1 /* 2 * net/sched/sch_fifo.c The simplest FIFO queue. 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 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> 10 */ 11 12 #include <linux/module.h> 13 #include <linux/slab.h> 14 #include <linux/types.h> 15 #include <linux/kernel.h> 16 #include <linux/errno.h> 17 #include <linux/skbuff.h> 18 #include <net/pkt_sched.h> 19 20 /* 1 band FIFO pseudo-"scheduler" */ 21 22 static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch, 23 struct sk_buff **to_free) 24 { 25 if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit)) 26 return qdisc_enqueue_tail(skb, sch); 27 28 return qdisc_drop(skb, sch, to_free); 29 } 30 31 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch, 32 struct sk_buff **to_free) 33 { 34 if (likely(sch->q.qlen < sch->limit)) 35 return qdisc_enqueue_tail(skb, sch); 36 37 return qdisc_drop(skb, sch, to_free); 38 } 39 40 static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch, 41 struct sk_buff **to_free) 42 { 43 unsigned int prev_backlog; 44 45 if (likely(sch->q.qlen < sch->limit)) 46 return qdisc_enqueue_tail(skb, sch); 47 48 prev_backlog = sch->qstats.backlog; 49 /* queue full, remove one skb to fulfill the limit */ 50 __qdisc_queue_drop_head(sch, &sch->q, to_free); 51 qdisc_qstats_drop(sch); 52 qdisc_enqueue_tail(skb, sch); 53 54 qdisc_tree_reduce_backlog(sch, 0, prev_backlog - sch->qstats.backlog); 55 return NET_XMIT_CN; 56 } 57 58 static int fifo_init(struct Qdisc *sch, struct nlattr *opt, 59 struct netlink_ext_ack *extack) 60 { 61 bool bypass; 62 bool is_bfifo = sch->ops == &bfifo_qdisc_ops; 63 64 if (opt == NULL) { 65 u32 limit = qdisc_dev(sch)->tx_queue_len; 66 67 if (is_bfifo) 68 limit *= psched_mtu(qdisc_dev(sch)); 69 70 sch->limit = limit; 71 } else { 72 struct tc_fifo_qopt *ctl = nla_data(opt); 73 74 if (nla_len(opt) < sizeof(*ctl)) 75 return -EINVAL; 76 77 sch->limit = ctl->limit; 78 } 79 80 if (is_bfifo) 81 bypass = sch->limit >= psched_mtu(qdisc_dev(sch)); 82 else 83 bypass = sch->limit >= 1; 84 85 if (bypass) 86 sch->flags |= TCQ_F_CAN_BYPASS; 87 else 88 sch->flags &= ~TCQ_F_CAN_BYPASS; 89 return 0; 90 } 91 92 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb) 93 { 94 struct tc_fifo_qopt opt = { .limit = sch->limit }; 95 96 if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt)) 97 goto nla_put_failure; 98 return skb->len; 99 100 nla_put_failure: 101 return -1; 102 } 103 104 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = { 105 .id = "pfifo", 106 .priv_size = 0, 107 .enqueue = pfifo_enqueue, 108 .dequeue = qdisc_dequeue_head, 109 .peek = qdisc_peek_head, 110 .init = fifo_init, 111 .reset = qdisc_reset_queue, 112 .change = fifo_init, 113 .dump = fifo_dump, 114 .owner = THIS_MODULE, 115 }; 116 EXPORT_SYMBOL(pfifo_qdisc_ops); 117 118 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = { 119 .id = "bfifo", 120 .priv_size = 0, 121 .enqueue = bfifo_enqueue, 122 .dequeue = qdisc_dequeue_head, 123 .peek = qdisc_peek_head, 124 .init = fifo_init, 125 .reset = qdisc_reset_queue, 126 .change = fifo_init, 127 .dump = fifo_dump, 128 .owner = THIS_MODULE, 129 }; 130 EXPORT_SYMBOL(bfifo_qdisc_ops); 131 132 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = { 133 .id = "pfifo_head_drop", 134 .priv_size = 0, 135 .enqueue = pfifo_tail_enqueue, 136 .dequeue = qdisc_dequeue_head, 137 .peek = qdisc_peek_head, 138 .init = fifo_init, 139 .reset = qdisc_reset_queue, 140 .change = fifo_init, 141 .dump = fifo_dump, 142 .owner = THIS_MODULE, 143 }; 144 145 /* Pass size change message down to embedded FIFO */ 146 int fifo_set_limit(struct Qdisc *q, unsigned int limit) 147 { 148 struct nlattr *nla; 149 int ret = -ENOMEM; 150 151 /* Hack to avoid sending change message to non-FIFO */ 152 if (strncmp(q->ops->id + 1, "fifo", 4) != 0) 153 return 0; 154 155 nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL); 156 if (nla) { 157 nla->nla_type = RTM_NEWQDISC; 158 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt)); 159 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit; 160 161 ret = q->ops->change(q, nla, NULL); 162 kfree(nla); 163 } 164 return ret; 165 } 166 EXPORT_SYMBOL(fifo_set_limit); 167 168 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops, 169 unsigned int limit, 170 struct netlink_ext_ack *extack) 171 { 172 struct Qdisc *q; 173 int err = -ENOMEM; 174 175 q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1), 176 extack); 177 if (q) { 178 err = fifo_set_limit(q, limit); 179 if (err < 0) { 180 qdisc_destroy(q); 181 q = NULL; 182 } 183 } 184 185 return q ? : ERR_PTR(err); 186 } 187 EXPORT_SYMBOL(fifo_create_dflt); 188