> I'm looking for the mechanism that suppots following requirements.

> 1. the way that an application can send the ethernet frame to the
> ethernet device driver - ether_input() - directly.

As far as I know this does not exist.  It would be trivial to add,
though, as a character special device driver.

> 2. the way that an application can receive the ethernet frame
> directly and then the ethernet frame should not be passed in the
> above network layer.

As you discovered, bpf for the first part.  I wanted the second part
too, and I added an interface flag BPFONLY for it - if an interface is
set BPFONLY, it receives packets for bpf purposes but never passes them
anywhere else.

If you want the BPFONLY patches, see the patch tree in
ftp.netbsd.org:/pub/NetBSD/misc/mouse/patch-tree/ - you want
src/sbin/ifconfig/ifconfig.8, src/sbin/ifconfig/ifconfig.c,
src/sys/net/if.h, and src/sys/net/if_ethersubr.c.  (Actually, you may
want only parts of some of those, and there's some chance you may want
something else; they're just what grepping for bpfonly turned up.  I
think the change was pretty much self-contained....)

As for the ether_input() interface, what you really want is something
tun(4)-like but that works at the Ethernet level rather than the IP
level.  You could probably start by copying if_tun.c and hacking on it
to use ether_input rather than enqueueing stuff on ipintrq....

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