/*
 * PIE - Proportional Integral controller Enhanced AQM algorithm.
 * 
 * Copyright (C) 2016 Centre for Advanced Internet Architectures,
 *  Swinburne University of Technology, Melbourne, Australia.
 * Portions of this code were made possible in part by a gift from 
 *  The Comcast Innovation Fund.
 * Implemented by Rasool Al-Saadi <ralsaadi@swin.edu.au>
 *
 * 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.
 */

#include <sys/cdefs.h>
#include "opt_inet6.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/rwlock.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/sysctl.h>

#include <net/if.h>     /* IFNAMSIZ, struct ifaddr, ifq head, lock.h mutex.h */
#include <net/netisr.h>
#include <net/vnet.h>

#include <netinet/in.h>
#include <netinet/ip.h>         /* ip_len, ip_off */
#include <netinet/ip_var.h>     /* ip_output(), IP_FORWARDING */
#include <netinet/ip_fw.h>
#include <netinet/ip_dummynet.h>
#include <netinet/if_ether.h> /* various ether_* routines */
#include <netinet/ip6.h>       /* for ip6_input, ip6_output prototypes */
#include <netinet6/ip6_var.h>
#include <netpfil/ipfw/dn_heap.h>

#ifdef NEW_AQM
#include <netpfil/ipfw/ip_fw_private.h>
#include <netpfil/ipfw/ip_dn_private.h>
#include <netpfil/ipfw/dn_aqm.h>
#include <netpfil/ipfw/dn_aqm_pie.h>
#include <netpfil/ipfw/dn_sched.h>

/* for debugging */
#include <sys/syslog.h>

static struct dn_aqm pie_desc;

/*  PIE defaults
 * target=15ms, tupdate=15ms, max_burst=150ms, 
 * max_ecnth=0.1, alpha=0.125, beta=1.25, 
 */
struct dn_aqm_pie_parms pie_sysctl = 
        { 15 * AQM_TIME_1MS,  15 * AQM_TIME_1MS, 150 * AQM_TIME_1MS,
        PIE_SCALE/10 , PIE_SCALE * 0.125,  PIE_SCALE * 1.25 ,
        PIE_CAPDROP_ENABLED | PIE_DEPRATEEST_ENABLED | PIE_DERAND_ENABLED };

static int
pie_sysctl_alpha_beta_handler(SYSCTL_HANDLER_ARGS)
{
        int error;
        long  value;

        if (!strcmp(oidp->oid_name,"alpha"))
                value = pie_sysctl.alpha;
        else
                value = pie_sysctl.beta;
                
        value = value * 1000 / PIE_SCALE;
        error = sysctl_handle_long(oidp, &value, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        if (value < 1 || value > 7 * PIE_SCALE)
                return (EINVAL);
        value = (value * PIE_SCALE) / 1000;
        if (!strcmp(oidp->oid_name,"alpha"))
                        pie_sysctl.alpha = value;
        else
                pie_sysctl.beta = value;
        return (0);
}

static int
pie_sysctl_target_tupdate_maxb_handler(SYSCTL_HANDLER_ARGS)
{
        int error;
        long  value;

        if (!strcmp(oidp->oid_name,"target"))
                value = pie_sysctl.qdelay_ref;
        else if (!strcmp(oidp->oid_name,"tupdate"))
                value = pie_sysctl.tupdate;
        else
                value = pie_sysctl.max_burst;

        value = value / AQM_TIME_1US;
        error = sysctl_handle_long(oidp, &value, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        if (value < 1 || value > 10 * AQM_TIME_1S)
                return (EINVAL);
        value = value * AQM_TIME_1US;

        if (!strcmp(oidp->oid_name,"target"))
                pie_sysctl.qdelay_ref  = value;
        else if (!strcmp(oidp->oid_name,"tupdate"))
                pie_sysctl.tupdate  = value;
        else
                pie_sysctl.max_burst = value;
        return (0);
}

static int
pie_sysctl_max_ecnth_handler(SYSCTL_HANDLER_ARGS)
{
        int error;
        long  value;

        value = pie_sysctl.max_ecnth;
        value = value * 1000 / PIE_SCALE;
        error = sysctl_handle_long(oidp, &value, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        if (value < 1 || value > PIE_SCALE)
                return (EINVAL);
        value = (value * PIE_SCALE) / 1000;
        pie_sysctl.max_ecnth = value;
        return (0);
}

