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========================================================================
Updated codebase
James Cowling ([email protected]). 9 Dec 2008
========================================================================

This repository now represents an updated version of the BFT library,
modified to work with modern compilers (tested up to gcc 4.3) and the
SFSlite library.  To compile BASE instead of BFT, uncomment
'#define BASE' in libbyz/State_defs.h.

This code has multicast disabled by default.  To reenable see Node.cc.

Thanks to Petros Maniatis for some bug fixes, and probably other
people I've forgotten - thanks tho!  I haven't tested the BFS or
BASEFS code in some time.  If it doesn't work for you let me know.

Compilation instructions (assumes bash shell):

cd sfslite-1.2
mkdir install
export SFSHOME=`pwd`
./configure --prefix=$SFSHOME/install
make
make install
cd ..
ln -s sfslite-1.2/install sfs
ln -s /usr/lib gmp
cd libbyz
makedepend
make clobber
make
cd ..

To compile a simple BFT test program
// make sure libbyz was compiled with 'BASE' *undefined* in State_defs.h
cd bft-simple
makedepend
make clobber
make
ln -s ../config .
ln -s ../config_private .
cd .. 

To compile BFS:
// make sure libbyz was compiled with 'BASE' *undefined* in State_defs.h
cd bfs
makedepend
make clobber
make
ln -s ../config .
ln -s ../config_private .
cd ..

To compile a simple BASE test program
// make sure libbyz was compiled with 'BASE' *defined* in State_defs.h
cd simple
makedepend
make clobber
make
ln -s ../config .
ln -s ../config_private .
cd .. 

To compile BASEFS:
// make sure libbyz was compiled with 'BASE' *defined* in State_defs.h
cd difs
makedepend
make clobber
make
ln -s ../config .
ln -s ../config_private .
cd ..

Execution instructions are way below in this README.  To get a quick
start:

- Make sure there's a file in config_private/ corresponding to each of
  your servers and clients.  To get things running quickly you can just
  copy the 'template' file.
- Change ./config to match your hosts. The first four machines in the
  current file are replicas, and the last two are clients. 'farmX' is
  just the hostname of our machines.
- Run ./bft-simple/simple-server on each replica
- Run ./bft-simple/simple-client on the clients

You'll have to look at the bft-simple source to do anything more
interesting.

========================================================================
BFT / BASE libraries.
Rodrigo Rodrigues ([email protected]). 02 Apr 2003
========================================================================

This implements the BFT algorithm described in [1,2], and the
extensions for BASE described in [3].

The generic programming library that implements the algorithm and can
be used to build new services can be found in the libbyz/
subdirectory.  It uses cryptographic functions from the SFS library.

BFT and BASE have different programming interfaces as described in
[3]. To switch from the BASE interface to the BFT interface, edit
libbyz/State_defs.h, define NO_STATE_TRANSLATION and undefine OBJ_REP.

This distribution includes a simple example service built using
the BFT library (in bft-simple/) and the BASE library (in simple/)

It also includes the BFS [1] file system (in bfs/), and the BASEFS
file system [3] (in difs/)

To compile bft-simple or bfs you need to change libbyz/State_defs.h
as described before, in order to use the original BFT interface.

Two instruction files are presented next. The first one, produced
by Russ Fink from NAI is a detailed description of how to install
the library and how to build and run BASEFS (a.k.a. difs).

The second one is the original README file that accompanied the first
BFT distribution, and explains how to run BFS. This was produced
by Miguel Castro ([email protected]) who is the primary author
of the BFT algorithm and code (with the exception of BASE/BASEFS). 

References:

[1] M. Castro and B. Liskov. Practical Byzantine Fault Tolerance.
In Proceedings of the Third Symposium on Operating Systems Design and
Implementation (OSDI '99), New Orleans, USA, February 1999.

[2] M. Castro and B. Liskov. Proactive Recovery in a
Byzantine-Fault-Tolerant System.
In Proceedings of the Fourth Symposium on Operating Systems Design and
Implementation (OSDI '00), San Diego, USA, October 2000.

[3] R. Rodrigues, M. Castro, and B. Liskov. BASE: Using Abstraction to
Improve Fault Tolerance.
Proceedings of the 18th Symposium on Operating Systems Principles
(SOSP '01), Banff, Canada, October 2001.

