U-ISDN
======

Once upon a time, I hacked an ISDN interface into Linux.

It supported networking, multiple "passive" ISDN cards (i.e. those without
a CPU of their own), some active cards, TTYs, private virtual circuits,
both German and European signalling standards, and some other bits and
pieces.

We ran an actual ISP business with that code.

That's the good part.

The bad part is that this code is an unholy mess. At the time, Linux
networking was "mostly" working; see the numerous kernel patches that are
in this archive. In fact, for the first versions of this code (now happily
resting in the digital nirvana), Linux networking was so abysmally bad that
I hacked the BSD networking code into it and used that instead.

Yes, seriously. No, I don't have that code any more. Or rather, it is on a
bunch of slowly-disintegrating Streamer cartridges in my basement, and if
you have working hardware that can actually read these things we might come
to an agreement. (I don't, as the capstan of the tape drives was made of
synthetic rubber … which has disintegrated by now.)

Also, when I started to cobble all of this together I was a student and
didn't actually care all that much about copyright and whatnot. As a
result, this archive contains some pieces that strictly speaking should not
be redistributed.

On the other hand, the company (which I'll not name here) that held said
copyrights doesn't exist any more, more or less, and even if somebody did
care about stone-age C code that doesn't even compile any more (unless your
compiler is 20+ years old … and so are your kernel headers …) most likely
they'd have a hard time proving that they really do hold the rights to that
code.

Thus, I'll leave the decision of whether to read any of the code contained
herein, try to use it, and/or delete it in abject horror, to the esteemed
reader.

Matthias Urlichs
<matthias@urlichs.de>
2022-02-16