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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" */
43struct 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 */
51struct sfb_bins {
52 u32 perturbation; /* jhash perturbation */
53 struct sfb_bucket bins[SFB_LEVELS][SFB_NUMBUCKETS];
54};
55
56struct 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 */
91struct sfb_skb_cb {
92 u32 hashes[2];
93};
94
95static inline struct sfb_skb_cb *sfb_skb_cb(const struct sk_buff *skb)
96{
97 qdisc_cb_private_validate(skb, sizeof(struct sfb_skb_cb));
98 return (struct sfb_skb_cb *)qdisc_skb_cb(skb)->data;
99}
100
101/*
102 * If using 'internal' SFB flow classifier, hash comes from skb rxhash
103 * If using external classifier, hash comes from the classid.
104 */
105static u32 sfb_hash(const struct sk_buff *skb, u32 slot)
106{
107 return sfb_skb_cb(skb)->hashes[slot];
108}
109
110/* Probabilities are coded as Q0.16 fixed-point values,
111 * with 0xFFFF representing 65535/65536 (almost 1.0)
112 * Addition and subtraction are saturating in [0, 65535]
113 */
114static u32 prob_plus(u32 p1, u32 p2)
115{
116 u32 res = p1 + p2;
117
118 return min_t(u32, res, SFB_MAX_PROB);
119}
120
121static u32 prob_minus(u32 p1, u32 p2)
122{
123 return p1 > p2 ? p1 - p2 : 0;
124}
125
126static void increment_one_qlen(u32 sfbhash, u32 slot, struct sfb_sched_data *q)
127{
128 int i;
129 struct sfb_bucket *b = &q->bins[slot].bins[0][0];
130
131 for (i = 0; i < SFB_LEVELS; i++) {
132 u32 hash = sfbhash & SFB_BUCKET_MASK;
133
134 sfbhash >>= SFB_BUCKET_SHIFT;
135 if (b[hash].qlen < 0xFFFF)
136 b[hash].qlen++;
137 b += SFB_NUMBUCKETS; /* next level */
138 }
139}
140
141static void increment_qlen(const struct sk_buff *skb, struct sfb_sched_data *q)
142{
143 u32 sfbhash;
144
145 sfbhash = sfb_hash(skb, 0);
146 if (sfbhash)
147 increment_one_qlen(sfbhash, 0, q);
148
149 sfbhash = sfb_hash(skb, 1);
150 if (sfbhash)
151 increment_one_qlen(sfbhash, 1, q);
152}
153
154static void decrement_one_qlen(u32 sfbhash, u32 slot,
155 struct sfb_sched_data *q)
156{
157 int i;
158 struct sfb_bucket *b = &q->bins[slot].bins[0][0];
159
160 for (i = 0; i < SFB_LEVELS; i++) {
161 u32 hash = sfbhash & SFB_BUCKET_MASK;
162
163 sfbhash >>= SFB_BUCKET_SHIFT;
164 if (b[hash].qlen > 0)
165 b[hash].qlen--;
166 b += SFB_NUMBUCKETS; /* next level */
167 }
168}
169
170static void decrement_qlen(const struct sk_buff *skb, struct sfb_sched_data *q)
171{
172 u32 sfbhash;
173
174 sfbhash = sfb_hash(skb, 0);
175 if (sfbhash)
176 decrement_one_qlen(sfbhash, 0, q);
177
178 sfbhash = sfb_hash(skb, 1);
179 if (sfbhash)
180 decrement_one_qlen(sfbhash, 1, q);
181}
182
183static void decrement_prob(struct sfb_bucket *b, struct sfb_sched_data *q)
184{
185 b->p_mark = prob_minus(b->p_mark, q->decrement);
186}
187
188static void increment_prob(struct sfb_bucket *b, struct sfb_sched_data *q)
189{
190 b->p_mark = prob_plus(b->p_mark, q->increment);
191}
192
193static void sfb_zero_all_buckets(struct sfb_sched_data *q)
194{
195 memset(&q->bins, 0, sizeof(q->bins));
196}
197
198/*
199 * compute max qlen, max p_mark, and avg p_mark
200 */
201static u32 sfb_compute_qlen(u32 *prob_r, u32 *avgpm_r, const struct sfb_sched_data *q)
202{
203 int i;
204 u32 qlen = 0, prob = 0, totalpm = 0;
205 const struct sfb_bucket *b = &q->bins[q->slot].bins[0][0];
206
207 for (i = 0; i < SFB_LEVELS * SFB_NUMBUCKETS; i++) {
208 if (qlen < b->qlen)
209 qlen = b->qlen;
210 totalpm += b->p_mark;
211 if (prob < b->p_mark)
212 prob = b->p_mark;
213 b++;
214 }
215 *prob_r = prob;
216 *avgpm_r = totalpm / (SFB_LEVELS * SFB_NUMBUCKETS);
217 return qlen;
218}
219
220
221static void sfb_init_perturbation(u32 slot, struct sfb_sched_data *q)
222{
223 q->bins[slot].perturbation = net_random();
