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129.\" ========================================================================
130.\"
131.IX Title "BIO_s_bio 3"
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124.\" ========================================================================
125.\"
126.IX Title "BIO_s_bio 3"
|
132.TH BIO_s_bio 3 "2010-03-24" "0.9.8n" "OpenSSL"
| 127.TH BIO_s_bio 3 "2010-11-16" "0.9.8p" "OpenSSL"
128.\" For nroff, turn off justification. Always turn off hyphenation; it makes
129.\" way too many mistakes in technical documents.
130.if n .ad l
131.nh
|
133.SH "NAME"
134BIO_s_bio, BIO_make_bio_pair, BIO_destroy_bio_pair, BIO_shutdown_wr,
135BIO_set_write_buf_size, BIO_get_write_buf_size, BIO_new_bio_pair,
136BIO_get_write_guarantee, BIO_ctrl_get_write_guarantee, BIO_get_read_request,
137BIO_ctrl_get_read_request, BIO_ctrl_reset_read_request \- BIO pair BIO
138.SH "SYNOPSIS"
139.IX Header "SYNOPSIS"
140.Vb 1
141\& #include <openssl/bio.h>
| 132.SH "NAME"
133BIO_s_bio, BIO_make_bio_pair, BIO_destroy_bio_pair, BIO_shutdown_wr,
134BIO_set_write_buf_size, BIO_get_write_buf_size, BIO_new_bio_pair,
135BIO_get_write_guarantee, BIO_ctrl_get_write_guarantee, BIO_get_read_request,
136BIO_ctrl_get_read_request, BIO_ctrl_reset_read_request \- BIO pair BIO
137.SH "SYNOPSIS"
138.IX Header "SYNOPSIS"
139.Vb 1
140\& #include <openssl/bio.h>
|
142.Ve
143.PP
144.Vb 1
| 141\&
|
145\& BIO_METHOD *BIO_s_bio(void);
| 142\& BIO_METHOD *BIO_s_bio(void);
|
146.Ve
147.PP
148.Vb 2
| 143\&
|
149\& #define BIO_make_bio_pair(b1,b2) (int)BIO_ctrl(b1,BIO_C_MAKE_BIO_PAIR,0,b2)
150\& #define BIO_destroy_bio_pair(b) (int)BIO_ctrl(b,BIO_C_DESTROY_BIO_PAIR,0,NULL)
| 144\& #define BIO_make_bio_pair(b1,b2) (int)BIO_ctrl(b1,BIO_C_MAKE_BIO_PAIR,0,b2)
145\& #define BIO_destroy_bio_pair(b) (int)BIO_ctrl(b,BIO_C_DESTROY_BIO_PAIR,0,NULL)
|
151.Ve
152.PP
153.Vb 1
| 146\&
|
154\& #define BIO_shutdown_wr(b) (int)BIO_ctrl(b, BIO_C_SHUTDOWN_WR, 0, NULL)
| 147\& #define BIO_shutdown_wr(b) (int)BIO_ctrl(b, BIO_C_SHUTDOWN_WR, 0, NULL)
|
155.Ve
156.PP
157.Vb 2
| 148\&
|
158\& #define BIO_set_write_buf_size(b,size) (int)BIO_ctrl(b,BIO_C_SET_WRITE_BUF_SIZE,size,NULL)
159\& #define BIO_get_write_buf_size(b,size) (size_t)BIO_ctrl(b,BIO_C_GET_WRITE_BUF_SIZE,size,NULL)
| 149\& #define BIO_set_write_buf_size(b,size) (int)BIO_ctrl(b,BIO_C_SET_WRITE_BUF_SIZE,size,NULL)
150\& #define BIO_get_write_buf_size(b,size) (size_t)BIO_ctrl(b,BIO_C_GET_WRITE_BUF_SIZE,size,NULL)
|
160.Ve
161.PP
162.Vb 1
| 151\&
|
163\& int BIO_new_bio_pair(BIO **bio1, size_t writebuf1, BIO **bio2, size_t writebuf2);
| 152\& int BIO_new_bio_pair(BIO **bio1, size_t writebuf1, BIO **bio2, size_t writebuf2);
|
164.Ve
165.PP
166.Vb 2
| 153\&
|
167\& #define BIO_get_write_guarantee(b) (int)BIO_ctrl(b,BIO_C_GET_WRITE_GUARANTEE,0,NULL)
168\& size_t BIO_ctrl_get_write_guarantee(BIO *b);
| 154\& #define BIO_get_write_guarantee(b) (int)BIO_ctrl(b,BIO_C_GET_WRITE_GUARANTEE,0,NULL)
155\& size_t BIO_ctrl_get_write_guarantee(BIO *b);
|
169.Ve
170.PP
171.Vb 2
| 156\&
|
172\& #define BIO_get_read_request(b) (int)BIO_ctrl(b,BIO_C_GET_READ_REQUEST,0,NULL)
173\& size_t BIO_ctrl_get_read_request(BIO *b);
| 157\& #define BIO_get_read_request(b) (int)BIO_ctrl(b,BIO_C_GET_READ_REQUEST,0,NULL)
158\& size_t BIO_ctrl_get_read_request(BIO *b);
|
174.Ve
175.PP
176.Vb 1
| 159\&
|
177\& int BIO_ctrl_reset_read_request(BIO *b);
178.Ve
179.SH "DESCRIPTION"
180.IX Header "DESCRIPTION"
181\&\fIBIO_s_bio()\fR returns the method for a \s-1BIO\s0 pair. A \s-1BIO\s0 pair is a pair of source/sink
182BIOs where data written to either half of the pair is buffered and can be read from
183the other half. Both halves must usually by handled by the same application thread
184since no locking is done on the internal data structures.
