xref: /openbmc/linux/net/sched/sch_gred.c (revision e23feb16) 
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