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authorJung-uk Kim <jkim@FreeBSD.org>2020-02-21 00:33:21 +0000
committerJung-uk Kim <jkim@FreeBSD.org>2020-02-21 00:33:21 +0000
commit6b4382c4054d7c169c6140feaa144ca360a90ead (patch)
tree176bf7fdbae226099058e11e9a429805b6e0af42 /secure/lib/libcrypto/man/man3/BIO_s_bio.3
parent24722aacdb06a5ac6780beef7db856a0f99095c3 (diff)
downloadsrc-6b4382c4054d7c169c6140feaa144ca360a90ead.tar.gz
src-6b4382c4054d7c169c6140feaa144ca360a90ead.zip
MFC: r356963
Install man5 and man7 for OpenSSL.
Notes
Notes: svn path=/stable/12/; revision=358188
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+.rm #[ #] #H #V #F C
+.\" ========================================================================
+.\"
+.IX Title "BIO_S_BIO 3"
+.TH BIO_S_BIO 3 "2019-09-10" "1.1.1d" "OpenSSL"
+.\" For nroff, turn off justification. Always turn off hyphenation; it makes
+.\" way too many mistakes in technical documents.
+.if n .ad l
+.nh
+.SH "NAME"
+BIO_s_bio, BIO_make_bio_pair, BIO_destroy_bio_pair, BIO_shutdown_wr, BIO_set_write_buf_size, BIO_get_write_buf_size, BIO_new_bio_pair, BIO_get_write_guarantee, BIO_ctrl_get_write_guarantee, BIO_get_read_request, BIO_ctrl_get_read_request, BIO_ctrl_reset_read_request \- BIO pair BIO
+.SH "SYNOPSIS"
+.IX Header "SYNOPSIS"
+.Vb 1
+\& #include <openssl/bio.h>
+\&
+\& const BIO_METHOD *BIO_s_bio(void);
+\&
+\& int BIO_make_bio_pair(BIO *b1, BIO *b2);
+\& int BIO_destroy_bio_pair(BIO *b);
+\& int BIO_shutdown_wr(BIO *b);
+\&
+\& int BIO_set_write_buf_size(BIO *b, long size);
+\& size_t BIO_get_write_buf_size(BIO *b, long size);
+\&
+\& int BIO_new_bio_pair(BIO **bio1, size_t writebuf1, BIO **bio2, size_t writebuf2);
+\&
+\& int BIO_get_write_guarantee(BIO *b);
+\& size_t BIO_ctrl_get_write_guarantee(BIO *b);
+\& int BIO_get_read_request(BIO *b);
+\& size_t BIO_ctrl_get_read_request(BIO *b);
+\& int BIO_ctrl_reset_read_request(BIO *b);
+.Ve
+.SH "DESCRIPTION"
+.IX Header "DESCRIPTION"
+\&\fBBIO_s_bio()\fR returns the method for a \s-1BIO\s0 pair. A \s-1BIO\s0 pair is a pair of source/sink
+BIOs where data written to either half of the pair is buffered and can be read from
+the other half. Both halves must usually by handled by the same application thread
+since no locking is done on the internal data structures.
+.PP
+Since \s-1BIO\s0 chains typically end in a source/sink \s-1BIO\s0 it is possible to make this
+one half of a \s-1BIO\s0 pair and have all the data processed by the chain under application
+control.
+.PP
+One typical use of \s-1BIO\s0 pairs is to place \s-1TLS/SSL I/O\s0 under application control, this
+can be used when the application wishes to use a non standard transport for
+\&\s-1TLS/SSL\s0 or the normal socket routines are inappropriate.
+.PP
+Calls to \fBBIO_read_ex()\fR will read data from the buffer or request a retry if no
+data is available.
+.PP
+Calls to \fBBIO_write_ex()\fR will place data in the buffer or request a retry if the
+buffer is full.
+.PP
+The standard calls \fBBIO_ctrl_pending()\fR and \fBBIO_ctrl_wpending()\fR can be used to
+determine the amount of pending data in the read or write buffer.
+.PP
+\&\fBBIO_reset()\fR clears any data in the write buffer.
