xref: /linux/net/sched/sch_sfb.c (revision 9e8ba5f3ec35cba4fd8a8bebda548c4db2651e40) 
1 /*
2  * net/sched/sch_sfb.c	  Stochastic Fair Blue
3  *
4  * Copyright (c) 2008-2011 Juliusz Chroboczek <jch@pps.jussieu.fr>
5  * Copyright (c) 2011 Eric Dumazet <eric.dumazet@gmail.com>
6  *
7  * This program is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU General Public License
9  * version 2 as published by the Free Software Foundation.
10  *
11  * W. Feng, D. Kandlur, D. Saha, K. Shin. Blue:
12  * A New Class of Active Queue Management Algorithms.
13  * U. Michigan CSE-TR-387-99, April 1999.
14  *
15  * http://www.thefengs.com/wuchang/blue/CSE-TR-387-99.pdf
16  *
17  */
18 
19 #include <linux/module.h>
20 #include <linux/types.h>
21 #include <linux/kernel.h>
22 #include <linux/errno.h>
23 #include <linux/skbuff.h>
24 #include <linux/random.h>
25 #include <linux/jhash.h>
26 #include <net/ip.h>
27 #include <net/pkt_sched.h>
28 #include <net/inet_ecn.h>
29 #include <net/flow_keys.h>
30 
31 /*
32  * SFB uses two B[l][n] : L x N arrays of bins (L levels, N bins per level)
33  * This implementation uses L = 8 and N = 16
34  * This permits us to split one 32bit hash (provided per packet by rxhash or
35  * external classifier) into 8 subhashes of 4 bits.
36  */
37 #define SFB_BUCKET_SHIFT 4
38 #define SFB_NUMBUCKETS	(1 << SFB_BUCKET_SHIFT) /* N bins per Level */
39 #define SFB_BUCKET_MASK (SFB_NUMBUCKETS - 1)
40 #define SFB_LEVELS	(32 / SFB_BUCKET_SHIFT) /* L */
41 
42 /* SFB algo uses a virtual queue, named "bin" */
43 struct sfb_bucket {
44 	u16		qlen; /* length of virtual queue */
45 	u16		p_mark; /* marking probability */
46 };
47 
48 /* We use a double buffering right before hash change
49  * (Section 4.4 of SFB reference : moving hash functions)
50  */
51 struct sfb_bins {
52 	u32		  perturbation; /* jhash perturbation */
53 	struct sfb_bucket bins[SFB_LEVELS][SFB_NUMBUCKETS];
54 };
55 
56 struct sfb_sched_data {
57 	struct Qdisc	*qdisc;
58 	struct tcf_proto *filter_list;
59 	unsigned long	rehash_interval;
60 	unsigned long	warmup_time;	/* double buffering warmup time in jiffies */
61 	u32		max;
62 	u32		bin_size;	/* maximum queue length per bin */
63 	u32		increment;	/* d1 */
64 	u32		decrement;	/* d2 */
65 	u32		limit;		/* HARD maximal queue length */
66 	u32		penalty_rate;
67 	u32		penalty_burst;
68 	u32		tokens_avail;
69 	unsigned long	rehash_time;
70 	unsigned long	token_time;
71 
72 	u8		slot;		/* current active bins (0 or 1) */
73 	bool		double_buffering;
74 	struct sfb_bins bins[2];
75 
76 	struct {
77 		u32	earlydrop;
78 		u32	penaltydrop;
79 		u32	bucketdrop;
80 		u32	queuedrop;
81 		u32	childdrop;	/* drops in child qdisc */
82 		u32	marked;		/* ECN mark */
83 	} stats;
84 };
85 
86 /*
87  * Each queued skb might be hashed on one or two bins
88  * We store in skb_cb the two hash values.
