summaryrefslogtreecommitdiffstats
path: root/net/sched/sch_netem.c
blob: 74fbdb52baedae504bf09d23a266e1abde884260 (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
/*
 * net/sched/sch_netem.c	Network emulator
 *
 * 		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.
 *
 *  		Many of the algorithms and ideas for this came from
 *		NIST Net which is not copyrighted.
 *
 * Authors:	Stephen Hemminger <shemminger@osdl.org>
 *		Catalin(ux aka Dino) BOIE <catab at umbrella dot ro>
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>

#include <net/netlink.h>
#include <net/pkt_sched.h>

#define VERSION "1.2"

/*	Network Emulation Queuing algorithm.
	====================================

	Sources: [1] Mark Carson, Darrin Santay, "NIST Net - A Linux-based
		 Network Emulation Tool
		 [2] Luigi Rizzo, DummyNet for FreeBSD

	 ----------------------------------------------------------------

	 This started out as a simple way to delay outgoing packets to
	 test TCP but has grown to include most of the functionality
	 of a full blown network emulator like NISTnet. It can delay
	 packets and add random jitter (and correlation). The random
	 distribution can be loaded from a table as well to provide
	 normal, Pareto, or experimental curves. Packet loss,
	 duplication, and reordering can also be emulated.

	 This qdisc does not do classification that can be handled in
	 layering other disciplines.  It does not need to do bandwidth
	 control either since that can be handled by using token
	 bucket or other rate control.

	 The simulator is limited by the Linux timer resolution
	 and will create packet bursts on the HZ boundary (1ms).
*/

struct netem_sched_data {
	struct Qdisc	*qdisc;
	struct qdisc_watchdog watchdog;

	psched_tdiff_t latency;
	psched_tdiff_t jitter;

	u32 loss;
	u32 limit;
	u32 counter;
	u32 gap;
	u32 duplicate;
	u32 reorder;
	u32 corrupt;

	struct crndstate {
		u32 last;
		u32 rho;
	} delay_cor, loss_cor, dup_cor, reorder_cor, corrupt_cor;

	struct disttable {
		u32  size;
		s16 table[0];
	} *delay_dist;
};

/* Time stamp put into socket buffer control block */
struct netem_skb_cb {
	psched_time_t	time_to_send;
};

static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)
{
	BUILD_BUG_ON(sizeof(skb->cb) <
		sizeof(struct qdisc_skb_cb) + sizeof(struct netem_skb_cb));
	return (struct netem_skb_cb *)qdisc_skb_cb(skb)->data;
}

/* init_crandom - initialize correlated random number generator
 * Use entropy source for initial seed.
 */
static void init_crandom(struct crndstate *state, unsigned long rho)
{
	state->rho = rho;
	state->last = net_random();
}

/* get_crandom - correlated random number generator
 * Next number depends on last value.
 * rho is scaled to avoid floating point.
 */
static u32 get_crandom(struct crndstate *state)
{
	u64 value, rho;
	unsigned long answer;

	if (state->rho == 0)	/* no correlation */
		return net_random();

	value = net_random();
	rho = (u64)state->rho + 1;
	answer = (value * ((1ull<<32) - rho) + state->last * rho) >> 32;
	state->last = answer;
	return answer;
}

/* tabledist - return a pseudo-randomly distributed value with mean mu and
 * std deviation sigma.  Uses table lookup to approximate the desired
 * distribution, and a uniformly-distributed pseudo-random source.
 */
static psched_tdiff_t tabledist(psched_tdiff_t mu, psched_tdiff_t sigma,
				struct crndstate *state,
				const struct disttable *dist)
{
	psched_tdiff_t x;
	long t;
	u32 rnd;

	if (sigma == 0)
		return mu;

	rnd = get_crandom(state);

	/* default uniform distribution */
	if (dist == NULL)
		return (rnd % (2*sigma)) - sigma + mu;

	t = dist->table[rnd % dist->size];
	x = (sigma % NETEM_DIST_SCALE) * t;
	if (x >= 0)
		x += NETEM_DIST_SCALE/2;
	else
		x -= NETEM_DIST_SCALE/2;

	return  x / NETEM_DIST_SCALE + (sigma / NETEM_DIST_SCALE) * t + mu;
}

/*
 * Insert one skb into qdisc.
 * Note: parent depends on return value to account for queue length.
 * 	NET_XMIT_DROP: queue length didn't change.
 *      NET_XMIT_SUCCESS: one skb was queued.
 */
static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
{
	struct netem_sched_data *q = qdisc_priv(sch);
	/* We don't fill cb now as skb_unshare() may invalidate it */
	struct netem_skb_cb *cb;
	struct sk_buff *skb2;
	int ret;
	int count = 1;

	pr_debug("netem_enqueue skb=%p\n", skb);

