<br>

	<dt>
	  <strong>info</strong> <em>channel major minor message type</em>
	</dt>
	<dd>
	  This form of callback is invoked by the OpenSSL function
	  <code>SSL_CTX_set_info_callback()</code> during connection setup
	  and use.
	  <br>


	  <ul>
	  <li>Possible values for <em>major</em> are:
	  <code>handshake, alert, connect, accept</code>.</li>
	  <li>Possible values for <em>minor</em> are:
	  <code>start, done, read, write, loop, exit</code>.</li>
	  <li>The <em>message</em> argument is a descriptive string which may
	  be generated either by <code>SSL_state_string_long()</code> or by
	  <code>SSL_alert_desc_string_long()</code>, depending on context.</li>
	  <li>For alerts, the possible values for <em>type</em> are:
	  <code>warning, fatal, and unknown</code>. For others,
	  <code>info</code> is used.</li>
	  </ul>
	</dd>

	<dt>
	  <strong>message</strong> <em>channel direction version content_type data</em>
	</dt>
	<dd>
	  This form of callback is invoked by the OpenSSL function
	  <code>SSL_set_msg_callback()</code> whenever a message is sent or
	  received. It is only available when
	  OpenSSL is complied with the <em>enable-ssl-trace</em> option.
	  Where <em>direction</em> is Sent or Received, <em>version</em> is the
	  protocol version, <em>content_type</em> is the message content type,
	  and <em>data</em> is more info on the message from the <code>SSL_trace</code> API.
	</dd>
	<br>

	<dt>
	  <strong>session</strong> <em>session_id ticket lifetime</em>
	</dt>
	<dd>
	  This form of callback is invoked by the OpenSSL function
	  <code>SSL_CTX_sess_set_new_cb()</code>.

	<dl>

	<dt>
	  <strong>alpn</strong> <em>protocol</em>
	</dt>
	<dd>
	  For servers, this form of callback is invoked when the client ALPN
	  extension is received. Where <em>protocol</em> is the first
	  <b>-alpn</b> specified protocol common to the both the client and
	  server. If none, the first client specified protocol is used.
	</dd>

	<br>

	<dt>
	  <strong>hello</strong> <em>servername</em>
	</dt>

	<br>

	<dt>
	  <strong>sni</strong> <em>servername</em>
	</dt>
	<dd>
	  For servers, this form of callback is invoked when the SNI extension
	  from the client is received. Where <em>servername</em> is the client
	  provided server name from the <b>-servername</b> option. This is
	  used when a server supports multiple names, so the right certificate
	  can be used. Called after hello callback but before ALPN callback.
	</dd>

	<br>

	<dt>
	  <strong>verify</strong> <em>channel depth cert status error</em>
	</dt>
	<dd>
	  This form of callback is invoked by OpenSSL when a new certificate
	  is received from the peer. It allows the client to check the
	  certificate verification results and choose whether to continue
	  or not. It is called for each certificate in the certificate chain.
	  <ul>
	  <li>The <em>depth</em> argument is an integer representing the
	  current depth on the certificate chain, with
	  <code>0</code> as the peer certificate and higher values going
	  up to the Certificate Authority (CA).</li>
	  <li>The <em>cert</em> argument is a list of key-value pairs similar
	  to those returned by

}

/*
 *-------------------------------------------------------------------
 *
 * InfoCallback --
 *
 *	Monitors SSL connection process
 *
 * Results:
 *	None
 *
 * Side effects:
 *	Calls callback (if defined)
 *

    EvalCallback(interp, statePtr, cmdPtr);
    Tcl_DecrRefCount(cmdPtr);
}

/*
 *-------------------------------------------------------------------
 *
 * MessageCallback --
 *
 *	Monitors SSL protocol messages
 *
 * Results:
 *	None
 *
 * Side effects:
 *	Calls callback (if defined)
 *
 *-------------------------------------------------------------------
 */
#ifndef OPENSSL_NO_SSL_TRACE
static void
MessageCallback(int write_p, int version, int content_type, const void *buf, size_t len, SSL *ssl, void *arg) {
    State *statePtr = (State*)arg;
    Tcl_Interp *interp	= statePtr->interp;
    Tcl_Obj *cmdPtr;
    char *ver, *type;
    BIO *bio;
    char buffer[15000];
    buffer[0] = 0;

    dprintf("Called");

