From f50c982fb39ae99c71afe5c0719399f5162891b7 Mon Sep 17 00:00:00 2001
From: BornToBeRoot <16019165+BornToBeRoot@users.noreply.github.com>
Date: Sat, 6 Jan 2024 23:55:41 +0100
Subject: [PATCH] Fix: DNS server resolve is finished too early if queries are
 timed out (#2612)

* Fix: DNS server resolve is finished too early if queries are timed out

* Docs: #2612
---
 .../Network/DNSLookup.cs                      | 39 +++++++++++++------
 Website/docs/changelog/next-release.md        |  1 +
 2 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/Source/NETworkManager.Models/Network/DNSLookup.cs b/Source/NETworkManager.Models/Network/DNSLookup.cs
index 069031be64..226ff290a9 100644
--- a/Source/NETworkManager.Models/Network/DNSLookup.cs
+++ b/Source/NETworkManager.Models/Network/DNSLookup.cs
@@ -6,7 +6,6 @@
 using System.Threading.Tasks;
 using DnsClient;
 using DnsClient.Protocol;
-using NETworkManager.Utilities;
 
 namespace NETworkManager.Models.Network;
 
@@ -90,7 +89,7 @@ private void OnLookupComplete()
     /// <returns>List of DNS servers as <see cref="IPEndPoint" />.</returns>
     private IEnumerable<IPEndPoint> GetDnsServer(IEnumerable<ServerConnectionInfo> dnsServers = null)
     {
-        List<IPEndPoint> servers = new();
+        List<IPEndPoint> servers = [];
 
         // Use windows dns servers
         servers.AddRange(dnsServers == null
@@ -122,16 +121,9 @@ public void ResolveAsync(IEnumerable<string> hosts)
             // Append dns suffix to hostname, if option is set, otherwise just copy the list
             var queries = _addSuffix && _settings.QueryType != QueryType.PTR ? GetHostWithSuffix(hosts) : hosts;
 
-            // Foreach dns server
-            Parallel.ForEach(_servers, async dnsServer =>
+            // For each dns server
+            Parallel.ForEach(_servers, dnsServer =>
             {
-                // Get the dns server hostname for some additional information
-                var dnsServerHostName = string.Empty;
-
-                var dnsResult = await DNSClient.GetInstance().ResolvePtrAsync(dnsServer.Address);
-                if (!dnsResult.HasError)
-                    dnsServerHostName = dnsResult.Value;
-
                 // Init each dns server once
                 LookupClientOptions lookupClientOptions = new(dnsServer)
                 {
@@ -143,8 +135,27 @@ public void ResolveAsync(IEnumerable<string> hosts)
                 };
 
                 LookupClient lookupClient = new(lookupClientOptions);
+                
+                // Get the dns server hostname for some additional information
+                var dnsServerHostName = string.Empty;
+
+                try
+                {
+                    var result = lookupClient.QueryReverse(dnsServer.Address);
+
+                    if (!result.HasError)
+                    {
+                        var record = result.Answers.PtrRecords().FirstOrDefault();
+                        
+                        if (record != null)
+                            dnsServerHostName = record.PtrDomainName;
+                    }
+                }
+                catch { 
+                    // ignored
+                }
 
-                // Foreach host
+                // For each host
                 Parallel.ForEach(queries, query =>
                 {
                     try
@@ -159,15 +170,18 @@ public void ResolveAsync(IEnumerable<string> hosts)
                         {
                             OnLookupError(new DNSLookupErrorArgs(query, $"{dnsServer.Address}",
                                 $"{dnsServer.Address}:{dnsServer.Port}", dnsResponse.ErrorMessage));
+                            
                             return; // continue
                         }
 
                         if (dnsResponse.Answers.Count == 0)
                         {
                             var digAdditionalCommand = _settings.QueryType == QueryType.PTR ? " -x " : " ";
+                            
                             OnLookupError(new DNSLookupErrorArgs(query, $"{dnsServer.Address}",
                                 $"{dnsServer.Address}:{dnsServer.Port}",
                                 $"No DNS resource records received for query \"{query}\" (Query type: \"{_settings.QueryType}\") and the DNS server did not return an error. Try to check your DNS server with: dig @{dnsServer.Address}{digAdditionalCommand}{query}"));
+                           
                             return; // continue
                         }
 
@@ -191,6 +205,7 @@ public void ResolveAsync(IEnumerable<string> hosts)
     /// </summary>
     /// <param name="answers">List of DNS resource records.</param>
     /// <param name="nameServer">DNS name server that answered the query.</param>
+    /// <param name="nameServerHostname">DNS name server hostname.</param>
     private void ProcessDnsAnswers(IEnumerable<DnsResourceRecord> answers, NameServer nameServer,
         string nameServerHostname = null)
     {
diff --git a/Website/docs/changelog/next-release.md b/Website/docs/changelog/next-release.md
index e09f52aa35..8dbd8dd837 100644
--- a/Website/docs/changelog/next-release.md
+++ b/Website/docs/changelog/next-release.md
@@ -43,6 +43,7 @@ Release date: **xx.xx.2023**
   - Scan is no longer aborted if the IP of a single host in a series of hosts cannot be resolved (the host is skipped and an error is displayed) [#2573](https://github.com/BornToBeRoot/NETworkManager/pull/2573)
 - DNS Lookup
   - Hostname of the nameserver added to group [#2573](https://github.com/BornToBeRoot/NETworkManager/pull/2573)
+  - Resolve was finished too early if a request timed [#2612](https://github.com/BornToBeRoot/NETworkManager/pull/2612)
   - Sort improved [#2583](https://github.com/BornToBeRoot/NETworkManager/pull/2583)
 - SNMP
   OID profile column sort fixed [#2583](https://github.com/BornToBeRoot/NETworkManager/pull/2583)