kernel/net/sched/sch_fq_codel.c

   1 /*
   2  * Fair Queue CoDel discipline
   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  *  Copyright (C) 2012 Eric Dumazet <edumazet@google.com>
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/types.h>
  14 #include <linux/kernel.h>
  15 #include <linux/jiffies.h>
  16 #include <linux/string.h>
  17 #include <linux/in.h>
  18 #include <linux/errno.h>
  19 #include <linux/init.h>
  20 #include <linux/skbuff.h>
  21 #include <linux/jhash.h>
  22 #include <linux/slab.h>
  23 #include <linux/vmalloc.h>
  24 #include <net/netlink.h>
  25 #include <net/pkt_sched.h>
  26 #include <net/flow_keys.h>
  27 #include <net/codel.h>
  28
  29 /*      Fair Queue CoDel.
  30  *
  31  * Principles :
  32  * Packets are classified (internal classifier or external) on flows.
  33  * This is a Stochastic model (as we use a hash, several flows
  34  *                             might be hashed on same slot)
  35  * Each flow has a CoDel managed queue.
  36  * Flows are linked onto two (Round Robin) lists,
  37  * so that new flows have priority on old ones.
  38  *
  39  * For a given flow, packets are not reordered (CoDel uses a FIFO)
  40  * head drops only.
  41  * ECN capability is on by default.
  42  * Low memory footprint (64 bytes per flow)
  43  */
  44
  45 struct fq_codel_flow {
  46         struct sk_buff    *head;
  47         struct sk_buff    *tail;
  48         struct list_head  flowchain;
  49         int               deficit;
  50         u32               dropped; /* number of drops (or ECN marks) on this flow */
  51         struct codel_vars cvars;
  52 }; /* please try to keep this structure <= 64 bytes */
  53
  54 struct fq_codel_sched_data {
  55         struct tcf_proto __rcu *filter_list; /* optional external classifier */
  56         struct fq_codel_flow *flows;    /* Flows table [flows_cnt] */
  57         u32             *backlogs;      /* backlog table [flows_cnt] */
  58         u32             flows_cnt;      /* number of flows */
  59         u32             perturbation;   /* hash perturbation */
  60         u32             quantum;        /* psched_mtu(qdisc_dev(sch)); */
  61         struct codel_params cparams;
  62         struct codel_stats cstats;
  63         u32             drop_overlimit;
  64         u32             new_flow_count;
  65
  66         struct list_head new_flows;     /* list of new flows */
  67         struct list_head old_flows;     /* list of old flows */
  68 };
  69
  70 static unsigned int fq_codel_hash(const struct fq_codel_sched_data *q,
  71                                   const struct sk_buff *skb)
  72 {
  73         struct flow_keys keys;
  74         unsigned int hash;
  75
  76         skb_flow_dissect(skb, &keys);
  77         hash = jhash_3words((__force u32)keys.dst,
  78                             (__force u32)keys.src ^ keys.ip_proto,
  79                             (__force u32)keys.ports, q->perturbation);
  80
  81         return reciprocal_scale(hash, q->flows_cnt);
  82 }
  83
  84 static unsigned int fq_codel_classify(struct sk_buff *skb, struct Qdisc *sch,
  85                                       int *qerr)
  86 {
  87         struct fq_codel_sched_data *q = qdisc_priv(sch);
  88         struct tcf_proto *filter;
  89         struct tcf_result res;
  90         int result;
  91
  92         if (TC_H_MAJ(skb->priority) == sch->handle &&
  93             TC_H_MIN(skb->priority) > 0 &&
  94             TC_H_MIN(skb->priority) <= q->flows_cnt)
  95                 return TC_H_MIN(skb->priority);
  96
  97         filter = rcu_dereference_bh(q->filter_list);
  98         if (!filter)
  99                 return fq_codel_hash(q, skb) + 1;
 100
 101         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
 102         result = tc_classify(skb, filter, &res);
 103         if (result >= 0) {
 104 #ifdef CONFIG_NET_CLS_ACT
 105                 switch (result) {
 106                 case TC_ACT_STOLEN:
 107                 case TC_ACT_QUEUED:
