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Linux/net/sched/sch_netem.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  * net/sched/sch_netem.c        Network emulator
  4  *
  5  *              Many of the algorithms and ideas for this came from
  6  *              NIST Net which is not copyrighted.
  7  *
  8  * Authors:     Stephen Hemminger <shemminger@osdl.org>
  9  *              Catalin(ux aka Dino) BOIE <catab at umbrella dot ro>
 10  */
 11 
 12 #include <linux/mm.h>
 13 #include <linux/module.h>
 14 #include <linux/slab.h>
 15 #include <linux/types.h>
 16 #include <linux/kernel.h>
 17 #include <linux/errno.h>
 18 #include <linux/skbuff.h>
 19 #include <linux/vmalloc.h>
 20 #include <linux/rtnetlink.h>
 21 #include <linux/reciprocal_div.h>
 22 #include <linux/rbtree.h>
 23 
 24 #include <net/netlink.h>
 25 #include <net/pkt_sched.h>
 26 #include <net/inet_ecn.h>
 27 
 28 #define VERSION "1.3"
 29 
 30 /*      Network Emulation Queuing algorithm.
 31         ====================================
 32 
 33         Sources: [1] Mark Carson, Darrin Santay, "NIST Net - A Linux-based
 34                  Network Emulation Tool
 35                  [2] Luigi Rizzo, DummyNet for FreeBSD
 36 
 37          ----------------------------------------------------------------
 38 
 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.
 46 
 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.
 51 
 52      Correlated Loss Generator models
 53 
 54         Added generation of correlated loss according to the
 55         "Gilbert-Elliot" model, a 4-state markov model.
 56 
 57         References:
 58         [1] NetemCLG Home http://netgroup.uniroma2.it/NetemCLG
 59         [2] S. Salsano, F. Ludovici, A. Ordine, "Definition of a general
 60         and intuitive loss model for packet networks and its implementation
 61         in the Netem module in the Linux kernel", available in [1]
 62 
 63         Authors: Stefano Salsano <stefano.salsano at uniroma2.it
 64                  Fabio Ludovici <fabio.ludovici at yahoo.it>
 65 */
 66 
 67 struct disttable {
 68         u32  size;
 69         s16 table[0];
 70 };
 71 
 72 struct netem_sched_data {
 73         /* internal t(ime)fifo qdisc uses t_root and sch->limit */
 74         struct rb_root t_root;
 75 
 76         /* a linear queue; reduces rbtree rebalancing when jitter is low */
 77         struct sk_buff  *t_head;
 78         struct sk_buff  *t_tail;
 79 
 80         /* optional qdisc for classful handling (NULL at netem init) */
 81         struct Qdisc    *qdisc;
 82 
 83         struct qdisc_watchdog watchdog;
 84 
 85         s64 latency;
 86         s64 jitter;
 87 
 88         u32 loss;
 89         u32 ecn;
 90         u32 limit;
 91         u32 counter;
 92         u32 gap;
 93         u32 duplicate;
 94         u32 reorder;
 95         u32 corrupt;
 96         u64 rate;
 97         s32 packet_overhead;
 98         u32 cell_size;
 99         struct reciprocal_value cell_size_reciprocal;
100         s32 cell_overhead;
101 
102         struct crndstate {
103                 u32 last;
104                 u32 rho;
105         } delay_cor, loss_cor, dup_cor, reorder_cor, corrupt_cor;
106 
107         struct disttable *delay_dist;
108 
109         enum  {
110                 CLG_RANDOM,
111                 CLG_4_STATES,
112                 CLG_GILB_ELL,
113         } loss_model;
114 
115         enum {
116                 TX_IN_GAP_PERIOD = 1,
117                 TX_IN_BURST_PERIOD,
118                 LOST_IN_GAP_PERIOD,
119                 LOST_IN_BURST_PERIOD,
120         } _4_state_model;
121 
122         enum {
123                 GOOD_STATE = 1,
124                 BAD_STATE,
125         } GE_state_model;
126 
127         /* Correlated Loss Generation models */
128         struct clgstate {
129                 /* state of the Markov chain */
130                 u8 state;
131 
132                 /* 4-states and Gilbert-Elliot models */
133                 u32 a1; /* p13 for 4-states or p for GE */
134                 u32 a2; /* p31 for 4-states or r for GE */
135                 u32 a3; /* p32 for 4-states or h for GE */
136                 u32 a4; /* p14 for 4-states or 1-k for GE */
137                 u32 a5; /* p23 used only in 4-states */
138         } clg;
139 
140         struct tc_netem_slot slot_config;
141         struct slotstate {
142                 u64 slot_next;
143                 s32 packets_left;
144                 s32 bytes_left;
145         } slot;
146 
147         struct disttable *slot_dist;
148 };
149 
150 /* Time stamp put into socket buffer control block
151  * Only valid when skbs are in our internal t(ime)fifo queue.
152  *
153  * As skb->rbnode uses same storage than skb->next, skb->prev and skb->tstamp,
154  * and skb->next & skb->prev are scratch space for a qdisc,
155  * we save skb->tstamp value in skb->cb[] before destroying it.
156  */
157 struct netem_skb_cb {
158         u64             time_to_send;
159 };
160 
161 static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)
162 {
163         /* we assume we can use skb next/prev/tstamp as storage for rb_node */
164         qdisc_cb_private_validate(skb, sizeof(struct netem_skb_cb));
165         return (struct netem_skb_cb *)qdisc_skb_cb(skb)->data;
166 }
167 
168 /* init_crandom - initialize correlated random number generator
169  * Use entropy source for initial seed.
170  */
171 static void init_crandom(struct crndstate *state, unsigned long rho)
172 {
173         state->rho = rho;
174         state->last = prandom_u32();
175 }
176 
177 /* get_crandom - correlated random number generator
178  * Next number depends on last value.
179  * rho is scaled to avoid floating point.
