2 * net/sched/sch_netem.c Network emulator
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
9 * Many of the algorithms and ideas for this came from
10 * NIST Net which is not copyrighted.
12 * Authors: Stephen Hemminger <shemminger@osdl.org>
13 * Catalin(ux aka Dino) BOIE <catab at umbrella dot ro>
17 #include <linux/module.h>
18 #include <linux/slab.h>
19 #include <linux/types.h>
20 #include <linux/kernel.h>
21 #include <linux/errno.h>
22 #include <linux/skbuff.h>
23 #include <linux/vmalloc.h>
24 #include <linux/rtnetlink.h>
26 #include <net/netlink.h>
27 #include <net/pkt_sched.h>
31 /* Network Emulation Queuing algorithm.
32 ====================================
34 Sources: [1] Mark Carson, Darrin Santay, "NIST Net - A Linux-based
35 Network Emulation Tool
36 [2] Luigi Rizzo, DummyNet for FreeBSD
38 ----------------------------------------------------------------
40 This started out as a simple way to delay outgoing packets to
41 test TCP but has grown to include most of the functionality
42 of a full blown network emulator like NISTnet. It can delay
43 packets and add random jitter (and correlation). The random
44 distribution can be loaded from a table as well to provide
45 normal, Pareto, or experimental curves. Packet loss,
46 duplication, and reordering can also be emulated.
48 This qdisc does not do classification that can be handled in
49 layering other disciplines. It does not need to do bandwidth
50 control either since that can be handled by using token
51 bucket or other rate control.
53 Correlated Loss Generator models
55 Added generation of correlated loss according to the
56 "Gilbert-Elliot" model, a 4-state markov model.
59 [1] NetemCLG Home http://netgroup.uniroma2.it/NetemCLG
60 [2] S. Salsano, F. Ludovici, A. Ordine, "Definition of a general
61 and intuitive loss model for packet networks and its implementation
62 in the Netem module in the Linux kernel", available in [1]
64 Authors: Stefano Salsano <stefano.salsano at uniroma2.it
65 Fabio Ludovici <fabio.ludovici at yahoo.it>
68 struct netem_sched_data {
70 struct qdisc_watchdog watchdog;
72 psched_tdiff_t latency;
73 psched_tdiff_t jitter;
86 } delay_cor, loss_cor, dup_cor, reorder_cor, corrupt_cor;
99 /* Correlated Loss Generation models */
101 /* state of the Markov chain */
104 /* 4-states and Gilbert-Elliot models */
105 u32 a1; /* p13 for 4-states or p for GE */
106 u32 a2; /* p31 for 4-states or r for GE */
107 u32 a3; /* p32 for 4-states or h for GE */
108 u32 a4; /* p14 for 4-states or 1-k for GE */
109 u32 a5; /* p23 used only in 4-states */
114 /* Time stamp put into socket buffer control block */
115 struct netem_skb_cb {
116 psched_time_t time_to_send;
119 static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)
121 BUILD_BUG_ON(sizeof(skb->cb) <
122 sizeof(struct qdisc_skb_cb) + sizeof(struct netem_skb_cb));
123 return (struct netem_skb_cb *)qdisc_skb_cb(skb)->data;
126 /* init_crandom - initialize correlated random number generator
127 * Use entropy source for initial seed.
129 static void init_crandom(struct crndstate *state, unsigned long rho)
132 state->last = net_random();
135 /* get_crandom - correlated random number generator
136 * Next number depends on last value.
137 * rho is scaled to avoid floating point.
139 static u32 get_crandom(struct crndstate *state)
142 unsigned long answer;
144 if (state->rho == 0) /* no correlation */
147 value = net_random();
148 rho = (u64)state->rho + 1;
149 answer = (value * ((1ull<<32) - rho) + state->last * rho) >> 32;
150 state->last = answer;
154 /* loss_4state - 4-state model loss generator
155 * Generates losses according to the 4-state Markov chain adopted in
156 * the GI (General and Intuitive) loss model.
