/*
 * Copyright (c) 2008 The DragonFly Project.  All rights reserved.
 * 
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 * 
 * 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.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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
 * COPYRIGHT HOLDERS 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.
 * 
 * $DragonFly: src/sys/net/altq/altq_fairq.c,v 1.1 2008/04/06 18:58:15 dillon Exp $
 */
/*
 * Matt: I gutted altq_priq.c and used it as a skeleton on which to build
 * fairq.  The fairq algorithm is completely different then priq, of course,
 * but because I used priq's skeleton I believe I should include priq's
 * copyright.
 *
 * Copyright (C) 2000-2003
 *      Sony Computer Science Laboratories Inc.  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 SONY CSL 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 SONY CSL 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.
 */

/*
 * FAIRQ - take traffic classified by keep state (hashed into
 * mbuf->m_pkthdr.altq_state_hash) and bucketize it.  Fairly extract
 * the first packet from each bucket in a round-robin fashion.
 *
 * TODO - better overall qlimit support (right now it is per-bucket).
 *      - NOTE: red etc is per bucket, not overall.
 *      - better service curve support.
 *
 * EXAMPLE:
 *
 *  altq on em0 fairq bandwidth 650Kb queue { std, bulk }
 *  queue std  priority 3 bandwidth 400Kb \
 *      fairq (buckets 64, default, hogs 1Kb) qlimit 50
 *  queue bulk priority 2 bandwidth 100Kb \
 *      fairq (buckets 64, hogs 1Kb) qlimit 50
 *
 *  pass out on em0 from any to any keep state queue std
 *  pass out on em0 inet proto tcp ..... port ... keep state queue bulk
 */
#include "opt_altq.h"
#include "opt_inet.h"
#include "opt_inet6.h"

#ifdef ALTQ_FAIRQ  /* fairq is enabled in the kernel conf */

#include <sys/param.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/errno.h>
#include <sys/kernel.h>
#include <sys/queue.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/if_private.h>
#include <netinet/in.h>

#include <netpfil/pf/pf.h>
#include <netpfil/pf/pf_altq.h>
#include <netpfil/pf/pf_mtag.h>
#include <net/altq/altq.h>
#include <net/altq/altq_fairq.h>

/*
 * function prototypes
 */
static int      fairq_clear_interface(struct fairq_if *);
static int      fairq_request(struct ifaltq *, int, void *);
static void     fairq_purge(struct fairq_if *);
static struct fairq_class *fairq_class_create(struct fairq_if *, int, int, u_int, struct fairq_opts *, int);
static int      fairq_class_destroy(struct fairq_class *);
static int      fairq_enqueue(struct ifaltq *, struct mbuf *, struct altq_pktattr *);
static struct mbuf *fairq_dequeue(struct ifaltq *, int);

static int      fairq_addq(struct fairq_class *, struct mbuf *, u_int32_t);
static struct mbuf *fairq_getq(struct fairq_class *, uint64_t);
static struct mbuf *fairq_pollq(struct fairq_class *, uint64_t, int *);
static fairq_bucket_t *fairq_selectq(struct fairq_class *, int);
static void     fairq_purgeq(struct fairq_class *);

static void     get_class_stats(struct fairq_classstats *, struct fairq_class *);
static struct fairq_class *clh_to_clp(struct fairq_if *, uint32_t);

int
fairq_pfattach(struct pf_altq *a)
{
        struct ifnet *ifp;
        int error;

        if ((ifp = ifunit(a->ifname)) == NULL || a->altq_disc == NULL)
                return (EINVAL);

        error = altq_attach(&ifp->if_snd, ALTQT_FAIRQ, a->altq_disc,
            fairq_enqueue, fairq_dequeue, fairq_request);

        return (error);
}

int
fairq_add_altq(struct ifnet *ifp, struct pf_altq *a)
{
        struct fairq_if *pif;

        if (ifp == NULL)
                return (EINVAL);
        if (!ALTQ_IS_READY(&ifp->if_snd))
                return (ENODEV);

        pif = malloc(sizeof(struct fairq_if),
                        M_DEVBUF, M_WAITOK | M_ZERO);
        pif->pif_bandwidth = a->ifbandwidth;
        pif->pif_maxpri = -1;
        pif->pif_ifq = &ifp->if_snd;

