Exemplo n.º 1
0
func (s *Server) composeBrowsingAnswers(resp *dns.Msg, ttl uint32) {
	ptr := &dns.PTR{
		Hdr: dns.RR_Header{
			Name:   s.service.ServiceName(),
			Rrtype: dns.TypePTR,
			Class:  dns.ClassINET,
			Ttl:    ttl,
		},
		Ptr: s.service.ServiceInstanceName(),
	}
	resp.Answer = append(resp.Answer, ptr)

	txt := &dns.TXT{
		Hdr: dns.RR_Header{
			Name:   s.service.ServiceInstanceName(),
			Rrtype: dns.TypeTXT,
			Class:  dns.ClassINET,
			Ttl:    ttl,
		},
		Txt: s.service.Text,
	}
	srv := &dns.SRV{
		Hdr: dns.RR_Header{
			Name:   s.service.ServiceInstanceName(),
			Rrtype: dns.TypeSRV,
			Class:  dns.ClassINET,
			Ttl:    ttl,
		},
		Priority: 0,
		Weight:   0,
		Port:     uint16(s.service.Port),
		Target:   s.service.HostName,
	}
	resp.Extra = append(resp.Extra, srv, txt)

	if s.service.AddrIPv4 != nil {
		a := &dns.A{
			Hdr: dns.RR_Header{
				Name:   s.service.HostName,
				Rrtype: dns.TypeA,
				Class:  dns.ClassINET,
				Ttl:    ttl,
			},
			A: s.service.AddrIPv4,
		}
		resp.Extra = append(resp.Extra, a)
	}
	if s.service.AddrIPv6 != nil {
		aaaa := &dns.AAAA{
			Hdr: dns.RR_Header{
				Name:   s.service.HostName,
				Rrtype: dns.TypeAAAA,
				Class:  dns.ClassINET,
				Ttl:    ttl,
			},
			AAAA: s.service.AddrIPv6,
		}
		resp.Extra = append(resp.Extra, aaaa)
	}
}
Exemplo n.º 2
0
// Sign signs a message m, it takes care of negative or nodata responses as
// well by synthesising NSEC3 records. It will also cache the signatures, using
// a hash of the signed data as a key.
// We also fake the origin TTL in the signature, because we don't want to
// throw away signatures when services decide to have longer TTL. So we just
// set the origTTL to 60.
// TODO(miek): revisit origTTL
func (s *server) Sign(m *dns.Msg, bufsize uint16) {
	now := time.Now().UTC()
	incep := uint32(now.Add(-3 * time.Hour).Unix())     // 2+1 hours, be sure to catch daylight saving time and such
	expir := uint32(now.Add(7 * 24 * time.Hour).Unix()) // sign for a week

	defer func() {
		promCacheSize.WithLabelValues("signature").Set(float64(s.scache.Size()))
	}()

	for _, r := range rrSets(m.Answer) {
		if r[0].Header().Rrtype == dns.TypeRRSIG {
			continue
		}
		if !dns.IsSubDomain(s.config.Domain, r[0].Header().Name) {
			continue
		}
		if sig, err := s.signSet(r, now, incep, expir); err == nil {
			m.Answer = append(m.Answer, sig)
		}
	}
	for _, r := range rrSets(m.Ns) {
		if r[0].Header().Rrtype == dns.TypeRRSIG {
			continue
		}
		if !dns.IsSubDomain(s.config.Domain, r[0].Header().Name) {
			continue
		}
		if sig, err := s.signSet(r, now, incep, expir); err == nil {
			m.Ns = append(m.Ns, sig)
		}
	}
	for _, r := range rrSets(m.Extra) {
		if r[0].Header().Rrtype == dns.TypeRRSIG || r[0].Header().Rrtype == dns.TypeOPT {
			continue
		}
		if !dns.IsSubDomain(s.config.Domain, r[0].Header().Name) {
			continue
		}
		if sig, err := s.signSet(r, now, incep, expir); err == nil {
			m.Extra = append(m.Extra, sig)
		}
	}
	if bufsize >= 512 || bufsize <= 4096 {
		// TCP here?
		promErrorCount.WithLabelValues("truncated").Inc()
		m.Truncated = m.Len() > int(bufsize)
	}
	o := new(dns.OPT)
	o.Hdr.Name = "."
	o.Hdr.Rrtype = dns.TypeOPT
	o.SetDo()
	o.SetUDPSize(4096) // TODO(miek): echo client
	m.Extra = append(m.Extra, o)
	return
}
Exemplo n.º 3
0
func (c *config) registerVersionHandler() { // special handler for reporting version: dig . @host TXT
	dns.HandleFunc(".", func(w dns.ResponseWriter, req *dns.Msg) {
		m := new(dns.Msg)
		m.SetReply(req)
		if req.Question[0].Name == "." && req.Question[0].Qtype == dns.TypeTXT {
			m.Authoritative = true
			m.Answer = []dns.RR{}
			m.Answer = append(m.Answer, &dns.TXT{Hdr: dns.RR_Header{Name: m.Question[0].Name, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}, Txt: []string{"v" + version}})
			m.Extra = []dns.RR{}
			m.Extra = append(m.Extra, &dns.TXT{Hdr: dns.RR_Header{Name: m.Question[0].Name, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}, Txt: []string{"NedDNS"}})
		}
		w.WriteMsg(m)
	})
}
Exemplo n.º 4
0
func Respond(w dns.ResponseWriter, req *dns.Msg, records []dns.RR) {
	m := new(dns.Msg)
	m.SetReply(req)
	m.Authoritative = true
	m.RecursionAvailable = true
	m.Compress = true
	m.Answer = records

