summaryrefslogtreecommitdiffstats
path: root/modules/http/http_protocol.c
blob: e419eb6cd45f02041e681355be5335eb4625da87 (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
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * http_protocol.c --- routines which directly communicate with the client.
 *
 * Code originally by Rob McCool; much redone by Robert S. Thau
 * and the Apache Software Foundation.
 */

#include "apr.h"
#include "apr_strings.h"
#include "apr_buckets.h"
#include "apr_lib.h"
#include "apr_signal.h"

#define APR_WANT_STDIO          /* for sscanf */
#define APR_WANT_STRFUNC
#define APR_WANT_MEMFUNC
#include "apr_want.h"

#include "util_filter.h"
#include "ap_config.h"
#include "httpd.h"
#include "http_config.h"
#include "http_core.h"
#include "http_protocol.h"
#include "http_main.h"
#include "http_request.h"
#include "http_vhost.h"
#include "http_log.h"           /* For errors detected in basic auth common
                                 * support code... */
#include "apr_date.h"           /* For apr_date_parse_http and APR_DATE_BAD */
#include "util_charset.h"
#include "util_ebcdic.h"
#include "util_time.h"
#include "ap_mpm.h"

#include "mod_core.h"

#if APR_HAVE_STDARG_H
#include <stdarg.h>
#endif
#if APR_HAVE_UNISTD_H
#include <unistd.h>
#endif

APLOG_USE_MODULE(http);

/* New Apache routine to map status codes into array indicies
 *  e.g.  100 -> 0,  101 -> 1,  200 -> 2 ...
 * The number of status lines must equal the value of
 * RESPONSE_CODES (httpd.h) and must be listed in order.
 * No gaps are allowed between X00 and the largest Xnn
 * for any X (see ap_index_of_response).
 * When adding a new code here, add a define to httpd.h
 * as well.
 */

static const char * const status_lines[RESPONSE_CODES] =
{
    "100 Continue",
    "101 Switching Protocols",
    "102 Processing",
#define LEVEL_200  3
    "200 OK",
    "201 Created",
    "202 Accepted",
    "203 Non-Authoritative Information",
    "204 No Content",
    "205 Reset Content",
    "206 Partial Content",
    "207 Multi-Status",
    "208 Already Reported",
    NULL, /* 209 */
    NULL, /* 210 */
    NULL, /* 211 */
    NULL, /* 212 */
    NULL, /* 213 */
    NULL, /* 214 */
    NULL, /* 215 */
    NULL, /* 216 */
    NULL, /* 217 */
    NULL, /* 218 */
    NULL, /* 219 */
    NULL, /* 220 */
    NULL, /* 221 */
    NULL, /* 222 */
    NULL, /* 223 */
    NULL, /* 224 */
    NULL, /* 225 */
    "226 IM Used",
#define LEVEL_300 30
    "300 Multiple Choices",
    "301 Moved Permanently",
    "302 Found",
    "303 See Other",
    "304 Not Modified",
    "305 Use Proxy",
    NULL, /* 306 */
    "307 Temporary Redirect",
    "308 Permanent Redirect",
#define LEVEL_400 39
    "400 Bad Request",
    "401 Unauthorized",
    "402 Payment Required",
    "403 Forbidden",
    "404 Not Found",
    "405 Method Not Allowed",
    "406 Not Acceptable",
    "407 Proxy Authentication Required",
    "408 Request Timeout",
    "409 Conflict",
    "410 Gone",
    "411 Length Required",
    "412 Precondition Failed",
    "413 Request Entity Too Large",
    "414 Request-URI Too Long",
    "415 Unsupported Media Type",
    "416 Requested Range Not Satisfiable",
    "417 Expectation Failed",
    NULL, /* 418 */
    NULL, /* 419 */
    NULL, /* 420 */
    "421 Misdirected Request",
    "422 Unprocessable Entity",
    "423 Locked",
    "424 Failed Dependency",
    NULL, /* 425 */
    "426 Upgrade Required",
    NULL, /* 427 */
    "428 Precondition Required",
    "429 Too Many Requests",
    NULL, /* 430 */
    "431 Request Header Fields Too Large",
    NULL, /* 432 */
    NULL, /* 433 */
    NULL, /* 434 */
    NULL, /* 435 */
    NULL, /* 436 */
    NULL, /* 437 */
    NULL, /* 438 */
    NULL, /* 439 */
    NULL, /* 440 */
    NULL, /* 441 */
    NULL, /* 442 */
    NULL, /* 443 */
    NULL, /* 444 */
    NULL, /* 445 */
    NULL, /* 446 */
    NULL, /* 447 */
    NULL, /* 448 */
    NULL, /* 449 */
    NULL, /* 450 */
    "451 Unavailable For Legal Reasons",
#define LEVEL_500 91
    "500 Internal Server Error",
    "501 Not Implemented",
    "502 Bad Gateway",
    "503 Service Unavailable",
    "504 Gateway Timeout",
    "505 HTTP Version Not Supported",
    "506 Variant Also Negotiates",
    "507 Insufficient Storage",
    "508 Loop Detected",
    NULL, /* 509 */
    "510 Not Extended",
    "511 Network Authentication Required"
};

APR_HOOK_STRUCT(
    APR_HOOK_LINK(insert_error_filter)
)

AP_IMPLEMENT_HOOK_VOID(insert_error_filter, (request_rec *r), (r))

/* The index of the first bit field that is used to index into a limit
 * bitmask. M_INVALID + 1 to METHOD_NUMBER_LAST.
 */
#define METHOD_NUMBER_FIRST (M_INVALID + 1)

/* The max method number. Method numbers are used to shift bitmasks,
 * so this cannot exceed 63, and all bits high is equal to -1, which is a
 * special flag, so the last bit used has index 62.
 */
#define METHOD_NUMBER_LAST  62

static int is_mpm_running(void)
{
    int mpm_state = 0;

    if (ap_mpm_query(AP_MPMQ_MPM_STATE, &mpm_state)) {
      return 0;
    }

    if (mpm_state == AP_MPMQ_STOPPING) {
      return 0;
    }

    return 1;
}


AP_DECLARE(int) ap_set_keepalive(request_rec *r)
{
    int ka_sent = 0;
    int left = r->server->keep_alive_max - r->connection->keepalives;
    int wimpy = ap_find_token(r->pool,
                              apr_table_get(r->headers_out, "Connection"),
                              "close");
    const char *conn = apr_table_get(r->headers_in, "Connection");

