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d2912cb1 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
45e14433 | 2 | /* |
3 | * net/sched/sch_choke.c CHOKE scheduler | |
4 | * | |
5 | * Copyright (c) 2011 Stephen Hemminger <shemminger@vyatta.com> | |
6 | * Copyright (c) 2011 Eric Dumazet <eric.dumazet@gmail.com> | |
45e14433 | 7 | */ |
8 | ||
9 | #include <linux/module.h> | |
10 | #include <linux/types.h> | |
11 | #include <linux/kernel.h> | |
12 | #include <linux/skbuff.h> | |
cdfb74d4 | 13 | #include <linux/vmalloc.h> |
45e14433 | 14 | #include <net/pkt_sched.h> |
cf1facda | 15 | #include <net/pkt_cls.h> |
45e14433 | 16 | #include <net/inet_ecn.h> |
17 | #include <net/red.h> | |
1bd758eb | 18 | #include <net/flow_dissector.h> |
45e14433 | 19 | |
20 | /* | |
21 | CHOKe stateless AQM for fair bandwidth allocation | |
22 | ================================================= | |
23 | ||
24 | CHOKe (CHOose and Keep for responsive flows, CHOose and Kill for | |
25 | unresponsive flows) is a variant of RED that penalizes misbehaving flows but | |
26 | maintains no flow state. The difference from RED is an additional step | |
27 | during the enqueuing process. If average queue size is over the | |
28 | low threshold (qmin), a packet is chosen at random from the queue. | |
29 | If both the new and chosen packet are from the same flow, both | |
30 | are dropped. Unlike RED, CHOKe is not really a "classful" qdisc because it | |
31 | needs to access packets in queue randomly. It has a minimal class | |
32 | interface to allow overriding the builtin flow classifier with | |
33 | filters. | |
34 | ||
35 | Source: | |
36 | R. Pan, B. Prabhakar, and K. Psounis, "CHOKe, A Stateless | |
37 | Active Queue Management Scheme for Approximating Fair Bandwidth Allocation", | |
38 | IEEE INFOCOM, 2000. | |
39 | ||
40 | A. Tang, J. Wang, S. Low, "Understanding CHOKe: Throughput and Spatial | |
41 | Characteristics", IEEE/ACM Transactions on Networking, 2004 | |
42 | ||
43 | */ | |
44 | ||
45 | /* Upper bound on size of sk_buff table (packets) */ | |
46 | #define CHOKE_MAX_QUEUE (128*1024 - 1) | |
47 | ||
48 | struct choke_sched_data { | |
49 | /* Parameters */ | |
50 | u32 limit; | |
51 | unsigned char flags; | |
52 | ||
53 | struct red_parms parms; | |
54 | ||
55 | /* Variables */ | |
eeca6688 | 56 | struct red_vars vars; |
45e14433 | 57 | struct { |
58 | u32 prob_drop; /* Early probability drops */ | |
59 | u32 prob_mark; /* Early probability marks */ | |
60 | u32 forced_drop; /* Forced drops, qavg > max_thresh */ | |
61 | u32 forced_mark; /* Forced marks, qavg > max_thresh */ | |
62 | u32 pdrop; /* Drops due to queue limits */ | |
45e14433 | 63 | u32 matched; /* Drops to flow match */ |
64 | } stats; | |
65 | ||
66 | unsigned int head; | |
67 | unsigned int tail; | |
68 | ||
69 | unsigned int tab_mask; /* size - 1 */ | |
70 | ||
71 | struct sk_buff **tab; | |
72 | }; | |
73 | ||
45e14433 | 74 | /* number of elements in queue including holes */ |
