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Harald Welte laforge at gnumonks.orgOn Fri, Jun 05, 2009 at 02:35:39PM +0200, Nordin wrote:
> Hi guys,
>
> I'm a bit ashamed to ask, but I'll ask anyway, could someone help me
> explaining the OpenBSC source?
>
> make_sock():
> I didn't know it's possible to call select() on a read signal to finally
> call the accept() for the socket_fd. Logically seen, socket_fd receives
> something (in this case a new connection), so it works. I just thought
> select() is only used for reading/writing data (or an except) on file
> descriptors.
This is normal operation for asynchronous select() based network daemons.
> Why is OpenBSC written to work synchronously and not multihtreaded? If
> somewhere in the chain hangs (by a bug), telnet for example won't
> respond, right? What is the idea behind this concept?
The idea is to avoid the significant increase in complexity making all data
structures and the code architecture thread safe, avoid race conditions,
etc.
Threads just horribly complicate things, and typically they're not really
needed.
As indicated, I'm perfectly fine with putting the actual voice data processing
and TRAU muxing into a separate process. But more than that would be simply
over-engineering. We're not trying to build a commercial grade BSC with
hundreds of BTS and [tens of] thousands of handsets roaming back and forth
between them.
We want to build something simple for protocol and security experiments,
which will likely only see deployment in small setups.
So we stick to KISS (Keep It Simple / Stupid)
> Is it a popular concept in the Linux world (so I can be familiar with)?
Yes, I think it is fairly popular in the unix network daemon world.
> Which other functions does timer.c has besides returning a timevalue for
> the select() call (nearest_timer) time-out. I mean what more other
> purposes has timer.c Cause I don't really understand why timer_values
> also be put in a doubly linked list...
it manages a list of timers, and determines the timeout to the shortest
current timer. once a timer expires, it calls the per-timer specific callback
functoin.
Regards,
--
- Harald Welte <laforge at gnumonks.org> http://laforge.gnumonks.org/
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