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>
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>
23 #include <net/netlink.h>
24 #include <net/pkt_sched.h>
28 /* Network Emulation Queuing algorithm.
29 ====================================
31 Sources: [1] Mark Carson, Darrin Santay, "NIST Net - A Linux-based
32 Network Emulation Tool
33 [2] Luigi Rizzo, DummyNet for FreeBSD
35 ----------------------------------------------------------------
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.
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.
50 The simulator is limited by the Linux timer resolution
51 and will create packet bursts on the HZ boundary (1ms).
54 struct netem_sched_data {
56 struct qdisc_watchdog watchdog;
58 psched_tdiff_t latency;
59 psched_tdiff_t jitter;
72 } delay_cor, loss_cor, dup_cor, reorder_cor, corrupt_cor;
80 /* Time stamp put into socket buffer control block */
82 psched_time_t time_to_send;
85 static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)
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;
92 /* init_crandom - initialize correlated random number generator
93 * Use entropy source for initial seed.
95 static void init_crandom(struct crndstate *state, unsigned long rho)
98 state->last = net_random();
101 /* get_crandom - correlated random number generator
102 * Next number depends on last value.
103 * rho is scaled to avoid floating point.
105 static u32 get_crandom(struct crndstate *state)
108 unsigned long answer;
110 if (state->rho == 0) /* no correlation */
113 value = net_random();
114 rho = (u64)state->rho + 1;
115 answer = (value * ((1ull<<32) - rho) + state->last * rho) >> 32;
116 state->last = answer;
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.
124 static psched_tdiff_t tabledist(psched_tdiff_t mu, psched_tdiff_t sigma,
125 struct crndstate *state,
126 const struct disttable *dist)
135 rnd = get_crandom(state);
137 /* default uniform distribution */
139 return (rnd % (2*sigma)) - sigma + mu;
141 t = dist->table[rnd % dist->size];
142 x = (sigma % NETEM_DIST_SCALE) * t;
144 x += NETEM_DIST_SCALE/2;
146 x -= NETEM_DIST_SCALE/2;
148 return x / NETEM_DIST_SCALE + (sigma / NETEM_DIST_SCALE) * t + mu;
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.
157 static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
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;
166 pr_debug("netem_enqueue skb=%p\n", skb);
168 /* Random duplication */
169 if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor))
172 /* Random packet drop 0 => none, ~0 => all */
173 if (q->loss && q->loss >= get_crandom(&q->loss_cor))
179 return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
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.
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... */
194 qdisc_enqueue_root(skb2, rootq);
195 q->duplicate = dupsave;
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.
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))) {
209 return NET_XMIT_DROP;
212 skb->data[net_random() % skb_headlen(skb)] ^= 1<<(net_random() % 8);
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)) {
220 psched_tdiff_t delay;
222 delay = tabledist(q->latency, q->jitter,
223 &q->delay_cor, q->delay_dist);
225 now = psched_get_time();
226 cb->time_to_send = now + delay;
228 ret = qdisc_enqueue(skb, q->qdisc);
231 * Do re-ordering by putting one out of N packets at the front
234 cb->time_to_send = psched_get_time();
236 ret = q->qdisc->ops->requeue(skb, q->qdisc);
239 if (likely(ret == NET_XMIT_SUCCESS)) {
241 sch->bstats.bytes += qdisc_pkt_len(skb);
242 sch->bstats.packets++;
243 } else if (net_xmit_drop_count(ret)) {
247 pr_debug("netem: enqueue ret %d\n", ret);
251 /* Requeue packets but don't change time stamp */
252 static int netem_requeue(struct sk_buff *skb, struct Qdisc *sch)
254 struct netem_sched_data *q = qdisc_priv(sch);
257 if ((ret = q->qdisc->ops->requeue(skb, q->qdisc)) == 0) {
259 sch->qstats.requeues++;
265 static unsigned int netem_drop(struct Qdisc* sch)
267 struct netem_sched_data *q = qdisc_priv(sch);
268 unsigned int len = 0;
270 if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
277 static struct sk_buff *netem_dequeue(struct Qdisc *sch)
279 struct netem_sched_data *q = qdisc_priv(sch);
283 if (sch->flags & TCQ_F_THROTTLED)
286 skb = q->qdisc->dequeue(q->qdisc);
288 const struct netem_skb_cb *cb = netem_skb_cb(skb);
289 psched_time_t now = psched_get_time();
291 /* if more time remaining? */
292 if (cb->time_to_send <= now) {
293 pr_debug("netem_dequeue: return skb=%p\n", skb);
298 if (unlikely(q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS)) {
299 qdisc_tree_decrease_qlen(q->qdisc, 1);
301 printk(KERN_ERR "netem: %s could not requeue\n",
305 qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
311 static void netem_reset(struct Qdisc *sch)
313 struct netem_sched_data *q = qdisc_priv(sch);
315 qdisc_reset(q->qdisc);
317 qdisc_watchdog_cancel(&q->watchdog);
321 * Distribution data is a variable size payload containing
322 * signed 16 bit values.
