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sch_gred.c
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1 /*
2  * net/sched/sch_gred.c Generic Random Early Detection queue.
3  *
4  *
5  * This program is free software; you can redistribute it and/or
6  * modify it under the terms of the GNU General Public License
7  * as published by the Free Software Foundation; either version
8  * 2 of the License, or (at your option) any later version.
9  *
10  * Authors: J Hadi Salim ([email protected]) 1998-2002
11  *
12  * 991129: - Bug fix with grio mode
13  * - a better sing. AvgQ mode with Grio(WRED)
14  * - A finer grained VQ dequeue based on sugestion
15  * from Ren Liu
16  * - More error checks
17  *
18  * For all the glorious comments look at include/net/red.h
19  */
20 
21 #include <linux/slab.h>
22 #include <linux/module.h>
23 #include <linux/types.h>
24 #include <linux/kernel.h>
25 #include <linux/skbuff.h>
26 #include <net/pkt_sched.h>
27 #include <net/red.h>
28 
29 #define GRED_DEF_PRIO (MAX_DPs / 2)
30 #define GRED_VQ_MASK (MAX_DPs - 1)
31 
32 struct gred_sched_data;
33 struct gred_sched;
34 
35 struct gred_sched_data {
36  u32 limit; /* HARD maximal queue length */
37  u32 DP; /* the drop parameters */
38  u32 bytesin; /* bytes seen on virtualQ so far*/
39  u32 packetsin; /* packets seen on virtualQ so far*/
40  u32 backlog; /* bytes on the virtualQ */
41  u8 prio; /* the prio of this vq */
42 
43  struct red_parms parms;
44  struct red_vars vars;
45  struct red_stats stats;
46 };
47 
48 enum {
49  GRED_WRED_MODE = 1,
50  GRED_RIO_MODE,
51 };
52 
53 struct gred_sched {
54  struct gred_sched_data *tab[MAX_DPs];
55  unsigned long flags;
56  u32 red_flags;
57  u32 DPs;
58  u32 def;
59  struct red_vars wred_set;
60 };
61 
62 static inline int gred_wred_mode(struct gred_sched *table)
63 {
64  return test_bit(GRED_WRED_MODE, &table->flags);
65 }
66 
67 static inline void gred_enable_wred_mode(struct gred_sched *table)
68 {
69  __set_bit(GRED_WRED_MODE, &table->flags);
70 }
71 
72 static inline void gred_disable_wred_mode(struct gred_sched *table)
73 {
74  __clear_bit(GRED_WRED_MODE, &table->flags);
75 }
76 
77 static inline int gred_rio_mode(struct gred_sched *table)
78 {
79  return test_bit(GRED_RIO_MODE, &table->flags);
80 }
81 
82 static inline void gred_enable_rio_mode(struct gred_sched *table)
83 {
84  __set_bit(GRED_RIO_MODE, &table->flags);
85 }
86 
87 static inline void gred_disable_rio_mode(struct gred_sched *table)
88 {
89  __clear_bit(GRED_RIO_MODE, &table->flags);
90 }
91 
92 static inline int gred_wred_mode_check(struct Qdisc *sch)
93 {
94  struct gred_sched *table = qdisc_priv(sch);
95  int i;
96 
97  /* Really ugly O(n^2) but shouldn't be necessary too frequent. */
98  for (i = 0; i < table->DPs; i++) {
99  struct gred_sched_data *q = table->tab[i];
100  int n;
101 
102  if (q == NULL)
103  continue;
104 
105  for (n = i + 1; n < table->DPs; n++)
106  if (table->tab[n] && table->tab[n]->prio == q->prio)
107  return 1;
108  }
109 
110  return 0;
111 }
112 
113 static inline unsigned int gred_backlog(struct gred_sched *table,
114  struct gred_sched_data *q,
115  struct Qdisc *sch)
116 {
117  if (gred_wred_mode(table))
118  return sch->qstats.backlog;
119  else
120  return q->backlog;
121 }
122 
123 static inline u16 tc_index_to_dp(struct sk_buff *skb)
124 {
125  return skb->tc_index & GRED_VQ_MASK;
126 }
127 
128 static inline void gred_load_wred_set(const struct gred_sched *table,
129  struct gred_sched_data *q)
130 {
131  q->vars.qavg = table->wred_set.qavg;
132  q->vars.qidlestart = table->wred_set.qidlestart;
133 }
134 
135 static inline void gred_store_wred_set(struct gred_sched *table,
136  struct gred_sched_data *q)
137 {
138  table->wred_set.qavg = q->vars.qavg;
139  table->wred_set.qidlestart = q->vars.qidlestart;
140 }
141 
142 static inline int gred_use_ecn(struct gred_sched *t)
143 {
144  return t->red_flags & TC_RED_ECN;
145 }
146 
147 static inline int gred_use_harddrop(struct gred_sched *t)
148 {
149  return t->red_flags & TC_RED_HARDDROP;
150 }
151 
152 static int gred_enqueue(struct sk_buff *skb, struct Qdisc *sch)
153 {
154  struct gred_sched_data *q = NULL;
155  struct gred_sched *t = qdisc_priv(sch);
156  unsigned long qavg = 0;
157  u16 dp = tc_index_to_dp(skb);
158 
159  if (dp >= t->DPs || (q = t->tab[dp]) == NULL) {
160  dp = t->def;
161 
162  q = t->tab[dp];
163  if (!q) {
164  /* Pass through packets not assigned to a DP
165  * if no default DP has been configured. This
166  * allows for DP flows to be left untouched.