        /* keep the state in pf_altq */
        a->altq_disc = pif;

        return (0);
}

int
fairq_remove_altq(struct pf_altq *a)
{
        struct fairq_if *pif;

        if ((pif = a->altq_disc) == NULL)
                return (EINVAL);
        a->altq_disc = NULL;

        fairq_clear_interface(pif);

        free(pif, M_DEVBUF);
        return (0);
}

int
fairq_add_queue(struct pf_altq *a)
{
        struct fairq_if *pif;
        struct fairq_class *cl;

        if ((pif = a->altq_disc) == NULL)
                return (EINVAL);

        /* check parameters */
        if (a->priority >= FAIRQ_MAXPRI)
                return (EINVAL);
        if (a->qid == 0)
                return (EINVAL);
        if (pif->pif_classes[a->priority] != NULL)
                return (EBUSY);
        if (clh_to_clp(pif, a->qid) != NULL)
                return (EBUSY);

        cl = fairq_class_create(pif, a->priority, a->qlimit, a->bandwidth,
                               &a->pq_u.fairq_opts, a->qid);
        if (cl == NULL)
                return (ENOMEM);

        return (0);
}

int
fairq_remove_queue(struct pf_altq *a)
{
        struct fairq_if *pif;
        struct fairq_class *cl;

        if ((pif = a->altq_disc) == NULL)
                return (EINVAL);

        if ((cl = clh_to_clp(pif, a->qid)) == NULL)
                return (EINVAL);

        return (fairq_class_destroy(cl));
}

int
fairq_getqstats(struct pf_altq *a, void *ubuf, int *nbytes, int version)
{
        struct fairq_if *pif;
        struct fairq_class *cl;
        struct fairq_classstats stats;
        int error = 0;

        if ((pif = altq_lookup(a->ifname, ALTQT_FAIRQ)) == NULL)
                return (EBADF);

        if ((cl = clh_to_clp(pif, a->qid)) == NULL)
                return (EINVAL);

        if (*nbytes < sizeof(stats))
                return (EINVAL);

        get_class_stats(&stats, cl);

        if ((error = copyout((caddr_t)&stats, ubuf, sizeof(stats))) != 0)
                return (error);
        *nbytes = sizeof(stats);
        return (0);
}

/*
 * bring the interface back to the initial state by discarding
 * all the filters and classes.
 */
static int
fairq_clear_interface(struct fairq_if *pif)
{
        struct fairq_class *cl;
        int pri;

        /* clear out the classes */
        for (pri = 0; pri <= pif->pif_maxpri; pri++) {
                if ((cl = pif->pif_classes[pri]) != NULL)
                        fairq_class_destroy(cl);
        }

        return (0);
}

static int
fairq_request(struct ifaltq *ifq, int req, void *arg)
{
        struct fairq_if *pif = (struct fairq_if *)ifq->altq_disc;

        IFQ_LOCK_ASSERT(ifq);

        switch (req) {
        case ALTRQ_PURGE:
                fairq_purge(pif);
                break;
        }
        return (0);
}

/* discard all the queued packets on the interface */
static void
fairq_purge(struct fairq_if *pif)
{
        struct fairq_class *cl;
        int pri;

        for (pri = 0; pri <= pif->pif_maxpri; pri++) {
                if ((cl = pif->pif_classes[pri]) != NULL && cl->cl_head)
                        fairq_purgeq(cl);
        }
        if (ALTQ_IS_ENABLED(pif->pif_ifq))
                pif->pif_ifq->ifq_len = 0;
}

static struct fairq_class *
fairq_class_create(struct fairq_if *pif, int pri, int qlimit,
                   u_int bandwidth, struct fairq_opts *opts, int qid)
{
        struct fairq_class *cl;
        int flags = opts->flags;
        u_int nbuckets = opts->nbuckets;
        int i;

