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 __rcu *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 81 return reciprocal_scale(hash, q->flows_cnt); 82 } 83 84 static unsigned int fq_codel_classify(struct sk_buff *skb, struct Qdisc *sch, 85 int *qerr) 86 { 87 struct fq_codel_sched_data *q = qdisc_priv(sch); 88 struct tcf_proto *filter; 89 struct tcf_result res; 90 int result; 91 92 if (TC_H_MAJ(skb->priority) == sch->handle && 93 TC_H_MIN(skb->priority) > 0 && 94 TC_H_MIN(skb->priority) <= q->flows_cnt) 95 return TC_H_MIN(skb->priority); 96 97 filter = rcu_dereference_bh(q->filter_list); 98 if (!filter) 99 return fq_codel_hash(q, skb) + 1; 100 101 *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS; 102 result = tc_classify(skb, filter, &res); 103 if (result >= 0) { 104 #ifdef CONFIG_NET_CLS_ACT 105 switch (result) { 106 case TC_ACT_STOLEN: 107 case TC_ACT_QUEUED: 108 *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN; 109 case TC_ACT_SHOT: 110 return 0; 111 } 112 #endif 113 if (TC_H_MIN(res.classid) <= q->flows_cnt) 114 return TC_H_MIN(res.classid); 115 } 116 return 0; 117 } 118 119 /* helper functions : might be changed when/if skb use a standard list_head */ 120 121 /* remove one skb from head of slot queue */ 122 static inline struct sk_buff *dequeue_head(struct fq_codel_flow *flow) 123 { 124 struct sk_buff *skb = flow->head; 125 126 flow->head = skb->next; 127 skb->next = NULL; 128 return skb; 129 } 130 131 /* add skb to flow queue (tail add) */ 132 static inline void flow_queue_add(struct fq_codel_flow *flow, 133 struct sk_buff *skb) 134 { 135 if (flow->head == NULL) 136 flow->head = skb; 137 else 138 flow->tail->next = skb; 139 flow->tail = skb; 140 skb->next = NULL; 141 } 142 143 static unsigned int fq_codel_drop(struct Qdisc *sch) 144 { 145 struct fq_codel_sched_data *q = qdisc_priv(sch); 146 struct sk_buff *skb; 147 unsigned int maxbacklog = 0, idx = 0, i, len; 148 struct fq_codel_flow *flow; 149 150 /* Queue is full! Find the fat flow and drop packet from it. 151 * This might sound expensive, but with 1024 flows, we scan 152 * 4KB of memory, and we dont need to handle a complex tree 153 * in fast path (packet queue/enqueue) with many cache misses. 154 */ 155 for (i = 0; i < q->flows_cnt; i++) { 156 if (q->backlogs[i] > maxbacklog) { 157 maxbacklog = q->backlogs[i]; 158 idx = i; 159 } 160 } 161 flow = &q->flows[idx]; 162 skb = dequeue_head(flow); 163 len = qdisc_pkt_len(skb); 164 q->backlogs[idx] -= len; 165 kfree_skb(skb); 166 sch->q.qlen--; 167 qdisc_qstats_drop(sch); 168 qdisc_qstats_backlog_dec(sch, skb); 169 flow->dropped++; 170 return idx; 171 } 172 173 static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch) 174 { 175 struct fq_codel_sched_data *q = qdisc_priv(sch); 176 unsigned int idx; 177 struct fq_codel_flow *flow; 178 int uninitialized_var(ret); 179 180 idx = fq_codel_classify(skb, sch, &ret); 181 if (idx == 0) { 182 if (ret & __NET_XMIT_BYPASS) 183 qdisc_qstats_drop(sch); 184 kfree_skb(skb); 