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