although this version has been changed somewhat:
- reference counting on ifaddrs isn't as complete as Bill's original
work was. This is hard to get right, and we should attack one
protocol at a time.
- This doesn't do reference counting or dynamic allocation of ifnets yet.
- This version introduces a new PRU -- PRU_PURGEADDR, which is used to
purge an ifaddr from a protocol. The old method Bill used didn't work
on all protocols, and it only worked on some because it was Very Lucky.
This mostly works ... i.e. works for my USB Ethernet, except for a dangling
ifaddr reference left by the IPv6 code; have not yet tracked this down.
use of mbuf external storage and increasing performance (by eliminating
an m_pullup() for clusters in the IP reassembly code).
Changes from Koji Imada <koji@math.human.nagoya-u.ac.jp>, in PR #3628
and #3480, with ever-so-slight integration changes by me.
