/// <summary>
/// Attempts to parse raw data into a structured packet
/// </summary>
/// <param name="buffer">Raw data to parse</param>
/// <param name="packet">Parsed packet</param>
/// <param name="count">The length of the packet in bytes</param>
/// <param name="index">The index into the buffer at which the packet begins</param>
/// <returns>True if parsing was successful, false if it is not.</returns>
internal static bool TryParse(byte[] buffer, int index, int count, out DNSQuery packet)
{
try
{
if (count < MinimumParseableBytes)
{
packet = null;
return(false);
}
using (var ms = new MemoryStream(buffer, index, count, false))
{
using (var br = new BinaryReader(ms))
{
var messageBytes = br.ReadBytes(count);
var header = Header.FromArray(messageBytes);
if (header.Response || header.QuestionCount == 0 ||
header.AdditionalRecordCount + header.AnswerRecordCount + header.AuthorityRecordCount > 0 ||
header.ResponseCode != ResponseCode.NoError)
{
packet = null;
return(false);
}
var questions = Question.GetAllFromArray(messageBytes, header.Size, header.QuestionCount);
packet = new DNSQuery(header, questions);
return(true);
}
}
}
catch (Exception)
{
packet = null;
return(false);
}
}
/// <summary>
/// Attempts to parse raw data into a structured packet
/// </summary>
/// <param name="buffer">Raw data to parse</param>
/// <param name="packet">Parsed packet</param>
/// <param name="count">The length of the packet in bytes</param>
/// <param name="index">The index into the buffer at which the packet begins</param>
/// <returns>True if parsing was successful, false if it is not.</returns>
internal static bool TryParse(byte[] buffer, int index, int count, out UDP packet)
{
try
{
if (count < MinimumParseableBytes)
{
packet = null;
return(false);
}
using (var ms = new MemoryStream(buffer, index, count, false))
{
using (var br = new BinaryReader(ms))
{
var sourcePort = ByteOrder.NetworkToHostOrder(br.ReadUInt16());
var destPort = ByteOrder.NetworkToHostOrder(br.ReadUInt16());
var totalLength = ByteOrder.NetworkToHostOrder(br.ReadUInt16());
var checksum = ByteOrder.NetworkToHostOrder(br.ReadUInt16());
packet = null;
if (destPort == 53)
{
if (DNSQuery.TryParse(buffer, index + (int)br.BaseStream.Position, count - 8, out DNSQuery payload))
{
packet = new UDP <DNSQuery> {
Payload = payload
};
}
}
else if (sourcePort == 53)
{
if (DNSReply.TryParse(buffer, index + (int)br.BaseStream.Position, count - 8, out DNSReply payload))
{
packet = new UDP <DNSReply> {
Payload = payload
};
}
}
if (packet == null)
{
// This can never fail, so I'm not checking the output
Generic.TryParse(buffer, index + (int)br.BaseStream.Position, count - 8, out Generic payload);
packet = new UDP <Generic>()
{
Payload = payload
};
}
packet.SourcePort = sourcePort;
packet.DestPort = destPort;
packet.TotalLength = totalLength;
packet.Checksum = checksum;
return(true);
}
}
}
catch (Exception)
{
packet = null;
return(false);
}
}
