SSL_shutdown(3)

NAME
SSL_shutdown - shut down a TLS/SSL connection

SYNOPSIS

 #include <openssl/ssl.h>
 int SSL_shutdown(SSL *ssl);

DESCRIPTION
SSL_shutdown() shuts down an active TLS/SSL connection. It sends the "close notify" shutdown alert to the peer.

NOTES
SSL_shutdown() tries to send the "close notify" shutdown alert to the peer. Whether the operation succeeds or not, the SSL_SENT_SHUTDOWN flag is set and a currently open session is considered closed and good and will be kept in the session cache for further reuse.

The behaviour of SSL_shutdown() depends on the underlying BIO.

If the underlying BIO is blocking, SSL_shutdown() will only return once the handshake has been finished or an error occurred.

If the underlying BIO is non-blocking, SSL_shutdown() will also return when the underlying BIO could not satisfy the needs of SSL_shutdown() to continue the handshake. In this case a call to SSL_get_error() with the return value of SSL_shutdown() will yield SSL_ERROR_WANT_READ or SSL_ERROR_WANT_WRITE. The calling process then must repeat the call after taking appropriate action to satisfy the needs of SSL_shutdown(). The action depends on the underlying BIO. When using a non-blocking socket, nothing is to be done, but select() can be used to check for the required condition. When using a buffering BIO, like a BIO pair, data must be written into or retrieved out of the BIO before being able to continue.

RETURN VALUES
The following return values can occur: The shutdown was successfully completed. The shutdown was not successful. Call SSL_get_error() with the return value ret to find out the reason. The shutdown was not successful because a fatal error occurred either at the protocol level or a connection failure occurred. It can also occur of action is need to continue the operation for non-blocking BIOs. Call SSL_get_error() with the return value ret to find out the reason.

SEE ALSO
SSL_get_error(3), SSL_connect(3), SSL_accept(3), SSL_set_shutdown(3), SSL_clear ssl(3), bio(3)