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
  51 struct netem_sched_data {
  52         struct Qdisc    *qdisc;
  53         struct qdisc_watchdog watchdog;
  54
  55         psched_tdiff_t latency;
  56         psched_tdiff_t jitter;
  57
  58         u32 loss;
  59         u32 limit;
  60         u32 counter;
  61         u32 gap;
  62         u32 duplicate;
  63         u32 reorder;
  64         u32 corrupt;
  65
  66         struct crndstate {
  67                 u32 last;
  68                 u32 rho;
  69         } delay_cor, loss_cor, dup_cor, reorder_cor, corrupt_cor;
  70
  71         struct disttable {
  72                 u32  size;
  73                 s16 table[0];
  74         } *delay_dist;
  75 };
  76
  77 /* Time stamp put into socket buffer control block */
  78 struct netem_skb_cb {
  79         psched_time_t   time_to_send;
  80 };
  81
  82 static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)
  83 {
  84         BUILD_BUG_ON(sizeof(skb->cb) <
  85                 sizeof(struct qdisc_skb_cb) + sizeof(struct netem_skb_cb));
  86         return (struct netem_skb_cb *)qdisc_skb_cb(skb)->data;
  87 }
  88
  89 /* init_crandom - initialize correlated random number generator
  90  * Use entropy source for initial seed.
  91  */
  92 static void init_crandom(struct crndstate *state, unsigned long rho)
  93 {
  94         state->rho = rho;
  95         state->last = net_random();
  96 }
  97
  98 /* get_crandom - correlated random number generator
  99  * Next number depends on last value.
 100  * rho is scaled to avoid floating point.
 101  */
 102 static u32 get_crandom(struct crndstate *state)
 103 {
 104         u64 value, rho;
 105         unsigned long answer;
 106
 107         if (state->rho == 0)    /* no correlation */
 108                 return net_random();
 109
 110         value = net_random();
 111         rho = (u64)state->rho + 1;
 112         answer = (value * ((1ull<<32) - rho) + state->last * rho) >> 32;
 113         state->last = answer;
 114         return answer;
 115 }
 116
 117 /* tabledist - return a pseudo-randomly distributed value with mean mu and
 118  * std deviation sigma.  Uses table lookup to approximate the desired
 119  * distribution, and a uniformly-distributed pseudo-random source.
 120  */
 121 static psched_tdiff_t tabledist(psched_tdiff_t mu, psched_tdiff_t sigma,
 122                                 struct crndstate *state,
 123                                 const struct disttable *dist)
 124 {
 125         psched_tdiff_t x;
 126         long t;
 127         u32 rnd;
 128
 129         if (sigma == 0)
 130                 return mu;
 131
 132         rnd = get_crandom(state);
 133
 134         /* default uniform distribution */
 135         if (dist == NULL)
 136                 return (rnd % (2*sigma)) - sigma + mu;
 137
 138         t = dist->table[rnd % dist->size];
 139         x = (sigma % NETEM_DIST_SCALE) * t;
 140         if (x >= 0)
 141                 x += NETEM_DIST_SCALE/2;
 142         else
 143                 x -= NETEM_DIST_SCALE/2;
 144
 145         return  x / NETEM_DIST_SCALE + (sigma / NETEM_DIST_SCALE) * t + mu;
 146 }
 147
 148 /*
 149  * Insert one skb into qdisc.
 150  * Note: parent depends on return value to account for queue length.
 151  *      NET_XMIT_DROP: queue length didn't change.
 152  *      NET_XMIT_SUCCESS: one skb was queued.
 153  */
 154 static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 155 {
 156         struct netem_sched_data *q = qdisc_priv(sch);
 157         /* We don't fill cb now as skb_unshare() may invalidate it */
 158         struct netem_skb_cb *cb;
 159         struct sk_buff *skb2;
 160         int ret;
 161         int count = 1;
 162
 163         pr_debug("netem_enqueue skb=%p\n", skb);
 164
 165         /* Random duplication */
 166         if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor))
 167                 ++count;
 168
 169         /* Random packet drop 0 => none, ~0 => all */
 170         if (q->loss && q->loss >= get_crandom(&q->loss_cor))
 171                 --count;
 172
 173         if (count == 0) {
 174                 sch->qstats.drops++;
 175                 kfree_skb(skb);
 176                 return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
 177         }
 178
 179         skb_orphan(skb);
 180
 181         /*
 182          * If we need to duplicate packet, then re-insert at top of the
 183          * qdisc tree, since parent queuer expects that only one
 184          * skb will be queued.
