net/sched/sch_codel.c

   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
  28 struct 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  */
  39 static 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(&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
  51 static void drop_func(struct sk_buff *skb, void *ctx)
  52 {
  53         struct Qdisc *sch = ctx;
  54
  55         kfree_skb_reason(skb, SKB_DROP_REASON_QDISC_CONGESTED);
  56         qdisc_qstats_drop(sch);
  57 }
  58
  59 static 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(sch, &sch->qstats.backlog, &q->params, &q->vars,
  65                             &q->stats, qdisc_pkt_len, 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(sch, q->stats.drop_count, 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
  81 static 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_reason(skb, sch, to_free,
  93                                  SKB_DROP_REASON_QDISC_OVERLIMIT);
  94 }
  95
  96 static const struct nla_policy codel_policy[TCA_CODEL_MAX + 1] = {
  97         [TCA_CODEL_TARGET]      = { .type = NLA_U32 },
  98         [TCA_CODEL_LIMIT]       = { .type = NLA_U32 },
  99         [TCA_CODEL_INTERVAL]    = { .type = NLA_U32 },
 100         [TCA_CODEL_ECN]         = { .type = NLA_U32 },
 101         [TCA_CODEL_CE_THRESHOLD]= { .type = NLA_U32 },
 102 };
 103
 104 static int codel_change(struct Qdisc *sch, struct nlattr *opt,
 105                         struct netlink_ext_ack *extack)
 106 {
 107         struct codel_sched_data *q = qdisc_priv(sch);
 108         struct nlattr *tb[TCA_CODEL_MAX + 1];
 109         unsigned int qlen, dropped = 0;
 110         int err;
 111
 112         err = nla_parse_nested_deprecated(tb, TCA_CODEL_MAX, opt,
 113                                           codel_policy, NULL);
 114         if (err < 0)
 115                 return err;
 116
 117         sch_tree_lock(sch);
 118
 119         if (tb[TCA_CODEL_TARGET]) {
 120                 u32 target = nla_get_u32(tb[TCA_CODEL_TARGET]);
 121
 122                 WRITE_ONCE(q->params.target,
 123                            ((u64)target * NSEC_PER_USEC) >> CODEL_SHIFT);
 124         }
 125
 126         if (tb[TCA_CODEL_CE_THRESHOLD]) {
 127                 u64 val = nla_get_u32(tb[TCA_CODEL_CE_THRESHOLD]);
 128
 129                 WRITE_ONCE(q->params.ce_threshold,
 130                            (val * NSEC_PER_USEC) >> CODEL_SHIFT);
 131         }
 132
 133         if (tb[TCA_CODEL_INTERVAL]) {
 134                 u32 interval = nla_get_u32(tb[TCA_CODEL_INTERVAL]);
 135
 136                 WRITE_ONCE(q->params.interval,
 137                            ((u64)interval * NSEC_PER_USEC) >> CODEL_SHIFT);
 138         }
 139
 140         if (tb[TCA_CODEL_LIMIT])
 141                 WRITE_ONCE(sch->limit,
 142                            nla_get_u32(tb[TCA_CODEL_LIMIT]));
 143
 144         if (tb[TCA_CODEL_ECN])
 145                 WRITE_ONCE(q->params.ecn,
 146                            !!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 = __qdisc_dequeue_head(&sch->q);
 151
 152                 dropped += qdisc_pkt_len(skb);
 153                 qdisc_qstats_backlog_dec(sch, skb);
 154                 rtnl_qdisc_drop(skb, sch);
 155         }
 156         qdisc_tree_reduce_backlog(sch, qlen - sch->q.qlen, dropped);
 157
 158         sch_tree_unlock(sch);
 159         return 0;
 160 }
 161
 162 static int codel_init(struct Qdisc *sch, struct nlattr *opt,
 163                       struct netlink_ext_ack *extack)
 164 {
 165         struct codel_sched_data *q = qdisc_priv(sch);
 166
 167         sch->limit = DEFAULT_CODEL_LIMIT;
 168
 169         codel_params_init(&q->params);
 170         codel_vars_init(&q->vars);
 171         codel_stats_init(&q->stats);
 172         q->params.mtu = psched_mtu(qdisc_dev(sch));
 173
 174         if (opt) {
 175                 int err = codel_change(sch, opt, extack);
 176
 177                 if (err)
 178                         return err;
 179         }