89  * (A zero value means double buffering was not used)
90  */
91 struct sfb_skb_cb {
92 	u32 hashes[2];
93 };
94 
95 static inline struct sfb_skb_cb *sfb_skb_cb(const struct sk_buff *skb)
96 {
97 	BUILD_BUG_ON(sizeof(skb->cb) <
98 		sizeof(struct qdisc_skb_cb) + sizeof(struct sfb_skb_cb));
99 	return (struct sfb_skb_cb *)qdisc_skb_cb(skb)->data;
100 }
101 
102 /*
103  * If using 'internal' SFB flow classifier, hash comes from skb rxhash
104  * If using external classifier, hash comes from the classid.
105  */
106 static u32 sfb_hash(const struct sk_buff *skb, u32 slot)
107 {
108 	return sfb_skb_cb(skb)->hashes[slot];
109 }
110 
111 /* Probabilities are coded as Q0.16 fixed-point values,
112  * with 0xFFFF representing 65535/65536 (almost 1.0)
113  * Addition and subtraction are saturating in [0, 65535]
114  */
115 static u32 prob_plus(u32 p1, u32 p2)
116 {
117 	u32 res = p1 + p2;
118 
119 	return min_t(u32, res, SFB_MAX_PROB);
120 }
121 
122 static u32 prob_minus(u32 p1, u32 p2)
123 {
124 	return p1 > p2 ? p1 - p2 : 0;
125 }
126 
127 static void increment_one_qlen(u32 sfbhash, u32 slot, struct sfb_sched_data *q)
128 {
129 	int i;
130 	struct sfb_bucket *b = &q->bins[slot].bins[0][0];
131 
132 	for (i = 0; i < SFB_LEVELS; i++) {
133 		u32 hash = sfbhash & SFB_BUCKET_MASK;
134 
135 		sfbhash >>= SFB_BUCKET_SHIFT;
136 		if (b[hash].qlen < 0xFFFF)
137 			b[hash].qlen++;
138 		b += SFB_NUMBUCKETS; /* next level */
139 	}
140 }
141 
142 static void increment_qlen(const struct sk_buff *skb, struct sfb_sched_data *q)
143 {
144 	u32 sfbhash;
145 
146 	sfbhash = sfb_hash(skb, 0);
147 	if (sfbhash)
148 		increment_one_qlen(sfbhash, 0, q);
149 
150 	sfbhash = sfb_hash(skb, 1);
151 	if (sfbhash)
152 		increment_one_qlen(sfbhash, 1, q);
153 }
154 
155 static void decrement_one_qlen(u32 sfbhash, u32 slot,
156 			       struct sfb_sched_data *q)
157 {
158 	int i;
159 	struct sfb_bucket *b = &q->bins[slot].bins[0][0];
160 
161 	for (i = 0; i < SFB_LEVELS; i++) {
162 		u32 hash = sfbhash & SFB_BUCKET_MASK;
163 
164 		sfbhash >>= SFB_BUCKET_SHIFT;
165 		if (b[hash].qlen > 0)
166 			b[hash].qlen--;
167 		b += SFB_NUMBUCKETS; /* next level */
168 	}
169 }
170 
171 static void decrement_qlen(const struct sk_buff *skb, struct sfb_sched_data *q)
172 {
173 	u32 sfbhash;
174 
175 	sfbhash = sfb_hash(skb, 0);
176 	if (sfbhash)
177 		decrement_one_qlen(sfbhash, 0, q);
178 
179 	sfbhash = sfb_hash(skb, 1);
180 	if (sfbhash)
181 		decrement_one_qlen(sfbhash, 1, q);
182 }
183 
184 static void decrement_prob(struct sfb_bucket *b, struct sfb_sched_data *q)
185 {
186 	b->p_mark = prob_minus(b->p_mark, q->decrement);
187 }
188 
189 static void increment_prob(struct sfb_bucket *b, struct sfb_sched_data *q)
190 {
191 	b->p_mark = prob_plus(b->p_mark, q->increment);
192 }
