xref: /csrg-svn/libexec/telnetd/state.c (revision 45234)

/*
 * Copyright (c) 1989 Regents of the University of California.
 * All rights reserved.
 *
 * %sccs.include.redist.c%
 */

#ifndef lint
static char sccsid[] = "@(#)state.c	5.8 (Berkeley) 09/14/90";
#endif /* not lint */

#include "telnetd.h"

char	doopt[] = { IAC, DO, '%', 'c', 0 };
char	dont[] = { IAC, DONT, '%', 'c', 0 };
char	will[] = { IAC, WILL, '%', 'c', 0 };
char	wont[] = { IAC, WONT, '%', 'c', 0 };
int	not42 = 1;

/*
 * Buffer for sub-options, and macros
 * for suboptions buffer manipulations
 */
char	subbuffer[100], *subpointer= subbuffer, *subend= subbuffer;

#define	SB_CLEAR()	subpointer = subbuffer;
#define	SB_TERM()	{ subend = subpointer; SB_CLEAR(); }
#define	SB_ACCUM(c)	if (subpointer < (subbuffer+sizeof subbuffer)) { \
				*subpointer++ = (c); \
			}
#define	SB_GET()	((*subpointer++)&0xff)
#define	SB_EOF()	(subpointer >= subend)
#define	SB_LEN()	(subend - subpointer)



/*
 * State for recv fsm
 */
#define	TS_DATA		0	/* base state */
#define	TS_IAC		1	/* look for double IAC's */
#define	TS_CR		2	/* CR-LF ->'s CR */
#define	TS_SB		3	/* throw away begin's... */
#define	TS_SE		4	/* ...end's (suboption negotiation) */
#define	TS_WILL		5	/* will option negotiation */
#define	TS_WONT		6	/* wont " */
#define	TS_DO		7	/* do " */
#define	TS_DONT		8	/* dont " */

telrcv()
{
	register int c;
	static int state = TS_DATA;
#if	defined(CRAY2) && defined(UNICOS5)
	char *opfrontp = pfrontp;
#endif

	while (ncc > 0) {
		if ((&ptyobuf[BUFSIZ] - pfrontp) < 2)
			break;
		c = *netip++ & 0377, ncc--;
		switch (state) {

		case TS_CR:
			state = TS_DATA;
			/* Strip off \n or \0 after a \r */
			if ((c == 0) || (c == '\n')) {
				break;
			}
			/* FALL THROUGH */

		case TS_DATA:
			if (c == IAC) {
				state = TS_IAC;
				break;
			}
			/*
			 * We now map \r\n ==> \r for pragmatic reasons.
			 * Many client implementations send \r\n when
			 * the user hits the CarriageReturn key.
			 *
			 * We USED to map \r\n ==> \n, since \r\n says
			 * that we want to be in column 1 of the next
			 * printable line, and \n is the standard
			 * unix way of saying that (\r is only good
			 * if CRMOD is set, which it normally is).
			 */
			if ((c == '\r') && his_state_is_wont(TELOPT_BINARY)) {
				/*
				 * If we are operating in linemode,
				 * convert to local end-of-line.
				 */
				if ((linemode) && (ncc > 0)&&('\n' == *netip)) {
					netip++; ncc--;
					c = '\n';
				} else {
					state = TS_CR;
				}
			}
			*pfrontp++ = c;
			break;

		case TS_IAC:
gotiac:			switch (c) {

			/*
			 * Send the process on the pty side an
			 * interrupt.  Do this with a NULL or
			 * interrupt char; depending on the tty mode.
			 */
			case IP:
#ifdef DIAGNOSTICS
				if (diagnostic & TD_OPTIONS)
					printoption("td: recv IAC", c);
#endif /* DIAGNOSTICS */
				interrupt();
				break;

			case BREAK:
#ifdef DIAGNOSTICS
				if (diagnostic & TD_OPTIONS)
					printoption("td: recv IAC", c);
#endif /* DIAGNOSTICS */
				sendbrk();
				break;

			/*
			 * Are You There?
			 */
			case AYT:
#ifdef DIAGNOSTICS
				if (diagnostic & TD_OPTIONS)
					printoption("td: recv IAC", c);
#endif /* DIAGNOSTICS */
				recv_ayt();
				break;

