aboutsummaryrefslogtreecommitdiff
path: root/networking/udhcp/dhcpc.c
blob: dfd5ca6061aa8519748667ce9e6848e58f415d88 (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
/* vi: set sw=4 ts=4: */
/*
 * udhcp client
 *
 * Russ Dill <Russ.Dill@asu.edu> July 2001
 *
 * 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; either 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
#include <syslog.h>
/* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */
#define WANT_PIDFILE 1
#include "common.h"
#include "dhcpd.h"
#include "dhcpc.h"

#include <netinet/if_ether.h>
#include <linux/filter.h>
#include <linux/if_packet.h>

#ifndef PACKET_AUXDATA
# define PACKET_AUXDATA 8
struct tpacket_auxdata {
	uint32_t tp_status;
	uint32_t tp_len;
	uint32_t tp_snaplen;
	uint16_t tp_mac;
	uint16_t tp_net;
	uint16_t tp_vlan_tci;
	uint16_t tp_padding;
};
#endif


/* "struct client_config_t client_config" is in bb_common_bufsiz1 */


#if ENABLE_LONG_OPTS
static const char udhcpc_longopts[] ALIGN1 =
	"clientid-none\0"  No_argument       "C"
	"vendorclass\0"    Required_argument "V"
	"hostname\0"       Required_argument "H"
	"fqdn\0"           Required_argument "F"
	"interface\0"      Required_argument "i"
	"now\0"            No_argument       "n"
	"pidfile\0"        Required_argument "p"
	"quit\0"           No_argument       "q"
	"release\0"        No_argument       "R"
	"request\0"        Required_argument "r"
	"script\0"         Required_argument "s"
	"timeout\0"        Required_argument "T"
	"retries\0"        Required_argument "t"
	"tryagain\0"       Required_argument "A"
	"syslog\0"         No_argument       "S"
	"request-option\0" Required_argument "O"
	"no-default-options\0" No_argument   "o"
	"foreground\0"     No_argument       "f"
	"background\0"     No_argument       "b"
	"broadcast\0"      No_argument       "B"
	IF_FEATURE_UDHCPC_ARPING("arping\0"	Optional_argument "a")
	IF_FEATURE_UDHCP_PORT("client-port\0"	Required_argument "P")
	;
#endif
/* Must match getopt32 option string order */
enum {
	OPT_C = 1 << 0,
	OPT_V = 1 << 1,
	OPT_H = 1 << 2,
	OPT_h = 1 << 3,
	OPT_F = 1 << 4,
	OPT_i = 1 << 5,
	OPT_n = 1 << 6,
	OPT_p = 1 << 7,
	OPT_q = 1 << 8,
	OPT_R = 1 << 9,
	OPT_r = 1 << 10,
	OPT_s = 1 << 11,
	OPT_T = 1 << 12,
	OPT_t = 1 << 13,
	OPT_S = 1 << 14,
	OPT_A = 1 << 15,
	OPT_O = 1 << 16,
	OPT_o = 1 << 17,
	OPT_x = 1 << 18,
	OPT_f = 1 << 19,
	OPT_B = 1 << 20,
/* The rest has variable bit positions, need to be clever */
	OPTBIT_B = 20,
	USE_FOR_MMU(             OPTBIT_b,)
	IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
	IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
	USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
	IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
	IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
};


/*** Script execution code ***/

/* get a rough idea of how long an option will be (rounding up...) */
static const uint8_t len_of_option_as_string[] = {
	[OPTION_IP              ] = sizeof("255.255.255.255 "),
	[OPTION_IP_PAIR         ] = sizeof("255.255.255.255 ") * 2,
	[OPTION_STATIC_ROUTES   ] = sizeof("255.255.255.255/32 255.255.255.255 "),
	[OPTION_6RD             ] = sizeof("132 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "),
	[OPTION_STRING          ] = 1,
	[OPTION_STRING_HOST     ] = 1,
#if ENABLE_FEATURE_UDHCP_RFC3397
	[OPTION_DNS_STRING      ] = 1, /* unused */
	/* Hmmm, this severely overestimates size if SIP_SERVERS option
	 * is in domain name form: N-byte option in binary form
	 * mallocs ~16*N bytes. But it is freed almost at once.
	 */
	[OPTION_SIP_SERVERS     ] = sizeof("255.255.255.255 "),
#endif
//	[OPTION_BOOLEAN         ] = sizeof("yes "),
	[OPTION_U8              ] = sizeof("255 "),
	[OPTION_U16             ] = sizeof("65535 "),
//	[OPTION_S16             ] = sizeof("-32768 "),
	[OPTION_U32             ] = sizeof("4294967295 "),
	[OPTION_S32             ] = sizeof("-2147483684 "),
};

/* note: ip is a pointer to an IP in network order, possibly misaliged */
static int sprint_nip(char *dest, const char *pre, const uint8_t *ip)
{
	return sprintf(dest, "%s%u.%u.%u.%u", pre, ip[0], ip[1], ip[2], ip[3]);
}

/* really simple implementation, just count the bits */
static int mton(uint32_t mask)
{
	int i = 0;
	mask = ntohl(mask); /* 111110000-like bit pattern */
	while (mask) {
		i++;
		mask <<= 1;
	}
	return i;
}

#if ENABLE_FEATURE_UDHCPC_SANITIZEOPT
/* Check if a given label represents a valid DNS label
 * Return pointer to the first character after the label upon success,
 * NULL otherwise.
 * See RFC1035, 2.3.1
 */
/* We don't need to be particularly anal. For example, allowing _, hyphen
 * at the end, or leading and trailing dots would be ok, since it
 * can't be used for attacks. (Leading hyphen can be, if someone uses
 * cmd "$hostname"
 * in the script: then hostname may be treated as an option)
 */
static const char *valid_domain_label(const char *label)
{
	unsigned char ch;
	unsigned pos = 0;

	for (;;) {
		ch = *label;
		if ((ch|0x20) < 'a' || (ch|0x20) > 'z') {
			if (ch < '0' || ch > '9') {
				if (ch == '\0' || ch == '.')
					return label;
				/* DNS allows only '-', but we are more permissive */
				if (ch != '-' && ch != '_')
					return NULL;
			}
		}
		label++;
		pos++;
		//Do we want this?
		//if (pos > 63) /* NS_MAXLABEL; labels must be 63 chars or less */
		//	return NULL;
	}
}

/* Check if a given name represents a valid DNS name */
/* See RFC1035, 2.3.1 */
static int good_hostname(const char *name)
{
	//const char *start = name;

	for (;;) {
		name = valid_domain_label(name);
		if (!name)
			return 0;
		if (!name[0])
			return 1;
			//Do we want this?
			//return ((name - start) < 1025); /* NS_MAXDNAME */
		name++;
		if (*name == '\0')
			return 1; // We allow trailing dot too
	}
}
#else
# define good_hostname(name) 1
#endif

/* Create "opt_name=opt_value" string */
static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_optflag *optflag, const char *opt_name)
{
	unsigned upper_length;
	int len, type, optlen;
	char *dest, *ret;