193 
194 static void sfb_zero_all_buckets(struct sfb_sched_data *q)
195 {
196 	memset(&q->bins, 0, sizeof(q->bins));
197 }
198 
199 /*
200  * compute max qlen, max p_mark, and avg p_mark
201  */
202 static u32 sfb_compute_qlen(u32 *prob_r, u32 *avgpm_r, const struct sfb_sched_data *q)
203 {
204 	int i;
205 	u32 qlen = 0, prob = 0, totalpm = 0;
206 	const struct sfb_bucket *b = &q->bins[q->slot].bins[0][0];
207 
208 	for (i = 0; i < SFB_LEVELS * SFB_NUMBUCKETS; i++) {
209 		if (qlen < b->qlen)
210 			qlen = b->qlen;
211 		totalpm += b->p_mark;
212 		if (prob < b->p_mark)
213 			prob = b->p_mark;
214 		b++;
215 	}
216 	*prob_r = prob;
217 	*avgpm_r = totalpm / (SFB_LEVELS * SFB_NUMBUCKETS);
218 	return qlen;
219 }
220 
221 
222 static void sfb_init_perturbation(u32 slot, struct sfb_sched_data *q)
223 {
224 	q->bins[slot].perturbation = net_random();
225 }
226 
227 static void sfb_swap_slot(struct sfb_sched_data *q)
228 {
229 	sfb_init_perturbation(q->slot, q);
230 	q->slot ^= 1;
231 	q->double_buffering = false;
232 }
233 
234 /* Non elastic flows are allowed to use part of the bandwidth, expressed
235  * in "penalty_rate" packets per second, with "penalty_burst" burst
236  */
237 static bool sfb_rate_limit(struct sk_buff *skb, struct sfb_sched_data *q)
238 {
239 	if (q->penalty_rate == 0 || q->penalty_burst == 0)
240 		return true;
241 
242 	if (q->tokens_avail < 1) {
243 		unsigned long age = min(10UL * HZ, jiffies - q->token_time);
244 
245 		q->tokens_avail = (age * q->penalty_rate) / HZ;
246 		if (q->tokens_avail > q->penalty_burst)
247 			q->tokens_avail = q->penalty_burst;
248 		q->token_time = jiffies;
249 		if (q->tokens_avail < 1)
250 			return true;
251 	}
252 
253 	q->tokens_avail--;
254 	return false;
255 }
256 
257 static bool sfb_classify(struct sk_buff *skb, struct sfb_sched_data *q,
258 			 int *qerr, u32 *salt)
259 {
260 	struct tcf_result res;
261 	int result;
262 
263 	result = tc_classify(skb, q->filter_list, &res);
264 	if (result >= 0) {
265 #ifdef CONFIG_NET_CLS_ACT
266 		switch (result) {
267 		case TC_ACT_STOLEN:
268 		case TC_ACT_QUEUED:
269 			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
270 		case TC_ACT_SHOT:
271 			return false;
272 		}
273 #endif
274 		*salt = TC_H_MIN(res.classid);
275 		return true;
276 	}
277 	return false;
278 }
279 
280 static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch)
281 {
282 
283 	struct sfb_sched_data *q = qdisc_priv(sch);
284 	struct Qdisc *child = q->qdisc;
285 	int i;
286 	u32 p_min = ~0;
287 	u32 minqlen = ~0;
288 	u32 r, slot, salt, sfbhash;
289 	int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
290 	struct flow_keys keys;
291 
292 	if (unlikely(sch->q.qlen >= q->limit)) {
293 		sch->qstats.overlimits++;
294 		q->stats.queuedrop++;
295 		goto drop;
