// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * net/sched/sch_prio.c Simple 3-band priority "scheduler".
 *
 * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 * Fixes:       19990609: J Hadi Salim <hadi@nortelnetworks.com>:
 *              Init --  EINVAL when opt undefined
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>

struct prio_sched_data {
        int bands;
        struct tcf_proto __rcu *filter_list;
        struct tcf_block *block;
        u8  prio2band[TC_PRIO_MAX+1];
        struct Qdisc *queues[TCQ_PRIO_BANDS];
};


static struct Qdisc *
prio_classify(struct sk_buff *skb, struct Qdisc *sch, int *qerr)
{
        struct prio_sched_data *q = qdisc_priv(sch);
        u32 band = skb->priority;
        struct tcf_result res;
        struct tcf_proto *fl;
        int err;

        *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
        if (TC_H_MAJ(skb->priority) != sch->handle) {
                fl = rcu_dereference_bh(q->filter_list);
                err = tcf_classify(skb, NULL, fl, &res, false);
#ifdef CONFIG_NET_CLS_ACT
                switch (err) {
                case TC_ACT_STOLEN:
                case TC_ACT_QUEUED:
                case TC_ACT_TRAP:
                        *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
                        fallthrough;
                case TC_ACT_SHOT:
                        return NULL;
                }
#endif
                if (!fl || err < 0) {
                        if (TC_H_MAJ(band))
                                band = 0;
                        return q->queues[q->prio2band[band & TC_PRIO_MAX]];
                }
                band = res.classid;
        }
        band = TC_H_MIN(band) - 1;
        if (band >= q->bands)
                return q->queues[q->prio2band[0]];

        return q->queues[band];
}

static int
prio_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
{
        unsigned int len = qdisc_pkt_len(skb);
        struct Qdisc *qdisc;
        int ret;

        qdisc = prio_classify(skb, sch, &ret);
#ifdef CONFIG_NET_CLS_ACT
        if (qdisc == NULL) {

                if (ret & __NET_XMIT_BYPASS)
                        qdisc_qstats_drop(sch);
                __qdisc_drop(skb, to_free);
                return ret;
        }
#endif

        ret = qdisc_enqueue(skb, qdisc, to_free);
        if (ret == NET_XMIT_SUCCESS) {
                sch->qstats.backlog += len;
                sch->q.qlen++;
                return NET_XMIT_SUCCESS;
        }
        if (net_xmit_drop_count(ret))
                qdisc_qstats_drop(sch);
        return ret;
}

static struct sk_buff *prio_peek(struct Qdisc *sch)
{
        struct prio_sched_data *q = qdisc_priv(sch);
        int prio;

        for (prio = 0; prio < q->bands; prio++) {
                struct Qdisc *qdisc = q->queues[prio];
                struct sk_buff *skb = qdisc->ops->peek(qdisc);
                if (skb)
                        return skb;
        }
        return NULL;
}

static struct sk_buff *prio_dequeue(struct Qdisc *sch)
{
        struct prio_sched_data *q = qdisc_priv(sch);
        int prio;

        for (prio = 0; prio < q->bands; prio++) {
                struct Qdisc *qdisc = q->queues[prio];
                struct sk_buff *skb = qdisc_dequeue_peeked(qdisc);
                if (skb) {
                        qdisc_bstats_update(sch, skb);
                        qdisc_qstats_backlog_dec(sch, skb);
                        sch->q.qlen--;
                        return skb;
                }
        }
        return NULL;

}

static void
prio_reset(struct Qdisc *sch)
{
        int prio;
        struct prio_sched_data *q = qdisc_priv(sch);

        for (prio = 0; prio < q->bands; prio++)
                qdisc_reset(q->queues[prio]);
}

static int prio_offload(struct Qdisc *sch, struct tc_prio_qopt *qopt)
{
        struct net_device *dev = qdisc_dev(sch);
        struct tc_prio_qopt_offload opt = {
                .handle = sch->handle,
                .parent = sch->parent,
        };

        if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
                return -EOPNOTSUPP;

