[u/mdw/putty] / telnet.c

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>

#include "putty.h"

#ifndef FALSE
#define FALSE 0
#endif
#ifndef TRUE
#define TRUE 1
#endif

static Socket s = NULL;

#define	IAC	255		/* interpret as command: */
#define	DONT	254		/* you are not to use option */
#define	DO	253		/* please, you use option */
#define	WONT	252		/* I won't use option */
#define	WILL	251		/* I will use option */
#define	SB	250		/* interpret as subnegotiation */
#define	SE	240		/* end sub negotiation */

#define GA      249             /* you may reverse the line */
#define EL      248             /* erase the current line */
#define EC      247             /* erase the current character */
#define	AYT	246		/* are you there */
#define	AO	245		/* abort output--but let prog finish */
#define	IP	244		/* interrupt process--permanently */
#define	BREAK	243		/* break */
#define DM      242             /* data mark--for connect. cleaning */
#define NOP     241             /* nop */
#define EOR     239             /* end of record (transparent mode) */
#define ABORT   238             /* Abort process */
#define SUSP    237             /* Suspend process */
#define xEOF    236             /* End of file: EOF is already used... */

#define TELOPT_BINARY	0	/* 8-bit data path */
#define TELOPT_ECHO	1	/* echo */
#define	TELOPT_RCP	2	/* prepare to reconnect */
#define	TELOPT_SGA	3	/* suppress go ahead */
#define	TELOPT_NAMS	4	/* approximate message size */
#define	TELOPT_STATUS	5	/* give status */
#define	TELOPT_TM	6	/* timing mark */
#define	TELOPT_RCTE	7	/* remote controlled transmission and echo */
#define TELOPT_NAOL 	8	/* negotiate about output line width */
#define TELOPT_NAOP 	9	/* negotiate about output page size */
#define TELOPT_NAOCRD	10	/* negotiate about CR disposition */
#define TELOPT_NAOHTS	11	/* negotiate about horizontal tabstops */
#define TELOPT_NAOHTD	12	/* negotiate about horizontal tab disposition */
#define TELOPT_NAOFFD	13	/* negotiate about formfeed disposition */
#define TELOPT_NAOVTS	14	/* negotiate about vertical tab stops */
#define TELOPT_NAOVTD	15	/* negotiate about vertical tab disposition */
#define TELOPT_NAOLFD	16	/* negotiate about output LF disposition */
#define TELOPT_XASCII	17	/* extended ascic character set */
#define	TELOPT_LOGOUT	18	/* force logout */
#define	TELOPT_BM	19	/* byte macro */
#define	TELOPT_DET	20	/* data entry terminal */
#define	TELOPT_SUPDUP	21	/* supdup protocol */
#define	TELOPT_SUPDUPOUTPUT 22	/* supdup output */
#define	TELOPT_SNDLOC	23	/* send location */
#define	TELOPT_TTYPE	24	/* terminal type */
#define	TELOPT_EOR	25	/* end or record */
#define	TELOPT_TUID	26	/* TACACS user identification */
#define	TELOPT_OUTMRK	27	/* output marking */
#define	TELOPT_TTYLOC	28	/* terminal location number */
#define	TELOPT_3270REGIME 29	/* 3270 regime */
#define	TELOPT_X3PAD	30	/* X.3 PAD */
#define	TELOPT_NAWS	31	/* window size */
#define	TELOPT_TSPEED	32	/* terminal speed */
#define	TELOPT_LFLOW	33	/* remote flow control */
#define TELOPT_LINEMODE	34	/* Linemode option */
#define TELOPT_XDISPLOC	35	/* X Display Location */
#define TELOPT_OLD_ENVIRON 36	/* Old - Environment variables */
#define	TELOPT_AUTHENTICATION 37/* Authenticate */
#define	TELOPT_ENCRYPT	38	/* Encryption option */
#define TELOPT_NEW_ENVIRON 39	/* New - Environment variables */
#define	TELOPT_EXOPL	255	/* extended-options-list */

#define	TELQUAL_IS	0	/* option is... */
#define	TELQUAL_SEND	1	/* send option */
#define	TELQUAL_INFO	2	/* ENVIRON: informational version of IS */
#define BSD_VAR 1
#define BSD_VALUE 0
#define RFC_VAR 0
#define RFC_VALUE 1

#define CR 13
#define LF 10
#define NUL 0

#define iswritable(x) ( (x) != IAC && (x) != CR )

static char *telopt(int opt) {
#define i(x) if (opt == TELOPT_ ## x) return #x;
    i(BINARY); i(ECHO); i(RCP); i(SGA); i(NAMS); i(STATUS); i(TM); i(RCTE);
    i(NAOL); i(NAOP); i(NAOCRD); i(NAOHTS); i(NAOHTD); i(NAOFFD); i(NAOVTS);
    i(NAOVTD); i(NAOLFD); i(XASCII); i(LOGOUT); i(BM); i(DET); i(SUPDUP);
    i(SUPDUPOUTPUT); i(SNDLOC); i(TTYPE); i(EOR); i(TUID); i(OUTMRK);
    i(TTYLOC); i(X3PAD); i(NAWS); i(TSPEED); i(LFLOW); i(LINEMODE);
    i(XDISPLOC); i(OLD_ENVIRON); i(AUTHENTICATION); i(ENCRYPT);
    i(NEW_ENVIRON); i(EXOPL);
#undef i
    return "<unknown>";
}

static void telnet_size(void);

struct Opt {
    int send;			       /* what we initially send */
    int nsend;			       /* -ve send if requested to stop it */
    int ack, nak;		       /* +ve and -ve acknowledgements */
    int option;			       /* the option code */
    enum {
	REQUESTED, ACTIVE, INACTIVE, REALLY_INACTIVE
    } state;
};

static struct Opt o_naws = {WILL, WONT, DO, DONT, TELOPT_NAWS, REQUESTED};
static struct Opt o_tspeed = {WILL, WONT, DO, DONT, TELOPT_TSPEED, REQUESTED};
static struct Opt o_ttype = {WILL, WONT, DO, DONT, TELOPT_TTYPE, REQUESTED};
static struct Opt o_oenv = {WILL, WONT, DO, DONT, TELOPT_OLD_ENVIRON,
    INACTIVE};
static struct Opt o_nenv = {WILL, WONT, DO, DONT, TELOPT_NEW_ENVIRON,
    REQUESTED};
static struct Opt o_echo = {DO, DONT, WILL, WONT, TELOPT_ECHO, REQUESTED};
static struct Opt o_we_sga = {WILL, WONT, DO, DONT, TELOPT_SGA, REQUESTED};
static struct Opt o_they_sga = {DO, DONT, WILL, WONT, TELOPT_SGA, REQUESTED};

