net/sched/sch_tbf.c

   1 /*
   2  * net/sched/sch_tbf.c  Token Bucket Filter queue.
   3  *
   4  *              This program is free software; you can redistribute it and/or
   5  *              modify it under the terms of the GNU General Public License
   6  *              as published by the Free Software Foundation; either version
   7  *              2 of the License, or (at your option) any later version.
   8  *
   9  * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
  10  *              Dmitry Torokhov <dtor@mail.ru> - allow attaching inner qdiscs -
  11  *                                               original idea by Martin Devera
  12  *
  13  */
  14
  15 #include <linux/module.h>
  16 #include <linux/types.h>
  17 #include <linux/kernel.h>
  18 #include <linux/string.h>
  19 #include <linux/errno.h>
  20 #include <linux/skbuff.h>
  21 #include <net/netlink.h>
  22 #include <net/pkt_sched.h>
  23
  24
  25 /*      Simple Token Bucket Filter.
  26         =======================================
  27
  28         SOURCE.
  29         -------
  30
  31         None.
  32
  33         Description.
  34         ------------
  35
  36         A data flow obeys TBF with rate R and depth B, if for any
  37         time interval t_i...t_f the number of transmitted bits
  38         does not exceed B + R*(t_f-t_i).
  39
  40         Packetized version of this definition:
  41         The sequence of packets of sizes s_i served at moments t_i
  42         obeys TBF, if for any i<=k:
  43
  44         s_i+....+s_k <= B + R*(t_k - t_i)
  45
  46         Algorithm.
  47         ----------
  48
  49         Let N(t_i) be B/R initially and N(t) grow continuously with time as:
  50
  51         N(t+delta) = min{B/R, N(t) + delta}
  52
  53         If the first packet in queue has length S, it may be
  54         transmitted only at the time t_* when S/R <= N(t_*),
  55         and in this case N(t) jumps:
  56
  57         N(t_* + 0) = N(t_* - 0) - S/R.
  58
  59
  60
  61         Actually, QoS requires two TBF to be applied to a data stream.
  62         One of them controls steady state burst size, another
  63         one with rate P (peak rate) and depth M (equal to link MTU)
  64         limits bursts at a smaller time scale.
  65
  66         It is easy to see that P>R, and B>M. If P is infinity, this double
  67         TBF is equivalent to a single one.
  68
  69         When TBF works in reshaping mode, latency is estimated as:
  70
  71         lat = max ((L-B)/R, (L-M)/P)
  72
  73
  74         NOTES.
  75         ------
  76
  77         If TBF throttles, it starts a watchdog timer, which will wake it up
  78         when it is ready to transmit.
  79         Note that the minimal timer resolution is 1/HZ.
  80         If no new packets arrive during this period,
  81         or if the device is not awaken by EOI for some previous packet,
  82         TBF can stop its activity for 1/HZ.
  83
  84
  85         This means, that with depth B, the maximal rate is
  86
  87         R_crit = B*HZ
  88
  89         F.e. for 10Mbit ethernet and HZ=100 the minimal allowed B is ~10Kbytes.
  90
  91         Note that the peak rate TBF is much more tough: with MTU 1500
  92         P_crit = 150Kbytes/sec. So, if you need greater peak
  93         rates, use alpha with HZ=1000 :-)
  94
  95         With classful TBF, limit is just kept for backwards compatibility.
  96         It is passed to the default bfifo qdisc - if the inner qdisc is
  97         changed the limit is not effective anymore.
