aboutsummaryrefslogtreecommitdiff
path: root/lib/telnet.c
blob: 5962719813ade5ee92a777d56e4e5117e3241e99 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2006, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at http://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * $Id$
 ***************************************************************************/

#include "setup.h"

#ifndef CURL_DISABLE_TELNET
/* -- WIN32 approved -- */
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <stdlib.h>
#include <ctype.h>
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif

#if defined(WIN32)
#include <time.h>
#include <io.h>
#else
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#include <netinet/in.h>
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <netdb.h>
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#ifdef HAVE_NET_IF_H
#include <net/if.h>
#endif
#include <sys/ioctl.h>
#include <signal.h>

#ifdef HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif


#endif

#include "urldata.h"
#include <curl/curl.h>
#include "transfer.h"
#include "sendf.h"
#include "telnet.h"
#include "connect.h"

#define _MPRINTF_REPLACE /* use our functions only */
#include <curl/mprintf.h>

#define  TELOPTS
#define  TELCMDS

#include "arpa_telnet.h"
#include "memory.h"
#include "select.h"

/* The last #include file should be: */
#include "memdebug.h"

#define SUBBUFSIZE 512

#define CURL_SB_CLEAR(x)  x->subpointer = x->subbuffer;
#define CURL_SB_TERM(x)   { x->subend = x->subpointer; CURL_SB_CLEAR(x); }
#define CURL_SB_ACCUM(x,c) \
  if (x->subpointer < (x->subbuffer+sizeof x->subbuffer)) { \
    *x->subpointer++ = (c); \
  }

#define  CURL_SB_GET(x) ((*x->subpointer++)&0xff)
#define  CURL_SB_PEEK(x)   ((*x->subpointer)&0xff)
#define  CURL_SB_EOF(x) (x->subpointer >= x->subend)
#define  CURL_SB_LEN(x) (x->subend - x->subpointer)

#ifdef WIN32
typedef FARPROC WSOCK2_FUNC;
static CURLcode check_wsock2 ( struct SessionHandle *data );
#endif

static
void telrcv(struct connectdata *,
            unsigned char *inbuf,       /* Data received from socket */
            ssize_t count);             /* Number of bytes received */

static void printoption(struct SessionHandle *data,
                        const char *direction,
                        int cmd, int option);

static void negotiate(struct connectdata *);
static void send_negotiation(struct connectdata *, int cmd, int option);
static void set_local_option(struct connectdata *, int cmd, int option);
static void set_remote_option(struct connectdata *, int cmd, int option);

static void printsub(struct SessionHandle *data,
                     int direction, unsigned char *pointer,
                     size_t length);
static void suboption(struct connectdata *);

/* For negotiation compliant to RFC 1143 */
#define CURL_NO          0
#define CURL_YES         1
#define CURL_WANTYES     2
#define CURL_WANTNO      3

#define CURL_EMPTY       0
#define CURL_OPPOSITE    1

/*
 * Telnet receiver states for fsm
 */
typedef enum
{
   CURL_TS_DATA = 0,
   CURL_TS_IAC,
   CURL_TS_WILL,
   CURL_TS_WONT,
   CURL_TS_DO,
   CURL_TS_DONT,
   CURL_TS_CR,
   CURL_TS_SB,   /* sub-option collection */
   CURL_TS_SE   /* looking for sub-option end */
} TelnetReceive;

struct TELNET {
  int please_negotiate;
  int already_negotiated;
  int us[256];
  int usq[256];
  int us_preferred[256];
  int him[256];
  int himq[256];
  int him_preferred[256];
  char subopt_ttype[32];             /* Set with suboption TTYPE */
  char subopt_xdisploc[128];          /* Set with suboption XDISPLOC */
  struct curl_slist *telnet_vars; /* Environment variables */

  /* suboptions */
  unsigned char subbuffer[SUBBUFSIZE];
  unsigned char *subpointer, *subend;      /* buffer for sub-options */

  TelnetReceive telrcv_state;
};

#ifdef WIN32
static CURLcode
check_wsock2 ( struct SessionHandle *data )
{
  int err;
  WORD wVersionRequested;
  WSADATA wsaData;

  curlassert(data);

  /* telnet requires at least WinSock 2.0 so ask for it. */
  wVersionRequested = MAKEWORD(2, 0);

  err = WSAStartup(wVersionRequested, &wsaData);

  /* We must've called this once already, so this call */
  /* should always succeed.  But, just in case... */
  if (err != 0) {
    failf(data,"WSAStartup failed (%d)",err);
    return CURLE_FAILED_INIT;
  }

  /* We have to have a WSACleanup call for every successful */
  /* WSAStartup call. */
  WSACleanup();

  /* Check that our version is supported */
  if (LOBYTE(wsaData.wVersion) != LOBYTE(wVersionRequested) ||
      HIBYTE(wsaData.wVersion) != HIBYTE(wVersionRequested)) {
      /* Our version isn't supported */
      failf(data,"insufficient winsock version to support "
            "telnet");
      return CURLE_FAILED_INIT;
  }