167  */
168  if (skb_queue_len(&sch->q) < qdisc_dev(sch)->tx_queue_len)
169  return qdisc_enqueue_tail(skb, sch);
170  else
171  goto drop;
172  }
173 
174  /* fix tc_index? --could be controversial but needed for
175  requeueing */
176  skb->tc_index = (skb->tc_index & ~GRED_VQ_MASK) | dp;
177  }
178 
179  /* sum up all the qaves of prios < ours to get the new qave */
180  if (!gred_wred_mode(t) && gred_rio_mode(t)) {
181  int i;
182 
183  for (i = 0; i < t->DPs; i++) {
184  if (t->tab[i] && t->tab[i]->prio < q->prio &&
185  !red_is_idling(&t->tab[i]->vars))
186  qavg += t->tab[i]->vars.qavg;
187  }
188 
189  }
190 
191  q->packetsin++;
192  q->bytesin += qdisc_pkt_len(skb);
193 
194  if (gred_wred_mode(t))
195  gred_load_wred_set(t, q);
196 
197  q->vars.qavg = red_calc_qavg(&q->parms,
198  &q->vars,
199  gred_backlog(t, q, sch));
200 
201  if (red_is_idling(&q->vars))
202  red_end_of_idle_period(&q->vars);
203 
204  if (gred_wred_mode(t))
205  gred_store_wred_set(t, q);
206 
207  switch (red_action(&q->parms, &q->vars, q->vars.qavg + qavg)) {
208  case RED_DONT_MARK:
209  break;
210 
211  case RED_PROB_MARK:
212  sch->qstats.overlimits++;
213  if (!gred_use_ecn(t) || !INET_ECN_set_ce(skb)) {
214  q->stats.prob_drop++;
215  goto congestion_drop;
216  }
217 
218  q->stats.prob_mark++;
219  break;
220 
221  case RED_HARD_MARK:
222  sch->qstats.overlimits++;
223  if (gred_use_harddrop(t) || !gred_use_ecn(t) ||
224  !INET_ECN_set_ce(skb)) {
225  q->stats.forced_drop++;
226  goto congestion_drop;
227  }
228  q->stats.forced_mark++;
229  break;
230  }
231 
232  if (q->backlog + qdisc_pkt_len(skb) <= q->limit) {
233  q->backlog += qdisc_pkt_len(skb);
234  return qdisc_enqueue_tail(skb, sch);
235  }
236 
237  q->stats.pdrop++;
238 drop:
239  return qdisc_drop(skb, sch);
240 
241 congestion_drop:
242  qdisc_drop(skb, sch);
243  return NET_XMIT_CN;
244 }
245 
246 static struct sk_buff *gred_dequeue(struct Qdisc *sch)
247 {
248  struct sk_buff *skb;
249  struct gred_sched *t = qdisc_priv(sch);
250 
251  skb = qdisc_dequeue_head(sch);
252 
253  if (skb) {
254  struct gred_sched_data *q;
255  u16 dp = tc_index_to_dp(skb);
256 
257  if (dp >= t->DPs || (q = t->tab[dp]) == NULL) {
258  net_warn_ratelimited("GRED: Unable to relocate VQ 0x%x after dequeue, screwing up backlog\n",
