summaryrefslogtreecommitdiff
path: root/net/batman-adv/distributed-arp-table.c
blob: ec7bf5a4a9fc724b63da7bfd7ece79f32b104d99 (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
// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2011-2019  B.A.T.M.A.N. contributors:
 *
 * Antonio Quartulli
 */

#include "distributed-arp-table.h"
#include "main.h"

#include <asm/unaligned.h>
#include <linux/atomic.h>
#include <linux/bitops.h>
#include <linux/byteorder/generic.h>
#include <linux/errno.h>
#include <linux/etherdevice.h>
#include <linux/gfp.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/if_vlan.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/kref.h>
#include <linux/list.h>
#include <linux/netlink.h>
#include <linux/rculist.h>
#include <linux/rcupdate.h>
#include <linux/seq_file.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/stddef.h>
#include <linux/string.h>
#include <linux/udp.h>
#include <linux/workqueue.h>
#include <net/arp.h>
#include <net/genetlink.h>
#include <net/netlink.h>
#include <net/sock.h>
#include <uapi/linux/batman_adv.h>

#include "bridge_loop_avoidance.h"
#include "hard-interface.h"
#include "hash.h"
#include "log.h"
#include "netlink.h"
#include "originator.h"
#include "send.h"
#include "soft-interface.h"
#include "translation-table.h"
#include "tvlv.h"

enum batadv_bootpop {
	BATADV_BOOTREPLY	= 2,
};

enum batadv_boothtype {
	BATADV_HTYPE_ETHERNET	= 1,
};

enum batadv_dhcpoptioncode {
	BATADV_DHCP_OPT_PAD		= 0,
	BATADV_DHCP_OPT_MSG_TYPE	= 53,
	BATADV_DHCP_OPT_END		= 255,
};

enum batadv_dhcptype {
	BATADV_DHCPACK		= 5,
};

/* { 99, 130, 83, 99 } */
#define BATADV_DHCP_MAGIC 1669485411

struct batadv_dhcp_packet {
	__u8 op;
	__u8 htype;
	__u8 hlen;
	__u8 hops;
	__be32 xid;
	__be16 secs;
	__be16 flags;
	__be32 ciaddr;
	__be32 yiaddr;
	__be32 siaddr;
	__be32 giaddr;
	__u8 chaddr[16];
	__u8 sname[64];
	__u8 file[128];
	__be32 magic;
	__u8 options[0];
};

#define BATADV_DHCP_YIADDR_LEN sizeof(((struct batadv_dhcp_packet *)0)->yiaddr)
#define BATADV_DHCP_CHADDR_LEN sizeof(((struct batadv_dhcp_packet *)0)->chaddr)

static void batadv_dat_purge(struct work_struct *work);

/**
 * batadv_dat_start_timer() - initialise the DAT periodic worker
 * @bat_priv: the bat priv with all the soft interface information
 */
static void batadv_dat_start_timer(struct batadv_priv *bat_priv)
{
	INIT_DELAYED_WORK(&bat_priv->dat.work, batadv_dat_purge);
	queue_delayed_work(batadv_event_workqueue, &bat_priv->dat.work,
			   msecs_to_jiffies(10000));
}

/**
 * batadv_dat_entry_release() - release dat_entry from lists and queue for free
 *  after rcu grace period
 * @ref: kref pointer of the dat_entry
 */
static void batadv_dat_entry_release(struct kref *ref)
{
	struct batadv_dat_entry *dat_entry;

	dat_entry = container_of(ref, struct batadv_dat_entry, refcount);

	kfree_rcu(dat_entry, rcu);
}

/**
 * batadv_dat_entry_put() - decrement the dat_entry refcounter and possibly
 *  release it
 * @dat_entry: dat_entry to be free'd
 */
static void batadv_dat_entry_put(struct batadv_dat_entry *dat_entry)
{
	kref_put(&dat_entry->refcount, batadv_dat_entry_release);
}

/**
 * batadv_dat_to_purge() - check whether a dat_entry has to be purged or not
 * @dat_entry: the entry to check
 *
 * Return: true if the entry has to be purged now, false otherwise.
 */
static bool batadv_dat_to_purge(struct batadv_dat_entry *dat_entry)
{
	return batadv_has_timed_out(dat_entry->last_update,
				    BATADV_DAT_ENTRY_TIMEOUT);
}

/**
 * __batadv_dat_purge() - delete entries from the DAT local storage
 * @bat_priv: the bat priv with all the soft interface information
 * @to_purge: function in charge to decide whether an entry has to be purged or
 *	      not. This function takes the dat_entry as argument and has to
 *	      returns a boolean value: true is the entry has to be deleted,
 *	      false otherwise
 *
 * Loops over each entry in the DAT local storage and deletes it if and only if
 * the to_purge function passed as argument returns true.
 */
static void __batadv_dat_purge(struct batadv_priv *bat_priv,
			       bool (*to_purge)(struct batadv_dat_entry *))
{
	spinlock_t *list_lock; /* protects write access to the hash lists */
	struct batadv_dat_entry *dat_entry;
	struct hlist_node *node_tmp;
	struct hlist_head *head;
	u32 i;

	if (!bat_priv->dat.hash)
		return;

	for (i = 0; i < bat_priv->dat.hash->size; i++) {
		head = &bat_priv->dat.hash->table[i];
		list_lock = &bat_priv->dat.hash->list_locks[i];

		spin_lock_bh(list_lock);
		hlist_for_each_entry_safe(dat_entry, node_tmp, head,
					  hash_entry) {
			/* if a helper function has been passed as parameter,
			 * ask it if the entry has to be purged or not
			 */
			if (to_purge && !to_purge(dat_entry))
				continue;

			hlist_del_rcu(&dat_entry->hash_entry);
			batadv_dat_entry_put(dat_entry);
		}
		spin_unlock_bh(list_lock);
	}
}

/**
 * batadv_dat_purge() - periodic task that deletes old entries from the local
 *  DAT hash table
 * @work: kernel work struct
 */
static void batadv_dat_purge(struct work_struct *work)
{
	struct delayed_work *delayed_work;
	struct batadv_priv_dat *priv_dat;
	struct batadv_priv *bat_priv;

	delayed_work = to_delayed_work(work);
	priv_dat = container_of(delayed_work, struct batadv_priv_dat, work);
	bat_priv = container_of(priv_dat, struct batadv_priv, dat);

	__batadv_dat_purge(bat_priv, batadv_dat_to_purge);
	batadv_dat_start_timer(bat_priv);
}

/**
 * batadv_compare_dat() - comparing function used in the local DAT hash table
 * @node: node in the local table
 * @data2: second object to compare the node to
 *
 * Return: true if the two entries are the same, false otherwise.
 */
static bool batadv_compare_dat(const struct hlist_node *node, const void *data2)
{
	const void *data1 = container_of(node, struct batadv_dat_entry,
					 hash_entry);

	return memcmp(data1, data2, sizeof(__be32)) == 0;
}

/**
 * batadv_arp_hw_src() - extract the hw_src field from an ARP packet
 * @skb: ARP packet
 * @hdr_size: size of the possible header before the ARP packet
 *
 * Return: the value of the hw_src field in the ARP packet.
 */
static u8 *batadv_arp_hw_src(struct sk_buff *skb, int hdr_size)
{
	u8 *addr;

	addr = (u8 *)(skb->data + hdr_size);
	addr += ETH_HLEN + sizeof(struct arphdr);

	return addr;
}

/**
 * batadv_arp_ip_src() - extract the ip_src field from an ARP packet
 * @skb: ARP packet
 * @hdr_size: size of the possible header before the ARP packet
 *
 * Return: the value of the ip_src field in the ARP packet.
 */
static __be32 batadv_arp_ip_src(struct sk_buff *skb, int hdr_size)
{
	return *(__be32 *)(batadv_arp_hw_src(skb, hdr_size) + ETH_ALEN);
}