75 | static unsigned int choke_len(const struct choke_sched_data *q) | |
76 | { | |
77 | return (q->tail - q->head) & q->tab_mask; | |
78 | } | |
79 | ||
80 | /* Is ECN parameter configured */ | |
81 | static int use_ecn(const struct choke_sched_data *q) | |
82 | { | |
83 | return q->flags & TC_RED_ECN; | |
84 | } | |
85 | ||
86 | /* Should packets over max just be dropped (versus marked) */ | |
87 | static int use_harddrop(const struct choke_sched_data *q) | |
88 | { | |
89 | return q->flags & TC_RED_HARDDROP; | |
90 | } | |
91 | ||
92 | /* Move head pointer forward to skip over holes */ | |
93 | static void choke_zap_head_holes(struct choke_sched_data *q) | |
94 | { | |
95 | do { | |
96 | q->head = (q->head + 1) & q->tab_mask; | |
97 | if (q->head == q->tail) | |
98 | break; | |
99 | } while (q->tab[q->head] == NULL); | |
100 | } | |
101 | ||
102 | /* Move tail pointer backwards to reuse holes */ | |
103 | static void choke_zap_tail_holes(struct choke_sched_data *q) | |
104 | { | |
105 | do { | |
106 | q->tail = (q->tail - 1) & q->tab_mask; | |
107 | if (q->head == q->tail) | |
108 | break; | |
109 | } while (q->tab[q->tail] == NULL); | |
110 | } | |
111 | ||
112 | /* Drop packet from queue array by creating a "hole" */ | |
520ac30f ED |
113 | static void choke_drop_by_idx(struct Qdisc *sch, unsigned int idx, |
114 | struct sk_buff **to_free) | |
45e14433 | 115 | { |
116 | struct choke_sched_data *q = qdisc_priv(sch); | |
117 | struct sk_buff *skb = q->tab[idx]; | |
118 | ||
119 | q->tab[idx] = NULL; | |
120 | ||
121 | if (idx == q->head) | |
122 | choke_zap_head_holes(q); | |
123 | if (idx == q->tail) | |
124 | choke_zap_tail_holes(q); | |
125 | ||
25331d6c | 126 | qdisc_qstats_backlog_dec(sch, skb); |
2ccccf5f | 127 | qdisc_tree_reduce_backlog(sch, 1, qdisc_pkt_len(skb)); |
520ac30f | 128 | qdisc_drop(skb, sch, to_free); |
45e14433 | 129 | --sch->q.qlen; |
130 | } | |
131 | ||
26f70e12 | 132 | struct choke_skb_cb { |
2bcc34bb | 133 | u8 keys_valid; |
2e99403d | 134 | struct flow_keys_digest keys; |
26f70e12 ED |
135 | }; |
136 | ||
137 | static inline struct choke_skb_cb *choke_skb_cb(const struct sk_buff *skb) | |
138 | { | |
16bda13d | 139 | qdisc_cb_private_validate(skb, sizeof(struct choke_skb_cb)); |
26f70e12 ED |
140 | return (struct choke_skb_cb *)qdisc_skb_cb(skb)->data; |
141 | } | |
142 | ||
2bcc34bb ED |
143 | /* |
144 | * Compare flow of two packets | |
145 | * Returns true only if source and destination address and port match. | |
146 | * false for special cases | |
147 | */ | |
148 | static bool choke_match_flow(struct sk_buff *skb1, | |
149 | struct sk_buff *skb2) | |
150 | { | |
25711786 ED |
151 | struct flow_keys temp; |
152 | ||
2bcc34bb ED |
153 | if (skb1->protocol != skb2->protocol) |
154 | return false; | |
155 | ||
156 | if (!choke_skb_cb(skb1)->keys_valid) { | |
157 | choke_skb_cb(skb1)->keys_valid = 1; | |
cd79a238 | 158 | skb_flow_dissect_flow_keys(skb1, &temp, 0); |
2e99403d | 159 | make_flow_keys_digest(&choke_skb_cb(skb1)->keys, &temp); |
2bcc34bb ED |
160 | } |
