reorganize code
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@ -10,6 +10,10 @@ It was inspired by [local-ip.co](http://local-ip.co) and
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```sh
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$ dig 10-0-1-29.my.local-ip.dev +short
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10.0.1.29
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$ dig app.10-0-1-29.my.local-ip.dev +short
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10.0.1.29
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$ dig foo.bar.10.0.1.29.my.local-ip.dev +short
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10.0.1.29
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$ dig 127.0.0.1.my.local-ip.dev +short
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127.0.0.1
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```
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103
main.go
103
main.go
@ -1,104 +1,21 @@
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package main
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import (
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"fmt"
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"log"
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"net"
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"os"
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"regexp"
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"strconv"
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"flag"
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"strings"
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"github.com/miekg/dns"
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xip "local-ip.dev/xip"
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)
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const zone = "my.local-ip.dev."
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const (
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zone = "my.local-ip.dev."
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nameservers = "ns.local-ip.dev."
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)
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func main() {
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dns.HandleFunc(zone, handleDnsRequest)
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var port = flag.Int("port", 53, "port the DNS server should bind to")
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flag.Parse()
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port, err := strconv.Atoi(os.Getenv("PORT"))
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if err != nil {
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port = 9053
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}
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server := &dns.Server{
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Addr: ":" + strconv.Itoa(port),
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Net: "udp",
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}
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log.Printf("Starting at %d\n", port)
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err = server.ListenAndServe()
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defer server.Shutdown()
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if err != nil {
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log.Fatalf("Failed to start server: %s\n ", err.Error())
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}
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}
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func handleDnsRequest(response dns.ResponseWriter, request *dns.Msg) {
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go func() {
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message := new(dns.Msg)
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message.SetReply(request)
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message.Compress = true
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switch request.Opcode {
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case dns.OpcodeQuery:
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handleQuery(message)
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default:
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refuseMessage(message)
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}
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response.WriteMsg(message)
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}()
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}
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func handleQuery(message *dns.Msg) {
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for _, question := range message.Question {
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switch question.Qtype {
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case dns.TypeA:
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ip := extractIp(question.Name)
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log.Printf("%s => %s\n", question.Name, ip)
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if ip == nil {
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refuseMessage(message)
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break
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}
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resource := new(dns.A)
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resource.Hdr = dns.RR_Header{Ttl: 10, Name: question.Name, Rrtype: dns.TypeA, Class: dns.ClassINET}
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resource.A = ip
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message.Answer = append(message.Answer, resource)
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}
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}
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}
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func extractIp(fqdn string) net.IP {
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var ip string
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dashedIpRegex := regexp.MustCompile(fmt.Sprintf(`^(((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\-?\b){4}).%s$`, zone))
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matches := dashedIpRegex.FindStringSubmatch(fqdn)
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if len(matches) < 2 {
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return nil
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}
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ip = strings.ReplaceAll(matches[1], "-", ".")
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return net.ParseIP(ip)
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}
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func refuseMessage(message *dns.Msg) {
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message.MsgHdr.Rcode = dns.RcodeRefused
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soa := new(dns.SOA)
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soa.Hdr = dns.RR_Header{
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Name: "my.local-ip.dev.",
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Rrtype: dns.TypeSOA,
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Class: dns.ClassINET,
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Ttl: 10,
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Rdlength: 0,
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}
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soa.Ns = "ns-1.local-ip.dev."
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soa.Mbox = "admin.local-ip.dev."
