/*
 * net/sched/sch_drr.c         Deficit Round Robin scheduler
 *
 * Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/pkt_sched.h>
#include <net/sch_generic.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>

struct drr_class {
        struct Qdisc_class_common       common;
        unsigned int                    refcnt;
        unsigned int                    filter_cnt;

        struct gnet_stats_basic_packed          bstats;
        struct gnet_stats_queue         qstats;
        struct gnet_stats_rate_est      rate_est;
        struct list_head                alist;
        struct Qdisc                    *qdisc;

        u32                             quantum;
        u32                             deficit;
};

struct drr_sched {
        struct list_head                active;
        struct tcf_proto                *filter_list;
        struct Qdisc_class_hash         clhash;
};

static struct drr_class *drr_find_class(struct Qdisc *sch, u32 classid)
{
        struct drr_sched *q = qdisc_priv(sch);
        struct Qdisc_class_common *clc;

        clc = qdisc_class_find(&q->clhash, classid);
        if (clc == NULL)
                return NULL;
        return container_of(clc, struct drr_class, common);
}

static void drr_purge_queue(struct drr_class *cl)
{
        unsigned int len = cl->qdisc->q.qlen;

        qdisc_reset(cl->qdisc);
        qdisc_tree_decrease_qlen(cl->qdisc, len);
}

static const struct nla_policy drr_policy[TCA_DRR_MAX + 1] = {
        [TCA_DRR_QUANTUM]       = { .type = NLA_U32 },
};

static int drr_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
                            struct nlattr **tca, unsigned long *arg)
{
        struct drr_sched *q = qdisc_priv(sch);
        struct drr_class *cl = (struct drr_class *)*arg;
        struct nlattr *opt = tca[TCA_OPTIONS];
        struct nlattr *tb[TCA_DRR_MAX + 1];
        u32 quantum;
        int err;

        if (!opt)
                return -EINVAL;

        err = nla_parse_nested(tb, TCA_DRR_MAX, opt, drr_policy);
        if (err < 0)
                return err;

        if (tb[TCA_DRR_QUANTUM]) {
                quantum = nla_get_u32(tb[TCA_DRR_QUANTUM]);
                if (quantum == 0)
                        return -EINVAL;
        } else
                quantum = psched_mtu(qdisc_dev(sch));

        if (cl != NULL) {
                if (tca[TCA_RATE]) {
                        err = gen_replace_estimator(&cl->bstats, &cl->rate_est,
                                                    qdisc_root_sleeping_lock(sch),
                                                    tca[TCA_RATE]);
                        if (err)
                                return err;
                }

                sch_tree_lock(sch);
                if (tb[TCA_DRR_QUANTUM])
                        cl->quantum = quantum;
                sch_tree_unlock(sch);

                return 0;
        }

        cl = kzalloc(sizeof(struct drr_class), GFP_KERNEL);
        if (cl == NULL)
                return -ENOBUFS;

        cl->refcnt         = 1;
        cl->common.classid = classid;
        cl->quantum        = quantum;
        cl->qdisc          = qdisc_create_dflt(qdisc_dev(sch), sch->dev_queue,
                                               &pfifo_qdisc_ops, classid);
        if (cl->qdisc == NULL)
                cl->qdisc = &noop_qdisc;

        if (tca[TCA_RATE]) {
                err = gen_replace_estimator(&cl->bstats, &cl->rate_est,
                                            qdisc_root_sleeping_lock(sch),
                                            tca[TCA_RATE]);
                if (err) {
                        qdisc_destroy(cl->qdisc);
                        kfree(cl);
                        return err;
                }
        }

        sch_tree_lock(sch);
        qdisc_class_hash_insert(&q->clhash, &cl->common);
        sch_tree_unlock(sch);

        qdisc_class_hash_grow(sch, &q->clhash);