static struct Opt *opts[] = {
    &o_naws, &o_tspeed, &o_ttype, &o_oenv, &o_nenv, &o_echo,
    &o_we_sga, &o_they_sga, NULL
};

static int echoing = TRUE, editing = TRUE;

static int in_synch;
static int sb_opt, sb_len;
static char *sb_buf = NULL;
static int sb_size = 0;
#define SB_DELTA 1024

static void c_write1(int c) {
    char cc = (char)c;
    from_backend(0, &cc, 1);
}

static void log_option (char *sender, int cmd, int option) {
    char buf[50];
    sprintf(buf, "%s:\t%s %s", sender,
	    (cmd == WILL ? "WILL" : cmd == WONT ? "WONT" :
	     cmd == DO ? "DO" : cmd == DONT ? "DONT" : "<??>"),
	    telopt(option));
    logevent(buf);
}

static void send_opt (int cmd, int option) {
    unsigned char b[3];

    b[0] = IAC; b[1] = cmd; b[2] = option;
    sk_write(s, b, 3);
    log_option("client", cmd, option);
}

static void deactivate_option (struct Opt *o) {
    if (o->state == REQUESTED || o->state == ACTIVE)
	send_opt (o->nsend, o->option);
    o->state = REALLY_INACTIVE;
}

/*
 * Generate side effects of enabling or disabling an option.
 */
static void option_side_effects(struct Opt *o, int enabled) {
    if (o->option == TELOPT_ECHO && o->send == DO)
        echoing = !enabled;
    else if (o->option = TELOPT_SGA && o->send == DO)
        editing = !enabled;
    ldisc_send(NULL, 0);               /* cause ldisc to notice the change */
}

static void activate_option (struct Opt *o) {
    if (o->send == WILL && o->option == TELOPT_NAWS)
	telnet_size();
    if (o->send == WILL &&
	(o->option == TELOPT_NEW_ENVIRON ||
	 o->option == TELOPT_OLD_ENVIRON)) {
	/*
	 * We may only have one kind of ENVIRON going at a time.
	 * This is a hack, but who cares.
	 */
	deactivate_option (o->option==TELOPT_NEW_ENVIRON ? &o_oenv : &o_nenv);
    }
    option_side_effects(o, 1);
}

static void refused_option (struct Opt *o) {
    if (o->send == WILL && o->option == TELOPT_NEW_ENVIRON &&
	o_oenv.state == INACTIVE) {
	send_opt (WILL, TELOPT_OLD_ENVIRON);
	o_oenv.state = REQUESTED;
    }
    option_side_effects(o, 0);
}

static void proc_rec_opt (int cmd, int option) {
    struct Opt **o;

    log_option ("server", cmd, option);
    for (o = opts; *o; o++) {
	if ((*o)->option == option && (*o)->ack == cmd) {
	    switch ((*o)->state) {
	      case REQUESTED:
		(*o)->state = ACTIVE;
		activate_option (*o);
		break;
	      case ACTIVE:
		break;
	      case INACTIVE:
		(*o)->state = ACTIVE;
		send_opt ((*o)->send, option);
		activate_option (*o);
		break;
	      case REALLY_INACTIVE:
		send_opt ((*o)->nsend, option);
		break;
	    }
	    return;
	} else if ((*o)->option == option && (*o)->nak == cmd) {
	    switch ((*o)->state) {
	      case REQUESTED:
		(*o)->state = INACTIVE;
		refused_option (*o);
		break;
	      case ACTIVE:
		(*o)->state = INACTIVE;
		send_opt ((*o)->nsend, option);
                option_side_effects(*o, 0);
		break;
	      case INACTIVE:
	      case REALLY_INACTIVE:
		break;
	    }
	    return;
	}
    }
    /*
     * If we reach here, the option was one we weren't prepared to
     * cope with. So send a negative ack.
     */
    send_opt ((cmd == WILL ? DONT : WONT), option);
}

static void process_subneg (void) {
    unsigned char b[2048], *p, *q;
    int var, value, n;
    char *e;

    switch (sb_opt) {
      case TELOPT_TSPEED:
	if (sb_len == 1 && sb_buf[0] == TELQUAL_SEND) {
	    char logbuf[sizeof(cfg.termspeed)+80];
	    b[0] = IAC; b[1] = SB; b[2] = TELOPT_TSPEED;
	    b[3] = TELQUAL_IS;
	    strcpy(b+4, cfg.termspeed);
	    n = 4 + strlen(cfg.termspeed);
	    b[n] = IAC; b[n+1] = SE;
	    sk_write(s, b, n+2);
	    logevent("server:\tSB TSPEED SEND");
	    sprintf(logbuf, "client:\tSB TSPEED IS %s", cfg.termspeed);
	    logevent (logbuf);
	} else
	    logevent ("server:\tSB TSPEED <something weird>");
	break;
      case TELOPT_TTYPE:
	if (sb_len == 1 && sb_buf[0] == TELQUAL_SEND) {
	    char logbuf[sizeof(cfg.termtype)+80];
	    b[0] = IAC; b[1] = SB; b[2] = TELOPT_TTYPE;
	    b[3] = TELQUAL_IS;
	    for (n = 0; cfg.termtype[n]; n++)
		b[n+4] = (cfg.termtype[n] >= 'a' && cfg.termtype[n] <= 'z' ?
			  cfg.termtype[n] + 'A'-'a' : cfg.termtype[n]);
	    b[n+4] = IAC; b[n+5] = SE;
	    sk_write(s, b, n+6);
	    b[n+4] = 0;
	    logevent("server:\tSB TTYPE SEND");
	    sprintf(logbuf, "client:\tSB TTYPE IS %s", b+4);
	    logevent(logbuf);
	} else
	    logevent("server:\tSB TTYPE <something weird>\r\n");
	break;
      case TELOPT_OLD_ENVIRON:
      case TELOPT_NEW_ENVIRON:	
	p = sb_buf;
	q = p + sb_len;
	if (p < q && *p == TELQUAL_SEND) {
	    char logbuf[50];
	    p++;
	    sprintf (logbuf, "server:\tSB %s SEND", telopt(sb_opt));
	    logevent (logbuf);
	    if (sb_opt == TELOPT_OLD_ENVIRON) {
		if (cfg.rfc_environ) {
		    value = RFC_VALUE;
		    var = RFC_VAR;
		} else {
		    value = BSD_VALUE;
		    var = BSD_VAR;
		}
		/*
		 * Try to guess the sense of VAR and VALUE.
		 */
		while (p < q) {
		    if (*p == RFC_VAR) {
			value = RFC_VALUE;
			var = RFC_VAR;
		    } else if (*p == BSD_VAR) {
			value = BSD_VALUE;
			var = BSD_VAR;
		    }
		    p++;
		}
	    } else {
		/*
		 * With NEW_ENVIRON, the sense of VAR and VALUE
		 * isn't in doubt.
		 */
		value = RFC_VALUE;
		var = RFC_VAR;
	    }
	    b[0] = IAC; b[1] = SB; b[2] = sb_opt;
	    b[3] = TELQUAL_IS;
	    n = 4;
          e = cfg.environmt;
	    while (*e) {
		b[n++] = var;
		while (*e && *e != '\t') b[n++] = *e++;
		if (*e == '\t') e++;
		b[n++] = value;
		while (*e) b[n++] = *e++;
		e++;
	    }
	    if (*cfg.username) {
		b[n++] = var; b[n++] = 'U'; b[n++] = 'S';
		b[n++] = 'E'; b[n++] = 'R'; b[n++] = value;
		e = cfg.username;
		while (*e) b[n++] = *e++;
	    }
	    b[n++] = IAC; b[n++] = SE;
	    sk_write(s, b, n);
	    sprintf(logbuf, "client:\tSB %s IS %s", telopt(sb_opt),
		    n==6 ? "<nothing>" : "<stuff>");
	    logevent (logbuf);
	}
	break;
    }
}

