linux/net/sched/sch_sfb.c
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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");
 726
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