/**
 * batadv_arp_hw_dst() - extract the hw_dst field from an ARP packet
 * @skb: ARP packet
 * @hdr_size: size of the possible header before the ARP packet
 *
 * Return: the value of the hw_dst field in the ARP packet.
 */
static u8 *batadv_arp_hw_dst(struct sk_buff *skb, int hdr_size)
{
	return batadv_arp_hw_src(skb, hdr_size) + ETH_ALEN + 4;
}

/**
 * batadv_arp_ip_dst() - extract the ip_dst field from an ARP packet
 * @skb: ARP packet
 * @hdr_size: size of the possible header before the ARP packet
 *
 * Return: the value of the ip_dst field in the ARP packet.
 */
static __be32 batadv_arp_ip_dst(struct sk_buff *skb, int hdr_size)
{
	return *(__be32 *)(batadv_arp_hw_src(skb, hdr_size) + ETH_ALEN * 2 + 4);
}

/**
 * batadv_hash_dat() - compute the hash value for an IP address
 * @data: data to hash
 * @size: size of the hash table
 *
 * Return: the selected index in the hash table for the given data.
 */
static u32 batadv_hash_dat(const void *data, u32 size)
{
	u32 hash = 0;
	const struct batadv_dat_entry *dat = data;
	const unsigned char *key;
	__be16 vid;
	u32 i;

	key = (const unsigned char *)&dat->ip;
	for (i = 0; i < sizeof(dat->ip); i++) {
		hash += key[i];
		hash += (hash << 10);
		hash ^= (hash >> 6);
	}

	vid = htons(dat->vid);
	key = (__force const unsigned char *)&vid;
	for (i = 0; i < sizeof(dat->vid); i++) {
		hash += key[i];
		hash += (hash << 10);
		hash ^= (hash >> 6);
	}

	hash += (hash << 3);
	hash ^= (hash >> 11);
	hash += (hash << 15);

	return hash % size;
}

/**
 * batadv_dat_entry_hash_find() - look for a given dat_entry in the local hash
 * table
 * @bat_priv: the bat priv with all the soft interface information
 * @ip: search key
 * @vid: VLAN identifier
 *
 * Return: the dat_entry if found, NULL otherwise.
 */
static struct batadv_dat_entry *
batadv_dat_entry_hash_find(struct batadv_priv *bat_priv, __be32 ip,
			   unsigned short vid)
{
	struct hlist_head *head;
	struct batadv_dat_entry to_find, *dat_entry, *dat_entry_tmp = NULL;
	struct batadv_hashtable *hash = bat_priv->dat.hash;
	u32 index;

	if (!hash)
		return NULL;

	to_find.ip = ip;
	to_find.vid = vid;

	index = batadv_hash_dat(&to_find, hash->size);
	head = &hash->table[index];

	rcu_read_lock();
	hlist_for_each_entry_rcu(dat_entry, head, hash_entry) {
		if (dat_entry->ip != ip)
			continue;

		if (!kref_get_unless_zero(&dat_entry->refcount))
			continue;

		dat_entry_tmp = dat_entry;
		break;
	}
	rcu_read_unlock();

	return dat_entry_tmp;
}

/**
 * batadv_dat_entry_add() - add a new dat entry or update it if already exists
 * @bat_priv: the bat priv with all the soft interface information
 * @ip: ipv4 to add/edit
 * @mac_addr: mac address to assign to the given ipv4
 * @vid: VLAN identifier
 */
static void batadv_dat_entry_add(struct batadv_priv *bat_priv, __be32 ip,
				 u8 *mac_addr, unsigned short vid)
{
	struct batadv_dat_entry *dat_entry;
	int hash_added;

	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip, vid);
	/* if this entry is already known, just update it */
	if (dat_entry) {
		if (!batadv_compare_eth(dat_entry->mac_addr, mac_addr))
			ether_addr_copy(dat_entry->mac_addr, mac_addr);
		dat_entry->last_update = jiffies;
		batadv_dbg(BATADV_DBG_DAT, bat_priv,
			   "Entry updated: %pI4 %pM (vid: %d)\n",
			   &dat_entry->ip, dat_entry->mac_addr,
			   batadv_print_vid(vid));
		goto out;
	}

	dat_entry = kmalloc(sizeof(*dat_entry), GFP_ATOMIC);
	if (!dat_entry)
		goto out;

	dat_entry->ip = ip;
	dat_entry->vid = vid;
	ether_addr_copy(dat_entry->mac_addr, mac_addr);
	dat_entry->last_update = jiffies;
	kref_init(&dat_entry->refcount);

	kref_get(&dat_entry->refcount);
	hash_added = batadv_hash_add(bat_priv->dat.hash, batadv_compare_dat,
				     batadv_hash_dat, dat_entry,
				     &dat_entry->hash_entry);

	if (unlikely(hash_added != 0)) {
		/* remove the reference for the hash */
		batadv_dat_entry_put(dat_entry);
		goto out;
	}

	batadv_dbg(BATADV_DBG_DAT, bat_priv, "New entry added: %pI4 %pM (vid: %d)\n",
		   &dat_entry->ip, dat_entry->mac_addr, batadv_print_vid(vid));

out:
	if (dat_entry)
		batadv_dat_entry_put(dat_entry);
}

#ifdef CONFIG_BATMAN_ADV_DEBUG

/**
 * batadv_dbg_arp() - print a debug message containing all the ARP packet
 *  details
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: ARP packet
 * @hdr_size: size of the possible header before the ARP packet
 * @msg: message to print together with the debugging information
 */
static void batadv_dbg_arp(struct batadv_priv *bat_priv, struct sk_buff *skb,
			   int hdr_size, char *msg)
{
	struct batadv_unicast_4addr_packet *unicast_4addr_packet;
	struct batadv_bcast_packet *bcast_pkt;
	u8 *orig_addr;
	__be32 ip_src, ip_dst;

	if (msg)
		batadv_dbg(BATADV_DBG_DAT, bat_priv, "%s\n", msg);

	ip_src = batadv_arp_ip_src(skb, hdr_size);
	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
	batadv_dbg(BATADV_DBG_DAT, bat_priv,
		   "ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]\n",
		   batadv_arp_hw_src(skb, hdr_size), &ip_src,
		   batadv_arp_hw_dst(skb, hdr_size), &ip_dst);

	if (hdr_size < sizeof(struct batadv_unicast_packet))
		return;

	unicast_4addr_packet = (struct batadv_unicast_4addr_packet *)skb->data;

	switch (unicast_4addr_packet->u.packet_type) {
	case BATADV_UNICAST:
		batadv_dbg(BATADV_DBG_DAT, bat_priv,
			   "* encapsulated within a UNICAST packet\n");
		break;
	case BATADV_UNICAST_4ADDR:
		batadv_dbg(BATADV_DBG_DAT, bat_priv,
			   "* encapsulated within a UNICAST_4ADDR packet (src: %pM)\n",
			   unicast_4addr_packet->src);
		switch (unicast_4addr_packet->subtype) {
		case BATADV_P_DAT_DHT_PUT:
			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DAT_DHT_PUT\n");
			break;
		case BATADV_P_DAT_DHT_GET:
			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DAT_DHT_GET\n");
			break;
		case BATADV_P_DAT_CACHE_REPLY:
			batadv_dbg(BATADV_DBG_DAT, bat_priv,
				   "* type: DAT_CACHE_REPLY\n");
			break;
		case BATADV_P_DATA:
			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DATA\n");
			break;
		default:
			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: Unknown (%u)!\n",
				   unicast_4addr_packet->u.packet_type);
		}
		break;
	case BATADV_BCAST:
		bcast_pkt = (struct batadv_bcast_packet *)unicast_4addr_packet;
		orig_addr = bcast_pkt->orig;
		batadv_dbg(BATADV_DBG_DAT, bat_priv,
			   "* encapsulated within a BCAST packet (src: %pM)\n",
			   orig_addr);
		break;
	default:
		batadv_dbg(BATADV_DBG_DAT, bat_priv,
			   "* encapsulated within an unknown packet type (0x%x)\n",
			   unicast_4addr_packet->u.packet_type);
	}
}

#else

static void batadv_dbg_arp(struct batadv_priv *bat_priv, struct sk_buff *skb,
			   int hdr_size, char *msg)
{
}

