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
7 * 2 of the License, or (at your option) any later 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/config.h>
17 #include <linux/module.h>
18 #include <linux/bitops.h>
19 #include <linux/types.h>
20 #include <linux/kernel.h>
21 #include <linux/errno.h>
22 #include <linux/netdevice.h>
23 #include <linux/skbuff.h>
24 #include <linux/rtnetlink.h>
26 #include <net/pkt_sched.h>
30 /* Network Emulation Queuing algorithm.
31 ====================================
33 Sources: [1] Mark Carson, Darrin Santay, "NIST Net - A Linux-based
34 Network Emulation Tool
35 [2] Luigi Rizzo, DummyNet for FreeBSD
37 ----------------------------------------------------------------
39 This started out as a simple way to delay outgoing packets to
40 test TCP but has grown to include most of the functionality
41 of a full blown network emulator like NISTnet. It can delay
42 packets and add random jitter (and correlation). The random
43 distribution can be loaded from a table as well to provide
44 normal, Pareto, or experimental curves. Packet loss,
45 duplication, and reordering can also be emulated.
47 This qdisc does not do classification that can be handled in
48 layering other disciplines. It does not need to do bandwidth
49 control either since that can be handled by using token
50 bucket or other rate control.
52 The simulator is limited by the Linux timer resolution
53 and will create packet bursts on the HZ boundary (1ms).
56 struct netem_sched_data
{
58 struct timer_list timer
;
73 } delay_cor
, loss_cor
, dup_cor
, reorder_cor
, corrupt_cor
;
81 /* Time stamp put into socket buffer control block */
83 psched_time_t time_to_send
;
86 /* init_crandom - initialize correlated random number generator
87 * Use entropy source for initial seed.
89 static void init_crandom(struct crndstate
*state
, unsigned long rho
)
92 state
->last
= net_random();
95 /* get_crandom - correlated random number generator
96 * Next number depends on last value.
97 * rho is scaled to avoid floating point.
99 static unsigned long get_crandom(struct crndstate
*state
)
102 unsigned long answer
;
104 if (state
->rho
== 0) /* no correllation */
107 value
= net_random();
108 rho
= (u64
)state
->rho
+ 1;
109 answer
= (value
* ((1ull<<32) - rho
) + state
->last
* rho
) >> 32;
110 state
->last
= answer
;
114 /* tabledist - return a pseudo-randomly distributed value with mean mu and
115 * std deviation sigma. Uses table lookup to approximate the desired
116 * distribution, and a uniformly-distributed pseudo-random source.
118 static long tabledist(unsigned long mu
, long sigma
,
119 struct crndstate
*state
, const struct disttable
*dist
)
127 rnd
= get_crandom(state
);
129 /* default uniform distribution */
131 return (rnd
% (2*sigma
)) - sigma
+ mu
;
133 t
= dist
->table
[rnd
% dist
->size
];
134 x
= (sigma
% NETEM_DIST_SCALE
) * t
;
136 x
+= NETEM_DIST_SCALE
/2;
138 x
-= NETEM_DIST_SCALE
/2;
140 return x
/ NETEM_DIST_SCALE
+ (sigma
/ NETEM_DIST_SCALE
) * t
+ mu
;
144 * Insert one skb into qdisc.
145 * Note: parent depends on return value to account for queue length.
146 * NET_XMIT_DROP: queue length didn't change.
147 * NET_XMIT_SUCCESS: one skb was queued.
149 static int netem_enqueue(struct sk_buff
*skb
, struct Qdisc
*sch
)
151 struct netem_sched_data
*q
= qdisc_priv(sch
);
152 struct netem_skb_cb
*cb
= (struct netem_skb_cb
*)skb
->cb
;
153 struct sk_buff
*skb2
;
157 pr_debug("netem_enqueue skb=%p\n", skb
);
159 /* Random duplication */
160 if (q
->duplicate
&& q
->duplicate
>= get_crandom(&q
->dup_cor
))
163 /* Random packet drop 0 => none, ~0 => all */
164 if (q
->loss
&& q
->loss
>= get_crandom(&q
->loss_cor
))
170 return NET_XMIT_DROP
;
174 * If we need to duplicate packet, then re-insert at top of the
175 * qdisc tree, since parent queuer expects that only one
176 * skb will be queued.
