1 // SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause 2 /* 3 * Codel - The Controlled-Delay Active Queue Management algorithm 4 * 5 * Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com> 6 * Copyright (C) 2011-2012 Van Jacobson <van@pollere.net> 7 * 8 * Implemented on linux by : 9 * Copyright (C) 2012 Michael D. Taht <dave.taht@bufferbloat.net> 10 * Copyright (C) 2012,2015 Eric Dumazet <edumazet@google.com> 11 */ 12 13 #include <linux/module.h> 14 #include <linux/slab.h> 15 #include <linux/types.h> 16 #include <linux/kernel.h> 17 #include <linux/errno.h> 18 #include <linux/skbuff.h> 19 #include <linux/prefetch.h> 20 #include <net/pkt_sched.h> 21 #include <net/codel.h> 22 #include <net/codel_impl.h> 23 #include <net/codel_qdisc.h> 24 25 26 #define DEFAULT_CODEL_LIMIT 1000 27 28 struct codel_sched_data { 29 struct codel_params params; 30 struct codel_vars vars; 31 struct codel_stats stats; 32 u32 drop_overlimit; 33 }; 34 35 /* This is the specific function called from codel_dequeue() 36 * to dequeue a packet from queue. Note: backlog is handled in 37 * codel, we dont need to reduce it here. 38 */ 39 static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx) 40 { 41 struct Qdisc *sch = ctx; 42 struct sk_buff *skb = __qdisc_dequeue_head(&sch->q); 43 44 if (skb) { 45 qstats_backlog_sub(sch, qdisc_pkt_len(skb)); 46 prefetch(&skb->end); /* we'll need skb_shinfo() */ 47 } 48 return skb; 49 } 50 51 static void drop_func(struct sk_buff *skb, void *ctx) 52 { 53 struct Qdisc *sch = ctx; 54 55 qdisc_dequeue_drop(sch, skb, QDISC_DROP_CONGESTED); 56 qdisc_qstats_drop(sch); 57 } 58 59 static struct sk_buff *__codel_qdisc_dequeue(struct Qdisc *sch) 60 { 61 struct codel_sched_data *q = qdisc_priv(sch); 62 struct sk_buff *skb; 63 64 skb = codel_dequeue(sch, &sch->qstats.backlog, &q->params, &q->vars, 65 &q->stats, qdisc_pkt_len, codel_get_enqueue_time, 66 drop_func, dequeue_func); 67 68 if (skb) 69 qdisc_bstats_update(sch, skb); 70 return skb; 71 } 72 73 static void codel_dequeue_drop(struct Qdisc *sch) 74 { 75 struct codel_sched_data *q = qdisc_priv(sch); 76 77 if (q->stats.drop_count) { 78 qdisc_tree_reduce_backlog(sch, q->stats.drop_count, 79 q->stats.drop_len); 80 q->stats.drop_count = 0; 81 q->stats.drop_len = 0; 82 } 83 } 84 85 static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch) 86 { 87 struct sk_buff *skb; 88 89 skb = __codel_qdisc_dequeue(sch); 90 91 codel_dequeue_drop(sch); 92 93 return skb; 94 } 95 96 static struct sk_buff *codel_peek(struct Qdisc *sch) 97 { 98 struct sk_buff *skb = skb_peek(&sch->gso_skb); 99 100 if (!skb) { 101 skb = __codel_qdisc_dequeue(sch); 102 103 if (skb) { 104 __skb_queue_head(&sch->gso_skb, skb); 105 /* it's still part of the queue */ 106 qdisc_qstats_backlog_inc(sch, skb); 107 sch->q.qlen++; 108 } 109 110 codel_dequeue_drop(sch); 111 } 112 113 return skb; 114 } 115 116 static int