/*
* Each resource record has the following format:
* 1 1 1 1 1 1
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| |
| / /
| / NAME /
| |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| TYPE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| CLASS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| TTL |
| |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| RDLENGTH |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
| / RDATA /
| / /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
*/
public static byte[] EncodeDnsResource(DnsResource record)
{
MemoryStream stream = new MemoryStream(256);
BinaryWriter writer = new BinaryWriter(stream);
//NAME
string[] labels = record.Name.Split('.');
foreach (string label in labels)
{
writer.Write((byte)label.Length);
writer.Write(Encoding.ASCII.GetBytes(label));
}
writer.Write((byte)0);
//TYPE
WriteUInt16BE(writer, (UInt16)record.QueryType);
//CLASS
WriteUInt16BE(writer, (UInt16)record.QueryClass);
//TTL
WriteInt32BE(writer, record.TimeToLive);
//RDLENGTH
WriteUInt16BE(writer, record.DataLength);
//RDATA
writer.Write(record.Data);
return(stream.ToArray());
}
public static DnsResource ReadResourceRecord(BinaryReader reader)
{
DnsResource record = new DnsResource();
record.Name = ReadDomainName(reader);
record.QueryType = (QueryType)ReadUInt16BE(reader);
record.QueryClass = (QueryClass)ReadUInt16BE(reader);
record.TimeToLive = ReadInt32BE(reader);
record.DataLength = ReadUInt16BE(reader);
long pos = reader.BaseStream.Position;
DecodeRecordContent(record, reader);
if (reader.BaseStream.Position != pos + record.DataLength)
{
throw new Exception("Error in decoding content of ResourceRecord");
}
return(record);
}
private static void DecodeRecordContent(DnsResource record, BinaryReader reader)
{
switch (record.QueryType)
{
case QueryType.Address:
record.Content = reader.ReadBytes(4);
break;
case QueryType.NameServer:
case QueryType.CanonicalName:
record.Content = ReadDomainName(reader);
break;
case QueryType.MailExchange:
record.Content = ReadMailExchange(reader);
break;
default:
record.Data = reader.ReadBytes(record.DataLength);
break;
}
}