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1// SPDX-License-Identifier: GPL-2.0-only
2/* Flow Queue PIE discipline
3 *
4 * Copyright (C) 2019 Mohit P. Tahiliani <tahiliani@nitk.edu.in>
5 * Copyright (C) 2019 Sachin D. Patil <sdp.sachin@gmail.com>
6 * Copyright (C) 2019 V. Saicharan <vsaicharan1998@gmail.com>
7 * Copyright (C) 2019 Mohit Bhasi <mohitbhasi1998@gmail.com>
8 * Copyright (C) 2019 Leslie Monis <lesliemonis@gmail.com>
9 * Copyright (C) 2019 Gautam Ramakrishnan <gautamramk@gmail.com>
10 */
11
12#include <linux/jhash.h>
13#include <linux/module.h>
14#include <linux/sizes.h>
15#include <linux/vmalloc.h>
16#include <net/pkt_cls.h>
17#include <net/pie.h>
18
19/* Flow Queue PIE
20 *
21 * Principles:
22 * - Packets are classified on flows.
23 * - This is a Stochastic model (as we use a hash, several flows might
24 * be hashed to the same slot)
25 * - Each flow has a PIE managed queue.
26 * - Flows are linked onto two (Round Robin) lists,
27 * so that new flows have priority on old ones.
28 * - For a given flow, packets are not reordered.
29 * - Drops during enqueue only.
30 * - ECN capability is off by default.
31 * - ECN threshold (if ECN is enabled) is at 10% by default.
32 * - Uses timestamps to calculate queue delay by default.
33 */
34
35/**
36 * struct fq_pie_flow - contains data for each flow
37 * @vars: pie vars associated with the flow
38 * @deficit: number of remaining byte credits
39 * @backlog: size of data in the flow
40 * @qlen: number of packets in the flow
41 * @flowchain: flowchain for the flow
42 * @head: first packet in the flow
43 * @tail: last packet in the flow
44 */
45struct fq_pie_flow {
46 struct pie_vars vars;
47 s32 deficit;
48 u32 backlog;
49 u32 qlen;
50 struct list_head flowchain;
51 struct sk_buff *head;
52 struct sk_buff *tail;
53};
54
55struct fq_pie_sched_data {
56 struct tcf_proto __rcu *filter_list; /* optional external classifier */
57 struct tcf_block *block;
58 struct fq_pie_flow *flows;
59 struct Qdisc *sch;
60 struct list_head old_flows;
61 struct list_head new_flows;
62 struct pie_params p_params;
63 u32 ecn_prob;
64 u32 flows_cnt;
65 u32 flows_cursor;
66 u32 quantum;
67 u32 memory_limit;
68 u32 new_flow_count;
69 u32 memory_usage;
70 u32 overmemory;
71 struct pie_stats stats;
72 struct timer_list adapt_timer;
73};
74
75static unsigned int fq_pie_hash(const struct fq_pie_sched_data *q,
76 struct sk_buff *skb)
77{
78 return reciprocal_scale(skb_get_hash(skb), q->flows_cnt);
79}
80
81static unsigned int fq_pie_classify(struct sk_buff *skb, struct Qdisc *sch,
82 int *qerr)
83{
84 struct fq_pie_sched_data *q = qdisc_priv(sch);
85 struct tcf_proto *filter;
86 struct tcf_result res;
87 int result;
88
89 if (TC_H_MAJ(skb->priority) == sch->handle &&
90 TC_H_MIN(skb->priority) > 0 &&
91 TC_H_MIN(skb->priority) <= q->flows_cnt)
