sched/sch_red.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * net/sched/sch_red.c  Random Early Detection queue.
   4  *
   5  * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
   6  *
   7  * Changes:
   8  * J Hadi Salim 980914: computation fixes
   9  * Alexey Makarenko <makar@phoenix.kharkov.ua> 990814: qave on idle link was calculated incorrectly.
  10  * J Hadi Salim 980816:  ECN support
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/types.h>
  15 #include <linux/kernel.h>
  16 #include <linux/skbuff.h>
  17 #include <net/pkt_sched.h>
  18 #include <net/pkt_cls.h>
  19 #include <net/inet_ecn.h>
  20 #include <net/red.h>
  21
  22
  23 /*      Parameters, settable by user:
  24         -----------------------------
  25
  26         limit           - bytes (must be > qth_max + burst)
  27
  28         Hard limit on queue length, should be chosen >qth_max
  29         to allow packet bursts. This parameter does not
  30         affect the algorithms behaviour and can be chosen
  31         arbitrarily high (well, less than ram size)
  32         Really, this limit will never be reached
  33         if RED works correctly.
  34  */
  35
  36 struct red_sched_data {
  37         u32                     limit;          /* HARD maximal queue length */
  38
  39         unsigned char           flags;
  40         /* Non-flags in tc_red_qopt.flags. */
  41         unsigned char           userbits;
  42
  43         struct timer_list       adapt_timer;
  44         struct Qdisc            *sch;
  45         struct red_parms        parms;
  46         struct red_vars         vars;
  47         struct red_stats        stats;
  48         struct Qdisc            *qdisc;
  49         struct tcf_qevent       qe_early_drop;
  50         struct tcf_qevent       qe_mark;
  51 };
  52
  53 #define TC_RED_SUPPORTED_FLAGS (TC_RED_HISTORIC_FLAGS | TC_RED_NODROP)
  54
  55 static inline int red_use_ecn(struct red_sched_data *q)
  56 {
  57         return q->flags & TC_RED_ECN;
  58 }
  59
  60 static inline int red_use_harddrop(struct red_sched_data *q)
  61 {
  62         return q->flags & TC_RED_HARDDROP;
  63 }
  64
  65 static int red_use_nodrop(struct red_sched_data *q)
  66 {
  67         return q->flags & TC_RED_NODROP;
  68 }
  69
  70 static int red_enqueue(struct sk_buff *skb, struct Qdisc *sch,
  71                        struct sk_buff **to_free)
  72 {
  73         struct red_sched_data *q = qdisc_priv(sch);
  74         struct Qdisc *child = q->qdisc;
  75         unsigned int len;
  76         int ret;
  77
  78         q->vars.qavg = red_calc_qavg(&q->parms,
  79                                      &q->vars,
  80                                      child->qstats.backlog);
  81
  82         if (red_is_idling(&q->vars))
  83                 red_end_of_idle_period(&q->vars);
  84
  85         switch (red_action(&q->parms, &q->vars, q->vars.qavg)) {
  86         case RED_DONT_MARK:
  87                 break;
  88
  89         case RED_PROB_MARK:
  90                 qdisc_qstats_overlimit(sch);
  91                 if (!red_use_ecn(q)) {
  92                         q->stats.prob_drop++;
  93                         goto congestion_drop;
  94                 }
  95
  96                 if (INET_ECN_set_ce(skb)) {
  97                         q->stats.prob_mark++;
  98                         skb = tcf_qevent_handle(&q->qe_mark, sch, skb, to_free, &ret);
  99                         if (!skb)
 100                                 return NET_XMIT_CN | ret;
 101                 } else if (!red_use_nodrop(q)) {
 102                         q->stats.prob_drop++;
 103                         goto congestion_drop;
 104                 }
 105
 106                 /* Non-ECT packet in ECN nodrop mode: queue it. */
 107                 break;
 108
 109         case RED_HARD_MARK:
 110                 qdisc_qstats_overlimit(sch);
 111                 if (red_use_harddrop(q) || !red_use_ecn(q)) {
 112                         q->stats.forced_drop++;
 113                         goto congestion_drop;
 114                 }
 115
 116                 if (INET_ECN_set_ce(skb)) {