158 static bool loss_4state(struct netem_sched_data *q)
160 struct clgstate *clg = &q->clg;
161 u32 rnd = net_random();
164 * Makes a comparison between rnd and the transition
165 * probabilities outgoing from the current state, then decides the
166 * next state and if the next packet has to be transmitted or lost.
167 * The four states correspond to:
168 * 1 => successfully transmitted packets within a gap period
169 * 4 => isolated losses within a gap period
170 * 3 => lost packets within a burst period
171 * 2 => successfully transmitted packets within a burst period
173 switch (clg->state) {
178 } else if (clg->a4 < rnd && rnd < clg->a1) {
181 } else if (clg->a1 < rnd)
196 else if (clg->a3 < rnd && rnd < clg->a2 + clg->a3) {
199 } else if (clg->a2 + clg->a3 < rnd) {
212 /* loss_gilb_ell - Gilbert-Elliot model loss generator
213 * Generates losses according to the Gilbert-Elliot loss model or
214 * its special cases (Gilbert or Simple Gilbert)
216 * Makes a comparison between random number and the transition
217 * probabilities outgoing from the current state, then decides the
218 * next state. A second random number is extracted and the comparison
219 * with the loss probability of the current state decides if the next
220 * packet will be transmitted or lost.
222 static bool loss_gilb_ell(struct netem_sched_data *q)
224 struct clgstate *clg = &q->clg;
226 switch (clg->state) {
228 if (net_random() < clg->a1)
230 if (net_random() < clg->a4)
233 if (net_random() < clg->a2)
235 if (clg->a3 > net_random())
242 static bool loss_event(struct netem_sched_data *q)
244 switch (q->loss_model) {
246 /* Random packet drop 0 => none, ~0 => all */
247 return q->loss && q->loss >= get_crandom(&q->loss_cor);
250 /* 4state loss model algorithm (used also for GI model)
251 * Extracts a value from the markov 4 state loss generator,
252 * if it is 1 drops a packet and if needed writes the event in
255 return loss_4state(q);
258 /* Gilbert-Elliot loss model algorithm
259 * Extracts a value from the Gilbert-Elliot loss generator,
260 * if it is 1 drops a packet and if needed writes the event in
263 return loss_gilb_ell(q);
266 return false; /* not reached */
270 /* tabledist - return a pseudo-randomly distributed value with mean mu and
271 * std deviation sigma. Uses table lookup to approximate the desired
272 * distribution, and a uniformly-distributed pseudo-random source.
274 static psched_tdiff_t tabledist(psched_tdiff_t mu, psched_tdiff_t sigma,
275 struct crndstate *state,
276 const struct disttable *dist)
285 rnd = get_crandom(state);
287 /* default uniform distribution */
289 return (rnd % (2*sigma)) - sigma + mu;
291 t = dist->table[rnd % dist->size];
292 x = (sigma % NETEM_DIST_SCALE) * t;
294 x += NETEM_DIST_SCALE/2;
296 x -= NETEM_DIST_SCALE/2;
298 return x / NETEM_DIST_SCALE + (sigma / NETEM_DIST_SCALE) * t + mu;
302 * Insert one skb into qdisc.
303 * Note: parent depends on return value to account for queue length.
304 * NET_XMIT_DROP: queue length didn't change.
305 * NET_XMIT_SUCCESS: one skb was queued.
307 static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
309 struct netem_sched_data *q = qdisc_priv(sch);
310 /* We don't fill cb now as skb_unshare() may invalidate it */
311 struct netem_skb_cb *cb;
312 struct sk_buff *skb2;
316 /* Random duplication */
317 if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor))
327 return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
333 * If we need to duplicate packet, then re-insert at top of the
334 * qdisc tree, since parent queuer expects that only one
335 * skb will be queued.
