test.go

package main

import (
	"fmt"
	"github.com/miekg/dns"
	"net"
	"time"
)

const domain = "consul."
const MAXREC = 3

func handleQuery(resp dns.ResponseWriter, req *dns.Msg) {
	// Setup the message response
	m := new(dns.Msg)
	m.SetReply(req)
	m.Authoritative = true
	addSOA(domain, m)

	for i := 0; i < MAXREC; i++ {
		aRec := &dns.A{
			Hdr: dns.RR_Header{
				Name:   req.Question[0].Name,
				Rrtype: dns.TypeA,
				Class:  dns.ClassINET,
				Ttl:    0,
			},
			A: net.ParseIP(fmt.Sprintf("127.0.0.%d", i+1)),
		}
		m.Answer = append(m.Answer, aRec)
	}
	for i := 0; i < MAXREC; i++ {
		srvRec := &dns.SRV{
			Hdr: dns.RR_Header{
				Name:   req.Question[0].Name,
				Rrtype: dns.TypeSRV,
				Class:  dns.ClassINET,
				Ttl:    0,
			},
			Priority: 1,
			Weight:   1,
			Port:     12345,
			Target:   fmt.Sprintf("foobar%d.node.dc1.consul.", i),
		}
		m.Answer = append(m.Answer, srvRec)

		aRec := &dns.A{
			Hdr: dns.RR_Header{
				Name:   srvRec.Target,
				Rrtype: dns.TypeA,
				Class:  dns.ClassINET,
				Ttl:    0,
			},
			A: net.ParseIP(fmt.Sprintf("127.0.0.%d", i+1)),
		}
		m.Extra = append(m.Extra, aRec)
	}
	fmt.Printf("IN:  %#v\n\n", m)

	// Write out the complete response
	if err := resp.WriteMsg(m); err != nil {
		panic(err)
	}
}

func addSOA(domain string, msg *dns.Msg) {
	soa := &dns.SOA{
		Hdr: dns.RR_Header{
			Name:   domain,
			Rrtype: dns.TypeSOA,
			Class:  dns.ClassINET,
			Ttl:    0,
		},
		Ns:      "ns." + domain,
		Mbox:    "postmaster." + domain,
		Serial:  uint32(time.Now().Unix()),
		Refresh: 3600,
		Retry:   600,
		Expire:  86400,
		Minttl:  0,
	}
	msg.Ns = append(msg.Ns, soa)
}

func main() {
	// Start DNS server
	mux := dns.NewServeMux()
	mux.HandleFunc(domain, handleQuery)

	server := &dns.Server{
		Addr:    "127.0.0.1:10000",
		Net:     "udp",
		Handler: mux,
		UDPSize: 65535,
	}

	go func() {
		err := server.ListenAndServe()
		panic(err)
	}()
	time.Sleep(50 * time.Millisecond)

	// Create request
	m := new(dns.Msg)
	m.SetQuestion("web.service.consul.", dns.TypeANY)

	c := new(dns.Client)
	out, _, err := c.Exchange(m, "127.0.0.1:10000")
	if err != nil {
		panic(err)
	}

	fmt.Printf("OUT: %#v\n\n", out)
}