    /* The following convoluted conditional determines whether or not
     * the current connection should remain persistent after this response
     * (a.k.a. HTTP Keep-Alive) and whether or not the output message
     * body should use the HTTP/1.1 chunked transfer-coding.  In English,
     *
     *   IF  we have not marked this connection as errored;
     *   and the client isn't expecting 100-continue (PR47087 - more
     *       input here could be the client continuing when we're
     *       closing the request).
     *   and the response body has a defined length due to the status code
     *       being 304 or 204, the request method being HEAD, already
     *       having defined Content-Length or Transfer-Encoding: chunked, or
     *       the request version being HTTP/1.1 and thus capable of being set
     *       as chunked [we know the (r->chunked = 1) side-effect is ugly];
     *   and the server configuration enables keep-alive;
     *   and the server configuration has a reasonable inter-request timeout;
     *   and there is no maximum # requests or the max hasn't been reached;
     *   and the response status does not require a close;
     *   and the response generator has not already indicated close;
     *   and the client did not request non-persistence (Connection: close);
     *   and    we haven't been configured to ignore the buggy twit
     *       or they're a buggy twit coming through a HTTP/1.1 proxy
     *   and    the client is requesting an HTTP/1.0-style keep-alive
     *       or the client claims to be HTTP/1.1 compliant (perhaps a proxy);
     *   and this MPM process is not already exiting
     *   THEN we can be persistent, which requires more headers be output.
     *
     * Note that the condition evaluation order is extremely important.
     */
    if ((r->connection->keepalive != AP_CONN_CLOSE)
        && !r->expecting_100
        && (r->header_only
            || AP_STATUS_IS_HEADER_ONLY(r->status)
            || apr_table_get(r->headers_out, "Content-Length")
            || ap_find_last_token(r->pool,
                                  apr_table_get(r->headers_out,
                                                "Transfer-Encoding"),
                                  "chunked")
            || ((r->proto_num >= HTTP_VERSION(1,1))
                && (r->chunked = 1))) /* THIS CODE IS CORRECT, see above. */
        && r->server->keep_alive
        && (r->server->keep_alive_timeout > 0)
        && ((r->server->keep_alive_max == 0)
            || (left > 0))
        && !ap_status_drops_connection(r->status)
        && !wimpy
        && !ap_find_token(r->pool, conn, "close")
        && (!apr_table_get(r->subprocess_env, "nokeepalive")
            || apr_table_get(r->headers_in, "Via"))
        && ((ka_sent = ap_find_token(r->pool, conn, "keep-alive"))
            || (r->proto_num >= HTTP_VERSION(1,1)))
        && is_mpm_running()) {

        r->connection->keepalive = AP_CONN_KEEPALIVE;
        r->connection->keepalives++;

        /* If they sent a Keep-Alive token, send one back */
        if (ka_sent) {
            if (r->server->keep_alive_max) {
                apr_table_setn(r->headers_out, "Keep-Alive",
                       apr_psprintf(r->pool, "timeout=%d, max=%d",
                            (int)apr_time_sec(r->server->keep_alive_timeout),
                            left));
            }
            else {
                apr_table_setn(r->headers_out, "Keep-Alive",
                      apr_psprintf(r->pool, "timeout=%d",
                            (int)apr_time_sec(r->server->keep_alive_timeout)));
            }
            apr_table_mergen(r->headers_out, "Connection", "Keep-Alive");
        }

        return 1;
    }

    /* Otherwise, we need to indicate that we will be closing this
     * connection immediately after the current response.
     *
     * We only really need to send "close" to HTTP/1.1 clients, but we
     * always send it anyway, because a broken proxy may identify itself
     * as HTTP/1.0, but pass our request along with our HTTP/1.1 tag
     * to a HTTP/1.1 client. Better safe than sorry.
     */
    if (!wimpy) {
        apr_table_mergen(r->headers_out, "Connection", "close");
    }

    /*
     * If we had previously been a keepalive connection and this
     * is the last one, then bump up the number of keepalives
     * we've had
     */
    if ((r->connection->keepalive != AP_CONN_CLOSE)
        && r->server->keep_alive_max
        && !left) {
        r->connection->keepalives++;
    }
    r->connection->keepalive = AP_CONN_CLOSE;

    return 0;
}

AP_DECLARE(ap_condition_e) ap_condition_if_match(request_rec *r,
        apr_table_t *headers)
{
    const char *if_match, *etag;

    /* A server MUST use the strong comparison function (see section 13.3.3)
     * to compare the entity tags in If-Match.
     */
    if ((if_match = apr_table_get(r->headers_in, "If-Match")) != NULL) {
        if (if_match[0] == '*'
                || ((etag = apr_table_get(headers, "ETag")) != NULL
                        && ap_find_etag_strong(r->pool, if_match, etag))) {
            return AP_CONDITION_STRONG;
        }
        else {
            return AP_CONDITION_NOMATCH;
        }
    }

    return AP_CONDITION_NONE;
}

AP_DECLARE(ap_condition_e) ap_condition_if_unmodified_since(request_rec *r,
        apr_table_t *headers)
{
    const char *if_unmodified;

    if_unmodified = apr_table_get(r->headers_in, "If-Unmodified-Since");
    if (if_unmodified) {
        apr_int64_t mtime, reqtime;

        apr_time_t ius = apr_time_sec(apr_date_parse_http(if_unmodified));

        /* All of our comparisons must be in seconds, because that's the
         * highest time resolution the HTTP specification allows.
         */
        mtime = apr_time_sec(apr_date_parse_http(
                        apr_table_get(headers, "Last-Modified")));
        if (mtime == APR_DATE_BAD) {
            mtime = apr_time_sec(r->mtime ? r->mtime : apr_time_now());
        }

        reqtime = apr_time_sec(apr_date_parse_http(
                        apr_table_get(headers, "Date")));
        if (!reqtime) {
            reqtime = apr_time_sec(r->request_time);
        }

        if ((ius != APR_DATE_BAD) && (mtime > ius)) {
            if (reqtime < mtime + 60) {
                if (apr_table_get(r->headers_in, "Range")) {
                    /* weak matches not allowed with Range requests */
                    return AP_CONDITION_NOMATCH;
                }
                else {
                    return AP_CONDITION_WEAK;
                }
            }
            else {
                return AP_CONDITION_STRONG;
            }
        }
        else {
            return AP_CONDITION_NOMATCH;
        }
    }

    return AP_CONDITION_NONE;
}

AP_DECLARE(ap_condition_e) ap_condition_if_none_match(request_rec *r,
        apr_table_t *headers)
{
    const char *if_nonematch, *etag;

    if_nonematch = apr_table_get(r->headers_in, "If-None-Match");
    if (if_nonematch != NULL) {

        if (if_nonematch[0] == '*') {
            return AP_CONDITION_STRONG;
        }

        /* See section 13.3.3 for rules on how to determine if two entities tags
         * match. The weak comparison function can only be used with GET or HEAD
         * requests.
         */
        if (r->method_number == M_GET) {
            if ((etag = apr_table_get(headers, "ETag")) != NULL) {
                if (apr_table_get(r->headers_in, "Range")) {
                    if (ap_find_etag_strong(r->pool, if_nonematch, etag)) {
                        return AP_CONDITION_STRONG;
                    }
                }
                else {
                    if (ap_find_etag_weak(r->pool, if_nonematch, etag)) {
                        return AP_CONDITION_WEAK;
                    }
                }
            }
        }

        else if ((etag = apr_table_get(headers, "ETag")) != NULL
                && ap_find_etag_strong(r->pool, if_nonematch, etag)) {
            return AP_CONDITION_STRONG;
        }
        return AP_CONDITION_NOMATCH;
    }

    return AP_CONDITION_NONE;
}

AP_DECLARE(ap_condition_e) ap_condition_if_modified_since(request_rec *r,
        apr_table_t *headers)
{
    const char *if_modified_since;

    if ((if_modified_since = apr_table_get(r->headers_in, "If-Modified-Since"))
            != NULL) {
        apr_int64_t mtime;
        apr_int64_t ims, reqtime;

