=pod

=head1 NAME

SSL_CTX_set_info_callback, SSL_CTX_get_info_callback, SSL_set_info_callback, SSL_get_info_callback - handle information callback for SSL connections

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 void SSL_CTX_set_info_callback(SSL_CTX *ctx, void (*callback)());
 void (*SSL_CTX_get_info_callback(const SSL_CTX *ctx))();

 void SSL_set_info_callback(SSL *ssl, void (*callback)());
 void (*SSL_get_info_callback(const SSL *ssl))();

=head1 DESCRIPTION

SSL_CTX_set_info_callback() sets the B<callback> function, that can be used to
obtain state information for SSL objects created from B<ctx> during connection
setup and use. The setting for B<ctx> is overridden from the setting for
a specific SSL object, if specified.
When B<callback> is NULL, no callback function is used.

SSL_set_info_callback() sets the B<callback> function, that can be used to
obtain state information for B<ssl> during connection setup and use.
When B<callback> is NULL, the callback setting currently valid for
B<ctx> is used.

SSL_CTX_get_info_callback() returns a pointer to the currently set information
callback function for B<ctx>.

SSL_get_info_callback() returns a pointer to the currently set information
callback function for B<ssl>.

=head1 NOTES

When setting up a connection and during use, it is possible to obtain state
information from the SSL/TLS engine. When set, an information callback function
is called whenever the state changes, an alert appears, or an error occurs.

The callback function is called as B<callback(SSL *ssl, int where, int ret)>.
The B<where> argument specifies information about where (in which context)
the callback function was called. If B<ret> is 0, an error condition occurred.
If an alert is handled, SSL_CB_ALERT is set and B<ret> specifies the alert
information.

B<where> is a bitmask made up of the following bits:

=over 4

=item SSL_CB_LOOP

Callback has been called to indicate state change inside a loop.

=item SSL_CB_EXIT

Callback has been called to indicate error exit of a handshake function.
(May be soft error with retry option for non-blocking setups.)

=item SSL_CB_READ

Callback has been called during read operation.

=item SSL_CB_WRITE

Callback has been called during write operation.

=item SSL_CB_ALERT

Callback has been called due to an alert being sent or received.

=item SSL_CB_READ_ALERT               (SSL_CB_ALERT|SSL_CB_READ)

=item SSL_CB_WRITE_ALERT              (SSL_CB_ALERT|SSL_CB_WRITE)

=item SSL_CB_ACCEPT_LOOP              (SSL_ST_ACCEPT|SSL_CB_LOOP)

=item SSL_CB_ACCEPT_EXIT              (SSL_ST_ACCEPT|SSL_CB_EXIT)

=item SSL_CB_CONNECT_LOOP             (SSL_ST_CONNECT|SSL_CB_LOOP)

=item SSL_CB_CONNECT_EXIT             (SSL_ST_CONNECT|SSL_CB_EXIT)

=item SSL_CB_HANDSHAKE_START

Callback has been called because a new handshake is started.

=item SSL_CB_HANDSHAKE_DONE           0x20

Callback has been called because a handshake is finished.

=back

The current state information can be obtained using the
L<SSL_state_string(3)> family of functions.

The B<ret> information can be evaluated using the
L<SSL_alert_type_string(3)> family of functions.

=head1 RETURN VALUES

SSL_set_info_callback() does not provide diagnostic information.

SSL_get_info_callback() returns the current setting.

=head1 EXAMPLES

The following example callback function prints state strings, information
about alerts being handled and error messages to the B<bio_err> BIO.

 void apps_ssl_info_callback(SSL *s, int where, int ret)
        {
        const char *str;
        int w;

        w = where & ~SSL_ST_MASK;

        if (w & SSL_ST_CONNECT) str = "SSL_connect";
        else if (w & SSL_ST_ACCEPT) str = "SSL_accept";
        else str = "undefined";

        if (where & SSL_CB_LOOP)
                {
                BIO_printf(bio_err, "%s:%s\n", str, SSL_state_string_long(s));
                }
        else if (where & SSL_CB_ALERT)
                {
                str = (where & SSL_CB_READ) ? "read" : "write";
                BIO_printf(bio_err, "SSL3 alert %s:%s:%s\n",
                        str,
                        SSL_alert_type_string_long(ret),
                        SSL_alert_desc_string_long(ret));
                }
        else if (where & SSL_CB_EXIT)
                {
                if (ret == 0)
                        BIO_printf(bio_err, "%s:failed in %s\n",
                                str, SSL_state_string_long(s));
                else if (ret < 0)
                        {
                        BIO_printf(bio_err, "%s:error in %s\n",
                                str, SSL_state_string_long(s));
                        }
                }
        }

=head1 SEE ALSO

L<ssl(3)>, L<SSL_state_string(3)>,
L<SSL_alert_type_string(3)>

=head1 COPYRIGHT

Copyright 2001-2016 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the "License").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file LICENSE in the source distribution or at
L<https://www.openssl.org/source/license.html>.

=cut