codel_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch, 117 struct sk_buff **to_free) 118 { 119 struct codel_sched_data *q; 120 121 if (likely(qdisc_qlen(sch) < sch->limit)) { 122 codel_set_enqueue_time(skb); 123 return qdisc_enqueue_tail(skb, sch); 124 } 125 q = qdisc_priv(sch); 126 WRITE_ONCE(q->drop_overlimit, q->drop_overlimit + 1); 127 return qdisc_drop_reason(skb, sch, to_free, QDISC_DROP_OVERLIMIT); 128 } 129 130 static const struct nla_policy codel_policy[TCA_CODEL_MAX + 1] = { 131 [TCA_CODEL_TARGET] = { .type = NLA_U32 }, 132 [TCA_CODEL_LIMIT] = { .type = NLA_U32 }, 133 [TCA_CODEL_INTERVAL] = { .type = NLA_U32 }, 134 [TCA_CODEL_ECN] = { .type = NLA_U32 }, 135 [TCA_CODEL_CE_THRESHOLD]= { .type = NLA_U32 }, 136 }; 137 138 static int codel_change(struct Qdisc *sch, struct nlattr *opt, 139 struct netlink_ext_ack *extack) 140 { 141 unsigned int dropped_pkts = 0, dropped_bytes = 0; 142 struct codel_sched_data *q = qdisc_priv(sch); 143 struct nlattr *tb[TCA_CODEL_MAX + 1]; 144 int err; 145 146 err = nla_parse_nested_deprecated(tb, TCA_CODEL_MAX, opt, 147 codel_policy, NULL); 148 if (err < 0) 149 return err; 150 151 sch_tree_lock(sch); 152 153 if (tb[TCA_CODEL_TARGET]) { 154 u32 target = nla_get_u32(tb[TCA_CODEL_TARGET]); 155 156 WRITE_ONCE(q->params.target, 157 ((u64)target * NSEC_PER_USEC) >> CODEL_SHIFT); 158 } 159 160 if (tb[TCA_CODEL_CE_THRESHOLD]) { 161 u64 val = nla_get_u32(tb[TCA_CODEL_CE_THRESHOLD]); 162 163 WRITE_ONCE(q->params.ce_threshold, 164 (val * NSEC_PER_USEC) >> CODEL_SHIFT); 165 } 166 167 if (tb[TCA_CODEL_INTERVAL]) { 168 u32 interval = nla_get_u32(tb[TCA_CODEL_INTERVAL]); 169 170 WRITE_ONCE(q->params.interval, 171 ((u64)interval * NSEC_PER_USEC) >> CODEL_SHIFT); 172 } 173 174 if (tb[TCA_CODEL_LIMIT]) 175 WRITE_ONCE(sch->limit, 176 nla_get_u32(tb[TCA_CODEL_LIMIT])); 177 178 if (tb[TCA_CODEL_ECN]) 179 WRITE_ONCE(q->params.ecn, 180 !!nla_get_u32(tb[TCA_CODEL_ECN])); 181 182 while (sch->q.qlen > sch->limit) { 183 struct sk_buff *skb = qdisc_dequeue_internal(sch, true); 184 185 if (!skb) 186 break; 187 188 dropped_pkts++; 189 dropped_bytes += qdisc_pkt_len(skb); 190 rtnl_qdisc_drop(skb, sch); 191 } 192 qdisc_tree_reduce_backlog(sch, dropped_pkts, dropped_bytes); 193 194 sch_tree_unlock(sch); 195 return 0; 196 } 197 198 static int codel_init(struct Qdisc *sch, struct nlattr *opt, 199 struct netlink_ext_ack *extack) 200 { 201 struct codel_sched_data *q = qdisc_priv(sch); 202 203 sch->limit = DEFAULT_CODEL_LIMIT; 204 205 codel_params_init(&q->params); 206 codel_vars_init(&q->vars); 207 codel_stats_init(&q->stats); 208 q->params.mtu = psched_mtu(qdisc_dev(sch)); 209 210 if (opt) { 211 int err = codel_change(sch, opt, extack); 212 213 if (err) 214 return err; 215 } 216 217 if (sch->limit >= 1) 218 sch->flags |= TCQ_F_CAN_BYPASS; 219 else 220 sch->flags &= ~TCQ_F_CAN_BYPASS; 221 222 sch->flags |= TCQ_F_DEQUEUE_DROPS; 223 224 return 0; 225 } 226 