296 	}
297 
298 	if (q->rehash_interval > 0) {
299 		unsigned long limit = q->rehash_time + q->rehash_interval;
300 
301 		if (unlikely(time_after(jiffies, limit))) {
302 			sfb_swap_slot(q);
303 			q->rehash_time = jiffies;
304 		} else if (unlikely(!q->double_buffering && q->warmup_time > 0 &&
305 				    time_after(jiffies, limit - q->warmup_time))) {
306 			q->double_buffering = true;
307 		}
308 	}
309 
310 	if (q->filter_list) {
311 		/* If using external classifiers, get result and record it. */
312 		if (!sfb_classify(skb, q, &ret, &salt))
313 			goto other_drop;
314 		keys.src = salt;
315 		keys.dst = 0;
316 		keys.ports = 0;
317 	} else {
318 		skb_flow_dissect(skb, &keys);
319 	}
320 
321 	slot = q->slot;
322 
323 	sfbhash = jhash_3words((__force u32)keys.dst,
324 			       (__force u32)keys.src,
325 			       (__force u32)keys.ports,
326 			       q->bins[slot].perturbation);
327 	if (!sfbhash)
328 		sfbhash = 1;
329 	sfb_skb_cb(skb)->hashes[slot] = sfbhash;
330 
331 	for (i = 0; i < SFB_LEVELS; i++) {
332 		u32 hash = sfbhash & SFB_BUCKET_MASK;
333 		struct sfb_bucket *b = &q->bins[slot].bins[i][hash];
334 
335 		sfbhash >>= SFB_BUCKET_SHIFT;
336 		if (b->qlen == 0)
337 			decrement_prob(b, q);
338 		else if (b->qlen >= q->bin_size)
339 			increment_prob(b, q);
340 		if (minqlen > b->qlen)
341 			minqlen = b->qlen;
342 		if (p_min > b->p_mark)
343 			p_min = b->p_mark;
344 	}
345 
346 	slot ^= 1;
347 	sfb_skb_cb(skb)->hashes[slot] = 0;
348 
349 	if (unlikely(minqlen >= q->max)) {
350 		sch->qstats.overlimits++;
351 		q->stats.bucketdrop++;
352 		goto drop;
353 	}
354 
355 	if (unlikely(p_min >= SFB_MAX_PROB)) {
356 		/* Inelastic flow */
357 		if (q->double_buffering) {
358 			sfbhash = jhash_3words((__force u32)keys.dst,
359 					       (__force u32)keys.src,
360 					       (__force u32)keys.ports,
361 					       q->bins[slot].perturbation);
362 			if (!sfbhash)
363 				sfbhash = 1;
364 			sfb_skb_cb(skb)->hashes[slot] = sfbhash;
365 
366 			for (i = 0; i < SFB_LEVELS; i++) {
367 				u32 hash = sfbhash & SFB_BUCKET_MASK;
368 				struct sfb_bucket *b = &q->bins[slot].bins[i][hash];
369 
370 				sfbhash >>= SFB_BUCKET_SHIFT;
371 				if (b->qlen == 0)
372 					decrement_prob(b, q);
373 				else if (b->qlen >= q->bin_size)
374 					increment_prob(b, q);
375 			}
376 		}
377 		if (sfb_rate_limit(skb, q)) {
378 			sch->qstats.overlimits++;
379 			q->stats.penaltydrop++;
380 			goto drop;
381 		}
382 		goto enqueue;
383 	}
384 
385 	r = net_random() & SFB_MAX_PROB;
386 
387 	if (unlikely(r < p_min)) {
388 		if (unlikely(p_min > SFB_MAX_PROB / 2)) {
389 			/* If we're marking that many packets, then either
390 			 * this flow is unresponsive, or we're badly congested.
391 			 * In either case, we want to start dropping packets.