 185          */
 186         if (count > 1 && (skb2 = skb_clone(skb, GFP_ATOMIC)) != NULL) {
 187                 struct Qdisc *rootq = qdisc_root(sch);
 188                 u32 dupsave = q->duplicate; /* prevent duplicating a dup... */
 189                 q->duplicate = 0;
 190
 191                 qdisc_enqueue_root(skb2, rootq);
 192                 q->duplicate = dupsave;
 193         }
 194
 195         /*
 196          * Randomized packet corruption.
 197          * Make copy if needed since we are modifying
 198          * If packet is going to be hardware checksummed, then
 199          * do it now in software before we mangle it.
 200          */
 201         if (q->corrupt && q->corrupt >= get_crandom(&q->corrupt_cor)) {
 202                 if (!(skb = skb_unshare(skb, GFP_ATOMIC))
 203                     || (skb->ip_summed == CHECKSUM_PARTIAL
 204                         && skb_checksum_help(skb))) {
 205                         sch->qstats.drops++;
 206                         return NET_XMIT_DROP;
 207                 }
 208
 209                 skb->data[net_random() % skb_headlen(skb)] ^= 1<<(net_random() % 8);
 210         }
 211
 212         cb = netem_skb_cb(skb);
 213         if (q->gap == 0                 /* not doing reordering */
 214             || q->counter < q->gap      /* inside last reordering gap */
 215             || q->reorder < get_crandom(&q->reorder_cor)) {
 216                 psched_time_t now;
 217                 psched_tdiff_t delay;
 218
 219                 delay = tabledist(q->latency, q->jitter,
 220                                   &q->delay_cor, q->delay_dist);
 221
 222                 now = psched_get_time();
 223                 cb->time_to_send = now + delay;
 224                 ++q->counter;
 225                 ret = qdisc_enqueue(skb, q->qdisc);
 226         } else {
 227                 /*
 228                  * Do re-ordering by putting one out of N packets at the front
 229                  * of the queue.
 230                  */
 231                 cb->time_to_send = psched_get_time();
 232                 q->counter = 0;
 233
 234                 __skb_queue_head(&q->qdisc->q, skb);
 235                 q->qdisc->qstats.backlog += qdisc_pkt_len(skb);
 236                 q->qdisc->qstats.requeues++;
 237                 ret = NET_XMIT_SUCCESS;
 238         }
 239
 240         if (likely(ret == NET_XMIT_SUCCESS)) {
 241                 sch->q.qlen++;
 242                 sch->bstats.bytes += qdisc_pkt_len(skb);
 243                 sch->bstats.packets++;
 244         } else if (net_xmit_drop_count(ret)) {
 245                 sch->qstats.drops++;
 246         }
 247
 248         pr_debug("netem: enqueue ret %d\n", ret);
 249         return ret;
 250 }
 251
 252 static unsigned int netem_drop(struct Qdisc* sch)
 253 {
 254         struct netem_sched_data *q = qdisc_priv(sch);
 255         unsigned int len = 0;
 256
 257         if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
 258                 sch->q.qlen--;
 259                 sch->qstats.drops++;
 260         }
 261         return len;
 262 }
 263
 264 static struct sk_buff *netem_dequeue(struct Qdisc *sch)
 265 {
 266         struct netem_sched_data *q = qdisc_priv(sch);
 267         struct sk_buff *skb;
 268
 269         if (sch->flags & TCQ_F_THROTTLED)
 270                 return NULL;
 271
 272         skb = q->qdisc->ops->peek(q->qdisc);
 273         if (skb) {
 274                 const struct netem_skb_cb *cb = netem_skb_cb(skb);
 275                 psched_time_t now = psched_get_time();
 276
 277                 /* if more time remaining? */
 278                 if (cb->time_to_send <= now) {
 279                         skb = qdisc_dequeue_peeked(q->qdisc);
 280                         if (unlikely(!skb))
 281                                 return NULL;
 282
 283                         pr_debug("netem_dequeue: return skb=%p\n", skb);
 284                         sch->q.qlen--;
 285                         return skb;
 286                 }
 287
 288                 qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
 289         }
 290
 291         return NULL;
 292 }
 293
 294 static void netem_reset(struct Qdisc *sch)
 295 {
 296         struct netem_sched_data *q = qdisc_priv(sch);
 297
 298         qdisc_reset(q->qdisc);
 299         sch->q.qlen = 0;
 300         qdisc_watchdog_cancel(&q->watchdog);
 301 }
 302
 303 /*
 304  * Distribution data is a variable size payload containing
 305  * signed 16 bit values.
