Free Electrons

Embedded Linux Experts

  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
/*
 * Copyright 2011, Siemens AG
 * written by Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
 */

/*
 * Based on patches from Jon Smirl <jonsmirl@gmail.com>
 * Copyright (c) 2011 Jon Smirl <jonsmirl@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

/* Jon's code is based on 6lowpan implementation for Contiki which is:
 * Copyright (c) 2008, Swedish Institute of Computer Science.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <linux/bitops.h>
#include <linux/if_arp.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/netdevice.h>
#include <net/af_ieee802154.h>
#include <net/ieee802154.h>
#include <net/ieee802154_netdev.h>
#include <net/ipv6.h>

#include "6lowpan.h"

static LIST_HEAD(lowpan_devices);

/* private device info */
struct lowpan_dev_info {
	struct net_device	*real_dev; /* real WPAN device ptr */
	struct mutex		dev_list_mtx; /* mutex for list ops */
	unsigned short		fragment_tag;
};

struct lowpan_dev_record {
	struct net_device *ldev;
	struct list_head list;
};

struct lowpan_fragment {
	struct sk_buff		*skb;		/* skb to be assembled */
	u16			length;		/* length to be assemled */
	u32			bytes_rcv;	/* bytes received */
	u16			tag;		/* current fragment tag */
	struct timer_list	timer;		/* assembling timer */
	struct list_head	list;		/* fragments list */
};

static LIST_HEAD(lowpan_fragments);
static DEFINE_SPINLOCK(flist_lock);

static inline struct
lowpan_dev_info *lowpan_dev_info(const struct net_device *dev)
{
	return netdev_priv(dev);
}

static inline void lowpan_address_flip(u8 *src, u8 *dest)
{
	int i;
	for (i = 0; i < IEEE802154_ADDR_LEN; i++)
		(dest)[IEEE802154_ADDR_LEN - i - 1] = (src)[i];
}

static int lowpan_header_create(struct sk_buff *skb,
			   struct net_device *dev,
			   unsigned short type, const void *_daddr,
			   const void *_saddr, unsigned int len)
{
	const u8 *saddr = _saddr;
	const u8 *daddr = _daddr;
	struct ieee802154_addr sa, da;

	/* TODO:
	 * if this package isn't ipv6 one, where should it be routed?
	 */
	if (type != ETH_P_IPV6)
		return 0;

	if (!saddr)
		saddr = dev->dev_addr;

	raw_dump_inline(__func__, "saddr", (unsigned char *)saddr, 8);
	raw_dump_inline(__func__, "daddr", (unsigned char *)daddr, 8);

	lowpan_header_compress(skb, dev, type, daddr, saddr, len);

	/*
	 * NOTE1: I'm still unsure about the fact that compression and WPAN
	 * header are created here and not later in the xmit. So wait for
	 * an opinion of net maintainers.
	 */
	/*
	 * NOTE2: to be absolutely correct, we must derive PANid information
	 * from MAC subif of the 'dev' and 'real_dev' network devices, but
	 * this isn't implemented in mainline yet, so currently we assign 0xff
	 */
	mac_cb(skb)->flags = IEEE802154_FC_TYPE_DATA;
	mac_cb(skb)->seq = ieee802154_mlme_ops(dev)->get_dsn(dev);

	/* prepare wpan address data */
	sa.addr_type = IEEE802154_ADDR_LONG;
	sa.pan_id = ieee802154_mlme_ops(dev)->get_pan_id(dev);

	memcpy(&(sa.hwaddr), saddr, 8);
	/* intra-PAN communications */
	da.pan_id = ieee802154_mlme_ops(dev)->get_pan_id(dev);

	/*
	 * if the destination address is the broadcast address, use the
	 * corresponding short address
	 */
	if (lowpan_is_addr_broadcast(daddr)) {
		da.addr_type = IEEE802154_ADDR_SHORT;
		da.short_addr = IEEE802154_ADDR_BROADCAST;
	} else {
		da.addr_type = IEEE802154_ADDR_LONG;
		memcpy(&(da.hwaddr), daddr, IEEE802154_ADDR_LEN);