227 static int codel_dump(struct Qdisc *sch, struct sk_buff *skb) 228 { 229 struct codel_sched_data *q = qdisc_priv(sch); 230 codel_time_t ce_threshold; 231 struct nlattr *opts; 232 233 opts = nla_nest_start_noflag(skb, TCA_OPTIONS); 234 if (opts == NULL) 235 goto nla_put_failure; 236 237 if (nla_put_u32(skb, TCA_CODEL_TARGET, 238 codel_time_to_us(READ_ONCE(q->params.target))) || 239 nla_put_u32(skb, TCA_CODEL_LIMIT, 240 READ_ONCE(sch->limit)) || 241 nla_put_u32(skb, TCA_CODEL_INTERVAL, 242 codel_time_to_us(READ_ONCE(q->params.interval))) || 243 nla_put_u32(skb, TCA_CODEL_ECN, 244 READ_ONCE(q->params.ecn))) 245 goto nla_put_failure; 246 ce_threshold = READ_ONCE(q->params.ce_threshold); 247 if (ce_threshold != CODEL_DISABLED_THRESHOLD && 248 nla_put_u32(skb, TCA_CODEL_CE_THRESHOLD, 249 codel_time_to_us(ce_threshold))) 250 goto nla_put_failure; 251 return nla_nest_end(skb, opts); 252 253 nla_put_failure: 254 nla_nest_cancel(skb, opts); 255 return -1; 256 } 257 258 static int codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d) 259 { 260 const struct codel_sched_data *q = qdisc_priv(sch); 261 struct tc_codel_xstats st = { 262 .maxpacket = READ_ONCE(q->stats.maxpacket), 263 .count = READ_ONCE(q->vars.count), 264 .lastcount = READ_ONCE(q->vars.lastcount), 265 .drop_overlimit = READ_ONCE(q->drop_overlimit), 266 .ldelay = codel_time_to_us(READ_ONCE(q->vars.ldelay)), 267 .dropping = READ_ONCE(q->vars.dropping), 268 .ecn_mark = READ_ONCE(q->stats.ecn_mark), 269 .ce_mark = READ_ONCE(q->stats.ce_mark), 270 }; 271 272 if (st.dropping) { 273 codel_tdiff_t delta = READ_ONCE(q->vars.drop_next) - codel_get_time(); 274 275 if (delta >= 0) 276 st.drop_next = codel_time_to_us(delta); 277 else 278 st.drop_next = -codel_time_to_us(-delta); 279 } 280 281 return gnet_stats_copy_app(d, &st, sizeof(st)); 282 } 283 284 static void codel_reset(struct Qdisc *sch) 285 { 286 struct codel_sched_data *q = qdisc_priv(sch); 287 288 qdisc_reset_queue(sch); 289 codel_vars_init(&q->vars); 290 } 291 292 static struct Qdisc_ops codel_qdisc_ops __read_mostly = { 293 .id = "codel", 294 .priv_size = sizeof(struct codel_sched_data), 295 296 .enqueue = codel_qdisc_enqueue, 297 .dequeue = codel_qdisc_dequeue, 298 .peek = codel_peek, 299 .init = codel_init, 300 .reset = codel_reset, 301 .change = codel_change, 302 .dump = codel_dump, 303 .dump_stats = codel_dump_stats, 304 .owner = THIS_MODULE, 305 }; 306 MODULE_ALIAS_NET_SCH("codel"); 307 308 static int __init codel_module_init(void) 309 { 310 return register_qdisc(&codel_qdisc_ops); 311 } 312 313 static void __exit codel_module_exit(void) 314 { 315 unregister_qdisc(&codel_qdisc_ops); 316 } 317 318 module_init(codel_module_init) 319 module_exit(codel_module_exit) 320 321 MODULE_DESCRIPTION("Controlled Delay queue discipline"); 322 MODULE_AUTHOR("Dave Taht"); 323 MODULE_AUTHOR("Eric Dumazet"); 324 MODULE_LICENSE("Dual BSD/GPL"); 325