/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2010 Fabio Checconi, Luigi Rizzo, Paolo Valente
 * 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

#ifdef QFQ_DEBUG
#define _P64    unsigned long long      /* cast for printing uint64_t */
struct qfq_sched;
static void dump_sched(struct qfq_sched *q, const char *msg);
#define NO(x)   x
#else
#define NO(x)
#endif
#define DN_SCHED_QFQ    4 // XXX Where?
typedef unsigned long   bitmap;

/*
 * bitmaps ops are critical. Some linux versions have __fls
 * and the bitmap ops. Some machines have ffs
 * NOTE: fls() returns 1 for the least significant bit,
 *       __fls() returns 0 for the same case.
 * We use the base-0 version __fls() to match the description in
 * the ToN QFQ paper
 */
#if defined(_WIN32) || (defined(__MIPSEL__) && defined(LINUX_24))
int fls(unsigned int n)
{
        int i = 0;
        for (i = 0; n > 0; n >>= 1, i++)
                ;
        return i;
}
#endif

#if !defined(_KERNEL) || defined( __FreeBSD__ ) || defined(_WIN32) || (defined(__MIPSEL__) && defined(LINUX_24))
static inline unsigned long __fls(unsigned long word)
{
        return fls(word) - 1;
}
#endif

#if !defined(_KERNEL) || !defined(__linux__)
#ifdef QFQ_DEBUG
static int test_bit(int ix, bitmap *p)
{
        if (ix < 0 || ix > 31)
                D("bad index %d", ix);
        return *p & (1<<ix);
}
static void __set_bit(int ix, bitmap *p)
{
        if (ix < 0 || ix > 31)
                D("bad index %d", ix);
        *p |= (1<<ix);
}
static void __clear_bit(int ix, bitmap *p)
{
        if (ix < 0 || ix > 31)
                D("bad index %d", ix);
        *p &= ~(1<<ix);
}
#else /* !QFQ_DEBUG */
/* XXX do we have fast version, or leave it to the compiler ? */
#define test_bit(ix, pData)     ((*pData) & (1<<(ix)))
#define __set_bit(ix, pData)    (*pData) |= (1<<(ix))
#define __clear_bit(ix, pData)  (*pData) &= ~(1<<(ix))
#endif /* !QFQ_DEBUG */
#endif /* !__linux__ */

#ifdef __MIPSEL__
#define __clear_bit(ix, pData)  (*pData) &= ~(1<<(ix))
#endif

/*-------------------------------------------*/
/*

Virtual time computations.

S, F and V are all computed in fixed point arithmetic with
FRAC_BITS decimal bits.

   QFQ_MAX_INDEX is the maximum index allowed for a group. We need
        one bit per index.
   QFQ_MAX_WSHIFT is the maximum power of two supported as a weight.
   The layout of the bits is as below:
  
                   [ MTU_SHIFT ][      FRAC_BITS    ]
                   [ MAX_INDEX    ][ MIN_SLOT_SHIFT ]
                                 ^.__grp->index = 0
                                 *.__grp->slot_shift
  
   where MIN_SLOT_SHIFT is derived by difference from the others.

The max group index corresponds to Lmax/w_min, where
Lmax=1<<MTU_SHIFT, w_min = 1 .
From this, and knowing how many groups (MAX_INDEX) we want,
we can derive the shift corresponding to each group.

Because we often need to compute
        F = S + len/w_i  and V = V + len/wsum
instead of storing w_i store the value
        inv_w = (1<<FRAC_BITS)/w_i
so we can do F = S + len * inv_w * wsum.
We use W_TOT in the formulas so we can easily move between
static and adaptive weight sum.

The per-scheduler-instance data contain all the data structures
for the scheduler: bitmaps and bucket lists.

