// 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
}
// 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 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())
}
}
}