	/* option points to OPT_DATA, need to go back to get OPT_LEN */
	len = option[-OPT_DATA + OPT_LEN];

	type = optflag->flags & OPTION_TYPE_MASK;
	optlen = dhcp_option_lengths[type];
	upper_length = len_of_option_as_string[type]
		* ((unsigned)(len + optlen) / (unsigned)optlen);

	dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
	dest += sprintf(ret, "%s=", opt_name);

	while (len >= optlen) {
		switch (type) {
		case OPTION_IP:
		case OPTION_IP_PAIR:
			dest += sprint_nip(dest, "", option);
			if (type == OPTION_IP)
				break;
			dest += sprint_nip(dest, "/", option + 4);
			break;
//		case OPTION_BOOLEAN:
//			dest += sprintf(dest, *option ? "yes" : "no");
//			break;
		case OPTION_U8:
			dest += sprintf(dest, "%u", *option);
			break;
//		case OPTION_S16:
		case OPTION_U16: {
			uint16_t val_u16;
			move_from_unaligned16(val_u16, option);
			dest += sprintf(dest, "%u", ntohs(val_u16));
			break;
		}
		case OPTION_S32:
		case OPTION_U32: {
			uint32_t val_u32;
			move_from_unaligned32(val_u32, option);
			dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32));
			break;
		}
		/* Note: options which use 'return' instead of 'break'
		 * (for example, OPTION_STRING) skip the code which handles
		 * the case of list of options.
		 */
		case OPTION_STRING:
		case OPTION_STRING_HOST:
			memcpy(dest, option, len);
			dest[len] = '\0';
			if (type == OPTION_STRING_HOST && !good_hostname(dest))
				safe_strncpy(dest, "bad", len);
			return ret;
		case OPTION_STATIC_ROUTES: {
			/* Option binary format:
			 * mask [one byte, 0..32]
			 * ip [big endian, 0..4 bytes depending on mask]
			 * router [big endian, 4 bytes]
			 * may be repeated
			 *
			 * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2"
			 */
			const char *pfx = "";

			while (len >= 1 + 4) { /* mask + 0-byte ip + router */
				uint32_t nip;
				uint8_t *p;
				unsigned mask;
				int bytes;

				mask = *option++;
				if (mask > 32)
					break;
				len--;

				nip = 0;
				p = (void*) &nip;
				bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */
				while (--bytes >= 0) {
					*p++ = *option++;
					len--;
				}
				if (len < 4)
					break;

				/* print ip/mask */
				dest += sprint_nip(dest, pfx, (void*) &nip);
				pfx = " ";
				dest += sprintf(dest, "/%u ", mask);
				/* print router */
				dest += sprint_nip(dest, "", option);
				option += 4;
				len -= 4;
			}

			return ret;
		}
		case OPTION_6RD:
			/* Option binary format (see RFC 5969):
			 *  0                   1                   2                   3
			 *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			 * |  OPTION_6RD   | option-length |  IPv4MaskLen  |  6rdPrefixLen |
			 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			 * |                           6rdPrefix                           |
			 * ...                        (16 octets)                        ...
			 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			 * ...                   6rdBRIPv4Address(es)                    ...
			 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			 * We convert it to a string
			 * "IPv4MaskLen 6rdPrefixLen 6rdPrefix 6rdBRIPv4Address..."
			 *
			 * Sanity check: ensure that our length is at least 22 bytes, that
			 * IPv4MaskLen <= 32,
			 * 6rdPrefixLen <= 128,
			 * 6rdPrefixLen + (32 - IPv4MaskLen) <= 128
			 * (2nd condition need no check - it follows from 1st and 3rd).
			 * Else, return envvar with empty value ("optname=")
			 */
			if (len >= (1 + 1 + 16 + 4)
			 && option[0] <= 32
			 && (option[1] + 32 - option[0]) <= 128
			) {
				/* IPv4MaskLen */
				dest += sprintf(dest, "%u ", *option++);
				/* 6rdPrefixLen */
				dest += sprintf(dest, "%u ", *option++);
				/* 6rdPrefix */
				dest += sprint_nip6(dest, /* "", */ option);
				option += 16;
				len -= 1 + 1 + 16 + 4;
				/* "+ 4" above corresponds to the length of IPv4 addr
				 * we consume in the loop below */
				while (1) {
					/* 6rdBRIPv4Address(es) */
					dest += sprint_nip(dest, " ", option);
					option += 4;
					len -= 4; /* do we have yet another 4+ bytes? */
					if (len < 0)
						break; /* no */
				}
			}

			return ret;
#if ENABLE_FEATURE_UDHCP_RFC3397
		case OPTION_DNS_STRING:
			/* unpack option into dest; use ret for prefix (i.e., "optname=") */
			dest = dname_dec(option, len, ret);
			if (dest) {
				free(ret);
				return dest;
			}
			/* error. return "optname=" string */
			return ret;
		case OPTION_SIP_SERVERS:
			/* Option binary format:
			 * type: byte
			 * type=0: domain names, dns-compressed
			 * type=1: IP addrs
			 */
			option++;
			len--;
			if (option[-1] == 0) {
				dest = dname_dec(option, len, ret);
				if (dest) {
					free(ret);
					return dest;
				}
			} else
			if (option[-1] == 1) {
				const char *pfx = "";
				while (1) {
					len -= 4;
					if (len < 0)
						break;
					dest += sprint_nip(dest, pfx, option);
					pfx = " ";
					option += 4;
				}
			}
			return ret;
#endif
		} /* switch */

		/* If we are here, try to format any remaining data
		 * in the option as another, similarly-formatted option
		 */
		option += optlen;
		len -= optlen;
// TODO: it can be a list only if (optflag->flags & OPTION_LIST).
// Should we bail out/warn if we see multi-ip option which is
// not allowed to be such (for example, DHCP_BROADCAST)? -
		if (len < optlen /* || !(optflag->flags & OPTION_LIST) */)
			break;
		*dest++ = ' ';
		*dest = '\0';
	} /* while */

	return ret;
}

/* put all the parameters into the environment */
static char **fill_envp(struct dhcp_packet *packet)
{
	int envc;
	int i;
	char **envp, **curr;
	const char *opt_name;
	uint8_t *temp;
	uint8_t overload = 0;

#define BITMAP unsigned
#define BBITS (sizeof(BITMAP) * 8)
#define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1)))
#define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS])
	BITMAP found_opts[256 / BBITS];

	memset(found_opts, 0, sizeof(found_opts));

	/* We need 6 elements for:
	 * "interface=IFACE"
	 * "ip=N.N.N.N" from packet->yiaddr
	 * "siaddr=IP" from packet->siaddr_nip (unless 0)
	 * "boot_file=FILE" from packet->file (unless overloaded)
	 * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
	 * terminating NULL
	 */
	envc = 6;
	/* +1 element for each option, +2 for subnet option: */
	if (packet) {
		/* note: do not search for "pad" (0) and "end" (255) options */
//TODO: change logic to scan packet _once_
		for (i = 1; i < 255; i++) {
			temp = udhcp_get_option(packet, i);
			if (temp) {
				if (i == DHCP_OPTION_OVERLOAD)
					overload = *temp;
				else if (i == DHCP_SUBNET)
					envc++; /* for $mask */
				envc++;
				/*if (i != DHCP_MESSAGE_TYPE)*/
				FOUND_OPTS(i) |= BMASK(i);
			}
		}
	}
	curr = envp = xzalloc(sizeof(envp[0]) * envc);

	*curr = xasprintf("interface=%s", client_config.interface);
	putenv(*curr++);

	if (!packet)
		return envp;

	/* Export BOOTP fields. Fields we don't (yet?) export:
	 * uint8_t op;      // always BOOTREPLY
	 * uint8_t htype;   // hardware address type. 1 = 10mb ethernet
	 * uint8_t hlen;    // hardware address length
	 * uint8_t hops;    // used by relay agents only
	 * uint32_t xid;
	 * uint16_t secs;   // elapsed since client began acquisition/renewal
	 * uint16_t flags;  // only one flag so far: bcast. Never set by server
	 * uint32_t ciaddr; // client IP (usually == yiaddr. can it be different
	 *                  // if during renew server wants to give us differn IP?)
	 * uint32_t gateway_nip; // relay agent IP address
	 * uint8_t chaddr[16]; // link-layer client hardware address (MAC)
	 * TODO: export gateway_nip as $giaddr?
	 */
	/* Most important one: yiaddr as $ip */
	*curr = xmalloc(sizeof("ip=255.255.255.255"));
	sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
	putenv(*curr++);
	if (packet->siaddr_nip) {
		/* IP address of next server to use in bootstrap */
		*curr = xmalloc(sizeof("siaddr=255.255.255.255"));
		sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
		putenv(*curr++);
	}
	if (!(overload & FILE_FIELD) && packet->file[0]) {
		/* watch out for invalid packets */
		*curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
		putenv(*curr++);
	}
	if (!(overload & SNAME_FIELD) && packet->sname[0]) {
		/* watch out for invalid packets */
		*curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
		putenv(*curr++);
	}