185 return ret; 186 } 187 idx--; 188 189 codel_set_enqueue_time(skb); 190 flow = &q->flows[idx]; 191 flow_queue_add(flow, skb); 192 q->backlogs[idx] += qdisc_pkt_len(skb); 193 qdisc_qstats_backlog_inc(sch, skb); 194 195 if (list_empty(&flow->flowchain)) { 196 list_add_tail(&flow->flowchain, &q->new_flows); 197 q->new_flow_count++; 198 flow->deficit = q->quantum; 199 flow->dropped = 0; 200 } 201 if (++sch->q.qlen <= sch->limit) 202 return NET_XMIT_SUCCESS; 203 204 q->drop_overlimit++; 205 /* Return Congestion Notification only if we dropped a packet 206 * from this flow. 207 */ 208 if (fq_codel_drop(sch) == idx) 209 return NET_XMIT_CN; 210 211 /* As we dropped a packet, better let upper stack know this */ 212 qdisc_tree_decrease_qlen(sch, 1); 213 return NET_XMIT_SUCCESS; 214 } 215 216 /* This is the specific function called from codel_dequeue() 217 * to dequeue a packet from queue. Note: backlog is handled in 218 * codel, we dont need to reduce it here. 219 */ 220 static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch) 221 { 222 struct fq_codel_sched_data *q = qdisc_priv(sch); 223 struct fq_codel_flow *flow; 224 struct sk_buff *skb = NULL; 225 226 flow = container_of(vars, struct fq_codel_flow, cvars); 227 if (flow->head) { 228 skb = dequeue_head(flow); 229 q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb); 230 sch->q.qlen--; 231 } 232 return skb; 233 } 234 235 static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch) 236 { 237 struct fq_codel_sched_data *q = qdisc_priv(sch); 238 struct sk_buff *skb; 239 struct fq_codel_flow *flow; 240 struct list_head *head; 241 u32 prev_drop_count, prev_ecn_mark; 242 243 begin: 244 head = &q->new_flows; 245 if (list_empty(head)) { 246 head = &q->old_flows; 247 if (list_empty(head)) 248 return NULL; 249 } 250 flow = list_first_entry(head, struct fq_codel_flow, flowchain); 251 252 if (flow->deficit <= 0) { 253 flow->deficit += q->quantum; 254 list_move_tail(&flow->flowchain, &q->old_flows); 255 goto begin; 256 } 257 258 prev_drop_count = q->cstats.drop_count; 259 prev_ecn_mark = q->cstats.ecn_mark; 260 261 skb = codel_dequeue(sch, &q->cparams, &flow->cvars, &q->cstats, 262 dequeue); 263 264 flow->dropped += q->cstats.drop_count - prev_drop_count; 265 flow->dropped += q->cstats.ecn_mark - prev_ecn_mark; 266 267 if (!skb) { 268 /* force a pass through old_flows to prevent starvation */ 269 if ((head == &q->new_flows) && !list_empty(&q->old_flows)) 270 list_move_tail(&flow->flowchain, &q->old_flows); 271 else 272 list_del_init(&flow->flowchain); 273 goto begin; 274 } 275 qdisc_bstats_update(sch, skb); 276 flow->deficit -= qdisc_pkt_len(skb); 277 /* We cant call qdisc_tree_decrease_qlen() if our qlen is 0, 278 * or HTB crashes. Defer it for next round. 