Update files for OpenSSL-1.0.0f import.
[dragonfly.git] / secure / lib / libssl / man / SSL_write.3
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124.\" ========================================================================
125.\"
126.IX Title "SSL_write 3"
e3261593 127.TH SSL_write 3 "2012-01-04" "1.0.0f" "OpenSSL"
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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
984263bc 132.SH "NAME"
a7d27d5a 133SSL_write \- write bytes to a TLS/SSL connection.
984263bc 134.SH "SYNOPSIS"
e056f0e0 135.IX Header "SYNOPSIS"
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136.Vb 1
137\& #include <openssl/ssl.h>
e257b235 138\&
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139\& int SSL_write(SSL *ssl, const void *buf, int num);
140.Ve
141.SH "DESCRIPTION"
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142.IX Header "DESCRIPTION"
143\&\fISSL_write()\fR writes \fBnum\fR bytes from the buffer \fBbuf\fR into the specified
144\&\fBssl\fR connection.
984263bc 145.SH "NOTES"
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146.IX Header "NOTES"
147If necessary, \fISSL_write()\fR will negotiate a \s-1TLS/SSL\s0 session, if
148not already explicitly performed by \fISSL_connect\fR\|(3) or
149\&\fISSL_accept\fR\|(3). If the
e257b235 150peer requests a re-negotiation, it will be performed transparently during
984263bc 151the \fISSL_write()\fR operation. The behaviour of \fISSL_write()\fR depends on the
e257b235 152underlying \s-1BIO\s0.
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153.PP
154For the transparent negotiation to succeed, the \fBssl\fR must have been
155initialized to client or server mode. This is being done by calling
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156\&\fISSL_set_connect_state\fR\|(3) or \fISSL_set_accept_state()\fR
157before the first call to an \fISSL_read\fR\|(3) or \fISSL_write()\fR function.
984263bc 158.PP
e056f0e0 159If the underlying \s-1BIO\s0 is \fBblocking\fR, \fISSL_write()\fR will only return, once the
984263bc 160write operation has been finished or an error occurred, except when a
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161renegotiation take place, in which case a \s-1SSL_ERROR_WANT_READ\s0 may occur.
162This behaviour can be controlled with the \s-1SSL_MODE_AUTO_RETRY\s0 flag of the
163\&\fISSL_CTX_set_mode\fR\|(3) call.
984263bc 164.PP
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165If the underlying \s-1BIO\s0 is \fBnon-blocking\fR, \fISSL_write()\fR will also return,
166when the underlying \s-1BIO\s0 could not satisfy the needs of \fISSL_write()\fR
984263bc 167to continue the operation. In this case a call to
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168\&\fISSL_get_error\fR\|(3) with the
169return value of \fISSL_write()\fR will yield \fB\s-1SSL_ERROR_WANT_READ\s0\fR or
170\&\fB\s-1SSL_ERROR_WANT_WRITE\s0\fR. As at any time a re-negotiation is possible, a
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171call to \fISSL_write()\fR can also cause read operations! The calling process
172then must repeat the call after taking appropriate action to satisfy the
e056f0e0 173needs of \fISSL_write()\fR. The action depends on the underlying \s-1BIO\s0. When using a
984263bc 174non-blocking socket, nothing is to be done, but \fIselect()\fR can be used to check
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175for the required condition. When using a buffering \s-1BIO\s0, like a \s-1BIO\s0 pair, data
176must be written into or retrieved out of the \s-1BIO\s0 before being able to continue.
984263bc 177.PP
e056f0e0 178\&\fISSL_write()\fR will only return with success, when the complete contents
984263bc 179of \fBbuf\fR of length \fBnum\fR has been written. This default behaviour
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180can be changed with the \s-1SSL_MODE_ENABLE_PARTIAL_WRITE\s0 option of
181\&\fISSL_CTX_set_mode\fR\|(3). When this flag is set,
182\&\fISSL_write()\fR will also return with success, when a partial write has been
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183successfully completed. In this case the \fISSL_write()\fR operation is considered
184completed. The bytes are sent and a new \fISSL_write()\fR operation with a new
185buffer (with the already sent bytes removed) must be started.
186A partial write is performed with the size of a message block, which is
18716kB for SSLv3/TLSv1.
188.SH "WARNING"
e056f0e0 189.IX Header "WARNING"
984263bc 190When an \fISSL_write()\fR operation has to be repeated because of
e056f0e0 191\&\fB\s-1SSL_ERROR_WANT_READ\s0\fR or \fB\s-1SSL_ERROR_WANT_WRITE\s0\fR, it must be repeated
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192with the same arguments.
193.PP
194When calling \fISSL_write()\fR with num=0 bytes to be sent the behaviour is
195undefined.
196.SH "RETURN VALUES"
e056f0e0 197.IX Header "RETURN VALUES"
984263bc 198The following return values can occur:
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199.IP ">0" 4
200.IX Item ">0"
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201The write operation was successful, the return value is the number of
202bytes actually written to the \s-1TLS/SSL\s0 connection.
e056f0e0 203.IP "0" 4
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204The write operation was not successful. Probably the underlying connection
205was closed. Call \fISSL_get_error()\fR with the return value \fBret\fR to find out,
206whether an error occurred or the connection was shut down cleanly
207(\s-1SSL_ERROR_ZERO_RETURN\s0).
208.Sp
209SSLv2 (deprecated) does not support a shutdown alert protocol, so it can
210only be detected, whether the underlying connection was closed. It cannot
211be checked, why the closure happened.
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212.IP "<0" 4
213.IX Item "<0"
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214The write operation was not successful, because either an error occurred
215or action must be taken by the calling process. Call \fISSL_get_error()\fR with the
216return value \fBret\fR to find out the reason.
217.SH "SEE ALSO"
a7d27d5a 218.IX Header "SEE ALSO"
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219\&\fISSL_get_error\fR\|(3), \fISSL_read\fR\|(3),
220\&\fISSL_CTX_set_mode\fR\|(3), \fISSL_CTX_new\fR\|(3),
221\&\fISSL_connect\fR\|(3), \fISSL_accept\fR\|(3)
222\&\fISSL_set_connect_state\fR\|(3),
223\&\fIssl\fR\|(3), \fIbio\fR\|(3)