259  tc_index_to_dp(skb));
260  } else {
261  q->backlog -= qdisc_pkt_len(skb);
262 
263  if (gred_wred_mode(t)) {
264  if (!sch->qstats.backlog)
265  red_start_of_idle_period(&t->wred_set);
266  } else {
267  if (!q->backlog)
268  red_start_of_idle_period(&q->vars);
269  }
270  }
271 
272  return skb;
273  }
274 
275  return NULL;
276 }
277 
278 static unsigned int gred_drop(struct Qdisc *sch)
279 {
280  struct sk_buff *skb;
281  struct gred_sched *t = qdisc_priv(sch);
282 
283  skb = qdisc_dequeue_tail(sch);
284  if (skb) {
285  unsigned int len = qdisc_pkt_len(skb);
286  struct gred_sched_data *q;
287  u16 dp = tc_index_to_dp(skb);
288 
289  if (dp >= t->DPs || (q = t->tab[dp]) == NULL) {
290  net_warn_ratelimited("GRED: Unable to relocate VQ 0x%x while dropping, screwing up backlog\n",
291  tc_index_to_dp(skb));
292  } else {
293  q->backlog -= len;
294  q->stats.other++;
295 
296  if (gred_wred_mode(t)) {
297  if (!sch->qstats.backlog)
298  red_start_of_idle_period(&t->wred_set);
299  } else {
300  if (!q->backlog)
301  red_start_of_idle_period(&q->vars);
302  }
303  }
304 
305  qdisc_drop(skb, sch);
306  return len;
307  }
308 
309  return 0;
310 }
311 
312 static void gred_reset(struct Qdisc *sch)
313 {
314  int i;
315  struct gred_sched *t = qdisc_priv(sch);
316 
317  qdisc_reset_queue(sch);
318 
319  for (i = 0; i < t->DPs; i++) {
320  struct gred_sched_data *q = t->tab[i];
321 
322  if (!q)
323  continue;
324 
325  red_restart(&q->vars);
326  q->backlog = 0;
327  }
328 }
329 
330 static inline void gred_destroy_vq(struct gred_sched_data *q)
331 {
332  kfree(q);
333 }
334 
335 static inline int gred_change_table_def(struct Qdisc *sch, struct nlattr *dps)
336 {
337  struct gred_sched *table = qdisc_priv(sch);
338  struct tc_gred_sopt *sopt;
339  int i;
340 
341  if (dps == NULL)
342  return -EINVAL;
343 
344  sopt = nla_data(dps);
345 
346  if (sopt->DPs > MAX_DPs || sopt->DPs == 0 || sopt->def_DP >= sopt->DPs)
347  return -EINVAL;
348 
349  sch_tree_lock(sch);
350  table->DPs = sopt->DPs;
351  table->def = sopt->def_DP;
352  table->red_flags = sopt->flags;
353 
354  /*
355  * Every entry point to GRED is synchronized with the above code
356  * and the DP is checked against DPs, i.e. shadowed VQs can no
357  * longer be found so we can unlock right here.
