1// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
2/*
3 * Codel - The Controlled-Delay Active Queue Management algorithm
4 *
5 * Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com>
6 * Copyright (C) 2011-2012 Van Jacobson <van@pollere.net>
7 *
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>
11 */
12
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>
24
25
26#define DEFAULT_CODEL_LIMIT 1000
27
28struct codel_sched_data {
29 struct codel_params params;
30 struct codel_vars vars;
31 struct codel_stats stats;
32 u32 drop_overlimit;
33};
34
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.
38 */
39static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx)
40{
41 struct Qdisc *sch = ctx;
42 struct sk_buff *skb = __qdisc_dequeue_head(qh: &sch->q);
43
44 if (skb) {
45 sch->qstats.backlog -= qdisc_pkt_len(skb);
46 prefetch(&skb->end); /* we'll need skb_shinfo() */
47 }
48 return skb;
49}
50
51static void drop_func(struct sk_buff *skb, void *ctx)
52{
53 struct Qdisc *sch = ctx;
54
55 kfree_skb(skb);
56 qdisc_qstats_drop(sch);
57}
58
59static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
60{
61 struct codel_sched_data *q = qdisc_priv(sch);
62 struct sk_buff *skb;
63
64 skb = codel_dequeue(ctx: sch, backlog: &sch->qstats.backlog, params: &q->params, vars: &q->vars,
65 stats: &q->stats, skb_len_func: qdisc_pkt_len, skb_time_func: codel_get_enqueue_time,
66 drop_func, dequeue_func);
67
68 /* We cant call qdisc_tree_reduce_backlog() if our qlen is 0,
69 * or HTB crashes. Defer it for next round.
70 */
71 if (q->stats.drop_count && sch->q.qlen) {
72 qdisc_tree_reduce_backlog(qdisc: sch, n: q->stats.drop_count, len: q->stats.drop_len);
73 q->stats.drop_count = 0;
74 q->stats.drop_len = 0;
75 }
76 if (skb)
77 qdisc_bstats_update(sch, skb);
78 return skb;
79}
80
81static int codel_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
82 struct sk_buff **to_free)
83{
84 struct codel_sched_data *q;
85
86 if (likely(qdisc_qlen(sch) < sch->limit)) {
87 codel_set_enqueue_time(skb);
88 return qdisc_enqueue_tail(skb, sch);
89 }
90 q = qdisc_priv(sch);
91 q->drop_overlimit++;
92 return qdisc_drop(skb, sch, to_free);
93}
94
95static 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 },
101};
102
103static int codel_change(struct Qdisc *sch, struct nlattr *opt,
104 struct netlink_ext_ack *extack)
105{
106 struct codel_sched_data *q = qdisc_priv(sch);
107 struct nlattr *tb[TCA_CODEL_MAX + 1];
108 unsigned int qlen, dropped = 0;
109 int err;
110
111 err = nla_parse_nested_deprecated(tb, TCA_CODEL_MAX, nla: opt,
112 policy: codel_policy, NULL);
113 if (err < 0)
114 return err;
115
116 sch_tree_lock(q: sch);
117
118 if (tb[TCA_CODEL_TARGET]) {
119 u32 target = nla_get_u32(nla: tb[TCA_CODEL_TARGET]);
120
121 q->params.target = ((u64)target * NSEC_PER_USEC) >> CODEL_SHIFT;
122 }
123
124 if (tb[TCA_CODEL_CE_THRESHOLD]) {
125 u64 val = nla_get_u32(nla: tb[TCA_CODEL_CE_THRESHOLD]);
126
127 q->params.ce_threshold = (val * NSEC_PER_USEC) >> CODEL_SHIFT;
128 }
129
130 if (tb[TCA_CODEL_INTERVAL]) {
131 u32 interval = nla_get_u32(nla: tb[TCA_CODEL_INTERVAL]);
132
133 q->params.interval = ((u64)interval * NSEC_PER_USEC) >> CODEL_SHIFT;
134 }
135
136 if (tb[TCA_CODEL_LIMIT])
137 sch->limit = nla_get_u32(nla: tb[TCA_CODEL_LIMIT]);
138
139 if (tb[TCA_CODEL_ECN])
140 q->params.ecn = !!nla_get_u32(nla: tb[TCA_CODEL_ECN]);
141
142 qlen = sch->q.qlen;
143 while (sch->q.qlen > sch->limit) {
