linux/net/sched/sch_sfb.c
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   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                        /* fall through */
 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{
 654        return -ENOSYS;
 655}
 656
 657static void sfb_walk(struct Qdisc *sch, struct qdisc_walker *walker)
 658{
 659        if (!walker->stop) {
 660                if (walker->count >= walker->skip)
 661                        if (walker->fn(sch, 1, walker) < 0) {
 662                                walker->stop = 1;
 663                                return;
 664                        }
 665                walker->count++;
 666        }
 667}
 668
 669static struct tcf_block *sfb_tcf_block(struct Qdisc *sch, unsigned long cl,
 670                                       struct netlink_ext_ack *extack)
 671{
 672        struct sfb_sched_data *q = qdisc_priv(sch);
 673
 674        if (cl)
 675                return NULL;
 676        return q->block;
 677}
 678
 679static unsigned long sfb_bind(struct Qdisc *sch, unsigned long parent,
 680                              u32 classid)
 681{
 682        return 0;
 683}
 684
 685
 686static const struct Qdisc_class_ops sfb_class_ops = {
 687        .graft          =       sfb_graft,
 688        .leaf           =       sfb_leaf,
 689        .find           =       sfb_find,
 690        .change         =       sfb_change_class,
 691        .delete         =       sfb_delete,
 692        .walk           =       sfb_walk,
 693        .tcf_block      =       sfb_tcf_block,
 694        .bind_tcf       =       sfb_bind,
 695        .unbind_tcf     =       sfb_unbind,
 696        .dump           =       sfb_dump_class,
 697};
 698
 699static struct Qdisc_ops sfb_qdisc_ops __read_mostly = {
 700        .id             =       "sfb",
 701        .priv_size      =       sizeof(struct sfb_sched_data),
 702        .cl_ops         =       &sfb_class_ops,
 703        .enqueue        =       sfb_enqueue,
 704        .dequeue        =       sfb_dequeue,
 705        .peek           =       sfb_peek,
 706        .init           =       sfb_init,
 707        .reset          =       sfb_reset,
 708        .destroy        =       sfb_destroy,
 709        .change         =       sfb_change,
 710        .dump           =       sfb_dump,
 711        .dump_stats     =       sfb_dump_stats,
 712        .owner          =       THIS_MODULE,
 713};
 714
 715static int __init sfb_module_init(void)
 716{
 717        return register_qdisc(&sfb_qdisc_ops);
 718}
 719
 720static void __exit sfb_module_exit(void)
 721{
 722        unregister_qdisc(&sfb_qdisc_ops);
 723}
 724
 725module_init(sfb_module_init)
 726module_exit(sfb_module_exit)
 727
 728MODULE_DESCRIPTION("Stochastic Fair Blue queue discipline");
 729MODULE_AUTHOR("Juliusz Chroboczek");
 730MODULE_AUTHOR("Eric Dumazet");
 731MODULE_LICENSE("GPL");
 732