xref: /openbmc/linux/net/sched/sch_sfb.c (revision 8ee90c5c) 
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/pkt_cls.h>
29 #include <net/inet_ecn.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 __rcu *filter_list;
59 	struct tcf_block *block;
60 	unsigned long	rehash_interval;
61 	unsigned long	warmup_time;	/* double buffering warmup time in jiffies */
62 	u32		max;
63 	u32		bin_size;	/* maximum queue length per bin */
64 	u32		increment;	/* d1 */
65 	u32		decrement;	/* d2 */
66 	u32		limit;		/* HARD maximal queue length */
67 	u32		penalty_rate;
68 	u32		penalty_burst;
69 	u32		tokens_avail;
70 	unsigned long	rehash_time;
71 	unsigned long	token_time;
72 
73 	u8		slot;		/* current active bins (0 or 1) */
74 	bool		double_buffering;
75 	struct sfb_bins bins[2];
76 
77 	struct {
78 		u32	earlydrop;
79 		u32	penaltydrop;
80 		u32	bucketdrop;
81 		u32	queuedrop;
82 		u32	childdrop;	/* drops in child qdisc */
83 		u32	marked;		/* ECN mark */
84 	} stats;
85 };
86 
87 /*
88  * Each queued skb might be hashed on one or two bins
89  * We store in skb_cb the two hash values.
90  * (A zero value means double buffering was not used)
91  */
92 struct sfb_skb_cb {
93 	u32 hashes[2];
94 };
95 
96 static inline struct sfb_skb_cb *sfb_skb_cb(const struct sk_buff *skb)
97 {
98 	qdisc_cb_private_validate(skb, 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 = prandom_u32();
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 tcf_proto *fl,
258 			 int *qerr, u32 *salt)
259 {
260 	struct tcf_result res;
261 	int result;
262 
263 	result = tcf_classify(skb, fl, &res, false);
264 	if (result >= 0) {
265 #ifdef CONFIG_NET_CLS_ACT
266 		switch (result) {
267 		case TC_ACT_STOLEN:
268 		case TC_ACT_QUEUED:
269 		case TC_ACT_TRAP:
270 			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
271 		case TC_ACT_SHOT:
272 			return false;
273 		}
274 #endif
275 		*salt = TC_H_MIN(res.classid);
276 		return true;
277 	}
278 	return false;
279 }
280 
281 static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
282 		       struct sk_buff **to_free)
283 {
284 
285 	struct sfb_sched_data *q = qdisc_priv(sch);
286 	struct Qdisc *child = q->qdisc;
287 	struct tcf_proto *fl;
288 	int i;
289 	u32 p_min = ~0;
290 	u32 minqlen = ~0;
291 	u32 r, sfbhash;
292 	u32 slot = q->slot;
293 	int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
294 
295 	if (unlikely(sch->q.qlen >= q->limit)) {
296 		qdisc_qstats_overlimit(sch);
297 		q->stats.queuedrop++;
298 		goto drop;
299 	}
300 
301 	if (q->rehash_interval > 0) {
302 		unsigned long limit = q->rehash_time + q->rehash_interval;
303 
304 		if (unlikely(time_after(jiffies, limit))) {
305 			sfb_swap_slot(q);
306 			q->rehash_time = jiffies;
307 		} else if (unlikely(!q->double_buffering && q->warmup_time > 0 &&
308 				    time_after(jiffies, limit - q->warmup_time))) {
309 			q->double_buffering = true;
310 		}
311 	}
312 
313 	fl = rcu_dereference_bh(q->filter_list);
314 	if (fl) {
315 		u32 salt;
316 
317 		/* If using external classifiers, get result and record it. */
318 		if (!sfb_classify(skb, fl, &ret, &salt))
319 			goto other_drop;
320 		sfbhash = jhash_1word(salt, q->bins[slot].perturbation);