        /* All of our comparisons must be in seconds, because that's the
         * highest time resolution the HTTP specification allows.
         */

        mtime = apr_time_sec(apr_date_parse_http(
                        apr_table_get(headers, "Last-Modified")));
        if (mtime == APR_DATE_BAD) {
            mtime = apr_time_sec(r->mtime ? r->mtime : apr_time_now());
        }

        reqtime = apr_time_sec(apr_date_parse_http(
                        apr_table_get(headers, "Date")));
        if (!reqtime) {
            reqtime = apr_time_sec(r->request_time);
        }

        ims = apr_time_sec(apr_date_parse_http(if_modified_since));

        if (ims >= mtime && ims <= reqtime) {
            if (reqtime < mtime + 60) {
                if (apr_table_get(r->headers_in, "Range")) {
                    /* weak matches not allowed with Range requests */
                    return AP_CONDITION_NOMATCH;
                }
                else {
                    return AP_CONDITION_WEAK;
                }
            }
            else {
                return AP_CONDITION_STRONG;
            }
        }
        else {
            return AP_CONDITION_NOMATCH;
        }
    }

    return AP_CONDITION_NONE;
}

AP_DECLARE(ap_condition_e) ap_condition_if_range(request_rec *r,
        apr_table_t *headers)
{
    const char *if_range, *etag;

    if ((if_range = apr_table_get(r->headers_in, "If-Range"))
            && apr_table_get(r->headers_in, "Range")) {
        if (if_range[0] == '"') {

            if ((etag = apr_table_get(headers, "ETag"))
                    && !strcmp(if_range, etag)) {
                return AP_CONDITION_STRONG;
            }
            else {
                return AP_CONDITION_NOMATCH;
            }

        }
        else {
            apr_int64_t mtime;
            apr_int64_t rtime, reqtime;

            /* All of our comparisons must be in seconds, because that's the
             * highest time resolution the HTTP specification allows.
             */

            mtime = apr_time_sec(apr_date_parse_http(
                            apr_table_get(headers, "Last-Modified")));
            if (mtime == APR_DATE_BAD) {
                mtime = apr_time_sec(r->mtime ? r->mtime : apr_time_now());
            }

            reqtime = apr_time_sec(apr_date_parse_http(
                            apr_table_get(headers, "Date")));
            if (!reqtime) {
                reqtime = apr_time_sec(r->request_time);
            }

            rtime = apr_time_sec(apr_date_parse_http(if_range));

            if (rtime == mtime) {
                if (reqtime < mtime + 60) {
                    /* weak matches not allowed with Range requests */
                    return AP_CONDITION_NOMATCH;
                }
                else {
                    return AP_CONDITION_STRONG;
                }
            }
            else {
                return AP_CONDITION_NOMATCH;
            }
        }
    }

    return AP_CONDITION_NONE;
}

AP_DECLARE(int) ap_meets_conditions(request_rec *r)
{
    int not_modified = -1; /* unset by default */
    ap_condition_e cond;

    /* Check for conditional requests --- note that we only want to do
     * this if we are successful so far and we are not processing a
     * subrequest or an ErrorDocument.
     *
     * The order of the checks is important, since ETag checks are supposed
     * to be more accurate than checks relative to the modification time.
     * However, not all documents are guaranteed to *have* ETags, and some
     * might have Last-Modified values w/o ETags, so this gets a little
     * complicated.
     */

    if (!ap_is_HTTP_SUCCESS(r->status) || r->no_local_copy) {
        return OK;
    }

    /* If an If-Match request-header field was given
     * AND the field value is not "*" (meaning match anything)
     * AND if our strong ETag does not match any entity tag in that field,
     *     respond with a status of 412 (Precondition Failed).
     */
    cond = ap_condition_if_match(r, r->headers_out);
    if (AP_CONDITION_NOMATCH == cond) {
        return HTTP_PRECONDITION_FAILED;
    }

    /* Else if a valid If-Unmodified-Since request-header field was given
     * AND the requested resource has been modified since the time
     * specified in this field, then the server MUST
     *     respond with a status of 412 (Precondition Failed).
     */
    cond = ap_condition_if_unmodified_since(r, r->headers_out);
    if (AP_CONDITION_NOMATCH == cond) {
        not_modified = 0;
    }
    else if (cond >= AP_CONDITION_WEAK) {
        return HTTP_PRECONDITION_FAILED;
    }

    /* If an If-None-Match request-header field was given
     * AND the field value is "*" (meaning match anything)
     *     OR our ETag matches any of the entity tags in that field, fail.
     *
     * If the request method was GET or HEAD, failure means the server
     *    SHOULD respond with a 304 (Not Modified) response.
     * For all other request methods, failure means the server MUST
     *    respond with a status of 412 (Precondition Failed).
     *
     * GET or HEAD allow weak etag comparison, all other methods require
     * strong comparison.  We can only use weak if it's not a range request.
     */
    cond = ap_condition_if_none_match(r, r->headers_out);
    if (AP_CONDITION_NOMATCH == cond) {
        not_modified = 0;
    }
    else if (cond >= AP_CONDITION_WEAK) {
        if (r->method_number == M_GET) {
            if (not_modified) {
                not_modified = 1;
            }
        }
        else {
            return HTTP_PRECONDITION_FAILED;
        }
    }

    /* If a valid If-Modified-Since request-header field was given
     * AND it is a GET or HEAD request
     * AND the requested resource has not been modified since the time
     * specified in this field, then the server MUST
     *    respond with a status of 304 (Not Modified).
     * A date later than the server's current request time is invalid.
     */
    cond = ap_condition_if_modified_since(r, r->headers_out);
    if (AP_CONDITION_NOMATCH == cond) {
        not_modified = 0;
    }
    else if (cond >= AP_CONDITION_WEAK) {
        if (r->method_number == M_GET) {
            if (not_modified) {
                not_modified = 1;
            }
        }
    }

    /* If an If-Range and an Range header is present, we must return
     * 200 OK. The byterange filter will convert it to a range response.
     */
    cond = ap_condition_if_range(r, r->headers_out);
    if (cond > AP_CONDITION_NONE) {
        return OK;
    }

    if (not_modified == 1) {
        return HTTP_NOT_MODIFIED;
    }

    return OK;
}

/**
 * Singleton registry of additional methods. This maps new method names
 * such as "MYGET" to methnums, which are int offsets into bitmasks.
 *
 * This follows the same technique as standard M_GET, M_POST, etc. These
 * are dynamically assigned when modules are loaded and <Limit GET MYGET>
 * directives are processed.
 */
static apr_hash_t *methods_registry = NULL;
static int cur_method_number = METHOD_NUMBER_FIRST;

/* internal function to register one method/number pair */
static void register_one_method(apr_pool_t *p, const char *methname,
                                int methnum)
{
    int *pnum = apr_palloc(p, sizeof(*pnum));

