net/sched/sch_netem.c

   1 /*
   2  * net/sched/sch_netem.c        Network emulator
   3  *
   4  *              This program is free software; you can redistribute it and/or
   5  *              modify it under the terms of the GNU General Public License
   6  *              as published by the Free Software Foundation; either version
   7  *              2 of the License.
   8  *
   9  *              Many of the algorithms and ideas for this came from
  10  *              NIST Net which is not copyrighted.
  11  *
  12  * Authors:     Stephen Hemminger <shemminger@osdl.org>
  13  *              Catalin(ux aka Dino) BOIE <catab at umbrella dot ro>
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/types.h>
  18 #include <linux/kernel.h>
  19 #include <linux/errno.h>
  20 #include <linux/skbuff.h>
  21 #include <linux/rtnetlink.h>
  22
  23 #include <net/netlink.h>
  24 #include <net/pkt_sched.h>
  25
  26 #define VERSION "1.2"
  27
  28 /*      Network Emulation Queuing algorithm.
  29         ====================================
  30
  31         Sources: [1] Mark Carson, Darrin Santay, "NIST Net - A Linux-based
  32                  Network Emulation Tool
  33                  [2] Luigi Rizzo, DummyNet for FreeBSD
  34
  35          ----------------------------------------------------------------
  36
  37          This started out as a simple way to delay outgoing packets to
  38          test TCP but has grown to include most of the functionality
  39          of a full blown network emulator like NISTnet. It can delay
  40          packets and add random jitter (and correlation). The random
  41          distribution can be loaded from a table as well to provide
  42          normal, Pareto, or experimental curves. Packet loss,
  43          duplication, and reordering can also be emulated.
  44
  45          This qdisc does not do classification that can be handled in
  46          layering other disciplines.  It does not need to do bandwidth
  47          control either since that can be handled by using token
  48          bucket or other rate control.
  49
  50          The simulator is limited by the Linux timer resolution
  51          and will create packet bursts on the HZ boundary (1ms).
  52 */
  53
  54 struct netem_sched_data {
  55         struct Qdisc    *qdisc;
  56         struct qdisc_watchdog watchdog;
  57
  58         psched_tdiff_t latency;
  59         psched_tdiff_t jitter;
  60
  61         u32 loss;
  62         u32 limit;
  63         u32 counter;
  64         u32 gap;
  65         u32 duplicate;
  66         u32 reorder;
  67         u32 corrupt;
  68
  69         struct crndstate {
  70                 u32 last;
  71                 u32 rho;
  72         } delay_cor, loss_cor, dup_cor, reorder_cor, corrupt_cor;
  73
  74         struct disttable {
  75                 u32  size;
  76                 s16 table[0];
  77         } *delay_dist;
  78 };
  79
  80 /* Time stamp put into socket buffer control block */
  81 struct netem_skb_cb {
  82         psched_time_t   time_to_send;
  83 };
  84
  85 static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)
  86 {
  87         BUILD_BUG_ON(sizeof(skb->cb) <
  88                 sizeof(struct qdisc_skb_cb) + sizeof(struct netem_skb_cb));
  89         return (struct netem_skb_cb *)qdisc_skb_cb(skb)->data;
  90 }
  91
  92 /* init_crandom - initialize correlated random number generator
  93  * Use entropy source for initial seed.
  94  */
  95 static void init_crandom(struct crndstate *state, unsigned long rho)
  96 {
  97         state->rho = rho;
  98         state->last = net_random();
  99 }
 100
 101 /* get_crandom - correlated random number generator
 102  * Next number depends on last value.
 103  * rho is scaled to avoid floating point.
 104  */
 105 static u32 get_crandom(struct crndstate *state)
 106 {
 107         u64 value, rho;
 108         unsigned long answer;
 109
 110         if (state->rho == 0)    /* no correlation */
 111                 return net_random();
 112
 113         value = net_random();
 114         rho = (u64)state->rho + 1;
 115         answer = (value * ((1ull<<32) - rho) + state->last * rho) >> 32;
 116         state->last = answer;
 117         return answer;
 118 }
 119
 120 /* tabledist - return a pseudo-randomly distributed value with mean mu and
 121  * std deviation sigma.  Uses table lookup to approximate the desired
 122  * distribution, and a uniformly-distributed pseudo-random source.