		/* request acknowledgment */
		mac_cb(skb)->flags |= MAC_CB_FLAG_ACKREQ;
	}

	return dev_hard_header(skb, lowpan_dev_info(dev)->real_dev,
			type, (void *)&da, (void *)&sa, skb->len);
}

static int lowpan_give_skb_to_devices(struct sk_buff *skb,
					struct net_device *dev)
{
	struct lowpan_dev_record *entry;
	struct sk_buff *skb_cp;
	int stat = NET_RX_SUCCESS;

	rcu_read_lock();
	list_for_each_entry_rcu(entry, &lowpan_devices, list)
		if (lowpan_dev_info(entry->ldev)->real_dev == skb->dev) {
			skb_cp = skb_copy(skb, GFP_ATOMIC);
			if (!skb_cp) {
				stat = -ENOMEM;
				break;
			}

			skb_cp->dev = entry->ldev;
			stat = netif_rx(skb_cp);
		}
	rcu_read_unlock();

	return stat;
}

static void lowpan_fragment_timer_expired(unsigned long entry_addr)
{
	struct lowpan_fragment *entry = (struct lowpan_fragment *)entry_addr;

	pr_debug("timer expired for frame with tag %d\n", entry->tag);

	list_del(&entry->list);
	dev_kfree_skb(entry->skb);
	kfree(entry);
}

static struct lowpan_fragment *
lowpan_alloc_new_frame(struct sk_buff *skb, u16 len, u16 tag)
{
	struct lowpan_fragment *frame;

	frame = kzalloc(sizeof(struct lowpan_fragment),
			GFP_ATOMIC);
	if (!frame)
		goto frame_err;

	INIT_LIST_HEAD(&frame->list);

	frame->length = len;
	frame->tag = tag;

	/* allocate buffer for frame assembling */
	frame->skb = netdev_alloc_skb_ip_align(skb->dev, frame->length +
					       sizeof(struct ipv6hdr));

	if (!frame->skb)
		goto skb_err;

	frame->skb->priority = skb->priority;

	/* reserve headroom for uncompressed ipv6 header */
	skb_reserve(frame->skb, sizeof(struct ipv6hdr));
	skb_put(frame->skb, frame->length);

	/* copy the first control block to keep a
	 * trace of the link-layer addresses in case
	 * of a link-local compressed address
	 */
	memcpy(frame->skb->cb, skb->cb, sizeof(skb->cb));

	init_timer(&frame->timer);
	/* time out is the same as for ipv6 - 60 sec */
	frame->timer.expires = jiffies + LOWPAN_FRAG_TIMEOUT;
	frame->timer.data = (unsigned long)frame;
	frame->timer.function = lowpan_fragment_timer_expired;

	add_timer(&frame->timer);

	list_add_tail(&frame->list, &lowpan_fragments);

	return frame;

skb_err:
	kfree(frame);
frame_err:
	return NULL;
}

static int process_data(struct sk_buff *skb)
{
	u8 iphc0, iphc1;
	const struct ieee802154_addr *_saddr, *_daddr;

	raw_dump_table(__func__, "raw skb data dump", skb->data, skb->len);
	/* at least two bytes will be used for the encoding */
	if (skb->len < 2)
		goto drop;

	if (lowpan_fetch_skb_u8(skb, &iphc0))
		goto drop;

	/* fragments assembling */
	switch (iphc0 & LOWPAN_DISPATCH_MASK) {
	case LOWPAN_DISPATCH_FRAG1:
	case LOWPAN_DISPATCH_FRAGN:
	{
		struct lowpan_fragment *frame;
		/* slen stores the rightmost 8 bits of the 11 bits length */
		u8 slen, offset = 0;
		u16 len, tag;
		bool found = false;

		if (lowpan_fetch_skb_u8(skb, &slen) || /* frame length */
		    lowpan_fetch_skb_u16(skb, &tag))  /* fragment tag */
			goto drop;

		/* adds the 3 MSB to the 8 LSB to retrieve the 11 bits length */
		len = ((iphc0 & 7) << 8) | slen;

		if ((iphc0 & LOWPAN_DISPATCH_MASK) == LOWPAN_DISPATCH_FRAG1) {
			pr_debug("%s received a FRAG1 packet (tag: %d, "
				 "size of the entire IP packet: %d)",
				 __func__, tag, len);
		} else { /* FRAGN */
			if (lowpan_fetch_skb_u8(skb, &offset))
				goto unlock_and_drop;
			pr_debug("%s received a FRAGN packet (tag: %d, "
				 "size of the entire IP packet: %d, "
				 "offset: %d)", __func__, tag, len, offset * 8);
		}

