summaryrefslogtreecommitdiff
path: root/net/bridge/br_netfilter.c
blob: 008ff6c4eecf3da16c55901afd9e9fbde9f5ee2f (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
/*
 *	Handle firewalling
 *	Linux ethernet bridge
 *
 *	Authors:
 *	Lennert Buytenhek		<buytenh@gnu.org>
 *	Bart De Schuymer		<bdschuym@pandora.be>
 *
 *	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.
 *
 *	Lennert dedicates this file to Kerstin Wurdinger.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/ip.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/if_vlan.h>
#include <linux/if_pppox.h>
#include <linux/ppp_defs.h>
#include <linux/netfilter_bridge.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv6.h>
#include <linux/netfilter_arp.h>
#include <linux/in_route.h>
#include <linux/inetdevice.h>

#include <net/ip.h>
#include <net/ipv6.h>
#include <net/route.h>

#include <asm/uaccess.h>
#include "br_private.h"
#ifdef CONFIG_SYSCTL
#include <linux/sysctl.h>
#endif

#define skb_origaddr(skb)	 (((struct bridge_skb_cb *) \
				 (skb->nf_bridge->data))->daddr.ipv4)
#define store_orig_dstaddr(skb)	 (skb_origaddr(skb) = ip_hdr(skb)->daddr)
#define dnat_took_place(skb)	 (skb_origaddr(skb) != ip_hdr(skb)->daddr)

#ifdef CONFIG_SYSCTL
static struct ctl_table_header *brnf_sysctl_header;
static int brnf_call_iptables __read_mostly = 1;
static int brnf_call_ip6tables __read_mostly = 1;
static int brnf_call_arptables __read_mostly = 1;
static int brnf_filter_vlan_tagged __read_mostly = 0;
static int brnf_filter_pppoe_tagged __read_mostly = 0;
#else
#define brnf_call_iptables 1
#define brnf_call_ip6tables 1
#define brnf_call_arptables 1
#define brnf_filter_vlan_tagged 0
#define brnf_filter_pppoe_tagged 0
#endif

static inline __be16 vlan_proto(const struct sk_buff *skb)
{
	if (vlan_tx_tag_present(skb))
		return skb->protocol;
	else if (skb->protocol == htons(ETH_P_8021Q))
		return vlan_eth_hdr(skb)->h_vlan_encapsulated_proto;
	else
		return 0;
}

#define IS_VLAN_IP(skb) \
	(vlan_proto(skb) == htons(ETH_P_IP) && \
	 brnf_filter_vlan_tagged)

#define IS_VLAN_IPV6(skb) \
	(vlan_proto(skb) == htons(ETH_P_IPV6) && \
	 brnf_filter_vlan_tagged)

#define IS_VLAN_ARP(skb) \
	(vlan_proto(skb) == htons(ETH_P_ARP) &&	\
	 brnf_filter_vlan_tagged)

static inline __be16 pppoe_proto(const struct sk_buff *skb)
{
	return *((__be16 *)(skb_mac_header(skb) + ETH_HLEN +
			    sizeof(struct pppoe_hdr)));
}

#define IS_PPPOE_IP(skb) \
	(skb->protocol == htons(ETH_P_PPP_SES) && \
	 pppoe_proto(skb) == htons(PPP_IP) && \
	 brnf_filter_pppoe_tagged)

#define IS_PPPOE_IPV6(skb) \
	(skb->protocol == htons(ETH_P_PPP_SES) && \
	 pppoe_proto(skb) == htons(PPP_IPV6) && \
	 brnf_filter_pppoe_tagged)

static void fake_update_pmtu(struct dst_entry *dst, u32 mtu)
{
}

static struct dst_ops fake_dst_ops = {
	.family =		AF_INET,
	.protocol =		cpu_to_be16(ETH_P_IP),
	.update_pmtu =		fake_update_pmtu,
};

