xnu-3789.70.16.tar.gz

[apple/xnu.git] / bsd / net / classq / classq_sfb.c

/*
 * Copyright (c) 2011-2013 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

#include <sys/cdefs.h>
#include <sys/param.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/systm.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/proc.h>
#include <sys/errno.h>
#include <sys/kernel.h>
#include <sys/kauth.h>

#include <kern/zalloc.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/if_types.h>
#include <net/dlil.h>
#include <net/flowadv.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#if INET6
#include <netinet/ip6.h>
#endif

#include <net/classq/classq_sfb.h>
#include <net/flowhash.h>
#include <net/net_osdep.h>
#include <dev/random/randomdev.h>

/*
 * Stochastic Fair Blue
 *
 * Wu-chang Feng, Dilip D. Kandlur, Debanjan Saha, Kang G. Shin
 * http://www.thefengs.com/wuchang/blue/CSE-TR-387-99.pdf
 *
 * Based on the NS code with the following parameters:
 *
 *   bytes:     false
 *   decrement: 0.001
 *   increment: 0.005
 *   hold-time: 10ms-50ms (randomized)
 *   algorithm: 0
 *   pbox:      1
 *   pbox-time: 50-100ms (randomized)
 *   hinterval: 11-23 (randomized)
 *
 * This implementation uses L = 2 and N = 32 for 2 sets of:
 *
 *      B[L][N]: L x N array of bins (L levels, N bins per level)
 *
 * Each set effectively creates 32^2 virtual buckets (bin combinations)
 * while using only O(32*2) states.
 *
 * Given a 32-bit hash value, we divide it such that octets [0,1,2,3] are
 * used as index for the bins across the 2 levels, where level 1 uses [0,2]
 * and level 2 uses [1,3].  The 2 values per level correspond to the indices
 * for the current and warm-up sets (section 4.4. in the SFB paper regarding
 * Moving Hash Functions explains the purposes of these 2 sets.)
 */

/*
 * Use Murmur3A_x86_32 for hash function.  It seems to perform consistently
 * across platforms for 1-word key (32-bit flowhash value).  See flowhash.h
 * for other alternatives.  We only need 16-bit hash output.
 */
#define SFB_HASH        net_flowhash_mh3_x86_32
#define SFB_HASHMASK    HASHMASK(16)

#define SFB_BINMASK(_x) \
        ((_x) & HASHMASK(SFB_BINS_SHIFT))

#define SFB_BINST(_sp, _l, _n, _c) \
        (&(*(_sp)->sfb_bins)[_c].stats[_l][_n])

#define SFB_BINFT(_sp, _l, _n, _c) \
        (&(*(_sp)->sfb_bins)[_c].freezetime[_l][_n])

#define SFB_FC_LIST(_sp, _n) \
        (&(*(_sp)->sfb_fc_lists)[_n])

/*
 * The holdtime parameter determines the minimum time interval between
 * two successive updates of the marking probability.  In the event the
 * uplink speed is not known, a default value is chosen and is randomized
 * to be within the following range.
 */
#define HOLDTIME_BASE   (100ULL * 1000 * 1000)  /* 100ms */
#define HOLDTIME_MIN    (10ULL * 1000 * 1000)   /* 10ms */
#define HOLDTIME_MAX    (100ULL * 1000 * 1000)  /* 100ms */

/*
 * The pboxtime parameter determines the bandwidth allocated for rogue
 * flows, i.e. the rate limiting bandwidth.  In the event the uplink speed
 * is not known, a default value is chosen and is randomized to be within
 * the following range.
 */
#define PBOXTIME_BASE   (300ULL * 1000 * 1000)  /* 300ms */
#define PBOXTIME_MIN    (30ULL * 1000 * 1000)   /* 30ms */
#define PBOXTIME_MAX    (300ULL * 1000 * 1000)  /* 300ms */

/*
 * Target queueing delay is the amount of extra delay that can be added
 * to accommodate variations in the link bandwidth. The queue should be
 * large enough to induce this much delay and nothing more than that.
 */
#define TARGET_QDELAY_BASE      (10ULL * 1000 * 1000)   /* 10ms */
#define TARGET_QDELAY_MIN       (10ULL * 1000)  /* 10us */
#define TARGET_QDELAY_MAX       (20ULL * 1000 * 1000 * 1000)    /* 20s */

/*
 * Update interval for checking the extra delay added by the queue. This
 * should be 90-95 percentile of RTT experienced by any TCP connection
 * so that it will take care of the burst traffic.
 */
#define UPDATE_INTERVAL_BASE    (100ULL * 1000 * 1000)  /* 100ms */
#define UPDATE_INTERVAL_MIN     (100ULL * 1000 * 1000)  /* 100ms */
#define UPDATE_INTERVAL_MAX     (10ULL * 1000 * 1000 * 1000)    /* 10s */

#define SFB_RANDOM(sp, tmin, tmax)      ((sfb_random(sp) % (tmax)) + (tmin))

#define SFB_PKT_PBOX    0x1             /* in penalty box */

/* The following mantissa values are in SFB_FP_SHIFT Q format */
#define SFB_MAX_PMARK   (1 << SFB_FP_SHIFT) /* Q14 representation of 1.00 */

/*
 * These are d1 (increment) and d2 (decrement) parameters, used to determine
 * the amount by which the marking probability is incremented when the queue
 * overflows, or is decremented when the link is idle.  d1 is set higher than
 * d2, because link underutilization can occur when congestion management is
 * either too conservative or too aggressive, but packet loss occurs only
 * when congestion management is too conservative.  By weighing heavily
 * against packet loss, it can quickly reach to a substantial increase in
 * traffic load.
 */
#define SFB_INCREMENT   82              /* Q14 representation of 0.005 */
#define SFB_DECREMENT   16              /* Q14 representation of 0.001 */

#define SFB_PMARK_TH    16056           /* Q14 representation of 0.98 */
#define SFB_PMARK_WARM  3276            /* Q14 representation of 0.2 */

#define SFB_PMARK_INC(_bin) do {                                        \
        (_bin)->pmark += sfb_increment;                                 \
        if ((_bin)->pmark > SFB_MAX_PMARK)                              \
                (_bin)->pmark = SFB_MAX_PMARK;                          \
} while (0)

#define SFB_PMARK_DEC(_bin) do {                                        \
        if ((_bin)->pmark > 0) {                                        \
                (_bin)->pmark -= sfb_decrement;                         \
                if ((_bin)->pmark < 0)                                  \
                        (_bin)->pmark = 0;                              \
        }                                                               \
} while (0)

/* Minimum nuber of bytes in queue to get flow controlled */
#define SFB_MIN_FC_THRESHOLD_BYTES      7500

#define SFB_SET_DELAY_HIGH(_sp_, _q_) do {                              \
        (_sp_)->sfb_flags |= SFBF_DELAYHIGH;                            \
        (_sp_)->sfb_fc_threshold = max(SFB_MIN_FC_THRESHOLD_BYTES,      \
                (qsize((_q_)) >> 3));           \
} while (0)

#define SFB_QUEUE_DELAYBASED(_sp_) ((_sp_)->sfb_flags & SFBF_DELAYBASED)
#define SFB_IS_DELAYHIGH(_sp_) ((_sp_)->sfb_flags & SFBF_DELAYHIGH)
#define SFB_QUEUE_DELAYBASED_MAXSIZE    2048    /* max pkts */

#define HINTERVAL_MIN   (10)    /* 10 seconds */
#define HINTERVAL_MAX   (20)    /* 20 seconds */
#define SFB_HINTERVAL(sp) ((sfb_random(sp) % HINTERVAL_MAX) + HINTERVAL_MIN)

