/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2010 Riccardo Panicucci, Universita` di Pisa
 * All rights reserved
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 */

#ifdef _KERNEL
#include <sys/malloc.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mbuf.h>
#include <sys/module.h>
#include <sys/rwlock.h>
#include <net/if.h>     /* IFNAMSIZ */
#include <netinet/in.h>
#include <netinet/ip_var.h>             /* ipfw_rule_ref */
#include <netinet/ip_fw.h>      /* flow_id */
#include <netinet/ip_dummynet.h>
#include <netpfil/ipfw/ip_fw_private.h>
#include <netpfil/ipfw/dn_heap.h>
#include <netpfil/ipfw/ip_dn_private.h>
#ifdef NEW_AQM
#include <netpfil/ipfw/dn_aqm.h>
#endif
#include <netpfil/ipfw/dn_sched.h>
#else
#include <dn_test.h>
#endif

#define DN_SCHED_RR     3 // XXX Where?

struct rr_queue {
        struct dn_queue q;              /* Standard queue */
        int status;                     /* 1: queue is in the list */
        uint32_t credit;                /* max bytes we can transmit */
        uint32_t quantum;               /* quantum * weight */
        struct rr_queue *qnext;         /* */
};

/* struct rr_schk contains global config parameters
 * and is right after dn_schk
 */
struct rr_schk {
        uint32_t min_q;         /* Min quantum */
        uint32_t max_q;         /* Max quantum */
        uint32_t q_bytes;       /* default quantum in bytes */
};

/* per-instance round robin list, right after dn_sch_inst */
struct rr_si {
        struct rr_queue *head, *tail;   /* Pointer to current queue */
};

/* Append a queue to the rr list */
static inline void
rr_append(struct rr_queue *q, struct rr_si *si)
{
        q->status = 1;          /* mark as in-rr_list */
        q->credit = q->quantum; /* initialize credit */

        /* append to the tail */
        if (si->head == NULL)
                si->head = q;
        else
                si->tail->qnext = q;
        si->tail = q;           /* advance the tail pointer */
        q->qnext = si->head;    /* make it circular */
}

/* Remove the head queue from circular list. */
static inline void
rr_remove_head(struct rr_si *si)
{
        if (si->head == NULL)
                return; /* empty queue */
        si->head->status = 0;

        if (si->head == si->tail) {
                si->head = si->tail = NULL;
                return;
        }

        si->head = si->head->qnext;
        si->tail->qnext = si->head;
}

/* Remove a queue from circular list.
 * XXX see if ti can be merge with remove_queue()
 */
static inline void
remove_queue_q(struct rr_queue *q, struct rr_si *si)
{
        struct rr_queue *prev;

        if (q->status != 1)
                return;
        if (q == si->head) {
                rr_remove_head(si);
                return;
        }

        for (prev = si->head; prev; prev = prev->qnext) {
                if (prev->qnext != q)
                        continue;
                prev->qnext = q->qnext;
                if (q == si->tail)
                        si->tail = prev;
                q->status = 0;
                break;
        }
}

static inline void
next_pointer(struct rr_si *si)
{
        if (si->head == NULL)
                return; /* empty queue */

        si->head = si->head->qnext;
        si->tail = si->tail->qnext;
}

static int
rr_enqueue(struct dn_sch_inst *_si, struct dn_queue *q, struct mbuf *m)
{
        struct rr_si *si;
        struct rr_queue *rrq;

        if (m != q->mq.head) {
                if (dn_enqueue(q, m, 0)) /* packet was dropped */
                        return 1;
                if (m != q->mq.head)
                        return 0;
        }

        /* If reach this point, queue q was idle */
        si = (struct rr_si *)(_si + 1);
        rrq = (struct rr_queue *)q;

        if (rrq->status == 1) /* Queue is already in the queue list */
                return 0;

