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;
 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         err = nla_parse_nested(tb, TCA_TBF_PTAB, opt, NULL);
 285         if (err < 0)
 286                 return err;
 287
 288         err = -EINVAL;
 289         if (tb[TCA_TBF_PARMS] == NULL ||
 290             nla_len(tb[TCA_TBF_PARMS]) < sizeof(*qopt))
 291                 goto done;
 292
 293         qopt = nla_data(tb[TCA_TBF_PARMS]);
 294         rtab = qdisc_get_rtab(&qopt->rate, tb[TCA_TBF_RTAB]);
 295         if (rtab == NULL)
 296                 goto done;
 297
 298         if (qopt->peakrate.rate) {
 299                 if (qopt->peakrate.rate > qopt->rate.rate)
 300                         ptab = qdisc_get_rtab(&qopt->peakrate, tb[TCA_TBF_PTAB]);
 301                 if (ptab == NULL)
 302                         goto done;
 303         }
 304
 305         for (n = 0; n < 256; n++)
 306                 if (rtab->data[n] > qopt->buffer) break;
 307         max_size = (n << qopt->rate.cell_log)-1;
 308         if (ptab) {
 309                 int size;
 310
 311                 for (n = 0; n < 256; n++)
 312                         if (ptab->data[n] > qopt->mtu) break;
 313                 size = (n << qopt->peakrate.cell_log)-1;
 314                 if (size < max_size) max_size = size;
 315         }
 316         if (max_size < 0)
 317                 goto done;
 318
 319         if (qopt->limit > 0) {
 320                 if ((child = tbf_create_dflt_qdisc(sch, qopt->limit)) == NULL)
 321                         goto done;
 322         }
 323
 324         sch_tree_lock(sch);
 325         if (child) {
 326                 qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
 327                 qdisc_destroy(xchg(&q->qdisc, child));
 328         }
 329         q->limit = qopt->limit;
 330         q->mtu = qopt->mtu;
 331         q->max_size = max_size;
 332         q->buffer = qopt->buffer;
 333         q->tokens = q->buffer;
 334         q->ptokens = q->mtu;
 335         rtab = xchg(&q->R_tab, rtab);
 336         ptab = xchg(&q->P_tab, ptab);
 337         sch_tree_unlock(sch);
 338         err = 0;
 339 done:
 340         if (rtab)
 341                 qdisc_put_rtab(rtab);
 342         if (ptab)
 343                 qdisc_put_rtab(ptab);
 344         return err;
 345 }
 346
 347 static int tbf_init(struct Qdisc* sch, struct nlattr *opt)
 348 {
 349         struct tbf_sched_data *q = qdisc_priv(sch);
 350
 351         if (opt == NULL)
 352                 return -EINVAL;
 353
 354         q->t_c = psched_get_time();
 355         qdisc_watchdog_init(&q->watchdog, sch);
 356         q->qdisc = &noop_qdisc;
 357
 358         return tbf_change(sch, opt);
 359 }
 360
 361 static void tbf_destroy(struct Qdisc *sch)
 362 {
 363         struct tbf_sched_data *q = qdisc_priv(sch);
 364
 365         qdisc_watchdog_cancel(&q->watchdog);
 366
 367         if (q->P_tab)
 368                 qdisc_put_rtab(q->P_tab);
 369         if (q->R_tab)
 370                 qdisc_put_rtab(q->R_tab);
 371
 372         qdisc_destroy(q->qdisc);
 373 }
 374
 375 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb)
 376 {
 377         struct tbf_sched_data *q = qdisc_priv(sch);
 378         struct nlattr *nest;
 379         struct tc_tbf_qopt opt;
 380
 381         nest = nla_nest_start(skb, TCA_OPTIONS);
 382         if (nest == NULL)
 383                 goto nla_put_failure;
 384
 385         opt.limit = q->limit;
 386         opt.rate = q->R_tab->rate;
 387         if (q->P_tab)
 388                 opt.peakrate = q->P_tab->rate;
 389         else
 390                 memset(&opt.peakrate, 0, sizeof(opt.peakrate));
 391         opt.mtu = q->mtu;
 392         opt.buffer = q->buffer;
 393         NLA_PUT(skb, TCA_TBF_PARMS, sizeof(opt), &opt);
 394
 395         nla_nest_end(skb, nest);