324 static int get_dist_table(struct Qdisc *sch, const struct nlattr *attr)
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;
336 d = kmalloc(sizeof(*d) + n*sizeof(d->table[0]), GFP_KERNEL);
341 for (i = 0; i < n; i++)
342 d->table[i] = data[i];
344 root_lock = qdisc_root_sleeping_lock(sch);
346 spin_lock_bh(root_lock);
347 d = xchg(&q->delay_dist, d);
348 spin_unlock_bh(root_lock);
354 static int get_correlation(struct Qdisc *sch, const struct nlattr *attr)
356 struct netem_sched_data *q = qdisc_priv(sch);
357 const struct tc_netem_corr *c = nla_data(attr);
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);
365 static int get_reorder(struct Qdisc *sch, const struct nlattr *attr)
367 struct netem_sched_data *q = qdisc_priv(sch);
368 const struct tc_netem_reorder *r = nla_data(attr);
370 q->reorder = r->probability;
371 init_crandom(&q->reorder_cor, r->correlation);
375 static int get_corrupt(struct Qdisc *sch, const struct nlattr *attr)
377 struct netem_sched_data *q = qdisc_priv(sch);
378 const struct tc_netem_corrupt *r = nla_data(attr);
380 q->corrupt = r->probability;
381 init_crandom(&q->corrupt_cor, r->correlation);
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) },
391 static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
392 const struct nla_policy *policy, int len)
394 int nested_len = nla_len(nla) - NLA_ALIGN(len);
398 if (nested_len >= nla_attr_size(0))
399 return nla_parse(tb, maxtype, nla_data(nla) + NLA_ALIGN(len),
401 memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
405 /* Parse netlink message to set options */
406 static int netem_change(struct Qdisc *sch, struct nlattr *opt)
408 struct netem_sched_data *q = qdisc_priv(sch);
409 struct nlattr *tb[TCA_NETEM_MAX + 1];
410 struct tc_netem_qopt *qopt;
416 qopt = nla_data(opt);
417 ret = parse_attr(tb, TCA_NETEM_MAX, opt, netem_policy, sizeof(*qopt));
421 ret = fifo_set_limit(q->qdisc, qopt->limit);
423 pr_debug("netem: can't set fifo limit\n");
427 q->latency = qopt->latency;
428 q->jitter = qopt->jitter;
429 q->limit = qopt->limit;
432 q->loss = qopt->loss;
433 q->duplicate = qopt->duplicate;
435 /* for compatibility with earlier versions.
436 * if gap is set, need to assume 100% probability
441 if (tb[TCA_NETEM_CORR]) {
442 ret = get_correlation(sch, tb[TCA_NETEM_CORR]);
447 if (tb[TCA_NETEM_DELAY_DIST]) {
448 ret = get_dist_table(sch, tb[TCA_NETEM_DELAY_DIST]);
453 if (tb[TCA_NETEM_REORDER]) {
454 ret = get_reorder(sch, tb[TCA_NETEM_REORDER]);
459 if (tb[TCA_NETEM_CORRUPT]) {
460 ret = get_corrupt(sch, tb[TCA_NETEM_CORRUPT]);
469 * Special case version of FIFO queue for use by netem.
470 * It queues in order based on timestamps in skb's
472 struct fifo_sched_data {
474 psched_time_t oldest;
477 static int tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
479 struct fifo_sched_data *q = qdisc_priv(sch);
480 struct sk_buff_head *list = &sch->q;
481 psched_time_t tnext = netem_skb_cb(nskb)->time_to_send;
484 if (likely(skb_queue_len(list) < q->limit)) {
485 /* Optimize for add at tail */
486 if (likely(skb_queue_empty(list) || tnext >= q->oldest)) {
488 return qdisc_enqueue_tail(nskb, sch);
491 skb_queue_reverse_walk(list, skb) {
492 const struct netem_skb_cb *cb = netem_skb_cb(skb);
494 if (tnext >= cb->time_to_send)
498 __skb_queue_after(list, skb, nskb);
500 sch->qstats.backlog += qdisc_pkt_len(nskb);
501 sch->bstats.bytes += qdisc_pkt_len(nskb);
502 sch->bstats.packets++;
504 return NET_XMIT_SUCCESS;
507 return qdisc_reshape_fail(nskb, sch);
510 static int tfifo_init(struct Qdisc *sch, struct nlattr *opt)
512 struct fifo_sched_data *q = qdisc_priv(sch);
515 struct tc_fifo_qopt *ctl = nla_data(opt);
516 if (nla_len(opt) < sizeof(*ctl))
519 q->limit = ctl->limit;
521 q->limit = max_t(u32, qdisc_dev(sch)->tx_queue_len, 1);
523 q->oldest = PSCHED_PASTPERFECT;
527 static int tfifo_dump(struct Qdisc *sch, struct sk_buff *skb)
529 struct fifo_sched_data *q = qdisc_priv(sch);
530 struct tc_fifo_qopt opt = { .limit = q->limit };