224}
225
226static void sfb_swap_slot(struct sfb_sched_data *q)
227{
228 sfb_init_perturbation(q->slot, q);
229 q->slot ^= 1;
230 q->double_buffering = false;
231}
232
233/* Non elastic flows are allowed to use part of the bandwidth, expressed
234 * in "penalty_rate" packets per second, with "penalty_burst" burst
235 */
236static bool sfb_rate_limit(struct sk_buff *skb, struct sfb_sched_data *q)
237{
238 if (q->penalty_rate == 0 || q->penalty_burst == 0)
239 return true;
240
241 if (q->tokens_avail < 1) {
242 unsigned long age = min(10UL * HZ, jiffies - q->token_time);
243
244 q->tokens_avail = (age * q->penalty_rate) / HZ;
245 if (q->tokens_avail > q->penalty_burst)
246 q->tokens_avail = q->penalty_burst;
247 q->token_time = jiffies;
248 if (q->tokens_avail < 1)
249 return true;
250 }
251
252 q->tokens_avail--;
253 return false;
254}
255
256static bool sfb_classify(struct sk_buff *skb, struct sfb_sched_data *q,
257 int *qerr, u32 *salt)
258{
259 struct tcf_result res;
260 int result;
261
262 result = tc_classify(skb, q->filter_list, &res);
263 if (result >= 0) {
264#ifdef CONFIG_NET_CLS_ACT
265 switch (result) {
266 case TC_ACT_STOLEN:
267 case TC_ACT_QUEUED:
268 *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
269 case TC_ACT_SHOT:
270 return false;
271 }
272#endif
273 *salt = TC_H_MIN(res.classid);
274 return true;
275 }
276 return false;
277}
278
279static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch)
280{
281
282 struct sfb_sched_data *q = qdisc_priv(sch);
283 struct Qdisc *child = q->qdisc;
284 int i;
285 u32 p_min = ~0;
286 u32 minqlen = ~0;
287 u32 r, slot, salt, sfbhash;
288 int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
289 struct flow_keys keys;
290
291 if (unlikely(sch->q.qlen >= q->limit)) {
292 sch->qstats.overlimits++;
293 q->stats.queuedrop++;
294 goto drop;
295 }
296
297 if (q->rehash_interval > 0) {
298 unsigned long limit = q->rehash_time + q->rehash_interval;
299
300 if (unlikely(time_after(jiffies, limit))) {
301 sfb_swap_slot(q);
302 q->rehash_time = jiffies;
303 } else if (unlikely(!q->double_buffering && q->warmup_time > 0 &&
304 time_after(jiffies, limit - q->warmup_time))) {
305 q->double_buffering = true;
306 }
307 }
308
309 if (q->filter_list) {
310 /* If using external classifiers, get result and record it. */
311 if (!sfb_classify(skb, q, &ret, &salt))
312 goto other_drop;
313 keys.src = salt;
314 keys.dst = 0;
315 keys.ports = 0;
316 } else {
317 skb_flow_dissect(skb, &keys);
318 }
319
320 slot = q->slot;
321
322 sfbhash = jhash_3words((__force u32)keys.dst,
323 (__force u32)keys.src,
324 (__force u32)keys.ports,
325 q->bins[slot].perturbation);
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 sch->qstats.overlimits++;
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 = jhash_3words((__force u32)keys.dst,
358 (__force u32)keys.src,
359 (__force u32)keys.ports,
360 q->bins[slot].perturbation);
361 if (!sfbhash)
362 sfbhash = 1;
363 sfb_skb_cb(skb)->hashes[slot] = sfbhash;
364
365 for (i = 0; i < SFB_LEVELS; i++) {
366 u32 hash = sfbhash & SFB_BUCKET_MASK;
367 struct sfb_bucket *b = &q->bins[slot].bins[i][hash];
368
369 sfbhash >>= SFB_BUCKET_SHIFT;
370 if (b->qlen == 0)
371 decrement_prob(b, q);
372 else if (b->qlen >= q->bin_size)
373 increment_prob(b, q);
374 }
375 }
376 if (sfb_rate_limit(skb, q)) {
377 sch->qstats.overlimits++;
378 q->stats.penaltydrop++;
379 goto drop;
380 }
381 goto enqueue;
382 }
383
384 r = net_random() & SFB_MAX_PROB;
385
386 if (unlikely(r < p_min)) {
387 if (unlikely(p_min > SFB_MAX_PROB / 2)) {
388 /* If we're marking that many packets, then either
389 * this flow is unresponsive, or we're badly congested.
390 * In either case, we want to start dropping packets.
