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                 return qdisc_reshape_fail(skb, sch);
 128
 129         if ((ret = q->qdisc->enqueue(skb, q->qdisc)) != 0) {
 130                 sch->qstats.drops++;
 131                 return ret;
 132         }
 133
 134         sch->q.qlen++;
 135         sch->bstats.bytes += skb->len;
 136         sch->bstats.packets++;
 137         return 0;
 138 }
 139
 140 static int tbf_requeue(struct sk_buff *skb, struct Qdisc* sch)
 141 {
 142         struct tbf_sched_data *q = qdisc_priv(sch);
 143         int ret;
 144
 145         if ((ret = q->qdisc->ops->requeue(skb, q->qdisc)) == 0) {
 146                 sch->q.qlen++;
 147                 sch->qstats.requeues++;
 148         }
 149
 150         return ret;
 151 }
 152
 153 static unsigned int tbf_drop(struct Qdisc* sch)
 154 {
 155         struct tbf_sched_data *q = qdisc_priv(sch);
 156         unsigned int len = 0;
 157
 158         if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
 159                 sch->q.qlen--;
 160                 sch->qstats.drops++;
 161         }
 162         return len;
 163 }
 164
 165 static struct sk_buff *tbf_dequeue(struct Qdisc* sch)
 166 {
 167         struct tbf_sched_data *q = qdisc_priv(sch);
 168         struct sk_buff *skb;
 169
 170         skb = q->qdisc->dequeue(q->qdisc);
 171
 172         if (skb) {
 173                 psched_time_t now;
 174                 long toks;
 175                 long ptoks = 0;
 176                 unsigned int len = skb->len;
 177
 178                 now = psched_get_time();
 179                 toks = psched_tdiff_bounded(now, q->t_c, q->buffer);
 180
 181                 if (q->P_tab) {
 182                         ptoks = toks + q->ptokens;
 183                         if (ptoks > (long)q->mtu)
 184                                 ptoks = q->mtu;
 185                         ptoks -= L2T_P(q, len);
 186                 }
 187                 toks += q->tokens;
 188                 if (toks > (long)q->buffer)
 189                         toks = q->buffer;
 190                 toks -= L2T(q, len);
 191
 192                 if ((toks|ptoks) >= 0) {
 193                         q->t_c = now;
 194                         q->tokens = toks;
 195                         q->ptokens = ptoks;
 196                         sch->q.qlen--;
 197                         sch->flags &= ~TCQ_F_THROTTLED;
 198                         return skb;
 199                 }
 200
 201                 qdisc_watchdog_schedule(&q->watchdog,
 202                                         now + max_t(long, -toks, -ptoks));
 203
 204                 /* Maybe we have a shorter packet in the queue,
 205                    which can be sent now. It sounds cool,
 206                    but, however, this is wrong in principle.
 207                    We MUST NOT reorder packets under these circumstances.
 208
 209                    Really, if we split the flow into independent
 210                    subflows, it would be a very good solution.
 211                    This is the main idea of all FQ algorithms
 212                    (cf. CSZ, HPFQ, HFSC)
 213                  */
 214
 215                 if (q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS) {
 216                         /* When requeue fails skb is dropped */
 217                         qdisc_tree_decrease_qlen(q->qdisc, 1);
 218                         sch->qstats.drops++;
 219                 }
 220
 221                 sch->qstats.overlimits++;
 222         }
 223         return NULL;
 224 }
 225
 226 static void tbf_reset(struct Qdisc* sch)
 227 {
 228         struct tbf_sched_data *q = qdisc_priv(sch);
 229
 230         qdisc_reset(q->qdisc);
 231         sch->q.qlen = 0;
 232         q->t_c = psched_get_time();
 233         q->tokens = q->buffer;
 234         q->ptokens = q->mtu;
 235         qdisc_watchdog_cancel(&q->watchdog);
 236 }
 237
 238 static struct Qdisc *tbf_create_dflt_qdisc(struct Qdisc *sch, u32 limit)
 239 {
 240         struct Qdisc *q;
 241         struct nlattr *nla;
 242         int ret;
 243
 244         q = qdisc_create_dflt(sch->dev, &bfifo_qdisc_ops,
 245                               TC_H_MAKE(sch->handle, 1));
 246         if (q) {
 247                 nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)),
 248                               GFP_KERNEL);
 249                 if (nla) {