Copying:

  Copyright (C) 1999 Miguel Castro, Barbara Liskov
  Copyright (C) 2000, 2001 Miguel Castro, Rodrigo Rodrigues, Barbara Liskov

    These programs are free software; you can redistribute them and/or modify
    them under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    These programs are distributed in the hope that they will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with these programs; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.




========================================================================
BASE - BFT with Abstraction
Ultra*Log Notes, NAI
$Id: README,v 1.3 2002/05/01 20:56:14 rfink Exp $
========================================================================
Introduction:
  This is the BASE extensions to libbyz, and includes an NFS wrapper
  daemon in the difs directory.  This file contains installation notes,
  and should generally be followed in order.  Operational instructions
  are also included.  At the end is the original README contents,
  preserved for historic reasons.

Dependencies:
  depends on sfs-0.5k for crypto;
  sfs-0.5k depends on gmp version 3

Check Your Versions:
  using RedHat version redhat-release-7.2-1 (rpm -qa | grep 'redhat-release')
  using GNU Make version 3.79.1 (make --version)
  must compile using GNU gcc 2.95.3.

Complete Version Map:
  This is a snapshot of the build machine; probably not all of the versions
  need to match, but the gcc, sfs, and RedHat releases are the important
  ones.
  gcc version 2.95.3 "unicorn" with GCC versions: 
    GNU C Library stable release version 2.2.4 (/lib/libc.so.6 - run it)
    Compiled by GNU CC version 2.96 20000731 (Red Hat Linux 7.1 2.96-97).
    crypt add-on version 2.1 by Michael Glad and others
    The C stubs add-on version 2.1.2.
  installed RedHat packages with versions (rpm -qa | grep various):
    compat-glibc-6.2-2.1.3.2
    compat-libstdc++-6.2-2.9.0.16
    gcc-2.96-98 (note - 2.95.3 was installed overtop by hand, not via RPM)
    gcc3-3.0.1-3
    gcc3-c++-3.0.1-3
    gcc3-g77-3.0.1-3
    gcc3-java-3.0.1-3
    gcc3-objc-3.0.1-3
    gcc-c++-2.96-98
    gcc-chill-2.96-98
    gcc-g77-2.96-98
    gcc-java-2.96-98
    gcc-objc-2.96-98
    glibc-2.2.4-13
    glibc-common-2.2.4-13
    glibc-devel-2.2.4-13
    glibc-profile-2.2.4-13
    gmp-3.1.1-4 (stock RedHat 7.2... did not downgrade)
	gmp-devel-3.1.1-4
    libgcc-3.0.1-3
    libstdc++-2.96-98
    libstdc++3-3.0.1-3
    libstdc++3-devel-3.0.1-3
    libstdc++-devel-2.96-98

Preliminary:
  Unpack the source
  Create a new directory, call this <top-dir>
  Uncompress byz-code in that directory (note, this is the CVS archive)
  Uncompress sfs-0.5k in same directory (obtain from vend directory)
  Should see BASE + sfs directories at top level:
    bfs/  config_private/  difs/  libbyz/  sfs-0.5k/	simple/

Building sfs-0.5k:
  # note - must create user sfs and group sfs or configure will fail
  # dependencies: 
  # GMP library: gmp- and gmp-devel (appropriate versions for your OS)
  cd <sfs-directory>
  groupadd sfs
  useradd -d /export/home/sfs -g sfs sfs
  mkdir ./install
  setenv SFSHOME `pwd`
  ./configure --prefix=${SFSHOME}/install
  make
    # make takes about 15 minutes on a Dell 1.7Ghz Optiplex
	# ...  takes forever on other platforms
	# Note - might get some errors compiling under RH 6.2; edit Makefiles
	# and remove '-Werror' flag and recompile - also, had to fix some 
	# problems in template files, expanding a suspicious return statement
	# near line 1001 of some header file.
	# 
	# If all else fails, make sure libsfscrypt.a and libasync.a are built
  make check
  make install
  cd $SFSHOME/install/include ; rm -f sfs ; ln -s sfs-0.5 sfs

