1/*
2 * Codel - The Controlled-Delay Active Queue Management algorithm
3 *
4 *  Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com>
5 *  Copyright (C) 2011-2012 Van Jacobson <van@pollere.net>
6 *
7 *  Implemented on linux by :
8 *  Copyright (C) 2012 Michael D. Taht <dave.taht@bufferbloat.net>
9 *  Copyright (C) 2012 Eric Dumazet <edumazet@google.com>
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 *    notice, this list of conditions, and the following disclaimer,
16 *    without modification.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 *    notice, this list of conditions and the following disclaimer in the
19 *    documentation and/or other materials provided with the distribution.
20 * 3. The names of the authors may not be used to endorse or promote products
21 *    derived from this software without specific prior written permission.
22 *
23 * Alternatively, provided that this notice is retained in full, this
24 * software may be distributed under the terms of the GNU General
25 * Public License ("GPL") version 2, in which case the provisions of the
26 * GPL apply INSTEAD OF those given above.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
39 * DAMAGE.
40 *
41 */
42
43#include <linux/module.h>
44#include <linux/slab.h>
45#include <linux/types.h>
46#include <linux/kernel.h>
47#include <linux/errno.h>
48#include <linux/skbuff.h>
49#include <linux/prefetch.h>
50#include <net/pkt_sched.h>
51#include <net/codel.h>
52
53
54#define DEFAULT_CODEL_LIMIT 1000
55
56struct codel_sched_data {
57	struct codel_params	params;
58	struct codel_vars	vars;
59	struct codel_stats	stats;
60	u32			drop_overlimit;
61};
62
63/* This is the specific function called from codel_dequeue()
64 * to dequeue a packet from queue. Note: backlog is handled in
65 * codel, we dont need to reduce it here.
66 */
67static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
68{
69	struct sk_buff *skb = __skb_dequeue(&sch->q);
70
71	prefetch(&skb->end); /* we'll need skb_shinfo() */
72	return skb;
73}
74
75static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
76{
77	struct codel_sched_data *q = qdisc_priv(sch);
78	struct sk_buff *skb;
79
80	skb = codel_dequeue(sch, &q->params, &q->vars, &q->stats, dequeue);
81
82	/* We cant call qdisc_tree_decrease_qlen() if our qlen is 0,
83	 * or HTB crashes. Defer it for next round.
84	 */
85	if (q->stats.drop_count && sch->q.qlen) {
86		qdisc_tree_decrease_qlen(sch, q->stats.drop_count);
87		q->stats.drop_count = 0;
88	}
89	if (skb)
90		qdisc_bstats_update(sch, skb);
91	return skb;
92}
93
94static int codel_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch)
95{
96	struct codel_sched_data *q;
97
98	if (likely(qdisc_qlen(sch) < sch->limit)) {
99		codel_set_enqueue_time(skb);
100		return qdisc_enqueue_tail(skb, sch);
101	}
102	q = qdisc_priv(sch);
103	q->drop_overlimit++;
104	return qdisc_drop(skb, sch);
105}
106
107static const struct nla_policy codel_policy[TCA_CODEL_MAX + 1] = {
108	[TCA_CODEL_TARGET]	= { .type = NLA_U32 },
109	[TCA_CODEL_LIMIT]	= { .type = NLA_U32 },
110	[TCA_CODEL_INTERVAL]	= { .type = NLA_U32 },
111	[TCA_CODEL_ECN]		= { .type = NLA_U32 },
112};
113
114static int codel_change(struct Qdisc *sch, struct nlattr *opt)
115{
116	struct codel_sched_data *q = qdisc_priv(sch);
117	struct nlattr *tb[TCA_CODEL_MAX + 1];
118	unsigned int qlen;
119	int err;
120
121	if (!opt)
122		return -EINVAL;
123
124	err = nla_parse_nested(tb, TCA_CODEL_MAX, opt, codel_policy);
125	if (err < 0)
126		return err;
127
128	sch_tree_lock(sch);
129
130	if (tb[TCA_CODEL_TARGET]) {
131		u32 target = nla_get_u32(tb[TCA_CODEL_TARGET]);
132
133		q->params.target = ((u64)target * NSEC_PER_USEC) >> CODEL_SHIFT;