#ifndef ALTQ_RED
        if (flags & FARF_RED) {
#ifdef ALTQ_DEBUG
                printf("fairq_class_create: RED not configured for FAIRQ!\n");
#endif
                return (NULL);
        }
#endif
#ifndef ALTQ_CODEL
        if (flags & FARF_CODEL) {
#ifdef ALTQ_DEBUG
                printf("fairq_class_create: CODEL not configured for FAIRQ!\n");
#endif
                return (NULL);
        }
#endif
        if (nbuckets == 0)
                nbuckets = 256;
        if (nbuckets > FAIRQ_MAX_BUCKETS)
                nbuckets = FAIRQ_MAX_BUCKETS;
        /* enforce power-of-2 size */
        while ((nbuckets ^ (nbuckets - 1)) != ((nbuckets << 1) - 1))
                ++nbuckets;

        if ((cl = pif->pif_classes[pri]) != NULL) {
                /* modify the class instead of creating a new one */
                IFQ_LOCK(cl->cl_pif->pif_ifq);
                if (cl->cl_head)
                        fairq_purgeq(cl);
                IFQ_UNLOCK(cl->cl_pif->pif_ifq);
#ifdef ALTQ_RIO
                if (cl->cl_qtype == Q_RIO)
                        rio_destroy((rio_t *)cl->cl_red);
#endif
#ifdef ALTQ_RED
                if (cl->cl_qtype == Q_RED)
                        red_destroy(cl->cl_red);
#endif
#ifdef ALTQ_CODEL
                if (cl->cl_qtype == Q_CODEL)
                        codel_destroy(cl->cl_codel);
#endif
        } else {
                cl = malloc(sizeof(struct fairq_class),
                                M_DEVBUF, M_WAITOK | M_ZERO);
                cl->cl_nbuckets = nbuckets;
                cl->cl_nbucket_mask = nbuckets - 1;

                cl->cl_buckets = malloc(
                        sizeof(struct fairq_bucket) * cl->cl_nbuckets,
                        M_DEVBUF, M_WAITOK | M_ZERO);
                cl->cl_head = NULL;
        }

        pif->pif_classes[pri] = cl;
        if (flags & FARF_DEFAULTCLASS)
                pif->pif_default = cl;
        if (qlimit == 0)
                qlimit = 50;  /* use default */
        cl->cl_qlimit = qlimit;
        for (i = 0; i < cl->cl_nbuckets; ++i) {
                qlimit(&cl->cl_buckets[i].queue) = qlimit;
        }
        cl->cl_bandwidth = bandwidth / 8;
        cl->cl_qtype = Q_DROPTAIL;
        cl->cl_flags = flags & FARF_USERFLAGS;
        cl->cl_pri = pri;
        if (pri > pif->pif_maxpri)
                pif->pif_maxpri = pri;
        cl->cl_pif = pif;
        cl->cl_handle = qid;
        cl->cl_hogs_m1 = opts->hogs_m1 / 8;
        cl->cl_lssc_m1 = opts->lssc_m1 / 8;     /* NOT YET USED */

#ifdef ALTQ_RED
        if (flags & (FARF_RED|FARF_RIO)) {
                int red_flags, red_pkttime;