185.PP
186Since \s-1BIO\s0 chains typically end in a source/sink \s-1BIO\s0 it is possible to make this
187one half of a \s-1BIO\s0 pair and have all the data processed by the chain under application
188control.
189.PP
190One typical use of \s-1BIO\s0 pairs is to place \s-1TLS/SSL\s0 I/O under application control, this
191can be used when the application wishes to use a non standard transport for
192\&\s-1TLS/SSL\s0 or the normal socket routines are inappropriate.
193.PP
194Calls to \fIBIO_read()\fR will read data from the buffer or request a retry if no
195data is available.
196.PP
197Calls to \fIBIO_write()\fR will place data in the buffer or request a retry if the
198buffer is full.
199.PP
200The standard calls \fIBIO_ctrl_pending()\fR and \fIBIO_ctrl_wpending()\fR can be used to
201determine the amount of pending data in the read or write buffer.
202.PP
203\&\fIBIO_reset()\fR clears any data in the write buffer.
204.PP
205\&\fIBIO_make_bio_pair()\fR joins two separate BIOs into a connected pair.
206.PP
207\&\fIBIO_destroy_pair()\fR destroys the association between two connected BIOs. Freeing
208up any half of the pair will automatically destroy the association.
209.PP
210\&\fIBIO_shutdown_wr()\fR is used to close down a \s-1BIO\s0 \fBb\fR. After this call no further
211writes on \s-1BIO\s0 \fBb\fR are allowed (they will return an error). Reads on the other
212half of the pair will return any pending data or \s-1EOF\s0 when all pending data has
| 160\& int BIO_ctrl_reset_read_request(BIO *b);
161.Ve
162.SH "DESCRIPTION"
163.IX Header "DESCRIPTION"
164\&\fIBIO_s_bio()\fR returns the method for a \s-1BIO\s0 pair. A \s-1BIO\s0 pair is a pair of source/sink
165BIOs where data written to either half of the pair is buffered and can be read from
166the other half. Both halves must usually by handled by the same application thread
167since no locking is done on the internal data structures.
168.PP
169Since \s-1BIO\s0 chains typically end in a source/sink \s-1BIO\s0 it is possible to make this
170one half of a \s-1BIO\s0 pair and have all the data processed by the chain under application
171control.
172.PP
173One typical use of \s-1BIO\s0 pairs is to place \s-1TLS/SSL\s0 I/O under application control, this
174can be used when the application wishes to use a non standard transport for
175\&\s-1TLS/SSL\s0 or the normal socket routines are inappropriate.
176.PP
177Calls to \fIBIO_read()\fR will read data from the buffer or request a retry if no
178data is available.
179.PP
180Calls to \fIBIO_write()\fR will place data in the buffer or request a retry if the
181buffer is full.
182.PP
183The standard calls \fIBIO_ctrl_pending()\fR and \fIBIO_ctrl_wpending()\fR can be used to
184determine the amount of pending data in the read or write buffer.
185.PP
186\&\fIBIO_reset()\fR clears any data in the write buffer.
187.PP
188\&\fIBIO_make_bio_pair()\fR joins two separate BIOs into a connected pair.
