1=pod 2 3=head1 NAME 4 5SSL_get_error - obtain result code for TLS/SSL I/O operation 6 7=head1 SYNOPSIS 8 9 #include <openssl/ssl.h> 10 11 int SSL_get_error(const SSL *ssl, int ret); 12 13=head1 DESCRIPTION 14 15SSL_get_error() returns a result code (suitable for the C "switch" 16statement) for a preceding call to SSL_connect(), SSL_accept(), SSL_do_handshake(), 17SSL_read(), SSL_peek(), or SSL_write() on B<ssl>. The value returned by 18that TLS/SSL I/O function must be passed to SSL_get_error() in parameter 19B<ret>. 20 21In addition to B<ssl> and B<ret>, SSL_get_error() inspects the 22current thread's OpenSSL error queue. Thus, SSL_get_error() must be 23used in the same thread that performed the TLS/SSL I/O operation, and no 24other OpenSSL function calls should appear in between. The current 25thread's error queue must be empty before the TLS/SSL I/O operation is 26attempted, or SSL_get_error() will not work reliably. 27 28=head1 RETURN VALUES 29 30The following return values can currently occur: 31 32=over 4 33 34=item SSL_ERROR_NONE 35 36The TLS/SSL I/O operation completed. This result code is returned 37if and only if B<ret E<gt> 0>. 38 39=item SSL_ERROR_ZERO_RETURN 40 41The TLS/SSL connection has been closed. If the protocol version is SSL 3.0 42or TLS 1.0, this result code is returned only if a closure 43alert has occurred in the protocol, i.e. if the connection has been 44closed cleanly. Note that in this case B<SSL_ERROR_ZERO_RETURN> 45does not necessarily indicate that the underlying transport 46has been closed. 47 48=item SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE 49 50The operation did not complete; the same TLS/SSL I/O function should be 51called again later. If, by then, the underlying B<BIO> has data 52available for reading (if the result code is B<SSL_ERROR_WANT_READ>) 53or allows writing data (B<SSL_ERROR_WANT_WRITE>), then some TLS/SSL 54protocol progress will take place, i.e. at least part of an TLS/SSL 55record will be read or written. Note that the retry may again lead to 56a B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE> condition. 57There is no fixed upper limit for the number of iterations that 58may be necessary until progress becomes visible at application 59protocol level. 60 61For socket B<BIO>s (e.g. when SSL_set_fd() was used), select() or 62poll() on the underlying socket can be used to find out when the 63TLS/SSL I/O function should be retried. 64 65Caveat: Any TLS/SSL I/O function can lead to either of 66B<SSL_ERROR_WANT_READ> and B<SSL_ERROR_WANT_WRITE>. In particular, 67SSL_read() or SSL_peek() may want to write data and SSL_write() may want 68to read data. This is mainly because TLS/SSL handshakes may occur at any 69time during the protocol (initiated by either the client or the server); 70SSL_read(), SSL_peek(), and SSL_write() will handle any pending handshakes. 71 72=item SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT 73 74The operation did not complete; the same TLS/SSL I/O function should be 75called again later. The underlying BIO was not connected yet to the peer 76and the call would block in connect()/accept(). The SSL function should be 77called again when the connection is established. These messages can only 78appear with a BIO_s_connect() or BIO_s_accept() BIO, respectively. 79In order to find out, when the connection has been successfully established, 80on many platforms select() or poll() for writing on the socket file descriptor 81can be used. 82 83=item SSL_ERROR_WANT_X509_LOOKUP 84 85The operation did not complete because an application callback set by 86SSL_CTX_set_client_cert_cb() has asked to be called again. 87The TLS/SSL I/O function should be called again later. 88Details depend on the application. 89 90=item SSL_ERROR_SYSCALL 91 92Some I/O error occurred. The OpenSSL error queue may contain more 93information on the error. If the error queue is empty 94(i.e. ERR_get_error() returns 0), B<ret> can be used to find out more 95about the error: If B<ret == 0>, an EOF was observed that violates 96the protocol. If B<ret == -1>, the underlying B<BIO> reported an 97I/O error (for socket I/O on Unix systems, consult B<errno> for details). 98 99=item SSL_ERROR_SSL 100 101A failure in the SSL library occurred, usually a protocol error. The 102OpenSSL error queue contains more information on the error. 103 104=back 105 106=head1 SEE ALSO 107 108L<ssl(3)|ssl(3)>, L<err(3)|err(3)> 109 110=head1 HISTORY 111 112SSL_get_error() was added in SSLeay 0.8. 113 114=cut 115