180  */
181 static u32 get_crandom(struct crndstate *state)
182 {
183         u64 value, rho;
184         unsigned long answer;
185 
186         if (!state || state->rho == 0)  /* no correlation */
187                 return prandom_u32();
188 
189         value = prandom_u32();
190         rho = (u64)state->rho + 1;
191         answer = (value * ((1ull<<32) - rho) + state->last * rho) >> 32;
192         state->last = answer;
193         return answer;
194 }
195 
196 /* loss_4state - 4-state model loss generator
197  * Generates losses according to the 4-state Markov chain adopted in
198  * the GI (General and Intuitive) loss model.
199  */
200 static bool loss_4state(struct netem_sched_data *q)
201 {
202         struct clgstate *clg = &q->clg;
203         u32 rnd = prandom_u32();
204 
205         /*
206          * Makes a comparison between rnd and the transition
207          * probabilities outgoing from the current state, then decides the
208          * next state and if the next packet has to be transmitted or lost.
209          * The four states correspond to:
210          *   TX_IN_GAP_PERIOD => successfully transmitted packets within a gap period
211          *   LOST_IN_BURST_PERIOD => isolated losses within a gap period
212          *   LOST_IN_GAP_PERIOD => lost packets within a burst period
213          *   TX_IN_GAP_PERIOD => successfully transmitted packets within a burst period
214          */
215         switch (clg->state) {
216         case TX_IN_GAP_PERIOD:
217                 if (rnd < clg->a4) {
218                         clg->state = LOST_IN_BURST_PERIOD;
219                         return true;
220                 } else if (clg->a4 < rnd && rnd < clg->a1 + clg->a4) {
221                         clg->state = LOST_IN_GAP_PERIOD;
222                         return true;
223                 } else if (clg->a1 + clg->a4 < rnd) {
224                         clg->state = TX_IN_GAP_PERIOD;
225                 }
226 
227                 break;
228         case TX_IN_BURST_PERIOD:
229                 if (rnd < clg->a5) {
230                         clg->state = LOST_IN_GAP_PERIOD;
231                         return true;
232                 } else {
233                         clg->state = TX_IN_BURST_PERIOD;
234                 }
235 
236                 break;
237         case LOST_IN_GAP_PERIOD:
238                 if (rnd < clg->a3)
239                         clg->state = TX_IN_BURST_PERIOD;
240                 else if (clg->a3 < rnd && rnd < clg->a2 + clg->a3) {
241                         clg->state = TX_IN_GAP_PERIOD;
242                 } else if (clg->a2 + clg->a3 < rnd) {
243                         clg->state = LOST_IN_GAP_PERIOD;
244                         return true;
245                 }
246                 break;
247         case LOST_IN_BURST_PERIOD:
248                 clg->state = TX_IN_GAP_PERIOD;
249                 break;
250         }
251 
252         return false;
253 }
254 
255 /* loss_gilb_ell - Gilbert-Elliot model loss generator
256  * Generates losses according to the Gilbert-Elliot loss model or
257  * its special cases  (Gilbert or Simple Gilbert)
258  *
259  * Makes a comparison between random number and the transition
260  * probabilities outgoing from the current state, then decides the
261  * next state. A second random number is extracted and the comparison
262  * with the loss probability of the current state decides if the next
263  * packet will be transmitted or lost.
264  */
265 static bool loss_gilb_ell(struct netem_sched_data *q)
266 {
267         struct clgstate *clg = &q->clg;
268 
269         switch (clg->state) {
270         case GOOD_STATE:
271                 if (prandom_u32() < clg->a1)
272                         clg->state = BAD_STATE;
273                 if (prandom_u32() < clg->a4)
274                         return true;
275                 break;
276         case BAD_STATE:
277                 if (prandom_u32() < clg->a2)
278                         clg->state = GOOD_STATE;
279                 if (prandom_u32() > clg->a3)
280                         return true;
281         }
282 
283         return false;
284 }
285 
286 static bool loss_event(struct netem_sched_data *q)
287 {
288         switch (q->loss_model) {
289         case CLG_RANDOM:
290                 /* Random packet drop 0 => none, ~0 => all */
291                 return q->loss && q->loss >= get_crandom(&q->loss_cor);
292 
293         case CLG_4_STATES:
294                 /* 4state loss model algorithm (used also for GI model)
295                 * Extracts a value from the markov 4 state loss generator,
296                 * if it is 1 drops a packet and if needed writes the event in
297                 * the kernel logs
298                 */
299                 return loss_4state(q);
300 
301         case CLG_GILB_ELL:
302                 /* Gilbert-Elliot loss model algorithm
303                 * Extracts a value from the Gilbert-Elliot loss generator,
304                 * if it is 1 drops a packet and if needed writes the event in
305                 * the kernel logs
306                 */
307                 return loss_gilb_ell(q);
308         }
309 
310         return false;   /* not reached */
311 }
312 
313 
314 /* tabledist - return a pseudo-randomly distributed value with mean mu and
315  * std deviation sigma.  Uses table lookup to approximate the desired
316  * distribution, and a uniformly-distributed pseudo-random source.
