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/slab.h>
  18 #include <linux/types.h>
  19 #include <linux/kernel.h>
  20 #include <linux/errno.h>
  21 #include <linux/skbuff.h>
  22 #include <linux/rtnetlink.h>
  23
  24 #include <net/netlink.h>
  25 #include <net/pkt_sched.h>
  26
  27 #define VERSION "1.2"
  28
  29 /*      Network Emulation Queuing algorithm.
  30         ====================================
  31
  32         Sources: [1] Mark Carson, Darrin Santay, "NIST Net - A Linux-based
  33                  Network Emulation Tool
  34                  [2] Luigi Rizzo, DummyNet for FreeBSD
  35
  36          ----------------------------------------------------------------
  37
  38          This started out as a simple way to delay outgoing packets to
  39          test TCP but has grown to include most of the functionality
  40          of a full blown network emulator like NISTnet. It can delay
  41          packets and add random jitter (and correlation). The random
  42          distribution can be loaded from a table as well to provide
  43          normal, Pareto, or experimental curves. Packet loss,
  44          duplication, and reordering can also be emulated.
  45
  46          This qdisc does not do classification that can be handled in
  47          layering other disciplines.  It does not need to do bandwidth
  48          control either since that can be handled by using token
  49          bucket or other rate control.
  50 */
  51
  52 struct netem_sched_data {
  53         struct Qdisc    *qdisc;
  54         struct qdisc_watchdog watchdog;
  55
  56         psched_tdiff_t latency;
  57         psched_tdiff_t jitter;
  58
  59         u32 loss;
  60         u32 limit;
  61         u32 counter;
  62         u32 gap;
  63         u32 duplicate;
  64         u32 reorder;
  65         u32 corrupt;
  66
  67         struct crndstate {
  68                 u32 last;
  69                 u32 rho;
  70         } delay_cor, loss_cor, dup_cor, reorder_cor, corrupt_cor;
  71
  72         struct disttable {
  73                 u32  size;
  74                 s16 table[0];
  75         } *delay_dist;
  76 };
  77
  78 /* Time stamp put into socket buffer control block */
  79 struct netem_skb_cb {
  80         psched_time_t   time_to_send;
  81 };
  82
  83 static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)
  84 {
  85         BUILD_BUG_ON(sizeof(skb->cb) <
  86                 sizeof(struct qdisc_skb_cb) + sizeof(struct netem_skb_cb));
  87         return (struct netem_skb_cb *)qdisc_skb_cb(skb)->data;
  88 }
  89
  90 /* init_crandom - initialize correlated random number generator
  91  * Use entropy source for initial seed.
  92  */
  93 static void init_crandom(struct crndstate *state, unsigned long rho)
  94 {
  95         state->rho = rho;
  96         state->last = net_random();
  97 }
  98
  99 /* get_crandom - correlated random number generator
 100  * Next number depends on last value.
 101  * rho is scaled to avoid floating point.
 102  */
 103 static u32 get_crandom(struct crndstate *state)
 104 {
 105         u64 value, rho;
 106         unsigned long answer;
 107
 108         if (state->rho == 0)    /* no correlation */
 109                 return net_random();
 110
 111         value = net_random();
 112         rho = (u64)state->rho + 1;
 113         answer = (value * ((1ull<<32) - rho) + state->last * rho) >> 32;
 114         state->last = answer;
 115         return answer;
 116 }
 117
 118 /* tabledist - return a pseudo-randomly distributed value with mean mu and
 119  * std deviation sigma.  Uses table lookup to approximate the desired
 120  * distribution, and a uniformly-distributed pseudo-random source.
 121  */
 122 static psched_tdiff_t tabledist(psched_tdiff_t mu, psched_tdiff_t sigma,
 123                                 struct crndstate *state,
 124                                 const struct disttable *dist)
 125 {
 126         psched_tdiff_t x;
 127         long t;
 128         u32 rnd;
 129
 130         if (sigma == 0)
 131                 return mu;
 132
 133         rnd = get_crandom(state);
 134
 135         /* default uniform distribution */
 136         if (dist == NULL)
 137                 return (rnd % (2*sigma)) - sigma + mu;
 138
 139         t = dist->table[rnd % dist->size];
 140         x = (sigma % NETEM_DIST_SCALE) * t;
 141         if (x >= 0)
 142                 x += NETEM_DIST_SCALE/2;
 143         else
 144                 x -= NETEM_DIST_SCALE/2;
 145
 146         return  x / NETEM_DIST_SCALE + (sigma / NETEM_DIST_SCALE) * t + mu;
 147 }
 148
 149 /*
 150  * Insert one skb into qdisc.