#endif /* CONFIG_BATMAN_ADV_DEBUG */

/**
 * batadv_is_orig_node_eligible() - check whether a node can be a DHT candidate
 * @res: the array with the already selected candidates
 * @select: number of already selected candidates
 * @tmp_max: address of the currently evaluated node
 * @max: current round max address
 * @last_max: address of the last selected candidate
 * @candidate: orig_node under evaluation
 * @max_orig_node: last selected candidate
 *
 * Return: true if the node has been elected as next candidate or false
 * otherwise.
 */
static bool batadv_is_orig_node_eligible(struct batadv_dat_candidate *res,
					 int select, batadv_dat_addr_t tmp_max,
					 batadv_dat_addr_t max,
					 batadv_dat_addr_t last_max,
					 struct batadv_orig_node *candidate,
					 struct batadv_orig_node *max_orig_node)
{
	bool ret = false;
	int j;

	/* check if orig node candidate is running DAT */
	if (!test_bit(BATADV_ORIG_CAPA_HAS_DAT, &candidate->capabilities))
		goto out;

	/* Check if this node has already been selected... */
	for (j = 0; j < select; j++)
		if (res[j].orig_node == candidate)
			break;
	/* ..and possibly skip it */
	if (j < select)
		goto out;
	/* sanity check: has it already been selected? This should not happen */
	if (tmp_max > last_max)
		goto out;
	/* check if during this iteration an originator with a closer dht
	 * address has already been found
	 */
	if (tmp_max < max)
		goto out;
	/* this is an hash collision with the temporary selected node. Choose
	 * the one with the lowest address
	 */
	if (tmp_max == max && max_orig_node &&
	    batadv_compare_eth(candidate->orig, max_orig_node->orig))
		goto out;

	ret = true;
out:
	return ret;
}

/**
 * batadv_choose_next_candidate() - select the next DHT candidate
 * @bat_priv: the bat priv with all the soft interface information
 * @cands: candidates array
 * @select: number of candidates already present in the array
 * @ip_key: key to look up in the DHT
 * @last_max: pointer where the address of the selected candidate will be saved
 */
static void batadv_choose_next_candidate(struct batadv_priv *bat_priv,
					 struct batadv_dat_candidate *cands,
					 int select, batadv_dat_addr_t ip_key,
					 batadv_dat_addr_t *last_max)
{
	batadv_dat_addr_t max = 0;
	batadv_dat_addr_t tmp_max = 0;
	struct batadv_orig_node *orig_node, *max_orig_node = NULL;
	struct batadv_hashtable *hash = bat_priv->orig_hash;
	struct hlist_head *head;
	int i;

	/* if no node is eligible as candidate, leave the candidate type as
	 * NOT_FOUND
	 */
	cands[select].type = BATADV_DAT_CANDIDATE_NOT_FOUND;

	/* iterate over the originator list and find the node with the closest
	 * dat_address which has not been selected yet
	 */
	for (i = 0; i < hash->size; i++) {
		head = &hash->table[i];

		rcu_read_lock();
		hlist_for_each_entry_rcu(orig_node, head, hash_entry) {
			/* the dht space is a ring using unsigned addresses */
			tmp_max = BATADV_DAT_ADDR_MAX - orig_node->dat_addr +
				  ip_key;

			if (!batadv_is_orig_node_eligible(cands, select,
							  tmp_max, max,
							  *last_max, orig_node,
							  max_orig_node))
				continue;

			if (!kref_get_unless_zero(&orig_node->refcount))
				continue;

			max = tmp_max;
			if (max_orig_node)
				batadv_orig_node_put(max_orig_node);
			max_orig_node = orig_node;
		}
		rcu_read_unlock();
	}
	if (max_orig_node) {
		cands[select].type = BATADV_DAT_CANDIDATE_ORIG;
		cands[select].orig_node = max_orig_node;
		batadv_dbg(BATADV_DBG_DAT, bat_priv,
			   "dat_select_candidates() %d: selected %pM addr=%u dist=%u\n",
			   select, max_orig_node->orig, max_orig_node->dat_addr,
			   max);
	}
	*last_max = max;
}

/**
 * batadv_dat_select_candidates() - select the nodes which the DHT message has
 *  to be sent to
 * @bat_priv: the bat priv with all the soft interface information
 * @ip_dst: ipv4 to look up in the DHT
 * @vid: VLAN identifier
 *
 * An originator O is selected if and only if its DHT_ID value is one of three
 * closest values (from the LEFT, with wrap around if needed) then the hash
 * value of the key. ip_dst is the key.
 *
 * Return: the candidate array of size BATADV_DAT_CANDIDATE_NUM.
 */
static struct batadv_dat_candidate *
batadv_dat_select_candidates(struct batadv_priv *bat_priv, __be32 ip_dst,
			     unsigned short vid)
{
	int select;
	batadv_dat_addr_t last_max = BATADV_DAT_ADDR_MAX, ip_key;
	struct batadv_dat_candidate *res;
	struct batadv_dat_entry dat;

	if (!bat_priv->orig_hash)
		return NULL;

	res = kmalloc_array(BATADV_DAT_CANDIDATES_NUM, sizeof(*res),
			    GFP_ATOMIC);
	if (!res)
		return NULL;

	dat.ip = ip_dst;
	dat.vid = vid;
	ip_key = (batadv_dat_addr_t)batadv_hash_dat(&dat,
						    BATADV_DAT_ADDR_MAX);

	batadv_dbg(BATADV_DBG_DAT, bat_priv,
		   "%s(): IP=%pI4 hash(IP)=%u\n", __func__, &ip_dst,
		   ip_key);

	for (select = 0; select < BATADV_DAT_CANDIDATES_NUM; select++)
		batadv_choose_next_candidate(bat_priv, res, select, ip_key,
					     &last_max);

	return res;
}

/**
 * batadv_dat_forward_data() - copy and send payload to the selected candidates
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: payload to send
 * @ip: the DHT key
 * @vid: VLAN identifier
 * @packet_subtype: unicast4addr packet subtype to use
 *
 * This function copies the skb with pskb_copy() and is sent as unicast packet
 * to each of the selected candidates.
 *
 * Return: true if the packet is sent to at least one candidate, false
 * otherwise.
 */
static bool batadv_dat_forward_data(struct batadv_priv *bat_priv,
				    struct sk_buff *skb, __be32 ip,
				    unsigned short vid, int packet_subtype)
{
	int i;
	bool ret = false;
	int send_status;
	struct batadv_neigh_node *neigh_node = NULL;
	struct sk_buff *tmp_skb;
	struct batadv_dat_candidate *cand;

	cand = batadv_dat_select_candidates(bat_priv, ip, vid);
	if (!cand)
		goto out;

	batadv_dbg(BATADV_DBG_DAT, bat_priv, "DHT_SEND for %pI4\n", &ip);

	for (i = 0; i < BATADV_DAT_CANDIDATES_NUM; i++) {
		if (cand[i].type == BATADV_DAT_CANDIDATE_NOT_FOUND)
			continue;

		neigh_node = batadv_orig_router_get(cand[i].orig_node,
						    BATADV_IF_DEFAULT);
		if (!neigh_node)
			goto free_orig;

		tmp_skb = pskb_copy_for_clone(skb, GFP_ATOMIC);
		if (!batadv_send_skb_prepare_unicast_4addr(bat_priv, tmp_skb,
							   cand[i].orig_node,
							   packet_subtype)) {
			kfree_skb(tmp_skb);
			goto free_neigh;
		}

		send_status = batadv_send_unicast_skb(tmp_skb, neigh_node);
		if (send_status == NET_XMIT_SUCCESS) {
			/* count the sent packet */
			switch (packet_subtype) {
			case BATADV_P_DAT_DHT_GET:
				batadv_inc_counter(bat_priv,
						   BATADV_CNT_DAT_GET_TX);
				break;
			case BATADV_P_DAT_DHT_PUT:
				batadv_inc_counter(bat_priv,
						   BATADV_CNT_DAT_PUT_TX);
				break;
			}

