xref: /openbmc/linux/net/sched/sch_red.c (revision 64fc2a94) 
1 /*
2  * net/sched/sch_red.c	Random Early Detection queue.
3  *
4  *		This program is free software; you can redistribute it and/or
5  *		modify it under the terms of the GNU General Public License
6  *		as published by the Free Software Foundation; either version
7  *		2 of the License, or (at your option) any later version.
8  *
9  * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
10  *
11  * Changes:
12  * J Hadi Salim 980914:	computation fixes
13  * Alexey Makarenko <makar@phoenix.kharkov.ua> 990814: qave on idle link was calculated incorrectly.
14  * J Hadi Salim 980816:  ECN support
15  */
16 
17 #include <linux/module.h>
18 #include <linux/types.h>
19 #include <linux/kernel.h>
20 #include <linux/skbuff.h>
21 #include <net/pkt_sched.h>
22 #include <net/inet_ecn.h>
23 #include <net/red.h>
24 
25 
26 /*	Parameters, settable by user:
27 	-----------------------------
28 
29 	limit		- bytes (must be > qth_max + burst)
30 
31 	Hard limit on queue length, should be chosen >qth_max
32 	to allow packet bursts. This parameter does not
33 	affect the algorithms behaviour and can be chosen
34 	arbitrarily high (well, less than ram size)
35 	Really, this limit will never be reached
36 	if RED works correctly.
37  */
38 
39 struct red_sched_data {
40 	u32			limit;		/* HARD maximal queue length */
41 	unsigned char		flags;
42 	struct timer_list	adapt_timer;
43 	struct red_parms	parms;
44 	struct red_vars		vars;
45 	struct red_stats	stats;
46 	struct Qdisc		*qdisc;
47 };
48 
49 static inline int red_use_ecn(struct red_sched_data *q)
50 {
51 	return q->flags & TC_RED_ECN;
52 }
53 
54 static inline int red_use_harddrop(struct red_sched_data *q)
55 {
56 	return q->flags & TC_RED_HARDDROP;
57 }
58 
59 static int red_enqueue(struct sk_buff *skb, struct Qdisc *sch,
60 		       struct sk_buff **to_free)
61 {
62 	struct red_sched_data *q = qdisc_priv(sch);
63 	struct Qdisc *child = q->qdisc;
64 	int ret;
65 
66 	q->vars.qavg = red_calc_qavg(&q->parms,
67 				     &q->vars,
68 				     child->qstats.backlog);
69 
70 	if (red_is_idling(&q->vars))
71 		red_end_of_idle_period(&q->vars);
72 
73 	switch (red_action(&q->parms, &q->vars, q->vars.qavg)) {
74 	case RED_DONT_MARK:
75 		break;
76 
77 	case RED_PROB_MARK:
78 		qdisc_qstats_overlimit(sch);
79 		if (!red_use_ecn(q) || !INET_ECN_set_ce(skb)) {
80 			q->stats.prob_drop++;
81 			goto congestion_drop;
82 		}
83 
84 		q->stats.prob_mark++;
85 		break;
86 
87 	case RED_HARD_MARK:
88 		qdisc_qstats_overlimit(sch);
89 		if (red_use_harddrop(q) || !red_use_ecn(q) ||
90 		    !INET_ECN_set_ce(skb)) {
91 			q->stats.forced_drop++;
92 			goto congestion_drop;
93 		}
94 
95 		q->stats.forced_mark++;
96 		break;
97 	}
98 
99 	ret = qdisc_enqueue(skb, child, to_free);
100 	if (likely(ret == NET_XMIT_SUCCESS)) {
101 		qdisc_qstats_backlog_inc(sch, skb);
102 		sch->q.qlen++;
103 	} else if (net_xmit_drop_count(ret)) {
104 		q->stats.pdrop++;
105 		qdisc_qstats_drop(sch);
106 	}
107 	return ret;
108 
109 congestion_drop:
110 	qdisc_drop(skb, sch, to_free);
111 	return NET_XMIT_CN;
112 }
113 
114 static struct sk_buff *red_dequeue(struct Qdisc *sch)
115 {
116 	struct sk_buff *skb;
117 	struct red_sched_data *q = qdisc_priv(sch);
118 	struct Qdisc *child = q->qdisc;
119 
120 	skb = child->dequeue(child);
121 	if (skb) {
