230 lines
8.2 KiB
Groff
Executable File
230 lines
8.2 KiB
Groff
Executable File
.\" Automatically generated by Pod::Man 2.25 (Pod::Simple 3.16)
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.\" ========================================================================
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.\"
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.IX Title "SSL_SET_ASYNC_CALLBACK 3"
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.TH SSL_SET_ASYNC_CALLBACK 3 "2020-03-02" "3.0.0-dev" "OpenSSL"
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.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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.\" way too many mistakes in technical documents.
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.if n .ad l
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.nh
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.SH "NAME"
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SSL_CTX_set_async_callback,
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SSL_CTX_set_async_callback_arg,
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SSL_set_async_callback,
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SSL_set_async_callback_arg,
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SSL_get_async_status,
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SSL_async_callback_fn
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\&\- manage asynchronous operations
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.SH "SYNOPSIS"
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.IX Header "SYNOPSIS"
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.Vb 1
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\& #include <openssl/ssl.h>
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\&
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\& typedef int (*SSL_async_callback_fn)(SSL *s, void *arg);
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\& int SSL_CTX_set_async_callback(SSL_CTX *ctx, SSL_async_callback_fn callback);
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\& int SSL_CTX_set_async_callback_arg(SSL_CTX *ctx, void *arg);
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\& int SSL_set_async_callback(SSL *s, SSL_async_callback_fn callback);
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\& int SSL_set_async_callback_arg(SSL *s, void *arg);
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\& int SSL_get_async_status(SSL *s, int *status);
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.Ve
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.SH "DESCRIPTION"
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.IX Header "DESCRIPTION"
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\&\fISSL_CTX_set_async_callback()\fR sets an asynchronous callback function. All \fB\s-1SSL\s0\fR
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objects generated based on this \fB\s-1SSL_CTX\s0\fR will get this callback. If an engine
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supports the callback mechanism, it will be automatically called if
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\&\fB\s-1SSL_MODE_ASYNC\s0\fR has been set and an asynchronous capable engine completes a
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cryptography operation to notify the application to resume the paused work flow.
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.PP
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\&\fISSL_CTX_set_async_callback_arg()\fR sets the callback argument.
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.PP
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\&\fISSL_set_async_callback()\fR allows an application to set a callback in an
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asynchronous \fB\s-1SSL\s0\fR object, so that when an engine completes a cryptography
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operation, the callback will be called to notify the application to resume the
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paused work flow.
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.PP
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\&\fISSL_set_async_callback_arg()\fR sets an argument for the \fB\s-1SSL\s0\fR object when the
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above callback is called.
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.PP
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\&\fISSL_get_async_status()\fR returns the engine status. This function facilitates the
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communication from the engine to the application. During an \s-1SSL\s0 session,
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cryptographic operations are dispatched to an engine. The engine status is very
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useful for an application to know if the operation has been successfully
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dispatched. If the engine does not support this additional callback method,
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\&\fB\s-1ASYNC_STATUS_UNSUPPORTED\s0\fR will be returned. See \fIASYNC_WAIT_CTX_set_status()\fR
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for a description of all of the status values.
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.PP
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An example of the above functions would be the following:
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.IP "1." 4
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Application sets the async callback and callback data on an \s-1SSL\s0 connection
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by calling \fISSL_set_async_callback()\fR.
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.IP "2." 4
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Application sets \fB\s-1SSL_MODE_ASYNC\s0\fR and makes an asynchronous \s-1SSL\s0 call
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.IP "3." 4
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OpenSSL submits the asynchronous request to the engine. If a retry occurs at
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this point then the status within the \fB\s-1ASYNC_WAIT_CTX\s0\fR would be set and the
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async callback function would be called (goto Step 7).
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.IP "4." 4
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The OpenSSL engine pauses the current job and returns, so that the
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application can continue processing other connections.
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.IP "5." 4
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At a future point in time (probably via a polling mechanism or via an
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interrupt) the engine will become aware that the asynchronous request has
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finished processing.
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.IP "6." 4
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The engine will call the application's callback passing the callback data as
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a parameter.
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.IP "7." 4
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The callback function should then run. Note: it is a requirement that the
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callback function is small and non-blocking as it will be run in the context of
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a polling mechanism or an interrupt.
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.IP "8." 4
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It is the application's responsibility via the callback function to schedule
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recalling the OpenSSL asynchronous function and to continue processing.
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.IP "9." 4
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The callback function has the option to check the status returned via
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\&\fISSL_get_async_status()\fR to determine whether a retry happened instead of the
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request being submitted, allowing different processing if required.
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.SH "RETURN VALUES"
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.IX Header "RETURN VALUES"
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\&\fISSL_CTX_set_async_callback()\fR, \fISSL_set_async_callback()\fR,
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\&\fISSL_CTX_set_async_callback_arg()\fR, \fISSL_CTX_set_async_callback_arg()\fR and
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\&\fISSL_get_async_status()\fR return 1 on success or 0 on error.
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.SH "SEE ALSO"
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.IX Header "SEE ALSO"
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\&\fIssl\fR\|(7)
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.SH "HISTORY"
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.IX Header "HISTORY"
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\&\fISSL_CTX_set_async_callback()\fR, \fISSL_CTX_set_async_callback_arg()\fR,
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\&\fISSL_set_async_callback()\fR, \fISSL_set_async_callback_arg()\fR and
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\&\fISSL_get_async_status()\fR were first added to OpenSSL 3.0.
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.SH "COPYRIGHT"
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.IX Header "COPYRIGHT"
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Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
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.PP
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Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file \s-1LICENSE\s0 in the source distribution or at
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<https://www.openssl.org/source/license.html>.
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