92 return TC_H_MIN(skb->priority);
93
94 filter = rcu_dereference_bh(q->filter_list);
95 if (!filter)
96 return fq_pie_hash(q, skb) + 1;
97
98 *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
99 result = tcf_classify(skb, NULL, filter, &res, false);
100 if (result >= 0) {
101#ifdef CONFIG_NET_CLS_ACT
102 switch (result) {
103 case TC_ACT_STOLEN:
104 case TC_ACT_QUEUED:
105 case TC_ACT_TRAP:
106 *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
107 fallthrough;
108 case TC_ACT_SHOT:
109 return 0;
110 }
111#endif
112 if (TC_H_MIN(res.classid) <= q->flows_cnt)
113 return TC_H_MIN(res.classid);
114 }
115 return 0;
116}
117
118/* add skb to flow queue (tail add) */
119static inline void flow_queue_add(struct fq_pie_flow *flow,
120 struct sk_buff *skb)
121{
122 if (!flow->head)
123 flow->head = skb;
124 else
125 flow->tail->next = skb;
126 flow->tail = skb;
127 skb->next = NULL;
128}
129
130static int fq_pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
131 struct sk_buff **to_free)
132{
133 struct fq_pie_sched_data *q = qdisc_priv(sch);
134 struct fq_pie_flow *sel_flow;
135 int ret;
136 u8 memory_limited = false;
137 u8 enqueue = false;
138 u32 pkt_len;
139 u32 idx;
140
141 /* Classifies packet into corresponding flow */
142 idx = fq_pie_classify(skb, sch, &ret);
143 if (idx == 0) {
144 if (ret & __NET_XMIT_BYPASS)
145 qdisc_qstats_drop(sch);
146 __qdisc_drop(skb, to_free);
147 return ret;
148 }
149 idx--;
150
151 sel_flow = &q->flows[idx];
152 /* Checks whether adding a new packet would exceed memory limit */
153 get_pie_cb(skb)->mem_usage = skb->truesize;
154 memory_limited = q->memory_usage > q->memory_limit + skb->truesize;
155
156 /* Checks if the qdisc is full */
157 if (unlikely(qdisc_qlen(sch) >= sch->limit)) {
158 q->stats.overlimit++;
159 goto out;
160 } else if (unlikely(memory_limited)) {
161 q->overmemory++;
162 }
163
164 if (!pie_drop_early(sch, &q->p_params, &sel_flow->vars,
165 sel_flow->backlog, skb->len)) {
166 enqueue = true;
167 } else if (q->p_params.ecn &&
168 sel_flow->vars.prob <= (MAX_PROB / 100) * q->ecn_prob &&
169 INET_ECN_set_ce(skb)) {
170 /* If packet is ecn capable, mark it if drop probability
171 * is lower than the parameter ecn_prob, else drop it.
172 */
173 q->stats.ecn_mark++;
174 enqueue = true;
175 }
176 if (enqueue) {
177 /* Set enqueue time only when dq_rate_estimator is disabled. */
178 if (!q->p_params.dq_rate_estimator)
179 pie_set_enqueue_time(skb);
180
181 pkt_len = qdisc_pkt_len(skb);
182 q->stats.packets_in++;
183 q->memory_usage += skb->truesize;
184 sch->qstats.backlog += pkt_len;
185 sch->q.qlen++;
186 flow_queue_add(sel_flow, skb);
187 if (list_empty(&sel_flow->flowchain)) {
188 list_add_tail(&sel_flow->flowchain, &q->new_flows);
189 q->new_flow_count++;
190 sel_flow->deficit = q->quantum;