134	}
135
136	if (tb[TCA_CODEL_INTERVAL]) {
137		u32 interval = nla_get_u32(tb[TCA_CODEL_INTERVAL]);
138
139		q->params.interval = ((u64)interval * NSEC_PER_USEC) >> CODEL_SHIFT;
140	}
141
142	if (tb[TCA_CODEL_LIMIT])
143		sch->limit = nla_get_u32(tb[TCA_CODEL_LIMIT]);
144
145	if (tb[TCA_CODEL_ECN])
146		q->params.ecn = !!nla_get_u32(tb[TCA_CODEL_ECN]);
147
148	qlen = sch->q.qlen;
149	while (sch->q.qlen > sch->limit) {
150		struct sk_buff *skb = __skb_dequeue(&sch->q);
151
152		sch->qstats.backlog -= qdisc_pkt_len(skb);
153		qdisc_drop(skb, sch);
154	}
155	qdisc_tree_decrease_qlen(sch, qlen - sch->q.qlen);
156
157	sch_tree_unlock(sch);
158	return 0;
159}
160
161static int codel_init(struct Qdisc *sch, struct nlattr *opt)
162{
163	struct codel_sched_data *q = qdisc_priv(sch);
164
165	sch->limit = DEFAULT_CODEL_LIMIT;
166
167	codel_params_init(&q->params);
168	codel_vars_init(&q->vars);
169	codel_stats_init(&q->stats);
170
171	if (opt) {
172		int err = codel_change(sch, opt);
173
174		if (err)
175			return err;
176	}
177
178	if (sch->limit >= 1)
179		sch->flags |= TCQ_F_CAN_BYPASS;
180	else
181		sch->flags &= ~TCQ_F_CAN_BYPASS;
182
183	return 0;
184}
185
186static int codel_dump(struct Qdisc *sch, struct sk_buff *skb)
187{
188	struct codel_sched_data *q = qdisc_priv(sch);
189	struct nlattr *opts;
190
191	opts = nla_nest_start(skb, TCA_OPTIONS);
192	if (opts == NULL)
193		goto nla_put_failure;
194
195	if (nla_put_u32(skb, TCA_CODEL_TARGET,
196			codel_time_to_us(q->params.target)) ||
197	    nla_put_u32(skb, TCA_CODEL_LIMIT,
198			sch->limit) ||
199	    nla_put_u32(skb, TCA_CODEL_INTERVAL,
200			codel_time_to_us(q->params.interval)) ||
201	    nla_put_u32(skb, TCA_CODEL_ECN,
202			q->params.ecn))
203		goto nla_put_failure;
204
205	return nla_nest_end(skb, opts);
206
207nla_put_failure:
208	nla_nest_cancel(skb, opts);
209	return -1;
210}
211
212static int codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
213{
214	const struct codel_sched_data *q = qdisc_priv(sch);
215	struct tc_codel_xstats st = {
216		.maxpacket	= q->stats.maxpacket,
217		.count		= q->vars.count,
218		.lastcount	= q->vars.lastcount,
219		.drop_overlimit = q->drop_overlimit,
220		.ldelay		= codel_time_to_us(q->vars.ldelay),
221		.dropping	= q->vars.dropping,
222		.ecn_mark	= q->stats.ecn_mark,
223	};
224
225	if (q->vars.dropping) {
226		codel_tdiff_t delta = q->vars.drop_next - codel_get_time();
227
228		if (delta >= 0)
229			st.drop_next = codel_time_to_us(delta);
230		else
231			st.drop_next = -codel_time_to_us(-delta);
232	}
233
234	return gnet_stats_copy_app(d, &st, sizeof(st));
235}
236
237static void codel_reset(struct Qdisc *sch)
238{
239	struct codel_sched_data *q = qdisc_priv(sch);
240
241	qdisc_reset_queue(sch);
242	codel_vars_init(&q->vars);
243}
244
245static struct Qdisc_ops codel_qdisc_ops __read_mostly = {
246	.id		=	"codel",
247	.priv_size	=	sizeof(struct codel_sched_data),
248
249	.enqueue	=	codel_qdisc_enqueue,
250	.dequeue	=	codel_qdisc_dequeue,
251	.peek		=	qdisc_peek_dequeued,
252	.init		=	codel_init,
253	.reset		=	codel_reset,
254	.change 	=	codel_change,
255	.dump		=	codel_dump,
256	.dump_stats	=	codel_dump_stats,
257	.owner		=	THIS_MODULE,
258};
259
260static int __init codel_module_init(void)
261{
262	return register_qdisc(&codel_qdisc_ops);
263}
264
265static void __exit codel_module_exit(void)
266{
267	unregister_qdisc(&codel_qdisc_ops);
268}
269
270module_init(codel_module_init)
271module_exit(codel_module_exit)
272
273MODULE_DESCRIPTION("Controlled Delay queue discipline");
274MODULE_AUTHOR("Dave Taht");
275MODULE_AUTHOR("Eric Dumazet");
276MODULE_LICENSE("Dual BSD/GPL");
277