aboutsummaryrefslogtreecommitdiff
path: root/lib/connect.c
blob: 89216200d2b90a998b5ea7db1b94659e5eaadb92 (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
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2019, 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 https://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.
 *
 ***************************************************************************/

#include "curl_setup.h"

#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h> /* <netinet/tcp.h> may need it */
#endif
#ifdef HAVE_SYS_UN_H
#include <sys/un.h> /* for sockaddr_un */
#endif
#ifdef HAVE_LINUX_TCP_H
#include <linux/tcp.h>
#elif defined(HAVE_NETINET_TCP_H)
#include <netinet/tcp.h>
#endif
#ifdef HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#endif
#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif
#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif

#if (defined(HAVE_IOCTL_FIONBIO) && defined(NETWARE))
#include <sys/filio.h>
#endif
#ifdef NETWARE
#undef in_addr_t
#define in_addr_t unsigned long
#endif
#ifdef __VMS
#include <in.h>
#include <inet.h>
#endif

#include "urldata.h"
#include "sendf.h"
#include "if2ip.h"
#include "strerror.h"
#include "connect.h"
#include "select.h"
#include "url.h" /* for Curl_safefree() */
#include "multiif.h"
#include "sockaddr.h" /* required for Curl_sockaddr_storage */
#include "inet_ntop.h"
#include "inet_pton.h"
#include "vtls/vtls.h" /* for Curl_ssl_check_cxn() */
#include "progress.h"
#include "warnless.h"
#include "conncache.h"
#include "multihandle.h"
#include "system_win32.h"

/* The last 3 #include files should be in this order */
#include "curl_printf.h"
#include "curl_memory.h"
#include "memdebug.h"

#ifdef __SYMBIAN32__
/* This isn't actually supported under Symbian OS */
#undef SO_NOSIGPIPE
#endif

static bool verifyconnect(curl_socket_t sockfd, int *error);

#if defined(__DragonFly__) || defined(HAVE_WINSOCK_H)
/* DragonFlyBSD and Windows use millisecond units */
#define KEEPALIVE_FACTOR(x) (x *= 1000)
#else
#define KEEPALIVE_FACTOR(x)
#endif

#if defined(HAVE_WINSOCK2_H) && !defined(SIO_KEEPALIVE_VALS)
#define SIO_KEEPALIVE_VALS    _WSAIOW(IOC_VENDOR,4)

struct tcp_keepalive {
  u_long onoff;
  u_long keepalivetime;
  u_long keepaliveinterval;
};
#endif

static void
tcpkeepalive(struct Curl_easy *data,
             curl_socket_t sockfd)
{
  int optval = data->set.tcp_keepalive?1:0;

  /* only set IDLE and INTVL if setting KEEPALIVE is successful */
  if(setsockopt(sockfd, SOL_SOCKET, SO_KEEPALIVE,
        (void *)&optval, sizeof(optval)) < 0) {
    infof(data, "Failed to set SO_KEEPALIVE on fd %d\n", sockfd);
  }
  else {
#if defined(SIO_KEEPALIVE_VALS)
    struct tcp_keepalive vals;
    DWORD dummy;
    vals.onoff = 1;
    optval = curlx_sltosi(data->set.tcp_keepidle);
    KEEPALIVE_FACTOR(optval);
    vals.keepalivetime = optval;
    optval = curlx_sltosi(data->set.tcp_keepintvl);
    KEEPALIVE_FACTOR(optval);
    vals.keepaliveinterval = optval;
    if(WSAIoctl(sockfd, SIO_KEEPALIVE_VALS, (LPVOID) &vals, sizeof(vals),
                NULL, 0, &dummy, NULL, NULL) != 0) {
      infof(data, "Failed to set SIO_KEEPALIVE_VALS on fd %d: %d\n",
            (int)sockfd, WSAGetLastError());
    }
#else
#ifdef TCP_KEEPIDLE
    optval = curlx_sltosi(data->set.tcp_keepidle);
    KEEPALIVE_FACTOR(optval);
    if(setsockopt(sockfd, IPPROTO_TCP, TCP_KEEPIDLE,
          (void *)&optval, sizeof(optval)) < 0) {
      infof(data, "Failed to set TCP_KEEPIDLE on fd %d\n", sockfd);
    }
#endif
#ifdef TCP_KEEPINTVL
    optval = curlx_sltosi(data->set.tcp_keepintvl);
    KEEPALIVE_FACTOR(optval);
    if(setsockopt(sockfd, IPPROTO_TCP, TCP_KEEPINTVL,
          (void *)&optval, sizeof(optval)) < 0) {
      infof(data, "Failed to set TCP_KEEPINTVL on fd %d\n", sockfd);
    }
#endif
#ifdef TCP_KEEPALIVE
    /* Mac OS X style */
    optval = curlx_sltosi(data->set.tcp_keepidle);
    KEEPALIVE_FACTOR(optval);
    if(setsockopt(sockfd, IPPROTO_TCP, TCP_KEEPALIVE,
          (void *)&optval, sizeof(optval)) < 0) {
      infof(data, "Failed to set TCP_KEEPALIVE on fd %d\n", sockfd);
    }
#endif
#endif
  }
}

static CURLcode
singleipconnect(struct connectdata *conn,
                const Curl_addrinfo *ai, /* start connecting to this */
                curl_socket_t *sock);

/*
 * Curl_timeleft() returns the amount of milliseconds left allowed for the
 * transfer/connection. If the value is negative, the timeout time has already
 * elapsed.
 *
 * The start time is stored in progress.t_startsingle - as set with
 * Curl_pgrsTime(..., TIMER_STARTSINGLE);
 *
 * If 'nowp' is non-NULL, it points to the current time.
 * 'duringconnect' is FALSE if not during a connect, as then of course the
 * connect timeout is not taken into account!
 *
 * @unittest: 1303
 */
timediff_t Curl_timeleft(struct Curl_easy *data,
                         struct curltime *nowp,
                         bool duringconnect)
{
  int timeout_set = 0;
  timediff_t timeout_ms = duringconnect?DEFAULT_CONNECT_TIMEOUT:0;
  struct curltime now;