191 sel_flow->qlen = 0;
192 sel_flow->backlog = 0;
193 }
194 sel_flow->qlen++;
195 sel_flow->backlog += pkt_len;
196 return NET_XMIT_SUCCESS;
197 }
198out:
199 q->stats.dropped++;
200 sel_flow->vars.accu_prob = 0;
201 __qdisc_drop(skb, to_free);
202 qdisc_qstats_drop(sch);
203 return NET_XMIT_CN;
204}
205
206static const struct netlink_range_validation fq_pie_q_range = {
207 .min = 1,
208 .max = 1 << 20,
209};
210
211static const struct nla_policy fq_pie_policy[TCA_FQ_PIE_MAX + 1] = {
212 [TCA_FQ_PIE_LIMIT] = {.type = NLA_U32},
213 [TCA_FQ_PIE_FLOWS] = {.type = NLA_U32},
214 [TCA_FQ_PIE_TARGET] = {.type = NLA_U32},
215 [TCA_FQ_PIE_TUPDATE] = {.type = NLA_U32},
216 [TCA_FQ_PIE_ALPHA] = {.type = NLA_U32},
217 [TCA_FQ_PIE_BETA] = {.type = NLA_U32},
218 [TCA_FQ_PIE_QUANTUM] =
219 NLA_POLICY_FULL_RANGE(NLA_U32, &fq_pie_q_range),
220 [TCA_FQ_PIE_MEMORY_LIMIT] = {.type = NLA_U32},
221 [TCA_FQ_PIE_ECN_PROB] = {.type = NLA_U32},
222 [TCA_FQ_PIE_ECN] = {.type = NLA_U32},
223 [TCA_FQ_PIE_BYTEMODE] = {.type = NLA_U32},
224 [TCA_FQ_PIE_DQ_RATE_ESTIMATOR] = {.type = NLA_U32},
225};
226
227static inline struct sk_buff *dequeue_head(struct fq_pie_flow *flow)
228{
229 struct sk_buff *skb = flow->head;
230
231 flow->head = skb->next;
232 skb->next = NULL;
233 return skb;
234}
235
236static struct sk_buff *fq_pie_qdisc_dequeue(struct Qdisc *sch)
237{
238 struct fq_pie_sched_data *q = qdisc_priv(sch);
239 struct sk_buff *skb = NULL;
240 struct fq_pie_flow *flow;
241 struct list_head *head;
242 u32 pkt_len;
243
244begin:
245 head = &q->new_flows;
246 if (list_empty(head)) {
247 head = &q->old_flows;
248 if (list_empty(head))
249 return NULL;
250 }
251
252 flow = list_first_entry(head, struct fq_pie_flow, flowchain);
253 /* Flow has exhausted all its credits */
254 if (flow->deficit <= 0) {
255 flow->deficit += q->quantum;
256 list_move_tail(&flow->flowchain, &q->old_flows);
257 goto begin;
258 }
259
260 if (flow->head) {
261 skb = dequeue_head(flow);
262 pkt_len = qdisc_pkt_len(skb);
263 sch->qstats.backlog -= pkt_len;
264 sch->q.qlen--;
265 qdisc_bstats_update(sch, skb);
266 }
267
268 if (!skb) {
269 /* force a pass through old_flows to prevent starvation */
270 if (head == &q->new_flows && !list_empty(&q->old_flows))
271 list_move_tail(&flow->flowchain, &q->old_flows);
272 else
273 list_del_init(&flow->flowchain);
274 goto begin;
275 }
276
277 flow->qlen--;
278 flow->deficit -= pkt_len;
279 flow->backlog -= pkt_len;
280 q->memory_usage -= get_pie_cb(skb)->mem_usage;
281 pie_process_dequeue(skb, &q->p_params, &flow->vars, flow->backlog);
282 return skb;
283}
284
285static int fq_pie_change(struct Qdisc *sch, struct nlattr *opt,
286 struct netlink_ext_ack *extack)
287{
288 struct fq_pie_sched_data *q = qdisc_priv(sch);
289 struct nlattr *tb[TCA_FQ_PIE_MAX + 1];
290 unsigned int len_dropped = 0;