279 */ 280 if (q->cstats.drop_count && sch->q.qlen) { 281 qdisc_tree_decrease_qlen(sch, q->cstats.drop_count); 282 q->cstats.drop_count = 0; 283 } 284 return skb; 285 } 286 287 static void fq_codel_reset(struct Qdisc *sch) 288 { 289 struct sk_buff *skb; 290 291 while ((skb = fq_codel_dequeue(sch)) != NULL) 292 kfree_skb(skb); 293 } 294 295 static const struct nla_policy fq_codel_policy[TCA_FQ_CODEL_MAX + 1] = { 296 [TCA_FQ_CODEL_TARGET] = { .type = NLA_U32 }, 297 [TCA_FQ_CODEL_LIMIT] = { .type = NLA_U32 }, 298 [TCA_FQ_CODEL_INTERVAL] = { .type = NLA_U32 }, 299 [TCA_FQ_CODEL_ECN] = { .type = NLA_U32 }, 300 [TCA_FQ_CODEL_FLOWS] = { .type = NLA_U32 }, 301 [TCA_FQ_CODEL_QUANTUM] = { .type = NLA_U32 }, 302 }; 303 304 static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt) 305 { 306 struct fq_codel_sched_data *q = qdisc_priv(sch); 307 struct nlattr *tb[TCA_FQ_CODEL_MAX + 1]; 308 int err; 309 310 if (!opt) 311 return -EINVAL; 312 313 err = nla_parse_nested(tb, TCA_FQ_CODEL_MAX, opt, fq_codel_policy); 314 if (err < 0) 315 return err; 316 if (tb[TCA_FQ_CODEL_FLOWS]) { 317 if (q->flows) 318 return -EINVAL; 319 q->flows_cnt = nla_get_u32(tb[TCA_FQ_CODEL_FLOWS]); 320 if (!q->flows_cnt || 321 q->flows_cnt > 65536) 322 return -EINVAL; 323 } 324 sch_tree_lock(sch); 325 326 if (tb[TCA_FQ_CODEL_TARGET]) { 327 u64 target = nla_get_u32(tb[TCA_FQ_CODEL_TARGET]); 328 329 q->cparams.target = (target * NSEC_PER_USEC) >> CODEL_SHIFT; 330 } 331 332 if (tb[TCA_FQ_CODEL_INTERVAL]) { 333 u64 interval = nla_get_u32(tb[TCA_FQ_CODEL_INTERVAL]); 334 335 q->cparams.interval = (interval * NSEC_PER_USEC) >> CODEL_SHIFT; 336 } 337 338 if (tb[TCA_FQ_CODEL_LIMIT]) 339 sch->limit = nla_get_u32(tb[TCA_FQ_CODEL_LIMIT]); 340 341 if (tb[TCA_FQ_CODEL_ECN]) 342 q->cparams.ecn = !!nla_get_u32(tb[TCA_FQ_CODEL_ECN]); 343 344 if (tb[TCA_FQ_CODEL_QUANTUM]) 345 q->quantum = max(256U, nla_get_u32(tb[TCA_FQ_CODEL_QUANTUM])); 346 347 while (sch->q.qlen > sch->limit) { 348 struct sk_buff *skb = fq_codel_dequeue(sch); 349 350 kfree_skb(skb); 351 q->cstats.drop_count++; 352 } 353 qdisc_tree_decrease_qlen(sch, q->cstats.drop_count); 354 q->cstats.drop_count = 0; 355 356 sch_tree_unlock(sch); 357 return 0; 358 } 359 360 static void *fq_codel_zalloc(size_t sz) 361 { 362 void *ptr = kzalloc(sz, GFP_KERNEL | __GFP_NOWARN); 363 364 if (!ptr) 365 ptr = vzalloc(sz); 366 return ptr; 367 } 368 369 static void fq_codel_free(void *addr) 370 { 371 kvfree(addr); 372 } 373 374 static void fq_codel_destroy(struct Qdisc *sch) 375 { 376 struct fq_codel_sched_data *q = qdisc_priv(sch); 377 378 tcf_destroy_chain(&q->filter_list); 379 fq_codel_free(q->backlogs); 380 fq_codel_free(q->flows); 381 } 382 383 static int fq_codel_init(struct Qdisc *sch, struct nlattr *opt) 384 { 385 struct fq_codel_sched_data *q = qdisc_priv(sch); 386 int i; 387 388 sch->limit = 10*1024; 389 q->flows_cnt = 1024; 390 q->quantum = psched_mtu(qdisc_dev(sch)); 391 q->perturbation = prandom_u32(); 392 INIT_LIST_HEAD(&q->new_flows); 393 INIT_LIST_HEAD(&q->old_flows); 394 codel_params_init(&q->cparams); 395 codel_stats_init(&q->cstats); 396 q->cparams.ecn = true; 397 398 if (opt) { 399 int err = fq_codel_change(sch, opt); 400 if (err) 401 return err; 402 } 403 404 if (!q->flows) { 405 q->flows = fq_codel_zalloc(q->flows_cnt * 406 sizeof(struct fq_codel_flow)); 407 if (!q->flows) 408 return -ENOMEM; 409 q->backlogs = fq_codel_zalloc(q->flows_cnt * sizeof(u32)); 410 if (!q->backlogs) { 411 fq_codel_free(q->flows); 412 return -ENOMEM; 413 } 414 for (i = 0; i < q->flows_cnt; i++) { 415 struct fq_codel_flow *flow = q->flows + i; 416 417 INIT_LIST_HEAD(&flow->flowchain); 418 codel_vars_init(&flow->cvars); 419 } 420 } 421 if (sch->limit >= 1) 422 sch->flags |= TCQ_F_CAN_BYPASS; 423 else 424 sch->flags &= ~TCQ_F_CAN_BYPASS; 425 return 0; 426 } 427 428 static int fq_codel_dump(struct Qdisc *sch, struct sk_buff *skb) 429 { 430 struct fq_codel_sched_data *q = qdisc_priv(sch); 431 struct nlattr *opts; 432 433 opts = nla_nest_start(skb, TCA_OPTIONS); 434 if (opts == NULL) 435 goto nla_put_failure; 436 437 if (nla_put_u32(skb, TCA_FQ_CODEL_TARGET, 438 codel_time_to_us(q->cparams.target)) || 439 nla_put_u32(skb, TCA_FQ_CODEL_LIMIT, 440 sch->limit) || 441 nla_put_u32(skb, TCA_FQ_CODEL_INTERVAL, 442 codel_time_to_us(q->cparams.interval)) || 443 nla_put_u32(skb, TCA_FQ_CODEL_ECN, 444 q->cparams.ecn) || 445 nla_put_u32(skb, TCA_FQ_CODEL_QUANTUM, 446 q->quantum) || 447 nla_put_u32(skb, TCA_FQ_CODEL_FLOWS, 448 q->flows_cnt)) 449 goto nla_put_failure; 450 451 return nla_nest_end(skb, opts); 452 453 nla_put_failure: 454 return -1; 455 } 456 457 static int fq_codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d) 458 { 459 struct fq_codel_sched_data *q = qdisc_priv(sch); 460 struct tc_fq_codel_xstats st = { 461 .type = TCA_FQ_CODEL_XSTATS_QDISC, 462 }; 463 struct list_head *pos; 464 465 st.qdisc_stats.maxpacket = q->cstats.maxpacket; 466 st.qdisc_stats.drop_overlimit = q->drop_overlimit; 467 st.qdisc_stats.ecn_mark = q->cstats.ecn_mark; 468 st.qdisc_stats.new_flow_count = q->new_flow_count; 469 470 list_for_each(pos, &q->new_flows) 471 st.qdisc_stats.new_flows_len++; 472 473 list_for_each(pos, &q->old_flows) 474 st.qdisc_stats.old_flows_len++; 475 476 return gnet_stats_copy_app(d, &st, sizeof(st)); 477 } 478 479 static struct Qdisc *fq_codel_leaf(struct Qdisc *sch, unsigned long arg) 480 { 481 return NULL; 482 } 483 484 static unsigned long fq_codel_get(struct Qdisc *sch, u32 classid) 485 { 486 return 0; 487 } 488 489 static unsigned long fq_codel_bind(struct Qdisc *sch, unsigned long parent, 490 u32 classid) 491 { 492 /* we cannot bypass queue discipline anymore */ 493 sch->flags &= ~TCQ_F_CAN_BYPASS; 494 return 0; 495 } 496 497 static void fq_codel_put(struct Qdisc *q, unsigned long cl) 498 { 499 } 500 501 static struct tcf_proto __rcu **fq_codel_find_tcf(struct Qdisc *sch, 502 unsigned long cl) 503 { 504 struct fq_codel_sched_data *q = qdisc_priv(sch); 505 506 if (cl) 507 return NULL; 508 return &q->filter_list; 509 } 510 511 static int fq_codel_dump_class(struct Qdisc *sch, unsigned long cl, 512 struct sk_buff *skb, struct tcmsg *tcm) 513 { 514 tcm->tcm_handle |= TC_H_MIN(cl); 515 return 0; 516 } 517 518 static int