  /* if a timeout is set, use the most restrictive one */

  if(data->set.timeout > 0)
    timeout_set |= 1;
  if(duringconnect && (data->set.connecttimeout > 0))
    timeout_set |= 2;

  switch(timeout_set) {
  case 1:
    timeout_ms = data->set.timeout;
    break;
  case 2:
    timeout_ms = data->set.connecttimeout;
    break;
  case 3:
    if(data->set.timeout < data->set.connecttimeout)
      timeout_ms = data->set.timeout;
    else
      timeout_ms = data->set.connecttimeout;
    break;
  default:
    /* use the default */
    if(!duringconnect)
      /* if we're not during connect, there's no default timeout so if we're
         at zero we better just return zero and not make it a negative number
         by the math below */
      return 0;
    break;
  }

  if(!nowp) {
    now = Curl_now();
    nowp = &now;
  }

  /* subtract elapsed time */
  if(duringconnect)
    /* since this most recent connect started */
    timeout_ms -= Curl_timediff(*nowp, data->progress.t_startsingle);
  else
    /* since the entire operation started */
    timeout_ms -= Curl_timediff(*nowp, data->progress.t_startop);
  if(!timeout_ms)
    /* avoid returning 0 as that means no timeout! */
    return -1;

  return timeout_ms;
}

static CURLcode bindlocal(struct connectdata *conn,
                          curl_socket_t sockfd, int af, unsigned int scope)
{
  struct Curl_easy *data = conn->data;

  struct Curl_sockaddr_storage sa;
  struct sockaddr *sock = (struct sockaddr *)&sa;  /* bind to this address */
  curl_socklen_t sizeof_sa = 0; /* size of the data sock points to */
  struct sockaddr_in *si4 = (struct sockaddr_in *)&sa;
#ifdef ENABLE_IPV6
  struct sockaddr_in6 *si6 = (struct sockaddr_in6 *)&sa;
#endif

  struct Curl_dns_entry *h = NULL;
  unsigned short port = data->set.localport; /* use this port number, 0 for
                                                "random" */
  /* how many port numbers to try to bind to, increasing one at a time */
  int portnum = data->set.localportrange;
  const char *dev = data->set.str[STRING_DEVICE];
  int error;

  /*************************************************************
   * Select device to bind socket to
   *************************************************************/
  if(!dev && !port)
    /* no local kind of binding was requested */
    return CURLE_OK;

  memset(&sa, 0, sizeof(struct Curl_sockaddr_storage));

  if(dev && (strlen(dev)<255) ) {
    char myhost[256] = "";
    int done = 0; /* -1 for error, 1 for address found */
    bool is_interface = FALSE;
    bool is_host = FALSE;
    static const char *if_prefix = "if!";
    static const char *host_prefix = "host!";

    if(strncmp(if_prefix, dev, strlen(if_prefix)) == 0) {
      dev += strlen(if_prefix);
      is_interface = TRUE;
    }
    else if(strncmp(host_prefix, dev, strlen(host_prefix)) == 0) {
      dev += strlen(host_prefix);
      is_host = TRUE;
    }

    /* interface */
    if(!is_host) {
#ifdef SO_BINDTODEVICE
      /* I am not sure any other OSs than Linux that provide this feature,
       * and at the least I cannot test. --Ben
       *
       * This feature allows one to tightly bind the local socket to a
       * particular interface.  This will force even requests to other
       * local interfaces to go out the external interface.
       *
       *
       * Only bind to the interface when specified as interface, not just
       * as a hostname or ip address.
       *
       * interface might be a VRF, eg: vrf-blue, which means it cannot be
       * converted to an IP address and would fail Curl_if2ip. Simply try
       * to use it straight away.
       */
      if(setsockopt(sockfd, SOL_SOCKET, SO_BINDTODEVICE,
                    dev, (curl_socklen_t)strlen(dev) + 1) == 0) {
        /* This is typically "errno 1, error: Operation not permitted" if
         * you're not running as root or another suitable privileged
         * user.
         * If it succeeds it means the parameter was a valid interface and
         * not an IP address. Return immediately.
         */
        return CURLE_OK;
      }
#endif

      switch(Curl_if2ip(af, scope, conn->scope_id, dev,
                        myhost, sizeof(myhost))) {
        case IF2IP_NOT_FOUND:
          if(is_interface) {
            /* Do not fall back to treating it as a host name */
            failf(data, "Couldn't bind to interface '%s'", dev);
            return CURLE_INTERFACE_FAILED;
          }
          break;
        case IF2IP_AF_NOT_SUPPORTED:
          /* Signal the caller to try another address family if available */
          return CURLE_UNSUPPORTED_PROTOCOL;
        case IF2IP_FOUND:
          is_interface = TRUE;
          /*
           * We now have the numerical IP address in the 'myhost' buffer
           */
          infof(data, "Local Interface %s is ip %s using address family %i\n",
                dev, myhost, af);
          done = 1;
          break;
      }
    }
    if(!is_interface) {
      /*
       * This was not an interface, resolve the name as a host name
       * or IP number
       *
       * Temporarily force name resolution to use only the address type
       * of the connection. The resolve functions should really be changed
       * to take a type parameter instead.
       */
      long ipver = conn->ip_version;
      int rc;

      if(af == AF_INET)
        conn->ip_version = CURL_IPRESOLVE_V4;
#ifdef ENABLE_IPV6
      else if(af == AF_INET6)
        conn->ip_version = CURL_IPRESOLVE_V6;
#endif

      rc = Curl_resolv(conn, dev, 0, &h);
      if(rc == CURLRESOLV_PENDING)
        (void)Curl_resolver_wait_resolv(conn, &h);
      conn->ip_version = ipver;

      if(h) {
        /* convert the resolved address, sizeof myhost >= INET_ADDRSTRLEN */
        Curl_printable_address(h->addr, myhost, sizeof(myhost));
        infof(data, "Name '%s' family %i resolved to '%s' family %i\n",
              dev, af, myhost, h->addr->ai_family);
        Curl_resolv_unlock(data, h);
        done = 1;
      }
      else {
        /*
         * provided dev was no interface (or interfaces are not supported
         * e.g. solaris) no ip address and no domain we fail here
         */
        done = -1;
      }
    }