			/* packet sent to a candidate: return true */
			ret = true;
		}
free_neigh:
		batadv_neigh_node_put(neigh_node);
free_orig:
		batadv_orig_node_put(cand[i].orig_node);
	}

out:
	kfree(cand);
	return ret;
}

/**
 * batadv_dat_tvlv_container_update() - update the dat tvlv container after dat
 *  setting change
 * @bat_priv: the bat priv with all the soft interface information
 */
static void batadv_dat_tvlv_container_update(struct batadv_priv *bat_priv)
{
	char dat_mode;

	dat_mode = atomic_read(&bat_priv->distributed_arp_table);

	switch (dat_mode) {
	case 0:
		batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_DAT, 1);
		break;
	case 1:
		batadv_tvlv_container_register(bat_priv, BATADV_TVLV_DAT, 1,
					       NULL, 0);
		break;
	}
}

/**
 * batadv_dat_status_update() - update the dat tvlv container after dat
 *  setting change
 * @net_dev: the soft interface net device
 */
void batadv_dat_status_update(struct net_device *net_dev)
{
	struct batadv_priv *bat_priv = netdev_priv(net_dev);

	batadv_dat_tvlv_container_update(bat_priv);
}

/**
 * batadv_dat_tvlv_ogm_handler_v1() - process incoming dat tvlv container
 * @bat_priv: the bat priv with all the soft interface information
 * @orig: the orig_node of the ogm
 * @flags: flags indicating the tvlv state (see batadv_tvlv_handler_flags)
 * @tvlv_value: tvlv buffer containing the gateway data
 * @tvlv_value_len: tvlv buffer length
 */
static void batadv_dat_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
					   struct batadv_orig_node *orig,
					   u8 flags,
					   void *tvlv_value, u16 tvlv_value_len)
{
	if (flags & BATADV_TVLV_HANDLER_OGM_CIFNOTFND)
		clear_bit(BATADV_ORIG_CAPA_HAS_DAT, &orig->capabilities);
	else
		set_bit(BATADV_ORIG_CAPA_HAS_DAT, &orig->capabilities);
}

/**
 * batadv_dat_hash_free() - free the local DAT hash table
 * @bat_priv: the bat priv with all the soft interface information
 */
static void batadv_dat_hash_free(struct batadv_priv *bat_priv)
{
	if (!bat_priv->dat.hash)
		return;

	__batadv_dat_purge(bat_priv, NULL);

	batadv_hash_destroy(bat_priv->dat.hash);

	bat_priv->dat.hash = NULL;
}

/**
 * batadv_dat_init() - initialise the DAT internals
 * @bat_priv: the bat priv with all the soft interface information
 *
 * Return: 0 in case of success, a negative error code otherwise
 */
int batadv_dat_init(struct batadv_priv *bat_priv)
{
	if (bat_priv->dat.hash)
		return 0;

	bat_priv->dat.hash = batadv_hash_new(1024);

	if (!bat_priv->dat.hash)
		return -ENOMEM;

	batadv_dat_start_timer(bat_priv);

	batadv_tvlv_handler_register(bat_priv, batadv_dat_tvlv_ogm_handler_v1,
				     NULL, BATADV_TVLV_DAT, 1,
				     BATADV_TVLV_HANDLER_OGM_CIFNOTFND);
	batadv_dat_tvlv_container_update(bat_priv);
	return 0;
}

/**
 * batadv_dat_free() - free the DAT internals
 * @bat_priv: the bat priv with all the soft interface information
 */
void batadv_dat_free(struct batadv_priv *bat_priv)
{
	batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_DAT, 1);
	batadv_tvlv_handler_unregister(bat_priv, BATADV_TVLV_DAT, 1);

	cancel_delayed_work_sync(&bat_priv->dat.work);

	batadv_dat_hash_free(bat_priv);
}

#ifdef CONFIG_BATMAN_ADV_DEBUGFS
/**
 * batadv_dat_cache_seq_print_text() - print the local DAT hash table
 * @seq: seq file to print on
 * @offset: not used
 *
 * Return: always 0
 */
int batadv_dat_cache_seq_print_text(struct seq_file *seq, void *offset)
{
	struct net_device *net_dev = (struct net_device *)seq->private;
	struct batadv_priv *bat_priv = netdev_priv(net_dev);
	struct batadv_hashtable *hash = bat_priv->dat.hash;
	struct batadv_dat_entry *dat_entry;
	struct batadv_hard_iface *primary_if;
	struct hlist_head *head;
	unsigned long last_seen_jiffies;
	int last_seen_msecs, last_seen_secs, last_seen_mins;
	u32 i;

	primary_if = batadv_seq_print_text_primary_if_get(seq);
	if (!primary_if)
		goto out;

	seq_printf(seq, "Distributed ARP Table (%s):\n", net_dev->name);
	seq_puts(seq,
		 "          IPv4             MAC        VID   last-seen\n");

	for (i = 0; i < hash->size; i++) {
		head = &hash->table[i];

		rcu_read_lock();
		hlist_for_each_entry_rcu(dat_entry, head, hash_entry) {
			last_seen_jiffies = jiffies - dat_entry->last_update;
			last_seen_msecs = jiffies_to_msecs(last_seen_jiffies);
			last_seen_mins = last_seen_msecs / 60000;
			last_seen_msecs = last_seen_msecs % 60000;
			last_seen_secs = last_seen_msecs / 1000;

			seq_printf(seq, " * %15pI4 %pM %4i %6i:%02i\n",
				   &dat_entry->ip, dat_entry->mac_addr,
				   batadv_print_vid(dat_entry->vid),
				   last_seen_mins, last_seen_secs);
		}
		rcu_read_unlock();
	}

out:
	if (primary_if)
		batadv_hardif_put(primary_if);
	return 0;
}
#endif

/**
 * batadv_dat_cache_dump_entry() - dump one entry of the DAT cache table to a
 *  netlink socket
 * @msg: buffer for the message
 * @portid: netlink port
 * @cb: Control block containing additional options
 * @dat_entry: entry to dump
 *
 * Return: 0 or error code.
 */
static int
batadv_dat_cache_dump_entry(struct sk_buff *msg, u32 portid,
			    struct netlink_callback *cb,
			    struct batadv_dat_entry *dat_entry)
{
	int msecs;
	void *hdr;

	hdr = genlmsg_put(msg, portid, cb->nlh->nlmsg_seq,
			  &batadv_netlink_family, NLM_F_MULTI,
			  BATADV_CMD_GET_DAT_CACHE);
	if (!hdr)
		return -ENOBUFS;

	genl_dump_check_consistent(cb, hdr);

	msecs = jiffies_to_msecs(jiffies - dat_entry->last_update);

	if (nla_put_in_addr(msg, BATADV_ATTR_DAT_CACHE_IP4ADDRESS,
			    dat_entry->ip) ||
	    nla_put(msg, BATADV_ATTR_DAT_CACHE_HWADDRESS, ETH_ALEN,
		    dat_entry->mac_addr) ||
	    nla_put_u16(msg, BATADV_ATTR_DAT_CACHE_VID, dat_entry->vid) ||
	    nla_put_u32(msg, BATADV_ATTR_LAST_SEEN_MSECS, msecs)) {
		genlmsg_cancel(msg, hdr);
		return -EMSGSIZE;
	}

	genlmsg_end(msg, hdr);
	return 0;
}

/**
 * batadv_dat_cache_dump_bucket() - dump one bucket of the DAT cache table to
 *  a netlink socket
 * @msg: buffer for the message
 * @portid: netlink port
 * @cb: Control block containing additional options
 * @hash: hash to dump
 * @bucket: bucket index to dump
 * @idx_skip: How many entries to skip
 *
 * Return: 0 or error code.
 */
static int
batadv_dat_cache_dump_bucket(struct sk_buff *msg, u32 portid,
			     struct netlink_callback *cb,
			     struct batadv_hashtable *hash, unsigned int bucket,
			     int *idx_skip)
{
	struct batadv_dat_entry *dat_entry;
	int idx = 0;

	spin_lock_bh(&hash->list_locks[bucket]);
	cb->seq = atomic_read(&hash->generation) << 1 | 1;

