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 *child = NULL;
 240         int max_size,n;
 241
 242         err = nla_parse_nested(tb, TCA_TBF_PTAB, opt, tbf_policy);
 243         if (err < 0)
 244                 return err;
 245
 246         err = -EINVAL;
 247         if (tb[TCA_TBF_PARMS] == NULL)
 248                 goto done;
 249
 250         qopt = nla_data(tb[TCA_TBF_PARMS]);
 251         rtab = qdisc_get_rtab(&qopt->rate, tb[TCA_TBF_RTAB]);
 252         if (rtab == NULL)
 253                 goto done;
 254
 255         if (qopt->peakrate.rate) {
 256                 if (qopt->peakrate.rate > qopt->rate.rate)
 257                         ptab = qdisc_get_rtab(&qopt->peakrate, tb[TCA_TBF_PTAB]);
 258                 if (ptab == NULL)
 259                         goto done;
 260         }
 261
 262         for (n = 0; n < 256; n++)
 263                 if (rtab->data[n] > qopt->buffer) break;
 264         max_size = (n << qopt->rate.cell_log)-1;
 265         if (ptab) {
 266                 int size;
 267
 268                 for (n = 0; n < 256; n++)
 269                         if (ptab->data[n] > qopt->mtu) break;
 270                 size = (n << qopt->peakrate.cell_log)-1;
 271                 if (size < max_size) max_size = size;
 272         }
 273         if (max_size < 0)
 274                 goto done;
 275
 276         if (qopt->limit > 0) {
 277                 child = fifo_create_dflt(sch, &bfifo_qdisc_ops, qopt->limit);
 278                 if (IS_ERR(child)) {
 279                         err = PTR_ERR(child);
 280                         goto done;
 281                 }
 282         }
 283
 284         sch_tree_lock(sch);
 285         if (child) {
 286                 qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
 287                 qdisc_destroy(xchg(&q->qdisc, child));
 288         }
 289         q->limit = qopt->limit;
 290         q->mtu = qopt->mtu;
 291         q->max_size = max_size;
 292         q->buffer = qopt->buffer;
 293         q->tokens = q->buffer;
 294         q->ptokens = q->mtu;
 295         rtab = xchg(&q->R_tab, rtab);
 296         ptab = xchg(&q->P_tab, ptab);
 297         sch_tree_unlock(sch);
 298         err = 0;
 299 done:
 300         if (rtab)
 301                 qdisc_put_rtab(rtab);
 302         if (ptab)
 303                 qdisc_put_rtab(ptab);
 304         return err;
 305 }
 306
 307 static int tbf_init(struct Qdisc* sch, struct nlattr *opt)
 308 {
 309         struct tbf_sched_data *q = qdisc_priv(sch);
 310
 311         if (opt == NULL)
 312                 return -EINVAL;
 313
 314         q->t_c = psched_get_time();
 315         qdisc_watchdog_init(&q->watchdog, sch);
 316         q->qdisc = &noop_qdisc;
 317
 318         return tbf_change(sch, opt);
 319 }
 320
 321 static void tbf_destroy(struct Qdisc *sch)
 322 {
 323         struct tbf_sched_data *q = qdisc_priv(sch);
 324
 325         qdisc_watchdog_cancel(&q->watchdog);
 326
 327         if (q->P_tab)
 328                 qdisc_put_rtab(q->P_tab);
 329         if (q->R_tab)
 330                 qdisc_put_rtab(q->R_tab);
 331
 332         qdisc_destroy(q->qdisc);
 333 }
 334
 335 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb)
 336 {
 337         struct tbf_sched_data *q = qdisc_priv(sch);
 338         struct nlattr *nest;
 339         struct tc_tbf_qopt opt;
 340
 341         nest = nla_nest_start(skb, TCA_OPTIONS);
 342         if (nest == NULL)
 343                 goto nla_put_failure;
 344
 345         opt.limit = q->limit;
 346         opt.rate = q->R_tab->rate;
 347         if (q->P_tab)
 348                 opt.peakrate = q->P_tab->rate;
 349         else
 350                 memset(&opt.peakrate, 0, sizeof(opt.peakrate));
 351         opt.mtu = q->mtu;
 352         opt.buffer = q->buffer;
 353         NLA_PUT(skb, TCA_TBF_PARMS, sizeof(opt), &opt);
 354
 355         nla_nest_end(skb, nest);