+.PP
+\&\fBBIO_make_bio_pair()\fR joins two separate BIOs into a connected pair.
+.PP
+\&\fBBIO_destroy_pair()\fR destroys the association between two connected BIOs. Freeing
+up any half of the pair will automatically destroy the association.
+.PP
+\&\fBBIO_shutdown_wr()\fR is used to close down a \s-1BIO\s0 \fBb\fR. After this call no further
+writes on \s-1BIO\s0 \fBb\fR are allowed (they will return an error). Reads on the other
+half of the pair will return any pending data or \s-1EOF\s0 when all pending data has
+been read.
+.PP
+\&\fBBIO_set_write_buf_size()\fR sets the write buffer size of \s-1BIO\s0 \fBb\fR to \fBsize\fR.
+If the size is not initialized a default value is used. This is currently
+17K, sufficient for a maximum size \s-1TLS\s0 record.
+.PP
+\&\fBBIO_get_write_buf_size()\fR returns the size of the write buffer.
+.PP
+\&\fBBIO_new_bio_pair()\fR combines the calls to \fBBIO_new()\fR, \fBBIO_make_bio_pair()\fR and
+\&\fBBIO_set_write_buf_size()\fR to create a connected pair of BIOs \fBbio1\fR, \fBbio2\fR
+with write buffer sizes \fBwritebuf1\fR and \fBwritebuf2\fR. If either size is
+zero then the default size is used. \fBBIO_new_bio_pair()\fR does not check whether
+\&\fBbio1\fR or \fBbio2\fR do point to some other \s-1BIO,\s0 the values are overwritten,
+\&\fBBIO_free()\fR is not called.
+.PP
+\&\fBBIO_get_write_guarantee()\fR and \fBBIO_ctrl_get_write_guarantee()\fR return the maximum
+length of data that can be currently written to the \s-1BIO.\s0 Writes larger than this
+value will return a value from \fBBIO_write_ex()\fR less than the amount requested or
+if the buffer is full request a retry. \fBBIO_ctrl_get_write_guarantee()\fR is a
+function whereas \fBBIO_get_write_guarantee()\fR is a macro.
+.PP
+\&\fBBIO_get_read_request()\fR and \fBBIO_ctrl_get_read_request()\fR return the
+amount of data requested, or the buffer size if it is less, if the
+last read attempt at the other half of the \s-1BIO\s0 pair failed due to an
+empty buffer. This can be used to determine how much data should be
+written to the \s-1BIO\s0 so the next read will succeed: this is most useful
+in \s-1TLS/SSL\s0 applications where the amount of data read is usually
+meaningful rather than just a buffer size. After a successful read
+this call will return zero. It also will return zero once new data
+has been written satisfying the read request or part of it.
+Note that \fBBIO_get_read_request()\fR never returns an amount larger
+than that returned by \fBBIO_get_write_guarantee()\fR.
+.PP
+\&\fBBIO_ctrl_reset_read_request()\fR can also be used to reset the value returned by
+\&\fBBIO_get_read_request()\fR to zero.
+.SH "NOTES"
+.IX Header "NOTES"
+Both halves of a \s-1BIO\s0 pair should be freed. That is even if one half is implicit
+freed due to a \fBBIO_free_all()\fR or \fBSSL_free()\fR call the other half needs to be freed.
+.PP
+When used in bidirectional applications (such as \s-1TLS/SSL\s0) care should be taken to
+flush any data in the write buffer. This can be done by calling \fBBIO_pending()\fR
+on the other half of the pair and, if any data is pending, reading it and sending
+it to the underlying transport. This must be done before any normal processing
+(such as calling \fBselect()\fR ) due to a request and \fBBIO_should_read()\fR being true.
+.PP
+To see why this is important consider a case where a request is sent using
+\&\fBBIO_write_ex()\fR and a response read with \fBBIO_read_ex()\fR, this can occur during an
+\&\s-1TLS/SSL\s0 handshake for example. \fBBIO_write_ex()\fR will succeed and place data in the
+write buffer. \fBBIO_read_ex()\fR will initially fail and \fBBIO_should_read()\fR will be
+true. If the application then waits for data to be available on the underlying
+transport before flushing the write buffer it will never succeed because the
+request was never sent!