 117                         q->stats.forced_mark++;
 118                         skb = tcf_qevent_handle(&q->qe_mark, sch, skb, to_free, &ret);
 119                         if (!skb)
 120                                 return NET_XMIT_CN | ret;
 121                 } else if (!red_use_nodrop(q)) {
 122                         q->stats.forced_drop++;
 123                         goto congestion_drop;
 124                 }
 125
 126                 /* Non-ECT packet in ECN nodrop mode: queue it. */
 127                 break;
 128         }
 129
 130         len = qdisc_pkt_len(skb);
 131         ret = qdisc_enqueue(skb, child, to_free);
 132         if (likely(ret == NET_XMIT_SUCCESS)) {
 133                 sch->qstats.backlog += len;
 134                 sch->q.qlen++;
 135         } else if (net_xmit_drop_count(ret)) {
 136                 q->stats.pdrop++;
 137                 qdisc_qstats_drop(sch);
 138         }
 139         return ret;
 140
 141 congestion_drop:
 142         skb = tcf_qevent_handle(&q->qe_early_drop, sch, skb, to_free, &ret);
 143         if (!skb)
 144                 return NET_XMIT_CN | ret;
 145
 146         qdisc_drop(skb, sch, to_free);
 147         return NET_XMIT_CN;
 148 }
 149
 150 static struct sk_buff *red_dequeue(struct Qdisc *sch)
 151 {
 152         struct sk_buff *skb;
 153         struct red_sched_data *q = qdisc_priv(sch);
 154         struct Qdisc *child = q->qdisc;
 155
 156         skb = child->dequeue(child);
 157         if (skb) {
 158                 qdisc_bstats_update(sch, skb);
 159                 qdisc_qstats_backlog_dec(sch, skb);
 160                 sch->q.qlen--;
 161         } else {
 162                 if (!red_is_idling(&q->vars))
 163                         red_start_of_idle_period(&q->vars);
 164         }
 165         return skb;
 166 }
 167
 168 static struct sk_buff *red_peek(struct Qdisc *sch)
 169 {
 170         struct red_sched_data *q = qdisc_priv(sch);
 171         struct Qdisc *child = q->qdisc;
 172
 173         return child->ops->peek(child);
 174 }
 175
 176 static void red_reset(struct Qdisc *sch)
 177 {
 178         struct red_sched_data *q = qdisc_priv(sch);
 179
 180         qdisc_reset(q->qdisc);
 181         red_restart(&q->vars);
 182 }
 183
 184 static int red_offload(struct Qdisc *sch, bool enable)
 185 {
 186         struct red_sched_data *q = qdisc_priv(sch);
 187         struct net_device *dev = qdisc_dev(sch);
 188         struct tc_red_qopt_offload opt = {
 189                 .handle = sch->handle,
 190                 .parent = sch->parent,
 191         };
 192
 193         if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
 194                 return -EOPNOTSUPP;
 195
 196         if (enable) {
 197                 opt.command = TC_RED_REPLACE;
 198                 opt.set.min = q->parms.qth_min >> q->parms.Wlog;
 199                 opt.set.max = q->parms.qth_max >> q->parms.Wlog;
 200                 opt.set.probability = q->parms.max_P;
 201                 opt.set.limit = q->limit;
 202                 opt.set.is_ecn = red_use_ecn(q);
 203                 opt.set.is_harddrop = red_use_harddrop(q);
 204                 opt.set.is_nodrop = red_use_nodrop(q);
 205                 opt.set.qstats = &sch->qstats;
 206         } else {
 207                 opt.command = TC_RED_DESTROY;
 208         }
 209
 210         return dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_RED, &opt);
 211 }
 212
 213 static void red_destroy(struct Qdisc *sch)
 214 {
 215         struct red_sched_data *q = qdisc_priv(sch);
 216
 217         tcf_qevent_destroy(&q->qe_mark, sch);
 218         tcf_qevent_destroy(&q->qe_early_drop, sch);
 219         del_timer_sync(&q->adapt_timer);
 220         red_offload(sch, false);
 221         qdisc_put(q->qdisc);
 222 }
 223
 224 static const struct nla_policy red_policy[TCA_RED_MAX + 1] = {
 225         [TCA_RED_UNSPEC] = { .strict_start_type = TCA_RED_FLAGS },
 226         [TCA_RED_PARMS] = { .len = sizeof(struct tc_red_qopt) },
 227         [TCA_RED_STAB]  = { .len = RED_STAB_SIZE },
 228         [TCA_RED_MAX_P] = { .type = NLA_U32 },
 229         [TCA_RED_FLAGS] = NLA_POLICY_BITFIELD32(TC_RED_SUPPORTED_FLAGS),
