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// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
/*
* Codel - The Controlled-Delay Active Queue Management algorithm
*
* Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com>
* Copyright (C) 2011-2012 Van Jacobson <van@pollere.net>
*
* Implemented on linux by :
* Copyright (C) 2012 Michael D. Taht <dave.taht@bufferbloat.net>
* Copyright (C) 2012,2015 Eric Dumazet <edumazet@google.com>
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/prefetch.h>
#include <net/pkt_sched.h>
#include <net/codel.h>
#include <net/codel_impl.h>
#include <net/codel_qdisc.h>
#define DEFAULT_CODEL_LIMIT 1000
struct codel_sched_data {
struct codel_params params;
struct codel_vars vars;
struct codel_stats stats;
u32 drop_overlimit;
};
/* This is the specific function called from codel_dequeue()
* to dequeue a packet from queue. Note: backlog is handled in
* codel, we dont need to reduce it here.
*/
static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx)
{
struct Qdisc *sch = ctx;
struct sk_buff *skb = __qdisc_dequeue_head(&sch->q);
if (skb) {
sch->qstats.backlog -= qdisc_pkt_len(skb);
prefetch(&skb->end); /* we'll need skb_shinfo() */
}
return skb;
}
static void drop_func(struct sk_buff *skb, void *ctx)
{
struct Qdisc *sch = ctx;
kfree_skb(skb);
qdisc_qstats_drop(sch);
}
static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
{
struct codel_sched_data *q = qdisc_priv(sch);
struct sk_buff *skb;
skb = codel_dequeue(sch, &sch->qstats.backlog, &q->params, &q->vars,
&q->stats, qdisc_pkt_len, codel_get_enqueue_time,
drop_func, dequeue_func);
/* We cant call qdisc_tree_reduce_backlog() if our qlen is 0,
* or HTB crashes. Defer it for next round.
*/
if (q->stats.drop_count && sch->q.qlen) {
qdisc_tree_reduce_backlog(sch, q->stats.drop_count, q->stats.drop_len);
q->stats.drop_count = 0;
q->stats.drop_len = 0;
}
if (skb)
qdisc_bstats_update(sch, skb);
return skb;
}
static int codel_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
struct sk_buff **to_free)
{
struct codel_sched_data *q;
if (likely(qdisc_qlen(sch) < sch->limit)) {
codel_set_enqueue_time(skb);
return qdisc_enqueue_tail(skb, sch);
}
q = qdisc_priv(sch);
q->drop_overlimit++;
return qdisc_drop(skb, sch, to_free);
}
static const struct nla_policy codel_policy[TCA_CODEL_MAX + 1] = {
[TCA_CODEL_TARGET] = { .type = NLA_U32 },
[TCA_CODEL_LIMIT] = { .type = NLA_U32 },
[TCA_CODEL_INTERVAL] = { .type = NLA_U32 },
[TCA_CODEL_ECN] = { .type = NLA_U32 },
[TCA_CODEL_CE_THRESHOLD]= { .type = NLA_U32 },
};
static int codel_change(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
{
struct codel_sched_data *q = qdisc_priv(sch);
struct nlattr *tb[TCA_CODEL_MAX + 1];
unsigned int qlen, dropped = 0;
int err;
err = nla_parse_nested_deprecated(tb, TCA_CODEL_MAX, opt,
codel_policy, NULL);
if (err < 0)
return err;
sch_tree_lock(sch);
if (tb[TCA_CODEL_TARGET]) {
u32 target = nla_get_u32(tb[TCA_CODEL_TARGET]);
WRITE_ONCE(q->params.target,
((u64)target * NSEC_PER_USEC) >> CODEL_SHIFT);
}
if (tb[TCA_CODEL_CE_THRESHOLD]) {
u64 val = nla_get_u32(tb[TCA_CODEL_CE_THRESHOLD]);
WRITE_ONCE(q->params.ce_threshold,
(val * NSEC_PER_USEC) >> CODEL_SHIFT);
}
if (tb[TCA_CODEL_INTERVAL]) {
u32 interval = nla_get_u32(tb[TCA_CODEL_INTERVAL]);
WRITE_ONCE(q->params.interval,
((u64)interval * NSEC_PER_USEC) >> CODEL_SHIFT);
}
if (tb[TCA_CODEL_LIMIT])