static enum {
    TOPLEVEL, SEENIAC, SEENWILL, SEENWONT, SEENDO, SEENDONT,
    SEENSB, SUBNEGOT, SUBNEG_IAC, SEENCR
} telnet_state = TOPLEVEL;

static void do_telnet_read (char *buf, int len) {

    while (len--) {
	int c = (unsigned char) *buf++;

	switch (telnet_state) {
	  case TOPLEVEL:
	  case SEENCR:
	    if (c == NUL && telnet_state == SEENCR)
		telnet_state = TOPLEVEL;
	    else if (c == IAC)
		telnet_state = SEENIAC;
	    else {
		if (!in_synch)
		    c_write1(c);

#if 1
		/* I can't get the F***ing winsock to insert the urgent IAC
		 * into the right position! Even with SO_OOBINLINE it gives
		 * it to recv too soon. And of course the DM byte (that
		 * arrives in the same packet!) appears several K later!!
		 *
		 * Oh well, we do get the DM in the right place so I'll
		 * just stop hiding on the next 0xf2 and hope for the best.
		 */
		else if (c == DM) in_synch = 0;
#endif
		if (c == CR)
		    telnet_state = SEENCR;
		else
		    telnet_state = TOPLEVEL;
	    }
	    break;
	  case SEENIAC:
	    if (c == DO) telnet_state = SEENDO;
	    else if (c == DONT) telnet_state = SEENDONT;
	    else if (c == WILL) telnet_state = SEENWILL;
	    else if (c == WONT) telnet_state = SEENWONT;
	    else if (c == SB) telnet_state = SEENSB;
	    else if (c == DM) {
	        in_synch = 0;
		telnet_state = TOPLEVEL;
	    } 
	    else {
		/* ignore everything else; print it if it's IAC */
		if (c == IAC) {
		    c_write1(c);
		}
		telnet_state = TOPLEVEL;
	    }
	    break;
	  case SEENWILL:
	    proc_rec_opt (WILL, c);
	    telnet_state = TOPLEVEL;
	    break;
	  case SEENWONT:
	    proc_rec_opt (WONT, c);
	    telnet_state = TOPLEVEL;
	    break;
	  case SEENDO:
	    proc_rec_opt (DO, c);
	    telnet_state = TOPLEVEL;
	    break;
	  case SEENDONT:
	    proc_rec_opt (DONT, c);
	    telnet_state = TOPLEVEL;
	    break;
	  case SEENSB:
	    sb_opt = c;
	    sb_len = 0;
	    telnet_state = SUBNEGOT;
	    break;
	  case SUBNEGOT:
	    if (c == IAC)
		telnet_state = SUBNEG_IAC;
	    else {
		subneg_addchar:
		if (sb_len >= sb_size) {
		    char *newbuf;
		    sb_size += SB_DELTA;
		    newbuf = (sb_buf ?
			      srealloc(sb_buf, sb_size) :
			      smalloc(sb_size));
		    if (newbuf)
			sb_buf = newbuf;
		    else
			sb_size -= SB_DELTA;
		}
		if (sb_len < sb_size)
		    sb_buf[sb_len++] = c;
		telnet_state = SUBNEGOT;/* in case we came here by goto */
	    }
	    break;
	  case SUBNEG_IAC:
	    if (c != SE)
		goto subneg_addchar;   /* yes, it's a hack, I know, but... */
	    else {
		process_subneg();
		telnet_state = TOPLEVEL;
	    }
	    break;
	}
    }
}

static int telnet_receive(Socket skt, int urgent, char *data, int len) {
    if (urgent==3) {
        /* A socket error has occurred. */
        sk_close(s);
        s = NULL;
        connection_fatal(data);
        return 0;
    } else if (!len) {
	/* Connection has closed. */
	sk_close(s);
	s = NULL;
	return 0;
    }
    if(urgent) in_synch = TRUE;
    do_telnet_read (data, len);
    return 1;
}

/*
 * Called to set up the Telnet connection.
 *
 * Returns an error message, or NULL on success.
 *
 * Also places the canonical host name into `realhost'.
 */
static char *telnet_init (char *host, int port, char **realhost) {
    SockAddr addr;
    char *err;

    /*
     * Try to find host.
     */
    addr = sk_namelookup(host, realhost);
    if ( (err = sk_addr_error(addr)) )
	return err;

    if (port < 0)
	port = 23;		       /* default telnet port */

    /*
     * Open socket.
     */
    s = sk_new(addr, port, 0, 1, telnet_receive);
    if ( (err = sk_socket_error(s)) )
	return err;

    sk_addr_free(addr);

    /*
     * Initialise option states.
     */
    {
	struct Opt **o;

	for (o = opts; *o; o++)
	    if ((*o)->state == REQUESTED)
		send_opt ((*o)->send, (*o)->option);
    }