 356         return skb->len;
 357
 358 nla_put_failure:
 359         nla_nest_cancel(skb, nest);
 360         return -1;
 361 }
 362
 363 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl,
 364                           struct sk_buff *skb, struct tcmsg *tcm)
 365 {
 366         struct tbf_sched_data *q = qdisc_priv(sch);
 367
 368         if (cl != 1)    /* only one class */
 369                 return -ENOENT;
 370
 371         tcm->tcm_handle |= TC_H_MIN(1);
 372         tcm->tcm_info = q->qdisc->handle;
 373
 374         return 0;
 375 }
 376
 377 static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 378                      struct Qdisc **old)
 379 {
 380         struct tbf_sched_data *q = qdisc_priv(sch);
 381
 382         if (new == NULL)
 383                 new = &noop_qdisc;
 384
 385         sch_tree_lock(sch);
 386         *old = xchg(&q->qdisc, new);
 387         qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 388         qdisc_reset(*old);
 389         sch_tree_unlock(sch);
 390
 391         return 0;
 392 }
 393
 394 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg)
 395 {
 396         struct tbf_sched_data *q = qdisc_priv(sch);
 397         return q->qdisc;
 398 }
 399
 400 static unsigned long tbf_get(struct Qdisc *sch, u32 classid)
 401 {
 402         return 1;
 403 }
 404
 405 static void tbf_put(struct Qdisc *sch, unsigned long arg)
 406 {
 407 }
 408
 409 static int tbf_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 410                             struct nlattr **tca, unsigned long *arg)
 411 {
 412         return -ENOSYS;
 413 }
 414
 415 static int tbf_delete(struct Qdisc *sch, unsigned long arg)
 416 {
 417         return -ENOSYS;
 418 }
 419
 420 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker)
 421 {
 422         if (!walker->stop) {
 423                 if (walker->count >= walker->skip)
 424                         if (walker->fn(sch, 1, walker) < 0) {
 425                                 walker->stop = 1;
 426                                 return;
 427                         }
 428                 walker->count++;
 429         }
 430 }
 431
 432 static struct tcf_proto **tbf_find_tcf(struct Qdisc *sch, unsigned long cl)
 433 {
 434         return NULL;
 435 }
 436
 437 static const struct Qdisc_class_ops tbf_class_ops =
 438 {
 439         .graft          =       tbf_graft,
 440         .leaf           =       tbf_leaf,
 441         .get            =       tbf_get,
 442         .put            =       tbf_put,
 443         .change         =       tbf_change_class,
 444         .delete         =       tbf_delete,
 445         .walk           =       tbf_walk,
 446         .tcf_chain      =       tbf_find_tcf,
 447         .dump           =       tbf_dump_class,
 448 };
 449
 450 static struct Qdisc_ops tbf_qdisc_ops __read_mostly = {
 451         .next           =       NULL,
 452         .cl_ops         =       &tbf_class_ops,
 453         .id             =       "tbf",
 454         .priv_size      =       sizeof(struct tbf_sched_data),
 455         .enqueue        =       tbf_enqueue,
 456         .dequeue        =       tbf_dequeue,
 457         .peek           =       qdisc_peek_dequeued,
 458         .drop           =       tbf_drop,
 459         .init           =       tbf_init,
 460         .reset          =       tbf_reset,
 461         .destroy        =       tbf_destroy,
 462         .change         =       tbf_change,
 463         .dump           =       tbf_dump,
 464         .owner          =       THIS_MODULE,
 465 };
 466
 467 static int __init tbf_module_init(void)
 468 {
 469         return register_qdisc(&tbf_qdisc_ops);
 470 }
 471
 472 static void __exit tbf_module_exit(void)
 473 {
 474         unregister_qdisc(&tbf_qdisc_ops);
 475 }
 476 module_init(tbf_module_init)
 477 module_exit(tbf_module_exit)
 478 MODULE_LICENSE("GPL");