#define DEQUEUE_DECAY   7               /* ilog2 of EWMA decay rate, (128) */
#define DEQUEUE_SPIKE(_new, _old)       \
        ((u_int64_t)ABS((int64_t)(_new) - (int64_t)(_old)) > ((_old) << 11))

#define ABS(v)  (((v) > 0) ? (v) : -(v))

#define SFB_ZONE_MAX            32              /* maximum elements in zone */
#define SFB_ZONE_NAME           "classq_sfb"    /* zone name */

#define SFB_BINS_ZONE_MAX       32              /* maximum elements in zone */
#define SFB_BINS_ZONE_NAME      "classq_sfb_bins" /* zone name */

#define SFB_FCL_ZONE_MAX        32              /* maximum elements in zone */
#define SFB_FCL_ZONE_NAME       "classq_sfb_fcl" /* zone name */

/* Place the flow control entries in current bin on level 0 */
#define SFB_FC_LEVEL    0

/* Store SFB hash and flags in the module private scratch space */
#define pkt_sfb_hash8   pkt_mpriv.__mpriv_u.__mpriv32[0].__mpriv32_u.__val8
#define pkt_sfb_hash16  pkt_mpriv.__mpriv_u.__mpriv32[0].__mpriv32_u.__val16
#define pkt_sfb_hash32  pkt_mpriv.__mpriv_u.__mpriv32[0].__mpriv32_u.__val32
#define pkt_sfb_flags   pkt_mpriv.__mpriv_u.__mpriv32[1].__mpriv32_u.__val32

static unsigned int sfb_size;           /* size of zone element */
static struct zone *sfb_zone;           /* zone for sfb */

static unsigned int sfb_bins_size;      /* size of zone element */
static struct zone *sfb_bins_zone;      /* zone for sfb_bins */

static unsigned int sfb_fcl_size;       /* size of zone element */
static struct zone *sfb_fcl_zone;       /* zone for sfb_fc_lists */

/* internal function prototypes */
static u_int32_t sfb_random(struct sfb *);
static struct mbuf *sfb_getq_flow(struct sfb *, class_queue_t *, u_int32_t,
    boolean_t);
static void sfb_resetq(struct sfb *, cqev_t);
static void sfb_calc_holdtime(struct sfb *, u_int64_t);
static void sfb_calc_pboxtime(struct sfb *, u_int64_t);
static void sfb_calc_hinterval(struct sfb *, u_int64_t *);
static void sfb_calc_update_interval(struct sfb *, u_int64_t);
static void sfb_swap_bins(struct sfb *, u_int32_t);
static inline int sfb_pcheck(struct sfb *, struct pkthdr *);
static int sfb_penalize(struct sfb *, struct pkthdr *, struct timespec *);
static void sfb_adjust_bin(struct sfb *, struct sfbbinstats *,
    struct timespec *, struct timespec *, boolean_t);
static void sfb_decrement_bin(struct sfb *, struct sfbbinstats *,
    struct timespec *, struct timespec *);
static void sfb_increment_bin(struct sfb *, struct sfbbinstats *,
    struct timespec *, struct timespec *);
static inline void sfb_dq_update_bins(struct sfb *, struct pkthdr *,
    struct timespec *, u_int32_t qsize);
static inline void sfb_eq_update_bins(struct sfb *, struct pkthdr *);
static int sfb_drop_early(struct sfb *, struct pkthdr *, u_int16_t *,
    struct timespec *);
static boolean_t sfb_bin_addfcentry(struct sfb *, struct pkthdr *);
static void sfb_fclist_append(struct sfb *, struct sfb_fcl *);
static void sfb_fclists_clean(struct sfb *sp);
static int sfb_bin_mark_or_drop(struct sfb *sp, struct sfbbinstats *bin);
static void sfb_detect_dequeue_stall(struct sfb *sp, class_queue_t *,
    struct timespec *);

SYSCTL_NODE(_net_classq, OID_AUTO, sfb, CTLFLAG_RW|CTLFLAG_LOCKED, 0, "SFB");

static u_int64_t sfb_holdtime = 0;      /* 0 indicates "automatic" */
SYSCTL_QUAD(_net_classq_sfb, OID_AUTO, holdtime, CTLFLAG_RW|CTLFLAG_LOCKED,
    &sfb_holdtime, "SFB freeze time in nanoseconds");

static u_int64_t sfb_pboxtime = 0;      /* 0 indicates "automatic" */
SYSCTL_QUAD(_net_classq_sfb, OID_AUTO, pboxtime, CTLFLAG_RW|CTLFLAG_LOCKED,
    &sfb_pboxtime, "SFB penalty box time in nanoseconds");

static u_int64_t sfb_hinterval;
SYSCTL_QUAD(_net_classq_sfb, OID_AUTO, hinterval, CTLFLAG_RW|CTLFLAG_LOCKED,
    &sfb_hinterval, "SFB hash interval in nanoseconds");

static u_int32_t sfb_increment = SFB_INCREMENT;
SYSCTL_UINT(_net_classq_sfb, OID_AUTO, increment, CTLFLAG_RW|CTLFLAG_LOCKED,
    &sfb_increment, SFB_INCREMENT, "SFB increment [d1]");

static u_int32_t sfb_decrement = SFB_DECREMENT;
SYSCTL_UINT(_net_classq_sfb, OID_AUTO, decrement, CTLFLAG_RW|CTLFLAG_LOCKED,
    &sfb_decrement, SFB_DECREMENT, "SFB decrement [d2]");

static u_int32_t sfb_allocation = 0;    /* 0 means "automatic" */
SYSCTL_UINT(_net_classq_sfb, OID_AUTO, allocation, CTLFLAG_RW|CTLFLAG_LOCKED,
    &sfb_allocation, 0, "SFB bin allocation");

static u_int32_t sfb_ratelimit = 0;
SYSCTL_UINT(_net_classq_sfb, OID_AUTO, ratelimit, CTLFLAG_RW|CTLFLAG_LOCKED,
        &sfb_ratelimit, 0, "SFB rate limit");

#define KBPS    (1ULL * 1000)           /* 1 Kbits per second */
#define MBPS    (1ULL * 1000 * 1000)    /* 1 Mbits per second */
#define GBPS    (MBPS * 1000)           /* 1 Gbits per second */

struct sfb_time_tbl {
        u_int64_t       speed;          /* uplink speed */
        u_int64_t       holdtime;       /* hold time */
        u_int64_t       pboxtime;       /* penalty box time */
};

static struct sfb_time_tbl sfb_ttbl[] = {
        {   1 * MBPS,   HOLDTIME_BASE * 1000,   PBOXTIME_BASE * 1000    },
        {  10 * MBPS,   HOLDTIME_BASE * 100,    PBOXTIME_BASE * 100     },
        { 100 * MBPS,   HOLDTIME_BASE * 10,     PBOXTIME_BASE * 10      },
        {   1 * GBPS,   HOLDTIME_BASE,          PBOXTIME_BASE           },
        {  10 * GBPS,   HOLDTIME_BASE / 10,     PBOXTIME_BASE / 10      },
        { 100 * GBPS,   HOLDTIME_BASE / 100,    PBOXTIME_BASE / 100     },
        { 0, 0, 0 }
};

void
sfb_init(void)
{
        _CASSERT(SFBF_ECN4 == CLASSQF_ECN4);
        _CASSERT(SFBF_ECN6 == CLASSQF_ECN6);