/*
 * Initialize bogus route table used to keep netfilter happy.
 * Currently, we fill in the PMTU entry because netfilter
 * refragmentation needs it, and the rt_flags entry because
 * ipt_REJECT needs it.  Future netfilter modules might
 * require us to fill additional fields.
 */
void br_netfilter_rtable_init(struct net_bridge *br)
{
	struct rtable *rt = &br->fake_rtable;

	atomic_set(&rt->dst.__refcnt, 1);
	rt->dst.dev = br->dev;
	rt->dst.path = &rt->dst;
	dst_metric_set(&rt->dst, RTAX_MTU, 1500);
	rt->dst.flags	= DST_NOXFRM;
	rt->dst.ops = &fake_dst_ops;
}

static inline struct rtable *bridge_parent_rtable(const struct net_device *dev)
{
	struct net_bridge_port *port;

	port = br_port_get_rcu(dev);
	return port ? &port->br->fake_rtable : NULL;
}

static inline struct net_device *bridge_parent(const struct net_device *dev)
{
	struct net_bridge_port *port;

	port = br_port_get_rcu(dev);
	return port ? port->br->dev : NULL;
}

static inline struct nf_bridge_info *nf_bridge_alloc(struct sk_buff *skb)
{
	skb->nf_bridge = kzalloc(sizeof(struct nf_bridge_info), GFP_ATOMIC);
	if (likely(skb->nf_bridge))
		atomic_set(&(skb->nf_bridge->use), 1);

	return skb->nf_bridge;
}

static inline struct nf_bridge_info *nf_bridge_unshare(struct sk_buff *skb)
{
	struct nf_bridge_info *nf_bridge = skb->nf_bridge;

	if (atomic_read(&nf_bridge->use) > 1) {
		struct nf_bridge_info *tmp = nf_bridge_alloc(skb);

		if (tmp) {
			memcpy(tmp, nf_bridge, sizeof(struct nf_bridge_info));
			atomic_set(&tmp->use, 1);
		}
		nf_bridge_put(nf_bridge);
		nf_bridge = tmp;
	}
	return nf_bridge;
}

static inline void nf_bridge_push_encap_header(struct sk_buff *skb)
{
	unsigned int len = nf_bridge_encap_header_len(skb);

	skb_push(skb, len);
	skb->network_header -= len;
}

static inline void nf_bridge_pull_encap_header(struct sk_buff *skb)
{
	unsigned int len = nf_bridge_encap_header_len(skb);

	skb_pull(skb, len);
	skb->network_header += len;
}

static inline void nf_bridge_pull_encap_header_rcsum(struct sk_buff *skb)
{
	unsigned int len = nf_bridge_encap_header_len(skb);

	skb_pull_rcsum(skb, len);
	skb->network_header += len;
}

static inline void nf_bridge_save_header(struct sk_buff *skb)
{
	int header_size = ETH_HLEN + nf_bridge_encap_header_len(skb);

	skb_copy_from_linear_data_offset(skb, -header_size,
					 skb->nf_bridge->data, header_size);
}

static inline void nf_bridge_update_protocol(struct sk_buff *skb)
{
	if (skb->nf_bridge->mask & BRNF_8021Q)
		skb->protocol = htons(ETH_P_8021Q);
	else if (skb->nf_bridge->mask & BRNF_PPPoE)
		skb->protocol = htons(ETH_P_PPP_SES);
}

/* When handing a packet over to the IP layer
 * check whether we have a skb that is in the
 * expected format
 */

static int br_parse_ip_options(struct sk_buff *skb)
{
	struct ip_options *opt;
	struct iphdr *iph;
	struct net_device *dev = skb->dev;
	u32 len;

	iph = ip_hdr(skb);
	opt = &(IPCB(skb)->opt);

	/* Basic sanity checks */
	if (iph->ihl < 5 || iph->version != 4)
		goto inhdr_error;

	if (!pskb_may_pull(skb, iph->ihl*4))
		goto inhdr_error;

	iph = ip_hdr(skb);
	if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
		goto inhdr_error;

	len = ntohs(iph->tot_len);
	if (skb->len < len) {
		IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS);
		goto drop;
	} else if (len < (iph->ihl*4))
		goto inhdr_error;

	if (pskb_trim_rcsum(skb, len)) {
		IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
		goto drop;
	}

	/* Zero out the CB buffer if no options present */
	if (iph->ihl == 5) {
		memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
		return 0;
	}

	opt->optlen = iph->ihl*4 - sizeof(struct iphdr);
	if (ip_options_compile(dev_net(dev), opt, skb))
		goto inhdr_error;

	/* Check correct handling of SRR option */
	if (unlikely(opt->srr)) {
		struct in_device *in_dev = __in_dev_get_rcu(dev);
		if (in_dev && !IN_DEV_SOURCE_ROUTE(in_dev))
			goto drop;

		if (ip_options_rcv_srr(skb))
			goto drop;
	}

	return 0;

inhdr_error:
	IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
drop:
	return -1;
}

