Goodness, I would have been noisier if I knew everyone wanted
pseudo-ethernets.  A little while back, I built a tap driver that works
enough like FreeBSD's tap driver that OpenVPN works with it (in tap
mode - OpenVPN also has a tun mode).  I've personally used bridging
between a real ethernet and a tap ethernet, with OpenVPN, to get a
Windows box's network neighbourhood to see machines on the local LAN
(which was basically why $ORK wanted me to do the tap driver).

ftp.rodents.montreal.qc.ca:/mouse/misc/tap-for-1.6.2/ holds the driver
itself.  All that's missing is the glue - config lines, cdevsw entries
(or whatever the modern analog is), MAKEDEV clause, that sort of thing.
(Plus, rolling forward to 2.0, which didn't exist when I wrote it.)

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