1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * net/sched/sch_drr.c         Deficit Round Robin scheduler
4 *
5 * Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
6 */
7
8#include <linux/module.h>
9#include <linux/slab.h>
10#include <linux/init.h>
11#include <linux/errno.h>
12#include <linux/netdevice.h>
13#include <linux/pkt_sched.h>
14#include <net/sch_generic.h>
15#include <net/pkt_sched.h>
16#include <net/pkt_cls.h>
17
18struct drr_class {
19	struct Qdisc_class_common	common;
20
21	struct gnet_stats_basic_sync		bstats;
22	struct gnet_stats_queue		qstats;
23	struct net_rate_estimator __rcu *rate_est;
24	struct list_head		alist;
25	struct Qdisc			*qdisc;
26
27	u32				quantum;
28	u32				deficit;
29};
30
31struct drr_sched {
32	struct list_head		active;
33	struct tcf_proto __rcu		*filter_list;
34	struct tcf_block		*block;
35	struct Qdisc_class_hash		clhash;
36};
37
38static struct drr_class *drr_find_class(struct Qdisc *sch, u32 classid)
39{
40	struct drr_sched *q = qdisc_priv(sch);
41	struct Qdisc_class_common *clc;
42
43	clc = qdisc_class_find(&q->clhash, classid);
44	if (clc == NULL)
45		return NULL;
46	return container_of(clc, struct drr_class, common);
47}
48
49static const struct nla_policy drr_policy[TCA_DRR_MAX + 1] = {
50	[TCA_DRR_QUANTUM]	= { .type = NLA_U32 },
51};
52
53static int drr_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
54			    struct nlattr **tca, unsigned long *arg,
55			    struct netlink_ext_ack *extack)
56{
57	struct drr_sched *q = qdisc_priv(sch);
58	struct drr_class *cl = (struct drr_class *)*arg;
59	struct nlattr *opt = tca[TCA_OPTIONS];
60	struct nlattr *tb[TCA_DRR_MAX + 1];
61	u32 quantum;
62	int err;
63
64	if (!opt) {
65		NL_SET_ERR_MSG(extack, "DRR options are required for this operation");
66		return -EINVAL;
67	}
68
69	err = nla_parse_nested_deprecated(tb, TCA_DRR_MAX, opt, drr_policy,
70					  extack);
71	if (err < 0)
72		return err;
73
74	if (tb[TCA_DRR_QUANTUM]) {
75		quantum = nla_get_u32(tb[TCA_DRR_QUANTUM]);
76		if (quantum == 0) {
77			NL_SET_ERR_MSG(extack, "Specified DRR quantum cannot be zero");
78			return -EINVAL;
79		}
80	} else
81		quantum = psched_mtu(qdisc_dev(sch));
82
83	if (cl != NULL) {
84		if (tca[TCA_RATE]) {
85			err = gen_replace_estimator(&cl->bstats, NULL,
86						    &cl->rate_est,
87						    NULL, true,
88						    tca[TCA_RATE]);
89			if (err) {
90				NL_SET_ERR_MSG(extack, "Failed to replace estimator");
91				return err;
92			}
93		}
94
95		sch_tree_lock(sch);
96		if (tb[TCA_DRR_QUANTUM])
97			cl->quantum = quantum;
98		sch_tree_unlock(sch);
99
100		return 0;
101	}
102
103	cl = kzalloc(sizeof(struct drr_class), GFP_KERNEL);
104	if (cl == NULL)
105		return -ENOBUFS;
106
107	gnet_stats_basic_sync_init(&cl->bstats);
108	cl->common.classid = classid;
109	cl->quantum	   = quantum;
110	cl->qdisc	   = qdisc_create_dflt(sch->dev_queue,
111					       &pfifo_qdisc_ops, classid,
112					       NULL);
113	if (cl->qdisc == NULL)
114		cl->qdisc = &noop_qdisc;
115	else
116		qdisc_hash_add(cl->qdisc, true);
117
118	if (tca[TCA_RATE]) {
119		err = gen_replace_estimator(&cl->bstats, NULL, &cl->rate_est,
120					    NULL, true, tca[TCA_RATE]);
121		if (err) {
