root/net/sched/sch_fifo.c

DEFINITIONS

1. bfifo_enqueue
2. pfifo_enqueue
3. fifo_init
4. fifo_dump
5. fifo_set_limit
6. fifo_create_dflt

/*
 * net/sched/sch_fifo.c The simplest FIFO queue.
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <net/pkt_sched.h>

/* 1 band FIFO pseudo-"scheduler" */

struct fifo_sched_data
{
        u32 limit;
};

static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc* sch)
{
        struct fifo_sched_data *q = qdisc_priv(sch);

        if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= q->limit))
                return qdisc_enqueue_tail(skb, sch);

        return qdisc_reshape_fail(skb, sch);
}

static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc* sch)
{
        struct fifo_sched_data *q = qdisc_priv(sch);

        if (likely(skb_queue_len(&sch->q) < q->limit))
                return qdisc_enqueue_tail(skb, sch);

        return qdisc_reshape_fail(skb, sch);
}

static int fifo_init(struct Qdisc *sch, struct nlattr *opt)
{
        struct fifo_sched_data *q = qdisc_priv(sch);

        if (opt == NULL) {
                u32 limit = qdisc_dev(sch)->tx_queue_len ? : 1;

                if (sch->ops == &bfifo_qdisc_ops)
                        limit *= qdisc_dev(sch)->mtu;

                q->limit = limit;
        } else {
                struct tc_fifo_qopt *ctl = nla_data(opt);

                if (nla_len(opt) < sizeof(*ctl))
                        return -EINVAL;

                q->limit = ctl->limit;
        }

        return 0;
}

static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
{
        struct fifo_sched_data *q = qdisc_priv(sch);
        struct tc_fifo_qopt opt = { .limit = q->limit };

        NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
        return skb->len;

nla_put_failure:
        return -1;
}

struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
        .id             =       "pfifo",
        .priv_size      =       sizeof(struct fifo_sched_data),
        .enqueue        =       pfifo_enqueue,
        .dequeue        =       qdisc_dequeue_head,
        .requeue        =       qdisc_requeue,
        .drop           =       qdisc_queue_drop,
        .init           =       fifo_init,
        .reset          =       qdisc_reset_queue,
        .change         =       fifo_init,
        .dump           =       fifo_dump,
        .owner          =       THIS_MODULE,
};
EXPORT_SYMBOL(pfifo_qdisc_ops);

struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
        .id             =       "bfifo",
        .priv_size      =       sizeof(struct fifo_sched_data),
        .enqueue        =       bfifo_enqueue,
        .dequeue        =       qdisc_dequeue_head,
        .requeue        =       qdisc_requeue,
        .drop           =       qdisc_queue_drop,
        .init           =       fifo_init,
        .reset          =       qdisc_reset_queue,
        .change         =       fifo_init,
        .dump           =       fifo_dump,
        .owner          =       THIS_MODULE,
};
EXPORT_SYMBOL(bfifo_qdisc_ops);

/* Pass size change message down to embedded FIFO */
int fifo_set_limit(struct Qdisc *q, unsigned int limit)
{
        struct nlattr *nla;
        int ret = -ENOMEM;

        /* Hack to avoid sending change message to non-FIFO */
        if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
                return 0;

        nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
        if (nla) {
                nla->nla_type = RTM_NEWQDISC;
                nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
                ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;

                ret = q->ops->change(q, nla);
                kfree(nla);
        }
        return ret;
}
EXPORT_SYMBOL(fifo_set_limit);

struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
                               unsigned int limit)
{
        struct Qdisc *q;
        int err = -ENOMEM;

        q = qdisc_create_dflt(qdisc_dev(sch), sch->dev_queue,
                              ops, TC_H_MAKE(sch->handle, 1));
        if (q) {
                err = fifo_set_limit(q, limit);
                if (err < 0) {
                        qdisc_destroy(q);
                        q = NULL;
                }
        }

        return q ? : ERR_PTR(err);
}
EXPORT_SYMBOL(fifo_create_dflt);