Description:
- A BSD pseudo-device initialization routine is declared as
void <pseudo-device name>attach __P((int count));
in ioconf.c by config(8). main() calls these functions
from a table.
- IP Filter has functions iplattach() and ipldetach() (or,
in the NetBSD case, were erroneously renamed ipfilterattach()
and ipfilterdetach()). These functions are used to establish
and disestablish the IP Filter "filter rule check" hook in
the IP input/output stream. They are declared:
int iplattach __P((void));
int ipldetach __P((void));
..and are expected to return a value by iplioctl().
- When main() calls (by sheer coincidence!) iplattach(),
the filter hook is established, and the IP Filter machinery
labeled as "initialized". This causes all packets, whether or
not the user intents to use filter rules, to be passed to
the filter rule checker if "ipfilter" is configured into the
kernel.
- As a result of the above, a kludge existed to default to
passing all packets (I can only assume that when this was
originally committed, the symptom of the bug was noticed by
the integrator, but the bug not actually found/fixed).
- In iplioctl(), if the SIOCFRENB ioctl is issued with an
argument of "enable" (i.e. user executed "ipf -E"), iplattach()
will notice that the machinery is already initialized and
return EBUSY.
Fix:
- Rename iplattach()/ipldetach() to ipl_enable() and ipl_disable().
- Create a pseudo-device entry stub named ipfilterattach()
(NetBSD case) or iplattach() (all other). This is a noop; none
of the machinery should be initialized until the caller expicitly
enables the filter with ipf -E. Add a comment to note that.
XXX !!! XXX !!!
I noticed a few semi-serious bugs while doing this merge, one of which
has existed for a fairly long time. Some of them are addressed in this
commit (because they caused the kernel to not compile), and are annoted
by "XXX" and "--thorpej". The other one will be addressed shortly in
a future commit, and, as far as I can tell, affects all operating systems
which IP Filter supports.
cgd