317  */
318 static s64 tabledist(s64 mu, s32 sigma,
319                      struct crndstate *state,
320                      const struct disttable *dist)
321 {
322         s64 x;
323         long t;
324         u32 rnd;
325 
326         if (sigma == 0)
327                 return mu;
328 
329         rnd = get_crandom(state);
330 
331         /* default uniform distribution */
332         if (dist == NULL)
333                 return ((rnd % (2 * sigma)) + mu) - sigma;
334 
335         t = dist->table[rnd % dist->size];
336         x = (sigma % NETEM_DIST_SCALE) * t;
337         if (x >= 0)
338                 x += NETEM_DIST_SCALE/2;
339         else
340                 x -= NETEM_DIST_SCALE/2;
341 
342         return  x / NETEM_DIST_SCALE + (sigma / NETEM_DIST_SCALE) * t + mu;
343 }
344 
345 static u64 packet_time_ns(u64 len, const struct netem_sched_data *q)
346 {
347         len += q->packet_overhead;
348 
349         if (q->cell_size) {
350                 u32 cells = reciprocal_divide(len, q->cell_size_reciprocal);
351 
352                 if (len > cells * q->cell_size) /* extra cell needed for remainder */
353                         cells++;
354                 len = cells * (q->cell_size + q->cell_overhead);
355         }
356 
357         return div64_u64(len * NSEC_PER_SEC, q->rate);
358 }
359 
360 static void tfifo_reset(struct Qdisc *sch)
361 {
362         struct netem_sched_data *q = qdisc_priv(sch);
363         struct rb_node *p = rb_first(&q->t_root);
364 
365         while (p) {
366                 struct sk_buff *skb = rb_to_skb(p);
367 
368                 p = rb_next(p);
369                 rb_erase(&skb->rbnode, &q->t_root);
370                 rtnl_kfree_skbs(skb, skb);
371         }
372 
373         rtnl_kfree_skbs(q->t_head, q->t_tail);
374         q->t_head = NULL;
375         q->t_tail = NULL;
376 }
377 
378 static void tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
379 {
380         struct netem_sched_data *q = qdisc_priv(sch);
381         u64 tnext = netem_skb_cb(nskb)->time_to_send;
382 
383         if (!q->t_tail || tnext >= netem_skb_cb(q->t_tail)->time_to_send) {
384                 if (q->t_tail)
385                         q->t_tail->next = nskb;
386                 else
387                         q->t_head = nskb;
388                 q->t_tail = nskb;
389         } else {
390                 struct rb_node **p = &q->t_root.rb_node, *parent = NULL;
391 
392                 while (*p) {
393                         struct sk_buff *skb;
394 
395                         parent = *p;
396                         skb = rb_to_skb(parent);
397                         if (tnext >= netem_skb_cb(skb)->time_to_send)
398                                 p = &parent->rb_right;
399                         else
400                                 p = &parent->rb_left;
401                 }
402                 rb_link_node(&nskb->rbnode, parent, p);
403                 rb_insert_color(&nskb->rbnode, &q->t_root);
404         }
405         sch->q.qlen++;
406 }
407 
408 /* netem can't properly corrupt a megapacket (like we get from GSO), so instead
409  * when we statistically choose to corrupt one, we instead segment it, returning
410  * the first packet to be corrupted, and re-enqueue the remaining frames
411  */
412 static struct sk_buff *netem_segment(struct sk_buff *skb, struct Qdisc *sch,
413                                      struct sk_buff **to_free)
414 {
415         struct sk_buff *segs;
416         netdev_features_t features = netif_skb_features(skb);
417 
418         segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
419 
420         if (IS_ERR_OR_NULL(segs)) {
421                 qdisc_drop(skb, sch, to_free);
422                 return NULL;
423         }
424         consume_skb(skb);
425         return segs;
426 }
427 
428 /*
429  * Insert one skb into qdisc.
430  * Note: parent depends on return value to account for queue length.
431  *      NET_XMIT_DROP: queue length didn't change.
432  *      NET_XMIT_SUCCESS: one skb was queued.
433  */
434 static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
435                          struct sk_buff **to_free)
436 {
437         struct netem_sched_data *q = qdisc_priv(sch);
438         /* We don't fill cb now as skb_unshare() may invalidate it */
439         struct netem_skb_cb *cb;
440         struct sk_buff *skb2;
441         struct sk_buff *segs = NULL;
442         unsigned int prev_len = qdisc_pkt_len(skb);
443         int count = 1;
444         int rc = NET_XMIT_SUCCESS;
445         int rc_drop = NET_XMIT_DROP;
446 
447         /* Do not fool qdisc_drop_all() */
448         skb->prev = NULL;
449 
450         /* Random duplication */
451         if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor))
452                 ++count;
453 
454         /* Drop packet? */
455         if (loss_event(q)) {
456                 if (q->ecn && INET_ECN_set_ce(skb))
457                         qdisc_qstats_drop(sch); /* mark packet */
458                 else
459                         --count;
460         }
461         if (count == 0) {
462                 qdisc_qstats_drop(sch);
463                 __qdisc_drop(skb, to_free);
464                 return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
465         }
466 
467         /* If a delay is expected, orphan the skb. (orphaning usually takes
468          * place at TX completion time, so _before_ the link transit delay)
469          */
470         if (q->latency || q->jitter || q->rate)
471                 skb_orphan_partial(skb);
472 
473         /*
474          * If we need to duplicate packet, then re-insert at top of the
475          * qdisc tree, since parent queuer expects that only one
476          * skb will be queued.
477          */
478         if (count > 1 && (skb2 = skb_clone(skb, GFP_ATOMIC)) != NULL) {
479                 struct Qdisc *rootq = qdisc_root_bh(sch);
480                 u32 dupsave = q->duplicate; /* prevent duplicating a dup... */
481 
482                 q->duplicate = 0;
483                 rootq->enqueue(skb2, rootq, to_free);
484                 q->duplicate = dupsave;
485                 rc_drop = NET_XMIT_SUCCESS;
486         }
487 
488         /*
489          * Randomized packet corruption.
490          * Make copy if needed since we are modifying
491          * If packet is going to be hardware checksummed, then
492          * do it now in software before we mangle it.