 230         [TCA_RED_EARLY_DROP_BLOCK] = { .type = NLA_U32 },
 231         [TCA_RED_MARK_BLOCK] = { .type = NLA_U32 },
 232 };
 233
 234 static int __red_change(struct Qdisc *sch, struct nlattr **tb,
 235                         struct netlink_ext_ack *extack)
 236 {
 237         struct Qdisc *old_child = NULL, *child = NULL;
 238         struct red_sched_data *q = qdisc_priv(sch);
 239         struct nla_bitfield32 flags_bf;
 240         struct tc_red_qopt *ctl;
 241         unsigned char userbits;
 242         unsigned char flags;
 243         int err;
 244         u32 max_P;
 245         u8 *stab;
 246
 247         if (tb[TCA_RED_PARMS] == NULL ||
 248             tb[TCA_RED_STAB] == NULL)
 249                 return -EINVAL;
 250
 251         max_P = tb[TCA_RED_MAX_P] ? nla_get_u32(tb[TCA_RED_MAX_P]) : 0;
 252
 253         ctl = nla_data(tb[TCA_RED_PARMS]);
 254         stab = nla_data(tb[TCA_RED_STAB]);
 255         if (!red_check_params(ctl->qth_min, ctl->qth_max, ctl->Wlog,
 256                               ctl->Scell_log, stab))
 257                 return -EINVAL;
 258
 259         err = red_get_flags(ctl->flags, TC_RED_HISTORIC_FLAGS,
 260                             tb[TCA_RED_FLAGS], TC_RED_SUPPORTED_FLAGS,
 261                             &flags_bf, &userbits, extack);
 262         if (err)
 263                 return err;
 264
 265         if (ctl->limit > 0) {
 266                 child = fifo_create_dflt(sch, &bfifo_qdisc_ops, ctl->limit,
 267                                          extack);
 268                 if (IS_ERR(child))
 269                         return PTR_ERR(child);
 270
 271                 /* child is fifo, no need to check for noop_qdisc */
 272                 qdisc_hash_add(child, true);
 273         }
 274
 275         sch_tree_lock(sch);
 276
 277         flags = (q->flags & ~flags_bf.selector) | flags_bf.value;
 278         err = red_validate_flags(flags, extack);
 279         if (err)
 280                 goto unlock_out;
 281
 282         q->flags = flags;
 283         q->userbits = userbits;
 284         q->limit = ctl->limit;
 285         if (child) {
 286                 qdisc_tree_flush_backlog(q->qdisc);
 287                 old_child = q->qdisc;
 288                 q->qdisc = child;
 289         }
 290
 291         red_set_parms(&q->parms,
 292                       ctl->qth_min, ctl->qth_max, ctl->Wlog,
 293                       ctl->Plog, ctl->Scell_log,
 294                       stab,
 295                       max_P);
 296         red_set_vars(&q->vars);
 297
 298         del_timer(&q->adapt_timer);
 299         if (ctl->flags & TC_RED_ADAPTATIVE)
 300                 mod_timer(&q->adapt_timer, jiffies + HZ/2);
 301
 302         if (!q->qdisc->q.qlen)
 303                 red_start_of_idle_period(&q->vars);
 304
 305         sch_tree_unlock(sch);
 306
 307         red_offload(sch, true);
 308
 309         if (old_child)
 310                 qdisc_put(old_child);
 311         return 0;
 312
 313 unlock_out:
 314         sch_tree_unlock(sch);
 315         if (child)
 316                 qdisc_put(child);
 317         return err;
 318 }
 319
 320 static inline void red_adaptative_timer(struct timer_list *t)
 321 {
 322         struct red_sched_data *q = from_timer(q, t, adapt_timer);
 323         struct Qdisc *sch = q->sch;
 324         spinlock_t *root_lock;
 325
 326         rcu_read_lock();
 327         root_lock = qdisc_lock(qdisc_root_sleeping(sch));
 328         spin_lock(root_lock);
 329         red_adaptative_algo(&q->parms, &q->vars);
 330         mod_timer(&q->adapt_timer, jiffies + HZ/2);
 331         spin_unlock(root_lock);
 332         rcu_read_unlock();
 333 }
 334
 335 static int red_init(struct Qdisc *sch, struct nlattr *opt,
 336                     struct netlink_ext_ack *extack)
 337 {
 338         struct red_sched_data *q = qdisc_priv(sch);
 339         struct nlattr *tb[TCA_RED_MAX + 1];
 340         int err;
 341
 342         q->qdisc = &noop_qdisc;
 343         q->sch = sch;
 344         timer_setup(&q->adapt_timer, red_adaptative_timer, 0);
 345
 346         if (!opt)
 347                 return -EINVAL;