392 			 */
393 			if (r < (p_min - SFB_MAX_PROB / 2) * 2) {
394 				q->stats.earlydrop++;
395 				goto drop;
396 			}
397 		}
398 		if (INET_ECN_set_ce(skb)) {
399 			q->stats.marked++;
400 		} else {
401 			q->stats.earlydrop++;
402 			goto drop;
403 		}
404 	}
405 
406 enqueue:
407 	ret = qdisc_enqueue(skb, child);
408 	if (likely(ret == NET_XMIT_SUCCESS)) {
409 		sch->q.qlen++;
410 		increment_qlen(skb, q);
411 	} else if (net_xmit_drop_count(ret)) {
412 		q->stats.childdrop++;
413 		sch->qstats.drops++;
414 	}
415 	return ret;
416 
417 drop:
418 	qdisc_drop(skb, sch);
419 	return NET_XMIT_CN;
420 other_drop:
421 	if (ret & __NET_XMIT_BYPASS)
422 		sch->qstats.drops++;
423 	kfree_skb(skb);
424 	return ret;
425 }
426 
427 static struct sk_buff *sfb_dequeue(struct Qdisc *sch)
428 {
429 	struct sfb_sched_data *q = qdisc_priv(sch);
430 	struct Qdisc *child = q->qdisc;
431 	struct sk_buff *skb;
432 
433 	skb = child->dequeue(q->qdisc);
434 
435 	if (skb) {
436 		qdisc_bstats_update(sch, skb);
437 		sch->q.qlen--;
438 		decrement_qlen(skb, q);
439 	}
440 
441 	return skb;
442 }
443 
444 static struct sk_buff *sfb_peek(struct Qdisc *sch)
445 {
446 	struct sfb_sched_data *q = qdisc_priv(sch);
447 	struct Qdisc *child = q->qdisc;
448 
449 	return child->ops->peek(child);
450 }
451 
452 /* No sfb_drop -- impossible since the child doesn't return the dropped skb. */
453 
454 static void sfb_reset(struct Qdisc *sch)
455 {
456 	struct sfb_sched_data *q = qdisc_priv(sch);
457 
458 	qdisc_reset(q->qdisc);
459 	sch->q.qlen = 0;
460 	q->slot = 0;
461 	q->double_buffering = false;
462 	sfb_zero_all_buckets(q);
463 	sfb_init_perturbation(0, q);
464 }
465 
466 static void sfb_destroy(struct Qdisc *sch)
467 {
468 	struct sfb_sched_data *q = qdisc_priv(sch);
469 
470 	tcf_destroy_chain(&q->filter_list);
471 	qdisc_destroy(q->qdisc);
472 }
473 
474 static const struct nla_policy sfb_policy[TCA_SFB_MAX + 1] = {
475 	[TCA_SFB_PARMS]	= { .len = sizeof(struct tc_sfb_qopt) },
476 };
477 
478 static const struct tc_sfb_qopt sfb_default_ops = {
479 	.rehash_interval = 600 * MSEC_PER_SEC,
480 	.warmup_time = 60 * MSEC_PER_SEC,
481 	.limit = 0,
482 	.max = 25,
483 	.bin_size = 20,
484 	.increment = (SFB_MAX_PROB + 500) / 1000, /* 0.1 % */
485 	.decrement = (SFB_MAX_PROB + 3000) / 6000,
486 	.penalty_rate = 10,
487 	.penalty_burst = 20,
488 };
489 
490 static int sfb_change(struct Qdisc *sch, struct nlattr *opt)
491 {
492 	struct sfb_sched_data *q = qdisc_priv(sch);
493 	struct Qdisc *child;
494 	struct nlattr *tb[TCA_SFB_MAX + 1];
495 	const struct tc_sfb_qopt *ctl = &sfb_default_ops;
496 	u32 limit;
497 	int err;
498 
499 	if (opt) {
500 		err = nla_parse_nested(tb, TCA_SFB_MAX, opt, sfb_policy);
501 		if (err < 0)
502 			return -EINVAL;
503 
504 		if (tb[TCA_SFB_PARMS] == NULL)
505 			return -EINVAL;
506 
507 		ctl = nla_data(tb[TCA_SFB_PARMS]);