  /* Our version is supported */
  return CURLE_OK;
}
#endif
static
CURLcode init_telnet(struct connectdata *conn)
{
  struct TELNET *tn;

  tn = (struct TELNET *)calloc(1, sizeof(struct TELNET));
  if(!tn)
    return CURLE_OUT_OF_MEMORY;

  conn->proto.telnet = (void *)tn; /* make us known */

  tn->telrcv_state = CURL_TS_DATA;

  /* Init suboptions */
  CURL_SB_CLEAR(tn);

  /* Set the options we want by default */
  tn->us_preferred[CURL_TELOPT_BINARY] = CURL_YES;
  tn->us_preferred[CURL_TELOPT_SGA] = CURL_YES;
  tn->him_preferred[CURL_TELOPT_BINARY] = CURL_YES;
  tn->him_preferred[CURL_TELOPT_SGA] = CURL_YES;

  return CURLE_OK;
}

static void negotiate(struct connectdata *conn)
{
  int i;
  struct TELNET *tn = (struct TELNET *)conn->proto.telnet;

  for(i = 0;i < CURL_NTELOPTS;i++)
  {
    if(tn->us_preferred[i] == CURL_YES)
      set_local_option(conn, i, CURL_YES);

    if(tn->him_preferred[i] == CURL_YES)
      set_remote_option(conn, i, CURL_YES);
  }
}

static void printoption(struct SessionHandle *data,
                        const char *direction, int cmd, int option)
{
  const char *fmt;
  const char *opt;

  if (data->set.verbose)
  {
    if (cmd == CURL_IAC)
    {
      if (CURL_TELCMD_OK(option))
        infof(data, "%s IAC %s\n", direction, CURL_TELCMD(option));
      else
        infof(data, "%s IAC %d\n", direction, option);
    }
    else
    {
      fmt = (cmd == CURL_WILL) ? "WILL" : (cmd == CURL_WONT) ? "WONT" :
        (cmd == CURL_DO) ? "DO" : (cmd == CURL_DONT) ? "DONT" : 0;
      if (fmt)
      {
        if (CURL_TELOPT_OK(option))
          opt = CURL_TELOPT(option);
        else if (option == CURL_TELOPT_EXOPL)
          opt = "EXOPL";
        else
          opt = NULL;

        if(opt)
          infof(data, "%s %s %s\n", direction, fmt, opt);
        else
          infof(data, "%s %s %d\n", direction, fmt, option);
      }
      else
        infof(data, "%s %d %d\n", direction, cmd, option);
    }
  }
}

static void send_negotiation(struct connectdata *conn, int cmd, int option)
{
   unsigned char buf[3];
   ssize_t bytes_written;
   int err;
   struct SessionHandle *data = conn->data;

   buf[0] = CURL_IAC;
   buf[1] = (unsigned char)cmd;
   buf[2] = (unsigned char)option;

   bytes_written = swrite(conn->sock[FIRSTSOCKET], buf, 3);
   if(bytes_written < 0) {
     err = Curl_sockerrno();
     failf(data,"Sending data failed (%d)",err);
   }

   printoption(conn->data, "SENT", cmd, option);
}

static
void set_remote_option(struct connectdata *conn, int option, int newstate)
{
  struct TELNET *tn = (struct TELNET *)conn->proto.telnet;
  if(newstate == CURL_YES)
  {
    switch(tn->him[option])
    {
      case CURL_NO:
        tn->him[option] = CURL_WANTYES;
        send_negotiation(conn, CURL_DO, option);
        break;

      case CURL_YES:
        /* Already enabled */
        break;

      case CURL_WANTNO:
        switch(tn->himq[option])
        {
          case CURL_EMPTY:
            /* Already negotiating for CURL_YES, queue the request */
            tn->himq[option] = CURL_OPPOSITE;
            break;
          case CURL_OPPOSITE:
            /* Error: already queued an enable request */
            break;
        }
        break;

      case CURL_WANTYES:
        switch(tn->himq[option])
        {
          case CURL_EMPTY:
            /* Error: already negotiating for enable */
            break;
          case CURL_OPPOSITE:
            tn->himq[option] = CURL_EMPTY;
            break;
        }
        break;
    }
  }
  else /* NO */
  {
    switch(tn->him[option])
    {
      case CURL_NO:
        /* Already disabled */
        break;

      case CURL_YES:
        tn->him[option] = CURL_WANTNO;
        send_negotiation(conn, CURL_DONT, option);
        break;

      case CURL_WANTNO:
        switch(tn->himq[option])
        {
          case CURL_EMPTY:
            /* Already negotiating for NO */
            break;
          case CURL_OPPOSITE:
            tn->himq[option] = CURL_EMPTY;
            break;
        }
        break;

      case CURL_WANTYES:
        switch(tn->himq[option])
        {
          case CURL_EMPTY:
            tn->himq[option] = CURL_OPPOSITE;
            break;
          case CURL_OPPOSITE:
            break;
        }
        break;
    }
  }
}

