summaryrefslogtreecommitdiffstats
path: root/net/802/garp.c
blob: 5dbe8967bbd56b0f60b08d926ae3bbf4ce68003f (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
/*
 *	IEEE 802.1D Generic Attribute Registration Protocol (GARP)
 *
 *	Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
 *
 *	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.
 */
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/rtnetlink.h>
#include <linux/llc.h>
#include <linux/slab.h>
#include <net/llc.h>
#include <net/llc_pdu.h>
#include <net/garp.h>
#include <asm/unaligned.h>

static unsigned int garp_join_time __read_mostly = 200;
module_param(garp_join_time, uint, 0644);
MODULE_PARM_DESC(garp_join_time, "Join time in ms (default 200ms)");
MODULE_LICENSE("GPL");

static const struct garp_state_trans {
	u8	state;
	u8	action;
} garp_applicant_state_table[GARP_APPLICANT_MAX + 1][GARP_EVENT_MAX + 1] = {
	[GARP_APPLICANT_VA] = {
		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_AA,
						    .action = GARP_ACTION_S_JOIN_IN },
		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_AA },
		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VA },
		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VA },
		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VA },
		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_INVALID },
		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_LA },
	},
	[GARP_APPLICANT_AA] = {
		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_QA,
						    .action = GARP_ACTION_S_JOIN_IN },
		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_QA },
		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VA },
		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VA },
		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VA },
		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_INVALID },
		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_LA },
	},
	[GARP_APPLICANT_QA] = {
		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_INVALID },
		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_QA },
		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VA },
		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VA },
		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_INVALID },
		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_LA },
	},
	[GARP_APPLICANT_LA] = {
		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_VO,
						    .action = GARP_ACTION_S_LEAVE_EMPTY },
		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_LA },
		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_LA },
		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_LA },
		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_VA },
		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_INVALID },
	},
	[GARP_APPLICANT_VP] = {
		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_AA,
						    .action = GARP_ACTION_S_JOIN_IN },
		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_AP },
		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_INVALID },
		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_VO },
	},
	[GARP_APPLICANT_AP] = {
		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_QA,
						    .action = GARP_ACTION_S_JOIN_IN },
		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_QP },
		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_INVALID },
		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_AO },
	},
	[GARP_APPLICANT_QP] = {
		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_INVALID },
		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_QP },
		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_INVALID },
		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_QO },
	},
	[GARP_APPLICANT_VO] = {
		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_INVALID },
		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_AO },
		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_VP },
		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_INVALID },
	},
	[GARP_APPLICANT_AO] = {
		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_INVALID },
		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_QO },
		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_AP },
		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_INVALID },
	},
	[GARP_APPLICANT_QO] = {
		[GARP_EVENT_TRANSMIT_PDU]	= { .state = GARP_APPLICANT_INVALID },
		[GARP_EVENT_R_JOIN_IN]		= { .state = GARP_APPLICANT_QO },
		[GARP_EVENT_R_JOIN_EMPTY]	= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_R_EMPTY]		= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_R_LEAVE_IN]		= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_R_LEAVE_EMPTY]	= { .state = GARP_APPLICANT_VO },
		[GARP_EVENT_REQ_JOIN]		= { .state = GARP_APPLICANT_QP },
		[GARP_EVENT_REQ_LEAVE]		= { .state = GARP_APPLICANT_INVALID },
	},
};

static int garp_attr_cmp(const struct garp_attr *attr,
			 const void *data, u8 len, u8 type)
{
	if (attr->type != type)
		return attr->type - type;
	if (attr->dlen != len)
		return attr->dlen - len;
	return memcmp(attr->data, data, len);
}

static struct garp_attr *garp_attr_lookup(const struct garp_applicant *app,
					  const void *data, u8 len, u8 type)
{
	struct rb_node *parent = app->gid.rb_node;
	struct garp_attr *attr;
	int d;

	while (parent) {
		attr = rb_entry(parent, struct garp_attr, node);
		d = garp_attr_cmp(attr, data, len, type);
		if (d < 0)
			parent = parent->rb_left;
		else if (d > 0)
			parent = parent->rb_right;
		else
			return attr;
	}
	return NULL;
}

static void garp_attr_insert(struct garp_applicant *app, struct garp_attr *new)
{
	struct rb_node *parent = NULL, **p = &app->gid.rb_node;
	struct garp_attr *attr;
	int d;

	while (*p) {
		parent = *p;
		attr = rb_entry(parent, struct garp_attr, node);
		d = garp_attr_cmp(attr, new->data, new->dlen, new->type);
		if (d < 0)
			p = &parent->rb_left;
		else if (d > 0)
			p = &parent->rb_right;
	}
	rb_link_node(&new->node, parent, p);
	rb_insert_color(&new->node, &app->gid);
}

