local-ip.sh/xip/xip.go

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package xip
import (
"log"
"net"
"os"
"regexp"
"strconv"
"strings"
"time"
"github.com/miekg/dns"
)
type Xip struct {
Server dns.Server
NameServers []*dns.NS
Zone string
}
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type HardcodedRecord struct {
A net.IP
TXT []string
}
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var (
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flyRegion = os.Getenv("FLY_REGION")
dottedIpV4Regex = regexp.MustCompile(`(?:^|(?:[\w\d])+\.)(((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\.?\b){4})($|[.-])`)
dashedIpV4Regex = regexp.MustCompile(`(?:^|(?:[\w\d])+\.)(((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\-?\b){4})($|[.-])`)
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hardcodedRecords = map[string]HardcodedRecord{
"ns.local-ip.sh.": {
A: net.IPv4(137, 66, 38, 214),
},
"local-ip.sh.": {
A: net.IPv4(137, 66, 53, 22),
TXT: []string{"sl-verification=frudknyqpqlpgzbglkqnsmorfcvxrf"},
},
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}
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)
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func (xip *Xip) fqdnToA(fqdn string) *dns.A {
var ipV4Address net.IP
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if hardcodedRecords[strings.ToLower(fqdn)].A != nil {
ipV4Address = hardcodedRecords[strings.ToLower(fqdn)].A
}
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for _, ipV4RE := range []*regexp.Regexp{dashedIpV4Regex, dottedIpV4Regex} {
if ipV4RE.MatchString(fqdn) {
match := ipV4RE.FindStringSubmatch(fqdn)[1]
match = strings.ReplaceAll(match, "-", ".")
ipV4Address = net.ParseIP(match).To4()
break
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}
}
if ipV4Address == nil {
return nil
}
return &dns.A{
Hdr: dns.RR_Header{
// Ttl: uint32((time.Hour * 24 * 7).Seconds()),
Ttl: uint32((time.Second * 10).Seconds()),
Name: fqdn,
Rrtype: dns.TypeA,
Class: dns.ClassINET,
},
A: ipV4Address,
}
}
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func (xip *Xip) handleA(question dns.Question, message *dns.Msg) {
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fqdn := question.Name
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record := xip.fqdnToA(fqdn)
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if record == nil {
message.Rcode = dns.RcodeNameError
message.Ns = append(message.Ns, xip.SOARecord(question))
return
}
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log.Printf("(%s) %s => %s\n", flyRegion, fqdn, record.A)
message.Answer = append(message.Answer, record)
}
func (xip *Xip) handleNS(question dns.Question, message *dns.Msg) {
fqdn := question.Name
nameServers := []*dns.NS{}
additionals := []*dns.A{}
for _, ns := range xip.NameServers {
nameServers = append(nameServers, &dns.NS{
Hdr: dns.RR_Header{
// Ttl: uint32((time.Hour * 24 * 7).Seconds()),
Ttl: uint32((time.Second * 10).Seconds()),
Name: fqdn,
Rrtype: dns.TypeNS,
Class: dns.ClassINET,
},
Ns: ns.Ns,
})
additionals = append(additionals, xip.fqdnToA(ns.Ns))
}
for _, record := range nameServers {
message.Answer = append(message.Answer, record)
}
for _, record := range additionals {
message.Extra = append(message.Extra, record)
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}
}
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func (xip *Xip) handleTXT(question dns.Question, message *dns.Msg) {
fqdn := question.Name
if hardcodedRecords[strings.ToLower(fqdn)].TXT == nil {
return
}
message.Answer = append(message.Answer, &dns.TXT{
Hdr: dns.RR_Header{
// Ttl: uint32((time.Hour * 24 * 7).Seconds()),
Ttl: uint32((time.Second * 10).Seconds()),
Name: fqdn,
Rrtype: dns.TypeTXT,
Class: dns.ClassINET,
},
Txt: hardcodedRecords[strings.ToLower(fqdn)].TXT,
})
}
func (xip *Xip) SOARecord(question dns.Question) *dns.SOA {
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soa := new(dns.SOA)
soa.Hdr = dns.RR_Header{
Name: question.Name,
Rrtype: dns.TypeSOA,
Class: dns.ClassINET,
// Ttl: uint32((time.Hour * 24 * 7).Seconds()),
Ttl: uint32((time.Second * 10).Seconds()),
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Rdlength: 0,
}
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soa.Ns = "ns.local-ip.sh."
soa.Mbox = "admin.local-ip.sh."
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soa.Serial = 2022102800
// soa.Refresh = uint32((time.Minute * 15).Seconds())
soa.Refresh = uint32((time.Second * 10).Seconds())
// soa.Retry = uint32((time.Minute * 15).Seconds())
soa.Retry = uint32((time.Second * 10).Seconds())
// soa.Expire = uint32((time.Minute * 30).Seconds())
soa.Expire = uint32((time.Second * 10).Seconds())
// soa.Minttl = uint32((time.Minute * 5).Seconds())
soa.Minttl = uint32((time.Second * 10).Seconds())
return soa
}
func (xip *Xip) handleQuery(message *dns.Msg) {
for _, question := range message.Question {
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log.Printf("name: %s\n", question.Name)
log.Printf("class: %d\n", question.Qclass)
log.Printf("type: %d\n", question.Qtype)
switch question.Qtype {
case dns.TypeA:
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xip.handleA(question, message)
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case dns.TypeNS:
xip.handleNS(question, message)
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case dns.TypeTXT:
xip.handleTXT(question, message)
}
}
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}
func (xip *Xip) handleDnsRequest(response dns.ResponseWriter, request *dns.Msg) {
go func() {
message := new(dns.Msg)
message.SetReply(request)
message.Compress = true
message.Authoritative = true
message.RecursionAvailable = false
switch request.Opcode {
case dns.OpcodeQuery:
xip.handleQuery(message)
default:
message.MsgHdr.Rcode = dns.RcodeRefused
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}
response.WriteMsg(message)
}()
}
func (xip *Xip) StartServer() {
log.Printf("Listening on %s\n", xip.Server.Addr)
err := xip.Server.ListenAndServe()
defer xip.Server.Shutdown()
if err != nil {
log.Fatalf("Failed to start server: %s\n ", err.Error())
}
}
func NewXip(zone string, nameservers []string, port int) (xip *Xip) {
xip = &Xip{}
for _, ns := range nameservers {
xip.NameServers = append(xip.NameServers, &dns.NS{Ns: ns})
}
xip.Server = dns.Server{
Addr: ":" + strconv.Itoa(port),
Net: "udp",
}
dns.HandleFunc(zone, xip.handleDnsRequest)
return xip
}