    if(done > 0) {
#ifdef ENABLE_IPV6
      /* IPv6 address */
      if(af == AF_INET6) {
#ifdef HAVE_SOCKADDR_IN6_SIN6_SCOPE_ID
        char *scope_ptr = strchr(myhost, '%');
        if(scope_ptr)
          *(scope_ptr++) = 0;
#endif
        if(Curl_inet_pton(AF_INET6, myhost, &si6->sin6_addr) > 0) {
          si6->sin6_family = AF_INET6;
          si6->sin6_port = htons(port);
#ifdef HAVE_SOCKADDR_IN6_SIN6_SCOPE_ID
          if(scope_ptr)
            /* The "myhost" string either comes from Curl_if2ip or from
               Curl_printable_address. The latter returns only numeric scope
               IDs and the former returns none at all.  So the scope ID, if
               present, is known to be numeric */
            si6->sin6_scope_id = atoi(scope_ptr);
#endif
        }
        sizeof_sa = sizeof(struct sockaddr_in6);
      }
      else
#endif
      /* IPv4 address */
      if((af == AF_INET) &&
         (Curl_inet_pton(AF_INET, myhost, &si4->sin_addr) > 0)) {
        si4->sin_family = AF_INET;
        si4->sin_port = htons(port);
        sizeof_sa = sizeof(struct sockaddr_in);
      }
    }

    if(done < 1) {
      /* errorbuf is set false so failf will overwrite any message already in
         the error buffer, so the user receives this error message instead of a
         generic resolve error. */
      data->state.errorbuf = FALSE;
      failf(data, "Couldn't bind to '%s'", dev);
      return CURLE_INTERFACE_FAILED;
    }
  }
  else {
    /* no device was given, prepare sa to match af's needs */
#ifdef ENABLE_IPV6
    if(af == AF_INET6) {
      si6->sin6_family = AF_INET6;
      si6->sin6_port = htons(port);
      sizeof_sa = sizeof(struct sockaddr_in6);
    }
    else
#endif
    if(af == AF_INET) {
      si4->sin_family = AF_INET;
      si4->sin_port = htons(port);
      sizeof_sa = sizeof(struct sockaddr_in);
    }
  }

  for(;;) {
    if(bind(sockfd, sock, sizeof_sa) >= 0) {
      /* we succeeded to bind */
      struct Curl_sockaddr_storage add;
      curl_socklen_t size = sizeof(add);
      memset(&add, 0, sizeof(struct Curl_sockaddr_storage));
      if(getsockname(sockfd, (struct sockaddr *) &add, &size) < 0) {
        char buffer[STRERROR_LEN];
        data->state.os_errno = error = SOCKERRNO;
        failf(data, "getsockname() failed with errno %d: %s",
              error, Curl_strerror(error, buffer, sizeof(buffer)));
        return CURLE_INTERFACE_FAILED;
      }
      infof(data, "Local port: %hu\n", port);
      conn->bits.bound = TRUE;
      return CURLE_OK;
    }

    if(--portnum > 0) {
      infof(data, "Bind to local port %hu failed, trying next\n", port);
      port++; /* try next port */
      /* We re-use/clobber the port variable here below */
      if(sock->sa_family == AF_INET)
        si4->sin_port = ntohs(port);
#ifdef ENABLE_IPV6
      else
        si6->sin6_port = ntohs(port);
#endif
    }
    else
      break;
  }
  {
    char buffer[STRERROR_LEN];
    data->state.os_errno = error = SOCKERRNO;
    failf(data, "bind failed with errno %d: %s",
          error, Curl_strerror(error, buffer, sizeof(buffer)));
  }

  return CURLE_INTERFACE_FAILED;
}

/*
 * verifyconnect() returns TRUE if the connect really has happened.
 */
static bool verifyconnect(curl_socket_t sockfd, int *error)
{
  bool rc = TRUE;
#ifdef SO_ERROR
  int err = 0;
  curl_socklen_t errSize = sizeof(err);

#ifdef WIN32
  /*
   * In October 2003 we effectively nullified this function on Windows due to
   * problems with it using all CPU in multi-threaded cases.
   *
   * In May 2004, we bring it back to offer more info back on connect failures.
   * Gisle Vanem could reproduce the former problems with this function, but
   * could avoid them by adding this SleepEx() call below:
   *
   *    "I don't have Rational Quantify, but the hint from his post was
   *    ntdll::NtRemoveIoCompletion(). So I'd assume the SleepEx (or maybe
   *    just Sleep(0) would be enough?) would release whatever
   *    mutex/critical-section the ntdll call is waiting on.
   *
   *    Someone got to verify this on Win-NT 4.0, 2000."
   */

#ifdef _WIN32_WCE
  Sleep(0);
#else
  SleepEx(0, FALSE);
#endif

#endif

  if(0 != getsockopt(sockfd, SOL_SOCKET, SO_ERROR, (void *)&err, &errSize))
    err = SOCKERRNO;
#ifdef _WIN32_WCE
  /* Old WinCE versions don't support SO_ERROR */
  if(WSAENOPROTOOPT == err) {
    SET_SOCKERRNO(0);
    err = 0;
  }
#endif
#if defined(EBADIOCTL) && defined(__minix)
  /* Minix 3.1.x doesn't support getsockopt on UDP sockets */
  if(EBADIOCTL == err) {
    SET_SOCKERRNO(0);
    err = 0;
  }
#endif
  if((0 == err) || (EISCONN == err))
    /* we are connected, awesome! */
    rc = TRUE;
  else
    /* This wasn't a successful connect */
    rc = FALSE;
  if(error)
    *error = err;
#else
  (void)sockfd;
  if(error)
    *error = SOCKERRNO;
#endif
  return rc;
}

/* Used within the multi interface. Try next IP address, return TRUE if no
   more address exists or error */
static CURLcode trynextip(struct connectdata *conn,
                          int sockindex,
                          int tempindex)
{
  const int other = tempindex ^ 1;
  CURLcode result = CURLE_COULDNT_CONNECT;