	/* Random duplication */
	if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor))
		++count;

	/* Random packet drop 0 => none, ~0 => all */
	if (q->loss && q->loss >= get_crandom(&q->loss_cor))
		--count;

	if (count == 0) {
		sch->qstats.drops++;
		kfree_skb(skb);
		return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
	}

	skb_orphan(skb);

	/*
	 * If we need to duplicate packet, then re-insert at top of the
	 * qdisc tree, since parent queuer expects that only one
	 * skb will be queued.
	 */
	if (count > 1 && (skb2 = skb_clone(skb, GFP_ATOMIC)) != NULL) {
		struct Qdisc *rootq = qdisc_root(sch);
		u32 dupsave = q->duplicate; /* prevent duplicating a dup... */
		q->duplicate = 0;

		qdisc_enqueue_root(skb2, rootq);
		q->duplicate = dupsave;
	}

	/*
	 * Randomized packet corruption.
	 * Make copy if needed since we are modifying
	 * If packet is going to be hardware checksummed, then
	 * do it now in software before we mangle it.
	 */
	if (q->corrupt && q->corrupt >= get_crandom(&q->corrupt_cor)) {
		if (!(skb = skb_unshare(skb, GFP_ATOMIC))
		    || (skb->ip_summed == CHECKSUM_PARTIAL
			&& skb_checksum_help(skb))) {
			sch->qstats.drops++;
			return NET_XMIT_DROP;
		}

		skb->data[net_random() % skb_headlen(skb)] ^= 1<<(net_random() % 8);
	}

	cb = netem_skb_cb(skb);
	if (q->gap == 0 		/* not doing reordering */
	    || q->counter < q->gap 	/* inside last reordering gap */
	    || q->reorder < get_crandom(&q->reorder_cor)) {
		psched_time_t now;
		psched_tdiff_t delay;

		delay = tabledist(q->latency, q->jitter,
				  &q->delay_cor, q->delay_dist);

		now = psched_get_time();
		cb->time_to_send = now + delay;
		++q->counter;
		ret = qdisc_enqueue(skb, q->qdisc);
	} else {
		/*
		 * Do re-ordering by putting one out of N packets at the front
		 * of the queue.
		 */
		cb->time_to_send = psched_get_time();
		q->counter = 0;
		ret = q->qdisc->ops->requeue(skb, q->qdisc);
	}

	if (likely(ret == NET_XMIT_SUCCESS)) {
		sch->q.qlen++;
		sch->bstats.bytes += qdisc_pkt_len(skb);
		sch->bstats.packets++;
	} else if (net_xmit_drop_count(ret)) {
		sch->qstats.drops++;
	}

	pr_debug("netem: enqueue ret %d\n", ret);
	return ret;
}

/* Requeue packets but don't change time stamp */
static int netem_requeue(struct sk_buff *skb, struct Qdisc *sch)
{
	struct netem_sched_data *q = qdisc_priv(sch);
	int ret;

	if ((ret = q->qdisc->ops->requeue(skb, q->qdisc)) == 0) {
		sch->q.qlen++;
		sch->qstats.requeues++;
	}

	return ret;
}

static unsigned int netem_drop(struct Qdisc* sch)
{
	struct netem_sched_data *q = qdisc_priv(sch);
	unsigned int len = 0;

	if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
		sch->q.qlen--;
		sch->qstats.drops++;
	}
	return len;
}

static struct sk_buff *netem_dequeue(struct Qdisc *sch)
{
	struct netem_sched_data *q = qdisc_priv(sch);
	struct sk_buff *skb;

	smp_mb();
	if (sch->flags & TCQ_F_THROTTLED)
		return NULL;

	skb = q->qdisc->ops->peek(q->qdisc);
	if (skb) {
		const struct netem_skb_cb *cb = netem_skb_cb(skb);
		psched_time_t now = psched_get_time();