321 	} else {
322 		sfbhash = skb_get_hash_perturb(skb, q->bins[slot].perturbation);
323 	}
324 
325 
326 	if (!sfbhash)
327 		sfbhash = 1;
328 	sfb_skb_cb(skb)->hashes[slot] = sfbhash;
329 
330 	for (i = 0; i < SFB_LEVELS; i++) {
331 		u32 hash = sfbhash & SFB_BUCKET_MASK;
332 		struct sfb_bucket *b = &q->bins[slot].bins[i][hash];
333 
334 		sfbhash >>= SFB_BUCKET_SHIFT;
335 		if (b->qlen == 0)
336 			decrement_prob(b, q);
337 		else if (b->qlen >= q->bin_size)
338 			increment_prob(b, q);
339 		if (minqlen > b->qlen)
340 			minqlen = b->qlen;
341 		if (p_min > b->p_mark)
342 			p_min = b->p_mark;
343 	}
344 
345 	slot ^= 1;
346 	sfb_skb_cb(skb)->hashes[slot] = 0;
347 
348 	if (unlikely(minqlen >= q->max)) {
349 		qdisc_qstats_overlimit(sch);
350 		q->stats.bucketdrop++;
351 		goto drop;
352 	}
353 
354 	if (unlikely(p_min >= SFB_MAX_PROB)) {
355 		/* Inelastic flow */
356 		if (q->double_buffering) {
357 			sfbhash = skb_get_hash_perturb(skb,
358 			    q->bins[slot].perturbation);
359 			if (!sfbhash)
360 				sfbhash = 1;
361 			sfb_skb_cb(skb)->hashes[slot] = sfbhash;
362 
363 			for (i = 0; i < SFB_LEVELS; i++) {
364 				u32 hash = sfbhash & SFB_BUCKET_MASK;
365 				struct sfb_bucket *b = &q->bins[slot].bins[i][hash];
366 
367 				sfbhash >>= SFB_BUCKET_SHIFT;
368 				if (b->qlen == 0)
369 					decrement_prob(b, q);
370 				else if (b->qlen >= q->bin_size)
371 					increment_prob(b, q);
372 			}
373 		}
374 		if (sfb_rate_limit(skb, q)) {
375 			qdisc_qstats_overlimit(sch);
376 			q->stats.penaltydrop++;
377 			goto drop;
378 		}
379 		goto enqueue;
380 	}
381 
382 	r = prandom_u32() & SFB_MAX_PROB;
383 
384 	if (unlikely(r < p_min)) {
385 		if (unlikely(p_min > SFB_MAX_PROB / 2)) {
386 			/* If we're marking that many packets, then either
387 			 * this flow is unresponsive, or we're badly congested.
388 			 * In either case, we want to start dropping packets.
389 			 */
390 			if (r < (p_min - SFB_MAX_PROB / 2) * 2) {
391 				q->stats.earlydrop++;
392 				goto drop;
393 			}
394 		}
395 		if (INET_ECN_set_ce(skb)) {
396 			q->stats.marked++;
397 		} else {
398 			q->stats.earlydrop++;
399 			goto drop;
400 		}
401 	}
402 
403 enqueue:
404 	ret = qdisc_enqueue(skb, child, to_free);
405 	if (likely(ret == NET_XMIT_SUCCESS)) {
406 		qdisc_qstats_backlog_inc(sch, skb);
407 		sch->q.qlen++;
408 		increment_qlen(skb, q);
409 	} else if (net_xmit_drop_count(ret)) {
410 		q->stats.childdrop++;
411 		qdisc_qstats_drop(sch);
412 	}
413 	return ret;
414 
415 drop:
416 	qdisc_drop(skb, sch, to_free);
417 	return NET_XMIT_CN;
418 other_drop:
419 	if (ret & __NET_XMIT_BYPASS)
420 		qdisc_qstats_drop(sch);
421 	kfree_skb(skb);
422 	return ret;
423 }
424 
425 static struct sk_buff *sfb_dequeue(struct Qdisc *sch)
426 {
427 	struct sfb_sched_data *q = qdisc_priv(sch);
428 	struct Qdisc *child = q->qdisc;
429 	struct sk_buff *skb;
430 
431 	skb = child->dequeue(q->qdisc);
432 
433 	if (skb) {
434 		qdisc_bstats_update(sch, skb);
435 		qdisc_qstats_backlog_dec(sch, skb);
436 		sch->q.qlen--;
437 		decrement_qlen(skb, q);
438 	}
439 
440 	return skb;
441 }
442 
443 static struct sk_buff *sfb_peek(struct Qdisc *sch)
