# FECDMP timeline (kern.fechg.dumpk)
MARK1 (tap0,tap1 added to fec0):
 tap0 ac_netgraph=0xfffff801179b28a0   (== fec0 node)
 tap1 ac_netgraph=0xfffff801179b28a0
MARK2 (fec1 created; ADD_IFACE tap0 to fec1 -> rc=0):
 tap0 ac_netgraph=0xfffff8011752ea00   (== fec1 node)  <-- silently re-enslaved
 fec1 ac_netgraph=0xfffff8011752ea00
MARK3 (DEL_IFACE tap0 from fec1 -> rc=0):
 tap0 ac_netgraph=0xfffff8011752ea00   <-- STILL fec1's node after removal
# teardown (rmnode) attempt on INVARIANTS:
panic: assertion "IS_SERIALIZED((s))" failed in lwkt_serialize_exit
 ng_fec_stop() <- ng_fec_rmnode() <- fechg_op()
# freed-node deref arm code-certain; blocked here by the earlier serializer panic