161 | ||
162 | if (!choke_skb_cb(skb2)->keys_valid) { | |
163 | choke_skb_cb(skb2)->keys_valid = 1; | |
cd79a238 | 164 | skb_flow_dissect_flow_keys(skb2, &temp, 0); |
2e99403d | 165 | make_flow_keys_digest(&choke_skb_cb(skb2)->keys, &temp); |
2bcc34bb ED |
166 | } |
167 | ||
168 | return !memcmp(&choke_skb_cb(skb1)->keys, | |
169 | &choke_skb_cb(skb2)->keys, | |
2e99403d | 170 | sizeof(choke_skb_cb(skb1)->keys)); |
2bcc34bb ED |
171 | } |
172 | ||
45e14433 | 173 | /* |
174 | * Select a packet at random from queue | |
175 | * HACK: since queue can have holes from previous deletion; retry several | |
176 | * times to find a random skb but then just give up and return the head | |
177 | * Will return NULL if queue is empty (q->head == q->tail) | |
178 | */ | |
179 | static struct sk_buff *choke_peek_random(const struct choke_sched_data *q, | |
180 | unsigned int *pidx) | |
181 | { | |
182 | struct sk_buff *skb; | |
183 | int retrys = 3; | |
184 | ||
185 | do { | |
8032bf12 | 186 | *pidx = (q->head + get_random_u32_below(choke_len(q))) & q->tab_mask; |
45e14433 | 187 | skb = q->tab[*pidx]; |
188 | if (skb) | |
189 | return skb; | |
190 | } while (--retrys > 0); | |
191 | ||
192 | return q->tab[*pidx = q->head]; | |
193 | } | |
194 | ||
195 | /* | |
196 | * Compare new packet with random packet in queue | |
197 | * returns true if matched and sets *pidx | |
198 | */ | |
199 | static bool choke_match_random(const struct choke_sched_data *q, | |
200 | struct sk_buff *nskb, | |
201 | unsigned int *pidx) | |
202 | { | |
203 | struct sk_buff *oskb; | |
204 | ||
205 | if (q->head == q->tail) | |
206 | return false; | |
207 | ||
208 | oskb = choke_peek_random(q, pidx); | |
45e14433 | 209 | return choke_match_flow(oskb, nskb); |
210 | } | |
211 | ||
520ac30f ED |
212 | static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch, |
213 | struct sk_buff **to_free) | |
45e14433 | 214 | { |
215 | struct choke_sched_data *q = qdisc_priv(sch); | |
eeca6688 | 216 | const struct red_parms *p = &q->parms; |
45e14433 | 217 | |
2bcc34bb | 218 | choke_skb_cb(skb)->keys_valid = 0; |
45e14433 | 219 | /* Compute average queue usage (see RED) */ |
eeca6688 ED |
220 | q->vars.qavg = red_calc_qavg(p, &q->vars, sch->q.qlen); |
221 | if (red_is_idling(&q->vars)) | |
222 | red_end_of_idle_period(&q->vars); | |
45e14433 | 223 | |
224 | /* Is queue small? */ | |
eeca6688 ED |
225 | if (q->vars.qavg <= p->qth_min) |
226 | q->vars.qcount = -1; | |
45e14433 | 227 | else { |
228 | unsigned int idx; | |
229 | ||
230 | /* Draw a packet at random from queue and compare flow */ | |
231 | if (choke_match_random(q, skb, &idx)) { | |
232 | q->stats.matched++; | |
520ac30f | 233 | choke_drop_by_idx(sch, idx, to_free); |
45e14433 | 234 | goto congestion_drop; |
235 | } | |
236 | ||
237 | /* Queue is large, always mark/drop */ | |
eeca6688 ED |
238 | if (q->vars.qavg > p->qth_max) { |
239 | q->vars.qcount = -1; | |
45e14433 | 240 | |
25331d6c | 241 | qdisc_qstats_overlimit(sch); |
45e14433 | 242 | if (use_harddrop(q) || !use_ecn(q) || |