/* Fill in the header for fragmented IP packets handled by
 * the IPv4 connection tracking code.
 */
int nf_bridge_copy_header(struct sk_buff *skb)
{
	int err;
	unsigned int header_size;

	nf_bridge_update_protocol(skb);
	header_size = ETH_HLEN + nf_bridge_encap_header_len(skb);
	err = skb_cow_head(skb, header_size);
	if (err)
		return err;

	skb_copy_to_linear_data_offset(skb, -header_size,
				       skb->nf_bridge->data, header_size);
	__skb_push(skb, nf_bridge_encap_header_len(skb));
	return 0;
}

/* PF_BRIDGE/PRE_ROUTING *********************************************/
/* Undo the changes made for ip6tables PREROUTING and continue the
 * bridge PRE_ROUTING hook. */
static int br_nf_pre_routing_finish_ipv6(struct sk_buff *skb)
{
	struct nf_bridge_info *nf_bridge = skb->nf_bridge;
	struct rtable *rt;

	if (nf_bridge->mask & BRNF_PKT_TYPE) {
		skb->pkt_type = PACKET_OTHERHOST;
		nf_bridge->mask ^= BRNF_PKT_TYPE;
	}
	nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING;

	rt = bridge_parent_rtable(nf_bridge->physindev);
	if (!rt) {
		kfree_skb(skb);
		return 0;
	}
	skb_dst_set_noref(skb, &rt->dst);

	skb->dev = nf_bridge->physindev;
	nf_bridge_update_protocol(skb);
	nf_bridge_push_encap_header(skb);
	NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
		       br_handle_frame_finish, 1);

	return 0;
}

/* Obtain the correct destination MAC address, while preserving the original
 * source MAC address. If we already know this address, we just copy it. If we
 * don't, we use the neighbour framework to find out. In both cases, we make
 * sure that br_handle_frame_finish() is called afterwards.
 */
static int br_nf_pre_routing_finish_bridge(struct sk_buff *skb)
{
	struct nf_bridge_info *nf_bridge = skb->nf_bridge;
	struct dst_entry *dst;

	skb->dev = bridge_parent(skb->dev);
	if (!skb->dev)
		goto free_skb;
	dst = skb_dst(skb);
	if (dst->hh) {
		neigh_hh_bridge(dst->hh, skb);
		skb->dev = nf_bridge->physindev;
		return br_handle_frame_finish(skb);
	} else if (dst->neighbour) {
		/* the neighbour function below overwrites the complete
		 * MAC header, so we save the Ethernet source address and
		 * protocol number. */
		skb_copy_from_linear_data_offset(skb, -(ETH_HLEN-ETH_ALEN), skb->nf_bridge->data, ETH_HLEN-ETH_ALEN);
		/* tell br_dev_xmit to continue with forwarding */
		nf_bridge->mask |= BRNF_BRIDGED_DNAT;
		return dst->neighbour->output(skb);
	}
free_skb:
	kfree_skb(skb);
	return 0;
}

/* This requires some explaining. If DNAT has taken place,
 * we will need to fix up the destination Ethernet address.
 *
 * There are two cases to consider:
 * 1. The packet was DNAT'ed to a device in the same bridge
 *    port group as it was received on. We can still bridge
 *    the packet.
 * 2. The packet was DNAT'ed to a different device, either
 *    a non-bridged device or another bridge port group.
 *    The packet will need to be routed.
 *
 * The correct way of distinguishing between these two cases is to
 * call ip_route_input() and to look at skb->dst->dev, which is
 * changed to the destination device if ip_route_input() succeeds.
 *
 * Let's first consider the case that ip_route_input() succeeds:
 *
 * If the output device equals the logical bridge device the packet
 * came in on, we can consider this bridging. The corresponding MAC
 * address will be obtained in br_nf_pre_routing_finish_bridge.
 * Otherwise, the packet is considered to be routed and we just
 * change the destination MAC address so that the packet will
 * later be passed up to the IP stack to be routed. For a redirected
 * packet, ip_route_input() will give back the localhost as output device,
 * which differs from the bridge device.
 *
 * Let's now consider the case that ip_route_input() fails:
 *
 * This can be because the destination address is martian, in which case
 * the packet will be dropped.
 * If IP forwarding is disabled, ip_route_input() will fail, while
 * ip_route_output_key() can return success. The source
 * address for ip_route_output_key() is set to zero, so ip_route_output_key()
 * thinks we're handling a locally generated packet and won't care
 * if IP forwarding is enabled. If the output device equals the logical bridge
 * device, we proceed as if ip_route_input() succeeded. If it differs from the
 * logical bridge port or if ip_route_output_key() fails we drop the packet.
 */
static int br_nf_pre_routing_finish(struct sk_buff *skb)
{
	struct net_device *dev = skb->dev;
	struct iphdr *iph = ip_hdr(skb);
	struct nf_bridge_info *nf_bridge = skb->nf_bridge;
	struct rtable *rt;
	int err;