 180
 181         if (sch->limit >= 1)
 182                 sch->flags |= TCQ_F_CAN_BYPASS;
 183         else
 184                 sch->flags &= ~TCQ_F_CAN_BYPASS;
 185
 186         return 0;
 187 }
 188
 189 static int codel_dump(struct Qdisc *sch, struct sk_buff *skb)
 190 {
 191         struct codel_sched_data *q = qdisc_priv(sch);
 192         codel_time_t ce_threshold;
 193         struct nlattr *opts;
 194
 195         opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
 196         if (opts == NULL)
 197                 goto nla_put_failure;
 198
 199         if (nla_put_u32(skb, TCA_CODEL_TARGET,
 200                         codel_time_to_us(READ_ONCE(q->params.target))) ||
 201             nla_put_u32(skb, TCA_CODEL_LIMIT,
 202                         READ_ONCE(sch->limit)) ||
 203             nla_put_u32(skb, TCA_CODEL_INTERVAL,
 204                         codel_time_to_us(READ_ONCE(q->params.interval))) ||
 205             nla_put_u32(skb, TCA_CODEL_ECN,
 206                         READ_ONCE(q->params.ecn)))
 207                 goto nla_put_failure;
 208         ce_threshold = READ_ONCE(q->params.ce_threshold);
 209         if (ce_threshold != CODEL_DISABLED_THRESHOLD &&
 210             nla_put_u32(skb, TCA_CODEL_CE_THRESHOLD,
 211                         codel_time_to_us(ce_threshold)))
 212                 goto nla_put_failure;
 213         return nla_nest_end(skb, opts);
 214
 215 nla_put_failure:
 216         nla_nest_cancel(skb, opts);
 217         return -1;
 218 }
 219
 220 static int codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
 221 {
 222         const struct codel_sched_data *q = qdisc_priv(sch);
 223         struct tc_codel_xstats st = {
 224                 .maxpacket      = q->stats.maxpacket,
 225                 .count          = q->vars.count,
 226                 .lastcount      = q->vars.lastcount,
 227                 .drop_overlimit = q->drop_overlimit,
 228                 .ldelay         = codel_time_to_us(q->vars.ldelay),
 229                 .dropping       = q->vars.dropping,
 230                 .ecn_mark       = q->stats.ecn_mark,
 231                 .ce_mark        = q->stats.ce_mark,
 232         };
 233
 234         if (q->vars.dropping) {
 235                 codel_tdiff_t delta = q->vars.drop_next - codel_get_time();
 236
 237                 if (delta >= 0)
 238                         st.drop_next = codel_time_to_us(delta);
 239                 else
 240                         st.drop_next = -codel_time_to_us(-delta);
 241         }
 242
 243         return gnet_stats_copy_app(d, &st, sizeof(st));
 244 }
 245
 246 static void codel_reset(struct Qdisc *sch)
 247 {
 248         struct codel_sched_data *q = qdisc_priv(sch);
 249
 250         qdisc_reset_queue(sch);
 251         codel_vars_init(&q->vars);
 252 }
 253
 254 static struct Qdisc_ops codel_qdisc_ops __read_mostly = {
 255         .id             =       "codel",
 256         .priv_size      =       sizeof(struct codel_sched_data),
 257
 258         .enqueue        =       codel_qdisc_enqueue,
 259         .dequeue        =       codel_qdisc_dequeue,
 260         .peek           =       qdisc_peek_dequeued,
 261         .init           =       codel_init,
 262         .reset          =       codel_reset,
 263         .change         =       codel_change,
 264         .dump           =       codel_dump,
 265         .dump_stats     =       codel_dump_stats,
 266         .owner          =       THIS_MODULE,
 267 };
 268 MODULE_ALIAS_NET_SCH("codel");
 269
 270 static int __init codel_module_init(void)
 271 {
 272         return register_qdisc(&codel_qdisc_ops);
 273 }
 274
 275 static void __exit codel_module_exit(void)
 276 {
 277         unregister_qdisc(&codel_qdisc_ops);
 278 }
 279
 280 module_init(codel_module_init)
 281 module_exit(codel_module_exit)
 282
 283 MODULE_DESCRIPTION("Controlled Delay queue discipline");
 284 MODULE_AUTHOR("Dave Taht");
 285 MODULE_AUTHOR("Eric Dumazet");
 286 MODULE_LICENSE("Dual BSD/GPL");