 151  * Note: parent depends on return value to account for queue length.
 152  *      NET_XMIT_DROP: queue length didn't change.
 153  *      NET_XMIT_SUCCESS: one skb was queued.
 154  */
 155 static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 156 {
 157         struct netem_sched_data *q = qdisc_priv(sch);
 158         /* We don't fill cb now as skb_unshare() may invalidate it */
 159         struct netem_skb_cb *cb;
 160         struct sk_buff *skb2;
 161         int ret;
 162         int count = 1;
 163
 164         pr_debug("netem_enqueue skb=%p\n", skb);
 165
 166         /* Random duplication */
 167         if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor))
 168                 ++count;
 169
 170         /* Random packet drop 0 => none, ~0 => all */
 171         if (q->loss && q->loss >= get_crandom(&q->loss_cor))
 172                 --count;
 173
 174         if (count == 0) {
 175                 sch->qstats.drops++;
 176                 kfree_skb(skb);
 177                 return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
 178         }
 179
 180         skb_orphan(skb);
 181
 182         /*
 183          * If we need to duplicate packet, then re-insert at top of the
 184          * qdisc tree, since parent queuer expects that only one
 185          * skb will be queued.
 186          */
 187         if (count > 1 && (skb2 = skb_clone(skb, GFP_ATOMIC)) != NULL) {
 188                 struct Qdisc *rootq = qdisc_root(sch);
 189                 u32 dupsave = q->duplicate; /* prevent duplicating a dup... */
 190                 q->duplicate = 0;
 191
 192                 qdisc_enqueue_root(skb2, rootq);
 193                 q->duplicate = dupsave;
 194         }
 195
 196         /*
 197          * Randomized packet corruption.
 198          * Make copy if needed since we are modifying
 199          * If packet is going to be hardware checksummed, then
 200          * do it now in software before we mangle it.
 201          */
 202         if (q->corrupt && q->corrupt >= get_crandom(&q->corrupt_cor)) {
 203                 if (!(skb = skb_unshare(skb, GFP_ATOMIC)) ||
 204                     (skb->ip_summed == CHECKSUM_PARTIAL &&
 205                      skb_checksum_help(skb))) {
 206                         sch->qstats.drops++;
 207                         return NET_XMIT_DROP;
 208                 }
 209
 210                 skb->data[net_random() % skb_headlen(skb)] ^= 1<<(net_random() % 8);
 211         }
 212
 213         cb = netem_skb_cb(skb);
 214         if (q->gap == 0 ||              /* not doing reordering */
 215             q->counter < q->gap ||      /* inside last reordering gap */
 216             q->reorder < get_crandom(&q->reorder_cor)) {
 217                 psched_time_t now;
 218                 psched_tdiff_t delay;
 219
 220                 delay = tabledist(q->latency, q->jitter,
 221                                   &q->delay_cor, q->delay_dist);
 222
 223                 now = psched_get_time();
 224                 cb->time_to_send = now + delay;
 225                 ++q->counter;
 226                 ret = qdisc_enqueue(skb, q->qdisc);
 227         } else {
 228                 /*
 229                  * Do re-ordering by putting one out of N packets at the front
 230                  * of the queue.
 231                  */
 232                 cb->time_to_send = psched_get_time();
 233                 q->counter = 0;
 234
 235                 __skb_queue_head(&q->qdisc->q, skb);
 236                 q->qdisc->qstats.backlog += qdisc_pkt_len(skb);
 237                 q->qdisc->qstats.requeues++;
 238                 ret = NET_XMIT_SUCCESS;
 239         }
 240
 241         if (likely(ret == NET_XMIT_SUCCESS)) {
 242                 sch->q.qlen++;
 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 static unsigned int netem_drop(struct Qdisc* sch)
 252 {
 253         struct netem_sched_data *q = qdisc_priv(sch);
 254         unsigned int len = 0;
 255
 256         if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
 257                 sch->q.qlen--;
 258                 sch->qstats.drops++;
 259         }
 260         return len;
 261 }
 262
 263 static struct sk_buff *netem_dequeue(struct Qdisc *sch)
 264 {
 265         struct netem_sched_data *q = qdisc_priv(sch);
 266         struct sk_buff *skb;
 267
 268         if (sch->flags & TCQ_F_THROTTLED)
 269                 return NULL;
 270
 271         skb = q->qdisc->ops->peek(q->qdisc);
 272         if (skb) {
 273                 const struct netem_skb_cb *cb = netem_skb_cb(skb);
 274                 psched_time_t now = psched_get_time();
 275
 276                 /* if more time remaining? */
 277                 if (cb->time_to_send <= now) {
 278                         skb = qdisc_dequeue_peeked(q->qdisc);
 279                         if (unlikely(!skb))
 280                                 return NULL;
 281
 282 #ifdef CONFIG_NET_CLS_ACT
 283                         /*
 284                          * If it's at ingress let's pretend the delay is
 285                          * from the network (tstamp will be updated).