  98 */
  99
 100 struct tbf_sched_data
 101 {
 102 /* Parameters */
 103         u32             limit;          /* Maximal length of backlog: bytes */
 104         u32             buffer;         /* Token bucket depth/rate: MUST BE >= MTU/B */
 105         u32             mtu;
 106         u32             max_size;
 107         struct qdisc_rate_table *R_tab;
 108         struct qdisc_rate_table *P_tab;
 109
 110 /* Variables */
 111         long    tokens;                 /* Current number of B tokens */
 112         long    ptokens;                /* Current number of P tokens */
 113         psched_time_t   t_c;            /* Time check-point */
 114         struct Qdisc    *qdisc;         /* Inner qdisc, default - bfifo queue */
 115         struct qdisc_watchdog watchdog; /* Watchdog timer */
 116 };
 117
 118 #define L2T(q,L)   qdisc_l2t((q)->R_tab,L)
 119 #define L2T_P(q,L) qdisc_l2t((q)->P_tab,L)
 120
 121 static int tbf_enqueue(struct sk_buff *skb, struct Qdisc* sch)
 122 {
 123         struct tbf_sched_data *q = qdisc_priv(sch);
 124         int ret;
 125
 126         if (skb->len > q->max_size) {
 127                 sch->qstats.drops++;
 128 #ifdef CONFIG_NET_CLS_ACT
 129                 if (sch->reshape_fail == NULL || sch->reshape_fail(skb, sch))
 130 #endif
 131                         kfree_skb(skb);
 132
 133                 return NET_XMIT_DROP;
 134         }
 135
 136         if ((ret = q->qdisc->enqueue(skb, q->qdisc)) != 0) {
 137                 sch->qstats.drops++;
 138                 return ret;
 139         }
 140
 141         sch->q.qlen++;
 142         sch->bstats.bytes += skb->len;
 143         sch->bstats.packets++;
 144         return 0;
 145 }
 146
 147 static int tbf_requeue(struct sk_buff *skb, struct Qdisc* sch)
 148 {
 149         struct tbf_sched_data *q = qdisc_priv(sch);
 150         int ret;
 151
 152         if ((ret = q->qdisc->ops->requeue(skb, q->qdisc)) == 0) {
 153                 sch->q.qlen++;
 154                 sch->qstats.requeues++;
 155         }
 156
 157         return ret;
 158 }
 159
 160 static unsigned int tbf_drop(struct Qdisc* sch)
 161 {
 162         struct tbf_sched_data *q = qdisc_priv(sch);
 163         unsigned int len = 0;
 164
 165         if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
 166                 sch->q.qlen--;
 167                 sch->qstats.drops++;
 168         }
 169         return len;
 170 }
 171
 172 static struct sk_buff *tbf_dequeue(struct Qdisc* sch)
 173 {
 174         struct tbf_sched_data *q = qdisc_priv(sch);
 175         struct sk_buff *skb;
 176
 177         skb = q->qdisc->dequeue(q->qdisc);
 178
 179         if (skb) {
 180                 psched_time_t now;
 181                 long toks;
 182                 long ptoks = 0;
 183                 unsigned int len = skb->len;
 184
 185                 now = psched_get_time();
 186                 toks = psched_tdiff_bounded(now, q->t_c, q->buffer);
 187
 188                 if (q->P_tab) {
 189                         ptoks = toks + q->ptokens;
 190                         if (ptoks > (long)q->mtu)
 191                                 ptoks = q->mtu;
 192                         ptoks -= L2T_P(q, len);
 193                 }
 194                 toks += q->tokens;
 195                 if (toks > (long)q->buffer)
 196                         toks = q->buffer;
 197                 toks -= L2T(q, len);
 198
 199                 if ((toks|ptoks) >= 0) {
 200                         q->t_c = now;
 201                         q->tokens = toks;
 202                         q->ptokens = ptoks;
 203                         sch->q.qlen--;
 204                         sch->flags &= ~TCQ_F_THROTTLED;
 205                         return skb;
 206                 }
 207
 208                 qdisc_watchdog_schedule(&q->watchdog,
 209                                         now + max_t(long, -toks, -ptoks));
 210
 211                 /* Maybe we have a shorter packet in the queue,
 212                    which can be sent now. It sounds cool,
 213                    but, however, this is wrong in principle.
 214                    We MUST NOT reorder packets under these circumstances.
 215
 216                    Really, if we split the flow into independent
 217                    subflows, it would be a very good solution.
