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Linux/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         if (addr) {
369                 if (is_vmalloc_addr(addr))
370                         vfree(addr);
371                 else
372                         kfree(addr);
373         }
374 }
375 
376 static void fq_codel_destroy(struct Qdisc *sch)
377 {
378         struct fq_codel_sched_data *q = qdisc_priv(sch);
379 
380         tcf_destroy_chain(&q->filter_list);
381         fq_codel_free(q->backlogs);
382         fq_codel_free(q->flows);
383 }
384 
385 static int fq_codel_init(struct Qdisc *sch, struct nlattr *opt)
386 {
387         struct fq_codel_sched_data *q = qdisc_priv(sch);
388         int i;
389 
390         sch->limit = 10*1024;
391         q->flows_cnt = 1024;
392         q->quantum = psched_mtu(qdisc_dev(sch));
393         q->perturbation = prandom_u32();
394         INIT_LIST_HEAD(&q->new_flows);
395         INIT_LIST_HEAD(&q->old_flows);
396         codel_params_init(&q->cparams);
397         codel_stats_init(&q->cstats);
398         q->cparams.ecn = true;
399 
400         if (opt) {
401                 int err = fq_codel_change(sch, opt);
402                 if (err)
403                         return err;
404         }
405 
406         if (!q->flows) {
407                 q->flows = fq_codel_zalloc(q->flows_cnt *
408                                            sizeof(struct fq_codel_flow));
409                 if (!q->flows)
410                         return -ENOMEM;
411                 q->backlogs = fq_codel_zalloc(q->flows_cnt * sizeof(u32));
412                 if (!q->backlogs) {
413                         fq_codel_free(q->flows);
414                         return -ENOMEM;
415                 }
416                 for (i = 0; i < q->flows_cnt; i++) {
417                         struct fq_codel_flow *flow = q->flows + i;
418 
419                         INIT_LIST_HEAD(&flow->flowchain);
420                         codel_vars_init(&flow->cvars);
421                 }
422         }
423         if (sch->limit >= 1)
424                 sch->flags |= TCQ_F_CAN_BYPASS;
425         else
426                 sch->flags &= ~TCQ_F_CAN_BYPASS;
427         return 0;
428 }
429 
430 static int fq_codel_dump(struct Qdisc *sch, struct sk_buff *skb)
431 {
432         struct fq_codel_sched_data *q = qdisc_priv(sch);
433         struct nlattr *opts;
434 
435         opts = nla_nest_start(skb, TCA_OPTIONS);
436         if (opts == NULL)
437                 goto nla_put_failure;
438 
439         if (nla_put_u32(skb, TCA_FQ_CODEL_TARGET,
440                         codel_time_to_us(q->cparams.target)) ||
441             nla_put_u32(skb, TCA_FQ_CODEL_LIMIT,
442                         sch->limit) ||
443             nla_put_u32(skb, TCA_FQ_CODEL_INTERVAL,
444                         codel_time_to_us(q->cparams.interval)) ||
445             nla_put_u32(skb, TCA_FQ_CODEL_ECN,
446                         q->cparams.ecn) ||
447             nla_put_u32(skb, TCA_FQ_CODEL_QUANTUM,
448                         q->quantum) ||
449             nla_put_u32(skb, TCA_FQ_CODEL_FLOWS,
450                         q->flows_cnt))
451                 goto nla_put_failure;
452 
453         nla_nest_end(skb, opts);
454         return skb->len;
455 
456 nla_put_failure:
457         return -1;
458 }
459 
460 static int fq_codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
461 {
462         struct fq_codel_sched_data *q = qdisc_priv(sch);
463         struct tc_fq_codel_xstats st = {
464                 .type                           = TCA_FQ_CODEL_XSTATS_QDISC,
465         };
466         struct list_head *pos;
467 
468         st.qdisc_stats.maxpacket = q->cstats.maxpacket;
469         st.qdisc_stats.drop_overlimit = q->drop_overlimit;
470         st.qdisc_stats.ecn_mark = q->cstats.ecn_mark;
471         st.qdisc_stats.new_flow_count = q->new_flow_count;
472 
473         list_for_each(pos, &q->new_flows)
474                 st.qdisc_stats.new_flows_len++;
475 
476         list_for_each(pos, &q->old_flows)
477                 st.qdisc_stats.old_flows_len++;
478 
479         return gnet_stats_copy_app(d, &st, sizeof(st));
480 }
481 
482 static struct Qdisc *fq_codel_leaf(struct Qdisc *sch, unsigned long arg)
483 {
484         return NULL;
485 }
486 
487 static unsigned long fq_codel_get(struct Qdisc *sch, u32 classid)
488 {
489         return 0;
490 }
491 
492 static unsigned long fq_codel_bind(struct Qdisc *sch, unsigned long parent,
493                               u32 classid)
494 {
495         /* we cannot bypass queue discipline anymore */
496         sch->flags &= ~TCQ_F_CAN_BYPASS;
497         return 0;
498 }
499 
500 static void fq_codel_put(struct Qdisc *q, unsigned long cl)
501 {
502 }
503 
504 static struct tcf_proto **fq_codel_find_tcf(struct Qdisc *sch, unsigned long cl)
