BIO_set_callback_ex, BIO_get_callback_ex, BIO_set_callback, BIO_get_callback,
BIO_set_callback_arg, BIO_get_callback_arg, BIO_debug_callback,
BIO_debug_callback_ex, BIO_callback_fn_ex, BIO_callback_fn - BIO callback
functions
#include <openssl/bio.h>
typedef long (*BIO_callback_fn_ex)(BIO *b, int oper, const char *argp,
size_t len, int argi,
long argl, int ret, size_t *processed);
void BIO_set_callback_ex(BIO *b, BIO_callback_fn_ex callback);
BIO_callback_fn_ex BIO_get_callback_ex(const BIO *b);
void BIO_set_callback_arg(BIO *b, char *arg);
char *BIO_get_callback_arg(const BIO *b);
long BIO_debug_callback_ex(BIO *bio, int oper, const char *argp, size_t len,
int argi, long argl, int ret, size_t *processed);
The following functions have been deprecated since OpenSSL 3.0, and can be
hidden entirely by defining
OPENSSL_API_COMPAT with a suitable version
value, see
openssl_user_macros(7):
typedef long (*BIO_callback_fn)(BIO *b, int oper, const char *argp, int argi,
long argl, long ret);
void BIO_set_callback(BIO *b, BIO_callback_fn cb);
BIO_callback_fn BIO_get_callback(const BIO *b);
long BIO_debug_callback(BIO *bio, int cmd, const char *argp, int argi,
long argl, long ret);
BIO_set_callback_ex() and
BIO_get_callback_ex() set and retrieve
the BIO callback. The callback is called during most high-level BIO
operations. It can be used for debugging purposes to trace operations on a BIO
or to modify its operation.
BIO_set_callback() and
BIO_get_callback() set and retrieve the old
format BIO callback. New code should not use these functions, but they are
retained for backwards compatibility. Any callback set via
BIO_set_callback_ex() will get called in preference to any set by
BIO_set_callback().
BIO_set_callback_arg() and
BIO_get_callback_arg() are macros which
can be used to set and retrieve an argument for use in the callback.
BIO_debug_callback_ex() is a standard debugging callback which prints out
information relating to each BIO operation. If the callback argument is set it
is interpreted as a BIO to send the information to, otherwise stderr is used.
The
BIO_debug_callback() function is the deprecated version of the same
callback for use with the old callback format
BIO_set_callback()
function.
BIO_callback_fn_ex is the type of the callback function and BIO_callback_fn is
the type of the old format callback function. The meaning of each argument is
described below:
- b
- The BIO the callback is attached to is passed in
b.
- oper
-
oper is set to the operation being performed. For
some operations the callback is called twice, once before and once after
the actual operation, the latter case has oper or'ed with
BIO_CB_RETURN.
- len
- The length of the data requested to be read or written.
This is only useful if oper is BIO_CB_READ, BIO_CB_WRITE or
BIO_CB_GETS.
-
argp argi argl
- The meaning of the arguments argp, argi and
argl depends on the value of oper, that is the operation
being performed.
- processed
-
processed is a pointer to a location which will be
updated with the amount of data that was actually read or written. Only
used for BIO_CB_READ, BIO_CB_WRITE, BIO_CB_GETS and BIO_CB_PUTS.
- ret
-
ret is the return value that would be returned to
the application if no callback were present. The actual value returned is
the return value of the callback itself. In the case of callbacks called
before the actual BIO operation 1 is placed in ret, if the return
value is not positive it will be immediately returned to the application
and the BIO operation will not be performed.
The callback should normally simply return
ret when it has finished
processing, unless it specifically wishes to modify the value returned to the
application.
In the notes below,
callback defers to the actual callback function that
is called.
- BIO_free(b)
-
callback_ex(b, BIO_CB_FREE, NULL, 0, 0, 0L, 1L, NULL)
or
callback(b, BIO_CB_FREE, NULL, 0L, 0L, 1L)
is called before the free operation.
- BIO_read_ex(b, data, dlen, readbytes)
-
callback_ex(b, BIO_CB_READ, data, dlen, 0, 0L, 1L, NULL)
or
callback(b, BIO_CB_READ, data, dlen, 0L, 1L)
is called before the read and
callback_ex(b, BIO_CB_READ | BIO_CB_RETURN, data, dlen, 0, 0L, retvalue,
&readbytes)
or
callback(b, BIO_CB_READ|BIO_CB_RETURN, data, dlen, 0L, retvalue)
after.
- BIO_write(b, data, dlen, written)
-
callback_ex(b, BIO_CB_WRITE, data, dlen, 0, 0L, 1L, NULL)
or
callback(b, BIO_CB_WRITE, datat, dlen, 0L, 1L)
is called before the write and
callback_ex(b, BIO_CB_WRITE | BIO_CB_RETURN, data, dlen, 0, 0L, retvalue,
&written)
or
callback(b, BIO_CB_WRITE|BIO_CB_RETURN, data, dlen, 0L, retvalue)
after.
- BIO_gets(b, buf, size)
-
callback_ex(b, BIO_CB_GETS, buf, size, 0, 0L, 1, NULL, NULL)
or
callback(b, BIO_CB_GETS, buf, size, 0L, 1L)
is called before the operation and
callback_ex(b, BIO_CB_GETS | BIO_CB_RETURN, buf, size, 0, 0L, retvalue,
&readbytes)
or
callback(b, BIO_CB_GETS|BIO_CB_RETURN, buf, size, 0L, retvalue)
after.
- BIO_puts(b, buf)
-
callback_ex(b, BIO_CB_PUTS, buf, 0, 0, 0L, 1L, NULL);
or
callback(b, BIO_CB_PUTS, buf, 0, 0L, 1L)
is called before the operation and
callback_ex(b, BIO_CB_PUTS | BIO_CB_RETURN, buf, 0, 0, 0L, retvalue, &written)
or
callback(b, BIO_CB_PUTS|BIO_CB_RETURN, buf, 0, 0L, retvalue)
after.
- BIO_ctrl(BIO *b, int cmd, long larg, void
*parg)
-
callback_ex(b, BIO_CB_CTRL, parg, 0, cmd, larg, 1L, NULL)
or
callback(b, BIO_CB_CTRL, parg, cmd, larg, 1L)
is called before the call and
callback_ex(b, BIO_CB_CTRL | BIO_CB_RETURN, parg, 0, cmd, larg, ret, NULL)
or
callback(b, BIO_CB_CTRL|BIO_CB_RETURN, parg, cmd, larg, ret)
after.
Note: cmd == BIO_CTRL_SET_CALLBACK is special, because
parg is not the argument of type BIO_info_cb itself. In this
case parg is a pointer to the actual call parameter, see
BIO_callback_ctrl.
BIO_get_callback_ex() and
BIO_get_callback() return the callback
function previously set by a call to
BIO_set_callback_ex() and
BIO_set_callback() respectively.
BIO_get_callback_arg() returns a
char pointer to the value
previously set via a call to
BIO_set_callback_arg().
BIO_debug_callback() returns 1 or
ret if it's called after
specific BIO operations.
The
BIO_debug_callback_ex() function is an example, its source is in
crypto/bio/bio_cb.c
The
BIO_debug_callback_ex() function was added in OpenSSL 3.0.
BIO_set_callback(),
BIO_get_callback(), and
BIO_debug_callback() were deprecated in OpenSSL 3.0. Use the
non-deprecated _ex functions instead.
Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy in the
file LICENSE in the source distribution or at
<
https://www.openssl.org/source/license.html>.