summaryrefslogtreecommitdiffstats
path: root/net/sched/sch_choke.c
blob: 06afbaeb4c88aceb565af85dbab35baf3d4ae6d6 (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
/*
 * net/sched/sch_choke.c	CHOKE scheduler
 *
 * Copyright (c) 2011 Stephen Hemminger <shemminger@vyatta.com>
 * Copyright (c) 2011 Eric Dumazet <eric.dumazet@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.
 *
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/reciprocal_div.h>
#include <linux/vmalloc.h>
#include <net/pkt_sched.h>
#include <net/inet_ecn.h>
#include <net/red.h>
#include <linux/ip.h>
#include <net/ip.h>
#include <linux/ipv6.h>
#include <net/ipv6.h>

/*
   CHOKe stateless AQM for fair bandwidth allocation
   =================================================

   CHOKe (CHOose and Keep for responsive flows, CHOose and Kill for
   unresponsive flows) is a variant of RED that penalizes misbehaving flows but
   maintains no flow state. The difference from RED is an additional step
   during the enqueuing process. If average queue size is over the
   low threshold (qmin), a packet is chosen at random from the queue.
   If both the new and chosen packet are from the same flow, both
   are dropped. Unlike RED, CHOKe is not really a "classful" qdisc because it
   needs to access packets in queue randomly. It has a minimal class
   interface to allow overriding the builtin flow classifier with
   filters.

   Source:
   R. Pan, B. Prabhakar, and K. Psounis, "CHOKe, A Stateless
   Active Queue Management Scheme for Approximating Fair Bandwidth Allocation",
   IEEE INFOCOM, 2000.

   A. Tang, J. Wang, S. Low, "Understanding CHOKe: Throughput and Spatial
   Characteristics", IEEE/ACM Transactions on Networking, 2004

 */

/* Upper bound on size of sk_buff table (packets) */
#define CHOKE_MAX_QUEUE	(128*1024 - 1)

struct choke_sched_data {
/* Parameters */
	u32		 limit;
	unsigned char	 flags;

	struct red_parms parms;

/* Variables */
	struct tcf_proto *filter_list;
	struct {
		u32	prob_drop;	/* Early probability drops */
		u32	prob_mark;	/* Early probability marks */
		u32	forced_drop;	/* Forced drops, qavg > max_thresh */
		u32	forced_mark;	/* Forced marks, qavg > max_thresh */
		u32	pdrop;          /* Drops due to queue limits */
		u32	other;          /* Drops due to drop() calls */
		u32	matched;	/* Drops to flow match */
	} stats;

	unsigned int	 head;
	unsigned int	 tail;

	unsigned int	 tab_mask; /* size - 1 */

	struct sk_buff **tab;
};

/* deliver a random number between 0 and N - 1 */
static u32 random_N(unsigned int N)
{
	return reciprocal_divide(random32(), N);
}

/* number of elements in queue including holes */
static unsigned int choke_len(const struct choke_sched_data *q)
{
	return (q->tail - q->head) & q->tab_mask;
}

/* Is ECN parameter configured */
static int use_ecn(const struct choke_sched_data *q)
{
	return q->flags & TC_RED_ECN;
}

/* Should packets over max just be dropped (versus marked) */
static int use_harddrop(const struct choke_sched_data *q)
{
	return q->flags & TC_RED_HARDDROP;
}

/* Move head pointer forward to skip over holes */
static void choke_zap_head_holes(struct choke_sched_data *q)
{
	do {
		q->head = (q->head + 1) & q->tab_mask;
		if (q->head == q->tail)
			break;
	} while (q->tab[q->head] == NULL);
}

/* Move tail pointer backwards to reuse holes */
static void choke_zap_tail_holes(struct choke_sched_data *q)
{
	do {
		q->tail = (q->tail - 1) & q->tab_mask;
		if (q->head == q->tail)
			break;
	} while (q->tab[q->tail] == NULL);
}