 286                          */
 287                         if (G_TC_FROM(skb->tc_verd) & AT_INGRESS)
 288                                 skb->tstamp.tv64 = 0;
 289 #endif
 290                         pr_debug("netem_dequeue: return skb=%p\n", skb);
 291                         qdisc_bstats_update(sch, skb);
 292                         sch->q.qlen--;
 293                         return skb;
 294                 }
 295
 296                 qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
 297         }
 298
 299         return NULL;
 300 }
 301
 302 static void netem_reset(struct Qdisc *sch)
 303 {
 304         struct netem_sched_data *q = qdisc_priv(sch);
 305
 306         qdisc_reset(q->qdisc);
 307         sch->q.qlen = 0;
 308         qdisc_watchdog_cancel(&q->watchdog);
 309 }
 310
 311 /*
 312  * Distribution data is a variable size payload containing
 313  * signed 16 bit values.
 314  */
 315 static int get_dist_table(struct Qdisc *sch, const struct nlattr *attr)
 316 {
 317         struct netem_sched_data *q = qdisc_priv(sch);
 318         unsigned long n = nla_len(attr)/sizeof(__s16);
 319         const __s16 *data = nla_data(attr);
 320         spinlock_t *root_lock;
 321         struct disttable *d;
 322         int i;
 323
 324         if (n > 65536)
 325                 return -EINVAL;
 326
 327         d = kmalloc(sizeof(*d) + n*sizeof(d->table[0]), GFP_KERNEL);
 328         if (!d)
 329                 return -ENOMEM;
 330
 331         d->size = n;
 332         for (i = 0; i < n; i++)
 333                 d->table[i] = data[i];
 334
 335         root_lock = qdisc_root_sleeping_lock(sch);
 336
 337         spin_lock_bh(root_lock);
 338         kfree(q->delay_dist);
 339         q->delay_dist = d;
 340         spin_unlock_bh(root_lock);
 341         return 0;
 342 }
 343
 344 static void get_correlation(struct Qdisc *sch, const struct nlattr *attr)
 345 {
 346         struct netem_sched_data *q = qdisc_priv(sch);
 347         const struct tc_netem_corr *c = nla_data(attr);
 348
 349         init_crandom(&q->delay_cor, c->delay_corr);
 350         init_crandom(&q->loss_cor, c->loss_corr);
 351         init_crandom(&q->dup_cor, c->dup_corr);
 352 }
 353
 354 static void get_reorder(struct Qdisc *sch, const struct nlattr *attr)
 355 {
 356         struct netem_sched_data *q = qdisc_priv(sch);
 357         const struct tc_netem_reorder *r = nla_data(attr);
 358
 359         q->reorder = r->probability;
 360         init_crandom(&q->reorder_cor, r->correlation);
 361 }
 362
 363 static void get_corrupt(struct Qdisc *sch, const struct nlattr *attr)
 364 {
 365         struct netem_sched_data *q = qdisc_priv(sch);
 366         const struct tc_netem_corrupt *r = nla_data(attr);
 367
 368         q->corrupt = r->probability;
 369         init_crandom(&q->corrupt_cor, r->correlation);
 370 }
 371
 372 static const struct nla_policy netem_policy[TCA_NETEM_MAX + 1] = {
 373         [TCA_NETEM_CORR]        = { .len = sizeof(struct tc_netem_corr) },
 374         [TCA_NETEM_REORDER]     = { .len = sizeof(struct tc_netem_reorder) },
 375         [TCA_NETEM_CORRUPT]     = { .len = sizeof(struct tc_netem_corrupt) },
 376 };
 377
 378 static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
 379                       const struct nla_policy *policy, int len)
 380 {
 381         int nested_len = nla_len(nla) - NLA_ALIGN(len);
 382
 383         if (nested_len < 0)
 384                 return -EINVAL;
 385         if (nested_len >= nla_attr_size(0))
 386                 return nla_parse(tb, maxtype, nla_data(nla) + NLA_ALIGN(len),
 387                                  nested_len, policy);
 388         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 389         return 0;
 390 }
 391
 392 /* Parse netlink message to set options */
 393 static int netem_change(struct Qdisc *sch, struct nlattr *opt)
 394 {
 395         struct netem_sched_data *q = qdisc_priv(sch);
 396         struct nlattr *tb[TCA_NETEM_MAX + 1];
 397         struct tc_netem_qopt *qopt;
 398         int ret;
 399
 400         if (opt == NULL)
 401                 return -EINVAL;
 402
 403         qopt = nla_data(opt);
 404         ret = parse_attr(tb, TCA_NETEM_MAX, opt, netem_policy, sizeof(*qopt));
 405         if (ret < 0)
 406                 return ret;
 407
 408         ret = fifo_set_limit(q->qdisc, qopt->limit);
 409         if (ret) {
 410                 pr_debug("netem: can't set fifo limit\n");
 411                 return ret;
 412         }
 413
 414         q->latency = qopt->latency;
 415         q->jitter = qopt->jitter;
 416         q->limit = qopt->limit;
 417         q->gap = qopt->gap;
 418         q->counter = 0;
 419         q->loss = qopt->loss;
 420         q->duplicate = qopt->duplicate;
 421
 422         /* for compatibility with earlier versions.