358  */
359  sch_tree_unlock(sch);
360 
361  if (sopt->grio) {
362  gred_enable_rio_mode(table);
363  gred_disable_wred_mode(table);
364  if (gred_wred_mode_check(sch))
365  gred_enable_wred_mode(table);
366  } else {
367  gred_disable_rio_mode(table);
368  gred_disable_wred_mode(table);
369  }
370 
371  for (i = table->DPs; i < MAX_DPs; i++) {
372  if (table->tab[i]) {
373  pr_warning("GRED: Warning: Destroying "
374  "shadowed VQ 0x%x\n", i);
375  gred_destroy_vq(table->tab[i]);
376  table->tab[i] = NULL;
377  }
378  }
379 
380  return 0;
381 }
382 
383 static inline int gred_change_vq(struct Qdisc *sch, int dp,
384  struct tc_gred_qopt *ctl, int prio,
385  u8 *stab, u32 max_P,
386  struct gred_sched_data **prealloc)
387 {
388  struct gred_sched *table = qdisc_priv(sch);
389  struct gred_sched_data *q = table->tab[dp];
390 
391  if (!q) {
392  table->tab[dp] = q = *prealloc;
393  *prealloc = NULL;
394  if (!q)
395  return -ENOMEM;
396  }
397 
398  q->DP = dp;
399  q->prio = prio;
400  q->limit = ctl->limit;
401 
402  if (q->backlog == 0)
403  red_end_of_idle_period(&q->vars);
404 
405  red_set_parms(&q->parms,
406  ctl->qth_min, ctl->qth_max, ctl->Wlog, ctl->Plog,
407  ctl->Scell_log, stab, max_P);
408  red_set_vars(&q->vars);
409  return 0;
410 }
411 
412 static const struct nla_policy gred_policy[TCA_GRED_MAX + 1] = {
413  [TCA_GRED_PARMS] = { .len = sizeof(struct tc_gred_qopt) },
414  [TCA_GRED_STAB] = { .len = 256 },
415  [TCA_GRED_DPS] = { .len = sizeof(struct tc_gred_sopt) },
416  [TCA_GRED_MAX_P] = { .type = NLA_U32 },
417 };
418 
419 static int gred_change(struct Qdisc *sch, struct nlattr *opt)
420 {
421  struct gred_sched *table = qdisc_priv(sch);
422  struct tc_gred_qopt *ctl;
423  struct nlattr *tb[TCA_GRED_MAX + 1];
424  int err, prio = GRED_DEF_PRIO;
425  u8 *stab;
426  u32 max_P;
427  struct gred_sched_data *prealloc;
428 
429  if (opt == NULL)
430  return -EINVAL;
431 
432  err = nla_parse_nested(tb, TCA_GRED_MAX, opt, gred_policy);
433  if (err < 0)
434  return err;
435 
436  if (tb[TCA_GRED_PARMS] == NULL && tb[TCA_GRED_STAB] == NULL)
437  return gred_change_table_def(sch, opt);
438 
439  if (tb[TCA_GRED_PARMS] == NULL ||
440  tb[TCA_GRED_STAB] == NULL)
441  return -EINVAL;
442 
443  max_P = tb[TCA_GRED_MAX_P] ? nla_get_u32(tb[TCA_GRED_MAX_P]) : 0;
444 
445  err = -EINVAL;
446  ctl = nla_data(tb[TCA_GRED_PARMS]);
447  stab = nla_data(tb[TCA_GRED_STAB]);
448 
449  if (ctl->DP >= table->DPs)
450  goto errout;
451 
452  if (gred_rio_mode(table)) {
453  if (ctl->prio == 0) {
454  int def_prio = GRED_DEF_PRIO;
455 
456  if (table->tab[table->def])
457  def_prio = table->tab[table->def]->prio;
458 
459  printk(KERN_DEBUG "GRED: DP %u does not have a prio "
460  "setting default to %d\n", ctl->DP, def_prio);
461 
462  prio = def_prio;
463  } else
464  prio = ctl->prio;
465  }
466 
467  prealloc = kzalloc(sizeof(*prealloc), GFP_KERNEL);
468  sch_tree_lock(sch);
469 
470  err = gred_change_vq(sch, ctl->DP, ctl, prio, stab, max_P, &prealloc);
471  if (err < 0)
472  goto errout_locked;
473 
474  if (gred_rio_mode(table)) {
475  gred_disable_wred_mode(table);
476  if (gred_wred_mode_check(sch))
477  gred_enable_wred_mode(table);
478  }
479 
480  err = 0;
481 
482 errout_locked:
483  sch_tree_unlock(sch);
484  kfree(prealloc);
485 errout:
486  return err;
487 }
488 
489 static int gred_init(struct Qdisc *sch, struct nlattr *opt)
490 {
491  struct nlattr *tb[TCA_GRED_MAX + 1];
492  int err;
493 
494  if (opt == NULL)
495  return -EINVAL;
496 