  /* First clean up after the failed socket.
     Don't close it yet to ensure that the next IP's socket gets a different
     file descriptor, which can prevent bugs when the curl_multi_socket_action
     interface is used with certain select() replacements such as kqueue. */
  curl_socket_t fd_to_close = conn->tempsock[tempindex];
  conn->tempsock[tempindex] = CURL_SOCKET_BAD;

  if(sockindex == FIRSTSOCKET) {
    Curl_addrinfo *ai = NULL;
    int family = AF_UNSPEC;

    if(conn->tempaddr[tempindex]) {
      /* find next address in the same protocol family */
      family = conn->tempaddr[tempindex]->ai_family;
      ai = conn->tempaddr[tempindex]->ai_next;
    }
#ifdef ENABLE_IPV6
    else if(conn->tempaddr[0]) {
      /* happy eyeballs - try the other protocol family */
      int firstfamily = conn->tempaddr[0]->ai_family;
      family = (firstfamily == AF_INET) ? AF_INET6 : AF_INET;
      ai = conn->tempaddr[0]->ai_next;
    }
#endif

    while(ai) {
      if(conn->tempaddr[other]) {
        /* we can safely skip addresses of the other protocol family */
        while(ai && ai->ai_family != family)
          ai = ai->ai_next;
      }

      if(ai) {
        result = singleipconnect(conn, ai, &conn->tempsock[tempindex]);
        if(result == CURLE_COULDNT_CONNECT) {
          ai = ai->ai_next;
          continue;
        }

        conn->tempaddr[tempindex] = ai;
      }
      break;
    }
  }

  if(fd_to_close != CURL_SOCKET_BAD)
    Curl_closesocket(conn, fd_to_close);

  return result;
}

/* Copies connection info into the session handle to make it available
   when the session handle is no longer associated with a connection. */
void Curl_persistconninfo(struct connectdata *conn)
{
  memcpy(conn->data->info.conn_primary_ip, conn->primary_ip, MAX_IPADR_LEN);
  memcpy(conn->data->info.conn_local_ip, conn->local_ip, MAX_IPADR_LEN);
  conn->data->info.conn_scheme = conn->handler->scheme;
  conn->data->info.conn_protocol = conn->handler->protocol;
  conn->data->info.conn_primary_port = conn->primary_port;
  conn->data->info.conn_local_port = conn->local_port;
}

UNITTEST bool getaddressinfo(struct sockaddr *sa, char *addr,
                             long *port);

/* retrieves ip address and port from a sockaddr structure.
   note it calls Curl_inet_ntop which sets errno on fail, not SOCKERRNO. */
UNITTEST bool getaddressinfo(struct sockaddr *sa, char *addr,
                             long *port)
{
  unsigned short us_port;
  struct sockaddr_in *si = NULL;
#ifdef ENABLE_IPV6
  struct sockaddr_in6 *si6 = NULL;
#endif
#if defined(HAVE_SYS_UN_H) && defined(AF_UNIX)
  struct sockaddr_un *su = NULL;
#endif

  switch(sa->sa_family) {
    case AF_INET:
      si = (struct sockaddr_in *)(void *) sa;
      if(Curl_inet_ntop(sa->sa_family, &si->sin_addr,
                        addr, MAX_IPADR_LEN)) {
        us_port = ntohs(si->sin_port);
        *port = us_port;
        return TRUE;
      }
      break;
#ifdef ENABLE_IPV6
    case AF_INET6:
      si6 = (struct sockaddr_in6 *)(void *) sa;
      if(Curl_inet_ntop(sa->sa_family, &si6->sin6_addr,
                        addr, MAX_IPADR_LEN)) {
        us_port = ntohs(si6->sin6_port);
        *port = us_port;
        return TRUE;
      }
      break;
#endif
#if defined(HAVE_SYS_UN_H) && defined(AF_UNIX)
    case AF_UNIX:
      su = (struct sockaddr_un*)sa;
      msnprintf(addr, MAX_IPADR_LEN, "%s", su->sun_path);
      *port = 0;
      return TRUE;
#endif
    default:
      break;
  }

  addr[0] = '\0';
  *port = 0;
  errno = EAFNOSUPPORT;
  return FALSE;
}

/* retrieves the start/end point information of a socket of an established
   connection */
void Curl_updateconninfo(struct connectdata *conn, curl_socket_t sockfd)
{
  curl_socklen_t len;
  struct Curl_sockaddr_storage ssrem;
  struct Curl_sockaddr_storage ssloc;
  struct Curl_easy *data = conn->data;

  if(conn->socktype == SOCK_DGRAM)
    /* there's no connection! */
    return;

  if(!conn->bits.reuse && !conn->bits.tcp_fastopen) {
    char buffer[STRERROR_LEN];
    len = sizeof(struct Curl_sockaddr_storage);
    if(getpeername(sockfd, (struct sockaddr*) &ssrem, &len)) {
      int error = SOCKERRNO;
      failf(data, "getpeername() failed with errno %d: %s",
            error, Curl_strerror(error, buffer, sizeof(buffer)));
      return;
    }

    len = sizeof(struct Curl_sockaddr_storage);
    memset(&ssloc, 0, sizeof(ssloc));
    if(getsockname(sockfd, (struct sockaddr*) &ssloc, &len)) {
      int error = SOCKERRNO;
      failf(data, "getsockname() failed with errno %d: %s",
            error, Curl_strerror(error, buffer, sizeof(buffer)));
      return;
    }

    if(!getaddressinfo((struct sockaddr*)&ssrem,
                       conn->primary_ip, &conn->primary_port)) {
      failf(data, "ssrem inet_ntop() failed with errno %d: %s",
            errno, Curl_strerror(errno, buffer, sizeof(buffer)));
      return;
    }
    memcpy(conn->ip_addr_str, conn->primary_ip, MAX_IPADR_LEN);

    if(!getaddressinfo((struct sockaddr*)&ssloc,
                       conn->local_ip, &conn->local_port)) {
      failf(data, "ssloc inet_ntop() failed with errno %d: %s",
            errno, Curl_strerror(errno, buffer, sizeof(buffer)));
      return;
    }

  }

  /* persist connection info in session handle */
  Curl_persistconninfo(conn);
}

/*
 * Curl_is_connected() checks if the socket has connected.
 */

CURLcode Curl_is_connected(struct connectdata *conn,
                           int sockindex,
                           bool *connected)
{
  struct Curl_easy *data = conn->data;
  CURLcode result = CURLE_OK;
  timediff_t allow;
  int error = 0;
  struct curltime now;
  int rc;
  int i;

  DEBUGASSERT(sockindex >= FIRSTSOCKET && sockindex <= SECONDARYSOCKET);