/* Drop packet from queue array by creating a "hole" */
static void choke_drop_by_idx(struct Qdisc *sch, unsigned int idx)
{
	struct choke_sched_data *q = qdisc_priv(sch);
	struct sk_buff *skb = q->tab[idx];

	q->tab[idx] = NULL;

	if (idx == q->head)
		choke_zap_head_holes(q);
	if (idx == q->tail)
		choke_zap_tail_holes(q);

	sch->qstats.backlog -= qdisc_pkt_len(skb);
	qdisc_drop(skb, sch);
	qdisc_tree_decrease_qlen(sch, 1);
	--sch->q.qlen;
}

/*
 * Compare flow of two packets
 *  Returns true only if source and destination address and port match.
 *          false for special cases
 */
static bool choke_match_flow(struct sk_buff *skb1,
			     struct sk_buff *skb2)
{
	int off1, off2, poff;
	const u32 *ports1, *ports2;
	u8 ip_proto;
	__u32 hash1;

	if (skb1->protocol != skb2->protocol)
		return false;

	/* Use hash value as quick check
	 * Assumes that __skb_get_rxhash makes IP header and ports linear
	 */
	hash1 = skb_get_rxhash(skb1);
	if (!hash1 || hash1 != skb_get_rxhash(skb2))
		return false;

	/* Probably match, but be sure to avoid hash collisions */
	off1 = skb_network_offset(skb1);
	off2 = skb_network_offset(skb2);

	switch (skb1->protocol) {
	case __constant_htons(ETH_P_IP): {
		const struct iphdr *ip1, *ip2;

		ip1 = (const struct iphdr *) (skb1->data + off1);
		ip2 = (const struct iphdr *) (skb2->data + off2);

		ip_proto = ip1->protocol;
		if (ip_proto != ip2->protocol ||
		    ip1->saddr != ip2->saddr || ip1->daddr != ip2->daddr)
			return false;

		if ((ip1->frag_off | ip2->frag_off) & htons(IP_MF | IP_OFFSET))
			ip_proto = 0;
		off1 += ip1->ihl * 4;
		off2 += ip2->ihl * 4;
		break;
	}

	case __constant_htons(ETH_P_IPV6): {
		const struct ipv6hdr *ip1, *ip2;

		ip1 = (const struct ipv6hdr *) (skb1->data + off1);
		ip2 = (const struct ipv6hdr *) (skb2->data + off2);

		ip_proto = ip1->nexthdr;
		if (ip_proto != ip2->nexthdr ||
		    ipv6_addr_cmp(&ip1->saddr, &ip2->saddr) ||
		    ipv6_addr_cmp(&ip1->daddr, &ip2->daddr))
			return false;
		off1 += 40;
		off2 += 40;
	}

	default: /* Maybe compare MAC header here? */
		return false;
	}

	poff = proto_ports_offset(ip_proto);
	if (poff < 0)
		return true;

	off1 += poff;
	off2 += poff;

	ports1 = (__force u32 *)(skb1->data + off1);
	ports2 = (__force u32 *)(skb2->data + off2);
	return *ports1 == *ports2;
}

struct choke_skb_cb {
	u16 classid;
};

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

static inline void choke_set_classid(struct sk_buff *skb, u16 classid)
{
	choke_skb_cb(skb)->classid = classid;
}

static u16 choke_get_classid(const struct sk_buff *skb)
{
	return choke_skb_cb(skb)->classid;
}

/*
 * Classify flow using either:
 *  1. pre-existing classification result in skb
 *  2. fast internal classification
 *  3. use TC filter based classification
 */
static bool choke_classify(struct sk_buff *skb,
			   struct Qdisc *sch, int *qerr)