391 */
392 if (r < (p_min - SFB_MAX_PROB / 2) * 2) {
393 q->stats.earlydrop++;
394 goto drop;
395 }
396 }
397 if (INET_ECN_set_ce(skb)) {
398 q->stats.marked++;
399 } else {
400 q->stats.earlydrop++;
401 goto drop;
402 }
403 }
404
405enqueue:
406 ret = qdisc_enqueue(skb, child);
407 if (likely(ret == NET_XMIT_SUCCESS)) {
408 sch->q.qlen++;
409 increment_qlen(skb, q);
410 } else if (net_xmit_drop_count(ret)) {
411 q->stats.childdrop++;
412 sch->qstats.drops++;
413 }
414 return ret;
415
416drop:
417 qdisc_drop(skb, sch);
418 return NET_XMIT_CN;
419other_drop:
420 if (ret & __NET_XMIT_BYPASS)
421 sch->qstats.drops++;
422 kfree_skb(skb);
423 return ret;
424}
425
426static struct sk_buff *sfb_dequeue(struct Qdisc *sch)
427{
428 struct sfb_sched_data *q = qdisc_priv(sch);
429 struct Qdisc *child = q->qdisc;
430 struct sk_buff *skb;
431
432 skb = child->dequeue(q->qdisc);
433
434 if (skb) {
435 qdisc_bstats_update(sch, skb);
436 sch->q.qlen--;
437 decrement_qlen(skb, q);
438 }
439
440 return skb;
441}
442
443static 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
453static void sfb_reset(struct Qdisc *sch)
454{
455 struct sfb_sched_data *q = qdisc_priv(sch);
456
457 qdisc_reset(q->qdisc);
458 sch->q.qlen = 0;
459 q->slot = 0;
460 q->double_buffering = false;
461 sfb_zero_all_buckets(q);
462 sfb_init_perturbation(0, q);
463}
464
465static void sfb_destroy(struct Qdisc *sch)
466{
467 struct sfb_sched_data *q = qdisc_priv(sch);
468
469 tcf_destroy_chain(&q->filter_list);
470 qdisc_destroy(q->qdisc);
471}
472
473static const struct nla_policy sfb_policy[TCA_SFB_MAX + 1] = {
474 [TCA_SFB_PARMS] = { .len = sizeof(struct tc_sfb_qopt) },
475};
476
477static const struct tc_sfb_qopt sfb_default_ops = {
478 .rehash_interval = 600 * MSEC_PER_SEC,
479 .warmup_time = 60 * MSEC_PER_SEC,
480 .limit = 0,
481 .max = 25,
482 .bin_size = 20,
483 .increment = (SFB_MAX_PROB + 500) / 1000, /* 0.1 % */
484 .decrement = (SFB_MAX_PROB + 3000) / 6000,
485 .penalty_rate = 10,
486 .penalty_burst = 20,
487};
488
489static int sfb_change(struct Qdisc *sch, struct nlattr *opt)
490{
491 struct sfb_sched_data *q = qdisc_priv(sch);
492 struct Qdisc *child;
493 struct nlattr *tb[TCA_SFB_MAX + 1];
494 const struct tc_sfb_qopt *ctl = &sfb_default_ops;
495 u32 limit;
496 int err;
497
498 if (opt) {
499 err = nla_parse_nested(tb, TCA_SFB_MAX, opt, sfb_policy);
500 if (err < 0)
501 return -EINVAL;
502
503 if (tb[TCA_SFB_PARMS] == NULL)
504 return -EINVAL;
505
506 ctl = nla_data(tb[TCA_SFB_PARMS]);
507 }
508
509 limit = ctl->limit;
510 if (limit == 0)
511 limit = max_t(u32, qdisc_dev(sch)->tx_queue_len, 1);
512
513 child = fifo_create_dflt(sch, &pfifo_qdisc_ops, limit);
514 if (IS_ERR(child))
515 return PTR_ERR(child);
516
517 sch_tree_lock(sch);
518
519 qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
520 qdisc_destroy(q->qdisc);
521 q->qdisc = child;
522
523 q->rehash_interval = msecs_to_jiffies(ctl->rehash_interval);
524 q->warmup_time = msecs_to_jiffies(ctl->warmup_time);
525 q->rehash_time = jiffies;
526 q->limit = limit;
527 q->increment = ctl->increment;
528 q->decrement = ctl->decrement;
529 q->max = ctl->max;
530 q->bin_size = ctl->bin_size;
531 q->penalty_rate = ctl->penalty_rate;
532 q->penalty_burst = ctl->penalty_burst;
533 q->tokens_avail = ctl->penalty_burst;
534 q->token_time = jiffies;
535
536 q->slot = 0;
537 q->double_buffering = false;
538 sfb_zero_all_buckets(q);
539 sfb_init_perturbation(0, q);
540 sfb_init_perturbation(1, q);
541
542 sch_tree_unlock(sch);
543
544 return 0;
545}
546
547static int sfb_init(struct Qdisc *sch, struct nlattr *opt)
548{
549 struct sfb_sched_data *q = qdisc_priv(sch);
550
551 q->qdisc = &noop_qdisc;
552 return sfb_change(sch, opt);
553}
554
555static int sfb_dump(struct Qdisc *sch, struct sk_buff *skb)
556{
557 struct sfb_sched_data *q = qdisc_priv(sch);
558 struct nlattr *opts;
559 struct tc_sfb_qopt opt = {
560 .rehash_interval = jiffies_to_msecs(q->rehash_interval),
561 .warmup_time = jiffies_to_msecs(q->warmup_time),
562 .limit = q->limit,
563 .max = q->max,
564 .bin_size = q->bin_size,
565 .increment = q->increment,
566 .decrement = q->decrement,
567 .penalty_rate = q->penalty_rate,
568 .penalty_burst = q->penalty_burst,
569 };
570
571 sch->qstats.backlog = q->qdisc->qstats.backlog;
572 opts = nla_nest_start(skb, TCA_OPTIONS);
573 if (opts == NULL)
574 goto nla_put_failure;
575 if (nla_put(skb, TCA_SFB_PARMS, sizeof(opt), &opt))
576 goto nla_put_failure;
577 return nla_nest_end(skb, opts);
578
579nla_put_failure:
