xref: /openbmc/linux/net/sched/sch_gred.c (revision 2572f00d) 
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 (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <=
169 					sch->limit))
170 				return qdisc_enqueue_tail(skb, sch);
171 			else
172 				goto drop;
173 		}
174 
175 		/* fix tc_index? --could be controversial but needed for
176 		   requeueing */
177 		skb->tc_index = (skb->tc_index & ~GRED_VQ_MASK) | dp;
178 	}
179 
180 	/* sum up all the qaves of prios < ours to get the new qave */
181 	if (!gred_wred_mode(t) && gred_rio_mode(t)) {
182 		int i;
183 
184 		for (i = 0; i < t->DPs; i++) {
185 			if (t->tab[i] && t->tab[i]->prio < q->prio &&
186 			    !red_is_idling(&t->tab[i]->vars))
187 				qavg += t->tab[i]->vars.qavg;
188 		}
189 
190 	}
191 
192 	q->packetsin++;
193 	q->bytesin += qdisc_pkt_len(skb);
194 
195 	if (gred_wred_mode(t))
196 		gred_load_wred_set(t, q);
197 
198 	q->vars.qavg = red_calc_qavg(&q->parms,
199 				     &q->vars,
200 				     gred_backlog(t, q, sch));
201 
202 	if (red_is_idling(&q->vars))
203 		red_end_of_idle_period(&q->vars);
204 
205 	if (gred_wred_mode(t))
206 		gred_store_wred_set(t, q);
207 
208 	switch (red_action(&q->parms, &q->vars, q->vars.qavg + qavg)) {
209 	case RED_DONT_MARK:
210 		break;
211 
212 	case RED_PROB_MARK:
213 		qdisc_qstats_overlimit(sch);
214 		if (!gred_use_ecn(t) || !INET_ECN_set_ce(skb)) {
215 			q->stats.prob_drop++;
216 			goto congestion_drop;
217 		}
218 
219 		q->stats.prob_mark++;
220 		break;
221 
222 	case RED_HARD_MARK:
223 		qdisc_qstats_overlimit(sch);
224 		if (gred_use_harddrop(t) || !gred_use_ecn(t) ||
225 		    !INET_ECN_set_ce(skb)) {
226 			q->stats.forced_drop++;
227 			goto congestion_drop;
228 		}
229 		q->stats.forced_mark++;
230 		break;
231 	}
232 
233 	if (gred_backlog(t, q, sch) + qdisc_pkt_len(skb) <= q->limit) {
234 		q->backlog += qdisc_pkt_len(skb);
235 		return qdisc_enqueue_tail(skb, sch);
236 	}
237 
238 	q->stats.pdrop++;
239 drop:
240 	return qdisc_drop(skb, sch);
241 
242 congestion_drop:
243 	qdisc_drop(skb, sch);
244 	return NET_XMIT_CN;
245 }
246 
247 static struct sk_buff *gred_dequeue(struct Qdisc *sch)
248 {
249 	struct sk_buff *skb;
250 	struct gred_sched *t = qdisc_priv(sch);
251 
252 	skb = qdisc_dequeue_head(sch);
253 
254 	if (skb) {
255 		struct gred_sched_data *q;
256 		u16 dp = tc_index_to_dp(skb);
257 
258 		if (dp >= t->DPs || (q = t->tab[dp]) == NULL) {
259 			net_warn_ratelimited("GRED: Unable to relocate VQ 0x%x after dequeue, screwing up backlog\n",
260 					     tc_index_to_dp(skb));
261 		} else {
262 			q->backlog -= qdisc_pkt_len(skb);
263 
264 			if (gred_wred_mode(t)) {
265 				if (!sch->qstats.backlog)
266 					red_start_of_idle_period(&t->wred_set);
267 			} else {
268 				if (!q->backlog)
269 					red_start_of_idle_period(&q->vars);
270 			}
271 		}
272 
273 		return skb;
274 	}
275 
276 	return NULL;
277 }
278 
279 static unsigned int gred_drop(struct Qdisc *sch)
280 {
281 	struct sk_buff *skb;
282 	struct gred_sched *t = qdisc_priv(sch);
283 
284 	skb = qdisc_dequeue_tail(sch);
285 	if (skb) {
286 		unsigned int len = qdisc_pkt_len(skb);
287 		struct gred_sched_data *q;