 348
 349         err = nla_parse_nested_deprecated(tb, TCA_RED_MAX, opt, red_policy,
 350                                           extack);
 351         if (err < 0)
 352                 return err;
 353
 354         err = __red_change(sch, tb, extack);
 355         if (err)
 356                 return err;
 357
 358         err = tcf_qevent_init(&q->qe_early_drop, sch,
 359                               FLOW_BLOCK_BINDER_TYPE_RED_EARLY_DROP,
 360                               tb[TCA_RED_EARLY_DROP_BLOCK], extack);
 361         if (err)
 362                 return err;
 363
 364         return tcf_qevent_init(&q->qe_mark, sch,
 365                                FLOW_BLOCK_BINDER_TYPE_RED_MARK,
 366                                tb[TCA_RED_MARK_BLOCK], extack);
 367 }
 368
 369 static int red_change(struct Qdisc *sch, struct nlattr *opt,
 370                       struct netlink_ext_ack *extack)
 371 {
 372         struct red_sched_data *q = qdisc_priv(sch);
 373         struct nlattr *tb[TCA_RED_MAX + 1];
 374         int err;
 375
 376         err = nla_parse_nested_deprecated(tb, TCA_RED_MAX, opt, red_policy,
 377                                           extack);
 378         if (err < 0)
 379                 return err;
 380
 381         err = tcf_qevent_validate_change(&q->qe_early_drop,
 382                                          tb[TCA_RED_EARLY_DROP_BLOCK], extack);
 383         if (err)
 384                 return err;
 385
 386         err = tcf_qevent_validate_change(&q->qe_mark,
 387                                          tb[TCA_RED_MARK_BLOCK], extack);
 388         if (err)
 389                 return err;
 390
 391         return __red_change(sch, tb, extack);
 392 }
 393
 394 static int red_dump_offload_stats(struct Qdisc *sch)
 395 {
 396         struct tc_red_qopt_offload hw_stats = {
 397                 .command = TC_RED_STATS,
 398                 .handle = sch->handle,
 399                 .parent = sch->parent,
 400                 {
 401                         .stats.bstats = &sch->bstats,
 402                         .stats.qstats = &sch->qstats,
 403                 },
 404         };
 405
 406         return qdisc_offload_dump_helper(sch, TC_SETUP_QDISC_RED, &hw_stats);
 407 }
 408
 409 static int red_dump(struct Qdisc *sch, struct sk_buff *skb)
 410 {
 411         struct red_sched_data *q = qdisc_priv(sch);
 412         struct nlattr *opts = NULL;
 413         struct tc_red_qopt opt = {
 414                 .limit          = q->limit,
 415                 .flags          = (q->flags & TC_RED_HISTORIC_FLAGS) |
 416                                   q->userbits,
 417                 .qth_min        = q->parms.qth_min >> q->parms.Wlog,
 418                 .qth_max        = q->parms.qth_max >> q->parms.Wlog,
 419                 .Wlog           = q->parms.Wlog,
 420                 .Plog           = q->parms.Plog,
 421                 .Scell_log      = q->parms.Scell_log,
 422         };
 423         int err;
 424
 425         err = red_dump_offload_stats(sch);
 426         if (err)
 427                 goto nla_put_failure;
 428
 429         opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
 430         if (opts == NULL)
 431                 goto nla_put_failure;
 432         if (nla_put(skb, TCA_RED_PARMS, sizeof(opt), &opt) ||
 433             nla_put_u32(skb, TCA_RED_MAX_P, q->parms.max_P) ||
 434             nla_put_bitfield32(skb, TCA_RED_FLAGS,
 435                                q->flags, TC_RED_SUPPORTED_FLAGS) ||
 436             tcf_qevent_dump(skb, TCA_RED_MARK_BLOCK, &q->qe_mark) ||
 437             tcf_qevent_dump(skb, TCA_RED_EARLY_DROP_BLOCK, &q->qe_early_drop))
 438                 goto nla_put_failure;
 439         return nla_nest_end(skb, opts);
 440
 441 nla_put_failure:
 442         nla_nest_cancel(skb, opts);
 443         return -EMSGSIZE;
 444 }
 445
 446 static int red_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
 447 {
 448         struct red_sched_data *q = qdisc_priv(sch);
 449         struct net_device *dev = qdisc_dev(sch);
 450         struct tc_red_xstats st = {0};
 451
 452         if (sch->flags & TCQ_F_OFFLOADED) {
