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 sch->qstats.backlog -= 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 kfree_skb(skb); 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 /* We cant call qdisc_tree_reduce_backlog() if our qlen is 0, 69 * or HTB crashes. Defer it for next round. 70 */ 71 if (q->stats.drop_count && sch->q.qlen) { 72 qdisc_tree_reduce_backlog(sch, q->stats.drop_count, q->stats.drop_len); 73 q->stats.drop_count = 0; 74 q->stats.drop_len = 0; 75 } 76 if (skb) 77 qdisc_bstats_update(sch, skb); 78 return skb; 79 } 80 81 static int codel_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch, 82 struct sk_buff **to_free) 83 { 84 struct codel_sched_data *q; 85 86 if (likely(qdisc_qlen(sch) < sch->limit)) { 87 codel_set_enqueue_time(skb); 88 return qdisc_enqueue_tail(skb, sch); 89 } 90 q = qdisc_priv(sch); 91 q->drop_overlimit++; 92 return qdisc_drop(skb, sch, to_free); 93 } 94 95 static const struct nla_policy codel_policy[TCA_CODEL_MAX + 1] = { 96 [TCA_CODEL_TARGET] = { .type = NLA_U32 }, 97 [TCA_CODEL_LIMIT] = { .type = NLA_U32 }, 98 [TCA_CODEL_INTERVAL] = { .type = NLA_U32 }, 99 [TCA_CODEL_ECN] = { .type = NLA_U32 }, 100 [TCA_CODEL_CE_THRESHOLD]= { .type = NLA_U32 }, 101 }; 102 103 static int codel_change(struct Qdisc *sch, struct nlattr *opt, 104 struct netlink_ext_ack *extack) 105 { 106 struct codel_sched_data *q = qdisc_priv(sch); 107 struct nlattr *tb[TCA_CODEL_MAX + 1]; 108 unsigned int qlen, dropped = 0; 109 int err; 110 111 err = nla_parse_nested_deprecated(tb, TCA_CODEL_MAX, opt, 112 codel_policy, NULL); 113 if (err < 0) 114 return err; 115 116 sch_tree_lock(sch); 117 118 if (tb[TCA_CODEL_TARGET]) { 119 u32 target = nla_get_u32(tb[TCA_CODEL_TARGET]); 120 121 q->params.target = ((u64)target * NSEC_PER_USEC) >> CODEL_SHIFT; 122 } 123 124 if (tb[TCA_CODEL_CE_THRESHOLD]) { 125 u64 val = nla_get_u32(tb[TCA_CODEL_CE_THRESHOLD]); 126 127 q->params.ce_threshold = (val * NSEC_PER_USEC) >> CODEL_SHIFT; 128 } 129 130 if (tb[TCA_CODEL_INTERVAL]) { 131 u32 interval = nla_get_u32(tb[TCA_CODEL_INTERVAL]); 132 133 q->params.interval = ((u64)interval * NSEC_PER_USEC) >> CODEL_SHIFT; 134 } 135 136 if (tb[TCA_CODEL_LIMIT]) 137 sch->limit = nla_get_u32(tb[TCA_CODEL_LIMIT]); 138 139 if (tb[TCA_CODEL_ECN]) 140 q->params.ecn = !!nla_get_u32(tb[TCA_CODEL_ECN]); 141 142 qlen = sch->q.qlen; 143 while (sch->q.qlen > sch->limit) { 144 struct sk_buff *skb = __qdisc_dequeue_head(&sch->q); 145 146 dropped += qdisc_pkt_len(skb); 147 qdisc_qstats_backlog_dec(sch, skb); 148 rtnl_qdisc_drop(skb, sch); 149 } 150 qdisc_tree_reduce_backlog(sch, qlen - sch->q.qlen, dropped); 151 152 sch_tree_unlock(sch); 153 return 0; 154 } 155 156 static int codel_init(struct Qdisc *sch, struct nlattr *opt, 157 struct netlink_ext_ack *extack) 158 { 159 struct codel_sched_data *q = qdisc_priv(sch); 160 161 sch->limit = DEFAULT_CODEL_LIMIT; 162 163 codel_params_init(&q->params); 164 codel_vars_init(&q->vars); 165 codel_stats_init(&q->stats); 