122			NL_SET_ERR_MSG(extack, "Failed to replace estimator");
123			qdisc_put(cl->qdisc);
124			kfree(cl);
125			return err;
126		}
127	}
128
129	sch_tree_lock(sch);
130	qdisc_class_hash_insert(&q->clhash, &cl->common);
131	sch_tree_unlock(sch);
132
133	qdisc_class_hash_grow(sch, &q->clhash);
134
135	*arg = (unsigned long)cl;
136	return 0;
137}
138
139static void drr_destroy_class(struct Qdisc *sch, struct drr_class *cl)
140{
141	gen_kill_estimator(&cl->rate_est);
142	qdisc_put(cl->qdisc);
143	kfree(cl);
144}
145
146static int drr_delete_class(struct Qdisc *sch, unsigned long arg,
147			    struct netlink_ext_ack *extack)
148{
149	struct drr_sched *q = qdisc_priv(sch);
150	struct drr_class *cl = (struct drr_class *)arg;
151
152	if (qdisc_class_in_use(&cl->common)) {
153		NL_SET_ERR_MSG(extack, "DRR class is in use");
154		return -EBUSY;
155	}
156
157	sch_tree_lock(sch);
158
159	qdisc_purge_queue(cl->qdisc);
160	qdisc_class_hash_remove(&q->clhash, &cl->common);
161
162	sch_tree_unlock(sch);
163
164	drr_destroy_class(sch, cl);
165	return 0;
166}
167
168static unsigned long drr_search_class(struct Qdisc *sch, u32 classid)
169{
170	return (unsigned long)drr_find_class(sch, classid);
171}
172
173static struct tcf_block *drr_tcf_block(struct Qdisc *sch, unsigned long cl,
174				       struct netlink_ext_ack *extack)
175{
176	struct drr_sched *q = qdisc_priv(sch);
177
178	if (cl) {
179		NL_SET_ERR_MSG(extack, "DRR classid must be zero");
180		return NULL;
181	}
182
183	return q->block;
184}
185
186static unsigned long drr_bind_tcf(struct Qdisc *sch, unsigned long parent,
187				  u32 classid)
188{
189	struct drr_class *cl = drr_find_class(sch, classid);
190
191	if (cl)
192		qdisc_class_get(&cl->common);
193
194	return (unsigned long)cl;
195}
196
197static void drr_unbind_tcf(struct Qdisc *sch, unsigned long arg)
198{
199	struct drr_class *cl = (struct drr_class *)arg;
200
201	qdisc_class_put(&cl->common);
202}
203
204static int drr_graft_class(struct Qdisc *sch, unsigned long arg,
205			   struct Qdisc *new, struct Qdisc **old,
206			   struct netlink_ext_ack *extack)
207{
208	struct drr_class *cl = (struct drr_class *)arg;
209
210	if (new == NULL) {
211		new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
212					cl->common.classid, NULL);
213		if (new == NULL)
214			new = &noop_qdisc;
215	}
216
217	*old = qdisc_replace(sch, new, &cl->qdisc);
218	return 0;
219}
220
221static struct Qdisc *drr_class_leaf(struct Qdisc *sch, unsigned long arg)
222{
223	struct drr_class *cl = (struct drr_class *)arg;
224
225	return cl->qdisc;
226}
227
228static void drr_qlen_notify(struct Qdisc *csh, unsigned long arg)
229{
230	struct drr_class *cl = (struct drr_class *)arg;
231
232	list_del(&cl->alist);
233}
234
235static int drr_dump_class(struct Qdisc *sch, unsigned long arg,
236			  struct sk_buff *skb, struct tcmsg *tcm)
237{
238	struct drr_class *cl = (struct drr_class *)arg;
239	struct nlattr *nest;
240
241	tcm->tcm_parent	= TC_H_ROOT;
242	tcm->tcm_handle	= cl->common.classid;
243	tcm->tcm_info	= cl->qdisc->handle;
244
245	nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
246	if (nest == NULL)
247		goto nla_put_failure;
248	if (nla_put_u32(skb, TCA_DRR_QUANTUM, cl->quantum))
249		goto nla_put_failure;
