summaryrefslogtreecommitdiff
path: root/nscd/connections.c
blob: 48e91e80fec10ef17155ea6665812683ba69da60 (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
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
/* Inner loops of cache daemon.
   Copyright (C) 1998-2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published
   by the Free Software Foundation; version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

#include <alloca.h>
#include <assert.h>
#include <atomic.h>
#include <error.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <libintl.h>
#include <pthread.h>
#include <pwd.h>
#include <resolv.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <arpa/inet.h>
#ifdef HAVE_EPOLL
# include <sys/epoll.h>
#endif
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/poll.h>
#ifdef HAVE_SENDFILE
# include <sys/sendfile.h>
#endif
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>

#include "nscd.h"
#include "dbg_log.h"
#include "selinux.h"
#ifdef HAVE_SENDFILE
# include <kernel-features.h>
#endif


/* Wrapper functions with error checking for standard functions.  */
extern void *xmalloc (size_t n);
extern void *xcalloc (size_t n, size_t s);
extern void *xrealloc (void *o, size_t n);

/* Support to run nscd as an unprivileged user */
const char *server_user;
static uid_t server_uid;
static gid_t server_gid;
const char *stat_user;
uid_t stat_uid;
static gid_t *server_groups;
#ifndef NGROUPS
# define NGROUPS 32
#endif
static int server_ngroups;

static pthread_attr_t attr;

static void begin_drop_privileges (void);
static void finish_drop_privileges (void);

/* Map request type to a string.  */
const char *const serv2str[LASTREQ] =
{
  [GETPWBYNAME] = "GETPWBYNAME",
  [GETPWBYUID] = "GETPWBYUID",
  [GETGRBYNAME] = "GETGRBYNAME",
  [GETGRBYGID] = "GETGRBYGID",
  [GETHOSTBYNAME] = "GETHOSTBYNAME",
  [GETHOSTBYNAMEv6] = "GETHOSTBYNAMEv6",
  [GETHOSTBYADDR] = "GETHOSTBYADDR",
  [GETHOSTBYADDRv6] = "GETHOSTBYADDRv6",
  [SHUTDOWN] = "SHUTDOWN",
  [GETSTAT] = "GETSTAT",
  [INVALIDATE] = "INVALIDATE",
  [GETFDPW] = "GETFDPW",
  [GETFDGR] = "GETFDGR",
  [GETFDHST] = "GETFDHST",
  [GETAI] = "GETAI",
  [INITGROUPS] = "INITGROUPS",
  [GETSERVBYNAME] = "GETSERVBYNAME",
  [GETSERVBYPORT] = "GETSERVBYPORT",
  [GETFDSERV] = "GETFDSERV"
};

/* The control data structures for the services.  */
struct database_dyn dbs[lastdb] =
{
  [pwddb] = {
    .lock = PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP,
    .prunelock = PTHREAD_MUTEX_INITIALIZER,
    .enabled = 0,
    .check_file = 1,
    .persistent = 0,
    .propagate = 1,
    .shared = 0,
    .max_db_size = DEFAULT_MAX_DB_SIZE,
    .reset_res = 0,
    .filename = "/etc/passwd",
    .db_filename = _PATH_NSCD_PASSWD_DB,
    .disabled_iov = &pwd_iov_disabled,
    .postimeout = 3600,
    .negtimeout = 20,
    .wr_fd = -1,
    .ro_fd = -1,
    .mmap_used = false
  },
  [grpdb] = {
    .lock = PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP,
    .prunelock = PTHREAD_MUTEX_INITIALIZER,
    .enabled = 0,
    .check_file = 1,
    .persistent = 0,
    .propagate = 1,
    .shared = 0,
    .max_db_size = DEFAULT_MAX_DB_SIZE,
    .reset_res = 0,
    .filename = "/etc/group",
    .db_filename = _PATH_NSCD_GROUP_DB,
    .disabled_iov = &grp_iov_disabled,
    .postimeout = 3600,
    .negtimeout = 60,
    .wr_fd = -1,
    .ro_fd = -1,
    .mmap_used = false
  },
  [hstdb] = {
    .lock = PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP,
    .prunelock = PTHREAD_MUTEX_INITIALIZER,
    .enabled = 0,
    .check_file = 1,
    .persistent = 0,
    .propagate = 0,		/* Not used.  */
    .shared = 0,
    .max_db_size = DEFAULT_MAX_DB_SIZE,
    .reset_res = 1,
    .filename = "/etc/hosts",
    .db_filename = _PATH_NSCD_HOSTS_DB,
    .disabled_iov = &hst_iov_disabled,
    .postimeout = 3600,
    .negtimeout = 20,
    .wr_fd = -1,
    .ro_fd = -1,
    .mmap_used = false
  },
  [servdb] = {
    .lock = PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP,
    .prunelock = PTHREAD_MUTEX_INITIALIZER,
    .enabled = 0,
    .check_file = 1,
    .persistent = 0,
    .propagate = 0,		/* Not used.  */
    .shared = 0,
    .max_db_size = DEFAULT_MAX_DB_SIZE,
    .reset_res = 0,
    .filename = "/etc/services",
    .db_filename = _PATH_NSCD_SERVICES_DB,
    .disabled_iov = &serv_iov_disabled,
    .postimeout = 28800,
    .negtimeout = 20,
    .wr_fd = -1,
    .ro_fd = -1,
    .mmap_used = false
  }
};


/* Mapping of request type to database.  */
static struct
{
  bool data_request;
  struct database_dyn *db;
} const reqinfo[LASTREQ] =
{
  [GETPWBYNAME] = { true, &dbs[pwddb] },
  [GETPWBYUID] = { true, &dbs[pwddb] },
  [GETGRBYNAME] = { true, &dbs[grpdb] },
  [GETGRBYGID] = { true, &dbs[grpdb] },
  [GETHOSTBYNAME] = { true, &dbs[hstdb] },
  [GETHOSTBYNAMEv6] = { true, &dbs[hstdb] },
  [GETHOSTBYADDR] = { true, &dbs[hstdb] },
  [GETHOSTBYADDRv6] = { true, &dbs[hstdb] },
  [SHUTDOWN] = { false, NULL },
  [GETSTAT] = { false, NULL },
  [SHUTDOWN] = { false, NULL },
  [GETFDPW] = { false, &dbs[pwddb] },
  [GETFDGR] = { false, &dbs[grpdb] },
  [GETFDHST] = { false, &dbs[hstdb] },
  [GETAI] = { true, &dbs[hstdb] },
  [INITGROUPS] = { true, &dbs[grpdb] },
  [GETSERVBYNAME] = { true, &dbs[servdb] },
  [GETSERVBYPORT] = { true, &dbs[servdb] },
  [GETFDSERV] = { false, &dbs[servdb] }
};


/* Number of seconds between two cache pruning runs.  */
#define CACHE_PRUNE_INTERVAL	15


/* Initial number of threads to use.  */
int nthreads = -1;
/* Maximum number of threads to use.  */
int max_nthreads = 32;

/* Socket for incoming connections.  */
static int sock;

/* Number of times clients had to wait.  */
unsigned long int client_queued;


ssize_t
writeall (int fd, const void *buf, size_t len)
{
  size_t n = len;
  ssize_t ret;
  do
    {
      ret = TEMP_FAILURE_RETRY (send (fd, buf, n, MSG_NOSIGNAL));
      if (ret <= 0)
	break;
      buf = (const char *) buf + ret;
      n -= ret;
    }
  while (n > 0);
  return ret < 0 ? ret : len - n;
}


