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 -[ Design of wellenreiter ]-
 
 written by: Martin J. Muench <mjm@codito.de>
 
 -[ Introduction
 
 This is just a short overview of the new design of wellenreiter.
 There will for sure be some changes and most parts will be specified
 in more detail. 
 
 
 -[ Program
 
 wellenreiter 1.7
 (will be named 2.0 after all the functions are implemented and the code
 is cleaned up and audited)
 
 
 -[ Short description
 
 Wellenreiter is a wireless sniffing tool like netstumbler, kismet et al.
 It discovers Access Points and Ad-Hoc networks and displays all available
 information about them so that you can simply join unencrypted network 
 (without access restrictions) with the given informations.
 For the latest version of wellenreiter look at:
 http://wellenreiter.sourceforge.net.
 
 
 -[ Overview
 
 The software is divided into 2 sections, the daemon and the GUI.
 The daemon does the active sniffing, analying stuff etc.pp. and
 sends the informations to the GUI which displays the results.
 
 
 -[ Configuration
 
 The configuration is done by both, the GUI and the daemon so that the
 GUI only provides the graphical interface to the configuration library
 of the daemon. That means that the daemon loads the config file on 
 startup and sends the informations to the GUI. The GUI contains an option
 "configure" where the settings can be changed. They will be sent to the
 daemon which actually changes the configuration file.
 The configuration file is placed in /usr/local/etc/wellenreiter.conf.
 The whole content of this file cannot be specified yet.
 
+OPIE specific: Opie contains a bunch of high-level configuration classes,
+which are used by most Opie applications. It should be discussed whether
+to use this structure / API (preferred) or use a proprietary one.
+
 
 -[ Interaction GUI<->daemon
 
 The GUI and the daemon will talk actively with eachother, meaning that 
 everyside who has informations for the other part will send it and not
 wait for the other part to poll.
 For example the sniffing function of the daemon is startet when a 
 "start_sniff" from the GUI arrived. And when the daemon found a network
 it will be directly send to the GUI to be able to sniff in realtime.
 
 
 -[ Communication GUI<->daemon
 
-Not yet specified.
+The GUI and the daemon run as threads within one process, where the GUI
+thread will be the main thread. Both the daemon and the GUI thread are
+(mostly) "free-running". Once the GUI thread is started and has finished
+its initializations, it jumps into the Qt event loop ( QApplication::exec() ).
+
+If the daemon thread is actively working and -
+for instance - has acquired interesting data for the GUI thread to display,
+it calls a special reentrant method of the GUI thread ( QApplication::postEvent )
+either transmitting the whole data structure or saying "Hey, there's interesting data
+for you", which the GUI thread then retrieves. 
+To enable a free running daemon thread to actually receive messages from the
+GUI thread, it's useful to to include a non-blocking check-for-messages-function
+within the daemon main loop <since it is waiting for messages from a GUI thread,
+this function has not be called very often>. If applicable, the daemon thread must
+not call this function but only monitor some guarded variables from time to time
+which the GUI thread can modify to alter the behaviour of the daemon thread.
+
+IMHO this is a much more leightweight design than to use a proprietary udp-socket protocol.
 
 
 -[ Setting card modes
 
 One of the most interesting parts is the switching of the wirelesscards to
 different channels, to monitor mode and so on. In the older versions this
 actions were done by the calling of external programs, that is now obsolete.
 We will use the API of the wireless drivers to set it up. 
 
 
 -[ Sniffing
 
 The sniffing will be done by capturing and analyzing all packets using the
 pcap library. The sniffer itself will be a function of the daemon which will
 probably be threaded so that this function is non-blocking.
 If a packet is found the sniffer sends it to an analyzer function which
 analyzes the packets, strips the results and sends it to the GUI.
 
 
 -[ Logging
 
 The GUI should not need to log that much so it logs to STDERR. The daemon
 will be able to run in foreground and log to STDERR and syslog but normally
 it will only log to syslog (INFO/ERR).
 Logging of found networks, packets and so on will also be done by the daemon
 but set up by the GUI.
 
 
 -[ GPS
 
 The gps daemon software will be used, hopefully by their API if they provide
 that. If not, we have to use system() calls, hope we do not.
 
 
 -[ Security
 
 The programm and the daemon will have to run with SUID privileges for being
 able to change card modes etc. so the code has to be audited several times.
 Setuid 0 will only be called when really needing the privileges and dropped
 directly after every single systemcall.
 The daemon will implement an access control list where it specifies which
 IPs or network interfaces will have access to it. 
 The configuration file will be chmod'ed 0400, for writing the configuration
 library will change the mode. Of course the file will be locked during
 writing so no race conditions can occur.
 
 
 -[ Documentation
 
 Wellenreiter will have it's own wellenreiter(8) manpage with most parts of 
 the README file in there.
 Also we will provide general documentation about wireless scanning, security
 risks with wireless devices and so on.
 Most documentation will be intern like this one. The GUI and the daemon
 should have a non-technical documentation and a developers version so we
 can easily develope with other peoples code without having to read it
 completely.