[thirdparty/openssl.git] / doc / man3 / SSL_set_async_callback.pod

=pod

=head1 NAME

SSL_CTX_set_async_callback,
SSL_CTX_set_async_callback_arg,
SSL_set_async_callback,
SSL_set_async_callback_arg,
SSL_get_async_status,
SSL_async_callback_fn
- manage asynchronous operations

=head1 SYNOPSIS

=for openssl multiple includes

 #include <openssl/ssl.h>

 typedef int (*SSL_async_callback_fn)(SSL *s, void *arg);
 int SSL_CTX_set_async_callback(SSL_CTX *ctx, SSL_async_callback_fn callback);
 int SSL_CTX_set_async_callback_arg(SSL_CTX *ctx, void *arg);
 int SSL_set_async_callback(SSL *s, SSL_async_callback_fn callback);
 int SSL_set_async_callback_arg(SSL *s, void *arg);
 int SSL_get_async_status(SSL *s, int *status);

=head1 DESCRIPTION

SSL_CTX_set_async_callback() sets an asynchronous callback function. All B<SSL>
objects generated based on this B<SSL_CTX> will get this callback. If an engine
supports the callback mechanism, it will be automatically called if
B<SSL_MODE_ASYNC> has been set and an asynchronous capable engine completes a
cryptography operation to notify the application to resume the paused work flow.

SSL_CTX_set_async_callback_arg() sets the callback argument.

SSL_set_async_callback() allows an application to set a callback in an
asynchronous B<SSL> object, so that when an engine completes a cryptography
operation, the callback will be called to notify the application to resume the
paused work flow.

SSL_set_async_callback_arg() sets an argument for the B<SSL> object when the
above callback is called.

SSL_get_async_status() returns the engine status. This function facilitates the
communication from the engine to the application. During an SSL session,
cryptographic operations are dispatched to an engine. The engine status is very
useful for an application to know if the operation has been successfully
dispatched. If the engine does not support this additional callback method,
B<ASYNC_STATUS_UNSUPPORTED> will be returned. See ASYNC_WAIT_CTX_set_status()
for a description of all of the status values.

An example of the above functions would be the following:

=over 4

=item 1.

Application sets the async callback and callback data on an SSL connection 
by calling SSL_set_async_callback().

=item 2.

Application sets B<SSL_MODE_ASYNC> and makes an asynchronous SSL call

=item 3.

OpenSSL submits the asynchronous request to the engine. If a retry occurs at
this point then the status within the B<ASYNC_WAIT_CTX> would be set and the
async callback function would be called (goto Step 7).

=item 4.

The OpenSSL engine pauses the current job and returns, so that the
application can continue processing other connections.

=item 5.

At a future point in time (probably via a polling mechanism or via an
interrupt) the engine will become aware that the asynchronous request has
finished processing.

=item 6.

The engine will call the application's callback passing the callback data as
a parameter.

=item 7.

The callback function should then run. Note: it is a requirement that the
callback function is small and non-blocking as it will be run in the context of
a polling mechanism or an interrupt.

=item 8.

It is the application's responsibility via the callback function to schedule
recalling the OpenSSL asynchronous function and to continue processing.

=item 9.

The callback function has the option to check the status returned via
SSL_get_async_status() to determine whether a retry happened instead of the
request being submitted, allowing different processing if required.

=back

=head1 RETURN VALUES

SSL_CTX_set_async_callback(), SSL_set_async_callback(),
SSL_CTX_set_async_callback_arg(), SSL_CTX_set_async_callback_arg() and
SSL_get_async_status() return 1 on success or 0 on error.