189.PP
190\&\fIBIO_destroy_pair()\fR destroys the association between two connected BIOs. Freeing
191up any half of the pair will automatically destroy the association.
192.PP
193\&\fIBIO_shutdown_wr()\fR is used to close down a \s-1BIO\s0 \fBb\fR. After this call no further
194writes on \s-1BIO\s0 \fBb\fR are allowed (they will return an error). Reads on the other
195half of the pair will return any pending data or \s-1EOF\s0 when all pending data has
|
213been read.
| 196been read.
|
214.PP
215\&\fIBIO_set_write_buf_size()\fR sets the write buffer size of \s-1BIO\s0 \fBb\fR to \fBsize\fR.
216If the size is not initialized a default value is used. This is currently
21717K, sufficient for a maximum size \s-1TLS\s0 record.
218.PP
219\&\fIBIO_get_write_buf_size()\fR returns the size of the write buffer.
220.PP
221\&\fIBIO_new_bio_pair()\fR combines the calls to \fIBIO_new()\fR, \fIBIO_make_bio_pair()\fR and
222\&\fIBIO_set_write_buf_size()\fR to create a connected pair of BIOs \fBbio1\fR, \fBbio2\fR
223with write buffer sizes \fBwritebuf1\fR and \fBwritebuf2\fR. If either size is
224zero then the default size is used. \fIBIO_new_bio_pair()\fR does not check whether
225\&\fBbio1\fR or \fBbio2\fR do point to some other \s-1BIO\s0, the values are overwritten,
226\&\fIBIO_free()\fR is not called.
227.PP
228\&\fIBIO_get_write_guarantee()\fR and \fIBIO_ctrl_get_write_guarantee()\fR return the maximum
229length of data that can be currently written to the \s-1BIO\s0. Writes larger than this
230value will return a value from \fIBIO_write()\fR less than the amount requested or if the
231buffer is full request a retry. \fIBIO_ctrl_get_write_guarantee()\fR is a function
232whereas \fIBIO_get_write_guarantee()\fR is a macro.
233.PP
234\&\fIBIO_get_read_request()\fR and \fIBIO_ctrl_get_read_request()\fR return the
235amount of data requested, or the buffer size if it is less, if the
236last read attempt at the other half of the \s-1BIO\s0 pair failed due to an
237empty buffer. This can be used to determine how much data should be
238written to the \s-1BIO\s0 so the next read will succeed: this is most useful
239in \s-1TLS/SSL\s0 applications where the amount of data read is usually
240meaningful rather than just a buffer size. After a successful read
241this call will return zero. It also will return zero once new data
242has been written satisfying the read request or part of it.
243Note that \fIBIO_get_read_request()\fR never returns an amount larger
244than that returned by \fIBIO_get_write_guarantee()\fR.
245.PP
246\&\fIBIO_ctrl_reset_read_request()\fR can also be used to reset the value returned by
247\&\fIBIO_get_read_request()\fR to zero.
248.SH "NOTES"
249.IX Header "NOTES"
250Both halves of a \s-1BIO\s0 pair should be freed. That is even if one half is implicit
251freed due to a \fIBIO_free_all()\fR or \fISSL_free()\fR call the other half needs to be freed.
252.PP
253When used in bidirectional applications (such as \s-1TLS/SSL\s0) care should be taken to
254flush any data in the write buffer. This can be done by calling \fIBIO_pending()\fR
255on the other half of the pair and, if any data is pending, reading it and sending
256it to the underlying transport. This must be done before any normal processing
257(such as calling \fIselect()\fR ) due to a request and \fIBIO_should_read()\fR being true.
258.PP
259To see why this is important consider a case where a request is sent using
260\&\fIBIO_write()\fR and a response read with \fIBIO_read()\fR, this can occur during an
261\&\s-1TLS/SSL\s0 handshake for example. \fIBIO_write()\fR will succeed and place data in the write
262buffer. \fIBIO_read()\fR will initially fail and \fIBIO_should_read()\fR will be true. If
263the application then waits for data to be available on the underlying transport
264before flushing the write buffer it will never succeed because the request was
265never sent!
266.SH "RETURN VALUES"
267.IX Header "RETURN VALUES"
268\&\fIBIO_new_bio_pair()\fR returns 1 on success, with the new BIOs available in
269\&\fBbio1\fR and \fBbio2\fR, or 0 on failure, with \s-1NULL\s0 pointers stored into the
270locations for \fBbio1\fR and \fBbio2\fR. Check the error stack for more information.