 396         return skb->len;
 397
 398 nla_put_failure:
 399         nla_nest_cancel(skb, nest);
 400         return -1;
 401 }
 402
 403 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl,
 404                           struct sk_buff *skb, struct tcmsg *tcm)
 405 {
 406         struct tbf_sched_data *q = qdisc_priv(sch);
 407
 408         if (cl != 1)    /* only one class */
 409                 return -ENOENT;
 410
 411         tcm->tcm_handle |= TC_H_MIN(1);
 412         tcm->tcm_info = q->qdisc->handle;
 413
 414         return 0;
 415 }
 416
 417 static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 418                      struct Qdisc **old)
 419 {
 420         struct tbf_sched_data *q = qdisc_priv(sch);
 421
 422         if (new == NULL)
 423                 new = &noop_qdisc;
 424
 425         sch_tree_lock(sch);
 426         *old = xchg(&q->qdisc, new);
 427         qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 428         qdisc_reset(*old);
 429         sch_tree_unlock(sch);
 430
 431         return 0;
 432 }
 433
 434 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg)
 435 {
 436         struct tbf_sched_data *q = qdisc_priv(sch);
 437         return q->qdisc;
 438 }
 439
 440 static unsigned long tbf_get(struct Qdisc *sch, u32 classid)
 441 {
 442         return 1;
 443 }
 444
 445 static void tbf_put(struct Qdisc *sch, unsigned long arg)
 446 {
 447 }
 448
 449 static int tbf_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 450                             struct nlattr **tca, unsigned long *arg)
 451 {
 452         return -ENOSYS;
 453 }
 454
 455 static int tbf_delete(struct Qdisc *sch, unsigned long arg)
 456 {
 457         return -ENOSYS;
 458 }
 459
 460 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker)
 461 {
 462         if (!walker->stop) {
 463                 if (walker->count >= walker->skip)
 464                         if (walker->fn(sch, 1, walker) < 0) {
 465                                 walker->stop = 1;
 466                                 return;
 467                         }
 468                 walker->count++;
 469         }
 470 }
 471
 472 static struct tcf_proto **tbf_find_tcf(struct Qdisc *sch, unsigned long cl)
 473 {
 474         return NULL;
 475 }
 476
 477 static const struct Qdisc_class_ops tbf_class_ops =
 478 {
 479         .graft          =       tbf_graft,
 480         .leaf           =       tbf_leaf,
 481         .get            =       tbf_get,
 482         .put            =       tbf_put,
 483         .change         =       tbf_change_class,
 484         .delete         =       tbf_delete,
 485         .walk           =       tbf_walk,
 486         .tcf_chain      =       tbf_find_tcf,
 487         .dump           =       tbf_dump_class,
 488 };
 489
 490 static struct Qdisc_ops tbf_qdisc_ops __read_mostly = {
 491         .next           =       NULL,
 492         .cl_ops         =       &tbf_class_ops,
 493         .id             =       "tbf",
 494         .priv_size      =       sizeof(struct tbf_sched_data),
 495         .enqueue        =       tbf_enqueue,
 496         .dequeue        =       tbf_dequeue,
 497         .requeue        =       tbf_requeue,
 498         .drop           =       tbf_drop,
 499         .init           =       tbf_init,
 500         .reset          =       tbf_reset,
 501         .destroy        =       tbf_destroy,
 502         .change         =       tbf_change,
 503         .dump           =       tbf_dump,
 504         .owner          =       THIS_MODULE,
 505 };
 506
 507 static int __init tbf_module_init(void)
 508 {
 509         return register_qdisc(&tbf_qdisc_ops);
 510 }
 511
 512 static void __exit tbf_module_exit(void)
 513 {
 514         unregister_qdisc(&tbf_qdisc_ops);
 515 }
 516 module_init(tbf_module_init)
 517 module_exit(tbf_module_exit)
 518 MODULE_LICENSE("GPL");