 123  */
 124 static psched_tdiff_t tabledist(psched_tdiff_t mu, psched_tdiff_t sigma,
 125                                 struct crndstate *state,
 126                                 const struct disttable *dist)
 127 {
 128         psched_tdiff_t x;
 129         long t;
 130         u32 rnd;
 131
 132         if (sigma == 0)
 133                 return mu;
 134
 135         rnd = get_crandom(state);
 136
 137         /* default uniform distribution */
 138         if (dist == NULL)
 139                 return (rnd % (2*sigma)) - sigma + mu;
 140
 141         t = dist->table[rnd % dist->size];
 142         x = (sigma % NETEM_DIST_SCALE) * t;
 143         if (x >= 0)
 144                 x += NETEM_DIST_SCALE/2;
 145         else
 146                 x -= NETEM_DIST_SCALE/2;
 147
 148         return  x / NETEM_DIST_SCALE + (sigma / NETEM_DIST_SCALE) * t + mu;
 149 }
 150
 151 /*
 152  * Insert one skb into qdisc.
 153  * Note: parent depends on return value to account for queue length.
 154  *      NET_XMIT_DROP: queue length didn't change.
 155  *      NET_XMIT_SUCCESS: one skb was queued.
 156  */
 157 static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 158 {
 159         struct netem_sched_data *q = qdisc_priv(sch);
 160         /* We don't fill cb now as skb_unshare() may invalidate it */
 161         struct netem_skb_cb *cb;
 162         struct sk_buff *skb2;
 163         int ret;
 164         int count = 1;
 165
 166         pr_debug("netem_enqueue skb=%p\n", skb);
 167
 168         /* Random duplication */
 169         if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor))
 170                 ++count;
 171
 172         /* Random packet drop 0 => none, ~0 => all */
 173         if (q->loss && q->loss >= get_crandom(&q->loss_cor))
 174                 --count;
 175
 176         if (count == 0) {
 177                 sch->qstats.drops++;
 178                 kfree_skb(skb);
 179                 return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
 180         }
 181
 182         skb_orphan(skb);
 183
 184         /*
 185          * If we need to duplicate packet, then re-insert at top of the
 186          * qdisc tree, since parent queuer expects that only one
 187          * skb will be queued.
 188          */
 189         if (count > 1 && (skb2 = skb_clone(skb, GFP_ATOMIC)) != NULL) {
 190                 struct Qdisc *rootq = qdisc_root(sch);
 191                 u32 dupsave = q->duplicate; /* prevent duplicating a dup... */
 192                 q->duplicate = 0;
 193
 194                 qdisc_enqueue_root(skb2, rootq);
 195                 q->duplicate = dupsave;
 196         }
 197
 198         /*
 199          * Randomized packet corruption.
 200          * Make copy if needed since we are modifying
 201          * If packet is going to be hardware checksummed, then
 202          * do it now in software before we mangle it.
 203          */
 204         if (q->corrupt && q->corrupt >= get_crandom(&q->corrupt_cor)) {
 205                 if (!(skb = skb_unshare(skb, GFP_ATOMIC))
 206                     || (skb->ip_summed == CHECKSUM_PARTIAL
 207                         && skb_checksum_help(skb))) {
 208                         sch->qstats.drops++;
 209                         return NET_XMIT_DROP;
 210                 }
 211
 212                 skb->data[net_random() % skb_headlen(skb)] ^= 1<<(net_random() % 8);
 213         }
 214
 215         cb = netem_skb_cb(skb);
 216         if (q->gap == 0                 /* not doing reordering */
 217             || q->counter < q->gap      /* inside last reordering gap */
 218             || q->reorder < get_crandom(&q->reorder_cor)) {
 219                 psched_time_t now;
 220                 psched_tdiff_t delay;
 221
 222                 delay = tabledist(q->latency, q->jitter,
 223                                   &q->delay_cor, q->delay_dist);
 224
 225                 now = psched_get_time();
 226                 cb->time_to_send = now + delay;
 227                 ++q->counter;
 228                 ret = qdisc_enqueue(skb, q->qdisc);
 229         } else {
 230                 /*
 231                  * Do re-ordering by putting one out of N packets at the front
 232                  * of the queue.