444 {
445 	struct sfb_sched_data *q = qdisc_priv(sch);
446 	struct Qdisc *child = q->qdisc;
447 
448 	return child->ops->peek(child);
449 }
450 
451 /* No sfb_drop -- impossible since the child doesn't return the dropped skb. */
452 
453 static void sfb_reset(struct Qdisc *sch)
454 {
455 	struct sfb_sched_data *q = qdisc_priv(sch);
456 
457 	qdisc_reset(q->qdisc);
458 	sch->qstats.backlog = 0;
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_block_put(q->block);
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, NULL);
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 = qdisc_dev(sch)->tx_queue_len;
513 
514 	child = fifo_create_dflt(sch, &pfifo_qdisc_ops, limit);
515 	if (IS_ERR(child))
516 		return PTR_ERR(child);
517 
518 	if (child != &noop_qdisc)
519 		qdisc_hash_add(child, true);
520 	sch_tree_lock(sch);
521 
522 	qdisc_tree_reduce_backlog(q->qdisc, q->qdisc->q.qlen,
523 				  q->qdisc->qstats.backlog);
524 	qdisc_destroy(q->qdisc);
525 	q->qdisc = child;
526 
527 	q->rehash_interval = msecs_to_jiffies(ctl->rehash_interval);
528 	q->warmup_time = msecs_to_jiffies(ctl->warmup_time);
529 	q->rehash_time = jiffies;
530 	q->limit = limit;
531 	q->increment = ctl->increment;
532 	q->decrement = ctl->decrement;
533 	q->max = ctl->max;
534 	q->bin_size = ctl->bin_size;
535 	q->penalty_rate = ctl->penalty_rate;
536 	q->penalty_burst = ctl->penalty_burst;
537 	q->tokens_avail = ctl->penalty_burst;
538 	q->token_time = jiffies;
539 
540 	q->slot = 0;
541 	q->double_buffering = false;
542 	sfb_zero_all_buckets(q);
543 	sfb_init_perturbation(0, q);
544 	sfb_init_perturbation(1, q);
545 
546 	sch_tree_unlock(sch);
547 
548 	return 0;
549 }
550 
551 static int sfb_init(struct Qdisc *sch, struct nlattr *opt)
552 {
553 	struct sfb_sched_data *q = qdisc_priv(sch);
554 	int err;
555 
556 	err = tcf_block_get(&q->block, &q->filter_list);
557 	if (err)
558 		return err;
559 
560 	q->qdisc = &noop_qdisc;
561 	return sfb_change(sch, opt);
562 }
563 
564 static int sfb_dump(struct Qdisc *sch, struct sk_buff *skb)
565 {
566 	struct sfb_sched_data *q = qdisc_priv(sch);
567 	struct nlattr *opts;
568 	struct tc_sfb_qopt opt = {
569 		.rehash_interval = jiffies_to_msecs(q->rehash_interval),
570 		.warmup_time = jiffies_to_msecs(q->warmup_time),
571 		.limit = q->limit,
572 		.max = q->max,
573 		.bin_size = q->bin_size,
574 		.increment = q->increment,
575 		.decrement = q->decrement,
576 		.penalty_rate = q->penalty_rate,
577 		.penalty_burst = q->penalty_burst,
578 	};
579 
580 	sch->qstats.backlog = q->qdisc->qstats.backlog;
581 	opts = nla_nest_start(skb, TCA_OPTIONS);
582 	if (opts == NULL)
583 		goto nla_put_failure;
584 	if (nla_put(skb, TCA_SFB_PARMS, sizeof(opt), &opt))
585 		goto nla_put_failure;
586 	return nla_nest_end(skb, opts);
587 
588 nla_put_failure:
589 	nla_nest_cancel(skb, opts);
590 	return -EMSGSIZE;
591 }
592 
593 static int sfb_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
594 {
595 	struct sfb_sched_data *q = qdisc_priv(sch);
596 	struct tc_sfb_xstats st = {
597 		.earlydrop = q->stats.earlydrop,
598 		.penaltydrop = q->stats.penaltydrop,
599 		.bucketdrop = q->stats.bucketdrop,
