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