	// Figure out the max response size
	bufsize := uint16(512)
	tcp := isTcp(w)

	if o := req.IsEdns0(); o != nil {
		bufsize = o.UDPSize()
	}

	if tcp {
		bufsize = dns.MaxMsgSize - 1
	} else if bufsize < 512 {
		bufsize = 512
	}

	if m.Len() > dns.MaxMsgSize {
		fqdn := dns.Fqdn(req.Question[0].Name)
		log.WithFields(log.Fields{"fqdn": fqdn}).Debug("Response too big, dropping Extra")
		m.Extra = nil
		if m.Len() > dns.MaxMsgSize {
			log.WithFields(log.Fields{"fqdn": fqdn}).Debug("Response still too big")
			m := new(dns.Msg)
			m.SetRcode(m, dns.RcodeServerFailure)
		}
	}

	if m.Len() > int(bufsize) && !tcp {
		log.Debug("Too big 1")
		m.Extra = nil
		if m.Len() > int(bufsize) {
			log.Debug("Too big 2")
			m.Answer = nil
			m.Truncated = true
		}
	}

	err := w.WriteMsg(m)
	if err != nil {
		log.Warn("Failed to return reply: ", err, m.Len())
	}

}
Exemplo n.º 5
0
func findGlue(m *dns.Msg, z *dns.Zone, nameserver string) {
	glue := z.Find(nameserver)
	if glue != nil {
		if a4, ok := glue.RR[dns.TypeAAAA]; ok {
			m.Extra = append(m.Extra, a4...)
			return
		}
		if a, ok := glue.RR[dns.TypeA]; ok {
			m.Extra = append(m.Extra, a...)
			return
		}
	}
	// length or the returned packet! TODO(mg)
	return
}
Exemplo n.º 6
0
func dnsAppend(q dns.Question, m *dns.Msg, rr dns.RR) {
	hdr := dns.RR_Header{Name: q.Name, Class: q.Qclass, Ttl: 0}

	if rrS, ok := rr.(*dns.A); ok {
		hdr.Rrtype = dns.TypeA
		rrS.Hdr = hdr
	} else if rrS, ok := rr.(*dns.AAAA); ok {
		hdr.Rrtype = dns.TypeAAAA
		rrS.Hdr = hdr
	} else if rrS, ok := rr.(*dns.CNAME); ok {
		hdr.Rrtype = dns.TypeCNAME
		rrS.Hdr = hdr
	} else if rrS, ok := rr.(*dns.TXT); ok {
		hdr.Rrtype = dns.TypeTXT
		rrS.Hdr = hdr
	} else {
		log.Printf("error: unknown dnsAppend RR type: %+v\n", rr)
		return
	}

	if q.Qtype == dns.TypeANY || q.Qtype == rr.Header().Rrtype {
		m.Answer = append(m.Answer, rr)
	} else {
		m.Extra = append(m.Extra, rr)
	}
}
Exemplo n.º 7
0
func lookup(msg *dns.Msg, client *dns.Client, server string, edns bool) (*dns.Msg, error) {
	if edns {
		opt := &dns.OPT{
			Hdr: dns.RR_Header{
				Name:   ".",
				Rrtype: dns.TypeOPT,
			},
		}
		opt.SetUDPSize(dns.DefaultMsgSize)
		msg.Extra = append(msg.Extra, opt)
	}

