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));
}