    *pnum = methnum;
    apr_hash_set(methods_registry, methname, APR_HASH_KEY_STRING, pnum);
}

/* This internal function is used to clear the method registry
 * and reset the cur_method_number counter.
 */
static apr_status_t ap_method_registry_destroy(void *notused)
{
    methods_registry = NULL;
    cur_method_number = METHOD_NUMBER_FIRST;
    return APR_SUCCESS;
}

AP_DECLARE(void) ap_method_registry_init(apr_pool_t *p)
{
    methods_registry = apr_hash_make(p);
    apr_pool_cleanup_register(p, NULL,
                              ap_method_registry_destroy,
                              apr_pool_cleanup_null);

    /* put all the standard methods into the registry hash to ease the
     * mapping operations between name and number
     * HEAD is a special-instance of the GET method and shares the same ID
     */
    register_one_method(p, "GET", M_GET);
    register_one_method(p, "HEAD", M_GET);
    register_one_method(p, "PUT", M_PUT);
    register_one_method(p, "POST", M_POST);
    register_one_method(p, "DELETE", M_DELETE);
    register_one_method(p, "CONNECT", M_CONNECT);
    register_one_method(p, "OPTIONS", M_OPTIONS);
    register_one_method(p, "TRACE", M_TRACE);
    register_one_method(p, "PATCH", M_PATCH);
    register_one_method(p, "PROPFIND", M_PROPFIND);
    register_one_method(p, "PROPPATCH", M_PROPPATCH);
    register_one_method(p, "MKCOL", M_MKCOL);
    register_one_method(p, "COPY", M_COPY);
    register_one_method(p, "MOVE", M_MOVE);
    register_one_method(p, "LOCK", M_LOCK);
    register_one_method(p, "UNLOCK", M_UNLOCK);
    register_one_method(p, "VERSION-CONTROL", M_VERSION_CONTROL);
    register_one_method(p, "CHECKOUT", M_CHECKOUT);
    register_one_method(p, "UNCHECKOUT", M_UNCHECKOUT);
    register_one_method(p, "CHECKIN", M_CHECKIN);
    register_one_method(p, "UPDATE", M_UPDATE);
    register_one_method(p, "LABEL", M_LABEL);
    register_one_method(p, "REPORT", M_REPORT);
    register_one_method(p, "MKWORKSPACE", M_MKWORKSPACE);
    register_one_method(p, "MKACTIVITY", M_MKACTIVITY);
    register_one_method(p, "BASELINE-CONTROL", M_BASELINE_CONTROL);
    register_one_method(p, "MERGE", M_MERGE);
}

AP_DECLARE(int) ap_method_register(apr_pool_t *p, const char *methname)
{
    int *methnum;

    if (methods_registry == NULL) {
        ap_method_registry_init(p);
    }

    if (methname == NULL) {
        return M_INVALID;
    }

    /* Check if the method was previously registered.  If it was
     * return the associated method number.
     */
    methnum = (int *)apr_hash_get(methods_registry, methname,
                                  APR_HASH_KEY_STRING);
    if (methnum != NULL)
        return *methnum;

    if (cur_method_number > METHOD_NUMBER_LAST) {
        /* The method registry  has run out of dynamically
         * assignable method numbers. Log this and return M_INVALID.
         */
        ap_log_perror(APLOG_MARK, APLOG_ERR, 0, p, APLOGNO(01610)
                      "Maximum new request methods %d reached while "
                      "registering method %s.",
                      METHOD_NUMBER_LAST, methname);
        return M_INVALID;
    }

    register_one_method(p, methname, cur_method_number);
    return cur_method_number++;
}

#define UNKNOWN_METHOD (-1)

static int lookup_builtin_method(const char *method, apr_size_t len)
{
    /* Note: the following code was generated by the "shilka" tool from
       the "cocom" parsing/compilation toolkit. It is an optimized lookup
       based on analysis of the input keywords. Postprocessing was done
       on the shilka output, but the basic structure and analysis is
       from there. Should new HTTP methods be added, then manual insertion
       into this code is fine, or simply re-running the shilka tool on
       the appropriate input. */

    /* Note: it is also quite reasonable to just use our method_registry,
       but I'm assuming (probably incorrectly) we want more speed here
       (based on the optimizations the previous code was doing). */

    switch (len)
    {
    case 3:
        switch (method[0])
        {
        case 'P':
            return (method[1] == 'U'
                    && method[2] == 'T'
                    ? M_PUT : UNKNOWN_METHOD);
        case 'G':
            return (method[1] == 'E'
                    && method[2] == 'T'
                    ? M_GET : UNKNOWN_METHOD);
        default:
            return UNKNOWN_METHOD;
        }

    case 4:
        switch (method[0])
        {
        case 'H':
            return (method[1] == 'E'
                    && method[2] == 'A'
                    && method[3] == 'D'
                    ? M_GET : UNKNOWN_METHOD);
        case 'P':
            return (method[1] == 'O'
                    && method[2] == 'S'
                    && method[3] == 'T'
                    ? M_POST : UNKNOWN_METHOD);
        case 'M':
            return (method[1] == 'O'
                    && method[2] == 'V'
                    && method[3] == 'E'
                    ? M_MOVE : UNKNOWN_METHOD);
        case 'L':
            return (method[1] == 'O'
                    && method[2] == 'C'
                    && method[3] == 'K'
                    ? M_LOCK : UNKNOWN_METHOD);
        case 'C':
            return (method[1] == 'O'
                    && method[2] == 'P'
                    && method[3] == 'Y'
                    ? M_COPY : UNKNOWN_METHOD);
        default:
            return UNKNOWN_METHOD;
        }

    case 5:
        switch (method[2])
        {
        case 'T':
            return (memcmp(method, "PATCH", 5) == 0
                    ? M_PATCH : UNKNOWN_METHOD);
        case 'R':
            return (memcmp(method, "MERGE", 5) == 0
                    ? M_MERGE : UNKNOWN_METHOD);
        case 'C':
            return (memcmp(method, "MKCOL", 5) == 0
                    ? M_MKCOL : UNKNOWN_METHOD);
        case 'B':
            return (memcmp(method, "LABEL", 5) == 0
                    ? M_LABEL : UNKNOWN_METHOD);
        case 'A':
            return (memcmp(method, "TRACE", 5) == 0
                    ? M_TRACE : UNKNOWN_METHOD);
        default:
            return UNKNOWN_METHOD;
        }

    case 6:
        switch (method[0])
        {
        case 'U':
            switch (method[5])
            {
            case 'K':
                return (memcmp(method, "UNLOCK", 6) == 0
                        ? M_UNLOCK : UNKNOWN_METHOD);
            case 'E':
                return (memcmp(method, "UPDATE", 6) == 0
                        ? M_UPDATE : UNKNOWN_METHOD);
            default:
                return UNKNOWN_METHOD;
            }
        case 'R':
            return (memcmp(method, "REPORT", 6) == 0
                    ? M_REPORT : UNKNOWN_METHOD);
        case 'D':
            return (memcmp(method, "DELETE", 6) == 0
                    ? M_DELETE : UNKNOWN_METHOD);
        default:
            return UNKNOWN_METHOD;
        }

