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 #ifdef CONFIG_NET_CLS_ACT
284 /*
285 * If it's at ingress let's pretend the delay is
286 * from the network (tstamp will be updated).
287 */
288 if (G_TC_FROM(skb->tc_verd) & AT_INGRESS)
289 skb->tstamp.tv64 = 0;
290 #endif
291 pr_debug("netem_dequeue: return skb=%p\n", 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 sch->bstats.bytes += qdisc_pkt_len(nskb);
480 sch->bstats.packets++;
481
482 return NET_XMIT_SUCCESS;
483 }
484
485 return qdisc_reshape_fail(nskb, sch);
486 }
487
488 static int tfifo_init(struct Qdisc *sch, struct nlattr *opt)
489 {
490 struct fifo_sched_data *q = qdisc_priv(sch);
491
492 if (opt) {
493 struct tc_fifo_qopt *ctl = nla_data(opt);
494 if (nla_len(opt) < sizeof(*ctl))
495 return -EINVAL;
496
497 q->limit = ctl->limit;
498 } else
499 q->limit = max_t(u32, qdisc_dev(sch)->tx_queue_len, 1);
500
501 q->oldest = PSCHED_PASTPERFECT;
502 return 0;
503 }
504
505 static int tfifo_dump(struct Qdisc *sch, struct sk_buff *skb)
506 {
507 struct fifo_sched_data *q = qdisc_priv(sch);
508 struct tc_fifo_qopt opt = { .limit = q->limit };
509
510 NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
511 return skb->len;
512
513 nla_put_failure:
514 return -1;
515 }
516
517 static struct Qdisc_ops tfifo_qdisc_ops __read_mostly = {
518 .id = "tfifo",
519 .priv_size = sizeof(struct fifo_sched_data),
520 .enqueue = tfifo_enqueue,
521 .dequeue = qdisc_dequeue_head,
522 .peek = qdisc_peek_head,
523 .drop = qdisc_queue_drop,
524 .init = tfifo_init,
525 .reset = qdisc_reset_queue,
526 .change = tfifo_init,
527 .dump = tfifo_dump,
528 };
529
530 static int netem_init(struct Qdisc *sch, struct nlattr *opt)
531 {
532 struct netem_sched_data *q = qdisc_priv(sch);
533 int ret;
534
535 if (!opt)
536 return -EINVAL;
537
538 qdisc_watchdog_init(&q->watchdog, sch);
539
540 q->qdisc = qdisc_create_dflt(qdisc_dev(sch), sch->dev_queue,
541 &tfifo_qdisc_ops,
542 TC_H_MAKE(sch->handle, 1));
543 if (!q->qdisc) {
544 pr_debug("netem: qdisc create failed\n");
545 return -ENOMEM;
546 }
547
548 ret = netem_change(sch, opt);
549 if (ret) {
550 pr_debug("netem: change failed\n");
551 qdisc_destroy(q->qdisc);
552 }
553 return ret;
554 }
555
556 static void netem_destroy(struct Qdisc *sch)
557 {
558 struct netem_sched_data *q = qdisc_priv(sch);
559
560 qdisc_watchdog_cancel(&q->watchdog);
561 qdisc_destroy(q->qdisc);
562 kfree(q->delay_dist);
563 }
564
565 static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
566 {
567 const struct netem_sched_data *q = qdisc_priv(sch);
568 unsigned char *b = skb_tail_pointer(skb);
569 struct nlattr *nla = (struct nlattr *) b;
570 struct tc_netem_qopt qopt;
571 struct tc_netem_corr cor;
572 struct tc_netem_reorder reorder;
573 struct tc_netem_corrupt corrupt;
574
575 qopt.latency = q->latency;
576 qopt.jitter = q->jitter;
577 qopt.limit = q->limit;
578 qopt.loss = q->loss;
579 qopt.gap = q->gap;
580 qopt.duplicate = q->duplicate;
581 NLA_PUT(skb, TCA_OPTIONS, sizeof(qopt), &qopt);
582
583 cor.delay_corr = q->delay_cor.rho;
584 cor.loss_corr = q->loss_cor.rho;
585 cor.dup_corr = q->dup_cor.rho;
586 NLA_PUT(skb, TCA_NETEM_CORR, sizeof(cor), &cor);
587
588 reorder.probability = q->reorder;
589 reorder.correlation = q->reorder_cor.rho;
590 NLA_PUT(skb, TCA_NETEM_REORDER, sizeof(reorder), &reorder);
591
592 corrupt.probability = q->corrupt;
593 corrupt.correlation = q->corrupt_cor.rho;
594 NLA_PUT(skb, TCA_NETEM_CORRUPT, sizeof(corrupt), &corrupt);
595
596 nla->nla_len = skb_tail_pointer(skb) - b;
597
598 return skb->len;
599
600 nla_put_failure:
601 nlmsg_trim(skb, b);
602 return -1;
603 }
604
605 static struct Qdisc_ops netem_qdisc_ops __read_mostly = {
606 .id = "netem",
607 .priv_size = sizeof(struct netem_sched_data),
608 .enqueue = netem_enqueue,
609 .dequeue = netem_dequeue,
610 .peek = qdisc_peek_dequeued,
611 .drop = netem_drop,
612 .init = netem_init,
613 .reset = netem_reset,
614 .destroy = netem_destroy,
615 .change = netem_change,
616 .dump = netem_dump,
617 .owner = THIS_MODULE,
618 };
619
620
621 static int __init netem_module_init(void)
622 {
623 pr_info("netem: version " VERSION "\n");
624 return register_qdisc(&netem_qdisc_ops);
625 }
626 static void __exit netem_module_exit(void)
627 {
628 unregister_qdisc(&netem_qdisc_ops);
629 }
630 module_init(netem_module_init)
631 module_exit(netem_module_exit)
632 MODULE_LICENSE("GPL");
633
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