Fallback to the gateway's DNS when resolving local addresses (leak pr…

…evention will disable upstream sources)
SmartHomeOS · Aug 6, 2024 · ac7faca · ac7faca
1 parent a527a46
commit ac7faca
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Showing 3 changed files with 29 additions and 1 deletion.
diff --git a/TinyDNS/DNSResolver.cs b/TinyDNS/DNSResolver.cs
@@ -69,14 +69,18 @@ private void ReloadNameservers()
         {
             globalNameservers.Clear();
             var nics = NetworkInterface.GetAllNetworkInterfaces();
+            IPAddress? gateway = null;
             foreach (var nic in nics)
             {
                 if (nic.OperationalStatus == OperationalStatus.Up && !nic.IsReceiveOnly && nic.NetworkInterfaceType != NetworkInterfaceType.Loopback)
                 {
                     foreach (IPAddress ns in nic.GetIPProperties().DnsAddresses)
                         globalNameservers.Add(ns);
+                    gateway ??= nic.GetIPProperties().GatewayAddresses.FirstOrDefault()?.Address;
                 }
             }
+            if (gateway != null)
+                globalNameservers.Add(gateway); //Always fall back to the gateway
         }
 
         /// <summary>

diff --git a/TinyDNS/MDNS.cs b/TinyDNS/MDNS.cs
@@ -206,6 +206,30 @@ public async Task Query(List<string> domain, DNSRecordType type, bool unicastRes
             await SendMessage(msg);
         }
 
+        /// <summary>
+        /// Lookup the domain name for an IP address
+        /// </summary>
+        /// <param name="address"></param>
+        /// <returns>The domain</returns>
+        public async Task<string?> ResolveIP(IPAddress address)
+        {
+            List<Message> responses = await ResolveInverseQuery(address);
+            foreach (Message response in responses)
+            {
+                foreach (ResourceRecord answer in response.Answers)
+                {
+                    if (answer is PtrRecord ptr)
+                    {
+                        var labels = ptr.DomainLabels;
+                        if (labels.Count > 1)
+                            labels.RemoveAt(labels.Count - 1); //Remove .local
+                        return string.Join('.', labels);
+                    }
+                }
+            }
+            return null;
+        }
+
         public async Task<List<Message>> ResolveInverseQuery(IPAddress address, bool unicastResponse = false)
         {
             var domain = DomainParser.FromIP(address);

diff --git a/TinyDNS/TinyDNS.csproj b/TinyDNS/TinyDNS.csproj
@@ -4,7 +4,7 @@
     <TargetFrameworks>net80</TargetFrameworks>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
-    <Version>0.7.1</Version>
+    <Version>0.7.2</Version>
     <PackageLicenseExpression>AGPL-3.0-or-later</PackageLicenseExpression>
     <PackageReadmeFile>README.md</PackageReadmeFile>
     <Authors>jdomnitz</Authors>