local-ip.sh/xip/xip.go
2022-10-29 00:28:10 +02:00

135 lines
3.2 KiB
Go

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
}
var (
flyRegion = os.Getenv("FLY_REGION")
dottedIpV4Regex = regexp.MustCompile(`(?:^|(?:[\w\d])+\.)(((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\.?\b){4})($|[.-])`)
dashedIpV4Regex = regexp.MustCompile(`(?:^|(?:[\w\d])+\.)(((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\-?\b){4})($|[.-])`)
)
func (xip *Xip) handleA(question dns.Question, message *dns.Msg) {
fqdn := question.Name
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()
if ipV4Address == nil {
message.Rcode = dns.RcodeNameError
message.Ns = append(message.Ns, xip.SOARecord(question))
return
}
record := &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,
}
log.Printf("(%s) %s => %s\n", flyRegion, fqdn, ipV4Address)
message.Answer = append(message.Answer, record)
}
}
}
func (xip *Xip) SOARecord(question dns.Question) *dns.SOA {
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()),
Rdlength: 0,
}
soa.Ns = "ns.local-ip.dev."
soa.Mbox = "admin.local-ip.dev."
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 {
switch question.Qtype {
case dns.TypeA:
xip.handleA(question, message)
}
}
}
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
}
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
}