termstat.c

这是关于远程登陆TELNET 的源代码 已经测试过的。

/*
 * Copyright (c) 1989 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * From: @(#)termstat.c	5.10 (Berkeley) 3/22/91
 */
char termstat_rcsid[] = 
  "$Id: termstat.c,v 1.6 1999/12/12 14:59:45 dholland Exp $";

#include "telnetd.h"

/*
 * local variables
 */
int def_tspeed = -1, def_rspeed = -1;
#ifdef	TIOCSWINSZ
int def_row = 0, def_col = 0;
#endif
#ifdef	LINEMODE
static int _terminit = 0;
#endif	/* LINEMODE */

#ifdef	LINEMODE
/*
 * localstat
 *
 * This function handles all management of linemode.
 *
 * Linemode allows the client to do the local editing of data
 * and send only complete lines to the server.  Linemode state is
 * based on the state of the pty driver.  If the pty is set for
 * external processing, then we can use linemode.  Further, if we
 * can use real linemode, then we can look at the edit control bits
 * in the pty to determine what editing the client should do.
 *
 * Linemode support uses the following state flags to keep track of
 * current and desired linemode state.
 *	alwayslinemode : true if -l was specified on the telnetd
 * 	command line.  It means to have linemode on as much as
 *	possible.
 *
 * 	lmodetype: signifies whether the client can
 *	handle real linemode, or if use of kludgeomatic linemode
 *	is preferred.  It will be set to one of the following:
 *		REAL_LINEMODE : use linemode option
 *		KLUDGE_LINEMODE : use kludge linemode
 *		NO_LINEMODE : client is ignorant of linemode
 *
 *	linemode, uselinemode : linemode is true if linemode
 *	is currently on, uselinemode is the state that we wish
 *	to be in.  If another function wishes to turn linemode
 *	on or off, it sets or clears uselinemode.
 *
 *	editmode, useeditmode : like linemode/uselinemode, but
 *	these contain the edit mode states (edit and trapsig).
 *
 * The state variables correspond to some of the state information
 * in the pty.
 *	linemode:
 *		In real linemode, this corresponds to whether the pty
 *		expects external processing of incoming data.
 *		In kludge linemode, this more closely corresponds to the
 *		whether normal processing is on or not.  (ICANON in
 *		system V, or COOKED mode in BSD.)
 *		If the -l option was specified (alwayslinemode), then
 *		an attempt is made to force external processing on at
 *		all times.
 *
 * The following heuristics are applied to determine linemode
 * handling within the server.
 *	1) Early on in starting up the server, an attempt is made
 *	   to negotiate the linemode option.  If this succeeds
 *	   then lmodetype is set to REAL_LINEMODE and all linemode
 *	   processing occurs in the context of the linemode option.
 *	2) If the attempt to negotiate the linemode option failed,
 *	   then we try to use kludge linemode.  We test for this
 *	   capability by sending "do Timing Mark".  If a positive
 *	   response comes back, then we assume that the client
 *	   understands kludge linemode (ech!) and the
 *	   lmodetype flag is set to KLUDGE_LINEMODE.
 *	3) Otherwise, linemode is not supported at all and
 *	   lmodetype remains set to NO_LINEMODE (which happens
 *	   to be 0 for convenience).
 *	4) At any time a command arrives that implies a higher
 *	   state of linemode support in the client, we move to that
 *	   linemode support.
 *
 * A short explanation of kludge linemode is in order here.
 *	1) The heuristic to determine support for kludge linemode
 *	   is to send a do timing mark.  We assume that a client
 *	   that supports timing marks also supports kludge linemode.
 *	   A risky proposition at best.
 *	2) Further negotiation of linemode is done by changing the
 *	   the server's state regarding SGA.  If server will SGA,
 *	   then linemode is off, if server won't SGA, then linemode
 *	   is on.
 */
	void
localstat()
{
	void netflush();
	int need_will_echo = 0;

	/*
	 * Check for state of BINARY options.
	 */
	if (tty_isbinaryin()) {
		if (his_want_state_is_wont(TELOPT_BINARY))
			send_do(TELOPT_BINARY, 1);
	} else {
		if (his_want_state_is_will(TELOPT_BINARY))
			send_dont(TELOPT_BINARY, 1);
	}

	if (tty_isbinaryout()) {
		if (my_want_state_is_wont(TELOPT_BINARY))
			send_will(TELOPT_BINARY, 1);
	} else {
		if (my_want_state_is_will(TELOPT_BINARY))
			send_wont(TELOPT_BINARY, 1);
	}

	/*
	 * Check for changes to flow control if client supports it.
	 */
	if (his_state_is_will(TELOPT_LFLOW)) {
		if (tty_flowmode() != flowmode) {
			flowmode = tty_flowmode();
			(void) netoprintf("%c%c%c%c%c%c", IAC, SB,
					  TELOPT_LFLOW, flowmode, IAC, SE);
		}
	}