 453                 struct tc_red_qopt_offload hw_stats_request = {
 454                         .command = TC_RED_XSTATS,
 455                         .handle = sch->handle,
 456                         .parent = sch->parent,
 457                         {
 458                                 .xstats = &q->stats,
 459                         },
 460                 };
 461                 dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_RED,
 462                                               &hw_stats_request);
 463         }
 464         st.early = q->stats.prob_drop + q->stats.forced_drop;
 465         st.pdrop = q->stats.pdrop;
 466         st.marked = q->stats.prob_mark + q->stats.forced_mark;
 467
 468         return gnet_stats_copy_app(d, &st, sizeof(st));
 469 }
 470
 471 static int red_dump_class(struct Qdisc *sch, unsigned long cl,
 472                           struct sk_buff *skb, struct tcmsg *tcm)
 473 {
 474         struct red_sched_data *q = qdisc_priv(sch);
 475
 476         tcm->tcm_handle |= TC_H_MIN(1);
 477         tcm->tcm_info = q->qdisc->handle;
 478         return 0;
 479 }
 480
 481 static void red_graft_offload(struct Qdisc *sch,
 482                               struct Qdisc *new, struct Qdisc *old,
 483                               struct netlink_ext_ack *extack)
 484 {
 485         struct tc_red_qopt_offload graft_offload = {
 486                 .handle         = sch->handle,
 487                 .parent         = sch->parent,
 488                 .child_handle   = new->handle,
 489                 .command        = TC_RED_GRAFT,
 490         };
 491
 492         qdisc_offload_graft_helper(qdisc_dev(sch), sch, new, old,
 493                                    TC_SETUP_QDISC_RED, &graft_offload, extack);
 494 }
 495
 496 static int red_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 497                      struct Qdisc **old, struct netlink_ext_ack *extack)
 498 {
 499         struct red_sched_data *q = qdisc_priv(sch);
 500
 501         if (new == NULL)
 502                 new = &noop_qdisc;
 503
 504         *old = qdisc_replace(sch, new, &q->qdisc);
 505
 506         red_graft_offload(sch, new, *old, extack);
 507         return 0;
 508 }
 509
 510 static struct Qdisc *red_leaf(struct Qdisc *sch, unsigned long arg)
 511 {
 512         struct red_sched_data *q = qdisc_priv(sch);
 513         return q->qdisc;
 514 }
 515
 516 static unsigned long red_find(struct Qdisc *sch, u32 classid)
 517 {
 518         return 1;
 519 }
 520
 521 static void red_walk(struct Qdisc *sch, struct qdisc_walker *walker)
 522 {
 523         if (!walker->stop) {
 524                 tc_qdisc_stats_dump(sch, 1, walker);
 525         }
 526 }
 527
 528 static const struct Qdisc_class_ops red_class_ops = {
 529         .graft          =       red_graft,
 530         .leaf           =       red_leaf,
 531         .find           =       red_find,
 532         .walk           =       red_walk,
 533         .dump           =       red_dump_class,
 534 };
 535
 536 static struct Qdisc_ops red_qdisc_ops __read_mostly = {
 537         .id             =       "red",
 538         .priv_size      =       sizeof(struct red_sched_data),
 539         .cl_ops         =       &red_class_ops,
 540         .enqueue        =       red_enqueue,
 541         .dequeue        =       red_dequeue,
 542         .peek           =       red_peek,
 543         .init           =       red_init,
 544         .reset          =       red_reset,
 545         .destroy        =       red_destroy,
 546         .change         =       red_change,
 547         .dump           =       red_dump,
 548         .dump_stats     =       red_dump_stats,
 549         .owner          =       THIS_MODULE,
 550 };
 551
 552 static int __init red_module_init(void)
 553 {
 554         return register_qdisc(&red_qdisc_ops);
 555 }
 556
 557 static void __exit red_module_exit(void)
 558 {
 559         unregister_qdisc(&red_qdisc_ops);
 560 }
 561
 562 module_init(red_module_init)
 563 module_exit(red_module_exit)
 564
 565 MODULE_LICENSE("GPL");
 566 MODULE_DESCRIPTION("Random Early Detection qdisc");