Golang Msg.Id方法代码示例

func handleSpecialNames(w dns.ResponseWriter, req *dns.Msg) bool {
	question := req.Question[0]
	nameLC := strings.ToLower(question.Name)
	for _, localRR := range localRRS {
		if nameLC == localRR.Name {
			m := new(dns.Msg)
			m.Id = req.Id
			m.Answer = []dns.RR{*localRR.RR}
			m.Response = true
			w.WriteMsg(m)
			return true
		}
	}
	if question.Qtype != dns.TypeANY {
		return false
	}
	m := new(dns.Msg)
	m.Id = req.Id
	hinfo := new(dns.HINFO)
	hinfo.Hdr = dns.RR_Header{Name: question.Name, Rrtype: dns.TypeHINFO,
		Class: dns.ClassINET, Ttl: 86400}
	hinfo.Cpu = "ANY is not supported any more"
	hinfo.Os = "See draft-jabley-dnsop-refuse-any"
	m.Answer = []dns.RR{hinfo}
	m.Response = true
	w.WriteMsg(m)
	return true
}

func (r *resolver) forwardQueryEnd(w dns.ResponseWriter, msg *dns.Msg) dns.ResponseWriter {
	var (
		cc clientConn
		ok bool
	)
	proto := w.LocalAddr().Network()

	r.queryLock.Lock()
	defer r.queryLock.Unlock()

	if r.count == 0 {
		log.Errorf("Invalid concurrent query count")
	} else {
		r.count--
	}

	switch proto {
	case "tcp":
		break
	case "udp":
		if cc, ok = r.client[msg.Id]; ok == false {
			log.Debugf("Can't retrieve client context for dns id %v", msg.Id)
			return nil
		}
		log.Debugf("dns msg id %v, client id %v", msg.Id, cc.dnsID)
		delete(r.client, msg.Id)
		msg.Id = cc.dnsID
		w = cc.respWriter
	default:
		log.Errorf("Invalid protocol")
		return nil
	}
	return w
}

func (r *resolver) forwardQueryStart(w dns.ResponseWriter, msg *dns.Msg, queryID uint16) bool {
	proto := w.LocalAddr().Network()
	dnsID := uint16(rand.Intn(maxDNSID))

	cc := clientConn{
		dnsID:      queryID,
		respWriter: w,
	}

	r.queryLock.Lock()
	defer r.queryLock.Unlock()

	if r.count == maxConcurrent {
		return false
	}
	r.count++

	switch proto {
	case "tcp":
		break
	case "udp":
		for ok := true; ok == true; dnsID = uint16(rand.Intn(maxDNSID)) {
			_, ok = r.client[dnsID]
		}
		log.Debugf("client dns id %v, changed id %v", queryID, dnsID)
		r.client[dnsID] = cc
		msg.Id = dnsID
	default:
		log.Errorf("Invalid protocol..")
		return false
	}

	return true
}

func ExamplePrivateHandle() {
	dns.PrivateHandle("APAIR", TypeAPAIR, NewAPAIR)
	defer dns.PrivateHandleRemove(TypeAPAIR)

	rr, err := dns.NewRR("miek.nl. APAIR (1.2.3.4    1.2.3.5)")
	if err != nil {
		log.Fatal("could not parse APAIR record: ", err)
	}
	fmt.Println(rr)
	// Output: miek.nl.	3600	IN	APAIR	1.2.3.4 1.2.3.5

	m := new(dns.Msg)
	m.Id = 12345
	m.SetQuestion("miek.nl.", TypeAPAIR)
	m.Answer = append(m.Answer, rr)

	fmt.Println(m)
	// ;; opcode: QUERY, status: NOERROR, id: 12345
	// ;; flags: rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
	//
	// ;; QUESTION SECTION:
	// ;miek.nl.	IN	 APAIR
	//
	// ;; ANSWER SECTION:
	// miek.nl.	3600	IN	APAIR	1.2.3.4 1.2.3.5
}

func (p ReverseProxy) ServeDNS(w dns.ResponseWriter, r *dns.Msg, extra []dns.RR) error {
	var (
		reply *dns.Msg
		err   error
	)

	switch {
	case middleware.Proto(w) == "tcp":
		reply, err = middleware.Exchange(p.Client.TCP, r, p.Host)
	default:
		reply, err = middleware.Exchange(p.Client.UDP, r, p.Host)
	}