        sfb_size = sizeof (struct sfb);
        sfb_zone = zinit(sfb_size, SFB_ZONE_MAX * sfb_size,
            0, SFB_ZONE_NAME);
        if (sfb_zone == NULL) {
                panic("%s: failed allocating %s", __func__, SFB_ZONE_NAME);
                /* NOTREACHED */
        }
        zone_change(sfb_zone, Z_EXPAND, TRUE);
        zone_change(sfb_zone, Z_CALLERACCT, TRUE);

        sfb_bins_size = sizeof (*((struct sfb *)0)->sfb_bins);
        sfb_bins_zone = zinit(sfb_bins_size, SFB_BINS_ZONE_MAX * sfb_bins_size,
            0, SFB_BINS_ZONE_NAME);
        if (sfb_bins_zone == NULL) {
                panic("%s: failed allocating %s", __func__, SFB_BINS_ZONE_NAME);
                /* NOTREACHED */
        }
        zone_change(sfb_bins_zone, Z_EXPAND, TRUE);
        zone_change(sfb_bins_zone, Z_CALLERACCT, TRUE);

        sfb_fcl_size = sizeof (*((struct sfb *)0)->sfb_fc_lists);
        sfb_fcl_zone = zinit(sfb_fcl_size, SFB_FCL_ZONE_MAX * sfb_fcl_size,
            0, SFB_FCL_ZONE_NAME);
        if (sfb_fcl_zone == NULL) {
                panic("%s: failed allocating %s", __func__, SFB_FCL_ZONE_NAME);
                /* NOTREACHED */
        }
        zone_change(sfb_fcl_zone, Z_EXPAND, TRUE);
        zone_change(sfb_fcl_zone, Z_CALLERACCT, TRUE);
}

static u_int32_t
sfb_random(struct sfb *sp)
{
        IFCQ_CONVERT_LOCK(&sp->sfb_ifp->if_snd);
        return (RandomULong());
}

static void
sfb_calc_holdtime(struct sfb *sp, u_int64_t outbw)
{
        u_int64_t holdtime;

        if (sfb_holdtime != 0) {
                holdtime = sfb_holdtime;
        } else if (outbw == 0) {
                holdtime = SFB_RANDOM(sp, HOLDTIME_MIN, HOLDTIME_MAX);
        } else {
                unsigned int n, i;

                n = sfb_ttbl[0].holdtime;
                for (i = 0; sfb_ttbl[i].speed != 0; i++) {
                        if (outbw < sfb_ttbl[i].speed)
                                break;
                        n = sfb_ttbl[i].holdtime;
                }
                holdtime = n;
        }
        net_nsectimer(&holdtime, &sp->sfb_holdtime);
}

static void
sfb_calc_pboxtime(struct sfb *sp, u_int64_t outbw)
{
        u_int64_t pboxtime;

        if (sfb_pboxtime != 0) {
                pboxtime = sfb_pboxtime;
        } else if (outbw == 0) {
                pboxtime = SFB_RANDOM(sp, PBOXTIME_MIN, PBOXTIME_MAX);
        } else {
                unsigned int n, i;

                n = sfb_ttbl[0].pboxtime;
                for (i = 0; sfb_ttbl[i].speed != 0; i++) {
                        if (outbw < sfb_ttbl[i].speed)
                                break;
                        n = sfb_ttbl[i].pboxtime;
                }
                pboxtime = n;
        }
        net_nsectimer(&pboxtime, &sp->sfb_pboxtime);
        net_timerclear(&sp->sfb_pboxfreeze);
}

static void
sfb_calc_hinterval(struct sfb *sp, u_int64_t *t)
{
        u_int64_t hinterval;
        struct timespec now;

        if (t != NULL) {
                /*
                 * TODO adi@apple.com: use dq_avg to derive hinterval.
                 */
                hinterval = *t;
        }

        if (sfb_hinterval != 0)
                hinterval = sfb_hinterval;
        else if (t == NULL || hinterval == 0)
                hinterval = ((u_int64_t)SFB_HINTERVAL(sp) * NSEC_PER_SEC);

        net_nsectimer(&hinterval, &sp->sfb_hinterval);

        nanouptime(&now);
        net_timeradd(&now, &sp->sfb_hinterval, &sp->sfb_nextreset);
}

static void
sfb_calc_update_interval(struct sfb *sp, u_int64_t out_bw)
{
#pragma unused(out_bw)
        u_int64_t update_interval = 0;
        ifclassq_calc_update_interval(&update_interval);
        net_nsectimer(&update_interval, &sp->sfb_update_interval);
}

/*
 * sfb support routines
 */
struct sfb *
sfb_alloc(struct ifnet *ifp, u_int32_t qid, u_int32_t qlim, u_int32_t flags)
{
        struct sfb *sp;
        int i;

        VERIFY(ifp != NULL && qlim > 0);

        sp = zalloc(sfb_zone);
        if (sp == NULL) {
                log(LOG_ERR, "%s: SFB unable to allocate\n", if_name(ifp));
                return (NULL);
        }
        bzero(sp, sfb_size);

        if ((sp->sfb_bins = zalloc(sfb_bins_zone)) == NULL) {
                log(LOG_ERR, "%s: SFB unable to allocate bins\n", if_name(ifp));
                sfb_destroy(sp);
                return (NULL);
        }
        bzero(sp->sfb_bins, sfb_bins_size);

        if ((sp->sfb_fc_lists = zalloc(sfb_fcl_zone)) == NULL) {
                log(LOG_ERR, "%s: SFB unable to allocate flow control lists\n",
                    if_name(ifp));
                sfb_destroy(sp);
                return (NULL);
        }
        bzero(sp->sfb_fc_lists, sfb_fcl_size);

        for (i = 0; i < SFB_BINS; ++i)
                STAILQ_INIT(&SFB_FC_LIST(sp, i)->fclist);

        sp->sfb_ifp = ifp;
        sp->sfb_qlim = qlim;
        sp->sfb_qid = qid;
        sp->sfb_flags = (flags & SFBF_USERFLAGS);
#if !PF_ECN
        if (sp->sfb_flags & SFBF_ECN) {
                sp->sfb_flags &= ~SFBF_ECN;
                log(LOG_ERR, "%s: SFB qid=%d, ECN not available; ignoring "
                    "SFBF_ECN flag!\n", if_name(ifp), sp->sfb_qid);
        }
#endif /* !PF_ECN */

        sfb_resetq(sp, -1);

        return (sp);
}

static void
sfb_fclist_append(struct sfb *sp, struct sfb_fcl *fcl)
{
        IFCQ_CONVERT_LOCK(&sp->sfb_ifp->if_snd);

        VERIFY(STAILQ_EMPTY(&fcl->fclist) || fcl->cnt > 0);
        sp->sfb_stats.flow_feedback += fcl->cnt;
        fcl->cnt = 0;

        flowadv_add(&fcl->fclist);
        VERIFY(fcl->cnt == 0 && STAILQ_EMPTY(&fcl->fclist));
}

static void
sfb_fclists_clean(struct sfb *sp)
{
        int i;

        /* Move all the flow control entries to the flowadv list */
        for (i = 0; i < SFB_BINS; ++i) {
                struct sfb_fcl *fcl = SFB_FC_LIST(sp, i);
                if (!STAILQ_EMPTY(&fcl->fclist))
                        sfb_fclist_append(sp, fcl);
        }
}

void
sfb_destroy(struct sfb *sp)
{
        sfb_fclists_clean(sp);
        if (sp->sfb_bins != NULL) {
                zfree(sfb_bins_zone, sp->sfb_bins);
                sp->sfb_bins = NULL;
        }
        if (sp->sfb_fc_lists != NULL) {
                zfree(sfb_fcl_zone, sp->sfb_fc_lists);
                sp->sfb_fc_lists = NULL;
        }
        zfree(sfb_zone, sp);
}

static void
sfb_resetq(struct sfb *sp, cqev_t ev)
{
        struct ifnet *ifp = sp->sfb_ifp;
        u_int64_t eff_rate;

