Implementing basic DNS Client

SMTPServer/DNSResolver/DNSResolver.csproj

@@ -1,16 +1,16 @@
-<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" />
-  
+  <PropertyGroup Label="Configuration">
+    <NoWarn>1701;1702;1705;1006</NoWarn>
+  </PropertyGroup>
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>netcoreapp1.0</TargetFramework>
   </PropertyGroup>
-
   <ItemGroup>
     <Compile Include="**\*.cs" />
     <EmbeddedResource Include="**\*.resx" />
   </ItemGroup>
-
   <ItemGroup>
     <PackageReference Include="Microsoft.NETCore.App">
       <Version>1.0.1</Version>
@@ -20,6 +20,5 @@
       <PrivateAssets>All</PrivateAssets>
     </PackageReference>
   </ItemGroup>
-  
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
 </Project>

SMTPServer/DNSResolver/DnsHelper.cs

@@ -0,0 +1,115 @@
+using System;
+using System.Text;
+
+namespace DNSResolver
+{
+    internal static class DnsHelpers
+    {
+        private const long Epoch = 621355968000000000;
+
+        internal static byte[] CanonicaliseDnsName(string name, bool lowerCase)
+        {
+            if (!name.EndsWith("."))
+            {
+                name += ".";
+            }
+
+            if (name == ".")
+            {
+                return new byte[1];
+            }
+
+            StringBuilder sb = new StringBuilder();
+
+            sb.Append('\0');
+
+            for (int i = 0, j = 0; i < name.Length; i++, j++)
+            {
+                if (lowerCase)
+                {
+                    sb.Append(char.ToLower(name[i]));
+                }
+                else
+                {
+                    sb.Append(name[i]);
+                }
+
+                if (name[i] == '.')
+                {
+                    sb[i - j] = (char)(j & 0xff);
+                    j = -1;
+                }
+            }
+
+            sb[sb.Length - 1] = '\0';
+
+            return Encoding.ASCII.GetBytes(sb.ToString());
+        }
+
+        internal static String DumpArrayToString(byte[] bytes)
+        {
+            StringBuilder builder = new StringBuilder();
+
+            builder.Append("[");
+
+            foreach (byte b in bytes)
+            {
+                builder.Append(" ");
+                builder.Append((sbyte)b);
+                builder.Append(" ");
+            }
+
+            builder.Append("]");
+
+            return builder.ToString();
+        }
+
+        /// <summary>
+        /// Converts a instance of a <see cref="DateTime"/> class to a 48 bit format time since epoch.
+        /// Epoch is defined as 1-Jan-70 UTC.
+        /// </summary>
+        /// <param name="dateTimeToConvert">The <see cref="DateTime"/> instance to convert to DNS format.</param>
+        /// <param name="timeHigh">The upper 16 bits of time.</param>
+        /// <param name="timeLow">The lower 32 bits of the time object.</param>
+        internal static void ConvertToDnsTime(DateTime dateTimeToConvert, out int timeHigh, out long timeLow)
+        {
+            long secondsFromEpoch = (dateTimeToConvert.ToUniversalTime().Ticks - Epoch) / 10000000;
+            timeHigh = (int)(secondsFromEpoch >> 32);
+            timeLow = (secondsFromEpoch & 0xFFFFFFFFL);
+
+            Logging.AddLogMessage(LoggingType.TRACE, "test");
+            Trace.WriteLine(String.Format("Date: {0}", dateTimeToConvert));
+            Trace.WriteLine(String.Format("secondsFromEpoch: {0}", secondsFromEpoch));
+            Trace.WriteLine(String.Format("timeHigh: {0}", timeHigh));
+            Trace.WriteLine(String.Format("timeLow: {0}", timeLow));
+        }
+
+        /// <summary>
+        /// Convert from DNS 48 but time format to a <see cref="DateTime"/> instance. 
+        /// </summary>
+        /// <param name="timeHigh">The upper 16 bits of time.</param>
+        /// <param name="timeLow">The lower 32 bits of the time object.</param>
+        /// <returns>The converted date time</returns>
+        internal static DateTime ConvertFromDnsTime(long timeLow, long timeHigh)
+        {
+            long time = (timeHigh << 32) + timeLow;
+            time = time * 10000000;
+            time += Epoch;
+
+            return new DateTime(time);
+        }
+
+        /// <summary>
+        /// Convert from DNS 48 but time format to a <see cref="DateTime"/> instance. 
+        /// </summary>
+        /// <param name="dnsTime">The upper 48 bits of time.</param>
+        /// <returns>The converted date time</returns>
+        internal static DateTime ConvertFromDnsTime(long dnsTime)
+        {
+            dnsTime = dnsTime * 10000000;
+            dnsTime += Epoch;
+
+            return new DateTime(dnsTime);
+        }
+    }
+}

SMTPServer/DNSResolver/Program.cs

@@ -1,9 +0,0 @@
-using System;
-
-class Program
-{
-    static void Main(string[] args)
-    {
-        Console.WriteLine("Hello World!");
-    }
-}