net/sched/sch_sfb.c

   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/jhash.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" */
  39 struct 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  */
  47 struct sfb_bins {
  48         u32               perturbation; /* jhash perturbation */
  49         struct sfb_bucket bins[SFB_LEVELS][SFB_NUMBUCKETS];
  50 };
  51
  52 struct 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  */
  88 struct sfb_skb_cb {
  89         u32 hashes[2];
  90 };
  91
  92 static 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  */
 102 static 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  */
 111 static 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
 118 static u32 prob_minus(u32 p1, u32 p2)
 119 {
 120         return p1 > p2 ? p1 - p2 : 0;
 121 }
 122
 123 static 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
 138 static 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
 151 static 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
 167 static 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
 180 static 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
 185 static 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
 190 static 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  */
 198 static 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
 218 static void sfb_init_perturbation(u32 slot, struct sfb_sched_data *q)
 219 {
 220         q->bins[slot].perturbation = prandom_u32();
 221 }
 222
 223 static void sfb_swap_slot(struct sfb_sched_data *q)
 224 {
 225         sfb_init_perturbation(q->slot, q);
 226         q->slot ^= 1;
 227         q->double_buffering = false;
 228 }
 229
 230 /* Non elastic flows are allowed to use part of the bandwidth, expressed
 231  * in "penalty_rate" packets per second, with "penalty_burst" burst
 232  */
 233 static bool sfb_rate_limit(struct sk_buff *skb, struct sfb_sched_data *q)
 234 {
 235         if (q->penalty_rate == 0 || q->penalty_burst == 0)
 236                 return true;
 237
 238         if (q->tokens_avail < 1) {
 239                 unsigned long age = min(10UL * HZ, jiffies - q->token_time);
 240
 241                 q->tokens_avail = (age * q->penalty_rate) / HZ;
 242                 if (q->tokens_avail > q->penalty_burst)
 243                         q->tokens_avail = q->penalty_burst;
 244                 q->token_time = jiffies;
 245                 if (q->tokens_avail < 1)
 246                         return true;
 247         }
 248
 249         q->tokens_avail--;
 250         return false;
 251 }
 252
 253 static bool sfb_classify(struct sk_buff *skb, struct tcf_proto *fl,
 254                          int *qerr, u32 *salt)
 255 {
 256         struct tcf_result res;
 257         int result;
 258
 259         result = tcf_classify(skb, fl, &res, false);
 260         if (result >= 0) {
 261 #ifdef CONFIG_NET_CLS_ACT
 262                 switch (result) {
 263                 case TC_ACT_STOLEN:
 264                 case TC_ACT_QUEUED:
 265                 case TC_ACT_TRAP:
 266                         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
 267                         /* fall through */
 268                 case TC_ACT_SHOT:
 269                         return false;
 270                 }
 271 #endif
 272                 *salt = TC_H_MIN(res.classid);
 273                 return true;
 274         }
 275         return false;
 276 }
 277
 278 static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 279                        struct sk_buff **to_free)
 280 {
 281
 282         struct sfb_sched_data *q = qdisc_priv(sch);
 283         struct Qdisc *child = q->qdisc;
 284         struct tcf_proto *fl;
 285         int i;
 286         u32 p_min = ~0;
 287         u32 minqlen = ~0;
 288         u32 r, sfbhash;
 289         u32 slot = q->slot;
 290         int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
 291
 292         if (unlikely(sch->q.qlen >= q->limit)) {
 293                 qdisc_qstats_overlimit(sch);
 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         fl = rcu_dereference_bh(q->filter_list);
 311         if (fl) {
 312                 u32 salt;
 313
 314                 /* If using external classifiers, get result and record it. */
 315                 if (!sfb_classify(skb, fl, &ret, &salt))
 316                         goto other_drop;
 317                 sfbhash = jhash_1word(salt, q->bins[slot].perturbation);
 318         } else {
