multicast packets from bpf

Hi,


At the moment packets injected via bpf do not get the M_BCAST or M_MCAST
flags set. One consequence of this is that it messes up broadcasting
from if_bridge which assumes these flags are correct, using dhcpd on a
bridge interface is one way to trigger it.

Attached is a patch (bpf_mcast.diff) that fixes this up. There is some
concern about having bpf inspecting the protocol headers but i seems
unavoidable in order to determine if its multicast. tap(4) was also
thought to have this problem but it turned out not to since it passes
the frames to ether_input.

The other way is for the bridge to recheck for multicast destinations
for locally generated packets (bridge_bpfmcast.diff), but this is less
desirable.


Andrew