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Run entire source base through GNU indent to tidy up the varying
[u/mdw/putty] / telnet.c
1 #include <windows.h>
2 #include <stdio.h>
3 #include <stdlib.h>
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
14 static Socket s = NULL;
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 {
96 #define i(x) if (opt == TELOPT_ ## x) return #x;
97 i(BINARY);
98 i(ECHO);
99 i(RCP);
100 i(SGA);
101 i(NAMS);
102 i(STATUS);
103 i(TM);
104 i(RCTE);
105 i(NAOL);
106 i(NAOP);
107 i(NAOCRD);
108 i(NAOHTS);
109 i(NAOHTD);
110 i(NAOFFD);
111 i(NAOVTS);
112 i(NAOVTD);
113 i(NAOLFD);
114 i(XASCII);
115 i(LOGOUT);
116 i(BM);
117 i(DET);
118 i(SUPDUP);
119 i(SUPDUPOUTPUT);
120 i(SNDLOC);
121 i(TTYPE);
122 i(EOR);
123 i(TUID);
124 i(OUTMRK);
125 i(TTYLOC);
126 i(X3PAD);
127 i(NAWS);
128 i(TSPEED);
129 i(LFLOW);
130 i(LINEMODE);
131 i(XDISPLOC);
132 i(OLD_ENVIRON);
133 i(AUTHENTICATION);
134 i(ENCRYPT);
135 i(NEW_ENVIRON);
136 i(EXOPL);
137 #undef i
138 return "<unknown>";
139 }
140
141 static void telnet_size(void);
142
143 struct Opt {
144 int send; /* what we initially send */
145 int nsend; /* -ve send if requested to stop it */
146 int ack, nak; /* +ve and -ve acknowledgements */
147 int option; /* the option code */
148 enum {
149 REQUESTED, ACTIVE, INACTIVE, REALLY_INACTIVE
150 } state;
151 };
152
153 static struct Opt o_naws =
154 { WILL, WONT, DO, DONT, TELOPT_NAWS, REQUESTED };
155 static struct Opt o_tspeed =
156 { WILL, WONT, DO, DONT, TELOPT_TSPEED, REQUESTED };
157 static struct Opt o_ttype =
158 { WILL, WONT, DO, DONT, TELOPT_TTYPE, REQUESTED };
159 static struct Opt o_oenv = { WILL, WONT, DO, DONT, TELOPT_OLD_ENVIRON,
160 INACTIVE
161 };
162 static struct Opt o_nenv = { WILL, WONT, DO, DONT, TELOPT_NEW_ENVIRON,
163 REQUESTED
164 };
165 static struct Opt o_echo =
166 { DO, DONT, WILL, WONT, TELOPT_ECHO, REQUESTED };
167 static struct Opt o_we_sga =
168 { WILL, WONT, DO, DONT, TELOPT_SGA, REQUESTED };
169 static struct Opt o_they_sga =
170 { DO, DONT, WILL, WONT, TELOPT_SGA, REQUESTED };
171
172 static struct Opt *opts[] = {
173 &o_naws, &o_tspeed, &o_ttype, &o_oenv, &o_nenv, &o_echo,
174 &o_we_sga, &o_they_sga, NULL
175 };
176
177 static int echoing = TRUE, editing = TRUE;
178
179 static int in_synch;
180 static int sb_opt, sb_len;
181 static char *sb_buf = NULL;
182 static int sb_size = 0;
183 #define SB_DELTA 1024
184
185 static void c_write1(int c)
186 {
187 char cc = (char) c;
188 from_backend(0, &cc, 1);
189 }
190
191 static void log_option(char *sender, int cmd, int option)
192 {
193 char buf[50];
194 sprintf(buf, "%s:\t%s %s", sender,
195 (cmd == WILL ? "WILL" : cmd == WONT ? "WONT" :
196 cmd == DO ? "DO" : cmd == DONT ? "DONT" : "<??>"),
197 telopt(option));
198 logevent(buf);
199 }
200
201 static void send_opt(int cmd, int option)
202 {
203 unsigned char b[3];
204
205 b[0] = IAC;
206 b[1] = cmd;
207 b[2] = option;
208 sk_write(s, b, 3);
209 log_option("client", cmd, option);
210 }
211
212 static void deactivate_option(struct Opt *o)
213 {
214 if (o->state == REQUESTED || o->state == ACTIVE)
215 send_opt(o->nsend, o->option);
216 o->state = REALLY_INACTIVE;
217 }
218
219 /*
220 * Generate side effects of enabling or disabling an option.
