Golang ResponseWriter.WriteMsg方法代码示例

// Handles an incoming DNS request packet. This function decides whether
// the hostname listed in the DNS packet is worthy of manipulation, or
// not. The IP addresses listed in the reply to the user for a target
// hostname are added to the routing table at this time before a
// reply is sent back to the user, otherwise the user agent of the client
// might connect faster than the routing changes can be made.
func handleRequest(w dns.ResponseWriter, req *dns.Msg) {
	var m *dns.Msg

	// check if the the hostname in the request matches the target

	if len(req.Question) > 0 && isTargetZone(req.Question[0].Name) {
		// handle `A` and `AAAA` types accordingly
		// other record types will be forwarded without manipulation

		switch req.Question[0].Qtype {

		case dns.TypeA:
			m = handleV4Hijack(w, req)

		case dns.TypeAAAA:
			m = handleV6Hijack(w, req)

		}
	}

	// if no reply was previously set, forward it

	if m == nil {
		m = getServerReply(w, req)
	}

	// send reply back to user

	w.WriteMsg(m)
}

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

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

	// Recursively resolve
	c := &dns.Client{Net: network}
	r, rtt, err := c.Exchange(req, d.recursor)

	// On failure, return a SERVFAIL message
	if err != nil {
		d.logger.Printf("[ERR] dns: recurse failed: %v", err)
		m := &dns.Msg{}
		m.SetReply(req)
		m.RecursionAvailable = true
		m.SetRcode(req, dns.RcodeServerFailure)
		resp.WriteMsg(m)
		return
	}
	d.logger.Printf("[DEBUG] dns: recurse RTT for %v (%v)", q, rtt)

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

// 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)
}

// 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)
	}
}

// ServeDNS implements the middleware.Handler interface.
func (d Dnssec) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
	state := middleware.State{W: w, Req: r}

	do := state.Do()
	qname := state.Name()
	qtype := state.QType()
	zone := middleware.Zones(d.zones).Matches(qname)
	if zone == "" {
		return d.Next.ServeDNS(ctx, w, r)
	}

	// Intercept queries for DNSKEY, but only if one of the zones matches the qname, otherwise we let
	// the query through.
	if qtype == dns.TypeDNSKEY {
		for _, z := range d.zones {
			if qname == z {
				resp := d.getDNSKEY(state, z, do)
				state.SizeAndDo(resp)
				w.WriteMsg(resp)
				return dns.RcodeSuccess, nil
			}
		}
	}

	drr := NewDnssecResponseWriter(w, d)
	return d.Next.ServeDNS(ctx, drr, r)
}

// 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 (h *Handler) handle(proto string, w dns.ResponseWriter, r *dns.Msg) {
	ques := question.NewQuestion(r.Question[0])

	subnet := ""
	if ip, ok := w.RemoteAddr().(*net.UDPAddr); ok {
		subnet = networks.Find(ip.IP)
	}
	if ip, ok := w.RemoteAddr().(*net.TCPAddr); ok {
		subnet = networks.Find(ip.IP)
	}

	if subnet == "" {
		dns.HandleFailed(w, r)
		return
	}

	if ques.IsIpQuery && ques.TopDomain == "vpn" {
		msg, err := h.reslvr.LookupUser(proto, ques, subnet, r)
		if err != nil {
			dns.HandleFailed(w, r)
			return
		}
		w.WriteMsg(msg)
	} else {
		servers := database.DnsServers[subnet]
		res, err := h.reslvr.Lookup(proto, servers, r)
		if err != nil {
			dns.HandleFailed(w, r)
			return
		}

		w.WriteMsg(res)
	}
}

func (h dnsHandler) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
	if len(r.Question) != 1 {
		h.t.Fatalf("bad: %#v", r.Question)
	}

	name := "join.service.consul."
	question := r.Question[0]
	if question.Name != name || question.Qtype != dns.TypeANY {
		h.t.Fatalf("bad: %#v", question)
	}

	m := new(dns.Msg)
	m.SetReply(r)
	m.Authoritative = true
	m.RecursionAvailable = false
	m.Answer = append(m.Answer, &dns.A{
		Hdr: dns.RR_Header{
			Name:   name,
			Rrtype: dns.TypeA,
			Class:  dns.ClassINET},
		A: net.ParseIP("127.0.0.1"),
	})
	m.Answer = append(m.Answer, &dns.AAAA{
		Hdr: dns.RR_Header{
			Name:   name,
			Rrtype: dns.TypeAAAA,
			Class:  dns.ClassINET},
		AAAA: net.ParseIP("2001:db8:a0b:12f0::1"),
	})
	if err := w.WriteMsg(m); err != nil {
		h.t.Fatalf("err: %v", err)
	}
}