static struct garp_attr *garp_attr_create(struct garp_applicant *app,
					  const void *data, u8 len, u8 type)
{
	struct garp_attr *attr;

	attr = kmalloc(sizeof(*attr) + len, GFP_ATOMIC);
	if (!attr)
		return attr;
	attr->state = GARP_APPLICANT_VO;
	attr->type  = type;
	attr->dlen  = len;
	memcpy(attr->data, data, len);
	garp_attr_insert(app, attr);
	return attr;
}

static void garp_attr_destroy(struct garp_applicant *app, struct garp_attr *attr)
{
	rb_erase(&attr->node, &app->gid);
	kfree(attr);
}

static int garp_pdu_init(struct garp_applicant *app)
{
	struct sk_buff *skb;
	struct garp_pdu_hdr *gp;

#define LLC_RESERVE	sizeof(struct llc_pdu_un)
	skb = alloc_skb(app->dev->mtu + LL_RESERVED_SPACE(app->dev),
			GFP_ATOMIC);
	if (!skb)
		return -ENOMEM;

	skb->dev = app->dev;
	skb->protocol = htons(ETH_P_802_2);
	skb_reserve(skb, LL_RESERVED_SPACE(app->dev) + LLC_RESERVE);

	gp = (struct garp_pdu_hdr *)__skb_put(skb, sizeof(*gp));
	put_unaligned(htons(GARP_PROTOCOL_ID), &gp->protocol);

	app->pdu = skb;
	return 0;
}

static int garp_pdu_append_end_mark(struct garp_applicant *app)
{
	if (skb_tailroom(app->pdu) < sizeof(u8))
		return -1;
	*(u8 *)__skb_put(app->pdu, sizeof(u8)) = GARP_END_MARK;
	return 0;
}

static void garp_pdu_queue(struct garp_applicant *app)
{
	if (!app->pdu)
		return;

	garp_pdu_append_end_mark(app);
	garp_pdu_append_end_mark(app);

	llc_pdu_header_init(app->pdu, LLC_PDU_TYPE_U, LLC_SAP_BSPAN,
			    LLC_SAP_BSPAN, LLC_PDU_CMD);
	llc_pdu_init_as_ui_cmd(app->pdu);
	llc_mac_hdr_init(app->pdu, app->dev->dev_addr,
			 app->app->proto.group_address);

	skb_queue_tail(&app->queue, app->pdu);
	app->pdu = NULL;
}

static void garp_queue_xmit(struct garp_applicant *app)
{
	struct sk_buff *skb;

	while ((skb = skb_dequeue(&app->queue)))
		dev_queue_xmit(skb);
}

static int garp_pdu_append_msg(struct garp_applicant *app, u8 attrtype)
{
	struct garp_msg_hdr *gm;

	if (skb_tailroom(app->pdu) < sizeof(*gm))
		return -1;
	gm = (struct garp_msg_hdr *)__skb_put(app->pdu, sizeof(*gm));
	gm->attrtype = attrtype;
	garp_cb(app->pdu)->cur_type = attrtype;
	return 0;
}

static int garp_pdu_append_attr(struct garp_applicant *app,
				const struct garp_attr *attr,
				enum garp_attr_event event)
{
	struct garp_attr_hdr *ga;
	unsigned int len;
	int err;
again:
	if (!app->pdu) {
		err = garp_pdu_init(app);
		if (err < 0)
			return err;
	}

	if (garp_cb(app->pdu)->cur_type != attr->type) {
		if (garp_cb(app->pdu)->cur_type &&
		    garp_pdu_append_end_mark(app) < 0)
			goto queue;
		if (garp_pdu_append_msg(app, attr->type) < 0)
			goto queue;
	}

	len = sizeof(*ga) + attr->dlen;
	if (skb_tailroom(app->pdu) < len)
		goto queue;
	ga = (struct garp_attr_hdr *)__skb_put(app->pdu, len);
	ga->len   = len;
	ga->event = event;
	memcpy(ga->data, attr->data, attr->dlen);
	return 0;

queue:
	garp_pdu_queue(app);
	goto again;
}

static void garp_attr_event(struct garp_applicant *app,
			    struct garp_attr *attr, enum garp_event event)
{
	enum garp_applicant_state state;

	state = garp_applicant_state_table[attr->state][event].state;
	if (state == GARP_APPLICANT_INVALID)
		return;

	switch (garp_applicant_state_table[attr->state][event].action) {
	case GARP_ACTION_NONE:
		break;
	case GARP_ACTION_S_JOIN_IN:
		/* When appending the attribute fails, don't update state in
		 * order to retry on next TRANSMIT_PDU event. */
		if (garp_pdu_append_attr(app, attr, GARP_JOIN_IN) < 0)
			return;
		break;
	case GARP_ACTION_S_LEAVE_EMPTY:
		garp_pdu_append_attr(app, attr, GARP_LEAVE_EMPTY);
		/* As a pure applicant, sending a leave message implies that
		 * the attribute was unregistered and can be destroyed. */
		garp_attr_destroy(app, attr);
		return;
	default:
		WARN_ON(1);
	}