#ifdef HAVE_SENDFILE
ssize_t
sendfileall (int tofd, int fromfd, off_t off, size_t len)
{
  ssize_t n = len;
  ssize_t ret;

  do
    {
      ret = TEMP_FAILURE_RETRY (sendfile (tofd, fromfd, &off, n));
      if (ret <= 0)
	break;
      n -= ret;
    }
  while (n > 0);
  return ret < 0 ? ret : len - n;
}
#endif


enum usekey
  {
    use_not = 0,
    /* The following three are not really used, they are symbolic constants.  */
    use_first = 16,
    use_begin = 32,
    use_end = 64,

    use_he = 1,
    use_he_begin = use_he | use_begin,
    use_he_end = use_he | use_end,
#if SEPARATE_KEY
    use_key = 2,
    use_key_begin = use_key | use_begin,
    use_key_end = use_key | use_end,
    use_key_first = use_key_begin | use_first,
#endif
    use_data = 3,
    use_data_begin = use_data | use_begin,
    use_data_end = use_data | use_end,
    use_data_first = use_data_begin | use_first
  };


static int
check_use (const char *data, nscd_ssize_t first_free, uint8_t *usemap,
	   enum usekey use, ref_t start, size_t len)
{
  assert (len >= 2);

  if (start > first_free || start + len > first_free
      || (start & BLOCK_ALIGN_M1))
    return 0;

  if (usemap[start] == use_not)
    {
      /* Add the start marker.  */
      usemap[start] = use | use_begin;
      use &= ~use_first;

      while (--len > 0)
	if (usemap[++start] != use_not)
	  return 0;
	else
	  usemap[start] = use;

      /* Add the end marker.  */
      usemap[start] = use | use_end;
    }
  else if ((usemap[start] & ~use_first) == ((use | use_begin) & ~use_first))
    {
      /* Hash entries can't be shared.  */
      if (use == use_he)
	return 0;

      usemap[start] |= (use & use_first);
      use &= ~use_first;

      while (--len > 1)
	if (usemap[++start] != use)
	  return 0;

      if (usemap[++start] != (use | use_end))
	return 0;
    }
  else
    /* Points to a wrong object or somewhere in the middle.  */
    return 0;

  return 1;
}


/* Verify data in persistent database.  */
static int
verify_persistent_db (void *mem, struct database_pers_head *readhead, int dbnr)
{
  assert (dbnr == pwddb || dbnr == grpdb || dbnr == hstdb || dbnr == servdb);

  time_t now = time (NULL);

  struct database_pers_head *head = mem;
  struct database_pers_head head_copy = *head;

  /* Check that the header that was read matches the head in the database.  */
  if (readhead != NULL && memcmp (head, readhead, sizeof (*head)) != 0)
    return 0;

  /* First some easy tests: make sure the database header is sane.  */
  if (head->version != DB_VERSION
      || head->header_size != sizeof (*head)
      /* We allow a timestamp to be one hour ahead of the current time.
	 This should cover daylight saving time changes.  */
      || head->timestamp > now + 60 * 60 + 60
      || (head->gc_cycle & 1)
      || (size_t) head->module > INT32_MAX / sizeof (ref_t)
      || (size_t) head->data_size > INT32_MAX - head->module * sizeof (ref_t)
      || head->first_free < 0
      || head->first_free > head->data_size
      || (head->first_free & BLOCK_ALIGN_M1) != 0
      || head->maxnentries < 0
      || head->maxnsearched < 0)
    return 0;

  uint8_t *usemap = calloc (head->first_free, 1);
  if (usemap == NULL)
    return 0;

  const char *data = (char *) &head->array[roundup (head->module,
						    ALIGN / sizeof (ref_t))];

  nscd_ssize_t he_cnt = 0;
  for (nscd_ssize_t cnt = 0; cnt < head->module; ++cnt)
    {
      ref_t work = head->array[cnt];

      while (work != ENDREF)
	{
	  if (! check_use (data, head->first_free, usemap, use_he, work,
			   sizeof (struct hashentry)))
	    goto fail;

	  /* Now we know we can dereference the record.  */
	  struct hashentry *here = (struct hashentry *) (data + work);

	  ++he_cnt;

	  /* Make sure the record is for this type of service.  */
	  if (here->type >= LASTREQ
	      || reqinfo[here->type].db != &dbs[dbnr])
	    goto fail;

	  /* Validate boolean field value.  */
	  if (here->first != false && here->first != true)
	    goto fail;

	  if (here->len < 0)
	    goto fail;

	  /* Now the data.  */
	  if (here->packet < 0
	      || here->packet > head->first_free
	      || here->packet + sizeof (struct datahead) > head->first_free)
	    goto fail;

	  struct datahead *dh = (struct datahead *) (data + here->packet);

	  if (! check_use (data, head->first_free, usemap,
			   use_data | (here->first ? use_first : 0),
			   here->packet, dh->allocsize))
	    goto fail;

	  if (dh->allocsize < sizeof (struct datahead)
	      || dh->recsize > dh->allocsize
	      || (dh->notfound != false && dh->notfound != true)
	      || (dh->usable != false && dh->usable != true))
	    goto fail;

	  if (here->key < here->packet + sizeof (struct datahead)
	      || here->key > here->packet + dh->allocsize
	      || here->key + here->len > here->packet + dh->allocsize)
	    {
#if SEPARATE_KEY
	      /* If keys can appear outside of data, this should be done
		 instead.  But gc doesn't mark the data in that case.  */
	      if (! check_use (data, head->first_free, usemap,
			       use_key | (here->first ? use_first : 0),
			       here->key, here->len))
#endif
		goto fail;
	    }

	  work = here->next;
	}
    }

  if (he_cnt != head->nentries)
    goto fail;

  /* See if all data and keys had at least one reference from
     he->first == true hashentry.  */
  for (ref_t idx = 0; idx < head->first_free; ++idx)
    {
#if SEPARATE_KEY
      if (usemap[idx] == use_key_begin)
	goto fail;
#endif
      if (usemap[idx] == use_data_begin)
	goto fail;
    }

  /* Finally, make sure the database hasn't changed since the first test.  */
  if (memcmp (mem, &head_copy, sizeof (*head)) != 0)
    goto fail;

  free (usemap);
  return 1;

fail:
  free (usemap);
  return 0;
}


/* Initialize database information structures.  */
void
nscd_init (void)
{
  /* Look up unprivileged uid/gid/groups before we start listening on the
     socket  */
  if (server_user != NULL)
    begin_drop_privileges ();

  if (nthreads == -1)
    /* No configuration for this value, assume a default.  */
    nthreads = 2 * lastdb;

  for (size_t cnt = 0; cnt < lastdb; ++cnt)
    if (dbs[cnt].enabled)
      {
	pthread_rwlock_init (&dbs[cnt].lock, NULL);
	pthread_mutex_init (&dbs[cnt].memlock, NULL);