271.PP
272[\s-1XXXXX:\s0 More return values need to be added here]
273.SH "EXAMPLE"
274.IX Header "EXAMPLE"
275The \s-1BIO\s0 pair can be used to have full control over the network access of an
276application. The application can call \fIselect()\fR on the socket as required
| 197.PP
198\&\fIBIO_set_write_buf_size()\fR sets the write buffer size of \s-1BIO\s0 \fBb\fR to \fBsize\fR.
199If the size is not initialized a default value is used. This is currently
20017K, sufficient for a maximum size \s-1TLS\s0 record.
201.PP
202\&\fIBIO_get_write_buf_size()\fR returns the size of the write buffer.
203.PP
204\&\fIBIO_new_bio_pair()\fR combines the calls to \fIBIO_new()\fR, \fIBIO_make_bio_pair()\fR and
205\&\fIBIO_set_write_buf_size()\fR to create a connected pair of BIOs \fBbio1\fR, \fBbio2\fR
206with write buffer sizes \fBwritebuf1\fR and \fBwritebuf2\fR. If either size is
207zero then the default size is used. \fIBIO_new_bio_pair()\fR does not check whether
208\&\fBbio1\fR or \fBbio2\fR do point to some other \s-1BIO\s0, the values are overwritten,
209\&\fIBIO_free()\fR is not called.
210.PP
211\&\fIBIO_get_write_guarantee()\fR and \fIBIO_ctrl_get_write_guarantee()\fR return the maximum
212length of data that can be currently written to the \s-1BIO\s0. Writes larger than this
213value will return a value from \fIBIO_write()\fR less than the amount requested or if the
214buffer is full request a retry. \fIBIO_ctrl_get_write_guarantee()\fR is a function
215whereas \fIBIO_get_write_guarantee()\fR is a macro.
216.PP
217\&\fIBIO_get_read_request()\fR and \fIBIO_ctrl_get_read_request()\fR return the
218amount of data requested, or the buffer size if it is less, if the
219last read attempt at the other half of the \s-1BIO\s0 pair failed due to an
220empty buffer. This can be used to determine how much data should be
221written to the \s-1BIO\s0 so the next read will succeed: this is most useful
222in \s-1TLS/SSL\s0 applications where the amount of data read is usually
223meaningful rather than just a buffer size. After a successful read
224this call will return zero. It also will return zero once new data
225has been written satisfying the read request or part of it.
226Note that \fIBIO_get_read_request()\fR never returns an amount larger
227than that returned by \fIBIO_get_write_guarantee()\fR.
228.PP
229\&\fIBIO_ctrl_reset_read_request()\fR can also be used to reset the value returned by
230\&\fIBIO_get_read_request()\fR to zero.
231.SH "NOTES"
232.IX Header "NOTES"
233Both halves of a \s-1BIO\s0 pair should be freed. That is even if one half is implicit
234freed due to a \fIBIO_free_all()\fR or \fISSL_free()\fR call the other half needs to be freed.
235.PP
236When used in bidirectional applications (such as \s-1TLS/SSL\s0) care should be taken to
237flush any data in the write buffer. This can be done by calling \fIBIO_pending()\fR
238on the other half of the pair and, if any data is pending, reading it and sending
239it to the underlying transport. This must be done before any normal processing
240(such as calling \fIselect()\fR ) due to a request and \fIBIO_should_read()\fR being true.
241.PP
242To see why this is important consider a case where a request is sent using
243\&\fIBIO_write()\fR and a response read with \fIBIO_read()\fR, this can occur during an
244\&\s-1TLS/SSL\s0 handshake for example. \fIBIO_write()\fR will succeed and place data in the write
245buffer. \fIBIO_read()\fR will initially fail and \fIBIO_should_read()\fR will be true. If
246the application then waits for data to be available on the underlying transport
247before flushing the write buffer it will never succeed because the request was
248never sent!
249.SH "RETURN VALUES"
250.IX Header "RETURN VALUES"
251\&\fIBIO_new_bio_pair()\fR returns 1 on success, with the new BIOs available in
252\&\fBbio1\fR and \fBbio2\fR, or 0 on failure, with \s-1NULL\s0 pointers stored into the
253locations for \fBbio1\fR and \fBbio2\fR. Check the error stack for more information.