508 	}
509 
510 	limit = ctl->limit;
511 	if (limit == 0)
512 		limit = max_t(u32, qdisc_dev(sch)->tx_queue_len, 1);
513 
514 	child = fifo_create_dflt(sch, &pfifo_qdisc_ops, limit);
515 	if (IS_ERR(child))
516 		return PTR_ERR(child);
517 
518 	sch_tree_lock(sch);
519 
520 	qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
521 	qdisc_destroy(q->qdisc);
522 	q->qdisc = child;
523 
524 	q->rehash_interval = msecs_to_jiffies(ctl->rehash_interval);
525 	q->warmup_time = msecs_to_jiffies(ctl->warmup_time);
526 	q->rehash_time = jiffies;
527 	q->limit = limit;
528 	q->increment = ctl->increment;
529 	q->decrement = ctl->decrement;
530 	q->max = ctl->max;
531 	q->bin_size = ctl->bin_size;
532 	q->penalty_rate = ctl->penalty_rate;
533 	q->penalty_burst = ctl->penalty_burst;
534 	q->tokens_avail = ctl->penalty_burst;
535 	q->token_time = jiffies;
536 
537 	q->slot = 0;
538 	q->double_buffering = false;
539 	sfb_zero_all_buckets(q);
540 	sfb_init_perturbation(0, q);
541 	sfb_init_perturbation(1, q);
542 
543 	sch_tree_unlock(sch);
544 
545 	return 0;
546 }
547 
548 static int sfb_init(struct Qdisc *sch, struct nlattr *opt)
549 {
550 	struct sfb_sched_data *q = qdisc_priv(sch);
551 
552 	q->qdisc = &noop_qdisc;
553 	return sfb_change(sch, opt);
554 }
555 
556 static int sfb_dump(struct Qdisc *sch, struct sk_buff *skb)
557 {
558 	struct sfb_sched_data *q = qdisc_priv(sch);
559 	struct nlattr *opts;
560 	struct tc_sfb_qopt opt = {
561 		.rehash_interval = jiffies_to_msecs(q->rehash_interval),
562 		.warmup_time = jiffies_to_msecs(q->warmup_time),
563 		.limit = q->limit,
564 		.max = q->max,
565 		.bin_size = q->bin_size,
566 		.increment = q->increment,
567 		.decrement = q->decrement,
568 		.penalty_rate = q->penalty_rate,
569 		.penalty_burst = q->penalty_burst,
570 	};
571 
572 	sch->qstats.backlog = q->qdisc->qstats.backlog;
573 	opts = nla_nest_start(skb, TCA_OPTIONS);
574 	NLA_PUT(skb, TCA_SFB_PARMS, sizeof(opt), &opt);
575 	return nla_nest_end(skb, opts);
576 
577 nla_put_failure:
578 	nla_nest_cancel(skb, opts);
579 	return -EMSGSIZE;
580 }
581 
582 static int sfb_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
583 {
584 	struct sfb_sched_data *q = qdisc_priv(sch);
585 	struct tc_sfb_xstats st = {
586 		.earlydrop = q->stats.earlydrop,
587 		.penaltydrop = q->stats.penaltydrop,
588 		.bucketdrop = q->stats.bucketdrop,
589 		.queuedrop = q->stats.queuedrop,
590 		.childdrop = q->stats.childdrop,
591 		.marked = q->stats.marked,
592 	};
593 
594 	st.maxqlen = sfb_compute_qlen(&st.maxprob, &st.avgprob, q);
595 
596 	return gnet_stats_copy_app(d, &st, sizeof(st));
597 }
598 
599 static int sfb_dump_class(struct Qdisc *sch, unsigned long cl,
600 			  struct sk_buff *skb, struct tcmsg *tcm)
601 {
602 	return -ENOSYS;
603 }
604 
605 static int sfb_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