 108                         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
 109                 case TC_ACT_SHOT:
 110                         return 0;
 111                 }
 112 #endif
 113                 if (TC_H_MIN(res.classid) <= q->flows_cnt)
 114                         return TC_H_MIN(res.classid);
 115         }
 116         return 0;
 117 }
 118
 119 /* helper functions : might be changed when/if skb use a standard list_head */
 120
 121 /* remove one skb from head of slot queue */
 122 static inline struct sk_buff *dequeue_head(struct fq_codel_flow *flow)
 123 {
 124         struct sk_buff *skb = flow->head;
 125
 126         flow->head = skb->next;
 127         skb->next = NULL;
 128         return skb;
 129 }
 130
 131 /* add skb to flow queue (tail add) */
 132 static inline void flow_queue_add(struct fq_codel_flow *flow,
 133                                   struct sk_buff *skb)
 134 {
 135         if (flow->head == NULL)
 136                 flow->head = skb;
 137         else
 138                 flow->tail->next = skb;
 139         flow->tail = skb;
 140         skb->next = NULL;
 141 }
 142
 143 static unsigned int fq_codel_drop(struct Qdisc *sch)
 144 {
 145         struct fq_codel_sched_data *q = qdisc_priv(sch);
 146         struct sk_buff *skb;
 147         unsigned int maxbacklog = 0, idx = 0, i, len;
 148         struct fq_codel_flow *flow;
 149
 150         /* Queue is full! Find the fat flow and drop packet from it.
 151          * This might sound expensive, but with 1024 flows, we scan
 152          * 4KB of memory, and we dont need to handle a complex tree
 153          * in fast path (packet queue/enqueue) with many cache misses.
 154          */
 155         for (i = 0; i < q->flows_cnt; i++) {
 156                 if (q->backlogs[i] > maxbacklog) {
 157                         maxbacklog = q->backlogs[i];
 158                         idx = i;
 159                 }
 160         }
 161         flow = &q->flows[idx];
 162         skb = dequeue_head(flow);
 163         len = qdisc_pkt_len(skb);
 164         q->backlogs[idx] -= len;
 165         sch->q.qlen--;
 166         qdisc_qstats_drop(sch);
 167         qdisc_qstats_backlog_dec(sch, skb);
 168         kfree_skb(skb);
 169         flow->dropped++;
 170         return idx;
 171 }
 172
 173 static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 174 {
 175         struct fq_codel_sched_data *q = qdisc_priv(sch);
 176         unsigned int idx;
 177         struct fq_codel_flow *flow;
 178         int uninitialized_var(ret);
 179
 180         idx = fq_codel_classify(skb, sch, &ret);
 181         if (idx == 0) {
 182                 if (ret & __NET_XMIT_BYPASS)
 183                         qdisc_qstats_drop(sch);
 184                 kfree_skb(skb);
 185                 return ret;
 186         }
 187         idx--;
 188
 189         codel_set_enqueue_time(skb);
 190         flow = &q->flows[idx];
 191         flow_queue_add(flow, skb);
 192         q->backlogs[idx] += qdisc_pkt_len(skb);
 193         qdisc_qstats_backlog_inc(sch, skb);
 194
 195         if (list_empty(&flow->flowchain)) {
 196                 list_add_tail(&flow->flowchain, &q->new_flows);
 197                 q->new_flow_count++;
 198                 flow->deficit = q->quantum;
 199                 flow->dropped = 0;
 200         }
 201         if (++sch->q.qlen <= sch->limit)
 202                 return NET_XMIT_SUCCESS;
 203
 204         q->drop_overlimit++;
 205         /* Return Congestion Notification only if we dropped a packet
 206          * from this flow.
 207          */
 208         if (fq_codel_drop(sch) == idx)
 209                 return NET_XMIT_CN;
 210
 211         /* As we dropped a packet, better let upper stack know this */
 212         qdisc_tree_decrease_qlen(sch, 1);
 213         return NET_XMIT_SUCCESS;
 214 }
 215
 216 /* This is the specific function called from codel_dequeue()
 217  * to dequeue a packet from queue. Note: backlog is handled in
 218  * codel, we dont need to reduce it here.