			/*
			 * Abort Output
			 */
			case AO:
			    {
#ifdef DIAGNOSTICS
				if (diagnostic & TD_OPTIONS)
					printoption("td: recv IAC", c);
#endif /* DIAGNOSTICS */
				ptyflush();	/* half-hearted */
				init_termbuf();

				if (slctab[SLC_AO].sptr &&
				    *slctab[SLC_AO].sptr != (cc_t)(_POSIX_VDISABLE)) {
				    *pfrontp++ =
					(unsigned char)*slctab[SLC_AO].sptr;
				}

				netclear();	/* clear buffer back */
				*nfrontp++ = IAC;
				*nfrontp++ = DM;
				neturg = nfrontp-1; /* off by one XXX */
#ifdef DIAGNOSTICS
				if (diagnostic & TD_OPTIONS)
					printoption("td: send IAC", DM);
#endif /* DIAGNOSTICS */
				break;
			    }

			/*
			 * Erase Character and
			 * Erase Line
			 */
			case EC:
			case EL:
			    {
				cc_t ch;

#ifdef DIAGNOSTICS
				if (diagnostic & TD_OPTIONS)
					printoption("td: recv IAC", c);
#endif /* DIAGNOSTICS */
				ptyflush();	/* half-hearted */
				init_termbuf();
				if (c == EC)
					ch = *slctab[SLC_EC].sptr;
				else
					ch = *slctab[SLC_EL].sptr;
				if (ch != (cc_t)(_POSIX_VDISABLE))
					*pfrontp++ = (unsigned char)ch;
				break;
			    }

			/*
			 * Check for urgent data...
			 */
			case DM:
#ifdef DIAGNOSTICS
				if (diagnostic & TD_OPTIONS)
					printoption("td: recv IAC", c);
#endif /* DIAGNOSTICS */
				SYNCHing = stilloob(net);
				settimer(gotDM);
				break;


			/*
			 * Begin option subnegotiation...
			 */
			case SB:
				state = TS_SB;
				SB_CLEAR();
				continue;

			case WILL:
				state = TS_WILL;
				continue;

			case WONT:
				state = TS_WONT;
				continue;

			case DO:
				state = TS_DO;
				continue;

			case DONT:
				state = TS_DONT;
				continue;
			case EOR:
				if (his_state_is_will(TELOPT_EOR))
					doeof();
				break;

			/*
			 * Handle RFC 10xx Telnet linemode option additions
			 * to command stream (EOF, SUSP, ABORT).
			 */
			case xEOF:
				doeof();
				break;

			case SUSP:
				sendsusp();
				break;

			case ABORT:
				sendbrk();
				break;

			case IAC:
				*pfrontp++ = c;
				break;
			}
			state = TS_DATA;
			break;

		case TS_SB:
			if (c == IAC) {
				state = TS_SE;
			} else {
				SB_ACCUM(c);
			}
			break;

		case TS_SE:
			if (c != SE) {
				if (c != IAC) {
					/*
					 * bad form of suboption negotiation.
					 * handle it in such a way as to avoid
					 * damage to local state.  Parse
					 * suboption buffer found so far,
					 * then treat remaining stream as
					 * another command sequence.
					 */
#ifdef	DIAGNOSTICS
					SB_ACCUM(IAC);
					SB_ACCUM(c);
					subpointer -= 2;
#endif
					SB_TERM();
					suboption();
					state = TS_IAC;
					goto gotiac;
				}
				SB_ACCUM(c);
				state = TS_SB;
			} else {
#ifdef	DIAGNOSTICS
				SB_ACCUM(IAC);
				SB_ACCUM(SE);
				subpointer -= 2;
#endif
				SB_TERM();
				suboption();	/* handle sub-option */
				state = TS_DATA;
			}
			break;

		case TS_WILL:
			willoption(c);
			state = TS_DATA;
			continue;

		case TS_WONT:
			wontoption(c);
			state = TS_DATA;
			continue;

		case TS_DO:
			dooption(c);
			state = TS_DATA;
			continue;

		case TS_DONT:
			dontoption(c);
			state = TS_DATA;
			continue;

		default:
			syslog(LOG_ERR, "telnetd: panic state=%d\n", state);
			printf("telnetd: panic state=%d\n", state);
			exit(1);
		}
	}
#if	defined(CRAY2) && defined(UNICOS5)
	if (!linemode) {
		char	xptyobuf[BUFSIZ+NETSLOP];
		char	xbuf2[BUFSIZ];
		register char *cp;
		int n = pfrontp - opfrontp, oc;
		bcopy(opfrontp, xptyobuf, n);
		pfrontp = opfrontp;
		pfrontp += term_input(xptyobuf, pfrontp, n, BUFSIZ+NETSLOP,
					xbuf2, &oc, BUFSIZ);
		for (cp = xbuf2; oc > 0; --oc)
			if ((*nfrontp++ = *cp++) == IAC)
				*nfrontp++ = IAC;
	}
#endif	/* defined(CRAY2) && defined(UNICOS5) */
}  /* end of telrcv */