600 		.queuedrop = q->stats.queuedrop,
601 		.childdrop = q->stats.childdrop,
602 		.marked = q->stats.marked,
603 	};
604 
605 	st.maxqlen = sfb_compute_qlen(&st.maxprob, &st.avgprob, q);
606 
607 	return gnet_stats_copy_app(d, &st, sizeof(st));
608 }
609 
610 static int sfb_dump_class(struct Qdisc *sch, unsigned long cl,
611 			  struct sk_buff *skb, struct tcmsg *tcm)
612 {
613 	return -ENOSYS;
614 }
615 
616 static int sfb_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
617 		     struct Qdisc **old)
618 {
619 	struct sfb_sched_data *q = qdisc_priv(sch);
620 
621 	if (new == NULL)
622 		new = &noop_qdisc;
623 
624 	*old = qdisc_replace(sch, new, &q->qdisc);
625 	return 0;
626 }
627 
628 static struct Qdisc *sfb_leaf(struct Qdisc *sch, unsigned long arg)
629 {
630 	struct sfb_sched_data *q = qdisc_priv(sch);
631 
632 	return q->qdisc;
633 }
634 
635 static unsigned long sfb_find(struct Qdisc *sch, u32 classid)
636 {
637 	return 1;
638 }
639 
640 static void sfb_unbind(struct Qdisc *sch, unsigned long arg)
641 {
642 }
643 
644 static int sfb_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
645 			    struct nlattr **tca, unsigned long *arg)
646 {
647 	return -ENOSYS;
648 }
649 
650 static int sfb_delete(struct Qdisc *sch, unsigned long cl)
651 {
652 	return -ENOSYS;
653 }
654 
655 static void sfb_walk(struct Qdisc *sch, struct qdisc_walker *walker)
656 {
657 	if (!walker->stop) {
658 		if (walker->count >= walker->skip)
659 			if (walker->fn(sch, 1, walker) < 0) {
660 				walker->stop = 1;
661 				return;
662 			}
663 		walker->count++;
664 	}
665 }
666 
667 static struct tcf_block *sfb_tcf_block(struct Qdisc *sch, unsigned long cl)
668 {
669 	struct sfb_sched_data *q = qdisc_priv(sch);
670 
671 	if (cl)
672 		return NULL;
673 	return q->block;
674 }
675 
676 static unsigned long sfb_bind(struct Qdisc *sch, unsigned long parent,
677 			      u32 classid)
678 {
679 	return 0;
680 }
681 
682 
683 static const struct Qdisc_class_ops sfb_class_ops = {
684 	.graft		=	sfb_graft,
685 	.leaf		=	sfb_leaf,
686 	.find		=	sfb_find,
687 	.change		=	sfb_change_class,
688 	.delete		=	sfb_delete,
689 	.walk		=	sfb_walk,
690 	.tcf_block	=	sfb_tcf_block,
691 	.bind_tcf	=	sfb_bind,
692 	.unbind_tcf	=	sfb_unbind,
693 	.dump		=	sfb_dump_class,
694 };
695 
696 static struct Qdisc_ops sfb_qdisc_ops __read_mostly = {
697 	.id		=	"sfb",
698 	.priv_size	=	sizeof(struct sfb_sched_data),
699 	.cl_ops		=	&sfb_class_ops,
700 	.enqueue	=	sfb_enqueue,
701 	.dequeue	=	sfb_dequeue,
702 	.peek		=	sfb_peek,
703 	.init		=	sfb_init,
704 	.reset		=	sfb_reset,
705 	.destroy	=	sfb_destroy,
706 	.change		=	sfb_change,
707 	.dump		=	sfb_dump,
708 	.dump_stats	=	sfb_dump_stats,
709 	.owner		=	THIS_MODULE,
710 };
711 
712 static int __init sfb_module_init(void)
713 {
714 	return register_qdisc(&sfb_qdisc_ops);
715 }
716 
717 static void __exit sfb_module_exit(void)
718 {
719 	unregister_qdisc(&sfb_qdisc_ops);
720 }
721 
722 module_init(sfb_module_init)
723 module_exit(sfb_module_exit)
724 
725 MODULE_DESCRIPTION("Stochastic Fair Blue queue discipline");
726 MODULE_AUTHOR("Juliusz Chroboczek");
727 MODULE_AUTHOR("Eric Dumazet");
728 MODULE_LICENSE("GPL");
729