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 or -1 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 or -1 for failure. 94 95BIO_eof() returns 1 if EOF has been reached 0 otherwise. 96 97BIO_set_close() always returns 1. 98 99BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE. 100 101BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending() 102return the amount of pending data. 103 104BIO_get_ktls_send() returns 1 if the BIO is using the Kernel TLS data-path for 105sending. Otherwise, it returns zero. 106BIO_get_ktls_recv() returns 1 if the BIO is using the Kernel TLS data-path for 107receiving. Otherwise, it returns zero. 108 109=head1 NOTES 110 111BIO_flush(), because it can write data may return 0 or -1 indicating 112that the call should be retried later in a similar manner to BIO_write_ex(). 113The BIO_should_retry() call should be used and appropriate action taken 114is the call fails. 115 116The return values of BIO_pending() and BIO_wpending() may not reliably 117determine the amount of pending data in all cases. For example in the 118case of a file BIO some data may be available in the FILE structures 119internal buffers but it is not possible to determine this in a 120portably way. For other types of BIO they may not be supported. 121 122Filter BIOs if they do not internally handle a particular BIO_ctrl() 123operation usually pass the operation to the next BIO in the chain. 124This often means there is no need to locate the required BIO for 125a particular operation, it can be called on a chain and it will 126be automatically passed to the relevant BIO. However, this can cause 127unexpected results: for example no current filter BIOs implement 128BIO_seek(), but this may still succeed if the chain ends in a FILE 129or file descriptor BIO. 130 131Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl() 132operation. 133 134=head1 BUGS 135 136Some of the return values are ambiguous and care should be taken. In 137particular a return value of 0 can be returned if an operation is not 138supported, if an error occurred, if EOF has not been reached and in 139the case of BIO_seek() on a file BIO for a successful operation. 140 141=head1 HISTORY 142 143The BIO_get_ktls_send() and BIO_get_ktls_recv() functions were added in 144OpenSSL 3.0.0. 145 146=head1 COPYRIGHT 147 148Copyright 2000-2022 The OpenSSL Project Authors. All Rights Reserved. 149 150Licensed under the OpenSSL license (the "License"). You may not use 151this file except in compliance with the License. You can obtain a copy 152in the file LICENSE in the source distribution or at 153L<https://www.openssl.org/source/license.html>. 154 155=cut 156