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
  22static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch)
  23{
  24        if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit))
  25                return qdisc_enqueue_tail(skb, sch);
  26
  27        return qdisc_reshape_fail(skb, sch);
  28}
  29
  30static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch)
  31{
  32        if (likely(skb_queue_len(&sch->q) < sch->limit))
  33                return qdisc_enqueue_tail(skb, sch);
  34
  35        return qdisc_reshape_fail(skb, sch);
  36}
  37
  38static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch)
  39{
  40        if (likely(skb_queue_len(&sch->q) < sch->limit))
  41                return qdisc_enqueue_tail(skb, sch);
  42
  43        /* queue full, remove one skb to fulfill the limit */
  44        __qdisc_queue_drop_head(sch, &sch->q);
  45        sch->qstats.drops++;
  46        qdisc_enqueue_tail(skb, sch);
  47
  48        return NET_XMIT_CN;
  49}
  50
  51static int fifo_init(struct Qdisc *sch, struct nlattr *opt)
  52{
  53        bool bypass;
  54        bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
  55
  56        if (opt == NULL) {
  57                u32 limit = qdisc_dev(sch)->tx_queue_len ? : 1;
  58
  59                if (is_bfifo)
  60                        limit *= psched_mtu(qdisc_dev(sch));
  61
  62                sch->limit = limit;
  63        } else {
  64                struct tc_fifo_qopt *ctl = nla_data(opt);
  65
  66                if (nla_len(opt) < sizeof(*ctl))
  67                        return -EINVAL;
  68
  69                sch->limit = ctl->limit;
  70        }
  71
  72        if (is_bfifo)
  73                bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
  74        else
  75                bypass = sch->limit >= 1;
  76
  77        if (bypass)
  78                sch->flags |= TCQ_F_CAN_BYPASS;
  79        else
  80                sch->flags &= ~TCQ_F_CAN_BYPASS;
  81        return 0;
  82}
  83
  84static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
  85{
  86        struct tc_fifo_qopt opt = { .limit = sch->limit };
  87
  88        if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
  89                goto nla_put_failure;
  90        return skb->len;
  91
  92nla_put_failure:
  93        return -1;
  94}
  95
  96struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
  97        .id             =       "pfifo",
  98        .priv_size      =       0,
  99        .enqueue        =       pfifo_enqueue,
 100        .dequeue        =       qdisc_dequeue_head,
 101        .peek           =       qdisc_peek_head,
 102        .drop           =       qdisc_queue_drop,
 103        .init           =       fifo_init,
 104        .reset          =       qdisc_reset_queue,
 105        .change         =       fifo_init,
 106        .dump           =       fifo_dump,
 107        .owner          =       THIS_MODULE,
 108};
 109EXPORT_SYMBOL(pfifo_qdisc_ops);
 110
 111struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
 112        .id             =       "bfifo",
 113        .priv_size      =       0,
 114        .enqueue        =       bfifo_enqueue,
 115        .dequeue        =       qdisc_dequeue_head,
 116        .peek           =       qdisc_peek_head,
 117        .drop           =       qdisc_queue_drop,
 118        .init           =       fifo_init,
 119        .reset          =       qdisc_reset_queue,
 120        .change         =       fifo_init,
 121        .dump           =       fifo_dump,
 122        .owner          =       THIS_MODULE,
 123};
 124EXPORT_SYMBOL(bfifo_qdisc_ops);
 125
 126struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
 127        .id             =       "pfifo_head_drop",
 128        .priv_size      =       0,
 129        .enqueue        =       pfifo_tail_enqueue,
 130        .dequeue        =       qdisc_dequeue_head,
 131        .peek           =       qdisc_peek_head,
 132        .drop           =       qdisc_queue_drop_head,
 133        .init           =       fifo_init,
 134        .reset          =       qdisc_reset_queue,
 135        .change         =       fifo_init,
 136        .dump           =       fifo_dump,
 137        .owner          =       THIS_MODULE,
 138};
 139
 140/* Pass size change message down to embedded FIFO */
 141int fifo_set_limit(struct Qdisc *q, unsigned int limit)
 142{
 143        struct nlattr *nla;
 144        int ret = -ENOMEM;
 145
 146        /* Hack to avoid sending change message to non-FIFO */
 147        if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
 148                return 0;
 149
 150        nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
 151        if (nla) {
 152                nla->nla_type = RTM_NEWQDISC;
 153                nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
 154                ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
 155
 156                ret = q->ops->change(q, nla);
 157                kfree(nla);
 158        }
 159        return ret;
 160}
 161EXPORT_SYMBOL(fifo_set_limit);
 162
 163struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
 164                               unsigned int limit)
 165{
 166        struct Qdisc *q;
 167        int err = -ENOMEM;
 168
 169        q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1));
 170        if (q) {
 171                err = fifo_set_limit(q, limit);
 172                if (err < 0) {
 173                        qdisc_destroy(q);
 174                        q = NULL;
 175                }
 176        }
 177
 178        return q ? : ERR_PTR(err);
 179}
 180EXPORT_SYMBOL(fifo_create_dflt);
 181
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