xref: /freebsd-11-stable/crypto/openssl/doc/ssl/SSL_get_error.pod

=pod

=head1 NAME

SSL_get_error - obtain result code for TLS/SSL I/O operation

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 int SSL_get_error(const 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_do_handshake(),
SSL_read(), SSL_peek(), or SSL_write() on B<ssl>.  The value returned by
that TLS/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 TLS/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 TLS/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 TLS/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 TLS/SSL connection has been closed.
If the protocol version is SSL 3.0 or higher, 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 TLS/SSL I/O function should be
called again later.  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>), then some TLS/SSL
protocol progress will take place, i.e. at least part of an TLS/SSL
record will be read or written.  Note that the retry may again lead to
a B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE> condition.
There is no fixed upper limit for the number of iterations that
may be necessary until progress becomes visible at application
protocol level.

For socket B<BIO>s (e.g. when SSL_set_fd() was used), select() or
poll() on the underlying socket can be used to find out when the
TLS/SSL I/O function should be retried.

Caveat: Any TLS/SSL I/O function can lead to either of
B<SSL_ERROR_WANT_READ> and B<SSL_ERROR_WANT_WRITE>.  In particular,
SSL_read() or SSL_peek() may want to write data and SSL_write() may want
to read data.  This is mainly because TLS/SSL handshakes may occur at any
time during the protocol (initiated by either the client or the server);
SSL_read(), SSL_peek(), and SSL_write() will handle any pending handshakes.

=item SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT

The operation did not complete; the same TLS/SSL I/O function should be
called again later. The underlying BIO was not connected yet to the peer
and the call would block in connect()/accept(). The SSL function should be
called again when the connection is established. These messages can only
appear with a BIO_s_connect() or BIO_s_accept() BIO, respectively.
In order to find out, when the connection has been successfully established,
on many platforms select() or poll() for writing on the socket file descriptor
can be used.

=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 TLS/SSL I/O function should be called again later.
Details depend on the application.

=item SSL_ERROR_SYSCALL

Some non-recoverable, fatal I/O error occurred. The OpenSSL error queue may
contain more information on the error. For socket I/O on Unix systems, consult
B<errno> for details. If this error occurs then no further I/O operations should
be performed on the connection and SSL_shutdown() must not be called.

=item SSL_ERROR_SSL

A non-recoverable, fatal error in the SSL library occurred, usually a protocol
error.  The OpenSSL error queue contains more information on the error. If this
error occurs then no further I/O operations should be performed on the
connection and SSL_shutdown() must not be called.

=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