Hello,
I'm trying to write an interface to OpenSSL using BIO pairs. For testing
purposes, I'm doing communication locally in two seperate threads (one
accessing a server context, the other a client context) so I figured I
should worry about thread safety. I read in the OpenSSL documentation that
one could find out if thread support was enabled using this:
#define OPENSSL_THREAD_DEFINES
#include <openssl/opensslconf.h>
#if defined(THREADS)
// thread support enabled
#else
// no thread support
#endif
If I stick to this it appears that I have no thread support here on my
system (Win32), but I see no mention of that OPENSSL_THREAD_DEFINES macro
in opensslconf.h, or anywhere else. Also, I see that OPENSSL_THREADS is
defined in opensslconf.h so I'm basically wondering if this part of the
documentation is out of date and if this OPENSSL_THREADS means that thread
support is enabled. If so, are the callbacks defined in th-lock.c still
valid ? I get a few warnings when I compile those with my project, but C is
like alcohol and cigarettes - you never watch the warnings.
Next question:
I'll probably do all the locking manually since the threads themselves
aren't defined at the C code level for my app (I'm not sure if thread
support will work transparently with OpenSSL for user level threads). So
I'm wondering if just locking all access to the C module in which OpenSSL
routines are called should be sufficient or are there particular sequences
of calls that should be made atomically (that OpenSSL thread support would
usually deal with) ?
Thanks for reading and eventually for answering.
--
Alain Damiral,
Université Catholique de Louvain - student
alain.damiral'at'student.info.ucl.ac.be
Hello Alain,
I think by default OpenSSL is build with multithread support
i.e. it links to multi-threaded version of CRT. But still you have provide
the locks and two callbacks (for locking and unlocking & for getting thread
id) then you are all set to use it in your multithreaded enviourment, I
guess the VS linker spits out warnings if there is a CRT mismatch between
the app & lib. And probably this THREADS flag is defined something like -D
for the compiler in either the make file or some compilation script so that
editing the .h/.c file is not needed.
As to your second question, I am doing the IO on BIO atomically, dont know
if its really required, :), But since my server's performance is quite
resonable with it, so it's OK with me.
Regards,
Usman.
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