Complete lock-up from using pkgsrc/net/darkstat

[John Klos <john%ziaspace.com@localhost>]

So here's an interesting problem:

On NetBSD 8, 9, current, with both ipfilter and with npf, with different 
kinds of ethernet interfaces (re*, wm*), run pkgsrc/net/darkstat. Pass a 
lot of traffic (like a week's worth of Internet traffic). Stop darkstat. 
Machine locks.

I've only recently been able to ascertain that it's directly related to 
darkstat, but because it hasn't happened locally, I don't have any more 
information than that, so not enough for a PR.

I'm going to try to reproduce the lockup on a physically local machine 
with a USB keyboard already attached in hopes that I can actually get in 
to the kernel debugger. I figured it's worth mentioning here in case 
anyone can imagine how and why a complete system lockup could happen as 
the result of an interface being used in promiscuous mode for long periods 
of time (and not when used that way for short periods of time.

Thanks,
John