 319                 sfbhash = skb_get_hash_perturb(skb, q->bins[slot].perturbation);
 320         }
 321
 322
 323         if (!sfbhash)
 324                 sfbhash = 1;
 325         sfb_skb_cb(skb)->hashes[slot] = sfbhash;
 326
 327         for (i = 0; i < SFB_LEVELS; i++) {
 328                 u32 hash = sfbhash & SFB_BUCKET_MASK;
 329                 struct sfb_bucket *b = &q->bins[slot].bins[i][hash];
 330
 331                 sfbhash >>= SFB_BUCKET_SHIFT;
 332                 if (b->qlen == 0)
 333                         decrement_prob(b, q);
 334                 else if (b->qlen >= q->bin_size)
 335                         increment_prob(b, q);
 336                 if (minqlen > b->qlen)
 337                         minqlen = b->qlen;
 338                 if (p_min > b->p_mark)
 339                         p_min = b->p_mark;
 340         }
 341
 342         slot ^= 1;
 343         sfb_skb_cb(skb)->hashes[slot] = 0;
 344
 345         if (unlikely(minqlen >= q->max)) {
 346                 qdisc_qstats_overlimit(sch);
 347                 q->stats.bucketdrop++;
 348                 goto drop;
 349         }
 350
 351         if (unlikely(p_min >= SFB_MAX_PROB)) {
 352                 /* Inelastic flow */
 353                 if (q->double_buffering) {
 354                         sfbhash = skb_get_hash_perturb(skb,
 355                             q->bins[slot].perturbation);
 356                         if (!sfbhash)
 357                                 sfbhash = 1;
 358                         sfb_skb_cb(skb)->hashes[slot] = sfbhash;
 359
 360                         for (i = 0; i < SFB_LEVELS; i++) {
 361                                 u32 hash = sfbhash & SFB_BUCKET_MASK;
 362                                 struct sfb_bucket *b = &q->bins[slot].bins[i][hash];
 363
 364                                 sfbhash >>= SFB_BUCKET_SHIFT;
 365                                 if (b->qlen == 0)
 366                                         decrement_prob(b, q);
 367                                 else if (b->qlen >= q->bin_size)
 368                                         increment_prob(b, q);
 369                         }
 370                 }
 371                 if (sfb_rate_limit(skb, q)) {
 372                         qdisc_qstats_overlimit(sch);
 373                         q->stats.penaltydrop++;
 374                         goto drop;
 375                 }
 376                 goto enqueue;
 377         }
 378
 379         r = prandom_u32() & SFB_MAX_PROB;
 380
 381         if (unlikely(r < p_min)) {
 382                 if (unlikely(p_min > SFB_MAX_PROB / 2)) {
 383                         /* If we're marking that many packets, then either
 384                          * this flow is unresponsive, or we're badly congested.
 385                          * In either case, we want to start dropping packets.
 386                          */
 387                         if (r < (p_min - SFB_MAX_PROB / 2) * 2) {
 388                                 q->stats.earlydrop++;
 389                                 goto drop;
 390                         }
 391                 }
 392                 if (INET_ECN_set_ce(skb)) {
 393                         q->stats.marked++;
 394                 } else {
 395                         q->stats.earlydrop++;
 396                         goto drop;
 397                 }
 398         }
 399
 400 enqueue:
 401         ret = qdisc_enqueue(skb, child, to_free);
 402         if (likely(ret == NET_XMIT_SUCCESS)) {
 403                 qdisc_qstats_backlog_inc(sch, skb);
 404                 sch->q.qlen++;
 405                 increment_qlen(skb, q);
 406         } else if (net_xmit_drop_count(ret)) {
 407                 q->stats.childdrop++;
 408                 qdisc_qstats_drop(sch);
 409         }
 410         return ret;
 411
 412 drop:
 413         qdisc_drop(skb, sch, to_free);
 414         return NET_XMIT_CN;
 415 other_drop:
 416         if (ret & __NET_XMIT_BYPASS)
 417                 qdisc_qstats_drop(sch);
 418         kfree_skb(skb);
 419         return ret;
 420 }
 421
 422 static struct sk_buff *sfb_dequeue(struct Qdisc *sch)
 423 {
 424         struct sfb_sched_data *q = qdisc_priv(sch);
 425         struct Qdisc *child = q->qdisc;
 426         struct sk_buff *skb;
 427
 428         skb = child->dequeue(q->qdisc);
 429
 430         if (skb) {
 431                 qdisc_bstats_update(sch, skb);
 432                 qdisc_qstats_backlog_dec(sch, skb);
 433                 sch->q.qlen--;
 434                 decrement_qlen(skb, q);
 435         }