	attr->state = state;
}

int garp_request_join(const struct net_device *dev,
		      const struct garp_application *appl,
		      const void *data, u8 len, u8 type)
{
	struct garp_port *port = rtnl_dereference(dev->garp_port);
	struct garp_applicant *app = rtnl_dereference(port->applicants[appl->type]);
	struct garp_attr *attr;

	spin_lock_bh(&app->lock);
	attr = garp_attr_create(app, data, len, type);
	if (!attr) {
		spin_unlock_bh(&app->lock);
		return -ENOMEM;
	}
	garp_attr_event(app, attr, GARP_EVENT_REQ_JOIN);
	spin_unlock_bh(&app->lock);
	return 0;
}
EXPORT_SYMBOL_GPL(garp_request_join);

void garp_request_leave(const struct net_device *dev,
			const struct garp_application *appl,
			const void *data, u8 len, u8 type)
{
	struct garp_port *port = rtnl_dereference(dev->garp_port);
	struct garp_applicant *app = rtnl_dereference(port->applicants[appl->type]);
	struct garp_attr *attr;

	spin_lock_bh(&app->lock);
	attr = garp_attr_lookup(app, data, len, type);
	if (!attr) {
		spin_unlock_bh(&app->lock);
		return;
	}
	garp_attr_event(app, attr, GARP_EVENT_REQ_LEAVE);
	spin_unlock_bh(&app->lock);
}
EXPORT_SYMBOL_GPL(garp_request_leave);

static void garp_gid_event(struct garp_applicant *app, enum garp_event event)
{
	struct rb_node *node, *next;
	struct garp_attr *attr;

	for (node = rb_first(&app->gid);
	     next = node ? rb_next(node) : NULL, node != NULL;
	     node = next) {
		attr = rb_entry(node, struct garp_attr, node);
		garp_attr_event(app, attr, event);
	}
}

static void garp_join_timer_arm(struct garp_applicant *app)
{
	unsigned long delay;

	delay = (u64)msecs_to_jiffies(garp_join_time) * net_random() >> 32;
	mod_timer(&app->join_timer, jiffies + delay);
}

static void garp_join_timer(unsigned long data)
{
	struct garp_applicant *app = (struct garp_applicant *)data;

	spin_lock(&app->lock);
	garp_gid_event(app, GARP_EVENT_TRANSMIT_PDU);
	garp_pdu_queue(app);
	spin_unlock(&app->lock);

	garp_queue_xmit(app);
	garp_join_timer_arm(app);
}

static int garp_pdu_parse_end_mark(struct sk_buff *skb)
{
	if (!pskb_may_pull(skb, sizeof(u8)))
		return -1;
	if (*skb->data == GARP_END_MARK) {
		skb_pull(skb, sizeof(u8));
		return -1;
	}
	return 0;
}

static int garp_pdu_parse_attr(struct garp_applicant *app, struct sk_buff *skb,
			       u8 attrtype)
{
	const struct garp_attr_hdr *ga;
	struct garp_attr *attr;
	enum garp_event event;
	unsigned int dlen;

	if (!pskb_may_pull(skb, sizeof(*ga)))
		return -1;
	ga = (struct garp_attr_hdr *)skb->data;
	if (ga->len < sizeof(*ga))
		return -1;

	if (!pskb_may_pull(skb, ga->len))
		return -1;
	skb_pull(skb, ga->len);
	dlen = sizeof(*ga) - ga->len;

	if (attrtype > app->app->maxattr)
		return 0;

	switch (ga->event) {
	case GARP_LEAVE_ALL:
		if (dlen != 0)
			return -1;
		garp_gid_event(app, GARP_EVENT_R_LEAVE_EMPTY);
		return 0;
	case GARP_JOIN_EMPTY:
		event = GARP_EVENT_R_JOIN_EMPTY;
		break;
	case GARP_JOIN_IN:
		event = GARP_EVENT_R_JOIN_IN;
		break;
	case GARP_LEAVE_EMPTY:
		event = GARP_EVENT_R_LEAVE_EMPTY;
		break;
	case GARP_EMPTY:
		event = GARP_EVENT_R_EMPTY;
		break;
	default:
		return 0;
	}

	if (dlen == 0)
		return -1;
	attr = garp_attr_lookup(app, ga->data, dlen, attrtype);
	if (attr == NULL)
		return 0;
	garp_attr_event(app, attr, event);
	return 0;
}

static int garp_pdu_parse_msg(struct garp_applicant *app, struct sk_buff *skb)
{
	const struct garp_msg_hdr *gm;

