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Linux/net/sched/sch_codel.c

  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 
 56 struct 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  */
 67 static 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 
 75 static 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 
 94 static 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 
107 static 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 
114 static 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 
161 static 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 
186 static 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 
207 nla_put_failure:
208         nla_nest_cancel(skb, opts);
209         return -1;
210 }
211 
212 static 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 
237 static 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 
245 static 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 
260 static int __init codel_module_init(void)
261 {
262         return register_qdisc(&codel_qdisc_ops);
263 }
264 
265 static void __exit codel_module_exit(void)
266 {
267         unregister_qdisc(&codel_qdisc_ops);
268 }
269 
270 module_init(codel_module_init)
271 module_exit(codel_module_exit)
272 
273 MODULE_DESCRIPTION("Controlled Delay queue discipline");
274 MODULE_AUTHOR("Dave Taht");
275 MODULE_AUTHOR("Eric Dumazet");
276 MODULE_LICENSE("Dual BSD/GPL");
277 

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