linux/net/sched/sch_tbf.c
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   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
 100struct tbf_sched_data {
 101/* Parameters */
 102        u32             limit;          /* Maximal length of backlog: bytes */
 103        u32             buffer;         /* Token bucket depth/rate: MUST BE >= MTU/B */
 104        u32             mtu;
 105        u32             max_size;
 106        struct qdisc_rate_table *R_tab;
 107        struct qdisc_rate_table *P_tab;
 108
 109/* Variables */
 110        long    tokens;                 /* Current number of B tokens */
 111        long    ptokens;                /* Current number of P tokens */
 112        psched_time_t   t_c;            /* Time check-point */
 113        struct Qdisc    *qdisc;         /* Inner qdisc, default - bfifo queue */
 114        struct qdisc_watchdog watchdog; /* Watchdog timer */
 115};
 116
 117#define L2T(q, L)   qdisc_l2t((q)->R_tab, L)
 118#define L2T_P(q, L) qdisc_l2t((q)->P_tab, L)
 119
 120static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 121{
 122        struct tbf_sched_data *q = qdisc_priv(sch);
 123        int ret;
 124
 125        if (qdisc_pkt_len(skb) > q->max_size)
 126                return qdisc_reshape_fail(skb, sch);
 127
 128        ret = qdisc_enqueue(skb, q->qdisc);
 129        if (ret != NET_XMIT_SUCCESS) {
 130                if (net_xmit_drop_count(ret))
 131                        sch->qstats.drops++;
 132                return ret;
 133        }
 134
 135        sch->q.qlen++;
 136        return NET_XMIT_SUCCESS;
 137}
 138
 139static unsigned int tbf_drop(struct Qdisc *sch)
 140{
 141        struct tbf_sched_data *q = qdisc_priv(sch);
 142        unsigned int len = 0;
 143
 144        if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
 145                sch->q.qlen--;
 146                sch->qstats.drops++;
 147        }
 148        return len;
 149}
 150
 151static struct sk_buff *tbf_dequeue(struct Qdisc *sch)
 152{
 153        struct tbf_sched_data *q = qdisc_priv(sch);
 154        struct sk_buff *skb;
 155
 156        skb = q->qdisc->ops->peek(q->qdisc);
 157
 158        if (skb) {
 159                psched_time_t now;
 160                long toks;
 161                long ptoks = 0;
 162                unsigned int len = qdisc_pkt_len(skb);
 163
 164                now = psched_get_time();
 165                toks = psched_tdiff_bounded(now, q->t_c, q->buffer);
 166
 167                if (q->P_tab) {
 168                        ptoks = toks + q->ptokens;
 169                        if (ptoks > (long)q->mtu)
 170                                ptoks = q->mtu;
 171                        ptoks -= L2T_P(q, len);
 172                }
 173                toks += q->tokens;
 174                if (toks > (long)q->buffer)
 175                        toks = q->buffer;
 176                toks -= L2T(q, len);
 177
 178                if ((toks|ptoks) >= 0) {
 179                        skb = qdisc_dequeue_peeked(q->qdisc);
 180                        if (unlikely(!skb))
 181                                return NULL;
 182
 183                        q->t_c = now;
 184                        q->tokens = toks;
 185                        q->ptokens = ptoks;
 186                        sch->q.qlen--;
 187                        qdisc_unthrottled(sch);
 188                        qdisc_bstats_update(sch, skb);
 189                        return skb;
 190                }
 191
 192                qdisc_watchdog_schedule(&q->watchdog,
 193                                        now + max_t(long, -toks, -ptoks));
 194
 195                /* Maybe we have a shorter packet in the queue,
 196                   which can be sent now. It sounds cool,
 197                   but, however, this is wrong in principle.
 198                   We MUST NOT reorder packets under these circumstances.
 199
 200                   Really, if we split the flow into independent
 201                   subflows, it would be a very good solution.
