5 SSL_get_error - obtain result code for TLS/SSL I/O operation
9 #include <openssl/ssl.h>
11 int SSL_get_error(const SSL *ssl, int ret);
15 SSL_get_error() returns a result code (suitable for the C "switch"
16 statement) for a preceding call to SSL_connect(), SSL_accept(), SSL_do_handshake(),
17 SSL_read(), SSL_peek(), or SSL_write() on B<ssl>. The value returned by
18 that TLS/SSL I/O function must be passed to SSL_get_error() in parameter
21 In addition to B<ssl> and B<ret>, SSL_get_error() inspects the
22 current thread's OpenSSL error queue. Thus, SSL_get_error() must be
23 used in the same thread that performed the TLS/SSL I/O operation, and no
24 other OpenSSL function calls should appear in between. The current
25 thread's error queue must be empty before the TLS/SSL I/O operation is
26 attempted, or SSL_get_error() will not work reliably.
30 The following return values can currently occur:
36 The TLS/SSL I/O operation completed. This result code is returned
37 if and only if B<ret E<gt> 0>.
39 =item SSL_ERROR_ZERO_RETURN
41 The TLS/SSL connection has been closed.
42 If the protocol version is SSL 3.0 or higher, this result code is returned only
43 if a closure alert has occurred in the protocol, i.e. if the connection has been
45 Note that in this case B<SSL_ERROR_ZERO_RETURN> does not necessarily
46 indicate that the underlying transport has been closed.
49 =item SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE
51 The operation did not complete; the same TLS/SSL I/O function should be
52 called again later. If, by then, the underlying B<BIO> has data
53 available for reading (if the result code is B<SSL_ERROR_WANT_READ>)
54 or allows writing data (B<SSL_ERROR_WANT_WRITE>), then some TLS/SSL
55 protocol progress will take place, i.e. at least part of an TLS/SSL
56 record will be read or written. Note that the retry may again lead to
57 a B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE> condition.
58 There is no fixed upper limit for the number of iterations that
59 may be necessary until progress becomes visible at application
62 For socket B<BIO>s (e.g. when SSL_set_fd() was used), select() or
63 poll() on the underlying socket can be used to find out when the
64 TLS/SSL I/O function should be retried.
66 Caveat: Any TLS/SSL I/O function can lead to either of
67 B<SSL_ERROR_WANT_READ> and B<SSL_ERROR_WANT_WRITE>. In particular,
68 SSL_read() or SSL_peek() may want to write data and SSL_write() may want
69 to read data. This is mainly because TLS/SSL handshakes may occur at any
70 time during the protocol (initiated by either the client or the server);
71 SSL_read(), SSL_peek(), and SSL_write() will handle any pending handshakes.
73 =item SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT
75 The operation did not complete; the same TLS/SSL I/O function should be
76 called again later. The underlying BIO was not connected yet to the peer
77 and the call would block in connect()/accept(). The SSL function should be
78 called again when the connection is established. These messages can only
79 appear with a BIO_s_connect() or BIO_s_accept() BIO, respectively.
80 In order to find out, when the connection has been successfully established,
81 on many platforms select() or poll() for writing on the socket file descriptor
84 =item SSL_ERROR_WANT_X509_LOOKUP
86 The operation did not complete because an application callback set by
87 SSL_CTX_set_client_cert_cb() has asked to be called again.
88 The TLS/SSL I/O function should be called again later.
89 Details depend on the application.
91 =item SSL_ERROR_SYSCALL
93 Some non-recoverable I/O error occurred.
94 The OpenSSL error queue may contain more information on the error.
95 For socket I/O on Unix systems, consult B<errno> for details.
99 A failure in the SSL library occurred, usually a protocol error. The
100 OpenSSL error queue contains more information on the error.
106 L<ssl(3)|ssl(3)>, L<err(3)|err(3)>
110 SSL_get_error() was added in SSLeay 0.8.