name) == "USER." {

	}

	// <zone>.ZONE.

	formerr(w, req)
	return
}

func (p *Parser) handleExplanation() string {
	resolvedDomain, err := ParseMacroToken(p, p.Explanation)
	if err != nil || isEmpty(&resolvedDomain) {
		// TODO(zaccone): Should we return some internal error
		return ""
	}
	resolvedDomain = NormalizeHost(resolvedDomain)
	query := new(dns.Msg)
	query.SetQuestion(resolvedDomain, dns.TypeTXT)
	c := new(dns.Client)
	response, _, err := c.Exchange(query, Nameserver)
	if err != nil || (response != nil && response.Rcode != dns.RcodeSuccess) {
		return ""
	}

	explanation := make([]string, 0, len(response.Answer))
	for _, answer := range response.Answer {
		if q, ok := answer.(*dns.TXT); ok {
			for _, txt := range q.Txt {
				explanation = append(explanation, txt)
			}
		}
	}

	// RFC 7208, section 6.2 specifies that result string should be
	// concatenated with no spaces.
	parsedExplanation, err := ParseMacro(p, strings.Join(explanation, ""))
	if err != nil {
		return ""
	}
	return parsedExplanation
}

// Check that we can prune an answer
func TestPrune(t *testing.T) {
	InitDefaultLogging(testing.Verbose())
	Info.Println("TestPrune starting")

	questionMsg := new(dns.Msg)
	questionMsg.SetQuestion("name", dns.TypeA)
	questionMsg.RecursionDesired = true
	question := &questionMsg.Question[0]
	records := []ZoneRecord{
		Record{"name", net.ParseIP("10.0.1.1"), 0, 0, 0},
		Record{"name", net.ParseIP("10.0.1.2"), 0, 0, 0},
		Record{"name", net.ParseIP("10.0.1.3"), 0, 0, 0},
		Record{"name", net.ParseIP("10.0.1.4"), 0, 0, 0},
	}

	reply := makeAddressReply(questionMsg, question, records, DefaultLocalTTL)
	reply.Answer[0].Header().Ttl = DefaultLocalTTL

	pruned := pruneAnswers(reply.Answer, 1)
	require.Equal(t, 1, len(pruned), "wrong number of answers")

	pruned = pruneAnswers(reply.Answer, 2)
	require.Equal(t, 2, len(pruned), "wrong number of answers")

	pruned = pruneAnswers(reply.Answer, 0)
	require.Equal(t, len(records), len(pruned), "wrong number of answers")
}

func (s *DNSServer) handleARequest(r *dns.Msg, m *dns.Msg) {
	m.Answer = make([]dns.RR, 0, 2)
	query := r.Question[0].Name

	if query[len(query)-1] == '.' {
		query = query[:len(query)-1]
	}

	for service := range s.queryServices(query) {
		rr := new(dns.A)

		var ttl int
		if service.Ttl != -1 {
			ttl = service.Ttl
		} else {
			ttl = s.config.ttl
		}

		rr.Hdr = dns.RR_Header{
			Name:   r.Question[0].Name,
			Rrtype: dns.TypeA,
			Class:  dns.ClassINET,
			Ttl:    uint32(ttl),
		}
		rr.A = service.Ip
		m.Answer = append(m.Answer, rr)
	}
}

func TestDNS_NonExistingLookup(t *testing.T) {
	dir, srv := makeDNSServer(t)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)

	// lookup a non-existing node, we should receive a SOA
	m := new(dns.Msg)
	m.SetQuestion("nonexisting.consul.", dns.TypeANY)

	c := new(dns.Client)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Ns) != 1 {
		t.Fatalf("Bad: %#v %#v", in, len(in.Answer))
	}

	soaRec, ok := in.Ns[0].(*dns.SOA)
	if !ok {
		t.Fatalf("Bad: %#v", in.Ns[0])
	}
	if soaRec.Hdr.Ttl != 0 {
		t.Fatalf("Bad: %#v", in.Ns[0])
	}

