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 { 24 if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit)) 25 return qdisc_enqueue_tail(skb, sch); 26 27 return qdisc_reshape_fail(skb, sch); 28 } 29 30 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch) 31 { 32 if (likely(skb_queue_len(&sch->q) < sch->limit)) 33 return qdisc_enqueue_tail(skb, sch); 34 35 return qdisc_reshape_fail(skb, sch); 36 } 37 38 static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch) 39 { 40 if (likely(skb_queue_len(&sch->q) < sch->limit)) 41 return qdisc_enqueue_tail(skb, sch); 42 43 /* queue full, remove one skb to fulfill the limit */ 44 __qdisc_queue_drop_head(sch, &sch->q); 45 sch->qstats.drops++; 46 qdisc_enqueue_tail(skb, sch); 47 48 return NET_XMIT_CN; 49 } 50 51 static int fifo_init(struct Qdisc *sch, struct nlattr *opt) 52 { 53 bool bypass; 54 bool is_bfifo = sch->ops == &bfifo_qdisc_ops; 55 56 if (opt == NULL) { 57 u32 limit = qdisc_dev(sch)->tx_queue_len ? : 1; 58 59 if (is_bfifo) 60 limit *= psched_mtu(qdisc_dev(sch)); 61 62 sch->limit = limit; 63 } else { 64 struct tc_fifo_qopt *ctl = nla_data(opt); 65 66 if (nla_len(opt) < sizeof(*ctl)) 67 return -EINVAL; 68 69 sch->limit = ctl->limit; 70 } 71 72 if (is_bfifo) 73 bypass = sch->limit >= psched_mtu(qdisc_dev(sch)); 74 else 75 bypass = sch->limit >= 1; 76 77 if (bypass) 78 sch->flags |= TCQ_F_CAN_BYPASS; 79 else 80 sch->flags &= ~TCQ_F_CAN_BYPASS; 81 return 0; 82 } 83 84 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb) 85 { 86 struct tc_fifo_qopt opt = { .limit = sch->limit }; 87 88 if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt)) 89 goto nla_put_failure; 90 return skb->len; 91 92 nla_put_failure: 93 return -1; 94 } 95 96 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = { 97 .id = "pfifo", 98 .priv_size = 0, 99 .enqueue = pfifo_enqueue, 100 .dequeue = qdisc_dequeue_head, 101 .peek = qdisc_peek_head, 102 .drop = qdisc_queue_drop, 103 .init = fifo_init, 104 .reset = qdisc_reset_queue, 105 .change = fifo_init, 106 .dump = fifo_dump, 107 .owner = THIS_MODULE, 108 }; 109 EXPORT_SYMBOL(pfifo_qdisc_ops); 110 111 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = { 112 .id = "bfifo", 113 .priv_size = 0, 114 .enqueue = bfifo_enqueue, 115 .dequeue = qdisc_dequeue_head, 116 .peek = qdisc_peek_head, 117 .drop = qdisc_queue_drop, 118 .init = fifo_init, 119 .reset = qdisc_reset_queue, 120 .change = fifo_init, 121 .dump = fifo_dump, 122 .owner = THIS_MODULE, 123 }; 124 EXPORT_SYMBOL(bfifo_qdisc_ops); 125 126 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = { 127 .id = "pfifo_head_drop", 128 .priv_size = 0, 129 .enqueue = pfifo_tail_enqueue, 130 .dequeue = qdisc_dequeue_head, 131 .peek = qdisc_peek_head, 132 .drop = qdisc_queue_drop_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