DF-3433 baseline run 1 (walk-instant variant, stf_race.c) - stock kernel #0
setup: 30 configured gif tunnels (walk lengtheners) + if_stf loaded (ep at
list head), 4 raw proto-41 floods to 127.0.0.1, stateless kldunload/kldload
if_stf bounce. 300 s:
t+300s: flood=79135119 unload_cyc=1969 err=0
done (no panic): flood=79135130 unload_cyc=1969 err=0
=> honest negative for the walk-instant sub-vector (the stf mutator is the
   ~120ms kldunload; gif's ioctl-speed reconfig churn in DF-3425 had a far
   higher mutation rate). The shared lock-free-walk defect is unchanged.

DF-3433 baseline run 2 (async variant, stf_async_race.c) - stock kernel #0
setup: tap0 10.99.0.1/24, stf0 inet6 2002:0a63:0001::1/16 (encapcheck
matches), debug.use_weird_array=1 (kfree poisons freed chunks 0xdeadc0de),
2 tap floods + kldunload/kldload+reconfig bounce:
racing: 2 tap floods + stf kldunload/kldload bounce
t+10s: flood=3702866 unload_cyc=551 err=0
t+20s: flood=7456279 unload_cyc=1062 err=0
t+30s: flood=11109097 unload_cyc=1620 err=0
... (~80s / ~4000 cycles / ~24M frames)
=> Fatal trap 9 (GP fault, non-canonical poison pointer)
   Stopped at nd6_purge+0xc9: cmpb $0x12,0x1(%rdx)
   current process = Idle (netisr0), cpuid = 0   [panic.txt]