	if reply != nil && reply.Truncated {
		// Suppress proxy error for truncated responses
		err = nil
	}

	if err != nil {
		return err
	}

	reply.Compress = true
	reply.Id = r.Id
	w.WriteMsg(reply)
	return nil
}

func (self *DnsResolver) lookupHost(host string, triesLeft int) ([]net.IP, error) {
	m1 := new(dns.Msg)
	m1.Id = dns.Id()
	m1.RecursionDesired = true
	m1.Question = make([]dns.Question, 1)
	m1.Question[0] = dns.Question{dns.Fqdn(host), dns.TypeA, dns.ClassINET}
	in, err := dns.Exchange(m1, self.Servers[self.r.Intn(len(self.Servers))])

	result := []net.IP{}

	if err != nil {
		if strings.HasSuffix(err.Error(), "i/o timeout") && triesLeft > 0 {
			triesLeft -= 1
			return self.lookupHost(host, triesLeft)
		} else {
			return result, err
		}
	}

	if in != nil && in.Rcode != dns.RcodeSuccess {
		return result, errors.New(dns.RcodeToString[in.Rcode])
	}

	for _, record := range in.Answer {
		if t, ok := record.(*dns.A); ok {
			result = append(result, t.A)
		}
	}
	return result, err
}

// ServeDNSForward forwards a request to a nameservers and returns the response.
func (s *server) ServeDNSForward(w dns.ResponseWriter, req *dns.Msg) *dns.Msg {

	if s.config.NoRec {
		m := s.ServerFailure(req)
		w.WriteMsg(m)
		return m
	}

	if len(s.config.Nameservers) == 0 || dns.CountLabel(req.Question[0].Name) < s.config.Ndots {
		if s.config.Verbose {
			if len(s.config.Nameservers) == 0 {
				logf("can not forward, no nameservers defined")
			} else {
				logf("can not forward, name too short (less than %d labels): `%s'", s.config.Ndots, req.Question[0].Name)
			}
		}
		m := s.ServerFailure(req)
		m.RecursionAvailable = true // this is still true
		w.WriteMsg(m)
		return m
	}

	tcp := isTCP(w)

	var (
		r   *dns.Msg
		err error
		try int
	)

	nsid := 0
	if s.config.NSRotate {
		// Use request Id for "random" nameserver selection.
		nsid = int(req.Id) % len(s.config.Nameservers)
	}
Redo:
	switch tcp {
	case false:
		r, _, err = s.dnsUDPclient.Exchange(req, s.config.Nameservers[nsid])
	case true:
		r, _, err = s.dnsTCPclient.Exchange(req, s.config.Nameservers[nsid])
	}
	if err == nil {
		r.Compress = true
		r.Id = req.Id
		w.WriteMsg(r)
		return r
	}
	// Seen an error, this can only mean, "server not reached", try again
	// but only if we have not exausted our nameservers.
	if try < len(s.config.Nameservers) {
		try++
		nsid = (nsid + 1) % len(s.config.Nameservers)
		goto Redo
	}

	logf("failure to forward request %q", err)
	m := s.ServerFailure(req)
	return m
}

func newMsg(host string, qClass uint16) *dns.Msg {
	m1 := new(dns.Msg)
	m1.Id = dns.Id()
	m1.RecursionDesired = true
	m1.Question = make([]dns.Question, 1)
	m1.Question[0] = dns.Question{host, qClass, dns.ClassINET}
	return m1
}

// ServeDNSStubForward forwards a request to a nameservers and returns the response.
func (s *server) ServeDNSStubForward(w dns.ResponseWriter, req *dns.Msg, ns []string) *dns.Msg {
	// Check EDNS0 Stub option, if set drop the packet.
	option := req.IsEdns0()
	if option != nil {
		for _, o := range option.Option {
			if o.Option() == ednsStubCode && len(o.(*dns.EDNS0_LOCAL).Data) == 1 &&
				o.(*dns.EDNS0_LOCAL).Data[0] == 1 {
				// Maybe log source IP here?
				logf("not fowarding stub request to another stub")
				return nil
			}
		}
	}

	tcp := isTCP(w)

	// Add a custom EDNS0 option to the packet, so we can detect loops
	// when 2 stubs are forwarding to each other.
	if option != nil {
		option.Option = append(option.Option, &dns.EDNS0_LOCAL{ednsStubCode, []byte{1}})
	} else {
		req.Extra = append(req.Extra, ednsStub)
	}

	var (
		r   *dns.Msg
		err error
		try int
	)