	/* Export known DHCP options */
	opt_name = dhcp_option_strings;
	i = 0;
	while (*opt_name) {
		uint8_t code = dhcp_optflags[i].code;
		BITMAP *found_ptr = &FOUND_OPTS(code);
		BITMAP found_mask = BMASK(code);
		if (!(*found_ptr & found_mask))
			goto next;
		*found_ptr &= ~found_mask; /* leave only unknown options */
		temp = udhcp_get_option(packet, code);
		*curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
		putenv(*curr++);
		if (code == DHCP_SUBNET) {
			/* Subnet option: make things like "$ip/$mask" possible */
			uint32_t subnet;
			move_from_unaligned32(subnet, temp);
			*curr = xasprintf("mask=%u", mton(subnet));
			putenv(*curr++);
		}
 next:
		opt_name += strlen(opt_name) + 1;
		i++;
	}
	/* Export unknown options */
	for (i = 0; i < 256;) {
		BITMAP bitmap = FOUND_OPTS(i);
		if (!bitmap) {
			i += BBITS;
			continue;
		}
		if (bitmap & BMASK(i)) {
			unsigned len, ofs;

			temp = udhcp_get_option(packet, i);
			/* udhcp_get_option returns ptr to data portion,
			 * need to go back to get len
			 */
			len = temp[-OPT_DATA + OPT_LEN];
			*curr = xmalloc(sizeof("optNNN=") + 1 + len*2);
			ofs = sprintf(*curr, "opt%u=", i);
			*bin2hex(*curr + ofs, (void*) temp, len) = '\0';
			putenv(*curr++);
		}
		i++;
	}

	return envp;
}

/* Call a script with a par file and env vars */
static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
{
	char **envp, **curr;
	char *argv[3];

	envp = fill_envp(packet);

	/* call script */
	log1("Executing %s %s", client_config.script, name);
	argv[0] = (char*) client_config.script;
	argv[1] = (char*) name;
	argv[2] = NULL;
	spawn_and_wait(argv);

	for (curr = envp; *curr; curr++) {
		log2(" %s", *curr);
		bb_unsetenv_and_free(*curr);
	}
	free(envp);
}


/*** Sending/receiving packets ***/

static ALWAYS_INLINE uint32_t random_xid(void)
{
	return rand();
}

/* Initialize the packet with the proper defaults */
static void init_packet(struct dhcp_packet *packet, char type)
{
	uint16_t secs;

	/* Fill in: op, htype, hlen, cookie fields; message type option: */
	udhcp_init_header(packet, type);

	packet->xid = random_xid();

	client_config.last_secs = monotonic_sec();
	if (client_config.first_secs == 0)
		client_config.first_secs = client_config.last_secs;
	secs = client_config.last_secs - client_config.first_secs;
	packet->secs = htons(secs);

	memcpy(packet->chaddr, client_config.client_mac, 6);
	if (client_config.clientid)
		udhcp_add_binary_option(packet, client_config.clientid);
}

static void add_client_options(struct dhcp_packet *packet)
{
	int i, end, len;

	udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE));

	/* Add a "param req" option with the list of options we'd like to have
	 * from stubborn DHCP servers. Pull the data from the struct in common.c.
	 * No bounds checking because it goes towards the head of the packet. */
	end = udhcp_end_option(packet->options);
	len = 0;
	for (i = 1; i < DHCP_END; i++) {
		if (client_config.opt_mask[i >> 3] & (1 << (i & 7))) {
			packet->options[end + OPT_DATA + len] = i;
			len++;
		}
	}
	if (len) {
		packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
		packet->options[end + OPT_LEN] = len;
		packet->options[end + OPT_DATA + len] = DHCP_END;
	}

	if (client_config.vendorclass)
		udhcp_add_binary_option(packet, client_config.vendorclass);
	if (client_config.hostname)
		udhcp_add_binary_option(packet, client_config.hostname);
	if (client_config.fqdn)
		udhcp_add_binary_option(packet, client_config.fqdn);

	/* Request broadcast replies if we have no IP addr */
	if ((option_mask32 & OPT_B) && packet->ciaddr == 0)
		packet->flags |= htons(BROADCAST_FLAG);

	/* Add -x options if any */
	{
		struct option_set *curr = client_config.options;
		while (curr) {
			udhcp_add_binary_option(packet, curr->data);
			curr = curr->next;
		}
//		if (client_config.sname)
//			strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1);
//		if (client_config.boot_file)
//			strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1);
	}

	// This will be needed if we remove -V VENDOR_STR in favor of
	// -x vendor:VENDOR_STR
	//if (!udhcp_find_option(packet.options, DHCP_VENDOR))
	//	/* not set, set the default vendor ID */
	//	...add (DHCP_VENDOR, "udhcp "BB_VER) opt...
}

/* RFC 2131
 * 4.4.4 Use of broadcast and unicast
 *
 * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
 * messages, unless the client knows the address of a DHCP server.
 * The client unicasts DHCPRELEASE messages to the server. Because
 * the client is declining the use of the IP address supplied by the server,
 * the client broadcasts DHCPDECLINE messages.
 *
 * When the DHCP client knows the address of a DHCP server, in either
 * INIT or REBOOTING state, the client may use that address
 * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
 * The client may also use unicast to send DHCPINFORM messages
 * to a known DHCP server. If the client receives no response to DHCP
 * messages sent to the IP address of a known DHCP server, the DHCP
 * client reverts to using the IP broadcast address.
 */

static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet, uint32_t src_nip)
{
	return udhcp_send_raw_packet(packet,
		/*src*/ src_nip, CLIENT_PORT,
		/*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
		client_config.ifindex);
}

static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t server)
{
	if (server)
		return udhcp_send_kernel_packet(packet,
			ciaddr, CLIENT_PORT,
			server, SERVER_PORT);
	return raw_bcast_from_client_config_ifindex(packet, ciaddr);
}

/* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
/* NOINLINE: limit stack usage in caller */
static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
{
	struct dhcp_packet packet;

	/* Fill in: op, htype, hlen, cookie, chaddr fields,
	 * random xid field (we override it below),
	 * client-id option (unless -C), message type option:
	 */
	init_packet(&packet, DHCPDISCOVER);

	packet.xid = xid;
	if (requested)
		udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);

	/* Add options: maxsize,
	 * optionally: hostname, fqdn, vendorclass,
	 * "param req" option according to -O, options specified with -x
	 */
	add_client_options(&packet);

	bb_info_msg("Sending discover...");
	return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
}

/* Broadcast a DHCP request message */
/* RFC 2131 3.1 paragraph 3:
 * "The client _broadcasts_ a DHCPREQUEST message..."
 */
/* NOINLINE: limit stack usage in caller */
static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
{
	struct dhcp_packet packet;
	struct in_addr addr;

