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>
25 #include <linux/reciprocal_div.h>
27 #include <net/netlink.h>
28 #include <net/pkt_sched.h>
32 /* Network Emulation Queuing algorithm.
33 ====================================
35 Sources: [1] Mark Carson, Darrin Santay, "NIST Net - A Linux-based
36 Network Emulation Tool
37 [2] Luigi Rizzo, DummyNet for FreeBSD
39 ----------------------------------------------------------------
41 This started out as a simple way to delay outgoing packets to
42 test TCP but has grown to include most of the functionality
43 of a full blown network emulator like NISTnet. It can delay
44 packets and add random jitter (and correlation). The random
45 distribution can be loaded from a table as well to provide
46 normal, Pareto, or experimental curves. Packet loss,
47 duplication, and reordering can also be emulated.
49 This qdisc does not do classification that can be handled in
50 layering other disciplines. It does not need to do bandwidth
51 control either since that can be handled by using token
52 bucket or other rate control.
54 Correlated Loss Generator models
56 Added generation of correlated loss according to the
57 "Gilbert-Elliot" model, a 4-state markov model.
60 [1] NetemCLG Home http://netgroup.uniroma2.it/NetemCLG
61 [2] S. Salsano, F. Ludovici, A. Ordine, "Definition of a general
62 and intuitive loss model for packet networks and its implementation
63 in the Netem module in the Linux kernel", available in [1]
65 Authors: Stefano Salsano <stefano.salsano at uniroma2.it
66 Fabio Ludovici <fabio.ludovici at yahoo.it>
69 struct netem_sched_data {
71 struct qdisc_watchdog watchdog;
73 psched_tdiff_t latency;
74 psched_tdiff_t jitter;
86 u32 cell_size_reciprocal;
92 } delay_cor, loss_cor, dup_cor, reorder_cor, corrupt_cor;
105 /* Correlated Loss Generation models */
107 /* state of the Markov chain */
110 /* 4-states and Gilbert-Elliot models */
111 u32 a1; /* p13 for 4-states or p for GE */
112 u32 a2; /* p31 for 4-states or r for GE */
113 u32 a3; /* p32 for 4-states or h for GE */
114 u32 a4; /* p14 for 4-states or 1-k for GE */
115 u32 a5; /* p23 used only in 4-states */
120 /* Time stamp put into socket buffer control block */
121 struct netem_skb_cb {
122 psched_time_t time_to_send;
125 static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)
127 BUILD_BUG_ON(sizeof(skb->cb) <
128 sizeof(struct qdisc_skb_cb) + sizeof(struct netem_skb_cb));
129 return (struct netem_skb_cb *)qdisc_skb_cb(skb)->data;
132 /* init_crandom - initialize correlated random number generator
133 * Use entropy source for initial seed.
135 static void init_crandom(struct crndstate *state, unsigned long rho)
138 state->last = net_random();
141 /* get_crandom - correlated random number generator
142 * Next number depends on last value.
143 * rho is scaled to avoid floating point.
145 static u32 get_crandom(struct crndstate *state)
148 unsigned long answer;
150 if (state->rho == 0) /* no correlation */
153 value = net_random();
154 rho = (u64)state->rho + 1;
155 answer = (value * ((1ull<<32) - rho) + state->last * rho) >> 32;
156 state->last = answer;
160 /* loss_4state - 4-state model loss generator
161 * Generates losses according to the 4-state Markov chain adopted in
162 * the GI (General and Intuitive) loss model.
164 static bool loss_4state(struct netem_sched_data *q)
166 struct clgstate *clg = &q->clg;
167 u32 rnd = net_random();
170 * Makes a comparison between rnd and the transition
171 * probabilities outgoing from the current state, then decides the
172 * next state and if the next packet has to be transmitted or lost.