580 nla_nest_cancel(skb, opts);
581 return -EMSGSIZE;
582}
583
584static int sfb_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
585{
586 struct sfb_sched_data *q = qdisc_priv(sch);
587 struct tc_sfb_xstats st = {
588 .earlydrop = q->stats.earlydrop,
589 .penaltydrop = q->stats.penaltydrop,
590 .bucketdrop = q->stats.bucketdrop,
591 .queuedrop = q->stats.queuedrop,
592 .childdrop = q->stats.childdrop,
593 .marked = q->stats.marked,
594 };
595
596 st.maxqlen = sfb_compute_qlen(&st.maxprob, &st.avgprob, q);
597
598 return gnet_stats_copy_app(d, &st, sizeof(st));
599}
600
601static int sfb_dump_class(struct Qdisc *sch, unsigned long cl,
602 struct sk_buff *skb, struct tcmsg *tcm)
603{
604 return -ENOSYS;
605}
606
607static int sfb_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
608 struct Qdisc **old)
609{
610 struct sfb_sched_data *q = qdisc_priv(sch);
611
612 if (new == NULL)
613 new = &noop_qdisc;
614
615 sch_tree_lock(sch);
616 *old = q->qdisc;
617 q->qdisc = new;
618 qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
619 qdisc_reset(*old);
620 sch_tree_unlock(sch);
621 return 0;
622}
623
624static struct Qdisc *sfb_leaf(struct Qdisc *sch, unsigned long arg)
625{
626 struct sfb_sched_data *q = qdisc_priv(sch);
627
628 return q->qdisc;
629}
630
631static unsigned long sfb_get(struct Qdisc *sch, u32 classid)
632{
633 return 1;
634}
635
636static void sfb_put(struct Qdisc *sch, unsigned long arg)
637{
638}
639
640static int sfb_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
641 struct nlattr **tca, unsigned long *arg)
642{
643 return -ENOSYS;
644}
645
646static int sfb_delete(struct Qdisc *sch, unsigned long cl)
647{
648 return -ENOSYS;
649}
650
651static void sfb_walk(struct Qdisc *sch, struct qdisc_walker *walker)
652{
653 if (!walker->stop) {
654 if (walker->count >= walker->skip)
655 if (walker->fn(sch, 1, walker) < 0) {
656 walker->stop = 1;
657 return;
658 }
659 walker->count++;
660 }
661}
662
663static struct tcf_proto **sfb_find_tcf(struct Qdisc *sch, unsigned long cl)
664{
665 struct sfb_sched_data *q = qdisc_priv(sch);
666
667 if (cl)
668 return NULL;
669 return &q->filter_list;
670}
671
672static unsigned long sfb_bind(struct Qdisc *sch, unsigned long parent,
673 u32 classid)
674{
675 return 0;
676}
677
678
679static const struct Qdisc_class_ops sfb_class_ops = {
680 .graft = sfb_graft,
681 .leaf = sfb_leaf,
682 .get = sfb_get,
683 .put = sfb_put,
684 .change = sfb_change_class,
685 .delete = sfb_delete,
686 .walk = sfb_walk,
687 .tcf_chain = sfb_find_tcf,
688 .bind_tcf = sfb_bind,
689 .unbind_tcf = sfb_put,
690 .dump = sfb_dump_class,
691};
692
693static struct Qdisc_ops sfb_qdisc_ops __read_mostly = {
694 .id = "sfb",
695 .priv_size = sizeof(struct sfb_sched_data),
696 .cl_ops = &sfb_class_ops,
697 .enqueue = sfb_enqueue,
698 .dequeue = sfb_dequeue,
699 .peek = sfb_peek,
700 .init = sfb_init,
701 .reset = sfb_reset,
702 .destroy = sfb_destroy,
703 .change = sfb_change,
704 .dump = sfb_dump,
705 .dump_stats = sfb_dump_stats,
706 .owner = THIS_MODULE,
707};
708
709static int __init sfb_module_init(void)
710{
711 return register_qdisc(&sfb_qdisc_ops);
712}
713
714static void __exit sfb_module_exit(void)
715{
716 unregister_qdisc(&sfb_qdisc_ops);
717}
718
719module_init(sfb_module_init)
720module_exit(sfb_module_exit)
721
722MODULE_DESCRIPTION("Stochastic Fair Blue queue discipline");
723MODULE_AUTHOR("Juliusz Chroboczek");
724MODULE_AUTHOR("Eric Dumazet");
725MODULE_LICENSE("GPL");
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * net/sched/sch_sfb.c Stochastic Fair Blue
4 *
5 * Copyright (c) 2008-2011 Juliusz Chroboczek <jch@pps.jussieu.fr>
6 * Copyright (c) 2011 Eric Dumazet <eric.dumazet@gmail.com>
7 *
8 * W. Feng, D. Kandlur, D. Saha, K. Shin. Blue:
9 * A New Class of Active Queue Management Algorithms.
10 * U. Michigan CSE-TR-387-99, April 1999.
11 *
12 * http://www.thefengs.com/wuchang/blue/CSE-TR-387-99.pdf
13 */
14
15#include <linux/module.h>
16#include <linux/types.h>
17#include <linux/kernel.h>
18#include <linux/errno.h>
19#include <linux/skbuff.h>
20#include <linux/random.h>
21#include <linux/siphash.h>
22#include <net/ip.h>
23#include <net/pkt_sched.h>
24#include <net/pkt_cls.h>
25#include <net/inet_ecn.h>
26
27/*
28 * SFB uses two B[l][n] : L x N arrays of bins (L levels, N bins per level)
29 * This implementation uses L = 8 and N = 16
30 * This permits us to split one 32bit hash (provided per packet by rxhash or
31 * external classifier) into 8 subhashes of 4 bits.