 233                  */
 234                 cb->time_to_send = psched_get_time();
 235                 q->counter = 0;
 236                 ret = q->qdisc->ops->requeue(skb, q->qdisc);
 237         }
 238
 239         if (likely(ret == NET_XMIT_SUCCESS)) {
 240                 sch->q.qlen++;
 241                 sch->bstats.bytes += qdisc_pkt_len(skb);
 242                 sch->bstats.packets++;
 243         } else if (net_xmit_drop_count(ret)) {
 244                 sch->qstats.drops++;
 245         }
 246
 247         pr_debug("netem: enqueue ret %d\n", ret);
 248         return ret;
 249 }
 250
 251 /* Requeue packets but don't change time stamp */
 252 static int netem_requeue(struct sk_buff *skb, struct Qdisc *sch)
 253 {
 254         struct netem_sched_data *q = qdisc_priv(sch);
 255         int ret;
 256
 257         if ((ret = q->qdisc->ops->requeue(skb, q->qdisc)) == 0) {
 258                 sch->q.qlen++;
 259                 sch->qstats.requeues++;
 260         }
 261
 262         return ret;
 263 }
 264
 265 static unsigned int netem_drop(struct Qdisc* sch)
 266 {
 267         struct netem_sched_data *q = qdisc_priv(sch);
 268         unsigned int len = 0;
 269
 270         if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
 271                 sch->q.qlen--;
 272                 sch->qstats.drops++;
 273         }
 274         return len;
 275 }
 276
 277 static struct sk_buff *netem_dequeue(struct Qdisc *sch)
 278 {
 279         struct netem_sched_data *q = qdisc_priv(sch);
 280         struct sk_buff *skb;
 281
 282         smp_mb();
 283         if (sch->flags & TCQ_F_THROTTLED)
 284                 return NULL;
 285
 286         skb = q->qdisc->dequeue(q->qdisc);
 287         if (skb) {
 288                 const struct netem_skb_cb *cb = netem_skb_cb(skb);
 289                 psched_time_t now = psched_get_time();
 290
 291                 /* if more time remaining? */
 292                 if (cb->time_to_send <= now) {
 293                         pr_debug("netem_dequeue: return skb=%p\n", skb);
 294                         sch->q.qlen--;
 295                         return skb;
 296                 }
 297
 298                 if (unlikely(q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS)) {
 299                         qdisc_tree_decrease_qlen(q->qdisc, 1);
 300                         sch->qstats.drops++;
 301                         printk(KERN_ERR "netem: %s could not requeue\n",
 302                                q->qdisc->ops->id);
 303                 }
 304
 305                 qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
 306         }
 307
 308         return NULL;
 309 }
 310
 311 static void netem_reset(struct Qdisc *sch)
 312 {
 313         struct netem_sched_data *q = qdisc_priv(sch);
 314
 315         qdisc_reset(q->qdisc);
 316         sch->q.qlen = 0;
 317         qdisc_watchdog_cancel(&q->watchdog);
 318 }
 319
 320 /*
 321  * Distribution data is a variable size payload containing
 322  * signed 16 bit values.
 323  */
 324 static int get_dist_table(struct Qdisc *sch, const struct nlattr *attr)
 325 {
 326         struct netem_sched_data *q = qdisc_priv(sch);
 327         unsigned long n = nla_len(attr)/sizeof(__s16);
 328         const __s16 *data = nla_data(attr);
 329         spinlock_t *root_lock;
 330         struct disttable *d;
 331         int i;
 332
 333         if (n > 65536)
 334                 return -EINVAL;
 335
 336         d = kmalloc(sizeof(*d) + n*sizeof(d->table[0]), GFP_KERNEL);
 337         if (!d)
 338                 return -ENOMEM;
 339
 340         d->size = n;
 341         for (i = 0; i < n; i++)
 342                 d->table[i] = data[i];
 343
 344         root_lock = qdisc_root_sleeping_lock(sch);
 345