173 * The four states correspond to:
174 * 1 => successfully transmitted packets within a gap period
175 * 4 => isolated losses within a gap period
176 * 3 => lost packets within a burst period
177 * 2 => successfully transmitted packets within a burst period
179 switch (clg->state) {
184 } else if (clg->a4 < rnd && rnd < clg->a1) {
187 } else if (clg->a1 < rnd)
202 else if (clg->a3 < rnd && rnd < clg->a2 + clg->a3) {
205 } else if (clg->a2 + clg->a3 < rnd) {
218 /* loss_gilb_ell - Gilbert-Elliot model loss generator
219 * Generates losses according to the Gilbert-Elliot loss model or
220 * its special cases (Gilbert or Simple Gilbert)
222 * Makes a comparison between random number and the transition
223 * probabilities outgoing from the current state, then decides the
224 * next state. A second random number is extracted and the comparison
225 * with the loss probability of the current state decides if the next
226 * packet will be transmitted or lost.
228 static bool loss_gilb_ell(struct netem_sched_data *q)
230 struct clgstate *clg = &q->clg;
232 switch (clg->state) {
234 if (net_random() < clg->a1)
236 if (net_random() < clg->a4)
239 if (net_random() < clg->a2)
241 if (clg->a3 > net_random())
248 static bool loss_event(struct netem_sched_data *q)
250 switch (q->loss_model) {
252 /* Random packet drop 0 => none, ~0 => all */
253 return q->loss && q->loss >= get_crandom(&q->loss_cor);
256 /* 4state loss model algorithm (used also for GI model)
257 * Extracts a value from the markov 4 state loss generator,
258 * if it is 1 drops a packet and if needed writes the event in
261 return loss_4state(q);
264 /* Gilbert-Elliot loss model algorithm
265 * Extracts a value from the Gilbert-Elliot loss generator,
266 * if it is 1 drops a packet and if needed writes the event in
269 return loss_gilb_ell(q);
272 return false; /* not reached */
276 /* tabledist - return a pseudo-randomly distributed value with mean mu and
277 * std deviation sigma. Uses table lookup to approximate the desired
278 * distribution, and a uniformly-distributed pseudo-random source.
280 static psched_tdiff_t tabledist(psched_tdiff_t mu, psched_tdiff_t sigma,
281 struct crndstate *state,
282 const struct disttable *dist)
291 rnd = get_crandom(state);
293 /* default uniform distribution */
295 return (rnd % (2*sigma)) - sigma + mu;
297 t = dist->table[rnd % dist->size];
298 x = (sigma % NETEM_DIST_SCALE) * t;
300 x += NETEM_DIST_SCALE/2;
302 x -= NETEM_DIST_SCALE/2;
304 return x / NETEM_DIST_SCALE + (sigma / NETEM_DIST_SCALE) * t + mu;
307 static psched_time_t packet_len_2_sched_time(unsigned int len, struct netem_sched_data *q)
311 len += q->packet_overhead;
314 u32 cells = reciprocal_divide(len, q->cell_size_reciprocal);
316 if (len > cells * q->cell_size) /* extra cell needed for remainder */
318 len = cells * (q->cell_size + q->cell_overhead);
321 ticks = (u64)len * NSEC_PER_SEC;
323 do_div(ticks, q->rate);
324 return PSCHED_NS2TICKS(ticks);
328 * Insert one skb into qdisc.
329 * Note: parent depends on return value to account for queue length.
330 * NET_XMIT_DROP: queue length didn't change.
331 * NET_XMIT_SUCCESS: one skb was queued.
333 static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
335 struct netem_sched_data *q = qdisc_priv(sch);
336 /* We don't fill cb now as skb_unshare() may invalidate it */
337 struct netem_skb_cb *cb;
338 struct sk_buff *skb2;
342 /* Random duplication */
343 if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor))
353 return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
359 * If we need to duplicate packet, then re-insert at top of the
360 * qdisc tree, since parent queuer expects that only one
361 * skb will be queued.
363 if (count > 1 && (skb2 = skb_clone(skb, GFP_ATOMIC)) != NULL) {
364 struct Qdisc *rootq = qdisc_root(sch);
365 u32 dupsave = q->duplicate; /* prevent duplicating a dup... */
368 qdisc_enqueue_root(skb2, rootq);
369 q->duplicate = dupsave;
373 * Randomized packet corruption.
374 * Make copy if needed since we are modifying
375 * If packet is going to be hardware checksummed, then
376 * do it now in software before we mangle it.