 219  */
 220 static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
 221 {
 222         struct fq_codel_sched_data *q = qdisc_priv(sch);
 223         struct fq_codel_flow *flow;
 224         struct sk_buff *skb = NULL;
 225
 226         flow = container_of(vars, struct fq_codel_flow, cvars);
 227         if (flow->head) {
 228                 skb = dequeue_head(flow);
 229                 q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb);
 230                 sch->q.qlen--;
 231         }
 232         return skb;
 233 }
 234
 235 static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch)
 236 {
 237         struct fq_codel_sched_data *q = qdisc_priv(sch);
 238         struct sk_buff *skb;
 239         struct fq_codel_flow *flow;
 240         struct list_head *head;
 241         u32 prev_drop_count, prev_ecn_mark;
 242
 243 begin:
 244         head = &q->new_flows;
 245         if (list_empty(head)) {
 246                 head = &q->old_flows;
 247                 if (list_empty(head))
 248                         return NULL;
 249         }
 250         flow = list_first_entry(head, struct fq_codel_flow, flowchain);
 251
 252         if (flow->deficit <= 0) {
 253                 flow->deficit += q->quantum;
 254                 list_move_tail(&flow->flowchain, &q->old_flows);
 255                 goto begin;
 256         }
 257
 258         prev_drop_count = q->cstats.drop_count;
 259         prev_ecn_mark = q->cstats.ecn_mark;
 260
 261         skb = codel_dequeue(sch, &q->cparams, &flow->cvars, &q->cstats,
 262                             dequeue);
 263
 264         flow->dropped += q->cstats.drop_count - prev_drop_count;
 265         flow->dropped += q->cstats.ecn_mark - prev_ecn_mark;
 266
 267         if (!skb) {
 268                 /* force a pass through old_flows to prevent starvation */
 269                 if ((head == &q->new_flows) && !list_empty(&q->old_flows))
 270                         list_move_tail(&flow->flowchain, &q->old_flows);
 271                 else
 272                         list_del_init(&flow->flowchain);
 273                 goto begin;
 274         }
 275         qdisc_bstats_update(sch, skb);
 276         flow->deficit -= qdisc_pkt_len(skb);
 277         /* We cant call qdisc_tree_decrease_qlen() if our qlen is 0,
 278          * or HTB crashes. Defer it for next round.
 279          */
 280         if (q->cstats.drop_count && sch->q.qlen) {
 281                 qdisc_tree_decrease_qlen(sch, q->cstats.drop_count);
 282                 q->cstats.drop_count = 0;
 283         }
 284         return skb;
 285 }
 286
 287 static void fq_codel_reset(struct Qdisc *sch)
 288 {
 289         struct sk_buff *skb;
 290
 291         while ((skb = fq_codel_dequeue(sch)) != NULL)
 292                 kfree_skb(skb);
 293 }
 294
 295 static const struct nla_policy fq_codel_policy[TCA_FQ_CODEL_MAX + 1] = {
 296         [TCA_FQ_CODEL_TARGET]   = { .type = NLA_U32 },
 297         [TCA_FQ_CODEL_LIMIT]    = { .type = NLA_U32 },
 298         [TCA_FQ_CODEL_INTERVAL] = { .type = NLA_U32 },
 299         [TCA_FQ_CODEL_ECN]      = { .type = NLA_U32 },
 300         [TCA_FQ_CODEL_FLOWS]    = { .type = NLA_U32 },
 301         [TCA_FQ_CODEL_QUANTUM]  = { .type = NLA_U32 },
 302 };
 303
 304 static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt)
 305 {
 306         struct fq_codel_sched_data *q = qdisc_priv(sch);
 307         struct nlattr *tb[TCA_FQ_CODEL_MAX + 1];
 308         int err;
 309
 310         if (!opt)
 311                 return -EINVAL;
 312
 313         err = nla_parse_nested(tb, TCA_FQ_CODEL_MAX, opt, fq_codel_policy);
 314         if (err < 0)
 315                 return err;
 316         if (tb[TCA_FQ_CODEL_FLOWS]) {
 317                 if (q->flows)
 318                         return -EINVAL;
 319                 q->flows_cnt = nla_get_u32(tb[TCA_FQ_CODEL_FLOWS]);
 320                 if (!q->flows_cnt ||
 321                     q->flows_cnt > 65536)
 322                         return -EINVAL;