Building libbyz:
  cd <top-dir>
  # find . -name 'CVS' -exec rm -rf {} \; # ONLY IF NOT USING CVS!!!
  rm -f sfs ; ln -s sfs-0.5/install sfs
  rm -f gmp ; ln -s /usr/lib gmp
  patch sfs/include/sfs/rabin.h as such (somewhat per instructions):
    add method to rabin_pub:
	  bool verify (const char *msg, const unsigned sz, const bigint &s) const {
	    return verify (str (msg, sz), s);
	  }
    add method to rabin_priv:
	  bigint sign (const char *msg, unsigned len) const {
	    return sign (str (msg, len));
      }
  edit Makefiles (vi */Makefile) - 
    go to INCS, add -I../sfs/include/sfs
	  (note - simple/Makefile did not have an include to sfs originally)
	go to LIBDIRS, add -L../sfs/lib/sfs
  edit libbyz/State_defs.h, undefine NO_STATE_TRANSITION and define OBJ_REP
  ( cd libbyz ; makedepend ; gmake clobber ; gmake )
    # If on RH 6.2, getting "cannot find any 64 bit data types,"
	# install upgraded compiler 2.95.3 
	# If getting error on /usr/include/assert.h, edit libbyz/th_assert.h,
	# and comment out line 67, starts with "#define __assert(str, file, line) 
	# fail("%s %s %d", str, file, line)" - comment that out and rebuild.
  edit simple/client_main.cc, change num_iter to 1000
  ( cd simple ; makedepend ; gmake clobber ; gmake )
    # NOTE: if getting include error on linux/limits.h, make sure
    # kernel headers and kernel source are installed on machine.
    # Both the kernel headers and full source are required to build.
  # ( cd bfs ; makedepend ; gmake clobber ; gmake )
    # Note - if want to build BFS, edit libbyz/State_defs.h, and 
	# define NO_STATE_TRANSITION and undefine OBJ_REF - but then simple 
	# and difs won't build
  ( cd difs ; makedepend ; gmake clobber ; gmake )
    # each takes less than 60 seconds on a Dell 1.7Ghz Optiplex
  ( cd libbyz ; gmake clean ) 
    # strikes out .o files only
  ( cd simple ; gmake clean ) 
  ( cd bfs ; gmake clean ) 
  ( cd difs ; gmake clean; rm -f *.o core )
    # clean target broken in difs because a file called 'clean' exists
  tar -czf base.tgz difs/*.[ch]* simple/*.[ch]* \
    `find difs/* -perm -0100` `find simple/* -perm -0100`
    # NOTE: this will zip up source and binaries for debug; if just want bins,
	# tar -czf bbin.tgz `find difs/* -perm -0100` `find simple/* -perm -0100`
  tar -czf conf.tgz config_private

Installing on RedHat 7.2 Machines:
  # Repeat this procedure for both client and server machines.
  # Need 5 machines - 4 for replicas (3f+1) and one as the client
  # Create ulog user (password similar to itdos password)
  # Unpack base.tgz and conf.tgz with the following:
  cd ~ulog ; tar -xvzf base.tgz ; tar -xvzf conf.tgz
  # Configure crypto key files:
    edit config_private/config
	  choose IP multicast address as 239.255.1.x as site local - see RFC2365
	  configure 4 hosts (4 servers, 1 client), reuse existing public keys
	    NOTE: put the replicas first, the clients second.  Set number of
	    principles = replicas + clients.  Do NOT put the clients in with
		the replicas, else it will think the client is a replica and not run.
      don't forget the view chg, status, and watchdog timeout at end
	  When choosing keys, reuse existing mit machine files, but rename
	    to names of actual hosts.  
	  For hosts that cannot resolve FQDN, add symbolic links.  For instance,
	    link "kirk" -> "kirk.itdos.tislabs.com"
    cp -f bfs/config bfs/config_private
    cp -f bfs/config simple
    cp -f bfs/config simple/config_private
    edits in bfs/config_private directory
	  use full DNS name to create files of private keys
	  pull down a copy of ../config locally, though not sure if needed
  Create links to config file and config_private directory:
    ln -s config_private/config .
	(cd difs ; ln -s ../config . ; ln -s ../config_private .)
	(cd simple ; ln -s ../config . ; ln -s ../config_private .)
  Verify GMP library exists: locate libgmp.so.3 
    if not, disk 1 - rpm -i gmp-3.1.1-4.i386.rpm
  Verify IP Multicast support - netstat -g (should see some info)
    Also, do ifconfig -
	  Should see MULTICAST in Ethernet interface.
    If don't see multicast, try this fix on RedHat:
      Edit /etc/sysconfig/network-scripts/ifcfg-eth0 (or 1)
	  Add the following two lines at the bottom:
        DEVNAME=`basename $CONFIG | sed 's/^ifcfg-//g'`
        /sbin/ifconfig $DEVNAME multicast >/dev/null 2>&1
      Down and up the interface; e.g., ifdown eth0 ; ifup eth0; ifconfig
  Install NFS - nfs-utils, which requires portmapper (portmap*.rpm)
  Start NFS - ntsysv, enable NFS, reboot or /etc/init.d/network restart