243 | !INET_ECN_set_ce(skb)) { | |
244 | q->stats.forced_drop++; | |
245 | goto congestion_drop; | |
246 | } | |
247 | ||
248 | q->stats.forced_mark++; | |
eeca6688 ED |
249 | } else if (++q->vars.qcount) { |
250 | if (red_mark_probability(p, &q->vars, q->vars.qavg)) { | |
251 | q->vars.qcount = 0; | |
252 | q->vars.qR = red_random(p); | |
45e14433 | 253 | |
25331d6c | 254 | qdisc_qstats_overlimit(sch); |
45e14433 | 255 | if (!use_ecn(q) || !INET_ECN_set_ce(skb)) { |
256 | q->stats.prob_drop++; | |
257 | goto congestion_drop; | |
258 | } | |
259 | ||
260 | q->stats.prob_mark++; | |
261 | } | |
262 | } else | |
eeca6688 | 263 | q->vars.qR = red_random(p); |
45e14433 | 264 | } |
265 | ||
266 | /* Admit new packet */ | |
267 | if (sch->q.qlen < q->limit) { | |
268 | q->tab[q->tail] = skb; | |
269 | q->tail = (q->tail + 1) & q->tab_mask; | |
270 | ++sch->q.qlen; | |
25331d6c | 271 | qdisc_qstats_backlog_inc(sch, skb); |
45e14433 | 272 | return NET_XMIT_SUCCESS; |
273 | } | |
274 | ||
275 | q->stats.pdrop++; | |
520ac30f | 276 | return qdisc_drop(skb, sch, to_free); |
45e14433 | 277 | |
17045755 | 278 | congestion_drop: |
520ac30f | 279 | qdisc_drop(skb, sch, to_free); |
45e14433 | 280 | return NET_XMIT_CN; |
45e14433 | 281 | } |
282 | ||
283 | static struct sk_buff *choke_dequeue(struct Qdisc *sch) | |
284 | { | |
285 | struct choke_sched_data *q = qdisc_priv(sch); | |
286 | struct sk_buff *skb; | |
287 | ||
288 | if (q->head == q->tail) { | |
eeca6688 ED |
289 | if (!red_is_idling(&q->vars)) |
290 | red_start_of_idle_period(&q->vars); | |
45e14433 | 291 | return NULL; |
292 | } | |
293 | ||
294 | skb = q->tab[q->head]; | |
295 | q->tab[q->head] = NULL; | |
296 | choke_zap_head_holes(q); | |
297 | --sch->q.qlen; | |
25331d6c | 298 | qdisc_qstats_backlog_dec(sch, skb); |
45e14433 | 299 | qdisc_bstats_update(sch, skb); |
300 | ||
301 | return skb; | |
302 | } | |
303 | ||
45e14433 | 304 | static void choke_reset(struct Qdisc *sch) |
305 | { | |
306 | struct choke_sched_data *q = qdisc_priv(sch); | |
307 | ||
77e62da6 WC |
308 | while (q->head != q->tail) { |
309 | struct sk_buff *skb = q->tab[q->head]; | |
310 | ||
311 | q->head = (q->head + 1) & q->tab_mask; | |
312 | if (!skb) | |
313 | continue; | |
f9aed311 | 314 | rtnl_qdisc_drop(skb, sch); |
77e62da6 WC |
315 | } |
316 | ||
8738c85c ED |
317 | if (q->tab) |
318 | memset(q->tab, 0, (q->tab_mask + 1) * sizeof(struct sk_buff *)); | |
77e62da6 | 319 | q->head = q->tail = 0; |
eeca6688 | 320 | red_restart(&q->vars); |
45e14433 | 321 | } |
322 | ||
323 | static const struct nla_policy choke_policy[TCA_CHOKE_MAX + 1] = { | |
324 | [TCA_CHOKE_PARMS] = { .len = sizeof(struct tc_red_qopt) }, | |
325 | [TCA_CHOKE_STAB] = { .len = RED_STAB_SIZE }, | |
a73ed26b | 326 | [TCA_CHOKE_MAX_P] = { .type = NLA_U32 }, |
45e14433 | 327 | }; |
328 | ||
329 | ||
330 | static void choke_free(void *addr) | |
331 | { | |
4cb28970 | 332 | kvfree(addr); |
45e14433 | 333 | } |
334 | ||
2030721c AA |