493          */
494         if (q->corrupt && q->corrupt >= get_crandom(&q->corrupt_cor)) {
495                 if (skb_is_gso(skb)) {
496                         skb = netem_segment(skb, sch, to_free);
497                         if (!skb)
498                                 return rc_drop;
499                         segs = skb->next;
500                         skb_mark_not_on_list(skb);
501                         qdisc_skb_cb(skb)->pkt_len = skb->len;
502                 }
503 
504                 skb = skb_unshare(skb, GFP_ATOMIC);
505                 if (unlikely(!skb)) {
506                         qdisc_qstats_drop(sch);
507                         goto finish_segs;
508                 }
509                 if (skb->ip_summed == CHECKSUM_PARTIAL &&
510                     skb_checksum_help(skb)) {
511                         qdisc_drop(skb, sch, to_free);
512                         skb = NULL;
513                         goto finish_segs;
514                 }
515 
516                 skb->data[prandom_u32() % skb_headlen(skb)] ^=
517                         1<<(prandom_u32() % 8);
518         }
519 
520         if (unlikely(sch->q.qlen >= sch->limit)) {
521                 /* re-link segs, so that qdisc_drop_all() frees them all */
522                 skb->next = segs;
523                 qdisc_drop_all(skb, sch, to_free);
524                 return rc_drop;
525         }
526 
527         qdisc_qstats_backlog_inc(sch, skb);
528 
529         cb = netem_skb_cb(skb);
530         if (q->gap == 0 ||              /* not doing reordering */
531             q->counter < q->gap - 1 ||  /* inside last reordering gap */
532             q->reorder < get_crandom(&q->reorder_cor)) {
533                 u64 now;
534                 s64 delay;
535 
536                 delay = tabledist(q->latency, q->jitter,
537                                   &q->delay_cor, q->delay_dist);
538 
539                 now = ktime_get_ns();
540 
541                 if (q->rate) {
542                         struct netem_skb_cb *last = NULL;
543 
544                         if (sch->q.tail)
545                                 last = netem_skb_cb(sch->q.tail);
546                         if (q->t_root.rb_node) {
547                                 struct sk_buff *t_skb;
548                                 struct netem_skb_cb *t_last;
549 
550                                 t_skb = skb_rb_last(&q->t_root);
551                                 t_last = netem_skb_cb(t_skb);
552                                 if (!last ||
553                                     t_last->time_to_send > last->time_to_send)
554                                         last = t_last;
555                         }
556                         if (q->t_tail) {
557                                 struct netem_skb_cb *t_last =
558                                         netem_skb_cb(q->t_tail);
559 
560                                 if (!last ||
561                                     t_last->time_to_send > last->time_to_send)
562                                         last = t_last;
563                         }
564 
565                         if (last) {
566                                 /*
567                                  * Last packet in queue is reference point (now),
568                                  * calculate this time bonus and subtract
569                                  * from delay.
570                                  */
571                                 delay -= last->time_to_send - now;
572                                 delay = max_t(s64, 0, delay);
573                                 now = last->time_to_send;
574                         }
575 
576                         delay += packet_time_ns(qdisc_pkt_len(skb), q);
577                 }
578 
579                 cb->time_to_send = now + delay;
580                 ++q->counter;
581                 tfifo_enqueue(skb, sch);
582         } else {
583                 /*
584                  * Do re-ordering by putting one out of N packets at the front
585                  * of the queue.
586                  */
587                 cb->time_to_send = ktime_get_ns();
588                 q->counter = 0;
589 
590                 __qdisc_enqueue_head(skb, &sch->q);
591                 sch->qstats.requeues++;
592         }
593 
594 finish_segs:
595         if (segs) {
596                 unsigned int len, last_len;
597                 int nb;
598 
599                 len = skb ? skb->len : 0;
600                 nb = skb ? 1 : 0;
601 
602                 while (segs) {
603                         skb2 = segs->next;
604                         skb_mark_not_on_list(segs);
605                         qdisc_skb_cb(segs)->pkt_len = segs->len;
606                         last_len = segs->len;
607                         rc = qdisc_enqueue(segs, sch, to_free);
608                         if (rc != NET_XMIT_SUCCESS) {
609                                 if (net_xmit_drop_count(rc))
610                                         qdisc_qstats_drop(sch);
611                         } else {
612                                 nb++;
613                                 len += last_len;
614                         }
615                         segs = skb2;
616                 }
617                 /* Parent qdiscs accounted for 1 skb of size @prev_len */
618                 qdisc_tree_reduce_backlog(sch, -(nb - 1), -(len - prev_len));
619         } else if (!skb) {
620                 return NET_XMIT_DROP;
621         }
622         return NET_XMIT_SUCCESS;
623 }
624 
625 /* Delay the next round with a new future slot with a
626  * correct number of bytes and packets.
627  */
628 
629 static void get_slot_next(struct netem_sched_data *q, u64 now)
630 {
631         s64 next_delay;
632 
633         if (!q->slot_dist)
634                 next_delay = q->slot_config.min_delay +
635                                 (prandom_u32() *
636                                  (q->slot_config.max_delay -
637                                   q->slot_config.min_delay) >> 32);
638         else
639                 next_delay = tabledist(q->slot_config.dist_delay,
640                                        (s32)(q->slot_config.dist_jitter),
641                                        NULL, q->slot_dist);
642 
643         q->slot.slot_next = now + next_delay;
644         q->slot.packets_left = q->slot_config.max_packets;
645         q->slot.bytes_left = q->slot_config.max_bytes;
646 }
647 
648 static struct sk_buff *netem_peek(struct netem_sched_data *q)
649 {
650         struct sk_buff *skb = skb_rb_first(&q->t_root);
651         u64 t1, t2;
652 
653         if (!skb)
654                 return q->t_head;
655         if (!q->t_head)
656                 return skb;
657 
658         t1 = netem_skb_cb(skb)->time_to_send;
659         t2 = netem_skb_cb(q->t_head)->time_to_send;
660         if (t1 < t2)
661                 return skb;
662         return q->t_head;
663 }
664 
665 static void netem_erase_head(struct netem_sched_data *q, struct sk_buff *skb)
666 {
667         if (skb == q->t_head) {
668                 q->t_head = skb->next;
669                 if (!q->t_head)
670                         q->t_tail = NULL;
671         } else {
672                 rb_erase(&skb->rbnode, &q->t_root);
673         }
674 }
675 
676 static struct sk_buff *netem_dequeue(struct Qdisc *sch)
677 {
678         struct netem_sched_data *q = qdisc_priv(sch);
679         struct sk_buff *skb;
680 
681 tfifo_dequeue:
682         skb = __qdisc_dequeue_head(&sch->q);
683         if (skb) {
684                 qdisc_qstats_backlog_dec(sch, skb);
685 deliver:
686                 qdisc_bstats_update(sch, skb);
687                 return skb;
688         }
689         skb = netem_peek(q);
690         if (skb) {
691                 u64 time_to_send;
692                 u64 now = ktime_get_ns();
693 
694                 /* if more time remaining? */
695                 time_to_send = netem_skb_cb(skb)->time_to_send;
696                 if (q->slot.slot_next && q->slot.slot_next < time_to_send)
697                         get_slot_next(q, now);
698 
699                 if (time_to_send <= now && q->slot.slot_next <= now) {
700                         netem_erase_head(q, skb);
701                         sch->q.qlen--;
702                         qdisc_qstats_backlog_dec(sch, skb);
703                         skb->next = NULL;
704                         skb->prev = NULL;
705                         /* skb->dev shares skb->rbnode area,
706                          * we need to restore its value.