                red_flags = 0;
                if (flags & FARF_ECN)
                        red_flags |= REDF_ECN;
#ifdef ALTQ_RIO
                if (flags & FARF_CLEARDSCP)
                        red_flags |= RIOF_CLEARDSCP;
#endif
                if (pif->pif_bandwidth < 8)
                        red_pkttime = 1000 * 1000 * 1000; /* 1 sec */
                else
                        red_pkttime = (int64_t)pif->pif_ifq->altq_ifp->if_mtu
                          * 1000 * 1000 * 1000 / (pif->pif_bandwidth / 8);
#ifdef ALTQ_RIO
                if (flags & FARF_RIO) {
                        cl->cl_red = (red_t *)rio_alloc(0, NULL,
                                                red_flags, red_pkttime);
                        if (cl->cl_red != NULL)
                                cl->cl_qtype = Q_RIO;
                } else
#endif
                if (flags & FARF_RED) {
                        cl->cl_red = red_alloc(0, 0,
                            cl->cl_qlimit * 10/100,
                            cl->cl_qlimit * 30/100,
                            red_flags, red_pkttime);
                        if (cl->cl_red != NULL)
                                cl->cl_qtype = Q_RED;
                }
        }
#endif /* ALTQ_RED */
#ifdef ALTQ_CODEL
        if (flags & FARF_CODEL) {
                cl->cl_codel = codel_alloc(5, 100, 0);
                if (cl->cl_codel != NULL)
                        cl->cl_qtype = Q_CODEL;
        }
#endif

        return (cl);
}

static int
fairq_class_destroy(struct fairq_class *cl)
{
        struct fairq_if *pif;
        int pri;

        IFQ_LOCK(cl->cl_pif->pif_ifq);

        if (cl->cl_head)
                fairq_purgeq(cl);

        pif = cl->cl_pif;
        pif->pif_classes[cl->cl_pri] = NULL;
        if (pif->pif_poll_cache == cl)
                pif->pif_poll_cache = NULL;
        if (pif->pif_maxpri == cl->cl_pri) {
                for (pri = cl->cl_pri; pri >= 0; pri--)
                        if (pif->pif_classes[pri] != NULL) {
                                pif->pif_maxpri = pri;
                                break;
                        }
                if (pri < 0)
                        pif->pif_maxpri = -1;
        }
        IFQ_UNLOCK(cl->cl_pif->pif_ifq);

        if (cl->cl_red != NULL) {
#ifdef ALTQ_RIO
                if (cl->cl_qtype == Q_RIO)
                        rio_destroy((rio_t *)cl->cl_red);
#endif
#ifdef ALTQ_RED
                if (cl->cl_qtype == Q_RED)
                        red_destroy(cl->cl_red);
#endif
#ifdef ALTQ_CODEL
                if (cl->cl_qtype == Q_CODEL)
                        codel_destroy(cl->cl_codel);
#endif
        }
        free(cl->cl_buckets, M_DEVBUF);
        free(cl, M_DEVBUF);

        return (0);
}

/*
 * fairq_enqueue is an enqueue function to be registered to
 * (*altq_enqueue) in struct ifaltq.
 */
static int
fairq_enqueue(struct ifaltq *ifq, struct mbuf *m, struct altq_pktattr *pktattr)
{
        struct fairq_if *pif = (struct fairq_if *)ifq->altq_disc;
        struct fairq_class *cl = NULL; /* Make compiler happy */
        struct pf_mtag *t;
        u_int32_t qid_hash = 0;
        int len;

        IFQ_LOCK_ASSERT(ifq);

        /* grab class set by classifier */
        if ((m->m_flags & M_PKTHDR) == 0) {
                /* should not happen */
                printf("altq: packet for %s does not have pkthdr\n",
                        ifq->altq_ifp->if_xname);
                m_freem(m);
                return (ENOBUFS);
        }

        if ((t = pf_find_mtag(m)) != NULL) {
                cl = clh_to_clp(pif, t->qid);
                qid_hash = t->qid_hash;
        }
        if (cl == NULL) {
                cl = pif->pif_default;
                if (cl == NULL) {
                        m_freem(m);
                        return (ENOBUFS);
                }
        }
        cl->cl_flags |= FARF_HAS_PACKETS;
        cl->cl_pktattr = NULL;
        len = m_pktlen(m);
        if (fairq_addq(cl, m, qid_hash) != 0) {
                /* drop occurred.  mbuf was freed in fairq_addq. */
                PKTCNTR_ADD(&cl->cl_dropcnt, len);
                return (ENOBUFS);
        }
        IFQ_INC_LEN(ifq);