335 | static int choke_change(struct Qdisc *sch, struct nlattr *opt, |
336 | struct netlink_ext_ack *extack) | |
45e14433 | 337 | { |
338 | struct choke_sched_data *q = qdisc_priv(sch); | |
339 | struct nlattr *tb[TCA_CHOKE_MAX + 1]; | |
340 | const struct tc_red_qopt *ctl; | |
341 | int err; | |
342 | struct sk_buff **old = NULL; | |
343 | unsigned int mask; | |
a73ed26b | 344 | u32 max_P; |
e323d865 | 345 | u8 *stab; |
45e14433 | 346 | |
347 | if (opt == NULL) | |
348 | return -EINVAL; | |
349 | ||
8cb08174 JB |
350 | err = nla_parse_nested_deprecated(tb, TCA_CHOKE_MAX, opt, |
351 | choke_policy, NULL); | |
45e14433 | 352 | if (err < 0) |
353 | return err; | |
354 | ||
355 | if (tb[TCA_CHOKE_PARMS] == NULL || | |
356 | tb[TCA_CHOKE_STAB] == NULL) | |
357 | return -EINVAL; | |
358 | ||
a73ed26b ED |
359 | max_P = tb[TCA_CHOKE_MAX_P] ? nla_get_u32(tb[TCA_CHOKE_MAX_P]) : 0; |
360 | ||
45e14433 | 361 | ctl = nla_data(tb[TCA_CHOKE_PARMS]); |
e323d865 ED |
362 | stab = nla_data(tb[TCA_CHOKE_STAB]); |
363 | if (!red_check_params(ctl->qth_min, ctl->qth_max, ctl->Wlog, ctl->Scell_log, stab)) | |
8afa10cb NF |
364 | return -EINVAL; |
365 | ||
45e14433 | 366 | if (ctl->limit > CHOKE_MAX_QUEUE) |
367 | return -EINVAL; | |
368 | ||
369 | mask = roundup_pow_of_two(ctl->limit + 1) - 1; | |
370 | if (mask != q->tab_mask) { | |
371 | struct sk_buff **ntab; | |
372 | ||
793da4bf | 373 | ntab = kvcalloc(mask + 1, sizeof(struct sk_buff *), GFP_KERNEL); |
45e14433 | 374 | if (!ntab) |
375 | return -ENOMEM; | |
376 | ||
377 | sch_tree_lock(sch); | |
378 | old = q->tab; | |
379 | if (old) { | |
380 | unsigned int oqlen = sch->q.qlen, tail = 0; | |
2ccccf5f | 381 | unsigned dropped = 0; |
45e14433 | 382 | |
383 | while (q->head != q->tail) { | |
384 | struct sk_buff *skb = q->tab[q->head]; | |
385 | ||
386 | q->head = (q->head + 1) & q->tab_mask; | |
387 | if (!skb) | |
388 | continue; | |
389 | if (tail < mask) { | |
390 | ntab[tail++] = skb; | |
391 | continue; | |
392 | } | |
2ccccf5f | 393 | dropped += qdisc_pkt_len(skb); |
25331d6c | 394 | qdisc_qstats_backlog_dec(sch, skb); |
45e14433 | 395 | --sch->q.qlen; |
f9aed311 | 396 | rtnl_qdisc_drop(skb, sch); |
45e14433 | 397 | } |
2ccccf5f | 398 | qdisc_tree_reduce_backlog(sch, oqlen - sch->q.qlen, dropped); |
45e14433 | 399 | q->head = 0; |
400 | q->tail = tail; | |
401 | } | |
402 | ||
403 | q->tab_mask = mask; | |
404 | q->tab = ntab; | |
405 | } else | |
406 | sch_tree_lock(sch); | |
407 | ||
408 | q->flags = ctl->flags; | |
409 | q->limit = ctl->limit; | |
410 | ||
411 | red_set_parms(&q->parms, ctl->qth_min, ctl->qth_max, ctl->Wlog, | |
412 | ctl->Plog, ctl->Scell_log, | |
e323d865 | 413 | stab, |
a73ed26b | 414 | max_P); |
eeca6688 | 415 | red_set_vars(&q->vars); |
45e14433 | 416 | |
417 | if (q->head == q->tail) | |
eeca6688 | 418 | red_end_of_idle_period(&q->vars); |
45e14433 | 419 | |
420 | sch_tree_unlock(sch); | |
421 | choke_free(old); | |
422 | return 0; | |
423 | } | |
424 | ||
e63d7dfd AA |
425 | static int choke_init(struct Qdisc *sch, struct nlattr *opt, |
