1=pod 2 3=head1 NAME 4 5BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl, BIO_reset, 6BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close, 7BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending, 8BIO_get_info_callback, BIO_set_info_callback, BIO_info_cb, BIO_get_ktls_send, 9BIO_get_ktls_recv 10- BIO control operations 11 12=head1 SYNOPSIS 13 14 #include <openssl/bio.h> 15 16 typedef int BIO_info_cb(BIO *b, int state, int res); 17 18 long BIO_ctrl(BIO *bp, int cmd, long larg, void *parg); 19 long BIO_callback_ctrl(BIO *b, int cmd, BIO_info_cb *cb); 20 void *BIO_ptr_ctrl(BIO *bp, int cmd, long larg); 21 long BIO_int_ctrl(BIO *bp, int cmd, long larg, int iarg); 22 23 int BIO_reset(BIO *b); 24 int BIO_seek(BIO *b, int ofs); 25 int BIO_tell(BIO *b); 26 int BIO_flush(BIO *b); 27 int BIO_eof(BIO *b); 28 int BIO_set_close(BIO *b, long flag); 29 int BIO_get_close(BIO *b); 30 int BIO_pending(BIO *b); 31 int BIO_wpending(BIO *b); 32 size_t BIO_ctrl_pending(BIO *b); 33 size_t BIO_ctrl_wpending(BIO *b); 34 35 int BIO_get_info_callback(BIO *b, BIO_info_cb **cbp); 36 int BIO_set_info_callback(BIO *b, BIO_info_cb *cb); 37 38 int BIO_get_ktls_send(BIO *b); 39 int BIO_get_ktls_recv(BIO *b); 40 41=head1 DESCRIPTION 42 43BIO_ctrl(), BIO_callback_ctrl(), BIO_ptr_ctrl() and BIO_int_ctrl() 44are BIO "control" operations taking arguments of various types. 45These functions are not normally called directly, various macros 46are used instead. The standard macros are described below, macros 47specific to a particular type of BIO are described in the specific 48BIOs manual page as well as any special features of the standard 49calls. 50 51BIO_reset() typically resets a BIO to some initial state, in the case 52of file related BIOs for example it rewinds the file pointer to the 53start of the file. 54 55BIO_seek() resets a file related BIO's (that is file descriptor and 56FILE BIOs) file position pointer to B<ofs> bytes from start of file. 57 58BIO_tell() returns the current file position of a file related BIO. 59 60BIO_flush() normally writes out any internally buffered data, in some 61cases it is used to signal EOF and that no more data will be written. 62 63BIO_eof() returns 1 if the BIO has read EOF, the precise meaning of 64"EOF" varies according to the BIO type. 65 66BIO_set_close() sets the BIO B<b> close flag to B<flag>. B<flag> can 67take the value BIO_CLOSE or BIO_NOCLOSE. Typically BIO_CLOSE is used 68in a source/sink BIO to indicate that the underlying I/O stream should 69be closed when the BIO is freed. 70 71BIO_get_close() returns the BIOs close flag. 72 73BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending() 74return the number of pending characters in the BIOs read and write buffers. 75Not all BIOs support these calls. BIO_ctrl_pending() and BIO_ctrl_wpending() 76return a size_t type and are functions, BIO_pending() and BIO_wpending() are 77macros which call BIO_ctrl(). 78 79BIO_get_ktls_send() returns 1 if the BIO is using the Kernel TLS data-path for 80sending. Otherwise, it returns zero. 81BIO_get_ktls_recv() returns 1 if the BIO is using the Kernel TLS data-path for 82receiving. Otherwise, it returns zero. 83 84=head1 RETURN VALUES 85 86BIO_reset() normally returns 1 for success and <=0 for failure. File 87BIOs are an exception, they return 0 for success and -1 for failure. 88 89BIO_seek() and BIO_tell() both return the current file position on success 90and -1 for failure, except file BIOs which for BIO_seek() always return 0 91for success and -1 for failure. 92 93BIO_flush() returns 1 for success and <=0 for failure. 94 95BIO_eof() returns 1 if EOF has been reached, 0 if not, or negative values for failure. 96 97BIO_set_close() returns 1 on success or <=0 for failure. 98 99BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE. It also 100returns other negative values if an error occurs. 101 102BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending() 103return the amount of pending data. BIO_pending() and BIO_wpending() return 104negative value or 0 on error. BIO_ctrl_pending() and BIO_ctrl_wpending() return 1050 on error. 106 107BIO_get_ktls_send() returns 1 if the BIO is using the Kernel TLS data-path for 108sending. Otherwise, it returns zero. 109BIO_get_ktls_recv() returns 1 if the BIO is using the Kernel TLS data-path for 110receiving. Otherwise, it returns zero. 111 112=head1 NOTES 113 114BIO_flush(), because it can write data may return 0 or -1 indicating 115that the call should be retried later in a similar manner to BIO_write_ex(). 116The BIO_should_retry() call should be used and appropriate action taken 117is the call fails. 118 119The return values of BIO_pending() and BIO_wpending() may not reliably 120determine the amount of pending data in all cases. For example in the 121case of a file BIO some data may be available in the FILE structures 122internal buffers but it is not possible to determine this in a 123portably way. For other types of BIO they may not be supported. 124 125Filter BIOs if they do not internally handle a particular BIO_ctrl() 126operation usually pass the operation to the next BIO in the chain. 127This often means there is no need to locate the required BIO for 128a particular operation, it can be called on a chain and it will 129be automatically passed to the relevant BIO. However, this can cause 130unexpected results: for example no current filter BIOs implement 131BIO_seek(), but this may still succeed if the chain ends in a FILE 132or file descriptor BIO. 133 134Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl() 135operation. 136 137=head1 BUGS 138 139Some of the return values are ambiguous and care should be taken. In 140particular a return value of 0 can be returned if an operation is not 141supported, if an error occurred, if EOF has not been reached and in 142the case of BIO_seek() on a file BIO for a successful operation. 143 144In older versions of OpenSSL the BIO_ctrl_pending() and 145BIO_ctrl_wpending() could return values greater than INT_MAX on error. 146 147=head1 HISTORY 148 149The BIO_get_ktls_send() and BIO_get_ktls_recv() macros were added in 150OpenSSL 3.0. They were modified to never return -1 in OpenSSL 3.0.4. 151 152=head1 COPYRIGHT 153 154Copyright 2000-2022 The OpenSSL Project Authors. All Rights Reserved. 155 156Licensed under the Apache License 2.0 (the "License"). You may not use 157this file except in compliance with the License. You can obtain a copy 158in the file LICENSE in the source distribution or at 159L<https://www.openssl.org/source/license.html>. 160 161=cut 162