221 */
222 static void option_side_effects(struct Opt *o, int enabled)
223 {
224 if (o->option == TELOPT_ECHO && o->send == DO)
225 echoing = !enabled;
226 else if (o->option == TELOPT_SGA && o->send == DO)
227 editing = !enabled;
228 ldisc_send(NULL, 0); /* cause ldisc to notice the change */
229 }
230
231 static void activate_option(struct Opt *o)
232 {
233 if (o->send == WILL && o->option == TELOPT_NAWS)
234 telnet_size();
235 if (o->send == WILL &&
236 (o->option == TELOPT_NEW_ENVIRON ||
237 o->option == TELOPT_OLD_ENVIRON)) {
238 /*
239 * We may only have one kind of ENVIRON going at a time.
240 * This is a hack, but who cares.
241 */
242 deactivate_option(o->option ==
243 TELOPT_NEW_ENVIRON ? &o_oenv : &o_nenv);
244 }
245 option_side_effects(o, 1);
246 }
247
248 static void refused_option(struct Opt *o)
249 {
250 if (o->send == WILL && o->option == TELOPT_NEW_ENVIRON &&
251 o_oenv.state == INACTIVE) {
252 send_opt(WILL, TELOPT_OLD_ENVIRON);
253 o_oenv.state = REQUESTED;
254 }
255 option_side_effects(o, 0);
256 }
257
258 static void proc_rec_opt(int cmd, int option)
259 {
260 struct Opt **o;
261
262 log_option("server", cmd, option);
263 for (o = opts; *o; o++) {
264 if ((*o)->option == option && (*o)->ack == cmd) {
265 switch ((*o)->state) {
266 case REQUESTED:
267 (*o)->state = ACTIVE;
268 activate_option(*o);
269 break;
270 case ACTIVE:
271 break;
272 case INACTIVE:
273 (*o)->state = ACTIVE;
274 send_opt((*o)->send, option);
275 activate_option(*o);
276 break;
277 case REALLY_INACTIVE:
278 send_opt((*o)->nsend, option);
279 break;
280 }
281 return;
282 } else if ((*o)->option == option && (*o)->nak == cmd) {
283 switch ((*o)->state) {
284 case REQUESTED:
285 (*o)->state = INACTIVE;
286 refused_option(*o);
287 break;
288 case ACTIVE:
289 (*o)->state = INACTIVE;
290 send_opt((*o)->nsend, option);
291 option_side_effects(*o, 0);
292 break;
293 case INACTIVE:
294 case REALLY_INACTIVE:
295 break;
296 }
297 return;
298 }
299 }
300 /*
301 * If we reach here, the option was one we weren't prepared to
302 * cope with. So send a negative ack.
303 */
304 send_opt((cmd == WILL ? DONT : WONT), option);
305 }
306
307 static void process_subneg(void)
308 {
309 unsigned char b[2048], *p, *q;
310 int var, value, n;
311 char *e;
312
313 switch (sb_opt) {
314 case TELOPT_TSPEED:
315 if (sb_len == 1 && sb_buf[0] == TELQUAL_SEND) {
316 char logbuf[sizeof(cfg.termspeed) + 80];
317 b[0] = IAC;
318 b[1] = SB;
319 b[2] = TELOPT_TSPEED;
320 b[3] = TELQUAL_IS;
321 strcpy(b + 4, cfg.termspeed);
322 n = 4 + strlen(cfg.termspeed);
323 b[n] = IAC;
324 b[n + 1] = SE;
325 sk_write(s, b, n + 2);
326 logevent("server:\tSB TSPEED SEND");
327 sprintf(logbuf, "client:\tSB TSPEED IS %s", cfg.termspeed);
328 logevent(logbuf);
329 } else
330 logevent("server:\tSB TSPEED <something weird>");
331 break;
332 case TELOPT_TTYPE:
333 if (sb_len == 1 && sb_buf[0] == TELQUAL_SEND) {
334 char logbuf[sizeof(cfg.termtype) + 80];
