From 5bc49a85da1a5d716bd04ee1cd2a1e70ae716f35 Mon Sep 17 00:00:00 2001
From: Shreyas Zare <shreyas@technitium.com>
Date: Sat, 14 Oct 2017 20:15:28 +0530
Subject: [PATCH] DnsServer: added code to ignore ICMP port unreachable
 responses which creates SocketException in ReceiveFrom(). other minor changes
 done.

---
 DnsServerCore/DnsServer.cs | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/DnsServerCore/DnsServer.cs b/DnsServerCore/DnsServer.cs
index f0f18a4c..8c0c57cb 100644
--- a/DnsServerCore/DnsServer.cs
+++ b/DnsServerCore/DnsServer.cs
@@ -35,6 +35,8 @@ namespace DnsServerCore
         const int TCP_SOCKET_SEND_TIMEOUT = 30000;
         const int TCP_SOCKET_RECV_TIMEOUT = 60000;
 
+        readonly IPEndPoint _localEP;
+
         readonly Socket _udpListener;
         readonly Thread _udpListenerThread;
 
@@ -65,15 +67,16 @@ namespace DnsServerCore
 
         public DnsServer(IPEndPoint localEP)
         {
+            _localEP = localEP;
             _dnsCache = new DnsCache(_cacheZoneRoot);
 
             _udpListener = new Socket(AddressFamily.InterNetworkV6, SocketType.Dgram, ProtocolType.Udp);
             _udpListener.SetSocketOption(SocketOptionLevel.IPv6, SocketOptionName.IPv6Only, false);
-            _udpListener.Bind(localEP);
+            _udpListener.Bind(_localEP);
 
             _tcpListener = new Socket(AddressFamily.InterNetworkV6, SocketType.Stream, ProtocolType.Tcp);
             _tcpListener.SetSocketOption(SocketOptionLevel.IPv6, SocketOptionName.IPv6Only, false);
-            _tcpListener.Bind(localEP);
+            _tcpListener.Bind(_localEP);
             _tcpListener.Listen(10);
 
             //start reading query packets
@@ -131,6 +134,16 @@ namespace DnsServerCore
             else
                 remoteEP = new IPEndPoint(IPAddress.IPv6Any, 0);
 
+            #region this code ignores ICMP port unreachable responses which creates SocketException in ReceiveFrom()
+
+            const uint IOC_IN = 0x80000000;
+            const uint IOC_VENDOR = 0x18000000;
+            const uint SIO_UDP_CONNRESET = IOC_IN | IOC_VENDOR | 12;
+
+            _udpListener.IOControl((IOControlCode)SIO_UDP_CONNRESET, new byte[] { Convert.ToByte(false) }, null);
+
+            #endregion
+
             while (true)
             {
                 bytesRecv = _udpListener.ReceiveFrom(recvBufferStream.Buffer, ref remoteEP);
@@ -344,6 +357,9 @@ namespace DnsServerCore
 
         #region properties
 
+        public IPEndPoint LocalEP
+        { get { return _localEP; } }
+
         public Zone AuthoritativeZoneRoot
         { get { return _authoritativeZoneRoot; } }