 346         spin_lock_bh(root_lock);
 347         d = xchg(&q->delay_dist, d);
 348         spin_unlock_bh(root_lock);
 349
 350         kfree(d);
 351         return 0;
 352 }
 353
 354 static int get_correlation(struct Qdisc *sch, const struct nlattr *attr)
 355 {
 356         struct netem_sched_data *q = qdisc_priv(sch);
 357         const struct tc_netem_corr *c = nla_data(attr);
 358
 359         init_crandom(&q->delay_cor, c->delay_corr);
 360         init_crandom(&q->loss_cor, c->loss_corr);
 361         init_crandom(&q->dup_cor, c->dup_corr);
 362         return 0;
 363 }
 364
 365 static int get_reorder(struct Qdisc *sch, const struct nlattr *attr)
 366 {
 367         struct netem_sched_data *q = qdisc_priv(sch);
 368         const struct tc_netem_reorder *r = nla_data(attr);
 369
 370         q->reorder = r->probability;
 371         init_crandom(&q->reorder_cor, r->correlation);
 372         return 0;
 373 }
 374
 375 static int get_corrupt(struct Qdisc *sch, const struct nlattr *attr)
 376 {
 377         struct netem_sched_data *q = qdisc_priv(sch);
 378         const struct tc_netem_corrupt *r = nla_data(attr);
 379
 380         q->corrupt = r->probability;
 381         init_crandom(&q->corrupt_cor, r->correlation);
 382         return 0;
 383 }
 384
 385 static const struct nla_policy netem_policy[TCA_NETEM_MAX + 1] = {
 386         [TCA_NETEM_CORR]        = { .len = sizeof(struct tc_netem_corr) },
 387         [TCA_NETEM_REORDER]     = { .len = sizeof(struct tc_netem_reorder) },
 388         [TCA_NETEM_CORRUPT]     = { .len = sizeof(struct tc_netem_corrupt) },
 389 };
 390
 391 /* Parse netlink message to set options */
 392 static int netem_change(struct Qdisc *sch, struct nlattr *opt)
 393 {
 394         struct netem_sched_data *q = qdisc_priv(sch);
 395         struct nlattr *tb[TCA_NETEM_MAX + 1];
 396         struct tc_netem_qopt *qopt;
 397         int ret;
 398
 399         if (opt == NULL)
 400                 return -EINVAL;
 401
 402         ret = nla_parse_nested_compat(tb, TCA_NETEM_MAX, opt, netem_policy,
 403                                       qopt, sizeof(*qopt));
 404         if (ret < 0)
 405                 return ret;
 406
 407         ret = fifo_set_limit(q->qdisc, qopt->limit);
 408         if (ret) {
 409                 pr_debug("netem: can't set fifo limit\n");
 410                 return ret;
 411         }
 412
 413         q->latency = qopt->latency;
 414         q->jitter = qopt->jitter;
 415         q->limit = qopt->limit;
 416         q->gap = qopt->gap;
 417         q->counter = 0;
 418         q->loss = qopt->loss;
 419         q->duplicate = qopt->duplicate;
 420
 421         /* for compatibility with earlier versions.
 422          * if gap is set, need to assume 100% probability
 423          */
 424         if (q->gap)
 425                 q->reorder = ~0;
 426
 427         if (tb[TCA_NETEM_CORR]) {
 428                 ret = get_correlation(sch, tb[TCA_NETEM_CORR]);
 429                 if (ret)
 430                         return ret;
 431         }
 432
 433         if (tb[TCA_NETEM_DELAY_DIST]) {
 434                 ret = get_dist_table(sch, tb[TCA_NETEM_DELAY_DIST]);
 435                 if (ret)
 436                         return ret;
 437         }
 438
 439         if (tb[TCA_NETEM_REORDER]) {
 440                 ret = get_reorder(sch, tb[TCA_NETEM_REORDER]);
 441                 if (ret)
 442                         return ret;
 443         }
 444
 445         if (tb[TCA_NETEM_CORRUPT]) {
 446                 ret = get_corrupt(sch, tb[TCA_NETEM_CORRUPT]);
 447                 if (ret)
 448                         return ret;
 449         }
 450
 451         return 0;
 452 }
 453
 454 /*
 455  * Special case version of FIFO queue for use by netem.
