1 /* 2 * net/sched/sch_choke.c CHOKE scheduler 3 * 4 * Copyright (c) 2011 Stephen Hemminger <shemminger@vyatta.com> 5 * Copyright (c) 2011 Eric Dumazet <eric.dumazet@gmail.com> 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public License 9 * version 2 as published by the Free Software Foundation. 10 * 11 */ 12 13 #include <linux/module.h> 14 #include <linux/types.h> 15 #include <linux/kernel.h> 16 #include <linux/skbuff.h> 17 #include <linux/reciprocal_div.h> 18 #include <linux/vmalloc.h> 19 #include <net/pkt_sched.h> 20 #include <net/inet_ecn.h> 21 #include <net/red.h> 22 #include <linux/ip.h> 23 #include <net/ip.h> 24 #include <linux/ipv6.h> 25 #include <net/ipv6.h> 26 27 /* 28 CHOKe stateless AQM for fair bandwidth allocation 29 ================================================= 30 31 CHOKe (CHOose and Keep for responsive flows, CHOose and Kill for 32 unresponsive flows) is a variant of RED that penalizes misbehaving flows but 33 maintains no flow state. The difference from RED is an additional step 34 during the enqueuing process. If average queue size is over the 35 low threshold (qmin), a packet is chosen at random from the queue. 36 If both the new and chosen packet are from the same flow, both 37 are dropped. Unlike RED, CHOKe is not really a "classful" qdisc because it 38 needs to access packets in queue randomly. It has a minimal class 39 interface to allow overriding the builtin flow classifier with 40 filters. 41 42 Source: 43 R. Pan, B. Prabhakar, and K. Psounis, "CHOKe, A Stateless 44 Active Queue Management Scheme for Approximating Fair Bandwidth Allocation", 45 IEEE INFOCOM, 2000. 46 47 A. Tang, J. Wang, S. Low, "Understanding CHOKe: Throughput and Spatial 48 Characteristics", IEEE/ACM Transactions on Networking, 2004 49 50 */ 51 52 /* Upper bound on size of sk_buff table (packets) */ 53 #define CHOKE_MAX_QUEUE (128*1024 - 1) 54 55 struct choke_sched_data { 56 /* Parameters */ 57 u32 limit; 58 unsigned char flags; 59 60 struct red_parms parms; 61 62 /* Variables */ 63 struct tcf_proto *filter_list; 64 struct { 65 u32 prob_drop; /* Early probability drops */ 66 u32 prob_mark; /* Early probability marks */ 67 u32 forced_drop; /* Forced drops, qavg > max_thresh */ 68 u32 forced_mark; /* Forced marks, qavg > max_thresh */ 69 u32 pdrop; /* Drops due to queue limits */ 70 u32 other; /* Drops due to drop() calls */ 71 u32 matched; /* Drops to flow match */ 72 } stats; 73 74 unsigned int head; 75 unsigned int tail; 76 77 unsigned int tab_mask; /* size - 1 */ 78 79 struct sk_buff **tab; 80 }; 81 82 /* deliver a random number between 0 and N - 1 */ 83 static u32 random_N(unsigned int N) 84 { 85 return reciprocal_divide(random32(), N); 86 } 87 88 /* number of elements in queue including holes */ 89 static unsigned int choke_len(const struct choke_sched_data *q) 90 { 91 return (q->tail - q->head) & q->tab_mask; 92 } 93 94 /* Is ECN parameter configured */ 95 static int use_ecn(const struct choke_sched_data *q) 96 { 97 return q->flags & TC_RED_ECN; 98 } 99 100 /* Should packets over max just be dropped (versus marked) */ 101 static int use_harddrop(const struct choke_sched_data *q) 102 { 103 return q->flags & TC_RED_HARDDROP; 104 } 105 106 /* Move head pointer forward to skip over holes */ 107 static void choke_zap_head_holes(struct choke_sched_data *q) 108 { 109 do { 110 q->head = (q->head + 1) & q->tab_mask; 111 if (q->head == q->tail) 112 break; 113 } while (q->tab[q->head] == NULL); 114 } 115 116 /* Move tail pointer backwards to reuse holes */ 117 static