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.\" ========================================================================
.\"
.IX Title "SSL_CTX_set_tlsext_servername_callback 3"
.TH SSL_CTX_set_tlsext_servername_callback 3 "2019-12-20" "1.0.2u" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
SSL_CTX_set_tlsext_servername_callback, SSL_CTX_set_tlsext_servername_arg,
SSL_get_servername_type, SSL_get_servername \- handle server name indication
(SNI)
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/ssl.h>
\&
\& long SSL_CTX_set_tlsext_servername_callback(SSL_CTX *ctx,
\&                                   int (*cb)(SSL *, int *, void *));
\& long SSL_CTX_set_tlsext_servername_arg(SSL_CTX *ctx, void *arg);
\&
\& const char *SSL_get_servername(const SSL *s, const int type);
\& int SSL_get_servername_type(const SSL *s);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBSSL_CTX_set_tlsext_servername_callback()\fR sets the application callback \fBcb\fR
used by a server to perform any actions or configuration required based on
the servername extension received in the incoming connection. When \fBcb\fR
is \s-1NULL, SNI\s0 is not used. The \fBarg\fR value is a pointer which is passed to
the application callback.
.PP
\&\fBSSL_CTX_set_tlsext_servername_arg()\fR sets a context-specific argument to be
passed into the callback for this \fB\s-1SSL_CTX\s0\fR.
.PP
\&\fBSSL_get_servername()\fR returns a servername extension value of the specified
type if provided in the Client Hello or \s-1NULL.\s0
.PP
\&\fBSSL_get_servername_type()\fR returns the servername type or \-1 if no servername
is present. Currently the only supported type (defined in \s-1RFC3546\s0) is
\&\fBTLSEXT_NAMETYPE_host_name\fR.
.SH "NOTES"
.IX Header "NOTES"
The \s-1ALPN\s0 and \s-1SNI\s0 callbacks are both executed during Client Hello processing.
The servername callback is executed first, followed by the \s-1ALPN\s0 callback.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBSSL_CTX_set_tlsext_servername_callback()\fR and
\&\fBSSL_CTX_set_tlsext_servername_arg()\fR both always return 1 indicating success.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBssl\fR\|(7), \fBSSL_CTX_set_alpn_select_cb\fR\|(3),
\&\fBSSL_get0_alpn_selected\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2017 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>.