 323         }
 324         sch_tree_lock(sch);
 325
 326         if (tb[TCA_FQ_CODEL_TARGET]) {
 327                 u64 target = nla_get_u32(tb[TCA_FQ_CODEL_TARGET]);
 328
 329                 q->cparams.target = (target * NSEC_PER_USEC) >> CODEL_SHIFT;
 330         }
 331
 332         if (tb[TCA_FQ_CODEL_INTERVAL]) {
 333                 u64 interval = nla_get_u32(tb[TCA_FQ_CODEL_INTERVAL]);
 334
 335                 q->cparams.interval = (interval * NSEC_PER_USEC) >> CODEL_SHIFT;
 336         }
 337
 338         if (tb[TCA_FQ_CODEL_LIMIT])
 339                 sch->limit = nla_get_u32(tb[TCA_FQ_CODEL_LIMIT]);
 340
 341         if (tb[TCA_FQ_CODEL_ECN])
 342                 q->cparams.ecn = !!nla_get_u32(tb[TCA_FQ_CODEL_ECN]);
 343
 344         if (tb[TCA_FQ_CODEL_QUANTUM])
 345                 q->quantum = max(256U, nla_get_u32(tb[TCA_FQ_CODEL_QUANTUM]));
 346
 347         while (sch->q.qlen > sch->limit) {
 348                 struct sk_buff *skb = fq_codel_dequeue(sch);
 349
 350                 kfree_skb(skb);
 351                 q->cstats.drop_count++;
 352         }
 353         qdisc_tree_decrease_qlen(sch, q->cstats.drop_count);
 354         q->cstats.drop_count = 0;
 355
 356         sch_tree_unlock(sch);
 357         return 0;
 358 }
 359
 360 static void *fq_codel_zalloc(size_t sz)
 361 {
 362         void *ptr = kzalloc(sz, GFP_KERNEL | __GFP_NOWARN);
 363
 364         if (!ptr)
 365                 ptr = vzalloc(sz);
 366         return ptr;
 367 }
 368
 369 static void fq_codel_free(void *addr)
 370 {
 371         kvfree(addr);
 372 }
 373
 374 static void fq_codel_destroy(struct Qdisc *sch)
 375 {
 376         struct fq_codel_sched_data *q = qdisc_priv(sch);
 377
 378         tcf_destroy_chain(&q->filter_list);
 379         fq_codel_free(q->backlogs);
 380         fq_codel_free(q->flows);
 381 }
 382
 383 static int fq_codel_init(struct Qdisc *sch, struct nlattr *opt)
 384 {
 385         struct fq_codel_sched_data *q = qdisc_priv(sch);
 386         int i;
 387
 388         sch->limit = 10*1024;
 389         q->flows_cnt = 1024;
 390         q->quantum = psched_mtu(qdisc_dev(sch));
 391         q->perturbation = prandom_u32();
 392         INIT_LIST_HEAD(&q->new_flows);
 393         INIT_LIST_HEAD(&q->old_flows);
 394         codel_params_init(&q->cparams, sch);
 395         codel_stats_init(&q->cstats);
 396         q->cparams.ecn = true;
 397
 398         if (opt) {
 399                 int err = fq_codel_change(sch, opt);
 400                 if (err)
 401                         return err;
 402         }
 403
 404         if (!q->flows) {
 405                 q->flows = fq_codel_zalloc(q->flows_cnt *
 406                                            sizeof(struct fq_codel_flow));
 407                 if (!q->flows)
 408                         return -ENOMEM;
 409                 q->backlogs = fq_codel_zalloc(q->flows_cnt * sizeof(u32));
 410                 if (!q->backlogs) {
 411                         fq_codel_free(q->flows);
 412                         return -ENOMEM;
 413                 }
 414                 for (i = 0; i < q->flows_cnt; i++) {
 415                         struct fq_codel_flow *flow = q->flows + i;
 416
 417                         INIT_LIST_HEAD(&flow->flowchain);
 418                         codel_vars_init(&flow->cvars);
 419                 }
 420         }
 421         if (sch->limit >= 1)
 422                 sch->flags |= TCQ_F_CAN_BYPASS;
 423         else
 424                 sch->flags &= ~TCQ_F_CAN_BYPASS;
 425         return 0;
 426 }
 427
 428 static int fq_codel_dump(struct Qdisc *sch, struct sk_buff *skb)
 429 {
 430         struct fq_codel_sched_data *q = qdisc_priv(sch);
 431         struct nlattr *opts;
 432
 433         opts = nla_nest_start(skb, TCA_OPTIONS);
 434         if (opts == NULL)
 435                 goto nla_put_failure;
 436
 437         if (nla_put_u32(skb, TCA_FQ_CODEL_TARGET,
 438                         codel_time_to_us(q->cparams.target)) ||