/*
 * The will/wont/do/dont state machines are based on Dave Borman's
 * Telnet option processing state machine.
 *
 * These correspond to the following states:
 *	my_state = the last negotiated state
 *	want_state = what I want the state to go to
 *	want_resp = how many requests I have sent
 * All state defaults are negative, and resp defaults to 0.
 *
 * When initiating a request to change state to new_state:
 *
 * if ((want_resp == 0 && new_state == my_state) || want_state == new_state) {
 *	do nothing;
 * } else {
 *	want_state = new_state;
 *	send new_state;
 *	want_resp++;
 * }
 *
 * When receiving new_state:
 *
 * if (want_resp) {
 *	want_resp--;
 *	if (want_resp && (new_state == my_state))
 *		want_resp--;
 * }
 * if ((want_resp == 0) && (new_state != want_state)) {
 *	if (ok_to_switch_to new_state)
 *		want_state = new_state;
 *	else
 *		want_resp++;
 *	send want_state;
 * }
 * my_state = new_state;
 *
 * Note that new_state is implied in these functions by the function itself.
 * will and do imply positive new_state, wont and dont imply negative.
 *
 * Finally, there is one catch.  If we send a negative response to a
 * positive request, my_state will be the positive while want_state will
 * remain negative.  my_state will revert to negative when the negative
 * acknowlegment arrives from the peer.  Thus, my_state generally tells
 * us not only the last negotiated state, but also tells us what the peer
 * wants to be doing as well.  It is important to understand this difference
 * as we may wish to be processing data streams based on our desired state
 * (want_state) or based on what the peer thinks the state is (my_state).
 *
 * This all works fine because if the peer sends a positive request, the data
 * that we receive prior to negative acknowlegment will probably be affected
 * by the positive state, and we can process it as such (if we can; if we
 * can't then it really doesn't matter).  If it is that important, then the
 * peer probably should be buffering until this option state negotiation
 * is complete.
 *
 */
send_do(option, init)
	int option, init;
{
	if (init) {
		if ((do_dont_resp[option] == 0 && his_state_is_will(option)) ||
		    his_want_state_is_will(option))
			return;
		/*
		 * Special case for TELOPT_TM:  We send a DO, but pretend
		 * that we sent a DONT, so that we can send more DOs if
		 * we want to.
		 */
		if (option == TELOPT_TM)
			set_his_want_state_wont(option);
		else
			set_his_want_state_will(option);
		do_dont_resp[option]++;
	}
	(void) sprintf(nfrontp, doopt, option);
	nfrontp += sizeof (dont) - 2;
#ifdef DIAGNOSTICS
	/*
	 * Report sending option to other side.
	 */
	if (diagnostic & TD_OPTIONS) {
		printoption("td: send do", option);
	}
#endif /* DIAGNOSTICS */
}

willoption(option)
	int option;
{
	int changeok = 0;

	/*
	 * process input from peer.
	 */

#ifdef DIAGNOSTICS
	/*
	 * Report receiving option from other side.
	 */
	if (diagnostic & TD_OPTIONS) {
		printoption("td: recv will", option);
	}
#endif /* DIAGNOSTICS */

	if (do_dont_resp[option]) {
		do_dont_resp[option]--;
		if (do_dont_resp[option] && his_state_is_will(option))
			do_dont_resp[option]--;
	}
	if (do_dont_resp[option] == 0) {
	    if (his_want_state_is_wont(option)) {
		switch (option) {

		case TELOPT_BINARY:
			init_termbuf();
			tty_binaryin(1);
			set_termbuf();
			changeok++;
			break;

		case TELOPT_ECHO:
			/*
			 * See comments below for more info.
			 */
			not42 = 0;	/* looks like a 4.2 system */
			break;

