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)
}
}
// 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
}
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)
})
}
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())
}
}
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
}
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)
}
}
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
}
// 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...)
}
}
}
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
}
// 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
}
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 RenewDnsMsg(m *dns.Msg) {
m.Extra = nil
m.Answer = nil
m.AuthenticatedData = false
m.CheckingDisabled = false
m.Question = nil
}
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
}
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)
}
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
}
// 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
}
// 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
}
// 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
}
// 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
}
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)
}
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
}
// 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
}
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)
}
// 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 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
}
// 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
}
}
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)
}
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
}
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)
}
// 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
}