Running:
  Running Simple -
    On the 4 replicas, do cd simple; ./server &
	Should see "replica ready" message
	On the client, do cd simple ; ./client
	Should see "Elapsed time ... for 1000 iterations of operation 0"

  Running BFS -
    See original NOTES (below)

  Running BASEFS -
    On server replicas:
	  ps -ef | grep nfsd
	    # verify that nfsd daemons are running; if not, /etc/init.d/nfs start
      su -
      mkdir -p /tmp/ulog/bfs
      chmod 1777 /tmp/ulog/bfs
	  # be careful on this command, run only if no other exports 
	  /usr/sbin/exportfs -ua
	  /usr/sbin/exportfs -o rw '*:/tmp/ulog/bfs'
      function runServer() {  # this line optional, for bash execution
	    /bin/rm -rf /tmp/ulog/bfs/*
	    /bin/rm -f /tmp/ulog/bfs/.[^.]*
        cd /home/ulog/difs ; ./nfsd -d /tmp/ulog/bfs
      } # this line optional, for bash execution
	  runServer  # if using bash and above 3 cmds are defined in a fcn
        # should get "replica ready"

    On client:
      su -
	  # make the mount point
      mkdir -p /tmp/ulog/bfs
      chmod 1777 /tmp/ulog/bfs
	  # first, try test-mounting the filesystem from one server replica
	    umount /tmp/ulog/bfs ; mount uhura:/tmp/ulog/bfs /tmp/ulog/bfs
	    echo hello > /tmp/ulog/bfs/1
		  # should not get error message
		[ -n "/tmp/ulog/bfs/1" -a -r "/tmp/ulog/bfs/1" ] && echo SUCCESS || \
		  echo FAILURE
	      # should see SUCCESS message
        rm -f /tmp/ulog/bfs/1
        umount /tmp/ulog/bfs
	  # end of test mounting
      # Now, run difs/basefs
      function runClient() { # this line optional, for bash execution
        cd /home/ulog/difs; ./client & 
	    sleep 5
	      # wait for "client ready" message
		  # If getting "recvfrom() failed or request too big" or other message,
		  # kill client and restart.  The problem usually corrects itself.
        ./bfsmount -d /tmp/ulog/bfs
      } # this line optional, for bash execution
      runClient # for bash
	    # If getting "mount: Invalid argument", then faulty NFS implementation
		# or bug in BFS code in difs/nfsd.c, likely some handler function
		# missing or providing incorrect data.  Debug using kernel 'dmesg'
		# command, specially-instrumented kernel, 'strace', other such tools
      # SHOULD WORK.  One note: mount -v will NOT show the file as mounted.
	  # I believe this is because the client proxy isn't setting status in
	  # the local kernel.
	  #
	  # To verify that it mounted, run the following test w/root on the client:
      /bin/cp -f /etc/passwd /tmp/ulog/bfs
	  [ -s "/tmp/ulog/bfs/passwd" -a -r "/tmp/ulog/bfs/passwd" ] && \
	    [ `grep ^root /etc/passwd | cut -f1 -d:` = "root" ] && \
		echo "COPY SUCCESSFUL" || echo "COPY FAILED"
      # remove the file, if needed
	  /bin/rm -f /tmp/ulog/bfs/passwd
	  [ -s "/tmp/ulog/bfs/passwd" -o -r "/tmp/ulog/bfs/passwd" ] && \
	    echo "DELETE FAILED" || echo "DELETE SUCCESSFUL"
      umount /tmp/ulog/bfs  # when done

