Merge branch 'vendor/OPENSSL'
[dragonfly.git] / secure / lib / libssl / man / SSL_write.3
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129.\" ========================================================================
130.\"
131.IX Title "SSL_write 3"
18ed9402 132.TH SSL_write 3 "2008-09-27" "0.9.8i" "OpenSSL"
984263bc 133.SH "NAME"
a7d27d5a 134SSL_write \- write bytes to a TLS/SSL connection.
984263bc 135.SH "SYNOPSIS"
e056f0e0 136.IX Header "SYNOPSIS"
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137.Vb 1
138\& #include <openssl/ssl.h>
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139.Ve
140.PP
141.Vb 1
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142\& int SSL_write(SSL *ssl, const void *buf, int num);
143.Ve
144.SH "DESCRIPTION"
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145.IX Header "DESCRIPTION"
146\&\fISSL_write()\fR writes \fBnum\fR bytes from the buffer \fBbuf\fR into the specified
147\&\fBssl\fR connection.
984263bc 148.SH "NOTES"
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149.IX Header "NOTES"
150If necessary, \fISSL_write()\fR will negotiate a \s-1TLS/SSL\s0 session, if
151not already explicitly performed by \fISSL_connect\fR\|(3) or
152\&\fISSL_accept\fR\|(3). If the
aac4ff6f 153peer requests a re\-negotiation, it will be performed transparently during
984263bc 154the \fISSL_write()\fR operation. The behaviour of \fISSL_write()\fR depends on the
aac4ff6f 155underlying \s-1BIO\s0.
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156.PP
157For the transparent negotiation to succeed, the \fBssl\fR must have been
158initialized to client or server mode. This is being done by calling
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159\&\fISSL_set_connect_state\fR\|(3) or \fISSL_set_accept_state()\fR
160before the first call to an \fISSL_read\fR\|(3) or \fISSL_write()\fR function.
984263bc 161.PP
e056f0e0 162If the underlying \s-1BIO\s0 is \fBblocking\fR, \fISSL_write()\fR will only return, once the
984263bc 163write operation has been finished or an error occurred, except when a
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164renegotiation take place, in which case a \s-1SSL_ERROR_WANT_READ\s0 may occur.
165This behaviour can be controlled with the \s-1SSL_MODE_AUTO_RETRY\s0 flag of the
166\&\fISSL_CTX_set_mode\fR\|(3) call.
984263bc 167.PP
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168If the underlying \s-1BIO\s0 is \fBnon-blocking\fR, \fISSL_write()\fR will also return,
169when the underlying \s-1BIO\s0 could not satisfy the needs of \fISSL_write()\fR
984263bc 170to continue the operation. In this case a call to
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171\&\fISSL_get_error\fR\|(3) with the
172return value of \fISSL_write()\fR will yield \fB\s-1SSL_ERROR_WANT_READ\s0\fR or
173\&\fB\s-1SSL_ERROR_WANT_WRITE\s0\fR. As at any time a re-negotiation is possible, a
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174call to \fISSL_write()\fR can also cause read operations! The calling process
175then must repeat the call after taking appropriate action to satisfy the
e056f0e0 176needs of \fISSL_write()\fR. The action depends on the underlying \s-1BIO\s0. When using a
984263bc 177non-blocking socket, nothing is to be done, but \fIselect()\fR can be used to check
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178for the required condition. When using a buffering \s-1BIO\s0, like a \s-1BIO\s0 pair, data
179must be written into or retrieved out of the \s-1BIO\s0 before being able to continue.
984263bc 180.PP
e056f0e0 181\&\fISSL_write()\fR will only return with success, when the complete contents
984263bc 182of \fBbuf\fR of length \fBnum\fR has been written. This default behaviour
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183can be changed with the \s-1SSL_MODE_ENABLE_PARTIAL_WRITE\s0 option of
184\&\fISSL_CTX_set_mode\fR\|(3). When this flag is set,
185\&\fISSL_write()\fR will also return with success, when a partial write has been
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186successfully completed. In this case the \fISSL_write()\fR operation is considered
187completed. The bytes are sent and a new \fISSL_write()\fR operation with a new
188buffer (with the already sent bytes removed) must be started.
189A partial write is performed with the size of a message block, which is
19016kB for SSLv3/TLSv1.
191.SH "WARNING"
e056f0e0 192.IX Header "WARNING"
984263bc 193When an \fISSL_write()\fR operation has to be repeated because of
e056f0e0 194\&\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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195with the same arguments.
196.PP
197When calling \fISSL_write()\fR with num=0 bytes to be sent the behaviour is
198undefined.
199.SH "RETURN VALUES"
e056f0e0 200.IX Header "RETURN VALUES"
984263bc 201The following return values can occur:
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202.IP ">0" 4
203.IX Item ">0"
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204The write operation was successful, the return value is the number of
205bytes actually written to the \s-1TLS/SSL\s0 connection.
e056f0e0 206.IP "0" 4
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207The write operation was not successful. Probably the underlying connection
208was closed. Call \fISSL_get_error()\fR with the return value \fBret\fR to find out,
209whether an error occurred or the connection was shut down cleanly
210(\s-1SSL_ERROR_ZERO_RETURN\s0).
211.Sp
212SSLv2 (deprecated) does not support a shutdown alert protocol, so it can
213only be detected, whether the underlying connection was closed. It cannot
214be checked, why the closure happened.
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215.IP "<0" 4
216.IX Item "<0"
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217The write operation was not successful, because either an error occurred
218or action must be taken by the calling process. Call \fISSL_get_error()\fR with the
219return value \fBret\fR to find out the reason.
220.SH "SEE ALSO"
a7d27d5a 221.IX Header "SEE ALSO"
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222\&\fISSL_get_error\fR\|(3), \fISSL_read\fR\|(3),
223\&\fISSL_CTX_set_mode\fR\|(3), \fISSL_CTX_new\fR\|(3),
224\&\fISSL_connect\fR\|(3), \fISSL_accept\fR\|(3)
225\&\fISSL_set_connect_state\fR\|(3),
226\&\fIssl\fR\|(3), \fIbio\fR\|(3)