fq_codel_dump_class_stats(struct Qdisc *sch, unsigned long cl, 519 struct gnet_dump *d) 520 { 521 struct fq_codel_sched_data *q = qdisc_priv(sch); 522 u32 idx = cl - 1; 523 struct gnet_stats_queue qs = { 0 }; 524 struct tc_fq_codel_xstats xstats; 525 526 if (idx < q->flows_cnt) { 527 const struct fq_codel_flow *flow = &q->flows[idx]; 528 const struct sk_buff *skb = flow->head; 529 530 memset(&xstats, 0, sizeof(xstats)); 531 xstats.type = TCA_FQ_CODEL_XSTATS_CLASS; 532 xstats.class_stats.deficit = flow->deficit; 533 xstats.class_stats.ldelay = 534 codel_time_to_us(flow->cvars.ldelay); 535 xstats.class_stats.count = flow->cvars.count; 536 xstats.class_stats.lastcount = flow->cvars.lastcount; 537 xstats.class_stats.dropping = flow->cvars.dropping; 538 if (flow->cvars.dropping) { 539 codel_tdiff_t delta = flow->cvars.drop_next - 540 codel_get_time(); 541 542 xstats.class_stats.drop_next = (delta >= 0) ? 543 codel_time_to_us(delta) : 544 -codel_time_to_us(-delta); 545 } 546 while (skb) { 547 qs.qlen++; 548 skb = skb->next; 549 } 550 qs.backlog = q->backlogs[idx]; 551 qs.drops = flow->dropped; 552 } 553 if (gnet_stats_copy_queue(d, NULL, &qs, 0) < 0) 554 return -1; 555 if (idx < q->flows_cnt) 556 return gnet_stats_copy_app(d, &xstats, sizeof(xstats)); 557 return 0; 558 } 559 560 static void fq_codel_walk(struct Qdisc *sch, struct qdisc_walker *arg) 561 { 562 struct fq_codel_sched_data *q = qdisc_priv(sch); 563 unsigned int i; 564 565 if (arg->stop) 566 return; 567 568 for (i = 0; i < q->flows_cnt; i++) { 569 if (list_empty(&q->flows[i].flowchain) || 570 arg->count < arg->skip) { 571 arg->count++; 572 continue; 573 } 574 if (arg->fn(sch, i + 1, arg) < 0) { 575 arg->stop = 1; 576 break; 577 } 578 arg->count++; 579 } 580 } 581 582 static const struct Qdisc_class_ops fq_codel_class_ops = { 583 .leaf = fq_codel_leaf, 584 .get = fq_codel_get, 585 .put = fq_codel_put, 586 .tcf_chain = fq_codel_find_tcf, 587 .bind_tcf = fq_codel_bind, 588 .unbind_tcf = fq_codel_put, 589 .dump = fq_codel_dump_class, 590 .dump_stats = fq_codel_dump_class_stats, 591 .walk = fq_codel_walk, 592 }; 593 594 static struct Qdisc_ops fq_codel_qdisc_ops __read_mostly = { 595 .cl_ops = &fq_codel_class_ops, 596 .id = "fq_codel", 597 .priv_size = sizeof(struct fq_codel_sched_data), 598 .enqueue = fq_codel_enqueue, 599 .dequeue = fq_codel_dequeue, 600 .peek = qdisc_peek_dequeued, 601 .drop = fq_codel_drop, 602 .init = fq_codel_init, 603 .reset = fq_codel_reset, 604 .destroy = fq_codel_destroy, 605 .change = fq_codel_change, 606 .dump = fq_codel_dump, 607 .dump_stats = fq_codel_dump_stats, 608 .owner = THIS_MODULE, 609 }; 610 611 static int __init fq_codel_module_init(void) 612 { 613 return register_qdisc(&fq_codel_qdisc_ops); 614 } 615 616 static void __exit fq_codel_module_exit(void) 617 { 618 unregister_qdisc(&fq_codel_qdisc_ops); 619 } 620 621 module_init(fq_codel_module_init) 622 module_exit(fq_codel_module_exit) 623 MODULE_AUTHOR("Eric Dumazet"); 624 MODULE_LICENSE("GPL"); 625