    /*
     * Set up SYNCH state.
     */
    in_synch = FALSE;

    return NULL;
}

/*
 * Called to send data down the Telnet connection.
 */
static void telnet_send (char *buf, int len) {
    char *p;
    static unsigned char iac[2] = { IAC, IAC };
    static unsigned char cr[2] = { CR, NUL };
    static unsigned char nl[2] = { CR, LF };

    if (s == NULL)
	return;

    p = buf;
    while (p < buf+len) {
	char *q = p;

	while (iswritable((unsigned char)*p) && p < buf+len) p++;
	sk_write(s, q, p-q);

	while (p < buf+len && !iswritable((unsigned char)*p)) {
	    sk_write(s, (unsigned char)*p == IAC ? iac : nl, 2);
	    p++;
	}
    }
}

/*
 * Called to set the size of the window from Telnet's POV.
 */
static void telnet_size(void) {
    unsigned char b[16];
    char logbuf[50];

    if (s == NULL || o_naws.state != ACTIVE)
	return;
    b[0] = IAC; b[1] = SB; b[2] = TELOPT_NAWS;
    b[3] = cols >> 8; b[4] = cols & 0xFF;
    b[5] = rows >> 8; b[6] = rows & 0xFF;
    b[7] = IAC; b[8] = SE;
    sk_write(s, b, 9);
    sprintf(logbuf, "client:\tSB NAWS %d,%d",
	    ((unsigned char)b[3] << 8) + (unsigned char)b[4],
	    ((unsigned char)b[5] << 8) + (unsigned char)b[6]);
    logevent (logbuf);
}

/*
 * Send Telnet special codes.
 */
static void telnet_special (Telnet_Special code) {
    unsigned char b[2];

    if (s == NULL)
	return;

    b[0] = IAC;
    switch (code) {
      case TS_AYT: b[1] = AYT; sk_write(s, b, 2); break;
      case TS_BRK: b[1] = BREAK; sk_write(s, b, 2); break;
      case TS_EC: b[1] = EC; sk_write(s, b, 2); break;
      case TS_EL: b[1] = EL; sk_write(s, b, 2); break;
      case TS_GA: b[1] = GA; sk_write(s, b, 2); break;
      case TS_NOP: b[1] = NOP; sk_write(s, b, 2); break;
      case TS_ABORT: b[1] = ABORT; sk_write(s, b, 2); break;
      case TS_AO: b[1] = AO; sk_write(s, b, 2); break;
      case TS_IP: b[1] = IP; sk_write(s, b, 2); break;
      case TS_SUSP: b[1] = SUSP; sk_write(s, b, 2); break;
      case TS_EOR: b[1] = EOR; sk_write(s, b, 2); break;
      case TS_EOF: b[1] = xEOF; sk_write(s, b, 2); break;
      case TS_SYNCH:
        b[1] = DM;
        sk_write (s, b, 1);
        sk_write_oob (s, b+1, 1);
        break;
      case TS_RECHO:
	if (o_echo.state == INACTIVE || o_echo.state == REALLY_INACTIVE) {
	    o_echo.state = REQUESTED;
	    send_opt (o_echo.send, o_echo.option);
	}
	break;
      case TS_LECHO:
	if (o_echo.state == ACTIVE) {
	    o_echo.state = REQUESTED;
	    send_opt (o_echo.nsend, o_echo.option);
	}
	break;
      case TS_PING: 
	if (o_they_sga.state == ACTIVE) {
	    b[1] = NOP; 
	    sk_write(s, b, 2); 
	}
        break;
    }
}

static Socket telnet_socket(void) { return s; }

static int telnet_sendok(void) { return 1; }

static int telnet_ldisc(int option) {
    if (option == LD_ECHO) return echoing;
    if (option == LD_EDIT) return editing;
    return FALSE;
}