		/* if more time remaining? */
		if (cb->time_to_send <= now) {
			skb = q->qdisc->dequeue(q->qdisc);
			if (!skb)
				return NULL;

			pr_debug("netem_dequeue: return skb=%p\n", skb);
			sch->q.qlen--;
			return skb;
		}

		qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
	}

	return NULL;
}

static void netem_reset(struct Qdisc *sch)
{
	struct netem_sched_data *q = qdisc_priv(sch);

	qdisc_reset(q->qdisc);
	sch->q.qlen = 0;
	qdisc_watchdog_cancel(&q->watchdog);
}

/*
 * Distribution data is a variable size payload containing
 * signed 16 bit values.
 */
static int get_dist_table(struct Qdisc *sch, const struct nlattr *attr)
{
	struct netem_sched_data *q = qdisc_priv(sch);
	unsigned long n = nla_len(attr)/sizeof(__s16);
	const __s16 *data = nla_data(attr);
	spinlock_t *root_lock;
	struct disttable *d;
	int i;

	if (n > 65536)
		return -EINVAL;

	d = kmalloc(sizeof(*d) + n*sizeof(d->table[0]), GFP_KERNEL);
	if (!d)
		return -ENOMEM;

	d->size = n;
	for (i = 0; i < n; i++)
		d->table[i] = data[i];

	root_lock = qdisc_root_sleeping_lock(sch);

	spin_lock_bh(root_lock);
	d = xchg(&q->delay_dist, d);
	spin_unlock_bh(root_lock);

	kfree(d);
	return 0;
}

static int get_correlation(struct Qdisc *sch, const struct nlattr *attr)
{
	struct netem_sched_data *q = qdisc_priv(sch);
	const struct tc_netem_corr *c = nla_data(attr);

	init_crandom(&q->delay_cor, c->delay_corr);
	init_crandom(&q->loss_cor, c->loss_corr);
	init_crandom(&q->dup_cor, c->dup_corr);
	return 0;
}

static int get_reorder(struct Qdisc *sch, const struct nlattr *attr)
{
	struct netem_sched_data *q = qdisc_priv(sch);
	const struct tc_netem_reorder *r = nla_data(attr);

	q->reorder = r->probability;
	init_crandom(&q->reorder_cor, r->correlation);
	return 0;
}

static int get_corrupt(struct Qdisc *sch, const struct nlattr *attr)
{
	struct netem_sched_data *q = qdisc_priv(sch);
	const struct tc_netem_corrupt *r = nla_data(attr);

	q->corrupt = r->probability;
	init_crandom(&q->corrupt_cor, r->correlation);
	return 0;
}

static const struct nla_policy netem_policy[TCA_NETEM_MAX + 1] = {
	[TCA_NETEM_CORR]	= { .len = sizeof(struct tc_netem_corr) },
	[TCA_NETEM_REORDER]	= { .len = sizeof(struct tc_netem_reorder) },
	[TCA_NETEM_CORRUPT]	= { .len = sizeof(struct tc_netem_corrupt) },
};

static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
		      const struct nla_policy *policy, int len)
{
	int nested_len = nla_len(nla) - NLA_ALIGN(len);

	if (nested_len < 0)
		return -EINVAL;
	if (nested_len >= nla_attr_size(0))
		return nla_parse(tb, maxtype, nla_data(nla) + NLA_ALIGN(len),
				 nested_len, policy);
	memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
	return 0;
}

/* Parse netlink message to set options */
static int netem_change(struct Qdisc *sch, struct nlattr *opt)
{
	struct netem_sched_data *q = qdisc_priv(sch);
	struct nlattr *tb[TCA_NETEM_MAX + 1];
	struct tc_netem_qopt *qopt;
	int ret;

	if (opt == NULL)
		return -EINVAL;

	qopt = nla_data(opt);
	ret = parse_attr(tb, TCA_NETEM_MAX, opt, netem_policy, sizeof(*qopt));
	if (ret < 0)
		return ret;

	ret = fifo_set_limit(q->qdisc, qopt->limit);
	if (ret) {
		pr_debug("netem: can't set fifo limit\n");
		return ret;
	}

	q->latency = qopt->latency;
	q->jitter = qopt->jitter;
	q->limit = qopt->limit;
	q->gap = qopt->gap;
	q->counter = 0;
	q->loss = qopt->loss;
	q->duplicate = qopt->duplicate;