288 		u16 dp = tc_index_to_dp(skb);
289 
290 		if (dp >= t->DPs || (q = t->tab[dp]) == NULL) {
291 			net_warn_ratelimited("GRED: Unable to relocate VQ 0x%x while dropping, screwing up backlog\n",
292 					     tc_index_to_dp(skb));
293 		} else {
294 			q->backlog -= len;
295 			q->stats.other++;
296 
297 			if (gred_wred_mode(t)) {
298 				if (!sch->qstats.backlog)
299 					red_start_of_idle_period(&t->wred_set);
300 			} else {
301 				if (!q->backlog)
302 					red_start_of_idle_period(&q->vars);
303 			}
304 		}
305 
306 		qdisc_drop(skb, sch);
307 		return len;
308 	}
309 
310 	return 0;
311 }
312 
313 static void gred_reset(struct Qdisc *sch)
314 {
315 	int i;
316 	struct gred_sched *t = qdisc_priv(sch);
317 
318 	qdisc_reset_queue(sch);
319 
320 	for (i = 0; i < t->DPs; i++) {
321 		struct gred_sched_data *q = t->tab[i];
322 
323 		if (!q)
324 			continue;
325 
326 		red_restart(&q->vars);
327 		q->backlog = 0;
328 	}
329 }
330 
331 static inline void gred_destroy_vq(struct gred_sched_data *q)
332 {
333 	kfree(q);
334 }
335 
336 static inline int gred_change_table_def(struct Qdisc *sch, struct nlattr *dps)
337 {
338 	struct gred_sched *table = qdisc_priv(sch);
339 	struct tc_gred_sopt *sopt;
340 	int i;
341 
342 	if (dps == NULL)
343 		return -EINVAL;
344 
345 	sopt = nla_data(dps);
346 
347 	if (sopt->DPs > MAX_DPs || sopt->DPs == 0 || sopt->def_DP >= sopt->DPs)
348 		return -EINVAL;
349 
350 	sch_tree_lock(sch);
351 	table->DPs = sopt->DPs;
352 	table->def = sopt->def_DP;
353 	table->red_flags = sopt->flags;
354 
355 	/*
356 	 * Every entry point to GRED is synchronized with the above code
357 	 * and the DP is checked against DPs, i.e. shadowed VQs can no
358 	 * longer be found so we can unlock right here.
359 	 */
360 	sch_tree_unlock(sch);
361 
362 	if (sopt->grio) {
363 		gred_enable_rio_mode(table);
364 		gred_disable_wred_mode(table);
365 		if (gred_wred_mode_check(sch))
366 			gred_enable_wred_mode(table);
367 	} else {
368 		gred_disable_rio_mode(table);
369 		gred_disable_wred_mode(table);
370 	}
371 
372 	for (i = table->DPs; i < MAX_DPs; i++) {
373 		if (table->tab[i]) {
374 			pr_warn("GRED: Warning: Destroying shadowed VQ 0x%x\n",
375 				i);
376 			gred_destroy_vq(table->tab[i]);
377 			table->tab[i] = NULL;
378 		}
379 	}
380 
381 	return 0;
382 }
383 
384 static inline int gred_change_vq(struct Qdisc *sch, int dp,
385 				 struct tc_gred_qopt *ctl, int prio,
386 				 u8 *stab, u32 max_P,
387 				 struct gred_sched_data **prealloc)
388 {
389 	struct gred_sched *table = qdisc_priv(sch);
390 	struct gred_sched_data *q = table->tab[dp];
391 
392 	if (!q) {
393 		table->tab[dp] = q = *prealloc;
394 		*prealloc = NULL;
395 		if (!q)
396 			return -ENOMEM;
397 	}
398 
399 	q->DP = dp;
400 	q->prio = prio;
401 	if (ctl->limit > sch->limit)
402 		q->limit = sch->limit;
403 	else
404 		q->limit = ctl->limit;
405 
406 	if (q->backlog == 0)
407 		red_end_of_idle_period(&q->vars);
408 
409 	red_set_parms(&q->parms,
410 		      ctl->qth_min, ctl->qth_max, ctl->Wlog, ctl->Plog,
411 		      ctl->Scell_log, stab, max_P);
412 	red_set_vars(&q->vars);
413 	return 0;
414 }
415 