 306  */
 307 static int get_dist_table(struct Qdisc *sch, const struct nlattr *attr)
 308 {
 309         struct netem_sched_data *q = qdisc_priv(sch);
 310         unsigned long n = nla_len(attr)/sizeof(__s16);
 311         const __s16 *data = nla_data(attr);
 312         spinlock_t *root_lock;
 313         struct disttable *d;
 314         int i;
 315
 316         if (n > 65536)
 317                 return -EINVAL;
 318
 319         d = kmalloc(sizeof(*d) + n*sizeof(d->table[0]), GFP_KERNEL);
 320         if (!d)
 321                 return -ENOMEM;
 322
 323         d->size = n;
 324         for (i = 0; i < n; i++)
 325                 d->table[i] = data[i];
 326
 327         root_lock = qdisc_root_sleeping_lock(sch);
 328
 329         spin_lock_bh(root_lock);
 330         kfree(q->delay_dist);
 331         q->delay_dist = d;
 332         spin_unlock_bh(root_lock);
 333         return 0;
 334 }
 335
 336 static void get_correlation(struct Qdisc *sch, const struct nlattr *attr)
 337 {
 338         struct netem_sched_data *q = qdisc_priv(sch);
 339         const struct tc_netem_corr *c = nla_data(attr);
 340
 341         init_crandom(&q->delay_cor, c->delay_corr);
 342         init_crandom(&q->loss_cor, c->loss_corr);
 343         init_crandom(&q->dup_cor, c->dup_corr);
 344 }
 345
 346 static void get_reorder(struct Qdisc *sch, const struct nlattr *attr)
 347 {
 348         struct netem_sched_data *q = qdisc_priv(sch);
 349         const struct tc_netem_reorder *r = nla_data(attr);
 350
 351         q->reorder = r->probability;
 352         init_crandom(&q->reorder_cor, r->correlation);
 353 }
 354
 355 static void get_corrupt(struct Qdisc *sch, const struct nlattr *attr)
 356 {
 357         struct netem_sched_data *q = qdisc_priv(sch);
 358         const struct tc_netem_corrupt *r = nla_data(attr);
 359
 360         q->corrupt = r->probability;
 361         init_crandom(&q->corrupt_cor, r->correlation);
 362 }
 363
 364 static const struct nla_policy netem_policy[TCA_NETEM_MAX + 1] = {
 365         [TCA_NETEM_CORR]        = { .len = sizeof(struct tc_netem_corr) },
 366         [TCA_NETEM_REORDER]     = { .len = sizeof(struct tc_netem_reorder) },
 367         [TCA_NETEM_CORRUPT]     = { .len = sizeof(struct tc_netem_corrupt) },
 368 };
 369
 370 static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
 371                       const struct nla_policy *policy, int len)
 372 {
 373         int nested_len = nla_len(nla) - NLA_ALIGN(len);
 374
 375         if (nested_len < 0)
 376                 return -EINVAL;
 377         if (nested_len >= nla_attr_size(0))
 378                 return nla_parse(tb, maxtype, nla_data(nla) + NLA_ALIGN(len),
 379                                  nested_len, policy);
 380         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 381         return 0;
 382 }
 383
 384 /* Parse netlink message to set options */
 385 static int netem_change(struct Qdisc *sch, struct nlattr *opt)
 386 {
 387         struct netem_sched_data *q = qdisc_priv(sch);
 388         struct nlattr *tb[TCA_NETEM_MAX + 1];
 389         struct tc_netem_qopt *qopt;
 390         int ret;
 391
 392         if (opt == NULL)
 393                 return -EINVAL;
 394
 395         qopt = nla_data(opt);
 396         ret = parse_attr(tb, TCA_NETEM_MAX, opt, netem_policy, sizeof(*qopt));
 397         if (ret < 0)
 398                 return ret;
 399
 400         ret = fifo_set_limit(q->qdisc, qopt->limit);
 401         if (ret) {
 402                 pr_debug("netem: can't set fifo limit\n");
 403                 return ret;
 404         }
 405
 406         q->latency = qopt->latency;
 407         q->jitter = qopt->jitter;
 408         q->limit = qopt->limit;
 409         q->gap = qopt->gap;
 410         q->counter = 0;
 411         q->loss = qopt->loss;
 412         q->duplicate = qopt->duplicate;
 413
 414         /* for compatibility with earlier versions.
