SSL_get_error.3 revision 110655
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Title "SSL_get_error 3"
Mon Feb 3 10:02:29 2003
Standard preamble:
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\\$1
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\*(C' expand to `' in nroff, nothing in troff, for use with C<>
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For nroff, turn off justification. Always turn off hyphenation; it
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Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
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Title "SSL_get_error 3"
SSL_get_error 3 "0.9.7" "2003-02-03" "OpenSSL"
C "NAME"
SSL_get_error - obtain result code for \s-1TLS/SSL\s0 I/O operation
"SYNOPSIS"
Header "SYNOPSIS" .Vb 1
#include <openssl/ssl.h>
.Ve
.Vb 1
int SSL_get_error(SSL *ssl, int ret);
.Ve
"DESCRIPTION"
Header "DESCRIPTION" \fISSL_get_error() returns a result code (suitable for the C \*(L"switch\*(R"
statement) for a preceding call to SSL_connect(), SSL_accept(), SSL_do_handshake(),
\fISSL_read(), SSL_peek(), or SSL_write() on ssl. The value returned by
that \s-1TLS/SSL\s0 I/O function must be passed to SSL_get_error() in parameter
\fBret.
In addition to ssl and 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 \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 SSL_get_error() will not work reliably.
"RETURN VALUES"
Header "RETURN VALUES" The following return values can currently occur:
p "\s-1SSL_ERROR_NONE\s0" 4 Item "SSL_ERROR_NONE" The \s-1TLS/SSL\s0 I/O operation completed. This result code is returned
if and only if ret > 0.
p "\s-1SSL_ERROR_ZERO_RETURN\s0" 4 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 \s-1SSL_ERROR_ZERO_RETURN\s0
does not necessarily indicate that the underlying transport
has been closed.
p "\s-1SSL_ERROR_WANT_READ\s0, \s-1SSL_ERROR_WANT_WRITE\s0" 4 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 \s-1BIO\s0 has data
available for reading (if the result code is \s-1SSL_ERROR_WANT_READ\s0)
or allows writing data (\s-1SSL_ERROR_WANT_WRITE\s0), 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 \s-1SSL_ERROR_WANT_READ\s0 or \s-1SSL_ERROR_WANT_WRITE\s0 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 \s-1BIO\s0s (e.g. when SSL_set_fd() was used), select() or
\fIpoll() 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 and \s-1SSL_ERROR_WANT_WRITE\s0. In particular,
\fISSL_read() or SSL_peek() may want to write data and SSL_write() 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(), SSL_peek(), and SSL_write() will handle any pending handshakes.
p "\s-1SSL_ERROR_WANT_CONNECT\s0, \s-1SSL_ERROR_WANT_ACCEPT\s0" 4 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 connect()/accept(). The \s-1SSL\s0 function should be
called again when the connection is established. These messages can only
appear with a BIO_s_connect() or BIO_s_accept() \s-1BIO\s0, 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.
p "\s-1SSL_ERROR_WANT_X509_LOOKUP\s0" 4 Item "SSL_ERROR_WANT_X509_LOOKUP" The operation did not complete because an application callback set by
\fISSL_CTX_set_client_cert_cb() has asked to be called again.
The \s-1TLS/SSL\s0 I/O function should be called again later.
Details depend on the application.
p "\s-1SSL_ERROR_SYSCALL\s0" 4 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), ret can be used to find out more
about the error: If ret == 0, an \s-1EOF\s0 was observed that violates
the protocol. If ret == -1, the underlying \s-1BIO\s0 reported an
I/O error (for socket I/O on Unix systems, consult errno for details).
p "\s-1SSL_ERROR_SSL\s0" 4 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.
"SEE ALSO"
Header "SEE ALSO" ssl(3), err(3)
"HISTORY"
Header "HISTORY" \fISSL_get_error() was added in SSLeay 0.8.