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