        if (qopt) {
                opt.command = TC_PRIO_REPLACE;
                opt.replace_params.bands = qopt->bands;
                memcpy(&opt.replace_params.priomap, qopt->priomap,
                       TC_PRIO_MAX + 1);
                opt.replace_params.qstats = &sch->qstats;
        } else {
                opt.command = TC_PRIO_DESTROY;
        }

        return dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_PRIO, &opt);
}

static void
prio_destroy(struct Qdisc *sch)
{
        int prio;
        struct prio_sched_data *q = qdisc_priv(sch);

        tcf_block_put(q->block);
        prio_offload(sch, NULL);
        for (prio = 0; prio < q->bands; prio++)
                qdisc_put(q->queues[prio]);
}

static int prio_tune(struct Qdisc *sch, struct nlattr *opt,
                     struct netlink_ext_ack *extack)
{
        struct prio_sched_data *q = qdisc_priv(sch);
        struct Qdisc *queues[TCQ_PRIO_BANDS];
        int oldbands = q->bands, i;
        struct tc_prio_qopt *qopt;

        if (nla_len(opt) < sizeof(*qopt))
                return -EINVAL;
        qopt = nla_data(opt);

        if (qopt->bands > TCQ_PRIO_BANDS || qopt->bands < TCQ_MIN_PRIO_BANDS)
                return -EINVAL;

        for (i = 0; i <= TC_PRIO_MAX; i++) {
                if (qopt->priomap[i] >= qopt->bands)
                        return -EINVAL;
        }

        /* Before commit, make sure we can allocate all new qdiscs */
        for (i = oldbands; i < qopt->bands; i++) {
                queues[i] = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
                                              TC_H_MAKE(sch->handle, i + 1),
                                              extack);
                if (!queues[i]) {
                        while (i > oldbands)
                                qdisc_put(queues[--i]);
                        return -ENOMEM;
                }
        }

        prio_offload(sch, qopt);
        sch_tree_lock(sch);
        q->bands = qopt->bands;
        memcpy(q->prio2band, qopt->priomap, TC_PRIO_MAX+1);

        for (i = q->bands; i < oldbands; i++)
                qdisc_purge_queue(q->queues[i]);

        for (i = oldbands; i < q->bands; i++) {
                q->queues[i] = queues[i];
                if (q->queues[i] != &noop_qdisc)
                        qdisc_hash_add(q->queues[i], true);
        }

        sch_tree_unlock(sch);

        for (i = q->bands; i < oldbands; i++)
                qdisc_put(q->queues[i]);
        return 0;
}

static int prio_init(struct Qdisc *sch, struct nlattr *opt,
                     struct netlink_ext_ack *extack)
{
        struct prio_sched_data *q = qdisc_priv(sch);
        int err;

        if (!opt)
                return -EINVAL;

        err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
        if (err)
                return err;

        return prio_tune(sch, opt, extack);
}

static int prio_dump_offload(struct Qdisc *sch)
{
        struct tc_prio_qopt_offload hw_stats = {
                .command = TC_PRIO_STATS,
                .handle = sch->handle,
                .parent = sch->parent,
                {
                        .stats = {
                                .bstats = &sch->bstats,
                                .qstats = &sch->qstats,
                        },
                },
        };

        return qdisc_offload_dump_helper(sch, TC_SETUP_QDISC_PRIO, &hw_stats);
}

static int prio_dump(struct Qdisc *sch, struct sk_buff *skb)
{
        struct prio_sched_data *q = qdisc_priv(sch);
        unsigned char *b = skb_tail_pointer(skb);
        struct tc_prio_qopt opt;
        int err;

        opt.bands = q->bands;
        memcpy(&opt.priomap, q->prio2band, TC_PRIO_MAX + 1);

        err = prio_dump_offload(sch);
        if (err)
                goto nla_put_failure;

        if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
                goto nla_put_failure;

        return skb->len;

nla_put_failure:
        nlmsg_trim(skb, b);
        return -1;
}

static int prio_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
                      struct Qdisc **old, struct netlink_ext_ack *extack)
{
        struct prio_sched_data *q = qdisc_priv(sch);
        struct tc_prio_qopt_offload graft_offload;
        unsigned long band = arg - 1;

        if (!new) {
                new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
                                        TC_H_MAKE(sch->handle, arg), extack);
                if (!new)
                        new = &noop_qdisc;
                else
                        qdisc_hash_add(new, true);
        }