{
	struct choke_sched_data *q = qdisc_priv(sch);
	struct tcf_result res;
	int result;

	result = tc_classify(skb, q->filter_list, &res);
	if (result >= 0) {
#ifdef CONFIG_NET_CLS_ACT
		switch (result) {
		case TC_ACT_STOLEN:
		case TC_ACT_QUEUED:
			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
		case TC_ACT_SHOT:
			return false;
		}
#endif
		choke_set_classid(skb, TC_H_MIN(res.classid));
		return true;
	}

	return false;
}

/*
 * Select a packet at random from queue
 * HACK: since queue can have holes from previous deletion; retry several
 *   times to find a random skb but then just give up and return the head
 * Will return NULL if queue is empty (q->head == q->tail)
 */
static struct sk_buff *choke_peek_random(const struct choke_sched_data *q,
					 unsigned int *pidx)
{
	struct sk_buff *skb;
	int retrys = 3;

	do {
		*pidx = (q->head + random_N(choke_len(q))) & q->tab_mask;
		skb = q->tab[*pidx];
		if (skb)
			return skb;
	} while (--retrys > 0);

	return q->tab[*pidx = q->head];
}

/*
 * Compare new packet with random packet in queue
 * returns true if matched and sets *pidx
 */
static bool choke_match_random(const struct choke_sched_data *q,
			       struct sk_buff *nskb,
			       unsigned int *pidx)
{
	struct sk_buff *oskb;

	if (q->head == q->tail)
		return false;

	oskb = choke_peek_random(q, pidx);
	if (q->filter_list)
		return choke_get_classid(nskb) == choke_get_classid(oskb);

	return choke_match_flow(oskb, nskb);
}

static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch)
{
	struct choke_sched_data *q = qdisc_priv(sch);
	struct red_parms *p = &q->parms;
	int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;

	if (q->filter_list) {
		/* If using external classifiers, get result and record it. */
		if (!choke_classify(skb, sch, &ret))
			goto other_drop;	/* Packet was eaten by filter */
	}

	/* Compute average queue usage (see RED) */
	p->qavg = red_calc_qavg(p, sch->q.qlen);
	if (red_is_idling(p))
		red_end_of_idle_period(p);

	/* Is queue small? */
	if (p->qavg <= p->qth_min)
		p->qcount = -1;
	else {
		unsigned int idx;

		/* Draw a packet at random from queue and compare flow */
		if (choke_match_random(q, skb, &idx)) {
			q->stats.matched++;
			choke_drop_by_idx(sch, idx);
			goto congestion_drop;
		}

		/* Queue is large, always mark/drop */
		if (p->qavg > p->qth_max) {
			p->qcount = -1;

			sch->qstats.overlimits++;
			if (use_harddrop(q) || !use_ecn(q) ||
			    !INET_ECN_set_ce(skb)) {
				q->stats.forced_drop++;
				goto congestion_drop;
			}

			q->stats.forced_mark++;
		} else if (++p->qcount) {
			if (red_mark_probability(p, p->qavg)) {
				p->qcount = 0;
				p->qR = red_random(p);

				sch->qstats.overlimits++;
				if (!use_ecn(q) || !INET_ECN_set_ce(skb)) {
					q->stats.prob_drop++;
					goto congestion_drop;
				}

				q->stats.prob_mark++;
			}
		} else
			p->qR = red_random(p);
	}

	/* Admit new packet */
	if (sch->q.qlen < q->limit) {
		q->tab[q->tail] = skb;
		q->tail = (q->tail + 1) & q->tab_mask;
		++sch->q.qlen;
		sch->qstats.backlog += qdisc_pkt_len(skb);
		return NET_XMIT_SUCCESS;
	}

	q->stats.pdrop++;
	sch->qstats.drops++;
	kfree_skb(skb);
	return NET_XMIT_DROP;

 congestion_drop:
	qdisc_drop(skb, sch);
	return NET_XMIT_CN;

 other_drop:
	if (ret & __NET_XMIT_BYPASS)
		sch->qstats.drops++;
	kfree_skb(skb);
	return ret;
}

static struct sk_buff *choke_dequeue(struct Qdisc *sch)
{
	struct choke_sched_data *q = qdisc_priv(sch);
	struct sk_buff *skb;

	if (q->head == q->tail) {
		if (!red_is_idling(&q->parms))
			red_start_of_idle_period(&q->parms);
		return NULL;
	}