250	return nla_nest_end(skb, nest);
251
252nla_put_failure:
253	nla_nest_cancel(skb, nest);
254	return -EMSGSIZE;
255}
256
257static int drr_dump_class_stats(struct Qdisc *sch, unsigned long arg,
258				struct gnet_dump *d)
259{
260	struct drr_class *cl = (struct drr_class *)arg;
261	__u32 qlen = qdisc_qlen_sum(cl->qdisc);
262	struct Qdisc *cl_q = cl->qdisc;
263	struct tc_drr_stats xstats;
264
265	memset(&xstats, 0, sizeof(xstats));
266	if (qlen)
267		xstats.deficit = cl->deficit;
268
269	if (gnet_stats_copy_basic(d, NULL, &cl->bstats, true) < 0 ||
270	    gnet_stats_copy_rate_est(d, &cl->rate_est) < 0 ||
271	    gnet_stats_copy_queue(d, cl_q->cpu_qstats, &cl_q->qstats, qlen) < 0)
272		return -1;
273
274	return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
275}
276
277static void drr_walk(struct Qdisc *sch, struct qdisc_walker *arg)
278{
279	struct drr_sched *q = qdisc_priv(sch);
280	struct drr_class *cl;
281	unsigned int i;
282
283	if (arg->stop)
284		return;
285
286	for (i = 0; i < q->clhash.hashsize; i++) {
287		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
288			if (!tc_qdisc_stats_dump(sch, (unsigned long)cl, arg))
289				return;
290		}
291	}
292}
293
294static struct drr_class *drr_classify(struct sk_buff *skb, struct Qdisc *sch,
295				      int *qerr)
296{
297	struct drr_sched *q = qdisc_priv(sch);
298	struct drr_class *cl;
299	struct tcf_result res;
300	struct tcf_proto *fl;
301	int result;
302
303	if (TC_H_MAJ(skb->priority ^ sch->handle) == 0) {
304		cl = drr_find_class(sch, skb->priority);
305		if (cl != NULL)
306			return cl;
307	}
308
309	*qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
310	fl = rcu_dereference_bh(q->filter_list);
311	result = tcf_classify(skb, NULL, fl, &res, false);
312	if (result >= 0) {
313#ifdef CONFIG_NET_CLS_ACT
314		switch (result) {
315		case TC_ACT_QUEUED:
316		case TC_ACT_STOLEN:
317		case TC_ACT_TRAP:
318			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
319			fallthrough;
320		case TC_ACT_SHOT:
321			return NULL;
322		}
323#endif
324		cl = (struct drr_class *)res.class;
325		if (cl == NULL)
326			cl = drr_find_class(sch, res.classid);
327		return cl;
328	}
329	return NULL;
330}
331
332static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch,
333		       struct sk_buff **to_free)
334{
335	unsigned int len = qdisc_pkt_len(skb);
336	struct drr_sched *q = qdisc_priv(sch);
337	struct drr_class *cl;
338	int err = 0;
339	bool first;
340
341	cl = drr_classify(skb, sch, &err);
342	if (cl == NULL) {
343		if (err & __NET_XMIT_BYPASS)
344			qdisc_qstats_drop(sch);
345		__qdisc_drop(skb, to_free);
346		return err;
347	}
348
349	first = !cl->qdisc->q.qlen;
350	err = qdisc_enqueue(skb, cl->qdisc, to_free);
351	if (unlikely(err != NET_XMIT_SUCCESS)) {
352		if (net_xmit_drop_count(err)) {
353			cl->qstats.drops++;
354			qdisc_qstats_drop(sch);
355		}
356		return err;
357	}
358
359	if (first) {
360		list_add_tail(&cl->alist, &q->active);
361		cl->deficit = cl->quantum;
362	}
363
364	sch->qstats.backlog += len;
365	sch->q.qlen++;
366	return err;
367}
368
369static struct sk_buff *drr_dequeue(struct Qdisc *sch)
370{
371	struct drr_sched *q = qdisc_priv(sch);
372	struct drr_class *cl;
