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 pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc* sch)
  47 {
  48         struct sk_buff *skb_head;
  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         skb_head = qdisc_dequeue_head(sch);
  56         sch->bstats.bytes -= qdisc_pkt_len(skb_head);
  57         sch->bstats.packets--;
  58         sch->qstats.drops++;
  59         kfree_skb(skb_head);
  60
  61         qdisc_enqueue_tail(skb, sch);
  62
  63         return NET_XMIT_CN;
  64 }
  65
  66 static int fifo_init(struct Qdisc *sch, struct nlattr *opt)
  67 {
  68         struct fifo_sched_data *q = qdisc_priv(sch);
  69
  70         if (opt == NULL) {
  71                 u32 limit = qdisc_dev(sch)->tx_queue_len ? : 1;
  72
  73                 if (sch->ops == &bfifo_qdisc_ops)
  74                         limit *= psched_mtu(qdisc_dev(sch));
  75
  76                 q->limit = limit;
  77         } else {
  78                 struct tc_fifo_qopt *ctl = nla_data(opt);
  79
  80                 if (nla_len(opt) < sizeof(*ctl))
  81                         return -EINVAL;
  82
  83                 q->limit = ctl->limit;
  84         }
  85
  86         return 0;
  87 }
  88
  89 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
  90 {
  91         struct fifo_sched_data *q = qdisc_priv(sch);
  92         struct tc_fifo_qopt opt = { .limit = q->limit };
  93
  94         NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
  95         return skb->len;
  96
  97 nla_put_failure:
  98         return -1;
  99 }
 100
 101 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
 102         .id             =       "pfifo",
 103         .priv_size      =       sizeof(struct fifo_sched_data),
 104         .enqueue        =       pfifo_enqueue,
 105         .dequeue        =       qdisc_dequeue_head,
 106         .peek           =       qdisc_peek_head,
 107         .drop           =       qdisc_queue_drop,
 108         .init           =       fifo_init,
 109         .reset          =       qdisc_reset_queue,
 110         .change         =       fifo_init,
 111         .dump           =       fifo_dump,
 112         .owner          =       THIS_MODULE,
 113 };
 114 EXPORT_SYMBOL(pfifo_qdisc_ops);
 115
 116 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
 117         .id             =       "bfifo",
 118         .priv_size      =       sizeof(struct fifo_sched_data),
 119         .enqueue        =       bfifo_enqueue,
 120         .dequeue        =       qdisc_dequeue_head,
 121         .peek           =       qdisc_peek_head,
 122         .drop           =       qdisc_queue_drop,
 123         .init           =       fifo_init,
 124         .reset          =       qdisc_reset_queue,
 125         .change         =       fifo_init,
 126         .dump           =       fifo_dump,
 127         .owner          =       THIS_MODULE,
 128 };
 129 EXPORT_SYMBOL(bfifo_qdisc_ops);
 130
 131 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
 132         .id             =       "pfifo_head_drop",
 133         .priv_size      =       sizeof(struct fifo_sched_data),
 134         .enqueue        =       pfifo_tail_enqueue,
 135         .dequeue        =       qdisc_dequeue_head,
 136         .peek           =       qdisc_peek_head,
 137         .drop           =       qdisc_queue_drop_head,
 138         .init           =       fifo_init,
 139         .reset          =       qdisc_reset_queue,
 140         .change         =       fifo_init,
 141         .dump           =       fifo_dump,
 142         .owner          =       THIS_MODULE,
 143 };
 144
 145 /* Pass size change message down to embedded FIFO */
 146 int fifo_set_limit(struct Qdisc *q, unsigned int limit)
 147 {
 148         struct nlattr *nla;
 149         int ret = -ENOMEM;
 150
 151         /* Hack to avoid sending change message to non-FIFO */
 152         if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
 153                 return 0;
 154
 155         nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
 156         if (nla) {
 157                 nla->nla_type = RTM_NEWQDISC;
 158                 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
 159                 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
 160
 161                 ret = q->ops->change(q, nla);
 162                 kfree(nla);
 163         }
 164         return ret;
 165 }
 166 EXPORT_SYMBOL(fifo_set_limit);
 167
 168 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
 169                                unsigned int limit)
 170 {
 171         struct Qdisc *q;
 172         int err = -ENOMEM;
 173
 174         q = qdisc_create_dflt(qdisc_dev(sch), sch->dev_queue,
 175                               ops, TC_H_MAKE(sch->handle, 1));
 176         if (q) {
 177                 err = fifo_set_limit(q, limit);
 178                 if (err < 0) {
 179                         qdisc_destroy(q);
 180                         q = NULL;
 181                 }
 182         }
 183
 184         return q ? : ERR_PTR(err);
 185 }
 186 EXPORT_SYMBOL(fifo_create_dflt);