- NAME
- SYNOPSIS
- DESCRIPTION
- RETURN VALUES
- SEE ALSO
- HISTORY
- COPYRIGHT

# 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

# 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);

# 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 SSL_free(3).

This function will block if the QUIC connection SSL object is configured in blocking mode (see SSL_set_blocking_mode(3)), but this may be bypassed by passing the flag SSL_ACCEPT_STREAM_NO_BLOCK in 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 SSL_ACCEPT_STREAM_UNI or 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 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 SSL_set_incoming_stream_policy(3). See also "MODES OF OPERATION" in openssl-quic(7) for more information on default stream functionality.

# 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. 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.

# SEE ALSO

"MODES OF OPERATION" in openssl-quic(7), SSL_new_stream(3), SSL_set_blocking_mode(3), SSL_free(3)

# HISTORY

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

# 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 https://www.openssl.org/source/license.html.