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 sk_buff *skb_head;
  50         struct fifo_sched_data *q = qdisc_priv(sch);
  51
  52         if (likely(skb_queue_len(&sch->q) < q->limit))
  53                 return qdisc_enqueue_tail(skb, sch);
  54
  55         /* queue full, remove one skb to fulfill the limit */
  56         skb_head = qdisc_dequeue_head(sch);
  57         sch->bstats.bytes -= qdisc_pkt_len(skb_head);
  58         sch->bstats.packets--;
  59         sch->qstats.drops++;
  60         kfree_skb(skb_head);
  61
  62         qdisc_enqueue_tail(skb, sch);
  63
  64         return NET_XMIT_CN;
  65 }
  66
  67 static int fifo_init(struct Qdisc *sch, struct nlattr *opt)
  68 {
  69         struct fifo_sched_data *q = qdisc_priv(sch);
  70
  71         if (opt == NULL) {
  72                 u32 limit = qdisc_dev(sch)->tx_queue_len ? : 1;
  73
  74                 if (sch->ops == &bfifo_qdisc_ops)
  75                         limit *= psched_mtu(qdisc_dev(sch));
  76
  77                 q->limit = limit;
  78         } else {
  79                 struct tc_fifo_qopt *ctl = nla_data(opt);
  80
  81                 if (nla_len(opt) < sizeof(*ctl))
  82                         return -EINVAL;
  83
  84                 q->limit = ctl->limit;
  85         }
  86
  87         return 0;
  88 }
  89
  90 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
  91 {
  92         struct fifo_sched_data *q = qdisc_priv(sch);
  93         struct tc_fifo_qopt opt = { .limit = q->limit };
  94
  95         NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
  96         return skb->len;
  97
  98 nla_put_failure:
  99         return -1;
 100 }
 101
 102 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
 103         .id             =       "pfifo",
 104         .priv_size      =       sizeof(struct fifo_sched_data),
 105         .enqueue        =       pfifo_enqueue,
 106         .dequeue        =       qdisc_dequeue_head,
 107         .peek           =       qdisc_peek_head,
 108         .drop           =       qdisc_queue_drop,
 109         .init           =       fifo_init,
 110         .reset          =       qdisc_reset_queue,
 111         .change         =       fifo_init,
 112         .dump           =       fifo_dump,
 113         .owner          =       THIS_MODULE,
 114 };
 115 EXPORT_SYMBOL(pfifo_qdisc_ops);
 116
 117 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
 118         .id             =       "bfifo",
 119         .priv_size      =       sizeof(struct fifo_sched_data),
 120         .enqueue        =       bfifo_enqueue,
 121         .dequeue        =       qdisc_dequeue_head,
 122         .peek           =       qdisc_peek_head,
 123         .drop           =       qdisc_queue_drop,
 124         .init           =       fifo_init,
 125         .reset          =       qdisc_reset_queue,
 126         .change         =       fifo_init,
 127         .dump           =       fifo_dump,
 128         .owner          =       THIS_MODULE,
 129 };
 130 EXPORT_SYMBOL(bfifo_qdisc_ops);
 131
 132 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
 133         .id             =       "pfifo_head_drop",
 134         .priv_size      =       sizeof(struct fifo_sched_data),
 135         .enqueue        =       pfifo_tail_enqueue,
 136         .dequeue        =       qdisc_dequeue_head,
 137         .peek           =       qdisc_peek_head,
 138         .drop           =       qdisc_queue_drop_head,
 139         .init           =       fifo_init,
 140         .reset          =       qdisc_reset_queue,
 141         .change         =       fifo_init,
 142         .dump           =       fifo_dump,
 143         .owner          =       THIS_MODULE,
 144 };
 145
 146 /* Pass size change message down to embedded FIFO */
 147 int fifo_set_limit(struct Qdisc *q, unsigned int limit)
 148 {
 149         struct nlattr *nla;
 150         int ret = -ENOMEM;
 151
 152         /* Hack to avoid sending change message to non-FIFO */
 153         if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
 154                 return 0;
 155
 156         nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
 157         if (nla) {
 158                 nla->nla_type = RTM_NEWQDISC;
 159                 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
 160                 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
 161
 162                 ret = q->ops->change(q, nla);
 163                 kfree(nla);
 164         }
 165         return ret;
 166 }
 167 EXPORT_SYMBOL(fifo_set_limit);
 168
 169 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
 170                                unsigned int limit)
 171 {
 172         struct Qdisc *q;
 173         int err = -ENOMEM;
 174
 175         q = qdisc_create_dflt(sch->dev_queue, 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);