 456  * It queues in order based on timestamps in skb's
 457  */
 458 struct fifo_sched_data {
 459         u32 limit;
 460         psched_time_t oldest;
 461 };
 462
 463 static int tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
 464 {
 465         struct fifo_sched_data *q = qdisc_priv(sch);
 466         struct sk_buff_head *list = &sch->q;
 467         psched_time_t tnext = netem_skb_cb(nskb)->time_to_send;
 468         struct sk_buff *skb;
 469
 470         if (likely(skb_queue_len(list) < q->limit)) {
 471                 /* Optimize for add at tail */
 472                 if (likely(skb_queue_empty(list) || tnext >= q->oldest)) {
 473                         q->oldest = tnext;
 474                         return qdisc_enqueue_tail(nskb, sch);
 475                 }
 476
 477                 skb_queue_reverse_walk(list, skb) {
 478                         const struct netem_skb_cb *cb = netem_skb_cb(skb);
 479
 480                         if (tnext >= cb->time_to_send)
 481                                 break;
 482                 }
 483
 484                 __skb_queue_after(list, skb, nskb);
 485
 486                 sch->qstats.backlog += qdisc_pkt_len(nskb);
 487                 sch->bstats.bytes += qdisc_pkt_len(nskb);
 488                 sch->bstats.packets++;
 489
 490                 return NET_XMIT_SUCCESS;
 491         }
 492
 493         return qdisc_reshape_fail(nskb, sch);
 494 }
 495
 496 static int tfifo_init(struct Qdisc *sch, struct nlattr *opt)
 497 {
 498         struct fifo_sched_data *q = qdisc_priv(sch);
 499
 500         if (opt) {
 501                 struct tc_fifo_qopt *ctl = nla_data(opt);
 502                 if (nla_len(opt) < sizeof(*ctl))
 503                         return -EINVAL;
 504
 505                 q->limit = ctl->limit;
 506         } else
 507                 q->limit = max_t(u32, qdisc_dev(sch)->tx_queue_len, 1);
 508
 509         q->oldest = PSCHED_PASTPERFECT;
 510         return 0;
 511 }
 512
 513 static int tfifo_dump(struct Qdisc *sch, struct sk_buff *skb)
 514 {
 515         struct fifo_sched_data *q = qdisc_priv(sch);
 516         struct tc_fifo_qopt opt = { .limit = q->limit };
 517
 518         NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
 519         return skb->len;
 520
 521 nla_put_failure:
 522         return -1;
 523 }
 524
 525 static struct Qdisc_ops tfifo_qdisc_ops __read_mostly = {
 526         .id             =       "tfifo",
 527         .priv_size      =       sizeof(struct fifo_sched_data),
 528         .enqueue        =       tfifo_enqueue,
 529         .dequeue        =       qdisc_dequeue_head,
 530         .requeue        =       qdisc_requeue,
 531         .drop           =       qdisc_queue_drop,
 532         .init           =       tfifo_init,
 533         .reset          =       qdisc_reset_queue,
 534         .change         =       tfifo_init,
 535         .dump           =       tfifo_dump,
 536 };
 537
 538 static int netem_init(struct Qdisc *sch, struct nlattr *opt)
 539 {
 540         struct netem_sched_data *q = qdisc_priv(sch);
 541         int ret;
 542
 543         if (!opt)
 544                 return -EINVAL;
 545
 546         qdisc_watchdog_init(&q->watchdog, sch);
 547
 548         q->qdisc = qdisc_create_dflt(qdisc_dev(sch), sch->dev_queue,
 549                                      &tfifo_qdisc_ops,
 550                                      TC_H_MAKE(sch->handle, 1));
 551         if (!q->qdisc) {
 552                 pr_debug("netem: qdisc create failed\n");
 553                 return -ENOMEM;
 554         }
 555
 556         ret = netem_change(sch, opt);
 557         if (ret) {
 558                 pr_debug("netem: change failed\n");
 559                 qdisc_destroy(q->qdisc);
 560         }
 561         return ret;
 562 }
 563
 564 static void netem_destroy(struct Qdisc *sch)
 565 {
 566         struct netem_sched_data *q = qdisc_priv(sch);
 567
 568         qdisc_watchdog_cancel(&q->watchdog);
 569         qdisc_destroy(q->qdisc);
 570         kfree(q->delay_dist);
 571 }
 572
 573 static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
 574 {
 575         const struct netem_sched_data *q = qdisc_priv(sch);
 576         unsigned char *b = skb_tail_pointer(skb);
 577         struct nlattr *nla = (struct nlattr *) b;
 578         struct tc_netem_qopt qopt;
 579         struct tc_netem_corr cor;
 580         struct tc_netem_reorder reorder;
 581         struct tc_netem_corrupt corrupt;
 582
 583         qopt.latency = q->latency;
 584         qopt.jitter = q->jitter;
 585         qopt.limit = q->limit;
 586         qopt.loss = q->loss;
 587         qopt.gap = q->gap;
 588         qopt.duplicate = q->duplicate;
