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DNS.NET Resolver (C#)

, 11 Mar 2013
A full implementation of a reusable DNS resolver component and a Dig.Net example application.
Article_Demo.zip
Article_Demo
DnsDig.exe
nunit.framework.dll
article_src-noexe.zip
DnsDig
DnsDig.suo
DnsDig
bin
Debug
Article_Demo.zip
DnsDig.vshost.exe.manifest
Dns
Records
NotUsed
Obsolete
Root
DnsDig.csproj.user
Doc
obj
Debug
DnsDig.AboutForm.resources
DnsDig.MainForm.resources
DnsDig.Properties.Resources.resources
Properties
Settings.settings
article_src.zip
DnsDig.suo
Article_Demo.zip
DnsDig.exe
DnsDig.pdb
DnsDig.vshost.exe
DnsDig.vshost.exe.manifest
nunit.framework.dll
Release
DnsDig.csproj.user
DesignTimeResolveAssemblyReferencesInput.cache
DnsDig.AboutForm.resources
DnsDig.csproj.GenerateResource.Cache
DnsDig.csprojResolveAssemblyReference.cache
DnsDig.exe
DnsDig.MainForm.resources
DnsDig.pdb
DnsDig.Properties.Resources.resources
TempPE
Properties.Resources.Designer.cs.dll
Settings.settings
article_src.zip.zip
DnsDig.suo
DnsDig.csproj.user
DnsExperiment.AboutForm.resources
DnsExperiment.csproj.GenerateResource.Cache
DnsExperiment.MainForm.resources
DnsExperiment.Properties.Resources.resources
Refactor
Properties.Resources.Designer.cs.dll
Settings.settings
using System;
using System.Text;
/*
 * http://tools.ietf.org/rfc/rfc2065.txt
 * 
5.2 NXT RDATA Format

   The RDATA for an NXT RR consists simply of a domain name followed by
   a bit map.

   The type number for the NXT RR is 30.

                           1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         next domain name                                      /
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    type bit map                               /
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The NXT RR type bit map is one bit per RR type present for the owner
   name similar to the WKS socket bit map.  The first bit represents RR
   type zero (an illegal type which should not be present.) A one bit
   indicates that at least one RR of that type is present for the owner
   name.  A zero indicates that no such RR is present.  All bits not
   specified because they are beyond the end of the bit map are assumed
   to be zero.  Note that bit 30, for NXT, will always be on so the
   minimum bit map length is actually four octets.  The NXT bit map
   should be printed as a list of RR type mnemonics or decimal numbers
   similar to the WKS RR.

   The domain name may be compressed with standard DNS name compression
   when being transmitted over the network.  The size of the bit map can
   be inferred from the RDLENGTH and the length of the next domain name.



 */
namespace Heijden.DNS
{
	public class RecordNXT : Record
	{
		public string NEXTDOMAINNAME;
		public byte[] BITMAP;

		public RecordNXT(RecordReader rr)
		{
			ushort length = rr.ReadUInt16(-2);
			NEXTDOMAINNAME = rr.ReadDomainName();
			length -= (ushort)rr.Position;
			BITMAP = new byte[length];
			BITMAP = rr.ReadBytes(length);
		}

		private bool IsSet(int bitNr)
		{
			int intByte = (int)(bitNr / 8);
			int intOffset = (bitNr % 8);
			byte b = BITMAP[intByte];
			int intTest = 1 << intOffset;
			if ((b & intTest) == 0)
				return false;
			else
				return true;
		}


		public override string ToString()
		{
			StringBuilder sb = new StringBuilder();
			for (int bitNr = 1; bitNr < (BITMAP.Length * 8); bitNr++)
			{
				if (IsSet(bitNr))
					sb.Append(" " + (Type)bitNr);
			}
			return string.Format("{0}{1}", NEXTDOMAINNAME, sb.ToString());
		}

	}
}

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License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Alphons van der Heijden
Retired Van der Heijden Holding BV
Netherlands Netherlands
I'm Alphons van der Heijden, living in Lelystad, Netherlands, Europa, Earth. And currently I'm retiring from hard working ( ;- ), owning my own company. Because I'm full of energy, and a little to young to relax ...., I don't sit down, but create and recreate software solutions, that I like. Reinventing the wheel is my second nature. My interest is in the area of Internet technologies, .NET etc. I was there in 1992 when Mosaic came out, and from that point, my life changed dramatically, and so did the world, in fact. (Y)

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