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 int tbf_change(struct Qdisc* sch, struct nlattr *opt)
 274 {
 275         int err = -EINVAL;
 276         struct tbf_sched_data *q = qdisc_priv(sch);
 277         struct nlattr *tb[TCA_TBF_PTAB + 1];
 278         struct tc_tbf_qopt *qopt;
 279         struct qdisc_rate_table *rtab = NULL;
 280         struct qdisc_rate_table *ptab = NULL;
 281         struct Qdisc *child = NULL;
 282         int max_size,n;
 283
 284         if (nla_parse_nested(tb, TCA_TBF_PTAB, opt, NULL) ||
 285             tb[TCA_TBF_PARMS] == NULL ||
 286             nla_len(tb[TCA_TBF_PARMS]) < sizeof(*qopt))
 287                 goto done;
 288
 289         qopt = nla_data(tb[TCA_TBF_PARMS]);
 290         rtab = qdisc_get_rtab(&qopt->rate, tb[TCA_TBF_RTAB]);
 291         if (rtab == NULL)
 292                 goto done;
 293
 294         if (qopt->peakrate.rate) {
 295                 if (qopt->peakrate.rate > qopt->rate.rate)
 296                         ptab = qdisc_get_rtab(&qopt->peakrate, tb[TCA_TBF_PTAB]);
 297                 if (ptab == NULL)
 298                         goto done;
 299         }
 300
 301         for (n = 0; n < 256; n++)
 302                 if (rtab->data[n] > qopt->buffer) break;
 303         max_size = (n << qopt->rate.cell_log)-1;
 304         if (ptab) {
 305                 int size;
 306
 307                 for (n = 0; n < 256; n++)
 308                         if (ptab->data[n] > qopt->mtu) break;
 309                 size = (n << qopt->peakrate.cell_log)-1;
 310                 if (size < max_size) max_size = size;
 311         }
 312         if (max_size < 0)
 313                 goto done;
 314
 315         if (qopt->limit > 0) {
 316                 if ((child = tbf_create_dflt_qdisc(sch, qopt->limit)) == NULL)
 317                         goto done;
 318         }
 319
 320         sch_tree_lock(sch);
 321         if (child) {
 322                 qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
 323                 qdisc_destroy(xchg(&q->qdisc, child));
 324         }
 325         q->limit = qopt->limit;
 326         q->mtu = qopt->mtu;
 327         q->max_size = max_size;
 328         q->buffer = qopt->buffer;
 329         q->tokens = q->buffer;
 330         q->ptokens = q->mtu;
 331         rtab = xchg(&q->R_tab, rtab);
 332         ptab = xchg(&q->P_tab, ptab);
 333         sch_tree_unlock(sch);
 334         err = 0;
 335 done:
 336         if (rtab)
 337                 qdisc_put_rtab(rtab);
 338         if (ptab)
 339                 qdisc_put_rtab(ptab);
 340         return err;
 341 }
 342
 343 static int tbf_init(struct Qdisc* sch, struct nlattr *opt)
 344 {
 345         struct tbf_sched_data *q = qdisc_priv(sch);
 346
 347         if (opt == NULL)
 348                 return -EINVAL;
 349
 350         q->t_c = psched_get_time();
 351         qdisc_watchdog_init(&q->watchdog, sch);
 352         q->qdisc = &noop_qdisc;
 353
 354         return tbf_change(sch, opt);
 355 }
 356
 357 static void tbf_destroy(struct Qdisc *sch)
 358 {
 359         struct tbf_sched_data *q = qdisc_priv(sch);
 360
 361         qdisc_watchdog_cancel(&q->watchdog);
 362
 363         if (q->P_tab)
 364                 qdisc_put_rtab(q->P_tab);
 365         if (q->R_tab)
 366                 qdisc_put_rtab(q->R_tab);
 367
 368         qdisc_destroy(q->qdisc);
 369 }
 370
 371 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb)
 372 {
 373         struct tbf_sched_data *q = qdisc_priv(sch);
 374         unsigned char *b = skb_tail_pointer(skb);
 375         struct nlattr *nla;
 376         struct tc_tbf_qopt opt;
 377
 378         nla = (struct nlattr*)b;
 379         NLA_PUT(skb, TCA_OPTIONS, 0, NULL);
 380
 381         opt.limit = q->limit;
 382         opt.rate = q->R_tab->rate;
 383         if (q->P_tab)
 384                 opt.peakrate = q->P_tab->rate;
 385         else
 386                 memset(&opt.peakrate, 0, sizeof(opt.peakrate));
 387         opt.mtu = q->mtu;
