/usr/man/cat.3/SSL_CTX_set_mode.3

SSL_CTX_set_mode(3)          OpenSSL          SSL_CTX_set_mode(3)

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,

1.0.2t               Last change: 2019-09-10                    1

SSL_CTX_set_mode(3)          OpenSSL          SSL_CTX_set_mode(3)

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

         DO NOT ENABLE THIS if your application attempts a normal
         handshake.  Only use this in explicit fallback retries,
         following the guidance in
         draft-ietf-tls-downgrade-scsv-00.

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.

1.0.2t               Last change: 2019-09-10                    2

See also SSL_CTX_get_mode(3)
See also SSL_get_mode(3)
See also SSL_set_mode(3)