HACKING file for libradsec (in Emacs -*- org -*- mode).

Status as of libradsec-0.0.5 (2014-02-03).

* Build instructions
sh autogen.sh
./configure
make

examples/client -r examples/client.conf blocking-tls; echo $?

* Design of the API
- There are three usage modes:

  - Application uses blocking send and receive calls (blocking
    mode). This is typically fine for a simple client.

  - Application registers callbacks with libradsec and runs the
    libevent dispatch loop (a.k.a. user dispatch mode). This would
    probably how to implement a server or a proxy.

  - Application runs its own event loop, using fd's for select and
    performs I/O using libradsec send/receive functions
    (a.k.a. on-your-own mode). Might be useful for an application
    which already has an event loop that wants to add RadSec
    functionality.

- Apart from configuration and error handling, an application
  shouldn't need to handle TCP and UDP connections
  differently. Similarly, the use of TLS/DTLS or not shouldn't
  influence the libradsec calls made by the application.

- Configuration is done either by using the API or by pointing at a
  configuration file which is parsed by libradsec.

- Fully reentrant.

- Application chooses allocation regime.

Note that as of 0.0.4 libradsec suffers from way too much focus on
the behaviour of a blocking client and is totally useless as a server.
Not only does it lack most of the functions needed for writing a
server but it also contains at least one architectural mishap which
kills the server idea -- a connection timeout (TCP) or a retransmit
timeout (UDP) will result in the event loop being broken. The same
thing will happen if there's an error on a TCP connection, f.ex. a
failing certificate validation (TLS).

* Dependencies
Details (within parentheses) apply to Debian Wheezy.

- libconfuse (2.7-4)
  sudo apt-get install libconfuse-dev libconfuse0
- libevent2 (2.0.19-stable-3)
  sudo apt-get install libevent-dev libevent-2.0-5
- OpenSSL (1.0.1c-4) -- optional, for TLS and DTLS support
  sudo apt-get install libssl-dev libssl1.0.0
  
* Functionality and quality in 0.0.x
** Not well tested
- reading config file
- [TCP] short read
- [TCP] short write
- [TLS] basic tls support
- [TLS] preshared key support
- [TLS] verification of CN

** Known issues
- error stack is only one entry deep
- custom allocation scheme is not used in all places

** Not implemented
- dispatch mode (planned for 0.1)
- [client] server failover / RFC3539 watchdog (planned for 0.1)
- [server] support (planned for 0.2)
- [client] TCP keepalive
- on-your-own mode
- [DTLS] support

* Found a bug?
Please report it. That is how we improve the quality of the code.

If possible, please build the library with DEBUG defined (CFLAGS="-g
-DDEBUG") and reproduce the problem. With DEBUG defined, lots of
asserts are enabled which might give a hint about what's gone wrong.

Running the library under gdb is another good idea. If you experience
a crash, catching the crash in gdb and providing a backtrace is highly
valuable for debugging.

Contact: mailto:linus+libradsec@nordu.net