        *arg = (unsigned long)cl;
        return 0;
}

static void drr_destroy_class(struct Qdisc *sch, struct drr_class *cl)
{
        gen_kill_estimator(&cl->bstats, &cl->rate_est);
        qdisc_destroy(cl->qdisc);
        kfree(cl);
}

static int drr_delete_class(struct Qdisc *sch, unsigned long arg)
{
        struct drr_sched *q = qdisc_priv(sch);
        struct drr_class *cl = (struct drr_class *)arg;

        if (cl->filter_cnt > 0)
                return -EBUSY;

        sch_tree_lock(sch);

        drr_purge_queue(cl);
        qdisc_class_hash_remove(&q->clhash, &cl->common);

        BUG_ON(--cl->refcnt == 0);
        /*
         * This shouldn't happen: we "hold" one cops->get() when called
         * from tc_ctl_tclass; the destroy method is done from cops->put().
         */

        sch_tree_unlock(sch);
        return 0;
}

static unsigned long drr_get_class(struct Qdisc *sch, u32 classid)
{
        struct drr_class *cl = drr_find_class(sch, classid);

        if (cl != NULL)
                cl->refcnt++;

        return (unsigned long)cl;
}

static void drr_put_class(struct Qdisc *sch, unsigned long arg)
{
        struct drr_class *cl = (struct drr_class *)arg;

        if (--cl->refcnt == 0)
                drr_destroy_class(sch, cl);
}

static struct tcf_proto **drr_tcf_chain(struct Qdisc *sch, unsigned long cl)
{
        struct drr_sched *q = qdisc_priv(sch);

        if (cl)
                return NULL;

        return &q->filter_list;
}

static unsigned long drr_bind_tcf(struct Qdisc *sch, unsigned long parent,
                                  u32 classid)
{
        struct drr_class *cl = drr_find_class(sch, classid);

        if (cl != NULL)
                cl->filter_cnt++;

        return (unsigned long)cl;
}

static void drr_unbind_tcf(struct Qdisc *sch, unsigned long arg)
{
        struct drr_class *cl = (struct drr_class *)arg;

        cl->filter_cnt--;
}

static int drr_graft_class(struct Qdisc *sch, unsigned long arg,
                           struct Qdisc *new, struct Qdisc **old)
{
        struct drr_class *cl = (struct drr_class *)arg;

        if (new == NULL) {
                new = qdisc_create_dflt(qdisc_dev(sch), sch->dev_queue,
                                        &pfifo_qdisc_ops, cl->common.classid);
                if (new == NULL)
                        new = &noop_qdisc;
        }

        sch_tree_lock(sch);
        drr_purge_queue(cl);
        *old = cl->qdisc;
        cl->qdisc = new;
        sch_tree_unlock(sch);
        return 0;
}

static struct Qdisc *drr_class_leaf(struct Qdisc *sch, unsigned long arg)
{
        struct drr_class *cl = (struct drr_class *)arg;

        return cl->qdisc;
}

static void drr_qlen_notify(struct Qdisc *csh, unsigned long arg)
{
        struct drr_class *cl = (struct drr_class *)arg;

        if (cl->qdisc->q.qlen == 0)
                list_del(&cl->alist);
}

static int drr_dump_class(struct Qdisc *sch, unsigned long arg,
                          struct sk_buff *skb, struct tcmsg *tcm)
{
        struct drr_class *cl = (struct drr_class *)arg;
        struct nlattr *nest;

        tcm->tcm_parent = TC_H_ROOT;
        tcm->tcm_handle = cl->common.classid;
        tcm->tcm_info   = cl->qdisc->handle;

        nest = nla_nest_start(skb, TCA_OPTIONS);
        if (nest == NULL)
                goto nla_put_failure;
        NLA_PUT_U32(skb, TCA_DRR_QUANTUM, cl->quantum);
        return nla_nest_end(skb, nest);

