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Linux/net/sched/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 (hadi@cyberus.ca) 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");
631 

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