		/*
		 * check if frame assembling with the same tag is
		 * already in progress
		 */
		spin_lock_bh(&flist_lock);

		list_for_each_entry(frame, &lowpan_fragments, list)
			if (frame->tag == tag) {
				found = true;
				break;
			}

		/* alloc new frame structure */
		if (!found) {
			pr_debug("%s first fragment received for tag %d, "
				 "begin packet reassembly", __func__, tag);
			frame = lowpan_alloc_new_frame(skb, len, tag);
			if (!frame)
				goto unlock_and_drop;
		}

		/* if payload fits buffer, copy it */
		if (likely((offset * 8 + skb->len) <= frame->length))
			skb_copy_to_linear_data_offset(frame->skb, offset * 8,
							skb->data, skb->len);
		else
			goto unlock_and_drop;

		frame->bytes_rcv += skb->len;

		/* frame assembling complete */
		if ((frame->bytes_rcv == frame->length) &&
		     frame->timer.expires > jiffies) {
			/* if timer haven't expired - first of all delete it */
			del_timer_sync(&frame->timer);
			list_del(&frame->list);
			spin_unlock_bh(&flist_lock);

			pr_debug("%s successfully reassembled fragment "
				 "(tag %d)", __func__, tag);

			dev_kfree_skb(skb);
			skb = frame->skb;
			kfree(frame);

			if (lowpan_fetch_skb_u8(skb, &iphc0))
				goto drop;

			break;
		}
		spin_unlock_bh(&flist_lock);

		return kfree_skb(skb), 0;
	}
	default:
		break;
	}

	if (lowpan_fetch_skb_u8(skb, &iphc1))
		goto drop;

	_saddr = &mac_cb(skb)->sa;
	_daddr = &mac_cb(skb)->da;

	return lowpan_process_data(skb, skb->dev, (u8 *)_saddr->hwaddr,
				_saddr->addr_type, IEEE802154_ADDR_LEN,
				(u8 *)_daddr->hwaddr, _daddr->addr_type,
				IEEE802154_ADDR_LEN, iphc0, iphc1,
				lowpan_give_skb_to_devices);

unlock_and_drop:
	spin_unlock_bh(&flist_lock);
drop:
	kfree_skb(skb);
	return -EINVAL;
}

static int lowpan_set_address(struct net_device *dev, void *p)
{
	struct sockaddr *sa = p;

	if (netif_running(dev))
		return -EBUSY;

	/* TODO: validate addr */
	memcpy(dev->dev_addr, sa->sa_data, dev->addr_len);

	return 0;
}

static int
lowpan_fragment_xmit(struct sk_buff *skb, u8 *head,
			int mlen, int plen, int offset, int type)
{
	struct sk_buff *frag;
	int hlen;

	hlen = (type == LOWPAN_DISPATCH_FRAG1) ?
			LOWPAN_FRAG1_HEAD_SIZE : LOWPAN_FRAGN_HEAD_SIZE;

	raw_dump_inline(__func__, "6lowpan fragment header", head, hlen);

	frag = netdev_alloc_skb(skb->dev,
				hlen + mlen + plen + IEEE802154_MFR_SIZE);
	if (!frag)
		return -ENOMEM;

	frag->priority = skb->priority;

	/* copy header, MFR and payload */
	skb_put(frag, mlen);
	skb_copy_to_linear_data(frag, skb_mac_header(skb), mlen);

	skb_put(frag, hlen);
	skb_copy_to_linear_data_offset(frag, mlen, head, hlen);

	skb_put(frag, plen);
	skb_copy_to_linear_data_offset(frag, mlen + hlen,
				       skb_network_header(skb) + offset, plen);

	raw_dump_table(__func__, " raw fragment dump", frag->data, frag->len);

	return dev_queue_xmit(frag);
}

static int
lowpan_skb_fragmentation(struct sk_buff *skb, struct net_device *dev)
{
	int  err, header_length, payload_length, tag, offset = 0;
	u8 head[5];

	header_length = skb->mac_len;
	payload_length = skb->len - header_length;
	tag = lowpan_dev_info(dev)->fragment_tag++;

