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