When the ipfilter kld is loaded, used within VNET jail, and unloaded,
then subsequent loading, use, and unloading of another packet filters
will cause the subsequently loaded netpfil kld's to panic.
The scenario is as follows:
cd /usr/tests/sys/netpfil/common
kldunload ipl
kldunload pfsync
kldunload ipfw
kyua test pass_block
kldload ipl
kyua test pass_block
kldunload ipl
kldload pfsync
kyua test pass_block
kldunload pfsync
-- page fault panic occurs here --
Reported by: "Ahsan Barkati" <ahsanbarkati@g.....com> via kp@
Discussed with: kp@
Tested by: kp@
MFC after: 3 days
a1601073bf