	/* first fragment header */
	head[0] = LOWPAN_DISPATCH_FRAG1 | ((payload_length >> 8) & 0x7);
	head[1] = payload_length & 0xff;
	head[2] = tag >> 8;
	head[3] = tag & 0xff;

	err = lowpan_fragment_xmit(skb, head, header_length, LOWPAN_FRAG_SIZE,
				   0, LOWPAN_DISPATCH_FRAG1);

	if (err) {
		pr_debug("%s unable to send FRAG1 packet (tag: %d)",
			 __func__, tag);
		goto exit;
	}

	offset = LOWPAN_FRAG_SIZE;

	/* next fragment header */
	head[0] &= ~LOWPAN_DISPATCH_FRAG1;
	head[0] |= LOWPAN_DISPATCH_FRAGN;

	while (payload_length - offset > 0) {
		int len = LOWPAN_FRAG_SIZE;

		head[4] = offset / 8;

		if (payload_length - offset < len)
			len = payload_length - offset;

		err = lowpan_fragment_xmit(skb, head, header_length,
					   len, offset, LOWPAN_DISPATCH_FRAGN);
		if (err) {
			pr_debug("%s unable to send a subsequent FRAGN packet "
				 "(tag: %d, offset: %d", __func__, tag, offset);
			goto exit;
		}

		offset += len;
	}

exit:
	return err;
}

static netdev_tx_t lowpan_xmit(struct sk_buff *skb, struct net_device *dev)
{
	int err = -1;

	pr_debug("package xmit\n");

	skb->dev = lowpan_dev_info(dev)->real_dev;
	if (skb->dev == NULL) {
		pr_debug("ERROR: no real wpan device found\n");
		goto error;
	}

	/* Send directly if less than the MTU minus the 2 checksum bytes. */
	if (skb->len <= IEEE802154_MTU - IEEE802154_MFR_SIZE) {
		err = dev_queue_xmit(skb);
		goto out;
	}

	pr_debug("frame is too big, fragmentation is needed\n");
	err = lowpan_skb_fragmentation(skb, dev);
error:
	dev_kfree_skb(skb);
out:
	if (err)
		pr_debug("ERROR: xmit failed\n");

	return (err < 0) ? NET_XMIT_DROP : err;
}

static struct wpan_phy *lowpan_get_phy(const struct net_device *dev)
{
	struct net_device *real_dev = lowpan_dev_info(dev)->real_dev;
	return ieee802154_mlme_ops(real_dev)->get_phy(real_dev);
}

static u16 lowpan_get_pan_id(const struct net_device *dev)
{
	struct net_device *real_dev = lowpan_dev_info(dev)->real_dev;
	return ieee802154_mlme_ops(real_dev)->get_pan_id(real_dev);
}

static u16 lowpan_get_short_addr(const struct net_device *dev)
{
	struct net_device *real_dev = lowpan_dev_info(dev)->real_dev;
	return ieee802154_mlme_ops(real_dev)->get_short_addr(real_dev);
}

static u8 lowpan_get_dsn(const struct net_device *dev)
{
	struct net_device *real_dev = lowpan_dev_info(dev)->real_dev;
	return ieee802154_mlme_ops(real_dev)->get_dsn(real_dev);
}

static struct header_ops lowpan_header_ops = {
	.create	= lowpan_header_create,
};

static struct lock_class_key lowpan_tx_busylock;
static struct lock_class_key lowpan_netdev_xmit_lock_key;

static void lowpan_set_lockdep_class_one(struct net_device *dev,
					 struct netdev_queue *txq,
					 void *_unused)
{
	lockdep_set_class(&txq->_xmit_lock,
			  &lowpan_netdev_xmit_lock_key);
}


static int lowpan_dev_init(struct net_device *dev)
{
	netdev_for_each_tx_queue(dev, lowpan_set_lockdep_class_one, NULL);
	dev->qdisc_tx_busylock = &lowpan_tx_busylock;
	return 0;
}

static const struct net_device_ops lowpan_netdev_ops = {
	.ndo_init		= lowpan_dev_init,
	.ndo_start_xmit		= lowpan_xmit,
	.ndo_set_mac_address	= lowpan_set_address,
};