178 if (count
> 1 && (skb2
= skb_clone(skb
, GFP_ATOMIC
)) != NULL
) {
179 struct Qdisc
*rootq
= sch
->dev
->qdisc
;
180 u32 dupsave
= q
->duplicate
; /* prevent duplicating a dup... */
183 rootq
->enqueue(skb2
, rootq
);
184 q
->duplicate
= dupsave
;
188 * Randomized packet corruption.
189 * Make copy if needed since we are modifying
190 * If packet is going to be hardware checksummed, then
191 * do it now in software before we mangle it.
193 if (q
->corrupt
&& q
->corrupt
>= get_crandom(&q
->corrupt_cor
)) {
194 if (!(skb
= skb_unshare(skb
, GFP_ATOMIC
))
195 || (skb
->ip_summed
== CHECKSUM_HW
196 && skb_checksum_help(skb
, 0))) {
198 return NET_XMIT_DROP
;
201 skb
->data
[net_random() % skb_headlen(skb
)] ^= 1<<(net_random() % 8);
204 if (q
->gap
== 0 /* not doing reordering */
205 || q
->counter
< q
->gap
/* inside last reordering gap */
206 || q
->reorder
< get_crandom(&q
->reorder_cor
)) {
208 psched_tdiff_t delay
;
210 delay
= tabledist(q
->latency
, q
->jitter
,
211 &q
->delay_cor
, q
->delay_dist
);
213 PSCHED_GET_TIME(now
);
214 PSCHED_TADD2(now
, delay
, cb
->time_to_send
);
216 ret
= q
->qdisc
->enqueue(skb
, q
->qdisc
);
219 * Do re-ordering by putting one out of N packets at the front
222 PSCHED_GET_TIME(cb
->time_to_send
);
224 ret
= q
->qdisc
->ops
->requeue(skb
, q
->qdisc
);
227 if (likely(ret
== NET_XMIT_SUCCESS
)) {
229 sch
->bstats
.bytes
+= skb
->len
;
230 sch
->bstats
.packets
++;
234 pr_debug("netem: enqueue ret %d\n", ret
);
238 /* Requeue packets but don't change time stamp */
239 static int netem_requeue(struct sk_buff
*skb
, struct Qdisc
*sch
)
241 struct netem_sched_data
*q
= qdisc_priv(sch
);
244 if ((ret
= q
->qdisc
->ops
->requeue(skb
, q
->qdisc
)) == 0) {
246 sch
->qstats
.requeues
++;
252 static unsigned int netem_drop(struct Qdisc
* sch
)
254 struct netem_sched_data
*q
= qdisc_priv(sch
);
255 unsigned int len
= 0;
257 if (q
->qdisc
->ops
->drop
&& (len
= q
->qdisc
->ops
->drop(q
->qdisc
)) != 0) {
264 static struct sk_buff
*netem_dequeue(struct Qdisc
*sch
)
266 struct netem_sched_data
*q
= qdisc_priv(sch
);
269 skb
= q
->qdisc
->dequeue(q
->qdisc
);
271 const struct netem_skb_cb
*cb
272 = (const struct netem_skb_cb
*)skb
->cb
;
275 /* if more time remaining? */
276 PSCHED_GET_TIME(now
);
278 if (PSCHED_TLESS(cb
->time_to_send
, now
)) {
279 pr_debug("netem_dequeue: return skb=%p\n", skb
);
281 sch
->flags
&= ~TCQ_F_THROTTLED
;
284 psched_tdiff_t delay
= PSCHED_TDIFF(cb
->time_to_send
, now
);
286 if (q
->qdisc
->ops
->requeue(skb
, q
->qdisc
) != NET_XMIT_SUCCESS
) {
289 /* After this qlen is confused */
290 printk(KERN_ERR
"netem: queue discpline %s could not requeue\n",
296 mod_timer(&q
->timer
, jiffies
+ PSCHED_US2JIFFIE(delay
));
297 sch
->flags
|= TCQ_F_THROTTLED
;
304 static void netem_watchdog(unsigned long arg
)
306 struct Qdisc
*sch
= (struct Qdisc
*)arg
;
308 pr_debug("netem_watchdog qlen=%d\n", sch
->q
.qlen
);
309 sch
->flags
&= ~TCQ_F_THROTTLED
;
310 netif_schedule(sch
->dev
);
313 static void netem_reset(struct Qdisc
*sch
)
315 struct netem_sched_data
*q
= qdisc_priv(sch
);
317 qdisc_reset(q
->qdisc
);
319 sch
->flags
&= ~TCQ_F_THROTTLED
;
320 del_timer_sync(&q
->timer
);
323 /* Pass size change message down to embedded FIFO */
324 static int set_fifo_limit(struct Qdisc
*q
, int limit
)
329 /* Hack to avoid sending change message to non-FIFO */
330 if (strncmp(q
->ops
->id
+ 1, "fifo", 4) != 0)
333 rta
= kmalloc(RTA_LENGTH(sizeof(struct tc_fifo_qopt
)), GFP_KERNEL
);
335 rta
->rta_type
= RTM_NEWQDISC
;
336 rta
->rta_len
= RTA_LENGTH(sizeof(struct tc_fifo_qopt
));
337 ((struct tc_fifo_qopt
*)RTA_DATA(rta
))->limit
= limit
;
339 ret
= q
->ops
->change(q
, rta
);
346 * Distribution data is a variable size payload containing
347 * signed 16 bit values.