/* define PIE sysctl variables */
SYSBEGIN(f4)
SYSCTL_DECL(_net_inet);
SYSCTL_DECL(_net_inet_ip);
SYSCTL_DECL(_net_inet_ip_dummynet);
static SYSCTL_NODE(_net_inet_ip_dummynet, OID_AUTO, pie,
    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "PIE");

#ifdef SYSCTL_NODE
SYSCTL_PROC(_net_inet_ip_dummynet_pie, OID_AUTO, target,
    CTLTYPE_LONG | CTLFLAG_RW | CTLFLAG_NEEDGIANT, NULL, 0,
    pie_sysctl_target_tupdate_maxb_handler, "L",
    "queue target in microsecond");
SYSCTL_PROC(_net_inet_ip_dummynet_pie, OID_AUTO, tupdate,
    CTLTYPE_LONG | CTLFLAG_RW | CTLFLAG_NEEDGIANT, NULL, 0,
    pie_sysctl_target_tupdate_maxb_handler, "L",
    "the frequency of drop probability calculation in microsecond");
SYSCTL_PROC(_net_inet_ip_dummynet_pie, OID_AUTO, max_burst,
    CTLTYPE_LONG | CTLFLAG_RW | CTLFLAG_NEEDGIANT, NULL, 0,
    pie_sysctl_target_tupdate_maxb_handler, "L",
    "Burst allowance interval in microsecond");

SYSCTL_PROC(_net_inet_ip_dummynet_pie, OID_AUTO, max_ecnth,
    CTLTYPE_LONG | CTLFLAG_RW | CTLFLAG_NEEDGIANT, NULL, 0,
    pie_sysctl_max_ecnth_handler, "L",
    "ECN safeguard threshold scaled by 1000");

SYSCTL_PROC(_net_inet_ip_dummynet_pie, OID_AUTO, alpha,
    CTLTYPE_LONG | CTLFLAG_RW | CTLFLAG_NEEDGIANT, NULL, 0,
    pie_sysctl_alpha_beta_handler, "L",
    "PIE alpha scaled by 1000");
SYSCTL_PROC(_net_inet_ip_dummynet_pie, OID_AUTO, beta,
    CTLTYPE_LONG | CTLFLAG_RW | CTLFLAG_NEEDGIANT, NULL, 0,
    pie_sysctl_alpha_beta_handler, "L",
    "beta scaled by 1000");
#endif

/*
 * Callout function for drop probability calculation 
 * This function is called over tupdate ms and takes pointer of PIE
 * status variables as an argument
  */
static void
calculate_drop_prob(void *x)
{
        int64_t p, prob, oldprob;
        struct dn_aqm_pie_parms *pprms;
        struct pie_status *pst = (struct pie_status *) x;
        int p_isneg;

        pprms = pst->parms;
        prob = pst->drop_prob;

        /* calculate current qdelay using DRE method.
         * If TS is used and no data in the queue, reset current_qdelay
         * as it stays at last value during dequeue process. 
        */
        if (pprms->flags & PIE_DEPRATEEST_ENABLED)
                pst->current_qdelay = ((uint64_t)pst->pq->ni.len_bytes *
                        pst->avg_dq_time) >> PIE_DQ_THRESHOLD_BITS;
        else 
                if (!pst->pq->ni.len_bytes)
                         pst->current_qdelay = 0;

        /* calculate drop probability */
        p = (int64_t)pprms->alpha * 
                ((int64_t)pst->current_qdelay - (int64_t)pprms->qdelay_ref); 
        p +=(int64_t) pprms->beta * 
                ((int64_t)pst->current_qdelay - (int64_t)pst->qdelay_old); 

        /* take absolute value so right shift result is well defined */
        p_isneg = p < 0;
        if (p_isneg) {
                p = -p;
        }
                
        /* We PIE_MAX_PROB shift by 12-bits to increase the division precision */
        p *= (PIE_MAX_PROB << 12) / AQM_TIME_1S;

        /* auto-tune drop probability */
        if (prob < (PIE_MAX_PROB / 1000000)) /* 0.000001 */
                p >>= 11 + PIE_FIX_POINT_BITS + 12;
        else if (prob < (PIE_MAX_PROB / 100000)) /* 0.00001 */
                p >>= 9 + PIE_FIX_POINT_BITS + 12;
        else if (prob < (PIE_MAX_PROB / 10000)) /* 0.0001 */
                p >>= 7 + PIE_FIX_POINT_BITS + 12;
        else if (prob < (PIE_MAX_PROB / 1000)) /* 0.001 */
                p >>= 5 + PIE_FIX_POINT_BITS + 12;
        else if (prob < (PIE_MAX_PROB / 100)) /* 0.01 */
                p >>= 3 + PIE_FIX_POINT_BITS + 12;
        else if (prob < (PIE_MAX_PROB / 10)) /* 0.1 */
                p >>= 1 + PIE_FIX_POINT_BITS + 12;
        else
                p >>= PIE_FIX_POINT_BITS + 12;

        oldprob = prob;

        if (p_isneg) {
                prob = prob - p;

