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NAMESSL_get_error - obtain result code for TLS/SSL I/O operation
#include <openssl/ssl.h> int SSL_get_error(const SSL *ssl, int ret);
DESCRIPTIONSSL_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 ssl. The value returned by that
TLS/SSL I/Ofunction must be passed to SSL_get_error() in parameter ret.
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
TLS/SSL I/Ooperation, and no other OpenSSL function calls should appear in between. The current thread's error queue must be empty before the
TLS/SSL I/Ooperation is attempted, or SSL_get_error() will not work reliably.
RETURN VALUESThe following return values can currently occur:
The TLS/SSL I/Ooperation completed. This result code is returned if and only if ret > 0.
The TLS/SSLconnection has been closed. If the protocol version isSSL 3.0orTLS 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 caseSSL_ERROR_ZERO_RETURNdoes not necessarily indicate that the underlying transport has been closed.
- SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE
The operation did not complete; the same TLS/SSL I/Ofunction should be called again later. If, by then, the underlyingBIOhas data available for reading (if the result code isSSL_ERROR_WANT_READ) or allows writing data (SSL_ERROR_WANT_WRITE), then someTLS/SSLprotocol progress will take place, i.e. at least part of anTLS/SSLrecord will be read or written. Note that the retry may again lead to aSSL_ERROR_WANT_READorSSL_ERROR_WANT_WRITEcondition. There is no fixed upper limit for the number of iterations that may be necessary until progress becomes visible at application protocol level.
For socketBIOs (e.g. when SSL_set_fd() was used), select() or poll() on the underlying socket can be used to find out when theTLS/SSL I/Ofunction should be retried.
Caveat: AnyTLS/SSL I/Ofunction can lead to either ofSSL_ERROR_WANT_READandSSL_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 becauseTLS/SSLhandshakes 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.
- SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT
The operation did not complete; the same TLS/SSL I/Ofunction should be called again later. The underlyingBIOwas not connected yet to the peer and the call would block in connect()/accept(). TheSSLfunction 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.
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/Ofunction should be called again later. Details depend on the application.
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 EOFwas observed that violates the protocol. If ret == -1, the underlyingBIOreported an I/O error (for socket I/O on Unix systems, consult errno for details).
A failure in the SSLlibrary occurred, usually a protocol error. The OpenSSL error queue contains more information on the error.