	hlist_for_each_entry(dat_entry, &hash->table[bucket], hash_entry) {
		if (idx < *idx_skip)
			goto skip;

		if (batadv_dat_cache_dump_entry(msg, portid, cb, dat_entry)) {
			spin_unlock_bh(&hash->list_locks[bucket]);
			*idx_skip = idx;

			return -EMSGSIZE;
		}

skip:
		idx++;
	}
	spin_unlock_bh(&hash->list_locks[bucket]);

	return 0;
}

/**
 * batadv_dat_cache_dump() - dump DAT cache table to a netlink socket
 * @msg: buffer for the message
 * @cb: callback structure containing arguments
 *
 * Return: message length.
 */
int batadv_dat_cache_dump(struct sk_buff *msg, struct netlink_callback *cb)
{
	struct batadv_hard_iface *primary_if = NULL;
	int portid = NETLINK_CB(cb->skb).portid;
	struct net *net = sock_net(cb->skb->sk);
	struct net_device *soft_iface;
	struct batadv_hashtable *hash;
	struct batadv_priv *bat_priv;
	int bucket = cb->args[0];
	int idx = cb->args[1];
	int ifindex;
	int ret = 0;

	ifindex = batadv_netlink_get_ifindex(cb->nlh,
					     BATADV_ATTR_MESH_IFINDEX);
	if (!ifindex)
		return -EINVAL;

	soft_iface = dev_get_by_index(net, ifindex);
	if (!soft_iface || !batadv_softif_is_valid(soft_iface)) {
		ret = -ENODEV;
		goto out;
	}

	bat_priv = netdev_priv(soft_iface);
	hash = bat_priv->dat.hash;

	primary_if = batadv_primary_if_get_selected(bat_priv);
	if (!primary_if || primary_if->if_status != BATADV_IF_ACTIVE) {
		ret = -ENOENT;
		goto out;
	}

	while (bucket < hash->size) {
		if (batadv_dat_cache_dump_bucket(msg, portid, cb, hash, bucket,
						 &idx))
			break;

		bucket++;
		idx = 0;
	}

	cb->args[0] = bucket;
	cb->args[1] = idx;

	ret = msg->len;

out:
	if (primary_if)
		batadv_hardif_put(primary_if);

	if (soft_iface)
		dev_put(soft_iface);

	return ret;
}

/**
 * batadv_arp_get_type() - parse an ARP packet and gets the type
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: packet to analyse
 * @hdr_size: size of the possible header before the ARP packet in the skb
 *
 * Return: the ARP type if the skb contains a valid ARP packet, 0 otherwise.
 */
static u16 batadv_arp_get_type(struct batadv_priv *bat_priv,
			       struct sk_buff *skb, int hdr_size)
{
	struct arphdr *arphdr;
	struct ethhdr *ethhdr;
	__be32 ip_src, ip_dst;
	u8 *hw_src, *hw_dst;
	u16 type = 0;

	/* pull the ethernet header */
	if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN)))
		goto out;

	ethhdr = (struct ethhdr *)(skb->data + hdr_size);

	if (ethhdr->h_proto != htons(ETH_P_ARP))
		goto out;

	/* pull the ARP payload */
	if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN +
				    arp_hdr_len(skb->dev))))
		goto out;

	arphdr = (struct arphdr *)(skb->data + hdr_size + ETH_HLEN);

	/* check whether the ARP packet carries a valid IP information */
	if (arphdr->ar_hrd != htons(ARPHRD_ETHER))
		goto out;

	if (arphdr->ar_pro != htons(ETH_P_IP))
		goto out;

	if (arphdr->ar_hln != ETH_ALEN)
		goto out;

	if (arphdr->ar_pln != 4)
		goto out;

	/* Check for bad reply/request. If the ARP message is not sane, DAT
	 * will simply ignore it
	 */
	ip_src = batadv_arp_ip_src(skb, hdr_size);
	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
	if (ipv4_is_loopback(ip_src) || ipv4_is_multicast(ip_src) ||
	    ipv4_is_loopback(ip_dst) || ipv4_is_multicast(ip_dst) ||
	    ipv4_is_zeronet(ip_src) || ipv4_is_lbcast(ip_src) ||
	    ipv4_is_zeronet(ip_dst) || ipv4_is_lbcast(ip_dst))
		goto out;

	hw_src = batadv_arp_hw_src(skb, hdr_size);
	if (is_zero_ether_addr(hw_src) || is_multicast_ether_addr(hw_src))
		goto out;

	/* don't care about the destination MAC address in ARP requests */
	if (arphdr->ar_op != htons(ARPOP_REQUEST)) {
		hw_dst = batadv_arp_hw_dst(skb, hdr_size);
		if (is_zero_ether_addr(hw_dst) ||
		    is_multicast_ether_addr(hw_dst))
			goto out;
	}

	type = ntohs(arphdr->ar_op);
out:
	return type;
}

/**
 * batadv_dat_get_vid() - extract the VLAN identifier from skb if any
 * @skb: the buffer containing the packet to extract the VID from
 * @hdr_size: the size of the batman-adv header encapsulating the packet
 *
 * Return: If the packet embedded in the skb is vlan tagged this function
 * returns the VID with the BATADV_VLAN_HAS_TAG flag. Otherwise BATADV_NO_FLAGS
 * is returned.
 */
static unsigned short batadv_dat_get_vid(struct sk_buff *skb, int *hdr_size)
{
	unsigned short vid;

	vid = batadv_get_vid(skb, *hdr_size);

	/* ARP parsing functions jump forward of hdr_size + ETH_HLEN.
	 * If the header contained in the packet is a VLAN one (which is longer)
	 * hdr_size is updated so that the functions will still skip the
	 * correct amount of bytes.
	 */
	if (vid & BATADV_VLAN_HAS_TAG)
		*hdr_size += VLAN_HLEN;

	return vid;
}

/**
 * batadv_dat_arp_create_reply() - create an ARP Reply
 * @bat_priv: the bat priv with all the soft interface information
 * @ip_src: ARP sender IP
 * @ip_dst: ARP target IP
 * @hw_src: Ethernet source and ARP sender MAC
 * @hw_dst: Ethernet destination and ARP target MAC
 * @vid: VLAN identifier (optional, set to zero otherwise)
 *
 * Creates an ARP Reply from the given values, optionally encapsulated in a
 * VLAN header.
 *
 * Return: An skb containing an ARP Reply.
 */
static struct sk_buff *
batadv_dat_arp_create_reply(struct batadv_priv *bat_priv, __be32 ip_src,
			    __be32 ip_dst, u8 *hw_src, u8 *hw_dst,
			    unsigned short vid)
{
	struct sk_buff *skb;

	skb = arp_create(ARPOP_REPLY, ETH_P_ARP, ip_dst, bat_priv->soft_iface,
			 ip_src, hw_dst, hw_src, hw_dst);
	if (!skb)
		return NULL;

	skb_reset_mac_header(skb);

	if (vid & BATADV_VLAN_HAS_TAG)
		skb = vlan_insert_tag(skb, htons(ETH_P_8021Q),
				      vid & VLAN_VID_MASK);

	return skb;
}

/**
 * batadv_dat_snoop_outgoing_arp_request() - snoop the ARP request and try to
 * answer using DAT
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: packet to check
 *
 * Return: true if the message has been sent to the dht candidates, false
 * otherwise. In case of a positive return value the message has to be enqueued
 * to permit the fallback.
 */
bool batadv_dat_snoop_outgoing_arp_request(struct batadv_priv *bat_priv,
					   struct sk_buff *skb)
{
	u16 type = 0;
	__be32 ip_dst, ip_src;
	u8 *hw_src;
	bool ret = false;
	struct batadv_dat_entry *dat_entry = NULL;
	struct sk_buff *skb_new;
	struct net_device *soft_iface = bat_priv->soft_iface;
	int hdr_size = 0;
	unsigned short vid;

	if (!atomic_read(&bat_priv->distributed_arp_table))
		goto out;

	vid = batadv_dat_get_vid(skb, &hdr_size);