                /* check for multiplication underflow */
                if (prob > oldprob) {
                        prob= 0;
                        D("underflow");
                }
        } else {
                /* Cap Drop adjustment */
                if ((pprms->flags & PIE_CAPDROP_ENABLED) &&
                    prob >= PIE_MAX_PROB / 10 &&
                    p > PIE_MAX_PROB / 50 ) {
                        p = PIE_MAX_PROB / 50;
                }

                prob = prob + p;

                /* check for multiplication overflow */
                if (prob<oldprob) {
                        D("overflow");
                        prob= PIE_MAX_PROB;
                }
        }

        /*
         * decay the drop probability exponentially
         * and restrict it to range 0 to PIE_MAX_PROB
         */
        if (prob < 0) {
                prob = 0;
        } else {
                if (pst->current_qdelay == 0 && pst->qdelay_old == 0) {
                        /* 0.98 ~= 1- 1/64 */
                        prob = prob - (prob >> 6); 
                }

                if (prob > PIE_MAX_PROB) {
                        prob = PIE_MAX_PROB;
                }
        }

        pst->drop_prob = prob;

        /* store current queue delay value in old queue delay*/
        pst->qdelay_old = pst->current_qdelay;

        /* update burst allowance */
        if ((pst->sflags & PIE_ACTIVE) && pst->burst_allowance>0) {
                
                if (pst->burst_allowance > pprms->tupdate )
                        pst->burst_allowance -= pprms->tupdate;
                else 
                        pst->burst_allowance = 0;
        }

        /* reschedule calculate_drop_prob function */
        if (pst->sflags & PIE_ACTIVE)
                callout_reset_sbt(&pst->aqm_pie_callout,
                        (uint64_t)pprms->tupdate * SBT_1US, 0, calculate_drop_prob, pst, 0);

        mtx_unlock(&pst->lock_mtx);
}

/*
 * Extract a packet from the head of queue 'q'
 * Return a packet or NULL if the queue is empty.
 * If getts is set, also extract packet's timestamp from mtag.
 */
static struct mbuf *
pie_extract_head(struct dn_queue *q, aqm_time_t *pkt_ts, int getts)
{
        struct m_tag *mtag;
        struct mbuf *m;

next:   m = q->mq.head;
        if (m == NULL)
                return m;
        q->mq.head = m->m_nextpkt;

        /* Update stats */
        update_stats(q, -m->m_pkthdr.len, 0);

        if (q->ni.length == 0) /* queue is now idle */
                        q->q_time = V_dn_cfg.curr_time;

        if (getts) {
                /* extract packet TS*/
                mtag = m_tag_locate(m, MTAG_ABI_COMPAT, DN_AQM_MTAG_TS, NULL);
                if (mtag == NULL) {
                        D("PIE timestamp mtag not found!");
                        *pkt_ts = 0;
                } else {
                        *pkt_ts = *(aqm_time_t *)(mtag + 1);
                        m_tag_delete(m,mtag); 
                }
        }
        if (m->m_pkthdr.rcvif != NULL &&
            __predict_false(m_rcvif_restore(m) == NULL)) {
                m_freem(m);
                goto next;
        }
        return m;
}

/* 
 * Initiate PIE  variable and optionally activate it
 */
__inline static void
init_activate_pie(struct pie_status *pst, int resettimer)
{
        struct dn_aqm_pie_parms *pprms;

        mtx_lock(&pst->lock_mtx);
        pprms = pst->parms;
        pst->drop_prob = 0;
        pst->qdelay_old = 0;
        pst->burst_allowance = pprms->max_burst;
        pst->accu_prob = 0;
        pst->dq_count = 0;
        pst->avg_dq_time = 0;
        pst->sflags = PIE_INMEASUREMENT;
        pst->measurement_start = AQM_UNOW;

        if (resettimer) {
                pst->sflags |= PIE_ACTIVE;
                callout_reset_sbt(&pst->aqm_pie_callout,
                        (uint64_t)pprms->tupdate * SBT_1US,
                        0, calculate_drop_prob, pst, 0);
        }
        //DX(2, "PIE Activated");
        mtx_unlock(&pst->lock_mtx);
}

