MFC r366908 (modified for stable/12 KBI):
Add dtrace SDT probe ipfw:::rule-matched. It helps to reduce complexity with debugging of large ipfw rulesets. Also define several constants and translators, that can by used by dtrace scripts with this probe. Obtained from: Yandex LLC Sponsored by: Yandex LLC Differential Revision: https://reviews.freebsd.org/D26879