	// Use request Id for "random" nameserver selection.
	nsid := int(req.Id) % len(ns)
Redo:
	switch tcp {
	case false:
		r, _, err = s.dnsUDPclient.Exchange(req, ns[nsid])
	case true:
		r, _, err = s.dnsTCPclient.Exchange(req, ns[nsid])
	}
	if err == nil {
		r.Compress = true
		r.Id = req.Id
		w.WriteMsg(r)
		return r
	}
	// Seen an error, this can only mean, "server not reached", try again
	// but only if we have not exausted our nameservers.
	if try < len(ns) {
		try++
		nsid = (nsid + 1) % len(ns)
		goto Redo
	}

	logf("failure to forward stub request %q", err)
	m := s.ServerFailure(req)
	w.WriteMsg(m)
	return m
}

func localQuery(mychan chan DNSreply, qname string, qtype uint16) {
	var result DNSreply
	var trials uint
	result.qname = qname
	result.qtype = qtype
	result.r = nil
	result.err = errors.New("No name server to answer the question")
	localm := new(dns.Msg)
	localm.Id = dns.Id()
	localm.RecursionDesired = true
	localm.Question = make([]dns.Question, 1)
	localm.SetEdns0(EDNSBUFFERSIZE, false) // Even if no EDNS requested, see #9 May be we should retry without it if timeout?
	localc := new(dns.Client)
	localc.ReadTimeout = timeout
	localm.Question[0] = dns.Question{qname, qtype, dns.ClassINET}
Tests:
	for trials = 0; trials < uint(*maxTrials); trials++ {
	Resolvers:
		for serverIndex := range conf.Servers {
			server := conf.Servers[serverIndex]
			result.nameserver = server
			// Brackets around the server address are necessary for IPv6 name servers
			r, rtt, err := localc.Exchange(localm, "["+server+"]:"+conf.Port) // Do not use net.JoinHostPort, see https://github.com/bortzmeyer/check-soa/commit/3e4edb13855d8c4016768796b2892aa83eda1933#commitcomment-2355543
			if r == nil {
				result.r = nil
				result.err = err
				if strings.Contains(err.Error(), "timeout") {
					// Try another resolver
					break Resolvers
				} else { // We give in
					break Tests
				}
			} else {
				result.rtt = rtt
				if r.Rcode == dns.RcodeSuccess {
					// TODO: as a result, NODATA (NOERROR/ANSWER=0) are silently ignored (try "foo", for instance, the name exists but no IP address)
					// TODO: for rcodes like SERVFAIL, trying another resolver could make sense
					result.r = r
					result.err = nil
					break Tests
				} else {
					// All the other codes are errors. Yes, it may
					// happens that one resolver returns REFUSED
					// and the others work but we do not handle
					// this case. TODO: delete the resolver from
					// the list and try another one
					result.r = r
					result.err = errors.New(dns.RcodeToString[r.Rcode])
					break Tests
				}
			}
		}
	}
	if *debug {
		fmt.Printf("DEBUG: end of DNS request \"%s\" / %d\n", qname, qtype)
	}
	mychan <- result
}

func prepareFailureMsg(req *dns.Msg) *dns.Msg {
	failMsg := new(dns.Msg)
	failMsg.Id = req.Id
	failMsg.Response = true
	failMsg.Authoritative = true
	failMsg.Question = req.Question
	failMsg.Rcode = dns.RcodeNameError
	return failMsg
}

func (ds *DNSServer) ServeDNS(rw dns.ResponseWriter, mes *dns.Msg) {
	resp := new(dns.Msg)

	for _, q := range mes.Question {
		log.Printf("DNS request from %s: %s", rw.RemoteAddr(), &q)
		switch q.Qtype {
		case dns.TypeA, dns.TypeAAAA:
			val, err := ds.HandleLookup(q.Name)
			if err != nil {
				log.Println(err)
				continue
			}

			if q.Qclass != dns.ClassINET {
				log.Printf("error: got invalid DNS question class %d\n", q.Qclass)
				continue
			}

			header := dns.RR_Header{
				Name:   q.Name,
				Rrtype: q.Qtype,
				Class:  dns.ClassINET,
				Ttl:    DefaultResponseTTL,
			}

