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