	if (nf_bridge->mask & BRNF_PKT_TYPE) {
		skb->pkt_type = PACKET_OTHERHOST;
		nf_bridge->mask ^= BRNF_PKT_TYPE;
	}
	nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING;
	if (dnat_took_place(skb)) {
		if ((err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))) {
			struct in_device *in_dev = __in_dev_get_rcu(dev);

			/* If err equals -EHOSTUNREACH the error is due to a
			 * martian destination or due to the fact that
			 * forwarding is disabled. For most martian packets,
			 * ip_route_output_key() will fail. It won't fail for 2 types of
			 * martian destinations: loopback destinations and destination
			 * 0.0.0.0. In both cases the packet will be dropped because the
			 * destination is the loopback device and not the bridge. */
			if (err != -EHOSTUNREACH || !in_dev || IN_DEV_FORWARD(in_dev))
				goto free_skb;

			rt = ip_route_output(dev_net(dev), iph->daddr, 0,
					     RT_TOS(iph->tos), 0);
			if (!IS_ERR(rt)) {
				/* - Bridged-and-DNAT'ed traffic doesn't
				 *   require ip_forwarding. */
				if (rt->dst.dev == dev) {
					skb_dst_set(skb, &rt->dst);
					goto bridged_dnat;
				}
				ip_rt_put(rt);
			}
free_skb:
			kfree_skb(skb);
			return 0;
		} else {
			if (skb_dst(skb)->dev == dev) {
bridged_dnat:
				skb->dev = nf_bridge->physindev;
				nf_bridge_update_protocol(skb);
				nf_bridge_push_encap_header(skb);
				NF_HOOK_THRESH(NFPROTO_BRIDGE,
					       NF_BR_PRE_ROUTING,
					       skb, skb->dev, NULL,
					       br_nf_pre_routing_finish_bridge,
					       1);
				return 0;
			}
			memcpy(eth_hdr(skb)->h_dest, dev->dev_addr, ETH_ALEN);
			skb->pkt_type = PACKET_HOST;
		}
	} else {
		rt = bridge_parent_rtable(nf_bridge->physindev);
		if (!rt) {
			kfree_skb(skb);
			return 0;
		}
		skb_dst_set_noref(skb, &rt->dst);
	}

	skb->dev = nf_bridge->physindev;
	nf_bridge_update_protocol(skb);
	nf_bridge_push_encap_header(skb);
	NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
		       br_handle_frame_finish, 1);

	return 0;
}

/* Some common code for IPv4/IPv6 */
static struct net_device *setup_pre_routing(struct sk_buff *skb)
{
	struct nf_bridge_info *nf_bridge = skb->nf_bridge;

	if (skb->pkt_type == PACKET_OTHERHOST) {
		skb->pkt_type = PACKET_HOST;
		nf_bridge->mask |= BRNF_PKT_TYPE;
	}

	nf_bridge->mask |= BRNF_NF_BRIDGE_PREROUTING;
	nf_bridge->physindev = skb->dev;
	skb->dev = bridge_parent(skb->dev);
	if (skb->protocol == htons(ETH_P_8021Q))
		nf_bridge->mask |= BRNF_8021Q;
	else if (skb->protocol == htons(ETH_P_PPP_SES))
		nf_bridge->mask |= BRNF_PPPoE;

	return skb->dev;
}

/* We only check the length. A bridge shouldn't do any hop-by-hop stuff anyway */
static int check_hbh_len(struct sk_buff *skb)
{
	unsigned char *raw = (u8 *)(ipv6_hdr(skb) + 1);
	u32 pkt_len;
	const unsigned char *nh = skb_network_header(skb);
	int off = raw - nh;
	int len = (raw[1] + 1) << 3;

