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SSL_CTX_SET_SPLIT_SEND_FRAGMENT(3)  OpenSSL SSL_CTX_SET_SPLIT_SEND_FRAGMENT(3)
NAME
       SSL_CTX_set_max_send_fragment, SSL_set_max_send_fragment,
       SSL_CTX_set_split_send_fragment, SSL_set_split_send_fragment,
       SSL_CTX_set_max_pipelines, SSL_set_max_pipelines,
       SSL_CTX_set_default_read_buffer_len, SSL_set_default_read_buffer_len,
       SSL_CTX_set_tlsext_max_fragment_length,
       SSL_set_tlsext_max_fragment_length, SSL_SESSION_get_max_fragment_length
       - Control fragment size settings and pipelining operations
SYNOPSIS
        #include <openssl/ssl.h>
        long SSL_CTX_set_max_send_fragment(SSL_CTX *ctx, long);
        long SSL_set_max_send_fragment(SSL *ssl, long m);
        long SSL_CTX_set_max_pipelines(SSL_CTX *ctx, long m);
        long SSL_set_max_pipelines(SSL_CTX *ssl, long m);
        long SSL_CTX_set_split_send_fragment(SSL_CTX *ctx, long m);
        long SSL_set_split_send_fragment(SSL *ssl, long m);
        void SSL_CTX_set_default_read_buffer_len(SSL_CTX *ctx, size_t len);
        void SSL_set_default_read_buffer_len(SSL *s, size_t len);
        int SSL_CTX_set_tlsext_max_fragment_length(SSL_CTX *ctx, uint8_t mode);
        int SSL_set_tlsext_max_fragment_length(SSL *ssl, uint8_t mode);
        uint8_t SSL_SESSION_get_max_fragment_length(SSL_SESSION *session);
DESCRIPTION
       Some engines are able to process multiple simultaneous crypto
       operations. This capability could be utilised to parallelise the
       processing of a single connection. For example a single write can be
       split into multiple records and each one encrypted independently and in
       parallel. Note: this will only work in TLS1.1+. There is no support in
       SSLv3, TLSv1.0 or DTLS (any version). This capability is known as
       "pipelining" within OpenSSL.
       In order to benefit from the pipelining capability. You need to have an
       engine that provides ciphers that support this. The OpenSSL "dasync"
       engine provides AES128-SHA based ciphers that have this capability.
       However, these are for development and test purposes only.
       SSL_CTX_set_max_send_fragment() and SSL_set_max_send_fragment() set the
       max_send_fragment parameter for SSL_CTX and SSL objects respectively.
       This value restricts the amount of plaintext bytes that will be sent in
       any one SSL/TLS record. By default its value is
       SSL3_RT_MAX_PLAIN_LENGTH (16384). These functions will only accept a
       value in the range 512 - SSL3_RT_MAX_PLAIN_LENGTH.
       SSL_CTX_set_max_pipelines() and SSL_set_max_pipelines() set the maximum
       number of pipelines that will be used at any one time. This value
       applies to both "read" pipelining and "write" pipelining. By default
       only one pipeline will be used (i.e. normal non-parallel operation).
       The number of pipelines set must be in the range 1 - SSL_MAX_PIPELINES
       (32). Setting this to a value > 1 will also automatically turn on
       "read_ahead" (see SSL_CTX_set_read_ahead(3)). This is explained further
       below. OpenSSL will only every use more than one pipeline if a cipher
       suite is negotiated that uses a pipeline capable cipher provided by an
       engine.
       Pipelining operates slightly differently for reading encrypted data
       compared to writing encrypted data. SSL_CTX_set_split_send_fragment()
       and SSL_set_split_send_fragment() define how data is split up into
       pipelines when writing encrypted data. The number of pipelines used
       will be determined by the amount of data provided to the SSL_write_ex()
       or SSL_write() call divided by split_send_fragment.
       For example if split_send_fragment is set to 2000 and max_pipelines is
       4 then:
       SSL_write/SSL_write_ex called with 0-2000 bytes == 1 pipeline used
       SSL_write/SSL_write_ex called with 2001-4000 bytes == 2 pipelines used
       SSL_write/SSL_write_ex called with 4001-6000 bytes == 3 pipelines used
       SSL_write/SSL_write_ex called with 6001+ bytes == 4 pipelines used
       split_send_fragment must always be less than or equal to
       max_send_fragment. By default it is set to be equal to
       max_send_fragment.  This will mean that the same number of records will
       always be created as would have been created in the non-parallel case,
       although the data will be apportioned differently. In the parallel case
       data will be spread equally between the pipelines.
