owlps/TODO

* Global

- Known bugs
   ° Valgrind / libconfuse bugs (Listener & Aggregator):
   .   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=639074
   .   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=639115
- Handle the aggregation format version
   In the aggregation files, a version number describing the file format
   should be added (as the 2nd field, right after the client's MAC
   address). That would allow the positioning server to handle several
   formats instead of just the last version.
- Check the size of the received packets to avoid buffer overflows.
- Use select(2) or poll(2)
   Using polling for sockets would avoid setting up some threads,
   especially the autocalibration threads in the Listener,
   i.e. autocalibrate() and autocalibrate_hello(), and listen_for_aps()
   in the Aggregator.
   See also select_tut(2).
- Option -V should tell if DEBUG is enabled or not.
- Eliminate remaining exit() calls to avoid memory leaks on exit.
- Use atexit() / on_exit() instead of goto to clean at exit?
- Add option dump-configuration (displays the config & exits).
- Makefiles:
   ° Use intall instead of cp?
   ° Merge Makefile and Makefile_atheros*. Use template makefiles,
   autohell, cmake…?
- Support string-based positioning requests
   Along with the binary requests, implement a string-based request
   format. Each packet will contain a CSV string describing the
   request's information. This will make easier to develop clients in
   other languages than C and over other protocols than UDP.
- Mark arguments as const in function headers if needed
   Mostly done in the Positioner C++ code (which should be checked
   though), but not constantly in C modules.
   [Done in libowlps & libowlps-client.]
- Allow to use hostnames instead of IP addresses in all modules
   getaddrinfo(3) (or gethostbyname(3)) should be used when opening
   sockets in libowlps, then string buffer size have to be adapted in
   all modules to be able to contain a long hostname.
- Use struct ether_addr to store MAC addresses?
   We could use the struct ether_addr to store binary MAC addresses,
   and convert them to strings with ether_ntoa() instead of
   owl_mac_bytes_to_string(). See ether_aton(3).


* libowlps

- Use stdbool.h instead of #define owl_bool.
- Currently unused functions:
   ° owl_timestamp_is_null()


* Aggregator

- -o should be optional.
- Add an option to (not) flush the output file.
- Outputs should include all the timestamps
   The CSV output file and the socket should include the capture
   timestamp and the reception timestamp on the aggregator. This would
   help the Positioner's --replay option (to be adapted to use the
   aggregation time instead of the request time).
- Refactoring:
   ° monitor_requests()
   ° got_request()
- Use the type of a request to identify it?
   (along with the mobile MAC address and the request time)
- got_request(): option for the maximal difference time
   For implicit packets, we consider that packets from the same MAC
   and received within an interval of 10ms are part of the same
   request. We should define an option to allow user to choose the
   time he wants.


* Listener

- Known bugs:
   ° On OpenWrt Backfire (10.03), when the program is statically linked,
   using both -D and -A at the same time makes the program to block on
   the first thread. This is a known issue of uClibc:
   https://dev.openwrt.org/ticket/4809
- Better handling of retried packets
   Currently we ignore any packet with the Retry bit. This can lead to
   completely ignore the given packet (or even request) if the original
   packet is never received, which can happen under certain
   circumstances.
- Refactor and review read_packet().
- Handle better the configuration file reading
   Get rid of the "Cannot open configuration file" error, in quiet
   mode and when the default configuration file has to be used (no
   file specified by the user with -f).
- Filter the number of implicit packets per mobile?
   Currently, in passive or mixed mode, *all* the received packets are
   transmitted to the aggregator.
- Option "read-only autocalibration"?
   Listen for autocalibration requests without sending requests.
- read_packet(): use ieee80211_header_size for all implicit packets
   Currently the size is corrected only for data packets.
- BSD port
   http://www.unixgarden.com/index.php/programmation/introduction-a-la-programmation-wifi-en-c-sous-netbsd
- Use the "official" radiotap parser? (Expat license)
   http://git.sipsolutions.net/?p=radiotap.git


* Client

- Add verbose & quiet options.
- Log sent requests?
- Allow to use a string for the direction?
   Could be nice, but probably useless.


* UDP to HTTP

- Command-line options (port numbers, -v/-q, -h, -V).
- Delete inactive clients after a given amount of time.
- Refactor prepare_answer().


* Positioner

- Known bugs
   ° Cannot compute the error (Real) for autocalibration requests.
   ° Unit tests are currently unmaintained. Do not try to run them.

- Algorithms
   ° Add to the result the information "area error" (whether on not the
   computed result is in the same room as the real position).
   ° Handle the power and antenna gain difference between the
   calibration mobile (or pseudo-mobile, for autocalibration) and the
   mobile to position.
   ° MinMax: add option to set the step (and use a different step for X,
   Y and Z?).
   ° MinMax: reduce the research space as proposed by F. Lassabe (PhD
   report, Fig. 2.6 p. 38 and explanations pp. 38-39).

- Autocalibration
   ° Generate reference points in 3D.
   ° To select the reference APs, we should use the distance along with
   the angle and coverage.
   ° Handle 2 APs, not only >2 APs.
   ° Find why some CalibrationRequest were not deleted when
   calling Stock::delete_calibration_request() (via
   ReferencePoint::delete_requests()).
   ° Option z-level-number: the Z coordinate represents the number of
   the building's level. If unactivated, the topology is used to
   determine a change of level.

- Refactoring
   ° Split Stock::generate_reference_point() into several functions.
   ° Write a class for Request::type?
   CalibrationRequest::direction uses a dedicated class Direction, why
   not Request::type? That would simplify writing of the type to
   streams (no need to cast each time anymore).
   ° Wi-Fi devices' list
   .   Merge Stock::mobiles & Stock::aps?
   .   Factorise AccessPointsReaderCSV & MobilesReaderCSV?
   ° Members renaming
   .   InputMedium:
   .   - current_line_nb & get_current_line_nb()
   .   - get_next_request() −> read_next_request()
   .   Input: get_next_request() −> read_next_request()
   .   Area: p_min et p_max −> coord_min et coord_max

- User interface
   ° When reading the APs, add them to the mobiles' list (or another
   way to be able to have a single entry for an AP).
   ° Add option positioning.self-calibrate (or autocalibrate), short
   option -A, to activate automatically the options needed by the
   autocalibration.
   ° Improve --verbose (and/or debug level): print the options, etc.
   ° Case-insensitive string comparison (for algorithm names, etc.).
   ° Use a prefix for configuration files (search for config files set
   with relative path in owlps-positioner.cfg in the same directory).

- Optimisation & code improvement
   ° Multithreading:
   .   algorithms (parallelize computation of the different algorithms
   for the same request);
   .   and/or requests (parallelize computation of several requests).
   It would be possible (overkill?) to have a group of worker threads
   and a job queue.
   ° ReferencePoint: the request list should be an unordered_set
   instead of a vector, to guarantee the unicity of the elements.
   ° Pre-allocate vectors' memory with reserve().
   "C++ en action", p. 217.
   ° Copy of containers to streams (in some operator<<() for
   instance).
   "C++ en action", p. 275.
   ° Review all the classes to respect principles exposed in "Coder
   proprement", chapter 6, p. 103: do not implement accessors for each
   class attribute, etc.

- Unit tests
   ° Update (rewrite?) tests.
   ° Unfinished tests:
   .   InputDataReader
   .   Input
   .   Output
   .   Positioning
   ° Test InterlinkNetworks::compute() ?
   ° Timestamp: there is a probability of 10^-6 that the value in
   nanoseconds and the rounded value in milliseconds are identical, in
   which case some tests can fail.