void choke_zap_tail_holes(struct choke_sched_data *q) 118 { 119 do { 120 q->tail = (q->tail - 1) & q->tab_mask; 121 if (q->head == q->tail) 122 break; 123 } while (q->tab[q->tail] == NULL); 124 } 125 126 /* Drop packet from queue array by creating a "hole" */ 127 static void choke_drop_by_idx(struct Qdisc *sch, unsigned int idx) 128 { 129 struct choke_sched_data *q = qdisc_priv(sch); 130 struct sk_buff *skb = q->tab[idx]; 131 132 q->tab[idx] = NULL; 133 134 if (idx == q->head) 135 choke_zap_head_holes(q); 136 if (idx == q->tail) 137 choke_zap_tail_holes(q); 138 139 sch->qstats.backlog -= qdisc_pkt_len(skb); 140 qdisc_drop(skb, sch); 141 qdisc_tree_decrease_qlen(sch, 1); 142 --sch->q.qlen; 143 } 144 145 /* 146 * Compare flow of two packets 147 * Returns true only if source and destination address and port match. 148 * false for special cases 149 */ 150 static bool choke_match_flow(struct sk_buff *skb1, 151 struct sk_buff *skb2) 152 { 153 int off1, off2, poff; 154 const u32 *ports1, *ports2; 155 u8 ip_proto; 156 __u32 hash1; 157 158 if (skb1->protocol != skb2->protocol) 159 return false; 160 161 /* Use hash value as quick check 162 * Assumes that __skb_get_rxhash makes IP header and ports linear 163 */ 164 hash1 = skb_get_rxhash(skb1); 165 if (!hash1 || hash1 != skb_get_rxhash(skb2)) 166 return false; 167 168 /* Probably match, but be sure to avoid hash collisions */ 169 off1 = skb_network_offset(skb1); 170 off2 = skb_network_offset(skb2); 171 172 switch (skb1->protocol) { 173 case __constant_htons(ETH_P_IP): { 174 const struct iphdr *ip1, *ip2; 175 176 ip1 = (const struct iphdr *) (skb1->data + off1); 177 ip2 = (const struct iphdr *) (skb2->data + off2); 178 179 ip_proto = ip1->protocol; 180 if (ip_proto != ip2->protocol || 181 ip1->saddr != ip2->saddr || ip1->daddr != ip2->daddr) 182 return false; 183 184 if ((ip1->frag_off | ip2->frag_off) & htons(IP_MF | IP_OFFSET)) 185 ip_proto = 0; 186 off1 += ip1->ihl * 4; 187 off2 += ip2->ihl * 4; 188 break; 189 } 190 191 case __constant_htons(ETH_P_IPV6): { 192 const struct ipv6hdr *ip1, *ip2; 193 194 ip1 = (const struct ipv6hdr *) (skb1->data + off1); 195 ip2 = (const struct ipv6hdr *) (skb2->data + off2); 196 197 ip_proto = ip1->nexthdr; 198 if (ip_proto != ip2->nexthdr || 199 ipv6_addr_cmp(&ip1->saddr, &ip2->saddr) || 200 ipv6_addr_cmp(&ip1->daddr, &ip2->daddr)) 201 return false; 202 off1 += 40; 203 off2 += 40; 204 } 205 206 default: /* Maybe compare MAC header here? */ 207 return false; 208 } 209 210 poff = proto_ports_offset(ip_proto); 211 if (poff < 0) 212 return true; 213 214 off1 += poff; 215 off2 += poff; 216 217 ports1 = (__force u32 *)(skb1->data + off1); 218 ports2 = (__force u32 *)(skb2->data + off2); 219 return *ports1 == *ports2; 220 } 221 222 struct choke_skb_cb { 223 u16 classid; 224 }; 225 226 static inline struct choke_skb_cb *choke_skb_cb(const struct sk_buff *skb) 227 { 228 BUILD_BUG_ON(sizeof(skb->cb) < 229 sizeof(struct qdisc_skb_cb) + sizeof(struct choke_skb_cb)); 230 return (struct choke_skb_cb *)qdisc_skb_cb(skb)->data; 231 } 232 233 static inline void choke_set_classid(struct sk_buff *skb, u16 classid) 234 { 235 choke_skb_cb(skb)->classid = classid; 236 } 237 238 static u16 choke_get_classid(const struct sk_buff *skb) 239 { 240 return choke_skb_cb(skb)->classid; 241 } 242 243 /* 244 * Classify flow using either: 245 * 1. pre-existing classification result in skb 246 * 2. fast internal classification 247 * 3. use TC filter based classification 248 */ 249 static bool choke_classify(struct sk_buff *skb, 