From 8a95b657eefc642772dbbcf3793fa180a09196a3 Mon Sep 17 00:00:00 2001
From: Ingmar Stein <IngmarStein@users.noreply.github.com>
Date: Mon, 14 Oct 2024 08:54:07 +0200
Subject: [PATCH] Add `filterDomains` setting to `Filter AAAA` app.

This allows filtering `AAAA` records only for specific domains. If
`filterDomains` is empty, all domains (except the ones listed in
`bypassDomains`) will be filtered.

See https://github.com/TechnitiumSoftware/DnsServer/discussions/1016
---
 Apps/FilterAaaaApp/App.cs        | 19 +++++++++++++++++++
 Apps/FilterAaaaApp/dnsApp.config |  2 ++
 2 files changed, 21 insertions(+)

diff --git a/Apps/FilterAaaaApp/App.cs b/Apps/FilterAaaaApp/App.cs
index 37f3110d..76ce2c8b 100644
--- a/Apps/FilterAaaaApp/App.cs
+++ b/Apps/FilterAaaaApp/App.cs
@@ -40,6 +40,7 @@ namespace FilterAaaa
         bool _bypassLocalZones;
         NetworkAddress[] _bypassNetworks;
         string[] _bypassDomains;
+        string[] _filterDomains;
 
         #endregion
 
@@ -74,6 +75,11 @@ namespace FilterAaaa
             else
                 _bypassDomains = [];
 
+            if (jsonConfig.TryReadArray("filterDomains", out string[] filterDomains))
+                _filterDomains = filterDomains;
+            else
+                _filterDomains = [];
+
             return Task.CompletedTask;
         }
 
@@ -95,6 +101,19 @@ namespace FilterAaaa
             if (question.Type != DnsResourceRecordType.AAAA)
                 return response;
 
+            bool filterDomain = _filterDomains.Length == 0;
+            foreach (string filterDomain in _filterDomains)
+            {
+                if (qname.Equals(filterDomain, StringComparison.OrdinalIgnoreCase) || qname.EndsWith("." + filterDomain, StringComparison.OrdinalIgnoreCase))
+                {
+                    filterDomain = true;
+                    break;
+                }
+            }
+
+            if (!filterDomain)
+                return response;
+
             bool hasAAAA = false;
 
             foreach (DnsResourceRecord record in response.Answer)
diff --git a/Apps/FilterAaaaApp/dnsApp.config b/Apps/FilterAaaaApp/dnsApp.config
index fd6a6285..23b998c3 100644
--- a/Apps/FilterAaaaApp/dnsApp.config
+++ b/Apps/FilterAaaaApp/dnsApp.config
@@ -5,5 +5,7 @@
   ],
   "bypassDomains": [
     "example.com"
+  ],
+  "filterDomains": [
   ]
 }
\ No newline at end of file