	if ((raw + len) - skb->data > skb_headlen(skb))
		goto bad;

	off += 2;
	len -= 2;

	while (len > 0) {
		int optlen = nh[off + 1] + 2;

		switch (nh[off]) {
		case IPV6_TLV_PAD0:
			optlen = 1;
			break;

		case IPV6_TLV_PADN:
			break;

		case IPV6_TLV_JUMBO:
			if (nh[off + 1] != 4 || (off & 3) != 2)
				goto bad;
			pkt_len = ntohl(*(__be32 *) (nh + off + 2));
			if (pkt_len <= IPV6_MAXPLEN ||
			    ipv6_hdr(skb)->payload_len)
				goto bad;
			if (pkt_len > skb->len - sizeof(struct ipv6hdr))
				goto bad;
			if (pskb_trim_rcsum(skb,
					    pkt_len + sizeof(struct ipv6hdr)))
				goto bad;
			nh = skb_network_header(skb);
			break;
		default:
			if (optlen > len)
				goto bad;
			break;
		}
		off += optlen;
		len -= optlen;
	}
	if (len == 0)
		return 0;
bad:
	return -1;

}

/* Replicate the checks that IPv6 does on packet reception and pass the packet
 * to ip6tables, which doesn't support NAT, so things are fairly simple. */
static unsigned int br_nf_pre_routing_ipv6(unsigned int hook,
					   struct sk_buff *skb,
					   const struct net_device *in,
					   const struct net_device *out,
					   int (*okfn)(struct sk_buff *))
{
	struct ipv6hdr *hdr;
	u32 pkt_len;

	if (skb->len < sizeof(struct ipv6hdr))
		return NF_DROP;

	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
		return NF_DROP;

	hdr = ipv6_hdr(skb);

	if (hdr->version != 6)
		return NF_DROP;

	pkt_len = ntohs(hdr->payload_len);

	if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
		if (pkt_len + sizeof(struct ipv6hdr) > skb->len)
			return NF_DROP;
		if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
			return NF_DROP;
	}
	if (hdr->nexthdr == NEXTHDR_HOP && check_hbh_len(skb))
		return NF_DROP;

	nf_bridge_put(skb->nf_bridge);
	if (!nf_bridge_alloc(skb))
		return NF_DROP;
	if (!setup_pre_routing(skb))
		return NF_DROP;

	skb->protocol = htons(ETH_P_IPV6);
	NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, skb, skb->dev, NULL,
		br_nf_pre_routing_finish_ipv6);

	return NF_STOLEN;
}

/* Direct IPv6 traffic to br_nf_pre_routing_ipv6.
 * Replicate the checks that IPv4 does on packet reception.
 * Set skb->dev to the bridge device (i.e. parent of the
 * receiving device) to make netfilter happy, the REDIRECT
 * target in particular.  Save the original destination IP
 * address to be able to detect DNAT afterwards. */
static unsigned int br_nf_pre_routing(unsigned int hook, struct sk_buff *skb,
				      const struct net_device *in,
				      const struct net_device *out,
				      int (*okfn)(struct sk_buff *))
{
	struct net_bridge_port *p;
	struct net_bridge *br;
	__u32 len = nf_bridge_encap_header_len(skb);

	if (unlikely(!pskb_may_pull(skb, len)))
		return NF_DROP;

	p = br_port_get_rcu(in);
	if (p == NULL)
		return NF_DROP;
	br = p->br;

	if (skb->protocol == htons(ETH_P_IPV6) || IS_VLAN_IPV6(skb) ||
	    IS_PPPOE_IPV6(skb)) {
		if (!brnf_call_ip6tables && !br->nf_call_ip6tables)
			return NF_ACCEPT;

		nf_bridge_pull_encap_header_rcsum(skb);
		return br_nf_pre_routing_ipv6(hook, skb, in, out, okfn);
	}

	if (!brnf_call_iptables && !br->nf_call_iptables)
		return NF_ACCEPT;

	if (skb->protocol != htons(ETH_P_IP) && !IS_VLAN_IP(skb) &&
	    !IS_PPPOE_IP(skb))
		return NF_ACCEPT;

	nf_bridge_pull_encap_header_rcsum(skb);

	if (br_parse_ip_options(skb))
		return NF_DROP;

	nf_bridge_put(skb->nf_bridge);
	if (!nf_bridge_alloc(skb))
		return NF_DROP;
	if (!setup_pre_routing(skb))
		return NF_DROP;
	store_orig_dstaddr(skb);
	skb->protocol = htons(ETH_P_IP);

	NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, skb->dev, NULL,
		br_nf_pre_routing_finish);

	return NF_STOLEN;
}


/* PF_BRIDGE/LOCAL_IN ************************************************/
/* The packet is locally destined, which requires a real
 * dst_entry, so detach the fake one.  On the way up, the
 * packet would pass through PRE_ROUTING again (which already
 * took place when the packet entered the bridge), but we
 * register an IPv4 PRE_ROUTING 'sabotage' hook that will
 * prevent this from happening. */
static unsigned int br_nf_local_in(unsigned int hook, struct sk_buff *skb,
				   const struct net_device *in,
				   const struct net_device *out,
				   int (*okfn)(struct sk_buff *))
{
	struct rtable *rt = skb_rtable(skb);

	if (rt && rt == bridge_parent_rtable(in))
		skb_dst_drop(skb);

	return NF_ACCEPT;
}

/* PF_BRIDGE/FORWARD *************************************************/
static int br_nf_forward_finish(struct sk_buff *skb)
{
	struct nf_bridge_info *nf_bridge = skb->nf_bridge;
	struct net_device *in;

	if (skb->protocol != htons(ETH_P_ARP) && !IS_VLAN_ARP(skb)) {
		in = nf_bridge->physindev;
		if (nf_bridge->mask & BRNF_PKT_TYPE) {
			skb->pkt_type = PACKET_OTHERHOST;
			nf_bridge->mask ^= BRNF_PKT_TYPE;
		}
		nf_bridge_update_protocol(skb);
	} else {
		in = *((struct net_device **)(skb->cb));
	}
	nf_bridge_push_encap_header(skb);

	NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_FORWARD, skb, in,
		       skb->dev, br_forward_finish, 1);
	return 0;
}

/* This is the 'purely bridged' case.  For IP, we pass the packet to
 * netfilter with indev and outdev set to the bridge device,
 * but we are still able to filter on the 'real' indev/outdev
 * because of the physdev module. For ARP, indev and outdev are the
 * bridge ports. */
static unsigned int br_nf_forward_ip(unsigned int hook, struct sk_buff *skb,
				     const struct net_device *in,
				     const struct net_device *out,
				     int (*okfn)(struct sk_buff *))
{
	struct nf_bridge_info *nf_bridge;
	struct net_device *parent;
	u_int8_t pf;

	if (!skb->nf_bridge)
		return NF_ACCEPT;

	/* Need exclusive nf_bridge_info since we might have multiple
	 * different physoutdevs. */
	if (!nf_bridge_unshare(skb))
		return NF_DROP;

	parent = bridge_parent(out);
	if (!parent)
		return NF_DROP;

	if (skb->protocol == htons(ETH_P_IP) || IS_VLAN_IP(skb) ||
	    IS_PPPOE_IP(skb))
		pf = PF_INET;
	else if (skb->protocol == htons(ETH_P_IPV6) || IS_VLAN_IPV6(skb) ||
		 IS_PPPOE_IPV6(skb))
		pf = PF_INET6;
	else
		return NF_ACCEPT;

	nf_bridge_pull_encap_header(skb);

	nf_bridge = skb->nf_bridge;
	if (skb->pkt_type == PACKET_OTHERHOST) {
		skb->pkt_type = PACKET_HOST;
		nf_bridge->mask |= BRNF_PKT_TYPE;
	}

	if (br_parse_ip_options(skb))
		return NF_DROP;

	/* The physdev module checks on this */
	nf_bridge->mask |= BRNF_BRIDGED;
	nf_bridge->physoutdev = skb->dev;
	if (pf == PF_INET)
		skb->protocol = htons(ETH_P_IP);
	else
		skb->protocol = htons(ETH_P_IPV6);