Backend telnet_backend = {
    telnet_init,
    telnet_send,
    telnet_size,
    telnet_special,
    telnet_socket,
    telnet_sendok,
    telnet_ldisc,
    23
};
Commit	Line	Data
374330e2	1	#include <windows.h>
	2	#include <stdio.h>
	3	#include <stdlib.h>
374330e2	4
	5	#include "putty.h"
	6
	7	#ifndef FALSE
	8	#define FALSE 0
	9	#endif
	10	#ifndef TRUE
	11	#define TRUE 1
	12	#endif
	13
8df7a775	14	static Socket s = NULL;
374330e2	15
	16	#define IAC 255 /* interpret as command: */
	17	#define DONT 254 /* you are not to use option */
	18	#define DO 253 /* please, you use option */
	19	#define WONT 252 /* I won't use option */
	20	#define WILL 251 /* I will use option */
	21	#define SB 250 /* interpret as subnegotiation */
	22	#define SE 240 /* end sub negotiation */
	23
	24	#define GA 249 /* you may reverse the line */
	25	#define EL 248 /* erase the current line */
	26	#define EC 247 /* erase the current character */
	27	#define AYT 246 /* are you there */
	28	#define AO 245 /* abort output--but let prog finish */
	29	#define IP 244 /* interrupt process--permanently */
	30	#define BREAK 243 /* break */
	31	#define DM 242 /* data mark--for connect. cleaning */
	32	#define NOP 241 /* nop */
	33	#define EOR 239 /* end of record (transparent mode) */
	34	#define ABORT 238 /* Abort process */
	35	#define SUSP 237 /* Suspend process */
	36	#define xEOF 236 /* End of file: EOF is already used... */
	37
	38	#define TELOPT_BINARY 0 /* 8-bit data path */
	39	#define TELOPT_ECHO 1 /* echo */
	40	#define TELOPT_RCP 2 /* prepare to reconnect */
	41	#define TELOPT_SGA 3 /* suppress go ahead */
	42	#define TELOPT_NAMS 4 /* approximate message size */
	43	#define TELOPT_STATUS 5 /* give status */
	44	#define TELOPT_TM 6 /* timing mark */
	45	#define TELOPT_RCTE 7 /* remote controlled transmission and echo */
	46	#define TELOPT_NAOL 8 /* negotiate about output line width */
	47	#define TELOPT_NAOP 9 /* negotiate about output page size */
	48	#define TELOPT_NAOCRD 10 /* negotiate about CR disposition */
	49	#define TELOPT_NAOHTS 11 /* negotiate about horizontal tabstops */
	50	#define TELOPT_NAOHTD 12 /* negotiate about horizontal tab disposition */
	51	#define TELOPT_NAOFFD 13 /* negotiate about formfeed disposition */
	52	#define TELOPT_NAOVTS 14 /* negotiate about vertical tab stops */
	53	#define TELOPT_NAOVTD 15 /* negotiate about vertical tab disposition */
	54	#define TELOPT_NAOLFD 16 /* negotiate about output LF disposition */
	55	#define TELOPT_XASCII 17 /* extended ascic character set */
	56	#define TELOPT_LOGOUT 18 /* force logout */
	57	#define TELOPT_BM 19 /* byte macro */
	58	#define TELOPT_DET 20 /* data entry terminal */
	59	#define TELOPT_SUPDUP 21 /* supdup protocol */
	60	#define TELOPT_SUPDUPOUTPUT 22 /* supdup output */
	61	#define TELOPT_SNDLOC 23 /* send location */
	62	#define TELOPT_TTYPE 24 /* terminal type */
	63	#define TELOPT_EOR 25 /* end or record */
	64	#define TELOPT_TUID 26 /* TACACS user identification */
	65	#define TELOPT_OUTMRK 27 /* output marking */
	66	#define TELOPT_TTYLOC 28 /* terminal location number */
	67	#define TELOPT_3270REGIME 29 /* 3270 regime */
	68	#define TELOPT_X3PAD 30 /* X.3 PAD */
	69	#define TELOPT_NAWS 31 /* window size */
	70	#define TELOPT_TSPEED 32 /* terminal speed */
	71	#define TELOPT_LFLOW 33 /* remote flow control */
	72	#define TELOPT_LINEMODE 34 /* Linemode option */
	73	#define TELOPT_XDISPLOC 35 /* X Display Location */
	74	#define TELOPT_OLD_ENVIRON 36 /* Old - Environment variables */
	75	#define TELOPT_AUTHENTICATION 37/* Authenticate */
	76	#define TELOPT_ENCRYPT 38 /* Encryption option */
	77	#define TELOPT_NEW_ENVIRON 39 /* New - Environment variables */
	78	#define TELOPT_EXOPL 255 /* extended-options-list */
79
80	#define TELQUAL_IS 0 /* option is... */
81	#define TELQUAL_SEND 1 /* send option */
82	#define TELQUAL_INFO 2 /* ENVIRON: informational version of IS */
83	#define BSD_VAR 1
84	#define BSD_VALUE 0
85	#define RFC_VAR 0
86	#define RFC_VALUE 1
87
88	#define CR 13
89	#define LF 10
90	#define NUL 0
91
92	#define iswritable(x) ( (x) != IAC && (x) != CR )
93
94	static char *telopt(int opt) {
95	#define i(x) if (opt == TELOPT_ ## x) return #x;
96	i(BINARY); i(ECHO); i(RCP); i(SGA); i(NAMS); i(STATUS); i(TM); i(RCTE);
97	i(NAOL); i(NAOP); i(NAOCRD); i(NAOHTS); i(NAOHTD); i(NAOFFD); i(NAOVTS);
98	i(NAOVTD); i(NAOLFD); i(XASCII); i(LOGOUT); i(BM); i(DET); i(SUPDUP);
99	i(SUPDUPOUTPUT); i(SNDLOC); i(TTYPE); i(EOR); i(TUID); i(OUTMRK);
100	i(TTYLOC); i(X3PAD); i(NAWS); i(TSPEED); i(LFLOW); i(LINEMODE);
101	i(XDISPLOC); i(OLD_ENVIRON); i(AUTHENTICATION); i(ENCRYPT);
102	i(NEW_ENVIRON); i(EXOPL);
103	#undef i
104	return "<unknown>";
105	}
106
107	static void telnet_size(void);
108
109	struct Opt {
110	int send; /* what we initially send */
111	int nsend; /* -ve send if requested to stop it */
112	int ack, nak; /* +ve and -ve acknowledgements */
113	int option; /* the option code */
114	enum {
115	REQUESTED, ACTIVE, INACTIVE, REALLY_INACTIVE
116	} state;
117	};
118
119	static struct Opt o_naws = {WILL, WONT, DO, DONT, TELOPT_NAWS, REQUESTED};