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soa.Serial = 2022102400
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soa.Refresh = 10
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soa.Retry = 10
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soa.Expire = 10
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soa.Minttl = 10
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message.Ns = append(message.Ns, soa)
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n := xip.NewXip(zone, strings.Split(nameservers, ","), *port)
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n.StartServer()
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}
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130
xip/xip.go
Normal file
130
xip/xip.go
Normal file
@ -0,0 +1,130 @@
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package xip
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import (
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"log"
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"net"
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"os"
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"regexp"
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"strconv"
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"strings"
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"time"
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"github.com/miekg/dns"
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)
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type Xip struct {
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Server dns.Server
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NameServers []*dns.NS
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Zone string
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}
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var (
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flyRegion = os.Getenv("FLY_REGION")
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dottedIpV4Regex = regexp.MustCompile(`(?:^|(?:[\w\d])+\.)(((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\.?\b){4})($|[.-])`)
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dashedIpV4Regex = regexp.MustCompile(`(?:^|(?:[\w\d])+\.)(((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\-?\b){4})($|[.-])`)
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)
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func (xip *Xip) handleA(question dns.Question, response *dns.Msg) *dns.A {
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fqdn := question.Name
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for _, ipV4RE := range []*regexp.Regexp{dashedIpV4Regex, dottedIpV4Regex} {
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if ipV4RE.MatchString(fqdn) {
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match := ipV4RE.FindStringSubmatch(fqdn)[1]
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match = strings.ReplaceAll(match, "-", ".")
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ipV4Address := net.ParseIP(match).To4()
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if ipV4Address == nil {
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return nil
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}
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resource := &dns.A{
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Hdr: dns.RR_Header{
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Ttl: uint32((time.Hour * 24 * 7).Seconds()),
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Name: fqdn,
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Rrtype: dns.TypeA,
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Class: dns.ClassINET,
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},
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A: ipV4Address,
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}
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log.Printf("(%s) %s => %s\n", flyRegion, fqdn, ipV4Address)
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return resource
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}
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}
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return nil
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}
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func (xip *Xip) handleQuery(message *dns.Msg) {
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for _, question := range message.Question {
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switch question.Qtype {
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case dns.TypeA:
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record := xip.handleA(question, message)
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message.Answer = append(message.Answer, record)
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}
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}
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}
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func (xip *Xip) refuseMessage(message *dns.Msg) {
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message.MsgHdr.Rcode = dns.RcodeRefused
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soa := new(dns.SOA)
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soa.Hdr = dns.RR_Header{
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Name: "my.local-ip.dev.",
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Rrtype: dns.TypeSOA,
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Class: dns.ClassINET,
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Ttl: uint32((time.Hour * 24 * 7).Seconds()),
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Rdlength: 0,
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}
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soa.Ns = "ns.local-ip.dev."
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soa.Mbox = "admin.local-ip.dev."
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soa.Serial = 2022102800
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soa.Refresh = uint32((time.Minute * 15).Seconds())
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soa.Retry = uint32((time.Minute * 15).Seconds())
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soa.Expire = uint32((time.Minute * 30).Seconds())
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soa.Minttl = uint32((time.Minute * 5).Seconds())
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message.Ns = append(message.Ns, soa)
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}
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func (xip *Xip) handleDnsRequest(response dns.ResponseWriter, request *dns.Msg) {
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go func() {
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message := new(dns.Msg)
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message.SetReply(request)
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message.Compress = true
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message.Authoritative = true
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message.RecursionAvailable = false
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switch request.Opcode {
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case dns.OpcodeQuery:
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xip.handleQuery(message)
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default:
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xip.refuseMessage(message)
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}
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response.WriteMsg(message)
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}()
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}
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func (xip *Xip) StartServer() {
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log.Printf("Listening on %s\n", xip.Server.Addr)
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err := xip.Server.ListenAndServe()
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defer xip.Server.Shutdown()
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if err != nil {
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log.Fatalf("Failed to start server: %s\n ", err.Error())
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}
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}
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func NewXip(zone string, nameservers []string, port int) (xip *Xip) {
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xip = &Xip{}
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for _, ns := range nameservers {
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xip.NameServers = append(xip.NameServers, &dns.NS{Ns: ns})
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}
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xip.Server = dns.Server{
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Addr: ":" + strconv.Itoa(port),
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Net: "udp",
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}
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dns.HandleFunc(zone, xip.handleDnsRequest)
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return xip
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}
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