606 		     struct Qdisc **old)
607 {
608 	struct sfb_sched_data *q = qdisc_priv(sch);
609 
610 	if (new == NULL)
611 		new = &noop_qdisc;
612 
613 	sch_tree_lock(sch);
614 	*old = q->qdisc;
615 	q->qdisc = new;
616 	qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
617 	qdisc_reset(*old);
618 	sch_tree_unlock(sch);
619 	return 0;
620 }
621 
622 static struct Qdisc *sfb_leaf(struct Qdisc *sch, unsigned long arg)
623 {
624 	struct sfb_sched_data *q = qdisc_priv(sch);
625 
626 	return q->qdisc;
627 }
628 
629 static unsigned long sfb_get(struct Qdisc *sch, u32 classid)
630 {
631 	return 1;
632 }
633 
634 static void sfb_put(struct Qdisc *sch, unsigned long arg)
635 {
636 }
637 
638 static int sfb_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
639 			    struct nlattr **tca, unsigned long *arg)
640 {
641 	return -ENOSYS;
642 }
643 
644 static int sfb_delete(struct Qdisc *sch, unsigned long cl)
645 {
646 	return -ENOSYS;
647 }
648 
649 static void sfb_walk(struct Qdisc *sch, struct qdisc_walker *walker)
650 {
651 	if (!walker->stop) {
652 		if (walker->count >= walker->skip)
653 			if (walker->fn(sch, 1, walker) < 0) {
654 				walker->stop = 1;
655 				return;
656 			}
657 		walker->count++;
658 	}
659 }
660 
661 static struct tcf_proto **sfb_find_tcf(struct Qdisc *sch, unsigned long cl)
662 {
663 	struct sfb_sched_data *q = qdisc_priv(sch);
664 
665 	if (cl)
666 		return NULL;
667 	return &q->filter_list;
668 }
669 
670 static unsigned long sfb_bind(struct Qdisc *sch, unsigned long parent,
671 			      u32 classid)
672 {
673 	return 0;
674 }
675 
676 
677 static const struct Qdisc_class_ops sfb_class_ops = {
678 	.graft		=	sfb_graft,
679 	.leaf		=	sfb_leaf,
680 	.get		=	sfb_get,
681 	.put		=	sfb_put,
682 	.change		=	sfb_change_class,
683 	.delete		=	sfb_delete,
684 	.walk		=	sfb_walk,
685 	.tcf_chain	=	sfb_find_tcf,
686 	.bind_tcf	=	sfb_bind,
687 	.unbind_tcf	=	sfb_put,
688 	.dump		=	sfb_dump_class,
689 };
690 
691 static struct Qdisc_ops sfb_qdisc_ops __read_mostly = {
692 	.id		=	"sfb",
693 	.priv_size	=	sizeof(struct sfb_sched_data),
694 	.cl_ops		=	&sfb_class_ops,
695 	.enqueue	=	sfb_enqueue,
696 	.dequeue	=	sfb_dequeue,
697 	.peek		=	sfb_peek,
698 	.init		=	sfb_init,
699 	.reset		=	sfb_reset,
700 	.destroy	=	sfb_destroy,
701 	.change		=	sfb_change,
702 	.dump		=	sfb_dump,
703 	.dump_stats	=	sfb_dump_stats,
704 	.owner		=	THIS_MODULE,
705 };
706 
707 static int __init sfb_module_init(void)
708 {
709 	return register_qdisc(&sfb_qdisc_ops);
710 }
711 
712 static void __exit sfb_module_exit(void)
713 {
714 	unregister_qdisc(&sfb_qdisc_ops);
715 }
716 
717 module_init(sfb_module_init)
718 module_exit(sfb_module_exit)
719 
720 MODULE_DESCRIPTION("Stochastic Fair Blue queue discipline");
721 MODULE_AUTHOR("Juliusz Chroboczek");
722 MODULE_AUTHOR("Eric Dumazet");
723 MODULE_LICENSE("GPL");
724