linux/net/sched/sch_fifo.c
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   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
  22struct fifo_sched_data
  23{
  24        u32 limit;
  25};
  26
  27static 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
  37static 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
  47static 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
  67static 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
  90static 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
  98nla_put_failure:
  99        return -1;
 100}
 101
 102struct 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};
 115EXPORT_SYMBOL(pfifo_qdisc_ops);
 116
 117struct 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};
 130EXPORT_SYMBOL(bfifo_qdisc_ops);
 131
 132struct 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 */
 147int 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}
 167EXPORT_SYMBOL(fifo_set_limit);
 168
 169struct 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}
 186EXPORT_SYMBOL(fifo_create_dflt);
 187