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131 .IX Title "SSL_CTX_SET_TLSEXT_SERVERNAME_CALLBACK 3"
132 .TH SSL_CTX_SET_TLSEXT_SERVERNAME_CALLBACK 3 "2018-09-11" "1.1.1" "OpenSSL"
133 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
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138 SSL_CTX_set_tlsext_servername_callback, SSL_CTX_set_tlsext_servername_arg, SSL_get_servername_type, SSL_get_servername, SSL_set_tlsext_host_name \- handle server name indication (SNI)
140 .IX Header "SYNOPSIS"
142 \& #include <openssl/ssl.h>
144 \& long SSL_CTX_set_tlsext_servername_callback(SSL_CTX *ctx,
145 \& int (*cb)(SSL *, int *, void *));
146 \& long SSL_CTX_set_tlsext_servername_arg(SSL_CTX *ctx, void *arg);
148 \& const char *SSL_get_servername(const SSL *s, const int type);
149 \& int SSL_get_servername_type(const SSL *s);
151 \& int SSL_set_tlsext_host_name(const SSL *s, const char *name);
154 .IX Header "DESCRIPTION"
155 The functionality provided by the servername callback is superseded by the
156 ClientHello callback, which can be set using \fISSL_CTX_set_client_hello_cb()\fR.
157 The servername callback is retained for historical compatibility.
159 \&\fISSL_CTX_set_tlsext_servername_callback()\fR sets the application callback \fBcb\fR
160 used by a server to perform any actions or configuration required based on
161 the servername extension received in the incoming connection. When \fBcb\fR
162 is \s-1NULL, SNI\s0 is not used. The \fBarg\fR value is a pointer which is passed to
163 the application callback.
165 \&\fISSL_CTX_set_tlsext_servername_arg()\fR sets a context-specific argument to be
166 passed into the callback for this \fB\s-1SSL_CTX\s0\fR.
168 \&\fISSL_get_servername()\fR returns a servername extension value of the specified
169 type if provided in the Client Hello or \s-1NULL.\s0
171 \&\fISSL_get_servername_type()\fR returns the servername type or \-1 if no servername
172 is present. Currently the only supported type (defined in \s-1RFC3546\s0) is
173 \&\fBTLSEXT_NAMETYPE_host_name\fR.
175 \&\fISSL_set_tlsext_host_name()\fR sets the server name indication ClientHello extension
176 to contain the value \fBname\fR. The type of server name indication extension is set
177 to \fBTLSEXT_NAMETYPE_host_name\fR (defined in \s-1RFC3546\s0).
180 Several callbacks are executed during ClientHello processing, including
181 the ClientHello, \s-1ALPN,\s0 and servername callbacks. The ClientHello callback is
182 executed first, then the servername callback, followed by the \s-1ALPN\s0 callback.
184 The \fISSL_set_tlsext_host_name()\fR function should only be called on \s-1SSL\s0 objects
185 that will act as clients; otherwise the configured \fBname\fR will be ignored.
187 .IX Header "RETURN VALUES"
188 \&\fISSL_CTX_set_tlsext_servername_callback()\fR and
189 \&\fISSL_CTX_set_tlsext_servername_arg()\fR both always return 1 indicating success.
190 \&\fISSL_set_tlsext_host_name()\fR returns 1 on success, 0 in case of error.
192 .IX Header "SEE ALSO"
193 \&\fIssl\fR\|(7), \fISSL_CTX_set_alpn_select_cb\fR\|(3),
194 \&\fISSL_get0_alpn_selected\fR\|(3), \fISSL_CTX_set_client_hello_cb\fR\|(3)
196 .IX Header "COPYRIGHT"
197 Copyright 2017 The OpenSSL Project Authors. All Rights Reserved.
199 Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use
200 this file except in compliance with the License. You can obtain a copy
201 in the file \s-1LICENSE\s0 in the source distribution or at
202 <https://www.openssl.org/source/license.html>.