 415          * if gap is set, need to assume 100% probability
 416          */
 417         if (q->gap)
 418                 q->reorder = ~0;
 419
 420         if (tb[TCA_NETEM_CORR])
 421                 get_correlation(sch, tb[TCA_NETEM_CORR]);
 422
 423         if (tb[TCA_NETEM_DELAY_DIST]) {
 424                 ret = get_dist_table(sch, tb[TCA_NETEM_DELAY_DIST]);
 425                 if (ret)
 426                         return ret;
 427         }
 428
 429         if (tb[TCA_NETEM_REORDER])
 430                 get_reorder(sch, tb[TCA_NETEM_REORDER]);
 431
 432         if (tb[TCA_NETEM_CORRUPT])
 433                 get_corrupt(sch, tb[TCA_NETEM_CORRUPT]);
 434
 435         return 0;
 436 }
 437
 438 /*
 439  * Special case version of FIFO queue for use by netem.
 440  * It queues in order based on timestamps in skb's
 441  */
 442 struct fifo_sched_data {
 443         u32 limit;
 444         psched_time_t oldest;
 445 };
 446
 447 static int tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
 448 {
 449         struct fifo_sched_data *q = qdisc_priv(sch);
 450         struct sk_buff_head *list = &sch->q;
 451         psched_time_t tnext = netem_skb_cb(nskb)->time_to_send;
 452         struct sk_buff *skb;
 453
 454         if (likely(skb_queue_len(list) < q->limit)) {
 455                 /* Optimize for add at tail */
 456                 if (likely(skb_queue_empty(list) || tnext >= q->oldest)) {
 457                         q->oldest = tnext;
 458                         return qdisc_enqueue_tail(nskb, sch);
 459                 }
 460
 461                 skb_queue_reverse_walk(list, skb) {
 462                         const struct netem_skb_cb *cb = netem_skb_cb(skb);
 463
 464                         if (tnext >= cb->time_to_send)
 465                                 break;
 466                 }
 467
 468                 __skb_queue_after(list, skb, nskb);
 469
 470                 sch->qstats.backlog += qdisc_pkt_len(nskb);
 471                 sch->bstats.bytes += qdisc_pkt_len(nskb);
 472                 sch->bstats.packets++;
 473
 474                 return NET_XMIT_SUCCESS;
 475         }
 476
 477         return qdisc_reshape_fail(nskb, sch);
 478 }
 479
 480 static int tfifo_init(struct Qdisc *sch, struct nlattr *opt)
 481 {
 482         struct fifo_sched_data *q = qdisc_priv(sch);
 483
 484         if (opt) {
 485                 struct tc_fifo_qopt *ctl = nla_data(opt);
 486                 if (nla_len(opt) < sizeof(*ctl))
 487                         return -EINVAL;
 488
 489                 q->limit = ctl->limit;
 490         } else
 491                 q->limit = max_t(u32, qdisc_dev(sch)->tx_queue_len, 1);
 492
 493         q->oldest = PSCHED_PASTPERFECT;
 494         return 0;
 495 }
 496
 497 static int tfifo_dump(struct Qdisc *sch, struct sk_buff *skb)
 498 {
 499         struct fifo_sched_data *q = qdisc_priv(sch);
 500         struct tc_fifo_qopt opt = { .limit = q->limit };
 501
 502         NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
 503         return skb->len;
 504
 505 nla_put_failure:
 506         return -1;
 507 }
 508
 509 static struct Qdisc_ops tfifo_qdisc_ops __read_mostly = {
 510         .id             =       "tfifo",
 511         .priv_size      =       sizeof(struct fifo_sched_data),
 512         .enqueue        =       tfifo_enqueue,
 513         .dequeue        =       qdisc_dequeue_head,
 514         .peek           =       qdisc_peek_head,
 515         .drop           =       qdisc_queue_drop,
 516         .init           =       tfifo_init,
 517         .reset          =       qdisc_reset_queue,
 518         .change         =       tfifo_init,
