THE CLICK MODULAR ROUTER
========================

    This is the README file for the source release for the Click modular
software router. More recent information may be available on the Web at

	http://www.read.cs.ucla.edu/click/

    Click is a modular router toolkit. To use it you'll need to know how to
compile and install the software, how to write router configurations, and
how to write new elements. Our ACM Transactions on Computer Systems paper,
available from the Web site, will give you a feeling for what Click can
do. Using the optimization tools under CLICKDIR/tools, you can get even
better performance than that paper describes.

CONTENTS
--------

CLICKDIR			this directory
CLICKDIR/apps			Click-related applications
CLICKDIR/apps/clicky		... GTK program for displaying configurations
				    and interacting with drivers
CLICKDIR/apps/ClickController	... Java program for interacting with drivers
CLICKDIR/bsdmodule		FreeBSD 4.5 kernel module driver [NOT WORKING]
CLICKDIR/conf			configuration files
CLICKDIR/doc			documentation
CLICKDIR/drivers		polling device drivers
CLICKDIR/elements		element source code
CLICKDIR/elements/analysis	... for trace analysis and manipulation
CLICKDIR/elements/app		... for application-level protocol elements
CLICKDIR/elements/aqm		... for active queue management (RED, etc.)
CLICKDIR/elements/bsdmodule	... for FreeBSD kernel-specific elements
CLICKDIR/elements/ethernet	... for Ethernet elements
CLICKDIR/elements/etherswitch	... for Ethernet-switch elements
CLICKDIR/elements/grid		... for Grid elements (experimental)
CLICKDIR/elements/icmp		... for ICMP elements
CLICKDIR/elements/ip		... for IP, ICMP, and TCP/UDP elements
CLICKDIR/elements/ip6		... for IPv6 elements
CLICKDIR/elements/ipsec		... for IPsec elements
CLICKDIR/elements/linuxmodule	... for Linux kernel-specific elements
CLICKDIR/elements/local		... for your own elements (empty)
CLICKDIR/elements/ns		... for 'ns'-specific elements
CLICKDIR/elements/radio		... for communicating with wireless radios
CLICKDIR/elements/standard	... for generic elements
CLICKDIR/elements/tcpudp	... for TCP and UDP elements
CLICKDIR/elements/test		... for regression test elements
CLICKDIR/elements/threads	... for thread management elements
CLICKDIR/elements/userlevel	... for user-level-specific elements
CLICKDIR/elements/wifi	        ... for 802.11-specific 'WiFi' elements
CLICKDIR/etc			Linux and NS patches and other files
CLICKDIR/etc/samplepackage	sample source code for Click element package
CLICKDIR/etc/samplellrpc	sample source code for reading Click LLRPCs
CLICKDIR/etc/diagrams		files for drawing Click diagrams
CLICKDIR/etc/libclick		files for standalone user-level Click library
CLICKDIR/include/click		common header files
CLICKDIR/include/clicknet	header files defining network headers
CLICKDIR/lib			common non-element source code
CLICKDIR/linuxmodule		Linux kernel module driver
CLICKDIR/ns			'ns' driver (integrates with the ns simulator)
CLICKDIR/test			regression tests
CLICKDIR/tools			Click tools
CLICKDIR/tools/lib		... common code for tools
CLICKDIR/tools/click-align	... handles alignment for non-x86 machines
CLICKDIR/tools/click-combine	... merges routers into combined configuration
CLICKDIR/tools/click-devirtualize   ... removes virtual functions from source
CLICKDIR/tools/click-fastclassifier ... specializes Classifiers into C++ code
CLICKDIR/tools/click-mkmindriver    ... build environments for minimal drivers
CLICKDIR/tools/click-install	... installs configuration into kernel module
CLICKDIR/tools/click-pretty	... pretty-prints Click configuration as HTML
CLICKDIR/tools/click-undead	... removes dead code from configurations
CLICKDIR/tools/click-xform	... pattern-based configuration optimizer
CLICKDIR/tools/click2xml	... convert Click language <-> XML
CLICKDIR/userlevel		user-level 'click' driver


DOCUMENTATION
-------------

    The 'INSTALL' file in this directory contains installation
instructions. User documentation is in the 'doc' subdirectory. This
directory contains manual pages for the Click language, the Linux kernel
module, and several tools; it also has a script that generates manual pages
for many of the elements distributed in this package. To install these
manual pages so you can read them, follow the 'INSTALL' instructions, but
'make install-man' instead of 'make install'.


