Introduce locking around use of ifindex_table, whose use was previously

unsynchronized.  While races were extremely rare, we've now had a
couple of reports of panics in environments involving large numbers of
IPSEC tunnels being added very quickly on an active system.

- Add accessor functions ifnet_byindex(), ifaddr_byindex(),
  ifdev_byindex() to replace existing accessor macros.  These functions
  now acquire the ifnet lock before derefencing the table.
- Add IFNET_WLOCK_ASSERT().
- Add static accessor functions ifnet_setbyindex(), ifdev_setbyindex(),
  which set values in the table either asserting of acquiring the ifnet
  lock.
- Use accessor functions throughout if.c to modify and read
  ifindex_table.
- Rework ifnet attach/detach to lock around ifindex_table modification.

Note that these changes simply close races around use of ifindex_table,
and make no attempt to solve the probem of disappearing ifnets.  Further
refinement of this work, including with respect to ifindex_table
resizing, is still required.

In a future change, the ifnet lock should be converted from a mutex to an
rwlock in order to reduce contention.

Reviewed and tested by:	brooks

0 files changed, 0 insertions, 0 deletions