Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r241832:
Covert regression test to python 3

Approved by: cperciva (implicit)

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

This is a regression test to verify the proper behavior of IP ID generation
code. It will push 200000 packets, then report back what the min and max
periods it saw for different IDs were.