122 		qdisc_bstats_update(sch, skb);
123 		qdisc_qstats_backlog_dec(sch, skb);
124 		sch->q.qlen--;
125 	} else {
126 		if (!red_is_idling(&q->vars))
127 			red_start_of_idle_period(&q->vars);
128 	}
129 	return skb;
130 }
131 
132 static struct sk_buff *red_peek(struct Qdisc *sch)
133 {
134 	struct red_sched_data *q = qdisc_priv(sch);
135 	struct Qdisc *child = q->qdisc;
136 
137 	return child->ops->peek(child);
138 }
139 
140 static void red_reset(struct Qdisc *sch)
141 {
142 	struct red_sched_data *q = qdisc_priv(sch);
143 
144 	qdisc_reset(q->qdisc);
145 	sch->qstats.backlog = 0;
146 	sch->q.qlen = 0;
147 	red_restart(&q->vars);
148 }
149 
150 static void red_destroy(struct Qdisc *sch)
151 {
152 	struct red_sched_data *q = qdisc_priv(sch);
153 
154 	del_timer_sync(&q->adapt_timer);
155 	qdisc_destroy(q->qdisc);
156 }
157 
158 static const struct nla_policy red_policy[TCA_RED_MAX + 1] = {
159 	[TCA_RED_PARMS]	= { .len = sizeof(struct tc_red_qopt) },
160 	[TCA_RED_STAB]	= { .len = RED_STAB_SIZE },
161 	[TCA_RED_MAX_P] = { .type = NLA_U32 },
162 };
163 
164 static int red_change(struct Qdisc *sch, struct nlattr *opt)
165 {
166 	struct red_sched_data *q = qdisc_priv(sch);
167 	struct nlattr *tb[TCA_RED_MAX + 1];
168 	struct tc_red_qopt *ctl;
169 	struct Qdisc *child = NULL;
170 	int err;
171 	u32 max_P;
172 
173 	if (opt == NULL)
174 		return -EINVAL;
175 
176 	err = nla_parse_nested(tb, TCA_RED_MAX, opt, red_policy);
177 	if (err < 0)
178 		return err;
179 
180 	if (tb[TCA_RED_PARMS] == NULL ||
181 	    tb[TCA_RED_STAB] == NULL)
182 		return -EINVAL;
183 
184 	max_P = tb[TCA_RED_MAX_P] ? nla_get_u32(tb[TCA_RED_MAX_P]) : 0;
185 
186 	ctl = nla_data(tb[TCA_RED_PARMS]);
187 
188 	if (ctl->limit > 0) {
189 		child = fifo_create_dflt(sch, &bfifo_qdisc_ops, ctl->limit);
190 		if (IS_ERR(child))
191 			return PTR_ERR(child);
192 	}
193 
194 	sch_tree_lock(sch);
195 	q->flags = ctl->flags;
196 	q->limit = ctl->limit;
197 	if (child) {
198 		qdisc_tree_reduce_backlog(q->qdisc, q->qdisc->q.qlen,
199 					  q->qdisc->qstats.backlog);
200 		qdisc_destroy(q->qdisc);
201 		q->qdisc = child;
202 	}
203 
204 	red_set_parms(&q->parms,
205 		      ctl->qth_min, ctl->qth_max, ctl->Wlog,
206 		      ctl->Plog, ctl->Scell_log,
207 		      nla_data(tb[TCA_RED_STAB]),
208 		      max_P);
209 	red_set_vars(&q->vars);
210 
211 	del_timer(&q->adapt_timer);
212 	if (ctl->flags & TC_RED_ADAPTATIVE)
213 		mod_timer(&q->adapt_timer, jiffies + HZ/2);
214 
215 	if (!q->qdisc->q.qlen)
216 		red_start_of_idle_period(&q->vars);
217 
218 	sch_tree_unlock(sch);
219 	return 0;
220 }
221 
222 static inline void red_adaptative_timer(unsigned long arg)
223 {
224 	struct Qdisc *sch = (struct Qdisc *)arg;
225 	struct red_sched_data *q = qdisc_priv(sch);
226 	spinlock_t *root_lock = qdisc_lock(qdisc_root_sleeping(sch));
227 
228 	spin_lock(root_lock);
229 	red_adaptative_algo(&q->parms, &q->vars);
230 	mod_timer(&q->adapt_timer, jiffies + HZ/2);
231 	spin_unlock(root_lock);
232 }
233 
234 static int red_init(struct Qdisc *sch, struct nlattr *opt)
235 {
236 	struct red_sched_data *q = qdisc_priv(sch);
237 
238 	q->qdisc = &noop_qdisc;
239 	setup_timer(&q->adapt_timer, red_adaptative_timer, (unsigned long)sch);
240 	return red_change(sch, opt);
241 }
242 
243 static int red_dump(struct Qdisc *sch, struct sk_buff *skb)
244 {
