public static string UDPToDebugString(IPAddress sourceAddr, IPAddress destAddr, UDPFrame frame)
{
var sb = new StringBuilder();
var srcAddrWords = string.Join(" ",
ChecksumFns.DataBytesToShorts(sourceAddr.GetAddressBytes())
.Select(s => $"{s:x4}"));
sb.AppendLine($"{srcAddrWords} source addr");
var dstAddrWords = string.Join(" ",
ChecksumFns.DataBytesToShorts(destAddr.GetAddressBytes())
.Select(s => $"{s:x4}"));
sb.AppendLine($"{dstAddrWords} dst addr");
sb.AppendLine($"{17:x} protocol");
sb.AppendLine($"{frame.Header.HeaderAndDataLength:x4} UDP length");
sb.AppendLine($"{frame.Header.SourcePort:x4} source port");
sb.AppendLine($"{frame.Header.DestinationPort:x4} dest port");
sb.AppendLine($"{frame.Header.HeaderAndDataLength:x4} Length");
sb.AppendLine($"{frame.Header.Checksum:x4} Checksum");
sb.AppendLine($"DATA ({frame.Data.Length}B):");
var byteStep = 8;
for (int i = 0; i < frame.Data.Length; i += byteStep)
{
var words = ChecksumFns.DataBytesToShorts(frame.Data.Skip(i).Take(byteStep).ToArray());
var wordLine = string.Join(" ", words.Select(s => $"{s:x4}"));
sb.AppendLine(wordLine);
}
return(sb.ToString());
}
public static ushort UDPChecksum(IPAddress sourceAddress, IPAddress destinationAddress, UDPFrame packet)
{
uint checksum = 0;
checksum += ChecksumFns.SumAsUShorts(sourceAddress.GetAddressBytes());
checksum += ChecksumFns.SumAsUShorts(destinationAddress.GetAddressBytes());
checksum += 17; // protocol udp = 17
checksum += packet.Header.HeaderAndDataLength;
checksum += packet.Header.SourcePort;
checksum += packet.Header.DestinationPort;
checksum += packet.Header.HeaderAndDataLength;
checksum += ChecksumFns.SumAsUShorts(packet.Data);
return(ChecksumFns.FinishChecksum(checksum));
}
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
});
}
}