707                          */
708                         skb->dev = qdisc_dev(sch);
709 
710                         if (q->slot.slot_next) {
711                                 q->slot.packets_left--;
712                                 q->slot.bytes_left -= qdisc_pkt_len(skb);
713                                 if (q->slot.packets_left <= 0 ||
714                                     q->slot.bytes_left <= 0)
715                                         get_slot_next(q, now);
716                         }
717 
718                         if (q->qdisc) {
719                                 unsigned int pkt_len = qdisc_pkt_len(skb);
720                                 struct sk_buff *to_free = NULL;
721                                 int err;
722 
723                                 err = qdisc_enqueue(skb, q->qdisc, &to_free);
724                                 kfree_skb_list(to_free);
725                                 if (err != NET_XMIT_SUCCESS &&
726                                     net_xmit_drop_count(err)) {
727                                         qdisc_qstats_drop(sch);
728                                         qdisc_tree_reduce_backlog(sch, 1,
729                                                                   pkt_len);
730                                 }
731                                 goto tfifo_dequeue;
732                         }
733                         goto deliver;
734                 }
735 
736                 if (q->qdisc) {
737                         skb = q->qdisc->ops->dequeue(q->qdisc);
738                         if (skb)
739                                 goto deliver;
740                 }
741 
742                 qdisc_watchdog_schedule_ns(&q->watchdog,
743                                            max(time_to_send,
744                                                q->slot.slot_next));
745         }
746 
747         if (q->qdisc) {
748                 skb = q->qdisc->ops->dequeue(q->qdisc);
749                 if (skb)
750                         goto deliver;
751         }
752         return NULL;
753 }
754 
755 static void netem_reset(struct Qdisc *sch)
756 {
757         struct netem_sched_data *q = qdisc_priv(sch);
758 
759         qdisc_reset_queue(sch);
760         tfifo_reset(sch);
761         if (q->qdisc)
762                 qdisc_reset(q->qdisc);
763         qdisc_watchdog_cancel(&q->watchdog);
764 }
765 
766 static void dist_free(struct disttable *d)
767 {
768         kvfree(d);
769 }
770 
771 /*
772  * Distribution data is a variable size payload containing
773  * signed 16 bit values.
774  */
775 
776 static int get_dist_table(struct Qdisc *sch, struct disttable **tbl,
777                           const struct nlattr *attr)
778 {
779         size_t n = nla_len(attr)/sizeof(__s16);
780         const __s16 *data = nla_data(attr);
781         spinlock_t *root_lock;
782         struct disttable *d;
783         int i;
784 
785         if (!n || n > NETEM_DIST_MAX)
786                 return -EINVAL;
787 
788         d = kvmalloc(sizeof(struct disttable) + n * sizeof(s16), GFP_KERNEL);
789         if (!d)
790                 return -ENOMEM;
791 
792         d->size = n;
793         for (i = 0; i < n; i++)
794                 d->table[i] = data[i];
795 
796         root_lock = qdisc_root_sleeping_lock(sch);
797 
798         spin_lock_bh(root_lock);
799         swap(*tbl, d);
800         spin_unlock_bh(root_lock);
801 
802         dist_free(d);
803         return 0;
804 }
805 
806 static void get_slot(struct netem_sched_data *q, const struct nlattr *attr)
807 {
808         const struct tc_netem_slot *c = nla_data(attr);
809 
810         q->slot_config = *c;
811         if (q->slot_config.max_packets == 0)
812                 q->slot_config.max_packets = INT_MAX;
813         if (q->slot_config.max_bytes == 0)
814                 q->slot_config.max_bytes = INT_MAX;
815         q->slot.packets_left = q->slot_config.max_packets;
816         q->slot.bytes_left = q->slot_config.max_bytes;
817         if (q->slot_config.min_delay | q->slot_config.max_delay |
818             q->slot_config.dist_jitter)
819                 q->slot.slot_next = ktime_get_ns();
820         else
821                 q->slot.slot_next = 0;
822 }
823 
824 static void get_correlation(struct netem_sched_data *q, const struct nlattr *attr)
825 {
826         const struct tc_netem_corr *c = nla_data(attr);
827 
828         init_crandom(&q->delay_cor, c->delay_corr);
829         init_crandom(&q->loss_cor, c->loss_corr);
830         init_crandom(&q->dup_cor, c->dup_corr);
831 }
832 
833 static void get_reorder(struct netem_sched_data *q, const struct nlattr *attr)
834 {
835         const struct tc_netem_reorder *r = nla_data(attr);
836 
837         q->reorder = r->probability;
838         init_crandom(&q->reorder_cor, r->correlation);
839 }
840 
841 static void get_corrupt(struct netem_sched_data *q, const struct nlattr *attr)
842 {
843         const struct tc_netem_corrupt *r = nla_data(attr);
844 
845         q->corrupt = r->probability;
846         init_crandom(&q->corrupt_cor, r->correlation);
847 }
848 
849 static void get_rate(struct netem_sched_data *q, const struct nlattr *attr)
850 {
851         const struct tc_netem_rate *r = nla_data(attr);
852 
853         q->rate = r->rate;
854         q->packet_overhead = r->packet_overhead;
855         q->cell_size = r->cell_size;
856         q->cell_overhead = r->cell_overhead;
857         if (q->cell_size)
858                 q->cell_size_reciprocal = reciprocal_value(q->cell_size);
859         else
860                 q->cell_size_reciprocal = (struct reciprocal_value) { 0 };
861 }
862 