/*
 * RFC 2131 4.3.2 DHCPREQUEST message
 * ...
 * If the DHCPREQUEST message contains a 'server identifier'
 * option, the message is in response to a DHCPOFFER message.
 * Otherwise, the message is a request to verify or extend an
 * existing lease. If the client uses a 'client identifier'
 * in a DHCPREQUEST message, it MUST use that same 'client identifier'
 * in all subsequent messages. If the client included a list
 * of requested parameters in a DHCPDISCOVER message, it MUST
 * include that list in all subsequent messages.
 */
	/* Fill in: op, htype, hlen, cookie, chaddr fields,
	 * random xid field (we override it below),
	 * client-id option (unless -C), message type option:
	 */
	init_packet(&packet, DHCPREQUEST);

	packet.xid = xid;
	udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);

	udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);

	/* Add options: maxsize,
	 * optionally: hostname, fqdn, vendorclass,
	 * "param req" option according to -O, and options specified with -x
	 */
	add_client_options(&packet);

	addr.s_addr = requested;
	bb_info_msg("Sending select for %s...", inet_ntoa(addr));
	return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
}

/* Unicast or broadcast a DHCP renew message */
/* NOINLINE: limit stack usage in caller */
static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
{
	struct dhcp_packet packet;

/*
 * RFC 2131 4.3.2 DHCPREQUEST message
 * ...
 * DHCPREQUEST generated during RENEWING state:
 *
 * 'server identifier' MUST NOT be filled in, 'requested IP address'
 * option MUST NOT be filled in, 'ciaddr' MUST be filled in with
 * client's IP address. In this situation, the client is completely
 * configured, and is trying to extend its lease. This message will
 * be unicast, so no relay agents will be involved in its
 * transmission.  Because 'giaddr' is therefore not filled in, the
 * DHCP server will trust the value in 'ciaddr', and use it when
 * replying to the client.
 */
	/* Fill in: op, htype, hlen, cookie, chaddr fields,
	 * random xid field (we override it below),
	 * client-id option (unless -C), message type option:
	 */
	init_packet(&packet, DHCPREQUEST);

	packet.xid = xid;
	packet.ciaddr = ciaddr;

	/* Add options: maxsize,
	 * optionally: hostname, fqdn, vendorclass,
	 * "param req" option according to -O, and options specified with -x
	 */
	add_client_options(&packet);

	bb_info_msg("Sending renew...");
	return bcast_or_ucast(&packet, ciaddr, server);
}

#if ENABLE_FEATURE_UDHCPC_ARPING
/* Broadcast a DHCP decline message */
/* NOINLINE: limit stack usage in caller */
static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t requested)
{
	struct dhcp_packet packet;

	/* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
	 * client-id option (unless -C), message type option:
	 */
	init_packet(&packet, DHCPDECLINE);

#if 0
	/* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
	 * but in case the server is buggy and wants DHCPDECLINE's xid
	 * to match the xid which started entire handshake,
	 * we use the same xid we used in initial DHCPDISCOVER:
	 */
	packet.xid = xid;
#endif
	/* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
	udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);

	udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);

	bb_info_msg("Sending decline...");
	return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
}
#endif

/* Unicast a DHCP release message */
static int send_release(uint32_t server, uint32_t ciaddr)
{
	struct dhcp_packet packet;

	/* Fill in: op, htype, hlen, cookie, chaddr, random xid fields,
	 * client-id option (unless -C), message type option:
	 */
	init_packet(&packet, DHCPRELEASE);

	/* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */
	packet.ciaddr = ciaddr;

	udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);

	bb_info_msg("Sending release...");
	/* Note: normally we unicast here since "server" is not zero.
	 * However, there _are_ people who run "address-less" DHCP servers,
	 * and reportedly ISC dhcp client and Windows allow that.
	 */
	return bcast_or_ucast(&packet, ciaddr, server);
}

/* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
/* NOINLINE: limit stack usage in caller */
static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
{
	int bytes;
	struct ip_udp_dhcp_packet packet;
	uint16_t check;
	unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
	struct iovec iov;
	struct msghdr msg;
	struct cmsghdr *cmsg;

	/* used to use just safe_read(fd, &packet, sizeof(packet))
	 * but we need to check for TP_STATUS_CSUMNOTREADY :(
	 */
	iov.iov_base = &packet;
	iov.iov_len = sizeof(packet);
	memset(&msg, 0, sizeof(msg));
	msg.msg_iov = &iov;
	msg.msg_iovlen = 1;
	msg.msg_control = cmsgbuf;
	msg.msg_controllen = sizeof(cmsgbuf);
	for (;;) {
		bytes = recvmsg(fd, &msg, 0);
		if (bytes < 0) {
			if (errno == EINTR)
				continue;
			log1("Packet read error, ignoring");
			/* NB: possible down interface, etc. Caller should pause. */
			return bytes; /* returns -1 */
		}
		break;
	}

	if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
		log1("Packet is too short, ignoring");
		return -2;
	}

	if (bytes < ntohs(packet.ip.tot_len)) {
		/* packet is bigger than sizeof(packet), we did partial read */
		log1("Oversized packet, ignoring");
		return -2;
	}

	/* ignore any extra garbage bytes */
	bytes = ntohs(packet.ip.tot_len);

	/* make sure its the right packet for us, and that it passes sanity checks */
	if (packet.ip.protocol != IPPROTO_UDP
	 || packet.ip.version != IPVERSION
	 || packet.ip.ihl != (sizeof(packet.ip) >> 2)
	 || packet.udp.dest != htons(CLIENT_PORT)
	/* || bytes > (int) sizeof(packet) - can't happen */
	 || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
	) {
		log1("Unrelated/bogus packet, ignoring");
		return -2;
	}

	/* verify IP checksum */
	check = packet.ip.check;
	packet.ip.check = 0;
	if (check != inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip))) {
		log1("Bad IP header checksum, ignoring");
		return -2;
	}

	for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
		if (cmsg->cmsg_level == SOL_PACKET
		 && cmsg->cmsg_type == PACKET_AUXDATA
		) {
			/* some VMs don't checksum UDP and TCP data
			 * they send to the same physical machine,
			 * here we detect this case:
			 */
			struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
			if (aux->tp_status & TP_STATUS_CSUMNOTREADY)
				goto skip_udp_sum_check;
		}
	}

	/* verify UDP checksum. IP header has to be modified for this */
	memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
	/* ip.xx fields which are not memset: protocol, check, saddr, daddr */
	packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
	check = packet.udp.check;
	packet.udp.check = 0;
	if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
		log1("Packet with bad UDP checksum received, ignoring");
		return -2;
	}
 skip_udp_sum_check:

	if (packet.data.cookie != htonl(DHCP_MAGIC)) {
		bb_info_msg("Packet with bad magic, ignoring");
		return -2;
	}

	log1("Received a packet");
	udhcp_dump_packet(&packet.data);

	bytes -= sizeof(packet.ip) + sizeof(packet.udp);
	memcpy(dhcp_pkt, &packet.data, bytes);
	return bytes;
}


/*** Main ***/

static int sockfd = -1;

#define LISTEN_NONE   0
#define LISTEN_KERNEL 1
#define LISTEN_RAW    2
static smallint listen_mode;

/* initial state: (re)start DHCP negotiation */
#define INIT_SELECTING  0
/* discover was sent, DHCPOFFER reply received */
#define REQUESTING      1
/* select/renew was sent, DHCPACK reply received */
#define BOUND           2
/* half of lease passed, want to renew it by sending unicast renew requests */
#define RENEWING        3
/* renew requests were not answered, lease is almost over, send broadcast renew */
#define REBINDING       4
/* manually requested renew (SIGUSR1) */
#define RENEW_REQUESTED 5
/* release, possibly manually requested (SIGUSR2) */
#define RELEASED        6
static smallint state;

static int udhcp_raw_socket(int ifindex)
{
	int fd;
	struct sockaddr_ll sock;

	log1("Opening raw socket on ifindex %d", ifindex); //log2?

	fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
	/* ^^^^^
	 * SOCK_DGRAM: remove link-layer headers on input (SOCK_RAW keeps them)
	 * ETH_P_IP: want to receive only packets with IPv4 eth type
	 */
	log1("Got raw socket fd"); //log2?

	sock.sll_family = AF_PACKET;
	sock.sll_protocol = htons(ETH_P_IP);
	sock.sll_ifindex = ifindex;
	xbind(fd, (struct sockaddr *) &sock, sizeof(sock));

#if 0 /* Several users reported breakage when BPF filter is used */
	if (CLIENT_PORT == 68) {
		/* Use only if standard port is in use */
		/*
		 *	I've selected not to see LL header, so BPF doesn't see it, too.
		 *	The filter may also pass non-IP and non-ARP packets, but we do
		 *	a more complete check when receiving the message in userspace.
		 *
		 * and filter shamelessly stolen from:
		 *
		 *	http://www.flamewarmaster.de/software/dhcpclient/
		 *
		 * There are a few other interesting ideas on that page (look under
		 * "Motivation").  Use of netlink events is most interesting.  Think
		 * of various network servers listening for events and reconfiguring.
		 * That would obsolete sending HUP signals and/or make use of restarts.
		 *
		 * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
		 * License: GPL v2.
		 */
		static const struct sock_filter filter_instr[] = {
			/* load 9th byte (protocol) */
			BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
			/* jump to L1 if it is IPPROTO_UDP, else to L4 */
			BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
			/* L1: load halfword from offset 6 (flags and frag offset) */
			BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
			/* jump to L4 if any bits in frag offset field are set, else to L2 */
			BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
			/* L2: skip IP header (load index reg with header len) */
			BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
			/* load udp destination port from halfword[header_len + 2] */
			BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
			/* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
			BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
			/* L3: accept packet ("accept 0x7fffffff bytes") */
			/* Accepting 0xffffffff works too but kernel 2.6.19 is buggy */
			BPF_STMT(BPF_RET|BPF_K, 0x7fffffff),
			/* L4: discard packet ("accept zero bytes") */
			BPF_STMT(BPF_RET|BPF_K, 0),
		};
		static const struct sock_fprog filter_prog = {
			.len = sizeof(filter_instr) / sizeof(filter_instr[0]),
			/* casting const away: */
			.filter = (struct sock_filter *) filter_instr,
		};
		/* Ignoring error (kernel may lack support for this) */
		if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
				sizeof(filter_prog)) >= 0)
			log1("Attached filter to raw socket fd"); // log?
	}
#endif

	if (setsockopt_1(fd, SOL_PACKET, PACKET_AUXDATA) != 0) {
		if (errno != ENOPROTOOPT)
			log1("Can't set PACKET_AUXDATA on raw socket");
	}

	log1("Created raw socket");

	return fd;
}

static void change_listen_mode(int new_mode)
{
	log1("Entering listen mode: %s",
		new_mode != LISTEN_NONE
			? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
			: "none"
	);

	listen_mode = new_mode;
	if (sockfd >= 0) {
		close(sockfd);
		sockfd = -1;
	}
	if (new_mode == LISTEN_KERNEL)
		sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
	else if (new_mode != LISTEN_NONE)
		sockfd = udhcp_raw_socket(client_config.ifindex);
	/* else LISTEN_NONE: sockfd stays closed */
}

/* Called only on SIGUSR1 */
static void perform_renew(void)
{
	bb_info_msg("Performing a DHCP renew");
	switch (state) {
	case BOUND:
		change_listen_mode(LISTEN_KERNEL);
	case RENEWING:
	case REBINDING:
		state = RENEW_REQUESTED;
		break;
	case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
		udhcp_run_script(NULL, "deconfig");
	case REQUESTING:
	case RELEASED:
		change_listen_mode(LISTEN_RAW);
		state = INIT_SELECTING;
		break;
	case INIT_SELECTING:
		break;
	}
}

static void perform_release(uint32_t server_addr, uint32_t requested_ip)
{
	char buffer[sizeof("255.255.255.255")];
	struct in_addr temp_addr;

	/* send release packet */
	if (state == BOUND || state == RENEWING || state == REBINDING) {
		temp_addr.s_addr = server_addr;
		strcpy(buffer, inet_ntoa(temp_addr));
		temp_addr.s_addr = requested_ip;
		bb_info_msg("Unicasting a release of %s to %s",
				inet_ntoa(temp_addr), buffer);
		send_release(server_addr, requested_ip); /* unicast */
		udhcp_run_script(NULL, "deconfig");
	}
	bb_info_msg("Entering released state");

	change_listen_mode(LISTEN_NONE);
	state = RELEASED;
}

static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
{
	uint8_t *storage;
	int len = strnlen(str, 255);
	storage = xzalloc(len + extra + OPT_DATA);
	storage[OPT_CODE] = code;
	storage[OPT_LEN] = len + extra;
	memcpy(storage + extra + OPT_DATA, str, len);
	return storage;
}

#if BB_MMU
static void client_background(void)
{
	bb_daemonize(0);
	logmode &= ~LOGMODE_STDIO;
	/* rewrite pidfile, as our pid is different now */
	write_pidfile(client_config.pidfile);
}
#endif

//usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
//usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
//usage:#else
//usage:# define IF_UDHCP_VERBOSE(...)
//usage:#endif
//usage:#define udhcpc_trivial_usage
//usage:       "[-fbq"IF_UDHCP_VERBOSE("v")"RB]"IF_FEATURE_UDHCPC_ARPING(" [-a[MSEC]]")" [-t N] [-T SEC] [-A SEC/-n]\n"
//usage:       "	[-i IFACE]"IF_FEATURE_UDHCP_PORT(" [-P PORT]")" [-s PROG] [-p PIDFILE]\n"
//usage:       "	[-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]..."
//usage:#define udhcpc_full_usage "\n"
//usage:	IF_LONG_OPTS(
//usage:     "\n	-i,--interface IFACE	Interface to use (default eth0)"
//usage:	IF_FEATURE_UDHCP_PORT(
//usage:     "\n	-P,--client-port PORT	Use PORT (default 68)"
//usage:	)
//usage:     "\n	-s,--script PROG	Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
//usage:     "\n	-p,--pidfile FILE	Create pidfile"
//usage:     "\n	-B,--broadcast		Request broadcast replies"
//usage:     "\n	-t,--retries N		Send up to N discover packets (default 3)"
//usage:     "\n	-T,--timeout SEC	Pause between packets (default 3)"
//usage:     "\n	-A,--tryagain SEC	Wait if lease is not obtained (default 20)"
//usage:     "\n	-n,--now		Exit if lease is not obtained"
//usage:     "\n	-q,--quit		Exit after obtaining lease"
//usage:     "\n	-R,--release		Release IP on exit"
//usage:     "\n	-f,--foreground		Run in foreground"
//usage:	USE_FOR_MMU(
//usage:     "\n	-b,--background		Background if lease is not obtained"
//usage:	)
//usage:     "\n	-S,--syslog		Log to syslog too"
//usage:	IF_FEATURE_UDHCPC_ARPING(
//usage:     "\n	-a[MSEC],--arping[=MSEC] Validate offered address with ARP ping"
//usage:	)
//usage:     "\n	-r,--request IP		Request this IP address"
//usage:     "\n	-o,--no-default-options	Don't request any options (unless -O is given)"
//usage:     "\n	-O,--request-option OPT	Request option OPT from server (cumulative)"
//usage:     "\n	-x OPT:VAL		Include option OPT in sent packets (cumulative)"
//usage:     "\n				Examples of string, numeric, and hex byte opts:"
//usage:     "\n				-x hostname:bbox - option 12"
//usage:     "\n				-x lease:3600 - option 51 (lease time)"
//usage:     "\n				-x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
//usage:     "\n	-F,--fqdn NAME		Ask server to update DNS mapping for NAME"
//usage:     "\n	-V,--vendorclass VENDOR	Vendor identifier (default 'udhcp VERSION')"
//usage:     "\n	-C,--clientid-none	Don't send MAC as client identifier"
//usage:	IF_UDHCP_VERBOSE(
//usage:     "\n	-v			Verbose"
//usage:	)
//usage:	)
//usage:	IF_NOT_LONG_OPTS(
//usage:     "\n	-i IFACE	Interface to use (default eth0)"
//usage:	IF_FEATURE_UDHCP_PORT(
//usage:     "\n	-P PORT		Use PORT (default 68)"
//usage:	)
//usage:     "\n	-s PROG		Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
//usage:     "\n	-p FILE		Create pidfile"
//usage:     "\n	-B		Request broadcast replies"
//usage:     "\n	-t N		Send up to N discover packets (default 3)"
//usage:     "\n	-T SEC		Pause between packets (default 3)"
//usage:     "\n	-A SEC		Wait if lease is not obtained (default 20)"
//usage:     "\n	-n		Exit if lease is not obtained"
//usage:     "\n	-q		Exit after obtaining lease"
//usage:     "\n	-R		Release IP on exit"
//usage:     "\n	-f		Run in foreground"
//usage:	USE_FOR_MMU(
//usage:     "\n	-b		Background if lease is not obtained"
//usage:	)
//usage:     "\n	-S		Log to syslog too"
//usage:	IF_FEATURE_UDHCPC_ARPING(
//usage:     "\n	-a[MSEC]	Validate offered address with ARP ping"
//usage:	)
//usage:     "\n	-r IP		Request this IP address"
//usage:     "\n	-o		Don't request any options (unless -O is given)"
//usage:     "\n	-O OPT		Request option OPT from server (cumulative)"
//usage:     "\n	-x OPT:VAL	Include option OPT in sent packets (cumulative)"
//usage:     "\n			Examples of string, numeric, and hex byte opts:"
//usage:     "\n			-x hostname:bbox - option 12"
//usage:     "\n			-x lease:3600 - option 51 (lease time)"
//usage:     "\n			-x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
//usage:     "\n	-F NAME		Ask server to update DNS mapping for NAME"
//usage:     "\n	-V VENDOR	Vendor identifier (default 'udhcp VERSION')"
//usage:     "\n	-C		Don't send MAC as client identifier"
//usage:	IF_UDHCP_VERBOSE(
//usage:     "\n	-v		Verbose"
//usage:	)
//usage:	)
//usage:     "\nSignals:"
//usage:     "\n	USR1	Renew lease"
//usage:     "\n	USR2	Release lease"


int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int udhcpc_main(int argc UNUSED_PARAM, char **argv)
{
	uint8_t *message;
	const char *str_V, *str_h, *str_F, *str_r;
	IF_FEATURE_UDHCPC_ARPING(const char *str_a = "2000";)
	IF_FEATURE_UDHCP_PORT(char *str_P;)
	void *clientid_mac_ptr;
	llist_t *list_O = NULL;
	llist_t *list_x = NULL;
	int tryagain_timeout = 20;
	int discover_timeout = 3;
	int discover_retries = 3;
	uint32_t server_addr = server_addr; /* for compiler */
	uint32_t requested_ip = 0;
	uint32_t xid = xid; /* for compiler */
	int packet_num;
	int timeout; /* must be signed */
	unsigned already_waited_sec;
	unsigned opt;
	IF_FEATURE_UDHCPC_ARPING(unsigned arpping_ms;)
	int max_fd;
	int retval;
	fd_set rfds;

	/* Default options */
	IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
	IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
	client_config.interface = "eth0";
	client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
	str_V = "udhcp "BB_VER;

	/* Parse command line */
	/* O,x: list; -T,-t,-A take numeric param */
	opt_complementary = "O::x::T+:t+:A+" IF_UDHCP_VERBOSE(":vv") ;
	IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
	opt = getopt32(argv, "CV:H:h:F:i:np:qRr:s:T:t:SA:O:ox:fB"
		USE_FOR_MMU("b")
		IF_FEATURE_UDHCPC_ARPING("a::")
		IF_FEATURE_UDHCP_PORT("P:")
		"v"
		, &str_V, &str_h, &str_h, &str_F
		, &client_config.interface, &client_config.pidfile, &str_r /* i,p */
		, &client_config.script /* s */
		, &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
		, &list_O
		, &list_x
		IF_FEATURE_UDHCPC_ARPING(, &str_a)
		IF_FEATURE_UDHCP_PORT(, &str_P)
		IF_UDHCP_VERBOSE(, &dhcp_verbose)
	);
	if (opt & (OPT_h|OPT_H)) {
		//msg added 2011-11
		bb_error_msg("option -h NAME is deprecated, use -x hostname:NAME");
		client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
	}
	if (opt & OPT_F) {
		/* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
		client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
		/* Flag bits: 0000NEOS
		 * S: 1 = Client requests server to update A RR in DNS as well as PTR
		 * O: 1 = Server indicates to client that DNS has been updated regardless
		 * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>,
		 *    not "host.domain.com". Format 0 is obsolete.
		 * N: 1 = Client requests server to not update DNS (S must be 0 then)
		 * Two [0] bytes which follow are deprecated and must be 0.
		 */
		client_config.fqdn[OPT_DATA + 0] = 0x1;
		/*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */
		/*client_config.fqdn[OPT_DATA + 2] = 0; */
	}
	if (opt & OPT_r)
		requested_ip = inet_addr(str_r);
#if ENABLE_FEATURE_UDHCP_PORT
	if (opt & OPT_P) {
		CLIENT_PORT = xatou16(str_P);
		SERVER_PORT = CLIENT_PORT - 1;
	}
#endif
	IF_FEATURE_UDHCPC_ARPING(arpping_ms = xatou(str_a);)
	while (list_O) {
		char *optstr = llist_pop(&list_O);
		unsigned n = bb_strtou(optstr, NULL, 0);
		if (errno || n > 254) {
			n = udhcp_option_idx(optstr);
			n = dhcp_optflags[n].code;
		}
		client_config.opt_mask[n >> 3] |= 1 << (n & 7);
	}
	if (!(opt & OPT_o)) {
		unsigned i, n;
		for (i = 0; (n = dhcp_optflags[i].code) != 0; i++) {
			if (dhcp_optflags[i].flags & OPTION_REQ) {
				client_config.opt_mask[n >> 3] |= 1 << (n & 7);
			}
		}
	}
	while (list_x) {
		char *optstr = llist_pop(&list_x);
		char *colon = strchr(optstr, ':');
		if (colon)
			*colon = ' ';
		/* now it looks similar to udhcpd's config file line:
		 * "optname optval", using the common routine: */
		udhcp_str2optset(optstr, &client_config.options);
	}

	if (udhcp_read_interface(client_config.interface,
			&client_config.ifindex,
			NULL,
			client_config.client_mac)
	) {
		return 1;
	}

	clientid_mac_ptr = NULL;
	if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) {
		/* not suppressed and not set, set the default client ID */
		client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
		client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
		clientid_mac_ptr = client_config.clientid + OPT_DATA+1;
		memcpy(clientid_mac_ptr, client_config.client_mac, 6);
	}
	if (str_V[0] != '\0') {
		// can drop -V, str_V, client_config.vendorclass,
		// but need to add "vendor" to the list of recognized
		// string opts for this to work;
		// and need to tweak add_client_options() too...
		// ...so the question is, should we?
		//bb_error_msg("option -V VENDOR is deprecated, use -x vendor:VENDOR");
		client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
	}

