internal static void WriteHeader(byte[] buffer, int offset,
byte trafficClass, int flowLabel, ushort payloadLength, IpV4Protocol?nextHeader, IpV4Protocol?nextLayerProtocol,
byte hopLimit, IpV6Address source, IpV6Address currentDestination, IpV6ExtensionHeaders extensionHeaders)
{
buffer.Write(offset + Offset.Version, (uint)((((DefaultVersion << 8) | trafficClass) << 20) | flowLabel), Endianity.Big);
buffer.Write(offset + Offset.PayloadLength, payloadLength, Endianity.Big);
IpV4Protocol actualNextHeader;
if (nextHeader.HasValue)
{
actualNextHeader = nextHeader.Value;
}
else if (extensionHeaders.Any())
{
actualNextHeader = extensionHeaders.FirstHeader.Value;
}
else if (nextLayerProtocol.HasValue)
{
actualNextHeader = nextLayerProtocol.Value;
}
else
{
throw new InvalidOperationException("Can't determine next header. No extension headers and no known next layer protocol.");
}
buffer.Write(offset + Offset.NextHeader, (byte)actualNextHeader);
buffer.Write(offset + Offset.HopLimit, hopLimit);
buffer.Write(offset + Offset.SourceAddress, source, Endianity.Big);
buffer.Write(offset + Offset.DestinationAddress, currentDestination, Endianity.Big);
extensionHeaders.Write(buffer, offset + HeaderLength, nextLayerProtocol);
}
/// <summary>
/// Two addresses are equal if the have the exact same value.
/// </summary>
public bool Equals(IpV6Address other)
{
return(_value == other._value);
}
private static ushort CalculateTransportChecksum(byte[] buffer, int offset, int fullHeaderLength, uint transportLength, int transportChecksumOffset, bool isChecksumOptional, IpV6Address destination)
{
int offsetAfterChecksum = offset + fullHeaderLength + transportChecksumOffset + sizeof(ushort);
uint sum = Sum16Bits(buffer, offset + Offset.SourceAddress, IpV6Address.SizeOf) +
Sum16Bits(destination) +
Sum16Bits(transportLength) + buffer[offset + Offset.NextHeader] +
Sum16Bits(buffer, offset + fullHeaderLength, transportChecksumOffset) +
Sum16Bits(buffer, offsetAfterChecksum, (int)(transportLength - transportChecksumOffset - sizeof(ushort)));
ushort checksumResult = Sum16BitsToChecksum(sum);
if (checksumResult == 0 && isChecksumOptional)
{
return(0xFFFF);
}
return(checksumResult);
}
internal static void WriteTransportChecksum(byte[] buffer, int offset, int headerLength, uint transportLength, int transportChecksumOffset,
bool isChecksumOptional, ushort?checksum, IpV6Address destination)
{
ushort checksumValue =
checksum ?? CalculateTransportChecksum(buffer, offset, headerLength, transportLength, transportChecksumOffset, isChecksumOptional, destination);
buffer.Write(offset + headerLength + transportChecksumOffset, checksumValue, Endianity.Big);
}