	response, _, err := client.Exchange(msg, server)
	if err != nil {
		return nil, err
	}

	if msg.Id != response.Id {
		return nil, fmt.Errorf("DNS ID mismatch, request: %d, response: %d", msg.Id, response.Id)
	}

	if response.MsgHdr.Truncated {
		if client.Net == "tcp" {
			return nil, fmt.Errorf("Got truncated message on tcp")
		}

		if edns { // Truncated even though EDNS is used
			client.Net = "tcp"
		}

		return lookup(msg, client, server, !edns)
	}

	return response, nil
}
Exemplo n.º 8
0
// serviceARecords is used to add the SRV records for a service lookup
func (d *DNSServer) serviceSRVRecords(dc string, nodes structs.CheckServiceNodes, req, resp *dns.Msg, ttl time.Duration) {
	handled := make(map[string]struct{})
	for _, node := range nodes {
		// Avoid duplicate entries, possible if a node has
		// the same service the same port, etc.
		tuple := fmt.Sprintf("%s:%d", node.Node.Node, node.Service.Port)
		if _, ok := handled[tuple]; ok {
			continue
		}
		handled[tuple] = struct{}{}

		// Add the SRV record
		srvRec := &dns.SRV{
			Hdr: dns.RR_Header{
				Name:   req.Question[0].Name,
				Rrtype: dns.TypeSRV,
				Class:  dns.ClassINET,
				Ttl:    uint32(ttl / time.Second),
			},
			Priority: 1,
			Weight:   1,
			Port:     uint16(node.Service.Port),
			Target:   fmt.Sprintf("%s.node.%s.%s", node.Node.Node, dc, d.domain),
		}
		resp.Answer = append(resp.Answer, srvRec)

		// Add the extra record
		records := d.formatNodeRecord(&node.Node, srvRec.Target, dns.TypeANY, ttl)
		if records != nil {
			resp.Extra = append(resp.Extra, records...)
		}
	}
}
Exemplo n.º 9
0
func dedup(m *dns.Msg) *dns.Msg {
	// TODO(miek): expensive!
	m.Answer = dns.Dedup(m.Answer, nil)
	m.Ns = dns.Dedup(m.Ns, nil)
	m.Extra = dns.Dedup(m.Extra, nil)
	return m
}
Exemplo n.º 10
0
// Construct a response for a single DNS request.
func (ds *DjdnsServer) Handle(query *dns.Msg) (*dns.Msg, error) {
	response := new(dns.Msg)
	response.MsgHdr.Id = query.MsgHdr.Id
	response.Question = query.Question
	if len(query.Question) > 0 {
		// Ignore secondary questions
		question := query.Question[0]
		records, err := ds.GetRecords(question.Name)
		if err != nil {
			return nil, err
		}
		response.Answer = make([]dns.RR, len(records))
		for i, record := range records {
			answer, err := record.ToDns()
			if err != nil {
				return nil, err
			}
			response.Answer[i] = answer
		}
		response.Ns = make([]dns.RR, 0)
		response.Extra = make([]dns.RR, 0)
	}

	return response, nil
}
Exemplo n.º 11
0
Arquivo: main.go Projeto: axw/jns
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)
}
Exemplo n.º 12
0
func RenewDnsMsg(m *dns.Msg) {
	m.Extra = nil
	m.Answer = nil
	m.AuthenticatedData = false
	m.CheckingDisabled = false
	m.Question = nil
}
Exemplo n.º 13
0
func (res *Resolver) handleSRV(rs *records.RecordGenerator, name string, m, r *dns.Msg) error {
	var errs multiError
	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 len(rs.As[host]) == 0 {
			continue
		}

		aRR, err := res.formatA(host, rs.As[host][0])
		if err != nil {
			errs.Add(err)
			continue
		}

		m.Extra = append(m.Extra, aRR)
	}
	return errs
}
Exemplo n.º 14
0
func (manager *DnsManager) dnsHandler(w dns.ResponseWriter, req *dns.Msg) {
	m := new(dns.Msg)
	m.SetReply(req)

	name := req.Question[0].Name
	name = strings.TrimSuffix(name, "."+manager.BaseName)