	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
	/* If the node gets an ARP_REQUEST it has to send a DHT_GET unicast
	 * message to the selected DHT candidates
	 */
	if (type != ARPOP_REQUEST)
		goto out;

	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing outgoing ARP REQUEST");

	ip_src = batadv_arp_ip_src(skb, hdr_size);
	hw_src = batadv_arp_hw_src(skb, hdr_size);
	ip_dst = batadv_arp_ip_dst(skb, hdr_size);

	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);

	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst, vid);
	if (dat_entry) {
		/* If the ARP request is destined for a local client the local
		 * client will answer itself. DAT would only generate a
		 * duplicate packet.
		 *
		 * Moreover, if the soft-interface is enslaved into a bridge, an
		 * additional DAT answer may trigger kernel warnings about
		 * a packet coming from the wrong port.
		 */
		if (batadv_is_my_client(bat_priv, dat_entry->mac_addr, vid)) {
			ret = true;
			goto out;
		}

		/* If BLA is enabled, only send ARP replies if we have claimed
		 * the destination for the ARP request or if no one else of
		 * the backbone gws belonging to our backbone has claimed the
		 * destination.
		 */
		if (!batadv_bla_check_claim(bat_priv,
					    dat_entry->mac_addr, vid)) {
			batadv_dbg(BATADV_DBG_DAT, bat_priv,
				   "Device %pM claimed by another backbone gw. Don't send ARP reply!",
				   dat_entry->mac_addr);
			ret = true;
			goto out;
		}

		skb_new = batadv_dat_arp_create_reply(bat_priv, ip_dst, ip_src,
						      dat_entry->mac_addr,
						      hw_src, vid);
		if (!skb_new)
			goto out;

		skb_new->protocol = eth_type_trans(skb_new, soft_iface);

		batadv_inc_counter(bat_priv, BATADV_CNT_RX);
		batadv_add_counter(bat_priv, BATADV_CNT_RX_BYTES,
				   skb->len + ETH_HLEN + hdr_size);

		netif_rx(skb_new);
		batadv_dbg(BATADV_DBG_DAT, bat_priv, "ARP request replied locally\n");
		ret = true;
	} else {
		/* Send the request to the DHT */
		ret = batadv_dat_forward_data(bat_priv, skb, ip_dst, vid,
					      BATADV_P_DAT_DHT_GET);
	}
out:
	if (dat_entry)
		batadv_dat_entry_put(dat_entry);
	return ret;
}

/**
 * batadv_dat_snoop_incoming_arp_request() - snoop the ARP request and try to
 * answer using the local DAT storage
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: packet to check
 * @hdr_size: size of the encapsulation header
 *
 * Return: true if the request has been answered, false otherwise.
 */
bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv,
					   struct sk_buff *skb, int hdr_size)
{
	u16 type;
	__be32 ip_src, ip_dst;
	u8 *hw_src;
	struct sk_buff *skb_new;
	struct batadv_dat_entry *dat_entry = NULL;
	bool ret = false;
	unsigned short vid;
	int err;

	if (!atomic_read(&bat_priv->distributed_arp_table))
		goto out;

	vid = batadv_dat_get_vid(skb, &hdr_size);

	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
	if (type != ARPOP_REQUEST)
		goto out;

	hw_src = batadv_arp_hw_src(skb, hdr_size);
	ip_src = batadv_arp_ip_src(skb, hdr_size);
	ip_dst = batadv_arp_ip_dst(skb, hdr_size);

	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing incoming ARP REQUEST");

	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);

	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst, vid);
	if (!dat_entry)
		goto out;

	skb_new = batadv_dat_arp_create_reply(bat_priv, ip_dst, ip_src,
					      dat_entry->mac_addr, hw_src, vid);
	if (!skb_new)
		goto out;

	/* To preserve backwards compatibility, the node has choose the outgoing
	 * format based on the incoming request packet type. The assumption is
	 * that a node not using the 4addr packet format doesn't support it.
	 */
	if (hdr_size == sizeof(struct batadv_unicast_4addr_packet))
		err = batadv_send_skb_via_tt_4addr(bat_priv, skb_new,
						   BATADV_P_DAT_CACHE_REPLY,
						   NULL, vid);
	else
		err = batadv_send_skb_via_tt(bat_priv, skb_new, NULL, vid);

	if (err != NET_XMIT_DROP) {
		batadv_inc_counter(bat_priv, BATADV_CNT_DAT_CACHED_REPLY_TX);
		ret = true;
	}
out:
	if (dat_entry)
		batadv_dat_entry_put(dat_entry);
	if (ret)
		kfree_skb(skb);
	return ret;
}

/**
 * batadv_dat_snoop_outgoing_arp_reply() - snoop the ARP reply and fill the DHT
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: packet to check
 */
void batadv_dat_snoop_outgoing_arp_reply(struct batadv_priv *bat_priv,
					 struct sk_buff *skb)
{
	u16 type;
	__be32 ip_src, ip_dst;
	u8 *hw_src, *hw_dst;
	int hdr_size = 0;
	unsigned short vid;

	if (!atomic_read(&bat_priv->distributed_arp_table))
		return;

	vid = batadv_dat_get_vid(skb, &hdr_size);

	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
	if (type != ARPOP_REPLY)
		return;

	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing outgoing ARP REPLY");

	hw_src = batadv_arp_hw_src(skb, hdr_size);
	ip_src = batadv_arp_ip_src(skb, hdr_size);
	hw_dst = batadv_arp_hw_dst(skb, hdr_size);
	ip_dst = batadv_arp_ip_dst(skb, hdr_size);

	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
	batadv_dat_entry_add(bat_priv, ip_dst, hw_dst, vid);

	/* Send the ARP reply to the candidates for both the IP addresses that
	 * the node obtained from the ARP reply
	 */
	batadv_dat_forward_data(bat_priv, skb, ip_src, vid,
				BATADV_P_DAT_DHT_PUT);
	batadv_dat_forward_data(bat_priv, skb, ip_dst, vid,
				BATADV_P_DAT_DHT_PUT);
}

/**
 * batadv_dat_snoop_incoming_arp_reply() - snoop the ARP reply and fill the
 *  local DAT storage only
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: packet to check
 * @hdr_size: size of the encapsulation header
 *
 * Return: true if the packet was snooped and consumed by DAT. False if the
 * packet has to be delivered to the interface
 */
bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv,
					 struct sk_buff *skb, int hdr_size)
{
	struct batadv_dat_entry *dat_entry = NULL;
	u16 type;
	__be32 ip_src, ip_dst;
	u8 *hw_src, *hw_dst;
	bool dropped = false;
	unsigned short vid;

	if (!atomic_read(&bat_priv->distributed_arp_table))
		goto out;

	vid = batadv_dat_get_vid(skb, &hdr_size);

	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
	if (type != ARPOP_REPLY)
		goto out;

	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing incoming ARP REPLY");

	hw_src = batadv_arp_hw_src(skb, hdr_size);
	ip_src = batadv_arp_ip_src(skb, hdr_size);
	hw_dst = batadv_arp_hw_dst(skb, hdr_size);
	ip_dst = batadv_arp_ip_dst(skb, hdr_size);

	/* If ip_dst is already in cache and has the right mac address,
	 * drop this frame if this ARP reply is destined for us because it's
	 * most probably an ARP reply generated by another node of the DHT.
	 * We have most probably received already a reply earlier. Delivering
	 * this frame would lead to doubled receive of an ARP reply.
	 */
	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_src, vid);
	if (dat_entry && batadv_compare_eth(hw_src, dat_entry->mac_addr)) {
		batadv_dbg(BATADV_DBG_DAT, bat_priv, "Doubled ARP reply removed: ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]; dat_entry: %pM-%pI4\n",
			   hw_src, &ip_src, hw_dst, &ip_dst,
			   dat_entry->mac_addr,	&dat_entry->ip);
		dropped = true;
	}

	/* Update our internal cache with both the IP addresses the node got
	 * within the ARP reply
	 */
	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
	batadv_dat_entry_add(bat_priv, ip_dst, hw_dst, vid);

	if (dropped)
		goto out;

