| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl, BIO_reset,
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| 6 | BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close,
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| 7 | BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending,
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| 8 | BIO_get_info_callback, BIO_set_info_callback, BIO_info_cb, BIO_get_ktls_send,
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| 9 | BIO_get_ktls_recv
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| 10 | - BIO control operations
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| 11 |
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| 12 | =head1 SYNOPSIS
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| 13 |
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| 14 | #include <openssl/bio.h>
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| 15 |
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| 16 | typedef int BIO_info_cb(BIO *b, int state, int res);
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| 17 |
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| 18 | long BIO_ctrl(BIO *bp, int cmd, long larg, void *parg);
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| 19 | long BIO_callback_ctrl(BIO *b, int cmd, BIO_info_cb *cb);
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| 20 | void *BIO_ptr_ctrl(BIO *bp, int cmd, long larg);
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| 21 | long BIO_int_ctrl(BIO *bp, int cmd, long larg, int iarg);
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| 22 |
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| 23 | int BIO_reset(BIO *b);
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| 24 | int BIO_seek(BIO *b, int ofs);
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| 25 | int BIO_tell(BIO *b);
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| 26 | int BIO_flush(BIO *b);
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| 27 | int BIO_eof(BIO *b);
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| 28 | int BIO_set_close(BIO *b, long flag);
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| 29 | int BIO_get_close(BIO *b);
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| 30 | int BIO_pending(BIO *b);
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| 31 | int BIO_wpending(BIO *b);
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| 32 | size_t BIO_ctrl_pending(BIO *b);
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| 33 | size_t BIO_ctrl_wpending(BIO *b);
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| 34 |
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| 35 | int BIO_get_info_callback(BIO *b, BIO_info_cb **cbp);
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| 36 | int BIO_set_info_callback(BIO *b, BIO_info_cb *cb);
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| 37 |
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| 38 | int BIO_get_ktls_send(BIO *b);
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| 39 | int BIO_get_ktls_recv(BIO *b);
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| 40 |
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| 41 | =head1 DESCRIPTION
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| 42 |
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| 43 | BIO_ctrl(), BIO_callback_ctrl(), BIO_ptr_ctrl() and BIO_int_ctrl()
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| 44 | are BIO "control" operations taking arguments of various types.
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| 45 | These functions are not normally called directly, various macros
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| 46 | are used instead. The standard macros are described below, macros
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| 47 | specific to a particular type of BIO are described in the specific
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| 48 | BIOs manual page as well as any special features of the standard
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| 49 | calls.
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| 50 |
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| 51 | BIO_reset() typically resets a BIO to some initial state, in the case
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| 52 | of file related BIOs for example it rewinds the file pointer to the
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| 53 | start of the file.
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| 54 |
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| 55 | BIO_seek() resets a file related BIO's (that is file descriptor and
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| 56 | FILE BIOs) file position pointer to B<ofs> bytes from start of file.
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| 57 |
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| 58 | BIO_tell() returns the current file position of a file related BIO.
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| 59 |
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| 60 | BIO_flush() normally writes out any internally buffered data, in some
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| 61 | cases it is used to signal EOF and that no more data will be written.
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| 62 |
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| 63 | BIO_eof() returns 1 if the BIO has read EOF, the precise meaning of
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| 64 | "EOF" varies according to the BIO type.
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| 65 |
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| 66 | BIO_set_close() sets the BIO B<b> close flag to B<flag>. B<flag> can
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| 67 | take the value BIO_CLOSE or BIO_NOCLOSE. Typically BIO_CLOSE is used
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| 68 | in a source/sink BIO to indicate that the underlying I/O stream should
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| 69 | be closed when the BIO is freed.
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| 70 |
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| 71 | BIO_get_close() returns the BIOs close flag.
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| 72 |
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| 73 | BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending()
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| 74 | return the number of pending characters in the BIOs read and write buffers.
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| 75 | Not all BIOs support these calls. BIO_ctrl_pending() and BIO_ctrl_wpending()
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| 76 | return a size_t type and are functions, BIO_pending() and BIO_wpending() are
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| 77 | macros which call BIO_ctrl().
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| 78 |
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| 79 | BIO_get_ktls_send() returns 1 if the BIO is using the Kernel TLS data-path for
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| 80 | sending. Otherwise, it returns zero.