static
void rec_will(struct connectdata *conn, int option)
{
  struct TELNET *tn = (struct TELNET *)conn->proto.telnet;
  switch(tn->him[option])
  {
    case CURL_NO:
      if(tn->him_preferred[option] == CURL_YES)
      {
        tn->him[option] = CURL_YES;
        send_negotiation(conn, CURL_DO, option);
      }
      else
      {
        send_negotiation(conn, CURL_DONT, option);
      }
      break;

    case CURL_YES:
      /* Already enabled */
      break;

    case CURL_WANTNO:
      switch(tn->himq[option])
      {
        case CURL_EMPTY:
          /* Error: DONT answered by WILL */
          tn->him[option] = CURL_NO;
          break;
        case CURL_OPPOSITE:
          /* Error: DONT answered by WILL */
          tn->him[option] = CURL_YES;
          tn->himq[option] = CURL_EMPTY;
          break;
      }
      break;

    case CURL_WANTYES:
      switch(tn->himq[option])
      {
        case CURL_EMPTY:
          tn->him[option] = CURL_YES;
          break;
        case CURL_OPPOSITE:
          tn->him[option] = CURL_WANTNO;
          tn->himq[option] = CURL_EMPTY;
          send_negotiation(conn, CURL_DONT, option);
          break;
      }
      break;
  }
}

static
void rec_wont(struct connectdata *conn, int option)
{
  struct TELNET *tn = (struct TELNET *)conn->proto.telnet;
  switch(tn->him[option])
  {
    case CURL_NO:
      /* Already disabled */
      break;

    case CURL_YES:
      tn->him[option] = CURL_NO;
      send_negotiation(conn, CURL_DONT, option);
      break;

    case CURL_WANTNO:
      switch(tn->himq[option])
      {
        case CURL_EMPTY:
          tn->him[option] = CURL_NO;
          break;

        case CURL_OPPOSITE:
          tn->him[option] = CURL_WANTYES;
          tn->himq[option] = CURL_EMPTY;
          send_negotiation(conn, CURL_DO, option);
          break;
      }
      break;

    case CURL_WANTYES:
      switch(tn->himq[option])
      {
        case CURL_EMPTY:
          tn->him[option] = CURL_NO;
          break;
        case CURL_OPPOSITE:
          tn->him[option] = CURL_NO;
          tn->himq[option] = CURL_EMPTY;
          break;
      }
      break;
  }
}

static void
set_local_option(struct connectdata *conn, int option, int newstate)
{
  struct TELNET *tn = (struct TELNET *)conn->proto.telnet;
  if(newstate == CURL_YES)
  {
    switch(tn->us[option])
    {
      case CURL_NO:
        tn->us[option] = CURL_WANTYES;
        send_negotiation(conn, CURL_WILL, option);
        break;

      case CURL_YES:
        /* Already enabled */
        break;

      case CURL_WANTNO:
        switch(tn->usq[option])
        {
          case CURL_EMPTY:
            /* Already negotiating for CURL_YES, queue the request */
            tn->usq[option] = CURL_OPPOSITE;
            break;
          case CURL_OPPOSITE:
            /* Error: already queued an enable request */
            break;
        }
        break;

      case CURL_WANTYES:
        switch(tn->usq[option])
        {
          case CURL_EMPTY:
            /* Error: already negotiating for enable */
            break;
          case CURL_OPPOSITE:
            tn->usq[option] = CURL_EMPTY;
            break;
        }
        break;
    }
  }
  else /* NO */
  {
    switch(tn->us[option])
    {
      case CURL_NO:
        /* Already disabled */
        break;

      case CURL_YES:
        tn->us[option] = CURL_WANTNO;
        send_negotiation(conn, CURL_WONT, option);
        break;

      case CURL_WANTNO:
        switch(tn->usq[option])
        {
          case CURL_EMPTY:
            /* Already negotiating for NO */
            break;
          case CURL_OPPOSITE:
            tn->usq[option] = CURL_EMPTY;
            break;
        }
        break;

      case CURL_WANTYES:
        switch(tn->usq[option])
        {
          case CURL_EMPTY:
            tn->usq[option] = CURL_OPPOSITE;
            break;
          case CURL_OPPOSITE:
            break;
        }
        break;
    }
  }
}

static
void rec_do(struct connectdata *conn, int option)
{
  struct TELNET *tn = (struct TELNET *)conn->proto.telnet;
  switch(tn->us[option])
  {
    case CURL_NO:
      if(tn->us_preferred[option] == CURL_YES)
      {
        tn->us[option] = CURL_YES;
        send_negotiation(conn, CURL_WILL, option);
      }
      else
      {
        send_negotiation(conn, CURL_WONT, option);
      }
      break;

    case CURL_YES:
      /* Already enabled */
      break;

    case CURL_WANTNO:
      switch(tn->usq[option])
      {
        case CURL_EMPTY:
          /* Error: DONT answered by WILL */
          tn->us[option] = CURL_NO;
          break;
        case CURL_OPPOSITE:
          /* Error: DONT answered by WILL */
          tn->us[option] = CURL_YES;
          tn->usq[option] = CURL_EMPTY;
          break;
      }
      break;