 589         NLA_PUT(skb, TCA_OPTIONS, sizeof(qopt), &qopt);
 590
 591         cor.delay_corr = q->delay_cor.rho;
 592         cor.loss_corr = q->loss_cor.rho;
 593         cor.dup_corr = q->dup_cor.rho;
 594         NLA_PUT(skb, TCA_NETEM_CORR, sizeof(cor), &cor);
 595
 596         reorder.probability = q->reorder;
 597         reorder.correlation = q->reorder_cor.rho;
 598         NLA_PUT(skb, TCA_NETEM_REORDER, sizeof(reorder), &reorder);
 599
 600         corrupt.probability = q->corrupt;
 601         corrupt.correlation = q->corrupt_cor.rho;
 602         NLA_PUT(skb, TCA_NETEM_CORRUPT, sizeof(corrupt), &corrupt);
 603
 604         nla->nla_len = skb_tail_pointer(skb) - b;
 605
 606         return skb->len;
 607
 608 nla_put_failure:
 609         nlmsg_trim(skb, b);
 610         return -1;
 611 }
 612
 613 static int netem_dump_class(struct Qdisc *sch, unsigned long cl,
 614                           struct sk_buff *skb, struct tcmsg *tcm)
 615 {
 616         struct netem_sched_data *q = qdisc_priv(sch);
 617
 618         if (cl != 1)    /* only one class */
 619                 return -ENOENT;
 620
 621         tcm->tcm_handle |= TC_H_MIN(1);
 622         tcm->tcm_info = q->qdisc->handle;
 623
 624         return 0;
 625 }
 626
 627 static int netem_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 628                      struct Qdisc **old)
 629 {
 630         struct netem_sched_data *q = qdisc_priv(sch);
 631
 632         if (new == NULL)
 633                 new = &noop_qdisc;
 634
 635         sch_tree_lock(sch);
 636         *old = xchg(&q->qdisc, new);
 637         qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 638         qdisc_reset(*old);
 639         sch_tree_unlock(sch);
 640
 641         return 0;
 642 }
 643
 644 static struct Qdisc *netem_leaf(struct Qdisc *sch, unsigned long arg)
 645 {
 646         struct netem_sched_data *q = qdisc_priv(sch);
 647         return q->qdisc;
 648 }
 649
 650 static unsigned long netem_get(struct Qdisc *sch, u32 classid)
 651 {
 652         return 1;
 653 }
 654
 655 static void netem_put(struct Qdisc *sch, unsigned long arg)
 656 {
 657 }
 658
 659 static int netem_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 660                             struct nlattr **tca, unsigned long *arg)
 661 {
 662         return -ENOSYS;
 663 }
 664
 665 static int netem_delete(struct Qdisc *sch, unsigned long arg)
 666 {
 667         return -ENOSYS;
 668 }
 669
 670 static void netem_walk(struct Qdisc *sch, struct qdisc_walker *walker)
 671 {
 672         if (!walker->stop) {
 673                 if (walker->count >= walker->skip)
 674                         if (walker->fn(sch, 1, walker) < 0) {
 675                                 walker->stop = 1;
 676                                 return;
 677                         }
 678                 walker->count++;
 679         }
 680 }
 681
 682 static struct tcf_proto **netem_find_tcf(struct Qdisc *sch, unsigned long cl)
 683 {
 684         return NULL;
 685 }
 686
 687 static const struct Qdisc_class_ops netem_class_ops = {
 688         .graft          =       netem_graft,
 689         .leaf           =       netem_leaf,
 690         .get            =       netem_get,
 691         .put            =       netem_put,
 692         .change         =       netem_change_class,
 693         .delete         =       netem_delete,
 694         .walk           =       netem_walk,
 695         .tcf_chain      =       netem_find_tcf,
 696         .dump           =       netem_dump_class,
 697 };
 698
 699 static struct Qdisc_ops netem_qdisc_ops __read_mostly = {
 700         .id             =       "netem",
 701         .cl_ops         =       &netem_class_ops,
 702         .priv_size      =       sizeof(struct netem_sched_data),
 703         .enqueue        =       netem_enqueue,
 704         .dequeue        =       netem_dequeue,
 705         .requeue        =       netem_requeue,
 706         .drop           =       netem_drop,
 707         .init           =       netem_init,
 708         .reset          =       netem_reset,
 709         .destroy        =       netem_destroy,
 710         .change         =       netem_change,
 711         .dump           =       netem_dump,
 712         .owner          =       THIS_MODULE,
 713 };
 714
 715
 716 static int __init netem_module_init(void)
 717 {
 718         pr_info("netem: version " VERSION "\n");
 719         return register_qdisc(&netem_qdisc_ops);
 720 }
 721 static void __exit netem_module_exit(void)
 722 {
 723         unregister_qdisc(&netem_qdisc_ops);
 724 }
 725 module_init(netem_module_init)
 726 module_exit(netem_module_exit)
 727 MODULE_LICENSE("GPL");