        return (0);
}

/*
 * fairq_dequeue is a dequeue function to be registered to
 * (*altq_dequeue) in struct ifaltq.
 *
 * note: ALTDQ_POLL returns the next packet without removing the packet
 *      from the queue.  ALTDQ_REMOVE is a normal dequeue operation.
 *      ALTDQ_REMOVE must return the same packet if called immediately
 *      after ALTDQ_POLL.
 */
static struct mbuf *
fairq_dequeue(struct ifaltq *ifq, int op)
{
        struct fairq_if *pif = (struct fairq_if *)ifq->altq_disc;
        struct fairq_class *cl;
        struct fairq_class *best_cl;
        struct mbuf *best_m;
        struct mbuf *m = NULL;
        uint64_t cur_time = read_machclk();
        int pri;
        int hit_limit;

        IFQ_LOCK_ASSERT(ifq);

        if (IFQ_IS_EMPTY(ifq)) {
                return (NULL);
        }

        if (pif->pif_poll_cache && op == ALTDQ_REMOVE) {
                best_cl = pif->pif_poll_cache;
                m = fairq_getq(best_cl, cur_time);
                pif->pif_poll_cache = NULL;
                if (m) {
                        IFQ_DEC_LEN(ifq);
                        PKTCNTR_ADD(&best_cl->cl_xmitcnt, m_pktlen(m));
                        return (m);
                }
        } else {
                best_cl = NULL;
                best_m = NULL;

                for (pri = pif->pif_maxpri;  pri >= 0; pri--) {
                        if ((cl = pif->pif_classes[pri]) == NULL)
                                continue;
                        if ((cl->cl_flags & FARF_HAS_PACKETS) == 0)
                                continue;
                        m = fairq_pollq(cl, cur_time, &hit_limit);
                        if (m == NULL) {
                                cl->cl_flags &= ~FARF_HAS_PACKETS;
                                continue;
                        }

                        /*
                         * Only override the best choice if we are under
                         * the BW limit.
                         */
                        if (hit_limit == 0 || best_cl == NULL) {
                                best_cl = cl;
                                best_m = m;
                        }

                        /*
                         * Remember the highest priority mbuf in case we
                         * do not find any lower priority mbufs.
                         */
                        if (hit_limit)
                                continue;
                        break;
                }
                if (op == ALTDQ_POLL) {
                        pif->pif_poll_cache = best_cl;
                        m = best_m;
                } else if (best_cl) {
                        m = fairq_getq(best_cl, cur_time);
                        if (m != NULL) {
                                IFQ_DEC_LEN(ifq);
                                PKTCNTR_ADD(&best_cl->cl_xmitcnt, m_pktlen(m));
                        }
                } 
                return (m);
        }
        return (NULL);
}

static int
fairq_addq(struct fairq_class *cl, struct mbuf *m, u_int32_t bucketid)
{
        fairq_bucket_t *b;
        u_int hindex;
        uint64_t bw;

        /*
         * If the packet doesn't have any keep state put it on the end of
         * our queue.  XXX this can result in out of order delivery.
         */
        if (bucketid == 0) {
                if (cl->cl_head)
                        b = cl->cl_head->prev;
                else
                        b = &cl->cl_buckets[0];
        } else {
                hindex = bucketid & cl->cl_nbucket_mask;
                b = &cl->cl_buckets[hindex];
        }

        /*
         * Add the bucket to the end of the circular list of active buckets.
         *
         * As a special case we add the bucket to the beginning of the list
         * instead of the end if it was not previously on the list and if
         * its traffic is less then the hog level.
         */
        if (b->in_use == 0) {
                b->in_use = 1;
                if (cl->cl_head == NULL) {
                        cl->cl_head = b;
                        b->next = b;
                        b->prev = b;
                } else {
                        b->next = cl->cl_head;
                        b->prev = cl->cl_head->prev;
                        b->prev->next = b;
                        b->next->prev = b;