        VERIFY(ifp != NULL);

        if (ev != CLASSQ_EV_LINK_DOWN) {
                (*sp->sfb_bins)[0].fudge = sfb_random(sp);
                (*sp->sfb_bins)[1].fudge = sfb_random(sp);
                sp->sfb_allocation = ((sfb_allocation == 0) ?
                    (sp->sfb_qlim / 3) : sfb_allocation);
                sp->sfb_drop_thresh = sp->sfb_allocation +
                    (sp->sfb_allocation >> 1);
        }

        sp->sfb_clearpkts = 0;
        sp->sfb_current = 0;

        eff_rate = ifnet_output_linkrate(ifp);
        sp->sfb_eff_rate = eff_rate;

        sfb_calc_holdtime(sp, eff_rate);
        sfb_calc_pboxtime(sp, eff_rate);
        sfb_calc_hinterval(sp, NULL);
        ifclassq_calc_target_qdelay(ifp, &sp->sfb_target_qdelay);
        sfb_calc_update_interval(sp, eff_rate);

        if (ev == CLASSQ_EV_LINK_DOWN ||
            ev == CLASSQ_EV_LINK_UP)
                sfb_fclists_clean(sp);

        bzero(sp->sfb_bins, sizeof (*sp->sfb_bins));
        bzero(&sp->sfb_stats, sizeof (sp->sfb_stats));

        if (ev == CLASSQ_EV_LINK_DOWN || !classq_verbose)
                return;

        log(LOG_DEBUG, "%s: SFB qid=%d, holdtime=%llu nsec, "
            "pboxtime=%llu nsec, allocation=%d, drop_thresh=%d, "
            "hinterval=%d sec, sfb_bins=%d bytes, eff_rate=%llu bps"
            "target_qdelay= %llu nsec "
            "update_interval=%llu sec %llu nsec flags=0x%x\n",
            if_name(ifp), sp->sfb_qid, (u_int64_t)sp->sfb_holdtime.tv_nsec,
            (u_int64_t)sp->sfb_pboxtime.tv_nsec,
            (u_int32_t)sp->sfb_allocation, (u_int32_t)sp->sfb_drop_thresh,
            (int)sp->sfb_hinterval.tv_sec, (int)sizeof (*sp->sfb_bins),
            eff_rate, (u_int64_t)sp->sfb_target_qdelay,
            (u_int64_t)sp->sfb_update_interval.tv_sec,
            (u_int64_t)sp->sfb_update_interval.tv_nsec, sp->sfb_flags);
}

void
sfb_getstats(struct sfb *sp, struct sfb_stats *sps)
{
        sps->allocation = sp->sfb_allocation;
        sps->dropthresh = sp->sfb_drop_thresh;
        sps->clearpkts = sp->sfb_clearpkts;
        sps->current = sp->sfb_current;
        sps->target_qdelay = sp->sfb_target_qdelay;
        sps->min_estdelay = sp->sfb_min_qdelay;
        sps->delay_fcthreshold = sp->sfb_fc_threshold;
        sps->flags = sp->sfb_flags;

        net_timernsec(&sp->sfb_holdtime, &sp->sfb_stats.hold_time);
        net_timernsec(&sp->sfb_pboxtime, &sp->sfb_stats.pbox_time);
        net_timernsec(&sp->sfb_hinterval, &sp->sfb_stats.rehash_intval);
        net_timernsec(&sp->sfb_update_interval, &sps->update_interval);
        *(&(sps->sfbstats)) = *(&(sp->sfb_stats));

        _CASSERT(sizeof ((*sp->sfb_bins)[0].stats) ==
            sizeof (sps->binstats[0].stats));

        bcopy(&(*sp->sfb_bins)[0].stats, &sps->binstats[0].stats,
            sizeof (sps->binstats[0].stats));
        bcopy(&(*sp->sfb_bins)[1].stats, &sps->binstats[1].stats,
            sizeof (sps->binstats[1].stats));
}

static void
sfb_swap_bins(struct sfb *sp, u_int32_t len)
{
        int i, j, s;

        if (sp->sfb_flags & SFBF_SUSPENDED)
                return;

        s = sp->sfb_current;
        VERIFY((s + (s ^ 1)) == 1);

        (*sp->sfb_bins)[s].fudge = sfb_random(sp); /* recompute perturbation */
        sp->sfb_clearpkts = len;
        sp->sfb_stats.num_rehash++;

        s = (sp->sfb_current ^= 1);     /* flip the bit (swap current) */

        if (classq_verbose) {
                log(LOG_DEBUG, "%s: SFB qid=%d, set %d is now current, "
                    "qlen=%d\n", if_name(sp->sfb_ifp), sp->sfb_qid, s, len);
        }

        /* clear freezetime for all current bins */
        bzero(&(*sp->sfb_bins)[s].freezetime,
            sizeof ((*sp->sfb_bins)[s].freezetime));

        /* clear/adjust bin statistics and flow control lists */
        for (i = 0; i < SFB_BINS; i++) {
                struct sfb_fcl *fcl = SFB_FC_LIST(sp, i);

                if (!STAILQ_EMPTY(&fcl->fclist))
                        sfb_fclist_append(sp, fcl);

                for (j = 0; j < SFB_LEVELS; j++) {
                        struct sfbbinstats *cbin, *wbin;

                        cbin = SFB_BINST(sp, j, i, s);          /* current */
                        wbin = SFB_BINST(sp, j, i, s ^ 1);      /* warm-up */

                        cbin->pkts = 0;
                        cbin->bytes = 0;
                        if (cbin->pmark > SFB_MAX_PMARK)
                                cbin->pmark = SFB_MAX_PMARK;
                        if (cbin->pmark < 0)
                                cbin->pmark = 0;

                        /*
                         * Keep pmark from before to identify
                         * non-responsives immediately.
                         */
                        if (wbin->pmark > SFB_PMARK_WARM)
                                wbin->pmark = SFB_PMARK_WARM;
                }
        }
}

static inline int
sfb_pcheck(struct sfb *sp, struct pkthdr *pkt)
{
#if SFB_LEVELS != 2
        int i, n;
#endif /* SFB_LEVELS != 2 */
        int s;

        s = sp->sfb_current;
        VERIFY((s + (s ^ 1)) == 1);

        /*
         * For current bins, returns 1 if all pmark >= SFB_PMARK_TH,
         * 0 otherwise; optimize for SFB_LEVELS=2.
         */
#if SFB_LEVELS == 2
        /*
         * Level 0: bin index at [0] for set 0; [2] for set 1
         * Level 1: bin index at [1] for set 0; [3] for set 1
         */
        if (SFB_BINST(sp, 0, SFB_BINMASK(pkt->pkt_sfb_hash8[(s << 1)]),
            s)->pmark < SFB_PMARK_TH ||
            SFB_BINST(sp, 1, SFB_BINMASK(pkt->pkt_sfb_hash8[(s << 1) + 1]),
            s)->pmark < SFB_PMARK_TH)
                return (0);
#else /* SFB_LEVELS != 2 */
        for (i = 0; i < SFB_LEVELS; i++) {
                if (s == 0)             /* set 0, bin index [0,1] */
                        n = SFB_BINMASK(pkt->pkt_sfb_hash8[i]);
                else                    /* set 1, bin index [2,3] */
                        n = SFB_BINMASK(pkt->pkt_sfb_hash8[i + 2]);

                if (SFB_BINST(sp, i, n, s)->pmark < SFB_PMARK_TH)
                        return (0);
        }
#endif /* SFB_LEVELS != 2 */
        return (1);
}

static int
sfb_penalize(struct sfb *sp, struct pkthdr *pkt, struct timespec *now)
{
        struct timespec delta = { 0, 0 };

