openssl/doc/ssl/SSL_get_error.pod
2000-09-06 07:56:03 +00:00

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=pod
=head1 NAME
SSL_get_error - obtain result code for SSL I/O operation
=head1 SYNOPSIS
#include <openssl/ssl.h>
int SSL_get_error(SSL *ssl, int ret);
=head1 DESCRIPTION
SSL_get_error() returns a result code (suitable for the C "switch"
statement) for a preceding call to SSL_connect(), SSL_accept(),
SSL_read(), or SSL_write() on B<ssl>. The value returned by that
SSL I/O function must be passed to SSL_get_error() in parameter
B<ret>.
In addition to B<ssl> and B<ret>, SSL_get_error() inspects the
current thread's OpenSSL error queue. Thus, SSL_get_error() must be
used in the same thread that performed the SSL I/O operation, and no
other OpenSSL function calls should appear in between. The current
thread's error queue must be empty before the SSL I/O operation is
attempted, or SSL_get_error() will not work reliably.
=head1 RETURN VALUES
The following return values can currently occur:
=over 4
=item SSL_ERROR_NONE
The SSL I/O operation completed. This result code is returned
if and only if B<ret E<gt> 0>.
=item SSL_ERROR_ZERO_RETURN
The SSL connection has been closed. If the protocol version is SSL 3.0
or TLS 1.0, this result code is returned only if a closure
alert has occurred in the protocol, i.e. if the connection has been
closed cleanly. Note that in this case B<SSL_ERROR_ZERO_RETURN>
does not necessarily indicate that the underlying transport
has been closed.
=item SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE
The operation did not complete; the same SSL I/O function should be
called again later. There will be protocol progress if, by then, the
underlying B<BIO> has data available for reading (if the result code is
B<SSL_ERROR_WANT_READ>) or allows writing data (B<SSL_ERROR_WANT_WRITE>).
For socket B<BIO>s (e.g. when SSL_set_fd() was used) this means that
select() or poll() on the underlying socket can be used to find out
when the SSL I/O function should be retried.
Caveat: Any SSL I/O function can lead to either of
B<SSL_ERROR_WANT_READ> and B<SSL_ERROR_WANT_WRITE>, i.e. SSL_read()
may want to write data and SSL_write() may want to read data.
=item SSL_ERROR_WANT_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.
The SSL I/O function should be called again later.
Details depend on the application.
=item SSL_ERROR_SYSCALL
Some I/O error occurred. The OpenSSL error queue may contain more
information on the error. If the error queue is empty
(i.e. ERR_get_error() returns 0), B<ret> can be used to find out more
about the error: If B<ret == 0>, an EOF was observed that violates
the protocol. If B<ret == -1>, the underlying B<BIO> reported an
I/O error (for socket I/O on Unix systems, consult B<errno> for details).
=item SSL_ERROR_SSL
A failure in the SSL library occurred, usually a protocol error. The
OpenSSL error queue contains more information on the error.
=back
=head1 SEE ALSO
L<ssl(3)|ssl(3)>, L<err(3)|err(3)>
=head1 HISTORY
SSL_get_error() was added in SSLeay 0.8.
=cut