 388         opt.buffer = q->buffer;
 389         NLA_PUT(skb, TCA_TBF_PARMS, sizeof(opt), &opt);
 390         nla->nla_len = skb_tail_pointer(skb) - b;
 391
 392         return skb->len;
 393
 394 nla_put_failure:
 395         nlmsg_trim(skb, b);
 396         return -1;
 397 }
 398
 399 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl,
 400                           struct sk_buff *skb, struct tcmsg *tcm)
 401 {
 402         struct tbf_sched_data *q = qdisc_priv(sch);
 403
 404         if (cl != 1)    /* only one class */
 405                 return -ENOENT;
 406
 407         tcm->tcm_handle |= TC_H_MIN(1);
 408         tcm->tcm_info = q->qdisc->handle;
 409
 410         return 0;
 411 }
 412
 413 static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 414                      struct Qdisc **old)
 415 {
 416         struct tbf_sched_data *q = qdisc_priv(sch);
 417
 418         if (new == NULL)
 419                 new = &noop_qdisc;
 420
 421         sch_tree_lock(sch);
 422         *old = xchg(&q->qdisc, new);
 423         qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 424         qdisc_reset(*old);
 425         sch_tree_unlock(sch);
 426
 427         return 0;
 428 }
 429
 430 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg)
 431 {
 432         struct tbf_sched_data *q = qdisc_priv(sch);
 433         return q->qdisc;
 434 }
 435
 436 static unsigned long tbf_get(struct Qdisc *sch, u32 classid)
 437 {
 438         return 1;
 439 }
 440
 441 static void tbf_put(struct Qdisc *sch, unsigned long arg)
 442 {
 443 }
 444
 445 static int tbf_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 446                             struct nlattr **tca, unsigned long *arg)
 447 {
 448         return -ENOSYS;
 449 }
 450
 451 static int tbf_delete(struct Qdisc *sch, unsigned long arg)
 452 {
 453         return -ENOSYS;
 454 }
 455
 456 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker)
 457 {
 458         if (!walker->stop) {
 459                 if (walker->count >= walker->skip)
 460                         if (walker->fn(sch, 1, walker) < 0) {
 461                                 walker->stop = 1;
 462                                 return;
 463                         }
 464                 walker->count++;
 465         }
 466 }
 467
 468 static struct tcf_proto **tbf_find_tcf(struct Qdisc *sch, unsigned long cl)
 469 {
 470         return NULL;
 471 }
 472
 473 static const struct Qdisc_class_ops tbf_class_ops =
 474 {
 475         .graft          =       tbf_graft,
 476         .leaf           =       tbf_leaf,
 477         .get            =       tbf_get,
 478         .put            =       tbf_put,
 479         .change         =       tbf_change_class,
 480         .delete         =       tbf_delete,
 481         .walk           =       tbf_walk,
 482         .tcf_chain      =       tbf_find_tcf,
 483         .dump           =       tbf_dump_class,
 484 };
 485
 486 static struct Qdisc_ops tbf_qdisc_ops __read_mostly = {
 487         .next           =       NULL,
 488         .cl_ops         =       &tbf_class_ops,
 489         .id             =       "tbf",
 490         .priv_size      =       sizeof(struct tbf_sched_data),
 491         .enqueue        =       tbf_enqueue,
 492         .dequeue        =       tbf_dequeue,
 493         .requeue        =       tbf_requeue,
 494         .drop           =       tbf_drop,
 495         .init           =       tbf_init,
 496         .reset          =       tbf_reset,
 497         .destroy        =       tbf_destroy,
 498         .change         =       tbf_change,
 499         .dump           =       tbf_dump,
 500         .owner          =       THIS_MODULE,
 501 };
 502
 503 static int __init tbf_module_init(void)
 504 {
 505         return register_qdisc(&tbf_qdisc_ops);
 506 }
 507
 508 static void __exit tbf_module_exit(void)
 509 {
 510         unregister_qdisc(&tbf_qdisc_ops);
 511 }
 512 module_init(tbf_module_init)
 513 module_exit(tbf_module_exit)
 514 MODULE_LICENSE("GPL");