120	static struct Opt o_tspeed = {WILL, WONT, DO, DONT, TELOPT_TSPEED, REQUESTED};
121	static struct Opt o_ttype = {WILL, WONT, DO, DONT, TELOPT_TTYPE, REQUESTED};
122	static struct Opt o_oenv = {WILL, WONT, DO, DONT, TELOPT_OLD_ENVIRON,
123	INACTIVE};
124	static struct Opt o_nenv = {WILL, WONT, DO, DONT, TELOPT_NEW_ENVIRON,
125	REQUESTED};
126	static struct Opt o_echo = {DO, DONT, WILL, WONT, TELOPT_ECHO, REQUESTED};
127	static struct Opt o_we_sga = {WILL, WONT, DO, DONT, TELOPT_SGA, REQUESTED};
128	static struct Opt o_they_sga = {DO, DONT, WILL, WONT, TELOPT_SGA, REQUESTED};
129
130	static struct Opt *opts[] = {
131	&o_naws, &o_tspeed, &o_ttype, &o_oenv, &o_nenv, &o_echo,
132	&o_we_sga, &o_they_sga, NULL
133	};
134
0965bee0	135	static int echoing = TRUE, editing = TRUE;
0965bee0	136
374330e2	137	static int in_synch;
374330e2	138	static int sb_opt, sb_len;
	139	static char *sb_buf = NULL;
	140	static int sb_size = 0;
	141	#define SB_DELTA 1024
	142
fe50e814	143	static void c_write1(int c) {
	144	char cc = (char)c;
	145	from_backend(0, &cc, 1);
	146	}
	147
374330e2	148	static void log_option (char *sender, int cmd, int option) {
	149	char buf[50];
	150	sprintf(buf, "%s:\t%s %s", sender,
	151	(cmd == WILL ? "WILL" : cmd == WONT ? "WONT" :
	152	cmd == DO ? "DO" : cmd == DONT ? "DONT" : "<??>"),
	153	telopt(option));
c5e9c988	154	logevent(buf);
374330e2	155	}
	156
	157	static void send_opt (int cmd, int option) {
	158	unsigned char b[3];
	159
	160	b[0] = IAC; b[1] = cmd; b[2] = option;
8df7a775	161	sk_write(s, b, 3);
374330e2	162	log_option("client", cmd, option);
	163	}
	164
	165	static void deactivate_option (struct Opt *o) {
	166	if (o->state == REQUESTED \|\| o->state == ACTIVE)
	167	send_opt (o->nsend, o->option);
	168	o->state = REALLY_INACTIVE;
	169	}
	170
708bbbbe	171	/*
	172	* Generate side effects of enabling or disabling an option.
	173	*/
	174	static void option_side_effects(struct Opt *o, int enabled) {
0965bee0	175	if (o->option == TELOPT_ECHO && o->send == DO)
	176	echoing = !enabled;
	177	else if (o->option = TELOPT_SGA && o->send == DO)
	178	editing = !enabled;
	179	ldisc_send(NULL, 0); /* cause ldisc to notice the change */
708bbbbe	180	}
708bbbbe	181
374330e2	182	static void activate_option (struct Opt *o) {
	183	if (o->send == WILL && o->option == TELOPT_NAWS)
	184	telnet_size();
	185	if (o->send == WILL &&
	186	(o->option == TELOPT_NEW_ENVIRON \|\|
	187	o->option == TELOPT_OLD_ENVIRON)) {
	188	/*
	189	* We may only have one kind of ENVIRON going at a time.
	190	* This is a hack, but who cares.
	191	*/
	192	deactivate_option (o->option==TELOPT_NEW_ENVIRON ? &o_oenv : &o_nenv);
	193	}
708bbbbe	194	option_side_effects(o, 1);
374330e2	195	}
	196
	197	static void refused_option (struct Opt *o) {
	198	if (o->send == WILL && o->option == TELOPT_NEW_ENVIRON &&
	199	o_oenv.state == INACTIVE) {
	200	send_opt (WILL, TELOPT_OLD_ENVIRON);
	201	o_oenv.state = REQUESTED;
	202	}
708bbbbe	203	option_side_effects(o, 0);
374330e2	204	}
	205
	206	static void proc_rec_opt (int cmd, int option) {
	207	struct Opt **o;
	208
	209	log_option ("server", cmd, option);
	210	for (o = opts; *o; o++) {
	211	if ((o)->option == option && (o)->ack == cmd) {
	212	switch ((*o)->state) {
	213	case REQUESTED:
	214	(*o)->state = ACTIVE;
	215	activate_option (*o);
	216	break;
	217	case ACTIVE:
	218	break;
	219	case INACTIVE:
	220	(*o)->state = ACTIVE;
	221	send_opt ((*o)->send, option);
	222	activate_option (*o);
	223	break;
	224	case REALLY_INACTIVE:
	225	send_opt ((*o)->nsend, option);
	226	break;
	227	}
	228	return;
	229	} else if ((o)->option == option && (o)->nak == cmd) {
	230	switch ((*o)->state) {
	231	case REQUESTED:
	232	(*o)->state = INACTIVE;
	233	refused_option (*o);
	234	break;
	235	case ACTIVE:
	236	(*o)->state = INACTIVE;
	237	send_opt ((*o)->nsend, option);
708bbbbe	238	option_side_effects(*o, 0);
374330e2	239	break;
	240	case INACTIVE:
	241	case REALLY_INACTIVE:
	242	break;
	243	}
	244	return;
	245	}
	246	}
	247	/*
	248	* If we reach here, the option was one we weren't prepared to
	249	* cope with. So send a negative ack.
	250	*/
	251	send_opt ((cmd == WILL ? DONT : WONT), option);
	252	}
	253
	254	static void process_subneg (void) {
	255	unsigned char b[2048], p, q;
	256	int var, value, n;
	257	char *e;
	258
	259	switch (sb_opt) {
	260	case TELOPT_TSPEED:
	261	if (sb_len == 1 && sb_buf[0] == TELQUAL_SEND) {
	262	char logbuf[sizeof(cfg.termspeed)+80];
	263	b[0] = IAC; b[1] = SB; b[2] = TELOPT_TSPEED;
	264	b[3] = TELQUAL_IS;
	265	strcpy(b+4, cfg.termspeed);
	266	n = 4 + strlen(cfg.termspeed);
	267	b[n] = IAC; b[n+1] = SE;
8df7a775	268	sk_write(s, b, n+2);
c5e9c988	269	logevent("server:\tSB TSPEED SEND");
374330e2	270	sprintf(logbuf, "client:\tSB TSPEED IS %s", cfg.termspeed);
c5e9c988	271	logevent (logbuf);
374330e2	272	} else
c5e9c988	273	logevent ("server:\tSB TSPEED <something weird>");
374330e2	274	break;
	275	case TELOPT_TTYPE:
	276	if (sb_len == 1 && sb_buf[0] == TELQUAL_SEND) {
	277	char logbuf[sizeof(cfg.termtype)+80];
	278	b[0] = IAC; b[1] = SB; b[2] = TELOPT_TTYPE;
