net/sched/sch_fifo.c

   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/types.h>
  14 #include <linux/kernel.h>
  15 #include <linux/errno.h>
  16 #include <linux/skbuff.h>
  17 #include <net/pkt_sched.h>
  18
  19 /* 1 band FIFO pseudo-"scheduler" */
  20
  21 struct fifo_sched_data
  22 {
  23         u32 limit;
  24 };
  25
  26 static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc* sch)
  27 {
  28         struct fifo_sched_data *q = qdisc_priv(sch);
  29
  30         if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= q->limit))
  31                 return qdisc_enqueue_tail(skb, sch);
  32
  33         return qdisc_reshape_fail(skb, sch);
  34 }
  35
  36 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc* sch)
  37 {
  38         struct fifo_sched_data *q = qdisc_priv(sch);
  39
  40         if (likely(skb_queue_len(&sch->q) < q->limit))
  41                 return qdisc_enqueue_tail(skb, sch);
  42
  43         return qdisc_reshape_fail(skb, sch);
  44 }
  45
  46 static int fifo_init(struct Qdisc *sch, struct nlattr *opt)
  47 {
  48         struct fifo_sched_data *q = qdisc_priv(sch);
  49
  50         if (opt == NULL) {
  51                 u32 limit = qdisc_dev(sch)->tx_queue_len ? : 1;
  52
  53                 if (sch->ops == &bfifo_qdisc_ops)
  54                         limit *= psched_mtu(qdisc_dev(sch));
  55
  56                 q->limit = limit;
  57         } else {
  58                 struct tc_fifo_qopt *ctl = nla_data(opt);
  59
  60                 if (nla_len(opt) < sizeof(*ctl))
  61                         return -EINVAL;
  62
  63                 q->limit = ctl->limit;
  64         }
  65
  66         return 0;
  67 }
  68
  69 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
  70 {
  71         struct fifo_sched_data *q = qdisc_priv(sch);
  72         struct tc_fifo_qopt opt = { .limit = q->limit };
  73
  74         NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
  75         return skb->len;
  76
  77 nla_put_failure:
  78         return -1;
  79 }
  80
  81 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
  82         .id             =       "pfifo",
  83         .priv_size      =       sizeof(struct fifo_sched_data),
  84         .enqueue        =       pfifo_enqueue,
  85         .dequeue        =       qdisc_dequeue_head,
  86         .peek           =       qdisc_peek_head,
  87         .drop           =       qdisc_queue_drop,
  88         .init           =       fifo_init,
  89         .reset          =       qdisc_reset_queue,
  90         .change         =       fifo_init,
  91         .dump           =       fifo_dump,
  92         .owner          =       THIS_MODULE,
  93 };
  94 EXPORT_SYMBOL(pfifo_qdisc_ops);
  95
  96 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
  97         .id             =       "bfifo",
  98         .priv_size      =       sizeof(struct fifo_sched_data),
  99         .enqueue        =       bfifo_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(bfifo_qdisc_ops);
 110
 111 /* Pass size change message down to embedded FIFO */
 112 int fifo_set_limit(struct Qdisc *q, unsigned int limit)
 113 {
 114         struct nlattr *nla;
 115         int ret = -ENOMEM;
 116
 117         /* Hack to avoid sending change message to non-FIFO */
 118         if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
 119                 return 0;
 120
 121         nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
 122         if (nla) {
 123                 nla->nla_type = RTM_NEWQDISC;
 124                 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
 125                 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
 126
 127                 ret = q->ops->change(q, nla);
 128                 kfree(nla);
 129         }
 130         return ret;
 131 }
 132 EXPORT_SYMBOL(fifo_set_limit);
 133
 134 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
 135                                unsigned int limit)
 136 {
 137         struct Qdisc *q;
 138         int err = -ENOMEM;
 139
 140         q = qdisc_create_dflt(qdisc_dev(sch), sch->dev_queue,
 141                               ops, TC_H_MAKE(sch->handle, 1));
 142         if (q) {
 143                 err = fifo_set_limit(q, limit);
 144                 if (err < 0) {
 145                         qdisc_destroy(q);
 146                         q = NULL;
 147                 }
 148         }
 149
 150         return q ? : ERR_PTR(err);
 151 }
 152 EXPORT_SYMBOL(fifo_create_dflt);