1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * net/sched/sch_fifo.c The simplest FIFO queue. 4 * 5 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> 6 */ 7 8 #include <linux/module.h> 9 #include <linux/slab.h> 10 #include <linux/types.h> 11 #include <linux/kernel.h> 12 #include <linux/errno.h> 13 #include <linux/skbuff.h> 14 #include <net/pkt_sched.h> 15 #include <net/pkt_cls.h> 16 17 /* 1 band FIFO pseudo-"scheduler" */ 18 19 static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch, 20 struct sk_buff **to_free) 21 { 22 if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= 23 READ_ONCE(sch->limit))) 24 return qdisc_enqueue_tail(skb, sch); 25 26 return qdisc_drop(skb, sch, to_free); 27 } 28 29 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch, 30 struct sk_buff **to_free) 31 { 32 if (likely(sch->q.qlen < READ_ONCE(sch->limit))) 33 return qdisc_enqueue_tail(skb, sch); 34 35 return qdisc_drop(skb, sch, to_free); 36 } 37 38 static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch, 39 struct sk_buff **to_free) 40 { 41 unsigned int prev_backlog; 42 43 if (likely(sch->q.qlen < READ_ONCE(sch->limit))) 44 return qdisc_enqueue_tail(skb, sch); 45 46 prev_backlog = sch->qstats.backlog; 47 /* queue full, remove one skb to fulfill the limit */ 48 __qdisc_queue_drop_head(sch, &sch->q, to_free); 49 qdisc_qstats_drop(sch); 50 qdisc_enqueue_tail(skb, sch); 51 52 qdisc_tree_reduce_backlog(sch, 0, prev_backlog - sch->qstats.backlog); 53 return NET_XMIT_CN; 54 } 55 56 static void fifo_offload_init(struct Qdisc *sch) 57 { 58 struct net_device *dev = qdisc_dev(sch); 59 struct tc_fifo_qopt_offload qopt; 60 61 if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc) 62 return; 63 64 qopt.command = TC_FIFO_REPLACE; 65 qopt.handle = sch->handle; 66 qopt.parent = sch->parent; 67 dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_FIFO, &qopt); 68 } 69 70 static void fifo_offload_destroy(struct Qdisc *sch) 71 { 72 struct net_device *dev = qdisc_dev(sch); 73 struct tc_fifo_qopt_offload qopt; 74 75 if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc) 76 return; 77 78 qopt.command = TC_FIFO_DESTROY; 79 qopt.handle = sch->handle; 80 qopt.parent = sch->parent; 81 dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_FIFO, &qopt); 82 } 83 84 static int fifo_offload_dump(struct Qdisc *sch) 85 { 86 struct tc_fifo_qopt_offload qopt; 87 88 qopt.command = TC_FIFO_STATS; 89 qopt.handle = sch->handle; 90 qopt.parent = sch->parent; 91 qopt.stats.bstats = &sch->bstats; 92 qopt.stats.qstats = &sch->qstats; 93 94 return qdisc_offload_dump_helper(sch, TC_SETUP_QDISC_FIFO, &qopt); 95 } 96 97 static int __fifo_init(struct Qdisc *sch, struct nlattr *opt, 98 struct netlink_ext_ack *extack) 99 { 100 bool bypass; 101 bool is_bfifo = sch->ops == &bfifo_qdisc_ops; 102 103 if (opt == NULL) { 104 u32 limit = qdisc_dev(sch)->tx_queue_len; 105 106 if (is_bfifo) 107 limit *= psched_mtu(qdisc_dev(sch)); 108 109 WRITE_ONCE(sch->limit, limit); 110 } else { 111 struct tc_fifo_qopt *ctl = nla_data(opt); 112 113 if (nla_len(opt) < sizeof(*ctl)) 114 return -EINVAL; 115 116 WRITE_ONCE(sch->limit, ctl->limit); 117 } 118 119 if (is_bfifo) 120 bypass = sch->limit >= psched_mtu(qdisc_dev(sch)); 121 else 122 bypass = sch->limit >= 1; 123 124 if (bypass) 125 sch->flags |= TCQ_F_CAN_BYPASS; 126 else 127 sch->flags &= ~TCQ_F_CAN_BYPASS; 128 129 return 0; 130 } 131 132 static int fifo_init(struct Qdisc *sch, struct nlattr *opt, 