337 if (count > 1 && (skb2 = skb_clone(skb, GFP_ATOMIC)) != NULL) {
338 struct Qdisc *rootq = qdisc_root(sch);
339 u32 dupsave = q->duplicate; /* prevent duplicating a dup... */
342 qdisc_enqueue_root(skb2, rootq);
343 q->duplicate = dupsave;
347 * Randomized packet corruption.
348 * Make copy if needed since we are modifying
349 * If packet is going to be hardware checksummed, then
350 * do it now in software before we mangle it.
352 if (q->corrupt && q->corrupt >= get_crandom(&q->corrupt_cor)) {
353 if (!(skb = skb_unshare(skb, GFP_ATOMIC)) ||
354 (skb->ip_summed == CHECKSUM_PARTIAL &&
355 skb_checksum_help(skb))) {
357 return NET_XMIT_DROP;
360 skb->data[net_random() % skb_headlen(skb)] ^= 1<<(net_random() % 8);
363 cb = netem_skb_cb(skb);
364 if (q->gap == 0 || /* not doing reordering */
365 q->counter < q->gap || /* inside last reordering gap */
366 q->reorder < get_crandom(&q->reorder_cor)) {
368 psched_tdiff_t delay;
370 delay = tabledist(q->latency, q->jitter,
371 &q->delay_cor, q->delay_dist);
373 now = psched_get_time();
374 cb->time_to_send = now + delay;
376 ret = qdisc_enqueue(skb, q->qdisc);
379 * Do re-ordering by putting one out of N packets at the front
382 cb->time_to_send = psched_get_time();
385 __skb_queue_head(&q->qdisc->q, skb);
386 q->qdisc->qstats.backlog += qdisc_pkt_len(skb);
387 q->qdisc->qstats.requeues++;
388 ret = NET_XMIT_SUCCESS;
391 if (ret != NET_XMIT_SUCCESS) {
392 if (net_xmit_drop_count(ret)) {
399 return NET_XMIT_SUCCESS;
402 static unsigned int netem_drop(struct Qdisc *sch)
404 struct netem_sched_data *q = qdisc_priv(sch);
405 unsigned int len = 0;
407 if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
414 static struct sk_buff *netem_dequeue(struct Qdisc *sch)
416 struct netem_sched_data *q = qdisc_priv(sch);
419 if (qdisc_is_throttled(sch))
422 skb = q->qdisc->ops->peek(q->qdisc);
424 const struct netem_skb_cb *cb = netem_skb_cb(skb);
425 psched_time_t now = psched_get_time();
427 /* if more time remaining? */
428 if (cb->time_to_send <= now) {
429 skb = qdisc_dequeue_peeked(q->qdisc);
433 #ifdef CONFIG_NET_CLS_ACT
435 * If it's at ingress let's pretend the delay is
436 * from the network (tstamp will be updated).
438 if (G_TC_FROM(skb->tc_verd) & AT_INGRESS)
439 skb->tstamp.tv64 = 0;
443 qdisc_unthrottled(sch);
444 qdisc_bstats_update(sch, skb);
448 qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
454 static void netem_reset(struct Qdisc *sch)
456 struct netem_sched_data *q = qdisc_priv(sch);
458 qdisc_reset(q->qdisc);
460 qdisc_watchdog_cancel(&q->watchdog);
463 static void dist_free(struct disttable *d)
466 if (is_vmalloc_addr(d))
474 * Distribution data is a variable size payload containing
475 * signed 16 bit values.
