/*
* Header Structure, the bit labeled 0 is the most significant bit.
*
* 0 1 2 3 4 5 6 7 8 9 A B C D E F
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR| Opcode |AA|TC|RD|RA| Z | RCODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QDCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ANCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| NSCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ARCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
*/
////////////////////////////////////////////////////////////////////////////////////////////////////
/// <summary> Encode header. </summary>
///
/// <param name="message"> The message. </param>
///
/// <returns> A byte[]. </returns>
////////////////////////////////////////////////////////////////////////////////////////////////////
public static byte[] EncodeHeader(DnsMessage message)
{
MemoryStream stream = new MemoryStream(12);
BinaryWriter writer = new BinaryWriter(stream);
WriteUInt16BE(writer, message.ID);
int fields = (int)message.ResponseCode;
if (message.IsRecursionAvailable)
{
fields |= 0x80;
}
if (message.IsRecursionDesired)
{
fields |= 0x100;
}
if (message.IsTruncated)
{
fields |= 0x200;
}
if (message.IsRecursionAvailable)
{
fields |= 0x400;
}
fields |= (int)message.QueryKind << 11; //Opcode
if (message.Type == MessageType.Response)
{
fields |= 0x8000;
}
WriteUInt16BE(writer, (UInt16)fields);
WriteUInt16BE(writer, (UInt16)message.Querys.Count);
WriteUInt16BE(writer, (UInt16)message.Answers.Count);
WriteUInt16BE(writer, (UInt16)message.AuthorityRecords.Count);
WriteUInt16BE(writer, (UInt16)message.AdditionalRecords.Count);
return(stream.ToArray());
}
////////////////////////////////////////////////////////////////////////////////////////////////////
/// <summary> Decode DNS message. </summary>
///
/// <param name="msgData"> Information describing the message. </param>
///
/// <returns> A DnsMessage. </returns>
////////////////////////////////////////////////////////////////////////////////////////////////////
public static DnsMessage DecodeDnsMessage(byte[] msgData)
{
DnsMessage message = new DnsMessage();
message.ID = (UInt16)(msgData[0] << 8 | msgData[1]);
message.Type = (MessageType)(msgData[2] >> 7);
message.QueryKind = (QueryKind)((msgData[2] >> 3) & 15);
message.ResponseCode = (ResponseCode)(msgData[3] & 15);
MemoryStream stream = new MemoryStream(msgData);
stream.Position = 4;
BinaryReader reader = new BinaryReader(stream);
int queryCount = ReadUInt16BE(reader);
int answerCount = ReadUInt16BE(reader);
int nsCount = ReadUInt16BE(reader);
int arCount = ReadUInt16BE(reader);
for (int i = 0; i < queryCount; i++)
{
message.Querys.Add(ReadDnsQuery(reader));
}
for (int i = 0; i < answerCount; i++)
{
message.Answers.Add(ReadResourceRecord(reader));
}
for (int i = 0; i < nsCount; i++)
{
message.AuthorityRecords.Add(ReadResourceRecord(reader));
}
for (int i = 0; i < arCount; i++)
{
message.AdditionalRecords.Add(ReadResourceRecord(reader));
}
return(message);
}