 423          * if gap is set, need to assume 100% probability
 424          */
 425         if (q->gap)
 426                 q->reorder = ~0;
 427
 428         if (tb[TCA_NETEM_CORR])
 429                 get_correlation(sch, tb[TCA_NETEM_CORR]);
 430
 431         if (tb[TCA_NETEM_DELAY_DIST]) {
 432                 ret = get_dist_table(sch, tb[TCA_NETEM_DELAY_DIST]);
 433                 if (ret)
 434                         return ret;
 435         }
 436
 437         if (tb[TCA_NETEM_REORDER])
 438                 get_reorder(sch, tb[TCA_NETEM_REORDER]);
 439
 440         if (tb[TCA_NETEM_CORRUPT])
 441                 get_corrupt(sch, tb[TCA_NETEM_CORRUPT]);
 442
 443         return 0;
 444 }
 445
 446 /*
 447  * Special case version of FIFO queue for use by netem.
 448  * It queues in order based on timestamps in skb's
 449  */
 450 struct fifo_sched_data {
 451         u32 limit;
 452         psched_time_t oldest;
 453 };
 454
 455 static int tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
 456 {
 457         struct fifo_sched_data *q = qdisc_priv(sch);
 458         struct sk_buff_head *list = &sch->q;
 459         psched_time_t tnext = netem_skb_cb(nskb)->time_to_send;
 460         struct sk_buff *skb;
 461
 462         if (likely(skb_queue_len(list) < q->limit)) {
 463                 /* Optimize for add at tail */
 464                 if (likely(skb_queue_empty(list) || tnext >= q->oldest)) {
 465                         q->oldest = tnext;
 466                         return qdisc_enqueue_tail(nskb, sch);
 467                 }
 468
 469                 skb_queue_reverse_walk(list, skb) {
 470                         const struct netem_skb_cb *cb = netem_skb_cb(skb);
 471
 472                         if (tnext >= cb->time_to_send)
 473                                 break;
 474                 }
 475
 476                 __skb_queue_after(list, skb, nskb);
 477
 478                 sch->qstats.backlog += qdisc_pkt_len(nskb);
 479
 480                 return NET_XMIT_SUCCESS;
 481         }
 482
 483         return qdisc_reshape_fail(nskb, sch);
 484 }
 485
 486 static int tfifo_init(struct Qdisc *sch, struct nlattr *opt)
 487 {
 488         struct fifo_sched_data *q = qdisc_priv(sch);
 489
 490         if (opt) {
 491                 struct tc_fifo_qopt *ctl = nla_data(opt);
 492                 if (nla_len(opt) < sizeof(*ctl))
 493                         return -EINVAL;
 494
 495                 q->limit = ctl->limit;
 496         } else
 497                 q->limit = max_t(u32, qdisc_dev(sch)->tx_queue_len, 1);
 498
 499         q->oldest = PSCHED_PASTPERFECT;
 500         return 0;
 501 }
 502
 503 static int tfifo_dump(struct Qdisc *sch, struct sk_buff *skb)
 504 {
 505         struct fifo_sched_data *q = qdisc_priv(sch);
 506         struct tc_fifo_qopt opt = { .limit = q->limit };
 507
 508         NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
 509         return skb->len;
 510
 511 nla_put_failure:
 512         return -1;
 513 }
 514
 515 static struct Qdisc_ops tfifo_qdisc_ops __read_mostly = {
 516         .id             =       "tfifo",
 517         .priv_size      =       sizeof(struct fifo_sched_data),
 518         .enqueue        =       tfifo_enqueue,
 519         .dequeue        =       qdisc_dequeue_head,
 520         .peek           =       qdisc_peek_head,
 521         .drop           =       qdisc_queue_drop,
 522         .init           =       tfifo_init,
 523         .reset          =       qdisc_reset_queue,
 524         .change         =       tfifo_init,
 525         .dump           =       tfifo_dump,