 202                   This is the main idea of all FQ algorithms
 203                   (cf. CSZ, HPFQ, HFSC)
 204                 */
 205
 206                sch->qstats.overlimits++;
 207        }
 208        return NULL;
 209}
 210
 211static void tbf_reset(struct Qdisc *sch)
 212{
 213        struct tbf_sched_data *q = qdisc_priv(sch);
 214
 215        qdisc_reset(q->qdisc);
 216        sch->q.qlen = 0;
 217        q->t_c = psched_get_time();
 218        q->tokens = q->buffer;
 219        q->ptokens = q->mtu;
 220        qdisc_watchdog_cancel(&q->watchdog);
 221}
 222
 223static const struct nla_policy tbf_policy[TCA_TBF_MAX + 1] = {
 224        [TCA_TBF_PARMS] = { .len = sizeof(struct tc_tbf_qopt) },
 225        [TCA_TBF_RTAB]  = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
 226        [TCA_TBF_PTAB]  = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
 227};
 228
 229static int tbf_change(struct Qdisc *sch, struct nlattr *opt)
 230{
 231        int err;
 232        struct tbf_sched_data *q = qdisc_priv(sch);
 233        struct nlattr *tb[TCA_TBF_PTAB + 1];
 234        struct tc_tbf_qopt *qopt;
 235        struct qdisc_rate_table *rtab = NULL;
 236        struct qdisc_rate_table *ptab = NULL;
 237        struct Qdisc *child = NULL;
 238        int max_size, n;
 239
 240        err = nla_parse_nested(tb, TCA_TBF_PTAB, opt, tbf_policy);
 241        if (err < 0)
 242                return err;
 243
 244        err = -EINVAL;
 245        if (tb[TCA_TBF_PARMS] == NULL)
 246                goto done;
 247
 248        qopt = nla_data(tb[TCA_TBF_PARMS]);
 249        rtab = qdisc_get_rtab(&qopt->rate, tb[TCA_TBF_RTAB]);
 250        if (rtab == NULL)
 251                goto done;
 252
 253        if (qopt->peakrate.rate) {
 254                if (qopt->peakrate.rate > qopt->rate.rate)
 255                        ptab = qdisc_get_rtab(&qopt->peakrate, tb[TCA_TBF_PTAB]);
 256                if (ptab == NULL)
 257                        goto done;
 258        }
 259
 260        for (n = 0; n < 256; n++)
 261                if (rtab->data[n] > qopt->buffer)
 262                        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)
 269                                break;
 270                size = (n << qopt->peakrate.cell_log) - 1;
 271                if (size < max_size)
 272                        max_size = size;
 273        }
 274        if (max_size < 0)
 275                goto done;
 276
 277        if (q->qdisc != &noop_qdisc) {
 278                err = fifo_set_limit(q->qdisc, qopt->limit);
 279                if (err)
 280                        goto done;
 281        } else if (qopt->limit > 0) {
 282                child = fifo_create_dflt(sch, &bfifo_qdisc_ops, qopt->limit);
 283                if (IS_ERR(child)) {
 284                        err = PTR_ERR(child);
 285                        goto done;
 286                }
 287        }
 288
 289        sch_tree_lock(sch);
 290        if (child) {
 291                qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
 292                qdisc_destroy(q->qdisc);
 293                q->qdisc = child;
 294        }
 295        q->limit = qopt->limit;
 296        q->mtu = qopt->mtu;
 297        q->max_size = max_size;
 298        q->buffer = qopt->buffer;
 299        q->tokens = q->buffer;
 300        q->ptokens = q->mtu;
 301
 302        swap(q->R_tab, rtab);
 303        swap(q->P_tab, ptab);
 304
 305        sch_tree_unlock(sch);
 306        err = 0;
 307done:
 308        if (rtab)
 309                qdisc_put_rtab(rtab);
 310        if (ptab)
 311                qdisc_put_rtab(ptab);
 312        return err;
 313}
 314
 315static 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
 329static 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
 343static 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        sch->qstats.backlog = q->qdisc->qstats.backlog;
