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)
}
}
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 (s *server) unregister() error {
resp := new(dns.Msg)
resp.Answer = []dns.RR{}
resp.Extra = []dns.RR{}
s.composeLookupAnswers(resp, 0)
return s.multicastResponse(resp)
}
// parsePacket is used to parse an incoming packet
func (s *server) parsePacket(packet []byte, from net.Addr) error {
var msg dns.Msg
if err := msg.Unpack(packet); err != nil {
log.Printf("[ERR] bonjour: Failed to unpack packet: %v", err)
return err
}
return s.handleQuery(&msg, from)
}
// Pack the dns.Msg and write to available connections (multicast)
func (c *client) sendQuery(msg *dns.Msg) error {
buf, err := msg.Pack()
if err != nil {
return err
}
if c.ipv4conn != nil {
c.ipv4conn.WriteTo(buf, ipv4Addr)
}
if c.ipv4conn != nil {
c.ipv4conn.WriteTo(buf, ipv6Addr)
}
return nil
}
// multicastResponse us used to send a multicast response packet
func (c *server) multicastResponse(msg *dns.Msg) error {
buf, err := msg.Pack()
if err != nil {
log.Println("Failed to pack message!")
return err
}
if c.ipv4conn != nil {
c.ipv4conn.WriteTo(buf, ipv4Addr)
}
if c.ipv4conn != nil {
c.ipv4conn.WriteTo(buf, ipv6Addr)
}
return nil
}
// sendResponse is used to send a unicast response packet
func (s *server) sendResponse(resp *dns.Msg, from net.Addr) error {
buf, err := resp.Pack()
if err != nil {
return err
}
addr := from.(*net.UDPAddr)
if addr.IP.To4() != nil {
_, err = s.ipv4conn.WriteToUDP(buf, addr)
return err
} else {
_, err = s.ipv6conn.WriteToUDP(buf, addr)
return err
}
}
// Retrieve the MX records for miek.nl.
func ExampleMX() {
config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
c := new(dns.Client)
m := new(dns.Msg)
m.SetQuestion("miek.nl.", dns.TypeMX)
m.RecursionDesired = true
r, _, err := c.Exchange(m, config.Servers[0]+":"+config.Port)
if err != nil {
return
}
if r.Rcode != dns.RcodeSuccess {
return
}
for _, a := range r.Answer {
if mx, ok := a.(*dns.MX); ok {
fmt.Printf("%s\n", mx.String())
}
}
}
// handleQuery is used to handle an incoming query
func (s *server) handleQuery(query *dns.Msg, from net.Addr) error {
// Ignore answer for now
if len(query.Answer) > 0 {
return nil
}
// Ignore questions with Authorative section for now
if len(query.Ns) > 0 {
return nil
}
// Handle each question
var (
resp dns.Msg
err error
)
if len(query.Question) > 0 {
for i, _ := range query.Question {
resp = dns.Msg{}
resp.SetReply(query)
resp.Answer = []dns.RR{}
resp.Extra = []dns.RR{}
if err = s.handleQuestion(query.Question[i], &resp); err != nil {
log.Printf("[ERR] bonjour: failed to handle question %v: %v",
query.Question[i], err)
continue
}
// Check if there is an answer
if len(resp.Answer) > 0 {
//return s.sendResponse(&resp, from)
//log.Println("====== BEGIN ======")
//log.Println(resp.String())
//log.Println("======= END =======")
if e := s.multicastResponse(&resp); e != nil {
err = e
}
}
}
}
return err
}
// Performs the actual query by service name (browse) or service instance name (lookup),
// start response listeners goroutines and loops over the entries channel.
func (c *client) query(params *LookupParams) error {
var serviceName, serviceInstanceName string
serviceName = fmt.Sprintf("%s.%s.", trimDot(params.Service), trimDot(params.Domain))
if params.Instance != "" {
serviceInstanceName = fmt.Sprintf("%s.%s", params.Instance, serviceName)
}
// send the query
m := new(dns.Msg)
if serviceInstanceName != "" {
m.Question = []dns.Question{
dns.Question{serviceInstanceName, dns.TypeSRV, dns.ClassINET},
dns.Question{serviceInstanceName, dns.TypeTXT, dns.ClassINET},
}
m.RecursionDesired = false
} else {
m.SetQuestion(serviceName, dns.TypePTR)
m.RecursionDesired = false
}
if err := c.sendQuery(m); err != nil {
return err
}
return nil
}
// Data receiving routine reads from connection, unpacks packets into dns.Msg
// structures and sends them to a given msgCh channel
func (c *client) recv(l *net.UDPConn, msgCh chan *dns.Msg) {
if l == nil {
return
}
buf := make([]byte, 65536)
for !c.closed {
n, _, err := l.ReadFrom(buf)
if err != nil {
continue
}
msg := new(dns.Msg)
if err := msg.Unpack(buf[:n]); err != nil {
log.Printf("[ERR] mdns: Failed to unpack packet: %v", err)
continue
}
select {
case msgCh <- msg:
case <-c.closedCh:
return
}
}
}
// 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: 3200,
},
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: 3200,
},
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.Answer = []dns.RR{}
resp.Extra = []dns.RR{}
s.composeLookupAnswers(resp, 3200)
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(2 * time.Second)
}
}
// Retrieve the DNSKEY records of a zone and convert them
// to DS records for SHA1, SHA256 and SHA384.
func ExampleDS(zone string) {
config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
c := new(dns.Client)
m := new(dns.Msg)
if zone == "" {
zone = "miek.nl"
}
m.SetQuestion(dns.Fqdn(zone), dns.TypeDNSKEY)
m.SetEdns0(4096, true)
r, _, err := c.Exchange(m, config.Servers[0]+":"+config.Port)
if err != nil {
return
}
if r.Rcode != dns.RcodeSuccess {
return
}
for _, k := range r.Answer {
if key, ok := k.(*dns.DNSKEY); ok {
for _, alg := range []uint8{dns.SHA1, dns.SHA256, dns.SHA384} {
fmt.Printf("%s; %d\n", key.ToDS(alg).String(), key.Flags)
}
}
}
}
func (s *server) composeLookupAnswers(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(),
}
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,
}
txt := &dns.TXT{
Hdr: dns.RR_Header{
Name: s.service.ServiceInstanceName(),
Rrtype: dns.TypeTXT,
Class: dns.ClassINET,
Ttl: ttl,
},
Txt: s.service.Text,
}
dnssd := &dns.PTR{
Hdr: dns.RR_Header{
Name: fmt.Sprintf("_services._dns-sd._udp.%s.", trimDot(s.service.Domain)),
Rrtype: dns.TypePTR,
Class: dns.ClassINET,
Ttl: ttl,
},
Ptr: s.service.ServiceName(),
}
resp.Answer = append(resp.Answer, srv, txt, ptr, dnssd)
if s.service.AddrIPv4 != nil {
a := &dns.A{
Hdr: dns.RR_Header{
Name: s.service.HostName,
Rrtype: dns.TypeA,
Class: dns.ClassINET,
Ttl: 120,
},
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: 120,
},
AAAA: s.service.AddrIPv6,
}
resp.Extra = append(resp.Extra, aaaa)
}
}