	279	b[3] = TELQUAL_IS;
	280	for (n = 0; cfg.termtype[n]; n++)
	281	b[n+4] = (cfg.termtype[n] >= 'a' && cfg.termtype[n] <= 'z' ?
	282	cfg.termtype[n] + 'A'-'a' : cfg.termtype[n]);
	283	b[n+4] = IAC; b[n+5] = SE;
8df7a775	284	sk_write(s, b, n+6);
374330e2	285	b[n+4] = 0;
c5e9c988	286	logevent("server:\tSB TTYPE SEND");
374330e2	287	sprintf(logbuf, "client:\tSB TTYPE IS %s", b+4);
c5e9c988	288	logevent(logbuf);
374330e2	289	} else
c5e9c988	290	logevent("server:\tSB TTYPE <something weird>\r\n");
374330e2	291	break;
	292	case TELOPT_OLD_ENVIRON:
	293	case TELOPT_NEW_ENVIRON:
	294	p = sb_buf;
	295	q = p + sb_len;
	296	if (p < q && *p == TELQUAL_SEND) {
	297	char logbuf[50];
	298	p++;
	299	sprintf (logbuf, "server:\tSB %s SEND", telopt(sb_opt));
c5e9c988	300	logevent (logbuf);
374330e2	301	if (sb_opt == TELOPT_OLD_ENVIRON) {
	302	if (cfg.rfc_environ) {
	303	value = RFC_VALUE;
	304	var = RFC_VAR;
	305	} else {
	306	value = BSD_VALUE;
	307	var = BSD_VAR;
	308	}
	309	/*
	310	* Try to guess the sense of VAR and VALUE.
	311	*/
	312	while (p < q) {
	313	if (*p == RFC_VAR) {
	314	value = RFC_VALUE;
	315	var = RFC_VAR;
	316	} else if (*p == BSD_VAR) {
	317	value = BSD_VALUE;
	318	var = BSD_VAR;
	319	}
	320	p++;
	321	}
	322	} else {
	323	/*
	324	* With NEW_ENVIRON, the sense of VAR and VALUE
	325	* isn't in doubt.
	326	*/
	327	value = RFC_VALUE;
	328	var = RFC_VAR;
	329	}
	330	b[0] = IAC; b[1] = SB; b[2] = sb_opt;
	331	b[3] = TELQUAL_IS;
	332	n = 4;
37508af4	333	e = cfg.environmt;
374330e2	334	while (*e) {
	335	b[n++] = var;
	336	while (e && e != '\t') b[n++] = *e++;
	337	if (*e == '\t') e++;
	338	b[n++] = value;
	339	while (e) b[n++] = e++;
	340	e++;
	341	}
	342	if (*cfg.username) {
	343	b[n++] = var; b[n++] = 'U'; b[n++] = 'S';
	344	b[n++] = 'E'; b[n++] = 'R'; b[n++] = value;
	345	e = cfg.username;
	346	while (e) b[n++] = e++;
	347	}
	348	b[n++] = IAC; b[n++] = SE;
8df7a775	349	sk_write(s, b, n);
374330e2	350	sprintf(logbuf, "client:\tSB %s IS %s", telopt(sb_opt),
374330e2	351	n==6 ? "<nothing>" : "<stuff>");
c5e9c988	352	logevent (logbuf);
374330e2	353	}
	354	break;
	355	}
	356	}
	357
	358	static enum {
	359	TOPLEVEL, SEENIAC, SEENWILL, SEENWONT, SEENDO, SEENDONT,
	360	SEENSB, SUBNEGOT, SUBNEG_IAC, SEENCR
	361	} telnet_state = TOPLEVEL;
	362
	363	static void do_telnet_read (char *buf, int len) {
374330e2	364
	365	while (len--) {
	366	int c = (unsigned char) *buf++;
	367
	368	switch (telnet_state) {
	369	case TOPLEVEL:
	370	case SEENCR:
	371	if (c == NUL && telnet_state == SEENCR)
	372	telnet_state = TOPLEVEL;
	373	else if (c == IAC)
	374	telnet_state = SEENIAC;
	375	else {
374330e2	376	if (!in_synch)
c9def1b8	377	c_write1(c);
2f938b83	378
	379	#if 1
	380	/* I can't get the F***ing winsock to insert the urgent IAC
	381	* into the right position! Even with SO_OOBINLINE it gives
	382	* it to recv too soon. And of course the DM byte (that
	383	* arrives in the same packet!) appears several K later!!
	384	*
	385	* Oh well, we do get the DM in the right place so I'll
	386	* just stop hiding on the next 0xf2 and hope for the best.
	387	*/
	388	else if (c == DM) in_synch = 0;
	389	#endif
374330e2	390	if (c == CR)
	391	telnet_state = SEENCR;
	392	else
	393	telnet_state = TOPLEVEL;
	394	}
	395	break;
	396	case SEENIAC:
	397	if (c == DO) telnet_state = SEENDO;
	398	else if (c == DONT) telnet_state = SEENDONT;
	399	else if (c == WILL) telnet_state = SEENWILL;
	400	else if (c == WONT) telnet_state = SEENWONT;
	401	else if (c == SB) telnet_state = SEENSB;
2f938b83	402	else if (c == DM) {
	403	in_synch = 0;
	404	telnet_state = TOPLEVEL;
	405	}
300d41b0	406	else {
ded38628	407	/* ignore everything else; print it if it's IAC */
ded38628	408	if (c == IAC) {
c9def1b8	409	c_write1(c);
ded38628	410	}
300d41b0	411	telnet_state = TOPLEVEL;
300d41b0	412	}
374330e2	413	break;
	414	case SEENWILL:
	415	proc_rec_opt (WILL, c);
	416	telnet_state = TOPLEVEL;
	417	break;
	418	case SEENWONT:
	419	proc_rec_opt (WONT, c);
	420	telnet_state = TOPLEVEL;
	421	break;
	422	case SEENDO:
	423	proc_rec_opt (DO, c);
	424	telnet_state = TOPLEVEL;
	425	break;
	426	case SEENDONT:
	427	proc_rec_opt (DONT, c);
	428	telnet_state = TOPLEVEL;
	429	break;
	430	case SEENSB:
	431	sb_opt = c;
	432	sb_len = 0;
	433	telnet_state = SUBNEGOT;
	434	break;
	435	case SUBNEGOT:
	436	if (c == IAC)
	437	telnet_state = SUBNEG_IAC;
	438	else {
	439	subneg_addchar:
	440	if (sb_len >= sb_size) {
	441	char *newbuf;
	442	sb_size += SB_DELTA;
	443	newbuf = (sb_buf ?
c9def1b8	444	srealloc(sb_buf, sb_size) :
c9def1b8	445	smalloc(sb_size));
374330e2	446	if (newbuf)
	447	sb_buf = newbuf;
	448	else
	449	sb_size -= SB_DELTA;
	450	}
	451	if (sb_len < sb_size)
	452	sb_buf[sb_len++] = c;
	453	telnet_state = SUBNEGOT;/* in case we came here by goto */
	454	}
	455	break;
	456	case SUBNEG_IAC:
	457	if (c != SE)
	458	goto subneg_addchar; /* yes, it's a hack, I know, but... */
	459	else {
	460	process_subneg();
	461	telnet_state = TOPLEVEL;
	462	}
	463	break;
	464	}
	465	}
	466	}
	467
7dbb9f56	468	static int telnet_receive(Socket skt, int urgent, char *data, int len) {