	if (dbs[cnt].persistent)
	  {
	    /* Try to open the appropriate file on disk.  */
	    int fd = open (dbs[cnt].db_filename, O_RDWR);
	    if (fd != -1)
	      {
		struct stat64 st;
		void *mem;
		size_t total;
		struct database_pers_head head;
		ssize_t n = TEMP_FAILURE_RETRY (read (fd, &head,
						      sizeof (head)));
		if (n != sizeof (head) || fstat64 (fd, &st) != 0)
		  {
		  fail_db:
		    dbg_log (_("invalid persistent database file \"%s\": %s"),
			     dbs[cnt].db_filename, strerror (errno));
		    unlink (dbs[cnt].db_filename);
		  }
		else if (head.module == 0 && head.data_size == 0)
		  {
		    /* The file has been created, but the head has not been
		       initialized yet.  Remove the old file.  */
		    unlink (dbs[cnt].db_filename);
		  }
		else if (head.header_size != (int) sizeof (head))
		  {
		    dbg_log (_("invalid persistent database file \"%s\": %s"),
			     dbs[cnt].db_filename,
			     _("header size does not match"));
		    unlink (dbs[cnt].db_filename);
		  }
		else if ((total = (sizeof (head)
				   + roundup (head.module * sizeof (ref_t),
					      ALIGN)
				   + head.data_size))
			 > st.st_size
			 || total < sizeof (head))
		  {
		    dbg_log (_("invalid persistent database file \"%s\": %s"),
			     dbs[cnt].db_filename,
			     _("file size does not match"));
		    unlink (dbs[cnt].db_filename);
		  }
		/* Note we map with the maximum size allowed for the
		   database.  This is likely much larger than the
		   actual file size.  This is OK on most OSes since
		   extensions of the underlying file will
		   automatically translate more pages available for
		   memory access.  */
		else if ((mem = mmap (NULL, dbs[cnt].max_db_size,
				      PROT_READ | PROT_WRITE,
				      MAP_SHARED, fd, 0))
			 == MAP_FAILED)
		  goto fail_db;
		else if (!verify_persistent_db (mem, &head, cnt))
		  {
		    munmap (mem, total);
		    dbg_log (_("invalid persistent database file \"%s\": %s"),
			     dbs[cnt].db_filename,
			     _("verification failed"));
		    unlink (dbs[cnt].db_filename);
		  }
		else
		  {
		    /* Success.  We have the database.  */
		    dbs[cnt].head = mem;
		    dbs[cnt].memsize = total;
		    dbs[cnt].data = (char *)
		      &dbs[cnt].head->array[roundup (dbs[cnt].head->module,
						     ALIGN / sizeof (ref_t))];
		    dbs[cnt].mmap_used = true;

		    if (dbs[cnt].suggested_module > head.module)
		      dbg_log (_("suggested size of table for database %s larger than the persistent database's table"),
			       dbnames[cnt]);

		    dbs[cnt].wr_fd = fd;
		    fd = -1;
		    /* We also need a read-only descriptor.  */
		    if (dbs[cnt].shared)
		      {
			dbs[cnt].ro_fd = open (dbs[cnt].db_filename, O_RDONLY);
			if (dbs[cnt].ro_fd == -1)
			  dbg_log (_("\
cannot create read-only descriptor for \"%s\"; no mmap"),
				   dbs[cnt].db_filename);
		      }

		    // XXX Shall we test whether the descriptors actually
		    // XXX point to the same file?
		  }

		/* Close the file descriptors in case something went
		   wrong in which case the variable have not been
		   assigned -1.  */
		if (fd != -1)
		  close (fd);
	      }
	  }

	if (dbs[cnt].head == NULL)
	  {
	    /* No database loaded.  Allocate the data structure,
	       possibly on disk.  */
	    struct database_pers_head head;
	    size_t total = (sizeof (head)
			    + roundup (dbs[cnt].suggested_module
				       * sizeof (ref_t), ALIGN)
			    + (dbs[cnt].suggested_module
			       * DEFAULT_DATASIZE_PER_BUCKET));

	    /* Try to create the database.  If we do not need a
	       persistent database create a temporary file.  */
	    int fd;
	    int ro_fd = -1;
	    if (dbs[cnt].persistent)
	      {
		fd = open (dbs[cnt].db_filename,
			   O_RDWR | O_CREAT | O_EXCL | O_TRUNC,
			   S_IRUSR | S_IWUSR);
		if (fd != -1 && dbs[cnt].shared)
		  ro_fd = open (dbs[cnt].db_filename, O_RDONLY);
	      }
	    else
	      {
		char fname[] = _PATH_NSCD_XYZ_DB_TMP;
		fd = mkstemp (fname);

		/* We do not need the file name anymore after we
		   opened another file descriptor in read-only mode.  */
		if (fd != -1)
		  {
		    if (dbs[cnt].shared)
		      ro_fd = open (fname, O_RDONLY);

		    unlink (fname);
		  }
	      }

	    if (fd == -1)
	      {
		if (errno == EEXIST)
		  {
		    dbg_log (_("database for %s corrupted or simultaneously used; remove %s manually if necessary and restart"),
			     dbnames[cnt], dbs[cnt].db_filename);
		    // XXX Correct way to terminate?
		    exit (1);
		  }

		if  (dbs[cnt].persistent)
		  dbg_log (_("cannot create %s; no persistent database used"),
			   dbs[cnt].db_filename);
		else
		  dbg_log (_("cannot create %s; no sharing possible"),
			   dbs[cnt].db_filename);

		dbs[cnt].persistent = 0;
		// XXX remember: no mmap
	      }
	    else
	      {
		/* Tell the user if we could not create the read-only
		   descriptor.  */
		if (ro_fd == -1 && dbs[cnt].shared)
		  dbg_log (_("\
cannot create read-only descriptor for \"%s\"; no mmap"),
			   dbs[cnt].db_filename);

		/* Before we create the header, initialiye the hash
		   table.  So that if we get interrupted if writing
		   the header we can recognize a partially initialized
		   database.  */
		size_t ps = sysconf (_SC_PAGESIZE);
		char tmpbuf[ps];
		assert (~ENDREF == 0);
		memset (tmpbuf, '\xff', ps);

		size_t remaining = dbs[cnt].suggested_module * sizeof (ref_t);
		off_t offset = sizeof (head);

		size_t towrite;
		if (offset % ps != 0)
		  {
		    towrite = MIN (remaining, ps - (offset % ps));
		    if (pwrite (fd, tmpbuf, towrite, offset) != towrite)
		      goto write_fail;
		    offset += towrite;
		    remaining -= towrite;
		  }

		while (remaining > ps)
		  {
		    if (pwrite (fd, tmpbuf, ps, offset) == -1)
		      goto write_fail;
		    offset += ps;
		    remaining -= ps;
		  }

		if (remaining > 0
		    && pwrite (fd, tmpbuf, remaining, offset) != remaining)
		  goto write_fail;

		/* Create the header of the file.  */
		struct database_pers_head head =
		  {
		    .version = DB_VERSION,
		    .header_size = sizeof (head),
		    .module = dbs[cnt].suggested_module,
		    .data_size = (dbs[cnt].suggested_module
				  * DEFAULT_DATASIZE_PER_BUCKET),
		    .first_free = 0
		  };
		void *mem;

		if ((TEMP_FAILURE_RETRY (write (fd, &head, sizeof (head)))
		     != sizeof (head))
		    || (TEMP_FAILURE_RETRY_VAL (posix_fallocate (fd, 0, total))
			!= 0)
		    || (mem = mmap (NULL, dbs[cnt].max_db_size,
				    PROT_READ | PROT_WRITE,
				    MAP_SHARED, fd, 0)) == MAP_FAILED)
		  {
		  write_fail:
		    unlink (dbs[cnt].db_filename);
		    dbg_log (_("cannot write to database file %s: %s"),
			     dbs[cnt].db_filename, strerror (errno));
		    dbs[cnt].persistent = 0;
		  }
		else
		  {
		    /* Success.  */
		    dbs[cnt].head = mem;
		    dbs[cnt].data = (char *)
		      &dbs[cnt].head->array[roundup (dbs[cnt].head->module,
						     ALIGN / sizeof (ref_t))];
		    dbs[cnt].memsize = total;
		    dbs[cnt].mmap_used = true;