 */
/*
 * Maximum number of consecutive slots occupied by backlogged classes
 * inside a group. This is approx lmax/lmin + 5.
 * XXX check because it poses constraints on MAX_INDEX
 */
#define QFQ_MAX_SLOTS   32
/*
 * Shifts used for class<->group mapping. Class weights are
 * in the range [1, QFQ_MAX_WEIGHT], we to map each class i to the
 * group with the smallest index that can support the L_i / r_i
 * configured for the class.
 *
 * grp->index is the index of the group; and grp->slot_shift
 * is the shift for the corresponding (scaled) sigma_i.
 *
 * When computing the group index, we do (len<<FP_SHIFT)/weight,
 * then compute an FLS (which is like a log2()), and if the result
 * is below the MAX_INDEX region we use 0 (which is the same as
 * using a larger len).
 */
#define QFQ_MAX_INDEX           19
#define QFQ_MAX_WSHIFT          16      /* log2(max_weight) */

#define QFQ_MAX_WEIGHT          (1<<QFQ_MAX_WSHIFT)
#define QFQ_MAX_WSUM            (2*QFQ_MAX_WEIGHT)

#define FRAC_BITS               30      /* fixed point arithmetic */
#define ONE_FP                  (1UL << FRAC_BITS)

#define QFQ_MTU_SHIFT           11      /* log2(max_len) */
#define QFQ_MIN_SLOT_SHIFT      (FRAC_BITS + QFQ_MTU_SHIFT - QFQ_MAX_INDEX)

/*
 * Possible group states, also indexes for the bitmaps array in
 * struct qfq_queue. We rely on ER, IR, EB, IB being numbered 0..3
 */
enum qfq_state { ER, IR, EB, IB, QFQ_MAX_STATE };

struct qfq_group;
/*
 * additional queue info. Some of this info should come from
 * the flowset, we copy them here for faster processing.
 * This is an overlay of the struct dn_queue
 */
struct qfq_class {
        struct dn_queue _q;
        uint64_t S, F;          /* flow timestamps (exact) */
        struct qfq_class *next; /* Link for the slot list. */

        /* group we belong to. In principle we would need the index,
         * which is log_2(lmax/weight), but we never reference it
         * directly, only the group.
         */
        struct qfq_group *grp;

        /* these are copied from the flowset. */
        uint32_t        inv_w;  /* ONE_FP/weight */
        uint32_t        lmax;   /* Max packet size for this flow. */
};

/* Group descriptor, see the paper for details.
 * Basically this contains the bucket lists
 */
struct qfq_group {
        uint64_t S, F;                  /* group timestamps (approx). */
        unsigned int slot_shift;        /* Slot shift. */
        unsigned int index;             /* Group index. */
        unsigned int front;             /* Index of the front slot. */
        bitmap full_slots;              /* non-empty slots */

        /* Array of lists of active classes. */
        struct qfq_class *slots[QFQ_MAX_SLOTS];
};

/* scheduler instance descriptor. */
struct qfq_sched {
        uint64_t        V;              /* Precise virtual time. */
        uint32_t        wsum;           /* weight sum */
        uint32_t        iwsum;          /* inverse weight sum */
        NO(uint32_t     i_wsum;)        /* ONE_FP/w_sum */
        NO(uint32_t     queued;)        /* debugging */
        NO(uint32_t     loops;)         /* debugging */
        bitmap bitmaps[QFQ_MAX_STATE];  /* Group bitmaps. */
        struct qfq_group groups[QFQ_MAX_INDEX + 1]; /* The groups. */
};

/*---- support functions ----------------------------*/

/* Generic comparison function, handling wraparound. */
static inline int qfq_gt(uint64_t a, uint64_t b)
{
        return (int64_t)(a - b) > 0;
}

/* Round a precise timestamp to its slotted value. */
static inline uint64_t qfq_round_down(uint64_t ts, unsigned int shift)
{
        return ts & ~((1ULL << shift) - 1);
}

/* return the pointer to the group with lowest index in the bitmap */
static inline struct qfq_group *qfq_ffs(struct qfq_sched *q,
                                        unsigned long bitmap)
{
        int index = ffs(bitmap) - 1; // zero-based
        return &q->groups[index];
}

/*
 * Calculate a flow index, given its weight and maximum packet length.
 * index = log_2(maxlen/weight) but we need to apply the scaling.
 * This is used only once at flow creation.
 */
static int qfq_calc_index(uint32_t inv_w, unsigned int maxlen)
{
        uint64_t slot_size = (uint64_t)maxlen *inv_w;
        unsigned long size_map;
        int index = 0;

        size_map = (unsigned long)(slot_size >> QFQ_MIN_SLOT_SHIFT);
        if (!size_map)
                goto out;

        index = __fls(size_map) + 1;    // basically a log_2()
        index -= !(slot_size - (1ULL << (index + QFQ_MIN_SLOT_SHIFT - 1)));

        if (index < 0)
                index = 0;

out:
        ND("W = %d, L = %d, I = %d\n", ONE_FP/inv_w, maxlen, index);
        return index;
}
/*---- end support functions ----*/