863 static int get_loss_clg(struct netem_sched_data *q, const struct nlattr *attr)
864 {
865         const struct nlattr *la;
866         int rem;
867 
868         nla_for_each_nested(la, attr, rem) {
869                 u16 type = nla_type(la);
870 
871                 switch (type) {
872                 case NETEM_LOSS_GI: {
873                         const struct tc_netem_gimodel *gi = nla_data(la);
874 
875                         if (nla_len(la) < sizeof(struct tc_netem_gimodel)) {
876                                 pr_info("netem: incorrect gi model size\n");
877                                 return -EINVAL;
878                         }
879 
880                         q->loss_model = CLG_4_STATES;
881 
882                         q->clg.state = TX_IN_GAP_PERIOD;
883                         q->clg.a1 = gi->p13;
884                         q->clg.a2 = gi->p31;
885                         q->clg.a3 = gi->p32;
886                         q->clg.a4 = gi->p14;
887                         q->clg.a5 = gi->p23;
888                         break;
889                 }
890 
891                 case NETEM_LOSS_GE: {
892                         const struct tc_netem_gemodel *ge = nla_data(la);
893 
894                         if (nla_len(la) < sizeof(struct tc_netem_gemodel)) {
895                                 pr_info("netem: incorrect ge model size\n");
896                                 return -EINVAL;
897                         }
898 
899                         q->loss_model = CLG_GILB_ELL;
900                         q->clg.state = GOOD_STATE;
901                         q->clg.a1 = ge->p;
902                         q->clg.a2 = ge->r;
903                         q->clg.a3 = ge->h;
904                         q->clg.a4 = ge->k1;
905                         break;
906                 }
907 
908                 default:
909                         pr_info("netem: unknown loss type %u\n", type);
910                         return -EINVAL;
911                 }
912         }
913 
914         return 0;
915 }
916 
917 static const struct nla_policy netem_policy[TCA_NETEM_MAX + 1] = {
918         [TCA_NETEM_CORR]        = { .len = sizeof(struct tc_netem_corr) },
919         [TCA_NETEM_REORDER]     = { .len = sizeof(struct tc_netem_reorder) },
920         [TCA_NETEM_CORRUPT]     = { .len = sizeof(struct tc_netem_corrupt) },
921         [TCA_NETEM_RATE]        = { .len = sizeof(struct tc_netem_rate) },
922         [TCA_NETEM_LOSS]        = { .type = NLA_NESTED },
923         [TCA_NETEM_ECN]         = { .type = NLA_U32 },
924         [TCA_NETEM_RATE64]      = { .type = NLA_U64 },
925         [TCA_NETEM_LATENCY64]   = { .type = NLA_S64 },
926         [TCA_NETEM_JITTER64]    = { .type = NLA_S64 },
927         [TCA_NETEM_SLOT]        = { .len = sizeof(struct tc_netem_slot) },
928 };
929 
930 static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
931                       const struct nla_policy *policy, int len)
932 {
933         int nested_len = nla_len(nla) - NLA_ALIGN(len);
934 
935         if (nested_len < 0) {
936                 pr_info("netem: invalid attributes len %d\n", nested_len);
937                 return -EINVAL;
938         }
939 
940         if (nested_len >= nla_attr_size(0))
941                 return nla_parse_deprecated(tb, maxtype,
942                                             nla_data(nla) + NLA_ALIGN(len),
943                                             nested_len, policy, NULL);
944 
945         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
946         return 0;
947 }
948 
949 /* Parse netlink message to set options */
950 static int netem_change(struct Qdisc *sch, struct nlattr *opt,
951                         struct netlink_ext_ack *extack)
952 {
953         struct netem_sched_data *q = qdisc_priv(sch);
954         struct nlattr *tb[TCA_NETEM_MAX + 1];
955         struct tc_netem_qopt *qopt;
956         struct clgstate old_clg;
957         int old_loss_model = CLG_RANDOM;
958         int ret;
959 
960         if (opt == NULL)
961                 return -EINVAL;
962 
963         qopt = nla_data(opt);
964         ret = parse_attr(tb, TCA_NETEM_MAX, opt, netem_policy, sizeof(*qopt));
965         if (ret < 0)
966                 return ret;
967 
968         /* backup q->clg and q->loss_model */
969         old_clg = q->clg;
970         old_loss_model = q->loss_model;
971 
972         if (tb[TCA_NETEM_LOSS]) {
973                 ret = get_loss_clg(q, tb[TCA_NETEM_LOSS]);
974                 if (ret) {
975                         q->loss_model = old_loss_model;
976                         return ret;
977                 }
978         } else {
979                 q->loss_model = CLG_RANDOM;
980         }
981 
982         if (tb[TCA_NETEM_DELAY_DIST]) {
983                 ret = get_dist_table(sch, &q->delay_dist,
984                                      tb[TCA_NETEM_DELAY_DIST]);
985                 if (ret)
986                         goto get_table_failure;
987         }
988 
989         if (tb[TCA_NETEM_SLOT_DIST]) {
990                 ret = get_dist_table(sch, &q->slot_dist,
991                                      tb[TCA_NETEM_SLOT_DIST]);
992                 if (ret)
993                         goto get_table_failure;
994         }
995 
996         sch->limit = qopt->limit;
997 
998         q->latency = PSCHED_TICKS2NS(qopt->latency);
999         q->jitter = PSCHED_TICKS2NS(qopt->jitter);
1000         q->limit = qopt->limit;
1001         q->gap = qopt->gap;
1002         q->counter = 0;
1003         q->loss = qopt->loss;
1004         q->duplicate = qopt->duplicate;
1005 
1006         /* for compatibility with earlier versions.