2c94fd1c	469	if (urgent==3) {
2c94fd1c	470	/* A socket error has occurred. */
b47b2198	471	sk_close(s);
7dbb9f56	472	s = NULL;
2c94fd1c	473	connection_fatal(data);
b47b2198	474	return 0;
b47b2198	475	} else if (!len) {
8df7a775	476	/* Connection has closed. */
	477	sk_close(s);
	478	s = NULL;
	479	return 0;
	480	}
1ad4eb6f	481	if(urgent) in_synch = TRUE;
8df7a775	482	do_telnet_read (data, len);
	483	return 1;
	484	}
	485
374330e2	486	/*
8df7a775	487	* Called to set up the Telnet connection.
374330e2	488	*
	489	* Returns an error message, or NULL on success.
	490	*
	491	* Also places the canonical host name into `realhost'.
	492	*/
8df7a775	493	static char telnet_init (char host, int port, char **realhost) {
	494	SockAddr addr;
	495	char *err;
374330e2	496
	497	/*
	498	* Try to find host.
	499	*/
8df7a775	500	addr = sk_namelookup(host, realhost);
	501	if ( (err = sk_addr_error(addr)) )
	502	return err;
374330e2	503
	504	if (port < 0)
	505	port = 23; /* default telnet port */
	506
	507	/*
	508	* Open socket.
	509	*/
4b1e8acc	510	s = sk_new(addr, port, 0, 1, telnet_receive);
8df7a775	511	if ( (err = sk_socket_error(s)) )
8df7a775	512	return err;
374330e2	513
8df7a775	514	sk_addr_free(addr);
374330e2	515
	516	/*
	517	* Initialise option states.
	518	*/
	519	{
	520	struct Opt **o;
	521
	522	for (o = opts; *o; o++)
	523	if ((*o)->state == REQUESTED)
	524	send_opt ((o)->send, (o)->option);
	525	}
	526
374330e2	527	/*
	528	* Set up SYNCH state.
	529	*/
	530	in_synch = FALSE;
6f34e365	531
374330e2	532	return NULL;
	533	}
	534
	535	/*
374330e2	536	* Called to send data down the Telnet connection.
	537	*/
	538	static void telnet_send (char *buf, int len) {
	539	char *p;
	540	static unsigned char iac[2] = { IAC, IAC };
	541	static unsigned char cr[2] = { CR, NUL };
eb5e1db9	542	static unsigned char nl[2] = { CR, LF };
374330e2	543
8df7a775	544	if (s == NULL)
374330e2	545	return;
	546
	547	p = buf;
2f938b83	548	while (p < buf+len) {
374330e2	549	char *q = p;
	550
	551	while (iswritable((unsigned char)*p) && p < buf+len) p++;
8df7a775	552	sk_write(s, q, p-q);
374330e2	553
374330e2	554	while (p < buf+len && !iswritable((unsigned char)*p)) {
8df7a775	555	sk_write(s, (unsigned char)*p == IAC ? iac : nl, 2);
374330e2	556	p++;
	557	}
	558	}
	559	}
	560
	561	/*
	562	* Called to set the size of the window from Telnet's POV.
	563	*/
	564	static void telnet_size(void) {
	565	unsigned char b[16];
	566	char logbuf[50];
	567
8df7a775	568	if (s == NULL \|\| o_naws.state != ACTIVE)
374330e2	569	return;
	570	b[0] = IAC; b[1] = SB; b[2] = TELOPT_NAWS;
	571	b[3] = cols >> 8; b[4] = cols & 0xFF;
	572	b[5] = rows >> 8; b[6] = rows & 0xFF;
	573	b[7] = IAC; b[8] = SE;
8df7a775	574	sk_write(s, b, 9);
374330e2	575	sprintf(logbuf, "client:\tSB NAWS %d,%d",
	576	((unsigned char)b[3] << 8) + (unsigned char)b[4],
	577	((unsigned char)b[5] << 8) + (unsigned char)b[6]);
c5e9c988	578	logevent (logbuf);
374330e2	579	}
	580
	581	/*
	582	* Send Telnet special codes.
	583	*/
	584	static void telnet_special (Telnet_Special code) {
	585	unsigned char b[2];
	586
8df7a775	587	if (s == NULL)
374330e2	588	return;
	589
	590	b[0] = IAC;
	591	switch (code) {
8df7a775	592	case TS_AYT: b[1] = AYT; sk_write(s, b, 2); break;
	593	case TS_BRK: b[1] = BREAK; sk_write(s, b, 2); break;
	594	case TS_EC: b[1] = EC; sk_write(s, b, 2); break;
	595	case TS_EL: b[1] = EL; sk_write(s, b, 2); break;
	596	case TS_GA: b[1] = GA; sk_write(s, b, 2); break;
	597	case TS_NOP: b[1] = NOP; sk_write(s, b, 2); break;
	598	case TS_ABORT: b[1] = ABORT; sk_write(s, b, 2); break;
	599	case TS_AO: b[1] = AO; sk_write(s, b, 2); break;
	600	case TS_IP: b[1] = IP; sk_write(s, b, 2); break;
	601	case TS_SUSP: b[1] = SUSP; sk_write(s, b, 2); break;
	602	case TS_EOR: b[1] = EOR; sk_write(s, b, 2); break;
	603	case TS_EOF: b[1] = xEOF; sk_write(s, b, 2); break;
374330e2	604	case TS_SYNCH:
8df7a775	605	b[1] = DM;
	606	sk_write (s, b, 1);
	607	sk_write_oob (s, b+1, 1);
	608	break;
684d367c	609	case TS_RECHO:
	610	if (o_echo.state == INACTIVE \|\| o_echo.state == REALLY_INACTIVE) {
	611	o_echo.state = REQUESTED;
	612	send_opt (o_echo.send, o_echo.option);
	613	}
	614	break;
	615	case TS_LECHO:
	616	if (o_echo.state == ACTIVE) {
	617	o_echo.state = REQUESTED;
	618	send_opt (o_echo.nsend, o_echo.option);
	619	}
374330e2	620	break;
ec55b220	621	case TS_PING:
	622	if (o_they_sga.state == ACTIVE) {
	623	b[1] = NOP;
8df7a775	624	sk_write(s, b, 2);
ec55b220	625	}
ec55b220	626	break;
374330e2	627	}
	628	}
	629
8df7a775	630	static Socket telnet_socket(void) { return s; }
8ccc75b0	631
8ccc75b0	632	static int telnet_sendok(void) { return 1; }
4017be6d	633
0965bee0	634	static int telnet_ldisc(int option) {
	635	if (option == LD_ECHO) return echoing;
	636	if (option == LD_EDIT) return editing;
	637	return FALSE;
	638	}
	639
374330e2	640	Backend telnet_backend = {
374330e2	641	telnet_init,
374330e2	642	telnet_send,
374330e2	643	telnet_size,
4017be6d	644	telnet_special,
8ccc75b0	645	telnet_socket,
97db3be4	646	telnet_sendok,
0965bee0	647	telnet_ldisc,
97db3be4	648	23
374330e2	649	};