245 	struct red_sched_data *q = qdisc_priv(sch);
246 	struct nlattr *opts = NULL;
247 	struct tc_red_qopt opt = {
248 		.limit		= q->limit,
249 		.flags		= q->flags,
250 		.qth_min	= q->parms.qth_min >> q->parms.Wlog,
251 		.qth_max	= q->parms.qth_max >> q->parms.Wlog,
252 		.Wlog		= q->parms.Wlog,
253 		.Plog		= q->parms.Plog,
254 		.Scell_log	= q->parms.Scell_log,
255 	};
256 
257 	sch->qstats.backlog = q->qdisc->qstats.backlog;
258 	opts = nla_nest_start(skb, TCA_OPTIONS);
259 	if (opts == NULL)
260 		goto nla_put_failure;
261 	if (nla_put(skb, TCA_RED_PARMS, sizeof(opt), &opt) ||
262 	    nla_put_u32(skb, TCA_RED_MAX_P, q->parms.max_P))
263 		goto nla_put_failure;
264 	return nla_nest_end(skb, opts);
265 
266 nla_put_failure:
267 	nla_nest_cancel(skb, opts);
268 	return -EMSGSIZE;
269 }
270 
271 static int red_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
272 {
273 	struct red_sched_data *q = qdisc_priv(sch);
274 	struct tc_red_xstats st = {
275 		.early	= q->stats.prob_drop + q->stats.forced_drop,
276 		.pdrop	= q->stats.pdrop,
277 		.other	= q->stats.other,
278 		.marked	= q->stats.prob_mark + q->stats.forced_mark,
279 	};
280 
281 	return gnet_stats_copy_app(d, &st, sizeof(st));
282 }
283 
284 static int red_dump_class(struct Qdisc *sch, unsigned long cl,
285 			  struct sk_buff *skb, struct tcmsg *tcm)
286 {
287 	struct red_sched_data *q = qdisc_priv(sch);
288 
289 	tcm->tcm_handle |= TC_H_MIN(1);
290 	tcm->tcm_info = q->qdisc->handle;
291 	return 0;
292 }
293 
294 static int red_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
295 		     struct Qdisc **old)
296 {
297 	struct red_sched_data *q = qdisc_priv(sch);
298 
299 	if (new == NULL)
300 		new = &noop_qdisc;
301 
302 	*old = qdisc_replace(sch, new, &q->qdisc);
303 	return 0;
304 }
305 
306 static struct Qdisc *red_leaf(struct Qdisc *sch, unsigned long arg)
307 {
308 	struct red_sched_data *q = qdisc_priv(sch);
309 	return q->qdisc;
310 }
311 
312 static unsigned long red_get(struct Qdisc *sch, u32 classid)
313 {
314 	return 1;
315 }
316 
317 static void red_put(struct Qdisc *sch, unsigned long arg)
318 {
319 }
320 
321 static void red_walk(struct Qdisc *sch, struct qdisc_walker *walker)
322 {
323 	if (!walker->stop) {
324 		if (walker->count >= walker->skip)
325 			if (walker->fn(sch, 1, walker) < 0) {
326 				walker->stop = 1;
327 				return;
328 			}
329 		walker->count++;
330 	}
331 }
332 
333 static const struct Qdisc_class_ops red_class_ops = {
334 	.graft		=	red_graft,
335 	.leaf		=	red_leaf,
336 	.get		=	red_get,
337 	.put		=	red_put,
338 	.walk		=	red_walk,
339 	.dump		=	red_dump_class,
340 };
341 
342 static struct Qdisc_ops red_qdisc_ops __read_mostly = {
343 	.id		=	"red",
344 	.priv_size	=	sizeof(struct red_sched_data),
345 	.cl_ops		=	&red_class_ops,
346 	.enqueue	=	red_enqueue,
347 	.dequeue	=	red_dequeue,
348 	.peek		=	red_peek,
349 	.init		=	red_init,
350 	.reset		=	red_reset,
351 	.destroy	=	red_destroy,
352 	.change		=	red_change,
353 	.dump		=	red_dump,
354 	.dump_stats	=	red_dump_stats,
355 	.owner		=	THIS_MODULE,
356 };
357 
358 static int __init red_module_init(void)
359 {
360 	return register_qdisc(&red_qdisc_ops);
361 }
362 
363 static void __exit red_module_exit(void)
364 {
365 	unregister_qdisc(&red_qdisc_ops);
366 }
367 
368 module_init(red_module_init)
369 module_exit(red_module_exit)
370 
371 MODULE_LICENSE("GPL");
372