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    Command:

    SSL_shutdown

    
    
    

    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 shutdown procedure consists of 2 steps: the sending of the "close
           notify" shutdown alert and the reception of the peer's "close notify"
           shutdown alert. According to the TLS standard, it is acceptable for an
           application to only send its shutdown alert and then close the
           underlying connection without waiting for the peer's response (this way
           resources can be saved, as the process can already terminate or serve
           another connection).  When the underlying connection shall be used for
           more communications, the complete shutdown procedure (bidirectional
           "close notify" alerts) must be performed, so that the peers stay
           synchronized.
    
           SSL_shutdown() supports both uni- and bidirectional shutdown by its 2
           step behaviour.
    
           When the application is the first party to send the "close notify"
           alert, SSL_shutdown() will only send the alert and then set the
           SSL_SENT_SHUTDOWN flag (so that the session is considered good and will
           be kept in cache). SSL_shutdown() will then return with 0. If a
           unidirectional shutdown is enough (the underlying connection shall be
           closed anyway), this first call to SSL_shutdown() is sufficient. In
           order to complete the bidirectional shutdown handshake, SSL_shutdown()
           must be called again. The second call will make SSL_shutdown() wait for
           the peer's "close notify" shutdown alert. On success, the second call
           to SSL_shutdown() will return with 1.
           If the peer already sent the "close notify" alert and it was already
           processed implicitly inside another function (SSL_read(3)), the
           SSL_RECEIVED_SHUTDOWN flag is set. SSL_shutdown() will send the "close
           notify" alert, set the SSL_SENT_SHUTDOWN flag and will immediately
           return with 1. Whether SSL_RECEIVED_SHUTDOWN is already set can be
           checked using the SSL_get_shutdown() (see also SSL_set_shutdown(3)
           call.
    
           It is therefore recommended, to check the return value of
           SSL_shutdown() and call SSL_shutdown() again, if the bidirectional
           shutdown is not yet complete (return value of the first call is 0). As
           the shutdown is not specially handled in the SSLv2 protocol,
           SSL_shutdown() will succeed on the first call.
           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.
    
           SSL_shutdown() can be modified to only set the connection to "shutdown"
           state but not actually send the "close notify" alert messages, see
           SSL_CTX_set_quiet_shutdown(3).  When "quiet shutdown" is enabled,
           SSL_shutdown() will always succeed and return 1.
    
    
    

    RETURN VALUES

           The following return values can occur:
    
           0   The shutdown is not yet finished. Call SSL_shutdown() for a second
               time, if a bidirectional shutdown shall be performed.  The output
               of SSL_get_error(3) may be misleading, as an erroneous
               SSL_ERROR_SYSCALL may be flagged even though no error occurred.
    
           1   The shutdown was successfully completed. The "close notify" alert
               was sent and the peer's "close notify" alert was received.
    
           -1  The shutdown was not successful because a fatal error occurred
               either at the protocol level or a connection failure occurred. It
               can also occur if action is need to continue the operation for non-
               blocking BIOs.  Call SSL_get_error(3) 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_CTX_set_quiet_shutdown(3), SSL_clear(3), SSL_free(3), ssl(3),
           bio(3)
    
    
    

    1.0.1e 2016-01-07 SSL_shutdown(3)

    
    
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