		case TELOPT_TM:
#if	defined(LINEMODE) && defined(KLUDGELINEMODE)
			/*
			 * This telnetd implementation does not really
			 * support timing marks, it just uses them to
			 * support the kludge linemode stuff.  If we
			 * receive a will or wont TM in response to our
			 * do TM request that may have been sent to
			 * determine kludge linemode support, process
			 * it, otherwise TM should get a negative
			 * response back.
			 */
			/*
			 * Handle the linemode kludge stuff.
			 * If we are not currently supporting any
			 * linemode at all, then we assume that this
			 * is the client telling us to use kludge
			 * linemode in response to our query.  Set the
			 * linemode type that is to be supported, note
			 * that the client wishes to use linemode, and
			 * eat the will TM as though it never arrived.
			 */
			if (lmodetype < KLUDGE_LINEMODE) {
				lmodetype = KLUDGE_LINEMODE;
				clientstat(TELOPT_LINEMODE, WILL, 0);
				send_wont(TELOPT_SGA, 1);
			}
#endif	/* defined(LINEMODE) && defined(KLUDGELINEMODE) */
			/*
			 * We never respond to a WILL TM, and
			 * we leave the state WONT.
			 */
			return;

		case TELOPT_LFLOW:
			/*
			 * If we are going to support flow control
			 * option, then don't worry peer that we can't
			 * change the flow control characters.
			 */
			slctab[SLC_XON].defset.flag &= ~SLC_LEVELBITS;
			slctab[SLC_XON].defset.flag |= SLC_DEFAULT;
			slctab[SLC_XOFF].defset.flag &= ~SLC_LEVELBITS;
			slctab[SLC_XOFF].defset.flag |= SLC_DEFAULT;
		case TELOPT_TTYPE:
		case TELOPT_SGA:
		case TELOPT_NAWS:
		case TELOPT_TSPEED:
		case TELOPT_XDISPLOC:
		case TELOPT_ENVIRON:
			changeok++;
			break;

#ifdef	LINEMODE
		case TELOPT_LINEMODE:
			/*
			 * Local processing of 'will linemode' should
			 * occur after placing 'do linemode' in the data
			 * stream, because we may wish to send other
			 * linemode related messages.  So, we duplicate
			 * the other three lines of code here, and then
			 * return.
			 */
			set_his_want_state_will(option);
			send_do(option, 0);
			set_his_state_will(option);
# ifdef	KLUDGELINEMODE
			/*
			 * Note client's desire to use linemode.
			 */
			lmodetype = REAL_LINEMODE;
# endif	/* KLUDGELINEMODE */
			clientstat(TELOPT_LINEMODE, WILL, 0);
			return;
#endif	/* LINEMODE */

		default:
			break;
		}
		if (changeok) {
			set_his_want_state_will(option);
			send_do(option, 0);
		} else {
			do_dont_resp[option]++;
			send_dont(option, 0);
		}
	    } else {
		/*
		 * Option processing that should happen when
		 * we receive conformation of a change in
		 * state that we had requested.
		 */
		switch (option) {
		case TELOPT_ECHO:
			not42 = 0;	/* looks like a 4.2 system */
			/*
			 * Egads, he responded "WILL ECHO".  Turn
			 * it off right now!
			 */
			send_dont(option, 1);
			/*
			 * "WILL ECHO".  Kludge upon kludge!
			 * A 4.2 client is now echoing user input at
			 * the tty.  This is probably undesireable and
			 * it should be stopped.  The client will
			 * respond WONT TM to the DO TM that we send to
			 * check for kludge linemode.  When the WONT TM
			 * arrives, linemode will be turned off and a
			 * change propogated to the pty.  This change
			 * will cause us to process the new pty state
			 * in localstat(), which will notice that
			 * linemode is off and send a WILL ECHO
			 * so that we are properly in character mode and
			 * all is well.
			 */
			break;
#ifdef	LINEMODE
		case TELOPT_LINEMODE:
# ifdef	KLUDGELINEMODE
			/*
			 * Note client's desire to use linemode.
			 */
			lmodetype = REAL_LINEMODE;
# endif	/* KLUDGELINEMODE */
			clientstat(TELOPT_LINEMODE, WILL, 0);
#endif	/* LINEMODE */
		}
	    }
	}
	set_his_state_will(option);
}  /* end of willoption */

send_dont(option, init)
	int option, init;
{
	if (init) {
		if ((do_dont_resp[option] == 0 && his_state_is_wont(option)) ||
		    his_want_state_is_wont(option))
			return;
		set_his_want_state_wont(option);
		do_dont_resp[option]++;
	}
	(void) sprintf(nfrontp, dont, option);
	nfrontp += sizeof (doopt) - 2;
#ifdef DIAGNOSTICS
	/*
	 * Report sending option to other side.
	 */
	if (diagnostic & TD_OPTIONS) {
		printoption("td: send dont", option);
	}
#endif /* DIAGNOSTICS */
}