			var rr dns.RR
			// not really super sure why these have to be different types
			if q.Qtype == dns.TypeA {
				rr = &dns.A{
					A:   net.ParseIP(val),
					Hdr: header,
				}
			} else if q.Qtype == dns.TypeAAAA {
				rr = &dns.AAAA{
					AAAA: net.ParseIP(val),
					Hdr:  header,
				}
			} else {
				panic("unreachable")
			}

			resp.Answer = append(resp.Answer, rr)

		default:
			log.Printf("unhandled qtype: %d\n", q.Qtype)
		}
	}

	resp.Authoritative = true
	resp.Id = mes.Id
	resp.Response = true

	if err := rw.WriteMsg(resp); err != nil {
		log.Printf("error responding to DNS query: %s", err)
	}
}

// DNS requests go to this function
func dnsHandle(w dns.ResponseWriter, r *dns.Msg) {
	name := r.Question[0].Name
	if !namePattern.MatchString(name) {
		kilog.Debug("%v does not match pattern, forwarding", name)
		dnsForward(w, r)
		return
	}
	// otherwise
	kilog.Debug("%v matches pattern, handling", name)
	dnsLock.Lock()
	defer dnsLock.Unlock()
	// check in table first
	fakeIP, ok := nameToIP[name]
	if !ok {
		// place in table
		var nwIP string
		for {
			haha := ipAlloc().String()
			_, exists := ipToName[haha]
			if exists {
				continue
			}
			nwIP = haha
			break
		}
		fakeIP = nwIP
		nameToIP[name] = fakeIP
		ipToName[fakeIP] = name
		// remove in 30 minutes
		go func() {
			time.Sleep(time.Minute * 30)
			dnsLock.Lock()
			defer dnsLock.Unlock()
			delete(nameToIP, name)
			delete(ipToName, fakeIP)
		}()
	}
	// return the fake IP to the user
	resp := new(dns.A)
	resp.Hdr.Name = name
	resp.Hdr.Ttl = 1 // very short
	resp.Hdr.Class = dns.ClassINET
	resp.Hdr.Rrtype = dns.TypeA
	resp.A = net.ParseIP(fakeIP)

	towrite := new(dns.Msg)
	towrite.Id = r.Id
	towrite.RecursionAvailable = true
	towrite.RecursionDesired = true
	towrite.Response = true
	towrite.Question = r.Question
	towrite.Answer = make([]dns.RR, 1)
	towrite.Answer[0] = resp
	w.WriteMsg(towrite)
	kilog.Debug("returning mapping %v -> %v", name, fakeIP)
}

func (d *DnsDomain) Test() bool {
	if !(*Domain)(d).Test() {
		return false
	}

	fqdn := d.Name
	if strings.HasPrefix(fqdn, "*.") {
		fqdn = "a" + fqdn[1:]
	}
	if !strings.HasSuffix(fqdn, ".") {
		fqdn = fqdn + "."
	}

	any_ok := false

	d.DNS = make([]*DnsRecords, 0, len(DNS_servers))
	for name, addr := range DNS_servers {
		records := new(DnsRecords)
		records.Server = name
		records.NS = addr
		d.DNS = append(d.DNS, records)

		req := new(dns.Msg)
		req.Id = dns.Id()
		req.RecursionDesired = true
		req.Question = []dns.Question{
			dns.Question{fqdn, dns.TypeA, dns.ClassINET},
		}

		resp, err := dns_client.Exchange(req, addr)
		if err != nil {
			records.Status = 900
			records.Message = err.Error()
			continue
		}

		records.IPs = make([]string, 0, len(resp.Answer))
		for _, rr := range resp.Answer {
			switch a := rr.(type) {
			case *dns.RR_A:
				records.IPs = append(records.IPs, a.A.String())
			}
		}

		if len(records.IPs) > 0 {
			any_ok = true
		} else {
			records.Status = 900
			records.Message = "No records"
		}
	}

	return any_ok
}

func DnsGetDoaminIP(domain string) (string, error) {
	m := new(dns.Msg)
	m.Id = dns.Id()
	m.SetQuestion(dns.Fqdn(domain), dns.TypeA)
	m.RecursionDesired = true
	res, err := dnsQuery(m)
	if nil != err {
		return "", err
	}
	return pickIP(res), nil
}