    case 7:
        switch (method[1])
        {
        case 'P':
            return (memcmp(method, "OPTIONS", 7) == 0
                    ? M_OPTIONS : UNKNOWN_METHOD);
        case 'O':
            return (memcmp(method, "CONNECT", 7) == 0
                    ? M_CONNECT : UNKNOWN_METHOD);
        case 'H':
            return (memcmp(method, "CHECKIN", 7) == 0
                    ? M_CHECKIN : UNKNOWN_METHOD);
        default:
            return UNKNOWN_METHOD;
        }

    case 8:
        switch (method[0])
        {
        case 'P':
            return (memcmp(method, "PROPFIND", 8) == 0
                    ? M_PROPFIND : UNKNOWN_METHOD);
        case 'C':
            return (memcmp(method, "CHECKOUT", 8) == 0
                    ? M_CHECKOUT : UNKNOWN_METHOD);
        default:
            return UNKNOWN_METHOD;
        }

    case 9:
        return (memcmp(method, "PROPPATCH", 9) == 0
                ? M_PROPPATCH : UNKNOWN_METHOD);

    case 10:
        switch (method[0])
        {
        case 'U':
            return (memcmp(method, "UNCHECKOUT", 10) == 0
                    ? M_UNCHECKOUT : UNKNOWN_METHOD);
        case 'M':
            return (memcmp(method, "MKACTIVITY", 10) == 0
                    ? M_MKACTIVITY : UNKNOWN_METHOD);
        default:
            return UNKNOWN_METHOD;
        }

    case 11:
        return (memcmp(method, "MKWORKSPACE", 11) == 0
                ? M_MKWORKSPACE : UNKNOWN_METHOD);

    case 15:
        return (memcmp(method, "VERSION-CONTROL", 15) == 0
                ? M_VERSION_CONTROL : UNKNOWN_METHOD);

    case 16:
        return (memcmp(method, "BASELINE-CONTROL", 16) == 0
                ? M_BASELINE_CONTROL : UNKNOWN_METHOD);

    default:
        return UNKNOWN_METHOD;
    }

    /* NOTREACHED */
}

/* Get the method number associated with the given string, assumed to
 * contain an HTTP method.  Returns M_INVALID if not recognized.
 *
 * This is the first step toward placing method names in a configurable
 * list.  Hopefully it (and other routines) can eventually be moved to
 * something like a mod_http_methods.c, complete with config stuff.
 */
AP_DECLARE(int) ap_method_number_of(const char *method)
{
    int len = strlen(method);
    int which = lookup_builtin_method(method, len);

    if (which != UNKNOWN_METHOD)
        return which;

    /* check if the method has been dynamically registered */
    if (methods_registry != NULL) {
        int *methnum = apr_hash_get(methods_registry, method, len);

        if (methnum != NULL) {
            return *methnum;
        }
    }

    return M_INVALID;
}

/*
 * Turn a known method number into a name.
 */
AP_DECLARE(const char *) ap_method_name_of(apr_pool_t *p, int methnum)
{
    apr_hash_index_t *hi = apr_hash_first(p, methods_registry);

    /* scan through the hash table, looking for a value that matches
       the provided method number. */
    for (; hi; hi = apr_hash_next(hi)) {
        const void *key;
        void *val;

        apr_hash_this(hi, &key, NULL, &val);
        if (*(int *)val == methnum)
            return key;
    }

    /* it wasn't found in the hash */
    return NULL;
}

/* The index is found by its offset from the x00 code of each level.
 * Although this is fast, it will need to be replaced if some nutcase
 * decides to define a high-numbered code before the lower numbers.
 * If that sad event occurs, replace the code below with a linear search
 * from status_lines[shortcut[i]] to status_lines[shortcut[i+1]-1];
 * or use NULL to fill the gaps.
 */
AP_DECLARE(int) ap_index_of_response(int status)
{
    static int shortcut[6] = {0, LEVEL_200, LEVEL_300, LEVEL_400,
    LEVEL_500, RESPONSE_CODES};
    int i, pos;

    if (status < 100) {               /* Below 100 is illegal for HTTP status */
        return LEVEL_500;
    }

    for (i = 0; i < 5; i++) {
        status -= 100;
        if (status < 100) {
            pos = (status + shortcut[i]);
            if (pos < shortcut[i + 1] && status_lines[pos] != NULL) {
                return pos;
            }
            else {
                return LEVEL_500;            /* status unknown (falls in gap) */
            }
        }
    }
    return LEVEL_500;                         /* 600 or above is also illegal */
}

AP_DECLARE(const char *) ap_get_status_line(int status)
{
    return status_lines[ap_index_of_response(status)];
}

/* Build the Allow field-value from the request handler method mask.
 */
static char *make_allow(request_rec *r)
{
    apr_int64_t mask;
    apr_array_header_t *allow = apr_array_make(r->pool, 10, sizeof(char *));
    apr_hash_index_t *hi = apr_hash_first(r->pool, methods_registry);
    /* For TRACE below */
    core_server_config *conf =
        ap_get_core_module_config(r->server->module_config);

    mask = r->allowed_methods->method_mask;

    for (; hi; hi = apr_hash_next(hi)) {
        const void *key;
        void *val;

        apr_hash_this(hi, &key, NULL, &val);
        if ((mask & (AP_METHOD_BIT << *(int *)val)) != 0) {
            APR_ARRAY_PUSH(allow, const char *) = key;
        }
    }

    /* TRACE is tested on a per-server basis */
    if (conf->trace_enable != AP_TRACE_DISABLE)
        *(const char **)apr_array_push(allow) = "TRACE";

    /* ### this is rather annoying. we should enforce registration of
       ### these methods */
    if ((mask & (AP_METHOD_BIT << M_INVALID))
        && (r->allowed_methods->method_list != NULL)
        && (r->allowed_methods->method_list->nelts != 0)) {
        apr_array_cat(allow, r->allowed_methods->method_list);
    }

    return apr_array_pstrcat(r->pool, allow, ',');
}

AP_DECLARE(int) ap_send_http_options(request_rec *r)
{
    if (r->assbackwards) {
        return DECLINED;
    }

    apr_table_setn(r->headers_out, "Allow", make_allow(r));

    /* the request finalization will send an EOS, which will flush all
     * the headers out (including the Allow header)
     */

    return OK;
}

AP_DECLARE(void) ap_set_content_type(request_rec *r, const char *ct)
{
    if (!ct) {
        r->content_type = NULL;
    }
    else if (!r->content_type || strcmp(r->content_type, ct)) {
        r->content_type = ct;
    }
}