    case CURL_WANTYES:
      switch(tn->usq[option])
      {
        case CURL_EMPTY:
          tn->us[option] = CURL_YES;
          break;
        case CURL_OPPOSITE:
          tn->us[option] = CURL_WANTNO;
          tn->himq[option] = CURL_EMPTY;
          send_negotiation(conn, CURL_WONT, option);
          break;
      }
      break;
  }
}

static
void rec_dont(struct connectdata *conn, int option)
{
  struct TELNET *tn = (struct TELNET *)conn->proto.telnet;
  switch(tn->us[option])
  {
    case CURL_NO:
      /* Already disabled */
      break;

    case CURL_YES:
      tn->us[option] = CURL_NO;
      send_negotiation(conn, CURL_WONT, option);
      break;

    case CURL_WANTNO:
      switch(tn->usq[option])
      {
        case CURL_EMPTY:
          tn->us[option] = CURL_NO;
          break;

        case CURL_OPPOSITE:
          tn->us[option] = CURL_WANTYES;
          tn->usq[option] = CURL_EMPTY;
          send_negotiation(conn, CURL_WILL, option);
          break;
      }
      break;

    case CURL_WANTYES:
      switch(tn->usq[option])
      {
        case CURL_EMPTY:
          tn->us[option] = CURL_NO;
          break;
        case CURL_OPPOSITE:
          tn->us[option] = CURL_NO;
          tn->usq[option] = CURL_EMPTY;
          break;
      }
      break;
  }
}


static void printsub(struct SessionHandle *data,
                     int direction,             /* '<' or '>' */
                     unsigned char *pointer,    /* where suboption data is */
                     size_t length)             /* length of suboption data */
{
  unsigned int i = 0;

  if (data->set.verbose)
  {
    if (direction)
    {
      infof(data, "%s IAC SB ", (direction == '<')? "RCVD":"SENT");
      if (length >= 3)
      {
        int j;

        i = pointer[length-2];
        j = pointer[length-1];

        if (i != CURL_IAC || j != CURL_SE)
        {
          infof(data, "(terminated by ");
          if (CURL_TELOPT_OK(i))
            infof(data, "%s ", CURL_TELOPT(i));
          else if (CURL_TELCMD_OK(i))
            infof(data, "%s ", CURL_TELCMD(i));
          else
            infof(data, "%d ", i);
          if (CURL_TELOPT_OK(j))
            infof(data, "%s", CURL_TELOPT(j));
          else if (CURL_TELCMD_OK(j))
            infof(data, "%s", CURL_TELCMD(j));
          else
            infof(data, "%d", j);
          infof(data, ", not IAC SE!) ");
        }
      }
      length -= 2;
    }
    if (length < 1)
    {
      infof(data, "(Empty suboption?)");
      return;
    }

    if (CURL_TELOPT_OK(pointer[0])) {
      switch(pointer[0]) {
        case CURL_TELOPT_TTYPE:
        case CURL_TELOPT_XDISPLOC:
        case CURL_TELOPT_NEW_ENVIRON:
          infof(data, "%s", CURL_TELOPT(pointer[0]));
          break;
        default:
          infof(data, "%s (unsupported)", CURL_TELOPT(pointer[0]));
          break;
      }
    }
    else
      infof(data, "%d (unknown)", pointer[i]);

    switch(pointer[1]) {
      case CURL_TELQUAL_IS:
        infof(data, " IS");
        break;
      case CURL_TELQUAL_SEND:
        infof(data, " SEND");
        break;
      case CURL_TELQUAL_INFO:
        infof(data, " INFO/REPLY");
        break;
      case CURL_TELQUAL_NAME:
        infof(data, " NAME");
        break;
    }

    switch(pointer[0]) {
      case CURL_TELOPT_TTYPE:
      case CURL_TELOPT_XDISPLOC:
        pointer[length] = 0;
        infof(data, " \"%s\"", &pointer[2]);
        break;
      case CURL_TELOPT_NEW_ENVIRON:
        if(pointer[1] == CURL_TELQUAL_IS) {
          infof(data, " ");
          for(i = 3;i < length;i++) {
            switch(pointer[i]) {
              case CURL_NEW_ENV_VAR:
                infof(data, ", ");
                break;
              case CURL_NEW_ENV_VALUE:
                infof(data, " = ");
                break;
              default:
                infof(data, "%c", pointer[i]);
                break;
            }
          }
        }
        break;
      default:
        for (i = 2; i < length; i++)
          infof(data, " %.2x", pointer[i]);
        break;
    }

    if (direction)
    {
      infof(data, "\n");
    }
  }
}

static CURLcode check_telnet_options(struct connectdata *conn)
{
  struct curl_slist *head;
  char option_keyword[128];
  char option_arg[256];
  char *buf;
  struct SessionHandle *data = conn->data;
  struct TELNET *tn = (struct TELNET *)conn->proto.telnet;