static struct ieee802154_mlme_ops lowpan_mlme = {
	.get_pan_id = lowpan_get_pan_id,
	.get_phy = lowpan_get_phy,
	.get_short_addr = lowpan_get_short_addr,
	.get_dsn = lowpan_get_dsn,
};

static void lowpan_setup(struct net_device *dev)
{
	dev->addr_len		= IEEE802154_ADDR_LEN;
	memset(dev->broadcast, 0xff, IEEE802154_ADDR_LEN);
	dev->type		= ARPHRD_IEEE802154;
	/* Frame Control + Sequence Number + Address fields + Security Header */
	dev->hard_header_len	= 2 + 1 + 20 + 14;
	dev->needed_tailroom	= 2; /* FCS */
	dev->mtu		= 1281;
	dev->tx_queue_len	= 0;
	dev->flags		= IFF_BROADCAST | IFF_MULTICAST;
	dev->watchdog_timeo	= 0;

	dev->netdev_ops		= &lowpan_netdev_ops;
	dev->header_ops		= &lowpan_header_ops;
	dev->ml_priv		= &lowpan_mlme;
	dev->destructor		= free_netdev;
}

static int lowpan_validate(struct nlattr *tb[], struct nlattr *data[])
{
	if (tb[IFLA_ADDRESS]) {
		if (nla_len(tb[IFLA_ADDRESS]) != IEEE802154_ADDR_LEN)
			return -EINVAL;
	}
	return 0;
}

static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev,
	struct packet_type *pt, struct net_device *orig_dev)
{
	struct sk_buff *local_skb;

	if (!netif_running(dev))
		goto drop;

	if (dev->type != ARPHRD_IEEE802154)
		goto drop;

	/* check that it's our buffer */
	if (skb->data[0] == LOWPAN_DISPATCH_IPV6) {
		/* Copy the packet so that the IPv6 header is
		 * properly aligned.
		 */
		local_skb = skb_copy_expand(skb, NET_SKB_PAD - 1,
					    skb_tailroom(skb), GFP_ATOMIC);
		if (!local_skb)
			goto drop;

		local_skb->protocol = htons(ETH_P_IPV6);
		local_skb->pkt_type = PACKET_HOST;

		/* Pull off the 1-byte of 6lowpan header. */
		skb_pull(local_skb, 1);

		lowpan_give_skb_to_devices(local_skb, NULL);

		kfree_skb(local_skb);
		kfree_skb(skb);
	} else {
		switch (skb->data[0] & 0xe0) {
		case LOWPAN_DISPATCH_IPHC:	/* ipv6 datagram */
		case LOWPAN_DISPATCH_FRAG1:	/* first fragment header */
		case LOWPAN_DISPATCH_FRAGN:	/* next fragments headers */
			local_skb = skb_clone(skb, GFP_ATOMIC);
			if (!local_skb)
				goto drop;
			process_data(local_skb);

			kfree_skb(skb);
			break;
		default:
			break;
		}
	}

	return NET_RX_SUCCESS;

drop:
	kfree_skb(skb);
	return NET_RX_DROP;
}

static int lowpan_newlink(struct net *src_net, struct net_device *dev,
			  struct nlattr *tb[], struct nlattr *data[])
{
	struct net_device *real_dev;
	struct lowpan_dev_record *entry;

	pr_debug("adding new link\n");

	if (!tb[IFLA_LINK])
		return -EINVAL;
	/* find and hold real wpan device */
	real_dev = dev_get_by_index(src_net, nla_get_u32(tb[IFLA_LINK]));
	if (!real_dev)
		return -ENODEV;
	if (real_dev->type != ARPHRD_IEEE802154) {
		dev_put(real_dev);
		return -EINVAL;
	}

	lowpan_dev_info(dev)->real_dev = real_dev;
	lowpan_dev_info(dev)->fragment_tag = 0;
	mutex_init(&lowpan_dev_info(dev)->dev_list_mtx);

	entry = kzalloc(sizeof(struct lowpan_dev_record), GFP_KERNEL);
	if (!entry) {
		dev_put(real_dev);
		lowpan_dev_info(dev)->real_dev = NULL;
		return -ENOMEM;
	}

	entry->ldev = dev;