AP_DECLARE(void) ap_set_accept_ranges(request_rec *r)
{
    core_dir_config *d = ap_get_core_module_config(r->per_dir_config);
    apr_table_setn(r->headers_out, "Accept-Ranges",
                  (d->max_ranges == AP_MAXRANGES_NORANGES) ? "none"
                                                           : "bytes");
}
static const char *add_optional_notes(request_rec *r,
                                      const char *prefix,
                                      const char *key,
                                      const char *suffix)
{
    const char *notes, *result;

    if ((notes = apr_table_get(r->notes, key)) == NULL) {
        result = apr_pstrcat(r->pool, prefix, suffix, NULL);
    }
    else {
        result = apr_pstrcat(r->pool, prefix, notes, suffix, NULL);
    }

    return result;
}

/* construct and return the default error message for a given
 * HTTP defined error code
 */
static const char *get_canned_error_string(int status,
                                           request_rec *r,
                                           const char *location)
{
    apr_pool_t *p = r->pool;
    const char *error_notes, *h1, *s1;

    switch (status) {
    case HTTP_MOVED_PERMANENTLY:
    case HTTP_MOVED_TEMPORARILY:
    case HTTP_TEMPORARY_REDIRECT:
    case HTTP_PERMANENT_REDIRECT:
        return(apr_pstrcat(p,
                           "<p>The document has moved <a href=\"",
                           ap_escape_html(r->pool, location),
                           "\">here</a>.</p>\n",
                           NULL));
    case HTTP_SEE_OTHER:
        return(apr_pstrcat(p,
                           "<p>The answer to your request is located "
                           "<a href=\"",
                           ap_escape_html(r->pool, location),
                           "\">here</a>.</p>\n",
                           NULL));
    case HTTP_USE_PROXY:
        return(apr_pstrcat(p,
                           "<p>This resource is only accessible "
                           "through the proxy\n",
                           ap_escape_html(r->pool, location),
                           "<br />\nYou will need to configure "
                           "your client to use that proxy.</p>\n",
                           NULL));
    case HTTP_PROXY_AUTHENTICATION_REQUIRED:
    case HTTP_UNAUTHORIZED:
        return("<p>This server could not verify that you\n"
               "are authorized to access the document\n"
               "requested.  Either you supplied the wrong\n"
               "credentials (e.g., bad password), or your\n"
               "browser doesn't understand how to supply\n"
               "the credentials required.</p>\n");
    case HTTP_BAD_REQUEST:
        return(add_optional_notes(r,
                                  "<p>Your browser sent a request that "
                                  "this server could not understand.<br />\n",
                                  "error-notes",
                                  "</p>\n"));
    case HTTP_FORBIDDEN:
        s1 = apr_pstrcat(p,
                         "<p>You don't have permission to access ",
                         ap_escape_html(r->pool, r->uri),
                         "\non this server.<br />\n",
                         NULL);
        return(add_optional_notes(r, s1, "error-notes", "</p>\n"));
    case HTTP_NOT_FOUND:
        return(apr_pstrcat(p,
                           "<p>The requested URL ",
                           ap_escape_html(r->pool, r->uri),
                           " was not found on this server.</p>\n",
                           NULL));
    case HTTP_METHOD_NOT_ALLOWED:
        return(apr_pstrcat(p,
                           "<p>The requested method ",
                           ap_escape_html(r->pool, r->method),
                           " is not allowed for the URL ",
                           ap_escape_html(r->pool, r->uri),
                           ".</p>\n",
                           NULL));
    case HTTP_NOT_ACCEPTABLE:
        s1 = apr_pstrcat(p,
                         "<p>An appropriate representation of the "
                         "requested resource ",
                         ap_escape_html(r->pool, r->uri),
                         " could not be found on this server.</p>\n",
                         NULL);
        return(add_optional_notes(r, s1, "variant-list", ""));
    case HTTP_MULTIPLE_CHOICES:
        return(add_optional_notes(r, "", "variant-list", ""));
    case HTTP_LENGTH_REQUIRED:
        s1 = apr_pstrcat(p,
                         "<p>A request of the requested method ",
                         ap_escape_html(r->pool, r->method),
                         " requires a valid Content-length.<br />\n",
                         NULL);
        return(add_optional_notes(r, s1, "error-notes", "</p>\n"));
    case HTTP_PRECONDITION_FAILED:
        return(apr_pstrcat(p,
                           "<p>The precondition on the request "
                           "for the URL ",
                           ap_escape_html(r->pool, r->uri),
                           " evaluated to false.</p>\n",
                           NULL));
    case HTTP_NOT_IMPLEMENTED:
        s1 = apr_pstrcat(p,
                         "<p>",
                         ap_escape_html(r->pool, r->method), " to ",
                         ap_escape_html(r->pool, r->uri),
                         " not supported.<br />\n",
                         NULL);
        return(add_optional_notes(r, s1, "error-notes", "</p>\n"));
    case HTTP_BAD_GATEWAY:
        s1 = "<p>The proxy server received an invalid" CRLF
            "response from an upstream server.<br />" CRLF;
        return(add_optional_notes(r, s1, "error-notes", "</p>\n"));
    case HTTP_VARIANT_ALSO_VARIES:
        return(apr_pstrcat(p,
                           "<p>A variant for the requested "
                           "resource\n<pre>\n",
                           ap_escape_html(r->pool, r->uri),
                           "\n</pre>\nis itself a negotiable resource. "
                           "This indicates a configuration error.</p>\n",
                           NULL));
    case HTTP_REQUEST_TIME_OUT:
        return("<p>Server timeout waiting for the HTTP request from the client.</p>\n");
    case HTTP_GONE:
        return(apr_pstrcat(p,
                           "<p>The requested resource<br />",
                           ap_escape_html(r->pool, r->uri),
                           "<br />\nis no longer available on this server "
                           "and there is no forwarding address.\n"
                           "Please remove all references to this "
                           "resource.</p>\n",
                           NULL));
    case HTTP_REQUEST_ENTITY_TOO_LARGE:
        return(apr_pstrcat(p,
                           "The requested resource<br />",
                           ap_escape_html(r->pool, r->uri), "<br />\n",
                           "does not allow request data with ",
                           ap_escape_html(r->pool, r->method),
                           " requests, or the amount of data provided in\n"
                           "the request exceeds the capacity limit.\n",
                           NULL));
    case HTTP_REQUEST_URI_TOO_LARGE:
        s1 = "<p>The requested URL's length exceeds the capacity\n"
             "limit for this server.<br />\n";
        return(add_optional_notes(r, s1, "error-notes", "</p>\n"));
    case HTTP_UNSUPPORTED_MEDIA_TYPE:
        return("<p>The supplied request data is not in a format\n"
               "acceptable for processing by this resource.</p>\n");
    case HTTP_RANGE_NOT_SATISFIABLE:
        return("<p>None of the range-specifier values in the Range\n"
               "request-header field overlap the current extent\n"
               "of the selected resource.</p>\n");
    case HTTP_EXPECTATION_FAILED:
        s1 = apr_table_get(r->headers_in, "Expect");
        if (s1)
            s1 = apr_pstrcat(p,
                     "<p>The expectation given in the Expect request-header\n"
                     "field could not be met by this server.\n"
                     "The client sent<pre>\n    Expect: ",
                     ap_escape_html(r->pool, s1), "\n</pre>\n",
                     NULL);
        else
            s1 = "<p>No expectation was seen, the Expect request-header \n"
                 "field was not presented by the client.\n";
        return add_optional_notes(r, s1, "error-notes", "</p>"
                   "<p>Only the 100-continue expectation is supported.</p>\n");
    case HTTP_UNPROCESSABLE_ENTITY:
        return("<p>The server understands the media type of the\n"
               "request entity, but was unable to process the\n"
               "contained instructions.</p>\n");
    case HTTP_LOCKED:
        return("<p>The requested resource is currently locked.\n"
               "The lock must be released or proper identification\n"
               "given before the method can be applied.</p>\n");
    case HTTP_FAILED_DEPENDENCY:
        return("<p>The method could not be performed on the resource\n"
               "because the requested action depended on another\n"
               "action and that other action failed.</p>\n");
    case HTTP_UPGRADE_REQUIRED:
        return("<p>The requested resource can only be retrieved\n"
               "using SSL.  The server is willing to upgrade the current\n"
               "connection to SSL, but your client doesn't support it.\n"
               "Either upgrade your client, or try requesting the page\n"
               "using https://\n");
    case HTTP_PRECONDITION_REQUIRED:
        return("<p>The request is required to be conditional.</p>\n");
    case HTTP_TOO_MANY_REQUESTS:
        return("<p>The user has sent too many requests\n"
               "in a given amount of time.</p>\n");
    case HTTP_REQUEST_HEADER_FIELDS_TOO_LARGE:
        return("<p>The server refused this request because\n"
               "the request header fields are too large.</p>\n");
    case HTTP_INSUFFICIENT_STORAGE:
        return("<p>The method could not be performed on the resource\n"
               "because the server is unable to store the\n"
               "representation needed to successfully complete the\n"
               "request.  There is insufficient free space left in\n"
               "your storage allocation.</p>\n");
    case HTTP_SERVICE_UNAVAILABLE:
        return("<p>The server is temporarily unable to service your\n"
               "request due to maintenance downtime or capacity\n"
               "problems. Please try again later.</p>\n");
    case HTTP_GATEWAY_TIME_OUT:
        return("<p>The gateway did not receive a timely response\n"
               "from the upstream server or application.</p>\n");
    case HTTP_LOOP_DETECTED:
        return("<p>The server terminated an operation because\n"
               "it encountered an infinite loop.</p>\n");
    case HTTP_NOT_EXTENDED:
        return("<p>A mandatory extension policy in the request is not\n"
               "accepted by the server for this resource.</p>\n");
    case HTTP_NETWORK_AUTHENTICATION_REQUIRED:
        return("<p>The client needs to authenticate to gain\n"
               "network access.</p>\n");
    case HTTP_MISDIRECTED_REQUEST:
        return("<p>The client needs a new connection for this\n"
               "request as the requested host name does not match\n"
               "the Server Name Indication (SNI) in use for this\n"
               "connection.</p>\n");
    case HTTP_UNAVAILABLE_FOR_LEGAL_REASONS:
        s1 = apr_pstrcat(p,
                         "<p>Access to ", ap_escape_html(r->pool, r->uri),
                         "\nhas been denied for legal reasons.<br />\n",
                         NULL);
        return(add_optional_notes(r, s1, "error-notes", "</p>\n"));
    default:                    /* HTTP_INTERNAL_SERVER_ERROR */
        /*
         * This comparison to expose error-notes could be modified to
         * use a configuration directive and export based on that
         * directive.  For now "*" is used to designate an error-notes
         * that is totally safe for any user to see (ie lacks paths,
         * database passwords, etc.)
         */
        if (((error_notes = apr_table_get(r->notes,
                                          "error-notes")) != NULL)
            && (h1 = apr_table_get(r->notes, "verbose-error-to")) != NULL
            && (strcmp(h1, "*") == 0)) {
            return(apr_pstrcat(p, error_notes, "<p />\n", NULL));
        }
        else {
            return(apr_pstrcat(p,
                               "<p>The server encountered an internal "
                               "error or\n"
                               "misconfiguration and was unable to complete\n"
                               "your request.</p>\n"
                               "<p>Please contact the server "
                               "administrator at \n ",
                               ap_escape_html(r->pool,
                                              r->server->server_admin),
                               " to inform them of the time this "
                               "error occurred,\n"
                               " and the actions you performed just before "
                               "this error.</p>\n"
                               "<p>More information about this error "
                               "may be available\n"
                               "in the server error log.</p>\n",
                               NULL));
        }
        /*
         * It would be nice to give the user the information they need to
         * fix the problem directly since many users don't have access to
         * the error_log (think University sites) even though they can easily
         * get this error by misconfiguring an htaccess file.  However, the
         * e error notes tend to include the real file pathname in this case,
         * which some people consider to be a breach of privacy.  Until we
         * can figure out a way to remove the pathname, leave this commented.
         *
         * if ((error_notes = apr_table_get(r->notes,
         *                                  "error-notes")) != NULL) {
         *     return(apr_pstrcat(p, error_notes, "<p />\n", NULL);
         * }
         * else {
         *     return "";
         * }
         */
    }
}

