Solution for Variable Length Headers

[00JCIV00]

Several Datagram Headers can be of a variable length. Typically, this just means that there's an associated length field in the fixed part of the header, then a number of "options" (or similar) that may or may not be at the end.

Datagrams.zig should include "Layer Options" that will be kept in slices between each layer. During the checksum/CRC calculations, these slices will be narrowed down to the required bytes which are then passed on to the required functions.