/*-------- API calls --------------------------------*/
/*
 * Validate and copy parameters from flowset.
 */
static int
qfq_new_queue(struct dn_queue *_q)
{
        struct qfq_sched *q = (struct qfq_sched *)(_q->_si + 1);
        struct qfq_class *cl = (struct qfq_class *)_q;
        int i;
        uint32_t w;     /* approximated weight */

        /* import parameters from the flowset. They should be correct
         * already.
         */
        w = _q->fs->fs.par[0];
        cl->lmax = _q->fs->fs.par[1];
        if (!w || w > QFQ_MAX_WEIGHT) {
                w = 1;
                D("rounding weight to 1");
        }
        cl->inv_w = ONE_FP/w;
        w = ONE_FP/cl->inv_w;   
        if (q->wsum + w > QFQ_MAX_WSUM)
                return EINVAL;

        i = qfq_calc_index(cl->inv_w, cl->lmax);
        cl->grp = &q->groups[i];
        q->wsum += w;
        q->iwsum = ONE_FP / q->wsum; /* XXX note theory */
        // XXX cl->S = q->V; ?
        return 0;
}

/* remove an empty queue */
static int
qfq_free_queue(struct dn_queue *_q)
{
        struct qfq_sched *q = (struct qfq_sched *)(_q->_si + 1);
        struct qfq_class *cl = (struct qfq_class *)_q;
        if (cl->inv_w) {
                q->wsum -= ONE_FP/cl->inv_w;
                if (q->wsum != 0)
                        q->iwsum = ONE_FP / q->wsum;
                cl->inv_w = 0; /* reset weight to avoid run twice */
        }
        return 0;
}

/* Calculate a mask to mimic what would be ffs_from(). */
static inline unsigned long
mask_from(unsigned long bitmap, int from)
{
        return bitmap & ~((1UL << from) - 1);
}

/*
 * The state computation relies on ER=0, IR=1, EB=2, IB=3
 * First compute eligibility comparing grp->S, q->V,
 * then check if someone is blocking us and possibly add EB
 */
static inline unsigned int
qfq_calc_state(struct qfq_sched *q, struct qfq_group *grp)
{
        /* if S > V we are not eligible */
        unsigned int state = qfq_gt(grp->S, q->V);
        unsigned long mask = mask_from(q->bitmaps[ER], grp->index);
        struct qfq_group *next;

        if (mask) {
                next = qfq_ffs(q, mask);
                if (qfq_gt(grp->F, next->F))
                        state |= EB;
        }

        return state;
}

/*
 * In principle
 *      q->bitmaps[dst] |= q->bitmaps[src] & mask;
 *      q->bitmaps[src] &= ~mask;
 * but we should make sure that src != dst
 */
static inline void
qfq_move_groups(struct qfq_sched *q, unsigned long mask, int src, int dst)
{
        q->bitmaps[dst] |= q->bitmaps[src] & mask;
        q->bitmaps[src] &= ~mask;
}

static inline void
qfq_unblock_groups(struct qfq_sched *q, int index, uint64_t old_finish)
{
        unsigned long mask = mask_from(q->bitmaps[ER], index + 1);
        struct qfq_group *next;

        if (mask) {
                next = qfq_ffs(q, mask);
                if (!qfq_gt(next->F, old_finish))
                        return;
        }

        mask = (1UL << index) - 1;
        qfq_move_groups(q, mask, EB, ER);
        qfq_move_groups(q, mask, IB, IR);
}