144 struct sk_buff *skb = __qdisc_dequeue_head(qh: &sch->q);
145
146 dropped += qdisc_pkt_len(skb);
147 qdisc_qstats_backlog_dec(sch, skb);
148 rtnl_qdisc_drop(skb, sch);
149 }
150 qdisc_tree_reduce_backlog(qdisc: sch, n: qlen - sch->q.qlen, len: dropped);
151
152 sch_tree_unlock(q: sch);
153 return 0;
154}
155
156static int codel_init(struct Qdisc *sch, struct nlattr *opt,
157 struct netlink_ext_ack *extack)
158{
159 struct codel_sched_data *q = qdisc_priv(sch);
160
161 sch->limit = DEFAULT_CODEL_LIMIT;
162
163 codel_params_init(params: &q->params);
164 codel_vars_init(vars: &q->vars);
165 codel_stats_init(stats: &q->stats);
166 q->params.mtu = psched_mtu(dev: qdisc_dev(qdisc: sch));
167
168 if (opt) {
169 int err = codel_change(sch, opt, extack);
170
171 if (err)
172 return err;
173 }
174
175 if (sch->limit >= 1)
176 sch->flags |= TCQ_F_CAN_BYPASS;
177 else
178 sch->flags &= ~TCQ_F_CAN_BYPASS;
179
180 return 0;
181}
182
183static int codel_dump(struct Qdisc *sch, struct sk_buff *skb)
184{
185 struct codel_sched_data *q = qdisc_priv(sch);
186 struct nlattr *opts;
187
188 opts = nla_nest_start_noflag(skb, attrtype: TCA_OPTIONS);
189 if (opts == NULL)
190 goto nla_put_failure;
191
192 if (nla_put_u32(skb, attrtype: TCA_CODEL_TARGET,
193 value: codel_time_to_us(val: q->params.target)) ||
194 nla_put_u32(skb, attrtype: TCA_CODEL_LIMIT,
195 value: sch->limit) ||
196 nla_put_u32(skb, attrtype: TCA_CODEL_INTERVAL,
197 value: codel_time_to_us(val: q->params.interval)) ||
198 nla_put_u32(skb, attrtype: TCA_CODEL_ECN,
199 value: q->params.ecn))
200 goto nla_put_failure;
201 if (q->params.ce_threshold != CODEL_DISABLED_THRESHOLD &&
202 nla_put_u32(skb, attrtype: TCA_CODEL_CE_THRESHOLD,
203 value: codel_time_to_us(val: q->params.ce_threshold)))
204 goto nla_put_failure;
205 return nla_nest_end(skb, start: opts);
206
207nla_put_failure:
208 nla_nest_cancel(skb, start: 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(val: q->vars.ldelay),
221 .dropping = q->vars.dropping,
222 .ecn_mark = q->stats.ecn_mark,
223 .ce_mark = q->stats.ce_mark,
224 };
225
226 if (q->vars.dropping) {
227 codel_tdiff_t delta = q->vars.drop_next - codel_get_time();
228
229 if (delta >= 0)
230 st.drop_next = codel_time_to_us(val: delta);
231 else
232 st.drop_next = -codel_time_to_us(val: -delta);
233 }
234
235 return gnet_stats_copy_app(d, st: &st, len: sizeof(st));
236}
237
238static void codel_reset(struct Qdisc *sch)
239{
240 struct codel_sched_data *q = qdisc_priv(sch);
241
242 qdisc_reset_queue(sch);
243 codel_vars_init(vars: &q->vars);
244}
245
246static struct Qdisc_ops codel_qdisc_ops __read_mostly = {
247 .id = "codel",
248 .priv_size = sizeof(struct codel_sched_data),
249
250 .enqueue = codel_qdisc_enqueue,
251 .dequeue = codel_qdisc_dequeue,
252 .peek = qdisc_peek_dequeued,
253 .init = codel_init,
254 .reset = codel_reset,
255 .change = codel_change,
256 .dump = codel_dump,
257 .dump_stats = codel_dump_stats,
258 .owner = THIS_MODULE,
259};
260MODULE_ALIAS_NET_SCH("codel");
261
262static int __init codel_module_init(void)
263{
264 return register_qdisc(qops: &codel_qdisc_ops);
265}
266
267static void __exit codel_module_exit(void)
268{
269 unregister_qdisc(qops: &codel_qdisc_ops);
270}
271
272module_init(codel_module_init)
273module_exit(codel_module_exit)
274
275MODULE_DESCRIPTION("Controlled Delay queue discipline");
276MODULE_AUTHOR("Dave Taht");
277MODULE_AUTHOR("Eric Dumazet");
278MODULE_LICENSE("Dual BSD/GPL");
279

source code of linux/net/sched/sch_codel.c