	NF_HOOK(pf, NF_INET_FORWARD, skb, bridge_parent(in), parent,
		br_nf_forward_finish);

	return NF_STOLEN;
}

static unsigned int br_nf_forward_arp(unsigned int hook, struct sk_buff *skb,
				      const struct net_device *in,
				      const struct net_device *out,
				      int (*okfn)(struct sk_buff *))
{
	struct net_bridge_port *p;
	struct net_bridge *br;
	struct net_device **d = (struct net_device **)(skb->cb);

	p = br_port_get_rcu(out);
	if (p == NULL)
		return NF_ACCEPT;
	br = p->br;

	if (!brnf_call_arptables && !br->nf_call_arptables)
		return NF_ACCEPT;

	if (skb->protocol != htons(ETH_P_ARP)) {
		if (!IS_VLAN_ARP(skb))
			return NF_ACCEPT;
		nf_bridge_pull_encap_header(skb);
	}

	if (arp_hdr(skb)->ar_pln != 4) {
		if (IS_VLAN_ARP(skb))
			nf_bridge_push_encap_header(skb);
		return NF_ACCEPT;
	}
	*d = (struct net_device *)in;
	NF_HOOK(NFPROTO_ARP, NF_ARP_FORWARD, skb, (struct net_device *)in,
		(struct net_device *)out, br_nf_forward_finish);

	return NF_STOLEN;
}

#if defined(CONFIG_NF_CONNTRACK_IPV4) || defined(CONFIG_NF_CONNTRACK_IPV4_MODULE)
static int br_nf_dev_queue_xmit(struct sk_buff *skb)
{
	int ret;

	if (skb->nfct != NULL && skb->protocol == htons(ETH_P_IP) &&
	    skb->len + nf_bridge_mtu_reduction(skb) > skb->dev->mtu &&
	    !skb_is_gso(skb)) {
		if (br_parse_ip_options(skb))
			/* Drop invalid packet */
			return NF_DROP;
		ret = ip_fragment(skb, br_dev_queue_push_xmit);
	} else
		ret = br_dev_queue_push_xmit(skb);

	return ret;
}
#else
static int br_nf_dev_queue_xmit(struct sk_buff *skb)
{
        return br_dev_queue_push_xmit(skb);
}
#endif

/* PF_BRIDGE/POST_ROUTING ********************************************/
static unsigned int br_nf_post_routing(unsigned int hook, struct sk_buff *skb,
				       const struct net_device *in,
				       const struct net_device *out,
				       int (*okfn)(struct sk_buff *))
{
	struct nf_bridge_info *nf_bridge = skb->nf_bridge;
	struct net_device *realoutdev = bridge_parent(skb->dev);
	u_int8_t pf;

	if (!nf_bridge || !(nf_bridge->mask & BRNF_BRIDGED))
		return NF_ACCEPT;

	if (!realoutdev)
		return NF_DROP;

	if (skb->protocol == htons(ETH_P_IP) || IS_VLAN_IP(skb) ||
	    IS_PPPOE_IP(skb))
		pf = PF_INET;
	else if (skb->protocol == htons(ETH_P_IPV6) || IS_VLAN_IPV6(skb) ||
		 IS_PPPOE_IPV6(skb))
		pf = PF_INET6;
	else
		return NF_ACCEPT;

	/* We assume any code from br_dev_queue_push_xmit onwards doesn't care
	 * about the value of skb->pkt_type. */
	if (skb->pkt_type == PACKET_OTHERHOST) {
		skb->pkt_type = PACKET_HOST;
		nf_bridge->mask |= BRNF_PKT_TYPE;
	}

	nf_bridge_pull_encap_header(skb);
	nf_bridge_save_header(skb);
	if (pf == PF_INET)
		skb->protocol = htons(ETH_P_IP);
	else
		skb->protocol = htons(ETH_P_IPV6);

	NF_HOOK(pf, NF_INET_POST_ROUTING, skb, NULL, realoutdev,
		br_nf_dev_queue_xmit);

	return NF_STOLEN;
}

/* IP/SABOTAGE *****************************************************/
/* Don't hand locally destined packets to PF_INET(6)/PRE_ROUTING
 * for the second time. */
static unsigned int ip_sabotage_in(unsigned int hook, struct sk_buff *skb,
				   const struct net_device *in,
				   const struct net_device *out,
				   int (*okfn)(struct sk_buff *))
{
	if (skb->nf_bridge &&
	    !(skb->nf_bridge->mask & BRNF_NF_BRIDGE_PREROUTING)) {
		return NF_STOP;
	}