  /* Add the user name as an environment variable if it
     was given on the command line */
  if(conn->bits.user_passwd)
  {
    snprintf(option_arg, sizeof(option_arg), "USER,%s", conn->user);
    tn->telnet_vars = curl_slist_append(tn->telnet_vars, option_arg);

    tn->us_preferred[CURL_TELOPT_NEW_ENVIRON] = CURL_YES;
  }

  for(head = data->set.telnet_options; head; head=head->next) {
    if(sscanf(head->data, "%127[^= ]%*[ =]%255s",
              option_keyword, option_arg) == 2) {

      /* Terminal type */
      if(curl_strequal(option_keyword, "TTYPE")) {
        strncpy(tn->subopt_ttype, option_arg, 31);
        tn->subopt_ttype[31] = 0; /* String termination */
        tn->us_preferred[CURL_TELOPT_TTYPE] = CURL_YES;
        continue;
      }

      /* Display variable */
      if(curl_strequal(option_keyword, "XDISPLOC")) {
        strncpy(tn->subopt_xdisploc, option_arg, 127);
        tn->subopt_xdisploc[127] = 0; /* String termination */
        tn->us_preferred[CURL_TELOPT_XDISPLOC] = CURL_YES;
        continue;
      }

      /* Environment variable */
      if(curl_strequal(option_keyword, "NEW_ENV")) {
        buf = strdup(option_arg);
        if(!buf)
          return CURLE_OUT_OF_MEMORY;
        tn->telnet_vars = curl_slist_append(tn->telnet_vars, buf);
        tn->us_preferred[CURL_TELOPT_NEW_ENVIRON] = CURL_YES;
        continue;
      }

      failf(data, "Unknown telnet option %s", head->data);
      return CURLE_UNKNOWN_TELNET_OPTION;
    } else {
      failf(data, "Syntax error in telnet option: %s", head->data);
      return CURLE_TELNET_OPTION_SYNTAX;
    }
  }

  return CURLE_OK;
}

/*
 * suboption()
 *
 * Look at the sub-option buffer, and try to be helpful to the other
 * side.
 */

static void suboption(struct connectdata *conn)
{
  struct curl_slist *v;
  unsigned char temp[2048];
  ssize_t bytes_written;
  size_t len;
  size_t tmplen;
  int err;
  char varname[128];
  char varval[128];
  struct SessionHandle *data = conn->data;
  struct TELNET *tn = (struct TELNET *)conn->proto.telnet;

  printsub(data, '<', (unsigned char *)tn->subbuffer, CURL_SB_LEN(tn)+2);
  switch (CURL_SB_GET(tn)) {
    case CURL_TELOPT_TTYPE:
      len = strlen(tn->subopt_ttype) + 4 + 2;
      snprintf((char *)temp, sizeof(temp),
               "%c%c%c%c%s%c%c", CURL_IAC, CURL_SB, CURL_TELOPT_TTYPE,
               CURL_TELQUAL_IS, tn->subopt_ttype, CURL_IAC, CURL_SE);
      bytes_written = swrite(conn->sock[FIRSTSOCKET], temp, len);
      if(bytes_written < 0) {
        err = Curl_sockerrno();
        failf(data,"Sending data failed (%d)",err);
      }
      printsub(data, '>', &temp[2], len-2);
      break;
    case CURL_TELOPT_XDISPLOC:
      len = strlen(tn->subopt_xdisploc) + 4 + 2;
      snprintf((char *)temp, sizeof(temp),
               "%c%c%c%c%s%c%c", CURL_IAC, CURL_SB, CURL_TELOPT_XDISPLOC,
               CURL_TELQUAL_IS, tn->subopt_xdisploc, CURL_IAC, CURL_SE);
      bytes_written = swrite(conn->sock[FIRSTSOCKET], temp, len);
      if(bytes_written < 0) {
        err = Curl_sockerrno();
        failf(data,"Sending data failed (%d)",err);
      }
      printsub(data, '>', &temp[2], len-2);
      break;
    case CURL_TELOPT_NEW_ENVIRON:
      snprintf((char *)temp, sizeof(temp),
               "%c%c%c%c", CURL_IAC, CURL_SB, CURL_TELOPT_NEW_ENVIRON,
               CURL_TELQUAL_IS);
      len = 4;

      for(v = tn->telnet_vars;v;v = v->next) {
        tmplen = (strlen(v->data) + 1);
        /* Add the variable only if it fits */
        if(len + tmplen < (int)sizeof(temp)-6) {
          sscanf(v->data, "%127[^,],%127s", varname, varval);
          snprintf((char *)&temp[len], sizeof(temp) - len,
                   "%c%s%c%s", CURL_NEW_ENV_VAR, varname,
                   CURL_NEW_ENV_VALUE, varval);
          len += tmplen;
        }
      }
      snprintf((char *)&temp[len], sizeof(temp) - len,
               "%c%c", CURL_IAC, CURL_SE);
      len += 2;
      bytes_written = swrite(conn->sock[FIRSTSOCKET], temp, len);
      if(bytes_written < 0) {
        err = Curl_sockerrno();
        failf(data,"Sending data failed (%d)",err);
      }
      printsub(data, '>', &temp[2], len-2);
      break;
  }
  return;
}

static
void telrcv(struct connectdata *conn,
            unsigned char *inbuf,       /* Data received from socket */
            ssize_t count)              /* Number of bytes received */
{
  unsigned char c;
  int in = 0;
  struct SessionHandle *data = conn->data;
  struct TELNET *tn = (struct TELNET *)conn->proto.telnet;

  while(count--)
  {
    c = inbuf[in++];

    switch (tn->telrcv_state)
    {
      case CURL_TS_CR:
        tn->telrcv_state = CURL_TS_DATA;
        if (c == '\0')
        {
          break;   /* Ignore \0 after CR */
        }