 526 };
 527
 528 static int netem_init(struct Qdisc *sch, struct nlattr *opt)
 529 {
 530         struct netem_sched_data *q = qdisc_priv(sch);
 531         int ret;
 532
 533         if (!opt)
 534                 return -EINVAL;
 535
 536         qdisc_watchdog_init(&q->watchdog, sch);
 537
 538         q->qdisc = qdisc_create_dflt(sch->dev_queue, &tfifo_qdisc_ops,
 539                                      TC_H_MAKE(sch->handle, 1));
 540         if (!q->qdisc) {
 541                 pr_debug("netem: qdisc create failed\n");
 542                 return -ENOMEM;
 543         }
 544
 545         ret = netem_change(sch, opt);
 546         if (ret) {
 547                 pr_debug("netem: change failed\n");
 548                 qdisc_destroy(q->qdisc);
 549         }
 550         return ret;
 551 }
 552
 553 static void netem_destroy(struct Qdisc *sch)
 554 {
 555         struct netem_sched_data *q = qdisc_priv(sch);
 556
 557         qdisc_watchdog_cancel(&q->watchdog);
 558         qdisc_destroy(q->qdisc);
 559         kfree(q->delay_dist);
 560 }
 561
 562 static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
 563 {
 564         const struct netem_sched_data *q = qdisc_priv(sch);
 565         unsigned char *b = skb_tail_pointer(skb);
 566         struct nlattr *nla = (struct nlattr *) b;
 567         struct tc_netem_qopt qopt;
 568         struct tc_netem_corr cor;
 569         struct tc_netem_reorder reorder;
 570         struct tc_netem_corrupt corrupt;
 571
 572         qopt.latency = q->latency;
 573         qopt.jitter = q->jitter;
 574         qopt.limit = q->limit;
 575         qopt.loss = q->loss;
 576         qopt.gap = q->gap;
 577         qopt.duplicate = q->duplicate;
 578         NLA_PUT(skb, TCA_OPTIONS, sizeof(qopt), &qopt);
 579
 580         cor.delay_corr = q->delay_cor.rho;
 581         cor.loss_corr = q->loss_cor.rho;
 582         cor.dup_corr = q->dup_cor.rho;
 583         NLA_PUT(skb, TCA_NETEM_CORR, sizeof(cor), &cor);
 584
 585         reorder.probability = q->reorder;
 586         reorder.correlation = q->reorder_cor.rho;
 587         NLA_PUT(skb, TCA_NETEM_REORDER, sizeof(reorder), &reorder);
 588
 589         corrupt.probability = q->corrupt;
 590         corrupt.correlation = q->corrupt_cor.rho;
 591         NLA_PUT(skb, TCA_NETEM_CORRUPT, sizeof(corrupt), &corrupt);
 592
 593         nla->nla_len = skb_tail_pointer(skb) - b;
 594
 595         return skb->len;
 596
 597 nla_put_failure:
 598         nlmsg_trim(skb, b);
 599         return -1;
 600 }
 601
 602 static struct Qdisc_ops netem_qdisc_ops __read_mostly = {
 603         .id             =       "netem",
 604         .priv_size      =       sizeof(struct netem_sched_data),
 605         .enqueue        =       netem_enqueue,
 606         .dequeue        =       netem_dequeue,
 607         .peek           =       qdisc_peek_dequeued,
 608         .drop           =       netem_drop,
 609         .init           =       netem_init,
 610         .reset          =       netem_reset,
 611         .destroy        =       netem_destroy,
 612         .change         =       netem_change,
 613         .dump           =       netem_dump,
 614         .owner          =       THIS_MODULE,
 615 };
 616
 617
 618 static int __init netem_module_init(void)
 619 {
 620         pr_info("netem: version " VERSION "\n");
 621         return register_qdisc(&netem_qdisc_ops);
 622 }
 623 static void __exit netem_module_exit(void)
 624 {
 625         unregister_qdisc(&netem_qdisc_ops);
 626 }
 627 module_init(netem_module_init)
 628 module_exit(netem_module_exit)
 629 MODULE_LICENSE("GPL");