ne_sock_init, ne_sock_exit — perform library initialization
#include <ne_socket.h>
int ne_sock_init( | void); |
void ne_sock_exit( | void); |
In some platforms and configurations, neon may be using
some socket or SSL libraries which require global initialization
before use. To perform this initialization, the
ne_sock_init function must be called before
any other library functions are used.
Once all use of neon is complete,
ne_sock_exit can be called to perform
de-initialization of socket or SSL libraries, if necessary. Uses
of ne_sock_init and
ne_sock_exit are "reference counted"; if N
calls to ne_sock_init are made, only the Nth
call to ne_sock_exit will have effect.
ne_sock_init will set the disposition
of the SIGPIPE signal to
ignored. No change is made to the
SIGPIPE disposition by
ne_sock_exit.
Both the SSL libraries supported by neon — OpenSSL and GnuTLS — require callbacks to be registered to allow thread-safe use of SSL. These callbacks are stored as global variables and so their state persists for as long as the library in question is loaded into the process. If multiple users of the SSL library exist within the process, this can be problematic, particularly if one is dynamically loaded (and may subsequently be unloaded).
If neon is configured using the
--enable-threadsafe-ssl flag, thread-safe SSL
support will be enabled automatically, as covered in the following
section. Otherwise, it is not safe to use neon with SSL in a
multi-threaded process. The ne_has_support
function can be used to determine whether neon is built to
enable thread-safety support in the SSL library.
neon follows two simple rules when dealing with the OpenSSL locking callbacks:
ne_sock_init will set
thread-safety locking callbacks if and only if no locking
callbacks are already registered.ne_sock_exit will
unset the thread-safety locking callbacks if and only if the
locking callbacks registered are those registered by
ne_sock_init.Applications and libraries should be able to co-operate to ensure that SSL use is always thread-safe if similar rules are always followed.
The cryptography library used by GnuTLS, libgcrypt, only
supports an initialization operation to register thread-safety
callbacks. ne_sock_init will register the
thread-safe locking callbacks on first use;
ne_sock_exit cannot unregister them. If
multiple users of GnuTLS are present within the process, it is
unsafe to dynamically unload neon from the process if neon
is configured with thread-safe SSL support enabled (since the
callbacks would be left pointing at unmapped memory once neon
is unloaded).