<dd>Handshake as server if true, else handshake as
            client. (default is <em>false</em>)</dd>
        <dt><strong>-servername</strong> <em>host</em></dt>
        <dd>Specify server hostname. Only available if the OpenSSL library
	    the package is linked against supports the TLS hostname extension
	    for 'Server Name Indication' (SNI). Use to name the logical host
	    we are talking to and expecting a certificate for.</dd>
        <dt><strong>-session_id</strong> <em>string</em></dt>
        <dd>Session id to resume session.</dd>
        <dt><strong>-ssl2</strong> <em>bool</em></dt>
        <dd>Enable use of SSL v2. (default is <em>false</em>)</dd>
        <dt><strong>-ssl3 </strong><em>bool</em></dt>
        <dd>Enable use of SSL v3. (default is <em>false</em>)</dd>
        <dt>-<strong>tls1</strong> <em>bool</em></dt>
        <dd>Enable use of TLS v1. (default is <em>true</em>)</dd>
        <dt>-<strong>tls1.1</strong> <em>bool</em></dt>

        <dd>The number of bits used for the session key.</dd>
        <dt><strong>certificate</strong> <em>cert</em></dt>
        <dd>The PEM encoded certificate.</dd>
        <dt><strong>sha1_hash</strong> <em>hash</em></dt>
        <dd>The SHA1 hash of the certificate.</dd>
        <dt><strong>sha256_hash</strong> <em>hash</em></dt>
        <dd>The SHA256 hash of the certificate.</dd>
        <dt><strong>validation</strong> <em>result</em></dt>
        <dd>Certificate validation result.</dd>
        <dt><strong>alpn</strong> <em>protocol</em></dt>
        <dd>The protocol selected after Application-Layer Protocol
	    Negotiation (ALPN).</dd>
        <dt><strong>version</strong> <em>value</em></dt>
        <dd>The protocol version used for the connection:
	  SSLv2, SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3, or unknown</dd>
    </dl>
</blockquote>

    <dt><a name="tls::connection"><strong>tls::connection</strong>
    <em>channel</em></a></dt>
    <dd>Returns the current connection status of an SSL channel. The
        result is a list of key-value pairs describing the
        connected peer.</dd>

<blockquote>
    <dl>
        <dt><strong>state</strong> <em>state</em></dt>
        <dd>State of the connection: initializing, handshake, established</dd>
        <dt><strong>servername</strong> <em>name</em></dt>
        <dd>The name of the connected to server.</dd>
        <dt><strong>protocol</strong> <em>version</em></dt>
        <dd>The protocol version used for the connection:
	    SSL2, SSL3, TLS1, TLS1.1, TLS1.2, TLS1.3, or unknown.</dd>
        <dt><strong>securitylevel</strong> <em>level</em></dt>
        <dd>The security level used for selection of ciphers, key size, etc.</dd>
        <dt><strong>cipher</strong> <em>cipher</em></dt>

        <dt><strong>renegotiation</strong> <em>state</em></dt>
        <dd>Whether protocol renegotiation is allowed or disallowed.</dd>
        <dt><strong>alpn</strong> <em>protocol</em></dt>
        <dd>The protocol selected after Application-Layer Protocol
	    Negotiation (ALPN).</dd>
        <dt><strong>session_reused</strong> <em>boolean</em></dt>
        <dd>Whether the session has been reused or not.</dd>
        <dt><strong>session_id</strong> <em>string</em></dt>
        <dd>Unique session id for use in resuming the session.</dd>
        <dt><strong>session_ticket</strong> <em>string</em></dt>
        <dd>Unique session ticket for use in resuming the session.</dd>
        <dt><strong>resumable</strong> <em>boolean</em></dt>
        <dd>Can the session be resumed or not.</dd>
        <dt><strong>start_time</strong> <em>seconds</em></dt>
        <dd>Time since session started in seconds since epoch.</dd>
        <dt><strong>timeout</strong> <em>seconds</em></dt>
        <dd>Max duration of session in seconds before time-out.</dd>
    </dl>
</blockquote>

    <dt><a name="tls::ciphers"><strong>tls::ciphers</strong> 
    <em>protocol ?verbose? ?supported?</em></a></dt>
    <dd>Returns a list of supported ciphers available for <em>protocol</em>,
        where protocol must be one of <b>ssl2, ssl3, tls1, tls1.1,

	  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.
	</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>.
	  Where <em>session_id</em> is the current session identifier,
	  <em>ticket</em> is the session ticket info, and <em>lifetime</em>
	  is the the ticket lifetime in seconds.
	</dd>