416 static const struct nla_policy gred_policy[TCA_GRED_MAX + 1] = {
417 	[TCA_GRED_PARMS]	= { .len = sizeof(struct tc_gred_qopt) },
418 	[TCA_GRED_STAB]		= { .len = 256 },
419 	[TCA_GRED_DPS]		= { .len = sizeof(struct tc_gred_sopt) },
420 	[TCA_GRED_MAX_P]	= { .type = NLA_U32 },
421 	[TCA_GRED_LIMIT]	= { .type = NLA_U32 },
422 };
423 
424 static int gred_change(struct Qdisc *sch, struct nlattr *opt)
425 {
426 	struct gred_sched *table = qdisc_priv(sch);
427 	struct tc_gred_qopt *ctl;
428 	struct nlattr *tb[TCA_GRED_MAX + 1];
429 	int err, prio = GRED_DEF_PRIO;
430 	u8 *stab;
431 	u32 max_P;
432 	struct gred_sched_data *prealloc;
433 
434 	if (opt == NULL)
435 		return -EINVAL;
436 
437 	err = nla_parse_nested(tb, TCA_GRED_MAX, opt, gred_policy);
438 	if (err < 0)
439 		return err;
440 
441 	if (tb[TCA_GRED_PARMS] == NULL && tb[TCA_GRED_STAB] == NULL) {
442 		if (tb[TCA_GRED_LIMIT] != NULL)
443 			sch->limit = nla_get_u32(tb[TCA_GRED_LIMIT]);
444 		return gred_change_table_def(sch, opt);
445 	}
446 
447 	if (tb[TCA_GRED_PARMS] == NULL ||
448 	    tb[TCA_GRED_STAB] == NULL ||
449 	    tb[TCA_GRED_LIMIT] != NULL)
450 		return -EINVAL;
451 
452 	max_P = tb[TCA_GRED_MAX_P] ? nla_get_u32(tb[TCA_GRED_MAX_P]) : 0;
453 
454 	err = -EINVAL;
455 	ctl = nla_data(tb[TCA_GRED_PARMS]);
456 	stab = nla_data(tb[TCA_GRED_STAB]);
457 
458 	if (ctl->DP >= table->DPs)
459 		goto errout;
460 
461 	if (gred_rio_mode(table)) {
462 		if (ctl->prio == 0) {
463 			int def_prio = GRED_DEF_PRIO;
464 
465 			if (table->tab[table->def])
466 				def_prio = table->tab[table->def]->prio;
467 
468 			printk(KERN_DEBUG "GRED: DP %u does not have a prio "
469 			       "setting default to %d\n", ctl->DP, def_prio);
470 
471 			prio = def_prio;
472 		} else
473 			prio = ctl->prio;
474 	}
475 
476 	prealloc = kzalloc(sizeof(*prealloc), GFP_KERNEL);
477 	sch_tree_lock(sch);
478 
479 	err = gred_change_vq(sch, ctl->DP, ctl, prio, stab, max_P, &prealloc);
480 	if (err < 0)
481 		goto errout_locked;
482 
483 	if (gred_rio_mode(table)) {
484 		gred_disable_wred_mode(table);
485 		if (gred_wred_mode_check(sch))
486 			gred_enable_wred_mode(table);
487 	}
488 
489 	err = 0;
490 
491 errout_locked:
492 	sch_tree_unlock(sch);
493 	kfree(prealloc);
494 errout:
495 	return err;
496 }
497 
498 static int gred_init(struct Qdisc *sch, struct nlattr *opt)
499 {
500 	struct nlattr *tb[TCA_GRED_MAX + 1];
501 	int err;
502 
503 	if (opt == NULL)
504 		return -EINVAL;
505 
506 	err = nla_parse_nested(tb, TCA_GRED_MAX, opt, gred_policy);
507 	if (err < 0)
508 		return err;
509 
510 	if (tb[TCA_GRED_PARMS] || tb[TCA_GRED_STAB])
511 		return -EINVAL;
512 
513 	if (tb[TCA_GRED_LIMIT])
514 		sch->limit = nla_get_u32(tb[TCA_GRED_LIMIT]);
515 	else
516 		sch->limit = qdisc_dev(sch)->tx_queue_len
517 		             * psched_mtu(qdisc_dev(sch));
518 
519 	return gred_change_table_def(sch, tb[TCA_GRED_DPS]);
520 }
521 
522 static int gred_dump(struct Qdisc *sch, struct sk_buff *skb)
523 {
524 	struct gred_sched *table = qdisc_priv(sch);
525 	struct nlattr *parms, *opts = NULL;
526 	int i;
527 	u32 max_p[MAX_DPs];
528 	struct tc_gred_sopt sopt = {
529 		.DPs	= table->DPs,
