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.\"
.IX Title "SSL_get_error 3"
.TH SSL_get_error 3 2019-12-20 1.0.2u OpenSSL
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH NAME
SSL_get_error \- obtain result code for TLS/SSL I/O operation
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/ssl.h>
\&
\& int SSL_get_error(const SSL *ssl, int ret);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\fBSSL_get_error()\fR returns a result code (suitable for the C "switch"
statement) for a preceding call to \fBSSL_connect()\fR, \fBSSL_accept()\fR, \fBSSL_do_handshake()\fR,
\&\fBSSL_read()\fR, \fBSSL_peek()\fR, or \fBSSL_write()\fR on \fBssl\fR.  The value returned by
that TLS/SSL I/O function must be passed to \fBSSL_get_error()\fR in parameter
\&\fBret\fR.
.PP
In addition to \fBssl\fR and \fBret\fR, \fBSSL_get_error()\fR inspects the
current thread's OpenSSL error queue.  Thus, \fBSSL_get_error()\fR 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 \fBSSL_get_error()\fR will not work reliably.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
The following return values can currently occur:
.IP SSL_ERROR_NONE 4
.IX Item "SSL_ERROR_NONE"
The TLS/SSL I/O operation completed.  This result code is returned
if and only if \fBret > 0\fR.
.IP SSL_ERROR_ZERO_RETURN 4
.IX 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 \fBSSL_ERROR_ZERO_RETURN\fR does not necessarily
indicate that the underlying transport has been closed.
.IP "SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE" 4
.IX 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 \fBBIO\fR has data
available for reading (if the result code is \fBSSL_ERROR_WANT_READ\fR)
or allows writing data (\fBSSL_ERROR_WANT_WRITE\fR), 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 \fBSSL_ERROR_WANT_READ\fR or \fBSSL_ERROR_WANT_WRITE\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 \fBBIO\fRs (e.g. when \fBSSL_set_fd()\fR was used), \fBselect()\fR or
\&\fBpoll()\fR on the underlying socket can be used to find out when the
TLS/SSL I/O function should be retried.
.Sp
Caveat: Any TLS/SSL I/O function can lead to either of
\&\fBSSL_ERROR_WANT_READ\fR and \fBSSL_ERROR_WANT_WRITE\fR.  In particular,
\&\fBSSL_read()\fR or \fBSSL_peek()\fR may want to write data and \fBSSL_write()\fR 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);
\&\fBSSL_read()\fR, \fBSSL_peek()\fR, and \fBSSL_write()\fR will handle any pending handshakes.
.IP "SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT" 4
.IX 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 \fBconnect()\fR/\fBaccept()\fR. The SSL function should be
called again when the connection is established. These messages can only
appear with a \fBBIO_s_connect()\fR or \fBBIO_s_accept()\fR BIO, respectively.
In order to find out, when the connection has been successfully established,
on many platforms \fBselect()\fR or \fBpoll()\fR for writing on the socket file descriptor
can be used.
.IP SSL_ERROR_WANT_X509_LOOKUP 4
.IX Item "SSL_ERROR_WANT_X509_LOOKUP"
The operation did not complete because an application callback set by
\&\fBSSL_CTX_set_client_cert_cb()\fR has asked to be called again.
The TLS/SSL I/O function should be called again later.
Details depend on the application.
.IP SSL_ERROR_SYSCALL 4
.IX 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
\&\fBerrno\fR for details. If this error occurs then no further I/O operations should
be performed on the connection and \fBSSL_shutdown()\fR must not be called.
.IP SSL_ERROR_SSL 4
.IX 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 \fBSSL_shutdown()\fR must not be called.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBssl\fR\|(3), \fBerr\fR\|(3)
.SH HISTORY
.IX Header "HISTORY"
\&\fBSSL_get_error()\fR was added in SSLeay 0.8.