duplicati/thirdparty/DnsLite/DnsLite.cs

//Dnslite.cs 
/** 
	csc /target:library /out:DnsLib.dll /keyfile:..\..\Duplicati\GUI\Duplicati.snk DnsLite.cs 
*/ 
using System; 
using System.Net; 
using System.IO; 
using System.Text; 
using System.Net.Sockets; 
using System.Collections; 
namespace DnsLib  
{ 
	public class MXRecord  
        { 
	 public int preference = -1; 
	 public string exchange = null; 
         public override string ToString()  
         { 
	  return "Preference : " + preference + " Exchange : " + exchange; 
         } 
        } 
	public class DnsLite  
        { 
		private byte[] data; 
		private int position, id, length; 
		private string name; 
		private ArrayList dnsServers; 
		private static int DNS_PORT = 53; 
		Encoding ASCII = Encoding.ASCII; 
		public DnsLite()  
                { 
     		  id = DateTime.Now.Millisecond * 60; 
		  dnsServers = new ArrayList(); 
 
		} 
		public void setDnsServers(ArrayList dnsServers)  
                { 
			this.dnsServers = dnsServers; 
		} 
		public ArrayList getMXRecords(string host)  
                { 
			ArrayList mxRecords = null; 
			for(int i=0; i < dnsServers.Count; i++)  
                        { 
			try  
                        { 
				mxRecords = getMXRecords(host,(string)dnsServers[i]); 
				break; 
			} 
                        catch(IOException)  
                        { 
				continue; 
			} 
		} 
		return mxRecords; 
		} 
  		private int getNewId() { 
			//return a new id 
    		return ++id; 
  		} 
		public ArrayList getMXRecords(string host,string serverAddress) { 
			//opening the UDP socket at DNS server 
			//use UDPClient, if you are still with Beta1 
			UdpClient dnsClient = new UdpClient(serverAddress, DNS_PORT); 
			//preparing the DNS query packet. 
			makeQuery(getNewId(),host); 
			//send the data packet 
			dnsClient.Send(data,data.Length); 
			IPEndPoint endpoint = null; 
			//receive the data packet from DNS server 
			data = dnsClient.Receive(ref endpoint); 
    		length = data.Length; 
    		//un pack the byte array & makes an array of MXRecord objects. 
    		return makeResponse(); 
		} 
		//for packing the information to the format accepted by server 
		public void makeQuery(int id,String name) { 
			data = new byte[512]; 
			for(int i = 0; i < 512; ++i)  
                        { 
				data[i] = 0; 
         		} 
		data[0]	 = (byte) (id >> 8); 
		data[1]  = (byte) (id & 0xFF ); 
		data[2]  = (byte) 1; data[3] = (byte) 0; 
		data[4]  = (byte) 0; data[5] = (byte) 1; 
		data[6]  = (byte) 0; data[7] = (byte) 0; 
	    	data[8]  = (byte) 0; data[9] = (byte) 0; 
    		data[10] = (byte) 0; data[11] = (byte) 0; 
    		string[] tokens = name.Split(new char[] {'.'}); 
  		string label; 
		position = 12; 
		for(int j=0; j < tokens.Length; j++) { 
		label = tokens[j]; 
		data[position++] = (byte) (label.Length & 0xFF); 
		byte[] b = ASCII.GetBytes(label); 
		for(int k=0; k < b.Length; k++) { 
     		   data[position++] = b[k]; 
		} 
		} 
		data[position++] = (byte) 0 ; data[position++] = (byte) 0; 
   	        data[position++] = (byte) 15; data[position++] = (byte) 0 ; 
		data[position++] = (byte) 1 ; 
		} 
		//for un packing the byte array 
		public ArrayList makeResponse() { 
		ArrayList mxRecords = new ArrayList(); 
		MXRecord mxRecord; 
		//NOTE: we are ignoring the unnecessary fields. 
  	         // and takes only the data required to build MX records. 
    		int qCount = ((data[4] & 0xFF) << 8) | (data[5] & 0xFF); 
		    if (qCount < 0) { 
      			throw new IOException("invalid question count"); 
    		} 
    		int aCount = ((data[6] & 0xFF) << 8) | (data[7] & 0xFF); 
	    	if (aCount < 0) { 
    			throw new IOException("invalid answer count"); 
    		} 
	    	position=12; 
    		for( int i=0;i<qCount; ++i) { 
			name = ""; 
	    		position = proc(position); 
	    		position += 4; 
			} 
    		for (int i = 0; i < aCount; ++i) { 
			name = ""; 
			position = proc(position); 
      			position+=10; 
			int pref = (data[position++] << 8) | (data[position++] & 0xFF); 
			name=""; 
			position = proc(position); 
			mxRecord = new MXRecord(); 
			mxRecord.preference = pref; 
			mxRecord.exchange = name; 
			mxRecords.Add(mxRecord); 
			} 
			return mxRecords; 
		} 
		private int proc(int position) { 
			int len = (data[position++] & 0xFF); 
    		if(len == 0) { 
      			return position; 
    		} 
    		int offset; 
    		do { 
     			if ((len & 0xC0) == 0xC0) { 
       			if (position >= length) { 
         				return -1; 
       			} 
        		offset = ((len & 0x3F) << 8) | (data[position++] & 0xFF); 
	        	proc(offset); 
        		return position; 
      			} else { 
       			if ((position + len) > length) { 
         				return -1; 
       			} 
       			name += ASCII.GetString(data, position, len); 
       			position += len; 
      			} 
      			if (position > length) { 
        			return -1; 
      			} 
			len = data[position++] & 0xFF; 
     			if (len != 0) { 
	        		name += "."; 
     			} 
    		}while (len != 0); 
	    	return position; 
		} 
	} 
}