 250                         nla->nla_type = RTM_NEWQDISC;
 251                         nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
 252                         ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
 253
 254                         ret = q->ops->change(q, nla);
 255                         kfree(nla);
 256
 257                         if (ret == 0)
 258                                 return q;
 259                 }
 260                 qdisc_destroy(q);
 261         }
 262
 263         return NULL;
 264 }
 265
 266 static const struct nla_policy tbf_policy[TCA_TBF_MAX + 1] = {
 267         [TCA_TBF_PARMS] = { .len = sizeof(struct tc_tbf_qopt) },
 268         [TCA_TBF_RTAB]  = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
 269         [TCA_TBF_PTAB]  = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
 270 };
 271
 272 static int tbf_change(struct Qdisc* sch, struct nlattr *opt)
 273 {
 274         int err;
 275         struct tbf_sched_data *q = qdisc_priv(sch);
 276         struct nlattr *tb[TCA_TBF_PTAB + 1];
 277         struct tc_tbf_qopt *qopt;
 278         struct qdisc_rate_table *rtab = NULL;
 279         struct qdisc_rate_table *ptab = NULL;
 280         struct Qdisc *child = NULL;
 281         int max_size,n;
 282
 283         err = nla_parse_nested(tb, TCA_TBF_PTAB, opt, tbf_policy);
 284         if (err < 0)
 285                 return err;
 286
 287         err = -EINVAL;
 288         if (tb[TCA_TBF_PARMS] == NULL)
 289                 goto done;
 290
 291         qopt = nla_data(tb[TCA_TBF_PARMS]);
 292         rtab = qdisc_get_rtab(&qopt->rate, tb[TCA_TBF_RTAB]);
 293         if (rtab == NULL)
 294                 goto done;
 295
 296         if (qopt->peakrate.rate) {
 297                 if (qopt->peakrate.rate > qopt->rate.rate)
 298                         ptab = qdisc_get_rtab(&qopt->peakrate, tb[TCA_TBF_PTAB]);
 299                 if (ptab == NULL)
 300                         goto done;
 301         }
 302
 303         for (n = 0; n < 256; n++)
 304                 if (rtab->data[n] > qopt->buffer) break;
 305         max_size = (n << qopt->rate.cell_log)-1;
 306         if (ptab) {
 307                 int size;
 308
 309                 for (n = 0; n < 256; n++)
 310                         if (ptab->data[n] > qopt->mtu) break;
 311                 size = (n << qopt->peakrate.cell_log)-1;
 312                 if (size < max_size) max_size = size;
 313         }
 314         if (max_size < 0)
 315                 goto done;
 316
 317         if (qopt->limit > 0) {
 318                 if ((child = tbf_create_dflt_qdisc(sch, qopt->limit)) == NULL)
 319                         goto done;
 320         }
 321
 322         sch_tree_lock(sch);
 323         if (child) {
 324                 qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
 325                 qdisc_destroy(xchg(&q->qdisc, child));
 326         }
 327         q->limit = qopt->limit;
 328         q->mtu = qopt->mtu;
 329         q->max_size = max_size;
 330         q->buffer = qopt->buffer;
 331         q->tokens = q->buffer;
 332         q->ptokens = q->mtu;
 333         rtab = xchg(&q->R_tab, rtab);
 334         ptab = xchg(&q->P_tab, ptab);
 335         sch_tree_unlock(sch);
 336         err = 0;
 337 done:
 338         if (rtab)
 339                 qdisc_put_rtab(rtab);
 340         if (ptab)
 341                 qdisc_put_rtab(ptab);
 342         return err;
 343 }
 344
 345 static int tbf_init(struct Qdisc* sch, struct nlattr *opt)
 346 {
 347         struct tbf_sched_data *q = qdisc_priv(sch);
 348
 349         if (opt == NULL)
 350                 return -EINVAL;
 351
 352         q->t_c = psched_get_time();
 353         qdisc_watchdog_init(&q->watchdog, sch);
 354         q->qdisc = &noop_qdisc;
 355
 356         return tbf_change(sch, opt);
 357 }
 358
 359 static void tbf_destroy(struct Qdisc *sch)
 360 {
 361         struct tbf_sched_data *q = qdisc_priv(sch);
 362
 363         qdisc_watchdog_cancel(&q->watchdog);
 364
 365         if (q->P_tab)
 366                 qdisc_put_rtab(q->P_tab);
 367         if (q->R_tab)
 368                 qdisc_put_rtab(q->R_tab);
 369
 370         qdisc_destroy(q->qdisc);
 371 }
 372
 373 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb)
 374 {
 375         struct tbf_sched_data *q = qdisc_priv(sch);
 376         struct nlattr *nest;
 377         struct tc_tbf_qopt opt;
 378