373	struct sk_buff *skb;
374	unsigned int len;
375
376	if (list_empty(&q->active))
377		goto out;
378	while (1) {
379		cl = list_first_entry(&q->active, struct drr_class, alist);
380		skb = cl->qdisc->ops->peek(cl->qdisc);
381		if (skb == NULL) {
382			qdisc_warn_nonwc(__func__, cl->qdisc);
383			goto out;
384		}
385
386		len = qdisc_pkt_len(skb);
387		if (len <= cl->deficit) {
388			cl->deficit -= len;
389			skb = qdisc_dequeue_peeked(cl->qdisc);
390			if (unlikely(skb == NULL))
391				goto out;
392			if (cl->qdisc->q.qlen == 0)
393				list_del(&cl->alist);
394
395			bstats_update(&cl->bstats, skb);
396			qdisc_bstats_update(sch, skb);
397			qdisc_qstats_backlog_dec(sch, skb);
398			sch->q.qlen--;
399			return skb;
400		}
401
402		cl->deficit += cl->quantum;
403		list_move_tail(&cl->alist, &q->active);
404	}
405out:
406	return NULL;
407}
408
409static int drr_init_qdisc(struct Qdisc *sch, struct nlattr *opt,
410			  struct netlink_ext_ack *extack)
411{
412	struct drr_sched *q = qdisc_priv(sch);
413	int err;
414
415	err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
416	if (err)
417		return err;
418	err = qdisc_class_hash_init(&q->clhash);
419	if (err < 0)
420		return err;
421	INIT_LIST_HEAD(&q->active);
422	return 0;
423}
424
425static void drr_reset_qdisc(struct Qdisc *sch)
426{
427	struct drr_sched *q = qdisc_priv(sch);
428	struct drr_class *cl;
429	unsigned int i;
430
431	for (i = 0; i < q->clhash.hashsize; i++) {
432		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
433			if (cl->qdisc->q.qlen)
434				list_del(&cl->alist);
435			qdisc_reset(cl->qdisc);
436		}
437	}
438}
439
440static void drr_destroy_qdisc(struct Qdisc *sch)
441{
442	struct drr_sched *q = qdisc_priv(sch);
443	struct drr_class *cl;
444	struct hlist_node *next;
445	unsigned int i;
446
447	tcf_block_put(q->block);
448
449	for (i = 0; i < q->clhash.hashsize; i++) {
450		hlist_for_each_entry_safe(cl, next, &q->clhash.hash[i],
451					  common.hnode)
452			drr_destroy_class(sch, cl);
453	}
454	qdisc_class_hash_destroy(&q->clhash);
455}
456
457static const struct Qdisc_class_ops drr_class_ops = {
458	.change		= drr_change_class,
459	.delete		= drr_delete_class,
460	.find		= drr_search_class,
461	.tcf_block	= drr_tcf_block,
462	.bind_tcf	= drr_bind_tcf,
463	.unbind_tcf	= drr_unbind_tcf,
464	.graft		= drr_graft_class,
465	.leaf		= drr_class_leaf,
466	.qlen_notify	= drr_qlen_notify,
467	.dump		= drr_dump_class,
468	.dump_stats	= drr_dump_class_stats,
469	.walk		= drr_walk,
470};
471
472static struct Qdisc_ops drr_qdisc_ops __read_mostly = {
473	.cl_ops		= &drr_class_ops,
474	.id		= "drr",
475	.priv_size	= sizeof(struct drr_sched),
476	.enqueue	= drr_enqueue,
477	.dequeue	= drr_dequeue,
478	.peek		= qdisc_peek_dequeued,
479	.init		= drr_init_qdisc,
480	.reset		= drr_reset_qdisc,
481	.destroy	= drr_destroy_qdisc,
482	.owner		= THIS_MODULE,
483};
484MODULE_ALIAS_NET_SCH("drr");
485
486static int __init drr_init(void)
487{
488	return register_qdisc(&drr_qdisc_ops);
489}
490
491static void __exit drr_exit(void)
492{
493	unregister_qdisc(&drr_qdisc_ops);
494}
495
496module_init(drr_init);
497module_exit(drr_exit);
498MODULE_LICENSE("GPL");
499MODULE_DESCRIPTION("Deficit Round Robin scheduler");
500