32 */
33#define SFB_BUCKET_SHIFT 4
34#define SFB_NUMBUCKETS (1 << SFB_BUCKET_SHIFT) /* N bins per Level */
35#define SFB_BUCKET_MASK (SFB_NUMBUCKETS - 1)
36#define SFB_LEVELS (32 / SFB_BUCKET_SHIFT) /* L */
37
38/* SFB algo uses a virtual queue, named "bin" */
39struct sfb_bucket {
40 u16 qlen; /* length of virtual queue */
41 u16 p_mark; /* marking probability */
42};
43
44/* We use a double buffering right before hash change
45 * (Section 4.4 of SFB reference : moving hash functions)
46 */
47struct sfb_bins {
48 siphash_key_t perturbation; /* siphash key */
49 struct sfb_bucket bins[SFB_LEVELS][SFB_NUMBUCKETS];
50};
51
52struct sfb_sched_data {
53 struct Qdisc *qdisc;
54 struct tcf_proto __rcu *filter_list;
55 struct tcf_block *block;
56 unsigned long rehash_interval;
57 unsigned long warmup_time; /* double buffering warmup time in jiffies */
58 u32 max;
59 u32 bin_size; /* maximum queue length per bin */
60 u32 increment; /* d1 */
61 u32 decrement; /* d2 */
62 u32 limit; /* HARD maximal queue length */
63 u32 penalty_rate;
64 u32 penalty_burst;
65 u32 tokens_avail;
66 unsigned long rehash_time;
67 unsigned long token_time;
68
69 u8 slot; /* current active bins (0 or 1) */
70 bool double_buffering;
71 struct sfb_bins bins[2];
72
73 struct {
74 u32 earlydrop;
75 u32 penaltydrop;
76 u32 bucketdrop;
77 u32 queuedrop;
78 u32 childdrop; /* drops in child qdisc */
79 u32 marked; /* ECN mark */
80 } stats;
81};
82
83/*
84 * Each queued skb might be hashed on one or two bins
85 * We store in skb_cb the two hash values.
86 * (A zero value means double buffering was not used)
87 */
88struct sfb_skb_cb {
89 u32 hashes[2];
90};
91
92static inline struct sfb_skb_cb *sfb_skb_cb(const struct sk_buff *skb)
93{
94 qdisc_cb_private_validate(skb, sizeof(struct sfb_skb_cb));
95 return (struct sfb_skb_cb *)qdisc_skb_cb(skb)->data;
96}
97
98/*
99 * If using 'internal' SFB flow classifier, hash comes from skb rxhash
100 * If using external classifier, hash comes from the classid.
101 */
102static u32 sfb_hash(const struct sk_buff *skb, u32 slot)
103{
104 return sfb_skb_cb(skb)->hashes[slot];
105}
106
107/* Probabilities are coded as Q0.16 fixed-point values,
108 * with 0xFFFF representing 65535/65536 (almost 1.0)
109 * Addition and subtraction are saturating in [0, 65535]
110 */
111static u32 prob_plus(u32 p1, u32 p2)
112{
113 u32 res = p1 + p2;
114
115 return min_t(u32, res, SFB_MAX_PROB);
116}
117
118static u32 prob_minus(u32 p1, u32 p2)
119{
120 return p1 > p2 ? p1 - p2 : 0;
121}
122
123static void increment_one_qlen(u32 sfbhash, u32 slot, struct sfb_sched_data *q)
124{
125 int i;
126 struct sfb_bucket *b = &q->bins[slot].bins[0][0];
127
128 for (i = 0; i < SFB_LEVELS; i++) {
129 u32 hash = sfbhash & SFB_BUCKET_MASK;
130
131 sfbhash >>= SFB_BUCKET_SHIFT;
132 if (b[hash].qlen < 0xFFFF)
133 b[hash].qlen++;
134 b += SFB_NUMBUCKETS; /* next level */
135 }
136}
137
138static void increment_qlen(const struct sk_buff *skb, struct sfb_sched_data *q)
139{
140 u32 sfbhash;
141
142 sfbhash = sfb_hash(skb, 0);
143 if (sfbhash)
144 increment_one_qlen(sfbhash, 0, q);
145
146 sfbhash = sfb_hash(skb, 1);
147 if (sfbhash)
148 increment_one_qlen(sfbhash, 1, q);
149}
150
151static void decrement_one_qlen(u32 sfbhash, u32 slot,
152 struct sfb_sched_data *q)
153{
154 int i;
155 struct sfb_bucket *b = &q->bins[slot].bins[0][0];
156
157 for (i = 0; i < SFB_LEVELS; i++) {
158 u32 hash = sfbhash & SFB_BUCKET_MASK;
159
160 sfbhash >>= SFB_BUCKET_SHIFT;
161 if (b[hash].qlen > 0)
162 b[hash].qlen--;
163 b += SFB_NUMBUCKETS; /* next level */
164 }
165}
166
167static void decrement_qlen(const struct sk_buff *skb, struct sfb_sched_data *q)
168{
169 u32 sfbhash;
170
171 sfbhash = sfb_hash(skb, 0);
172 if (sfbhash)
173 decrement_one_qlen(sfbhash, 0, q);
174
175 sfbhash = sfb_hash(skb, 1);
176 if (sfbhash)
177 decrement_one_qlen(sfbhash, 1, q);
178}
179
180static void decrement_prob(struct sfb_bucket *b, struct sfb_sched_data *q)
181{
182 b->p_mark = prob_minus(b->p_mark, q->decrement);
183}
184
185static void increment_prob(struct sfb_bucket *b, struct sfb_sched_data *q)
186{
187 b->p_mark = prob_plus(b->p_mark, q->increment);
188}
189
190static void sfb_zero_all_buckets(struct sfb_sched_data *q)
191{
192 memset(&q->bins, 0, sizeof(q->bins));
193}
194
195/*
196 * compute max qlen, max p_mark, and avg p_mark
197 */
198static u32 sfb_compute_qlen(u32 *prob_r, u32 *avgpm_r, const struct sfb_sched_data *q)
199{
200 int i;
201 u32 qlen = 0, prob = 0, totalpm = 0;
202 const struct sfb_bucket *b = &q->bins[q->slot].bins[0][0];
203
204 for (i = 0; i < SFB_LEVELS * SFB_NUMBUCKETS; i++) {
205 if (qlen < b->qlen)
