1 // SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
3 * Codel - The Controlled-Delay Active Queue Management algorithm
5 * Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com>
6 * Copyright (C) 2011-2012 Van Jacobson <van@pollere.net>
8 * Implemented on linux by :
9 * Copyright (C) 2012 Michael D. Taht <dave.taht@bufferbloat.net>
10 * Copyright (C) 2012,2015 Eric Dumazet <edumazet@google.com>
13 #include <linux/module.h>
14 #include <linux/slab.h>
15 #include <linux/types.h>
16 #include <linux/kernel.h>
17 #include <linux/errno.h>
18 #include <linux/skbuff.h>
19 #include <linux/prefetch.h>
20 #include <net/pkt_sched.h>
21 #include <net/codel.h>
22 #include <net/codel_impl.h>
23 #include <net/codel_qdisc.h>
26 #define DEFAULT_CODEL_LIMIT 1000
28 struct codel_sched_data {
29 struct codel_params params;
30 struct codel_vars vars;
31 struct codel_stats stats;
35 /* This is the specific function called from codel_dequeue()
36 * to dequeue a packet from queue. Note: backlog is handled in
37 * codel, we dont need to reduce it here.
39 static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx)
41 struct Qdisc *sch = ctx;
42 struct sk_buff *skb = __qdisc_dequeue_head(&sch->q);
45 sch->qstats.backlog -= qdisc_pkt_len(skb);
46 prefetch(&skb->end); /* we'll need skb_shinfo() */
51 static void drop_func(struct sk_buff *skb, void *ctx)
53 struct Qdisc *sch = ctx;
56 qdisc_qstats_drop(sch);
59 static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
61 struct codel_sched_data *q = qdisc_priv(sch);
64 skb = codel_dequeue(sch, &sch->qstats.backlog, &q->params, &q->vars,
65 &q->stats, qdisc_pkt_len, codel_get_enqueue_time,
66 drop_func, dequeue_func);
68 /* We cant call qdisc_tree_reduce_backlog() if our qlen is 0,
69 * or HTB crashes. Defer it for next round.
71 if (q->stats.drop_count && sch->q.qlen) {
72 qdisc_tree_reduce_backlog(sch, q->stats.drop_count, q->stats.drop_len);
73 q->stats.drop_count = 0;
74 q->stats.drop_len = 0;
77 qdisc_bstats_update(sch, skb);
81 static int codel_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
82 struct sk_buff **to_free)
84 struct codel_sched_data *q;
86 if (likely(qdisc_qlen(sch) < sch->limit)) {
87 codel_set_enqueue_time(skb);
88 return qdisc_enqueue_tail(skb, sch);
92 return qdisc_drop(skb, sch, to_free);
95 static const struct nla_policy codel_policy[TCA_CODEL_MAX + 1] = {
96 [TCA_CODEL_TARGET] = { .type = NLA_U32 },
97 [TCA_CODEL_LIMIT] = { .type = NLA_U32 },
98 [TCA_CODEL_INTERVAL] = { .type = NLA_U32 },
99 [TCA_CODEL_ECN] = { .type = NLA_U32 },
100 [TCA_CODEL_CE_THRESHOLD]= { .type = NLA_U32 },
103 static int codel_change(struct Qdisc *sch, struct nlattr *opt,
104 struct netlink_ext_ack *extack)
106 struct codel_sched_data *q = qdisc_priv(sch);
107 struct nlattr *tb[TCA_CODEL_MAX + 1];
108 unsigned int qlen, dropped = 0;
111 err = nla_parse_nested_deprecated(tb, TCA_CODEL_MAX, opt,
118 if (tb[TCA_CODEL_TARGET]) {
119 u32 target = nla_get_u32(tb[TCA_CODEL_TARGET]);
121 q->params.target = ((u64)target * NSEC_PER_USEC) >> CODEL_SHIFT;
124 if (tb[TCA_CODEL_CE_THRESHOLD]) {
125 u64 val = nla_get_u32(tb[TCA_CODEL_CE_THRESHOLD]);
