1BIO_CTRL(3ossl) OpenSSL BIO_CTRL(3ossl)
2
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
13 #include <openssl/bio.h>
14 typedef int BIO_info_cb(BIO *b, int state, int res);
16 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);
21 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);
33 int BIO_get_info_callback(BIO *b, BIO_info_cb **cbp);
35 int BIO_set_info_callback(BIO *b, BIO_info_cb *cb);
36 int BIO_get_ktls_send(BIO *b);
38 int BIO_get_ktls_recv(BIO *b);
39
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 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.
51 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.
54 BIO_tell() returns the current file position of a file related BIO.
56 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.
59 BIO_eof() returns 1 if the BIO has read EOF, the precise meaning of
61 "EOF" varies according to the BIO type.
62 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.
67 BIO_get_close() returns the BIOs close flag.
69 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().
76 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.
81
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.
85 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.
89 BIO_flush() returns 1 for success and <=0 for failure.
91 BIO_eof() returns 1 if EOF has been reached, 0 if not, or negative
93 values for failure.
94 BIO_set_close() returns 1 on success or <=0 for failure.
96 BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE.
98 It also returns other negative values if an error occurs.
99 BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and
101 BIO_ctrl_wpending() return the amount of pending data. BIO_pending()
102 and BIO_wpending() return negative value or 0 on error.
103 BIO_ctrl_pending() and BIO_ctrl_wpending() return 0 on error.
104 BIO_get_ktls_send() returns 1 if the BIO is using the Kernel TLS data-
106 path for sending. Otherwise, it returns zero. BIO_get_ktls_recv()
107 returns 1 if the BIO is using the Kernel TLS data-path for receiving.
108 Otherwise, it returns zero.
109
111 BIO_flush(), because it can write data may return 0 or -1 indicating
112 that the call should be retried later in a similar manner to
113 BIO_write_ex(). The BIO_should_retry() call should be used and
114 appropriate action taken is the call fails.
115 The return values of BIO_pending() and BIO_wpending() may not reliably
117 determine the amount of pending data in all cases. For example in the
118 case of a file BIO some data may be available in the FILE structures
119 internal buffers but it is not possible to determine this in a portably
120 way. For other types of BIO they may not be supported.
121 Filter BIOs if they do not internally handle a particular BIO_ctrl()
123 operation usually pass the operation to the next BIO in the chain.
124 This often means there is no need to locate the required BIO for a
125 particular operation, it can be called on a chain and it will be
126 automatically passed to the relevant BIO. However, this can cause
127 unexpected results: for example no current filter BIOs implement
128 BIO_seek(), but this may still succeed if the chain ends in a FILE or
129 file descriptor BIO.
130 Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl()
132 operation.
133
135 Some of the return values are ambiguous and care should be taken. In
136 particular a return value of 0 can be returned if an operation is not
137 supported, if an error occurred, if EOF has not been reached and in the
138 case of BIO_seek() on a file BIO for a successful operation.
139 In older versions of OpenSSL the BIO_ctrl_pending() and
141 BIO_ctrl_wpending() could return values greater than INT_MAX on error.
142
144 The BIO_get_ktls_send() and BIO_get_ktls_recv() macros were added in
145 OpenSSL 3.0. They were modified to never return -1 in OpenSSL 3.0.4.
146
148 Copyright 2000-2022 The OpenSSL Project Authors. All Rights Reserved.
149 Licensed under the Apache License 2.0 (the "License"). You may not use
151 this file except in compliance with the License. You can obtain a copy
152 in the file LICENSE in the source distribution or at
153 <https://www.openssl.org/source/license.html>.
1543.1.1 2023-08-31 BIO_CTRL(3ossl)