	return NF_ACCEPT;
}

/* For br_nf_post_routing, we need (prio = NF_BR_PRI_LAST), because
 * br_dev_queue_push_xmit is called afterwards */
static struct nf_hook_ops br_nf_ops[] __read_mostly = {
	{
		.hook = br_nf_pre_routing,
		.owner = THIS_MODULE,
		.pf = PF_BRIDGE,
		.hooknum = NF_BR_PRE_ROUTING,
		.priority = NF_BR_PRI_BRNF,
	},
	{
		.hook = br_nf_local_in,
		.owner = THIS_MODULE,
		.pf = PF_BRIDGE,
		.hooknum = NF_BR_LOCAL_IN,
		.priority = NF_BR_PRI_BRNF,
	},
	{
		.hook = br_nf_forward_ip,
		.owner = THIS_MODULE,
		.pf = PF_BRIDGE,
		.hooknum = NF_BR_FORWARD,
		.priority = NF_BR_PRI_BRNF - 1,
	},
	{
		.hook = br_nf_forward_arp,
		.owner = THIS_MODULE,
		.pf = PF_BRIDGE,
		.hooknum = NF_BR_FORWARD,
		.priority = NF_BR_PRI_BRNF,
	},
	{
		.hook = br_nf_post_routing,
		.owner = THIS_MODULE,
		.pf = PF_BRIDGE,
		.hooknum = NF_BR_POST_ROUTING,
		.priority = NF_BR_PRI_LAST,
	},
	{
		.hook = ip_sabotage_in,
		.owner = THIS_MODULE,
		.pf = PF_INET,
		.hooknum = NF_INET_PRE_ROUTING,
		.priority = NF_IP_PRI_FIRST,
	},
	{
		.hook = ip_sabotage_in,
		.owner = THIS_MODULE,
		.pf = PF_INET6,
		.hooknum = NF_INET_PRE_ROUTING,
		.priority = NF_IP6_PRI_FIRST,
	},
};

#ifdef CONFIG_SYSCTL
static
int brnf_sysctl_call_tables(ctl_table * ctl, int write,
			    void __user * buffer, size_t * lenp, loff_t * ppos)
{
	int ret;

	ret = proc_dointvec(ctl, write, buffer, lenp, ppos);

	if (write && *(int *)(ctl->data))
		*(int *)(ctl->data) = 1;
	return ret;
}

static ctl_table brnf_table[] = {
	{
		.procname	= "bridge-nf-call-arptables",
		.data		= &brnf_call_arptables,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= brnf_sysctl_call_tables,
	},
	{
		.procname	= "bridge-nf-call-iptables",
		.data		= &brnf_call_iptables,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= brnf_sysctl_call_tables,
	},
	{
		.procname	= "bridge-nf-call-ip6tables",
		.data		= &brnf_call_ip6tables,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= brnf_sysctl_call_tables,
	},
	{
		.procname	= "bridge-nf-filter-vlan-tagged",
		.data		= &brnf_filter_vlan_tagged,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= brnf_sysctl_call_tables,
	},
	{
		.procname	= "bridge-nf-filter-pppoe-tagged",
		.data		= &brnf_filter_pppoe_tagged,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= brnf_sysctl_call_tables,
	},
	{ }
};

static struct ctl_path brnf_path[] = {
	{ .procname = "net", },
	{ .procname = "bridge", },
	{ }
};
#endif

int __init br_netfilter_init(void)
{
	int ret;

	ret = dst_entries_init(&fake_dst_ops);
	if (ret < 0)
		return ret;

	ret = nf_register_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
	if (ret < 0) {
		dst_entries_destroy(&fake_dst_ops);
		return ret;
	}
#ifdef CONFIG_SYSCTL
	brnf_sysctl_header = register_sysctl_paths(brnf_path, brnf_table);
	if (brnf_sysctl_header == NULL) {
		printk(KERN_WARNING
		       "br_netfilter: can't register to sysctl.\n");
		nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
		dst_entries_destroy(&fake_dst_ops);
		return -ENOMEM;
	}
#endif
	printk(KERN_NOTICE "Bridge firewalling registered\n");
	return 0;
}

void br_netfilter_fini(void)
{
	nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
#ifdef CONFIG_SYSCTL
	unregister_sysctl_table(brnf_sysctl_header);
#endif
	dst_entries_destroy(&fake_dst_ops);
}