 519         .dump           =       tfifo_dump,
 520 };
 521
 522 static int netem_init(struct Qdisc *sch, struct nlattr *opt)
 523 {
 524         struct netem_sched_data *q = qdisc_priv(sch);
 525         int ret;
 526
 527         if (!opt)
 528                 return -EINVAL;
 529
 530         qdisc_watchdog_init(&q->watchdog, sch);
 531
 532         q->qdisc = qdisc_create_dflt(qdisc_dev(sch), sch->dev_queue,
 533                                      &tfifo_qdisc_ops,
 534                                      TC_H_MAKE(sch->handle, 1));
 535         if (!q->qdisc) {
 536                 pr_debug("netem: qdisc create failed\n");
 537                 return -ENOMEM;
 538         }
 539
 540         ret = netem_change(sch, opt);
 541         if (ret) {
 542                 pr_debug("netem: change failed\n");
 543                 qdisc_destroy(q->qdisc);
 544         }
 545         return ret;
 546 }
 547
 548 static void netem_destroy(struct Qdisc *sch)
 549 {
 550         struct netem_sched_data *q = qdisc_priv(sch);
 551
 552         qdisc_watchdog_cancel(&q->watchdog);
 553         qdisc_destroy(q->qdisc);
 554         kfree(q->delay_dist);
 555 }
 556
 557 static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
 558 {
 559         const struct netem_sched_data *q = qdisc_priv(sch);
 560         unsigned char *b = skb_tail_pointer(skb);
 561         struct nlattr *nla = (struct nlattr *) b;
 562         struct tc_netem_qopt qopt;
 563         struct tc_netem_corr cor;
 564         struct tc_netem_reorder reorder;
 565         struct tc_netem_corrupt corrupt;
 566
 567         qopt.latency = q->latency;
 568         qopt.jitter = q->jitter;
 569         qopt.limit = q->limit;
 570         qopt.loss = q->loss;
 571         qopt.gap = q->gap;
 572         qopt.duplicate = q->duplicate;
 573         NLA_PUT(skb, TCA_OPTIONS, sizeof(qopt), &qopt);
 574
 575         cor.delay_corr = q->delay_cor.rho;
 576         cor.loss_corr = q->loss_cor.rho;
 577         cor.dup_corr = q->dup_cor.rho;
 578         NLA_PUT(skb, TCA_NETEM_CORR, sizeof(cor), &cor);
 579
 580         reorder.probability = q->reorder;
 581         reorder.correlation = q->reorder_cor.rho;
 582         NLA_PUT(skb, TCA_NETEM_REORDER, sizeof(reorder), &reorder);
 583
 584         corrupt.probability = q->corrupt;
 585         corrupt.correlation = q->corrupt_cor.rho;
 586         NLA_PUT(skb, TCA_NETEM_CORRUPT, sizeof(corrupt), &corrupt);
 587
 588         nla->nla_len = skb_tail_pointer(skb) - b;
 589
 590         return skb->len;
 591
 592 nla_put_failure:
 593         nlmsg_trim(skb, b);
 594         return -1;
 595 }
 596
 597 static struct Qdisc_ops netem_qdisc_ops __read_mostly = {
 598         .id             =       "netem",
 599         .priv_size      =       sizeof(struct netem_sched_data),
 600         .enqueue        =       netem_enqueue,
 601         .dequeue        =       netem_dequeue,
 602         .peek           =       qdisc_peek_dequeued,
 603         .drop           =       netem_drop,
 604         .init           =       netem_init,
 605         .reset          =       netem_reset,
 606         .destroy        =       netem_destroy,
 607         .change         =       netem_change,
 608         .dump           =       netem_dump,
 609         .owner          =       THIS_MODULE,
 610 };
 611
 612
 613 static int __init netem_module_init(void)
 614 {
 615         pr_info("netem: version " VERSION "\n");
 616         return register_qdisc(&netem_qdisc_ops);
 617 }
 618 static void __exit netem_module_exit(void)
 619 {
 620         unregister_qdisc(&netem_qdisc_ops);
 621 }
 622 module_init(netem_module_init)
 623 module_exit(netem_module_exit)
 624 MODULE_LICENSE("GPL");