/* We should have named this send_canned_response, since it is used for any
 * response that can be generated by the server from the request record.
 * This includes all 204 (no content), 3xx (redirect), 4xx (client error),
 * and 5xx (server error) messages that have not been redirected to another
 * handler via the ErrorDocument feature.
 */
AP_DECLARE(void) ap_send_error_response(request_rec *r, int recursive_error)
{
    int status = r->status;
    int idx = ap_index_of_response(status);
    char *custom_response;
    const char *location = apr_table_get(r->headers_out, "Location");

    /* At this point, we are starting the response over, so we have to reset
     * this value.
     */
    r->eos_sent = 0;

    /* and we need to get rid of any RESOURCE filters that might be lurking
     * around, thinking they are in the middle of the original request
     */

    r->output_filters = r->proto_output_filters;

    ap_run_insert_error_filter(r);

    /* We need to special-case the handling of 204 and 304 responses,
     * since they have specific HTTP requirements and do not include a
     * message body.  Note that being assbackwards here is not an option.
     */
    if (AP_STATUS_IS_HEADER_ONLY(status)) {
        ap_finalize_request_protocol(r);
        return;
    }

    /*
     * It's possible that the Location field might be in r->err_headers_out
     * instead of r->headers_out; use the latter if possible, else the
     * former.
     */
    if (location == NULL) {
        location = apr_table_get(r->err_headers_out, "Location");
    }

    if (!r->assbackwards) {
        apr_table_t *tmp = r->headers_out;