	manager.dbMutex.Lock()
	entry, ok := manager.db[name]
	manager.dbMutex.Unlock()

	if ok {
		switch req.Question[0].Qtype {
		case dns.TypeSRV:
			m.Answer = manager.makeAllSRV(entry)
		case dns.TypeA:
			m.Answer = manager.makeAllA(entry)
			if manager.PushSRV {
				m.Extra = manager.makeAllSRV(entry)
			}
		}
	}

	w.WriteMsg(m)
}
Exemplo n.º 15
0
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
}
Exemplo n.º 16
0
// syncExtra takes a DNS response message and sets the extra data to the most
// minimal set needed to cover the answer data. A pre-made index of RRs is given
// so that can be re-used between calls. This assumes that the extra data is
// only used to provide info for SRV records. If that's not the case, then this
// will wipe out any additional data.
func syncExtra(index map[string]dns.RR, resp *dns.Msg) {
	extra := make([]dns.RR, 0, len(resp.Answer))
	resolved := make(map[string]struct{}, len(resp.Answer))
	for _, ansRR := range resp.Answer {
		srv, ok := ansRR.(*dns.SRV)
		if !ok {
			continue
		}

		// Note that we always use lower case when using the index so
		// that compares are not case-sensitive. We don't alter the actual
		// RRs we add into the extra section, however.
		target := strings.ToLower(srv.Target)

	RESOLVE:
		if _, ok := resolved[target]; ok {
			continue
		}
		resolved[target] = struct{}{}

		extraRR, ok := index[target]
		if ok {
			extra = append(extra, extraRR)
			if cname, ok := extraRR.(*dns.CNAME); ok {
				target = strings.ToLower(cname.Target)
				goto RESOLVE
			}
		}
	}
	resp.Extra = extra
}
Exemplo n.º 17
0
// Handle produces reply for NS question
func (n *nsHandler) Handle(msg *mdns.Msg, zone *config.Zone, question mdns.Question) (err error) {
	for _, server := range n.config.DNS.Servers {
		s := strings.Join([]string{
			question.Name,
			"3600",
			"IN",
			"NS",
			server.Name,
		}, " ")

		rr, err := mdns.NewRR(s)
		if err == nil {
			msg.Answer = append(msg.Answer, rr)
		}
	}

	for _, server := range n.config.DNS.Servers {
		s := strings.Join([]string{
			server.Name,
			"3600",
			"IN",
			"A",
			server.IP,
		}, " ")
		rr, err := mdns.NewRR(s)
		if err == nil {
			msg.Extra = append(msg.Extra, rr)
		}
	}
	return
}
Exemplo n.º 18
0
// truncate removes answers until the given dns.Msg fits the permitted
// length of the given transmission channel and sets the TC bit.
// See https://tools.ietf.org/html/rfc1035#section-4.2.1
func truncate(m *dns.Msg, udp bool) *dns.Msg {
	max := dns.MinMsgSize
	if !udp {
		max = dns.MaxMsgSize
	} else if opt := m.IsEdns0(); opt != nil {
		max = int(opt.UDPSize())
	}

	m.Truncated = m.Len() > max
	if !m.Truncated {
		return m
	}

	m.Extra = nil // Drop all extra records first
	if m.Len() < max {
		return m
	}
	answers := m.Answer[:]
	left, right := 0, len(m.Answer)
	for {
		if left == right {
			break
		}
		mid := (left + right) / 2
		m.Answer = answers[:mid]
		if m.Len() < max {
			left = mid + 1
			continue
		}
		right = mid
	}
	return m
}
Exemplo n.º 19
0
// Sign signs a message m, it takes care of negative or nodata responses as
// well by synthesising NSEC3 records. It will also cache the signatures, using
// a hash of the signed data as a key.
// We also fake the origin TTL in the signature, because we don't want to
// throw away signatures when services decide to have longer TTL. So we just
// set the origTTL to 60.
// TODO(miek): revisit origTTL
func (s *server) Sign(m *dns.Msg, bufsize uint16) {
	now := time.Now().UTC()
	incep := uint32(now.Add(-3 * time.Hour).Unix())     // 2+1 hours, be sure to catch daylight saving time and such
	expir := uint32(now.Add(7 * 24 * time.Hour).Unix()) // sign for a week