	<br>

	<dt>
	  <strong>verify</strong> <em>channel depth cert status error</em>
	</dt>
	<dd>
	  This form of callback is invoked by the OpenSSL function

    return -1;
	verify = verify;
}

/*
 *-------------------------------------------------------------------
 *
 * SessionCallback for Clients --
 *
 *	Called when a new session ticket has been received. In TLS 1.3
 *	this may be received multiple times after the handshake. For
 *	earlier versions, this will be received during the handshake.
 *
 * Results:
 *	None
 *
 * Side effects:
 *	Calls callback (if defined)
 *-------------------------------------------------------------------
 */
static int
SessionCallback(const SSL *ssl, SSL_SESSION *session) {
    State *statePtr = (State*)SSL_get_app_data((SSL *)ssl);
    Tcl_Interp *interp	= statePtr->interp;
    Tcl_Obj *cmdPtr;
    const unsigned char *ticket;
    const unsigned char *session_id;
    int len;
    int code;
    size_t len2;

    dprintf("Called");

    if (statePtr->callback == (Tcl_Obj*)NULL)
	return 0;

    cmdPtr = Tcl_DuplicateObj(statePtr->callback);

    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj( "session", -1));

    /* Session id */
    session = SSL_get_session(statePtr->ssl);
    session_id = SSL_SESSION_get0_id_context(session, &len);
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(session_id, len));

    /* Session ticket */
    SSL_SESSION_get0_ticket(session, &ticket, &len2);
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(ticket, (int)len2));

    /* Lifetime - number of seconds */
    Tcl_ListObjAppendElement(interp, cmdPtr,
	Tcl_NewLongObj((long) SSL_SESSION_get_ticket_lifetime_hint(session)));

    Tcl_Preserve((ClientData) interp);
    Tcl_Preserve((ClientData) statePtr);

    Tcl_IncrRefCount(cmdPtr);
    code = Tcl_EvalObjEx(interp, cmdPtr, TCL_EVAL_GLOBAL);
    if (code != TCL_OK) {
#if (TCL_MAJOR_VERSION == 8) && (TCL_MINOR_VERSION < 6)
	Tcl_BackgroundError(interp);
#else
	Tcl_BackgroundException(interp, code);
#endif
    }
    Tcl_DecrRefCount(cmdPtr);

    Tcl_Release((ClientData) statePtr);
    Tcl_Release((ClientData) interp);
    return 1;
}

/*
 *-------------------------------------------------------------------
 *
 * CiphersObjCmd -- list available ciphers
 *
 *	This procedure is invoked to process the "tls::ciphers" command
 *	to list available ciphers, based upon protocol selected.
 *
 * Results:
 *	A standard Tcl result list.

    char *ciphers	        = NULL;
    char *ciphersuites	        = NULL;
    char *CAfile	        = NULL;
    char *CAdir		        = NULL;
    char *DHparams	        = NULL;
    char *model		        = NULL;
    char *servername	        = NULL;	/* hostname for Server Name Indication */
    const unsigned char *session_id = NULL;
    Tcl_Obj *alpn		= NULL;
    int ssl2 = 0, ssl3 = 0;
    int tls1 = 1, tls1_1 = 1, tls1_2 = 1, tls1_3 = 1;
    int proto = 0, level = -1;
    int verify = 0, require = 0, request = 1;

    dprintf("Called");

	OPTSTR("-model", model);
	OPTOBJ("-password", password);
	OPTBOOL("-require", require);
	OPTBOOL("-request", request);
	OPTINT("-securitylevel", level);
	OPTBOOL("-server", server);
	OPTSTR("-servername", servername);
	OPTSTR("-session_id", session_id);
	OPTOBJ("-alpn", alpn);
	OPTBOOL("-ssl2", ssl2);
	OPTBOOL("-ssl3", ssl3);
	OPTBOOL("-tls1", tls1);
	OPTBOOL("-tls1.1", tls1_1);
	OPTBOOL("-tls1.2", tls1_2);
	OPTBOOL("-tls1.3", tls1_3);
	OPTBYTE("-cert", cert, cert_len);
	OPTBYTE("-key", key, key_len);

	OPTBAD("option", "-alpn, -cadir, -cafile, -cert, -certfile, -cipher, -ciphersuites, -command, -dhparams, -key, -keyfile, -model, -password, -require, -request, -securitylevel, -server, -servername, -session_id, -ssl2, -ssl3, -tls1, -tls1.1, -tls1.2, or -tls1.3");

	return TCL_ERROR;
    }
    if (request)	    verify |= SSL_VERIFY_CLIENT_ONCE | SSL_VERIFY_PEER;
    if (request && require) verify |= SSL_VERIFY_FAIL_IF_NO_PEER_CERT;
    if (verify == 0)	verify = SSL_VERIFY_NONE;

    if (!statePtr->ssl) {
	/* SSL library error */
	Tcl_AppendResult(interp, "couldn't construct ssl session: ", REASON(), (char *) NULL);
	Tls_Free((char *) statePtr);
	return TCL_ERROR;
    }

    /* Set host server name */
    if (servername) {
	if (!SSL_set_tlsext_host_name(statePtr->ssl, servername) && require) {
	    Tcl_AppendResult(interp, "setting TLS host name extension failed", (char *) NULL);
            Tls_Free((char *) statePtr);
            return TCL_ERROR;
        }
    }