		    /* Remember the descriptors.  */
		    dbs[cnt].wr_fd = fd;
		    dbs[cnt].ro_fd = ro_fd;
		    fd = -1;
		    ro_fd = -1;
		  }

		if (fd != -1)
		  close (fd);
		if (ro_fd != -1)
		  close (ro_fd);
	      }
	  }

	if (paranoia
	    && ((dbs[cnt].wr_fd != -1
		 && fcntl (dbs[cnt].wr_fd, F_SETFD, FD_CLOEXEC) == -1)
		|| (dbs[cnt].ro_fd != -1
		    && fcntl (dbs[cnt].ro_fd, F_SETFD, FD_CLOEXEC) == -1)))
	  {
	    dbg_log (_("\
cannot set socket to close on exec: %s; disabling paranoia mode"),
		     strerror (errno));
	    paranoia = 0;
	  }

	if (dbs[cnt].head == NULL)
	  {
	    /* We do not use the persistent database.  Just
	       create an in-memory data structure.  */
	    assert (! dbs[cnt].persistent);

	    dbs[cnt].head = xmalloc (sizeof (struct database_pers_head)
				     + (dbs[cnt].suggested_module
					* sizeof (ref_t)));
	    memset (dbs[cnt].head, '\0', sizeof (struct database_pers_head));
	    assert (~ENDREF == 0);
	    memset (dbs[cnt].head->array, '\xff',
		    dbs[cnt].suggested_module * sizeof (ref_t));
	    dbs[cnt].head->module = dbs[cnt].suggested_module;
	    dbs[cnt].head->data_size = (DEFAULT_DATASIZE_PER_BUCKET
					* dbs[cnt].head->module);
	    dbs[cnt].data = xmalloc (dbs[cnt].head->data_size);
	    dbs[cnt].head->first_free = 0;

	    dbs[cnt].shared = 0;
	    assert (dbs[cnt].ro_fd == -1);
	  }

	if (dbs[cnt].check_file)
	  {
	    /* We need the modification date of the file.  */
	    struct stat64 st;

	    if (stat64 (dbs[cnt].filename, &st) < 0)
	      {
		/* We cannot stat() the file, disable file checking.  */
		dbg_log (_("cannot stat() file `%s': %s"),
			 dbs[cnt].filename, strerror (errno));
		dbs[cnt].check_file = 0;
	      }
	    else
	      dbs[cnt].file_mtime = st.st_mtime;
	  }
      }

  /* Create the socket.  */
  sock = socket (AF_UNIX, SOCK_STREAM, 0);
  if (sock < 0)
    {
      dbg_log (_("cannot open socket: %s"), strerror (errno));
      exit (errno == EACCES ? 4 : 1);
    }
  /* Bind a name to the socket.  */
  struct sockaddr_un sock_addr;
  sock_addr.sun_family = AF_UNIX;
  strcpy (sock_addr.sun_path, _PATH_NSCDSOCKET);
  if (bind (sock, (struct sockaddr *) &sock_addr, sizeof (sock_addr)) < 0)
    {
      dbg_log ("%s: %s", _PATH_NSCDSOCKET, strerror (errno));
      exit (errno == EACCES ? 4 : 1);
    }

  /* We don't want to get stuck on accept.  */
  int fl = fcntl (sock, F_GETFL);
  if (fl == -1 || fcntl (sock, F_SETFL, fl | O_NONBLOCK) == -1)
    {
      dbg_log (_("cannot change socket to nonblocking mode: %s"),
	       strerror (errno));
      exit (1);
    }

  /* The descriptor needs to be closed on exec.  */
  if (paranoia && fcntl (sock, F_SETFD, FD_CLOEXEC) == -1)
    {
      dbg_log (_("cannot set socket to close on exec: %s"),
	       strerror (errno));
      exit (1);
    }

  /* Set permissions for the socket.  */
  chmod (_PATH_NSCDSOCKET, DEFFILEMODE);

  /* Set the socket up to accept connections.  */
  if (listen (sock, SOMAXCONN) < 0)
    {
      dbg_log (_("cannot enable socket to accept connections: %s"),
	       strerror (errno));
      exit (1);
    }

  /* Change to unprivileged uid/gid/groups if specifed in config file */
  if (server_user != NULL)
    finish_drop_privileges ();
}


/* Close the connections.  */
void
close_sockets (void)
{
  close (sock);
}


static void
invalidate_cache (char *key, int fd)
{
  dbtype number;
  int32_t resp;

  for (number = pwddb; number < lastdb; ++number)
    if (strcmp (key, dbnames[number]) == 0)
      {
	if (dbs[number].reset_res)
	  res_init ();

	break;
      }

  if (number == lastdb)
    {
      resp = EINVAL;
      writeall (fd, &resp, sizeof (resp));
      return;
    }

  if (dbs[number].enabled)
    prune_cache (&dbs[number], LONG_MAX, fd);
  else
    {
      resp = 0;
      writeall (fd, &resp, sizeof (resp));
    }
}


#ifdef SCM_RIGHTS
static void
send_ro_fd (struct database_dyn *db, char *key, int fd)
{
  /* If we do not have an read-only file descriptor do nothing.  */
  if (db->ro_fd == -1)
    return;

  /* We need to send some data along with the descriptor.  */
  struct iovec iov[1];
  iov[0].iov_base = key;
  iov[0].iov_len = strlen (key) + 1;

  /* Prepare the control message to transfer the descriptor.  */
  union
  {
    struct cmsghdr hdr;
    char bytes[CMSG_SPACE (sizeof (int))];
  } buf;
  struct msghdr msg = { .msg_iov = iov, .msg_iovlen = 1,
			.msg_control = buf.bytes,
			.msg_controllen = sizeof (buf) };
  struct cmsghdr *cmsg = CMSG_FIRSTHDR (&msg);

  cmsg->cmsg_level = SOL_SOCKET;
  cmsg->cmsg_type = SCM_RIGHTS;
  cmsg->cmsg_len = CMSG_LEN (sizeof (int));

  *(int *) CMSG_DATA (cmsg) = db->ro_fd;

  msg.msg_controllen = cmsg->cmsg_len;

  /* Send the control message.  We repeat when we are interrupted but
     everything else is ignored.  */
#ifndef MSG_NOSIGNAL
# define MSG_NOSIGNAL 0
#endif
  (void) TEMP_FAILURE_RETRY (sendmsg (fd, &msg, MSG_NOSIGNAL));

  if (__builtin_expect (debug_level > 0, 0))
    dbg_log (_("provide access to FD %d, for %s"), db->ro_fd, key);
}
#endif	/* SCM_RIGHTS */


/* Handle new request.  */
static void
handle_request (int fd, request_header *req, void *key, uid_t uid)
{
  if (__builtin_expect (req->version, NSCD_VERSION) != NSCD_VERSION)
    {
      if (debug_level > 0)
	dbg_log (_("\
cannot handle old request version %d; current version is %d"),
		 req->version, NSCD_VERSION);
      return;
    }