        /* If minimum pmark of current bins is < SFB_PMARK_TH, we're done */
        if (!sfb_ratelimit || !sfb_pcheck(sp, pkt))
                return (0);

        net_timersub(now, &sp->sfb_pboxfreeze, &delta);
        if (net_timercmp(&delta, &sp->sfb_pboxtime, <)) {
#if SFB_LEVELS != 2
                int i;
#endif /* SFB_LEVELS != 2 */
                struct sfbbinstats *bin;
                int n, w;

                w = sp->sfb_current ^ 1;
                VERIFY((w + (w ^ 1)) == 1);

                /*
                 * Update warm-up bins; optimize for SFB_LEVELS=2
                 */
#if SFB_LEVELS == 2
                /* Level 0: bin index at [0] for set 0; [2] for set 1 */
                n = SFB_BINMASK(pkt->pkt_sfb_hash8[(w << 1)]);
                bin = SFB_BINST(sp, 0, n, w);
                if (bin->pkts >= sp->sfb_allocation)
                        sfb_increment_bin(sp, bin, SFB_BINFT(sp, 0, n, w), now);

                /* Level 0: bin index at [1] for set 0; [3] for set 1 */
                n = SFB_BINMASK(pkt->pkt_sfb_hash8[(w << 1) + 1]);
                bin = SFB_BINST(sp, 1, n, w);
                if (bin->pkts >= sp->sfb_allocation)
                        sfb_increment_bin(sp, bin, SFB_BINFT(sp, 1, n, w), now);
#else /* SFB_LEVELS != 2 */
                for (i = 0; i < SFB_LEVELS; i++) {
                        if (w == 0)     /* set 0, bin index [0,1] */
                                n = SFB_BINMASK(pkt->pkt_sfb_hash8[i]);
                        else            /* set 1, bin index [2,3] */
                                n = SFB_BINMASK(pkt->pkt_sfb_hash8[i + 2]);

                        bin = SFB_BINST(sp, i, n, w);
                        if (bin->pkts >= sp->sfb_allocation) {
                                sfb_increment_bin(sp, bin,
                                    SFB_BINFT(sp, i, n, w), now);
                        }
                }
#endif /* SFB_LEVELS != 2 */
                return (1);
        }

        /* non-conformant or else misclassified flow; queue it anyway */
        pkt->pkt_sfb_flags |= SFB_PKT_PBOX;
        *(&sp->sfb_pboxfreeze) = *now;

        return (0);
}

static void
sfb_adjust_bin(struct sfb *sp, struct sfbbinstats *bin, struct timespec *ft,
    struct timespec *now, boolean_t inc)
{
        struct timespec delta;

        net_timersub(now, ft, &delta);
        if (net_timercmp(&delta, &sp->sfb_holdtime, <)) {
                if (classq_verbose > 1) {
                        log(LOG_DEBUG, "%s: SFB qid=%d, %s update frozen "
                            "(delta=%llu nsec)\n", if_name(sp->sfb_ifp),
                            sp->sfb_qid, inc ?  "increment" : "decrement",
                            (u_int64_t)delta.tv_nsec);
                }
                return;
        }

        /* increment/decrement marking probability */
        *ft = *now;
        if (inc)
                SFB_PMARK_INC(bin);
        else
                SFB_PMARK_DEC(bin);
}

static void
sfb_decrement_bin(struct sfb *sp, struct sfbbinstats *bin, struct timespec *ft,
    struct timespec *now)
{
        return (sfb_adjust_bin(sp, bin, ft, now, FALSE));
}

static void
sfb_increment_bin(struct sfb *sp, struct sfbbinstats *bin, struct timespec *ft,
    struct timespec *now)
{
        return (sfb_adjust_bin(sp, bin, ft, now, TRUE));
}

static inline void
sfb_dq_update_bins(struct sfb *sp, struct pkthdr *pkt,
    struct timespec *now, u_int32_t qsize)
{
#if SFB_LEVELS != 2 || SFB_FC_LEVEL != 0
        int i;
#endif /* SFB_LEVELS != 2 || SFB_FC_LEVEL != 0 */
        struct sfbbinstats *bin;
        int s, n;
        struct sfb_fcl *fcl = NULL;

        s = sp->sfb_current;
        VERIFY((s + (s ^ 1)) == 1);

        /*
         * Update current bins; optimize for SFB_LEVELS=2 and SFB_FC_LEVEL=0
         */
#if SFB_LEVELS == 2 && SFB_FC_LEVEL == 0
        /* Level 0: bin index at [0] for set 0; [2] for set 1 */
        n = SFB_BINMASK(pkt->pkt_sfb_hash8[(s << 1)]);
        bin = SFB_BINST(sp, 0, n, s);

        VERIFY(bin->pkts > 0 && bin->bytes >= (u_int32_t)pkt->len);
        bin->pkts--;
        bin->bytes -= pkt->len;

        if (bin->pkts == 0)
                sfb_decrement_bin(sp, bin, SFB_BINFT(sp, 0, n, s), now);

        /* Deliver flow control feedback to the sockets */
        if (SFB_QUEUE_DELAYBASED(sp)) {
                if (!(SFB_IS_DELAYHIGH(sp)) ||
                    bin->bytes <= sp->sfb_fc_threshold ||
                    bin->pkts == 0 || qsize == 0)
                        fcl = SFB_FC_LIST(sp, n);
        } else if (bin->pkts <= (sp->sfb_allocation >> 2)) {
                        fcl = SFB_FC_LIST(sp, n);
        }

        if (fcl != NULL && !STAILQ_EMPTY(&fcl->fclist))
                sfb_fclist_append(sp, fcl);
        fcl = NULL;

        /* Level 1: bin index at [1] for set 0; [3] for set 1 */
        n = SFB_BINMASK(pkt->pkt_sfb_hash8[(s << 1) + 1]);
        bin = SFB_BINST(sp, 1, n, s);

        VERIFY(bin->pkts > 0 && bin->bytes >= (u_int64_t)pkt->len);
        bin->pkts--;
        bin->bytes -= pkt->len;
        if (bin->pkts == 0)
                sfb_decrement_bin(sp, bin, SFB_BINFT(sp, 1, n, s), now);
#else /* SFB_LEVELS != 2 || SFB_FC_LEVEL != 0 */
        for (i = 0; i < SFB_LEVELS; i++) {
                if (s == 0)             /* set 0, bin index [0,1] */
                        n = SFB_BINMASK(pkt->pkt_sfb_hash8[i]);
                else                    /* set 1, bin index [2,3] */
                        n = SFB_BINMASK(pkt->pkt_sfb_hash8[i + 2]);

                bin = SFB_BINST(sp, i, n, s);