	for _, r := range rrSets(m.Answer) {
		if r[0].Header().Rrtype == dns.TypeRRSIG {
			continue
		}
		if !dns.IsSubDomain(s.config.Domain, r[0].Header().Name) {
			continue
		}
		if sig, err := s.signSet(r, now, incep, expir); err == nil {
			m.Answer = append(m.Answer, sig)
		}
	}
	for _, r := range rrSets(m.Ns) {
		if r[0].Header().Rrtype == dns.TypeRRSIG {
			continue
		}
		if !dns.IsSubDomain(s.config.Domain, r[0].Header().Name) {
			continue
		}
		if sig, err := s.signSet(r, now, incep, expir); err == nil {
			m.Ns = append(m.Ns, sig)
		}
	}
	for _, r := range rrSets(m.Extra) {
		if r[0].Header().Rrtype == dns.TypeRRSIG || r[0].Header().Rrtype == dns.TypeOPT {
			continue
		}
		if !dns.IsSubDomain(s.config.Domain, r[0].Header().Name) {
			continue
		}
		if sig, err := s.signSet(r, now, incep, expir); err == nil {
			m.Extra = append(m.Extra, sig)
		}
	}

	o := new(dns.OPT)
	o.Hdr.Name = "."
	o.Hdr.Rrtype = dns.TypeOPT
	o.SetDo()
	o.SetUDPSize(4096) // TODO(miek): echo client
	m.Extra = append(m.Extra, o)
	return
}
Exemplo n.º 20
0
func (s *Server) do(Net string, w dns.ResponseWriter, req *dns.Msg) {
	if len(req.Question) != 1 {
		dns.HandleFailed(w, req)
		return
	}
	zone, name := s.zones.match(req.Question[0].Name, req.Question[0].Qtype)
	if zone == nil {
		s.recurse(w, req)
		return
	}

	s.zones.Lock()
	defer s.zones.Unlock()

	m := new(dns.Msg)
	m.SetReply(req)

	var answerKnown bool
	dnsreq := dns.RR_Header{Name: req.Question[0].Name, Rrtype: req.Question[0].Qtype, Class: req.Question[0].Qclass}
	for _, r := range (*zone)[dnsreq] {
		m.Answer = append(m.Answer, r)
		answerKnown = true
	}
	// TODO: more logs here
	s.roundRobin(zone, dnsreq)

	if !answerKnown && s.recurseTo != "" {
		s.recurse(w, req)
		return
	}

	// Add Authority section
	for _, r := range (*zone)[dns.RR_Header{Name: name, Rrtype: dns.TypeNS, Class: dns.ClassINET}] {
		m.Ns = append(m.Ns, r)
		// Resolve Authority if possible and serve as Extra
		for _, r := range (*zone)[dns.RR_Header{Name: r.(*dns.NS).Ns, Rrtype: dns.TypeA, Class: dns.ClassINET}] {
			m.Extra = append(m.Extra, r)
		}
		for _, r := range (*zone)[dns.RR_Header{Name: r.(*dns.NS).Ns, Rrtype: dns.TypeAAAA, Class: dns.ClassINET}] {
			m.Extra = append(m.Extra, r)
		}
	}

	m.Authoritative = true
	w.WriteMsg(m)
}
Exemplo n.º 21
0
func Msg(zone string, typ uint16, o *dns.OPT) *dns.Msg {
	m := new(dns.Msg)
	m.SetQuestion(zone, typ)
	if o != nil {
		m.Extra = []dns.RR{o}
	}
	return m
}
Exemplo n.º 22
0
// Err write an error response to the client.
func (e Etcd) Err(zone string, rcode int, state middleware.State, debug []msg.Service, err error) (int, error) {
	m := new(dns.Msg)
	m.SetRcode(state.Req, rcode)
	m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true
	m.Ns, _, _ = e.SOA(zone, state)
	if e.debug != "" {
		m.Extra = servicesToTxt(debug)
		txt := errorToTxt(err)
		if txt != nil {
			m.Extra = append(m.Extra, errorToTxt(err))
		}
	}
	state.SizeAndDo(m)
	state.W.WriteMsg(m)
	// Return success as the rcode to signal we have written to the client.
	return dns.RcodeSuccess, nil
}
Exemplo n.º 23
0
func (s *Server) unregister() error {
	resp := new(dns.Msg)
	resp.MsgHdr.Response = true
	resp.Answer = []dns.RR{}
	resp.Extra = []dns.RR{}
	s.composeLookupAnswers(resp, 0)
	return s.multicastResponse(resp)
}
Exemplo n.º 24
0
// 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
}
Exemplo n.º 25
0
func ednsMsg() *dns.Msg {
	m := new(dns.Msg)
	m.SetQuestion("example.com.", dns.TypeA)
	o := new(dns.OPT)
	o.Hdr.Name = "."
	o.Hdr.Rrtype = dns.TypeOPT
	m.Extra = append(m.Extra, o)
	return m
}
Exemplo n.º 26
0
// Perform probing & announcement
//TODO: implement a proper probing & conflict resolution
func (s *Server) probe() {
	q := new(dns.Msg)
	q.SetQuestion(s.service.ServiceInstanceName(), dns.TypePTR)
	q.RecursionDesired = false