 350        nest = nla_nest_start(skb, TCA_OPTIONS);
 351        if (nest == NULL)
 352                goto nla_put_failure;
 353
 354        opt.limit = q->limit;
 355        opt.rate = q->R_tab->rate;
 356        if (q->P_tab)
 357                opt.peakrate = q->P_tab->rate;
 358        else
 359                memset(&opt.peakrate, 0, sizeof(opt.peakrate));
 360        opt.mtu = q->mtu;
 361        opt.buffer = q->buffer;
 362        if (nla_put(skb, TCA_TBF_PARMS, sizeof(opt), &opt))
 363                goto nla_put_failure;
 364
 365        nla_nest_end(skb, nest);
 366        return skb->len;
 367
 368nla_put_failure:
 369        nla_nest_cancel(skb, nest);
 370        return -1;
 371}
 372
 373static int tbf_dump_class(struct Qdisc *sch, unsigned long cl,
 374                          struct sk_buff *skb, struct tcmsg *tcm)
 375{
 376        struct tbf_sched_data *q = qdisc_priv(sch);
 377
 378        tcm->tcm_handle |= TC_H_MIN(1);
 379        tcm->tcm_info = q->qdisc->handle;
 380
 381        return 0;
 382}
 383
 384static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 385                     struct Qdisc **old)
 386{
 387        struct tbf_sched_data *q = qdisc_priv(sch);
 388
 389        if (new == NULL)
 390                new = &noop_qdisc;
 391
 392        sch_tree_lock(sch);
 393        *old = q->qdisc;
 394        q->qdisc = new;
 395        qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 396        qdisc_reset(*old);
 397        sch_tree_unlock(sch);
 398
 399        return 0;
 400}
 401
 402static struct Qdisc *tbf_leaf(struct Qdisc *sch, unsigned long arg)
 403{
 404        struct tbf_sched_data *q = qdisc_priv(sch);
 405        return q->qdisc;
 406}
 407
 408static unsigned long tbf_get(struct Qdisc *sch, u32 classid)
 409{
 410        return 1;
 411}
 412
 413static void tbf_put(struct Qdisc *sch, unsigned long arg)
 414{
 415}
 416
 417static void tbf_walk(struct Qdisc *sch, struct qdisc_walker *walker)
 418{
 419        if (!walker->stop) {
 420                if (walker->count >= walker->skip)
 421                        if (walker->fn(sch, 1, walker) < 0) {
 422                                walker->stop = 1;
 423                                return;
 424                        }
 425                walker->count++;
 426        }
 427}
 428
 429static const struct Qdisc_class_ops tbf_class_ops = {
 430        .graft          =       tbf_graft,
 431        .leaf           =       tbf_leaf,
 432        .get            =       tbf_get,
 433        .put            =       tbf_put,
 434        .walk           =       tbf_walk,
 435        .dump           =       tbf_dump_class,
 436};
 437
 438static struct Qdisc_ops tbf_qdisc_ops __read_mostly = {
 439        .next           =       NULL,
 440        .cl_ops         =       &tbf_class_ops,
 441        .id             =       "tbf",
 442        .priv_size      =       sizeof(struct tbf_sched_data),
 443        .enqueue        =       tbf_enqueue,
 444        .dequeue        =       tbf_dequeue,
 445        .peek           =       qdisc_peek_dequeued,
 446        .drop           =       tbf_drop,
 447        .init           =       tbf_init,
 448        .reset          =       tbf_reset,
 449        .destroy        =       tbf_destroy,
 450        .change         =       tbf_change,
 451        .dump           =       tbf_dump,
 452        .owner          =       THIS_MODULE,
 453};
 454
 455static int __init tbf_module_init(void)
 456{
 457        return register_qdisc(&tbf_qdisc_ops);
 458}
 459
 460static void __exit tbf_module_exit(void)
 461{
 462        unregister_qdisc(&tbf_qdisc_ops);
 463}
 464module_init(tbf_module_init)
 465module_exit(tbf_module_exit)
 466MODULE_LICENSE("GPL");
 467
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