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 struct fifo_sched_data 23 { 24 u32 limit; 25 }; 26 27 static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc* sch) 28 { 29 struct fifo_sched_data *q = qdisc_priv(sch); 30 31 if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= q->limit)) 32 return qdisc_enqueue_tail(skb, sch); 33 34 return qdisc_reshape_fail(skb, sch); 35 } 36 37 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc* sch) 38 { 39 struct fifo_sched_data *q = qdisc_priv(sch); 40 41 if (likely(skb_queue_len(&sch->q) < q->limit)) 42 return qdisc_enqueue_tail(skb, sch); 43 44 return qdisc_reshape_fail(skb, sch); 45 } 46 47 static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc* sch) 48 { 49 struct fifo_sched_data *q = qdisc_priv(sch); 50 51 if (likely(skb_queue_len(&sch->q) < q->limit)) 52 return qdisc_enqueue_tail(skb, sch); 53 54 /* queue full, remove one skb to fulfill the limit */ 55 __qdisc_queue_drop_head(sch, &sch->q); 56 sch->qstats.drops++; 57 qdisc_enqueue_tail(skb, sch); 58 59 return NET_XMIT_CN; 60 } 61 62 static int fifo_init(struct Qdisc *sch, struct nlattr *opt) 63 { 64 struct fifo_sched_data *q = qdisc_priv(sch); 65 66 if (opt == NULL) { 67 u32 limit = qdisc_dev(sch)->tx_queue_len ? : 1; 68 69 if (sch->ops == &bfifo_qdisc_ops) 70 limit *= psched_mtu(qdisc_dev(sch)); 71 72 q->limit = limit; 73 } else { 74 struct tc_fifo_qopt *ctl = nla_data(opt); 75 76 if (nla_len(opt) < sizeof(*ctl)) 77 return -EINVAL; 78 79 q->limit = ctl->limit; 80 } 81 82 return 0; 83 } 84 85 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb) 86 { 87 struct fifo_sched_data *q = qdisc_priv(sch); 88 struct tc_fifo_qopt opt = { .limit = q->limit }; 89 90 NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt); 91 return skb->len; 92 93 nla_put_failure: 94 return -1; 95 } 96 97 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = { 98 .id = "pfifo", 99 .priv_size = sizeof(struct fifo_sched_data), 100 .enqueue = pfifo_enqueue, 101 .dequeue = qdisc_dequeue_head, 102 .peek = qdisc_peek_head, 103 .drop = qdisc_queue_drop, 104 .init = fifo_init, 105 .reset = qdisc_reset_queue, 106 .change = fifo_init, 107 .dump = fifo_dump, 108 .owner = THIS_MODULE, 109 }; 110 EXPORT_SYMBOL(pfifo_qdisc_ops); 111 112 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = { 113 .id = "bfifo", 114 .priv_size = sizeof(struct fifo_sched_data), 115 .enqueue = bfifo_enqueue, 116 .dequeue = qdisc_dequeue_head, 117 .peek = qdisc_peek_head, 118 .drop = qdisc_queue_drop, 119 .init = fifo_init, 120 .reset = qdisc_reset_queue, 121 .change = fifo_init, 122 .dump = fifo_dump, 123 .owner = THIS_MODULE, 124 }; 125 EXPORT_SYMBOL(bfifo_qdisc_ops); 126 127 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = { 128 .id = "pfifo_head_drop", 129 .priv_size = sizeof(struct fifo_sched_data), 130 .enqueue = pfifo_tail_enqueue, 131 .dequeue = qdisc_dequeue_head, 132 .peek = qdisc_peek_head, 133 .drop = qdisc_queue_drop_head, 134 .init = fifo_init, 135 .reset = qdisc_reset_queue, 136 .change = fifo_init, 137 .dump = fifo_dump, 138 .owner = THIS_MODULE, 139 }; 140 141 /* Pass size change message down to embedded FIFO */ 142 int fifo_set_limit(struct Qdisc *q, unsigned int limit) 143 { 144 struct nlattr *nla; 145 int ret = -ENOMEM; 146 147 /* Hack to avoid sending change message to non-FIFO */ 148 if (strncmp(q->ops->id + 1, "fifo", 4) != 0) 149 return 0; 150 151 nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL); 152 if (nla) { 153 nla->nla_type = RTM_NEWQDISC; 154 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt)); 155 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit; 156 157 ret = q->ops->change(q, nla); 158 kfree(nla); 159 } 160 return ret; 161 } 162 EXPORT_SYMBOL(fifo_set_limit); 163 164 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops, 165 unsigned int limit) 166 { 167 struct Qdisc *q; 168 int err = -ENOMEM; 169 170 q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1)); 171 if (q) { 172 err = fifo_set_limit(q, limit); 173 if (err < 0) { 174 qdisc_destroy(q); 175 q = NULL; 176 } 177 } 178 179 return q ? : ERR_PTR(err); 180 } 181 EXPORT_SYMBOL(fifo_create_dflt); 182