477 static int get_dist_table(struct Qdisc *sch, const struct nlattr *attr)
479 struct netem_sched_data *q = qdisc_priv(sch);
480 size_t n = nla_len(attr)/sizeof(__s16);
481 const __s16 *data = nla_data(attr);
482 spinlock_t *root_lock;
487 if (n > NETEM_DIST_MAX)
490 s = sizeof(struct disttable) + n * sizeof(s16);
491 d = kmalloc(s, GFP_KERNEL | __GFP_NOWARN);
498 for (i = 0; i < n; i++)
499 d->table[i] = data[i];
501 root_lock = qdisc_root_sleeping_lock(sch);
503 spin_lock_bh(root_lock);
504 swap(q->delay_dist, d);
505 spin_unlock_bh(root_lock);
511 static void get_correlation(struct Qdisc *sch, const struct nlattr *attr)
513 struct netem_sched_data *q = qdisc_priv(sch);
514 const struct tc_netem_corr *c = nla_data(attr);
516 init_crandom(&q->delay_cor, c->delay_corr);
517 init_crandom(&q->loss_cor, c->loss_corr);
518 init_crandom(&q->dup_cor, c->dup_corr);
521 static void get_reorder(struct Qdisc *sch, const struct nlattr *attr)
523 struct netem_sched_data *q = qdisc_priv(sch);
524 const struct tc_netem_reorder *r = nla_data(attr);
526 q->reorder = r->probability;
527 init_crandom(&q->reorder_cor, r->correlation);
530 static void get_corrupt(struct Qdisc *sch, const struct nlattr *attr)
532 struct netem_sched_data *q = qdisc_priv(sch);
533 const struct tc_netem_corrupt *r = nla_data(attr);
535 q->corrupt = r->probability;
536 init_crandom(&q->corrupt_cor, r->correlation);
539 static int get_loss_clg(struct Qdisc *sch, const struct nlattr *attr)
541 struct netem_sched_data *q = qdisc_priv(sch);
542 const struct nlattr *la;
545 nla_for_each_nested(la, attr, rem) {
546 u16 type = nla_type(la);
549 case NETEM_LOSS_GI: {
550 const struct tc_netem_gimodel *gi = nla_data(la);
552 if (nla_len(la) != sizeof(struct tc_netem_gimodel)) {
553 pr_info("netem: incorrect gi model size\n");
557 q->loss_model = CLG_4_STATES;
568 case NETEM_LOSS_GE: {
569 const struct tc_netem_gemodel *ge = nla_data(la);
571 if (nla_len(la) != sizeof(struct tc_netem_gemodel)) {
572 pr_info("netem: incorrect gi model size\n");
576 q->loss_model = CLG_GILB_ELL;
586 pr_info("netem: unknown loss type %u\n", type);
594 static const struct nla_policy netem_policy[TCA_NETEM_MAX + 1] = {
595 [TCA_NETEM_CORR] = { .len = sizeof(struct tc_netem_corr) },
596 [TCA_NETEM_REORDER] = { .len = sizeof(struct tc_netem_reorder) },
597 [TCA_NETEM_CORRUPT] = { .len = sizeof(struct tc_netem_corrupt) },
598 [TCA_NETEM_LOSS] = { .type = NLA_NESTED },
601 static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
602 const struct nla_policy *policy, int len)
604 int nested_len = nla_len(nla) - NLA_ALIGN(len);
606 if (nested_len < 0) {
607 pr_info("netem: invalid attributes len %d\n", nested_len);
611 if (nested_len >= nla_attr_size(0))
612 return nla_parse(tb, maxtype, nla_data(nla) + NLA_ALIGN(len),
615 memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
619 /* Parse netlink message to set options */
620 static int netem_change(struct Qdisc *sch, struct nlattr *opt)
622 struct netem_sched_data *q = qdisc_priv(sch);
623 struct nlattr *tb[TCA_NETEM_MAX + 1];
624 struct tc_netem_qopt *qopt;
630 qopt = nla_data(opt);
631 ret = parse_attr(tb, TCA_NETEM_MAX, opt, netem_policy, sizeof(*qopt));
635 ret = fifo_set_limit(q->qdisc, qopt->limit);
637 pr_info("netem: can't set fifo limit\n");
641 q->latency = qopt->latency;
642 q->jitter = qopt->jitter;
643 q->limit = qopt->limit;
646 q->loss = qopt->loss;
647 q->duplicate = qopt->duplicate;
649 /* for compatibility with earlier versions.