  *connected = FALSE; /* a very negative world view is best */

  if(conn->bits.tcpconnect[sockindex]) {
    /* we are connected already! */
    *connected = TRUE;
    return CURLE_OK;
  }

  now = Curl_now();

  /* figure out how long time we have left to connect */
  allow = Curl_timeleft(data, &now, TRUE);

  if(allow < 0) {
    /* time-out, bail out, go home */
    failf(data, "Connection time-out");
    return CURLE_OPERATION_TIMEDOUT;
  }

  for(i = 0; i<2; i++) {
    const int other = i ^ 1;
    if(conn->tempsock[i] == CURL_SOCKET_BAD)
      continue;

#ifdef mpeix
    /* Call this function once now, and ignore the results. We do this to
       "clear" the error state on the socket so that we can later read it
       reliably. This is reported necessary on the MPE/iX operating system. */
    (void)verifyconnect(conn->tempsock[i], NULL);
#endif

    /* check socket for connect */
    rc = SOCKET_WRITABLE(conn->tempsock[i], 0);

    if(rc == 0) { /* no connection yet */
      error = 0;
      if(Curl_timediff(now, conn->connecttime) >= conn->timeoutms_per_addr) {
        infof(data, "After %ldms connect time, move on!\n",
              conn->timeoutms_per_addr);
        error = ETIMEDOUT;
      }

      /* should we try another protocol family? */
      if(i == 0 && conn->tempaddr[1] == NULL &&
         (Curl_timediff(now, conn->connecttime) >=
          data->set.happy_eyeballs_timeout)) {
        trynextip(conn, sockindex, 1);
      }
    }
    else if(rc == CURL_CSELECT_OUT || conn->bits.tcp_fastopen) {
      if(verifyconnect(conn->tempsock[i], &error)) {
        /* we are connected with TCP, awesome! */

        /* use this socket from now on */
        conn->sock[sockindex] = conn->tempsock[i];
        conn->ip_addr = conn->tempaddr[i];
        conn->tempsock[i] = CURL_SOCKET_BAD;
#ifdef ENABLE_IPV6
        conn->bits.ipv6 = (conn->ip_addr->ai_family == AF_INET6)?TRUE:FALSE;
#endif

        /* close the other socket, if open */
        if(conn->tempsock[other] != CURL_SOCKET_BAD) {
          Curl_closesocket(conn, conn->tempsock[other]);
          conn->tempsock[other] = CURL_SOCKET_BAD;
        }

        /* see if we need to do any proxy magic first once we connected */
        result = Curl_connected_proxy(conn, sockindex);
        if(result)
          return result;

        conn->bits.tcpconnect[sockindex] = TRUE;

        *connected = TRUE;
        if(sockindex == FIRSTSOCKET)
          Curl_pgrsTime(data, TIMER_CONNECT); /* connect done */
        Curl_updateconninfo(conn, conn->sock[sockindex]);
        Curl_verboseconnect(conn);

        return CURLE_OK;
      }
      infof(data, "Connection failed\n");
    }
    else if(rc & CURL_CSELECT_ERR)
      (void)verifyconnect(conn->tempsock[i], &error);

    /*
     * The connection failed here, we should attempt to connect to the "next
     * address" for the given host. But first remember the latest error.
     */
    if(error) {
      data->state.os_errno = error;
      SET_SOCKERRNO(error);
      if(conn->tempaddr[i]) {
        CURLcode status;
        char ipaddress[MAX_IPADR_LEN];
        char buffer[STRERROR_LEN];
        Curl_printable_address(conn->tempaddr[i], ipaddress, MAX_IPADR_LEN);
        infof(data, "connect to %s port %ld failed: %s\n",
              ipaddress, conn->port,
              Curl_strerror(error, buffer, sizeof(buffer)));

        conn->timeoutms_per_addr = conn->tempaddr[i]->ai_next == NULL ?
                                   allow : allow / 2;

        status = trynextip(conn, sockindex, i);
        if(status != CURLE_COULDNT_CONNECT
            || conn->tempsock[other] == CURL_SOCKET_BAD)
          /* the last attempt failed and no other sockets remain open */
          result = status;
      }
    }
  }

  if(result) {
    /* no more addresses to try */
    const char *hostname;
    char buffer[STRERROR_LEN];

    /* if the first address family runs out of addresses to try before
       the happy eyeball timeout, go ahead and try the next family now */
    if(conn->tempaddr[1] == NULL) {
      result = trynextip(conn, sockindex, 1);
      if(!result)
        return result;
    }

    if(conn->bits.socksproxy)
      hostname = conn->socks_proxy.host.name;
    else if(conn->bits.httpproxy)
      hostname = conn->http_proxy.host.name;
    else if(conn->bits.conn_to_host)
      hostname = conn->conn_to_host.name;
    else
      hostname = conn->host.name;

    failf(data, "Failed to connect to %s port %ld: %s",
          hostname, conn->port,
          Curl_strerror(error, buffer, sizeof(buffer)));
  }

  return result;
}

static void tcpnodelay(struct connectdata *conn, curl_socket_t sockfd)
{
#if defined(TCP_NODELAY)
#if !defined(CURL_DISABLE_VERBOSE_STRINGS)
  struct Curl_easy *data = conn->data;
#endif
  curl_socklen_t onoff = (curl_socklen_t) 1;
  int level = IPPROTO_TCP;
  char buffer[STRERROR_LEN];

#if defined(CURL_DISABLE_VERBOSE_STRINGS)
  (void) conn;
#endif

  if(setsockopt(sockfd, level, TCP_NODELAY, (void *)&onoff,
                sizeof(onoff)) < 0)
    infof(data, "Could not set TCP_NODELAY: %s\n",
          Curl_strerror(SOCKERRNO, buffer, sizeof(buffer)));
  else
    infof(data, "TCP_NODELAY set\n");
#else
  (void)conn;
  (void)sockfd;
#endif
}