        *old = qdisc_replace(sch, new, &q->queues[band]);

        graft_offload.handle = sch->handle;
        graft_offload.parent = sch->parent;
        graft_offload.graft_params.band = band;
        graft_offload.graft_params.child_handle = new->handle;
        graft_offload.command = TC_PRIO_GRAFT;

        qdisc_offload_graft_helper(qdisc_dev(sch), sch, new, *old,
                                   TC_SETUP_QDISC_PRIO, &graft_offload,
                                   extack);
        return 0;
}

static struct Qdisc *
prio_leaf(struct Qdisc *sch, unsigned long arg)
{
        struct prio_sched_data *q = qdisc_priv(sch);
        unsigned long band = arg - 1;

        return q->queues[band];
}

static unsigned long prio_find(struct Qdisc *sch, u32 classid)
{
        struct prio_sched_data *q = qdisc_priv(sch);
        unsigned long band = TC_H_MIN(classid);

        if (band - 1 >= q->bands)
                return 0;
        return band;
}

static unsigned long prio_bind(struct Qdisc *sch, unsigned long parent, u32 classid)
{
        return prio_find(sch, classid);
}


static void prio_unbind(struct Qdisc *q, unsigned long cl)
{
}

static int prio_dump_class(struct Qdisc *sch, unsigned long cl, struct sk_buff *skb,
                           struct tcmsg *tcm)
{
        struct prio_sched_data *q = qdisc_priv(sch);

        tcm->tcm_handle |= TC_H_MIN(cl);
        tcm->tcm_info = q->queues[cl-1]->handle;
        return 0;
}

static int prio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
                                 struct gnet_dump *d)
{
        struct prio_sched_data *q = qdisc_priv(sch);
        struct Qdisc *cl_q;

        cl_q = q->queues[cl - 1];
        if (gnet_stats_copy_basic(d, cl_q->cpu_bstats,
                                  &cl_q->bstats, true) < 0 ||
            qdisc_qstats_copy(d, cl_q) < 0)
                return -1;

        return 0;
}

static void prio_walk(struct Qdisc *sch, struct qdisc_walker *arg)
{
        struct prio_sched_data *q = qdisc_priv(sch);
        int prio;

        if (arg->stop)
                return;

        for (prio = 0; prio < q->bands; prio++) {
                if (!tc_qdisc_stats_dump(sch, prio + 1, arg))
                        break;
        }
}

static struct tcf_block *prio_tcf_block(struct Qdisc *sch, unsigned long cl,
                                        struct netlink_ext_ack *extack)
{
        struct prio_sched_data *q = qdisc_priv(sch);

        if (cl)
                return NULL;
        return q->block;
}

static const struct Qdisc_class_ops prio_class_ops = {
        .graft          =       prio_graft,
        .leaf           =       prio_leaf,
        .find           =       prio_find,
        .walk           =       prio_walk,
        .tcf_block      =       prio_tcf_block,
        .bind_tcf       =       prio_bind,
        .unbind_tcf     =       prio_unbind,
        .dump           =       prio_dump_class,
        .dump_stats     =       prio_dump_class_stats,
};

static struct Qdisc_ops prio_qdisc_ops __read_mostly = {
        .next           =       NULL,
        .cl_ops         =       &prio_class_ops,
        .id             =       "prio",
        .priv_size      =       sizeof(struct prio_sched_data),
        .enqueue        =       prio_enqueue,
        .dequeue        =       prio_dequeue,
        .peek           =       prio_peek,
        .init           =       prio_init,
        .reset          =       prio_reset,
        .destroy        =       prio_destroy,
        .change         =       prio_tune,
        .dump           =       prio_dump,
        .owner          =       THIS_MODULE,
};
MODULE_ALIAS_NET_SCH("prio");

static int __init prio_module_init(void)
{
        return register_qdisc(&prio_qdisc_ops);
}

static void __exit prio_module_exit(void)
{
        unregister_qdisc(&prio_qdisc_ops);
}

module_init(prio_module_init)
module_exit(prio_module_exit)

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Simple 3-band priority qdisc");