335 b[0] = IAC;
336 b[1] = SB;
337 b[2] = TELOPT_TTYPE;
338 b[3] = TELQUAL_IS;
339 for (n = 0; cfg.termtype[n]; n++)
340 b[n + 4] = (cfg.termtype[n] >= 'a'
341 && cfg.termtype[n] <=
342 'z' ? cfg.termtype[n] + 'A' -
343 'a' : cfg.termtype[n]);
344 b[n + 4] = IAC;
345 b[n + 5] = SE;
346 sk_write(s, b, n + 6);
347 b[n + 4] = 0;
348 logevent("server:\tSB TTYPE SEND");
349 sprintf(logbuf, "client:\tSB TTYPE IS %s", b + 4);
350 logevent(logbuf);
351 } else
352 logevent("server:\tSB TTYPE <something weird>\r\n");
353 break;
354 case TELOPT_OLD_ENVIRON:
355 case TELOPT_NEW_ENVIRON:
356 p = sb_buf;
357 q = p + sb_len;
358 if (p < q && *p == TELQUAL_SEND) {
359 char logbuf[50];
360 p++;
361 sprintf(logbuf, "server:\tSB %s SEND", telopt(sb_opt));
362 logevent(logbuf);
363 if (sb_opt == TELOPT_OLD_ENVIRON) {
364 if (cfg.rfc_environ) {
365 value = RFC_VALUE;
366 var = RFC_VAR;
367 } else {
368 value = BSD_VALUE;
369 var = BSD_VAR;
370 }
371 /*
372 * Try to guess the sense of VAR and VALUE.
373 */
374 while (p < q) {
375 if (*p == RFC_VAR) {
376 value = RFC_VALUE;
377 var = RFC_VAR;
378 } else if (*p == BSD_VAR) {
379 value = BSD_VALUE;
380 var = BSD_VAR;
381 }
382 p++;
383 }
384 } else {
385 /*
386 * With NEW_ENVIRON, the sense of VAR and VALUE
387 * isn't in doubt.
388 */
389 value = RFC_VALUE;
390 var = RFC_VAR;
391 }
392 b[0] = IAC;
393 b[1] = SB;
394 b[2] = sb_opt;
395 b[3] = TELQUAL_IS;
396 n = 4;
397 e = cfg.environmt;
398 while (*e) {
399 b[n++] = var;
400 while (*e && *e != '\t')
401 b[n++] = *e++;
402 if (*e == '\t')
403 e++;
404 b[n++] = value;
405 while (*e)
406 b[n++] = *e++;
407 e++;
408 }
409 if (*cfg.username) {
410 b[n++] = var;
411 b[n++] = 'U';
412 b[n++] = 'S';
413 b[n++] = 'E';
414 b[n++] = 'R';
415 b[n++] = value;
416 e = cfg.username;
417 while (*e)
418 b[n++] = *e++;
419 }
420 b[n++] = IAC;
421 b[n++] = SE;
422 sk_write(s, b, n);
423 sprintf(logbuf, "client:\tSB %s IS %s", telopt(sb_opt),
424 n == 6 ? "<nothing>" : "<stuff>");
425 logevent(logbuf);
426 }
427 break;
428 }
429 }
430
431 static enum {
432 TOPLEVEL, SEENIAC, SEENWILL, SEENWONT, SEENDO, SEENDONT,
433 SEENSB, SUBNEGOT, SUBNEG_IAC, SEENCR
434 } telnet_state = TOPLEVEL;
435
436 static void do_telnet_read(char *buf, int len)
437 {
438
439 while (len--) {
440 int c = (unsigned char) *buf++;
441
442 switch (telnet_state) {
443 case TOPLEVEL:
444 case SEENCR:
445 if (c == NUL && telnet_state == SEENCR)
446 telnet_state = TOPLEVEL;
447 else if (c == IAC)
448 telnet_state = SEENIAC;
449 else {
450 if (!in_synch)
451 c_write1(c);
452
453 #if 1
454 /* I can't get the F***ing winsock to insert the urgent IAC
455 * into the right position! Even with SO_OOBINLINE it gives
456 * it to recv too soon. And of course the DM byte (that
457 * arrives in the same packet!) appears several K later!!
458 *
459 * Oh well, we do get the DM in the right place so I'll
460 * just stop hiding on the next 0xf2 and hope for the best.
