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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_should_retry.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
Diffstat (limited to 'secure/lib/libcrypto/man/man3/BIO_should_retry.3')
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+.\" ========================================================================
+.\"
+.IX Title "BIO_SHOULD_RETRY 3"
+.TH BIO_SHOULD_RETRY 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_should_read, BIO_should_write, BIO_should_io_special, BIO_retry_type, BIO_should_retry, BIO_get_retry_BIO, BIO_get_retry_reason, BIO_set_retry_reason \- BIO retry functions
+.SH "SYNOPSIS"
+.IX Header "SYNOPSIS"
+.Vb 1
+\& #include <openssl/bio.h>
+\&
+\& int BIO_should_read(BIO *b);
+\& int BIO_should_write(BIO *b);
+\& int BIO_should_io_special(iBIO *b);
+\& int BIO_retry_type(BIO *b);
+\& int BIO_should_retry(BIO *b);
+\&
+\& BIO *BIO_get_retry_BIO(BIO *bio, int *reason);
+\& int BIO_get_retry_reason(BIO *bio);
+\& void BIO_set_retry_reason(BIO *bio, int reason);
+.Ve
+.SH "DESCRIPTION"
+.IX Header "DESCRIPTION"
+These functions determine why a \s-1BIO\s0 is not able to read or write data.
+They will typically be called after a failed \fBBIO_read_ex()\fR or \fBBIO_write_ex()\fR
+call.
+.PP
+\&\fBBIO_should_retry()\fR is true if the call that produced this condition
+should then be retried at a later time.
+.PP
+If \fBBIO_should_retry()\fR is false then the cause is an error condition.
+.PP
+\&\fBBIO_should_read()\fR is true if the cause of the condition is that the \s-1BIO\s0
+has insufficient data to return. Check for readability and/or retry the
+last operation.
+.PP
+\&\fBBIO_should_write()\fR is true if the cause of the condition is that the \s-1BIO\s0
+has pending data to write. Check for writability and/or retry the
+last operation.
+.PP
+\&\fBBIO_should_io_special()\fR is true if some \*(L"special\*(R" condition, that is a
+reason other than reading or writing is the cause of the condition.
+.PP
+\&\fBBIO_retry_type()\fR returns a mask of the cause of a retry condition
+consisting of the values \fB\s-1BIO_FLAGS_READ\s0\fR, \fB\s-1BIO_FLAGS_WRITE\s0\fR,
+\&\fB\s-1BIO_FLAGS_IO_SPECIAL\s0\fR though current \s-1BIO\s0 types will only set one of
+these.
+.PP
+\&\fBBIO_get_retry_BIO()\fR determines the precise reason for the special
+condition, it returns the \s-1BIO\s0 that caused this condition and if
+\&\fBreason\fR is not \s-1NULL\s0 it contains the reason code. The meaning of
+the reason code and the action that should be taken depends on
+the type of \s-1BIO\s0 that resulted in this condition.
+.PP
+\&\fBBIO_get_retry_reason()\fR returns the reason for a special condition if
+passed the relevant \s-1BIO,\s0 for example as returned by \fBBIO_get_retry_BIO()\fR.
+.PP
+\&\fBBIO_set_retry_reason()\fR sets the retry reason for a special condition for a given
+\&\s-1BIO.\s0 This would usually only be called by \s-1BIO\s0 implementations.
+.SH "NOTES"
+.IX Header "NOTES"
+\&\fBBIO_should_read()\fR, \fBBIO_should_write()\fR, \fBBIO_should_io_special()\fR,
+\&\fBBIO_retry_type()\fR, and \fBBIO_should_retry()\fR, are implemented as macros.
+.PP
+If \fBBIO_should_retry()\fR returns false then the precise \*(L"error condition\*(R"
+depends on the \s-1BIO\s0 type that caused it and the return code of the \s-1BIO\s0
+operation. For example if a call to \fBBIO_read_ex()\fR on a socket \s-1BIO\s0 returns
+0 and \fBBIO_should_retry()\fR is false then the cause will be that the
+connection closed. A similar condition on a file \s-1BIO\s0 will mean that it
+has reached \s-1EOF.\s0 Some \s-1BIO\s0 types may place additional information on
+the error queue. For more details see the individual \s-1BIO\s0 type manual
+pages.
+.PP
+If the underlying I/O structure is in a blocking mode almost all current
+\&\s-1BIO\s0 types will not request a retry, because the underlying I/O
+calls will not. If the application knows that the \s-1BIO\s0 type will never
+signal a retry then it need not call \fBBIO_should_retry()\fR after a failed
+\&\s-1BIO I/O\s0 call. This is typically done with file BIOs.
+.PP
+\&\s-1SSL\s0 BIOs are the only current exception to this rule: they can request a
+retry even if the underlying I/O structure is blocking, if a handshake
+occurs during a call to \fBBIO_read()\fR. An application can retry the failed
+call immediately or avoid this situation by setting \s-1SSL_MODE_AUTO_RETRY\s0
+on the underlying \s-1SSL\s0 structure.
+.PP
+While an application may retry a failed non blocking call immediately
+this is likely to be very inefficient because the call will fail
+repeatedly until data can be processed or is available. An application
+will normally wait until the necessary condition is satisfied. How
+this is done depends on the underlying I/O structure.
+.PP
+For example if the cause is ultimately a socket and \fBBIO_should_read()\fR
+is true then a call to \fBselect()\fR may be made to wait until data is
+available and then retry the \s-1BIO\s0 operation. By combining the retry
+conditions of several non blocking BIOs in a single \fBselect()\fR call
+it is possible to service several BIOs in a single thread, though
+the performance may be poor if \s-1SSL\s0 BIOs are present because long delays
+can occur during the initial handshake process.
+.PP
+It is possible for a \s-1BIO\s0 to block indefinitely if the underlying I/O
+structure cannot process or return any data. This depends on the behaviour of
+the platforms I/O functions. This is often not desirable: one solution
+is to use non blocking I/O and use a timeout on the \fBselect()\fR (or
+equivalent) call.
+.SH "BUGS"
+.IX Header "BUGS"
+The OpenSSL \s-1ASN1\s0 functions cannot gracefully deal with non blocking I/O:
+that is they cannot retry after a partial read or write. This is usually
+worked around by only passing the relevant data to \s-1ASN1\s0 functions when
+the entire structure can be read or written.
+.SH "RETURN VALUES"
+.IX Header "RETURN VALUES"
+\&\fBBIO_should_read()\fR, \fBBIO_should_write()\fR, \fBBIO_should_io_special()\fR, and
+\&\fBBIO_should_retry()\fR return either 1 or 0 based on the actual conditions
+of the \fB\s-1BIO\s0\fR.
+.PP
+\&\fBBIO_retry_type()\fR returns a flag combination presenting the cause of a retry
+condition or false if there is no retry condition.
+.PP
+\&\fBBIO_get_retry_BIO()\fR returns a valid \fB\s-1BIO\s0\fR structure.
+.PP
+\&\fBBIO_get_retry_reason()\fR returns the reason for a special condition.
+.SH "SEE ALSO"
+.IX Header "SEE ALSO"
+bio
+.SH "HISTORY"
+.IX Header "HISTORY"
+The \fBBIO_get_retry_reason()\fR and \fBBIO_set_retry_reason()\fR functions were added in
+OpenSSL 1.1.0.
+.SH "COPYRIGHT"
+.IX Header "COPYRIGHT"
+Copyright 2000\-2018 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>.