xref: /openbmc/linux/net/sched/sch_gred.c (revision 63dc02bd) 
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 = 0; n < table->DPs; n++)
106 			if (table->tab[n] && table->tab[n] != q &&
107 			    table->tab[n]->prio == q->prio)
108 				return 1;
109 	}
110 
111 	return 0;
112 }
113 
114 static inline unsigned int gred_backlog(struct gred_sched *table,
115 					struct gred_sched_data *q,
116 					struct Qdisc *sch)
117 {
118 	if (gred_wred_mode(table))
119 		return sch->qstats.backlog;
120 	else
121 		return q->backlog;
122 }
123 
124 static inline u16 tc_index_to_dp(struct sk_buff *skb)
125 {
126 	return skb->tc_index & GRED_VQ_MASK;
127 }
128 
129 static inline void gred_load_wred_set(const struct gred_sched *table,
130 				      struct gred_sched_data *q)
131 {
132 	q->vars.qavg = table->wred_set.qavg;
133 	q->vars.qidlestart = table->wred_set.qidlestart;
134 }
135 
136 static inline void gred_store_wred_set(struct gred_sched *table,
137 				       struct gred_sched_data *q)
138 {
139 	table->wred_set.qavg = q->vars.qavg;
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 <= to 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 			if (net_ratelimit())
259 				pr_warning("GRED: Unable to relocate VQ 0x%x "
260 					   "after dequeue, screwing up "
261 					   "backlog.\n", tc_index_to_dp(skb));
262 		} else {
263 			q->backlog -= qdisc_pkt_len(skb);
264 
265 			if (!q->backlog && !gred_wred_mode(t))
266 				red_start_of_idle_period(&q->vars);
267 		}
268 
269 		return skb;
270 	}
271 
272 	if (gred_wred_mode(t) && !red_is_idling(&t->wred_set))
273 		red_start_of_idle_period(&t->wred_set);
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 			if (net_ratelimit())
291 				pr_warning("GRED: Unable to relocate VQ 0x%x "
292 					   "while dropping, screwing up "
293 					   "backlog.\n", tc_index_to_dp(skb));
294 		} else {
295 			q->backlog -= len;
296 			q->stats.other++;
297 
298 			if (!q->backlog && !gred_wred_mode(t))
299 				red_start_of_idle_period(&q->vars);
300 		}
301 
302 		qdisc_drop(skb, sch);
303 		return len;
304 	}
305 
306 	if (gred_wred_mode(t) && !red_is_idling(&t->wred_set))
307 		red_start_of_idle_period(&t->wred_set);
308 
309 	return 0;
310 
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_warning("GRED: Warning: Destroying "
375 				   "shadowed VQ 0x%x\n", 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 	q->limit = ctl->limit;
402 
403 	if (q->backlog == 0)
404 		red_end_of_idle_period(&q->vars);
405 
406 	red_set_parms(&q->parms,
407 		      ctl->qth_min, ctl->qth_max, ctl->Wlog, ctl->Plog,
408 		      ctl->Scell_log, stab, max_P);
409 	red_set_vars(&q->vars);
410 	return 0;
411 }
412 
413 static const struct nla_policy gred_policy[TCA_GRED_MAX + 1] = {
414 	[TCA_GRED_PARMS]	= { .len = sizeof(struct tc_gred_qopt) },
415 	[TCA_GRED_STAB]		= { .len = 256 },
416 	[TCA_GRED_DPS]		= { .len = sizeof(struct tc_gred_sopt) },
417 	[TCA_GRED_MAX_P]	= { .type = NLA_U32 },
418 };
419 
420 static int gred_change(struct Qdisc *sch, struct nlattr *opt)
421 {
422 	struct gred_sched *table = qdisc_priv(sch);
423 	struct tc_gred_qopt *ctl;
424 	struct nlattr *tb[TCA_GRED_MAX + 1];
425 	int err, prio = GRED_DEF_PRIO;
426 	u8 *stab;
427 	u32 max_P;
428 	struct gred_sched_data *prealloc;
429 
430 	if (opt == NULL)
431 		return -EINVAL;
432 
433 	err = nla_parse_nested(tb, TCA_GRED_MAX, opt, gred_policy);
434 	if (err < 0)
435 		return err;
436 
437 	if (tb[TCA_GRED_PARMS] == NULL && tb[TCA_GRED_STAB] == NULL)
438 		return gred_change_table_def(sch, opt);
439 
440 	if (tb[TCA_GRED_PARMS] == NULL ||
441 	    tb[TCA_GRED_STAB] == NULL)
442 		return -EINVAL;
443 
444 	max_P = tb[TCA_GRED_MAX_P] ? nla_get_u32(tb[TCA_GRED_MAX_P]) : 0;
445 
446 	err = -EINVAL;
447 	ctl = nla_data(tb[TCA_GRED_PARMS]);
448 	stab = nla_data(tb[TCA_GRED_STAB]);
449 
450 	if (ctl->DP >= table->DPs)
451 		goto errout;
452 
453 	if (gred_rio_mode(table)) {
454 		if (ctl->prio == 0) {
455 			int def_prio = GRED_DEF_PRIO;
456 
457 			if (table->tab[table->def])
458 				def_prio = table->tab[table->def]->prio;
459 
460 			printk(KERN_DEBUG "GRED: DP %u does not have a prio "
