Add ifunit_ref(), a version of ifunit(), that returns not just an

interface pointer, but also a reference to it.

Modify ifioctl() to use ifunit_ref(), holding the reference until
all ioctls, etc, have completed.

This closes a class of reader-writer races in which interfaces
could be removed during long-running ioctls, leading to crashes.
Many other consumers of ifunit() should now use ifunit_ref() to
avoid similar races.

MFC after:	3 weeks

0 files changed, 0 insertions, 0 deletions