        /* Insert the queue in the queue list */
        rr_append(rrq, si);

        return 0;
}

static struct mbuf *
rr_dequeue(struct dn_sch_inst *_si)
{
        /* Access scheduler instance private data */
        struct rr_si *si = (struct rr_si *)(_si + 1);
        struct rr_queue *rrq;
        uint64_t len;

        while ( (rrq = si->head) ) {
                struct mbuf *m = rrq->q.mq.head;
                if ( m == NULL) {
                        /* empty queue, remove from list */
                        rr_remove_head(si);
                        continue;
                }
                len = m->m_pkthdr.len;

                if (len > rrq->credit) {
                        /* Packet too big */
                        rrq->credit += rrq->quantum;
                        /* Try next queue */
                        next_pointer(si);
                } else {
                        rrq->credit -= len;
                        return dn_dequeue(&rrq->q);
                }
        }

        /* no packet to dequeue*/
        return NULL;
}

static int
rr_config(struct dn_schk *_schk)
{
        struct rr_schk *schk = (struct rr_schk *)(_schk + 1);
        ND("called");

        /* use reasonable quantums (64..2k bytes, default 1500) */
        schk->min_q = 64;
        schk->max_q = 2048;
        schk->q_bytes = 1500;   /* quantum */

        return 0;
}

static int
rr_new_sched(struct dn_sch_inst *_si)
{
        struct rr_si *si = (struct rr_si *)(_si + 1);

        ND("called");
        si->head = si->tail = NULL;

        return 0;
}

static int
rr_free_sched(struct dn_sch_inst *_si)
{
        (void)_si;
        ND("called");
        /* Nothing to do? */
        return 0;
}

static int
rr_new_fsk(struct dn_fsk *fs)
{
        struct rr_schk *schk = (struct rr_schk *)(fs->sched + 1);
        /* par[0] is the weight, par[1] is the quantum step */
        /* make sure the product fits an uint32_t */
        ipdn_bound_var(&fs->fs.par[0], 1,
                1, 65536, "RR weight");
        ipdn_bound_var(&fs->fs.par[1], schk->q_bytes,
                schk->min_q, schk->max_q, "RR quantum");
        return 0;
}

static int
rr_new_queue(struct dn_queue *_q)
{
        struct rr_queue *q = (struct rr_queue *)_q;
        uint64_t quantum;

        _q->ni.oid.subtype = DN_SCHED_RR;

        quantum = (uint64_t)_q->fs->fs.par[0] * _q->fs->fs.par[1];
        if (quantum >= (1ULL<< 32)) {
                D("quantum too large, truncating to 4G - 1");
                quantum = (1ULL<< 32) - 1;
        }
        q->quantum = quantum;
        ND("called, q->quantum %d", q->quantum);
        q->credit = q->quantum;
        q->status = 0;

        if (_q->mq.head != NULL) {
                /* Queue NOT empty, insert in the queue list */
                rr_append(q, (struct rr_si *)(_q->_si + 1));
        }
        return 0;
}

static int
rr_free_queue(struct dn_queue *_q)
{
        struct rr_queue *q = (struct rr_queue *)_q;

        ND("called");
        if (q->status == 1) {
                struct rr_si *si = (struct rr_si *)(_q->_si + 1);
                remove_queue_q(q, si);
        }
        return 0;
}

/*
 * RR scheduler descriptor
 * contains the type of the scheduler, the name, the size of the
 * structures and function pointers.
 */
static struct dn_alg rr_desc = {
        _SI( .type = ) DN_SCHED_RR,
        _SI( .name = ) "RR",
        _SI( .flags = ) DN_MULTIQUEUE,

        _SI( .schk_datalen = ) sizeof(struct rr_schk),
        _SI( .si_datalen = ) sizeof(struct rr_si),
        _SI( .q_datalen = ) sizeof(struct rr_queue) - sizeof(struct dn_queue),

        _SI( .enqueue = ) rr_enqueue,
        _SI( .dequeue = ) rr_dequeue,

        _SI( .config = ) rr_config,
        _SI( .destroy = ) NULL,
        _SI( .new_sched = ) rr_new_sched,
        _SI( .free_sched = ) rr_free_sched,
        _SI( .new_fsk = ) rr_new_fsk,
        _SI( .free_fsk = ) NULL,
        _SI( .new_queue = ) rr_new_queue,
        _SI( .free_queue = ) rr_free_queue,
#ifdef NEW_AQM
        _SI( .getconfig = )  NULL,
#endif
};

DECLARE_DNSCHED_MODULE(dn_rr, &rr_desc);