133 struct netlink_ext_ack *extack) 134 { 135 int err; 136 137 err = __fifo_init(sch, opt, extack); 138 if (err) 139 return err; 140 141 fifo_offload_init(sch); 142 return 0; 143 } 144 145 static int fifo_hd_init(struct Qdisc *sch, struct nlattr *opt, 146 struct netlink_ext_ack *extack) 147 { 148 return __fifo_init(sch, opt, extack); 149 } 150 151 static void fifo_destroy(struct Qdisc *sch) 152 { 153 fifo_offload_destroy(sch); 154 } 155 156 static int __fifo_dump(struct Qdisc *sch, struct sk_buff *skb) 157 { 158 struct tc_fifo_qopt opt = { .limit = READ_ONCE(sch->limit) }; 159 160 if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt)) 161 goto nla_put_failure; 162 return skb->len; 163 164 nla_put_failure: 165 return -1; 166 } 167 168 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb) 169 { 170 int err; 171 172 err = fifo_offload_dump(sch); 173 if (err) 174 return err; 175 176 return __fifo_dump(sch, skb); 177 } 178 179 static int fifo_hd_dump(struct Qdisc *sch, struct sk_buff *skb) 180 { 181 return __fifo_dump(sch, skb); 182 } 183 184 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = { 185 .id = "pfifo", 186 .priv_size = 0, 187 .enqueue = pfifo_enqueue, 188 .dequeue = qdisc_dequeue_head, 189 .peek = qdisc_peek_head, 190 .init = fifo_init, 191 .destroy = fifo_destroy, 192 .reset = qdisc_reset_queue, 193 .change = fifo_init, 194 .dump = fifo_dump, 195 .owner = THIS_MODULE, 196 }; 197 EXPORT_SYMBOL(pfifo_qdisc_ops); 198 199 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = { 200 .id = "bfifo", 201 .priv_size = 0, 202 .enqueue = bfifo_enqueue, 203 .dequeue = qdisc_dequeue_head, 204 .peek = qdisc_peek_head, 205 .init = fifo_init, 206 .destroy = fifo_destroy, 207 .reset = qdisc_reset_queue, 208 .change = fifo_init, 209 .dump = fifo_dump, 210 .owner = THIS_MODULE, 211 }; 212 EXPORT_SYMBOL(bfifo_qdisc_ops); 213 214 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = { 215 .id = "pfifo_head_drop", 216 .priv_size = 0, 217 .enqueue = pfifo_tail_enqueue, 218 .dequeue = qdisc_dequeue_head, 219 .peek = qdisc_peek_head, 220 .init = fifo_hd_init, 221 .reset = qdisc_reset_queue, 222 .change = fifo_hd_init, 223 .dump = fifo_hd_dump, 224 .owner = THIS_MODULE, 225 }; 226 227 /* Pass size change message down to embedded FIFO */ 228 int fifo_set_limit(struct Qdisc *q, unsigned int limit) 229 { 230 struct nlattr *nla; 231 int ret = -ENOMEM; 232 233 /* Hack to avoid sending change message to non-FIFO */ 234 if (strncmp(q->ops->id + 1, "fifo", 4) != 0) 235 return 0; 236 237 if (!q->ops->change) 238 return 0; 239 240 nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL); 241 if (nla) { 242 nla->nla_type = RTM_NEWQDISC; 243 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt)); 244 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit; 245 246 ret = q->ops->change(q, nla, NULL); 247 kfree(nla); 248 } 249 return ret; 250 } 251 EXPORT_SYMBOL(fifo_set_limit); 252 253 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops, 254 unsigned int limit, 255 struct netlink_ext_ack *extack) 256 { 257 struct Qdisc *q; 258 int err = -ENOMEM; 259 260 q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1), 261 extack); 262 if (q) { 263 err = fifo_set_limit(q, limit); 264 if (err < 0) { 265 qdisc_put(q); 266 q = NULL; 267 } 268 } 269 270 return q ? : ERR_PTR(err); 271 } 272 EXPORT_SYMBOL(fifo_create_dflt); 273 MODULE_DESCRIPTION("Single queue packet and byte based First In First Out(P/BFIFO) scheduler"); 274