Add a dying flag to prevent races at detach.

I tried re-ordering ether_ifdetach(), but this created a new race
where sometimes, when under heavy receive load (>1Mpps) and running
tcpdump, the machine would panic.  At panic, the ithread was still in
the original (not dead) if_input() path, and was accessing stale BPF
data structs.  By using a dying flag, I can close the interface prior
to if_detach() to be certain the interface cannot send packets up in
the middle of ether_ifdetach.

0 files changed, 0 insertions, 0 deletions