=head1 SEE ALSO

L<ssl(7)>

=head1 HISTORY

SSL_CTX_set_async_callback(), SSL_CTX_set_async_callback_arg(),
SSL_set_async_callback(), SSL_set_async_callback_arg() and
SSL_get_async_status() were first added to OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (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
Commit	Line	Data
9f5a87fd PY	1	=pod
	2
	3	=head1 NAME
	4
	5	SSL_CTX_set_async_callback,
	6	SSL_CTX_set_async_callback_arg,
	7	SSL_set_async_callback,
	8	SSL_set_async_callback_arg,
	9	SSL_get_async_status,
	10	SSL_async_callback_fn
	11	- manage asynchronous operations
	12
	13	=head1 SYNOPSIS
	14
bb82531f	15	=for openssl multiple includes
9f5a87fd PY	16
	17	#include <openssl/ssl.h>
	18
	19	typedef int (SSL_async_callback_fn)(SSL s, void *arg);
	20	int SSL_CTX_set_async_callback(SSL_CTX *ctx, SSL_async_callback_fn callback);
	21	int SSL_CTX_set_async_callback_arg(SSL_CTX ctx, void arg);
	22	int SSL_set_async_callback(SSL *s, SSL_async_callback_fn callback);
	23	int SSL_set_async_callback_arg(SSL s, void arg);
	24	int SSL_get_async_status(SSL s, int status);
	25
	26	=head1 DESCRIPTION
	27
dfe1752c RL	28	SSL_CTX_set_async_callback() sets an asynchronous callback function. All B<SSL>
dfe1752c RL	29	objects generated based on this B<SSL_CTX> will get this callback. If an engine
9f5a87fd	30	supports the callback mechanism, it will be automatically called if
dfe1752c	31	B<SSL_MODE_ASYNC> has been set and an asynchronous capable engine completes a
9f5a87fd PY	32	cryptography operation to notify the application to resume the paused work flow.
	33
	34	SSL_CTX_set_async_callback_arg() sets the callback argument.
	35
	36	SSL_set_async_callback() allows an application to set a callback in an
dfe1752c	37	asynchronous B<SSL> object, so that when an engine completes a cryptography
9f5a87fd PY	38	operation, the callback will be called to notify the application to resume the
	39	paused work flow.
	40
dfe1752c RL	41	SSL_set_async_callback_arg() sets an argument for the B<SSL> object when the
dfe1752c RL	42	above callback is called.
9f5a87fd PY	43
	44	SSL_get_async_status() returns the engine status. This function facilitates the
	45	communication from the engine to the application. During an SSL session,
	46	cryptographic operations are dispatched to an engine. The engine status is very
	47	useful for an application to know if the operation has been successfully
	48	dispatched. If the engine does not support this additional callback method,
dfe1752c RL	49	B<ASYNC_STATUS_UNSUPPORTED> will be returned. See ASYNC_WAIT_CTX_set_status()
dfe1752c RL	50	for a description of all of the status values.
9f5a87fd	51
dfe1752c RL	52	An example of the above functions would be the following:
	53
	54	=over 4
	55
	56	=item 1.
	57
	58	Application sets the async callback and callback data on an SSL connection
9f5a87fd	59	by calling SSL_set_async_callback().
dfe1752c RL	60
	61	=item 2.
	62
	63	Application sets B<SSL_MODE_ASYNC> and makes an asynchronous SSL call
	64
	65	=item 3.
	66
	67	OpenSSL submits the asynchronous request to the engine. If a retry occurs at
	68	this point then the status within the B<ASYNC_WAIT_CTX> would be set and the
	69	async callback function would be called (goto Step 7).
	70
	71	=item 4.
	72
	73	The OpenSSL engine pauses the current job and returns, so that the
9f5a87fd	74	application can continue processing other connections.
dfe1752c RL	75
	76	=item 5.
	77
	78	At a future point in time (probably via a polling mechanism or via an
9f5a87fd PY	79	interrupt) the engine will become aware that the asynchronous request has
9f5a87fd PY	80	finished processing.
dfe1752c RL	81
	82	=item 6.
	83
	84	The engine will call the application's callback passing the callback data as
9f5a87fd	85	a parameter.
dfe1752c RL	86
	87	=item 7.
	88
	89	The callback function should then run. Note: it is a requirement that the
9f5a87fd PY	90	callback function is small and non-blocking as it will be run in the context of
9f5a87fd PY	91	a polling mechanism or an interrupt.
dfe1752c RL	92
	93	=item 8.
	94
	95	It is the application's responsibility via the callback function to schedule
9f5a87fd	96	recalling the OpenSSL asynchronous function and to continue processing.
dfe1752c RL	97
	98	=item 9.
	99
	100	The callback function has the option to check the status returned via
9f5a87fd PY	101	SSL_get_async_status() to determine whether a retry happened instead of the
	102	request being submitted, allowing different processing if required.
	103
dfe1752c RL	104	=back
dfe1752c RL	105
9f5a87fd PY	106	=head1 RETURN VALUES
	107
	108	SSL_CTX_set_async_callback(), SSL_set_async_callback(),
	109	SSL_CTX_set_async_callback_arg(), SSL_CTX_set_async_callback_arg() and
	110	SSL_get_async_status() return 1 on success or 0 on error.
	111
98ca37e4 RS	112	=head1 SEE ALSO
	113
	114	L<ssl(7)>
	115
9f5a87fd PY	116	=head1 HISTORY
	117
	118	SSL_CTX_set_async_callback(), SSL_CTX_set_async_callback_arg(),
	119	SSL_set_async_callback(), SSL_set_async_callback_arg() and
4674aaf4	120	SSL_get_async_status() were first added to OpenSSL 3.0.
9f5a87fd PY	121
	122	=head1 COPYRIGHT
	123
454afd98	124	Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.
9f5a87fd	125
a6ed19dc	126	Licensed under the Apache License 2.0 (the "License"). You may not use
9f5a87fd PY	127	this file except in compliance with the License. You can obtain a copy
	128	in the file LICENSE in the source distribution or at
	129	L<https://www.openssl.org/source/license.html>.
	130
	131	=cut