#if !BB_MMU
	/* on NOMMU reexec (i.e., background) early */
	if (!(opt & OPT_f)) {
		bb_daemonize_or_rexec(0 /* flags */, argv);
		logmode = LOGMODE_NONE;
	}
#endif
	if (opt & OPT_S) {
		openlog(applet_name, LOG_PID, LOG_DAEMON);
		logmode |= LOGMODE_SYSLOG;
	}

	/* Make sure fd 0,1,2 are open */
	bb_sanitize_stdio();
	/* Equivalent of doing a fflush after every \n */
	setlinebuf(stdout);
	/* Create pidfile */
	write_pidfile(client_config.pidfile);
	/* Goes to stdout (unless NOMMU) and possibly syslog */
	bb_info_msg("%s (v"BB_VER") started", applet_name);
	/* Set up the signal pipe */
	udhcp_sp_setup();
	/* We want random_xid to be random... */
	srand(monotonic_us());

	state = INIT_SELECTING;
	udhcp_run_script(NULL, "deconfig");
	change_listen_mode(LISTEN_RAW);
	packet_num = 0;
	timeout = 0;
	already_waited_sec = 0;

	/* Main event loop. select() waits on signal pipe and possibly
	 * on sockfd.
	 * "continue" statements in code below jump to the top of the loop.
	 */
	for (;;) {
		struct timeval tv;
		struct dhcp_packet packet;
		/* silence "uninitialized!" warning */
		unsigned timestamp_before_wait = timestamp_before_wait;

		//bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);

		/* Was opening raw or udp socket here
		 * if (listen_mode != LISTEN_NONE && sockfd < 0),
		 * but on fast network renew responses return faster
		 * than we open sockets. Thus this code is moved
		 * to change_listen_mode(). Thus we open listen socket
		 * BEFORE we send renew request (see "case BOUND:"). */

		max_fd = udhcp_sp_fd_set(&rfds, sockfd);

		tv.tv_sec = timeout - already_waited_sec;
		tv.tv_usec = 0;
		retval = 0;
		/* If we already timed out, fall through with retval = 0, else... */
		if ((int)tv.tv_sec > 0) {
			log1("Waiting on select %u seconds", (int)tv.tv_sec);
			timestamp_before_wait = (unsigned)monotonic_sec();
			retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
			if (retval < 0) {
				/* EINTR? A signal was caught, don't panic */
				if (errno == EINTR) {
					already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
					continue;
				}
				/* Else: an error occured, panic! */
				bb_perror_msg_and_die("select");
			}
		}

		/* If timeout dropped to zero, time to become active:
		 * resend discover/renew/whatever
		 */
		if (retval == 0) {
			/* When running on a bridge, the ifindex may have changed
			 * (e.g. if member interfaces were added/removed
			 * or if the status of the bridge changed).
			 * Refresh ifindex and client_mac:
			 */
			if (udhcp_read_interface(client_config.interface,
					&client_config.ifindex,
					NULL,
					client_config.client_mac)
			) {
				goto ret0; /* iface is gone? */
			}
			if (clientid_mac_ptr)
				memcpy(clientid_mac_ptr, client_config.client_mac, 6);

			/* We will restart the wait in any case */
			already_waited_sec = 0;

			switch (state) {
			case INIT_SELECTING:
				if (!discover_retries || packet_num < discover_retries) {
					if (packet_num == 0)
						xid = random_xid();
					/* broadcast */
					send_discover(xid, requested_ip);
					timeout = discover_timeout;
					packet_num++;
					continue;
				}
 leasefail:
				udhcp_run_script(NULL, "leasefail");
#if BB_MMU /* -b is not supported on NOMMU */
				if (opt & OPT_b) { /* background if no lease */
					bb_info_msg("No lease, forking to background");
					client_background();
					/* do not background again! */
					opt = ((opt & ~OPT_b) | OPT_f);
				} else
#endif
				if (opt & OPT_n) { /* abort if no lease */
					bb_info_msg("No lease, failing");
					retval = 1;
					goto ret;
				}
				/* wait before trying again */
				timeout = tryagain_timeout;
				packet_num = 0;
				continue;
			case REQUESTING:
				if (packet_num < 3) {
					/* send broadcast select packet */
					send_select(xid, server_addr, requested_ip);
					timeout = discover_timeout;
					packet_num++;
					continue;
				}
				/* Timed out, go back to init state.
				 * "discover...select...discover..." loops
				 * were seen in the wild. Treat them similarly
				 * to "no response to discover" case */
				change_listen_mode(LISTEN_RAW);
				state = INIT_SELECTING;
				goto leasefail;
			case BOUND:
				/* 1/2 lease passed, enter renewing state */
				state = RENEWING;
				client_config.first_secs = 0; /* make secs field count from 0 */
				change_listen_mode(LISTEN_KERNEL);
				log1("Entering renew state");
				/* fall right through */
			case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
			case_RENEW_REQUESTED:
			case RENEWING:
				if (timeout > 60) {
					/* send an unicast renew request */
			/* Sometimes observed to fail (EADDRNOTAVAIL) to bind
			 * a new UDP socket for sending inside send_renew.
			 * I hazard to guess existing listening socket
			 * is somehow conflicting with it, but why is it
			 * not deterministic then?! Strange.
			 * Anyway, it does recover by eventually failing through
			 * into INIT_SELECTING state.
			 */
					send_renew(xid, server_addr, requested_ip);
					timeout >>= 1;
					continue;
				}
				/* Timed out, enter rebinding state */
				log1("Entering rebinding state");
				state = REBINDING;
				/* fall right through */
			case REBINDING:
				/* Switch to bcast receive */
				change_listen_mode(LISTEN_RAW);
				/* Lease is *really* about to run out,
				 * try to find DHCP server using broadcast */
				if (timeout > 0) {
					/* send a broadcast renew request */
					send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
					timeout >>= 1;
					continue;
				}
				/* Timed out, enter init state */
				bb_info_msg("Lease lost, entering init state");
				udhcp_run_script(NULL, "deconfig");
				state = INIT_SELECTING;
				client_config.first_secs = 0; /* make secs field count from 0 */
				/*timeout = 0; - already is */
				packet_num = 0;
				continue;
			/* case RELEASED: */
			}
			/* yah, I know, *you* say it would never happen */
			timeout = INT_MAX;
			continue; /* back to main loop */
		} /* if select timed out */

		/* select() didn't timeout, something happened */

		/* Is it a signal? */
		/* note: udhcp_sp_read checks FD_ISSET before reading */
		switch (udhcp_sp_read(&rfds)) {
		case SIGUSR1:
			client_config.first_secs = 0; /* make secs field count from 0 */
			already_waited_sec = 0;
			perform_renew();
			if (state == RENEW_REQUESTED) {
				/* We might be either on the same network
				 * (in which case renew might work),
				 * or we might be on a completely different one
				 * (in which case renew won't ever succeed).
				 * For the second case, must make sure timeout
				 * is not too big, or else we can send
				 * futile renew requests for hours.
				 * (Ab)use -A TIMEOUT value (usually 20 sec)
				 * as a cap on the timeout.
				 */
				if (timeout > tryagain_timeout)
					timeout = tryagain_timeout;
				goto case_RENEW_REQUESTED;
			}
			/* Start things over */
			packet_num = 0;
			/* Kill any timeouts, user wants this to hurry along */
			timeout = 0;
			continue;
		case SIGUSR2:
			perform_release(server_addr, requested_ip);
			timeout = INT_MAX;
			continue;
		case SIGTERM:
			bb_info_msg("Received SIGTERM");
			goto ret0;
		}

		/* Is it a packet? */
		if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
			continue; /* no */

		{
			int len;