       Read pipelining is controlled in a slightly different way than with
       write pipelining. While reading we are constrained by the number of
       records that the peer (and the network) can provide to us in one go.
       The more records we can get in one go the more opportunity we have to
       parallelise the processing. As noted above when setting max_pipelines
       to a value greater than one, read_ahead is automatically set. The
       read_ahead parameter causes OpenSSL to attempt to read as much data
       into the read buffer as the network can provide and will fit into the
       buffer. Without this set data is read into the read buffer one record
       at a time. The more data that can be read, the more opportunity there
       is for parallelising the processing at the cost of increased memory
       overhead per connection. Setting read_ahead can impact the behaviour of
       the SSL_pending() function (see SSL_pending(3)).
       The SSL_CTX_set_default_read_buffer_len() and
       SSL_set_default_read_buffer_len() functions control the size of the
       read buffer that will be used. The len parameter sets the size of the
       buffer. The value will only be used if it is greater than the default
       that would have been used anyway. The normal default value depends on a
       number of factors but it will be at least SSL3_RT_MAX_PLAIN_LENGTH +
       SSL3_RT_MAX_ENCRYPTED_OVERHEAD (16704) bytes.
       SSL_CTX_set_tlsext_max_fragment_length() sets the default maximum
       fragment length negotiation mode via value mode to ctx.  This setting
       affects only SSL instances created after this function is called.  It
       affects the client-side as only its side may initiate this extension
       use.
       SSL_set_tlsext_max_fragment_length() sets the maximum fragment length
       negotiation mode via value mode to ssl.  This setting will be used
       during a handshake when extensions are exchanged between client and
       server.  So it only affects SSL sessions created after this function is
       called.  It affects the client-side as only its side may initiate this
       extension use.
       SSL_SESSION_get_max_fragment_length() gets the maximum fragment length
       negotiated in session.
RETURN VALUES
       All non-void functions return 1 on success and 0 on failure.
NOTES
       The Maximum Fragment Length extension support is optional on the server
       side.  If the server does not support this extension then
       SSL_SESSION_get_max_fragment_length() will return:
       TLSEXT_max_fragment_length_DISABLED.
       The following modes are available:
       TLSEXT_max_fragment_length_DISABLED
           Disables Maximum Fragment Length Negotiation (default).
       TLSEXT_max_fragment_length_512
           Sets Maximum Fragment Length to 512 bytes.
       TLSEXT_max_fragment_length_1024
           Sets Maximum Fragment Length to 1024.
       TLSEXT_max_fragment_length_2048
           Sets Maximum Fragment Length to 2048.
       TLSEXT_max_fragment_length_4096
           Sets Maximum Fragment Length to 4096.
       With the exception of SSL_CTX_set_default_read_buffer_len()
       SSL_set_default_read_buffer_len(),
       SSL_CTX_set_tlsext_max_fragment_length(),
       SSL_set_tlsext_max_fragment_length() and
       SSL_SESSION_get_max_fragment_length() all these functions are
       implemented using macros.
SEE ALSO
       SSL_CTX_set_read_ahead(3), SSL_pending(3)
HISTORY
       The SSL_CTX_set_max_pipelines(), SSL_set_max_pipelines(),
       SSL_CTX_set_split_send_fragment(), SSL_set_split_send_fragment(),
       SSL_CTX_set_default_read_buffer_len() and
       SSL_set_default_read_buffer_len() functions were added in OpenSSL
       1.1.0.
       The SSL_CTX_set_tlsext_max_fragment_length(),
       SSL_set_tlsext_max_fragment_length() and
       SSL_SESSION_get_max_fragment_length() functions were added in OpenSSL
       1.1.1.
COPYRIGHT
       Copyright 2016-2020 The OpenSSL Project Authors. All Rights Reserved.
       Licensed under the OpenSSL license (the "License").  You may not use
       this file except in compliance with the License.  You can obtain a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>;.
1.1.1k                            2021-03-25SSL_CTX_SET_SPLIT_SEND_FRAGMENT(3)