=pod

=head1 NAME

SSL_accept_stream, SSL_get_accept_stream_queue_len, SSL_ACCEPT_STREAM_NO_BLOCK,
SSL_ACCEPT_STREAM_UNI, SSL_ACCEPT_STREAM_BIDI -
accept an incoming QUIC stream from a QUIC peer

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 #define SSL_ACCEPT_STREAM_NO_BLOCK
 #define SSL_ACCEPT_STREAM_UNI
 #define SSL_ACCEPT_STREAM_BIDI

 SSL *SSL_accept_stream(SSL *ssl, uint64_t flags);

 size_t SSL_get_accept_stream_queue_len(SSL *ssl);

=head1 DESCRIPTION

The SSL_accept_stream() function attempts to dequeue an incoming stream from the
given QUIC connection SSL object and returns the newly allocated QUIC stream SSL
object.

If the queue of incoming streams is empty, this function returns NULL (in
nonblocking mode) or waits for an incoming stream (in blocking mode). This
function may still return NULL in blocking mode, for example if the underlying
connection is terminated.

The caller is responsible for managing the lifetime of the returned QUIC stream
SSL object; for more information, see L<SSL_free(3)>.

This function will block if the QUIC connection SSL object is configured in
blocking mode (see L<SSL_set_blocking_mode(3)>), but this may be bypassed by
passing the flag B<SSL_ACCEPT_STREAM_NO_BLOCK> in I<flags>. If this flag is set,
this function never blocks.

By default, this function will return the first incoming stream, whether it is
unidirectional or bidirectional. Passing the flag B<SSL_ACCEPT_STREAM_UNI> or
B<SSL_ACCEPT_STREAM_BIDI> will return the first stream that is unidirectional or
bidirectional, respectively. If these flags are both set, either type can be
returned. A NULL return value may mean that there are still streams that can
be dequeued.

Calling SSL_accept_stream() if there is no default stream already present
inhibits the future creation of a default stream. See L<openssl-quic(7)>.

SSL_get_accept_stream_queue_len() returns the number of incoming streams
currently waiting in the accept queue.

These functions can be used from multiple threads for the same QUIC connection.

Depending on whether default stream functionality is being used, it may be
necessary to explicitly configure the incoming stream policy before streams can
be accepted; see L<SSL_set_incoming_stream_policy(3)>. See also
L<openssl-quic(7)/MODES OF OPERATION> for more information on default stream
functionality.

=head1 RETURN VALUES

SSL_accept_stream() returns a newly allocated QUIC stream SSL object, or NULL if
no new incoming streams are available, or if the connection has been terminated,
or if called on an SSL object other than a QUIC connection SSL object.
L<SSL_get_error(3)> can be used to obtain further information in this case.

SSL_get_accept_stream_queue_len() returns the number of incoming streams
currently waiting in the accept queue, or 0 if called on an SSL object other than
a QUIC connection SSL object.

=head1 SEE ALSO

L<openssl-quic(7)/MODES OF OPERATION>, L<SSL_new_stream(3)>,
L<SSL_set_blocking_mode(3)>, L<SSL_free(3)>

=head1 HISTORY

SSL_accept_stream() and SSL_get_accept_stream_queue_len() were added in OpenSSL
3.2.

=head1 COPYRIGHT

Copyright 2002-2025 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