530 		.def_DP	= table->def,
531 		.grio	= gred_rio_mode(table),
532 		.flags	= table->red_flags,
533 	};
534 
535 	opts = nla_nest_start(skb, TCA_OPTIONS);
536 	if (opts == NULL)
537 		goto nla_put_failure;
538 	if (nla_put(skb, TCA_GRED_DPS, sizeof(sopt), &sopt))
539 		goto nla_put_failure;
540 
541 	for (i = 0; i < MAX_DPs; i++) {
542 		struct gred_sched_data *q = table->tab[i];
543 
544 		max_p[i] = q ? q->parms.max_P : 0;
545 	}
546 	if (nla_put(skb, TCA_GRED_MAX_P, sizeof(max_p), max_p))
547 		goto nla_put_failure;
548 
549 	if (nla_put_u32(skb, TCA_GRED_LIMIT, sch->limit))
550 		goto nla_put_failure;
551 
552 	parms = nla_nest_start(skb, TCA_GRED_PARMS);
553 	if (parms == NULL)
554 		goto nla_put_failure;
555 
556 	for (i = 0; i < MAX_DPs; i++) {
557 		struct gred_sched_data *q = table->tab[i];
558 		struct tc_gred_qopt opt;
559 		unsigned long qavg;
560 
561 		memset(&opt, 0, sizeof(opt));
562 
563 		if (!q) {
564 			/* hack -- fix at some point with proper message
565 			   This is how we indicate to tc that there is no VQ
566 			   at this DP */
567 
568 			opt.DP = MAX_DPs + i;
569 			goto append_opt;
570 		}
571 
572 		opt.limit	= q->limit;
573 		opt.DP		= q->DP;
574 		opt.backlog	= gred_backlog(table, q, sch);
575 		opt.prio	= q->prio;
576 		opt.qth_min	= q->parms.qth_min >> q->parms.Wlog;
577 		opt.qth_max	= q->parms.qth_max >> q->parms.Wlog;
578 		opt.Wlog	= q->parms.Wlog;
579 		opt.Plog	= q->parms.Plog;
580 		opt.Scell_log	= q->parms.Scell_log;
581 		opt.other	= q->stats.other;
582 		opt.early	= q->stats.prob_drop;
583 		opt.forced	= q->stats.forced_drop;
584 		opt.pdrop	= q->stats.pdrop;
585 		opt.packets	= q->packetsin;
586 		opt.bytesin	= q->bytesin;
587 
588 		if (gred_wred_mode(table))
589 			gred_load_wred_set(table, q);
590 
591 		qavg = red_calc_qavg(&q->parms, &q->vars,
592 				     q->vars.qavg >> q->parms.Wlog);
593 		opt.qave = qavg >> q->parms.Wlog;
594 
595 append_opt:
596 		if (nla_append(skb, sizeof(opt), &opt) < 0)
597 			goto nla_put_failure;
598 	}
599 
600 	nla_nest_end(skb, parms);
601 
602 	return nla_nest_end(skb, opts);
603 
604 nla_put_failure:
605 	nla_nest_cancel(skb, opts);
606 	return -EMSGSIZE;
607 }
608 
609 static void gred_destroy(struct Qdisc *sch)
610 {
611 	struct gred_sched *table = qdisc_priv(sch);
612 	int i;
613 
614 	for (i = 0; i < table->DPs; i++) {
615 		if (table->tab[i])
616 			gred_destroy_vq(table->tab[i]);
617 	}
618 }
619 
620 static struct Qdisc_ops gred_qdisc_ops __read_mostly = {
621 	.id		=	"gred",
622 	.priv_size	=	sizeof(struct gred_sched),
623 	.enqueue	=	gred_enqueue,
624 	.dequeue	=	gred_dequeue,
625 	.peek		=	qdisc_peek_head,
626 	.drop		=	gred_drop,
627 	.init		=	gred_init,
628 	.reset		=	gred_reset,
629 	.destroy	=	gred_destroy,
630 	.change		=	gred_change,
631 	.dump		=	gred_dump,
632 	.owner		=	THIS_MODULE,
633 };
634 
635 static int __init gred_module_init(void)
636 {
637 	return register_qdisc(&gred_qdisc_ops);
638 }
639 
640 static void __exit gred_module_exit(void)
641 {
642 	unregister_qdisc(&gred_qdisc_ops);
643 }
644 
645 module_init(gred_module_init)
646 module_exit(gred_module_exit)
647 
648 MODULE_LICENSE("GPL");
649