650 * if gap is set, need to assume 100% probability
655 if (tb[TCA_NETEM_CORR])
656 get_correlation(sch, tb[TCA_NETEM_CORR]);
658 if (tb[TCA_NETEM_DELAY_DIST]) {
659 ret = get_dist_table(sch, tb[TCA_NETEM_DELAY_DIST]);
664 if (tb[TCA_NETEM_REORDER])
665 get_reorder(sch, tb[TCA_NETEM_REORDER]);
667 if (tb[TCA_NETEM_CORRUPT])
668 get_corrupt(sch, tb[TCA_NETEM_CORRUPT]);
670 q->loss_model = CLG_RANDOM;
671 if (tb[TCA_NETEM_LOSS])
672 ret = get_loss_clg(sch, tb[TCA_NETEM_LOSS]);
678 * Special case version of FIFO queue for use by netem.
679 * It queues in order based on timestamps in skb's
681 struct fifo_sched_data {
683 psched_time_t oldest;
686 static int tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
688 struct fifo_sched_data *q = qdisc_priv(sch);
689 struct sk_buff_head *list = &sch->q;
690 psched_time_t tnext = netem_skb_cb(nskb)->time_to_send;
693 if (likely(skb_queue_len(list) < q->limit)) {
694 /* Optimize for add at tail */
695 if (likely(skb_queue_empty(list) || tnext >= q->oldest)) {
697 return qdisc_enqueue_tail(nskb, sch);
700 skb_queue_reverse_walk(list, skb) {
701 const struct netem_skb_cb *cb = netem_skb_cb(skb);
703 if (tnext >= cb->time_to_send)
707 __skb_queue_after(list, skb, nskb);
709 sch->qstats.backlog += qdisc_pkt_len(nskb);
711 return NET_XMIT_SUCCESS;
714 return qdisc_reshape_fail(nskb, sch);
717 static int tfifo_init(struct Qdisc *sch, struct nlattr *opt)
719 struct fifo_sched_data *q = qdisc_priv(sch);
722 struct tc_fifo_qopt *ctl = nla_data(opt);
723 if (nla_len(opt) < sizeof(*ctl))
726 q->limit = ctl->limit;
728 q->limit = max_t(u32, qdisc_dev(sch)->tx_queue_len, 1);
730 q->oldest = PSCHED_PASTPERFECT;
734 static int tfifo_dump(struct Qdisc *sch, struct sk_buff *skb)
736 struct fifo_sched_data *q = qdisc_priv(sch);
737 struct tc_fifo_qopt opt = { .limit = q->limit };
739 NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
746 static struct Qdisc_ops tfifo_qdisc_ops __read_mostly = {
748 .priv_size = sizeof(struct fifo_sched_data),
749 .enqueue = tfifo_enqueue,
750 .dequeue = qdisc_dequeue_head,
751 .peek = qdisc_peek_head,
752 .drop = qdisc_queue_drop,
754 .reset = qdisc_reset_queue,
755 .change = tfifo_init,
759 static int netem_init(struct Qdisc *sch, struct nlattr *opt)
761 struct netem_sched_data *q = qdisc_priv(sch);
767 qdisc_watchdog_init(&q->watchdog, sch);
769 q->loss_model = CLG_RANDOM;
770 q->qdisc = qdisc_create_dflt(sch->dev_queue, &tfifo_qdisc_ops,
771 TC_H_MAKE(sch->handle, 1));
773 pr_notice("netem: qdisc create tfifo qdisc failed\n");
777 ret = netem_change(sch, opt);
779 pr_info("netem: change failed\n");
780 qdisc_destroy(q->qdisc);
785 static void netem_destroy(struct Qdisc *sch)
787 struct netem_sched_data *q = qdisc_priv(sch);
789 qdisc_watchdog_cancel(&q->watchdog);
790 qdisc_destroy(q->qdisc);
791 dist_free(q->delay_dist);
794 static int dump_loss_model(const struct netem_sched_data *q,
799 nest = nla_nest_start(skb, TCA_NETEM_LOSS);
801 goto nla_put_failure;
803 switch (q->loss_model) {
805 /* legacy loss model */
