/// <summary>
/// Parse an EdnsOption based on the given type and array offset
/// </summary>
/// <param name="optionType"></param>
/// <param name="optionLength"></param>
/// <param name="array"></param>
/// <param name="offset"></param>
/// <returns></returns>
public static EdnsOption ParseOption(byte[] array, int offset, ref int bytesProcessed)
{
// 2 bytes ~ option code
uint optionCode = DnsEncoder.ParseUint16(array, offset);
offset += 2;
// 2 bytes ~ option length
uint optionLength = DnsEncoder.ParseUint16(array, offset);
offset += 2;
bytesProcessed += 4;
EdnsOption option = null;
// Load based on the option code
switch ((EdnsOptionCode)optionCode)
{
case EdnsOptionCode.ClientSubnet:
option = EdnsClientSubnetOption.Parse(array, offset, ref bytesProcessed);
break;
}
return(option);
}
/// <summary>
/// Parse the DnsEdnsRequestMessage from the given byte array
/// </summary>
/// <param name="array"></param>
/// <param name="offset"></param>
/// <returns></returns>
public static EdnsQuestion Parse(byte[] array, int offset, ref int bytesProcessed)
{
// Check the length
if (offset + 10 >= array.Length)
{
return(null);
}
// domain
var domain = array[offset++];
// 2 bytes - Question type
var type = (DnsZoneType)DnsEncoder.ParseUint16(array, offset);
offset += 2;
// 2 bytes - requestor UDP size
// TODO: save this, should be useful
var requestorUdpSize = DnsEncoder.ParseUint16(array, offset);
if (requestorUdpSize < 512)
{
requestorUdpSize = 512; // Don't allow smaller than 512 bytes
}
else if (requestorUdpSize > 4096)
{
requestorUdpSize = 4096; // Don't allow smaller than 4096 bytes
}
offset += 2;
// extended RCODE and flags ~ skip
offset += 4;
// Domain must be 0, type must be OPT
if (domain != 0 || type != DnsZoneType.OPT)
{
return(null);
}
// Read the RDATA length
var rdataLength = DnsEncoder.ParseUint16(array, offset);
offset += 2;
// Validate length
if (offset + rdataLength > array.Length)
{
return(null);
}
// Create a new question
var ednsQuestion = new EdnsQuestion();
// Read the options
int dataBytesProcessed = 0;
while (dataBytesProcessed < rdataLength)
{
// Load the option based on type
var option = EdnsOption.ParseOption(array, offset + dataBytesProcessed, ref dataBytesProcessed);
if (option != null)
{
ednsQuestion.Options.Add(option);
}
}
// Save the bytes processed
bytesProcessed = 10 + dataBytesProcessed;
return(ednsQuestion);
}