532 NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
539 static struct Qdisc_ops tfifo_qdisc_ops __read_mostly = {
541 .priv_size = sizeof(struct fifo_sched_data),
542 .enqueue = tfifo_enqueue,
543 .dequeue = qdisc_dequeue_head,
544 .requeue = qdisc_requeue,
545 .drop = qdisc_queue_drop,
547 .reset = qdisc_reset_queue,
548 .change = tfifo_init,
552 static int netem_init(struct Qdisc *sch, struct nlattr *opt)
554 struct netem_sched_data *q = qdisc_priv(sch);
560 qdisc_watchdog_init(&q->watchdog, sch);
562 q->qdisc = qdisc_create_dflt(qdisc_dev(sch), sch->dev_queue,
564 TC_H_MAKE(sch->handle, 1));
566 pr_debug("netem: qdisc create failed\n");
570 ret = netem_change(sch, opt);
572 pr_debug("netem: change failed\n");
573 qdisc_destroy(q->qdisc);
578 static void netem_destroy(struct Qdisc *sch)
580 struct netem_sched_data *q = qdisc_priv(sch);
582 qdisc_watchdog_cancel(&q->watchdog);
583 qdisc_destroy(q->qdisc);
584 kfree(q->delay_dist);
587 static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
589 const struct netem_sched_data *q = qdisc_priv(sch);
590 unsigned char *b = skb_tail_pointer(skb);
591 struct nlattr *nla = (struct nlattr *) b;
592 struct tc_netem_qopt qopt;
593 struct tc_netem_corr cor;
594 struct tc_netem_reorder reorder;
595 struct tc_netem_corrupt corrupt;
597 qopt.latency = q->latency;
598 qopt.jitter = q->jitter;
599 qopt.limit = q->limit;
602 qopt.duplicate = q->duplicate;
603 NLA_PUT(skb, TCA_OPTIONS, sizeof(qopt), &qopt);
605 cor.delay_corr = q->delay_cor.rho;
606 cor.loss_corr = q->loss_cor.rho;
607 cor.dup_corr = q->dup_cor.rho;
608 NLA_PUT(skb, TCA_NETEM_CORR, sizeof(cor), &cor);
610 reorder.probability = q->reorder;
611 reorder.correlation = q->reorder_cor.rho;
612 NLA_PUT(skb, TCA_NETEM_REORDER, sizeof(reorder), &reorder);
614 corrupt.probability = q->corrupt;
615 corrupt.correlation = q->corrupt_cor.rho;
616 NLA_PUT(skb, TCA_NETEM_CORRUPT, sizeof(corrupt), &corrupt);
618 nla->nla_len = skb_tail_pointer(skb) - b;
627 static int netem_dump_class(struct Qdisc *sch, unsigned long cl,
628 struct sk_buff *skb, struct tcmsg *tcm)
630 struct netem_sched_data *q = qdisc_priv(sch);
632 if (cl != 1) /* only one class */
635 tcm->tcm_handle |= TC_H_MIN(1);
636 tcm->tcm_info = q->qdisc->handle;
641 static int netem_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
644 struct netem_sched_data *q = qdisc_priv(sch);
650 *old = xchg(&q->qdisc, new);
651 qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
653 sch_tree_unlock(sch);
658 static struct Qdisc *netem_leaf(struct Qdisc *sch, unsigned long arg)
660 struct netem_sched_data *q = qdisc_priv(sch);
664 static unsigned long netem_get(struct Qdisc *sch, u32 classid)
669 static void netem_put(struct Qdisc *sch, unsigned long arg)
673 static int netem_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
674 struct nlattr **tca, unsigned long *arg)
679 static int netem_delete(struct Qdisc *sch, unsigned long arg)
684 static void netem_walk(struct Qdisc *sch, struct qdisc_walker *walker)
687 if (walker->count >= walker->skip)
688 if (walker->fn(sch, 1, walker) < 0) {
696 static struct tcf_proto **netem_find_tcf(struct Qdisc *sch, unsigned long cl)
701 static const struct Qdisc_class_ops netem_class_ops = {
702 .graft = netem_graft,
706 .change = netem_change_class,
707 .delete = netem_delete,
709 .tcf_chain = netem_find_tcf,
710 .dump = netem_dump_class,
713 static struct Qdisc_ops netem_qdisc_ops __read_mostly = {
715 .cl_ops = &netem_class_ops,
716 .priv_size = sizeof(struct netem_sched_data),
717 .enqueue = netem_enqueue,
718 .dequeue = netem_dequeue,
719 .requeue = netem_requeue,
722 .reset = netem_reset,
723 .destroy = netem_destroy,
724 .change = netem_change,
726 .owner = THIS_MODULE,
730 static int __init netem_module_init(void)
732 pr_info("netem: version " VERSION "\n");
733 return register_qdisc(&netem_qdisc_ops);
735 static void __exit netem_module_exit(void)
737 unregister_qdisc(&netem_qdisc_ops);
739 module_init(netem_module_init)
740 module_exit(netem_module_exit)
741 MODULE_LICENSE("GPL");