From fc033fdbfae1931c0c9fdb570da979406639248d Mon Sep 17 00:00:00 2001
From: root <noah@noahstride.co.uk>
Date: Mon, 14 Mar 2022 15:06:19 +0000
Subject: [PATCH] fix: properly reverse ip address

---
 backend/api_v1/rdns.go     |  3 ++-
 backend/dns/dns_resolve.go | 19 ++++++++++++-------
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/backend/api_v1/rdns.go b/backend/api_v1/rdns.go
index 10ede28..ff74b18 100644
--- a/backend/api_v1/rdns.go
+++ b/backend/api_v1/rdns.go
@@ -54,8 +54,9 @@ func rdns(g group, log *zap.Logger, dnsServer string) {
 			return
 		}
 
+		ipAddr := net.ParseIP(ip)
 		result, err := dnsLib.LookupRDNS(
-			log, ip, dnsServer,
+			log, ipAddr, dnsServer,
 		)
 		if err != nil {
 			ctx.Error(&gin.Error{
diff --git a/backend/dns/dns_resolve.go b/backend/dns/dns_resolve.go
index 437eab2..ae7fee6 100644
--- a/backend/dns/dns_resolve.go
+++ b/backend/dns/dns_resolve.go
@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"math/rand"
+	"net"
 	"reflect"
 	"strings"
 	"sync"
@@ -427,16 +428,20 @@ func Lookup(log *zap.Logger, dnsServer, recordType, hostname string, fullTrace b
 	return recursiveQuery(log, dnsServer, recordType, hostname)
 }
 
-func reverseString(s string) string {
-	chars := []rune(s)
-	for i, j := 0, len(chars)-1; i < j; i, j = i+1, j-1 {
-		chars[i], chars[j] = chars[j], chars[i]
+func reverseIP(ip net.IP) string {
+	addressParts := strings.Split(ip.String(), ".")
+	reversed := []string{}
+
+	for i := len(addressParts) - 1; i >= 0; i-- {
+		octet := addressParts[i]
+		reversed = append(reversed, octet)
 	}
-	return string(chars)
+
+	return strings.Join(reversed, ".")
 }
 
-func LookupRDNS(log *zap.Logger, ip, dnsServer string) (RecordType, error) {
-	hostname := reverseString(ip) + ".in-addr.arpa."
+func LookupRDNS(log *zap.Logger, ip net.IP, dnsServer string) (RecordType, error) {
+	hostname := reverseIP(ip) + ".in-addr.arpa."
 	resp, err := traceQuery(log, dnsServer, "PTR", hostname)
 	if err != nil {
 		return nil, err