	skb = q->tab[q->head];
	q->tab[q->head] = NULL;
	choke_zap_head_holes(q);
	--sch->q.qlen;
	sch->qstats.backlog -= qdisc_pkt_len(skb);
	qdisc_bstats_update(sch, skb);

	return skb;
}

static unsigned int choke_drop(struct Qdisc *sch)
{
	struct choke_sched_data *q = qdisc_priv(sch);
	unsigned int len;

	len = qdisc_queue_drop(sch);
	if (len > 0)
		q->stats.other++;
	else {
		if (!red_is_idling(&q->parms))
			red_start_of_idle_period(&q->parms);
	}

	return len;
}

static void choke_reset(struct Qdisc *sch)
{
	struct choke_sched_data *q = qdisc_priv(sch);

	red_restart(&q->parms);
}

static const struct nla_policy choke_policy[TCA_CHOKE_MAX + 1] = {
	[TCA_CHOKE_PARMS]	= { .len = sizeof(struct tc_red_qopt) },
	[TCA_CHOKE_STAB]	= { .len = RED_STAB_SIZE },
};


static void choke_free(void *addr)
{
	if (addr) {
		if (is_vmalloc_addr(addr))
			vfree(addr);
		else
			kfree(addr);
	}
}

static int choke_change(struct Qdisc *sch, struct nlattr *opt)
{
	struct choke_sched_data *q = qdisc_priv(sch);
	struct nlattr *tb[TCA_CHOKE_MAX + 1];
	const struct tc_red_qopt *ctl;
	int err;
	struct sk_buff **old = NULL;
	unsigned int mask;

	if (opt == NULL)
		return -EINVAL;

	err = nla_parse_nested(tb, TCA_CHOKE_MAX, opt, choke_policy);
	if (err < 0)
		return err;

	if (tb[TCA_CHOKE_PARMS] == NULL ||
	    tb[TCA_CHOKE_STAB] == NULL)
		return -EINVAL;

	ctl = nla_data(tb[TCA_CHOKE_PARMS]);

	if (ctl->limit > CHOKE_MAX_QUEUE)
		return -EINVAL;

	mask = roundup_pow_of_two(ctl->limit + 1) - 1;
	if (mask != q->tab_mask) {
		struct sk_buff **ntab;

		ntab = kcalloc(mask + 1, sizeof(struct sk_buff *), GFP_KERNEL);
		if (!ntab)
			ntab = vzalloc((mask + 1) * sizeof(struct sk_buff *));
		if (!ntab)
			return -ENOMEM;

		sch_tree_lock(sch);
		old = q->tab;
		if (old) {
			unsigned int oqlen = sch->q.qlen, tail = 0;

			while (q->head != q->tail) {
				struct sk_buff *skb = q->tab[q->head];

				q->head = (q->head + 1) & q->tab_mask;
				if (!skb)
					continue;
				if (tail < mask) {
					ntab[tail++] = skb;
					continue;
				}
				sch->qstats.backlog -= qdisc_pkt_len(skb);
				--sch->q.qlen;
				qdisc_drop(skb, sch);
			}
			qdisc_tree_decrease_qlen(sch, oqlen - sch->q.qlen);
			q->head = 0;
			q->tail = tail;
		}

		q->tab_mask = mask;
		q->tab = ntab;
	} else
		sch_tree_lock(sch);

	q->flags = ctl->flags;
	q->limit = ctl->limit;

	red_set_parms(&q->parms, ctl->qth_min, ctl->qth_max, ctl->Wlog,
		      ctl->Plog, ctl->Scell_log,
		      nla_data(tb[TCA_CHOKE_STAB]));

	if (q->head == q->tail)
		red_end_of_idle_period(&q->parms);

	sch_tree_unlock(sch);
	choke_free(old);
	return 0;
}

static int choke_init(struct Qdisc *sch, struct nlattr *opt)
{
	return choke_change(sch, opt);
}