1007          * if gap is set, need to assume 100% probability
1008          */
1009         if (q->gap)
1010                 q->reorder = ~0;
1011 
1012         if (tb[TCA_NETEM_CORR])
1013                 get_correlation(q, tb[TCA_NETEM_CORR]);
1014 
1015         if (tb[TCA_NETEM_REORDER])
1016                 get_reorder(q, tb[TCA_NETEM_REORDER]);
1017 
1018         if (tb[TCA_NETEM_CORRUPT])
1019                 get_corrupt(q, tb[TCA_NETEM_CORRUPT]);
1020 
1021         if (tb[TCA_NETEM_RATE])
1022                 get_rate(q, tb[TCA_NETEM_RATE]);
1023 
1024         if (tb[TCA_NETEM_RATE64])
1025                 q->rate = max_t(u64, q->rate,
1026                                 nla_get_u64(tb[TCA_NETEM_RATE64]));
1027 
1028         if (tb[TCA_NETEM_LATENCY64])
1029                 q->latency = nla_get_s64(tb[TCA_NETEM_LATENCY64]);
1030 
1031         if (tb[TCA_NETEM_JITTER64])
1032                 q->jitter = nla_get_s64(tb[TCA_NETEM_JITTER64]);
1033 
1034         if (tb[TCA_NETEM_ECN])
1035                 q->ecn = nla_get_u32(tb[TCA_NETEM_ECN]);
1036 
1037         if (tb[TCA_NETEM_SLOT])
1038                 get_slot(q, tb[TCA_NETEM_SLOT]);
1039 
1040         return ret;
1041 
1042 get_table_failure:
1043         /* recover clg and loss_model, in case of
1044          * q->clg and q->loss_model were modified
1045          * in get_loss_clg()
1046          */
1047         q->clg = old_clg;
1048         q->loss_model = old_loss_model;
1049         return ret;
1050 }
1051 
1052 static int netem_init(struct Qdisc *sch, struct nlattr *opt,
1053                       struct netlink_ext_ack *extack)
1054 {
1055         struct netem_sched_data *q = qdisc_priv(sch);
1056         int ret;
1057 
1058         qdisc_watchdog_init(&q->watchdog, sch);
1059 
1060         if (!opt)
1061                 return -EINVAL;
1062 
1063         q->loss_model = CLG_RANDOM;
1064         ret = netem_change(sch, opt, extack);
1065         if (ret)
1066                 pr_info("netem: change failed\n");
1067         return ret;
1068 }
1069 
1070 static void netem_destroy(struct Qdisc *sch)
1071 {
1072         struct netem_sched_data *q = qdisc_priv(sch);
1073 
1074         qdisc_watchdog_cancel(&q->watchdog);
1075         if (q->qdisc)
1076                 qdisc_put(q->qdisc);
1077         dist_free(q->delay_dist);
1078         dist_free(q->slot_dist);
1079 }
1080 
1081 static int dump_loss_model(const struct netem_sched_data *q,
1082                            struct sk_buff *skb)
1083 {
1084         struct nlattr *nest;
1085 
1086         nest = nla_nest_start_noflag(skb, TCA_NETEM_LOSS);
1087         if (nest == NULL)
1088                 goto nla_put_failure;
1089 
1090         switch (q->loss_model) {
1091         case CLG_RANDOM:
1092                 /* legacy loss model */
1093                 nla_nest_cancel(skb, nest);
1094                 return 0;       /* no data */
1095 
1096         case CLG_4_STATES: {
1097                 struct tc_netem_gimodel gi = {
1098                         .p13 = q->clg.a1,
1099                         .p31 = q->clg.a2,
1100                         .p32 = q->clg.a3,
1101                         .p14 = q->clg.a4,
1102                         .p23 = q->clg.a5,
1103                 };
1104 
1105                 if (nla_put(skb, NETEM_LOSS_GI, sizeof(gi), &gi))
1106                         goto nla_put_failure;
1107                 break;
1108         }
1109         case CLG_GILB_ELL: {
1110                 struct tc_netem_gemodel ge = {
1111                         .p = q->clg.a1,
1112                         .r = q->clg.a2,
1113                         .h = q->clg.a3,
1114                         .k1 = q->clg.a4,
1115                 };
1116 
1117                 if (nla_put(skb, NETEM_LOSS_GE, sizeof(ge), &ge))
1118                         goto nla_put_failure;
1119                 break;
1120         }
1121         }
1122 
1123         nla_nest_end(skb, nest);
1124         return 0;
1125 
1126 nla_put_failure:
1127         nla_nest_cancel(skb, nest);
1128         return -1;
1129 }
1130 
1131 static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
1132 {
1133         const struct netem_sched_data *q = qdisc_priv(sch);
1134         struct nlattr *nla = (struct nlattr *) skb_tail_pointer(skb);
1135         struct tc_netem_qopt qopt;
1136         struct tc_netem_corr cor;
1137         struct tc_netem_reorder reorder;
1138         struct tc_netem_corrupt corrupt;
1139         struct tc_netem_rate rate;
1140         struct tc_netem_slot slot;
1141 
1142         qopt.latency = min_t(psched_tdiff_t, PSCHED_NS2TICKS(q->latency),
1143                              UINT_MAX);
1144         qopt.jitter = min_t(psched_tdiff_t, PSCHED_NS2TICKS(q->jitter),
1145                             UINT_MAX);
1146         qopt.limit = q->limit;
1147         qopt.loss = q->loss;
1148         qopt.gap = q->gap;
1149         qopt.duplicate = q->duplicate;
1150         if (nla_put(skb, TCA_OPTIONS, sizeof(qopt), &qopt))
1151                 goto nla_put_failure;
1152 
1153         if (nla_put(skb, TCA_NETEM_LATENCY64, sizeof(q->latency), &q->latency))
1154                 goto nla_put_failure;
1155 
1156         if (nla_put(skb, TCA_NETEM_JITTER64, sizeof(q->jitter), &q->jitter))