  /* Make the SELinux check before we go on to the standard checks.  */
  if (selinux_enabled && nscd_request_avc_has_perm (fd, req->type) != 0)
    return;

  struct database_dyn *db = reqinfo[req->type].db;

  /* See whether we can service the request from the cache.  */
  if (__builtin_expect (reqinfo[req->type].data_request, true))
    {
      if (__builtin_expect (debug_level, 0) > 0)
	{
	  if (req->type == GETHOSTBYADDR || req->type == GETHOSTBYADDRv6)
	    {
	      char buf[INET6_ADDRSTRLEN];

	      dbg_log ("\t%s (%s)", serv2str[req->type],
		       inet_ntop (req->type == GETHOSTBYADDR
				  ? AF_INET : AF_INET6,
				  key, buf, sizeof (buf)));
	    }
	  else
	    dbg_log ("\t%s (%s)", serv2str[req->type], (char *) key);
	}

      /* Is this service enabled?  */
      if (__builtin_expect (!db->enabled, 0))
	{
	  /* No, sent the prepared record.  */
	  if (TEMP_FAILURE_RETRY (send (fd, db->disabled_iov->iov_base,
					db->disabled_iov->iov_len,
					MSG_NOSIGNAL))
	      != (ssize_t) db->disabled_iov->iov_len
	      && __builtin_expect (debug_level, 0) > 0)
	    {
	      /* We have problems sending the result.  */
	      char buf[256];
	      dbg_log (_("cannot write result: %s"),
		       strerror_r (errno, buf, sizeof (buf)));
	    }

	  return;
	}

      /* Be sure we can read the data.  */
      if (__builtin_expect (pthread_rwlock_tryrdlock (&db->lock) != 0, 0))
	{
	  ++db->head->rdlockdelayed;
	  pthread_rwlock_rdlock (&db->lock);
	}

      /* See whether we can handle it from the cache.  */
      struct datahead *cached;
      cached = (struct datahead *) cache_search (req->type, key, req->key_len,
						 db, uid);
      if (cached != NULL)
	{
	  /* Hurray it's in the cache.  */
	  ssize_t nwritten;

#ifdef HAVE_SENDFILE
	  if (db->mmap_used || !cached->notfound)
	    {
	      assert (db->wr_fd != -1);
	      assert ((char *) cached->data > (char *) db->data);
	      assert ((char *) cached->data - (char *) db->head
		      + cached->recsize
		      <= (sizeof (struct database_pers_head)
			  + db->head->module * sizeof (ref_t)
			  + db->head->data_size));
	      nwritten = sendfileall (fd, db->wr_fd,
				      (char *) cached->data
				      - (char *) db->head, cached->recsize);
# ifndef __ASSUME_SENDFILE
	      if (nwritten == -1 && errno == ENOSYS)
		goto use_write;
# endif
	    }
	  else
# ifndef __ASSUME_SENDFILE
	  use_write:
# endif
#endif
	    nwritten = writeall (fd, cached->data, cached->recsize);

	  if (nwritten != cached->recsize
	      && __builtin_expect (debug_level, 0) > 0)
	    {
	      /* We have problems sending the result.  */
	      char buf[256];
	      dbg_log (_("cannot write result: %s"),
		       strerror_r (errno, buf, sizeof (buf)));
	    }

	  pthread_rwlock_unlock (&db->lock);

	  return;
	}

      pthread_rwlock_unlock (&db->lock);
    }
  else if (__builtin_expect (debug_level, 0) > 0)
    {
      if (req->type == INVALIDATE)
	dbg_log ("\t%s (%s)", serv2str[req->type], (char *) key);
      else
	dbg_log ("\t%s", serv2str[req->type]);
    }

  /* Handle the request.  */
  switch (req->type)
    {
    case GETPWBYNAME:
      addpwbyname (db, fd, req, key, uid);
      break;

    case GETPWBYUID:
      addpwbyuid (db, fd, req, key, uid);
      break;

    case GETGRBYNAME:
      addgrbyname (db, fd, req, key, uid);
      break;

    case GETGRBYGID:
      addgrbygid (db, fd, req, key, uid);
      break;

    case GETHOSTBYNAME:
      addhstbyname (db, fd, req, key, uid);
      break;

    case GETHOSTBYNAMEv6:
      addhstbynamev6 (db, fd, req, key, uid);
      break;

    case GETHOSTBYADDR:
      addhstbyaddr (db, fd, req, key, uid);
      break;

    case GETHOSTBYADDRv6:
      addhstbyaddrv6 (db, fd, req, key, uid);
      break;

    case GETAI:
      addhstai (db, fd, req, key, uid);
      break;

    case INITGROUPS:
      addinitgroups (db, fd, req, key, uid);
      break;

    case GETSERVBYNAME:
      addservbyname (db, fd, req, key, uid);
      break;

    case GETSERVBYPORT:
      addservbyport (db, fd, req, key, uid);
      break;

    case GETSTAT:
    case SHUTDOWN:
    case INVALIDATE:
      {
	/* Get the callers credentials.  */
#ifdef SO_PEERCRED
	struct ucred caller;
	socklen_t optlen = sizeof (caller);

	if (getsockopt (fd, SOL_SOCKET, SO_PEERCRED, &caller, &optlen) < 0)
	  {
	    char buf[256];

	    dbg_log (_("error getting caller's id: %s"),
		     strerror_r (errno, buf, sizeof (buf)));
	    break;
	  }

	uid = caller.uid;
#else
	/* Some systems have no SO_PEERCRED implementation.  They don't
	   care about security so we don't as well.  */
	uid = 0;
#endif
      }

      /* Accept shutdown, getstat and invalidate only from root.  For
	 the stat call also allow the user specified in the config file.  */
      if (req->type == GETSTAT)
	{
	  if (uid == 0 || uid == stat_uid)
	    send_stats (fd, dbs);
	}
      else if (uid == 0)
	{
	  if (req->type == INVALIDATE)
	    invalidate_cache (key, fd);
	  else
	    termination_handler (0);
	}
      break;

    case GETFDPW:
    case GETFDGR:
    case GETFDHST:
    case GETFDSERV:
#ifdef SCM_RIGHTS
      send_ro_fd (reqinfo[req->type].db, key, fd);
#endif
      break;

    default:
      /* Ignore the command, it's nothing we know.  */
      break;
    }
}


/* Restart the process.  */
static void
restart (void)
{
  /* First determine the parameters.  We do not use the parameters
     passed to main() since in case nscd is started by running the
     dynamic linker this will not work.  Yes, this is not the usual
     case but nscd is part of glibc and we occasionally do this.  */
  size_t buflen = 1024;
  char *buf = alloca (buflen);
  size_t readlen = 0;
  int fd = open ("/proc/self/cmdline", O_RDONLY);
  if (fd == -1)
    {
      dbg_log (_("\
cannot open /proc/self/cmdline: %s; disabling paranoia mode"),
	       strerror (errno));

      paranoia = 0;
      return;
    }

  while (1)
    {
      ssize_t n = TEMP_FAILURE_RETRY (read (fd, buf + readlen,
					    buflen - readlen));
      if (n == -1)
	{
	  dbg_log (_("\
cannot read /proc/self/cmdline: %s; disabling paranoia mode"),
		   strerror (errno));

	  close (fd);
	  paranoia = 0;
	  return;
	}

      readlen += n;

      if (readlen < buflen)
	break;