}

func main() {
	if len(os.Args) != 2 {
		fmt.Printf("%s NAMESERVER\n", os.Args[0])
		os.Exit(1)
	}
	conf, _ := dns.ClientConfigFromFile("/etc/resolv.conf")

	m := new(dns.Msg)
	m.Question = make([]dns.Question, 1)
	c := new(dns.Client)

	addr := addresses(conf, c, os.Args[1])
	if len(addr) == 0 {
		fmt.Printf("No address found for %s\n", os.Args[1])
		os.Exit(1)
	}
	for _, a := range addr {
		m.Question[0] = dns.Question{"version.bind.", dns.TypeTXT, dns.ClassCHAOS}
		in, rtt, _ := c.ExchangeRtt(m, a)
		if in != nil && len(in.Answer) > 0 {
			fmt.Printf("(time %.3d µs) %v\n", rtt/1e3, in.Answer[0])
		}
		m.Question[0] = dns.Question{"hostname.bind.", dns.TypeTXT, dns.ClassCHAOS}
		in, rtt, _ = c.ExchangeRtt(m, a)
		if in != nil && len(in.Answer) > 0 {
			fmt.Printf("(time %.3d µs) %v\n", rtt/1e3, in.Answer[0])
		}
	}
}

func TestDNS_ServiceLookup_TagPeriod(t *testing.T) {
	dir, srv := makeDNSServer(t)
	defer os.RemoveAll(dir)
	defer srv.agent.Shutdown()

	testutil.WaitForLeader(t, srv.agent.RPC, "dc1")

	// Register node
	args := &structs.RegisterRequest{
		Datacenter: "dc1",
		Node:       "foo",
		Address:    "127.0.0.1",
		Service: &structs.NodeService{
			Service: "db",
			Tags:    []string{"v1.master"},
			Port:    12345,
		},
	}

	var out struct{}
	if err := srv.agent.RPC("Catalog.Register", args, &out); err != nil {
		t.Fatalf("err: %v", err)
	}

	m := new(dns.Msg)
	m.SetQuestion("v1.master.db.service.consul.", dns.TypeSRV)

	c := new(dns.Client)
	addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
	in, _, err := c.Exchange(m, addr.String())
	if err != nil {
		t.Fatalf("err: %v", err)
	}

	if len(in.Answer) != 1 {
		t.Fatalf("Bad: %#v", in)
	}

	srvRec, ok := in.Answer[0].(*dns.SRV)
	if !ok {
		t.Fatalf("Bad: %#v", in.Answer[0])
	}
	if srvRec.Port != 12345 {
		t.Fatalf("Bad: %#v", srvRec)
	}
	if srvRec.Target != "foo.node.dc1.consul." {
		t.Fatalf("Bad: %#v", srvRec)
	}

	aRec, ok := in.Extra[0].(*dns.A)
	if !ok {
		t.Fatalf("Bad: %#v", in.Extra[0])
	}
	if aRec.Hdr.Name != "foo.node.dc1.consul." {
		t.Fatalf("Bad: %#v", in.Extra[0])
	}
	if aRec.A.String() != "127.0.0.1" {
		t.Fatalf("Bad: %#v", in.Extra[0])
	}
}

// handleQUery is used to handle DNS queries in the configured domain
func (d *DNSServer) handleQuery(resp dns.ResponseWriter, req *dns.Msg) {
	q := req.Question[0]
	defer func(s time.Time) {
		d.logger.Printf("[DEBUG] dns: request for %v (%v)", q, time.Now().Sub(s))
	}(time.Now())

	// Switch to TCP if the client is
	network := "udp"
	if _, ok := resp.RemoteAddr().(*net.TCPAddr); ok {
		network = "tcp"
	}

	// Setup the message response
	m := new(dns.Msg)
	m.SetReply(req)
	m.Authoritative = true
	m.RecursionAvailable = (len(d.recursors) > 0)

	// Only add the SOA if requested
	if req.Question[0].Qtype == dns.TypeSOA {
		d.addSOA(d.domain, m)
	}

	// Dispatch the correct handler
	d.dispatch(network, req, m)

	// Write out the complete response
	if err := resp.WriteMsg(m); err != nil {
		d.logger.Printf("[WARN] dns: failed to respond: %v", err)
	}
}