206 qlen = b->qlen;
207 totalpm += b->p_mark;
208 if (prob < b->p_mark)
209 prob = b->p_mark;
210 b++;
211 }
212 *prob_r = prob;
213 *avgpm_r = totalpm / (SFB_LEVELS * SFB_NUMBUCKETS);
214 return qlen;
215}
216
217
218static void sfb_init_perturbation(u32 slot, struct sfb_sched_data *q)
219{
220 get_random_bytes(&q->bins[slot].perturbation,
221 sizeof(q->bins[slot].perturbation));
222}
223
224static void sfb_swap_slot(struct sfb_sched_data *q)
225{
226 sfb_init_perturbation(q->slot, q);
227 q->slot ^= 1;
228 q->double_buffering = false;
229}
230
231/* Non elastic flows are allowed to use part of the bandwidth, expressed
232 * in "penalty_rate" packets per second, with "penalty_burst" burst
233 */
234static bool sfb_rate_limit(struct sk_buff *skb, struct sfb_sched_data *q)
235{
236 if (q->penalty_rate == 0 || q->penalty_burst == 0)
237 return true;
238
239 if (q->tokens_avail < 1) {
240 unsigned long age = min(10UL * HZ, jiffies - q->token_time);
241
242 q->tokens_avail = (age * q->penalty_rate) / HZ;
243 if (q->tokens_avail > q->penalty_burst)
244 q->tokens_avail = q->penalty_burst;
245 q->token_time = jiffies;
246 if (q->tokens_avail < 1)
247 return true;
248 }
249
250 q->tokens_avail--;
251 return false;
252}
253
254static bool sfb_classify(struct sk_buff *skb, struct tcf_proto *fl,
255 int *qerr, u32 *salt)
256{
257 struct tcf_result res;
258 int result;
259
260 result = tcf_classify(skb, fl, &res, false);
261 if (result >= 0) {
262#ifdef CONFIG_NET_CLS_ACT
263 switch (result) {
264 case TC_ACT_STOLEN:
265 case TC_ACT_QUEUED:
266 case TC_ACT_TRAP:
267 *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
268 fallthrough;
269 case TC_ACT_SHOT:
270 return false;
271 }
272#endif
273 *salt = TC_H_MIN(res.classid);
274 return true;
275 }
276 return false;
277}
278
279static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
280 struct sk_buff **to_free)
281{
282
283 struct sfb_sched_data *q = qdisc_priv(sch);
284 struct Qdisc *child = q->qdisc;
285 struct tcf_proto *fl;
286 int i;
287 u32 p_min = ~0;
288 u32 minqlen = ~0;
289 u32 r, sfbhash;
290 u32 slot = q->slot;
291 int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
292
293 if (unlikely(sch->q.qlen >= q->limit)) {
294 qdisc_qstats_overlimit(sch);
295 q->stats.queuedrop++;
296 goto drop;
297 }
298
299 if (q->rehash_interval > 0) {
300 unsigned long limit = q->rehash_time + q->rehash_interval;
301
302 if (unlikely(time_after(jiffies, limit))) {
303 sfb_swap_slot(q);
304 q->rehash_time = jiffies;
305 } else if (unlikely(!q->double_buffering && q->warmup_time > 0 &&
306 time_after(jiffies, limit - q->warmup_time))) {
307 q->double_buffering = true;
308 }
309 }
310
311 fl = rcu_dereference_bh(q->filter_list);
312 if (fl) {
313 u32 salt;
314
315 /* If using external classifiers, get result and record it. */
316 if (!sfb_classify(skb, fl, &ret, &salt))
317 goto other_drop;
318 sfbhash = siphash_1u32(salt, &q->bins[slot].perturbation);
319 } else {
320 sfbhash = skb_get_hash_perturb(skb, &q->bins[slot].perturbation);
321 }
322
323
324 if (!sfbhash)
325 sfbhash = 1;
326 sfb_skb_cb(skb)->hashes[slot] = sfbhash;
327
328 for (i = 0; i < SFB_LEVELS; i++) {
329 u32 hash = sfbhash & SFB_BUCKET_MASK;
330 struct sfb_bucket *b = &q->bins[slot].bins[i][hash];
331
332 sfbhash >>= SFB_BUCKET_SHIFT;
333 if (b->qlen == 0)
334 decrement_prob(b, q);
335 else if (b->qlen >= q->bin_size)
336 increment_prob(b, q);
337 if (minqlen > b->qlen)
338 minqlen = b->qlen;
339 if (p_min > b->p_mark)
340 p_min = b->p_mark;
341 }
342
343 slot ^= 1;
344 sfb_skb_cb(skb)->hashes[slot] = 0;
345
346 if (unlikely(minqlen >= q->max)) {
347 qdisc_qstats_overlimit(sch);
348 q->stats.bucketdrop++;
349 goto drop;
350 }
351
352 if (unlikely(p_min >= SFB_MAX_PROB)) {
353 /* Inelastic flow */
354 if (q->double_buffering) {
355 sfbhash = skb_get_hash_perturb(skb,
356 &q->bins[slot].perturbation);
357 if (!sfbhash)
358 sfbhash = 1;
359 sfb_skb_cb(skb)->hashes[slot] = sfbhash;
360
361 for (i = 0; i < SFB_LEVELS; i++) {
362 u32 hash = sfbhash & SFB_BUCKET_MASK;
363 struct sfb_bucket *b = &q->bins[slot].bins[i][hash];
364
365 sfbhash >>= SFB_BUCKET_SHIFT;
366 if (b->qlen == 0)
367 decrement_prob(b, q);
368 else if (b->qlen >= q->bin_size)
369 increment_prob(b, q);
370 }
371 }
372 if (sfb_rate_limit(skb, q)) {
373 qdisc_qstats_overlimit(sch);
374 q->stats.penaltydrop++;
375 goto drop;
376 }
377 goto enqueue;
378 }
379
380 r = prandom_u32() & SFB_MAX_PROB;
381
382 if (unlikely(r < p_min)) {
383 if (unlikely(p_min > SFB_MAX_PROB / 2)) {
384 /* If we're marking that many packets, then either
385 * this flow is unresponsive, or we're badly congested.