wontoption(option)
	int option;
{
	/*
	 * Process client input.
	 */

#ifdef DIAGNOSTICS
	/*
	 * Report receiving option from other side.
	 */
	if (diagnostic & TD_OPTIONS) {
		printoption("td: recv wont", option);
	}
#endif /* DIAGNOSTICS */

	if (do_dont_resp[option]) {
		do_dont_resp[option]--;
		if (do_dont_resp[option] && his_state_is_wont(option))
			do_dont_resp[option]--;
	}
	if (do_dont_resp[option] == 0) {
	    if (his_want_state_is_will(option)) {
		/* it is always ok to change to negative state */
		switch (option) {
		case TELOPT_ECHO:
			not42 = 1; /* doesn't seem to be a 4.2 system */
			break;

		case TELOPT_BINARY:
			init_termbuf();
			tty_binaryin(0);
			set_termbuf();
			break;

#ifdef	LINEMODE
		case TELOPT_LINEMODE:
# ifdef	KLUDGELINEMODE
			/*
			 * If real linemode is supported, then client is
			 * asking to turn linemode off.
			 */
			if (lmodetype != REAL_LINEMODE)
				break;
			lmodetype = KLUDGE_LINEMODE;
# endif	/* KLUDGELINEMODE */
			clientstat(TELOPT_LINEMODE, WONT, 0);
			break;
#endif	LINEMODE

		case TELOPT_TM:
			/*
			 * If we get a WONT TM, and had sent a DO TM,
			 * don't respond with a DONT TM, just leave it
			 * as is.  Short circut the state machine to
			 * achive this.
			 */
			set_his_want_state_wont(TELOPT_TM);
			return;

		case TELOPT_LFLOW:
			/*
			 * If we are not going to support flow control
			 * option, then let peer know that we can't
			 * change the flow control characters.
			 */
			slctab[SLC_XON].defset.flag &= ~SLC_LEVELBITS;
			slctab[SLC_XON].defset.flag |= SLC_CANTCHANGE;
			slctab[SLC_XOFF].defset.flag &= ~SLC_LEVELBITS;
			slctab[SLC_XOFF].defset.flag |= SLC_CANTCHANGE;
			break;

		/*
		 * For options that we might spin waiting for
		 * sub-negotiation, if the client turns off the
		 * option rather than responding to the request,
		 * we have to treat it here as if we got a response
		 * to the sub-negotiation, (by updating the timers)
		 * so that we'll break out of the loop.
		 */
		case TELOPT_TTYPE:
			settimer(ttypesubopt);
			break;

		case TELOPT_TSPEED:
			settimer(tspeedsubopt);
			break;

		case TELOPT_XDISPLOC:
			settimer(xdisplocsubopt);
			break;

		case TELOPT_ENVIRON:
			settimer(environsubopt);
			break;

		default:
			break;
		}
		set_his_want_state_wont(option);
		if (his_state_is_will(option))
			send_dont(option, 0);
	    } else {
		switch (option) {
		case TELOPT_TM:
#if	defined(LINEMODE) && defined(KLUDGELINEMODE)
			if (lmodetype < REAL_LINEMODE) {
				lmodetype = NO_LINEMODE;
				clientstat(TELOPT_LINEMODE, WONT, 0);
				send_will(TELOPT_SGA, 1);
				send_will(TELOPT_ECHO, 1);
			}
#endif	/* defined(LINEMODE) && defined(KLUDGELINEMODE) */
		default:
			break;
		}
	    }
	}
	set_his_state_wont(option);

}  /* end of wontoption */

send_will(option, init)
	int option, init;
{
	if (init) {
		if ((will_wont_resp[option] == 0 && my_state_is_will(option))||
		    my_want_state_is_will(option))
			return;
		set_my_want_state_will(option);
		will_wont_resp[option]++;
	}
	(void) sprintf(nfrontp, will, option);
	nfrontp += sizeof (doopt) - 2;
#ifdef DIAGNOSTICS
	/*
	 * Report sending option to other side.
	 */
	if (diagnostic & TD_OPTIONS) {
		printoption("td: send will", option);
	}
#endif /* DIAGNOSTICS */
}

#if	!defined(LINEMODE) || !defined(KLUDGELINEMODE)
/*
 * When we get a DONT SGA, we will try once to turn it
 * back on.  If the other side responds DONT SGA, we
 * leave it at that.  This is so that when we talk to
 * clients that understand KLUDGELINEMODE but not LINEMODE,
 * we'll keep them in char-at-a-time mode.
 */
int turn_on_sga = 0;
#endif

dooption(option)
	int option;
{
	int changeok = 0;

