NAME

       SSL_CTX_set_mode, SSL_set_mode, SSL_CTX_get_mode, SSL_get_mode - manipulate SSL engine
       mode

SYNOPSIS

        #include <openssl/ssl.h>

        long SSL_CTX_set_mode(SSL_CTX *ctx, long mode);
        long SSL_set_mode(SSL *ssl, long mode);

        long SSL_CTX_get_mode(SSL_CTX *ctx);
        long SSL_get_mode(SSL *ssl);

DESCRIPTION

       SSL_CTX_set_mode() adds the mode set via bitmask in mode to ctx.  Options already set
       before are not cleared.

       SSL_set_mode() adds the mode set via bitmask in mode to ssl.  Options already set before
       are not cleared.

       SSL_CTX_get_mode() returns the mode set for ctx.

       SSL_get_mode() returns the mode set for ssl.

NOTES

       The following mode changes are available:

       SSL_MODE_ENABLE_PARTIAL_WRITE
           Allow SSL_write(..., n) to return r with 0 < r < n (i.e. report success when just a
           single record has been written). When not set (the default), SSL_write() will only
           report success once the complete chunk was written.  Once SSL_write() returns with r,
           r bytes have been successfully written and the next call to SSL_write() must only send
           the n-r bytes left, imitating the behaviour of write().

       SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER
           Make it possible to retry SSL_write() with changed buffer location (the buffer
           contents must stay the same). This is not the default to avoid the misconception that
           non-blocking SSL_write() behaves like non-blocking write().

       SSL_MODE_AUTO_RETRY
           Never bother the application with retries if the transport is blocking.  If a
           renegotiation take place during normal operation, a SSL_read(3) or SSL_write(3) would
           return with -1 and indicate the need to retry with SSL_ERROR_WANT_READ.  In a non-
           blocking environment applications must be prepared to handle incomplete read/write
           operations.  In a blocking environment, applications are not always prepared to deal
           with read/write operations returning without success report. The flag
           SSL_MODE_AUTO_RETRY will cause read/write operations to only return after the
           handshake and successful completion.

       SSL_MODE_RELEASE_BUFFERS
           When we no longer need a read buffer or a write buffer for a given SSL, then release
           the memory we were using to hold it.  Released memory is either appended to a list of
           unused RAM chunks on the SSL_CTX, or simply freed if the list of unused chunks would
           become longer than SSL_CTX->freelist_max_len, which defaults to 32.  Using this flag
           can save around 34k per idle SSL connection.  This flag has no effect on SSL v2
           connections, or on DTLS connections.

       SSL_MODE_FALLBACK_SCSV
           Send TLS_FALLBACK_SCSV in the ClientHello.  To be set by applications that reconnect
           with a downgraded protocol version; see draft-ietf-tls-downgrade-scsv-00 for details.

RETURN VALUES

       SSL_CTX_set_mode() and SSL_set_mode() return the new mode bitmask after adding mode.

       SSL_CTX_get_mode() and SSL_get_mode() return the current bitmask.

SEE ALSO

       ssl(3), SSL_read(3), SSL_write(3)

HISTORY

       SSL_MODE_AUTO_RETRY as been added in OpenSSL 0.9.6.