#ifdef SO_NOSIGPIPE
/* The preferred method on Mac OS X (10.2 and later) to prevent SIGPIPEs when
   sending data to a dead peer (instead of relying on the 4th argument to send
   being MSG_NOSIGNAL). Possibly also existing and in use on other BSD
   systems? */
static void nosigpipe(struct connectdata *conn,
                      curl_socket_t sockfd)
{
  struct Curl_easy *data = conn->data;
  int onoff = 1;
  if(setsockopt(sockfd, SOL_SOCKET, SO_NOSIGPIPE, (void *)&onoff,
                sizeof(onoff)) < 0) {
    char buffer[STRERROR_LEN];
    infof(data, "Could not set SO_NOSIGPIPE: %s\n",
          Curl_strerror(SOCKERRNO, buffer, sizeof(buffer)));
  }
}
#else
#define nosigpipe(x,y) Curl_nop_stmt
#endif

#ifdef USE_WINSOCK
/* When you run a program that uses the Windows Sockets API, you may
   experience slow performance when you copy data to a TCP server.

   https://support.microsoft.com/kb/823764

   Work-around: Make the Socket Send Buffer Size Larger Than the Program Send
   Buffer Size

   The problem described in this knowledge-base is applied only to pre-Vista
   Windows.  Following function trying to detect OS version and skips
   SO_SNDBUF adjustment for Windows Vista and above.
*/
#define DETECT_OS_NONE 0
#define DETECT_OS_PREVISTA 1
#define DETECT_OS_VISTA_OR_LATER 2

void Curl_sndbufset(curl_socket_t sockfd)
{
  int val = CURL_MAX_WRITE_SIZE + 32;
  int curval = 0;
  int curlen = sizeof(curval);

  static int detectOsState = DETECT_OS_NONE;

  if(detectOsState == DETECT_OS_NONE) {
    if(Curl_verify_windows_version(6, 0, PLATFORM_WINNT,
                                   VERSION_GREATER_THAN_EQUAL))
      detectOsState = DETECT_OS_VISTA_OR_LATER;
    else
      detectOsState = DETECT_OS_PREVISTA;
  }

  if(detectOsState == DETECT_OS_VISTA_OR_LATER)
    return;

  if(getsockopt(sockfd, SOL_SOCKET, SO_SNDBUF, (char *)&curval, &curlen) == 0)
    if(curval > val)
      return;

  setsockopt(sockfd, SOL_SOCKET, SO_SNDBUF, (const char *)&val, sizeof(val));
}
#endif

/*
 * singleipconnect()
 *
 * Note that even on connect fail it returns CURLE_OK, but with 'sock' set to
 * CURL_SOCKET_BAD. Other errors will however return proper errors.
 *
 * singleipconnect() connects to the given IP only, and it may return without
 * having connected.
 */
static CURLcode singleipconnect(struct connectdata *conn,
                                const Curl_addrinfo *ai,
                                curl_socket_t *sockp)
{
  struct Curl_sockaddr_ex addr;
  int rc = -1;
  int error = 0;
  bool isconnected = FALSE;
  struct Curl_easy *data = conn->data;
  curl_socket_t sockfd;
  CURLcode result;
  char ipaddress[MAX_IPADR_LEN];
  long port;
  bool is_tcp;
#ifdef TCP_FASTOPEN_CONNECT
  int optval = 1;
#endif
  char buffer[STRERROR_LEN];

  *sockp = CURL_SOCKET_BAD;

  result = Curl_socket(conn, ai, &addr, &sockfd);
  if(result)
    /* Failed to create the socket, but still return OK since we signal the
       lack of socket as well. This allows the parent function to keep looping
       over alternative addresses/socket families etc. */
    return CURLE_OK;

  /* store remote address and port used in this connection attempt */
  if(!getaddressinfo((struct sockaddr*)&addr.sa_addr,
                     ipaddress, &port)) {
    /* malformed address or bug in inet_ntop, try next address */
    failf(data, "sa_addr inet_ntop() failed with errno %d: %s",
          errno, Curl_strerror(errno, buffer, sizeof(buffer)));
    Curl_closesocket(conn, sockfd);
    return CURLE_OK;
  }
  infof(data, "  Trying %s...\n", ipaddress);

#ifdef ENABLE_IPV6
  is_tcp = (addr.family == AF_INET || addr.family == AF_INET6) &&
    addr.socktype == SOCK_STREAM;
#else
  is_tcp = (addr.family == AF_INET) && addr.socktype == SOCK_STREAM;
#endif
  if(is_tcp && data->set.tcp_nodelay)
    tcpnodelay(conn, sockfd);

  nosigpipe(conn, sockfd);

  Curl_sndbufset(sockfd);

  if(is_tcp && data->set.tcp_keepalive)
    tcpkeepalive(data, sockfd);

  if(data->set.fsockopt) {
    /* activate callback for setting socket options */
    Curl_set_in_callback(data, true);
    error = data->set.fsockopt(data->set.sockopt_client,
                               sockfd,
                               CURLSOCKTYPE_IPCXN);
    Curl_set_in_callback(data, false);

    if(error == CURL_SOCKOPT_ALREADY_CONNECTED)
      isconnected = TRUE;
    else if(error) {
      Curl_closesocket(conn, sockfd); /* close the socket and bail out */
      return CURLE_ABORTED_BY_CALLBACK;
    }
  }

  /* possibly bind the local end to an IP, interface or port */
  if(addr.family == AF_INET
#ifdef ENABLE_IPV6
     || addr.family == AF_INET6
#endif
    ) {
    result = bindlocal(conn, sockfd, addr.family,
                       Curl_ipv6_scope((struct sockaddr*)&addr.sa_addr));
    if(result) {
      Curl_closesocket(conn, sockfd); /* close socket and bail out */
      if(result == CURLE_UNSUPPORTED_PROTOCOL) {
        /* The address family is not supported on this interface.
           We can continue trying addresses */
        return CURLE_COULDNT_CONNECT;
      }
      return result;
    }
  }

  /* set socket non-blocking */
  (void)curlx_nonblock(sockfd, TRUE);

  conn->connecttime = Curl_now();
  if(conn->num_addr > 1)
    Curl_expire(data, conn->timeoutms_per_addr, EXPIRE_DNS_PER_NAME);