127 q->params.ce_threshold = (val * NSEC_PER_USEC) >> CODEL_SHIFT;
130 if (tb[TCA_CODEL_INTERVAL]) {
131 u32 interval = nla_get_u32(tb[TCA_CODEL_INTERVAL]);
133 q->params.interval = ((u64)interval * NSEC_PER_USEC) >> CODEL_SHIFT;
136 if (tb[TCA_CODEL_LIMIT])
137 sch->limit = nla_get_u32(tb[TCA_CODEL_LIMIT]);
139 if (tb[TCA_CODEL_ECN])
140 q->params.ecn = !!nla_get_u32(tb[TCA_CODEL_ECN]);
143 while (sch->q.qlen > sch->limit) {
144 struct sk_buff *skb = __qdisc_dequeue_head(&sch->q);
146 dropped += qdisc_pkt_len(skb);
147 qdisc_qstats_backlog_dec(sch, skb);
148 rtnl_qdisc_drop(skb, sch);
150 qdisc_tree_reduce_backlog(sch, qlen - sch->q.qlen, dropped);
152 sch_tree_unlock(sch);
156 static int codel_init(struct Qdisc *sch, struct nlattr *opt,
157 struct netlink_ext_ack *extack)
159 struct codel_sched_data *q = qdisc_priv(sch);
161 sch->limit = DEFAULT_CODEL_LIMIT;
163 codel_params_init(&q->params);
164 codel_vars_init(&q->vars);
165 codel_stats_init(&q->stats);
166 q->params.mtu = psched_mtu(qdisc_dev(sch));
169 int err = codel_change(sch, opt, extack);
176 sch->flags |= TCQ_F_CAN_BYPASS;
178 sch->flags &= ~TCQ_F_CAN_BYPASS;
183 static int codel_dump(struct Qdisc *sch, struct sk_buff *skb)
185 struct codel_sched_data *q = qdisc_priv(sch);
188 opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
190 goto nla_put_failure;
192 if (nla_put_u32(skb, TCA_CODEL_TARGET,
193 codel_time_to_us(q->params.target)) ||
194 nla_put_u32(skb, TCA_CODEL_LIMIT,
196 nla_put_u32(skb, TCA_CODEL_INTERVAL,
197 codel_time_to_us(q->params.interval)) ||
198 nla_put_u32(skb, TCA_CODEL_ECN,
200 goto nla_put_failure;
201 if (q->params.ce_threshold != CODEL_DISABLED_THRESHOLD &&
202 nla_put_u32(skb, TCA_CODEL_CE_THRESHOLD,
203 codel_time_to_us(q->params.ce_threshold)))
204 goto nla_put_failure;
205 return nla_nest_end(skb, opts);
208 nla_nest_cancel(skb, opts);
212 static int codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
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 .ce_mark = q->stats.ce_mark,
226 if (q->vars.dropping) {
227 codel_tdiff_t delta = q->vars.drop_next - codel_get_time();
230 st.drop_next = codel_time_to_us(delta);
232 st.drop_next = -codel_time_to_us(-delta);
235 return gnet_stats_copy_app(d, &st, sizeof(st));
238 static void codel_reset(struct Qdisc *sch)
240 struct codel_sched_data *q = qdisc_priv(sch);
242 qdisc_reset_queue(sch);
243 codel_vars_init(&q->vars);
246 static struct Qdisc_ops codel_qdisc_ops __read_mostly = {
248 .priv_size = sizeof(struct codel_sched_data),
250 .enqueue = codel_qdisc_enqueue,
251 .dequeue = codel_qdisc_dequeue,
252 .peek = qdisc_peek_dequeued,
254 .reset = codel_reset,
255 .change = codel_change,
257 .dump_stats = codel_dump_stats,
258 .owner = THIS_MODULE,
260 MODULE_ALIAS_NET_SCH("codel");
262 static int __init codel_module_init(void)
264 return register_qdisc(&codel_qdisc_ops);
267 static void __exit codel_module_exit(void)
269 unregister_qdisc(&codel_qdisc_ops);
272 module_init(codel_module_init)
273 module_exit(codel_module_exit)
275 MODULE_DESCRIPTION("Controlled Delay queue discipline");
276 MODULE_AUTHOR("Dave Taht");
277 MODULE_AUTHOR("Eric Dumazet");
278 MODULE_LICENSE("Dual BSD/GPL");