/*
 * perhaps
 *
        old_V ^= q->V;
        old_V >>= QFQ_MIN_SLOT_SHIFT;
        if (old_V) {
                ...
        }
 *
 */
static inline void
qfq_make_eligible(struct qfq_sched *q, uint64_t old_V)
{
        unsigned long mask, vslot, old_vslot;

        vslot = q->V >> QFQ_MIN_SLOT_SHIFT;
        old_vslot = old_V >> QFQ_MIN_SLOT_SHIFT;

        if (vslot != old_vslot) {
                /* must be 2ULL, see ToN QFQ article fig.5, we use base-0 fls */
                mask = (2ULL << (__fls(vslot ^ old_vslot))) - 1;
                qfq_move_groups(q, mask, IR, ER);
                qfq_move_groups(q, mask, IB, EB);
        }
}

/*
 * XXX we should make sure that slot becomes less than 32.
 * This is guaranteed by the input values.
 * roundedS is always cl->S rounded on grp->slot_shift bits.
 */
static inline void
qfq_slot_insert(struct qfq_group *grp, struct qfq_class *cl, uint64_t roundedS)
{
        uint64_t slot = (roundedS - grp->S) >> grp->slot_shift;
        unsigned int i = (grp->front + slot) % QFQ_MAX_SLOTS;

        cl->next = grp->slots[i];
        grp->slots[i] = cl;
        __set_bit(slot, &grp->full_slots);
}

/*
 * remove the entry from the slot
 */
static inline void
qfq_front_slot_remove(struct qfq_group *grp)
{
        struct qfq_class **h = &grp->slots[grp->front];

        *h = (*h)->next;
        if (!*h)
                __clear_bit(0, &grp->full_slots);
}

/*
 * Returns the first full queue in a group. As a side effect,
 * adjust the bucket list so the first non-empty bucket is at
 * position 0 in full_slots.
 */
static inline struct qfq_class *
qfq_slot_scan(struct qfq_group *grp)
{
        int i;

        ND("grp %d full %x", grp->index, grp->full_slots);
        if (!grp->full_slots)
                return NULL;

        i = ffs(grp->full_slots) - 1; // zero-based
        if (i > 0) {
                grp->front = (grp->front + i) % QFQ_MAX_SLOTS;
                grp->full_slots >>= i;
        }

        return grp->slots[grp->front];
}

/*
 * adjust the bucket list. When the start time of a group decreases,
 * we move the index down (modulo QFQ_MAX_SLOTS) so we don't need to
 * move the objects. The mask of occupied slots must be shifted
 * because we use ffs() to find the first non-empty slot.
 * This covers decreases in the group's start time, but what about
 * increases of the start time ?
 * Here too we should make sure that i is less than 32
 */
static inline void
qfq_slot_rotate(struct qfq_sched *q, struct qfq_group *grp, uint64_t roundedS)
{
        unsigned int i = (grp->S - roundedS) >> grp->slot_shift;

        (void)q;
        grp->full_slots <<= i;
        grp->front = (grp->front - i) % QFQ_MAX_SLOTS;
}

static inline void
qfq_update_eligible(struct qfq_sched *q, uint64_t old_V)
{
        bitmap ineligible;

        ineligible = q->bitmaps[IR] | q->bitmaps[IB];
        if (ineligible) {
                if (!q->bitmaps[ER]) {
                        struct qfq_group *grp;
                        grp = qfq_ffs(q, ineligible);
                        if (qfq_gt(grp->S, q->V))
                                q->V = grp->S;
                }
                qfq_make_eligible(q, old_V);
        }
}

/*
 * Updates the class, returns true if also the group needs to be updated.
 */
static inline int
qfq_update_class(struct qfq_sched *q, struct qfq_group *grp,
            struct qfq_class *cl)
{

        (void)q;
        cl->S = cl->F;
        if (cl->_q.mq.head == NULL)  {
                qfq_front_slot_remove(grp);
        } else {
                unsigned int len;
                uint64_t roundedS;

                len = cl->_q.mq.head->m_pkthdr.len;
                cl->F = cl->S + (uint64_t)len * cl->inv_w;
                roundedS = qfq_round_down(cl->S, grp->slot_shift);
                if (roundedS == grp->S)
                        return 0;

                qfq_front_slot_remove(grp);
                qfq_slot_insert(grp, cl, roundedS);
        }
        return 1;
}

static struct mbuf *
qfq_dequeue(struct dn_sch_inst *si)
{
        struct qfq_sched *q = (struct qfq_sched *)(si + 1);
        struct qfq_group *grp;
        struct qfq_class *cl;
        struct mbuf *m;
        uint64_t old_V;