  /* Connect TCP sockets, bind UDP */
  if(!isconnected && (conn->socktype == SOCK_STREAM)) {
    if(conn->bits.tcp_fastopen) {
#if defined(CONNECT_DATA_IDEMPOTENT) /* Darwin */
#  if defined(HAVE_BUILTIN_AVAILABLE)
      /* while connectx function is available since macOS 10.11 / iOS 9,
         it did not have the interface declared correctly until
         Xcode 9 / macOS SDK 10.13 */
      if(__builtin_available(macOS 10.11, iOS 9.0, tvOS 9.0, watchOS 2.0, *)) {
        sa_endpoints_t endpoints;
        endpoints.sae_srcif = 0;
        endpoints.sae_srcaddr = NULL;
        endpoints.sae_srcaddrlen = 0;
        endpoints.sae_dstaddr = &addr.sa_addr;
        endpoints.sae_dstaddrlen = addr.addrlen;

        rc = connectx(sockfd, &endpoints, SAE_ASSOCID_ANY,
                      CONNECT_RESUME_ON_READ_WRITE | CONNECT_DATA_IDEMPOTENT,
                      NULL, 0, NULL, NULL);
      }
      else {
        rc = connect(sockfd, &addr.sa_addr, addr.addrlen);
      }
#  else
      rc = connect(sockfd, &addr.sa_addr, addr.addrlen);
#  endif /* HAVE_BUILTIN_AVAILABLE */
#elif defined(TCP_FASTOPEN_CONNECT) /* Linux >= 4.11 */
      if(setsockopt(sockfd, IPPROTO_TCP, TCP_FASTOPEN_CONNECT,
                    (void *)&optval, sizeof(optval)) < 0)
        infof(data, "Failed to enable TCP Fast Open on fd %d\n", sockfd);
      else
        infof(data, "TCP_FASTOPEN_CONNECT set\n");

      rc = connect(sockfd, &addr.sa_addr, addr.addrlen);
#elif defined(MSG_FASTOPEN) /* old Linux */
      if(conn->given->flags & PROTOPT_SSL)
        rc = connect(sockfd, &addr.sa_addr, addr.addrlen);
      else
        rc = 0; /* Do nothing */
#endif
    }
    else {
      rc = connect(sockfd, &addr.sa_addr, addr.addrlen);
    }

    if(-1 == rc)
      error = SOCKERRNO;
  }
  else {
    *sockp = sockfd;
    return CURLE_OK;
  }

  if(-1 == rc) {
    switch(error) {
    case EINPROGRESS:
    case EWOULDBLOCK:
#if defined(EAGAIN)
#if (EAGAIN) != (EWOULDBLOCK)
      /* On some platforms EAGAIN and EWOULDBLOCK are the
       * same value, and on others they are different, hence
       * the odd #if
       */
    case EAGAIN:
#endif
#endif
      result = CURLE_OK;
      break;

    default:
      /* unknown error, fallthrough and try another address! */
      infof(data, "Immediate connect fail for %s: %s\n",
            ipaddress, Curl_strerror(error, buffer, sizeof(buffer)));
      data->state.os_errno = error;

      /* connect failed */
      Curl_closesocket(conn, sockfd);
      result = CURLE_COULDNT_CONNECT;
    }
  }

  if(!result)
    *sockp = sockfd;

  return result;
}

/*
 * TCP connect to the given host with timeout, proxy or remote doesn't matter.
 * There might be more than one IP address to try out. Fill in the passed
 * pointer with the connected socket.
 */

CURLcode Curl_connecthost(struct connectdata *conn,  /* context */
                          const struct Curl_dns_entry *remotehost)
{
  struct Curl_easy *data = conn->data;
  struct curltime before = Curl_now();
  CURLcode result = CURLE_COULDNT_CONNECT;

  timediff_t timeout_ms = Curl_timeleft(data, &before, TRUE);

  if(timeout_ms < 0) {
    /* a precaution, no need to continue if time already is up */
    failf(data, "Connection time-out");
    return CURLE_OPERATION_TIMEDOUT;
  }

  conn->num_addr = Curl_num_addresses(remotehost->addr);
  conn->tempaddr[0] = remotehost->addr;
  conn->tempaddr[1] = NULL;
  conn->tempsock[0] = CURL_SOCKET_BAD;
  conn->tempsock[1] = CURL_SOCKET_BAD;

  /* Max time for the next connection attempt */
  conn->timeoutms_per_addr =
    conn->tempaddr[0]->ai_next == NULL ? timeout_ms : timeout_ms / 2;

  /* start connecting to first IP */
  while(conn->tempaddr[0]) {
    result = singleipconnect(conn, conn->tempaddr[0], &(conn->tempsock[0]));
    if(!result)
      break;
    conn->tempaddr[0] = conn->tempaddr[0]->ai_next;
  }

  if(conn->tempsock[0] == CURL_SOCKET_BAD) {
    if(!result)
      result = CURLE_COULDNT_CONNECT;
    return result;
  }

  data->info.numconnects++; /* to track the number of connections made */
  Curl_expire(conn->data, data->set.happy_eyeballs_timeout,
              EXPIRE_HAPPY_EYEBALLS);

  return CURLE_OK;
}

struct connfind {
  struct connectdata *tofind;
  bool found;
};

static int conn_is_conn(struct connectdata *conn, void *param)
{
  struct connfind *f = (struct connfind *)param;
  if(conn == f->tofind) {
    f->found = TRUE;
    return 1;
  }
  return 0;
}

/*
 * Used to extract socket and connectdata struct for the most recent
 * transfer on the given Curl_easy.
 *
 * The returned socket will be CURL_SOCKET_BAD in case of failure!
 */
curl_socket_t Curl_getconnectinfo(struct Curl_easy *data,
                                  struct connectdata **connp)
{
  DEBUGASSERT(data);

  /* this works for an easy handle:
   * - that has been used for curl_easy_perform()
   * - that is associated with a multi handle, and whose connection
   *   was detached with CURLOPT_CONNECT_ONLY
   */
  if(data->state.lastconnect && (data->multi_easy || data->multi)) {
    struct connectdata *c = data->state.lastconnect;
    struct connfind find;
    find.tofind = data->state.lastconnect;
    find.found = FALSE;

    Curl_conncache_foreach(data, data->multi_easy?
                           &data->multi_easy->conn_cache:
                           &data->multi->conn_cache, &find, conn_is_conn);

    if(!find.found) {
      data->state.lastconnect = NULL;
      return CURL_SOCKET_BAD;
    }

    if(connp) {
      /* only store this if the caller cares for it */
      *connp = c;
      c->data = data;
    }
    return c->sock[FIRSTSOCKET];
  }
  else
    return CURL_SOCKET_BAD;
}