461 */
462 else if (c == DM)
463 in_synch = 0;
464 #endif
465 if (c == CR)
466 telnet_state = SEENCR;
467 else
468 telnet_state = TOPLEVEL;
469 }
470 break;
471 case SEENIAC:
472 if (c == DO)
473 telnet_state = SEENDO;
474 else if (c == DONT)
475 telnet_state = SEENDONT;
476 else if (c == WILL)
477 telnet_state = SEENWILL;
478 else if (c == WONT)
479 telnet_state = SEENWONT;
480 else if (c == SB)
481 telnet_state = SEENSB;
482 else if (c == DM) {
483 in_synch = 0;
484 telnet_state = TOPLEVEL;
485 } else {
486 /* ignore everything else; print it if it's IAC */
487 if (c == IAC) {
488 c_write1(c);
489 }
490 telnet_state = TOPLEVEL;
491 }
492 break;
493 case SEENWILL:
494 proc_rec_opt(WILL, c);
495 telnet_state = TOPLEVEL;
496 break;
497 case SEENWONT:
498 proc_rec_opt(WONT, c);
499 telnet_state = TOPLEVEL;
500 break;
501 case SEENDO:
502 proc_rec_opt(DO, c);
503 telnet_state = TOPLEVEL;
504 break;
505 case SEENDONT:
506 proc_rec_opt(DONT, c);
507 telnet_state = TOPLEVEL;
508 break;
509 case SEENSB:
510 sb_opt = c;
511 sb_len = 0;
512 telnet_state = SUBNEGOT;
513 break;
514 case SUBNEGOT:
515 if (c == IAC)
516 telnet_state = SUBNEG_IAC;
517 else {
518 subneg_addchar:
519 if (sb_len >= sb_size) {
520 char *newbuf;
521 sb_size += SB_DELTA;
522 newbuf = (sb_buf ?
523 srealloc(sb_buf, sb_size) :
524 smalloc(sb_size));
525 if (newbuf)
526 sb_buf = newbuf;
527 else
528 sb_size -= SB_DELTA;
529 }
530 if (sb_len < sb_size)
531 sb_buf[sb_len++] = c;
532 telnet_state = SUBNEGOT; /* in case we came here by goto */
533 }
534 break;
535 case SUBNEG_IAC:
536 if (c != SE)
537 goto subneg_addchar; /* yes, it's a hack, I know, but... */
538 else {
539 process_subneg();
540 telnet_state = TOPLEVEL;
541 }
542 break;
543 }
544 }
545 }
546
547 static int telnet_closing(Plug plug, char *error_msg, int error_code,
548 int calling_back)
549 {
550 sk_close(s);
551 s = NULL;
552 if (error_msg) {
553 /* A socket error has occurred. */
554 connection_fatal(error_msg);
555 } /* Otherwise, the remote side closed the connection normally. */
556 return 0;
557 }
558
559 static int telnet_receive(Plug plug, int urgent, char *data, int len)
560 {
561 if (urgent)
562 in_synch = TRUE;
563 do_telnet_read(data, len);
564 return 1;
565 }
566
567 /*
568 * Called to set up the Telnet connection.
569 *
570 * Returns an error message, or NULL on success.
571 *
572 * Also places the canonical host name into `realhost'.
573 */
574 static char *telnet_init(char *host, int port, char **realhost)
575 {
576 static struct plug_function_table fn_table = {
577 telnet_closing,
578 telnet_receive
579 }, *fn_table_ptr = &fn_table;
580
581 SockAddr addr;
582 char *err;
583
584 /*
585 * Try to find host.
586 */
587 addr = sk_namelookup(host, realhost);
588 if ((err = sk_addr_error(addr)))
589 return err;
590
591 if (port < 0)
592 port = 23; /* default telnet port */
593
594 /*
595 * Open socket.
596 */
597 s = sk_new(addr, port, 0, 1, &fn_table_ptr);
598 if ((err = sk_socket_error(s)))
599 return err;
600
601 sk_addr_free(addr);
602
603 /*
604 * Initialise option states.
605 */
606 {
607 struct Opt **o;
608
609 for (o = opts; *o; o++)
610 if ((*o)->state == REQUESTED)
611 send_opt((*o)->send, (*o)->option);
612 }
613
614 /*
615 * Set up SYNCH state.
616 */
617 in_synch = FALSE;
618
619 return NULL;
620 }
621
622 /*
623 * Called to send data down the Telnet connection.