WRITE_ONCE(sch->limit,
nla_get_u32(tb[TCA_CODEL_LIMIT]));
if (tb[TCA_CODEL_ECN])
WRITE_ONCE(q->params.ecn,
!!nla_get_u32(tb[TCA_CODEL_ECN]));
qlen = sch->q.qlen;
while (sch->q.qlen > sch->limit) {
struct sk_buff *skb = __qdisc_dequeue_head(&sch->q);
dropped += qdisc_pkt_len(skb);
qdisc_qstats_backlog_dec(sch, skb);
rtnl_qdisc_drop(skb, sch);
}
qdisc_tree_reduce_backlog(sch, qlen - sch->q.qlen, dropped);
sch_tree_unlock(sch);
return 0;
}
static int codel_init(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
{
struct codel_sched_data *q = qdisc_priv(sch);
sch->limit = DEFAULT_CODEL_LIMIT;
codel_params_init(&q->params);
codel_vars_init(&q->vars);
codel_stats_init(&q->stats);
q->params.mtu = psched_mtu(qdisc_dev(sch));
if (opt) {
int err = codel_change(sch, opt, extack);
if (err)
return err;
}
if (sch->limit >= 1)
sch->flags |= TCQ_F_CAN_BYPASS;
else
sch->flags &= ~TCQ_F_CAN_BYPASS;
return 0;
}
static int codel_dump(struct Qdisc *sch, struct sk_buff *skb)
{
struct codel_sched_data *q = qdisc_priv(sch);
codel_time_t ce_threshold;
struct nlattr *opts;
opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
if (opts == NULL)
goto nla_put_failure;
if (nla_put_u32(skb, TCA_CODEL_TARGET,
codel_time_to_us(READ_ONCE(q->params.target))) ||
nla_put_u32(skb, TCA_CODEL_LIMIT,
READ_ONCE(sch->limit)) ||
nla_put_u32(skb, TCA_CODEL_INTERVAL,
codel_time_to_us(READ_ONCE(q->params.interval))) ||
nla_put_u32(skb, TCA_CODEL_ECN,
READ_ONCE(q->params.ecn)))
goto nla_put_failure;
ce_threshold = READ_ONCE(q->params.ce_threshold);
if (ce_threshold != CODEL_DISABLED_THRESHOLD &&
nla_put_u32(skb, TCA_CODEL_CE_THRESHOLD,
codel_time_to_us(ce_threshold)))
goto nla_put_failure;
return nla_nest_end(skb, opts);
nla_put_failure:
nla_nest_cancel(skb, opts);
return -1;
}
static int codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
{
const struct codel_sched_data *q = qdisc_priv(sch);
struct tc_codel_xstats st = {
.maxpacket = q->stats.maxpacket,
.count = q->vars.count,
.lastcount = q->vars.lastcount,
.drop_overlimit = q->drop_overlimit,
.ldelay = codel_time_to_us(q->vars.ldelay),
.dropping = q->vars.dropping,
.ecn_mark = q->stats.ecn_mark,
.ce_mark = q->stats.ce_mark,
};
if (q->vars.dropping) {
codel_tdiff_t delta = q->vars.drop_next - codel_get_time();
if (delta >= 0)
st.drop_next = codel_time_to_us(delta);
else
st.drop_next = -codel_time_to_us(-delta);
}
return gnet_stats_copy_app(d, &st, sizeof(st));
}
static void codel_reset(struct Qdisc *sch)
{
struct codel_sched_data *q = qdisc_priv(sch);
qdisc_reset_queue(sch);
codel_vars_init(&q->vars);
}
static struct Qdisc_ops codel_qdisc_ops __read_mostly = {
.id = "codel",
.priv_size = sizeof(struct codel_sched_data),
.enqueue = codel_qdisc_enqueue,
.dequeue = codel_qdisc_dequeue,
.peek = qdisc_peek_dequeued,
.init = codel_init,
.reset = codel_reset,
.change = codel_change,
.dump = codel_dump,
.dump_stats = codel_dump_stats,
.owner = THIS_MODULE,
};
MODULE_ALIAS_NET_SCH("codel");
static int __init codel_module_init(void)
{
return register_qdisc(&codel_qdisc_ops);
}
static void __exit codel_module_exit(void)
{
unregister_qdisc(&codel_qdisc_ops);
}
module_init(codel_module_init)
module_exit(codel_module_exit)
MODULE_DESCRIPTION("Controlled Delay queue discipline");
MODULE_AUTHOR("Dave Taht");
MODULE_AUTHOR("Eric Dumazet");
MODULE_LICENSE("Dual BSD/GPL");
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