250 struct Qdisc *sch, int *qerr) 251 252 { 253 struct choke_sched_data *q = qdisc_priv(sch); 254 struct tcf_result res; 255 int result; 256 257 result = tc_classify(skb, q->filter_list, &res); 258 if (result >= 0) { 259 #ifdef CONFIG_NET_CLS_ACT 260 switch (result) { 261 case TC_ACT_STOLEN: 262 case TC_ACT_QUEUED: 263 *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN; 264 case TC_ACT_SHOT: 265 return false; 266 } 267 #endif 268 choke_set_classid(skb, TC_H_MIN(res.classid)); 269 return true; 270 } 271 272 return false; 273 } 274 275 /* 276 * Select a packet at random from queue 277 * HACK: since queue can have holes from previous deletion; retry several 278 * times to find a random skb but then just give up and return the head 279 * Will return NULL if queue is empty (q->head == q->tail) 280 */ 281 static struct sk_buff *choke_peek_random(const struct choke_sched_data *q, 282 unsigned int *pidx) 283 { 284 struct sk_buff *skb; 285 int retrys = 3; 286 287 do { 288 *pidx = (q->head + random_N(choke_len(q))) & q->tab_mask; 289 skb = q->tab[*pidx]; 290 if (skb) 291 return skb; 292 } while (--retrys > 0); 293 294 return q->tab[*pidx = q->head]; 295 } 296 297 /* 298 * Compare new packet with random packet in queue 299 * returns true if matched and sets *pidx 300 */ 301 static bool choke_match_random(const struct choke_sched_data *q, 302 struct sk_buff *nskb, 303 unsigned int *pidx) 304 { 305 struct sk_buff *oskb; 306 307 if (q->head == q->tail) 308 return false; 309 310 oskb = choke_peek_random(q, pidx); 311 if (q->filter_list) 312 return choke_get_classid(nskb) == choke_get_classid(oskb); 313 314 return choke_match_flow(oskb, nskb); 315 } 316 317 static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch) 318 { 319 struct choke_sched_data *q = qdisc_priv(sch); 320 struct red_parms *p = &q->parms; 321 int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS; 322 323 if (q->filter_list) { 324 /* If using external classifiers, get result and record it. */ 325 if (!choke_classify(skb, sch, &ret)) 326 goto other_drop; /* Packet was eaten by filter */ 327 } 328 329 /* Compute average queue usage (see RED) */ 330 p->qavg = red_calc_qavg(p, sch->q.qlen); 331 if (red_is_idling(p)) 332 red_end_of_idle_period(p); 333 334 /* Is queue small? */ 335 if (p->qavg <= p->qth_min) 336 p->qcount = -1; 337 else { 338 unsigned int idx; 339 340 /* Draw a packet at random from queue and compare flow */ 341 if (choke_match_random(q, skb, &idx)) { 342 q->stats.matched++; 343 choke_drop_by_idx(sch, idx); 344 goto congestion_drop; 345 } 346 347 /* Queue is large, always mark/drop */ 348 if (p->qavg > p->qth_max) { 349 p->qcount = -1; 350 351 sch->qstats.overlimits++; 352 if (use_harddrop(q) || !use_ecn(q) || 353 !INET_ECN_set_ce(skb)) { 354 q->stats.forced_drop++; 355 goto congestion_drop; 356 } 357 358 q->stats.forced_mark++; 359 } else if (++p->qcount) { 360 if (red_mark_probability(p, p->qavg)) { 361 p->qcount = 0; 362 p->qR = red_random(p); 363 364 sch->qstats.overlimits++; 365 if (!use_ecn(q) || !INET_ECN_set_ce(skb)) { 366 q->stats.prob_drop++; 367 goto congestion_drop; 368 } 369 370 q->stats.prob_mark++; 371 } 372 } else 373 p->qR = red_random(p); 374 } 375 376 /* Admit new packet */ 377 if (sch->q.qlen < q->limit) { 378 q->tab[q->tail] = skb; 379 q->tail = (q->tail + 1) & q->tab_mask; 380 ++sch->q.qlen; 381 sch->qstats.backlog += qdisc_pkt_len(skb); 382 return NET_XMIT_SUCCESS; 383 } 384 385 q->stats.pdrop++; 386 sch->qstats.drops++; 387 kfree_skb(skb); 388 return NET_XMIT_DROP; 389 