	/*
	 * Process client input.
	 */

#ifdef DIAGNOSTICS
	/*
	 * Report receiving option from other side.
	 */
	if (diagnostic & TD_OPTIONS) {
		printoption("td: recv do", option);
	}
#endif /* DIAGNOSTICS */

	if (will_wont_resp[option]) {
		will_wont_resp[option]--;
		if (will_wont_resp[option] && my_state_is_will(option))
			will_wont_resp[option]--;
	}
	if ((will_wont_resp[option] == 0) && (my_want_state_is_wont(option))) {
		switch (option) {
		case TELOPT_ECHO:
#ifdef	LINEMODE
# ifdef	KLUDGELINEMODE
			if (lmodetype == NO_LINEMODE)
# else
			if (his_state_is_wont(TELOPT_LINEMODE))
# endif
#endif
			{
				init_termbuf();
				tty_setecho(1);
				set_termbuf();
			}
			changeok++;
			break;

		case TELOPT_BINARY:
			init_termbuf();
			tty_binaryout(1);
			set_termbuf();
			changeok++;
			break;

		case TELOPT_SGA:
#if	defined(LINEMODE) && defined(KLUDGELINEMODE)
			/*
			 * If kludge linemode is in use, then we must
			 * process an incoming do SGA for linemode
			 * purposes.
			 */
			if (lmodetype == KLUDGE_LINEMODE) {
				/*
				 * Receipt of "do SGA" in kludge
				 * linemode is the peer asking us to
				 * turn off linemode.  Make note of
				 * the request.
				 */
				clientstat(TELOPT_LINEMODE, WONT, 0);
				/*
				 * If linemode did not get turned off
				 * then don't tell peer that we did.
				 * Breaking here forces a wont SGA to
				 * be returned.
				 */
				if (linemode)
					break;
			}
#else
			turn_on_sga = 0;
#endif	/* defined(LINEMODE) && defined(KLUDGELINEMODE) */
			changeok++;
			break;

		case TELOPT_STATUS:
			changeok++;
			break;

		case TELOPT_TM:
			/*
			 * Special case for TM.  We send a WILL, but
			 * pretend we sent a WONT.
			 */
			send_will(option, 0);
			set_my_want_state_wont(option);
			set_my_state_wont(option);
			return;

		case TELOPT_LINEMODE:
		case TELOPT_TTYPE:
		case TELOPT_NAWS:
		case TELOPT_TSPEED:
		case TELOPT_LFLOW:
		case TELOPT_XDISPLOC:
		case TELOPT_ENVIRON:
		default:
			break;
		}
		if (changeok) {
			set_my_want_state_will(option);
			send_will(option, 0);
		} else {
			will_wont_resp[option]++;
			send_wont(option, 0);
		}
	}
	set_my_state_will(option);

}  /* end of dooption */

send_wont(option, init)
	int option, init;
{
	if (init) {
		if ((will_wont_resp[option] == 0 && my_state_is_wont(option)) ||
		    my_want_state_is_wont(option))
			return;
		set_my_want_state_wont(option);
		will_wont_resp[option]++;
	}
	(void) sprintf(nfrontp, wont, option);
	nfrontp += sizeof (wont) - 2;
#ifdef DIAGNOSTICS
	/*
	 * Report sending option to other side.
	 */
	if (diagnostic & TD_OPTIONS) {
		printoption("td: send wont", option);
	}
#endif /* DIAGNOSTICS */
}

dontoption(option)
	int option;
{
	/*
	 * Process client input.
	 */
#ifdef DIAGNOSTICS
	/*
	 * Report receiving option from other side.
	 */
	if (diagnostic & TD_OPTIONS) {
		printoption("td: recv dont", option);
	}
#endif /* DIAGNOSTICS */

	if (will_wont_resp[option]) {
		will_wont_resp[option]--;
		if (will_wont_resp[option] && my_state_is_wont(option))
			will_wont_resp[option]--;
	}
	if ((will_wont_resp[option] == 0) && (my_want_state_is_will(option))) {
		switch (option) {
		case TELOPT_BINARY:
			init_termbuf();
			tty_binaryout(0);
			set_termbuf();
			break;

		case TELOPT_ECHO:	/* we should stop echoing */
#ifdef	LINEMODE
# ifdef	KLUDGELINEMODE
			if (lmodetype == NO_LINEMODE)
# else
			if (his_state_is_wont(TELOPT_LINEMODE))
# endif
#endif
			{
				init_termbuf();
				tty_setecho(0);
				set_termbuf();
			}
			break;