291 unsigned int num_dropped = 0;
292 int err;
293
294 err = nla_parse_nested(tb, TCA_FQ_PIE_MAX, opt, fq_pie_policy, extack);
295 if (err < 0)
296 return err;
297
298 sch_tree_lock(sch);
299 if (tb[TCA_FQ_PIE_LIMIT]) {
300 u32 limit = nla_get_u32(tb[TCA_FQ_PIE_LIMIT]);
301
302 WRITE_ONCE(q->p_params.limit, limit);
303 WRITE_ONCE(sch->limit, limit);
304 }
305 if (tb[TCA_FQ_PIE_FLOWS]) {
306 if (q->flows) {
307 NL_SET_ERR_MSG_MOD(extack,
308 "Number of flows cannot be changed");
309 goto flow_error;
310 }
311 q->flows_cnt = nla_get_u32(tb[TCA_FQ_PIE_FLOWS]);
312 if (!q->flows_cnt || q->flows_cnt > 65536) {
313 NL_SET_ERR_MSG_MOD(extack,
314 "Number of flows must range in [1..65536]");
315 goto flow_error;
316 }
317 }
318
319 /* convert from microseconds to pschedtime */
320 if (tb[TCA_FQ_PIE_TARGET]) {
321 /* target is in us */
322 u32 target = nla_get_u32(tb[TCA_FQ_PIE_TARGET]);
323
324 /* convert to pschedtime */
325 WRITE_ONCE(q->p_params.target,
326 PSCHED_NS2TICKS((u64)target * NSEC_PER_USEC));
327 }
328
329 /* tupdate is in jiffies */
330 if (tb[TCA_FQ_PIE_TUPDATE])
331 WRITE_ONCE(q->p_params.tupdate,
332 usecs_to_jiffies(nla_get_u32(tb[TCA_FQ_PIE_TUPDATE])));
333
334 if (tb[TCA_FQ_PIE_ALPHA])
335 WRITE_ONCE(q->p_params.alpha,
336 nla_get_u32(tb[TCA_FQ_PIE_ALPHA]));
337
338 if (tb[TCA_FQ_PIE_BETA])
339 WRITE_ONCE(q->p_params.beta,
340 nla_get_u32(tb[TCA_FQ_PIE_BETA]));
341
342 if (tb[TCA_FQ_PIE_QUANTUM])
343 WRITE_ONCE(q->quantum, nla_get_u32(tb[TCA_FQ_PIE_QUANTUM]));
344
345 if (tb[TCA_FQ_PIE_MEMORY_LIMIT])
346 WRITE_ONCE(q->memory_limit,
347 nla_get_u32(tb[TCA_FQ_PIE_MEMORY_LIMIT]));
348
349 if (tb[TCA_FQ_PIE_ECN_PROB])
350 WRITE_ONCE(q->ecn_prob,
351 nla_get_u32(tb[TCA_FQ_PIE_ECN_PROB]));
352
353 if (tb[TCA_FQ_PIE_ECN])
354 WRITE_ONCE(q->p_params.ecn,
355 nla_get_u32(tb[TCA_FQ_PIE_ECN]));
356
357 if (tb[TCA_FQ_PIE_BYTEMODE])
358 WRITE_ONCE(q->p_params.bytemode,
359 nla_get_u32(tb[TCA_FQ_PIE_BYTEMODE]));
360
361 if (tb[TCA_FQ_PIE_DQ_RATE_ESTIMATOR])
362 WRITE_ONCE(q->p_params.dq_rate_estimator,
363 nla_get_u32(tb[TCA_FQ_PIE_DQ_RATE_ESTIMATOR]));
364
365 /* Drop excess packets if new limit is lower */
366 while (sch->q.qlen > sch->limit) {
367 struct sk_buff *skb = fq_pie_qdisc_dequeue(sch);
368
369 len_dropped += qdisc_pkt_len(skb);
370 num_dropped += 1;
371 rtnl_kfree_skbs(skb, skb);
372 }
373 qdisc_tree_reduce_backlog(sch, num_dropped, len_dropped);
374
375 sch_tree_unlock(sch);
376 return 0;
377
378flow_error:
379 sch_tree_unlock(sch);
380 return -EINVAL;
381}
382
383static void fq_pie_timer(struct timer_list *t)
384{
385 struct fq_pie_sched_data *q = from_timer(q, t, adapt_timer);
386 unsigned long next, tupdate;
387 struct Qdisc *sch = q->sch;
388 spinlock_t *root_lock; /* to lock qdisc for probability calculations */
389 int max_cnt, i;
390
391 rcu_read_lock();