static int choke_dump(struct Qdisc *sch, struct sk_buff *skb)
{
	struct choke_sched_data *q = qdisc_priv(sch);
	struct nlattr *opts = NULL;
	struct tc_red_qopt opt = {
		.limit		= q->limit,
		.flags		= q->flags,
		.qth_min	= q->parms.qth_min >> q->parms.Wlog,
		.qth_max	= q->parms.qth_max >> q->parms.Wlog,
		.Wlog		= q->parms.Wlog,
		.Plog		= q->parms.Plog,
		.Scell_log	= q->parms.Scell_log,
	};

	opts = nla_nest_start(skb, TCA_OPTIONS);
	if (opts == NULL)
		goto nla_put_failure;

	NLA_PUT(skb, TCA_CHOKE_PARMS, sizeof(opt), &opt);
	return nla_nest_end(skb, opts);

nla_put_failure:
	nla_nest_cancel(skb, opts);
	return -EMSGSIZE;
}

static int choke_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
{
	struct choke_sched_data *q = qdisc_priv(sch);
	struct tc_choke_xstats st = {
		.early	= q->stats.prob_drop + q->stats.forced_drop,
		.marked	= q->stats.prob_mark + q->stats.forced_mark,
		.pdrop	= q->stats.pdrop,
		.other	= q->stats.other,
		.matched = q->stats.matched,
	};

	return gnet_stats_copy_app(d, &st, sizeof(st));
}

static void choke_destroy(struct Qdisc *sch)
{
	struct choke_sched_data *q = qdisc_priv(sch);

	tcf_destroy_chain(&q->filter_list);
	choke_free(q->tab);
}

static struct Qdisc *choke_leaf(struct Qdisc *sch, unsigned long arg)
{
	return NULL;
}

static unsigned long choke_get(struct Qdisc *sch, u32 classid)
{
	return 0;
}

static void choke_put(struct Qdisc *q, unsigned long cl)
{
}

static unsigned long choke_bind(struct Qdisc *sch, unsigned long parent,
				u32 classid)
{
	return 0;
}

static struct tcf_proto **choke_find_tcf(struct Qdisc *sch, unsigned long cl)
{
	struct choke_sched_data *q = qdisc_priv(sch);

	if (cl)
		return NULL;
	return &q->filter_list;
}

static int choke_dump_class(struct Qdisc *sch, unsigned long cl,
			  struct sk_buff *skb, struct tcmsg *tcm)
{
	tcm->tcm_handle |= TC_H_MIN(cl);
	return 0;
}

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

static const struct Qdisc_class_ops choke_class_ops = {
	.leaf		=	choke_leaf,
	.get		=	choke_get,
	.put		=	choke_put,
	.tcf_chain	=	choke_find_tcf,
	.bind_tcf	=	choke_bind,
	.unbind_tcf	=	choke_put,
	.dump		=	choke_dump_class,
	.walk		=	choke_walk,
};

static struct sk_buff *choke_peek_head(struct Qdisc *sch)
{
	struct choke_sched_data *q = qdisc_priv(sch);

	return (q->head != q->tail) ? q->tab[q->head] : NULL;
}

static struct Qdisc_ops choke_qdisc_ops __read_mostly = {
	.id		=	"choke",
	.priv_size	=	sizeof(struct choke_sched_data),

	.enqueue	=	choke_enqueue,
	.dequeue	=	choke_dequeue,
	.peek		=	choke_peek_head,
	.drop		=	choke_drop,
	.init		=	choke_init,
	.destroy	=	choke_destroy,
	.reset		=	choke_reset,
	.change		=	choke_change,
	.dump		=	choke_dump,
	.dump_stats	=	choke_dump_stats,
	.owner		=	THIS_MODULE,
};

static int __init choke_module_init(void)
{
	return register_qdisc(&choke_qdisc_ops);
}

static void __exit choke_module_exit(void)
{
	unregister_qdisc(&choke_qdisc_ops);
}

module_init(choke_module_init)
module_exit(choke_module_exit)

MODULE_LICENSE("GPL");