RUNNING A CLICK ROUTER
----------------------

    Before playing with a Click router, you should get familiar with the
Click configuration language. You use this to tell Click how to process
packets. The language describes a graph of "elements", or packet processing
modules. See the 'doc/click.5' manual page for a detailed description, or
check the 'conf' directory for some simple examples.

    Click can be compiled as a user-level program or as a kernel module for
Linux. Either driver can receive and send packets; the kernel module
directly interacts with device drivers, while the user-level driver uses
packet sockets (on Linux) or the pcap library (everywhere else).

User-Level Program
..................

    Run the user-level program by giving it the name of a configuration
file: 'click CONFIGFILE'.

Linux Kernel Module
...................

    See the 'doc/click.o.8' manual page for a detailed description. To
summarize, install a configuration by running 'click-install CONFIGFILE'.
This will also install the kernel module if necessary and report any errors
to standard error. (You must run 'make install' before 'click-install' will
work.)

NS-3 Simulator
..............

    See 'INSTALL' for more information on how to enable the NS-3 Click
Integration. Further information on ns-3-click is available in the ns-3
manual: http://www.nsnam.org/docs/models/html/click.html

NS-2 Simulator
..............

    See 'INSTALL' for more information.  Once a Click-enabled version of NS-2
is installed, the 'ns' command is able to run Click scripts as part of a
normal NS-2 simulation.

Configurations
..............

    A few configurations are included in the 'conf' directory, including a
Perl script that generated the IP router configurations used in our TOCS
paper ('conf/make-ip-conf.pl') and a set of patterns for the Click pattern
optimizer, click-xform ('conf/ip.clickpat'). Please check back to our Web
site for more up-to-date configurations.


ADDING YOUR OWN ELEMENTS
------------------------

    Please see the FAQ in this directory to learn how to add elements to
Click.


COPYRIGHT AND LICENSE
---------------------

    Most of Click is distributed under the Click license, a version of
the MIT License. See the 'LICENSE' file for details. Each source file
should identify its license. Source files that do not identify a
specific license are covered by the Click license.

    Parts of Click are distributed under different licenses. The
specific licenses are listed below.

    drivers/e1000*, etc/linux-*-patch, linuxmodule/proclikefs.c: These
portions of the Click software are derived from the Linux kernel, and
are thus distributed under the GNU General Public License, version 2.
The GNU General Public License is available via the Web at
<http://www.gnu.org/licenses/gpl.html>, or in the COPYING file in this
directory.

    include/click/bigint.hh: This portion of the Click software
derives from the GNU Multiple Precision Arithmetic Library, and is
thus distributed under the GNU Lesser General Public License, version
3. This license is available via the Web at
<http://www.gnu.org/licenses/lgpl.html>. The LGPL specifically permits
direct linking with code with other licenses.

    Element code that uses only Click's interfaces will *not* be
derived from the Linux kernel. (For instance, those interfaces have
multiple implementations, including some that run at user level.)
Thus, for element code that uses only Click's interfaces, the BSD-like
Click license applies, not the GPL or the LGPL.


BUGS, QUESTIONS, ETC.
---------------------

    We welcome bug reports, questions, comments, code, whatever you'd
like to give us. We also have a mailing list for software
announcements. Write us at

	click@pdos.lcs.mit.edu

	- The Click maintainers:
	  Eddie Kohler
	  and others