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(q->qdisc);
 288                 q->qdisc = child;
 289         }
 290         q->limit = qopt->limit;
 291         q->mtu = qopt->mtu;
 292         q->max_size = max_size;
 293         q->buffer = qopt->buffer;
 294         q->tokens = q->buffer;
 295         q->ptokens = q->mtu;
 296
 297         swap(q->R_tab, rtab);
 298         swap(q->P_tab, ptab);
 299
 300         sch_tree_unlock(sch);
 301         err = 0;
 302 done:
 303         if (rtab)
 304                 qdisc_put_rtab(rtab);
 305         if (ptab)
 306                 qdisc_put_rtab(ptab);
 307         return err;
 308 }
 309
 310 static int tbf_init(struct Qdisc* sch, struct nlattr *opt)
 311 {
 312         struct tbf_sched_data *q = qdisc_priv(sch);
 313
 314         if (opt == NULL)
 315                 return -EINVAL;
 316
 317         q->t_c = psched_get_time();
 318         qdisc_watchdog_init(&q->watchdog, sch);
 319         q->qdisc = &noop_qdisc;
 320
 321         return tbf_change(sch, opt);
 322 }
 323
 324 static void tbf_destroy(struct Qdisc *sch)
 325 {
 326         struct tbf_sched_data *q = qdisc_priv(sch);
 327
 328         qdisc_watchdog_cancel(&q->watchdog);
 329
 330         if (q->P_tab)
 331                 qdisc_put_rtab(q->P_tab);
 332         if (q->R_tab)
 333                 qdisc_put_rtab(q->R_tab);
 334
 335         qdisc_destroy(q->qdisc);
 336 }
 337
 338 static int tbf_dump(struct Qdisc *sch, struct sk_buff *skb)
 339 {
 340         struct tbf_sched_data *q = qdisc_priv(sch);
 341         struct nlattr *nest;
 342         struct tc_tbf_qopt opt;
 343
 344         nest = nla_nest_start(skb, TCA_OPTIONS);
 345         if (nest == NULL)
 346                 goto nla_put_failure;
 347
 348         opt.limit = q->limit;
 349         opt.rate = q->R_tab->rate;
 350         if (q->P_tab)
 351                 opt.peakrate = q->P_tab->rate;
 352         else
 353                 memset(&opt.peakrate, 0, sizeof(opt.peakrate));
 354         opt.mtu = q->mtu;
 355         opt.buffer = q->buffer;
 356         NLA_PUT(skb, TCA_TBF_PARMS, sizeof(opt), &opt);
 357
 358         nla_nest_end(skb, nest);
 359         return skb->len;
 360
 361 nla_put_failure:
 362         nla_nest_cancel(skb, nest);
 363         return -1;
 364 }
 365
 366 static int tbf_dump_class(struct Qdisc *sch, unsigned long cl,
 367                           struct sk_buff *skb, struct tcmsg *tcm)
 368 {
 369         struct tbf_sched_data *q = qdisc_priv(sch);
 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 = q->qdisc;
 387         q->qdisc = new;
 388         qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 389         qdisc_reset(*old);
 390         sch_tree_unlock(sch);
 391
 392         return 0;
 393 }
 394
 395 static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg)
 396 {
 397         struct tbf_sched_data *q = qdisc_priv(sch);
 398         return q->qdisc;
 399 }
 400
 401 static unsigned long tbf_get(struct Qdisc *sch, u32 classid)
 402 {
 403         return 1;
 404 }
 405
 406 static void tbf_put(struct Qdisc *sch, unsigned long arg)
 407 {
 408 }
 409
 410 static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker)
 411 {
 412         if (!walker->stop) {
 413                 if (walker->count >= walker->skip)
 414                         if (walker->fn(sch, 1, walker) < 0) {
 415                                 walker->stop = 1;
 416                                 return;
 417                         }
 418                 walker->count++;
 419         }
 420 }
 421
 422 static const struct Qdisc_class_ops tbf_class_ops =
 423 {
 424         .graft          =       tbf_graft,
 425         .leaf           =       tbf_leaf,
 426         .get            =       tbf_get,
 427         .put            =       tbf_put,
 428         .walk           =       tbf_walk,
 429         .dump           =       tbf_dump_class,
 430 };
 431
 432 static struct Qdisc_ops tbf_qdisc_ops __read_mostly = {
 433         .next           =       NULL,
 434         .cl_ops         =       &tbf_class_ops,
 435         .id             =       "tbf",
 436         .priv_size      =       sizeof(struct tbf_sched_data),
 437         .enqueue        =       tbf_enqueue,
 438         .dequeue        =       tbf_dequeue,
 439         .peek           =       qdisc_peek_dequeued,
 440         .drop           =       tbf_drop,
 441         .init           =       tbf_init,
 442         .reset          =       tbf_reset,
 443         .destroy        =       tbf_destroy,
 444         .change         =       tbf_change,
 445         .dump           =       tbf_dump,
 446         .owner          =       THIS_MODULE,
 447 };
 448
 449 static int __init tbf_module_init(void)
 450 {
 451         return register_qdisc(&tbf_qdisc_ops);
 452 }
 453
 454 static void __exit tbf_module_exit(void)
 455 {
 456         unregister_qdisc(&tbf_qdisc_ops);
 457 }
 458 module_init(tbf_module_init)
 459 module_exit(tbf_module_exit)
 460 MODULE_LICENSE("GPL");