378 if (q->corrupt && q->corrupt >= get_crandom(&q->corrupt_cor)) {
379 if (!(skb = skb_unshare(skb, GFP_ATOMIC)) ||
380 (skb->ip_summed == CHECKSUM_PARTIAL &&
381 skb_checksum_help(skb))) {
383 return NET_XMIT_DROP;
386 skb->data[net_random() % skb_headlen(skb)] ^= 1<<(net_random() % 8);
389 cb = netem_skb_cb(skb);
390 if (q->gap == 0 || /* not doing reordering */
391 q->counter < q->gap || /* inside last reordering gap */
392 q->reorder < get_crandom(&q->reorder_cor)) {
394 psched_tdiff_t delay;
396 delay = tabledist(q->latency, q->jitter,
397 &q->delay_cor, q->delay_dist);
399 now = psched_get_time();
402 struct sk_buff_head *list = &q->qdisc->q;
404 delay += packet_len_2_sched_time(skb->len, q);
406 if (!skb_queue_empty(list)) {
408 * Last packet in queue is reference point (now).
409 * First packet in queue is already in flight,
410 * calculate this time bonus and substract
413 delay -= now - netem_skb_cb(skb_peek(list))->time_to_send;
414 now = netem_skb_cb(skb_peek_tail(list))->time_to_send;
418 cb->time_to_send = now + delay;
420 ret = qdisc_enqueue(skb, q->qdisc);
423 * Do re-ordering by putting one out of N packets at the front
426 cb->time_to_send = psched_get_time();
429 __skb_queue_head(&q->qdisc->q, skb);
430 q->qdisc->qstats.backlog += qdisc_pkt_len(skb);
431 q->qdisc->qstats.requeues++;
432 ret = NET_XMIT_SUCCESS;
435 if (ret != NET_XMIT_SUCCESS) {
436 if (net_xmit_drop_count(ret)) {
443 return NET_XMIT_SUCCESS;
446 static unsigned int netem_drop(struct Qdisc *sch)
448 struct netem_sched_data *q = qdisc_priv(sch);
449 unsigned int len = 0;
451 if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
458 static struct sk_buff *netem_dequeue(struct Qdisc *sch)
460 struct netem_sched_data *q = qdisc_priv(sch);
463 if (qdisc_is_throttled(sch))
466 skb = q->qdisc->ops->peek(q->qdisc);
468 const struct netem_skb_cb *cb = netem_skb_cb(skb);
469 psched_time_t now = psched_get_time();
471 /* if more time remaining? */
472 if (cb->time_to_send <= now) {
473 skb = qdisc_dequeue_peeked(q->qdisc);
477 #ifdef CONFIG_NET_CLS_ACT
479 * If it's at ingress let's pretend the delay is
480 * from the network (tstamp will be updated).
482 if (G_TC_FROM(skb->tc_verd) & AT_INGRESS)
483 skb->tstamp.tv64 = 0;
487 qdisc_unthrottled(sch);
488 qdisc_bstats_update(sch, skb);
492 qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
498 static void netem_reset(struct Qdisc *sch)
500 struct netem_sched_data *q = qdisc_priv(sch);
502 qdisc_reset(q->qdisc);
504 qdisc_watchdog_cancel(&q->watchdog);
507 static void dist_free(struct disttable *d)
510 if (is_vmalloc_addr(d))
518 * Distribution data is a variable size payload containing
519 * signed 16 bit values.