461 			       "setting default to %d\n", ctl->DP, def_prio);
462 
463 			prio = def_prio;
464 		} else
465 			prio = ctl->prio;
466 	}
467 
468 	prealloc = kzalloc(sizeof(*prealloc), GFP_KERNEL);
469 	sch_tree_lock(sch);
470 
471 	err = gred_change_vq(sch, ctl->DP, ctl, prio, stab, max_P, &prealloc);
472 	if (err < 0)
473 		goto errout_locked;
474 
475 	if (gred_rio_mode(table)) {
476 		gred_disable_wred_mode(table);
477 		if (gred_wred_mode_check(sch))
478 			gred_enable_wred_mode(table);
479 	}
480 
481 	err = 0;
482 
483 errout_locked:
484 	sch_tree_unlock(sch);
485 	kfree(prealloc);
486 errout:
487 	return err;
488 }
489 
490 static int gred_init(struct Qdisc *sch, struct nlattr *opt)
491 {
492 	struct nlattr *tb[TCA_GRED_MAX + 1];
493 	int err;
494 
495 	if (opt == NULL)
496 		return -EINVAL;
497 
498 	err = nla_parse_nested(tb, TCA_GRED_MAX, opt, gred_policy);
499 	if (err < 0)
500 		return err;
501 
502 	if (tb[TCA_GRED_PARMS] || tb[TCA_GRED_STAB])
503 		return -EINVAL;
504 
505 	return gred_change_table_def(sch, tb[TCA_GRED_DPS]);
506 }
507 
508 static int gred_dump(struct Qdisc *sch, struct sk_buff *skb)
509 {
510 	struct gred_sched *table = qdisc_priv(sch);
511 	struct nlattr *parms, *opts = NULL;
512 	int i;
513 	u32 max_p[MAX_DPs];
514 	struct tc_gred_sopt sopt = {
515 		.DPs	= table->DPs,
516 		.def_DP	= table->def,
517 		.grio	= gred_rio_mode(table),
518 		.flags	= table->red_flags,
519 	};
520 
521 	opts = nla_nest_start(skb, TCA_OPTIONS);
522 	if (opts == NULL)
523 		goto nla_put_failure;
524 	NLA_PUT(skb, TCA_GRED_DPS, sizeof(sopt), &sopt);
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 	NLA_PUT(skb, TCA_GRED_MAX_P, sizeof(max_p), max_p);
532 
533 	parms = nla_nest_start(skb, TCA_GRED_PARMS);
534 	if (parms == NULL)
535 		goto nla_put_failure;
536 
537 	for (i = 0; i < MAX_DPs; i++) {
538 		struct gred_sched_data *q = table->tab[i];
539 		struct tc_gred_qopt opt;
540 
541 		memset(&opt, 0, sizeof(opt));
542 
543 		if (!q) {
544 			/* hack -- fix at some point with proper message
545 			   This is how we indicate to tc that there is no VQ
546 			   at this DP */
547 
548 			opt.DP = MAX_DPs + i;
549 			goto append_opt;
550 		}
551 
552 		opt.limit	= q->limit;
553 		opt.DP		= q->DP;
554 		opt.backlog	= q->backlog;
555 		opt.prio	= q->prio;
556 		opt.qth_min	= q->parms.qth_min >> q->parms.Wlog;
557 		opt.qth_max	= q->parms.qth_max >> q->parms.Wlog;
558 		opt.Wlog	= q->parms.Wlog;
559 		opt.Plog	= q->parms.Plog;
560 		opt.Scell_log	= q->parms.Scell_log;
561 		opt.other	= q->stats.other;
562 		opt.early	= q->stats.prob_drop;
563 		opt.forced	= q->stats.forced_drop;
564 		opt.pdrop	= q->stats.pdrop;
565 		opt.packets	= q->packetsin;
566 		opt.bytesin	= q->bytesin;
567 
568 		if (gred_wred_mode(table))
569 			gred_load_wred_set(table, q);
570 
571 		opt.qave = red_calc_qavg(&q->parms, &q->vars, q->vars.qavg);
572 
573 append_opt:
574 		if (nla_append(skb, sizeof(opt), &opt) < 0)
575 			goto nla_put_failure;
576 	}
577 
578 	nla_nest_end(skb, parms);
579 
580 	return nla_nest_end(skb, opts);
581 
582 nla_put_failure:
583 	nla_nest_cancel(skb, opts);
584 	return -EMSGSIZE;
585 }
586 
587 static void gred_destroy(struct Qdisc *sch)
588 {
589 	struct gred_sched *table = qdisc_priv(sch);
590 	int i;
591 
592 	for (i = 0; i < table->DPs; i++) {
593 		if (table->tab[i])
594 			gred_destroy_vq(table->tab[i]);
595 	}
596 }
597 
598 static struct Qdisc_ops gred_qdisc_ops __read_mostly = {
599 	.id		=	"gred",
600 	.priv_size	=	sizeof(struct gred_sched),
601 	.enqueue	=	gred_enqueue,
602 	.dequeue	=	gred_dequeue,
603 	.peek		=	qdisc_peek_head,
604 	.drop		=	gred_drop,
605 	.init		=	gred_init,
606 	.reset		=	gred_reset,
607 	.destroy	=	gred_destroy,
608 	.change		=	gred_change,
609 	.dump		=	gred_dump,
610 	.owner		=	THIS_MODULE,
611 };
612 
613 static int __init gred_module_init(void)
614 {
615 	return register_qdisc(&gred_qdisc_ops);
616 }
617 
618 static void __exit gred_module_exit(void)
619 {
620 	unregister_qdisc(&gred_qdisc_ops);
621 }
622 
623 module_init(gred_module_init)
624 module_exit(gred_module_exit)
625 
626 MODULE_LICENSE("GPL");
627