	if (!pskb_may_pull(skb, sizeof(*gm)))
		return -1;
	gm = (struct garp_msg_hdr *)skb->data;
	if (gm->attrtype == 0)
		return -1;
	skb_pull(skb, sizeof(*gm));

	while (skb->len > 0) {
		if (garp_pdu_parse_attr(app, skb, gm->attrtype) < 0)
			return -1;
		if (garp_pdu_parse_end_mark(skb) < 0)
			break;
	}
	return 0;
}

static void garp_pdu_rcv(const struct stp_proto *proto, struct sk_buff *skb,
			 struct net_device *dev)
{
	struct garp_application *appl = proto->data;
	struct garp_port *port;
	struct garp_applicant *app;
	const struct garp_pdu_hdr *gp;

	port = rcu_dereference(dev->garp_port);
	if (!port)
		goto err;
	app = rcu_dereference(port->applicants[appl->type]);
	if (!app)
		goto err;

	if (!pskb_may_pull(skb, sizeof(*gp)))
		goto err;
	gp = (struct garp_pdu_hdr *)skb->data;
	if (get_unaligned(&gp->protocol) != htons(GARP_PROTOCOL_ID))
		goto err;
	skb_pull(skb, sizeof(*gp));

	spin_lock(&app->lock);
	while (skb->len > 0) {
		if (garp_pdu_parse_msg(app, skb) < 0)
			break;
		if (garp_pdu_parse_end_mark(skb) < 0)
			break;
	}
	spin_unlock(&app->lock);
err:
	kfree_skb(skb);
}

static int garp_init_port(struct net_device *dev)
{
	struct garp_port *port;

	port = kzalloc(sizeof(*port), GFP_KERNEL);
	if (!port)
		return -ENOMEM;
	rcu_assign_pointer(dev->garp_port, port);
	return 0;
}

static void garp_kfree_rcu(struct rcu_head *head)
{
	kfree(container_of(head, struct garp_port, rcu));
}

static void garp_release_port(struct net_device *dev)
{
	struct garp_port *port = rtnl_dereference(dev->garp_port);
	unsigned int i;

	for (i = 0; i <= GARP_APPLICATION_MAX; i++) {
		if (rtnl_dereference(port->applicants[i]))
			return;
	}
	rcu_assign_pointer(dev->garp_port, NULL);
	call_rcu(&port->rcu, garp_kfree_rcu);
}

int garp_init_applicant(struct net_device *dev, struct garp_application *appl)
{
	struct garp_applicant *app;
	int err;

	ASSERT_RTNL();

	if (!rtnl_dereference(dev->garp_port)) {
		err = garp_init_port(dev);
		if (err < 0)
			goto err1;
	}

	err = -ENOMEM;
	app = kzalloc(sizeof(*app), GFP_KERNEL);
	if (!app)
		goto err2;

	err = dev_mc_add(dev, appl->proto.group_address);
	if (err < 0)
		goto err3;

	app->dev = dev;
	app->app = appl;
	app->gid = RB_ROOT;
	spin_lock_init(&app->lock);
	skb_queue_head_init(&app->queue);
	rcu_assign_pointer(dev->garp_port->applicants[appl->type], app);
	setup_timer(&app->join_timer, garp_join_timer, (unsigned long)app);
	garp_join_timer_arm(app);
	return 0;

err3:
	kfree(app);
err2:
	garp_release_port(dev);
err1:
	return err;
}
EXPORT_SYMBOL_GPL(garp_init_applicant);

void garp_uninit_applicant(struct net_device *dev, struct garp_application *appl)
{
	struct garp_port *port = rtnl_dereference(dev->garp_port);
	struct garp_applicant *app = rtnl_dereference(port->applicants[appl->type]);

	ASSERT_RTNL();

	rcu_assign_pointer(port->applicants[appl->type], NULL);
	synchronize_rcu();

	/* Delete timer and generate a final TRANSMIT_PDU event to flush out
	 * all pending messages before the applicant is gone. */
	del_timer_sync(&app->join_timer);
	garp_gid_event(app, GARP_EVENT_TRANSMIT_PDU);
	garp_pdu_queue(app);
	garp_queue_xmit(app);

	dev_mc_del(dev, appl->proto.group_address);
	kfree(app);
	garp_release_port(dev);
}
EXPORT_SYMBOL_GPL(garp_uninit_applicant);

int garp_register_application(struct garp_application *appl)
{
	appl->proto.rcv = garp_pdu_rcv;
	appl->proto.data = appl;
	return stp_proto_register(&appl->proto);
}
EXPORT_SYMBOL_GPL(garp_register_application);

void garp_unregister_application(struct garp_application *appl)
{
	stp_proto_unregister(&appl->proto);
}
EXPORT_SYMBOL_GPL(garp_unregister_application);