521 static int get_dist_table(struct Qdisc *sch, const struct nlattr *attr)
523 struct netem_sched_data *q = qdisc_priv(sch);
524 size_t n = nla_len(attr)/sizeof(__s16);
525 const __s16 *data = nla_data(attr);
526 spinlock_t *root_lock;
531 if (n > NETEM_DIST_MAX)
534 s = sizeof(struct disttable) + n * sizeof(s16);
535 d = kmalloc(s, GFP_KERNEL | __GFP_NOWARN);
542 for (i = 0; i < n; i++)
543 d->table[i] = data[i];
545 root_lock = qdisc_root_sleeping_lock(sch);
547 spin_lock_bh(root_lock);
548 swap(q->delay_dist, d);
549 spin_unlock_bh(root_lock);
555 static void get_correlation(struct Qdisc *sch, const struct nlattr *attr)
557 struct netem_sched_data *q = qdisc_priv(sch);
558 const struct tc_netem_corr *c = nla_data(attr);
560 init_crandom(&q->delay_cor, c->delay_corr);
561 init_crandom(&q->loss_cor, c->loss_corr);
562 init_crandom(&q->dup_cor, c->dup_corr);
565 static void get_reorder(struct Qdisc *sch, const struct nlattr *attr)
567 struct netem_sched_data *q = qdisc_priv(sch);
568 const struct tc_netem_reorder *r = nla_data(attr);
570 q->reorder = r->probability;
571 init_crandom(&q->reorder_cor, r->correlation);
574 static void get_corrupt(struct Qdisc *sch, const struct nlattr *attr)
576 struct netem_sched_data *q = qdisc_priv(sch);
577 const struct tc_netem_corrupt *r = nla_data(attr);
579 q->corrupt = r->probability;
580 init_crandom(&q->corrupt_cor, r->correlation);
583 static void get_rate(struct Qdisc *sch, const struct nlattr *attr)
585 struct netem_sched_data *q = qdisc_priv(sch);
586 const struct tc_netem_rate *r = nla_data(attr);
589 q->packet_overhead = r->packet_overhead;
590 q->cell_size = r->cell_size;
592 q->cell_size_reciprocal = reciprocal_value(q->cell_size);
593 q->cell_overhead = r->cell_overhead;
596 static int get_loss_clg(struct Qdisc *sch, const struct nlattr *attr)
598 struct netem_sched_data *q = qdisc_priv(sch);
599 const struct nlattr *la;
602 nla_for_each_nested(la, attr, rem) {
603 u16 type = nla_type(la);
606 case NETEM_LOSS_GI: {
607 const struct tc_netem_gimodel *gi = nla_data(la);
609 if (nla_len(la) < sizeof(struct tc_netem_gimodel)) {
610 pr_info("netem: incorrect gi model size\n");
614 q->loss_model = CLG_4_STATES;
625 case NETEM_LOSS_GE: {
626 const struct tc_netem_gemodel *ge = nla_data(la);
628 if (nla_len(la) < sizeof(struct tc_netem_gemodel)) {
629 pr_info("netem: incorrect ge model size\n");
633 q->loss_model = CLG_GILB_ELL;
643 pr_info("netem: unknown loss type %u\n", type);
651 static const struct nla_policy netem_policy[TCA_NETEM_MAX + 1] = {
652 [TCA_NETEM_CORR] = { .len = sizeof(struct tc_netem_corr) },
653 [TCA_NETEM_REORDER] = { .len = sizeof(struct tc_netem_reorder) },
654 [TCA_NETEM_CORRUPT] = { .len = sizeof(struct tc_netem_corrupt) },
655 [TCA_NETEM_RATE] = { .len = sizeof(struct tc_netem_rate) },
656 [TCA_NETEM_LOSS] = { .type = NLA_NESTED },
659 static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
660 const struct nla_policy *policy, int len)
662 int nested_len = nla_len(nla) - NLA_ALIGN(len);
664 if (nested_len < 0) {
665 pr_info("netem: invalid attributes len %d\n", nested_len);
669 if (nested_len >= nla_attr_size(0))
670 return nla_parse(tb, maxtype, nla_data(nla) + NLA_ALIGN(len),
673 memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
677 /* Parse netlink message to set options */
678 static int netem_change(struct Qdisc *sch, struct nlattr *opt)
680 struct netem_sched_data *q = qdisc_priv(sch);
681 struct nlattr *tb[TCA_NETEM_MAX + 1];
682 struct tc_netem_qopt *qopt;
688 qopt = nla_data(opt);
689 ret = parse_attr(tb, TCA_NETEM_MAX, opt, netem_policy, sizeof(*qopt));
693 ret = fifo_set_limit(q->qdisc, qopt->limit);
695 pr_info("netem: can't set fifo limit\n");
699 q->latency = qopt->latency;
700 q->jitter = qopt->jitter;
701 q->limit = qopt->limit;
704 q->loss = qopt->loss;
705 q->duplicate = qopt->duplicate;
707 /* for compatibility with earlier versions.
