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HACKING file for libradsec (in Emacs -*- org -*- mode).
Status as of libradsec-0.2.0.dev (2013-05-06).
* Build instructions
sh autogen.sh
./configure #--enable-tls
make
examples/client -r examples/client.conf blocking-tls; echo $?
* 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 0.2.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 handling when server can't bind to given listen_addr+port
- configuration of listen_addr/service is per realm
- 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
* 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 be how one would 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 0.0.2.dev 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).
* Notes on internals
** How to connect an outgoing connection?
Connecting is not done explicitly by the application but implicitly by
rs_message_send(). The application can treat connections in the same
way regardless of whether they're connection-oriented (i.e. TCP) or
not (UDP).
rs_message_send(msg)
if msg->conn is open: mesasge_do_send(msg)
else:
-> _conn_open(conn, msg)
pick configured peer
event_init_socket(peer)
if TCP or TLS:
init tcp timers
event_init_bufferevent(conn, peer)
else:
init udp timers
if not connected and not connecting:
event_do_connect(conn)
if TCP:
bufferevent_setcb()
bufferevent_enable()
else:
event_assign(write_ev) ; libevent func?
event_add(write_ev)
if not in user-dispatch-mode:
event_base_dispatch()
** How to bind a listener and start listening for incoming connections?
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