Back in 7/2006, we fixed an issue with the pkttype match mismatching
on locally generated packets.[1]  At the time, I didn't test the fix
in the OUTPUT chain, but only in the INPUT chain, where packets showed
up as PACKET_LOOPBACK.  Unfortunately, when packets are output, they
aren't tagged as PACKET_LOOPBACK so the fix was incomplete.

Below is another attempt at fixing the problem in all cases, and fixes
the original netfilter bugzilla #484 as well as a new bug submission (which
I can't get the number of since bugzilla is presently down).  

The fix is somewhat complicated because when broadcast packets hit the
OUTPUT chain they have no destination MAC attached, so the "simple"
test for 'all FF' doesn't work for us, and instead we have to consult the
routing table.

One other note: since IPv6 doesn't have the concept of "broadcast", perhaps
the userspace extension shouldn't allow broadcast rules to be added for
that family?

Phil

Signed-off-by: Phil Oester <kernel@linuxace.com>

[1] http://marc.info/?l=netfilter-devel&m=115318495708540&w=2