			/* A packet is ready, read it */
			if (listen_mode == LISTEN_KERNEL)
				len = udhcp_recv_kernel_packet(&packet, sockfd);
			else
				len = udhcp_recv_raw_packet(&packet, sockfd);
			if (len == -1) {
				/* Error is severe, reopen socket */
				bb_info_msg("Read error: %s, reopening socket", strerror(errno));
				sleep(discover_timeout); /* 3 seconds by default */
				change_listen_mode(listen_mode); /* just close and reopen */
			}
			/* If this packet will turn out to be unrelated/bogus,
			 * we will go back and wait for next one.
			 * Be sure timeout is properly decreased. */
			already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
			if (len < 0)
				continue;
		}

		if (packet.xid != xid) {
			log1("xid %x (our is %x), ignoring packet",
				(unsigned)packet.xid, (unsigned)xid);
			continue;
		}

		/* Ignore packets that aren't for us */
		if (packet.hlen != 6
		 || memcmp(packet.chaddr, client_config.client_mac, 6) != 0
		) {
//FIXME: need to also check that last 10 bytes are zero
			log1("chaddr does not match, ignoring packet"); // log2?
			continue;
		}

		message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
		if (message == NULL) {
			bb_error_msg("no message type option, ignoring packet");
			continue;
		}

		switch (state) {
		case INIT_SELECTING:
			/* Must be a DHCPOFFER */
			if (*message == DHCPOFFER) {
				uint8_t *temp;

/* What exactly is server's IP? There are several values.
 * Example DHCP offer captured with tchdump:
 *
 * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src
 * BOOTP fields:
 * Your-IP 10.34.25.202
 * Server-IP 10.34.32.125   // "next server" IP
 * Gateway-IP 10.34.25.254  // relay's address (if DHCP relays are in use)
 * DHCP options:
 * DHCP-Message Option 53, length 1: Offer
 * Server-ID Option 54, length 4: 10.34.255.7       // "server ID"
 * Default-Gateway Option 3, length 4: 10.34.25.254 // router
 *
 * We think that real server IP (one to use in renew/release)
 * is one in Server-ID option. But I am not 100% sure.
 * IP header's src and Gateway-IP (same in this example)
 * might work too.
 * "Next server" and router are definitely wrong ones to use, though...
 */
/* We used to ignore pcakets without DHCP_SERVER_ID.
 * I've got user reports from people who run "address-less" servers.
 * They either supply DHCP_SERVER_ID of 0.0.0.0 or don't supply it at all.
 * They say ISC DHCP client supports this case.
 */
				server_addr = 0;
				temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
				if (!temp) {
					bb_error_msg("no server ID, using 0.0.0.0");
				} else {
					/* it IS unaligned sometimes, don't "optimize" */
					move_from_unaligned32(server_addr, temp);
				}
				/*xid = packet.xid; - already is */
				requested_ip = packet.yiaddr;

				/* enter requesting state */
				state = REQUESTING;
				timeout = 0;
				packet_num = 0;
				already_waited_sec = 0;
			}
			continue;
		case REQUESTING:
		case RENEWING:
		case RENEW_REQUESTED:
		case REBINDING:
			if (*message == DHCPACK) {
				unsigned start;
				uint32_t lease_seconds;
				struct in_addr temp_addr;
				uint8_t *temp;

				temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
				if (!temp) {
					bb_error_msg("no lease time with ACK, using 1 hour lease");
					lease_seconds = 60 * 60;
				} else {
					/* it IS unaligned sometimes, don't "optimize" */
					move_from_unaligned32(lease_seconds, temp);
					lease_seconds = ntohl(lease_seconds);
					/* paranoia: must not be too small and not prone to overflows */
					if (lease_seconds < 0x10)
						lease_seconds = 0x10;
					if (lease_seconds >= 0x10000000)
						lease_seconds = 0x0fffffff;
				}
#if ENABLE_FEATURE_UDHCPC_ARPING
				if (opt & OPT_a) {
/* RFC 2131 3.1 paragraph 5:
 * "The client receives the DHCPACK message with configuration
 * parameters. The client SHOULD perform a final check on the
 * parameters (e.g., ARP for allocated network address), and notes
 * the duration of the lease specified in the DHCPACK message. At this
 * point, the client is configured. If the client detects that the
 * address is already in use (e.g., through the use of ARP),
 * the client MUST send a DHCPDECLINE message to the server and restarts
 * the configuration process..." */
					if (!arpping(packet.yiaddr,
							NULL,
							(uint32_t) 0,
							client_config.client_mac,
							client_config.interface,
							arpping_ms)
					) {
						bb_info_msg("Offered address is in use "
							"(got ARP reply), declining");
						send_decline(/*xid,*/ server_addr, packet.yiaddr);

						if (state != REQUESTING)
							udhcp_run_script(NULL, "deconfig");
						change_listen_mode(LISTEN_RAW);
						state = INIT_SELECTING;
						client_config.first_secs = 0; /* make secs field count from 0 */
						requested_ip = 0;
						timeout = tryagain_timeout;
						packet_num = 0;
						already_waited_sec = 0;
						continue; /* back to main loop */
					}
				}
#endif
				/* enter bound state */
				temp_addr.s_addr = packet.yiaddr;
				bb_info_msg("Lease of %s obtained, lease time %u",
					inet_ntoa(temp_addr), (unsigned)lease_seconds);
				requested_ip = packet.yiaddr;

				start = monotonic_sec();
				udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
				already_waited_sec = (unsigned)monotonic_sec() - start;
				timeout = lease_seconds / 2;
				if ((unsigned)timeout < already_waited_sec) {
					/* Something went wrong. Back to discover state */
					timeout = already_waited_sec = 0;
				}

				state = BOUND;
				change_listen_mode(LISTEN_NONE);
				if (opt & OPT_q) { /* quit after lease */
					goto ret0;
				}
				/* future renew failures should not exit (JM) */
				opt &= ~OPT_n;
#if BB_MMU /* NOMMU case backgrounded earlier */
				if (!(opt & OPT_f)) {
					client_background();
					/* do not background again! */
					opt = ((opt & ~OPT_b) | OPT_f);
				}
#endif
				/* make future renew packets use different xid */
				/* xid = random_xid(); ...but why bother? */

				continue; /* back to main loop */
			}
			if (*message == DHCPNAK) {
				/* If network has more than one DHCP server,
				 * "wrong" server can reply first, with a NAK.
				 * Do not interpret it as a NAK from "our" server.
				 */
				if (server_addr != 0) {
					uint32_t svid;
					uint8_t *temp;

					temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
					if (!temp) {
 non_matching_svid:
						log1("%s with wrong server ID, ignoring packet",
							"Received DHCP NAK"
						);
						continue;
					}
					move_from_unaligned32(svid, temp);
					if (svid != server_addr)
						goto non_matching_svid;
				}
				/* return to init state */
				bb_info_msg("Received DHCP NAK");
				udhcp_run_script(&packet, "nak");
				if (state != REQUESTING)
					udhcp_run_script(NULL, "deconfig");
				change_listen_mode(LISTEN_RAW);
				sleep(3); /* avoid excessive network traffic */
				state = INIT_SELECTING;
				client_config.first_secs = 0; /* make secs field count from 0 */
				requested_ip = 0;
				timeout = 0;
				packet_num = 0;
				already_waited_sec = 0;
			}
			continue;
		/* case BOUND: - ignore all packets */
		/* case RELEASED: - ignore all packets */
		}
		/* back to main loop */
	} /* for (;;) - main loop ends */

 ret0:
	if (opt & OPT_R) /* release on quit */
		perform_release(server_addr, requested_ip);
	retval = 0;
 ret:
	/*if (client_config.pidfile) - remove_pidfile has its own check */
		remove_pidfile(client_config.pidfile);
	return retval;
}