Problem with the file onepkt.py

This file has a flaw in the usage of the `ix` variable: https://github.com/eric-keller/npp-linux-01-intro/blob/7e05b0737c2da5a4304474b5111d91d7a61eaf8f/lab1/part1/provided/onepkt.py#L25

It is different from the version in the demo 3 as well. Should we use the demo3 version instead?