390 congestion_drop: 391 qdisc_drop(skb, sch); 392 return NET_XMIT_CN; 393 394 other_drop: 395 if (ret & __NET_XMIT_BYPASS) 396 sch->qstats.drops++; 397 kfree_skb(skb); 398 return ret; 399 } 400 401 static struct sk_buff *choke_dequeue(struct Qdisc *sch) 402 { 403 struct choke_sched_data *q = qdisc_priv(sch); 404 struct sk_buff *skb; 405 406 if (q->head == q->tail) { 407 if (!red_is_idling(&q->parms)) 408 red_start_of_idle_period(&q->parms); 409 return NULL; 410 } 411 412 skb = q->tab[q->head]; 413 q->tab[q->head] = NULL; 414 choke_zap_head_holes(q); 415 --sch->q.qlen; 416 sch->qstats.backlog -= qdisc_pkt_len(skb); 417 qdisc_bstats_update(sch, skb); 418 419 return skb; 420 } 421 422 static unsigned int choke_drop(struct Qdisc *sch) 423 { 424 struct choke_sched_data *q = qdisc_priv(sch); 425 unsigned int len; 426 427 len = qdisc_queue_drop(sch); 428 if (len > 0) 429 q->stats.other++; 430 else { 431 if (!red_is_idling(&q->parms)) 432 red_start_of_idle_period(&q->parms); 433 } 434 435 return len; 436 } 437 438 static void choke_reset(struct Qdisc *sch) 439 { 440 struct choke_sched_data *q = qdisc_priv(sch); 441 442 red_restart(&q->parms); 443 } 444 445 static const struct nla_policy choke_policy[TCA_CHOKE_MAX + 1] = { 446 [TCA_CHOKE_PARMS] = { .len = sizeof(struct tc_red_qopt) }, 447 [TCA_CHOKE_STAB] = { .len = RED_STAB_SIZE }, 448 }; 449 450 451 static void choke_free(void *addr) 452 { 453 if (addr) { 454 if (is_vmalloc_addr(addr)) 455 vfree(addr); 456 else 457 kfree(addr); 458 } 459 } 460 461 static int choke_change(struct Qdisc *sch, struct nlattr *opt) 462 { 463 struct choke_sched_data *q = qdisc_priv(sch); 464 struct nlattr *tb[TCA_CHOKE_MAX + 1]; 465 const struct tc_red_qopt *ctl; 466 int err; 467 struct sk_buff **old = NULL; 468 unsigned int mask; 469 470 if (opt == NULL) 471 return -EINVAL; 472 473 err = nla_parse_nested(tb, TCA_CHOKE_MAX, opt, choke_policy); 474 if (err < 0) 475 return err; 476 477 if (tb[TCA_CHOKE_PARMS] == NULL || 478 tb[TCA_CHOKE_STAB] == NULL) 479 return -EINVAL; 480 481 ctl = nla_data(tb[TCA_CHOKE_PARMS]); 482 483 if (ctl->limit > CHOKE_MAX_QUEUE) 484 return -EINVAL; 485 486 mask = roundup_pow_of_two(ctl->limit + 1) - 1; 487 if (mask != q->tab_mask) { 488 struct sk_buff **ntab; 489 490 ntab = kcalloc(mask + 1, sizeof(struct sk_buff *), GFP_KERNEL); 491 if (!ntab) 492 ntab = vzalloc((mask + 1) * sizeof(struct sk_buff *)); 493 if (!ntab) 494 return -ENOMEM; 495 496 sch_tree_lock(sch); 497 old = q->tab; 498 if (old) { 499 unsigned int oqlen = sch->q.qlen, tail = 0; 500 501 while (q->head != q->tail) { 502 struct sk_buff *skb = q->tab[q->head]; 503 504 q->head = (q->head + 1) & q->tab_mask; 505 if (!skb) 506 continue; 507 if (tail < mask) { 508 ntab[tail++] = skb; 509 continue; 510 } 511 sch->qstats.backlog -= qdisc_pkt_len(skb); 512 --sch->q.qlen; 513 qdisc_drop(skb, sch); 514 } 515 qdisc_tree_decrease_qlen(sch, oqlen - sch->q.qlen); 516 q->head = 0; 517 q->tail = tail; 518 } 519 520 q->tab_mask = mask; 521 q->tab = ntab; 522 } else 523 sch_tree_lock(sch); 524 525 q->flags = ctl->flags; 526 q->limit = ctl->limit; 527 528 red_set_parms(&q->parms, ctl->qth_min, ctl->qth_max, ctl->Wlog, 529 ctl->Plog, ctl->Scell_log, 530 nla_data(tb[TCA_CHOKE_STAB])); 531 532 if (q->head == q->tail) 533 red_end_of_idle_period(&q->parms); 534 535 sch_tree_unlock(sch); 536 choke_free(old); 537 return 0; 538 } 539 540 static int choke_init(struct Qdisc *sch, struct nlattr *opt) 541 { 542 return choke_change(sch, opt); 543 } 544 545 static int choke_dump(struct Qdisc *sch, struct sk_buff *skb) 546 { 547 struct choke_sched_data *q = qdisc_priv(sch); 548 struct nlattr *opts = NULL; 549 struct tc_red_qopt opt = { 550 .limit = q->limit, 551 .flags = q->flags, 552 .qth_min = q->parms.qth_min >> q->parms.Wlog, 553 .qth_max = q->parms.qth_max >> q->parms.Wlog, 554 .Wlog = q->parms.Wlog, 555 .Plog = q->parms.Plog, 556 .Scell_log = q->parms.Scell_log, 557 }; 558 559 opts = nla_nest_start(skb, TCA_OPTIONS); 560 if (opts == NULL) 561 goto nla_put_failure; 562 563 NLA_PUT(skb, TCA_CHOKE_PARMS, sizeof(opt), &opt); 564 return nla_nest_end(skb, opts); 565 566 nla_put_failure: 567 nla_nest_cancel(skb, opts); 568 return -EMSGSIZE; 569 } 570 571 static int choke_dump_stats(struct Qdisc *sch, struct gnet_dump *d) 572 { 573 struct choke_sched_data *q = qdisc_priv(sch); 574 struct tc_choke_xstats st = { 575 .early = q->stats.prob_drop + q->stats.forced_drop, 576 .marked = q->stats.prob_mark + q->stats.forced_mark, 577 .pdrop = q->stats.pdrop, 578 .other = q->stats.other, 579 .matched = q->stats.matched, 580 }; 581 582 return gnet_stats_copy_app(d, &st, sizeof(st)); 583 } 584 585 static void choke_destroy(struct Qdisc *sch) 586 { 587 struct choke_sched_data *q = qdisc_priv(sch); 588 589 tcf_destroy_chain(&q->filter_list); 590 choke_free(q->tab); 591 } 592 593 static struct Qdisc *choke_leaf(struct Qdisc *sch, unsigned long arg) 594 { 595 return NULL; 596 } 597 598 static unsigned long choke_get(struct Qdisc *sch, u32 classid) 599 { 600 return 0; 601 } 602 603 static void choke_put(struct Qdisc *q, unsigned long cl) 604 { 605 } 606 607 static unsigned long choke_bind(struct Qdisc *sch, unsigned long parent, 608 u32 classid) 609 { 610 return 0; 611 } 612 613 static struct tcf_proto **choke_find_tcf(struct Qdisc *sch, unsigned long cl) 614 { 615 struct choke_sched_data *q = qdisc_priv(sch); 616 617 if (cl) 618 return NULL; 619 return &q->filter_list; 620 } 621 622 static int choke_dump_class(struct Qdisc *sch, unsigned long cl, 623 struct sk_buff *skb, struct tcmsg *tcm) 624 { 625 tcm->tcm_handle |= TC_H_MIN(cl); 626 return 0; 627 } 628 629 static void choke_walk(struct Qdisc *sch, struct qdisc_walker *arg) 630 { 631 if (!arg->stop) { 632 if (arg->fn(sch, 1, arg) < 0) { 633 arg->stop = 1; 634 return; 635 } 636 arg->count++; 637 } 638 } 639 640 static const struct Qdisc_class_ops choke_class_ops = { 641 .leaf = choke_leaf, 642 .get = choke_get, 643 .put = choke_put, 644 .tcf_chain = choke_find_tcf, 645 .bind_tcf = choke_bind, 646 .unbind_tcf = choke_put, 647 .dump = choke_dump_class, 648 .walk = choke_walk, 649 }; 650 651 static struct sk_buff *choke_peek_head(struct Qdisc *sch) 652 { 653 struct choke_sched_data *q = qdisc_priv(sch); 654 655 return (q->head != q->tail) ? q->tab[q->head] : NULL; 656 } 657 658 static struct Qdisc_ops choke_qdisc_ops __read_mostly = { 659 .id = "choke", 660 .priv_size = sizeof(struct choke_sched_data), 661 662 .enqueue = choke_enqueue, 663 .dequeue = choke_dequeue, 664 .peek = choke_peek_head, 665 .drop = choke_drop, 666 .init = choke_init, 667 .destroy = choke_destroy, 668 .reset = choke_reset, 669 .change = choke_change, 670 .dump = choke_dump, 671 .dump_stats = choke_dump_stats, 672 .owner = THIS_MODULE, 673 }; 674 675 static int __init choke_module_init(void) 676 { 677 return register_qdisc(&choke_qdisc_ops); 678 } 679 680 static void __exit choke_module_exit(void) 681 { 682 unregister_qdisc(&choke_qdisc_ops); 683 } 684 685 module_init(choke_module_init) 686 module_exit(choke_module_exit) 687 688 MODULE_LICENSE("GPL"); 689