fc5ecaddd0
While stereotyped repetitions are frowned upon in literature, they serve a useful purpose in manual pages, because it is easier for the user to find certain information if it is always presented in the same way. For that reason, this commit harmonizes the varying formulations in the HISTORY section about which functions, flags, etc. were added in which OpenSSL version. It also attempts to make the pod files more grep friendly by avoiding to insert line breaks between the symbol names and the corresponding version number in which they were introduced (wherever possible). Some punctuation and typographical errors were fixed on the way. Reviewed-by: Tim Hudson <tjh@openssl.org> (Merged from https://github.com/openssl/openssl/pull/7854)
155 lines
5.6 KiB
Text
155 lines
5.6 KiB
Text
=pod
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=head1 NAME
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SSL_CTX_set_mode, SSL_CTX_clear_mode, SSL_set_mode, SSL_clear_mode, SSL_CTX_get_mode, SSL_get_mode - manipulate SSL engine mode
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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long SSL_CTX_set_mode(SSL_CTX *ctx, long mode);
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long SSL_CTX_clear_mode(SSL_CTX *ctx, long mode);
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long SSL_set_mode(SSL *ssl, long mode);
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long SSL_clear_mode(SSL *ssl, long mode);
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long SSL_CTX_get_mode(SSL_CTX *ctx);
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long SSL_get_mode(SSL *ssl);
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=head1 DESCRIPTION
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SSL_CTX_set_mode() adds the mode set via bitmask in B<mode> to B<ctx>.
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Options already set before are not cleared.
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SSL_CTX_clear_mode() removes the mode set via bitmask in B<mode> from B<ctx>.
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SSL_set_mode() adds the mode set via bitmask in B<mode> to B<ssl>.
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Options already set before are not cleared.
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SSL_clear_mode() removes the mode set via bitmask in B<mode> from B<ssl>.
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SSL_CTX_get_mode() returns the mode set for B<ctx>.
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SSL_get_mode() returns the mode set for B<ssl>.
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=head1 NOTES
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The following mode changes are available:
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=over 4
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=item SSL_MODE_ENABLE_PARTIAL_WRITE
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Allow SSL_write_ex(..., n, &r) to return with 0 < r < n (i.e. report success
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when just a single record has been written). This works in a similar way for
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SSL_write(). When not set (the default), SSL_write_ex() or SSL_write() will only
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report success once the complete chunk was written. Once SSL_write_ex() or
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SSL_write() returns successful, B<r> bytes have been written and the next call
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to SSL_write_ex() or SSL_write() must only send the n-r bytes left, imitating
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the behaviour of write().
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=item SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER
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Make it possible to retry SSL_write_ex() or SSL_write() with changed buffer
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location (the buffer contents must stay the same). This is not the default to
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avoid the misconception that non-blocking SSL_write() behaves like
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non-blocking write().
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=item SSL_MODE_AUTO_RETRY
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During normal operations, non-application data records might need to be sent or
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received that the application is not aware of.
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If a non-application data record was processed,
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L<SSL_read_ex(3)> and L<SSL_read(3)> can return with a failure and indicate the
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need to retry with B<SSL_ERROR_WANT_READ>.
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If such a non-application data record was processed, the flag
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B<SSL_MODE_AUTO_RETRY> causes it to try to process the next record instead of
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returning.
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In a non-blocking environment applications must be prepared to handle
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incomplete read/write operations.
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Setting B<SSL_MODE_AUTO_RETRY> for a non-blocking B<BIO> will process
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non-application data records until either no more data is available or
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an application data record has been processed.
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In a blocking environment, applications are not always prepared to
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deal with the functions returning intermediate reports such as retry
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requests, and setting the B<SSL_MODE_AUTO_RETRY> flag will cause the functions
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to only return after successfully processing an application data record or a
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failure.
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Turning off B<SSL_MODE_AUTO_RETRY> can be useful with blocking B<BIO>s in case
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they are used in combination with something like select() or poll().
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Otherwise the call to SSL_read() or SSL_read_ex() might hang when a
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non-application record was sent and no application data was sent.
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=item SSL_MODE_RELEASE_BUFFERS
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When we no longer need a read buffer or a write buffer for a given SSL,
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then release the memory we were using to hold it.
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Using this flag can
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save around 34k per idle SSL connection.
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This flag has no effect on SSL v2 connections, or on DTLS connections.
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=item SSL_MODE_SEND_FALLBACK_SCSV
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Send TLS_FALLBACK_SCSV in the ClientHello.
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To be set only by applications that reconnect with a downgraded protocol
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version; see draft-ietf-tls-downgrade-scsv-00 for details.
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DO NOT ENABLE THIS if your application attempts a normal handshake.
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Only use this in explicit fallback retries, following the guidance
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in draft-ietf-tls-downgrade-scsv-00.
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=item SSL_MODE_ASYNC
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Enable asynchronous processing. TLS I/O operations may indicate a retry with
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SSL_ERROR_WANT_ASYNC with this mode set if an asynchronous capable engine is
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used to perform cryptographic operations. See L<SSL_get_error(3)>.
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=item SSL_MODE_NO_KTLS_TX
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Disable the use of the kernel TLS egress data-path.
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By default kernel TLS is enabled if it is supported by the negotiated ciphersuites
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and extensions and OpenSSL has been compiled with support for it.
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The kernel TLS data-path implements the record layer,
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and the crypto algorithm. The kernel will utilize the best hardware
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available for crypto. Using the kernel data-path should reduce the memory
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footprint of OpenSSL because no buffering is required. Also, the throughput
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should improve because data copy is avoided when user data is encrypted into
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kernel memory instead of the usual encrypt than copy to kernel.
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Kernel TLS might not support all the features of OpenSSL. For instance,
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renegotiation, and setting the maximum fragment size is not possible as of
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Linux 4.20.
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=back
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All modes are off by default except for SSL_MODE_AUTO_RETRY which is on by
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default since 1.1.1.
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=head1 RETURN VALUES
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SSL_CTX_set_mode() and SSL_set_mode() return the new mode bitmask
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after adding B<mode>.
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SSL_CTX_get_mode() and SSL_get_mode() return the current bitmask.
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=head1 SEE ALSO
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L<ssl(7)>, L<SSL_read_ex(3)>, L<SSL_read(3)>, L<SSL_write_ex(3)> or
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L<SSL_write(3)>, L<SSL_get_error(3)>
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=head1 HISTORY
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SSL_MODE_ASYNC was added in OpenSSL 1.1.0.
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SSL_MODE_NO_KTLS_TX was added in OpenSSL 3.0.0.
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=head1 COPYRIGHT
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Copyright 2001-2018 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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