nla_put_failure:
        nla_nest_cancel(skb, nest);
        return -EMSGSIZE;
}

static int drr_dump_class_stats(struct Qdisc *sch, unsigned long arg,
                                struct gnet_dump *d)
{
        struct drr_class *cl = (struct drr_class *)arg;
        struct tc_drr_stats xstats;

        memset(&xstats, 0, sizeof(xstats));
        if (cl->qdisc->q.qlen) {
                xstats.deficit = cl->deficit;
                cl->qdisc->qstats.qlen = cl->qdisc->q.qlen;
        }

        if (gnet_stats_copy_basic(d, &cl->bstats) < 0 ||
            gnet_stats_copy_rate_est(d, &cl->bstats, &cl->rate_est) < 0 ||
            gnet_stats_copy_queue(d, &cl->qdisc->qstats) < 0)
                return -1;

        return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
}

static void drr_walk(struct Qdisc *sch, struct qdisc_walker *arg)
{
        struct drr_sched *q = qdisc_priv(sch);
        struct drr_class *cl;
        struct hlist_node *n;
        unsigned int i;

        if (arg->stop)
                return;

        for (i = 0; i < q->clhash.hashsize; i++) {
                hlist_for_each_entry(cl, n, &q->clhash.hash[i], common.hnode) {
                        if (arg->count < arg->skip) {
                                arg->count++;
                                continue;
                        }
                        if (arg->fn(sch, (unsigned long)cl, arg) < 0) {
                                arg->stop = 1;
                                return;
                        }
                        arg->count++;
                }
        }
}

static struct drr_class *drr_classify(struct sk_buff *skb, struct Qdisc *sch,
                                      int *qerr)
{
        struct drr_sched *q = qdisc_priv(sch);
        struct drr_class *cl;
        struct tcf_result res;
        int result;

        if (TC_H_MAJ(skb->priority ^ sch->handle) == 0) {
                cl = drr_find_class(sch, skb->priority);
                if (cl != NULL)
                        return cl;
        }

        *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
        result = tc_classify(skb, q->filter_list, &res);
        if (result >= 0) {
#ifdef CONFIG_NET_CLS_ACT
                switch (result) {
                case TC_ACT_QUEUED:
                case TC_ACT_STOLEN:
                        *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
                case TC_ACT_SHOT:
                        return NULL;
                }
#endif
                cl = (struct drr_class *)res.class;
                if (cl == NULL)
                        cl = drr_find_class(sch, res.classid);
                return cl;
        }
        return NULL;
}

static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch)
{
        struct drr_sched *q = qdisc_priv(sch);
        struct drr_class *cl;
        unsigned int len;
        int err;

        cl = drr_classify(skb, sch, &err);
        if (cl == NULL) {
                if (err & __NET_XMIT_BYPASS)
                        sch->qstats.drops++;
                kfree_skb(skb);
                return err;
        }

        len = qdisc_pkt_len(skb);
        err = qdisc_enqueue(skb, cl->qdisc);
        if (unlikely(err != NET_XMIT_SUCCESS)) {
                if (net_xmit_drop_count(err)) {
                        cl->qstats.drops++;
                        sch->qstats.drops++;
                }
                return err;
        }

        if (cl->qdisc->q.qlen == 1) {
                list_add_tail(&cl->alist, &q->active);
                cl->deficit = cl->quantum;
        }

        cl->bstats.packets++;
        cl->bstats.bytes += len;
        sch->bstats.packets++;
        sch->bstats.bytes += len;

        sch->q.qlen++;
        return err;
}

static struct sk_buff *drr_dequeue(struct Qdisc *sch)
{
        struct drr_sched *q = qdisc_priv(sch);
        struct drr_class *cl;
        struct sk_buff *skb;
        unsigned int len;

        if (list_empty(&q->active))
                goto out;
        while (1) {
                cl = list_first_entry(&q->active, struct drr_class, alist);
                skb = cl->qdisc->ops->peek(cl->qdisc);
                if (skb == NULL)
                        goto out;