        Curl_client_write(conn, CLIENTWRITE_BODY, (char *)&c, 1);
        continue;

      case CURL_TS_DATA:
        if (c == CURL_IAC)
        {
          tn->telrcv_state = CURL_TS_IAC;
          break;
        }
        else if(c == '\r')
        {
          tn->telrcv_state = CURL_TS_CR;
        }

        Curl_client_write(conn, CLIENTWRITE_BODY, (char *)&c, 1);
        continue;

      case CURL_TS_IAC:
      process_iac:
      switch (c)
      {
        case CURL_WILL:
          tn->telrcv_state = CURL_TS_WILL;
          continue;
        case CURL_WONT:
          tn->telrcv_state = CURL_TS_WONT;
          continue;
        case CURL_DO:
          tn->telrcv_state = CURL_TS_DO;
          continue;
        case CURL_DONT:
          tn->telrcv_state = CURL_TS_DONT;
          continue;
        case CURL_SB:
          CURL_SB_CLEAR(tn);
          tn->telrcv_state = CURL_TS_SB;
          continue;
        case CURL_IAC:
          Curl_client_write(conn, CLIENTWRITE_BODY, (char *)&c, 1);
          break;
        case CURL_DM:
        case CURL_NOP:
        case CURL_GA:
        default:
          printoption(data, "RCVD", CURL_IAC, c);
          break;
      }
      tn->telrcv_state = CURL_TS_DATA;
      continue;

      case CURL_TS_WILL:
        printoption(data, "RCVD", CURL_WILL, c);
        tn->please_negotiate = 1;
        rec_will(conn, c);
        tn->telrcv_state = CURL_TS_DATA;
        continue;

      case CURL_TS_WONT:
        printoption(data, "RCVD", CURL_WONT, c);
        tn->please_negotiate = 1;
        rec_wont(conn, c);
        tn->telrcv_state = CURL_TS_DATA;
        continue;

      case CURL_TS_DO:
        printoption(data, "RCVD", CURL_DO, c);
        tn->please_negotiate = 1;
        rec_do(conn, c);
        tn->telrcv_state = CURL_TS_DATA;
        continue;

      case CURL_TS_DONT:
        printoption(data, "RCVD", CURL_DONT, c);
        tn->please_negotiate = 1;
        rec_dont(conn, c);
        tn->telrcv_state = CURL_TS_DATA;
        continue;

      case CURL_TS_SB:
        if (c == CURL_IAC)
        {
          tn->telrcv_state = CURL_TS_SE;
        }
        else
        {
          CURL_SB_ACCUM(tn,c);
        }
        continue;

      case CURL_TS_SE:
        if (c != CURL_SE)
        {
          if (c != CURL_IAC)
          {
            /*
             * This is an error.  We only expect to get "IAC IAC" or "IAC SE".
             * Several things may have happend.  An IAC was not doubled, the
             * IAC SE was left off, or another option got inserted into the
             * suboption are all possibilities.  If we assume that the IAC was
             * not doubled, and really the IAC SE was left off, we could get
             * into an infinate loop here.  So, instead, we terminate the
             * suboption, and process the partial suboption if we can.
             */
            CURL_SB_ACCUM(tn, CURL_IAC);
            CURL_SB_ACCUM(tn, c);
            tn->subpointer -= 2;
            CURL_SB_TERM(tn);

            printoption(data, "In SUBOPTION processing, RCVD", CURL_IAC, c);
            suboption(conn);   /* handle sub-option */
            tn->telrcv_state = CURL_TS_IAC;
            goto process_iac;
          }
          CURL_SB_ACCUM(tn,c);
          tn->telrcv_state = CURL_TS_SB;
        }
        else
        {
          CURL_SB_ACCUM(tn, CURL_IAC);
          CURL_SB_ACCUM(tn, CURL_SE);
          tn->subpointer -= 2;
          CURL_SB_TERM(tn);
          suboption(conn);   /* handle sub-option */
          tn->telrcv_state = CURL_TS_DATA;
        }
        break;
    }
  }
}