 439             nla_put_u32(skb, TCA_FQ_CODEL_LIMIT,
 440                         sch->limit) ||
 441             nla_put_u32(skb, TCA_FQ_CODEL_INTERVAL,
 442                         codel_time_to_us(q->cparams.interval)) ||
 443             nla_put_u32(skb, TCA_FQ_CODEL_ECN,
 444                         q->cparams.ecn) ||
 445             nla_put_u32(skb, TCA_FQ_CODEL_QUANTUM,
 446                         q->quantum) ||
 447             nla_put_u32(skb, TCA_FQ_CODEL_FLOWS,
 448                         q->flows_cnt))
 449                 goto nla_put_failure;
 450
 451         return nla_nest_end(skb, opts);
 452
 453 nla_put_failure:
 454         return -1;
 455 }
 456
 457 static int fq_codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
 458 {
 459         struct fq_codel_sched_data *q = qdisc_priv(sch);
 460         struct tc_fq_codel_xstats st = {
 461                 .type                           = TCA_FQ_CODEL_XSTATS_QDISC,
 462         };
 463         struct list_head *pos;
 464
 465         st.qdisc_stats.maxpacket = q->cstats.maxpacket;
 466         st.qdisc_stats.drop_overlimit = q->drop_overlimit;
 467         st.qdisc_stats.ecn_mark = q->cstats.ecn_mark;
 468         st.qdisc_stats.new_flow_count = q->new_flow_count;
 469
 470         list_for_each(pos, &q->new_flows)
 471                 st.qdisc_stats.new_flows_len++;
 472
 473         list_for_each(pos, &q->old_flows)
 474                 st.qdisc_stats.old_flows_len++;
 475
 476         return gnet_stats_copy_app(d, &st, sizeof(st));
 477 }
 478
 479 static struct Qdisc *fq_codel_leaf(struct Qdisc *sch, unsigned long arg)
 480 {
 481         return NULL;
 482 }
 483
 484 static unsigned long fq_codel_get(struct Qdisc *sch, u32 classid)
 485 {
 486         return 0;
 487 }
 488
 489 static unsigned long fq_codel_bind(struct Qdisc *sch, unsigned long parent,
 490                               u32 classid)
 491 {
 492         /* we cannot bypass queue discipline anymore */
 493         sch->flags &= ~TCQ_F_CAN_BYPASS;
 494         return 0;
 495 }
 496
 497 static void fq_codel_put(struct Qdisc *q, unsigned long cl)
 498 {
 499 }
 500
 501 static struct tcf_proto __rcu **fq_codel_find_tcf(struct Qdisc *sch,
 502                                                   unsigned long cl)
 503 {
 504         struct fq_codel_sched_data *q = qdisc_priv(sch);
 505
 506         if (cl)
 507                 return NULL;
 508         return &q->filter_list;
 509 }
 510
 511 static int fq_codel_dump_class(struct Qdisc *sch, unsigned long cl,
 512                           struct sk_buff *skb, struct tcmsg *tcm)
 513 {
 514         tcm->tcm_handle |= TC_H_MIN(cl);
 515         return 0;
 516 }
 517
 518 static int fq_codel_dump_class_stats(struct Qdisc *sch, unsigned long cl,
 519                                      struct gnet_dump *d)
 520 {
 521         struct fq_codel_sched_data *q = qdisc_priv(sch);
 522         u32 idx = cl - 1;
 523         struct gnet_stats_queue qs = { 0 };
 524         struct tc_fq_codel_xstats xstats;
 525
 526         if (idx < q->flows_cnt) {
 527                 const struct fq_codel_flow *flow = &q->flows[idx];
 528                 const struct sk_buff *skb = flow->head;
 529
 530                 memset(&xstats, 0, sizeof(xstats));
 531                 xstats.type = TCA_FQ_CODEL_XSTATS_CLASS;
 532                 xstats.class_stats.deficit = flow->deficit;
 533                 xstats.class_stats.ldelay =
 534                         codel_time_to_us(flow->cvars.ldelay);
 535                 xstats.class_stats.count = flow->cvars.count;
 536                 xstats.class_stats.lastcount = flow->cvars.lastcount;
 537                 xstats.class_stats.dropping = flow->cvars.dropping;
 538                 if (flow->cvars.dropping) {
 539                         codel_tdiff_t delta = flow->cvars.drop_next -
 540                                               codel_get_time();
 541
 542                         xstats.class_stats.drop_next = (delta >= 0) ?