	/*
	 * Check linemode on/off state
	 */
	uselinemode = tty_linemode();

	/*
	 * If alwayslinemode is on, and pty is changing to turn it off, then
	 * force linemode back on.
	 */
	if (alwayslinemode && linemode && !uselinemode) {
		uselinemode = 1;
		tty_setlinemode(uselinemode);
	}

#if	defined(ENCRYPT)
	/*
	 * If the terminal is not echoing, but editing is enabled,
	 * something like password input is going to happen, so
	 * if we the other side is not currently sending encrypted
	 * data, ask the other side to start encrypting.
	 */
	if (his_state_is_will(TELOPT_ENCRYPT)) {
		static int enc_passwd = 0;
		if (uselinemode && !tty_isecho() && tty_isediting()
		    && (enc_passwd == 0) && !decrypt_input) {
			encrypt_send_request_start();
			enc_passwd = 1;
		} else if (enc_passwd) {
			encrypt_send_request_end();
			enc_passwd = 0;
		}
	}
#endif

	/*
	 * Do echo mode handling as soon as we know what the
	 * linemode is going to be.
	 * If the pty has echo turned off, then tell the client that
	 * the server will echo.  If echo is on, then the server
	 * will echo if in character mode, but in linemode the
	 * client should do local echoing.  The state machine will
	 * not send anything if it is unnecessary, so don't worry
	 * about that here.
	 *
	 * If we need to send the WILL ECHO (because echo is off),
	 * then delay that until after we have changed the MODE.
	 * This way, when the user is turning off both editing
	 * and echo, the client will get editing turned off first.
	 * This keeps the client from going into encryption mode
	 * and then right back out if it is doing auto-encryption
	 * when passwords are being typed.
	 */
	if (uselinemode) {
		if (tty_isecho())
			send_wont(TELOPT_ECHO, 1);
		else
			need_will_echo = 1;
	}

	/*
	 * If linemode is being turned off, send appropriate
	 * command and then we're all done.
	 */
	 if (!uselinemode && linemode) {
# ifdef	KLUDGELINEMODE
		if (lmodetype == REAL_LINEMODE) {
# endif	/* KLUDGELINEMODE */
			send_dont(TELOPT_LINEMODE, 1);
# ifdef	KLUDGELINEMODE
		} else if (lmodetype == KLUDGE_LINEMODE)
			send_will(TELOPT_SGA, 1);
# endif	/* KLUDGELINEMODE */
		send_will(TELOPT_ECHO, 1);
		linemode = uselinemode;
		goto done;
	}

# ifdef	KLUDGELINEMODE
	/*
	 * If using real linemode check edit modes for possible later use.
	 * If we are in kludge linemode, do the SGA negotiation.
	 */
	if (lmodetype == REAL_LINEMODE) {
# endif	/* KLUDGELINEMODE */
		useeditmode = 0;
		if (tty_isediting())
			useeditmode |= MODE_EDIT;
		if (tty_istrapsig())
			useeditmode |= MODE_TRAPSIG;
		if (tty_issofttab())
			useeditmode |= MODE_SOFT_TAB;
		if (tty_islitecho())
			useeditmode |= MODE_LIT_ECHO;
# ifdef	KLUDGELINEMODE
	} else if (lmodetype == KLUDGE_LINEMODE) {
		if (tty_isediting() && uselinemode)
			send_wont(TELOPT_SGA, 1);
		else
			send_will(TELOPT_SGA, 1);
	}
# endif	/* KLUDGELINEMODE */

	/*
	 * Negotiate linemode on if pty state has changed to turn it on.
	 * Send appropriate command and send along edit mode, then all done.
	 */
	if (uselinemode && !linemode) {
# ifdef	KLUDGELINEMODE
		if (lmodetype == KLUDGE_LINEMODE) {
			send_wont(TELOPT_SGA, 1);
		} else if (lmodetype == REAL_LINEMODE) {
# endif	/* KLUDGELINEMODE */
			send_do(TELOPT_LINEMODE, 1);
			/* send along edit modes */
			(void) netoprintf("%c%c%c%c%c%c%c", IAC, SB,
				TELOPT_LINEMODE, LM_MODE, useeditmode,
				IAC, SE);
			editmode = useeditmode;
# ifdef	KLUDGELINEMODE
		}
# endif	/* KLUDGELINEMODE */
		linemode = uselinemode;
		goto done;
	}

# ifdef	KLUDGELINEMODE
	/*
	 * None of what follows is of any value if not using
	 * real linemode.
	 */
	if (lmodetype < REAL_LINEMODE)
		goto done;