SSL_WANT(3)

NAME
SSL_want, SSL_want_nothing, SSL_want_read, SSL_want_write, SSL_want_x509_lookup, SSL_want_retry_verify, SSL_want_async, SSL_want_async_job, SSL_want_client_hello_cb - obtain state information TLS/SSL I/O operation

SYNOPSIS
 #include <openssl/ssl.h>

 int SSL_want(const SSL *ssl);
 int SSL_want_nothing(const SSL *ssl);
 int SSL_want_read(const SSL *ssl);
 int SSL_want_write(const SSL *ssl);
 int SSL_want_x509_lookup(const SSL *ssl);
 int SSL_want_retry_verify(const SSL *ssl);
 int SSL_want_async(const SSL *ssl);
 int SSL_want_async_job(const SSL *ssl);
 int SSL_want_client_hello_cb(const SSL *ssl);

DESCRIPTION
SSL_want() returns state information for the SSL object ssl. ssl MUST NOT be NULL.

The other SSL_want_*() calls are shortcuts for the possible states returned by SSL_want().

NOTES
SSL_want() examines the internal state information of the SSL object. Its return values are similar to that of SSL_get_error(3). Unlike SSL_get_error(3), which also evaluates (indirectly) the error queue, the results are obtained by examining an internal state flag only. The information must therefore only be used for normal operation under nonblocking I/O. Error conditions are not handled and must be treated using SSL_get_error(3).

The result returned by SSL_want() should always be consistent with the result of SSL_get_error(3).

RETURN VALUES
The following return values can currently occur for SSL_want():

SSL_NOTHING
    There is no data to be written or to be read.

SSL_WRITING
    There are data in the SSL buffer that must be written to the underlying BIO layer in order to complete the actual SSL_*() operation. A call to SSL_get_error(3) should return SSL_ERROR_WANT_WRITE.

SSL_READING
    More data must be read from the underlying BIO layer in order to complete the actual SSL_*() operation. A call to SSL_get_error(3) should return SSL_ERROR_WANT_READ.

SSL_X509_LOOKUP
    The operation did not complete because an application callback set by SSL_CTX_set_client_cert_cb() has asked to be called again. A call to SSL_get_error(3) should return SSL_ERROR_WANT_X509_LOOKUP.

SSL_RETRY_VERIFY
    The operation did not complete because a certificate verification callback has asked to be called again via SSL_set_retry_verify(3). A call to SSL_get_error(3) should return SSL_ERROR_WANT_RETRY_VERIFY.

SSL_ASYNC_PAUSED
    An asynchronous operation partially completed and was then paused. See SSL_get_all_async_fds(3). A call to SSL_get_error(3) should return SSL_ERROR_WANT_ASYNC.

SSL_ASYNC_NO_JOBS
    The asynchronous job could not be started because there were no async jobs available in the pool (see ASYNC_init_thread(3)). A call to SSL_get_error(3) should return SSL_ERROR_WANT_ASYNC_JOB.

SSL_CLIENT_HELLO_CB
    The operation did not complete because an application callback set by SSL_CTX_set_client_hello_cb() has asked to be called again. A call to SSL_get_error(3) should return SSL_ERROR_WANT_CLIENT_HELLO_CB.

SSL_want_nothing(), SSL_want_read(), SSL_want_write(), SSL_want_x509_lookup(), SSL_want_retry_verify(), SSL_want_async(), SSL_want_async_job(), and SSL_want_client_hello_cb() return 1 when the corresponding condition is true or 0 otherwise.

QUIC-SPECIFIC CONSIDERATIONS
For QUIC, these functions relate only to the TLS handshake layer.

SEE ALSO
ssl(7), SSL_get_error(3)

HISTORY
The SSL_want_client_hello_cb() function and the SSL_CLIENT_HELLO_CB return value were added in OpenSSL 1.1.1.

SSL_want_retry_verify() was added in OpenSSL 3.0.

COPYRIGHT
Copyright 2001-2026 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>.