505 {
506         struct fq_codel_sched_data *q = qdisc_priv(sch);
507 
508         if (cl)
509                 return NULL;
510         return &q->filter_list;
511 }
512 
513 static int fq_codel_dump_class(struct Qdisc *sch, unsigned long cl,
514                           struct sk_buff *skb, struct tcmsg *tcm)
515 {
516         tcm->tcm_handle |= TC_H_MIN(cl);
517         return 0;
518 }
519 
520 static int fq_codel_dump_class_stats(struct Qdisc *sch, unsigned long cl,
521                                      struct gnet_dump *d)
522 {
523         struct fq_codel_sched_data *q = qdisc_priv(sch);
524         u32 idx = cl - 1;
525         struct gnet_stats_queue qs = { 0 };
526         struct tc_fq_codel_xstats xstats;
527 
528         if (idx < q->flows_cnt) {
529                 const struct fq_codel_flow *flow = &q->flows[idx];
530                 const struct sk_buff *skb = flow->head;
531 
532                 memset(&xstats, 0, sizeof(xstats));
533                 xstats.type = TCA_FQ_CODEL_XSTATS_CLASS;
534                 xstats.class_stats.deficit = flow->deficit;
535                 xstats.class_stats.ldelay =
536                         codel_time_to_us(flow->cvars.ldelay);
537                 xstats.class_stats.count = flow->cvars.count;
538                 xstats.class_stats.lastcount = flow->cvars.lastcount;
539                 xstats.class_stats.dropping = flow->cvars.dropping;
540                 if (flow->cvars.dropping) {
541                         codel_tdiff_t delta = flow->cvars.drop_next -
542                                               codel_get_time();
543 
544                         xstats.class_stats.drop_next = (delta >= 0) ?
545                                 codel_time_to_us(delta) :
546                                 -codel_time_to_us(-delta);
547                 }
548                 while (skb) {
549                         qs.qlen++;
550                         skb = skb->next;
551                 }
552                 qs.backlog = q->backlogs[idx];
553                 qs.drops = flow->dropped;
554         }
555         if (gnet_stats_copy_queue(d, &qs) < 0)
556                 return -1;
557         if (idx < q->flows_cnt)
558                 return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
559         return 0;
560 }
561 
562 static void fq_codel_walk(struct Qdisc *sch, struct qdisc_walker *arg)
563 {
564         struct fq_codel_sched_data *q = qdisc_priv(sch);
565         unsigned int i;
566 
567         if (arg->stop)
568                 return;
569 
570         for (i = 0; i < q->flows_cnt; i++) {
571                 if (list_empty(&q->flows[i].flowchain) ||
572                     arg->count < arg->skip) {
573                         arg->count++;
574                         continue;
575                 }
576                 if (arg->fn(sch, i + 1, arg) < 0) {
577                         arg->stop = 1;
578                         break;
579                 }
580                 arg->count++;
581         }
582 }
583 
584 static const struct Qdisc_class_ops fq_codel_class_ops = {
585         .leaf           =       fq_codel_leaf,
586         .get            =       fq_codel_get,
587         .put            =       fq_codel_put,
588         .tcf_chain      =       fq_codel_find_tcf,
589         .bind_tcf       =       fq_codel_bind,
590         .unbind_tcf     =       fq_codel_put,
591         .dump           =       fq_codel_dump_class,
592         .dump_stats     =       fq_codel_dump_class_stats,
593         .walk           =       fq_codel_walk,
594 };
595 
596 static struct Qdisc_ops fq_codel_qdisc_ops __read_mostly = {
597         .cl_ops         =       &fq_codel_class_ops,
598         .id             =       "fq_codel",
599         .priv_size      =       sizeof(struct fq_codel_sched_data),
600         .enqueue        =       fq_codel_enqueue,
601         .dequeue        =       fq_codel_dequeue,
602         .peek           =       qdisc_peek_dequeued,
603         .drop           =       fq_codel_drop,
604         .init           =       fq_codel_init,
605         .reset          =       fq_codel_reset,
606         .destroy        =       fq_codel_destroy,
607         .change         =       fq_codel_change,
608         .dump           =       fq_codel_dump,
609         .dump_stats =   fq_codel_dump_stats,
610         .owner          =       THIS_MODULE,
611 };
612 
613 static int __init fq_codel_module_init(void)
614 {
615         return register_qdisc(&fq_codel_qdisc_ops);
616 }
617 
618 static void __exit fq_codel_module_exit(void)
619 {
620         unregister_qdisc(&fq_codel_qdisc_ops);
621 }
622 
623 module_init(fq_codel_module_init)
624 module_exit(fq_codel_module_exit)
625 MODULE_AUTHOR("Eric Dumazet");
626 MODULE_LICENSE("GPL");
627 

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