 218                    This is the main idea of all FQ algorithms
 219                    (cf. CSZ, HPFQ, HFSC)
 220                  */
 221
 222                 if (q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS) {
 223                         /* When requeue fails skb is dropped */
 224                         qdisc_tree_decrease_qlen(q->qdisc, 1);
 225                         sch->qstats.drops++;
 226                 }
 227
 228                 sch->qstats.overlimits++;
 229         }
 230         return NULL;
 231 }
 232
 233 static void tbf_reset(struct Qdisc* sch)
 234 {
 235         struct tbf_sched_data *q = qdisc_priv(sch);
 236
 237         qdisc_reset(q->qdisc);
 238         sch->q.qlen = 0;
 239         q->t_c = psched_get_time();
 240         q->tokens = q->buffer;
 241         q->ptokens = q->mtu;
 242         qdisc_watchdog_cancel(&q->watchdog);
 243 }
 244
 245 static struct Qdisc *tbf_create_dflt_qdisc(struct Qdisc *sch, u32 limit)
 246 {
 247         struct Qdisc *q;
 248         struct nlattr *nla;
 249         int ret;
 250
 251         q = qdisc_create_dflt(sch->dev, &bfifo_qdisc_ops,
 252                               TC_H_MAKE(sch->handle, 1));
 253         if (q) {
 254                 nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)),
 255                               GFP_KERNEL);
 256                 if (nla) {
 257                         nla->nla_type = RTM_NEWQDISC;
 258                         nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
 259                         ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
 260
 261                         ret = q->ops->change(q, nla);
 262                         kfree(nla);
 263
 264                         if (ret == 0)
 265                                 return q;
 266                 }
 267                 qdisc_destroy(q);
 268         }
 269
 270         return NULL;
 271 }
 272
 273 static const struct nla_policy tbf_policy[TCA_TBF_MAX + 1] = {
 274         [TCA_TBF_PARMS] = { .len = sizeof(struct tc_tbf_qopt) },
 275         [TCA_TBF_RTAB]  = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
 276         [TCA_TBF_PTAB]  = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
 277 };
 278
 279 static int tbf_change(struct Qdisc* sch, struct nlattr *opt)
 280 {
 281         int err;
 282         struct tbf_sched_data *q = qdisc_priv(sch);
 283         struct nlattr *tb[TCA_TBF_PTAB + 1];
 284         struct tc_tbf_qopt *qopt;
 285         struct qdisc_rate_table *rtab = NULL;
 286         struct qdisc_rate_table *ptab = NULL;
 287         struct Qdisc *child = NULL;
 288         int max_size,n;
 289
 290         err = nla_parse_nested(tb, TCA_TBF_PTAB, opt, tbf_policy);
 291         if (err < 0)
 292                 return err;
 293
 294         err = -EINVAL;
 295         if (tb[TCA_TBF_PARMS] == NULL)
 296                 goto done;
 297
 298         qopt = nla_data(tb[TCA_TBF_PARMS]);
 299         rtab = qdisc_get_rtab(&qopt->rate, tb[TCA_TBF_RTAB]);
 300         if (rtab == NULL)
 301                 goto done;
 302
 303         if (qopt->peakrate.rate) {
 304                 if (qopt->peakrate.rate > qopt->rate.rate)
 305                         ptab = qdisc_get_rtab(&qopt->peakrate, tb[TCA_TBF_PTAB]);
 306                 if (ptab == NULL)
 307                         goto done;
 308         }
 309
 310         for (n = 0; n < 256; n++)
 311                 if (rtab->data[n] > qopt->buffer) break;
 312         max_size = (n << qopt->rate.cell_log)-1;
 313         if (ptab) {
 314                 int size;
 315
 316                 for (n = 0; n < 256; n++)
 317                         if (ptab->data[n] > qopt->mtu) break;
 318                 size = (n << qopt->peakrate.cell_log)-1;
 319                 if (size < max_size) max_size = size;
 320         }
 321         if (max_size < 0)
 322                 goto done;
 323
 324         if (qopt->limit > 0) {
 325                 if ((child = tbf_create_dflt_qdisc(sch, qopt->limit)) == NULL)
 326                         goto done;
 327         }
 328
 329         sch_tree_lock(sch);
 330         if (child) {
 331                 qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
 332                 qdisc_destroy(xchg(&q->qdisc, child));
 333         }
 334         q->limit = qopt->limit;
 335         q->mtu = qopt->mtu;
 336         q->max_size = max_size;
 337         q->buffer = qopt->buffer;
 338         q->tokens = q->buffer;
 339         q->ptokens = q->mtu;
 340         rtab = xchg(&q->R_tab, rtab);
 341         ptab = xchg(&q->P_tab, ptab);
 342         sch_tree_unlock(sch);
 343         err = 0;
 344 done:
 345         if (rtab)
 346                 qdisc_put_rtab(rtab);
 347         if (ptab)
 348                 qdisc_put_rtab(ptab);
 349         return err;
 350 }
 351
 352 static int tbf_init(struct Qdisc* sch, struct nlattr *opt)
 353 {
 354         struct tbf_sched_data *q = qdisc_priv(sch);
 355
 356         if (opt == NULL)
 357                 return -EINVAL;
 358
 359         q->t_c = psched_get_time();
 360         qdisc_watchdog_init(&q->watchdog, sch);