	/* for compatibility with earlier versions.
	 * if gap is set, need to assume 100% probability
	 */
	if (q->gap)
		q->reorder = ~0;

	if (tb[TCA_NETEM_CORR]) {
		ret = get_correlation(sch, tb[TCA_NETEM_CORR]);
		if (ret)
			return ret;
	}

	if (tb[TCA_NETEM_DELAY_DIST]) {
		ret = get_dist_table(sch, tb[TCA_NETEM_DELAY_DIST]);
		if (ret)
			return ret;
	}

	if (tb[TCA_NETEM_REORDER]) {
		ret = get_reorder(sch, tb[TCA_NETEM_REORDER]);
		if (ret)
			return ret;
	}

	if (tb[TCA_NETEM_CORRUPT]) {
		ret = get_corrupt(sch, tb[TCA_NETEM_CORRUPT]);
		if (ret)
			return ret;
	}

	return 0;
}

/*
 * Special case version of FIFO queue for use by netem.
 * It queues in order based on timestamps in skb's
 */
struct fifo_sched_data {
	u32 limit;
	psched_time_t oldest;
};

static int tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
{
	struct fifo_sched_data *q = qdisc_priv(sch);
	struct sk_buff_head *list = &sch->q;
	psched_time_t tnext = netem_skb_cb(nskb)->time_to_send;
	struct sk_buff *skb;

	if (likely(skb_queue_len(list) < q->limit)) {
		/* Optimize for add at tail */
		if (likely(skb_queue_empty(list) || tnext >= q->oldest)) {
			q->oldest = tnext;
			return qdisc_enqueue_tail(nskb, sch);
		}

		skb_queue_reverse_walk(list, skb) {
			const struct netem_skb_cb *cb = netem_skb_cb(skb);

			if (tnext >= cb->time_to_send)
				break;
		}

		__skb_queue_after(list, skb, nskb);

		sch->qstats.backlog += qdisc_pkt_len(nskb);
		sch->bstats.bytes += qdisc_pkt_len(nskb);
		sch->bstats.packets++;

		return NET_XMIT_SUCCESS;
	}

	return qdisc_reshape_fail(nskb, sch);
}

static int tfifo_init(struct Qdisc *sch, struct nlattr *opt)
{
	struct fifo_sched_data *q = qdisc_priv(sch);

	if (opt) {
		struct tc_fifo_qopt *ctl = nla_data(opt);
		if (nla_len(opt) < sizeof(*ctl))
			return -EINVAL;

		q->limit = ctl->limit;
	} else
		q->limit = max_t(u32, qdisc_dev(sch)->tx_queue_len, 1);

	q->oldest = PSCHED_PASTPERFECT;
	return 0;
}

static int tfifo_dump(struct Qdisc *sch, struct sk_buff *skb)
{
	struct fifo_sched_data *q = qdisc_priv(sch);
	struct tc_fifo_qopt opt = { .limit = q->limit };

	NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
	return skb->len;

nla_put_failure:
	return -1;
}

static struct Qdisc_ops tfifo_qdisc_ops __read_mostly = {
	.id		=	"tfifo",
	.priv_size	=	sizeof(struct fifo_sched_data),
	.enqueue	=	tfifo_enqueue,
	.dequeue	=	qdisc_dequeue_head,
	.peek		=	qdisc_peek_head,
	.requeue	=	qdisc_requeue,
	.drop		=	qdisc_queue_drop,
	.init		=	tfifo_init,
	.reset		=	qdisc_reset_queue,
	.change		=	tfifo_init,
	.dump		=	tfifo_dump,
};

static int netem_init(struct Qdisc *sch, struct nlattr *opt)
{
	struct netem_sched_data *q = qdisc_priv(sch);
	int ret;

	if (!opt)
		return -EINVAL;

	qdisc_watchdog_init(&q->watchdog, sch);

	q->qdisc = qdisc_create_dflt(qdisc_dev(sch), sch->dev_queue,
				     &tfifo_qdisc_ops,
				     TC_H_MAKE(sch->handle, 1));
	if (!q->qdisc) {
		pr_debug("netem: qdisc create failed\n");
		return -ENOMEM;
	}

	ret = netem_change(sch, opt);
	if (ret) {
		pr_debug("netem: change failed\n");
		qdisc_destroy(q->qdisc);
	}
	return ret;
}

static void netem_destroy(struct Qdisc *sch)
{
	struct netem_sched_data *q = qdisc_priv(sch);

	qdisc_watchdog_cancel(&q->watchdog);
	qdisc_destroy(q->qdisc);
	kfree(q->delay_dist);
}

static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
{
	const struct netem_sched_data *q = qdisc_priv(sch);
	unsigned char *b = skb_tail_pointer(skb);
	struct nlattr *nla = (struct nlattr *) b;
	struct tc_netem_qopt qopt;
	struct tc_netem_corr cor;
	struct tc_netem_reorder reorder;
	struct tc_netem_corrupt corrupt;