        NO(q->loops++;)
        if (!q->bitmaps[ER]) {
                NO(if (q->queued)
                        dump_sched(q, "start dequeue");)
                return NULL;
        }

        grp = qfq_ffs(q, q->bitmaps[ER]);

        cl = grp->slots[grp->front];
        /* extract from the first bucket in the bucket list */
        m = dn_dequeue(&cl->_q);

        if (!m) {
                D("BUG/* non-workconserving leaf */");
                return NULL;
        }
        NO(q->queued--;)
        old_V = q->V;
        q->V += (uint64_t)m->m_pkthdr.len * q->iwsum;
        ND("m is %p F 0x%llx V now 0x%llx", m, cl->F, q->V);

        if (qfq_update_class(q, grp, cl)) {
                uint64_t old_F = grp->F;
                cl = qfq_slot_scan(grp);
                if (!cl) { /* group gone, remove from ER */
                        __clear_bit(grp->index, &q->bitmaps[ER]);
                        // grp->S = grp->F + 1; // XXX debugging only
                } else {
                        uint64_t roundedS = qfq_round_down(cl->S, grp->slot_shift);
                        unsigned int s;

                        if (grp->S == roundedS)
                                goto skip_unblock;
                        grp->S = roundedS;
                        grp->F = roundedS + (2ULL << grp->slot_shift);
                        /* remove from ER and put in the new set */
                        __clear_bit(grp->index, &q->bitmaps[ER]);
                        s = qfq_calc_state(q, grp);
                        __set_bit(grp->index, &q->bitmaps[s]);
                }
                /* we need to unblock even if the group has gone away */
                qfq_unblock_groups(q, grp->index, old_F);
        }

skip_unblock:
        qfq_update_eligible(q, old_V);
        NO(if (!q->bitmaps[ER] && q->queued)
                dump_sched(q, "end dequeue");)

        return m;
}

/*
 * Assign a reasonable start time for a new flow k in group i.
 * Admissible values for \hat(F) are multiples of \sigma_i
 * no greater than V+\sigma_i . Larger values mean that
 * we had a wraparound so we consider the timestamp to be stale.
 *
 * If F is not stale and F >= V then we set S = F.
 * Otherwise we should assign S = V, but this may violate
 * the ordering in ER. So, if we have groups in ER, set S to
 * the F_j of the first group j which would be blocking us.
 * We are guaranteed not to move S backward because
 * otherwise our group i would still be blocked.
 */
static inline void
qfq_update_start(struct qfq_sched *q, struct qfq_class *cl)
{
        unsigned long mask;
        uint64_t limit, roundedF;
        int slot_shift = cl->grp->slot_shift;

        roundedF = qfq_round_down(cl->F, slot_shift);
        limit = qfq_round_down(q->V, slot_shift) + (1ULL << slot_shift);

        if (!qfq_gt(cl->F, q->V) || qfq_gt(roundedF, limit)) {
                /* timestamp was stale */
                mask = mask_from(q->bitmaps[ER], cl->grp->index);
                if (mask) {
                        struct qfq_group *next = qfq_ffs(q, mask);
                        if (qfq_gt(roundedF, next->F)) {
                                /* from pv 71261956973ba9e0637848a5adb4a5819b4bae83 */
                                if (qfq_gt(limit, next->F))
                                        cl->S = next->F;
                                else /* preserve timestamp correctness */
                                        cl->S = limit;
                                return;
                        }
                }
                cl->S = q->V;
        } else { /* timestamp is not stale */
                cl->S = cl->F;
        }
}

static int
qfq_enqueue(struct dn_sch_inst *si, struct dn_queue *_q, struct mbuf *m)
{
        struct qfq_sched *q = (struct qfq_sched *)(si + 1);
        struct qfq_group *grp;
        struct qfq_class *cl = (struct qfq_class *)_q;
        uint64_t roundedS;
        int s;

