1BIO_CTRL(3ossl)                     OpenSSL                    BIO_CTRL(3ossl)
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NAME

6       BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl, BIO_reset,
7       BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close,
8       BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending,
9       BIO_get_info_callback, BIO_set_info_callback, BIO_info_cb,
10       BIO_get_ktls_send, BIO_get_ktls_recv - BIO control operations
11

SYNOPSIS

13        #include <openssl/bio.h>
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15        typedef int BIO_info_cb(BIO *b, int state, int res);
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17        long BIO_ctrl(BIO *bp, int cmd, long larg, void *parg);
18        long BIO_callback_ctrl(BIO *b, int cmd, BIO_info_cb *cb);
19        void *BIO_ptr_ctrl(BIO *bp, int cmd, long larg);
20        long BIO_int_ctrl(BIO *bp, int cmd, long larg, int iarg);
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22        int BIO_reset(BIO *b);
23        int BIO_seek(BIO *b, int ofs);
24        int BIO_tell(BIO *b);
25        int BIO_flush(BIO *b);
26        int BIO_eof(BIO *b);
27        int BIO_set_close(BIO *b, long flag);
28        int BIO_get_close(BIO *b);
29        int BIO_pending(BIO *b);
30        int BIO_wpending(BIO *b);
31        size_t BIO_ctrl_pending(BIO *b);
32        size_t BIO_ctrl_wpending(BIO *b);
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34        int BIO_get_info_callback(BIO *b, BIO_info_cb **cbp);
35        int BIO_set_info_callback(BIO *b, BIO_info_cb *cb);
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37        int BIO_get_ktls_send(BIO *b);
38        int BIO_get_ktls_recv(BIO *b);
39

DESCRIPTION

41       BIO_ctrl(), BIO_callback_ctrl(), BIO_ptr_ctrl() and BIO_int_ctrl() are
42       BIO "control" operations taking arguments of various types.  These
43       functions are not normally called directly, various macros are used
44       instead. The standard macros are described below, macros specific to a
45       particular type of BIO are described in the specific BIOs manual page
46       as well as any special features of the standard calls.
47
48       BIO_reset() typically resets a BIO to some initial state, in the case
49       of file related BIOs for example it rewinds the file pointer to the
50       start of the file.
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52       BIO_seek() resets a file related BIO's (that is file descriptor and
53       FILE BIOs) file position pointer to ofs bytes from start of file.
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55       BIO_tell() returns the current file position of a file related BIO.
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57       BIO_flush() normally writes out any internally buffered data, in some
58       cases it is used to signal EOF and that no more data will be written.
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60       BIO_eof() returns 1 if the BIO has read EOF, the precise meaning of
61       "EOF" varies according to the BIO type.
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63       BIO_set_close() sets the BIO b close flag to flag. flag can take the
64       value BIO_CLOSE or BIO_NOCLOSE. Typically BIO_CLOSE is used in a
65       source/sink BIO to indicate that the underlying I/O stream should be
66       closed when the BIO is freed.
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68       BIO_get_close() returns the BIOs close flag.
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70       BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and
71       BIO_ctrl_wpending() return the number of pending characters in the BIOs
72       read and write buffers.  Not all BIOs support these calls.
73       BIO_ctrl_pending() and BIO_ctrl_wpending() return a size_t type and are
74       functions, BIO_pending() and BIO_wpending() are macros which call
75       BIO_ctrl().
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77       BIO_get_ktls_send() returns 1 if the BIO is using the Kernel TLS data-
78       path for sending. Otherwise, it returns zero.  BIO_get_ktls_recv()
79       returns 1 if the BIO is using the Kernel TLS data-path for receiving.
80       Otherwise, it returns zero.
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RETURN VALUES

83       BIO_reset() normally returns 1 for success and <=0 for failure. File
84       BIOs are an exception, they return 0 for success and -1 for failure.
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86       BIO_seek() and BIO_tell() both return the current file position on
87       success and -1 for failure, except file BIOs which for BIO_seek()
88       always return 0 for success and -1 for failure.
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90       BIO_flush() returns 1 for success and <=0 for failure.
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92       BIO_eof() returns 1 if EOF has been reached, 0 if not, or negative
93       values for failure.
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95       BIO_set_close() returns 1 on success or <=0 for failure.
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97       BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE.
98       It also returns other negative values if an error occurs.
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100       BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and
101       BIO_ctrl_wpending() return the amount of pending data.
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103       BIO_get_ktls_send() returns 1 if the BIO is using the Kernel TLS data-
104       path for sending. Otherwise, it returns zero.  BIO_get_ktls_recv()
105       returns 1 if the BIO is using the Kernel TLS data-path for receiving.
106       Otherwise, it returns zero.
107

NOTES

109       BIO_flush(), because it can write data may return 0 or -1 indicating
110       that the call should be retried later in a similar manner to
111       BIO_write_ex().  The BIO_should_retry() call should be used and
112       appropriate action taken is the call fails.
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114       The return values of BIO_pending() and BIO_wpending() may not reliably
115       determine the amount of pending data in all cases. For example in the
116       case of a file BIO some data may be available in the FILE structures
117       internal buffers but it is not possible to determine this in a portably
118       way. For other types of BIO they may not be supported.
119
120       Filter BIOs if they do not internally handle a particular BIO_ctrl()
121       operation usually pass the operation to the next BIO in the chain.
122       This often means there is no need to locate the required BIO for a
123       particular operation, it can be called on a chain and it will be
124       automatically passed to the relevant BIO. However, this can cause
125       unexpected results: for example no current filter BIOs implement
126       BIO_seek(), but this may still succeed if the chain ends in a FILE or
127       file descriptor BIO.
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129       Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl()
130       operation.
131

BUGS

133       Some of the return values are ambiguous and care should be taken. In
134       particular a return value of 0 can be returned if an operation is not
135       supported, if an error occurred, if EOF has not been reached and in the
136       case of BIO_seek() on a file BIO for a successful operation.
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HISTORY

139       The BIO_get_ktls_send() and BIO_get_ktls_recv() macros were added in
140       OpenSSL 3.0. They were modified to never return -1 in OpenSSL 3.0.4.
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143       Copyright 2000-2022 The OpenSSL Project Authors. All Rights Reserved.
144
145       Licensed under the Apache License 2.0 (the "License").  You may not use
146       this file except in compliance with the License.  You can obtain a copy
147       in the file LICENSE in the source distribution or at
148       <https://www.openssl.org/source/license.html>.
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1523.0.5                             2022-11-01                   BIO_CTRL(3ossl)
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