                VERIFY(bin->pkts > 0 && bin->bytes >= pkt->len);
                bin->pkts--;
                bin->bytes -= pkt->len;
                if (bin->pkts == 0)
                        sfb_decrement_bin(sp, bin,
                            SFB_BINFT(sp, i, n, s), now);
                if (i != SFB_FC_LEVEL)
                        continue;
                if (SFB_QUEUE_DELAYBASED(sp)) {
                        if (!(SFB_IS_DELAYHIGH(sp)) ||
                            bin->bytes <= sp->sfb_fc_threshold)
                                fcl = SFB_FC_LIST(sp, n);
                } else if (bin->pkts <= (sp->sfb_allocation >> 2)) {
                        fcl = SFB_FC_LIST(sp, n);
                }
                if (fcl != NULL && !STAILQ_EMPTY(&fcl->fclist))
                        sfb_fclist_append(sp, fcl);
                fcl = NULL;
        }
#endif /* SFB_LEVELS != 2 || SFB_FC_LEVEL != 0 */
}

static inline void
sfb_eq_update_bins(struct sfb *sp, struct pkthdr *pkt)
{
#if SFB_LEVELS != 2
        int i, n;
#endif /* SFB_LEVELS != 2 */
        int s;
        struct sfbbinstats *bin;
        s = sp->sfb_current;
        VERIFY((s + (s ^ 1)) == 1);

        /*
         * Update current bins; optimize for SFB_LEVELS=2
         */
#if SFB_LEVELS == 2
        /* Level 0: bin index at [0] for set 0; [2] for set 1 */
        bin = SFB_BINST(sp, 0,
            SFB_BINMASK(pkt->pkt_sfb_hash8[(s << 1)]), s);
        bin->pkts++;
        bin->bytes += pkt->len;

        /* Level 1: bin index at [1] for set 0; [3] for set 1 */
        bin = SFB_BINST(sp, 1,
            SFB_BINMASK(pkt->pkt_sfb_hash8[(s << 1) + 1]), s);
        bin->pkts++;
        bin->bytes += pkt->len;

#else /* SFB_LEVELS != 2 */
        for (i = 0; i < SFB_LEVELS; i++) {
                if (s == 0)             /* set 0, bin index [0,1] */
                        n = SFB_BINMASK(pkt->pkt_sfb_hash8[i]);
                else                    /* set 1, bin index [2,3] */
                        n = SFB_BINMASK(pkt->pkt_sfb_hash8[i + 2]);

                bin = SFB_BINST(sp, i, n, s);
                bin->pkts++;
                bin->bytes += pkt->len;
        }
#endif /* SFB_LEVELS != 2 */
}

static boolean_t
sfb_bin_addfcentry(struct sfb *sp, struct pkthdr *pkt)
{
        struct flowadv_fcentry *fce;
        u_int32_t flowsrc, flowid;
        struct sfb_fcl *fcl;
        int s;

        s = sp->sfb_current;
        VERIFY((s + (s ^ 1)) == 1);

        flowsrc = pkt->pkt_flowsrc;
        flowid = pkt->pkt_flowid;

        if (flowid == 0) {
                sp->sfb_stats.null_flowid++;
                return (FALSE);
        }

        /*
         * Use value at index 0 for set 0 and
         * value at index 2 for set 1
         */
        fcl = SFB_FC_LIST(sp, SFB_BINMASK(pkt->pkt_sfb_hash8[(s << 1)]));
        STAILQ_FOREACH(fce, &fcl->fclist, fce_link) {
                if (fce->fce_flowsrc == flowsrc &&
                    fce->fce_flowid == flowid) {
                        /* Already on flow control list; just return */
                        return (TRUE);
                }
        }

        IFCQ_CONVERT_LOCK(&sp->sfb_ifp->if_snd);
        fce = flowadv_alloc_entry(M_WAITOK);
        if (fce != NULL) {
                fce->fce_flowsrc = flowsrc;
                fce->fce_flowid = flowid;
                STAILQ_INSERT_TAIL(&fcl->fclist, fce, fce_link);
                fcl->cnt++;
                sp->sfb_stats.flow_controlled++;
        }

        return (fce != NULL);
}

/*
 * check if this flow needs to be flow-controlled or if this
 * packet needs to be dropped.
 */
static int
sfb_bin_mark_or_drop(struct sfb *sp, struct sfbbinstats *bin)
{
        int ret = 0;
        if (SFB_QUEUE_DELAYBASED(sp)) {
                /*
                 * Mark or drop if this bin has more
                 * bytes than the flowcontrol threshold.
                 */
                if (SFB_IS_DELAYHIGH(sp) &&
                    bin->bytes >= (sp->sfb_fc_threshold << 1))
                        ret = 1;
        } else {
                if (bin->pkts >= sp->sfb_allocation &&
                    bin->pkts >= sp->sfb_drop_thresh)
                        ret = 1;        /* drop or mark */
        }
        return (ret);
}

/*
 * early-drop probability is kept in pmark of each bin of the flow
 */
static int
sfb_drop_early(struct sfb *sp, struct pkthdr *pkt, u_int16_t *pmin,
    struct timespec *now)
{
#if SFB_LEVELS != 2
        int i;
#endif /* SFB_LEVELS != 2 */
        struct sfbbinstats *bin;
        int s, n, ret = 0;

        s = sp->sfb_current;
        VERIFY((s + (s ^ 1)) == 1);

        *pmin = (u_int16_t)-1;

        /*
         * Update current bins; optimize for SFB_LEVELS=2
         */
#if SFB_LEVELS == 2
        /* Level 0: bin index at [0] for set 0; [2] for set 1 */
        n = SFB_BINMASK(pkt->pkt_sfb_hash8[(s << 1)]);
        bin = SFB_BINST(sp, 0, n, s);
        if (*pmin > (u_int16_t)bin->pmark)
                *pmin = (u_int16_t)bin->pmark;


        /* Update SFB probability */
        if (bin->pkts >= sp->sfb_allocation)
                sfb_increment_bin(sp, bin, SFB_BINFT(sp, 0, n, s), now);

        ret = sfb_bin_mark_or_drop(sp, bin);

        /* Level 1: bin index at [1] for set 0; [3] for set 1 */
        n = SFB_BINMASK(pkt->pkt_sfb_hash8[(s << 1) + 1]);
        bin = SFB_BINST(sp, 1, n, s);
        if (*pmin > (u_int16_t)bin->pmark)
                *pmin = (u_int16_t)bin->pmark;

        if (bin->pkts >= sp->sfb_allocation)
                sfb_increment_bin(sp, bin, SFB_BINFT(sp, 1, n, s), now);
#else /* SFB_LEVELS != 2 */
        for (i = 0; i < SFB_LEVELS; i++) {
                if (s == 0)             /* set 0, bin index [0,1] */
                        n = SFB_BINMASK(pkt->pkt_sfb_hash8[i]);
                else                    /* set 1, bin index [2,3] */
                        n = SFB_BINMASK(pkt->pkt_sfb_hash8[i + 2]);

                bin = SFB_BINST(sp, i, n, s);
                if (*pmin > (u_int16_t)bin->pmark)
                        *pmin = (u_int16_t)bin->pmark;

                if (bin->pkts >= sp->sfb_allocation)
                        sfb_increment_bin(sp, bin,
                            SFB_BINFT(sp, i, n, s), now);
                if (i == SFB_FC_LEVEL)
                        ret = sfb_bin_mark_or_drop(sp, bin);
        }
#endif /* SFB_LEVELS != 2 */

        if (sp->sfb_flags & SFBF_SUSPENDED)
                ret = 1;        /* drop or mark */

        return (ret);
}

void
sfb_detect_dequeue_stall(struct sfb *sp, class_queue_t *q,
    struct timespec *now)
{
        struct timespec max_getqtime;

        if (!SFB_QUEUE_DELAYBASED(sp) || SFB_IS_DELAYHIGH(sp) ||
            qsize(q) <= SFB_MIN_FC_THRESHOLD_BYTES ||
            !net_timerisset(&sp->sfb_getqtime))
                return;

        net_timeradd(&sp->sfb_getqtime, &sp->sfb_update_interval,
            &max_getqtime);
        if (net_timercmp(now, &max_getqtime, >)) {
                /*
                 * No packets have been dequeued in an update interval
                 * worth of time. It means that the queue is stalled
                 */
                SFB_SET_DELAY_HIGH(sp, q);
                sp->sfb_stats.dequeue_stall++;
        }
}