708 * if gap is set, need to assume 100% probability
713 if (tb[TCA_NETEM_CORR])
714 get_correlation(sch, tb[TCA_NETEM_CORR]);
716 if (tb[TCA_NETEM_DELAY_DIST]) {
717 ret = get_dist_table(sch, tb[TCA_NETEM_DELAY_DIST]);
722 if (tb[TCA_NETEM_REORDER])
723 get_reorder(sch, tb[TCA_NETEM_REORDER]);
725 if (tb[TCA_NETEM_CORRUPT])
726 get_corrupt(sch, tb[TCA_NETEM_CORRUPT]);
728 if (tb[TCA_NETEM_RATE])
729 get_rate(sch, tb[TCA_NETEM_RATE]);
731 q->loss_model = CLG_RANDOM;
732 if (tb[TCA_NETEM_LOSS])
733 ret = get_loss_clg(sch, tb[TCA_NETEM_LOSS]);
739 * Special case version of FIFO queue for use by netem.
740 * It queues in order based on timestamps in skb's
742 struct fifo_sched_data {
744 psched_time_t oldest;
747 static int tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
749 struct fifo_sched_data *q = qdisc_priv(sch);
750 struct sk_buff_head *list = &sch->q;
751 psched_time_t tnext = netem_skb_cb(nskb)->time_to_send;
754 if (likely(skb_queue_len(list) < q->limit)) {
755 /* Optimize for add at tail */
756 if (likely(skb_queue_empty(list) || tnext >= q->oldest)) {
758 return qdisc_enqueue_tail(nskb, sch);
761 skb_queue_reverse_walk(list, skb) {
762 const struct netem_skb_cb *cb = netem_skb_cb(skb);
764 if (tnext >= cb->time_to_send)
768 __skb_queue_after(list, skb, nskb);
770 sch->qstats.backlog += qdisc_pkt_len(nskb);
772 return NET_XMIT_SUCCESS;
775 return qdisc_reshape_fail(nskb, sch);
778 static int tfifo_init(struct Qdisc *sch, struct nlattr *opt)
780 struct fifo_sched_data *q = qdisc_priv(sch);
783 struct tc_fifo_qopt *ctl = nla_data(opt);
784 if (nla_len(opt) < sizeof(*ctl))
787 q->limit = ctl->limit;
789 q->limit = max_t(u32, qdisc_dev(sch)->tx_queue_len, 1);
791 q->oldest = PSCHED_PASTPERFECT;
795 static int tfifo_dump(struct Qdisc *sch, struct sk_buff *skb)
797 struct fifo_sched_data *q = qdisc_priv(sch);
798 struct tc_fifo_qopt opt = { .limit = q->limit };
800 NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
807 static struct Qdisc_ops tfifo_qdisc_ops __read_mostly = {
809 .priv_size = sizeof(struct fifo_sched_data),
810 .enqueue = tfifo_enqueue,
811 .dequeue = qdisc_dequeue_head,
812 .peek = qdisc_peek_head,
813 .drop = qdisc_queue_drop,
815 .reset = qdisc_reset_queue,
816 .change = tfifo_init,
820 static int netem_init(struct Qdisc *sch, struct nlattr *opt)
822 struct netem_sched_data *q = qdisc_priv(sch);
828 qdisc_watchdog_init(&q->watchdog, sch);
830 q->loss_model = CLG_RANDOM;
831 q->qdisc = qdisc_create_dflt(sch->dev_queue, &tfifo_qdisc_ops,
832 TC_H_MAKE(sch->handle, 1));
834 pr_notice("netem: qdisc create tfifo qdisc failed\n");
838 ret = netem_change(sch, opt);
840 pr_info("netem: change failed\n");
841 qdisc_destroy(q->qdisc);
846 static void netem_destroy(struct Qdisc *sch)
848 struct netem_sched_data *q = qdisc_priv(sch);
850 qdisc_watchdog_cancel(&q->watchdog);
851 qdisc_destroy(q->qdisc);
852 dist_free(q->delay_dist);
855 static int dump_loss_model(const struct netem_sched_data *q,
860 nest = nla_nest_start(skb, TCA_NETEM_LOSS);
862 goto nla_put_failure;
864 switch (q->loss_model) {
866 /* legacy loss model */
867 nla_nest_cancel(skb, nest);
868 return 0; /* no data */
871 struct tc_netem_gimodel gi = {