166 q->params.mtu = psched_mtu(qdisc_dev(sch)); 167 168 if (opt) { 169 int err = codel_change(sch, opt, extack); 170 171 if (err) 172 return err; 173 } 174 175 if (sch->limit >= 1) 176 sch->flags |= TCQ_F_CAN_BYPASS; 177 else 178 sch->flags &= ~TCQ_F_CAN_BYPASS; 179 180 return 0; 181 } 182 183 static int codel_dump(struct Qdisc *sch, struct sk_buff *skb) 184 { 185 struct codel_sched_data *q = qdisc_priv(sch); 186 struct nlattr *opts; 187 188 opts = nla_nest_start_noflag(skb, TCA_OPTIONS); 189 if (opts == NULL) 190 goto nla_put_failure; 191 192 if (nla_put_u32(skb, TCA_CODEL_TARGET, 193 codel_time_to_us(q->params.target)) || 194 nla_put_u32(skb, TCA_CODEL_LIMIT, 195 sch->limit) || 196 nla_put_u32(skb, TCA_CODEL_INTERVAL, 197 codel_time_to_us(q->params.interval)) || 198 nla_put_u32(skb, TCA_CODEL_ECN, 199 q->params.ecn)) 200 goto nla_put_failure; 201 if (q->params.ce_threshold != CODEL_DISABLED_THRESHOLD && 202 nla_put_u32(skb, TCA_CODEL_CE_THRESHOLD, 203 codel_time_to_us(q->params.ce_threshold))) 204 goto nla_put_failure; 205 return nla_nest_end(skb, opts); 206 207 nla_put_failure: 208 nla_nest_cancel(skb, opts); 209 return -1; 210 } 211 212 static int codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d) 213 { 214 const struct codel_sched_data *q = qdisc_priv(sch); 215 struct tc_codel_xstats st = { 216 .maxpacket = q->stats.maxpacket, 217 .count = q->vars.count, 218 .lastcount = q->vars.lastcount, 219 .drop_overlimit = q->drop_overlimit, 220 .ldelay = codel_time_to_us(q->vars.ldelay), 221 .dropping = q->vars.dropping, 222 .ecn_mark = q->stats.ecn_mark, 223 .ce_mark = q->stats.ce_mark, 224 }; 225 226 if (q->vars.dropping) { 227 codel_tdiff_t delta = q->vars.drop_next - codel_get_time(); 228 229 if (delta >= 0) 230 st.drop_next = codel_time_to_us(delta); 231 else 232 st.drop_next = -codel_time_to_us(-delta); 233 } 234 235 return gnet_stats_copy_app(d, &st, sizeof(st)); 236 } 237 238 static void codel_reset(struct Qdisc *sch) 239 { 240 struct codel_sched_data *q = qdisc_priv(sch); 241 242 qdisc_reset_queue(sch); 243 codel_vars_init(&q->vars); 244 } 245 246 static struct Qdisc_ops codel_qdisc_ops __read_mostly = { 247 .id = "codel", 248 .priv_size = sizeof(struct codel_sched_data), 249 250 .enqueue = codel_qdisc_enqueue, 251 .dequeue = codel_qdisc_dequeue, 252 .peek = qdisc_peek_dequeued, 253 .init = codel_init, 254 .reset = codel_reset, 255 .change = codel_change, 256 .dump = codel_dump, 257 .dump_stats = codel_dump_stats, 258 .owner = THIS_MODULE, 259 }; 260 MODULE_ALIAS_NET_SCH("codel"); 261 262 static int __init codel_module_init(void) 263 { 264 return register_qdisc(&codel_qdisc_ops); 265 } 266 267 static void __exit codel_module_exit(void) 268 { 269 unregister_qdisc(&codel_qdisc_ops); 270 } 271 272 module_init(codel_module_init) 273 module_exit(codel_module_exit) 274 275 MODULE_DESCRIPTION("Controlled Delay queue discipline"); 276 MODULE_AUTHOR("Dave Taht"); 277 MODULE_AUTHOR("Eric Dumazet"); 278 MODULE_LICENSE("Dual BSD/GPL"); 279