.\" Automatically generated by Pod::Man 2.25 (Pod::Simple 3.16) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. \*(C+ will .\" give a nicer C++. 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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" SSL_write \- write bytes to a TLS/SSL connection. .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include \& \& int SSL_write(SSL *ssl, const void *buf, int num); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" \&\fISSL_write()\fR writes \fBnum\fR bytes from the buffer \fBbuf\fR into the specified \&\fBssl\fR connection. .SH "NOTES" .IX Header "NOTES" If necessary, \fISSL_write()\fR will negotiate a \s-1TLS/SSL\s0 session, if not already explicitly performed by \fISSL_connect\fR\|(3) or \&\fISSL_accept\fR\|(3). If the peer requests a re-negotiation, it will be performed transparently during the \fISSL_write()\fR operation. The behaviour of \fISSL_write()\fR depends on the underlying \s-1BIO\s0. .PP For the transparent negotiation to succeed, the \fBssl\fR must have been initialized to client or server mode. This is being done by calling \&\fISSL_set_connect_state\fR\|(3) or \fISSL_set_accept_state()\fR before the first call to an \fISSL_read\fR\|(3) or \fISSL_write()\fR function. .PP If the underlying \s-1BIO\s0 is \fBblocking\fR, \fISSL_write()\fR will only return, once the write operation has been finished or an error occurred, except when a renegotiation take place, in which case a \s-1SSL_ERROR_WANT_READ\s0 may occur. This behaviour can be controlled with the \s-1SSL_MODE_AUTO_RETRY\s0 flag of the \&\fISSL_CTX_set_mode\fR\|(3) call. .PP If the underlying \s-1BIO\s0 is \fBnon-blocking\fR, \fISSL_write()\fR will also return, when the underlying \s-1BIO\s0 could not satisfy the needs of \fISSL_write()\fR to continue the operation. In this case a call to \&\fISSL_get_error\fR\|(3) with the return value of \fISSL_write()\fR will yield \fB\s-1SSL_ERROR_WANT_READ\s0\fR or \&\fB\s-1SSL_ERROR_WANT_WRITE\s0\fR. As at any time a re-negotiation is possible, a call to \fISSL_write()\fR can also cause read operations! The calling process then must repeat the call after taking appropriate action to satisfy the needs of \fISSL_write()\fR. The action depends on the underlying \s-1BIO\s0. When using a non-blocking socket, nothing is to be done, but \fIselect()\fR can be used to check for the required condition. When using a buffering \s-1BIO\s0, like a \s-1BIO\s0 pair, data must be written into or retrieved out of the \s-1BIO\s0 before being able to continue. .PP \&\fISSL_write()\fR will only return with success, when the complete contents of \fBbuf\fR of length \fBnum\fR has been written. This default behaviour can be changed with the \s-1SSL_MODE_ENABLE_PARTIAL_WRITE\s0 option of \&\fISSL_CTX_set_mode\fR\|(3). When this flag is set, \&\fISSL_write()\fR will also return with success, when a partial write has been successfully completed. In this case the \fISSL_write()\fR operation is considered completed. The bytes are sent and a new \fISSL_write()\fR operation with a new buffer (with the already sent bytes removed) must be started. A partial write is performed with the size of a message block, which is 16kB for SSLv3/TLSv1. .SH "WARNING" .IX Header "WARNING" When an \fISSL_write()\fR operation has to be repeated because of \&\fB\s-1SSL_ERROR_WANT_READ\s0\fR or \fB\s-1SSL_ERROR_WANT_WRITE\s0\fR, it must be repeated with the same arguments. .PP When calling \fISSL_write()\fR with num=0 bytes to be sent the behaviour is undefined. .SH "RETURN VALUES" .IX Header "RETURN VALUES" The following return values can occur: .IP ">0" 4 .IX Item ">0" The write operation was successful, the return value is the number of bytes actually written to the \s-1TLS/SSL\s0 connection. .IP "0" 4 The write operation was not successful. Probably the underlying connection was closed. Call \fISSL_get_error()\fR with the return value \fBret\fR to find out, whether an error occurred or the connection was shut down cleanly (\s-1SSL_ERROR_ZERO_RETURN\s0). .Sp SSLv2 (deprecated) does not support a shutdown alert protocol, so it can only be detected, whether the underlying connection was closed. It cannot be checked, why the closure happened. .IP "<0" 4 .IX Item "<0" The write operation was not successful, because either an error occurred or action must be taken by the calling process. Call \fISSL_get_error()\fR with the return value \fBret\fR to find out the reason. .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fISSL_get_error\fR\|(3), \fISSL_read\fR\|(3), \&\fISSL_CTX_set_mode\fR\|(3), \fISSL_CTX_new\fR\|(3), \&\fISSL_connect\fR\|(3), \fISSL_accept\fR\|(3) \&\fISSL_set_connect_state\fR\|(3), \&\fIssl\fR\|(3), \fIbio\fR\|(3)