    /* Resume session id */
    if (session_id && strlen(session_id) <= SSL_MAX_SID_CTX_LENGTH) {
	/* SSL_set_session() */
	if (!SSL_SESSION_set1_id_context(SSL_get_session(statePtr->ssl), session_id, (unsigned int) strlen(session_id))) {
	    Tcl_AppendResult(interp, "Resume session id ", session_id, " failed", (char *) NULL);
            Tls_Free((char *) statePtr);
            return TCL_ERROR;
	}
    }

    if (alpn) {
	/* Convert a Tcl list into a protocol-list in wire-format */
	unsigned char *protos, *p;
	unsigned int protos_len = 0;
	int i, len, cnt;
	Tcl_Obj **list;
	if (Tcl_ListObjGetElements(interp, alpn, &cnt, &list) != TCL_OK) {

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

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

    if (server) {
	statePtr->flags |= TLS_TCL_SERVER;

    ciphers = (char*)SSL_get_cipher(statePtr->ssl);
    if ((ciphers != NULL) && (strcmp(ciphers, "(NONE)") != 0)) {
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("cipher", -1));
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(SSL_get_cipher(statePtr->ssl), -1));
    }

    /* Verify the X509 certificate presented by the peer */
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("validation", -1));
    if (SSL_get_verify_result(statePtr->ssl) != X509_V_OK) {
	/* proto = "failed"; */
	proto = REASON();
    } else {
	proto = "ok";
    }
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(proto, -1));

    /* Report the selected protocol as a result of the negotiation */
    SSL_get0_alpn_selected(statePtr->ssl, &proto, &len);
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("alpn", -1));
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj((char *)proto, (int)len));
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("version", -1));
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(SSL_get_version(statePtr->ssl), -1));

static int ConnectionInfoObjCmd(ClientData clientData, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[]) {
    Tcl_Channel chan;		/* The channel to set a mode on. */
    State *statePtr;		/* client state for ssl socket */
    Tcl_Obj *objPtr;
    const SSL *ssl;
    const SSL_CIPHER *cipher;
    const SSL_SESSION *session;
    const unsigned char *proto;
    unsigned int len;
#if defined(HAVE_SSL_COMPRESSION)
    const COMP_METHOD *comp;
#endif

    if (objc != 2) {

	    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("description", -1));
	    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(buf, -1));
	}
    }

    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("renegotiation", -1));
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(
	SSL_get_secure_renegotiation_support(ssl) ? "allowed" : "not supported", -1));

    /* Report the selected protocol as a result of the negotiation */
    SSL_get0_alpn_selected(ssl, &proto, &len);
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("alpn", -1));
    Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj((char *)proto, (int)len));

    /* Session info */
    session = SSL_get_session(ssl);
    if (session != NULL) {
	const unsigned char *ticket;
	size_t len2;
	const unsigned char *session_id;

	/* Session info */
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("session_reused", -1));
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewIntObj(SSL_session_reused(ssl)));

	/* Session id */
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("session_id", -1));
	session_id = SSL_SESSION_get0_id_context(session, &len);
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(session_id, (int)len));

	/* Session ticket */
	SSL_SESSION_get0_ticket(session, &ticket, &len2);
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("session_ticket", -1));
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj(ticket, (int) len2));

	/* Resumable session */
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("resumable", -1));
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewIntObj(SSL_SESSION_is_resumable(session)));

	/* Start time */
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("start_time", -1));
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewLongObj(SSL_SESSION_get_time(session)));

	/* Timeout value */
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("timeout", -1));
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewLongObj(SSL_SESSION_get_timeout(session)));
    }

#if defined(HAVE_SSL_COMPRESSION)
    /* Compression info */
    comp = SSL_get_current_compression(ssl);
    if (comp != NULL) {
	expansion = SSL_get_current_expansion(ssl);
	Tcl_ListObjAppendElement(interp, objPtr, Tcl_NewStringObj("compression", -1));

		dprintf("Flushing the lower layers failed, this will probably terminate this session");
	    }
	}

	rc = SSL_get_error(statePtr->ssl, err);

	dprintf("Got error: %i (rc = %i)", err, rc);
	dprintf("Got error: %s", ERR_reason_error_string(ERR_get_error()));

	bioShouldRetry = 0;
	if (err <= 0) {
	    if (rc == SSL_ERROR_WANT_CONNECT || rc == SSL_ERROR_WANT_ACCEPT || rc == SSL_ERROR_WANT_READ || rc == SSL_ERROR_WANT_WRITE) {
		bioShouldRetry = 1;
	    } else if (BIO_should_retry(statePtr->bio)) {
		bioShouldRetry = 1;

        {* -keyfile iopts 1}
        {* -password iopts 1}
        {* -request iopts 1}
        {* -require iopts 1}
        {* -securitylevel iopts 1}
        {* -autoservername discardOpts 1}
        {* -servername iopts 1}
        {* -session_id iopts 1}
        {* -alpn iopts 1}
        {* -ssl2 iopts 1}
        {* -ssl3 iopts 1}
        {* -tls1 iopts 1}
        {* -tls1.1 iopts 1}
        {* -tls1.2 iopts 1}
        {* -tls1.3 iopts 1}