SSL_new_stream(3)

NAME
SSL_new_stream, SSL_STREAM_FLAG_UNI, SSL_STREAM_FLAG_NO_BLOCK, SSL_STREAM_FLAG_ADVANCE - create a new locally-initiated QUIC stream

SYNOPSIS
 #include <openssl/ssl.h>

 #define SSL_STREAM_FLAG_UNI          (1U << 0)
 #define SSL_STREAM_FLAG_NO_BLOCK     (1U << 1)
 #define SSL_STREAM_FLAG_ADVANCE      (1U << 2)
 SSL *SSL_new_stream(SSL *ssl, uint64_t flags);

DESCRIPTION
The SSL_new_stream() function, when passed a QUIC connection SSL object, creates a new locally-initiated bidirectional or unidirectional QUIC stream and returns the newly created QUIC stream SSL object.

If the SSL_STREAM_FLAG_UNI flag is passed, a unidirectional stream is created; else a bidirectional stream is created.

To retrieve the stream ID of the newly created stream, use SSL_get_stream_id(3).

It is the caller's responsibility to free the QUIC stream SSL object using SSL_free(3). The lifetime of the QUIC connection SSL object must exceed that of the QUIC stream SSL object; in other words, the QUIC stream SSL object must be freed first.

Once a stream has been created using SSL_new_stream(), it may be used in the normal way using SSL_read(3) and SSL_write(3).

This function can only be used to create stream objects for locally-initiated streams. To accept incoming streams initiated by a peer, use SSL_accept_stream(3).

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

The creation of new streams is subject to flow control by the QUIC protocol. If it is currently not possible to create a new locally initiated stream of the specified type, a call to SSL_new_stream() will either block (if the connection is configured in blocking mode) until a new stream can be created, or otherwise return NULL.

This function operates in blocking mode if the QUIC connection SSL object is configured in blocking mode (see SSL_set_blocking_mode(3)). It may also be used in nonblocking mode on a connection configured in blocking mode by passing the flag SSL_STREAM_FLAG_NO_BLOCK.

The flag SSL_STREAM_FLAG_ADVANCE may be used to create a QUIC stream SSL object even if a new QUIC stream cannot yet be opened due to flow control. The caller may begin to use the new stream and fill the write buffer of the stream by calling SSL_write(3). However, no actual stream data (or QUIC frames regarding the stream) will be sent until QUIC flow control allows it. Any queued data will be sent as soon as a peer permits it. There is no guarantee the stream will be eventually created; for example, the connection could fail, or a peer might simply decide never to increase the number of allowed streams for the remainder of the connection lifetime.

RETURN VALUES
SSL_new_stream() returns a new stream object, or NULL on error.

This function fails if called on a QUIC stream SSL object or on a non-QUIC SSL object.

SSL_new_stream() may also fail if the underlying connection has reached the maximum stream count, based on the max_streams_bidi or max_streams_uni transport parameter values negotiated with the peer. In this event the NULL return will be accompanied by an error on the error stack (obtainable via ERR_get_error()), which will contain a reason code of SSL_R_STREAM_COUNT_LIMITED. When this error is encountered, the operation may be retried. It is recommended that, prior to retry, the error stack be cleared via a call to ERR_clear_error(), and that the TLS state machine be activated via a call to SSL_handle_events() to process any potential updates from the server allowing additional streams to be created.

SEE ALSO
SSL_accept_stream(3), SSL_free(3)

HISTORY
SSL_new_stream() was 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>.