 543                                 codel_time_to_us(delta) :
 544                                 -codel_time_to_us(-delta);
 545                 }
 546                 while (skb) {
 547                         qs.qlen++;
 548                         skb = skb->next;
 549                 }
 550                 qs.backlog = q->backlogs[idx];
 551                 qs.drops = flow->dropped;
 552         }
 553         if (gnet_stats_copy_queue(d, NULL, &qs, 0) < 0)
 554                 return -1;
 555         if (idx < q->flows_cnt)
 556                 return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
 557         return 0;
 558 }
 559
 560 static void fq_codel_walk(struct Qdisc *sch, struct qdisc_walker *arg)
 561 {
 562         struct fq_codel_sched_data *q = qdisc_priv(sch);
 563         unsigned int i;
 564
 565         if (arg->stop)
 566                 return;
 567
 568         for (i = 0; i < q->flows_cnt; i++) {
 569                 if (list_empty(&q->flows[i].flowchain) ||
 570                     arg->count < arg->skip) {
 571                         arg->count++;
 572                         continue;
 573                 }
 574                 if (arg->fn(sch, i + 1, arg) < 0) {
 575                         arg->stop = 1;
 576                         break;
 577                 }
 578                 arg->count++;
 579         }
 580 }
 581
 582 static const struct Qdisc_class_ops fq_codel_class_ops = {
 583         .leaf           =       fq_codel_leaf,
 584         .get            =       fq_codel_get,
 585         .put            =       fq_codel_put,
 586         .tcf_chain      =       fq_codel_find_tcf,
 587         .bind_tcf       =       fq_codel_bind,
 588         .unbind_tcf     =       fq_codel_put,
 589         .dump           =       fq_codel_dump_class,
 590         .dump_stats     =       fq_codel_dump_class_stats,
 591         .walk           =       fq_codel_walk,
 592 };
 593
 594 static struct Qdisc_ops fq_codel_qdisc_ops __read_mostly = {
 595         .cl_ops         =       &fq_codel_class_ops,
 596         .id             =       "fq_codel",
 597         .priv_size      =       sizeof(struct fq_codel_sched_data),
 598         .enqueue        =       fq_codel_enqueue,
 599         .dequeue        =       fq_codel_dequeue,
 600         .peek           =       qdisc_peek_dequeued,
 601         .drop           =       fq_codel_drop,
 602         .init           =       fq_codel_init,
 603         .reset          =       fq_codel_reset,
 604         .destroy        =       fq_codel_destroy,
 605         .change         =       fq_codel_change,
 606         .dump           =       fq_codel_dump,
 607         .dump_stats =   fq_codel_dump_stats,
 608         .owner          =       THIS_MODULE,
 609 };
 610
 611 static int __init fq_codel_module_init(void)
 612 {
 613         return register_qdisc(&fq_codel_qdisc_ops);
 614 }
 615
 616 static void __exit fq_codel_module_exit(void)
 617 {
 618         unregister_qdisc(&fq_codel_qdisc_ops);
 619 }
 620
 621 module_init(fq_codel_module_init)
 622 module_exit(fq_codel_module_exit)
 623 MODULE_AUTHOR("Eric Dumazet");
 624 MODULE_LICENSE("GPL");