/*
 * Check if a connection seems to be alive.
 */
bool Curl_connalive(struct connectdata *conn)
{
  /* First determine if ssl */
  if(conn->ssl[FIRSTSOCKET].use) {
    /* use the SSL context */
    if(!Curl_ssl_check_cxn(conn))
      return false;   /* FIN received */
  }
/* Minix 3.1 doesn't support any flags on recv; just assume socket is OK */
#ifdef MSG_PEEK
  else if(conn->sock[FIRSTSOCKET] == CURL_SOCKET_BAD)
    return false;
  else {
    /* use the socket */
    char buf;
    if(recv((RECV_TYPE_ARG1)conn->sock[FIRSTSOCKET], (RECV_TYPE_ARG2)&buf,
            (RECV_TYPE_ARG3)1, (RECV_TYPE_ARG4)MSG_PEEK) == 0) {
      return false;   /* FIN received */
    }
  }
#endif
  return true;
}

/*
 * Close a socket.
 *
 * 'conn' can be NULL, beware!
 */
int Curl_closesocket(struct connectdata *conn,
                      curl_socket_t sock)
{
  if(conn && conn->fclosesocket) {
    if((sock == conn->sock[SECONDARYSOCKET]) &&
       conn->sock_accepted[SECONDARYSOCKET])
      /* if this socket matches the second socket, and that was created with
         accept, then we MUST NOT call the callback but clear the accepted
         status */
      conn->sock_accepted[SECONDARYSOCKET] = FALSE;
    else {
      int rc;
      Curl_multi_closed(conn->data, sock);
      Curl_set_in_callback(conn->data, true);
      rc = conn->fclosesocket(conn->closesocket_client, sock);
      Curl_set_in_callback(conn->data, false);
      return rc;
    }
  }

  if(conn)
    /* tell the multi-socket code about this */
    Curl_multi_closed(conn->data, sock);

  sclose(sock);

  return 0;
}

/*
 * Create a socket based on info from 'conn' and 'ai'.
 *
 * 'addr' should be a pointer to the correct struct to get data back, or NULL.
 * 'sockfd' must be a pointer to a socket descriptor.
 *
 * If the open socket callback is set, used that!
 *
 */
CURLcode Curl_socket(struct connectdata *conn,
                     const Curl_addrinfo *ai,
                     struct Curl_sockaddr_ex *addr,
                     curl_socket_t *sockfd)
{
  struct Curl_easy *data = conn->data;
  struct Curl_sockaddr_ex dummy;

  if(!addr)
    /* if the caller doesn't want info back, use a local temp copy */
    addr = &dummy;

  /*
   * The Curl_sockaddr_ex structure is basically libcurl's external API
   * curl_sockaddr structure with enough space available to directly hold
   * any protocol-specific address structures. The variable declared here
   * will be used to pass / receive data to/from the fopensocket callback
   * if this has been set, before that, it is initialized from parameters.
   */

  addr->family = ai->ai_family;
  addr->socktype = conn->socktype;
  addr->protocol = conn->socktype == SOCK_DGRAM?IPPROTO_UDP:ai->ai_protocol;
  addr->addrlen = ai->ai_addrlen;

  if(addr->addrlen > sizeof(struct Curl_sockaddr_storage))
     addr->addrlen = sizeof(struct Curl_sockaddr_storage);
  memcpy(&addr->sa_addr, ai->ai_addr, addr->addrlen);

  if(data->set.fopensocket) {
   /*
    * If the opensocket callback is set, all the destination address
    * information is passed to the callback. Depending on this information the
    * callback may opt to abort the connection, this is indicated returning
    * CURL_SOCKET_BAD; otherwise it will return a not-connected socket. When
    * the callback returns a valid socket the destination address information
    * might have been changed and this 'new' address will actually be used
    * here to connect.
    */
    Curl_set_in_callback(data, true);
    *sockfd = data->set.fopensocket(data->set.opensocket_client,
                                    CURLSOCKTYPE_IPCXN,
                                    (struct curl_sockaddr *)addr);
    Curl_set_in_callback(data, false);
  }
  else
    /* opensocket callback not set, so simply create the socket now */
    *sockfd = socket(addr->family, addr->socktype, addr->protocol);

  if(*sockfd == CURL_SOCKET_BAD)
    /* no socket, no connection */
    return CURLE_COULDNT_CONNECT;

#if defined(ENABLE_IPV6) && defined(HAVE_SOCKADDR_IN6_SIN6_SCOPE_ID)
  if(conn->scope_id && (addr->family == AF_INET6)) {
    struct sockaddr_in6 * const sa6 = (void *)&addr->sa_addr;
    sa6->sin6_scope_id = conn->scope_id;
  }
#endif

  return CURLE_OK;

}

/*
 * Curl_conncontrol() marks streams or connection for closure.
 */
void Curl_conncontrol(struct connectdata *conn,
                      int ctrl /* see defines in header */
#if defined(DEBUGBUILD) && !defined(CURL_DISABLE_VERBOSE_STRINGS)
                      , const char *reason
#endif
  )
{
  /* close if a connection, or a stream that isn't multiplexed */
  bool closeit = (ctrl == CONNCTRL_CONNECTION) ||
    ((ctrl == CONNCTRL_STREAM) && !(conn->handler->flags & PROTOPT_STREAM));
  if((ctrl == CONNCTRL_STREAM) &&
     (conn->handler->flags & PROTOPT_STREAM))
    DEBUGF(infof(conn->data, "Kill stream: %s\n", reason));
  else if(closeit != conn->bits.close) {
    DEBUGF(infof(conn->data, "Marked for [%s]: %s\n",
                 closeit?"closure":"keep alive", reason));
    conn->bits.close = closeit; /* the only place in the source code that
                                   should assign this bit */
  }
}

/* Data received can be cached at various levels, so check them all here. */
bool Curl_conn_data_pending(struct connectdata *conn, int sockindex)
{
  int readable;

  if(Curl_ssl_data_pending(conn, sockindex) ||
     Curl_recv_has_postponed_data(conn, sockindex))
    return true;

  readable = SOCKET_READABLE(conn->sock[sockindex], 0);
  return (readable > 0 && (readable & CURL_CSELECT_IN));
}