example code

[Ran-Xing]

package main

import (
	"github.com/miekg/dns"
	log "github.com/sirupsen/logrus"
	"net"
	"strconv"
	"strings"
)

var records = map[string]string{
	"test.service": "192.168.0.2",
}

func handleDnsRequest(w dns.ResponseWriter, m *dns.Msg) {
	r := new(dns.Msg)
	r.SetReply(m)
	r.Compress = true
	r.Authoritative = true
	r.RecursionAvailable = true
	IPAddress := "NULL"
	Domain := strings.TrimRight(r.Question[0].Name, ".")

	defer func(w dns.ResponseWriter, msg *dns.Msg) {
		log.Infof("Query: [%v ? %s --> %v]\n", w.RemoteAddr(), Domain, IPAddress)
		err := w.WriteMsg(msg)
		if err != nil {
			log.Errorf("Error writing response: %v", err)
			return
		}
	}(w, r)

	// not resolve
	if r.Question[0].Qtype != dns.TypeA {
		r.Rcode = dns.RcodeNotImplemented
		return
	}
	if addr := records[Domain]; addr != "" {
		IPAddress = addr
		r.Answer = append(r.Answer, &dns.A{
			Hdr: dns.RR_Header{
				Name:   m.Question[0].Name,
				Rrtype: dns.TypeA,
				Class:  dns.ClassINET,
				Ttl:    uint32(86400),
			},
			A: net.ParseIP(IPAddress).To4(),
		})
	}

	if len(r.Answer) == 0 {
		r.Rcode = dns.RcodeNameError
	}
}

func main() {
	// attach request handler func
	dns.HandleFunc("service.", handleDnsRequest)

	// start server
	port := 53
	server := &dns.Server{Addr: ":" + strconv.Itoa(port), Net: "udp"}
	log.Printf("Starting at %d\n", port)
	err := server.ListenAndServe()
	defer server.Shutdown()
	if err != nil {
		log.Fatalf("Failed to start server: %s\n ", err.Error())
	}
}