SSL_CTX_set_new_pending_conn_cb, SSL_set_new_pending_conn_cb_fn - callback function to report creation of

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       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>.

3.5.0                                              2025-06-04              SSL_CTX_SET_NEW_PENDING_CONN_CB(3SSL)

SSL_CTX_set_new_pending_conn_cb() sets the new_pending_conn callback function and associated application
       data argument arg.  When using the QUIC transport, TLS handshake processing may occur independently from
       the thread which accepts the connection that the handshake is establishing.  As such, SSL objects
       representing the connection may be allocated and initialized prior to a call to SSL_accept_connection().
       This registered callback may be used to decorate the preallocated SSL object or create other associations
       with its parent SSL prior to a call to SSL_accept_connection().

SSL_CTX_set_new_pending_conn_cb() was added in OpenSSL 3.5

       SSL_CTX_set_new_pending_conn_cb, SSL_set_new_pending_conn_cb_fn - callback function to report creation of
       QUIC connection SSL objects

       Callbacks in QUIC connections have some limitations to them that should be taken into consideration when
       writing an application.

           QUIC connections may begin processing prior to when an application calls SSL_accept_connection() on
           them.  As such, it may occur that callbacks are delivered to applications' registered TLS callbacks
           prior to those SSL objects being returned in SSL_accept_connection().  Applications should expect
           this possibility.

           In particular no references should be held on SSL objects passed to callbacks for QUIC connections
           until such time as they are returned through a call to SSL_accept_connection.

SSL_CTX_set_new_pending_conn_cb() returns no value.

       SSL_set_new_pending_conn_cb_fn() returns an integer value.  A return value of 0 indicates that the QUIC
       stack must discard this newly created SSL object, implying that the associated new connection will not be
       available for handling on a subsequent call to SSL_accept_connection().  A nonzero return value is
       treated as success, allowing the new connection to be enqueued to the accept queue.

SSL_set_ex_data(3)

        typedef int (*SSL_set_new_pending_conn_cb_fn)(SSL_CTX *c, SSL *new_ssl,
                                                      void *arg);
        void SSL_CTX_set_new_pending_conn_cb(SSL_CTX *c,
                                            SSL_set_new_pending_conn_cb_fn *f,
                                            void *arg);