 436
 437         return skb;
 438 }
 439
 440 static struct sk_buff *sfb_peek(struct Qdisc *sch)
 441 {
 442         struct sfb_sched_data *q = qdisc_priv(sch);
 443         struct Qdisc *child = q->qdisc;
 444
 445         return child->ops->peek(child);
 446 }
 447
 448 /* No sfb_drop -- impossible since the child doesn't return the dropped skb. */
 449
 450 static void sfb_reset(struct Qdisc *sch)
 451 {
 452         struct sfb_sched_data *q = qdisc_priv(sch);
 453
 454         qdisc_reset(q->qdisc);
 455         sch->qstats.backlog = 0;
 456         sch->q.qlen = 0;
 457         q->slot = 0;
 458         q->double_buffering = false;
 459         sfb_zero_all_buckets(q);
 460         sfb_init_perturbation(0, q);
 461 }
 462
 463 static void sfb_destroy(struct Qdisc *sch)
 464 {
 465         struct sfb_sched_data *q = qdisc_priv(sch);
 466
 467         tcf_block_put(q->block);
 468         qdisc_put(q->qdisc);
 469 }
 470
 471 static const struct nla_policy sfb_policy[TCA_SFB_MAX + 1] = {
 472         [TCA_SFB_PARMS] = { .len = sizeof(struct tc_sfb_qopt) },
 473 };
 474
 475 static const struct tc_sfb_qopt sfb_default_ops = {
 476         .rehash_interval = 600 * MSEC_PER_SEC,
 477         .warmup_time = 60 * MSEC_PER_SEC,
 478         .limit = 0,
 479         .max = 25,
 480         .bin_size = 20,
 481         .increment = (SFB_MAX_PROB + 500) / 1000, /* 0.1 % */
 482         .decrement = (SFB_MAX_PROB + 3000) / 6000,
 483         .penalty_rate = 10,
 484         .penalty_burst = 20,
 485 };
 486
 487 static int sfb_change(struct Qdisc *sch, struct nlattr *opt,
 488                       struct netlink_ext_ack *extack)
 489 {
 490         struct sfb_sched_data *q = qdisc_priv(sch);
 491         struct Qdisc *child;
 492         struct nlattr *tb[TCA_SFB_MAX + 1];
 493         const struct tc_sfb_qopt *ctl = &sfb_default_ops;
 494         u32 limit;
 495         int err;
 496
 497         if (opt) {
 498                 err = nla_parse_nested_deprecated(tb, TCA_SFB_MAX, opt,
 499                                                   sfb_policy, NULL);
 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 = qdisc_dev(sch)->tx_queue_len;
 512
 513         child = fifo_create_dflt(sch, &pfifo_qdisc_ops, limit, extack);
 514         if (IS_ERR(child))
 515                 return PTR_ERR(child);
 516
 517         if (child != &noop_qdisc)
 518                 qdisc_hash_add(child, true);
 519         sch_tree_lock(sch);
 520
 521         qdisc_tree_flush_backlog(q->qdisc);
 522         qdisc_put(q->qdisc);
 523         q->qdisc = child;
 524
 525         q->rehash_interval = msecs_to_jiffies(ctl->rehash_interval);
 526         q->warmup_time = msecs_to_jiffies(ctl->warmup_time);
 527         q->rehash_time = jiffies;
 528         q->limit = limit;
 529         q->increment = ctl->increment;
 530         q->decrement = ctl->decrement;
 531         q->max = ctl->max;
 532         q->bin_size = ctl->bin_size;
 533         q->penalty_rate = ctl->penalty_rate;
 534         q->penalty_burst = ctl->penalty_burst;
 535         q->tokens_avail = ctl->penalty_burst;
 536         q->token_time = jiffies;
 537
 538         q->slot = 0;
 539         q->double_buffering = false;
 540         sfb_zero_all_buckets(q);
 541         sfb_init_perturbation(0, q);
 542         sfb_init_perturbation(1, q);
 543
 544         sch_tree_unlock(sch);
 545
 546         return 0;
 547 }
 548
 549 static int sfb_init(struct Qdisc *sch, struct nlattr *opt,
 550                     struct netlink_ext_ack *extack)
 551 {
 552         struct sfb_sched_data *q = qdisc_priv(sch);
 553         int err;
 554
 555         err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
 556         if (err)
 557                 return err;
 558
 559         q->qdisc = &noop_qdisc;
 560         return sfb_change(sch, opt, extack);
 561 }
 562
 563 static int sfb_dump(struct Qdisc *sch, struct sk_buff *skb)
 564 {
 565         struct sfb_sched_data *q = qdisc_priv(sch);
 566         struct nlattr *opts;
 567         struct tc_sfb_qopt opt = {
 568                 .rehash_interval = jiffies_to_msecs(q->rehash_interval),
 569                 .warmup_time = jiffies_to_msecs(q->warmup_time),
 570                 .limit = q->limit,
 571                 .max = q->max,
 572                 .bin_size = q->bin_size,
 573                 .increment = q->increment,
 574                 .decrement = q->decrement,
 575                 .penalty_rate = q->penalty_rate,
 576                 .penalty_burst = q->penalty_burst,
 577         };