+.PP
+\&\fBBIO_eof()\fR is true if no data is in the peer \s-1BIO\s0 and the peer \s-1BIO\s0 has been
+shutdown.
+.PP
+\&\fBBIO_make_bio_pair()\fR, \fBBIO_destroy_bio_pair()\fR, \fBBIO_shutdown_wr()\fR,
+\&\fBBIO_set_write_buf_size()\fR, \fBBIO_get_write_buf_size()\fR,
+\&\fBBIO_get_write_guarantee()\fR, and \fBBIO_get_read_request()\fR are implemented
+as macros.
+.SH "RETURN VALUES"
+.IX Header "RETURN VALUES"
+\&\fBBIO_new_bio_pair()\fR returns 1 on success, with the new BIOs available in
+\&\fBbio1\fR and \fBbio2\fR, or 0 on failure, with \s-1NULL\s0 pointers stored into the
+locations for \fBbio1\fR and \fBbio2\fR. Check the error stack for more information.
+.PP
+[\s-1XXXXX:\s0 More return values need to be added here]
+.SH "EXAMPLES"
+.IX Header "EXAMPLES"
+The \s-1BIO\s0 pair can be used to have full control over the network access of an
+application. The application can call \fBselect()\fR on the socket as required
+without having to go through the SSL-interface.
+.PP
+.Vb 1
+\& BIO *internal_bio, *network_bio;
+\&
+\& ...
+\& BIO_new_bio_pair(&internal_bio, 0, &network_bio, 0);
+\& SSL_set_bio(ssl, internal_bio, internal_bio);
+\& SSL_operations(); /* e.g SSL_read and SSL_write */
+\& ...
+\&
+\& application | TLS\-engine
+\& | |
+\& +\-\-\-\-\-\-\-\-\-\-> SSL_operations()
+\& | /\e ||
+\& | || \e/
+\& | BIO\-pair (internal_bio)
+\& | BIO\-pair (network_bio)
+\& | || /\e
+\& | \e/ ||
+\& +\-\-\-\-\-\-\-\-\-\-\-< BIO_operations()
+\& | |
+\& | |
+\& socket
+\&
+\& ...
+\& SSL_free(ssl); /* implicitly frees internal_bio */
+\& BIO_free(network_bio);
+\& ...
+.Ve
+.PP
+As the \s-1BIO\s0 pair will only buffer the data and never directly access the
+connection, it behaves non-blocking and will return as soon as the write
+buffer is full or the read buffer is drained. Then the application has to
+flush the write buffer and/or fill the read buffer.
+.PP
+Use the \fBBIO_ctrl_pending()\fR, to find out whether data is buffered in the \s-1BIO\s0
+and must be transferred to the network. Use \fBBIO_ctrl_get_read_request()\fR to
+find out, how many bytes must be written into the buffer before the
+\&\fBSSL_operation()\fR can successfully be continued.
+.SH "WARNINGS"
+.IX Header "WARNINGS"
+As the data is buffered, \fBSSL_operation()\fR may return with an \s-1ERROR_SSL_WANT_READ\s0
+condition, but there is still data in the write buffer. An application must
+not rely on the error value of \fBSSL_operation()\fR but must assure that the
+write buffer is always flushed first. Otherwise a deadlock may occur as
+the peer might be waiting for the data before being able to continue.
+.SH "SEE ALSO"
+.IX Header "SEE ALSO"
+\&\fBSSL_set_bio\fR\|(3), \fBssl\fR\|(7), \fBbio\fR\|(7),
+\&\fBBIO_should_retry\fR\|(3), \fBBIO_read_ex\fR\|(3)
+.SH "COPYRIGHT"
+.IX Header "COPYRIGHT"
+Copyright 2000\-2019 The OpenSSL Project Authors. All Rights Reserved.
+.PP
+Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use
+this file except in compliance with the License. You can obtain a copy
+in the file \s-1LICENSE\s0 in the source distribution or at
+<https://www.openssl.org/source/license.html>.