386 * In either case, we want to start dropping packets.
387 */
388 if (r < (p_min - SFB_MAX_PROB / 2) * 2) {
389 q->stats.earlydrop++;
390 goto drop;
391 }
392 }
393 if (INET_ECN_set_ce(skb)) {
394 q->stats.marked++;
395 } else {
396 q->stats.earlydrop++;
397 goto drop;
398 }
399 }
400
401enqueue:
402 ret = qdisc_enqueue(skb, child, to_free);
403 if (likely(ret == NET_XMIT_SUCCESS)) {
404 qdisc_qstats_backlog_inc(sch, skb);
405 sch->q.qlen++;
406 increment_qlen(skb, q);
407 } else if (net_xmit_drop_count(ret)) {
408 q->stats.childdrop++;
409 qdisc_qstats_drop(sch);
410 }
411 return ret;
412
413drop:
414 qdisc_drop(skb, sch, to_free);
415 return NET_XMIT_CN;
416other_drop:
417 if (ret & __NET_XMIT_BYPASS)
418 qdisc_qstats_drop(sch);
419 kfree_skb(skb);
420 return ret;
421}
422
423static struct sk_buff *sfb_dequeue(struct Qdisc *sch)
424{
425 struct sfb_sched_data *q = qdisc_priv(sch);
426 struct Qdisc *child = q->qdisc;
427 struct sk_buff *skb;
428
429 skb = child->dequeue(q->qdisc);
430
431 if (skb) {
432 qdisc_bstats_update(sch, skb);
433 qdisc_qstats_backlog_dec(sch, skb);
434 sch->q.qlen--;
435 decrement_qlen(skb, q);
436 }
437
438 return skb;
439}
440
441static struct sk_buff *sfb_peek(struct Qdisc *sch)
442{
443 struct sfb_sched_data *q = qdisc_priv(sch);
444 struct Qdisc *child = q->qdisc;
445
446 return child->ops->peek(child);
447}
448
449/* No sfb_drop -- impossible since the child doesn't return the dropped skb. */
450
451static void sfb_reset(struct Qdisc *sch)
452{
453 struct sfb_sched_data *q = qdisc_priv(sch);
454
455 qdisc_reset(q->qdisc);
456 sch->qstats.backlog = 0;
457 sch->q.qlen = 0;
458 q->slot = 0;
459 q->double_buffering = false;
460 sfb_zero_all_buckets(q);
461 sfb_init_perturbation(0, q);
462}
463
464static void sfb_destroy(struct Qdisc *sch)
465{
466 struct sfb_sched_data *q = qdisc_priv(sch);
467
468 tcf_block_put(q->block);
469 qdisc_put(q->qdisc);
470}
471
472static const struct nla_policy sfb_policy[TCA_SFB_MAX + 1] = {
473 [TCA_SFB_PARMS] = { .len = sizeof(struct tc_sfb_qopt) },
474};
475
476static const struct tc_sfb_qopt sfb_default_ops = {
477 .rehash_interval = 600 * MSEC_PER_SEC,
478 .warmup_time = 60 * MSEC_PER_SEC,
479 .limit = 0,
480 .max = 25,
481 .bin_size = 20,
482 .increment = (SFB_MAX_PROB + 500) / 1000, /* 0.1 % */
483 .decrement = (SFB_MAX_PROB + 3000) / 6000,
484 .penalty_rate = 10,
485 .penalty_burst = 20,
486};
487
488static int sfb_change(struct Qdisc *sch, struct nlattr *opt,
489 struct netlink_ext_ack *extack)
490{
491 struct sfb_sched_data *q = qdisc_priv(sch);
492 struct Qdisc *child, *old;
493 struct nlattr *tb[TCA_SFB_MAX + 1];
494 const struct tc_sfb_qopt *ctl = &sfb_default_ops;
495 u32 limit;
496 int err;
497
498 if (opt) {
499 err = nla_parse_nested_deprecated(tb, TCA_SFB_MAX, opt,
500 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, extack);
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_purge_queue(q->qdisc);
523 old = q->qdisc;
524 q->qdisc = child;
525
526 q->rehash_interval = msecs_to_jiffies(ctl->rehash_interval);
527 q->warmup_time = msecs_to_jiffies(ctl->warmup_time);
528 q->rehash_time = jiffies;
529 q->limit = limit;
530 q->increment = ctl->increment;
531 q->decrement = ctl->decrement;
532 q->max = ctl->max;
533 q->bin_size = ctl->bin_size;
534 q->penalty_rate = ctl->penalty_rate;
535 q->penalty_burst = ctl->penalty_burst;
536 q->tokens_avail = ctl->penalty_burst;
537 q->token_time = jiffies;
538
539 q->slot = 0;
540 q->double_buffering = false;
541 sfb_zero_all_buckets(q);
542 sfb_init_perturbation(0, q);
543 sfb_init_perturbation(1, q);
544
545 sch_tree_unlock(sch);
546 qdisc_put(old);
547
548 return 0;
549}
550
551static int sfb_init(struct Qdisc *sch, struct nlattr *opt,
552 struct netlink_ext_ack *extack)
553{
554 struct sfb_sched_data *q = qdisc_priv(sch);
555 int err;
556
557 err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
558 if (err)
559 return err;
560
561 q->qdisc = &noop_qdisc;
562 return sfb_change(sch, opt, extack);
563}
564
565static int sfb_dump(struct Qdisc *sch, struct sk_buff *skb)
566{
567 struct sfb_sched_data *q = qdisc_priv(sch);
568 struct nlattr *opts;
