df75c2bfcd
While stereotyped repetitions are frowned upon in literature, they serve a useful purpose in manual pages, because it is easier for the user to find certain information if it is always presented in the same way. For that reason, this commit harmonizes the varying formulations in the HISTORY section about which functions, flags, etc. were added in which OpenSSL version. It also attempts to make the pod files more grep friendly by avoiding to insert line breaks between the symbol names and the corresponding version number in which they were introduced (wherever possible). Some punctuation and typographical errors were fixed on the way. Reviewed-by: Tim Hudson <tjh@openssl.org> (Merged from https://github.com/openssl/openssl/pull/7854)
173 lines
6.6 KiB
Text
173 lines
6.6 KiB
Text
=pod
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=head1 NAME
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SSL_get_error - obtain result code for TLS/SSL I/O operation
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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int SSL_get_error(const SSL *ssl, int ret);
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=head1 DESCRIPTION
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SSL_get_error() returns a result code (suitable for the C "switch"
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statement) for a preceding call to SSL_connect(), SSL_accept(), SSL_do_handshake(),
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SSL_read_ex(), SSL_read(), SSL_peek_ex(), SSL_peek(), SSL_write_ex() or
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SSL_write() on B<ssl>. The value returned by that TLS/SSL I/O function must be
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passed to SSL_get_error() in parameter B<ret>.
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In addition to B<ssl> and B<ret>, SSL_get_error() inspects the
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current thread's OpenSSL error queue. Thus, SSL_get_error() must be
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used in the same thread that performed the TLS/SSL I/O operation, and no
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other OpenSSL function calls should appear in between. The current
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thread's error queue must be empty before the TLS/SSL I/O operation is
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attempted, or SSL_get_error() will not work reliably.
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=head1 RETURN VALUES
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The following return values can currently occur:
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=over 4
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=item SSL_ERROR_NONE
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The TLS/SSL I/O operation completed. This result code is returned
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if and only if B<ret E<gt> 0>.
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=item SSL_ERROR_ZERO_RETURN
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The TLS/SSL peer has closed the connection for writing by sending the
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close_notify alert.
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No more data can be read.
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Note that B<SSL_ERROR_ZERO_RETURN> does not necessarily
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indicate that the underlying transport has been closed.
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=item SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE
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The operation did not complete and can be retried later.
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B<SSL_ERROR_WANT_READ> is returned when the last operation was a read
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operation from a non-blocking B<BIO>.
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It means that not enough data was available at this time to complete the
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operation.
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If at a later time the underlying B<BIO> has data available for reading the same
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function can be called again.
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SSL_read() and SSL_read_ex() can also set B<SSL_ERROR_WANT_READ> when there is
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still unprocessed data available at either the B<SSL> or the B<BIO> layer, even
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for a blocking B<BIO>.
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See L<SSL_read(3)> for more information.
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B<SSL_ERROR_WANT_WRITE> is returned when the last operation was a write
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to a non-blocking B<BIO> and it was unable to sent all data to the B<BIO>.
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When the B<BIO> is writeable again, the same function can be called again.
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Note that the retry may again lead to an B<SSL_ERROR_WANT_READ> or
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B<SSL_ERROR_WANT_WRITE> condition.
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There is no fixed upper limit for the number of iterations that
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may be necessary until progress becomes visible at application
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protocol level.
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It is safe to call SSL_read() or SSL_read_ex() when more data is available
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even when the call that set this error was an SSL_write() or SSL_write_ex().
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However if the call was an SSL_write() or SSL_write_ex(), it should be called
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again to continue sending the application data.
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For socket B<BIO>s (e.g. when SSL_set_fd() was used), select() or
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poll() on the underlying socket can be used to find out when the
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TLS/SSL I/O function should be retried.
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Caveat: Any TLS/SSL I/O function can lead to either of
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B<SSL_ERROR_WANT_READ> and B<SSL_ERROR_WANT_WRITE>.
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In particular,
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SSL_read_ex(), SSL_read(), SSL_peek_ex(), or SSL_peek() may want to write data
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and SSL_write() or SSL_write_ex() may want to read data.
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This is mainly because
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TLS/SSL handshakes may occur at any time during the protocol (initiated by
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either the client or the server); SSL_read_ex(), SSL_read(), SSL_peek_ex(),
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SSL_peek(), SSL_write_ex(), and SSL_write() will handle any pending handshakes.
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=item SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT
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The operation did not complete; the same TLS/SSL I/O function should be
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called again later. The underlying BIO was not connected yet to the peer
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and the call would block in connect()/accept(). The SSL function should be
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called again when the connection is established. These messages can only
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appear with a BIO_s_connect() or BIO_s_accept() BIO, respectively.
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In order to find out, when the connection has been successfully established,
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on many platforms select() or poll() for writing on the socket file descriptor
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can be used.
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=item SSL_ERROR_WANT_X509_LOOKUP
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The operation did not complete because an application callback set by
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SSL_CTX_set_client_cert_cb() has asked to be called again.
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The TLS/SSL I/O function should be called again later.
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Details depend on the application.
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=item SSL_ERROR_WANT_ASYNC
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The operation did not complete because an asynchronous engine is still
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processing data. This will only occur if the mode has been set to SSL_MODE_ASYNC
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using L<SSL_CTX_set_mode(3)> or L<SSL_set_mode(3)> and an asynchronous capable
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engine is being used. An application can determine whether the engine has
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completed its processing using select() or poll() on the asynchronous wait file
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descriptor. This file descriptor is available by calling
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L<SSL_get_all_async_fds(3)> or L<SSL_get_changed_async_fds(3)>. The TLS/SSL I/O
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function should be called again later. The function B<must> be called from the
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same thread that the original call was made from.
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=item SSL_ERROR_WANT_ASYNC_JOB
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The asynchronous job could not be started because there were no async jobs
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available in the pool (see ASYNC_init_thread(3)). This will only occur if the
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mode has been set to SSL_MODE_ASYNC using L<SSL_CTX_set_mode(3)> or
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L<SSL_set_mode(3)> and a maximum limit has been set on the async job pool
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through a call to L<ASYNC_init_thread(3)>. The application should retry the
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operation after a currently executing asynchronous operation for the current
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thread has completed.
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=item SSL_ERROR_WANT_CLIENT_HELLO_CB
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The operation did not complete because an application callback set by
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SSL_CTX_set_client_hello_cb() has asked to be called again.
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The TLS/SSL I/O function should be called again later.
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Details depend on the application.
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=item SSL_ERROR_SYSCALL
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Some non-recoverable I/O error occurred.
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The OpenSSL error queue may contain more information on the error.
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For socket I/O on Unix systems, consult B<errno> for details.
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This value can also be returned for other errors, check the error queue for
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details.
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=item SSL_ERROR_SSL
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A failure in the SSL library occurred, usually a protocol error. The
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OpenSSL error queue contains more information on the error.
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=back
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=head1 SEE ALSO
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L<ssl(7)>
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=head1 HISTORY
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The SSL_ERROR_WANT_ASYNC error code was added in OpenSSL 1.1.0.
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The SSL_ERROR_WANT_CLIENT_HELLO_CB error code was added in OpenSSL 1.1.1.
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=head1 COPYRIGHT
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Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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