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| 81 | BIO_get_ktls_recv() returns 1 if the BIO is using the Kernel TLS data-path for
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| 82 | receiving. Otherwise, it returns zero.
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| 83 |
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| 84 | =head1 RETURN VALUES
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| 85 |
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| 86 | BIO_reset() normally returns 1 for success and <=0 for failure. File
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| 87 | BIOs are an exception, they return 0 for success and -1 for failure.
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| 88 |
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| 89 | BIO_seek() and BIO_tell() both return the current file position on success
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| 90 | and -1 for failure, except file BIOs which for BIO_seek() always return 0
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| 91 | for success and -1 for failure.
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| 92 |
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| 93 | BIO_flush() returns 1 for success and <=0 for failure.
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| 94 |
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| 95 | BIO_eof() returns 1 if EOF has been reached, 0 if not, or negative values for failure.
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| 96 |
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| 97 | BIO_set_close() returns 1 on success or <=0 for failure.
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| 98 |
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| 99 | BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE. It also
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| 100 | returns other negative values if an error occurs.
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| 101 |
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| 102 | BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending()
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| 103 | return the amount of pending data. BIO_pending() and BIO_wpending() return
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| 104 | negative value or 0 on error. BIO_ctrl_pending() and BIO_ctrl_wpending() return
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| 105 | 0 on error.
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| 106 |
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| 107 | BIO_get_ktls_send() returns 1 if the BIO is using the Kernel TLS data-path for
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| 108 | sending. Otherwise, it returns zero.
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| 109 | BIO_get_ktls_recv() returns 1 if the BIO is using the Kernel TLS data-path for
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| 110 | receiving. Otherwise, it returns zero.
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| 111 |
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| 112 | =head1 NOTES
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| 113 |
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| 114 | BIO_flush(), because it can write data may return 0 or -1 indicating
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| 115 | that the call should be retried later in a similar manner to BIO_write_ex().
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| 116 | The BIO_should_retry() call should be used and appropriate action taken
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| 117 | is the call fails.
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| 118 |
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| 119 | The return values of BIO_pending() and BIO_wpending() may not reliably
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| 120 | determine the amount of pending data in all cases. For example in the
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| 121 | case of a file BIO some data may be available in the FILE structures
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| 122 | internal buffers but it is not possible to determine this in a
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| 123 | portably way. For other types of BIO they may not be supported.
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| 124 |
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| 125 | Filter BIOs if they do not internally handle a particular BIO_ctrl()
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| 126 | operation usually pass the operation to the next BIO in the chain.
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| 127 | This often means there is no need to locate the required BIO for
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| 128 | a particular operation, it can be called on a chain and it will
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| 129 | be automatically passed to the relevant BIO. However, this can cause
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| 130 | unexpected results: for example no current filter BIOs implement
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| 131 | BIO_seek(), but this may still succeed if the chain ends in a FILE
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| 132 | or file descriptor BIO.
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| 133 |
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| 134 | Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl()
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| 135 | operation.
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| 136 |
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| 137 | =head1 BUGS
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| 138 |
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| 139 | Some of the return values are ambiguous and care should be taken. In
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| 140 | particular a return value of 0 can be returned if an operation is not
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| 141 | supported, if an error occurred, if EOF has not been reached and in
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| 142 | the case of BIO_seek() on a file BIO for a successful operation.
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| 143 |
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| 144 | In older versions of OpenSSL the BIO_ctrl_pending() and
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| 145 | BIO_ctrl_wpending() could return values greater than INT_MAX on error.
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| 146 |
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| 147 | =head1 HISTORY
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| 148 |
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| 149 | The BIO_get_ktls_send() and BIO_get_ktls_recv() macros were added in
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| 150 | OpenSSL 3.0. They were modified to never return -1 in OpenSSL 3.0.4.
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| 151 |
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| 152 | =head1 COPYRIGHT
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| 153 |
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| 154 | Copyright 2000-2022 The OpenSSL Project Authors. All Rights Reserved.
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| 155 |
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| 156 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 157 | this file except in compliance with the License. You can obtain a copy
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| 158 | in the file LICENSE in the source distribution or at
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| 159 | L<https://www.openssl.org/source/license.html>.
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| 160 |
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| 161 | =cut
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