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.IX Title "SSL_SESSION_GET0_HOSTNAME 3ossl"
.TH SSL_SESSION_GET0_HOSTNAME 3ossl 2026-06-09 3.5.7 OpenSSL
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.nh
.SH NAME
SSL_SESSION_get0_hostname,
SSL_SESSION_set1_hostname,
SSL_SESSION_get0_alpn_selected,
SSL_SESSION_set1_alpn_selected
\&\- get and set SNI and ALPN data associated with a session
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/ssl.h>
\&
\& const char *SSL_SESSION_get0_hostname(const SSL_SESSION *s);
\& int SSL_SESSION_set1_hostname(SSL_SESSION *s, const char *hostname);
\&
\& void SSL_SESSION_get0_alpn_selected(const SSL_SESSION *s,
\&                                     const unsigned char **alpn,
\&                                     size_t *len);
\& int SSL_SESSION_set1_alpn_selected(SSL_SESSION *s, const unsigned char *alpn,
\&                                    size_t len);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\fBSSL_SESSION_get0_hostname()\fR retrieves the Server Name Indication (SNI) value
that was sent by the client when the session was created if the server
acknowledged the client\*(Aqs SNI extension by including an empty SNI extension
in response. Otherwise NULL is returned.
.PP
The value returned is a pointer to memory maintained within \fBs\fR and
should not be free\*(Aqd.
.PP
\&\fBSSL_SESSION_set1_hostname()\fR sets the SNI value for the hostname to a copy of
the string provided in hostname.
.PP
\&\fBSSL_SESSION_get0_alpn_selected()\fR retrieves the selected ALPN protocol for this
session and its associated length in bytes. The returned value of \fB*alpn\fR is a
pointer to memory maintained within \fBs\fR and should not be free\*(Aqd.
.PP
\&\fBSSL_SESSION_set1_alpn_selected()\fR sets the ALPN protocol for this session to the
value in \fBalpn\fR which should be of length \fBlen\fR bytes. A copy of the input
value is made, and the caller retains ownership of the memory pointed to by
\&\fBalpn\fR.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBSSL_SESSION_get0_hostname()\fR returns the SNI string if available, or NULL if not.
.PP
\&\fBSSL_SESSION_set1_hostname()\fR returns 1 on success or 0 on error.
.PP
\&\fBSSL_SESSION_set1_alpn_selected()\fR returns 1 on success or 0 on error.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBssl\fR\|(7),
\&\fBd2i_SSL_SESSION\fR\|(3),
\&\fBSSL_SESSION_get_time\fR\|(3),
\&\fBSSL_SESSION_free\fR\|(3)
.SH HISTORY
.IX Header "HISTORY"
The \fBSSL_SESSION_set1_hostname()\fR, \fBSSL_SESSION_get0_alpn_selected()\fR and
\&\fBSSL_SESSION_set1_alpn_selected()\fR functions were added in OpenSSL 1.1.1.
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright 2016\-2025 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (the "License").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.
