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