	  # Debug hints...
	  #	trying strace... if it shows mount returning ENOSYS,
	  #	not implemented, when trying to mount 127.0.0.1 on
	  #	/mnt/tmp as "nfs", then NFS not installed or running.
	  #	  install nfs-utils-0.3.1-13.i386.rpm
	  #	    needs portmap-4.0-38.i386.rpm
	  #	  ntsysv, enable nfs
	  #	    error - does it need rsh, rexec?? Verify (per clarke):
	  #	    netfs, network, nfs, nfslock, portmap, rexec, rlogin,
	  #	    rexec, xfs
      #  With NFS running, if still getting EINVAL, but not NOSYS errors,
	  #  then faulty nfsd.c implementation.

========================================================================
CASTRO (original) NOTES -

libbyz
------

This is version 0.1 of libbyz -- a library to build replicated
services that tolerate Byzantine faults. This code is not ready for
production use but the library is mostly complete and it its is
relatively stable (it can repeatedly run the benchmarks included in
the distribution).

Files
-----
You should have these files and directories:

libbyz -- The library

simple (now called simple-bft) -- A simple service that uses the
library. It benchmarks multi-RPC performance.

bfs -- A simple Byzantine fault tolerant NFS

config, config_private -- Example configuration files

COPYING -- The GNU General Public License.

README -- This file

How to build
------------

The current version of the library has been built on Intel P6's with 
Linux 2.2.16 using egcs-2.91.66. The kernel must be configured with IP
multicast support. It should be fairly easy to port the library to 
other machines. An older version of the library ran on DEC Alphas 
with Digital Unix.  

You will need the GNU gmp library (2.0.2) and SFS (0.2).
A later version of SFS can be obtained from www.fs.net.
The code should still work with that later version but I have
not tested it. The makefiles require gmake.

-- Create a symbolic link at the top level named gmp pointing to the 
directory where you installed gmp

-- Create a symbolic link at the top level named sfs pointing to the 
directory where you installed sfs

-- Patch the file sfs/crypt/rabin.h to add the following method
to rabin_pub:

 bool verify (const char *msg, const unsigned sz, const bigint &s) const {
    bigint m;
    E2 (m, s);
    D1 (m, m);
    sha1ctx sc;
    sc.update (msg, sz);
    return post_verify (&sc, m, nbits);
  }

and the following method to rabin_priv:

bigint sign (const char *msg, unsigned len) const {
    sha1ctx sc;
    sc.update(msg, len);
    bigint m = pre_sign (&sc, nbits);
    E1 (m, m);
    D2 (m, m, rnd.getword ());
    return m;
  }

- Edit makefiles in each subdirectory to match your environment

- type gmake in libbyz

- type gmake in simple (now called simple-bft)

- type gmake in bfs

How to run
----------

Edit the config file to match your environment. The following is an
example config file:
 