392 root_lock = qdisc_lock(qdisc_root_sleeping(sch));
393 spin_lock(root_lock);
394
395 /* Limit this expensive loop to 2048 flows per round. */
396 max_cnt = min_t(int, q->flows_cnt - q->flows_cursor, 2048);
397 for (i = 0; i < max_cnt; i++) {
398 pie_calculate_probability(&q->p_params,
399 &q->flows[q->flows_cursor].vars,
400 q->flows[q->flows_cursor].backlog);
401 q->flows_cursor++;
402 }
403
404 tupdate = q->p_params.tupdate;
405 next = 0;
406 if (q->flows_cursor >= q->flows_cnt) {
407 q->flows_cursor = 0;
408 next = tupdate;
409 }
410 if (tupdate)
411 mod_timer(&q->adapt_timer, jiffies + next);
412 spin_unlock(root_lock);
413 rcu_read_unlock();
414}
415
416static int fq_pie_init(struct Qdisc *sch, struct nlattr *opt,
417 struct netlink_ext_ack *extack)
418{
419 struct fq_pie_sched_data *q = qdisc_priv(sch);
420 int err;
421 u32 idx;
422
423 pie_params_init(&q->p_params);
424 sch->limit = 10 * 1024;
425 q->p_params.limit = sch->limit;
426 q->quantum = psched_mtu(qdisc_dev(sch));
427 q->sch = sch;
428 q->ecn_prob = 10;
429 q->flows_cnt = 1024;
430 q->memory_limit = SZ_32M;
431
432 INIT_LIST_HEAD(&q->new_flows);
433 INIT_LIST_HEAD(&q->old_flows);
434 timer_setup(&q->adapt_timer, fq_pie_timer, 0);
435
436 if (opt) {
437 err = fq_pie_change(sch, opt, extack);
438
439 if (err)
440 return err;
441 }
442
443 err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
444 if (err)
445 goto init_failure;
446
447 q->flows = kvcalloc(q->flows_cnt, sizeof(struct fq_pie_flow),
448 GFP_KERNEL);
449 if (!q->flows) {
450 err = -ENOMEM;
451 goto init_failure;
452 }
453 for (idx = 0; idx < q->flows_cnt; idx++) {
454 struct fq_pie_flow *flow = q->flows + idx;
455
456 INIT_LIST_HEAD(&flow->flowchain);
457 pie_vars_init(&flow->vars);
458 }
459
460 mod_timer(&q->adapt_timer, jiffies + HZ / 2);
461
462 return 0;
463
464init_failure:
465 q->flows_cnt = 0;
466
467 return err;
468}
469
470static int fq_pie_dump(struct Qdisc *sch, struct sk_buff *skb)
471{
472 struct fq_pie_sched_data *q = qdisc_priv(sch);
473 struct nlattr *opts;
474
475 opts = nla_nest_start(skb, TCA_OPTIONS);
476 if (!opts)
477 return -EMSGSIZE;
478
479 /* convert target from pschedtime to us */
480 if (nla_put_u32(skb, TCA_FQ_PIE_LIMIT, READ_ONCE(sch->limit)) ||
481 nla_put_u32(skb, TCA_FQ_PIE_FLOWS, READ_ONCE(q->flows_cnt)) ||
482 nla_put_u32(skb, TCA_FQ_PIE_TARGET,
483 ((u32)PSCHED_TICKS2NS(READ_ONCE(q->p_params.target))) /
484 NSEC_PER_USEC) ||
485 nla_put_u32(skb, TCA_FQ_PIE_TUPDATE,
486 jiffies_to_usecs(READ_ONCE(q->p_params.tupdate))) ||
487 nla_put_u32(skb, TCA_FQ_PIE_ALPHA, READ_ONCE(q->p_params.alpha)) ||
488 nla_put_u32(skb, TCA_FQ_PIE_BETA, READ_ONCE(q->p_params.beta)) ||
489 nla_put_u32(skb, TCA_FQ_PIE_QUANTUM, READ_ONCE(q->quantum)) ||
490 nla_put_u32(skb, TCA_FQ_PIE_MEMORY_LIMIT,
491 READ_ONCE(q->memory_limit)) ||