497  err = nla_parse_nested(tb, TCA_GRED_MAX, opt, gred_policy);
498  if (err < 0)
499  return err;
500 
501  if (tb[TCA_GRED_PARMS] || tb[TCA_GRED_STAB])
502  return -EINVAL;
503 
504  return gred_change_table_def(sch, tb[TCA_GRED_DPS]);
505 }
506 
507 static int gred_dump(struct Qdisc *sch, struct sk_buff *skb)
508 {
509  struct gred_sched *table = qdisc_priv(sch);
510  struct nlattr *parms, *opts = NULL;
511  int i;
512  u32 max_p[MAX_DPs];
513  struct tc_gred_sopt sopt = {
514  .DPs = table->DPs,
515  .def_DP = table->def,
516  .grio = gred_rio_mode(table),
517  .flags = table->red_flags,
518  };
519 
520  opts = nla_nest_start(skb, TCA_OPTIONS);
521  if (opts == NULL)
522  goto nla_put_failure;
523  if (nla_put(skb, TCA_GRED_DPS, sizeof(sopt), &sopt))
524  goto nla_put_failure;
525 
526  for (i = 0; i < MAX_DPs; i++) {
527  struct gred_sched_data *q = table->tab[i];
528 
529  max_p[i] = q ? q->parms.max_P : 0;
530  }
531  if (nla_put(skb, TCA_GRED_MAX_P, sizeof(max_p), max_p))
532  goto nla_put_failure;
533 
534  parms = nla_nest_start(skb, TCA_GRED_PARMS);
535  if (parms == NULL)
536  goto nla_put_failure;
537 
538  for (i = 0; i < MAX_DPs; i++) {
539  struct gred_sched_data *q = table->tab[i];
540  struct tc_gred_qopt opt;
541  unsigned long qavg;
542 
543  memset(&opt, 0, sizeof(opt));
544 
545  if (!q) {
546  /* hack -- fix at some point with proper message
547  This is how we indicate to tc that there is no VQ
548  at this DP */
549 
550  opt.DP = MAX_DPs + i;
551  goto append_opt;
552  }
553 
554  opt.limit = q->limit;
555  opt.DP = q->DP;
556  opt.backlog = q->backlog;
557  opt.prio = q->prio;
558  opt.qth_min = q->parms.qth_min >> q->parms.Wlog;
559  opt.qth_max = q->parms.qth_max >> q->parms.Wlog;
560  opt.Wlog = q->parms.Wlog;
561  opt.Plog = q->parms.Plog;
562  opt.Scell_log = q->parms.Scell_log;
563  opt.other = q->stats.other;
564  opt.early = q->stats.prob_drop;
565  opt.forced = q->stats.forced_drop;
566  opt.pdrop = q->stats.pdrop;
567  opt.packets = q->packetsin;
568  opt.bytesin = q->bytesin;
569 
570  if (gred_wred_mode(table))
571  gred_load_wred_set(table, q);
572 
573  qavg = red_calc_qavg(&q->parms, &q->vars,
574  q->vars.qavg >> q->parms.Wlog);
575  opt.qave = qavg >> q->parms.Wlog;
576 
577 append_opt:
578  if (nla_append(skb, sizeof(opt), &opt) < 0)
579  goto nla_put_failure;
580  }
581 
582  nla_nest_end(skb, parms);
583 
584  return nla_nest_end(skb, opts);
585 
586 nla_put_failure:
587  nla_nest_cancel(skb, opts);
588  return -EMSGSIZE;
589 }
590 
591 static void gred_destroy(struct Qdisc *sch)
592 {
593  struct gred_sched *table = qdisc_priv(sch);
594  int i;
595 
596  for (i = 0; i < table->DPs; i++) {
597  if (table->tab[i])
598  gred_destroy_vq(table->tab[i]);
599  }
600 }
601 
602 static struct Qdisc_ops gred_qdisc_ops __read_mostly = {
603  .id = "gred",
604  .priv_size = sizeof(struct gred_sched),
605  .enqueue = gred_enqueue,
606  .dequeue = gred_dequeue,
607  .peek = qdisc_peek_head,
608  .drop = gred_drop,
609  .init = gred_init,
610  .reset = gred_reset,
611  .destroy = gred_destroy,
612  .change = gred_change,
613  .dump = gred_dump,
614  .owner = THIS_MODULE,
615 };
616 
617 static int __init gred_module_init(void)
618 {
619  return register_qdisc(&gred_qdisc_ops);
620 }
621 
622 static void __exit gred_module_exit(void)
623 {
624  unregister_qdisc(&gred_qdisc_ops);
625 }
626 
627 module_init(gred_module_init)
628 module_exit(gred_module_exit)
629 
630 MODULE_LICENSE("GPL");
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