#define DTYPE_NODROP    0       /* no drop */
#define DTYPE_FORCED    1       /* a "forced" drop */
#define DTYPE_EARLY     2       /* an "unforced" (early) drop */

int
sfb_addq(struct sfb *sp, class_queue_t *q, struct mbuf *m, struct pf_mtag *t)
{
#if !PF_ECN
#pragma unused(t)
#endif /* !PF_ECN */
        struct pkthdr *pkt = &m->m_pkthdr;
        struct timespec now;
        int droptype, s;
        u_int16_t pmin;
        int fc_adv = 0;
        int ret = CLASSQEQ_SUCCESS;
        u_int32_t maxqsize = 0;

        s = sp->sfb_current;
        VERIFY((s + (s ^ 1)) == 1);

        /* See comments in <rdar://problem/14040693> */
        VERIFY(!(pkt->pkt_flags & PKTF_PRIV_GUARDED));
        pkt->pkt_flags |= PKTF_PRIV_GUARDED;

        if (pkt->pkt_timestamp > 0) {
                net_nsectimer(&pkt->pkt_timestamp, &now);
        } else {
                nanouptime(&now);
                net_timernsec(&now, &pkt->pkt_timestamp);
        }

        /* time to swap the bins? */
        if (net_timercmp(&now, &sp->sfb_nextreset, >=)) {
                net_timeradd(&now, &sp->sfb_hinterval, &sp->sfb_nextreset);
                sfb_swap_bins(sp, qlen(q));
                s = sp->sfb_current;
                VERIFY((s + (s ^ 1)) == 1);
        }

        if (!net_timerisset(&sp->sfb_update_time)) {
                net_timeradd(&now, &sp->sfb_update_interval,
                    &sp->sfb_update_time);
        }

        /*
         * If getq time is not set because this is the first packet
         * or after idle time, set it now so that we can detect a stall.
         */
        if (qsize(q) == 0 && !net_timerisset(&sp->sfb_getqtime))
                *(&sp->sfb_getqtime) = *(&now);

        pkt->pkt_sfb_flags = 0;
        pkt->pkt_sfb_hash16[s] =
            (SFB_HASH(&pkt->pkt_flowid, sizeof (pkt->pkt_flowid),
            (*sp->sfb_bins)[s].fudge) & SFB_HASHMASK);
        pkt->pkt_sfb_hash16[s ^ 1] =
            (SFB_HASH(&pkt->pkt_flowid, sizeof (pkt->pkt_flowid),
            (*sp->sfb_bins)[s ^ 1].fudge) & SFB_HASHMASK);

        /* check if the queue has been stalled */
        sfb_detect_dequeue_stall(sp, q, &now);

        /* see if we drop early */
        droptype = DTYPE_NODROP;
        if (sfb_drop_early(sp, pkt, &pmin, &now)) {
                /* flow control, mark or drop by sfb */
                if ((sp->sfb_flags & SFBF_FLOWCTL) &&
                    (pkt->pkt_flags & PKTF_FLOW_ADV)) {
                        fc_adv = 1;
                        /* drop all during suspension or for non-TCP */
                        if ((sp->sfb_flags & SFBF_SUSPENDED) ||
                            pkt->pkt_proto != IPPROTO_TCP) {
                                droptype = DTYPE_EARLY;
                                sp->sfb_stats.drop_early++;
                        }
                }
#if PF_ECN
                else if ((sp->sfb_flags & SFBF_ECN) &&
                    (pkt->pkt_proto == IPPROTO_TCP) && /* only for TCP */
                    ((sfb_random(sp) & SFB_MAX_PMARK) <= pmin) &&
                    mark_ecn(m, t, sp->sfb_flags) &&
                    !(sp->sfb_flags & SFBF_SUSPENDED)) {
                        /* successfully marked; do not drop. */
                        sp->sfb_stats.marked_packets++;
                }
#endif /* PF_ECN */
                else {
                        /* unforced drop by sfb */
                        droptype = DTYPE_EARLY;
                        sp->sfb_stats.drop_early++;
                }
        }

        /* non-responsive flow penalty? */
        if (droptype == DTYPE_NODROP && sfb_penalize(sp, pkt, &now)) {
                droptype = DTYPE_FORCED;
                sp->sfb_stats.drop_pbox++;
        }

        if (SFB_QUEUE_DELAYBASED(sp))
                maxqsize = SFB_QUEUE_DELAYBASED_MAXSIZE;
        else
                maxqsize = qlimit(q);

        /*
         * When the queue length hits the queue limit, make it a forced
         * drop
         */
        if (droptype == DTYPE_NODROP && qlen(q) >= maxqsize) {
                if (pkt->pkt_proto == IPPROTO_TCP &&
                    qlen(q) < (maxqsize + (maxqsize >> 1)) &&
                    ((pkt->pkt_flags & PKTF_TCP_REXMT) ||
                    (sp->sfb_flags & SFBF_LAST_PKT_DROPPED))) {
                        /*
                         * At some level, dropping packets will make the
                         * flows backoff and will keep memory requirements
                         * under control. But we should not cause a tail
                         * drop because it can take a long time for a
                         * TCP flow to recover. We should try to drop
                         * alternate packets instead.
                         */
                        sp->sfb_flags &= ~SFBF_LAST_PKT_DROPPED;
                } else {
                        droptype = DTYPE_FORCED;
                        sp->sfb_stats.drop_queue++;
                        sp->sfb_flags |= SFBF_LAST_PKT_DROPPED;
                }
        }

        if (fc_adv == 1 && droptype != DTYPE_FORCED &&
            sfb_bin_addfcentry(sp, pkt)) {
                /* deliver flow control advisory error */
                if (droptype == DTYPE_NODROP) {
                        ret = CLASSQEQ_SUCCESS_FC;
                        VERIFY(!(sp->sfb_flags & SFBF_SUSPENDED));
                } else if (sp->sfb_flags & SFBF_SUSPENDED) {
                        /* dropped due to suspension */
                        ret = CLASSQEQ_DROPPED_SP;
                } else {
                        /* dropped due to flow-control */
                        ret = CLASSQEQ_DROPPED_FC;
                }
        }
        /* if successful enqueue this packet, else drop it */
        if (droptype == DTYPE_NODROP) {
                _addq(q, m);
        } else {
                IFCQ_CONVERT_LOCK(&sp->sfb_ifp->if_snd);
                m_freem(m);
                return ((ret != CLASSQEQ_SUCCESS) ? ret : CLASSQEQ_DROPPED);
        }

        if (!(pkt->pkt_sfb_flags & SFB_PKT_PBOX))
                sfb_eq_update_bins(sp, pkt);
        else
                sp->sfb_stats.pbox_packets++;

        /* successfully queued */
        return (ret);
}

static struct mbuf *
sfb_getq_flow(struct sfb *sp, class_queue_t *q, u_int32_t flow, boolean_t purge)
{
        struct timespec now;
        struct mbuf *m;
        struct pkthdr *pkt;

        if (!purge && (sp->sfb_flags & SFBF_SUSPENDED))
                return (NULL);

        nanouptime(&now);