	/* Set the lowpan harware address to the wpan hardware address. */
	memcpy(dev->dev_addr, real_dev->dev_addr, IEEE802154_ADDR_LEN);

	mutex_lock(&lowpan_dev_info(dev)->dev_list_mtx);
	INIT_LIST_HEAD(&entry->list);
	list_add_tail(&entry->list, &lowpan_devices);
	mutex_unlock(&lowpan_dev_info(dev)->dev_list_mtx);

	register_netdevice(dev);

	return 0;
}

static void lowpan_dellink(struct net_device *dev, struct list_head *head)
{
	struct lowpan_dev_info *lowpan_dev = lowpan_dev_info(dev);
	struct net_device *real_dev = lowpan_dev->real_dev;
	struct lowpan_dev_record *entry, *tmp;

	ASSERT_RTNL();

	mutex_lock(&lowpan_dev_info(dev)->dev_list_mtx);
	list_for_each_entry_safe(entry, tmp, &lowpan_devices, list) {
		if (entry->ldev == dev) {
			list_del(&entry->list);
			kfree(entry);
		}
	}
	mutex_unlock(&lowpan_dev_info(dev)->dev_list_mtx);

	mutex_destroy(&lowpan_dev_info(dev)->dev_list_mtx);

	unregister_netdevice_queue(dev, head);

	dev_put(real_dev);
}

static struct rtnl_link_ops lowpan_link_ops __read_mostly = {
	.kind		= "lowpan",
	.priv_size	= sizeof(struct lowpan_dev_info),
	.setup		= lowpan_setup,
	.newlink	= lowpan_newlink,
	.dellink	= lowpan_dellink,
	.validate	= lowpan_validate,
};

static inline int __init lowpan_netlink_init(void)
{
	return rtnl_link_register(&lowpan_link_ops);
}

static inline void lowpan_netlink_fini(void)
{
	rtnl_link_unregister(&lowpan_link_ops);
}

static int lowpan_device_event(struct notifier_block *unused,
			       unsigned long event, void *ptr)
{
	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
	LIST_HEAD(del_list);
	struct lowpan_dev_record *entry, *tmp;

	if (dev->type != ARPHRD_IEEE802154)
		goto out;

	if (event == NETDEV_UNREGISTER) {
		list_for_each_entry_safe(entry, tmp, &lowpan_devices, list) {
			if (lowpan_dev_info(entry->ldev)->real_dev == dev)
				lowpan_dellink(entry->ldev, &del_list);
		}

		unregister_netdevice_many(&del_list);
	}

out:
	return NOTIFY_DONE;
}

static struct notifier_block lowpan_dev_notifier = {
	.notifier_call = lowpan_device_event,
};

static struct packet_type lowpan_packet_type = {
	.type = __constant_htons(ETH_P_IEEE802154),
	.func = lowpan_rcv,
};

static int __init lowpan_init_module(void)
{
	int err = 0;

	err = lowpan_netlink_init();
	if (err < 0)
		goto out;

	dev_add_pack(&lowpan_packet_type);

	err = register_netdevice_notifier(&lowpan_dev_notifier);
	if (err < 0) {
		dev_remove_pack(&lowpan_packet_type);
		lowpan_netlink_fini();
	}
out:
	return err;
}

static void __exit lowpan_cleanup_module(void)
{
	struct lowpan_fragment *frame, *tframe;

	lowpan_netlink_fini();

	dev_remove_pack(&lowpan_packet_type);

	unregister_netdevice_notifier(&lowpan_dev_notifier);

	/* Now 6lowpan packet_type is removed, so no new fragments are
	 * expected on RX, therefore that's the time to clean incomplete
	 * fragments.
	 */
	spin_lock_bh(&flist_lock);
	list_for_each_entry_safe(frame, tframe, &lowpan_fragments, list) {
		del_timer_sync(&frame->timer);
		list_del(&frame->list);
		dev_kfree_skb(frame->skb);
		kfree(frame);
	}
	spin_unlock_bh(&flist_lock);
}

module_init(lowpan_init_module);
module_exit(lowpan_cleanup_module);
MODULE_LICENSE("GPL");
MODULE_ALIAS_RTNL_LINK("lowpan");