 379         nest = nla_nest_start(skb, TCA_OPTIONS);
 380         if (nest == NULL)
 381                 goto nla_put_failure;
 382
 383         opt.limit = q->limit;
 384         opt.rate = q->R_tab->rate;
 385         if (q->P_tab)
 386                 opt.peakrate = q->P_tab->rate;
 387         else
 388                 memset(&opt.peakrate, 0, sizeof(opt.peakrate));
 389         opt.mtu = q->mtu;
 390         opt.buffer = q->buffer;
 391         NLA_PUT(skb, TCA_TBF_PARMS, sizeof(opt), &opt);
 392
 393         nla_nest_end(skb, nest);
 394         return skb->len;
 395
 396 nla_put_failure:
 397         nla_nest_cancel(skb, nest);
 398         return -1;
 399 }
 400
 401 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl,
 402                           struct sk_buff *skb, struct tcmsg *tcm)
 403 {
 404         struct tbf_sched_data *q = qdisc_priv(sch);
 405
 406         if (cl != 1)    /* only one class */
 407                 return -ENOENT;
 408
 409         tcm->tcm_handle |= TC_H_MIN(1);
 410         tcm->tcm_info = q->qdisc->handle;
 411
 412         return 0;
 413 }
 414
 415 static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 416                      struct Qdisc **old)
 417 {
 418         struct tbf_sched_data *q = qdisc_priv(sch);
 419
 420         if (new == NULL)
 421                 new = &noop_qdisc;
 422
 423         sch_tree_lock(sch);
 424         *old = xchg(&q->qdisc, new);
 425         qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 426         qdisc_reset(*old);
 427         sch_tree_unlock(sch);
 428
 429         return 0;
 430 }
 431
 432 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg)
 433 {
 434         struct tbf_sched_data *q = qdisc_priv(sch);
 435         return q->qdisc;
 436 }
 437
 438 static unsigned long tbf_get(struct Qdisc *sch, u32 classid)
 439 {
 440         return 1;
 441 }
 442
 443 static void tbf_put(struct Qdisc *sch, unsigned long arg)
 444 {
 445 }
 446
 447 static int tbf_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 448                             struct nlattr **tca, unsigned long *arg)
 449 {
 450         return -ENOSYS;
 451 }
 452
 453 static int tbf_delete(struct Qdisc *sch, unsigned long arg)
 454 {
 455         return -ENOSYS;
 456 }
 457
 458 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker)
 459 {
 460         if (!walker->stop) {
 461                 if (walker->count >= walker->skip)
 462                         if (walker->fn(sch, 1, walker) < 0) {
 463                                 walker->stop = 1;
 464                                 return;
 465                         }
 466                 walker->count++;
 467         }
 468 }
 469
 470 static struct tcf_proto **tbf_find_tcf(struct Qdisc *sch, unsigned long cl)
 471 {
 472         return NULL;
 473 }
 474
 475 static const struct Qdisc_class_ops tbf_class_ops =
 476 {
 477         .graft          =       tbf_graft,
 478         .leaf           =       tbf_leaf,
 479         .get            =       tbf_get,
 480         .put            =       tbf_put,
 481         .change         =       tbf_change_class,
 482         .delete         =       tbf_delete,
 483         .walk           =       tbf_walk,
 484         .tcf_chain      =       tbf_find_tcf,
 485         .dump           =       tbf_dump_class,
 486 };
 487
 488 static struct Qdisc_ops tbf_qdisc_ops __read_mostly = {
 489         .next           =       NULL,
 490         .cl_ops         =       &tbf_class_ops,
 491         .id             =       "tbf",
 492         .priv_size      =       sizeof(struct tbf_sched_data),
 493         .enqueue        =       tbf_enqueue,
 494         .dequeue        =       tbf_dequeue,
 495         .requeue        =       tbf_requeue,
 496         .drop           =       tbf_drop,
 497         .init           =       tbf_init,
 498         .reset          =       tbf_reset,
 499         .destroy        =       tbf_destroy,
 500         .change         =       tbf_change,
 501         .dump           =       tbf_dump,
 502         .owner          =       THIS_MODULE,
 503 };
 504
 505 static int __init tbf_module_init(void)
 506 {
 507         return register_qdisc(&tbf_qdisc_ops);
 508 }
 509
 510 static void __exit tbf_module_exit(void)
 511 {
 512         unregister_qdisc(&tbf_qdisc_ops);
 513 }
 514 module_init(tbf_module_init)
 515 module_exit(tbf_module_exit)
 516 MODULE_LICENSE("GPL");