        /* flow of 0 means head of queue */
        if ((m = ((flow == 0) ? _getq(q) : _getq_flow(q, flow))) == NULL) {
                if (!purge)
                        net_timerclear(&sp->sfb_getqtime);
                return (NULL);
        }

        VERIFY(m->m_flags & M_PKTHDR);

        pkt = &m->m_pkthdr;
        VERIFY(pkt->pkt_flags & PKTF_PRIV_GUARDED);

        if (!purge) {
                /* calculate EWMA of dequeues */
                if (net_timerisset(&sp->sfb_getqtime)) {
                        struct timespec delta;
                        u_int64_t avg, new;
                        net_timersub(&now, &sp->sfb_getqtime, &delta);
                        net_timernsec(&delta, &new);
                        avg = sp->sfb_stats.dequeue_avg;
                        if (avg > 0) {
                                int decay = DEQUEUE_DECAY;
                                /*
                                 * If the time since last dequeue is
                                 * significantly greater than the current
                                 * average, weigh the average more against
                                 * the old value.
                                 */
                                if (DEQUEUE_SPIKE(new, avg))
                                        decay += 5;
                                avg = (((avg << decay) - avg) + new) >> decay;
                        } else {
                                avg = new;
                        }
                        sp->sfb_stats.dequeue_avg = avg;
                }
                *(&sp->sfb_getqtime) = *(&now);
        }

        if (!purge && SFB_QUEUE_DELAYBASED(sp)) {
                u_int64_t dequeue_ns, queue_delay = 0;
                net_timernsec(&now, &dequeue_ns);
                if (dequeue_ns > pkt->pkt_timestamp)
                        queue_delay = dequeue_ns - pkt->pkt_timestamp;

                if (sp->sfb_min_qdelay == 0 ||
                    (queue_delay > 0 && queue_delay < sp->sfb_min_qdelay))
                        sp->sfb_min_qdelay = queue_delay;
                if (net_timercmp(&now, &sp->sfb_update_time, >=)) {
                        if (sp->sfb_min_qdelay > sp->sfb_target_qdelay) {
                                if (!SFB_IS_DELAYHIGH(sp))
                                        SFB_SET_DELAY_HIGH(sp, q);
                        } else {
                                sp->sfb_flags &= ~(SFBF_DELAYHIGH);
                                sp->sfb_fc_threshold = 0;

                        }
                        net_timeradd(&now, &sp->sfb_update_interval,
                            &sp->sfb_update_time);
                        sp->sfb_min_qdelay = 0;
                }
        }
        pkt->pkt_timestamp = 0;

        /*
         * Clearpkts are the ones which were in the queue when the hash
         * function was perturbed.  Since the perturbation value (fudge),
         * and thus bin information for these packets is not known, we do
         * not change accounting information while dequeuing these packets.
         * It is important not to set the hash interval too small due to
         * this reason.  A rule of thumb is to set it to K*D, where D is
         * the time taken to drain queue.
         */
        if (pkt->pkt_sfb_flags & SFB_PKT_PBOX) {
                pkt->pkt_sfb_flags &= ~SFB_PKT_PBOX;
                if (sp->sfb_clearpkts > 0)
                        sp->sfb_clearpkts--;
        } else if (sp->sfb_clearpkts > 0) {
                sp->sfb_clearpkts--;
        } else {
                sfb_dq_update_bins(sp, pkt, &now, qsize(q));
        }

        /* See comments in <rdar://problem/14040693> */
        pkt->pkt_flags &= ~PKTF_PRIV_GUARDED;

        /*
         * If the queue becomes empty before the update interval, reset
         * the flow control threshold
         */
        if (qsize(q) == 0) {
                sp->sfb_flags &= ~SFBF_DELAYHIGH;
                sp->sfb_min_qdelay = 0;
                sp->sfb_fc_threshold = 0;
                net_timerclear(&sp->sfb_update_time);
                net_timerclear(&sp->sfb_getqtime);
        }

        return (m);
}

struct mbuf *
sfb_getq(struct sfb *sp, class_queue_t *q)
{
        return (sfb_getq_flow(sp, q, 0, FALSE));
}

void
sfb_purgeq(struct sfb *sp, class_queue_t *q, u_int32_t flow, u_int32_t *packets,
    u_int32_t *bytes)
{
        u_int32_t cnt = 0, len = 0;
        struct mbuf *m;

        IFCQ_CONVERT_LOCK(&sp->sfb_ifp->if_snd);

        while ((m = sfb_getq_flow(sp, q, flow, TRUE)) != NULL) {
                cnt++;
                len += m_pktlen(m);
                m_freem(m);
        }

        if (packets != NULL)
                *packets = cnt;
        if (bytes != NULL)
                *bytes = len;
}

void
sfb_updateq(struct sfb *sp, cqev_t ev)
{
        struct ifnet *ifp = sp->sfb_ifp;

        VERIFY(ifp != NULL);

        switch (ev) {
        case CLASSQ_EV_LINK_BANDWIDTH: {
                u_int64_t eff_rate = ifnet_output_linkrate(ifp);

                /* update parameters only if rate has changed */
                if (eff_rate == sp->sfb_eff_rate)
                        break;

                if (classq_verbose) {
                        log(LOG_DEBUG, "%s: SFB qid=%d, adapting to new "
                            "eff_rate=%llu bps\n", if_name(ifp), sp->sfb_qid,
                            eff_rate);
                }
                sfb_calc_holdtime(sp, eff_rate);
                sfb_calc_pboxtime(sp, eff_rate);
                ifclassq_calc_target_qdelay(ifp, &sp->sfb_target_qdelay);
                sfb_calc_update_interval(sp, eff_rate);
                break;
        }

        case CLASSQ_EV_LINK_UP:
        case CLASSQ_EV_LINK_DOWN:
                if (classq_verbose) {
                        log(LOG_DEBUG, "%s: SFB qid=%d, resetting due to "
                            "link %s\n", if_name(ifp), sp->sfb_qid,
                            (ev == CLASSQ_EV_LINK_UP) ? "UP" : "DOWN");
                }
                sfb_resetq(sp, ev);
                break;

        case CLASSQ_EV_LINK_LATENCY:
        case CLASSQ_EV_LINK_MTU:
        default:
                break;
        }
}

int
sfb_suspendq(struct sfb *sp, class_queue_t *q, boolean_t on)
{
#pragma unused(q)
        struct ifnet *ifp = sp->sfb_ifp;

        VERIFY(ifp != NULL);

        if ((on && (sp->sfb_flags & SFBF_SUSPENDED)) ||
            (!on && !(sp->sfb_flags & SFBF_SUSPENDED)))
                return (0);

        if (!(sp->sfb_flags & SFBF_FLOWCTL)) {
                log(LOG_ERR, "%s: SFB qid=%d, unable to %s queue since "
                    "flow-control is not enabled", if_name(ifp), sp->sfb_qid,
                    (on ? "suspend" : "resume"));
                return (ENOTSUP);
        }

        if (classq_verbose) {
                log(LOG_DEBUG, "%s: SFB qid=%d, setting state to %s",
                    if_name(ifp), sp->sfb_qid, (on ? "SUSPENDED" : "RUNNING"));
        }

        if (on) {
                sp->sfb_flags |= SFBF_SUSPENDED;
        } else {
                sp->sfb_flags &= ~SFBF_SUSPENDED;
                sfb_swap_bins(sp, qlen(q));
        }

        return (0);
}