349 static int get_dist_table(struct Qdisc
*sch
, const struct rtattr
*attr
)
351 struct netem_sched_data
*q
= qdisc_priv(sch
);
352 unsigned long n
= RTA_PAYLOAD(attr
)/sizeof(__s16
);
353 const __s16
*data
= RTA_DATA(attr
);
360 d
= kmalloc(sizeof(*d
) + n
*sizeof(d
->table
[0]), GFP_KERNEL
);
365 for (i
= 0; i
< n
; i
++)
366 d
->table
[i
] = data
[i
];
368 spin_lock_bh(&sch
->dev
->queue_lock
);
369 d
= xchg(&q
->delay_dist
, d
);
370 spin_unlock_bh(&sch
->dev
->queue_lock
);
376 static int get_correlation(struct Qdisc
*sch
, const struct rtattr
*attr
)
378 struct netem_sched_data
*q
= qdisc_priv(sch
);
379 const struct tc_netem_corr
*c
= RTA_DATA(attr
);
381 if (RTA_PAYLOAD(attr
) != sizeof(*c
))
384 init_crandom(&q
->delay_cor
, c
->delay_corr
);
385 init_crandom(&q
->loss_cor
, c
->loss_corr
);
386 init_crandom(&q
->dup_cor
, c
->dup_corr
);
390 static int get_reorder(struct Qdisc
*sch
, const struct rtattr
*attr
)
392 struct netem_sched_data
*q
= qdisc_priv(sch
);
393 const struct tc_netem_reorder
*r
= RTA_DATA(attr
);
395 if (RTA_PAYLOAD(attr
) != sizeof(*r
))
398 q
->reorder
= r
->probability
;
399 init_crandom(&q
->reorder_cor
, r
->correlation
);
403 static int get_corrupt(struct Qdisc
*sch
, const struct rtattr
*attr
)
405 struct netem_sched_data
*q
= qdisc_priv(sch
);
406 const struct tc_netem_corrupt
*r
= RTA_DATA(attr
);
408 if (RTA_PAYLOAD(attr
) != sizeof(*r
))
411 q
->corrupt
= r
->probability
;
412 init_crandom(&q
->corrupt_cor
, r
->correlation
);
416 /* Parse netlink message to set options */
417 static int netem_change(struct Qdisc
*sch
, struct rtattr
*opt
)
419 struct netem_sched_data
*q
= qdisc_priv(sch
);
420 struct tc_netem_qopt
*qopt
;
423 if (opt
== NULL
|| RTA_PAYLOAD(opt
) < sizeof(*qopt
))
426 qopt
= RTA_DATA(opt
);
427 ret
= set_fifo_limit(q
->qdisc
, qopt
->limit
);
429 pr_debug("netem: can't set fifo limit\n");
433 q
->latency
= qopt
->latency
;
434 q
->jitter
= qopt
->jitter
;
435 q
->limit
= qopt
->limit
;
438 q
->loss
= qopt
->loss
;
439 q
->duplicate
= qopt
->duplicate
;
441 /* for compatiablity with earlier versions.
442 * if gap is set, need to assume 100% probablity
446 /* Handle nested options after initial queue options.
447 * Should have put all options in nested format but too late now.