 361         q->qdisc = &noop_qdisc;
 362
 363         return tbf_change(sch, opt);
 364 }
 365
 366 static void tbf_destroy(struct Qdisc *sch)
 367 {
 368         struct tbf_sched_data *q = qdisc_priv(sch);
 369
 370         qdisc_watchdog_cancel(&q->watchdog);
 371
 372         if (q->P_tab)
 373                 qdisc_put_rtab(q->P_tab);
 374         if (q->R_tab)
 375                 qdisc_put_rtab(q->R_tab);
 376
 377         qdisc_destroy(q->qdisc);
 378 }
 379
 380 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb)
 381 {
 382         struct tbf_sched_data *q = qdisc_priv(sch);
 383         struct nlattr *nest;
 384         struct tc_tbf_qopt opt;
 385
 386         nest = nla_nest_start(skb, TCA_OPTIONS);
 387         if (nest == NULL)
 388                 goto nla_put_failure;
 389
 390         opt.limit = q->limit;
 391         opt.rate = q->R_tab->rate;
 392         if (q->P_tab)
 393                 opt.peakrate = q->P_tab->rate;
 394         else
 395                 memset(&opt.peakrate, 0, sizeof(opt.peakrate));
 396         opt.mtu = q->mtu;
 397         opt.buffer = q->buffer;
 398         NLA_PUT(skb, TCA_TBF_PARMS, sizeof(opt), &opt);
 399
 400         nla_nest_end(skb, nest);
 401         return skb->len;
 402
 403 nla_put_failure:
 404         nla_nest_cancel(skb, nest);
 405         return -1;
 406 }
 407
 408 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl,
 409                           struct sk_buff *skb, struct tcmsg *tcm)
 410 {
 411         struct tbf_sched_data *q = qdisc_priv(sch);
 412
 413         if (cl != 1)    /* only one class */
 414                 return -ENOENT;
 415
 416         tcm->tcm_handle |= TC_H_MIN(1);
 417         tcm->tcm_info = q->qdisc->handle;
 418
 419         return 0;
 420 }
 421
 422 static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 423                      struct Qdisc **old)
 424 {
 425         struct tbf_sched_data *q = qdisc_priv(sch);
 426
 427         if (new == NULL)
 428                 new = &noop_qdisc;
 429
 430         sch_tree_lock(sch);
 431         *old = xchg(&q->qdisc, new);
 432         qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 433         qdisc_reset(*old);
 434         sch_tree_unlock(sch);
 435
 436         return 0;
 437 }
 438
 439 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg)
 440 {
 441         struct tbf_sched_data *q = qdisc_priv(sch);
 442         return q->qdisc;
 443 }
 444
 445 static unsigned long tbf_get(struct Qdisc *sch, u32 classid)
 446 {
 447         return 1;
 448 }
 449
 450 static void tbf_put(struct Qdisc *sch, unsigned long arg)
 451 {
 452 }
 453
 454 static int tbf_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 455                             struct nlattr **tca, unsigned long *arg)
 456 {
 457         return -ENOSYS;
 458 }
 459
 460 static int tbf_delete(struct Qdisc *sch, unsigned long arg)
 461 {
 462         return -ENOSYS;
 463 }
 464
 465 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker)
 466 {
 467         if (!walker->stop) {
 468                 if (walker->count >= walker->skip)
 469                         if (walker->fn(sch, 1, walker) < 0) {
 470                                 walker->stop = 1;
 471                                 return;
 472                         }
 473                 walker->count++;
 474         }
 475 }
 476
 477 static struct tcf_proto **tbf_find_tcf(struct Qdisc *sch, unsigned long cl)
 478 {
 479         return NULL;
 480 }
 481
 482 static const struct Qdisc_class_ops tbf_class_ops =
 483 {
 484         .graft          =       tbf_graft,
 485         .leaf           =       tbf_leaf,
 486         .get            =       tbf_get,
 487         .put            =       tbf_put,
 488         .change         =       tbf_change_class,
 489         .delete         =       tbf_delete,
 490         .walk           =       tbf_walk,
 491         .tcf_chain      =       tbf_find_tcf,
 492         .dump           =       tbf_dump_class,
 493 };
 494
 495 static struct Qdisc_ops tbf_qdisc_ops __read_mostly = {
 496         .next           =       NULL,
 497         .cl_ops         =       &tbf_class_ops,
 498         .id             =       "tbf",
 499         .priv_size      =       sizeof(struct tbf_sched_data),
 500         .enqueue        =       tbf_enqueue,
 501         .dequeue        =       tbf_dequeue,
 502         .requeue        =       tbf_requeue,
 503         .drop           =       tbf_drop,
 504         .init           =       tbf_init,
 505         .reset          =       tbf_reset,
 506         .destroy        =       tbf_destroy,
 507         .change         =       tbf_change,
 508         .dump           =       tbf_dump,
 509         .owner          =       THIS_MODULE,
 510 };
 511
 512 static int __init tbf_module_init(void)
 513 {
 514         return register_qdisc(&tbf_qdisc_ops);
 515 }
 516
 517 static void __exit tbf_module_exit(void)
 518 {
 519         unregister_qdisc(&tbf_qdisc_ops);
 520 }
 521 module_init(tbf_module_init)
 522 module_exit(tbf_module_exit)
 523 MODULE_LICENSE("GPL");