// ServeDNS resolution.
func (h *RandomUpstream) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
	ns := h.upstream[rand.Intn(len(h.upstream))]
	ns = defaultPort(ns)

	for _, q := range r.Question {
		log.Printf("[info] [%v] <== %s %s %v (ns %s)\n", r.Id,
			dns.ClassToString[q.Qclass],
			dns.TypeToString[q.Qtype],
			q.Name,
			ns)
	}

	client := &dns.Client{
		Net: w.RemoteAddr().Network(),
	}

	res, rtt, err := client.Exchange(r, ns)
	if err != nil {
		msg := new(dns.Msg)
		msg.SetRcode(r, dns.RcodeServerFailure)
		w.WriteMsg(msg)
		return
	}

	log.Printf("[info] [%v] ==> %s:", r.Id, rtt)
	for _, a := range res.Answer {
		log.Printf("[info] [%v] ----> %s\n", r.Id, a)
	}

	err = w.WriteMsg(res)
	if err != nil {
		log.Printf("[error] [%v] failed to respond – %s", r.Id, err)
	}
}

func handleDnsRequest(w dns.ResponseWriter, r *dns.Msg) {
	m := new(dns.Msg)
	m.SetReply(r)
	records := make([]dns.RR, 0)
	q := r.Question[0]

	if q.Qtype == dns.TypeA && strings.HasSuffix(q.Name, ".docker.") {
		docker, _ := dockerclient.NewDockerClient("unix:///var/run/docker.sock", &tls.Config{})
		name := strings.SplitN(q.Name, ".", 2)[0]
		containers, err := docker.ListContainers(false, false, fmt.Sprintf("{\"name\":[\"%s\"]}", name))
		if err != nil {
			log.Fatal(err)
		}
		for _, c := range containers {
			info, _ := docker.InspectContainer(c.Id)
			log.Printf("Container %s[%6s] has ip %s\n", name, info.Id, info.NetworkSettings.IPAddress)
			records = append(records,
				&dns.A{
					Hdr: dns.RR_Header{
						Name:   q.Name,
						Rrtype: dns.TypeA,
						Class:  dns.ClassINET,
						Ttl:    60},
					A: net.ParseIP(info.NetworkSettings.IPAddress),
				})
		}
	}

	m.Answer = append(m.Answer, records...)
	defer w.WriteMsg(m)
}

func (s *jujuNameServer) handleRequest(w dns.ResponseWriter, r *dns.Msg) {
	m := new(dns.Msg)
	m.SetReply(r)
	for _, q := range r.Question {
		rr, err := s.answer(q)
		if err != nil {
			m.SetRcodeFormatError(r)
			t := new(dns.TXT)
			t.Hdr = dns.RR_Header{
				Name:   q.Name,
				Rrtype: dns.TypeTXT,
				Class:  dns.ClassNONE,
			}
			t.Txt = []string{err.Error()}
			m.Extra = append(m.Extra, t)
			continue
		} else if rr != nil {
			m.Answer = append(m.Answer, rr)
		}
	}
	m.Authoritative = true
	// recursion isn't really available, but it's apparently
	// necessary to set this to make nslookup happy.
	m.RecursionAvailable = true
	w.WriteMsg(m)
}

func (s *DNS) handleDNSExternal(w dns.ResponseWriter, req *dns.Msg) {

	network := "udp"
	if _, ok := w.RemoteAddr().(*net.TCPAddr); ok {
		network = "tcp"
	}

	c := &dns.Client{Net: network}
	var r *dns.Msg
	var err error
	for _, recursor := range s.recursors {

		if recursor == "" {
			log.Printf("Found empty recursor")
			continue
		}

		log.Printf("Forwarding request to external recursor for: %s", req.Question[0].Name)

		r, _, err = c.Exchange(req, recursor)
		if err == nil {
			if err := w.WriteMsg(r); err != nil {
				log.Printf("DNS lookup failed %v", err)
			}
			return
		}
	}

	dns.HandleFailed(w, req)
}

func (s *DNS) handleDNSInternal(w dns.ResponseWriter, req *dns.Msg) {

	q := req.Question[0]

	if q.Qtype == dns.TypeA && q.Qclass == dns.ClassINET {
		if record, ok := s.cache.Get(q.Name); ok {

			log.Printf("Found internal record for %s", q.Name)

			m := new(dns.Msg)
			m.SetReply(req)
			rr_header := dns.RR_Header{
				Name:   q.Name,
				Rrtype: dns.TypeA,
				Class:  dns.ClassINET,
				Ttl:    0,
			}
			a := &dns.A{rr_header, net.ParseIP(record.ip)}
			m.Answer = append(m.Answer, a)
			w.WriteMsg(m)

			return
		}

		log.Printf("No internal record found for %s", q.Name)
		dns.HandleFailed(w, req)
	}

	log.Printf("Only handling type A requests, skipping")
	dns.HandleFailed(w, req)
}

func (s *DNS) handleReverseDNSLookup(w dns.ResponseWriter, req *dns.Msg) {

	q := req.Question[0]

	if q.Qtype == dns.TypePTR && q.Qclass == dns.ClassINET {

		if record, ok := s.cache.Get(q.Name); ok {

			log.Printf("Found internal record for %s", q.Name)

			m := new(dns.Msg)
			m.SetReply(req)
			rr_header := dns.RR_Header{
				Name:   q.Name,
				Rrtype: dns.TypePTR,
				Class:  dns.ClassINET,
				Ttl:    0,
			}

			a := &dns.PTR{rr_header, record.fqdn}
			m.Answer = append(m.Answer, a)
			w.WriteMsg(m)

			return

		}

		log.Printf("Forwarding request to external recursor for: %s", q.Name)

		// Forward the request
		s.handleDNSExternal(w, req)
	}

	dns.HandleFailed(w, req)
}

func (s *soa) TransferHandler(w dns.ResponseWriter, req *dns.Msg) {
	m := new(dns.Msg)
	m.SetReply(req)
	m.Answer = make([]dns.RR, 1)
	m.Answer[0] = test.SOA(fmt.Sprintf("%s IN SOA bla. bla. %d 0 0 0 0 ", testZone, s.serial))
	w.WriteMsg(m)
}