449 if (RTA_PAYLOAD(opt
) > sizeof(*qopt
)) {
450 struct rtattr
*tb
[TCA_NETEM_MAX
];
451 if (rtattr_parse(tb
, TCA_NETEM_MAX
,
452 RTA_DATA(opt
) + sizeof(*qopt
),
453 RTA_PAYLOAD(opt
) - sizeof(*qopt
)))
456 if (tb
[TCA_NETEM_CORR
-1]) {
457 ret
= get_correlation(sch
, tb
[TCA_NETEM_CORR
-1]);
462 if (tb
[TCA_NETEM_DELAY_DIST
-1]) {
463 ret
= get_dist_table(sch
, tb
[TCA_NETEM_DELAY_DIST
-1]);
468 if (tb
[TCA_NETEM_REORDER
-1]) {
469 ret
= get_reorder(sch
, tb
[TCA_NETEM_REORDER
-1]);
474 if (tb
[TCA_NETEM_CORRUPT
-1]) {
475 ret
= get_corrupt(sch
, tb
[TCA_NETEM_CORRUPT
-1]);
485 * Special case version of FIFO queue for use by netem.
486 * It queues in order based on timestamps in skb's
488 struct fifo_sched_data
{
492 static int tfifo_enqueue(struct sk_buff
*nskb
, struct Qdisc
*sch
)
494 struct fifo_sched_data
*q
= qdisc_priv(sch
);
495 struct sk_buff_head
*list
= &sch
->q
;
496 const struct netem_skb_cb
*ncb
497 = (const struct netem_skb_cb
*)nskb
->cb
;
500 if (likely(skb_queue_len(list
) < q
->limit
)) {
501 skb_queue_reverse_walk(list
, skb
) {
502 const struct netem_skb_cb
*cb
503 = (const struct netem_skb_cb
*)skb
->cb
;
505 if (!PSCHED_TLESS(ncb
->time_to_send
, cb
->time_to_send
))
509 __skb_queue_after(list
, skb
, nskb
);
511 sch
->qstats
.backlog
+= nskb
->len
;
512 sch
->bstats
.bytes
+= nskb
->len
;
513 sch
->bstats
.packets
++;
515 return NET_XMIT_SUCCESS
;
518 return qdisc_drop(nskb
, sch
);
521 static int tfifo_init(struct Qdisc
*sch
, struct rtattr
*opt
)
523 struct fifo_sched_data
*q
= qdisc_priv(sch
);
526 struct tc_fifo_qopt
*ctl
= RTA_DATA(opt
);
527 if (RTA_PAYLOAD(opt
) < sizeof(*ctl
))
530 q
->limit
= ctl
->limit
;
532 q
->limit
= max_t(u32
, sch
->dev
->tx_queue_len
, 1);
537 static int tfifo_dump(struct Qdisc
*sch
, struct sk_buff
*skb
)
539 struct fifo_sched_data
*q
= qdisc_priv(sch
);
540 struct tc_fifo_qopt opt
= { .limit
= q
->limit
};
542 RTA_PUT(skb
, TCA_OPTIONS
, sizeof(opt
), &opt
);
549 static struct Qdisc_ops tfifo_qdisc_ops
= {
551 .priv_size
= sizeof(struct fifo_sched_data
),
552 .enqueue
= tfifo_enqueue
,
553 .dequeue
= qdisc_dequeue_head
,
554 .requeue
= qdisc_requeue
,
555 .drop
= qdisc_queue_drop
,
557 .reset
= qdisc_reset_queue
,
558 .change
= tfifo_init
,
562 static int netem_init(struct Qdisc
*sch
, struct rtattr
*opt
)
564 struct netem_sched_data
*q
= qdisc_priv(sch
);
570 init_timer(&q
->timer
);
571 q
->timer
.function
= netem_watchdog
;
572 q
->timer
.data
= (unsigned long) sch
;
574 q
->qdisc
= qdisc_create_dflt(sch
->dev
, &tfifo_qdisc_ops
);
576 pr_debug("netem: qdisc create failed\n");
580 ret
= netem_change(sch
, opt
);
582 pr_debug("netem: change failed\n");
583 qdisc_destroy(q
->qdisc
);
588 static void netem_destroy(struct Qdisc
*sch
)
590 struct netem_sched_data
*q
= qdisc_priv(sch
);
592 del_timer_sync(&q
->timer
);
593 qdisc_destroy(q
->qdisc
);
594 kfree(q
->delay_dist
);
597 static int netem_dump(struct Qdisc
*sch
, struct sk_buff
*skb
)
599 const struct netem_sched_data
*q
= qdisc_priv(sch
);
600 unsigned char *b
