Replaced P/Invoke DNS implementation by HijdenDNS pure C# MIT-licensed library, to hopefully prevent crashes caused by WebApp feature.

src/AcaciaZPushPlugin/AcaciaZPushPlugin/AcaciaZPushPlugin.csproj

@@ -133,8 +133,12 @@
   -->
   <ItemGroup>
     <Reference Include="Accessibility" />
+    <Reference Include="Heijden.Dns, Version=2.0.0.6, Culture=neutral, processorArchitecture=MSIL">
+      <HintPath>..\packages\Heijden.Dns.2.0.0\lib\net35\Heijden.Dns.dll</HintPath>
+      <Private>True</Private>
+    </Reference>
     <Reference Include="NLog, Version=4.0.0.0, Culture=neutral, PublicKeyToken=5120e14c03d0593c, processorArchitecture=MSIL">
-      <HintPath>..\packages\NLog.4.2.3\lib\net45\NLog.dll</HintPath>
+      <HintPath>..\packages\NLog.4.4.1\lib\net45\NLog.dll</HintPath>
       <Private>True</Private>
     </Reference>
     <Reference Include="PresentationCore" />

src/AcaciaZPushPlugin/AcaciaZPushPlugin/Features/WebApp/FeatureWebApp.cs

@@ -124,7 +124,7 @@ namespace Acacia.Features.WebApp
         private string PerformAutoDiscover(ZPushAccount account)
         {
             // Fetch the txt record
-            List<string> txt = DnsUtil.GetTxtRecord(account.DomainName);
+            IList<string> txt = DnsUtil.GetTxtRecord(account.DomainName);
             if (txt == null)
                 return null;
 

src/AcaciaZPushPlugin/AcaciaZPushPlugin/Utils/DnsUtil.cs

@@ -1,4 +1,6 @@
-/// Copyright 2016 Kopano b.v.
+
+using Heijden.DNS;
+/// Copyright 2016 Kopano b.v.
 /// 
 /// This program is free software: you can redistribute it and/or modify
 /// it under the terms of the GNU Affero General Public License, version 3,
@@ -13,7 +15,6 @@
 /// along with this program.If not, see<http://www.gnu.org/licenses/>.
 /// 
 /// Consult LICENSE file for details
-
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
@@ -26,73 +27,11 @@ namespace Acacia.Utils
 {
     public static class DnsUtil
     {
-        public static List<string> GetTxtRecord(string name)
+        public static IList<string> GetTxtRecord(string name)
         {
-            const Int16 DNS_TYPE_TEXT = 0x0010;
-            const Int32 DNS_QUERY_STANDARD = 0x00000000;
-            const Int32 DNS_ERROR_RCODE_NAME_ERROR = 9003;
-            const Int32 DNS_INFO_NO_RECORDS = 9501;
-            var queryResultsSet = IntPtr.Zero;
-            try
-            {
-                var dnsStatus = DnsQuery(
-                  name,
-                  DNS_TYPE_TEXT,
-                  DNS_QUERY_STANDARD,
-                  IntPtr.Zero,
-                  ref queryResultsSet,
-                  IntPtr.Zero
-                );
-                if (dnsStatus == DNS_ERROR_RCODE_NAME_ERROR || dnsStatus == DNS_INFO_NO_RECORDS)
-                    return null;
-                if (dnsStatus != 0)
-                    throw new Win32Exception(dnsStatus);
-                DnsRecordTxt dnsRecord;
-                var lines = new List<String>();
-                for (var pointer = queryResultsSet; pointer != IntPtr.Zero; pointer = dnsRecord.pNext)
-                {
-                    dnsRecord = (DnsRecordTxt)Marshal.PtrToStructure(pointer, typeof(DnsRecordTxt));
-                    if (dnsRecord.wType == DNS_TYPE_TEXT)
-                    {
-                        var stringArrayPointer = pointer + Marshal.OffsetOf(typeof(DnsRecordTxt), "pStringArray").ToInt32();
-                        for (var i = 0; i < dnsRecord.dwStringCount; ++i)
-                        {
-                            var stringPointer = (IntPtr)Marshal.PtrToStructure(stringArrayPointer, typeof(IntPtr));
-                            lines.Add(Marshal.PtrToStringUni(stringPointer));
-                            stringArrayPointer += IntPtr.Size;
-                        }
-                    }
-                }
-                if (lines.Count == 0)
-                    return null;
-                return lines;
-            }
-            finally
-            {
-                const Int32 DnsFreeRecordList = 1;
-                if (queryResultsSet != IntPtr.Zero)
-                    DnsRecordListFree(queryResultsSet, DnsFreeRecordList);
-            }
-        }
-
-        [DllImport("Dnsapi.dll", EntryPoint = "DnsQuery_W", ExactSpelling = true, CharSet = CharSet.Unicode, SetLastError = true)]
-        static extern Int32 DnsQuery(String lpstrName, Int16 wType, Int32 options, IntPtr pExtra, ref IntPtr ppQueryResultsSet, IntPtr pReserved);
-
-        [DllImport("Dnsapi.dll")]
-        static extern void DnsRecordListFree(IntPtr pRecordList, Int32 freeType);
-
-        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
-        struct DnsRecordTxt
-        {
-            public IntPtr pNext;
-            public String pName;
-            public Int16 wType;
-            public Int16 wDataLength;
-            public Int32 flags;
-            public Int32 dwTtl;
-            public Int32 dwReserved;
-            public Int32 dwStringCount;
-            public String pStringArray;
+            Resolver resolver = new Resolver();
+            Response response = resolver.Query(name, QType.TXT, QClass.IN);
+            return response.RecordsTXT.Select(r => r.ToString()).ToList();
         }
     }
 }

src/AcaciaZPushPlugin/AcaciaZPushPlugin/packages.config

@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="NLog" version="4.2.3" targetFramework="net452" />
+  <package id="Heijden.Dns" version="2.0.0" targetFramework="net452" />
+  <package id="NLog" version="4.4.1" targetFramework="net452" />
 </packages>