1157                 goto nla_put_failure;
1158 
1159         cor.delay_corr = q->delay_cor.rho;
1160         cor.loss_corr = q->loss_cor.rho;
1161         cor.dup_corr = q->dup_cor.rho;
1162         if (nla_put(skb, TCA_NETEM_CORR, sizeof(cor), &cor))
1163                 goto nla_put_failure;
1164 
1165         reorder.probability = q->reorder;
1166         reorder.correlation = q->reorder_cor.rho;
1167         if (nla_put(skb, TCA_NETEM_REORDER, sizeof(reorder), &reorder))
1168                 goto nla_put_failure;
1169 
1170         corrupt.probability = q->corrupt;
1171         corrupt.correlation = q->corrupt_cor.rho;
1172         if (nla_put(skb, TCA_NETEM_CORRUPT, sizeof(corrupt), &corrupt))
1173                 goto nla_put_failure;
1174 
1175         if (q->rate >= (1ULL << 32)) {
1176                 if (nla_put_u64_64bit(skb, TCA_NETEM_RATE64, q->rate,
1177                                       TCA_NETEM_PAD))
1178                         goto nla_put_failure;
1179                 rate.rate = ~0U;
1180         } else {
1181                 rate.rate = q->rate;
1182         }
1183         rate.packet_overhead = q->packet_overhead;
1184         rate.cell_size = q->cell_size;
1185         rate.cell_overhead = q->cell_overhead;
1186         if (nla_put(skb, TCA_NETEM_RATE, sizeof(rate), &rate))
1187                 goto nla_put_failure;
1188 
1189         if (q->ecn && nla_put_u32(skb, TCA_NETEM_ECN, q->ecn))
1190                 goto nla_put_failure;
1191 
1192         if (dump_loss_model(q, skb) != 0)
1193                 goto nla_put_failure;
1194 
1195         if (q->slot_config.min_delay | q->slot_config.max_delay |
1196             q->slot_config.dist_jitter) {
1197                 slot = q->slot_config;
1198                 if (slot.max_packets == INT_MAX)
1199                         slot.max_packets = 0;
1200                 if (slot.max_bytes == INT_MAX)
1201                         slot.max_bytes = 0;
1202                 if (nla_put(skb, TCA_NETEM_SLOT, sizeof(slot), &slot))
1203                         goto nla_put_failure;
1204         }
1205 
1206         return nla_nest_end(skb, nla);
1207 
1208 nla_put_failure:
1209         nlmsg_trim(skb, nla);
1210         return -1;
1211 }
1212 
1213 static int netem_dump_class(struct Qdisc *sch, unsigned long cl,
1214                           struct sk_buff *skb, struct tcmsg *tcm)
1215 {
1216         struct netem_sched_data *q = qdisc_priv(sch);
1217 
1218         if (cl != 1 || !q->qdisc)       /* only one class */
1219                 return -ENOENT;
1220 
1221         tcm->tcm_handle |= TC_H_MIN(1);
1222         tcm->tcm_info = q->qdisc->handle;
1223 
1224         return 0;
1225 }
1226 
1227 static int netem_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
1228                      struct Qdisc **old, struct netlink_ext_ack *extack)
1229 {
1230         struct netem_sched_data *q = qdisc_priv(sch);
1231 
1232         *old = qdisc_replace(sch, new, &q->qdisc);
1233         return 0;
1234 }
1235 
1236 static struct Qdisc *netem_leaf(struct Qdisc *sch, unsigned long arg)
1237 {
1238         struct netem_sched_data *q = qdisc_priv(sch);
1239         return q->qdisc;
1240 }
1241 
1242 static unsigned long netem_find(struct Qdisc *sch, u32 classid)
1243 {
1244         return 1;
1245 }
1246 
1247 static void netem_walk(struct Qdisc *sch, struct qdisc_walker *walker)
1248 {
1249         if (!walker->stop) {
1250                 if (walker->count >= walker->skip)
1251                         if (walker->fn(sch, 1, walker) < 0) {
1252                                 walker->stop = 1;
1253                                 return;
1254                         }
1255                 walker->count++;
1256         }
1257 }
1258 
1259 static const struct Qdisc_class_ops netem_class_ops = {
1260         .graft          =       netem_graft,
1261         .leaf           =       netem_leaf,
1262         .find           =       netem_find,
1263         .walk           =       netem_walk,
1264         .dump           =       netem_dump_class,
1265 };
1266 
1267 static struct Qdisc_ops netem_qdisc_ops __read_mostly = {
1268         .id             =       "netem",
1269         .cl_ops         =       &netem_class_ops,
1270         .priv_size      =       sizeof(struct netem_sched_data),
1271         .enqueue        =       netem_enqueue,
1272         .dequeue        =       netem_dequeue,
1273         .peek           =       qdisc_peek_dequeued,
1274         .init           =       netem_init,
1275         .reset          =       netem_reset,
1276         .destroy        =       netem_destroy,
1277         .change         =       netem_change,
1278         .dump           =       netem_dump,
1279         .owner          =       THIS_MODULE,
1280 };
1281 
1282 
1283 static int __init netem_module_init(void)
1284 {
1285         pr_info("netem: version " VERSION "\n");
1286         return register_qdisc(&netem_qdisc_ops);
1287 }
1288 static void __exit netem_module_exit(void)
1289 {
1290         unregister_qdisc(&netem_qdisc_ops);
1291 }
1292 module_init(netem_module_init)
1293 module_exit(netem_module_exit)
1294 MODULE_LICENSE("GPL");
1295 

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