                len = qdisc_pkt_len(skb);
                if (len <= cl->deficit) {
                        cl->deficit -= len;
                        skb = qdisc_dequeue_peeked(cl->qdisc);
                        if (cl->qdisc->q.qlen == 0)
                                list_del(&cl->alist);
                        sch->q.qlen--;
                        return skb;
                }

                cl->deficit += cl->quantum;
                list_move_tail(&cl->alist, &q->active);
        }
out:
        return NULL;
}

static unsigned int drr_drop(struct Qdisc *sch)
{
        struct drr_sched *q = qdisc_priv(sch);
        struct drr_class *cl;
        unsigned int len;

        list_for_each_entry(cl, &q->active, alist) {
                if (cl->qdisc->ops->drop) {
                        len = cl->qdisc->ops->drop(cl->qdisc);
                        if (len > 0) {
                                sch->q.qlen--;
                                if (cl->qdisc->q.qlen == 0)
                                        list_del(&cl->alist);
                                return len;
                        }
                }
        }
        return 0;
}

static int drr_init_qdisc(struct Qdisc *sch, struct nlattr *opt)
{
        struct drr_sched *q = qdisc_priv(sch);
        int err;

        err = qdisc_class_hash_init(&q->clhash);
        if (err < 0)
                return err;
        INIT_LIST_HEAD(&q->active);
        return 0;
}

static void drr_reset_qdisc(struct Qdisc *sch)
{
        struct drr_sched *q = qdisc_priv(sch);
        struct drr_class *cl;
        struct hlist_node *n;
        unsigned int i;

        for (i = 0; i < q->clhash.hashsize; i++) {
                hlist_for_each_entry(cl, n, &q->clhash.hash[i], common.hnode) {
                        if (cl->qdisc->q.qlen)
                                list_del(&cl->alist);
                        qdisc_reset(cl->qdisc);
                }
        }
        sch->q.qlen = 0;
}

static void drr_destroy_qdisc(struct Qdisc *sch)
{
        struct drr_sched *q = qdisc_priv(sch);
        struct drr_class *cl;
        struct hlist_node *n, *next;
        unsigned int i;

        tcf_destroy_chain(&q->filter_list);

        for (i = 0; i < q->clhash.hashsize; i++) {
                hlist_for_each_entry_safe(cl, n, next, &q->clhash.hash[i],
                                          common.hnode)
                        drr_destroy_class(sch, cl);
        }
        qdisc_class_hash_destroy(&q->clhash);
}

static const struct Qdisc_class_ops drr_class_ops = {
        .change         = drr_change_class,
        .delete         = drr_delete_class,
        .get            = drr_get_class,
        .put            = drr_put_class,
        .tcf_chain      = drr_tcf_chain,
        .bind_tcf       = drr_bind_tcf,
        .unbind_tcf     = drr_unbind_tcf,
        .graft          = drr_graft_class,
        .leaf           = drr_class_leaf,
        .qlen_notify    = drr_qlen_notify,
        .dump           = drr_dump_class,
        .dump_stats     = drr_dump_class_stats,
        .walk           = drr_walk,
};

static struct Qdisc_ops drr_qdisc_ops __read_mostly = {
        .cl_ops         = &drr_class_ops,
        .id             = "drr",
        .priv_size      = sizeof(struct drr_sched),
        .enqueue        = drr_enqueue,
        .dequeue        = drr_dequeue,
        .peek           = qdisc_peek_dequeued,
        .drop           = drr_drop,
        .init           = drr_init_qdisc,
        .reset          = drr_reset_qdisc,
        .destroy        = drr_destroy_qdisc,
        .owner          = THIS_MODULE,
};

static int __init drr_init(void)
{
        return register_qdisc(&drr_qdisc_ops);
}

static void __exit drr_exit(void)
{
        unregister_qdisc(&drr_qdisc_ops);
}

module_init(drr_init);
module_exit(drr_exit);
MODULE_LICENSE("GPL");