=pod

=head1 NAME

OPENSSL_init_ssl - OpenSSL (libssl and libcrypto) initialisation

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 int OPENSSL_init_ssl(uint64_t opts, const OPENSSL_INIT_SETTINGS *settings);

=head1 DESCRIPTION

During normal operation OpenSSL (libssl and libcrypto) will allocate various
resources at start up that must, subsequently, be freed on close down of the
library. Additionally some resources are allocated on a per thread basis (if the
application is multi-threaded), and these resources must be freed prior to the
thread closing.

As of version 1.1.0 OpenSSL will automatically allocate all resources that it
needs so no explicit initialisation is required. Similarly it will also
automatically deinitialise as required.

However, there may be situations when explicit initialisation is desirable or
needed, for example when some non-default initialisation is required. The
function OPENSSL_init_ssl() can be used for this purpose. Calling
this function will explicitly initialise BOTH libcrypto and libssl. To
explicitly initialise ONLY libcrypto see the
L<OPENSSL_init_crypto(3)> function.

Numerous internal OpenSSL functions call OPENSSL_init_ssl().
Therefore, in order to perform non-default initialisation,
OPENSSL_init_ssl() MUST be called by application code prior to
any other OpenSSL function calls.

The B<opts> parameter specifies which aspects of libssl and libcrypto should be
initialised. Valid options for libcrypto are described on the
L<OPENSSL_init_crypto(3)> page. In addition to any libcrypto
specific option the following libssl options can also be used:

=over 4

=item OPENSSL_INIT_NO_LOAD_SSL_STRINGS

Suppress automatic loading of the libssl error strings. This option is
not a default option. Once selected subsequent calls to
OPENSSL_init_ssl() with the option
B<OPENSSL_INIT_LOAD_SSL_STRINGS> will be ignored.

=item OPENSSL_INIT_LOAD_SSL_STRINGS

Automatic loading of the libssl error strings. This option is a
default option. Once selected subsequent calls to
OPENSSL_init_ssl() with the option
B<OPENSSL_INIT_LOAD_SSL_STRINGS> will be ignored.

=back

OPENSSL_init_ssl() takes a B<settings> parameter which can be used to
set parameter values.  See L<OPENSSL_init_crypto(3)> for details.

=head1 RETURN VALUES

The function OPENSSL_init_ssl() returns 1 on success or 0 on error.

=head1 SEE ALSO

L<OPENSSL_init_crypto(3)>

=head1 HISTORY

The OPENSSL_init_ssl() function was added in OpenSSL 1.1.0.

=cut