    if (statePtr->callback == (Tcl_Obj*)NULL)
	return;

    switch(version) {
#if OPENSSL_VERSION_NUMBER < 0x10100000L && !defined(NO_SSL2) && !defined(OPENSSL_NO_SSL2)
    case SSL2_VERSION:
	ver = "SSLv2";
	break;
#endif
#if !defined(NO_SSL3) && !defined(OPENSSL_NO_SSL3)
    case SSL3_VERSION:
	ver = "SSLv3";
	break;
#endif
    case TLS1_VERSION:
	ver = "TLSv1";
	break;
    case TLS1_1_VERSION:
	ver = "TLSv1.1";
	break;
    case TLS1_2_VERSION:
	ver = "TLSv1.2";
	break;
    case TLS1_3_VERSION:
	ver = "TLSv1.3";
	break;
    case 0:
        ver = "none";
	break;
    default:
	ver = "unknown";
	break;
    }

    switch (content_type) {
    case SSL3_RT_HEADER:
	type = "Header";
        break;
    case SSL3_RT_INNER_CONTENT_TYPE:
	type = "Inner Content Type";
        break;
    case SSL3_RT_CHANGE_CIPHER_SPEC:
	type = "Change Cipher";
        break;
    case SSL3_RT_ALERT:
	type = "Alert";
        break;
    case SSL3_RT_HANDSHAKE:
	type = "Handshake";
        break;
    case SSL3_RT_APPLICATION_DATA:
	type = "App Data";
        break;
    case DTLS1_RT_HEARTBEAT:
	type = "Heartbeat";
        break;
    default:
	type = "unknown";
    }

    /* Needs compile time option "enable-ssl-trace". */
    if ((bio = BIO_new(BIO_s_mem())) != NULL) {
	int n;
	SSL_trace(write_p, version, content_type, buf, len, ssl, (void *)bio);
	n = BIO_read(bio, buffer, min(BIO_pending(bio), 14999));
	n = (n<0) ? 0 : n;
	buffer[n] = 0;
	(void)BIO_flush(bio);
 	BIO_free(bio);
   }

    /* Create command to eval */
    cmdPtr = Tcl_DuplicateObj(statePtr->callback);
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj("message", -1));
    Tcl_ListObjAppendElement(interp, cmdPtr,
	    Tcl_NewStringObj(Tcl_GetChannelName(statePtr->self), -1));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(write_p ? "Sent" : "Received", -1));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(ver, -1));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(type, -1));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(buffer, -1));

    /* Eval callback command */
    Tcl_IncrRefCount(cmdPtr);
    EvalCallback(interp, statePtr, cmdPtr);
    Tcl_DecrRefCount(cmdPtr);
}
#endif

/*
 *-------------------------------------------------------------------
 *
 * VerifyCallback --
 *
 *	Monitors SSL certificate validation process. Used to control the
 *	behavior when the SSL_VERIFY_PEER flag is set. This is called
 *	whenever a certificate is inspected or decided invalid. Called for
 *	each certificate in the cert chain.
 *
 * Checks:
 *	certificate chain is checked starting with the deepest nesting level
 *	  (the root CA certificate) and worked upward to the peer's certificate.
 *	All signatures are valid, current time is within first and last validity time.
 *	Check that the certificate is issued by the issuer certificate issuer.
 *	Check the revocation status for each certificate.

    /*
     * SSL Callbacks
     */
    SSL_set_app_data(statePtr->ssl, (void *)statePtr);	/* point back to us */
    SSL_set_verify(statePtr->ssl, verify, VerifyCallback);
    SSL_set_info_callback(statePtr->ssl, InfoCallback);

    /* Callback for observing protocol messages */
#ifndef OPENSSL_NO_SSL_TRACE
    /* void SSL_CTX_set_msg_callback_arg(statePtr->ctx, (void *)statePtr);
    void SSL_CTX_set_msg_callback(statePtr->ctx, MessageCallback); */
    SSL_set_msg_callback_arg(statePtr->ssl, (void *)statePtr);
    SSL_set_msg_callback(statePtr->ssl, MessageCallback);
#endif

    /* Create Tcl_Channel BIO Handler */
    statePtr->p_bio	= BIO_new_tcl(statePtr, BIO_NOCLOSE);
    statePtr->bio	= BIO_new(BIO_f_ssl());

    if (server) {
	/* Server callbacks */