426 | struct netlink_ext_ack *extack) | |
45e14433 | 427 | { |
2030721c | 428 | return choke_change(sch, opt, extack); |
45e14433 | 429 | } |
430 | ||
431 | static int choke_dump(struct Qdisc *sch, struct sk_buff *skb) | |
432 | { | |
433 | struct choke_sched_data *q = qdisc_priv(sch); | |
434 | struct nlattr *opts = NULL; | |
435 | struct tc_red_qopt opt = { | |
436 | .limit = q->limit, | |
437 | .flags = q->flags, | |
438 | .qth_min = q->parms.qth_min >> q->parms.Wlog, | |
439 | .qth_max = q->parms.qth_max >> q->parms.Wlog, | |
440 | .Wlog = q->parms.Wlog, | |
441 | .Plog = q->parms.Plog, | |
442 | .Scell_log = q->parms.Scell_log, | |
443 | }; | |
444 | ||
ae0be8de | 445 | opts = nla_nest_start_noflag(skb, TCA_OPTIONS); |
45e14433 | 446 | if (opts == NULL) |
447 | goto nla_put_failure; | |
448 | ||
1b34ec43 DM |
449 | if (nla_put(skb, TCA_CHOKE_PARMS, sizeof(opt), &opt) || |
450 | nla_put_u32(skb, TCA_CHOKE_MAX_P, q->parms.max_P)) | |
451 | goto nla_put_failure; | |
45e14433 | 452 | return nla_nest_end(skb, opts); |
453 | ||
454 | nla_put_failure: | |
455 | nla_nest_cancel(skb, opts); | |
456 | return -EMSGSIZE; | |
457 | } | |
458 | ||
459 | static int choke_dump_stats(struct Qdisc *sch, struct gnet_dump *d) | |
460 | { | |
461 | struct choke_sched_data *q = qdisc_priv(sch); | |
462 | struct tc_choke_xstats st = { | |
463 | .early = q->stats.prob_drop + q->stats.forced_drop, | |
464 | .marked = q->stats.prob_mark + q->stats.forced_mark, | |
465 | .pdrop = q->stats.pdrop, | |
45e14433 | 466 | .matched = q->stats.matched, |
467 | }; | |
468 | ||
469 | return gnet_stats_copy_app(d, &st, sizeof(st)); | |
470 | } | |
471 | ||
472 | static void choke_destroy(struct Qdisc *sch) | |
473 | { | |
474 | struct choke_sched_data *q = qdisc_priv(sch); | |
475 | ||
45e14433 | 476 | choke_free(q->tab); |
477 | } | |
478 | ||
45e14433 | 479 | static struct sk_buff *choke_peek_head(struct Qdisc *sch) |
480 | { | |
481 | struct choke_sched_data *q = qdisc_priv(sch); | |
482 | ||
483 | return (q->head != q->tail) ? q->tab[q->head] : NULL; | |
484 | } | |
485 | ||
486 | static struct Qdisc_ops choke_qdisc_ops __read_mostly = { | |
487 | .id = "choke", | |
488 | .priv_size = sizeof(struct choke_sched_data), | |
489 | ||
490 | .enqueue = choke_enqueue, | |
491 | .dequeue = choke_dequeue, | |
492 | .peek = choke_peek_head, | |
45e14433 | 493 | .init = choke_init, |
494 | .destroy = choke_destroy, | |
495 | .reset = choke_reset, | |
496 | .change = choke_change, | |
497 | .dump = choke_dump, | |
498 | .dump_stats = choke_dump_stats, | |
499 | .owner = THIS_MODULE, | |
500 | }; | |
501 | ||
502 | static int __init choke_module_init(void) | |
503 | { | |
504 | return register_qdisc(&choke_qdisc_ops); | |
505 | } | |
506 | ||
507 | static void __exit choke_module_exit(void) | |
508 | { | |
509 | unregister_qdisc(&choke_qdisc_ops); | |
510 | } | |
511 | ||
512 | module_init(choke_module_init) | |
513 | module_exit(choke_module_exit) | |
514 | ||
515 | MODULE_LICENSE("GPL"); |