From 025466f9d8a1c25989e69fdb0a366b335c0af802 Mon Sep 17 00:00:00 2001
From: jbergner <jan.bergner@hilden.de>
Date: Tue, 14 Jan 2025 08:12:13 +0100
Subject: [PATCH] PTR Fix + IPv6 Fix

---
 data/data.json |  2 +-
 main.go        | 51 ++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/data/data.json b/data/data.json
index fcfcdb2..5a564d3 100644
--- a/data/data.json
+++ b/data/data.json
@@ -2,7 +2,7 @@
   "friedhof8.hilden.de.": {
     "dns": "friedhof8.hilden.de",
     "ipv4": "1.1.1.2",
-    "ipv6": "",
+    "ipv6": "2001::5b:41",
     "user": "friedhof",
     "token": "ef797c8118f02dfb649607dd5d3f8c7623048c9c063d532cc95c5ed7a898a64f",
     "lastseen": "2025-01-14 06:53:45.7690632 +0100 CET m=+27.298316601"
diff --git a/main.go b/main.go
index 865bb3e..8918c4d 100644
--- a/main.go
+++ b/main.go
@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"log"
+	"net"
 	"net/http"
 	"os"
 	"os/signal"
@@ -79,6 +80,41 @@ func VerifyToken(token, storedHash string) bool {
 	return HashToken(token) == storedHash
 }
 
+func reverseString(s string) string {
+	// Konvertiere den String in eine Rune-Slice, um Unicode-Zeichen zu unterstützen
+	runes := []rune(s)
+	n := len(runes)
+	// Tausche die Elemente, um den String umzudrehen
+	for i := 0; i < n/2; i++ {
+		runes[i], runes[n-1-i] = runes[n-1-i], runes[i]
+	}
+	// Konvertiere die Rune-Slice zurück in einen String
+	return string(runes)
+}
+
+func IPv6ToPTR(ipv6 string) (string, error) {
+	// Parse the IPv6 address to validate it
+	parsedIP := net.ParseIP(ipv6)
+	if parsedIP == nil || parsedIP.To16() == nil || parsedIP.To4() != nil {
+		return "", fmt.Errorf("invalid IPv6 address: %s", ipv6)
+	}
+
+	// Expand the IPv6 address to its full form
+	expanded := parsedIP.To16()
+
+	// Convert to a reversed nibble format for PTR
+	var nibbles []string
+	for i := len(expanded) - 1; i >= 0; i-- {
+		hexByte := fmt.Sprintf("%02x", expanded[i])
+		// Add the nibbles in reverse order
+		nibbles = append(nibbles, string(hexByte[1]), string(hexByte[0]))
+	}
+
+	// Join the nibbles with dots and append the reverse domain
+	reversed := strings.Join(nibbles, ".")
+	return reversed + ".ip6.arpa.", nil
+}
+
 func handler(w http.ResponseWriter, r *http.Request) {
 	Dns := r.URL.Query().Get("DDNS")
 	Ip := r.URL.Query().Get("IP")
@@ -174,8 +210,19 @@ func handleDNSRequest(w dns.ResponseWriter, r *dns.Msg) {
 			}
 		case dns.TypePTR:
 			for a, b := range D {
-				fmt.Println(b.Ipv4, q.Name)
-				if b.Ipv4 == q.Name {
+
+				iptocheck := reverseString(b.Ipv4)
+				fmt.Println(iptocheck, q.Name)
+				if iptocheck+".in-addr.arpa." == q.Name {
+					rr, err := dns.NewRR(q.Name + " PTR " + a)
+					if err == nil {
+						msg.Answer = append(msg.Answer, rr)
+					}
+				}
+
+				ip6tocheck, _ := IPv6ToPTR(b.Ipv6)
+				fmt.Println(ip6tocheck, q.Name)
+				if ip6tocheck == q.Name {
 					rr, err := dns.NewRR(q.Name + " PTR " + a)
 					if err == nil {
 						msg.Answer = append(msg.Answer, rr)