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.\" -*- mode: troff; coding: utf-8 -*-
.\" Automatically generated by Pod::Man 5.01 (Pod::Simple 3.43)
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.\" If the F register is >0, we'll generate index entries on stderr for
.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
.\" entries marked with X<> in POD. Of course, you'll have to process the
.\" output yourself in some meaningful fashion.
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.\" ========================================================================
.\"
.IX Title "SSL_HANDLE_EVENTS 3SSL"
.TH SSL_HANDLE_EVENTS 3SSL 2024-04-04 3.2.2-dev OpenSSL
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
SSL_handle_events \- advance asynchronous state machine and perform network I/O
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/ssl.h>
\&
\& int SSL_handle_events(SSL *ssl);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\fBSSL_handle_events()\fR performs any internal processing which is due on a SSL object. The
exact operations performed by \fBSSL_handle_events()\fR vary depending on what kind of protocol
is being used with the given SSL object. For example, \fBSSL_handle_events()\fR may handle
timeout events which have become due, or may attempt, to the extent currently
possible, to perform network I/O operations on one of the BIOs underlying the
SSL object.
.PP
The primary use case for \fBSSL_handle_events()\fR is to allow an application which uses
OpenSSL in nonblocking mode to give OpenSSL an opportunity to handle timer
events, or to respond to the availability of new data to be read from an
underlying BIO, or to respond to the opportunity to write pending data to an
underlying BIO.
.PP
\&\fBSSL_handle_events()\fR can be used only with the following types of SSL object:
.IP "DTLS SSL objects" 4
.IX Item "DTLS SSL objects"
Using \fBSSL_handle_events()\fR on an SSL object being used with a DTLS method allows timeout
events to be handled properly. This is equivalent to a call to
\&\fBDTLSv1_handle_timeout\fR\|(3). Since \fBSSL_handle_events()\fR handles a superset of the use
cases of \fBDTLSv1_handle_timeout\fR\|(3), it should be preferred for new
applications which do not require support for OpenSSL 3.1 or older.
.Sp
When using DTLS, an application must call \fBSSL_handle_events()\fR as indicated by
calls to \fBSSL_get_event_timeout\fR\|(3); event handling is not performed
automatically by calls to other SSL functions such as \fBSSL_read\fR\|(3) or
\&\fBSSL_write\fR\|(3). Note that this is different to QUIC which also performs event
handling implicitly; see below.
.IP "QUIC connection SSL objects" 4
.IX Item "QUIC connection SSL objects"
Using \fBSSL_handle_events()\fR on an SSL object which represents a QUIC connection allows
timeout events to be handled properly, as well as incoming network data to be
processed, and queued outgoing network data to be written, if the underlying BIO
has the capacity to accept it.
.Sp
Ordinarily, when an application uses an SSL object in blocking mode, it does not
need to call \fBSSL_handle_events()\fR because OpenSSL performs ticking internally on an
automatic basis. However, if an application uses a QUIC connection in
nonblocking mode, it must at a minimum ensure that \fBSSL_handle_events()\fR is called
periodically to allow timeout events to be handled. An application can find out
when it next needs to call \fBSSL_handle_events()\fR for this purpose (if at all) by calling
\&\fBSSL_get_event_timeout\fR\|(3).
.Sp
Calling \fBSSL_handle_events()\fR on a QUIC connection SSL object being used in blocking mode
is not necessary unless no I/O calls (such as \fBSSL_read\fR\|(3) or \fBSSL_write\fR\|(3))
will be made to the object for a substantial period of time. So long as at least
one call to the SSL object is blocking, no such call is needed. However,
\&\fBSSL_handle_events()\fR may optionally be used on a QUIC connection object if desired.
.Sp
With the thread-assisted mode of operation \fBOSSL_QUIC_client_thread_method\fR\|(3)
it is unnecessary to call \fBSSL_handle_events()\fR as the assist thread handles the QUIC
connection events.
.PP
Calling \fBSSL_handle_events()\fR on any other kind of SSL object is a no-op. This is
considered a success case.
.PP
Note that \fBSSL_handle_events()\fR supersedes the older \fBDTLSv1_handle_timeout\fR\|(3) function
for all use cases.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
Returns 1 on success and 0 on failure.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBSSL_get_event_timeout\fR\|(3), \fBDTLSv1_handle_timeout\fR\|(3), \fBssl\fR\|(7)
.SH HISTORY
.IX Header "HISTORY"
The \fBSSL_handle_events()\fR function was added in OpenSSL 3.2.
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright 2023 The OpenSSL Project Authors. All Rights Reserved.
.PP
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
<https://www.openssl.org/source/license.html>.
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