		case TELOPT_SGA:
#if	defined(LINEMODE) && defined(KLUDGELINEMODE)
			/*
			 * If kludge linemode is in use, then we
			 * must process an incoming do SGA for
			 * linemode purposes.
			 */
			if (lmodetype == KLUDGE_LINEMODE) {
				/*
				 * The client is asking us to turn
				 * linemode on.
				 */
				clientstat(TELOPT_LINEMODE, WILL, 0);
				/*
				 * If we did not turn line mode on,
				 * then what do we say?  Will SGA?
				 * This violates design of telnet.
				 * Gross.  Very Gross.
				 */
			}
			break;
#else
			set_my_want_state_wont(option);
			if (my_state_is_will(option))
				send_wont(option, 0);
			set_my_state_wont(option);
			if (turn_on_sga ^= 1)
				send_will(option);
			return;
#endif	/* defined(LINEMODE) && defined(KLUDGELINEMODE) */

		default:
			break;
		}

		set_my_want_state_wont(option);
		if (my_state_is_will(option))
			send_wont(option, 0);
	}
	set_my_state_wont(option);

}  /* end of dontoption */

/*
 * suboption()
 *
 *	Look at the sub-option buffer, and try to be helpful to the other
 * side.
 *
 *	Currently we recognize:
 *
 *	Terminal type is
 *	Linemode
 *	Window size
 *	Terminal speed
 */
suboption()
{
    register int subchar;
    extern void unsetenv();

#ifdef DIAGNOSTICS
	/*
	 * Report receiving option from other side.
	 */
	if (diagnostic & TD_OPTIONS) {
		netflush();	/* get rid of anything waiting to go out */
		printsub("td: recv", subpointer, SB_LEN()+2);
	}
#endif	DIAGNOSTIC
    subchar = SB_GET();
    switch (subchar) {
    case TELOPT_TSPEED: {
	register int xspeed, rspeed;

	if (his_state_is_wont(TELOPT_TSPEED))	/* Ignore if option disabled */
		break;

	settimer(tspeedsubopt);

	if (SB_EOF() || SB_GET() != TELQUAL_IS)
		return;

	xspeed = atoi(subpointer);

	while (SB_GET() != ',' && !SB_EOF());
	if (SB_EOF())
		return;

	rspeed = atoi(subpointer);
	clientstat(TELOPT_TSPEED, xspeed, rspeed);

	break;

    }  /* end of case TELOPT_TSPEED */

    case TELOPT_TTYPE: {		/* Yaaaay! */
	static char terminalname[41];

	if (his_state_is_wont(TELOPT_TTYPE))	/* Ignore if option disabled */
		break;
	settimer(ttypesubopt);

	if (SB_GET() != TELQUAL_IS) {
	    return;		/* ??? XXX but, this is the most robust */
	}

	terminaltype = terminalname;

	while ((terminaltype < (terminalname + sizeof terminalname-1)) &&
								    !SB_EOF()) {
	    register int c;

	    c = SB_GET();
	    if (isupper(c)) {
		c = tolower(c);
	    }
	    *terminaltype++ = c;    /* accumulate name */
	}
	*terminaltype = 0;
	terminaltype = terminalname;
	break;
    }  /* end of case TELOPT_TTYPE */

    case TELOPT_NAWS: {
	register int xwinsize, ywinsize;

	if (his_state_is_wont(TELOPT_NAWS))	/* Ignore if option disabled */
		break;

	if (SB_EOF())
		return;
	xwinsize = SB_GET() << 8;
	if (SB_EOF())
		return;
	xwinsize |= SB_GET();
	if (SB_EOF())
		return;
	ywinsize = SB_GET() << 8;
	if (SB_EOF())
		return;
	ywinsize |= SB_GET();
	clientstat(TELOPT_NAWS, xwinsize, ywinsize);

	break;

    }  /* end of case TELOPT_NAWS */

#ifdef	LINEMODE
    case TELOPT_LINEMODE: {
	register int request;

	if (his_state_is_wont(TELOPT_LINEMODE))	/* Ignore if option disabled */
		break;
	/*
	 * Process linemode suboptions.
	 */
	if (SB_EOF()) break;  /* garbage was sent */
	request = SB_GET();  /* get will/wont */
	if (SB_EOF()) break;  /* another garbage check */

	if (request == LM_SLC) {  /* SLC is not preceeded by WILL or WONT */
		/*
		 * Process suboption buffer of slc's
		 */
		start_slc(1);
		do_opt_slc(subpointer, subend - subpointer);
		end_slc(0);

