hostname=

static VALUE
ossl_ssl_set_hostname(VALUE self, VALUE arg)
{
    SSL *ssl;
    char *hostname = NULL;

    GetSSL(self, ssl);

    if (!NIL_P(arg))
        hostname = StringValueCStr(arg);

    if (!SSL_set_tlsext_host_name(ssl, hostname))
        ossl_raise(eSSLError, NULL);

    /* for SSLSocket#hostname */
    rb_ivar_set(self, id_i_hostname, arg);

    return arg;
}