        NO(q->loops++;)
        DX(4, "len %d flow %p inv_w 0x%x grp %d", m->m_pkthdr.len,
                _q, cl->inv_w, cl->grp->index);
        /* XXX verify that the packet obeys the parameters */
        if (m != _q->mq.head) {
                if (dn_enqueue(_q, m, 0)) /* packet was dropped */
                        return 1;
                NO(q->queued++;)
                if (m != _q->mq.head)
                        return 0;
        }
        /* If reach this point, queue q was idle */
        grp = cl->grp;
        qfq_update_start(q, cl); /* adjust start time */
        /* compute new finish time and rounded start. */
        cl->F = cl->S + (uint64_t)(m->m_pkthdr.len) * cl->inv_w;
        roundedS = qfq_round_down(cl->S, grp->slot_shift);

        /*
         * insert cl in the correct bucket.
         * If cl->S >= grp->S we don't need to adjust the
         * bucket list and simply go to the insertion phase.
         * Otherwise grp->S is decreasing, we must make room
         * in the bucket list, and also recompute the group state.
         * Finally, if there were no flows in this group and nobody
         * was in ER make sure to adjust V.
         */
        if (grp->full_slots) {
                if (!qfq_gt(grp->S, cl->S))
                        goto skip_update;
                /* create a slot for this cl->S */
                qfq_slot_rotate(q, grp, roundedS);
                /* group was surely ineligible, remove */
                __clear_bit(grp->index, &q->bitmaps[IR]);
                __clear_bit(grp->index, &q->bitmaps[IB]);
        } else if (!q->bitmaps[ER] && qfq_gt(roundedS, q->V))
                q->V = roundedS;

        grp->S = roundedS;
        grp->F = roundedS + (2ULL << grp->slot_shift); // i.e. 2\sigma_i
        s = qfq_calc_state(q, grp);
        __set_bit(grp->index, &q->bitmaps[s]);
        ND("new state %d 0x%x", s, q->bitmaps[s]);
        ND("S %llx F %llx V %llx", cl->S, cl->F, q->V);
skip_update:
        qfq_slot_insert(grp, cl, roundedS);

        return 0;
}

#if 0
static inline void
qfq_slot_remove(struct qfq_sched *q, struct qfq_group *grp,
        struct qfq_class *cl, struct qfq_class **pprev)
{
        unsigned int i, offset;
        uint64_t roundedS;

        roundedS = qfq_round_down(cl->S, grp->slot_shift);
        offset = (roundedS - grp->S) >> grp->slot_shift;
        i = (grp->front + offset) % QFQ_MAX_SLOTS;

#ifdef notyet
        if (!pprev) {
                pprev = &grp->slots[i];
                while (*pprev && *pprev != cl)
                        pprev = &(*pprev)->next;
        }
#endif

        *pprev = cl->next;
        if (!grp->slots[i])
                __clear_bit(offset, &grp->full_slots);
}

/*
 * called to forcibly destroy a queue.
 * If the queue is not in the front bucket, or if it has
 * other queues in the front bucket, we can simply remove
 * the queue with no other side effects.
 * Otherwise we must propagate the event up.
 * XXX description to be completed.
 */
static void
qfq_deactivate_class(struct qfq_sched *q, struct qfq_class *cl,
                                 struct qfq_class **pprev)
{
        struct qfq_group *grp = &q->groups[cl->index];
        unsigned long mask;
        uint64_t roundedS;
        int s;

        cl->F = cl->S;  // not needed if the class goes away.
        qfq_slot_remove(q, grp, cl, pprev);

        if (!grp->full_slots) {
                /* nothing left in the group, remove from all sets.
                 * Do ER last because if we were blocking other groups
                 * we must unblock them.
                 */
                __clear_bit(grp->index, &q->bitmaps[IR]);
                __clear_bit(grp->index, &q->bitmaps[EB]);
                __clear_bit(grp->index, &q->bitmaps[IB]);

