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(skb_queue_len(&sch->q) < 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 if (likely(skb_queue_len(&sch->q) < sch->limit)) 44 return qdisc_enqueue_tail(skb, sch); 45 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 return NET_XMIT_CN; 52 } 53 54 static int fifo_init(struct Qdisc *sch, struct nlattr *opt) 55 { 56 bool bypass; 57 bool is_bfifo = sch->ops == &bfifo_qdisc_ops; 58 59 if (opt == NULL) { 60 u32 limit = qdisc_dev(sch)->tx_queue_len; 61 62 if (is_bfifo) 63 limit *= psched_mtu(qdisc_dev(sch)); 64 65 sch->limit = limit; 66 } else { 67 struct tc_fifo_qopt *ctl = nla_data(opt); 68 69 if (nla_len(opt) < sizeof(*ctl)) 70 return -EINVAL; 71 72 sch->limit = ctl->limit; 73 } 74 75 if (is_bfifo) 76 bypass = sch->limit >= psched_mtu(qdisc_dev(sch)); 77 else 78 bypass = sch->limit >= 1; 79 80 if (bypass) 81 sch->flags |= TCQ_F_CAN_BYPASS; 82 else 83 sch->flags &= ~TCQ_F_CAN_BYPASS; 84 return 0; 85 } 86 87 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb) 88 { 89 struct tc_fifo_qopt opt = { .limit = sch->limit }; 90 91 if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt)) 92 goto nla_put_failure; 93 return skb->len; 94 95 nla_put_failure: 96 return -1; 97 } 98 99 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = { 100 .id = "pfifo", 101 .priv_size = 0, 102 .enqueue = pfifo_enqueue, 103 .dequeue = qdisc_dequeue_head, 104 .peek = qdisc_peek_head, 105 .init = fifo_init, 106 .reset = qdisc_reset_queue, 107 .change = fifo_init, 108 .dump = fifo_dump, 109 .owner = THIS_MODULE, 110 }; 111 EXPORT_SYMBOL(pfifo_qdisc_ops); 112 113 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = { 114 .id = "bfifo", 115 .priv_size = 0, 116 .enqueue = bfifo_enqueue, 117 .dequeue = qdisc_dequeue_head, 118 .peek = qdisc_peek_head, 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 = 0, 130 .enqueue = pfifo_tail_enqueue, 131 .dequeue = qdisc_dequeue_head, 132 .peek = qdisc_peek_head, 133 .init = fifo_init, 134 .reset = qdisc_reset_queue, 135 .change = fifo_init, 136 .dump = fifo_dump, 137 .owner = THIS_MODULE, 138 }; 139 140 /* Pass size change message down to embedded FIFO */ 141 int fifo_set_limit(struct Qdisc *q, unsigned int limit) 142 { 143 struct nlattr *nla; 144 int ret = -ENOMEM; 145 146 /* Hack to avoid sending change message to non-FIFO */ 147 if (strncmp(q->ops->id + 1, "fifo", 4) != 0) 148 return 0; 149 150 nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL); 151 if (nla) { 152 nla->nla_type = RTM_NEWQDISC; 153 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt)); 154 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit; 155 156 ret = q->ops->change(q, nla); 157 kfree(nla); 158 } 159 return ret; 160 } 161 EXPORT_SYMBOL(fifo_set_limit); 162 163 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops, 164 unsigned int limit) 165 { 166 struct Qdisc *q; 167 int err = -ENOMEM; 168 169 q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1)); 170 if (q) { 171 err = fifo_set_limit(q, limit); 172 if (err < 0) { 173 qdisc_destroy(q); 174 q = NULL; 175 } 176 } 177 178 return q ? : ERR_PTR(err); 179 } 180 EXPORT_SYMBOL(fifo_create_dflt); 181