reorganize code

main.go

@@ -1,104 +1,21 @@
 package main
 
 import (
-	"fmt"
-	"log"
-	"net"
-	"os"
-	"regexp"
-	"strconv"
+	"flag"
 	"strings"
 
-	"github.com/miekg/dns"
+	xip "local-ip.dev/xip"
 )
 
-const zone = "my.local-ip.dev."
+const (
+	zone        = "my.local-ip.dev."
+	nameservers = "ns.local-ip.dev."
+)
 
 func main() {
-	dns.HandleFunc(zone, handleDnsRequest)
+	var port = flag.Int("port", 53, "port the DNS server should bind to")
+	flag.Parse()
 
-	port, err := strconv.Atoi(os.Getenv("PORT"))
-	if err != nil {
-		port = 9053
-	}
-	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())
-	}
-}
-
-func handleDnsRequest(response dns.ResponseWriter, request *dns.Msg) {
-	go func() {
-		message := new(dns.Msg)
-		message.SetReply(request)
-		message.Compress = true
-
-		switch request.Opcode {
-		case dns.OpcodeQuery:
-			handleQuery(message)
-		default:
-			refuseMessage(message)
-		}
-
-		response.WriteMsg(message)
-	}()
-}
-
-func handleQuery(message *dns.Msg) {
-	for _, question := range message.Question {
-		switch question.Qtype {
-		case dns.TypeA:
-			ip := extractIp(question.Name)
-			log.Printf("%s => %s\n", question.Name, ip)
-			if ip == nil {
-				refuseMessage(message)
-				break
-			}
-
-			resource := new(dns.A)
-			resource.Hdr = dns.RR_Header{Ttl: 10, Name: question.Name, Rrtype: dns.TypeA, Class: dns.ClassINET}
-			resource.A = ip
-			message.Answer = append(message.Answer, resource)
-		}
-	}
-}
-
-func extractIp(fqdn string) net.IP {
-	var ip string
-	dashedIpRegex := regexp.MustCompile(fmt.Sprintf(`^(((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\-?\b){4}).%s$`, zone))
-	matches := dashedIpRegex.FindStringSubmatch(fqdn)
-	if len(matches) < 2 {
-		return nil
-	}
-
-	ip = strings.ReplaceAll(matches[1], "-", ".")
-
-	return net.ParseIP(ip)
-}
-
-func refuseMessage(message *dns.Msg) {
-	message.MsgHdr.Rcode = dns.RcodeRefused
-
-	soa := new(dns.SOA)
-	soa.Hdr = dns.RR_Header{
-		Name:     "my.local-ip.dev.",
-		Rrtype:   dns.TypeSOA,
-		Class:    dns.ClassINET,
-		Ttl:      10,
-		Rdlength: 0,
-	}
-	soa.Ns = "ns-1.local-ip.dev."
-	soa.Mbox = "admin.local-ip.dev."
-	soa.Serial = 2022102400
-	soa.Refresh = 10
-	soa.Retry = 10
-	soa.Expire = 10
-	soa.Minttl = 10
-	message.Ns = append(message.Ns, soa)
+	n := xip.NewXip(zone, strings.Split(nameservers, ","), *port)
+	n.StartServer()
 }