        /* For all HTTP/1.x responses for which we generate the message,
         * we need to avoid inheriting the "normal status" header fields
         * that may have been set by the request handler before the
         * error or redirect, except for Location on external redirects.
         */
        r->headers_out = r->err_headers_out;
        r->err_headers_out = tmp;
        apr_table_clear(r->err_headers_out);

        if (ap_is_HTTP_REDIRECT(status) || (status == HTTP_CREATED)) {
            if ((location != NULL) && *location) {
                apr_table_setn(r->headers_out, "Location", location);
            }
            else {
                location = "";   /* avoids coredump when printing, below */
            }
        }

        r->content_languages = NULL;
        r->content_encoding = NULL;
        r->clength = 0;

        if (apr_table_get(r->subprocess_env,
                          "suppress-error-charset") != NULL) {
            core_request_config *request_conf =
                        ap_get_core_module_config(r->request_config);
            request_conf->suppress_charset = 1; /* avoid adding default
                                                 * charset later
                                                 */
            ap_set_content_type(r, "text/html");
        }
        else {
            ap_set_content_type(r, "text/html; charset=iso-8859-1");
        }

        if ((status == HTTP_METHOD_NOT_ALLOWED)
            || (status == HTTP_NOT_IMPLEMENTED)) {
            apr_table_setn(r->headers_out, "Allow", make_allow(r));
        }

        if (r->header_only) {
            ap_finalize_request_protocol(r);
            return;
        }
    }

    if ((custom_response = ap_response_code_string(r, idx))) {
        /*
         * We have a custom response output. This should only be
         * a text-string to write back. But if the ErrorDocument
         * was a local redirect and the requested resource failed
         * for any reason, the custom_response will still hold the
         * redirect URL. We don't really want to output this URL
         * as a text message, so first check the custom response
         * string to ensure that it is a text-string (using the
         * same test used in ap_die(), i.e. does it start with a ").
         *
         * If it's not a text string, we've got a recursive error or
         * an external redirect.  If it's a recursive error, ap_die passes
         * us the second error code so we can write both, and has already
         * backed up to the original error.  If it's an external redirect,
         * it hasn't happened yet; we may never know if it fails.
         */
        if (custom_response[0] == '\"') {
            ap_rputs(custom_response + 1, r);
            ap_finalize_request_protocol(r);
            return;
        }
    }
    {
        const char *title = status_lines[idx];
        const char *h1;

        /* Accept a status_line set by a module, but only if it begins
         * with the correct 3 digit status code
         */
        if (r->status_line) {
            char *end;
            int len = strlen(r->status_line);
            if (len >= 3
                && apr_strtoi64(r->status_line, &end, 10) == r->status
                && (end - 3) == r->status_line
                && (len < 4 || apr_isspace(r->status_line[3]))
                && (len < 5 || apr_isalnum(r->status_line[4]))) {
                /* Since we passed the above check, we know that length three
                 * is equivalent to only a 3 digit numeric http status.
                 * RFC2616 mandates a trailing space, let's add it.
                 * If we have an empty reason phrase, we also add "Unknown Reason".
                 */
                if (len == 3) {
                    r->status_line = apr_pstrcat(r->pool, r->status_line, " Unknown Reason", NULL);
                } else if (len == 4) {
                    r->status_line = apr_pstrcat(r->pool, r->status_line, "Unknown Reason", NULL);
                }
                title = r->status_line;
            }
        }

        /* folks decided they didn't want the error code in the H1 text */
        h1 = &title[4];

        /* can't count on a charset filter being in place here,
         * so do ebcdic->ascii translation explicitly (if needed)
         */

        ap_rvputs_proto_in_ascii(r,
                  DOCTYPE_HTML_2_0
                  "<html><head>\n<title>", title,
                  "</title>\n</head><body>\n<h1>", h1, "</h1>\n",
                  NULL);

        ap_rvputs_proto_in_ascii(r,
                                 get_canned_error_string(status, r, location),
                                 NULL);

        if (recursive_error) {
            ap_rvputs_proto_in_ascii(r, "<p>Additionally, a ",
                      status_lines[ap_index_of_response(recursive_error)],
                      "\nerror was encountered while trying to use an "
                      "ErrorDocument to handle the request.</p>\n", NULL);
        }
        ap_rvputs_proto_in_ascii(r, ap_psignature("<hr>\n", r), NULL);
        ap_rvputs_proto_in_ascii(r, "</body></html>\n", NULL);
    }
    ap_finalize_request_protocol(r);
}

/*
 * Create a new method list with the specified number of preallocated
 * extension slots.
 */
AP_DECLARE(ap_method_list_t *) ap_make_method_list(apr_pool_t *p, int nelts)
{
    ap_method_list_t *ml;

    ml = (ap_method_list_t *) apr_palloc(p, sizeof(ap_method_list_t));
    ml->method_mask = 0;
    ml->method_list = apr_array_make(p, nelts, sizeof(char *));
    return ml;
}

/*
 * Make a copy of a method list (primarily for subrequests that may
 * subsequently change it; don't want them changing the parent's, too!).
 */
AP_DECLARE(void) ap_copy_method_list(ap_method_list_t *dest,
                                     ap_method_list_t *src)
{
    int i;
    char **imethods;
    char **omethods;

    dest->method_mask = src->method_mask;
    imethods = (char **) src->method_list->elts;
    for (i = 0; i < src->method_list->nelts; ++i) {
        omethods = (char **) apr_array_push(dest->method_list);
        *omethods = apr_pstrdup(dest->method_list->pool, imethods[i]);
    }
}

/*
 * Return true if the specified HTTP method is in the provided
 * method list.
 */
AP_DECLARE(int) ap_method_in_list(ap_method_list_t *l, const char *method)
{
    int methnum;

    /*
     * If it's one of our known methods, use the shortcut and check the
     * bitmask.
     */
    methnum = ap_method_number_of(method);
    if (methnum != M_INVALID) {
        return !!(l->method_mask & (AP_METHOD_BIT << methnum));
    }
    /*
     * Otherwise, see if the method name is in the array of string names.
     */
    if ((l->method_list == NULL) || (l->method_list->nelts == 0)) {
        return 0;
    }

    return ap_array_str_contains(l->method_list, method);
}

/*
 * Add the specified method to a method list (if it isn't already there).
 */
AP_DECLARE(void) ap_method_list_add(ap_method_list_t *l, const char *method)
{
    int methnum;
    const char **xmethod;

    /*
     * If it's one of our known methods, use the shortcut and use the
     * bitmask.
     */
    methnum = ap_method_number_of(method);
    if (methnum != M_INVALID) {
        l->method_mask |= (AP_METHOD_BIT << methnum);
        return;
    }
    /*
     * Otherwise, see if the method name is in the array of string names.
     */
    if (ap_array_str_contains(l->method_list, method)) {
        return;
    }

    xmethod = (const char **) apr_array_push(l->method_list);
    *xmethod = method;
}

/*
 * Remove the specified method from a method list.
 */
AP_DECLARE(void) ap_method_list_remove(ap_method_list_t *l,
                                       const char *method)
{
    int methnum;
    char **methods;

    /*
     * If it's a known methods, either builtin or registered
     * by a module, use the bitmask.
     */
    methnum = ap_method_number_of(method);
    if (methnum != M_INVALID) {
        l->method_mask &= ~(AP_METHOD_BIT << methnum);
        return;
    }
    /*
     * Otherwise, see if the method name is in the array of string names.
     */
    if (l->method_list->nelts != 0) {
        int i, j, k;
        methods = (char **)l->method_list->elts;
        for (i = 0; i < l->method_list->nelts; ) {
            if (strcmp(method, methods[i]) == 0) {
                for (j = i, k = i + 1; k < l->method_list->nelts; ++j, ++k) {
                    methods[j] = methods[k];
                }
                --l->method_list->nelts;
            }
            else {
                ++i;
            }
        }
    }
}

/*
 * Reset a method list to be completely empty.
 */
AP_DECLARE(void) ap_clear_method_list(ap_method_list_t *l)
{
    l->method_mask = 0;
    l->method_list->nelts = 0;
}