reorganize code

This commit is contained in:
m5r 2022-10-28 23:36:57 +02:00
parent 2ab783c2ad
commit 16a757694e
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3 changed files with 144 additions and 93 deletions

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@ -10,6 +10,10 @@ It was inspired by [local-ip.co](http://local-ip.co) and
```sh ```sh
$ dig 10-0-1-29.my.local-ip.dev +short $ dig 10-0-1-29.my.local-ip.dev +short
10.0.1.29 10.0.1.29
$ dig app.10-0-1-29.my.local-ip.dev +short
10.0.1.29
$ dig foo.bar.10.0.1.29.my.local-ip.dev +short
10.0.1.29
$ dig 127.0.0.1.my.local-ip.dev +short $ dig 127.0.0.1.my.local-ip.dev +short
127.0.0.1 127.0.0.1
``` ```

103
main.go
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@ -1,104 +1,21 @@
package main package main
import ( import (
"fmt" "flag"
"log"
"net"
"os"
"regexp"
"strconv"
"strings" "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() { 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")) n := xip.NewXip(zone, strings.Split(nameservers, ","), *port)
if err != nil { n.StartServer()
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)
} }

130
xip/xip.go Normal file
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@ -0,0 +1,130 @@
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, response *dns.Msg) *dns.A {
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 {
return nil
}
resource := &dns.A{
Hdr: dns.RR_Header{
Ttl: uint32((time.Hour * 24 * 7).Seconds()),
Name: fqdn,
Rrtype: dns.TypeA,
Class: dns.ClassINET,
},
A: ipV4Address,
}
log.Printf("(%s) %s => %s\n", flyRegion, fqdn, ipV4Address)
return resource
}
}
return nil
}
func (xip *Xip) handleQuery(message *dns.Msg) {
for _, question := range message.Question {
switch question.Qtype {
case dns.TypeA:
record := xip.handleA(question, message)
message.Answer = append(message.Answer, record)
}
}
}
func (xip *Xip) 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: uint32((time.Hour * 24 * 7).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.Retry = uint32((time.Minute * 15).Seconds())
soa.Expire = uint32((time.Minute * 30).Seconds())
soa.Minttl = uint32((time.Minute * 5).Seconds())
message.Ns = append(message.Ns, soa)
}
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:
xip.refuseMessage(message)
}
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
}