      /* We might have to extend the buffer.  */
      size_t old_buflen = buflen;
      char *newp = extend_alloca (buf, buflen, 2 * buflen);
      buf = memmove (newp, buf, old_buflen);
    }

  close (fd);

  /* Parse the command line.  Worst case scenario: every two
     characters form one parameter (one character plus NUL).  */
  char **argv = alloca ((readlen / 2 + 1) * sizeof (argv[0]));
  int argc = 0;

  char *cp = buf;
  while (cp < buf + readlen)
    {
      argv[argc++] = cp;
      cp = (char *) rawmemchr (cp, '\0') + 1;
    }
  argv[argc] = NULL;

  /* Second, change back to the old user if we changed it.  */
  if (server_user != NULL)
    {
      if (setresuid (old_uid, old_uid, old_uid) != 0)
	{
	  dbg_log (_("\
cannot change to old UID: %s; disabling paranoia mode"),
		   strerror (errno));

	  paranoia = 0;
	  return;
	}

      if (setresgid (old_gid, old_gid, old_gid) != 0)
	{
	  dbg_log (_("\
cannot change to old GID: %s; disabling paranoia mode"),
		   strerror (errno));

	  setuid (server_uid);
	  paranoia = 0;
	  return;
	}
    }

  /* Next change back to the old working directory.  */
  if (chdir (oldcwd) == -1)
    {
      dbg_log (_("\
cannot change to old working directory: %s; disabling paranoia mode"),
	       strerror (errno));

      if (server_user != NULL)
	{
	  setuid (server_uid);
	  setgid (server_gid);
	}
      paranoia = 0;
      return;
    }

  /* Synchronize memory.  */
  for (int cnt = 0; cnt < lastdb; ++cnt)
    {
      /* Make sure nobody keeps using the database.  */
      dbs[cnt].head->timestamp = 0;

      if (dbs[cnt].persistent)
	// XXX async OK?
	msync (dbs[cnt].head, dbs[cnt].memsize, MS_ASYNC);
    }

  /* The preparations are done.  */
  execv ("/proc/self/exe", argv);

  /* If we come here, we will never be able to re-exec.  */
  dbg_log (_("re-exec failed: %s; disabling paranoia mode"),
	   strerror (errno));

  if (server_user != NULL)
    {
      setuid (server_uid);
      setgid (server_gid);
    }
  if (chdir ("/") != 0)
    dbg_log (_("cannot change current working directory to \"/\": %s"),
	     strerror (errno));
  paranoia = 0;
}


/* List of file descriptors.  */
struct fdlist
{
  int fd;
  struct fdlist *next;
};
/* Memory allocated for the list.  */
static struct fdlist *fdlist;
/* List of currently ready-to-read file descriptors.  */
static struct fdlist *readylist;

/* Conditional variable and mutex to signal availability of entries in
   READYLIST.  The condvar is initialized dynamically since we might
   use a different clock depending on availability.  */
static pthread_cond_t readylist_cond;
static pthread_mutex_t readylist_lock = PTHREAD_MUTEX_INITIALIZER;

/* The clock to use with the condvar.  */
static clockid_t timeout_clock = CLOCK_REALTIME;

/* Number of threads ready to handle the READYLIST.  */
static unsigned long int nready;


/* This is the main loop.  It is replicated in different threads but the
   `poll' call makes sure only one thread handles an incoming connection.  */
static void *
__attribute__ ((__noreturn__))
nscd_run (void *p)
{
  const long int my_number = (long int) p;
  const int run_prune = my_number < lastdb && dbs[my_number].enabled;
  struct timespec prune_ts;
  int to = 0;
  char buf[256];

  if (run_prune)
    {
      setup_thread (&dbs[my_number]);

      /* We are running.  */
      dbs[my_number].head->timestamp = time (NULL);

      if (clock_gettime (timeout_clock, &prune_ts) == -1)
	/* Should never happen.  */
	abort ();

      /* Compute timeout time.  */
      prune_ts.tv_sec += CACHE_PRUNE_INTERVAL;
    }

  /* Initial locking.  */
  pthread_mutex_lock (&readylist_lock);

  /* One more thread available.  */
  ++nready;

  while (1)
    {
      while (readylist == NULL)
	{
	  if (run_prune)
	    {
	      /* Wait, but not forever.  */
	      to = pthread_cond_timedwait (&readylist_cond, &readylist_lock,
					   &prune_ts);

	      /* If we were woken and there is no work to be done,
		 just start pruning.  */
	      if (readylist == NULL && to == ETIMEDOUT)
		{
		  --nready;
		  pthread_mutex_unlock (&readylist_lock);
		  goto only_prune;
		}
	    }
	  else
	    /* No need to timeout.  */
	    pthread_cond_wait (&readylist_cond, &readylist_lock);
	}

      struct fdlist *it = readylist->next;
      if (readylist->next == readylist)
	/* Just one entry on the list.  */
	readylist = NULL;
      else
	readylist->next = it->next;

      /* Extract the information and mark the record ready to be used
	 again.  */
      int fd = it->fd;
      it->next = NULL;

      /* One more thread available.  */
      --nready;

      /* We are done with the list.  */
      pthread_mutex_unlock (&readylist_lock);

      /* We do not want to block on a short read or so.  */
      int fl = fcntl (fd, F_GETFL);
      if (fl == -1 || fcntl (fd, F_SETFL, fl | O_NONBLOCK) == -1)
	goto close_and_out;

      /* Now read the request.  */
      request_header req;
      if (__builtin_expect (TEMP_FAILURE_RETRY (read (fd, &req, sizeof (req)))
			    != sizeof (req), 0))
	{
	  /* We failed to read data.  Note that this also might mean we
	     failed because we would have blocked.  */
	  if (debug_level > 0)
	    dbg_log (_("short read while reading request: %s"),
		     strerror_r (errno, buf, sizeof (buf)));
	  goto close_and_out;
	}

      /* Check whether this is a valid request type.  */
      if (req.type < GETPWBYNAME || req.type >= LASTREQ)
	goto close_and_out;

      /* Some systems have no SO_PEERCRED implementation.  They don't
	 care about security so we don't as well.  */
      uid_t uid = -1;
#ifdef SO_PEERCRED
      pid_t pid = 0;

      if (__builtin_expect (debug_level > 0, 0))
	{
	  struct ucred caller;
	  socklen_t optlen = sizeof (caller);

	  if (getsockopt (fd, SOL_SOCKET, SO_PEERCRED, &caller, &optlen) == 0)
	    pid = caller.pid;
	}
#endif

      /* It should not be possible to crash the nscd with a silly
	 request (i.e., a terribly large key).  We limit the size to 1kb.  */
      if (__builtin_expect (req.key_len, 1) < 0
	  || __builtin_expect (req.key_len, 1) > MAXKEYLEN)
	{
	  if (debug_level > 0)
	    dbg_log (_("key length in request too long: %d"), req.key_len);
	}
      else
	{
	  /* Get the key.  */
	  char keybuf[MAXKEYLEN];

	  if (__builtin_expect (TEMP_FAILURE_RETRY (read (fd, keybuf,
							  req.key_len))
				!= req.key_len, 0))
	    {
	      /* Again, this can also mean we would have blocked.  */
	      if (debug_level > 0)
		dbg_log (_("short read while reading request key: %s"),
			 strerror_r (errno, buf, sizeof (buf)));
	      goto close_and_out;
	    }

	  if (__builtin_expect (debug_level, 0) > 0)
	    {
#ifdef SO_PEERCRED
	      if (pid != 0)
		dbg_log (_("\
handle_request: request received (Version = %d) from PID %ld"),
			 req.version, (long int) pid);
	      else
#endif
		dbg_log (_("\
handle_request: request received (Version = %d)"), req.version);
	    }

