If your kernel version is before 2.1.102; you need the ipfwchains patch to the 2.1.x or 2.0.x kernel series.
You need to be running a kernel compiled with CONFIG_IP_FIREWALL (for 2.1.102 and above) or CONFIG_IP_FIREWALL_CHAINS set to `y'. You can tell that your current kernel is compiled with this by looking for `/proc/net/ip_fwchains' - if it exists, then your kernel is ready for the ipchains utility.
You should be able to simply type "make all", then (as root) "make install"; this will put the ipchains binary in /sbin/ipchains, and the man pages in /usr/man/man4/ipfw.4 and /usr/man/man8/ipchains.8. Set SBIN and MANDIR repectively (by specifying SBIN=xxx and/or MANDIR=xxx on "make install" command line, or editing the Makefile).
See the HOWTO (available from the web page at http://www.rustcorp.com/linux/ipchains) for details. Included is an excellent quick reference card by Scott Bronson, in PostScript (best printed double-side). This was written in WordPerfect 8 on Linux; you can get the WordPerfect source from
ftp://ftp.trestle.com/pub/ipchains-quickref.xwp
The concept and chunks of the implementation were grabbed from ipfwadm 2.3; the name has been changed to avoid confusion, as `ipfwadm' will NOT work with kernels with the new firewall code. Also, I took the opportunity to rationalize the command line parameters, making it perhaps more difficult for ipfwadm users (not necessarily a bad thing, as it highlights the differences) but hopefully making things more sane in the long run.
In recognition of the fantastic work done by Jos Vos, without whom I would have had no code or concepts to guide me, here is the original copyright notice from many of the files. (Do NOT contact Jos with problems in these utilities; they are almost certainly things I wrecked, and complaining to him would be unfair and unrewarding).
Copyright (c) 1995,1996 by X/OS Experts in Open Systems BV.
All rights reserved.
Author: Jos Vos <jos@xos.nl>
X/OS Experts in Open Systems BV
Kruislaan 419
1098 VA Amsterdam
The Netherlands
E-mail: info@xos.nl
WWW: http://www.xos.nl/
Paul ``Rusty'' Russell & Michael Neuling. ipchains@rustcorp.com