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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) 2012,2015 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         [TCA_CODEL_CE_THRESHOLD]= { .type = NLA_U32 },
113 };
114 
115 static int codel_change(struct Qdisc *sch, struct nlattr *opt)
116 {
117         struct codel_sched_data *q = qdisc_priv(sch);
118         struct nlattr *tb[TCA_CODEL_MAX + 1];
119         unsigned int qlen;
120         int err;
121 
122         if (!opt)
123                 return -EINVAL;
124 
125         err = nla_parse_nested(tb, TCA_CODEL_MAX, opt, codel_policy);
126         if (err < 0)
127                 return err;
128 
129         sch_tree_lock(sch);
130 
131         if (tb[TCA_CODEL_TARGET]) {
132                 u32 target = nla_get_u32(tb[TCA_CODEL_TARGET]);
133 
134                 q->params.target = ((u64)target * NSEC_PER_USEC) >> CODEL_SHIFT;
135         }
136 
137         if (tb[TCA_CODEL_CE_THRESHOLD]) {
138                 u64 val = nla_get_u32(tb[TCA_CODEL_CE_THRESHOLD]);
139 
140                 q->params.ce_threshold = (val * NSEC_PER_USEC) >> CODEL_SHIFT;
141         }
142 
143         if (tb[TCA_CODEL_INTERVAL]) {
144                 u32 interval = nla_get_u32(tb[TCA_CODEL_INTERVAL]);
145 
146                 q->params.interval = ((u64)interval * NSEC_PER_USEC) >> CODEL_SHIFT;
147         }
148 
149         if (tb[TCA_CODEL_LIMIT])
150                 sch->limit = nla_get_u32(tb[TCA_CODEL_LIMIT]);
151 
152         if (tb[TCA_CODEL_ECN])
153                 q->params.ecn = !!nla_get_u32(tb[TCA_CODEL_ECN]);
154 
155         qlen = sch->q.qlen;
156         while (sch->q.qlen > sch->limit) {
157                 struct sk_buff *skb = __skb_dequeue(&sch->q);
158 
159                 qdisc_qstats_backlog_dec(sch, skb);
160                 qdisc_drop(skb, sch);
161         }
162         qdisc_tree_decrease_qlen(sch, qlen - sch->q.qlen);
163 
164         sch_tree_unlock(sch);
165         return 0;
166 }
167 
168 static int codel_init(struct Qdisc *sch, struct nlattr *opt)
169 {
170         struct codel_sched_data *q = qdisc_priv(sch);
171 
172         sch->limit = DEFAULT_CODEL_LIMIT;
173 
174         codel_params_init(&q->params, sch);
175         codel_vars_init(&q->vars);
176         codel_stats_init(&q->stats);
177 
178         if (opt) {
179                 int err = codel_change(sch, opt);
180 
181                 if (err)
182                         return err;
183         }
184 
185         if (sch->limit >= 1)
186                 sch->flags |= TCQ_F_CAN_BYPASS;
187         else
188                 sch->flags &= ~TCQ_F_CAN_BYPASS;
189 
190         return 0;
191 }
192 
193 static int codel_dump(struct Qdisc *sch, struct sk_buff *skb)
194 {
195         struct codel_sched_data *q = qdisc_priv(sch);
196         struct nlattr *opts;
197 
198         opts = nla_nest_start(skb, TCA_OPTIONS);
199         if (opts == NULL)
200                 goto nla_put_failure;
201 
202         if (nla_put_u32(skb, TCA_CODEL_TARGET,
203                         codel_time_to_us(q->params.target)) ||
204             nla_put_u32(skb, TCA_CODEL_LIMIT,
205                         sch->limit) ||
206             nla_put_u32(skb, TCA_CODEL_INTERVAL,
207                         codel_time_to_us(q->params.interval)) ||
208             nla_put_u32(skb, TCA_CODEL_ECN,
209                         q->params.ecn))
210                 goto nla_put_failure;
211         if (q->params.ce_threshold != CODEL_DISABLED_THRESHOLD &&
212             nla_put_u32(skb, TCA_CODEL_CE_THRESHOLD,
213                         codel_time_to_us(q->params.ce_threshold)))
214                 goto nla_put_failure;
215         return nla_nest_end(skb, opts);
216 
217 nla_put_failure:
218         nla_nest_cancel(skb, opts);
219         return -1;
220 }
221 
222 static int codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
223 {
224         const struct codel_sched_data *q = qdisc_priv(sch);
225         struct tc_codel_xstats st = {
226                 .maxpacket      = q->stats.maxpacket,
227                 .count          = q->vars.count,
228                 .lastcount      = q->vars.lastcount,
229                 .drop_overlimit = q->drop_overlimit,
230                 .ldelay         = codel_time_to_us(q->vars.ldelay),
231                 .dropping       = q->vars.dropping,
232                 .ecn_mark       = q->stats.ecn_mark,
233                 .ce_mark        = q->stats.ce_mark,
234         };
235 
236         if (q->vars.dropping) {
237                 codel_tdiff_t delta = q->vars.drop_next - codel_get_time();
238 
239                 if (delta >= 0)
240                         st.drop_next = codel_time_to_us(delta);
241                 else
242                         st.drop_next = -codel_time_to_us(-delta);
243         }
244 
245         return gnet_stats_copy_app(d, &st, sizeof(st));
246 }
247 
248 static void codel_reset(struct Qdisc *sch)
249 {
250         struct codel_sched_data *q = qdisc_priv(sch);
251 
252         qdisc_reset_queue(sch);
253         codel_vars_init(&q->vars);
254 }
255 
256 static struct Qdisc_ops codel_qdisc_ops __read_mostly = {
257         .id             =       "codel",
258         .priv_size      =       sizeof(struct codel_sched_data),
259 
260         .enqueue        =       codel_qdisc_enqueue,
261         .dequeue        =       codel_qdisc_dequeue,
262         .peek           =       qdisc_peek_dequeued,
263         .init           =       codel_init,
264         .reset          =       codel_reset,
265         .change         =       codel_change,
266         .dump           =       codel_dump,
267         .dump_stats     =       codel_dump_stats,
268         .owner          =       THIS_MODULE,
269 };
270 
271 static int __init codel_module_init(void)
272 {
273         return register_qdisc(&codel_qdisc_ops);
274 }
275 
276 static void __exit codel_module_exit(void)
277 {
278         unregister_qdisc(&codel_qdisc_ops);
279 }
280 
281 module_init(codel_module_init)
282 module_exit(codel_module_exit)
283 
284 MODULE_DESCRIPTION("Controlled Delay queue discipline");
285 MODULE_AUTHOR("Dave Taht");
286 MODULE_AUTHOR("Eric Dumazet");
287 MODULE_LICENSE("Dual BSD/GPL");
288 

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