	/* If BLA is enabled, only forward ARP replies if we have claimed the
	 * source of the ARP reply or if no one else of the same backbone has
	 * already claimed that client. This prevents that different gateways
	 * to the same backbone all forward the ARP reply leading to multiple
	 * replies in the backbone.
	 */
	if (!batadv_bla_check_claim(bat_priv, hw_src, vid)) {
		batadv_dbg(BATADV_DBG_DAT, bat_priv,
			   "Device %pM claimed by another backbone gw. Drop ARP reply.\n",
			   hw_src);
		dropped = true;
		goto out;
	}

	/* if this REPLY is directed to a client of mine, let's deliver the
	 * packet to the interface
	 */
	dropped = !batadv_is_my_client(bat_priv, hw_dst, vid);

	/* if this REPLY is sent on behalf of a client of mine, let's drop the
	 * packet because the client will reply by itself
	 */
	dropped |= batadv_is_my_client(bat_priv, hw_src, vid);
out:
	if (dropped)
		kfree_skb(skb);
	if (dat_entry)
		batadv_dat_entry_put(dat_entry);
	/* if dropped == false -> deliver to the interface */
	return dropped;
}

/**
 * batadv_dat_check_dhcp_ipudp() - check skb for IP+UDP headers valid for DHCP
 * @skb: the packet to check
 * @ip_src: a buffer to store the IPv4 source address in
 *
 * Checks whether the given skb has an IP and UDP header valid for a DHCP
 * message from a DHCP server. And if so, stores the IPv4 source address in
 * the provided buffer.
 *
 * Return: True if valid, false otherwise.
 */
static bool
batadv_dat_check_dhcp_ipudp(struct sk_buff *skb, __be32 *ip_src)
{
	unsigned int offset = skb_network_offset(skb);
	struct udphdr *udphdr, _udphdr;
	struct iphdr *iphdr, _iphdr;

	iphdr = skb_header_pointer(skb, offset, sizeof(_iphdr), &_iphdr);
	if (!iphdr || iphdr->version != 4 || iphdr->ihl * 4 < sizeof(_iphdr))
		return false;

	if (iphdr->protocol != IPPROTO_UDP)
		return false;

	offset += iphdr->ihl * 4;
	skb_set_transport_header(skb, offset);

	udphdr = skb_header_pointer(skb, offset, sizeof(_udphdr), &_udphdr);
	if (!udphdr || udphdr->source != htons(67))
		return false;

	*ip_src = get_unaligned(&iphdr->saddr);

	return true;
}

/**
 * batadv_dat_check_dhcp() - examine packet for valid DHCP message
 * @skb: the packet to check
 * @proto: ethernet protocol hint (behind a potential vlan)
 * @ip_src: a buffer to store the IPv4 source address in
 *
 * Checks whether the given skb is a valid DHCP packet. And if so, stores the
 * IPv4 source address in the provided buffer.
 *
 * Caller needs to ensure that the skb network header is set correctly.
 *
 * Return: If skb is a valid DHCP packet, then returns its op code
 * (e.g. BOOTREPLY vs. BOOTREQUEST). Otherwise returns -EINVAL.
 */
static int
batadv_dat_check_dhcp(struct sk_buff *skb, __be16 proto, __be32 *ip_src)
{
	__be32 *magic, _magic;
	unsigned int offset;
	struct {
		__u8 op;
		__u8 htype;
		__u8 hlen;
		__u8 hops;
	} *dhcp_h, _dhcp_h;

	if (proto != htons(ETH_P_IP))
		return -EINVAL;

	if (!batadv_dat_check_dhcp_ipudp(skb, ip_src))
		return -EINVAL;

	offset = skb_transport_offset(skb) + sizeof(struct udphdr);
	if (skb->len < offset + sizeof(struct batadv_dhcp_packet))
		return -EINVAL;

	dhcp_h = skb_header_pointer(skb, offset, sizeof(_dhcp_h), &_dhcp_h);
	if (!dhcp_h || dhcp_h->htype != BATADV_HTYPE_ETHERNET ||
	    dhcp_h->hlen != ETH_ALEN)
		return -EINVAL;

	offset += offsetof(struct batadv_dhcp_packet, magic);

	magic = skb_header_pointer(skb, offset, sizeof(_magic), &_magic);
	if (!magic || get_unaligned(magic) != htonl(BATADV_DHCP_MAGIC))
		return -EINVAL;

	return dhcp_h->op;
}

/**
 * batadv_dat_get_dhcp_message_type() - get message type of a DHCP packet
 * @skb: the DHCP packet to parse
 *
 * Iterates over the DHCP options of the given DHCP packet to find a
 * DHCP Message Type option and parse it.
 *
 * Caller needs to ensure that the given skb is a valid DHCP packet and
 * that the skb transport header is set correctly.
 *
 * Return: The found DHCP message type value, if found. -EINVAL otherwise.
 */
static int batadv_dat_get_dhcp_message_type(struct sk_buff *skb)
{
	unsigned int offset = skb_transport_offset(skb) + sizeof(struct udphdr);
	u8 *type, _type;
	struct {
		u8 type;
		u8 len;
	} *tl, _tl;

	offset += sizeof(struct batadv_dhcp_packet);

	while ((tl = skb_header_pointer(skb, offset, sizeof(_tl), &_tl))) {
		if (tl->type == BATADV_DHCP_OPT_MSG_TYPE)
			break;

		if (tl->type == BATADV_DHCP_OPT_END)
			break;

		if (tl->type == BATADV_DHCP_OPT_PAD)
			offset++;
		else
			offset += tl->len + sizeof(_tl);
	}

	/* Option Overload Code not supported */
	if (!tl || tl->type != BATADV_DHCP_OPT_MSG_TYPE ||
	    tl->len != sizeof(_type))
		return -EINVAL;

	offset += sizeof(_tl);

	type = skb_header_pointer(skb, offset, sizeof(_type), &_type);
	if (!type)
		return -EINVAL;

	return *type;
}

/**
 * batadv_dat_get_dhcp_yiaddr() - get yiaddr from a DHCP packet
 * @skb: the DHCP packet to parse
 * @buf: a buffer to store the yiaddr in
 *
 * Caller needs to ensure that the given skb is a valid DHCP packet and
 * that the skb transport header is set correctly.
 *
 * Return: True on success, false otherwise.
 */
static bool batadv_dat_dhcp_get_yiaddr(struct sk_buff *skb, __be32 *buf)
{
	unsigned int offset = skb_transport_offset(skb) + sizeof(struct udphdr);
	__be32 *yiaddr;

	offset += offsetof(struct batadv_dhcp_packet, yiaddr);
	yiaddr = skb_header_pointer(skb, offset, BATADV_DHCP_YIADDR_LEN, buf);

	if (!yiaddr)
		return false;

	if (yiaddr != buf)
		*buf = get_unaligned(yiaddr);

	return true;
}

/**
 * batadv_dat_get_dhcp_chaddr() - get chaddr from a DHCP packet
 * @skb: the DHCP packet to parse
 * @buf: a buffer to store the chaddr in
 *
 * Caller needs to ensure that the given skb is a valid DHCP packet and
 * that the skb transport header is set correctly.
 *
 * Return: True on success, false otherwise
 */
static bool batadv_dat_get_dhcp_chaddr(struct sk_buff *skb, u8 *buf)
{
	unsigned int offset = skb_transport_offset(skb) + sizeof(struct udphdr);
	u8 *chaddr;

	offset += offsetof(struct batadv_dhcp_packet, chaddr);
	chaddr = skb_header_pointer(skb, offset, BATADV_DHCP_CHADDR_LEN, buf);

	if (!chaddr)
		return false;

	if (chaddr != buf)
		memcpy(buf, chaddr, BATADV_DHCP_CHADDR_LEN);