                        if (b->bw_delta && cl->cl_hogs_m1) {
                                bw = b->bw_bytes * machclk_freq / b->bw_delta;
                                if (bw < cl->cl_hogs_m1)
                                        cl->cl_head = b;
                        }
                }
        }

#ifdef ALTQ_RIO
        if (cl->cl_qtype == Q_RIO)
                return rio_addq((rio_t *)cl->cl_red, &b->queue, m, cl->cl_pktattr);
#endif
#ifdef ALTQ_RED
        if (cl->cl_qtype == Q_RED)
                return red_addq(cl->cl_red, &b->queue, m, cl->cl_pktattr);
#endif
#ifdef ALTQ_CODEL
        if (cl->cl_qtype == Q_CODEL)
                return codel_addq(cl->cl_codel, &b->queue, m);
#endif
        if (qlen(&b->queue) >= qlimit(&b->queue)) {
                m_freem(m);
                return (-1);
        }

        if (cl->cl_flags & FARF_CLEARDSCP)
                write_dsfield(m, cl->cl_pktattr, 0);

        _addq(&b->queue, m);

        return (0);
}

static struct mbuf *
fairq_getq(struct fairq_class *cl, uint64_t cur_time)
{
        fairq_bucket_t *b;
        struct mbuf *m;

        b = fairq_selectq(cl, 0);
        if (b == NULL)
                m = NULL;
#ifdef ALTQ_RIO
        else if (cl->cl_qtype == Q_RIO)
                m = rio_getq((rio_t *)cl->cl_red, &b->queue);
#endif
#ifdef ALTQ_RED
        else if (cl->cl_qtype == Q_RED)
                m = red_getq(cl->cl_red, &b->queue);
#endif
#ifdef ALTQ_CODEL
        else if (cl->cl_qtype == Q_CODEL)
                m = codel_getq(cl->cl_codel, &b->queue);
#endif
        else
                m = _getq(&b->queue);

        /*
         * Calculate the BW change
         */
        if (m != NULL) {
                uint64_t delta;

                /*
                 * Per-class bandwidth calculation
                 */
                delta = (cur_time - cl->cl_last_time);
                if (delta > machclk_freq * 8)
                        delta = machclk_freq * 8;
                cl->cl_bw_delta += delta;
                cl->cl_bw_bytes += m->m_pkthdr.len;
                cl->cl_last_time = cur_time;
                cl->cl_bw_delta -= cl->cl_bw_delta >> 3;
                cl->cl_bw_bytes -= cl->cl_bw_bytes >> 3;

                /*
                 * Per-bucket bandwidth calculation
                 */
                delta = (cur_time - b->last_time);
                if (delta > machclk_freq * 8)
                        delta = machclk_freq * 8;
                b->bw_delta += delta;
                b->bw_bytes += m->m_pkthdr.len;
                b->last_time = cur_time;
                b->bw_delta -= b->bw_delta >> 3;
                b->bw_bytes -= b->bw_bytes >> 3;
        }
        return(m);
}

/*
 * Figure out what the next packet would be if there were no limits.  If
 * this class hits its bandwidth limit *hit_limit is set to no-zero, otherwise
 * it is set to 0.  A non-NULL mbuf is returned either way.
 */
static struct mbuf *
fairq_pollq(struct fairq_class *cl, uint64_t cur_time, int *hit_limit)
{
        fairq_bucket_t *b;
        struct mbuf *m;
        uint64_t delta;
        uint64_t bw;

        *hit_limit = 0;
        b = fairq_selectq(cl, 1);
        if (b == NULL)
                return(NULL);
        m = qhead(&b->queue);

        /*
         * Did this packet exceed the class bandwidth?  Calculate the
         * bandwidth component of the packet.
         *
         * - Calculate bytes per second
         */
        delta = cur_time - cl->cl_last_time;
        if (delta > machclk_freq * 8)
                delta = machclk_freq * 8;
        cl->cl_bw_delta += delta;
        cl->cl_last_time = cur_time;
        if (cl->cl_bw_delta) {
                bw = cl->cl_bw_bytes * machclk_freq / cl->cl_bw_delta;

                if (bw > cl->cl_bandwidth)
                        *hit_limit = 1;
#ifdef ALTQ_DEBUG
                printf("BW %6ju relative to %6u %d queue %p\n",
                        (uintmax_t)bw, cl->cl_bandwidth, *hit_limit, b);
#endif
        }
        return(m);
}

