public static UDPFrame DecodeUDP(byte[] datagramBytes)
{
if (datagramBytes.Length < UDPHeaderLength)
{
throw new ArgumentException(nameof(UDPHeaderLength));
}
ushort sourcePort = ByteFns.MakeUshort(datagramBytes[0], datagramBytes[1]);
ushort destPort = ByteFns.MakeUshort(datagramBytes[2], datagramBytes[3]);
ushort headerAndDataLength = ByteFns.MakeUshort(datagramBytes[4], datagramBytes[5]);
ushort checksum = ByteFns.MakeUshort(datagramBytes[6], datagramBytes[7]);
var dataBuffer = new byte[datagramBytes.Length - UDPHeaderLength];
Array.Copy(datagramBytes, UDPHeaderLength, dataBuffer, 0, datagramBytes.Length - UDPHeaderLength);
return(new UDPFrame
{
Header = new UDPHeader()
{
SourcePort = sourcePort,
DestinationPort = destPort,
HeaderAndDataLength = headerAndDataLength,
Checksum = checksum
},
Data = dataBuffer
});
}
/// <remarks>
/// Big endian. Pads last ushort with a zero byte (least significant) if necessary
/// </remarks>
public static IEnumerable <ushort> DataBytesToShorts(byte[] data)
{
var oddByteAmount = data.Length % 2 == 1;
var neatLimit = oddByteAmount ? data.Length - 1 : data.Length;
for (var i = 0; i < neatLimit; i += 2)
{
yield return(ByteFns.MakeUshort(data[i], data[i + 1]));
}
if (oddByteAmount)
{
yield return(ByteFns.MakeUshort(data[data.Length - 1], 0));
}
yield break;
}
public static IEnumerable <IPv4Frame> IterateFrames(Stream bytes)
{
byte[] headerBuffer = new byte[HeaderMinSizeBytes];
while (bytes.CanRead)
{
int bytesRead = bytes.Read(headerBuffer, 0, HeaderMinSizeBytes);
if (bytesRead != HeaderMinSizeBytes)
{
yield break;
}
int internetHeaderLengthBytes = (int)(headerBuffer[0] & 0xf) * 4;
if (internetHeaderLengthBytes != HeaderMinSizeBytes)
{
throw new NotImplementedException("Header size other than 20 bytes not supported yet");
}
// Calculate header validity
uint sum = 0;
for (int ushortOffset = 0; ushortOffset < 20; ushortOffset += 2)
{
sum += ByteFns.MakeUshort(headerBuffer[ushortOffset], headerBuffer[ushortOffset + 1]);
}
ushort onesComplementSum = ChecksumFns.AddCarryGetUshort(sum);
int version = (int)((headerBuffer[0] & 0xf0) >> 4);
int totalLength = (int)((headerBuffer[2] << 16) | headerBuffer[3]);
int protocol = (int)headerBuffer[9];
byte[] sourceAddressBytes = new byte[4];
Array.Copy(headerBuffer, 12, sourceAddressBytes, 0, 4);
byte[] destAddressBytes = new byte[4];
Array.Copy(headerBuffer, 16, destAddressBytes, 0, 4);
int optionalBytesToSkip = internetHeaderLengthBytes - HeaderMinSizeBytes;
bytes.Position = bytes.Position + optionalBytesToSkip;
int dataLength = totalLength - internetHeaderLengthBytes;
byte[] data = new byte[dataLength];
int dataBytesRead = bytes.Read(data, 0, dataLength);
if (dataBytesRead != dataLength)
{
throw new InvalidOperationException($"Could not read {dataLength} data bytes, got only {dataBytesRead}");
}
yield return(new IPv4Frame()
{
Header = new IPv4Header()
{
InternetHeaderLength = internetHeaderLengthBytes,
TotalLength = totalLength,
SourceAddress = new IPAddress(sourceAddressBytes),
DestinationAddress = new IPAddress(destAddressBytes),
DatagramProtocol = protocol,
ChecksumOK = ((ushort)(onesComplementSum ^ 0xffff) == 0),
OnesComplementSum = onesComplementSum
},
Data = data
});
}
}