569 struct tc_sfb_qopt opt = {
570 .rehash_interval = jiffies_to_msecs(q->rehash_interval),
571 .warmup_time = jiffies_to_msecs(q->warmup_time),
572 .limit = q->limit,
573 .max = q->max,
574 .bin_size = q->bin_size,
575 .increment = q->increment,
576 .decrement = q->decrement,
577 .penalty_rate = q->penalty_rate,
578 .penalty_burst = q->penalty_burst,
579 };
580
581 sch->qstats.backlog = q->qdisc->qstats.backlog;
582 opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
583 if (opts == NULL)
584 goto nla_put_failure;
585 if (nla_put(skb, TCA_SFB_PARMS, sizeof(opt), &opt))
586 goto nla_put_failure;
587 return nla_nest_end(skb, opts);
588
589nla_put_failure:
590 nla_nest_cancel(skb, opts);
591 return -EMSGSIZE;
592}
593
594static int sfb_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
595{
596 struct sfb_sched_data *q = qdisc_priv(sch);
597 struct tc_sfb_xstats st = {
598 .earlydrop = q->stats.earlydrop,
599 .penaltydrop = q->stats.penaltydrop,
600 .bucketdrop = q->stats.bucketdrop,
601 .queuedrop = q->stats.queuedrop,
602 .childdrop = q->stats.childdrop,
603 .marked = q->stats.marked,
604 };
605
606 st.maxqlen = sfb_compute_qlen(&st.maxprob, &st.avgprob, q);
607
608 return gnet_stats_copy_app(d, &st, sizeof(st));
609}
610
611static int sfb_dump_class(struct Qdisc *sch, unsigned long cl,
612 struct sk_buff *skb, struct tcmsg *tcm)
613{
614 return -ENOSYS;
615}
616
617static int sfb_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
618 struct Qdisc **old, struct netlink_ext_ack *extack)
619{
620 struct sfb_sched_data *q = qdisc_priv(sch);
621
622 if (new == NULL)
623 new = &noop_qdisc;
624
625 *old = qdisc_replace(sch, new, &q->qdisc);
626 return 0;
627}
628
629static struct Qdisc *sfb_leaf(struct Qdisc *sch, unsigned long arg)
630{
631 struct sfb_sched_data *q = qdisc_priv(sch);
632
633 return q->qdisc;
634}
635
636static unsigned long sfb_find(struct Qdisc *sch, u32 classid)
637{
638 return 1;
639}
640
641static void sfb_unbind(struct Qdisc *sch, unsigned long arg)
642{
643}
644
645static int sfb_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
646 struct nlattr **tca, unsigned long *arg,
647 struct netlink_ext_ack *extack)
648{
649 return -ENOSYS;
650}
651
652static int sfb_delete(struct Qdisc *sch, unsigned long cl,
653 struct netlink_ext_ack *extack)
654{
655 return -ENOSYS;
656}
657
658static void sfb_walk(struct Qdisc *sch, struct qdisc_walker *walker)
659{
660 if (!walker->stop) {
661 if (walker->count >= walker->skip)
662 if (walker->fn(sch, 1, walker) < 0) {
663 walker->stop = 1;
664 return;
665 }
666 walker->count++;
667 }
668}
669
670static struct tcf_block *sfb_tcf_block(struct Qdisc *sch, unsigned long cl,
671 struct netlink_ext_ack *extack)
672{
673 struct sfb_sched_data *q = qdisc_priv(sch);
674
675 if (cl)
676 return NULL;
677 return q->block;
678}
679
680static unsigned long sfb_bind(struct Qdisc *sch, unsigned long parent,
681 u32 classid)
682{
683 return 0;
684}
685
686
687static const struct Qdisc_class_ops sfb_class_ops = {
688 .graft = sfb_graft,
689 .leaf = sfb_leaf,
690 .find = sfb_find,
691 .change = sfb_change_class,
692 .delete = sfb_delete,
693 .walk = sfb_walk,
694 .tcf_block = sfb_tcf_block,
695 .bind_tcf = sfb_bind,
696 .unbind_tcf = sfb_unbind,
697 .dump = sfb_dump_class,
698};
699
700static struct Qdisc_ops sfb_qdisc_ops __read_mostly = {
701 .id = "sfb",
702 .priv_size = sizeof(struct sfb_sched_data),
703 .cl_ops = &sfb_class_ops,
704 .enqueue = sfb_enqueue,
705 .dequeue = sfb_dequeue,
706 .peek = sfb_peek,
707 .init = sfb_init,
708 .reset = sfb_reset,
709 .destroy = sfb_destroy,
710 .change = sfb_change,
711 .dump = sfb_dump,
712 .dump_stats = sfb_dump_stats,
713 .owner = THIS_MODULE,
714};
715
716static int __init sfb_module_init(void)
717{
718 return register_qdisc(&sfb_qdisc_ops);
719}
720
721static void __exit sfb_module_exit(void)
722{
723 unregister_qdisc(&sfb_qdisc_ops);
724}
725
726module_init(sfb_module_init)
727module_exit(sfb_module_exit)
728
729MODULE_DESCRIPTION("Stochastic Fair Blue queue discipline");
730MODULE_AUTHOR("Juliusz Chroboczek");
731MODULE_AUTHOR("Eric Dumazet");
732MODULE_LICENSE("GPL");