/*
 * Locate the next queue we want to pull a packet out of.  This code
 * is also responsible for removing empty buckets from the circular list.
 */
static
fairq_bucket_t *
fairq_selectq(struct fairq_class *cl, int ispoll)
{
        fairq_bucket_t *b;
        uint64_t bw;

        if (ispoll == 0 && cl->cl_polled) {
                b = cl->cl_polled;
                cl->cl_polled = NULL;
                return(b);
        }

        while ((b = cl->cl_head) != NULL) {
                /*
                 * Remove empty queues from consideration
                 */
                if (qempty(&b->queue)) {
                        b->in_use = 0;
                        cl->cl_head = b->next;
                        if (cl->cl_head == b) {
                                cl->cl_head = NULL;
                        } else {
                                b->next->prev = b->prev;
                                b->prev->next = b->next;
                        }
                        continue;
                }

                /*
                 * Advance the round robin.  Queues with bandwidths less
                 * then the hog bandwidth are allowed to burst.
                 */
                if (cl->cl_hogs_m1 == 0) {
                        cl->cl_head = b->next;
                } else if (b->bw_delta) {
                        bw = b->bw_bytes * machclk_freq / b->bw_delta;
                        if (bw >= cl->cl_hogs_m1) {
                                cl->cl_head = b->next;
                        }
                        /*
                         * XXX TODO - 
                         */
                }

                /*
                 * Return bucket b.
                 */
                break;
        }
        if (ispoll)
                cl->cl_polled = b;
        return(b);
}

static void
fairq_purgeq(struct fairq_class *cl)
{
        fairq_bucket_t *b;
        struct mbuf *m;

        while ((b = fairq_selectq(cl, 0)) != NULL) {
                while ((m = _getq(&b->queue)) != NULL) {
                        PKTCNTR_ADD(&cl->cl_dropcnt, m_pktlen(m));
                        m_freem(m);
                }
                ASSERT(qlen(&b->queue) == 0);
        }
}

static void
get_class_stats(struct fairq_classstats *sp, struct fairq_class *cl)
{
        fairq_bucket_t *b;

        memset(sp, 0, sizeof(*sp));

        sp->class_handle = cl->cl_handle;
        sp->qlimit = cl->cl_qlimit;
        sp->xmit_cnt = cl->cl_xmitcnt;
        sp->drop_cnt = cl->cl_dropcnt;
        sp->qtype = cl->cl_qtype;
        sp->qlength = 0;

        if (cl->cl_head) {
                b = cl->cl_head;
                do {
                        sp->qlength += qlen(&b->queue);
                        b = b->next;
                } while (b != cl->cl_head);
        }

#ifdef ALTQ_RED
        if (cl->cl_qtype == Q_RED)
                red_getstats(cl->cl_red, &sp->red[0]);
#endif
#ifdef ALTQ_RIO
        if (cl->cl_qtype == Q_RIO)
                rio_getstats((rio_t *)cl->cl_red, &sp->red[0]);
#endif
#ifdef ALTQ_CODEL
        if (cl->cl_qtype == Q_CODEL)
                codel_getstats(cl->cl_codel, &sp->codel);
#endif
}

/* convert a class handle to the corresponding class pointer */
static struct fairq_class *
clh_to_clp(struct fairq_if *pif, uint32_t chandle)
{
        struct fairq_class *cl;
        int idx;

        if (chandle == 0)
                return (NULL);

        for (idx = pif->pif_maxpri; idx >= 0; idx--)
                if ((cl = pif->pif_classes[idx]) != NULL &&
                    cl->cl_handle == chandle)
                        return (cl);

        return (NULL);
}

#endif /* ALTQ_FAIRQ */