                if (test_bit(grp->index, &q->bitmaps[ER]) &&
                    !(q->bitmaps[ER] & ~((1UL << grp->index) - 1))) {
                        mask = q->bitmaps[ER] & ((1UL << grp->index) - 1);
                        if (mask)
                                mask = ~((1UL << __fls(mask)) - 1);
                        else
                                mask = ~0UL;
                        qfq_move_groups(q, mask, EB, ER);
                        qfq_move_groups(q, mask, IB, IR);
                }
                __clear_bit(grp->index, &q->bitmaps[ER]);
        } else if (!grp->slots[grp->front]) {
                cl = qfq_slot_scan(grp);
                roundedS = qfq_round_down(cl->S, grp->slot_shift);
                if (grp->S != roundedS) {
                        __clear_bit(grp->index, &q->bitmaps[ER]);
                        __clear_bit(grp->index, &q->bitmaps[IR]);
                        __clear_bit(grp->index, &q->bitmaps[EB]);
                        __clear_bit(grp->index, &q->bitmaps[IB]);
                        grp->S = roundedS;
                        grp->F = roundedS + (2ULL << grp->slot_shift);
                        s = qfq_calc_state(q, grp);
                        __set_bit(grp->index, &q->bitmaps[s]);
                }
        }
        qfq_update_eligible(q, q->V);
}
#endif

static int
qfq_new_fsk(struct dn_fsk *f)
{
        ipdn_bound_var(&f->fs.par[0], 1, 1, QFQ_MAX_WEIGHT, "qfq weight");
        ipdn_bound_var(&f->fs.par[1], 1500, 1, 2000, "qfq maxlen");
        ND("weight %d len %d\n", f->fs.par[0], f->fs.par[1]);
        return 0;
}

/*
 * initialize a new scheduler instance
 */
static int
qfq_new_sched(struct dn_sch_inst *si)
{
        struct qfq_sched *q = (struct qfq_sched *)(si + 1);
        struct qfq_group *grp;
        int i;

        for (i = 0; i <= QFQ_MAX_INDEX; i++) {
                grp = &q->groups[i];
                grp->index = i;
                grp->slot_shift = QFQ_MTU_SHIFT + FRAC_BITS -
                                        (QFQ_MAX_INDEX - i);
        }
        return 0;
}

/*
 * QFQ scheduler descriptor
 */
static struct dn_alg qfq_desc = {
        _SI( .type = ) DN_SCHED_QFQ,
        _SI( .name = ) "QFQ",
        _SI( .flags = ) DN_MULTIQUEUE,

        _SI( .schk_datalen = ) 0,
        _SI( .si_datalen = ) sizeof(struct qfq_sched),
        _SI( .q_datalen = ) sizeof(struct qfq_class) - sizeof(struct dn_queue),

        _SI( .enqueue = ) qfq_enqueue,
        _SI( .dequeue = ) qfq_dequeue,

        _SI( .config = )  NULL,
        _SI( .destroy = )  NULL,
        _SI( .new_sched = ) qfq_new_sched,
        _SI( .free_sched = )  NULL,
        _SI( .new_fsk = ) qfq_new_fsk,
        _SI( .free_fsk = )  NULL,
        _SI( .new_queue = ) qfq_new_queue,
        _SI( .free_queue = ) qfq_free_queue,
#ifdef NEW_AQM
        _SI( .getconfig = )  NULL,
#endif
};

DECLARE_DNSCHED_MODULE(dn_qfq, &qfq_desc);

#ifdef QFQ_DEBUG
static void
dump_groups(struct qfq_sched *q, uint32_t mask)
{
        int i, j;

        for (i = 0; i < QFQ_MAX_INDEX + 1; i++) {
                struct qfq_group *g = &q->groups[i];

                if (0 == (mask & (1<<i)))
                        continue;
                for (j = 0; j < QFQ_MAX_SLOTS; j++) {
                        if (g->slots[j])
                                D("    bucket %d %p", j, g->slots[j]);
                }
                D("full_slots 0x%llx", (_P64)g->full_slots);
                D("        %2d S 0x%20llx F 0x%llx %c", i,
                        (_P64)g->S, (_P64)g->F,
                        mask & (1<<i) ? '1' : '0');
        }
}

static void
dump_sched(struct qfq_sched *q, const char *msg)
{
        D("--- in %s: ---", msg);
        D("loops %d queued %d V 0x%llx", q->loops, q->queued, (_P64)q->V);
        D("    ER 0x%08x", (unsigned)q->bitmaps[ER]);
        D("    EB 0x%08x", (unsigned)q->bitmaps[EB]);
        D("    IR 0x%08x", (unsigned)q->bitmaps[IR]);
        D("    IB 0x%08x", (unsigned)q->bitmaps[IB]);
        dump_groups(q, 0xffffffff);
};
#endif /* QFQ_DEBUG */