	qopt.latency = q->latency;
	qopt.jitter = q->jitter;
	qopt.limit = q->limit;
	qopt.loss = q->loss;
	qopt.gap = q->gap;
	qopt.duplicate = q->duplicate;
	NLA_PUT(skb, TCA_OPTIONS, sizeof(qopt), &qopt);

	cor.delay_corr = q->delay_cor.rho;
	cor.loss_corr = q->loss_cor.rho;
	cor.dup_corr = q->dup_cor.rho;
	NLA_PUT(skb, TCA_NETEM_CORR, sizeof(cor), &cor);

	reorder.probability = q->reorder;
	reorder.correlation = q->reorder_cor.rho;
	NLA_PUT(skb, TCA_NETEM_REORDER, sizeof(reorder), &reorder);

	corrupt.probability = q->corrupt;
	corrupt.correlation = q->corrupt_cor.rho;
	NLA_PUT(skb, TCA_NETEM_CORRUPT, sizeof(corrupt), &corrupt);

	nla->nla_len = skb_tail_pointer(skb) - b;

	return skb->len;

nla_put_failure:
	nlmsg_trim(skb, b);
	return -1;
}

static int netem_dump_class(struct Qdisc *sch, unsigned long cl,
			  struct sk_buff *skb, struct tcmsg *tcm)
{
	struct netem_sched_data *q = qdisc_priv(sch);

	if (cl != 1) 	/* only one class */
		return -ENOENT;

	tcm->tcm_handle |= TC_H_MIN(1);
	tcm->tcm_info = q->qdisc->handle;

	return 0;
}

static int netem_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
		     struct Qdisc **old)
{
	struct netem_sched_data *q = qdisc_priv(sch);

	if (new == NULL)
		new = &noop_qdisc;

	sch_tree_lock(sch);
	*old = xchg(&q->qdisc, new);
	qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
	qdisc_reset(*old);
	sch_tree_unlock(sch);

	return 0;
}

static struct Qdisc *netem_leaf(struct Qdisc *sch, unsigned long arg)
{
	struct netem_sched_data *q = qdisc_priv(sch);
	return q->qdisc;
}

static unsigned long netem_get(struct Qdisc *sch, u32 classid)
{
	return 1;
}

static void netem_put(struct Qdisc *sch, unsigned long arg)
{
}

static int netem_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
			    struct nlattr **tca, unsigned long *arg)
{
	return -ENOSYS;
}

static int netem_delete(struct Qdisc *sch, unsigned long arg)
{
	return -ENOSYS;
}

static void netem_walk(struct Qdisc *sch, struct qdisc_walker *walker)
{
	if (!walker->stop) {
		if (walker->count >= walker->skip)
			if (walker->fn(sch, 1, walker) < 0) {
				walker->stop = 1;
				return;
			}
		walker->count++;
	}
}

static struct tcf_proto **netem_find_tcf(struct Qdisc *sch, unsigned long cl)
{
	return NULL;
}

static const struct Qdisc_class_ops netem_class_ops = {
	.graft		=	netem_graft,
	.leaf		=	netem_leaf,
	.get		=	netem_get,
	.put		=	netem_put,
	.change		=	netem_change_class,
	.delete		=	netem_delete,
	.walk		=	netem_walk,
	.tcf_chain	=	netem_find_tcf,
	.dump		=	netem_dump_class,
};

static struct Qdisc_ops netem_qdisc_ops __read_mostly = {
	.id		=	"netem",
	.cl_ops		=	&netem_class_ops,
	.priv_size	=	sizeof(struct netem_sched_data),
	.enqueue	=	netem_enqueue,
	.dequeue	=	netem_dequeue,
	.requeue	=	netem_requeue,
	.drop		=	netem_drop,
	.init		=	netem_init,
	.reset		=	netem_reset,
	.destroy	=	netem_destroy,
	.change		=	netem_change,
	.dump		=	netem_dump,
	.owner		=	THIS_MODULE,
};


static int __init netem_module_init(void)
{
	pr_info("netem: version " VERSION "\n");
	return register_qdisc(&netem_qdisc_ops);
}
static void __exit netem_module_exit(void)
{
	unregister_qdisc(&netem_qdisc_ops);
}
module_init(netem_module_init)
module_exit(netem_module_exit)
MODULE_LICENSE("GPL");
OpenPOWER on IntegriCloud