generic
1
15000000
5
234.5.6.9 3458
sarod.lcs.mit.edu 18.26.1.241 3458 bfaa873efc926cb91646a89e45f96582041e3eed35cde0ef60b5c006cfad883781ee807411b0df3c74dc3ebbbce59c21d67711c83ecf596357c23dba33da338fb5577179a3b6188c59590aa1301eb852c0e14fa9225c0b377fee944eb9fa110ad7a316269e4b13b153887426a347c7c3c5feb1e3107bac4c6e29327b3343c405
fado.lcs.mit.edu 18.26.1.243 3458 bfaa873efc926cb91646a89e45f96582041e3eed35cde0ef60b5c006cfad883781ee807411b0df3c74dc3ebbbce59c21d67711c83ecf596357c23dba33da338fb5577179a3b6188c59590aa1301eb852c0e14fa9225c0b377fee944eb9fa110ad7a316269e4b13b153887426a347c7c3c5feb1e3107bac4c6e29327b3343c405
pipa.lcs.mit.edu 18.26.1.240 3458 bfaa873efc926cb91646a89e45f96582041e3eed35cde0ef60b5c006cfad883781ee807411b0df3c74dc3ebbbce59c21d67711c83ecf596357c23dba33da338fb5577179a3b6188c59590aa1301eb852c0e14fa9225c0b377fee944eb9fa110ad7a316269e4b13b153887426a347c7c3c5feb1e3107bac4c6e29327b3343c405
sygyt.lcs.mit.edu 18.26.1.242 3458 bfaa873efc926cb91646a89e45f96582041e3eed35cde0ef60b5c006cfad883781ee807411b0df3c74dc3ebbbce59c21d67711c83ecf596357c23dba33da338fb5577179a3b6188c59590aa1301eb852c0e14fa9225c0b377fee944eb9fa110ad7a316269e4b13b153887426a347c7c3c5feb1e3107bac4c6e29327b3343c405
lirone.lcs.mit.edu 18.26.1.36 3458 bfaa873efc926cb91646a89e45f96582041e3eed35cde0ef60b5c006cfad883781ee807411b0df3c74dc3ebbbce59c21d67711c83ecf596357c23dba33da338fb5577179a3b6188c59590aa1301eb852c0e14fa9225c0b377fee944eb9fa110ad7a316269e4b13b153887426a347c7c3c5feb1e3107bac4c6e29327b3343c405
5000
100
2000000000
// The format is:
// Service name
// Maximum number of faults that can be tolerated (f)
// Period between key changes (ms)
// Number of principals (excluding group)
// IP multicast group address and port
// DNS_name IP_address port public_key_base16
// .... (x Number of principals)
// Then the replica specific portion:
// view change timeout (ms)
// status timeout for retransmissions (ms)
// watchdog timeout (ms)

The first 3f+1 machines in the config file are the replicas (here f is
in the second line in the file). The remaining principals can be used
as clients. You need to replace names and IP addresses of the machines
to match your environment.

There is also a configuration file with a matching private key.
We supply a set of files that match the example above:

d3bf9ada150474e93d21a4818ccf40e97df94f565c0528973a7799fc3e9ee69e0561fff15631850e2c5b8f9accee851cfc170cd0193052d4f75dfee18ab1d24b e7b8885fa504355a686140181ae956e726e490ac2f905e52a78bea2ef16acef31788b827f35f0de1343766e6f2cbe44f436d7e5eceeb67791ccd296422fb50ef

You can use SFS to generate more keys. 

By default, the programs in this distribution assume the config file
is in a file named "./config" and the file with the private keys is in
a file named "./config_private/full.dns.machine.name".  But there are
command line options to change these.


How to run simple (now called simple-bft):
------------------

After you have these files and you have built the code in simple, you
can start "server" in the replica machines. Then you can start client
in the client machine/s. The clients will run for a while and print a
message saying how long it took to execute a series of operations.

How to run BFS:
---------------

Create a large file of zeros in each replica machine (these files must
have the same size in each replica). You can do this by typing:

newbfs filename filesize 

(The file size should be in KB.)

Then you can start a server in each replica by typing:

nfsd -f filename

The next step is to start the client in a client machine by typing:

client &

After starting the client you can call bfsmount to mount BFS in the
client machine:

bfsmount -d directory_where_to_mount

Then you can do whatever you would do in a normal Unix file system.

How to implement new services:
------------------------------

You should use the "C" interface in "libbyz/libbyz.h"
The "replica_main.cc" and "client_main.cc" files in "simple"
are a simple example of how the library should be used.
 
Contributors
------------

This implementation was written by Miguel Castro. The library, simple
(now called simple-bft) and bfs were first described in "Practical
Byzantine Fault Tolerance", by Miguel Castro and Barbara Liskov, which
appeared in the Proceedings of the Third Symposium on Operating
Systems Design and implementation, February 1999.

More information can be found on 
http://www.pmg.lcs.mit.edu/~castro/byz.html

Copying
-------

    Copyright (C) 1999,2000 Miguel Castro and Barbara Liskov

    These programs are free software; you can redistribute them and/or modify
    them under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    These programs are distributed in the hope that they will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with these programs; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

Bugs
----

Please send bug reports and extensions or improvements you may write
to Miguel Castro ([email protected])