Merge branch 'vendor/OPENSSL'
[dragonfly.git] / secure / lib / libssl / man / SSL_write.3
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132.\" ========================================================================
133.\"
134.IX Title "SSL_write 3"
fc468453 135.TH SSL_write 3 "2010-02-27" "0.9.8m" "OpenSSL"
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136.\" For nroff, turn off justification. Always turn off hyphenation; it makes
137.\" way too many mistakes in technical documents.
138.if n .ad l
139.nh
984263bc 140.SH "NAME"
a7d27d5a 141SSL_write \- write bytes to a TLS/SSL connection.
984263bc 142.SH "SYNOPSIS"
e056f0e0 143.IX Header "SYNOPSIS"
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144.Vb 1
145\& #include <openssl/ssl.h>
e257b235 146\&
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147\& int SSL_write(SSL *ssl, const void *buf, int num);
148.Ve
149.SH "DESCRIPTION"
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150.IX Header "DESCRIPTION"
151\&\fISSL_write()\fR writes \fBnum\fR bytes from the buffer \fBbuf\fR into the specified
152\&\fBssl\fR connection.
984263bc 153.SH "NOTES"
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154.IX Header "NOTES"
155If necessary, \fISSL_write()\fR will negotiate a \s-1TLS/SSL\s0 session, if
156not already explicitly performed by \fISSL_connect\fR\|(3) or
157\&\fISSL_accept\fR\|(3). If the
e257b235 158peer requests a re-negotiation, it will be performed transparently during
984263bc 159the \fISSL_write()\fR operation. The behaviour of \fISSL_write()\fR depends on the
e257b235 160underlying \s-1BIO\s0.
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161.PP
162For the transparent negotiation to succeed, the \fBssl\fR must have been
163initialized to client or server mode. This is being done by calling
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164\&\fISSL_set_connect_state\fR\|(3) or \fISSL_set_accept_state()\fR
165before the first call to an \fISSL_read\fR\|(3) or \fISSL_write()\fR function.
984263bc 166.PP
e056f0e0 167If the underlying \s-1BIO\s0 is \fBblocking\fR, \fISSL_write()\fR will only return, once the
984263bc 168write operation has been finished or an error occurred, except when a
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169renegotiation take place, in which case a \s-1SSL_ERROR_WANT_READ\s0 may occur.
170This behaviour can be controlled with the \s-1SSL_MODE_AUTO_RETRY\s0 flag of the
171\&\fISSL_CTX_set_mode\fR\|(3) call.
984263bc 172.PP
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173If the underlying \s-1BIO\s0 is \fBnon-blocking\fR, \fISSL_write()\fR will also return,
174when the underlying \s-1BIO\s0 could not satisfy the needs of \fISSL_write()\fR
984263bc 175to continue the operation. In this case a call to
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176\&\fISSL_get_error\fR\|(3) with the
177return value of \fISSL_write()\fR will yield \fB\s-1SSL_ERROR_WANT_READ\s0\fR or
178\&\fB\s-1SSL_ERROR_WANT_WRITE\s0\fR. As at any time a re-negotiation is possible, a
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179call to \fISSL_write()\fR can also cause read operations! The calling process
180then must repeat the call after taking appropriate action to satisfy the
e056f0e0 181needs of \fISSL_write()\fR. The action depends on the underlying \s-1BIO\s0. When using a
984263bc 182non-blocking socket, nothing is to be done, but \fIselect()\fR can be used to check
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183for the required condition. When using a buffering \s-1BIO\s0, like a \s-1BIO\s0 pair, data
184must be written into or retrieved out of the \s-1BIO\s0 before being able to continue.
984263bc 185.PP
e056f0e0 186\&\fISSL_write()\fR will only return with success, when the complete contents
984263bc 187of \fBbuf\fR of length \fBnum\fR has been written. This default behaviour
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188can be changed with the \s-1SSL_MODE_ENABLE_PARTIAL_WRITE\s0 option of
189\&\fISSL_CTX_set_mode\fR\|(3). When this flag is set,
190\&\fISSL_write()\fR will also return with success, when a partial write has been
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191successfully completed. In this case the \fISSL_write()\fR operation is considered
192completed. The bytes are sent and a new \fISSL_write()\fR operation with a new
193buffer (with the already sent bytes removed) must be started.
194A partial write is performed with the size of a message block, which is
19516kB for SSLv3/TLSv1.
196.SH "WARNING"
e056f0e0 197.IX Header "WARNING"
984263bc 198When an \fISSL_write()\fR operation has to be repeated because of
e056f0e0 199\&\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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200with the same arguments.
201.PP
202When calling \fISSL_write()\fR with num=0 bytes to be sent the behaviour is
203undefined.
204.SH "RETURN VALUES"
e056f0e0 205.IX Header "RETURN VALUES"
984263bc 206The following return values can occur:
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207.IP ">0" 4
208.IX Item ">0"
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209The write operation was successful, the return value is the number of
210bytes actually written to the \s-1TLS/SSL\s0 connection.
e056f0e0 211.IP "0" 4
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212The write operation was not successful. Probably the underlying connection
213was closed. Call \fISSL_get_error()\fR with the return value \fBret\fR to find out,
214whether an error occurred or the connection was shut down cleanly
215(\s-1SSL_ERROR_ZERO_RETURN\s0).
216.Sp
217SSLv2 (deprecated) does not support a shutdown alert protocol, so it can
218only be detected, whether the underlying connection was closed. It cannot
219be checked, why the closure happened.
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220.IP "<0" 4
221.IX Item "<0"
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222The write operation was not successful, because either an error occurred
223or action must be taken by the calling process. Call \fISSL_get_error()\fR with the
224return value \fBret\fR to find out the reason.
225.SH "SEE ALSO"
a7d27d5a 226.IX Header "SEE ALSO"
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227\&\fISSL_get_error\fR\|(3), \fISSL_read\fR\|(3),
228\&\fISSL_CTX_set_mode\fR\|(3), \fISSL_CTX_new\fR\|(3),
229\&\fISSL_connect\fR\|(3), \fISSL_accept\fR\|(3)
230\&\fISSL_set_connect_state\fR\|(3),
231\&\fIssl\fR\|(3), \fIbio\fR\|(3)