	  /* Phew, we got all the data, now process it.  */
	  handle_request (fd, &req, keybuf, uid);
	}

    close_and_out:
      /* We are done.  */
      close (fd);

      /* Check whether we should be pruning the cache. */
      assert (run_prune || to == 0);
      if (to == ETIMEDOUT)
	{
	only_prune:
	  /* The pthread_cond_timedwait() call timed out.  It is time
		 to clean up the cache.  */
	  assert (my_number < lastdb);
	  prune_cache (&dbs[my_number], time (NULL), -1);

	  if (clock_gettime (timeout_clock, &prune_ts) == -1)
	    /* Should never happen.  */
	    abort ();

	  /* Compute next timeout time.  */
	  prune_ts.tv_sec += CACHE_PRUNE_INTERVAL;

	  /* In case the list is emtpy we do not want to run the prune
	     code right away again.  */
	  to = 0;
	}

      /* Re-locking.  */
      pthread_mutex_lock (&readylist_lock);

      /* One more thread available.  */
      ++nready;
    }
}


static unsigned int nconns;

static void
fd_ready (int fd)
{
  pthread_mutex_lock (&readylist_lock);

  /* Find an empty entry in FDLIST.  */
  size_t inner;
  for (inner = 0; inner < nconns; ++inner)
    if (fdlist[inner].next == NULL)
      break;
  assert (inner < nconns);

  fdlist[inner].fd = fd;

  if (readylist == NULL)
    readylist = fdlist[inner].next = &fdlist[inner];
  else
    {
      fdlist[inner].next = readylist->next;
      readylist = readylist->next = &fdlist[inner];
    }

  bool do_signal = true;
  if (__builtin_expect (nready == 0, 0))
    {
      ++client_queued;
      do_signal = false;

      /* Try to start another thread to help out.  */
      pthread_t th;
      if (nthreads < max_nthreads
	  && pthread_create (&th, &attr, nscd_run,
			     (void *) (long int) nthreads) == 0)
	{
	  /* We got another thread.  */
	  ++nthreads;
	  /* The new thread might need a kick.  */
	  do_signal = true;
	}

    }

  pthread_mutex_unlock (&readylist_lock);

  /* Tell one of the worker threads there is work to do.  */
  if (do_signal)
    pthread_cond_signal (&readylist_cond);
}


/* Check whether restarting should happen.  */
static inline int
restart_p (time_t now)
{
  return (paranoia && readylist == NULL && nready == nthreads
	  && now >= restart_time);
}


/* Array for times a connection was accepted.  */
static time_t *starttime;


static void
__attribute__ ((__noreturn__))
main_loop_poll (void)
{
  struct pollfd *conns = (struct pollfd *) xmalloc (nconns
						    * sizeof (conns[0]));

  conns[0].fd = sock;
  conns[0].events = POLLRDNORM;
  size_t nused = 1;
  size_t firstfree = 1;

  while (1)
    {
      /* Wait for any event.  We wait at most a couple of seconds so
	 that we can check whether we should close any of the accepted
	 connections since we have not received a request.  */
#define MAX_ACCEPT_TIMEOUT 30
#define MIN_ACCEPT_TIMEOUT 5
#define MAIN_THREAD_TIMEOUT \
  (MAX_ACCEPT_TIMEOUT * 1000						      \
   - ((MAX_ACCEPT_TIMEOUT - MIN_ACCEPT_TIMEOUT) * 1000 * nused) / (2 * nconns))

      int n = poll (conns, nused, MAIN_THREAD_TIMEOUT);

      time_t now = time (NULL);

      /* If there is a descriptor ready for reading or there is a new
	 connection, process this now.  */
      if (n > 0)
	{
	  if (conns[0].revents != 0)
	    {
	      /* We have a new incoming connection.  Accept the connection.  */
	      int fd = TEMP_FAILURE_RETRY (accept (sock, NULL, NULL));

	      /* Use the descriptor if we have not reached the limit.  */
	      if (fd >= 0)
		{
		  if (firstfree < nconns)
		    {
		      conns[firstfree].fd = fd;
		      conns[firstfree].events = POLLRDNORM;
		      starttime[firstfree] = now;
		      if (firstfree >= nused)
			nused = firstfree + 1;

		      do
			++firstfree;
		      while (firstfree < nused && conns[firstfree].fd != -1);
		    }
		  else
		    /* We cannot use the connection so close it.  */
		    close (fd);
		}

	      --n;
	    }

	  for (size_t cnt = 1; cnt < nused && n > 0; ++cnt)
	    if (conns[cnt].revents != 0)
	      {
		fd_ready (conns[cnt].fd);

		/* Clean up the CONNS array.  */
		conns[cnt].fd = -1;
		if (cnt < firstfree)
		  firstfree = cnt;
		if (cnt == nused - 1)
		  do
		    --nused;
		  while (conns[nused - 1].fd == -1);

		--n;
	      }
	}

      /* Now find entries which have timed out.  */
      assert (nused > 0);

      /* We make the timeout length depend on the number of file
	 descriptors currently used.  */
#define ACCEPT_TIMEOUT \
  (MAX_ACCEPT_TIMEOUT							      \
   - ((MAX_ACCEPT_TIMEOUT - MIN_ACCEPT_TIMEOUT) * nused) / nconns)
      time_t laststart = now - ACCEPT_TIMEOUT;

      for (size_t cnt = nused - 1; cnt > 0; --cnt)
	{
	  if (conns[cnt].fd != -1 && starttime[cnt] < laststart)
	    {
	      /* Remove the entry, it timed out.  */
	      (void) close (conns[cnt].fd);
	      conns[cnt].fd = -1;

	      if (cnt < firstfree)
		firstfree = cnt;
	      if (cnt == nused - 1)
		do
		  --nused;
		while (conns[nused - 1].fd == -1);
	    }
	}

      if (restart_p (now))
	restart ();
    }
}


#ifdef HAVE_EPOLL
static void
main_loop_epoll (int efd)
{
  struct epoll_event ev = { 0, };
  int nused = 1;
  size_t highest = 0;

  /* Add the socket.  */
  ev.events = EPOLLRDNORM;
  ev.data.fd = sock;
  if (epoll_ctl (efd, EPOLL_CTL_ADD, sock, &ev) == -1)
    /* We cannot use epoll.  */
    return;

  while (1)
    {
      struct epoll_event revs[100];
# define nrevs (sizeof (revs) / sizeof (revs[0]))

      int n = epoll_wait (efd, revs, nrevs, MAIN_THREAD_TIMEOUT);

      time_t now = time (NULL);

      for (int cnt = 0; cnt < n; ++cnt)
	if (revs[cnt].data.fd == sock)
	  {
	    /* A new connection.  */
	    int fd = TEMP_FAILURE_RETRY (accept (sock, NULL, NULL));

	    if (fd >= 0)
	      {
		/* Try to add the  new descriptor.  */
		ev.data.fd = fd;
		if (fd >= nconns
		    || epoll_ctl (efd, EPOLL_CTL_ADD, fd, &ev) == -1)
		  /* The descriptor is too large or something went
		     wrong.  Close the descriptor.  */
		  close (fd);
		else
		  {
		    /* Remember when we accepted the connection.  */
		    starttime[fd] = now;

		    if (fd > highest)
		      highest = fd;

