.\"	$NetBSD: SSL_get_error.3,v 1.16 2005/11/25 21:09:34 christos Exp $
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.\" ========================================================================
.\"
.IX Title "SSL_get_error 3"
.TH SSL_get_error 3 "2005-04-23" "0.9.8a" "OpenSSL"
.SH "NAME"
SSL_get_error \- obtain result code for TLS/SSL I/O operation
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/ssl.h>
.Ve
.PP
.Vb 1
\& int SSL_get_error(const SSL *ssl, int ret);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fISSL_get_error()\fR returns a result code (suitable for the C \*(L"switch\*(R"
statement) for a preceding call to \fISSL_connect()\fR, \fISSL_accept()\fR, \fISSL_do_handshake()\fR,
\&\fISSL_read()\fR, \fISSL_peek()\fR, or \fISSL_write()\fR on \fBssl\fR.  The value returned by
that \s-1TLS/SSL\s0 I/O function must be passed to \fISSL_get_error()\fR in parameter
\&\fBret\fR.
.PP
In addition to \fBssl\fR and \fBret\fR, \fISSL_get_error()\fR inspects the
current thread's OpenSSL error queue.  Thus, \fISSL_get_error()\fR must be
used in the same thread that performed the \s-1TLS/SSL\s0 I/O operation, and no
other OpenSSL function calls should appear in between.  The current
thread's error queue must be empty before the \s-1TLS/SSL\s0 I/O operation is
attempted, or \fISSL_get_error()\fR will not work reliably.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
The following return values can currently occur:
.IP "\s-1SSL_ERROR_NONE\s0" 4
.IX Item "SSL_ERROR_NONE"
The \s-1TLS/SSL\s0 I/O operation completed.  This result code is returned
if and only if \fBret > 0\fR.
.IP "\s-1SSL_ERROR_ZERO_RETURN\s0" 4
.IX Item "SSL_ERROR_ZERO_RETURN"
The \s-1TLS/SSL\s0 connection has been closed.  If the protocol version is \s-1SSL\s0 3.0
or \s-1TLS\s0 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 \fB\s-1SSL_ERROR_ZERO_RETURN\s0\fR
does not necessarily indicate that the underlying transport
has been closed.
.IP "\s-1SSL_ERROR_WANT_READ\s0, \s-1SSL_ERROR_WANT_WRITE\s0" 4
.IX Item "SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE"
The operation did not complete; the same \s-1TLS/SSL\s0 I/O function should be
called again later.  If, by then, the underlying \fB\s-1BIO\s0\fR has data
available for reading (if the result code is \fB\s-1SSL_ERROR_WANT_READ\s0\fR)
or allows writing data (\fB\s-1SSL_ERROR_WANT_WRITE\s0\fR), then some \s-1TLS/SSL\s0
protocol progress will take place, i.e. at least part of an \s-1TLS/SSL\s0
record will be read or written.  Note that the retry may again lead to
a \fB\s-1SSL_ERROR_WANT_READ\s0\fR or \fB\s-1SSL_ERROR_WANT_WRITE\s0\fR condition.
There is no fixed upper limit for the number of iterations that
may be necessary until progress becomes visible at application
protocol level.
.Sp
For socket \fB\s-1BIO\s0\fRs (e.g. when \fISSL_set_fd()\fR was used), \fIselect()\fR or
\&\fIpoll()\fR on the underlying socket can be used to find out when the
\&\s-1TLS/SSL\s0 I/O function should be retried.
.Sp
Caveat: Any \s-1TLS/SSL\s0 I/O function can lead to either of
\&\fB\s-1SSL_ERROR_WANT_READ\s0\fR and \fB\s-1SSL_ERROR_WANT_WRITE\s0\fR.  In particular,
\&\fISSL_read()\fR or \fISSL_peek()\fR may want to write data and \fISSL_write()\fR may want
to read data.  This is mainly because \s-1TLS/SSL\s0 handshakes may occur at any
time during the protocol (initiated by either the client or the server);
\&\fISSL_read()\fR, \fISSL_peek()\fR, and \fISSL_write()\fR will handle any pending handshakes.
.IP "\s-1SSL_ERROR_WANT_CONNECT\s0, \s-1SSL_ERROR_WANT_ACCEPT\s0" 4
.IX Item "SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT"
The operation did not complete; the same \s-1TLS/SSL\s0 I/O function should be
called again later. The underlying \s-1BIO\s0 was not connected yet to the peer
and the call would block in \fIconnect()\fR/\fIaccept()\fR. The \s-1SSL\s0 function should be
called again when the connection is established. These messages can only
appear with a \fIBIO_s_connect()\fR or \fIBIO_s_accept()\fR \s-1BIO\s0, respectively.
In order to find out, when the connection has been successfully established,
on many platforms \fIselect()\fR or \fIpoll()\fR for writing on the socket file descriptor
can be used.
.IP "\s-1SSL_ERROR_WANT_X509_LOOKUP\s0" 4
.IX Item "SSL_ERROR_WANT_X509_LOOKUP"
The operation did not complete because an application callback set by
\&\fISSL_CTX_set_client_cert_cb()\fR has asked to be called again.
The \s-1TLS/SSL\s0 I/O function should be called again later.
Details depend on the application.
.IP "\s-1SSL_ERROR_SYSCALL\s0" 4
.IX 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. \fIERR_get_error()\fR returns 0), \fBret\fR can be used to find out more
about the error: If \fBret == 0\fR, an \s-1EOF\s0 was observed that violates
the protocol.  If \fBret == \-1\fR, the underlying \fB\s-1BIO\s0\fR reported an
I/O error (for socket I/O on Unix systems, consult \fBerrno\fR for details).
.IP "\s-1SSL_ERROR_SSL\s0" 4
.IX Item "SSL_ERROR_SSL"
A failure in the \s-1SSL\s0 library occurred, usually a protocol error.  The
OpenSSL error queue contains more information on the error.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fIssl\fR\|(3), \fIerr\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\fISSL_get_error()\fR was added in SSLeay 0.8.