CURLcode Curl_telnet_done(struct connectdata *conn, CURLcode status)
{
  struct TELNET *tn = (struct TELNET *)conn->proto.telnet;
  (void)status; /* unused */

  curl_slist_free_all(tn->telnet_vars);

  free(conn->proto.telnet);
  conn->proto.telnet = NULL;

  return CURLE_OK;
}

CURLcode Curl_telnet(struct connectdata *conn, bool *done)
{
  CURLcode code;
  struct SessionHandle *data = conn->data;
  curl_socket_t sockfd = conn->sock[FIRSTSOCKET];
#ifdef WIN32
  HMODULE wsock2;
  WSOCK2_FUNC close_event_func;
  WSOCK2_FUNC create_event_func;
  WSOCK2_FUNC event_select_func;
  WSOCK2_FUNC enum_netevents_func;
  WSAEVENT event_handle;
  WSANETWORKEVENTS events;
  HANDLE stdin_handle;
  HANDLE objs[2];
  DWORD  obj_count;
  DWORD  wait_timeout;
  DWORD waitret;
  DWORD readfile_read;
#else
  int interval_ms;
  struct pollfd pfd[2];
#endif
  ssize_t nread;
  bool keepon = TRUE;
  char *buf = data->state.buffer;
  struct TELNET *tn;

  *done = TRUE; /* uncontionally */

  code = init_telnet(conn);
  if(code)
    return code;

  tn = (struct TELNET *)conn->proto.telnet;

  code = check_telnet_options(conn);
  if(code)
    return code;

#ifdef WIN32
  /*
  ** This functionality only works with WinSock >= 2.0.  So,
  ** make sure have it.
  */
  code = check_wsock2(data);
  if (code)
    return code;

  /* OK, so we have WinSock 2.0.  We need to dynamically */
  /* load ws2_32.dll and get the function pointers we need. */
  wsock2 = LoadLibrary("WS2_32.DLL");
  if (wsock2 == NULL) {
    failf(data,"failed to load WS2_32.DLL (%d)",GetLastError());
    return CURLE_FAILED_INIT;
  }

  /* Grab a pointer to WSACreateEvent */
  create_event_func = GetProcAddress(wsock2,"WSACreateEvent");
  if (create_event_func == NULL) {
    failf(data,"failed to find WSACreateEvent function (%d)",
          GetLastError());
    FreeLibrary(wsock2);
    return CURLE_FAILED_INIT;
  }

  /* And WSACloseEvent */
  close_event_func = GetProcAddress(wsock2,"WSACloseEvent");
  if (create_event_func == NULL) {
    failf(data,"failed to find WSACloseEvent function (%d)",
          GetLastError());
    FreeLibrary(wsock2);
    return CURLE_FAILED_INIT;
  }

  /* And WSAEventSelect */
  event_select_func = GetProcAddress(wsock2,"WSAEventSelect");
  if (event_select_func == NULL) {
    failf(data,"failed to find WSAEventSelect function (%d)",
          GetLastError());
    FreeLibrary(wsock2);
    return CURLE_FAILED_INIT;
  }

  /* And WSAEnumNetworkEvents */
  enum_netevents_func = GetProcAddress(wsock2,"WSAEnumNetworkEvents");
  if (enum_netevents_func == NULL) {
    failf(data,"failed to find WSAEnumNetworkEvents function (%d)",
          GetLastError());
    FreeLibrary(wsock2);
    return CURLE_FAILED_INIT;
  }

  /* We want to wait for both stdin and the socket. Since
  ** the select() function in winsock only works on sockets
  ** we have to use the WaitForMultipleObjects() call.
  */

  /* First, create a sockets event object */
  event_handle = (WSAEVENT)create_event_func();
  if (event_handle == WSA_INVALID_EVENT) {
    failf(data,"WSACreateEvent failed (%d)",WSAGetLastError());
    FreeLibrary(wsock2);
    return CURLE_FAILED_INIT;
  }

  /* The get the Windows file handle for stdin */
  stdin_handle = GetStdHandle(STD_INPUT_HANDLE);

  /* Create the list of objects to wait for */
  objs[0] = event_handle;
  objs[1] = stdin_handle;

  /* Tell winsock what events we want to listen to */
  if(event_select_func(sockfd, event_handle, FD_READ|FD_CLOSE) == SOCKET_ERROR) {
    close_event_func(event_handle);
    FreeLibrary(wsock2);
    return 0;
  }

  /* If stdin_handle is a pipe, use PeekNamedPipe() method to check it,
     else use the old WaitForMultipleObjects() way */
  if(GetFileType(stdin_handle) == FILE_TYPE_PIPE) {
    /* Don't wait for stdin_handle, just wait for event_handle */
    obj_count = 1;
    /* Check stdin_handle per 100 milliseconds */
    wait_timeout = 100;
  } else {
    obj_count = 2;
    wait_timeout = INFINITE;
  }