		    ++nused;
		  }
	      }
	  }
	else
	  {
	    /* Remove the descriptor from the epoll descriptor.  */
	    (void) epoll_ctl (efd, EPOLL_CTL_DEL, revs[cnt].data.fd, NULL);

	    /* Get a worker to handle the request.  */
	    fd_ready (revs[cnt].data.fd);

	    /* Reset the time.  */
	    starttime[revs[cnt].data.fd] = 0;
	    if (revs[cnt].data.fd == highest)
	      do
		--highest;
	      while (highest > 0 && starttime[highest] == 0);

	    --nused;
	  }

      /*  Now look for descriptors for accepted connections which have
	  no reply in too long of a time.  */
      time_t laststart = now - ACCEPT_TIMEOUT;
      for (int cnt = highest; cnt > STDERR_FILENO; --cnt)
	if (cnt != sock && starttime[cnt] != 0 && starttime[cnt] < laststart)
	  {
	    /* We are waiting for this one for too long.  Close it.  */
	    (void) epoll_ctl (efd, EPOLL_CTL_DEL, cnt, NULL);

	    (void) close (cnt);

	    starttime[cnt] = 0;
	    if (cnt == highest)
	      --highest;
	  }
	else if (cnt != sock && starttime[cnt] == 0 && cnt == highest)
	  --highest;

      if (restart_p (now))
	restart ();
    }
}
#endif


/* Start all the threads we want.  The initial process is thread no. 1.  */
void
start_threads (void)
{
  /* Initialize the conditional variable we will use.  The only
     non-standard attribute we might use is the clock selection.  */
  pthread_condattr_t condattr;
  pthread_condattr_init (&condattr);

#if defined _POSIX_CLOCK_SELECTION && _POSIX_CLOCK_SELECTION >= 0 \
    && defined _POSIX_MONOTONIC_CLOCK && _POSIX_MONOTONIC_CLOCK >= 0
  /* Determine whether the monotonous clock is available.  */
  struct timespec dummy;
# if _POSIX_MONOTONIC_CLOCK == 0
  if (sysconf (_SC_MONOTONIC_CLOCK) > 0)
# endif
# if _POSIX_CLOCK_SELECTION == 0
    if (sysconf (_SC_CLOCK_SELECTION) > 0)
# endif
      if (clock_getres (CLOCK_MONOTONIC, &dummy) == 0
	  && pthread_condattr_setclock (&condattr, CLOCK_MONOTONIC) == 0)
	timeout_clock = CLOCK_MONOTONIC;
#endif

  pthread_cond_init (&readylist_cond, &condattr);
  pthread_condattr_destroy (&condattr);


  /* Create the attribute for the threads.  They are all created
     detached.  */
  pthread_attr_init (&attr);
  pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
  /* Use 1MB stacks, twice as much for 64-bit architectures.  */
  pthread_attr_setstacksize (&attr, 1024 * 1024 * (sizeof (void *) / 4));

  /* We allow less than LASTDB threads only for debugging.  */
  if (debug_level == 0)
    nthreads = MAX (nthreads, lastdb);

  int nfailed = 0;
  for (long int i = 0; i < nthreads; ++i)
    {
      pthread_t th;
      if (pthread_create (&th, &attr, nscd_run, (void *) (i - nfailed)) != 0)
	++nfailed;
    }
  if (nthreads - nfailed < lastdb)
    {
      /* We could not start enough threads.  */
      dbg_log (_("could only start %d threads; terminating"),
	       nthreads - nfailed);
      exit (1);
    }

  /* Determine how much room for descriptors we should initially
     allocate.  This might need to change later if we cap the number
     with MAXCONN.  */
  const long int nfds = sysconf (_SC_OPEN_MAX);
#define MINCONN 32
#define MAXCONN 16384
  if (nfds == -1 || nfds > MAXCONN)
    nconns = MAXCONN;
  else if (nfds < MINCONN)
    nconns = MINCONN;
  else
    nconns = nfds;

  /* We need memory to pass descriptors on to the worker threads.  */
  fdlist = (struct fdlist *) xcalloc (nconns, sizeof (fdlist[0]));
  /* Array to keep track when connection was accepted.  */
  starttime = (time_t *) xcalloc (nconns, sizeof (starttime[0]));

  /* In the main thread we execute the loop which handles incoming
     connections.  */
#ifdef HAVE_EPOLL
  int efd = epoll_create (100);
  if (efd != -1)
    {
      main_loop_epoll (efd);
      close (efd);
    }
#endif

  main_loop_poll ();
}


/* Look up the uid, gid, and supplementary groups to run nscd as. When
   this function is called, we are not listening on the nscd socket yet so
   we can just use the ordinary lookup functions without causing a lockup  */
static void
begin_drop_privileges (void)
{
  struct passwd *pwd = getpwnam (server_user);

  if (pwd == NULL)
    {
      dbg_log (_("Failed to run nscd as user '%s'"), server_user);
      error (EXIT_FAILURE, 0, _("Failed to run nscd as user '%s'"),
	     server_user);
    }

  server_uid = pwd->pw_uid;
  server_gid = pwd->pw_gid;

  /* Save the old UID/GID if we have to change back.  */
  if (paranoia)
    {
      old_uid = getuid ();
      old_gid = getgid ();
    }

  if (getgrouplist (server_user, server_gid, NULL, &server_ngroups) == 0)
    {
      /* This really must never happen.  */
      dbg_log (_("Failed to run nscd as user '%s'"), server_user);
      error (EXIT_FAILURE, errno, _("initial getgrouplist failed"));
    }

  server_groups = (gid_t *) xmalloc (server_ngroups * sizeof (gid_t));

  if (getgrouplist (server_user, server_gid, server_groups, &server_ngroups)
      == -1)
    {
      dbg_log (_("Failed to run nscd as user '%s'"), server_user);
      error (EXIT_FAILURE, errno, _("getgrouplist failed"));
    }
}


/* Call setgroups(), setgid(), and setuid() to drop root privileges and
   run nscd as the user specified in the configuration file.  */
static void
finish_drop_privileges (void)
{
#if defined HAVE_LIBAUDIT && defined HAVE_LIBCAP
  /* We need to preserve the capabilities to connect to the audit daemon.  */
  cap_t new_caps = preserve_capabilities ();
#endif

  if (setgroups (server_ngroups, server_groups) == -1)
    {
      dbg_log (_("Failed to run nscd as user '%s'"), server_user);
      error (EXIT_FAILURE, errno, _("setgroups failed"));
    }

  int res;
  if (paranoia)
    res = setresgid (server_gid, server_gid, old_gid);
  else
    res = setgid (server_gid);
  if (res == -1)
    {
      dbg_log (_("Failed to run nscd as user '%s'"), server_user);
      perror ("setgid");
      exit (4);
    }

  if (paranoia)
    res = setresuid (server_uid, server_uid, old_uid);
  else
    res = setuid (server_uid);
  if (res == -1)
    {
      dbg_log (_("Failed to run nscd as user '%s'"), server_user);
      perror ("setuid");
      exit (4);
    }

#if defined HAVE_LIBAUDIT && defined HAVE_LIBCAP
  /* Remove the temporary capabilities.  */
  install_real_capabilities (new_caps);
#endif
}