806 nla_nest_cancel(skb, nest);
807 return 0; /* no data */
810 struct tc_netem_gimodel gi = {
818 NLA_PUT(skb, NETEM_LOSS_GI, sizeof(gi), &gi);
822 struct tc_netem_gemodel ge = {
829 NLA_PUT(skb, NETEM_LOSS_GE, sizeof(ge), &ge);
834 nla_nest_end(skb, nest);
838 nla_nest_cancel(skb, nest);
842 static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
844 const struct netem_sched_data *q = qdisc_priv(sch);
845 struct nlattr *nla = (struct nlattr *) skb_tail_pointer(skb);
846 struct tc_netem_qopt qopt;
847 struct tc_netem_corr cor;
848 struct tc_netem_reorder reorder;
849 struct tc_netem_corrupt corrupt;
851 qopt.latency = q->latency;
852 qopt.jitter = q->jitter;
853 qopt.limit = q->limit;
856 qopt.duplicate = q->duplicate;
857 NLA_PUT(skb, TCA_OPTIONS, sizeof(qopt), &qopt);
859 cor.delay_corr = q->delay_cor.rho;
860 cor.loss_corr = q->loss_cor.rho;
861 cor.dup_corr = q->dup_cor.rho;
862 NLA_PUT(skb, TCA_NETEM_CORR, sizeof(cor), &cor);
864 reorder.probability = q->reorder;
865 reorder.correlation = q->reorder_cor.rho;
866 NLA_PUT(skb, TCA_NETEM_REORDER, sizeof(reorder), &reorder);
868 corrupt.probability = q->corrupt;
869 corrupt.correlation = q->corrupt_cor.rho;
870 NLA_PUT(skb, TCA_NETEM_CORRUPT, sizeof(corrupt), &corrupt);
872 if (dump_loss_model(q, skb) != 0)
873 goto nla_put_failure;
875 return nla_nest_end(skb, nla);
878 nlmsg_trim(skb, nla);
882 static int netem_dump_class(struct Qdisc *sch, unsigned long cl,
883 struct sk_buff *skb, struct tcmsg *tcm)
885 struct netem_sched_data *q = qdisc_priv(sch);
887 if (cl != 1) /* only one class */
890 tcm->tcm_handle |= TC_H_MIN(1);
891 tcm->tcm_info = q->qdisc->handle;
896 static int netem_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
899 struct netem_sched_data *q = qdisc_priv(sch);
907 qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
909 sch_tree_unlock(sch);
914 static struct Qdisc *netem_leaf(struct Qdisc *sch, unsigned long arg)
916 struct netem_sched_data *q = qdisc_priv(sch);
920 static unsigned long netem_get(struct Qdisc *sch, u32 classid)
925 static void netem_put(struct Qdisc *sch, unsigned long arg)
929 static void netem_walk(struct Qdisc *sch, struct qdisc_walker *walker)
932 if (walker->count >= walker->skip)
933 if (walker->fn(sch, 1, walker) < 0) {
941 static const struct Qdisc_class_ops netem_class_ops = {
942 .graft = netem_graft,
947 .dump = netem_dump_class,
950 static struct Qdisc_ops netem_qdisc_ops __read_mostly = {
952 .cl_ops = &netem_class_ops,
953 .priv_size = sizeof(struct netem_sched_data),
954 .enqueue = netem_enqueue,
955 .dequeue = netem_dequeue,
956 .peek = qdisc_peek_dequeued,
959 .reset = netem_reset,
960 .destroy = netem_destroy,
961 .change = netem_change,
963 .owner = THIS_MODULE,
967 static int __init netem_module_init(void)
969 pr_info("netem: version " VERSION "\n");
970 return register_qdisc(&netem_qdisc_ops);
972 static void __exit netem_module_exit(void)
974 unregister_qdisc(&netem_qdisc_ops);
976 module_init(netem_module_init)
977 module_exit(netem_module_exit)
978 MODULE_LICENSE("GPL");