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/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);