= skb
->tail
;
601 struct rtattr
*rta
= (struct rtattr
*) b
;
602 struct tc_netem_qopt qopt
;
603 struct tc_netem_corr cor
;
604 struct tc_netem_reorder reorder
;
605 struct tc_netem_corrupt corrupt
;
607 qopt
.latency
= q
->latency
;
608 qopt
.jitter
= q
->jitter
;
609 qopt
.limit
= q
->limit
;
612 qopt
.duplicate
= q
->duplicate
;
613 RTA_PUT(skb
, TCA_OPTIONS
, sizeof(qopt
), &qopt
);
615 cor
.delay_corr
= q
->delay_cor
.rho
;
616 cor
.loss_corr
= q
->loss_cor
.rho
;
617 cor
.dup_corr
= q
->dup_cor
.rho
;
618 RTA_PUT(skb
, TCA_NETEM_CORR
, sizeof(cor
), &cor
);
620 reorder
.probability
= q
->reorder
;
621 reorder
.correlation
= q
->reorder_cor
.rho
;
622 RTA_PUT(skb
, TCA_NETEM_REORDER
, sizeof(reorder
), &reorder
);
624 corrupt
.probability
= q
->corrupt
;
625 corrupt
.correlation
= q
->corrupt_cor
.rho
;
626 RTA_PUT(skb
, TCA_NETEM_CORRUPT
, sizeof(corrupt
), &corrupt
);
628 rta
->rta_len
= skb
->tail
- b
;
633 skb_trim(skb
, b
- skb
->data
);
637 static int netem_dump_class(struct Qdisc
*sch
, unsigned long cl
,
638 struct sk_buff
*skb
, struct tcmsg
*tcm
)
640 struct netem_sched_data
*q
= qdisc_priv(sch
);
642 if (cl
!= 1) /* only one class */
645 tcm
->tcm_handle
|= TC_H_MIN(1);
646 tcm
->tcm_info
= q
->qdisc
->handle
;
651 static int netem_graft(struct Qdisc
*sch
, unsigned long arg
, struct Qdisc
*new,
654 struct netem_sched_data
*q
= qdisc_priv(sch
);
660 *old
= xchg(&q
->qdisc
, new);
663 sch_tree_unlock(sch
);
668 static struct Qdisc
*netem_leaf(struct Qdisc
*sch
, unsigned long arg
)
670 struct netem_sched_data
*q
= qdisc_priv(sch
);
674 static unsigned long netem_get(struct Qdisc
*sch
, u32 classid
)
679 static void netem_put(struct Qdisc
*sch
, unsigned long arg
)
683 static int netem_change_class(struct Qdisc
*sch
, u32 classid
, u32 parentid
,
684 struct rtattr
**tca
, unsigned long *arg
)
689 static int netem_delete(struct Qdisc
*sch
, unsigned long arg
)
694 static void netem_walk(struct Qdisc
*sch
, struct qdisc_walker
*walker
)
697 if (walker
->count
>= walker
->skip
)
698 if (walker
->fn(sch
, 1, walker
) < 0) {
706 static struct tcf_proto
**netem_find_tcf(struct Qdisc
*sch
, unsigned long cl
)
711 static struct Qdisc_class_ops netem_class_ops
= {
712 .graft
= netem_graft
,
716 .change
= netem_change_class
,
717 .delete = netem_delete
,
719 .tcf_chain
= netem_find_tcf
,
720 .dump
= netem_dump_class
,
723 static struct Qdisc_ops netem_qdisc_ops
= {
725 .cl_ops
= &netem_class_ops
,
726 .priv_size
= sizeof(struct netem_sched_data
),
727 .enqueue
= netem_enqueue
,
728 .dequeue
= netem_dequeue
,
729 .requeue
= netem_requeue
,
732 .reset
= netem_reset
,
733 .destroy
= netem_destroy
,
734 .change
= netem_change
,
736 .owner
= THIS_MODULE
,
740 static int __init
netem_module_init(void)
742 pr_info("netem: version " VERSION
"\n");
743 return register_qdisc(&netem_qdisc_ops
);
745 static void __exit
netem_module_exit(void)
747 unregister_qdisc(&netem_qdisc_ops
);
749 module_init(netem_module_init
)
750 module_exit(netem_module_exit
)
751 MODULE_LICENSE("GPL");