	return true;
}

/**
 * batadv_dat_put_dhcp() - puts addresses from a DHCP packet into the DHT and
 *  DAT cache
 * @bat_priv: the bat priv with all the soft interface information
 * @chaddr: the DHCP client MAC address
 * @yiaddr: the DHCP client IP address
 * @hw_dst: the DHCP server MAC address
 * @ip_dst: the DHCP server IP address
 * @vid: VLAN identifier
 *
 * Adds given MAC/IP pairs to the local DAT cache and propagates them further
 * into the DHT.
 *
 * For the DHT propagation, client MAC + IP will appear as the ARP Reply
 * transmitter (and hw_dst/ip_dst as the target).
 */
static void batadv_dat_put_dhcp(struct batadv_priv *bat_priv, u8 *chaddr,
				__be32 yiaddr, u8 *hw_dst, __be32 ip_dst,
				unsigned short vid)
{
	struct sk_buff *skb;

	skb = batadv_dat_arp_create_reply(bat_priv, yiaddr, ip_dst, chaddr,
					  hw_dst, vid);
	if (!skb)
		return;

	skb_set_network_header(skb, ETH_HLEN);

	batadv_dat_entry_add(bat_priv, yiaddr, chaddr, vid);
	batadv_dat_entry_add(bat_priv, ip_dst, hw_dst, vid);

	batadv_dat_forward_data(bat_priv, skb, yiaddr, vid,
				BATADV_P_DAT_DHT_PUT);
	batadv_dat_forward_data(bat_priv, skb, ip_dst, vid,
				BATADV_P_DAT_DHT_PUT);

	consume_skb(skb);

	batadv_dbg(BATADV_DBG_DAT, bat_priv,
		   "Snooped from outgoing DHCPACK (server address): %pI4, %pM (vid: %i)\n",
		   &ip_dst, hw_dst, batadv_print_vid(vid));
	batadv_dbg(BATADV_DBG_DAT, bat_priv,
		   "Snooped from outgoing DHCPACK (client address): %pI4, %pM (vid: %i)\n",
		   &yiaddr, chaddr, batadv_print_vid(vid));
}

/**
 * batadv_dat_check_dhcp_ack() - examine packet for valid DHCP message
 * @skb: the packet to check
 * @proto: ethernet protocol hint (behind a potential vlan)
 * @ip_src: a buffer to store the IPv4 source address in
 * @chaddr: a buffer to store the DHCP Client Hardware Address in
 * @yiaddr: a buffer to store the DHCP Your IP Address in
 *
 * Checks whether the given skb is a valid DHCPACK. And if so, stores the
 * IPv4 server source address (ip_src), client MAC address (chaddr) and client
 * IPv4 address (yiaddr) in the provided buffers.
 *
 * Caller needs to ensure that the skb network header is set correctly.
 *
 * Return: True if the skb is a valid DHCPACK. False otherwise.
 */
static bool
batadv_dat_check_dhcp_ack(struct sk_buff *skb, __be16 proto, __be32 *ip_src,
			  u8 *chaddr, __be32 *yiaddr)
{
	int type;

	type = batadv_dat_check_dhcp(skb, proto, ip_src);
	if (type != BATADV_BOOTREPLY)
		return false;

	type = batadv_dat_get_dhcp_message_type(skb);
	if (type != BATADV_DHCPACK)
		return false;

	if (!batadv_dat_dhcp_get_yiaddr(skb, yiaddr))
		return false;

	if (!batadv_dat_get_dhcp_chaddr(skb, chaddr))
		return false;

	return true;
}

/**
 * batadv_dat_snoop_outgoing_dhcp_ack() - snoop DHCPACK and fill DAT with it
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: the packet to snoop
 * @proto: ethernet protocol hint (behind a potential vlan)
 * @vid: VLAN identifier
 *
 * This function first checks whether the given skb is a valid DHCPACK. If
 * so then its source MAC and IP as well as its DHCP Client Hardware Address
 * field and DHCP Your IP Address field are added to the local DAT cache and
 * propagated into the DHT.
 *
 * Caller needs to ensure that the skb mac and network headers are set
 * correctly.
 */
void batadv_dat_snoop_outgoing_dhcp_ack(struct batadv_priv *bat_priv,
					struct sk_buff *skb,
					__be16 proto,
					unsigned short vid)
{
	u8 chaddr[BATADV_DHCP_CHADDR_LEN];
	__be32 ip_src, yiaddr;

	if (!atomic_read(&bat_priv->distributed_arp_table))
		return;

	if (!batadv_dat_check_dhcp_ack(skb, proto, &ip_src, chaddr, &yiaddr))
		return;

	batadv_dat_put_dhcp(bat_priv, chaddr, yiaddr, eth_hdr(skb)->h_source,
			    ip_src, vid);
}

/**
 * batadv_dat_snoop_incoming_dhcp_ack() - snoop DHCPACK and fill DAT cache
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: the packet to snoop
 * @hdr_size: header size, up to the tail of the batman-adv header
 *
 * This function first checks whether the given skb is a valid DHCPACK. If
 * so then its source MAC and IP as well as its DHCP Client Hardware Address
 * field and DHCP Your IP Address field are added to the local DAT cache.
 */
void batadv_dat_snoop_incoming_dhcp_ack(struct batadv_priv *bat_priv,
					struct sk_buff *skb, int hdr_size)
{
	u8 chaddr[BATADV_DHCP_CHADDR_LEN];
	struct ethhdr *ethhdr;
	__be32 ip_src, yiaddr;
	unsigned short vid;
	__be16 proto;
	u8 *hw_src;

	if (!atomic_read(&bat_priv->distributed_arp_table))
		return;

	if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN)))
		return;

	ethhdr = (struct ethhdr *)(skb->data + hdr_size);
	skb_set_network_header(skb, hdr_size + ETH_HLEN);
	proto = ethhdr->h_proto;

	if (!batadv_dat_check_dhcp_ack(skb, proto, &ip_src, chaddr, &yiaddr))
		return;

	hw_src = ethhdr->h_source;
	vid = batadv_dat_get_vid(skb, &hdr_size);

	batadv_dat_entry_add(bat_priv, yiaddr, chaddr, vid);
	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);

	batadv_dbg(BATADV_DBG_DAT, bat_priv,
		   "Snooped from incoming DHCPACK (server address): %pI4, %pM (vid: %i)\n",
		   &ip_src, hw_src, batadv_print_vid(vid));
	batadv_dbg(BATADV_DBG_DAT, bat_priv,
		   "Snooped from incoming DHCPACK (client address): %pI4, %pM (vid: %i)\n",
		   &yiaddr, chaddr, batadv_print_vid(vid));
}

/**
 * batadv_dat_drop_broadcast_packet() - check if an ARP request has to be
 *  dropped (because the node has already obtained the reply via DAT) or not
 * @bat_priv: the bat priv with all the soft interface information
 * @forw_packet: the broadcast packet
 *
 * Return: true if the node can drop the packet, false otherwise.
 */
bool batadv_dat_drop_broadcast_packet(struct batadv_priv *bat_priv,
				      struct batadv_forw_packet *forw_packet)
{
	u16 type;
	__be32 ip_dst;
	struct batadv_dat_entry *dat_entry = NULL;
	bool ret = false;
	int hdr_size = sizeof(struct batadv_bcast_packet);
	unsigned short vid;

	if (!atomic_read(&bat_priv->distributed_arp_table))
		goto out;

	/* If this packet is an ARP_REQUEST and the node already has the
	 * information that it is going to ask, then the packet can be dropped
	 */
	if (batadv_forw_packet_is_rebroadcast(forw_packet))
		goto out;

	vid = batadv_dat_get_vid(forw_packet->skb, &hdr_size);

	type = batadv_arp_get_type(bat_priv, forw_packet->skb, hdr_size);
	if (type != ARPOP_REQUEST)
		goto out;

	ip_dst = batadv_arp_ip_dst(forw_packet->skb, hdr_size);
	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst, vid);
	/* check if the node already got this entry */
	if (!dat_entry) {
		batadv_dbg(BATADV_DBG_DAT, bat_priv,
			   "ARP Request for %pI4: fallback\n", &ip_dst);
		goto out;
	}

	batadv_dbg(BATADV_DBG_DAT, bat_priv,
		   "ARP Request for %pI4: fallback prevented\n", &ip_dst);
	ret = true;

out:
	if (dat_entry)
		batadv_dat_entry_put(dat_entry);
	return ret;
}