492 nla_put_u32(skb, TCA_FQ_PIE_ECN_PROB, READ_ONCE(q->ecn_prob)) ||
493 nla_put_u32(skb, TCA_FQ_PIE_ECN, READ_ONCE(q->p_params.ecn)) ||
494 nla_put_u32(skb, TCA_FQ_PIE_BYTEMODE, READ_ONCE(q->p_params.bytemode)) ||
495 nla_put_u32(skb, TCA_FQ_PIE_DQ_RATE_ESTIMATOR,
496 READ_ONCE(q->p_params.dq_rate_estimator)))
497 goto nla_put_failure;
498
499 return nla_nest_end(skb, opts);
500
501nla_put_failure:
502 nla_nest_cancel(skb, opts);
503 return -EMSGSIZE;
504}
505
506static int fq_pie_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
507{
508 struct fq_pie_sched_data *q = qdisc_priv(sch);
509 struct tc_fq_pie_xstats st = {
510 .packets_in = q->stats.packets_in,
511 .overlimit = q->stats.overlimit,
512 .overmemory = q->overmemory,
513 .dropped = q->stats.dropped,
514 .ecn_mark = q->stats.ecn_mark,
515 .new_flow_count = q->new_flow_count,
516 .memory_usage = q->memory_usage,
517 };
518 struct list_head *pos;
519
520 sch_tree_lock(sch);
521 list_for_each(pos, &q->new_flows)
522 st.new_flows_len++;
523
524 list_for_each(pos, &q->old_flows)
525 st.old_flows_len++;
526 sch_tree_unlock(sch);
527
528 return gnet_stats_copy_app(d, &st, sizeof(st));
529}
530
531static void fq_pie_reset(struct Qdisc *sch)
532{
533 struct fq_pie_sched_data *q = qdisc_priv(sch);
534 u32 idx;
535
536 INIT_LIST_HEAD(&q->new_flows);
537 INIT_LIST_HEAD(&q->old_flows);
538 for (idx = 0; idx < q->flows_cnt; idx++) {
539 struct fq_pie_flow *flow = q->flows + idx;
540
541 /* Removes all packets from flow */
542 rtnl_kfree_skbs(flow->head, flow->tail);
543 flow->head = NULL;
544
545 INIT_LIST_HEAD(&flow->flowchain);
546 pie_vars_init(&flow->vars);
547 }
548}
549
550static void fq_pie_destroy(struct Qdisc *sch)
551{
552 struct fq_pie_sched_data *q = qdisc_priv(sch);
553
554 tcf_block_put(q->block);
555 q->p_params.tupdate = 0;
556 del_timer_sync(&q->adapt_timer);
557 kvfree(q->flows);
558}
559
560static struct Qdisc_ops fq_pie_qdisc_ops __read_mostly = {
561 .id = "fq_pie",
562 .priv_size = sizeof(struct fq_pie_sched_data),
563 .enqueue = fq_pie_qdisc_enqueue,
564 .dequeue = fq_pie_qdisc_dequeue,
565 .peek = qdisc_peek_dequeued,
566 .init = fq_pie_init,
567 .destroy = fq_pie_destroy,
568 .reset = fq_pie_reset,
569 .change = fq_pie_change,
570 .dump = fq_pie_dump,
571 .dump_stats = fq_pie_dump_stats,
572 .owner = THIS_MODULE,
573};
574MODULE_ALIAS_NET_SCH("fq_pie");
575
576static int __init fq_pie_module_init(void)
577{
578 return register_qdisc(&fq_pie_qdisc_ops);
579}
580
581static void __exit fq_pie_module_exit(void)
582{
583 unregister_qdisc(&fq_pie_qdisc_ops);
584}
585
586module_init(fq_pie_module_init);
587module_exit(fq_pie_module_exit);
588
589MODULE_DESCRIPTION("Flow Queue Proportional Integral controller Enhanced (FQ-PIE)");
590MODULE_AUTHOR("Mohit P. Tahiliani");
591MODULE_LICENSE("GPL");