624 */
625 static void telnet_send(char *buf, int len)
626 {
627 char *p;
628 static unsigned char iac[2] = { IAC, IAC };
629 static unsigned char cr[2] = { CR, NUL };
630 static unsigned char nl[2] = { CR, LF };
631
632 if (s == NULL)
633 return;
634
635 p = buf;
636 while (p < buf + len) {
637 char *q = p;
638
639 while (iswritable((unsigned char) *p) && p < buf + len)
640 p++;
641 sk_write(s, q, p - q);
642
643 while (p < buf + len && !iswritable((unsigned char) *p)) {
644 sk_write(s, (unsigned char) *p == IAC ? iac : nl, 2);
645 p++;
646 }
647 }
648 }
649
650 /*
651 * Called to set the size of the window from Telnet's POV.
652 */
653 static void telnet_size(void)
654 {
655 unsigned char b[16];
656 char logbuf[50];
657
658 if (s == NULL || o_naws.state != ACTIVE)
659 return;
660 b[0] = IAC;
661 b[1] = SB;
662 b[2] = TELOPT_NAWS;
663 b[3] = cols >> 8;
664 b[4] = cols & 0xFF;
665 b[5] = rows >> 8;
666 b[6] = rows & 0xFF;
667 b[7] = IAC;
668 b[8] = SE;
669 sk_write(s, b, 9);
670 sprintf(logbuf, "client:\tSB NAWS %d,%d",
671 ((unsigned char) b[3] << 8) + (unsigned char) b[4],
672 ((unsigned char) b[5] << 8) + (unsigned char) b[6]);
673 logevent(logbuf);
674 }
675
676 /*
677 * Send Telnet special codes.
678 */
679 static void telnet_special(Telnet_Special code)
680 {
681 unsigned char b[2];
682
683 if (s == NULL)
684 return;
685
686 b[0] = IAC;
687 switch (code) {
688 case TS_AYT:
689 b[1] = AYT;
690 sk_write(s, b, 2);
691 break;
692 case TS_BRK:
693 b[1] = BREAK;
694 sk_write(s, b, 2);
695 break;
696 case TS_EC:
697 b[1] = EC;
698 sk_write(s, b, 2);
699 break;
700 case TS_EL:
701 b[1] = EL;
702 sk_write(s, b, 2);
703 break;
704 case TS_GA:
705 b[1] = GA;
706 sk_write(s, b, 2);
707 break;
708 case TS_NOP:
709 b[1] = NOP;
710 sk_write(s, b, 2);
711 break;
712 case TS_ABORT:
713 b[1] = ABORT;
714 sk_write(s, b, 2);
715 break;
716 case TS_AO:
717 b[1] = AO;
718 sk_write(s, b, 2);
719 break;
720 case TS_IP:
721 b[1] = IP;
722 sk_write(s, b, 2);
723 break;
724 case TS_SUSP:
725 b[1] = SUSP;
726 sk_write(s, b, 2);
727 break;
728 case TS_EOR:
729 b[1] = EOR;
730 sk_write(s, b, 2);
731 break;
732 case TS_EOF:
733 b[1] = xEOF;
734 sk_write(s, b, 2);
735 break;
736 case TS_SYNCH:
737 b[1] = DM;
738 sk_write(s, b, 1);
739 sk_write_oob(s, b + 1, 1);
740 break;
741 case TS_RECHO:
742 if (o_echo.state == INACTIVE || o_echo.state == REALLY_INACTIVE) {
743 o_echo.state = REQUESTED;
744 send_opt(o_echo.send, o_echo.option);
745 }
746 break;
747 case TS_LECHO:
748 if (o_echo.state == ACTIVE) {
749 o_echo.state = REQUESTED;
750 send_opt(o_echo.nsend, o_echo.option);
751 }
752 break;
753 case TS_PING:
754 if (o_they_sga.state == ACTIVE) {
755 b[1] = NOP;
756 sk_write(s, b, 2);
757 }
758 break;
759 }
760 }
761
762 static Socket telnet_socket(void)
763 {
764 return s;
765 }
766
767 static int telnet_sendok(void)
768 {
769 return 1;
770 }
771
772 static int telnet_ldisc(int option)
773 {
774 if (option == LD_ECHO)
775 return echoing;
776 if (option == LD_EDIT)
777 return editing;
778 return FALSE;
779 }
780
781 Backend telnet_backend = {
782 telnet_init,
783 telnet_send,
784 telnet_size,
785 telnet_special,
786 telnet_socket,
787 telnet_sendok,
788 telnet_ldisc,
789 23
790 };
Local modifications for Simon Tatham's `PuTTY' SSH client and terminal emulator