	srv := &dns.SRV{
		Hdr: dns.RR_Header{
			Name:   s.service.ServiceInstanceName(),
			Rrtype: dns.TypeSRV,
			Class:  dns.ClassINET,
			Ttl:    s.ttl,
		},
		Priority: 0,
		Weight:   0,
		Port:     uint16(s.service.Port),
		Target:   s.service.HostName,
	}
	txt := &dns.TXT{
		Hdr: dns.RR_Header{
			Name:   s.service.ServiceInstanceName(),
			Rrtype: dns.TypeTXT,
			Class:  dns.ClassINET,
			Ttl:    s.ttl,
		},
		Txt: s.service.Text,
	}
	q.Ns = []dns.RR{srv, txt}

	randomizer := rand.New(rand.NewSource(time.Now().UnixNano()))
	for i := 0; i < 3; i++ {
		if err := s.multicastResponse(q); err != nil {
			log.Println("[ERR] bonjour: failed to send probe:", err.Error())
		}
		time.Sleep(time.Duration(randomizer.Intn(250)) * time.Millisecond)
	}
	resp := new(dns.Msg)
	resp.MsgHdr.Response = true
	resp.Answer = []dns.RR{}
	resp.Extra = []dns.RR{}
	s.composeLookupAnswers(resp, s.ttl)

	// From RFC6762
	//    The Multicast DNS responder MUST send at least two unsolicited
	//    responses, one second apart. To provide increased robustness against
	//    packet loss, a responder MAY send up to eight unsolicited responses,
	//    provided that the interval between unsolicited responses increases by
	//    at least a factor of two with every response sent.
	timeout := 1 * time.Second
	for i := 0; i < 3; i++ {
		if err := s.multicastResponse(resp); err != nil {
			log.Println("[ERR] bonjour: failed to send announcement:", err.Error())
		}
		time.Sleep(timeout)
		timeout *= 2
	}
}
Exemplo n.º 27
0
func serverHandlerHello(w dns.ResponseWriter, req *dns.Msg) {
	m := new(dns.Msg)
	m.SetReply(req)
	m.Extra = make([]dns.RR, 1)
	m.Extra[0] = &dns.TXT{
		Hdr: dns.RR_Header{Name: m.Question[0].Name, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0},
		Txt: []string{"Hello world"},
	}
	w.WriteMsg(m)
}
Exemplo n.º 28
0
func prepareAnswerMsg(req *dns.Msg, answers []dns.RR) *dns.Msg {
	answerMsg := new(dns.Msg)
	answerMsg.Id = req.Id
	answerMsg.Response = true
	answerMsg.Authoritative = true
	answerMsg.Question = req.Question
	answerMsg.Answer = answers
	answerMsg.Rcode = dns.RcodeSuccess
	answerMsg.Extra = []dns.RR{}
	return answerMsg
}
Exemplo n.º 29
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func (r *RoundRobinResponseWriter) WriteMsg(res *dns.Msg) error {
	if res.Rcode != dns.RcodeSuccess {
		return r.ResponseWriter.WriteMsg(res)
	}

	res.Answer = roundRobin(res.Answer)
	res.Ns = roundRobin(res.Ns)
	res.Extra = roundRobin(res.Extra)

	return r.ResponseWriter.WriteMsg(res)
}
Exemplo n.º 30
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// addStubEdns0 adds our special option to the message's OPT record.
func addStubEdns0(m *dns.Msg) *dns.Msg {
	option := m.IsEdns0()
	// 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{Code: ednsStubCode, Data: []byte{1}})
		return m
	}

	m.Extra = append(m.Extra, ednsStub)
	return m
}