	} else if (request == LM_MODE) {
		useeditmode = SB_GET();  /* get mode flag */
		clientstat(LM_MODE, 0, 0);
	}

	switch (SB_GET()) {  /* what suboption? */
	case LM_FORWARDMASK:
		/*
		 * According to spec, only server can send request for
		 * forwardmask, and client can only return a positive response.
		 * So don't worry about it.
		 */

	default:
		break;
	}
	break;
    }  /* end of case TELOPT_LINEMODE */
#endif
    case TELOPT_STATUS: {
	int mode;

	mode = SB_GET();
	switch (mode) {
	case TELQUAL_SEND:
	    if (my_state_is_will(TELOPT_STATUS))
		send_status();
	    break;

	case TELQUAL_IS:
	    break;

	default:
	    break;
	}
	break;
    }  /* end of case TELOPT_STATUS */

    case TELOPT_XDISPLOC: {
	if (SB_EOF() || SB_GET() != TELQUAL_IS)
		return;
	settimer(xdisplocsubopt);
	subpointer[SB_LEN()] = '\0';
	setenv("DISPLAY", subpointer, 1);
	break;
    }  /* end of case TELOPT_XDISPLOC */

    case TELOPT_ENVIRON: {
	register int c;
	register char *cp, *varp, *valp;

	if (SB_EOF())
		return;
	c = SB_GET();
	if (c == TELQUAL_IS)
		settimer(environsubopt);
	else if (c != TELQUAL_INFO)
		return;

	while (!SB_EOF() && SB_GET() != ENV_VAR)
		;

	if (SB_EOF())
		return;

	cp = varp = subpointer;
	valp = 0;

	while (!SB_EOF()) {
		switch (c = SB_GET()) {
		case ENV_VALUE:
			*cp = '\0';
			cp = valp = subpointer;
			break;

		case ENV_VAR:
			*cp = '\0';
			if (valp)
				setenv(varp, valp, 1);
			else
				unsetenv(varp);
			cp = varp = subpointer;
			valp = 0;
			break;

		case ENV_ESC:
			if (SB_EOF())
				break;
			c = SB_GET();
			/* FALL THROUGH */
		default:
			*cp++ = c;
			break;
		}
	}
	*cp = '\0';
	if (valp)
		setenv(varp, valp, 1);
	else
		unsetenv(varp);
	break;
    }  /* end of case TELOPT_ENVIRON */

    default:
	break;
    }  /* end of switch */

}  /* end of suboption */

#define	ADD(c)	 *ncp++ = c;
#define	ADD_DATA(c) { *ncp++ = c; if (c == SE) *ncp++ = c; }
send_status()
{
	unsigned char statusbuf[256];
	register unsigned char *ncp;
	register unsigned char i;

	ncp = statusbuf;

	netflush();	/* get rid of anything waiting to go out */

	ADD(IAC);
	ADD(SB);
	ADD(TELOPT_STATUS);
	ADD(TELQUAL_IS);

	for (i = 0; i < NTELOPTS; i++) {
		if (my_state_is_will(i)) {
			ADD(WILL);
			ADD_DATA(i);
			if (i == IAC)
				ADD(IAC);
		}
		if (his_state_is_will(i)) {
			ADD(DO);
			ADD_DATA(i);
			if (i == IAC)
				ADD(IAC);
		}
	}

#ifdef	LINEMODE
	if (his_state_is_will(TELOPT_LINEMODE)) {
		unsigned char *cp, *cpe;
		int len;

		ADD(SB);
		ADD(TELOPT_LINEMODE);
		ADD(LM_MODE);
		ADD_DATA(editmode);
		if (editmode == IAC)
			ADD(IAC);
		ADD(SE);

		ADD(SB);
		ADD(TELOPT_LINEMODE);
		ADD(LM_SLC);
		start_slc(0);
		send_slc();
		len = end_slc(&cp);
		for (cpe = cp + len; cp < cpe; cp++)
			ADD_DATA(*cp);
		ADD(SE);
	}
#endif	/* LINEMODE */

	ADD(IAC);
	ADD(SE);

	writenet(statusbuf, ncp - statusbuf);
	netflush();	/* Send it on its way */
#ifdef DIAGNOSTICS
	/*
	 * Report sending status suboption.
	 */
	if (diagnostic & TD_OPTIONS) {
		printsub("td: send", statusbuf, ncp - statusbuf);
		netflush();	/* Send it on its way */
	}
#endif	DIAGNOSTIC
}

#ifdef	NO_SETENV
#include "setenv.c"
#endif