879 NLA_PUT(skb, NETEM_LOSS_GI, sizeof(gi), &gi);
883 struct tc_netem_gemodel ge = {
890 NLA_PUT(skb, NETEM_LOSS_GE, sizeof(ge), &ge);
895 nla_nest_end(skb, nest);
899 nla_nest_cancel(skb, nest);
903 static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
905 const struct netem_sched_data *q = qdisc_priv(sch);
906 struct nlattr *nla = (struct nlattr *) skb_tail_pointer(skb);
907 struct tc_netem_qopt qopt;
908 struct tc_netem_corr cor;
909 struct tc_netem_reorder reorder;
910 struct tc_netem_corrupt corrupt;
911 struct tc_netem_rate rate;
913 qopt.latency = q->latency;
914 qopt.jitter = q->jitter;
915 qopt.limit = q->limit;
918 qopt.duplicate = q->duplicate;
919 NLA_PUT(skb, TCA_OPTIONS, sizeof(qopt), &qopt);
921 cor.delay_corr = q->delay_cor.rho;
922 cor.loss_corr = q->loss_cor.rho;
923 cor.dup_corr = q->dup_cor.rho;
924 NLA_PUT(skb, TCA_NETEM_CORR, sizeof(cor), &cor);
926 reorder.probability = q->reorder;
927 reorder.correlation = q->reorder_cor.rho;
928 NLA_PUT(skb, TCA_NETEM_REORDER, sizeof(reorder), &reorder);
930 corrupt.probability = q->corrupt;
931 corrupt.correlation = q->corrupt_cor.rho;
932 NLA_PUT(skb, TCA_NETEM_CORRUPT, sizeof(corrupt), &corrupt);
935 rate.packet_overhead = q->packet_overhead;
936 rate.cell_size = q->cell_size;
937 rate.cell_overhead = q->cell_overhead;
938 NLA_PUT(skb, TCA_NETEM_RATE, sizeof(rate), &rate);
940 if (dump_loss_model(q, skb) != 0)
941 goto nla_put_failure;
943 return nla_nest_end(skb, nla);
946 nlmsg_trim(skb, nla);
950 static int netem_dump_class(struct Qdisc *sch, unsigned long cl,
951 struct sk_buff *skb, struct tcmsg *tcm)
953 struct netem_sched_data *q = qdisc_priv(sch);
955 if (cl != 1) /* only one class */
958 tcm->tcm_handle |= TC_H_MIN(1);
959 tcm->tcm_info = q->qdisc->handle;
964 static int netem_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
967 struct netem_sched_data *q = qdisc_priv(sch);
975 qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
977 sch_tree_unlock(sch);
982 static struct Qdisc *netem_leaf(struct Qdisc *sch, unsigned long arg)
984 struct netem_sched_data *q = qdisc_priv(sch);
988 static unsigned long netem_get(struct Qdisc *sch, u32 classid)
993 static void netem_put(struct Qdisc *sch, unsigned long arg)
997 static void netem_walk(struct Qdisc *sch, struct qdisc_walker *walker)
1000 if (walker->count >= walker->skip)
1001 if (walker->fn(sch, 1, walker) < 0) {
1009 static const struct Qdisc_class_ops netem_class_ops = {
1010 .graft = netem_graft,
1015 .dump = netem_dump_class,
1018 static struct Qdisc_ops netem_qdisc_ops __read_mostly = {
1020 .cl_ops = &netem_class_ops,
1021 .priv_size = sizeof(struct netem_sched_data),
1022 .enqueue = netem_enqueue,
1023 .dequeue = netem_dequeue,
1024 .peek = qdisc_peek_dequeued,
1027 .reset = netem_reset,
1028 .destroy = netem_destroy,
1029 .change = netem_change,
1031 .owner = THIS_MODULE,
1035 static int __init netem_module_init(void)
1037 pr_info("netem: version " VERSION "\n");
1038 return register_qdisc(&netem_qdisc_ops);
1040 static void __exit netem_module_exit(void)
1042 unregister_qdisc(&netem_qdisc_ops);
1044 module_init(netem_module_init)
1045 module_exit(netem_module_exit)
1046 MODULE_LICENSE("GPL");