On current, there seem to be two problems with lo(4) interfaces:
1. "ifconfig lo6 up" fails
# ifconfig lo6 create
# ifconfig lo6 up
ifconfig: SIOCSIFFLAGS: Inappropriate ioctl for device
# ifconfig lo6 destroy
#
The sys/net/rdomains regress test fails because of this, and i think
sys/net/if.c rev 1.473 might be the cause.
It still works on a kernel from early December.
2. "ifconfig lo6 destroy" fails on an interface in an rdomain
# ifconfig lo6 create
# ifconfig lo6 rdomain 6
# ifconfig lo6
lo6: flags=8008<LOOPBACK,MULTICAST> rdomain 6 mtu 32768
index 12 priority 0 llprio 3
groups: lo
# ifconfig lo6 destroy
ifconfig: SIOCIFDESTROY: Operation not permitted
This has been broken a bit longer, it still works in 6.0.