  /* Keep on listening and act on events */
  while(keepon) {
    waitret = WaitForMultipleObjects(obj_count, objs, FALSE, wait_timeout);
    switch(waitret) {
    case WAIT_TIMEOUT:
    {
      unsigned char outbuf[2];
      int out_count = 0;
      ssize_t bytes_written;
      char *buffer = buf;

      while(1) {
        if(!PeekNamedPipe(stdin_handle, NULL, 0, NULL, &readfile_read, NULL)) {
          keepon = FALSE;
          break;
        }
        nread = readfile_read;

        if(!nread)
          break;

        if(!ReadFile(stdin_handle, buf, sizeof(data->state.buffer),
                     &readfile_read, NULL)) {
          keepon = FALSE;
          break;
        }
        nread = readfile_read;

        while(nread--) {
          outbuf[0] = *buffer++;
          out_count = 1;
          if(outbuf[0] == CURL_IAC)
            outbuf[out_count++] = CURL_IAC;

          Curl_write(conn, conn->sock[FIRSTSOCKET], outbuf,
                     out_count, &bytes_written);
        }
      }
    }
    break;

    case WAIT_OBJECT_0 + 1:
    {
      unsigned char outbuf[2];
      int out_count = 0;
      ssize_t bytes_written;
      char *buffer = buf;

      if(!ReadFile(stdin_handle, buf, sizeof(data->state.buffer),
                   &readfile_read, NULL)) {
        keepon = FALSE;
        break;
      }
      nread = readfile_read;

      while(nread--) {
        outbuf[0] = *buffer++;
        out_count = 1;
        if(outbuf[0] == CURL_IAC)
          outbuf[out_count++] = CURL_IAC;

        Curl_write(conn, conn->sock[FIRSTSOCKET], outbuf,
                   out_count, &bytes_written);
      }
    }
    break;

    case WAIT_OBJECT_0:
      if(enum_netevents_func(sockfd, event_handle, &events)
         != SOCKET_ERROR) {
        if(events.lNetworkEvents & FD_READ) {
          /* This reallu OUGHT to check its return code. */
          (void)Curl_read(conn, sockfd, buf, BUFSIZE - 1, &nread);

          telrcv(conn, (unsigned char *)buf, nread);

          fflush(stdout);

          /* Negotiate if the peer has started negotiating,
             otherwise don't. We don't want to speak telnet with
             non-telnet servers, like POP or SMTP. */
          if(tn->please_negotiate && !tn->already_negotiated) {
            negotiate(conn);
            tn->already_negotiated = 1;
          }
        }

        if(events.lNetworkEvents & FD_CLOSE) {
          keepon = FALSE;
        }
      }
      break;
    }
  }

  /* We called WSACreateEvent, so call WSACloseEvent */
  if (close_event_func(event_handle) == FALSE) {
    infof(data,"WSACloseEvent failed (%d)",WSAGetLastError());
  }

  /* "Forget" pointers into the library we're about to free */
  create_event_func = NULL;
  close_event_func = NULL;
  event_select_func = NULL;
  enum_netevents_func = NULL;

  /* We called LoadLibrary, so call FreeLibrary */
  if (!FreeLibrary(wsock2))
    infof(data,"FreeLibrary(wsock2) failed (%d)",GetLastError());
#else
  pfd[0].fd = sockfd;
  pfd[0].events = POLLIN;
  pfd[1].fd = 0;
  pfd[1].events = POLLIN;
  interval_ms = 1 * 1000;

  while (keepon) {
    switch (Curl_poll(pfd, 2, interval_ms)) {
    case -1:                    /* error, stop reading */
      keepon = FALSE;
      continue;
    case 0:                     /* timeout */
      break;
    default:                    /* read! */
      if(pfd[1].revents & POLLIN) { /* read from stdin */
        unsigned char outbuf[2];
        int out_count = 0;
        ssize_t bytes_written;
        char *buffer = buf;

        nread = read(0, buf, 255);

        while(nread--) {
          outbuf[0] = *buffer++;
          out_count = 1;
          if(outbuf[0] == CURL_IAC)
            outbuf[out_count++] = CURL_IAC;

          Curl_write(conn, conn->sock[FIRSTSOCKET], outbuf,
                     out_count, &bytes_written);
        }
      }

      if(pfd[0].revents & POLLIN) {
        /* This OUGHT to check the return code... */
        (void)Curl_read(conn, sockfd, buf, BUFSIZE - 1, &nread);

        /* if we receive 0 or less here, the server closed the connection and
           we bail out from this! */
        if (nread <= 0) {
          keepon = FALSE;
          break;
        }

        telrcv(conn, (unsigned char *)buf, nread);

        /* Negotiate if the peer has started negotiating,
           otherwise don't. We don't want to speak telnet with
           non-telnet servers, like POP or SMTP. */
        if(tn->please_negotiate && !tn->already_negotiated) {
          negotiate(conn);
          tn->already_negotiated = 1;
        }
      }
    }
    if(data->set.timeout) {
      struct timeval now;           /* current time */
      now = Curl_tvnow();
      if(Curl_tvdiff(now, conn->created)/1000 >= data->set.timeout) {
        failf(data, "Time-out");
        code = CURLE_OPERATION_TIMEOUTED;
        keepon = FALSE;
      }
    }
  }
#endif
  /* mark this as "no further transfer wanted" */
  Curl_Transfer(conn, -1, -1, FALSE, NULL, -1, NULL);

  return code;
}
#endif