254.PP
255[\s-1XXXXX:\s0 More return values need to be added here]
256.SH "EXAMPLE"
257.IX Header "EXAMPLE"
258The \s-1BIO\s0 pair can be used to have full control over the network access of an
259application. The application can call \fIselect()\fR on the socket as required
|
277without having to go through the SSL\-interface.
| 260without having to go through the SSL-interface.
|
278.PP
279.Vb 6
280\& BIO *internal_bio, *network_bio;
281\& ...
282\& BIO_new_bio_pair(internal_bio, 0, network_bio, 0);
283\& SSL_set_bio(ssl, internal_bio, internal_bio);
284\& SSL_operations();
285\& ...
| 261.PP
262.Vb 6
263\& BIO *internal_bio, *network_bio;
264\& ...
265\& BIO_new_bio_pair(internal_bio, 0, network_bio, 0);
266\& SSL_set_bio(ssl, internal_bio, internal_bio);
267\& SSL_operations();
268\& ...
|
286.Ve
287.PP
288.Vb 9
289\& application | TLS-engine
| 269\&
270\& application | TLS\-engine
|
290\& | |
| 271\& | |
|
291\& +----------> SSL_operations()
| 272\& +\-\-\-\-\-\-\-\-\-\-> SSL_operations()
|
292\& | /\e ||
293\& | || \e/
| 273\& | /\e ||
274\& | || \e/
|
294\& | BIO-pair (internal_bio)
295\& +----------< BIO-pair (network_bio)
| 275\& | BIO\-pair (internal_bio)
276\& +\-\-\-\-\-\-\-\-\-\-< BIO\-pair (network_bio)
|
296\& | |
297\& socket |
| 277\& | |
278\& socket |
|
298.Ve
299.PP
300.Vb 4
| 279\&
|
301\& ...
302\& SSL_free(ssl); /* implicitly frees internal_bio */
303\& BIO_free(network_bio);
304\& ...
305.Ve
306.PP
307As the \s-1BIO\s0 pair will only buffer the data and never directly access the
308connection, it behaves non-blocking and will return as soon as the write
309buffer is full or the read buffer is drained. Then the application has to
310flush the write buffer and/or fill the read buffer.
311.PP
312Use the \fIBIO_ctrl_pending()\fR, to find out whether data is buffered in the \s-1BIO\s0
313and must be transfered to the network. Use \fIBIO_ctrl_get_read_request()\fR to
314find out, how many bytes must be written into the buffer before the
315\&\fISSL_operation()\fR can successfully be continued.
316.SH "WARNING"
317.IX Header "WARNING"
318As the data is buffered, \fISSL_operation()\fR may return with a \s-1ERROR_SSL_WANT_READ\s0
319condition, but there is still data in the write buffer. An application must
320not rely on the error value of \fISSL_operation()\fR but must assure that the
321write buffer is always flushed first. Otherwise a deadlock may occur as
322the peer might be waiting for the data before being able to continue.
323.SH "SEE ALSO"
324.IX Header "SEE ALSO"
325\&\fISSL_set_bio\fR\|(3), \fIssl\fR\|(3), \fIbio\fR\|(3),
326\&\fIBIO_should_retry\fR\|(3), \fIBIO_read\fR\|(3)
| 280\& ...
281\& SSL_free(ssl); /* implicitly frees internal_bio */
282\& BIO_free(network_bio);
283\& ...
284.Ve
285.PP
286As the \s-1BIO\s0 pair will only buffer the data and never directly access the
287connection, it behaves non-blocking and will return as soon as the write
288buffer is full or the read buffer is drained. Then the application has to
289flush the write buffer and/or fill the read buffer.
290.PP
291Use the \fIBIO_ctrl_pending()\fR, to find out whether data is buffered in the \s-1BIO\s0
292and must be transfered to the network. Use \fIBIO_ctrl_get_read_request()\fR to
293find out, how many bytes must be written into the buffer before the
294\&\fISSL_operation()\fR can successfully be continued.
295.SH "WARNING"
296.IX Header "WARNING"
297As the data is buffered, \fISSL_operation()\fR may return with a \s-1ERROR_SSL_WANT_READ\s0
298condition, but there is still data in the write buffer. An application must
299not rely on the error value of \fISSL_operation()\fR but must assure that the
300write buffer is always flushed first. Otherwise a deadlock may occur as
301the peer might be waiting for the data before being able to continue.
302.SH "SEE ALSO"
303.IX Header "SEE ALSO"
304\&\fISSL_set_bio\fR\|(3), \fIssl\fR\|(3), \fIbio\fR\|(3),
305\&\fIBIO_should_retry\fR\|(3), \fIBIO_read\fR\|(3)
|