 578
 579         sch->qstats.backlog = q->qdisc->qstats.backlog;
 580         opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
 581         if (opts == NULL)
 582                 goto nla_put_failure;
 583         if (nla_put(skb, TCA_SFB_PARMS, sizeof(opt), &opt))
 584                 goto nla_put_failure;
 585         return nla_nest_end(skb, opts);
 586
 587 nla_put_failure:
 588         nla_nest_cancel(skb, opts);
 589         return -EMSGSIZE;
 590 }
 591
 592 static int sfb_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
 593 {
 594         struct sfb_sched_data *q = qdisc_priv(sch);
 595         struct tc_sfb_xstats st = {
 596                 .earlydrop = q->stats.earlydrop,
 597                 .penaltydrop = q->stats.penaltydrop,
 598                 .bucketdrop = q->stats.bucketdrop,
 599                 .queuedrop = q->stats.queuedrop,
 600                 .childdrop = q->stats.childdrop,
 601                 .marked = q->stats.marked,
 602         };
 603
 604         st.maxqlen = sfb_compute_qlen(&st.maxprob, &st.avgprob, q);
 605
 606         return gnet_stats_copy_app(d, &st, sizeof(st));
 607 }
 608
 609 static int sfb_dump_class(struct Qdisc *sch, unsigned long cl,
 610                           struct sk_buff *skb, struct tcmsg *tcm)
 611 {
 612         return -ENOSYS;
 613 }
 614
 615 static int sfb_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 616                      struct Qdisc **old, struct netlink_ext_ack *extack)
 617 {
 618         struct sfb_sched_data *q = qdisc_priv(sch);
 619
 620         if (new == NULL)
 621                 new = &noop_qdisc;
 622
 623         *old = qdisc_replace(sch, new, &q->qdisc);
 624         return 0;
 625 }
 626
 627 static struct Qdisc *sfb_leaf(struct Qdisc *sch, unsigned long arg)
 628 {
 629         struct sfb_sched_data *q = qdisc_priv(sch);
 630
 631         return q->qdisc;
 632 }
 633
 634 static unsigned long sfb_find(struct Qdisc *sch, u32 classid)
 635 {
 636         return 1;
 637 }
 638
 639 static void sfb_unbind(struct Qdisc *sch, unsigned long arg)
 640 {
 641 }
 642
 643 static int sfb_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 644                             struct nlattr **tca, unsigned long *arg,
 645                             struct netlink_ext_ack *extack)
 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                                        struct netlink_ext_ack *extack)
 669 {
 670         struct sfb_sched_data *q = qdisc_priv(sch);
 671
 672         if (cl)
 673                 return NULL;
 674         return q->block;
 675 }
 676
 677 static unsigned long sfb_bind(struct Qdisc *sch, unsigned long parent,
 678                               u32 classid)
 679 {
 680         return 0;
 681 }
 682
 683
 684 static const struct Qdisc_class_ops sfb_class_ops = {
 685         .graft          =       sfb_graft,
 686         .leaf           =       sfb_leaf,
 687         .find           =       sfb_find,
 688         .change         =       sfb_change_class,
 689         .delete         =       sfb_delete,
 690         .walk           =       sfb_walk,
 691         .tcf_block      =       sfb_tcf_block,
 692         .bind_tcf       =       sfb_bind,
 693         .unbind_tcf     =       sfb_unbind,
 694         .dump           =       sfb_dump_class,
 695 };
 696
 697 static struct Qdisc_ops sfb_qdisc_ops __read_mostly = {
 698         .id             =       "sfb",
 699         .priv_size      =       sizeof(struct sfb_sched_data),
 700         .cl_ops         =       &sfb_class_ops,
 701         .enqueue        =       sfb_enqueue,
 702         .dequeue        =       sfb_dequeue,
 703         .peek           =       sfb_peek,
 704         .init           =       sfb_init,
 705         .reset          =       sfb_reset,
 706         .destroy        =       sfb_destroy,
 707         .change         =       sfb_change,
 708         .dump           =       sfb_dump,
 709         .dump_stats     =       sfb_dump_stats,
 710         .owner          =       THIS_MODULE,
 711 };
 712
 713 static int __init sfb_module_init(void)
 714 {
 715         return register_qdisc(&sfb_qdisc_ops);
 716 }
 717
 718 static void __exit sfb_module_exit(void)
 719 {
 720         unregister_qdisc(&sfb_qdisc_ops);
 721 }
 722
 723 module_init(sfb_module_init)
 724 module_exit(sfb_module_exit)
 725
 726 MODULE_DESCRIPTION("Stochastic Fair Blue queue discipline");
 727 MODULE_AUTHOR("Juliusz Chroboczek");
 728 MODULE_AUTHOR("Eric Dumazet");
 729 MODULE_LICENSE("GPL");