/* 
 * Deactivate PIE and stop probe update callout 
 */
__inline static void
deactivate_pie(struct pie_status *pst)
{
        mtx_lock(&pst->lock_mtx);
        pst->sflags &= ~(PIE_ACTIVE | PIE_INMEASUREMENT);
        callout_stop(&pst->aqm_pie_callout);
        //D("PIE Deactivated");
        mtx_unlock(&pst->lock_mtx);
}

/* 
 * Dequeue and return a pcaket from queue 'q' or NULL if 'q' is empty.
 * Also, caculate depature time or queue delay using timestamp
 */
static struct mbuf *
aqm_pie_dequeue(struct dn_queue *q)
{
        struct mbuf *m;
        struct dn_aqm_pie_parms *pprms;
        struct pie_status *pst;
        aqm_time_t now;
        aqm_time_t pkt_ts, dq_time;
        int32_t w;

        pst  = q->aqm_status;
        pprms = pst->parms;

        /*we extarct packet ts only when Departure Rate Estimation dis not used*/
        m = pie_extract_head(q, &pkt_ts, !(pprms->flags & PIE_DEPRATEEST_ENABLED));

        if (!m || !(pst->sflags & PIE_ACTIVE))
                return m;

        now = AQM_UNOW;
        if (pprms->flags & PIE_DEPRATEEST_ENABLED) {
                /* calculate average depature time */
                if(pst->sflags & PIE_INMEASUREMENT) {
                        pst->dq_count += m->m_pkthdr.len;

                        if (pst->dq_count >= PIE_DQ_THRESHOLD) {
                                dq_time = now - pst->measurement_start;

                                /* 
                                 * if we don't have old avg dq_time i.e PIE is (re)initialized, 
                                 * don't use weight to calculate new avg_dq_time
                                 */
                                if(pst->avg_dq_time == 0)
                                        pst->avg_dq_time = dq_time;
                                else {
                                        /*
                                         * weight = PIE_DQ_THRESHOLD/2^6, but we scaled
                                         * weight by 2^8. Thus, scaled
                                         * weight = PIE_DQ_THRESHOLD /2^8
                                         * */
                                        w = PIE_DQ_THRESHOLD >> 8;
                                        pst->avg_dq_time = (dq_time* w
                                                + (pst->avg_dq_time * ((1L << 8) - w))) >> 8;
                                        pst->sflags &= ~PIE_INMEASUREMENT;
                                }
                        }
                }

                /*
                 * Start new measurement cycle when the queue has
                 * PIE_DQ_THRESHOLD worth of bytes.
                 */
                if(!(pst->sflags & PIE_INMEASUREMENT) &&
                        q->ni.len_bytes >= PIE_DQ_THRESHOLD) {
                        pst->sflags |= PIE_INMEASUREMENT;
                        pst->measurement_start = now;
                        pst->dq_count = 0;
                }
        }
        /* Optionally, use packet timestamp to estimate queue delay */
        else
                pst->current_qdelay = now - pkt_ts;

        return m;
}

/*
 * Enqueue a packet in q, subject to space and  PIE queue management policy
 * (whose parameters are in q->fs).
 * Update stats for the queue and the scheduler.
 * Return 0 on success, 1 on drop. The packet is consumed anyways.
 */
static int
aqm_pie_enqueue(struct dn_queue *q, struct mbuf* m)
{
        struct dn_fs *f;
        uint64_t len;
        uint32_t qlen;
        struct pie_status *pst;
        struct dn_aqm_pie_parms *pprms;
        int t;

        len = m->m_pkthdr.len;
        pst  = q->aqm_status;
        if(!pst) {
                DX(2, "PIE queue is not initialized\n");
                update_stats(q, 0, 1);
                FREE_PKT(m);
                return 1;
        }

        f = &(q->fs->fs);
        pprms = pst->parms;
        t = ENQUE;

        /* get current queue length in bytes or packets*/
        qlen = (f->flags & DN_QSIZE_BYTES) ?
                q->ni.len_bytes : q->ni.length;

        /* check for queue size and drop the tail if exceed queue limit*/
        if (qlen >= f->qsize)
                t = DROP;
        /* drop/mark the packet when PIE is active and burst time elapsed */
        else if ((pst->sflags & PIE_ACTIVE) && pst->burst_allowance==0
                        && drop_early(pst, q->ni.len_bytes) == DROP) {
                                /* 
                                 * if drop_prob over ECN threshold, drop the packet 
                                 * otherwise mark and enqueue it.
                                 */
                                if ((pprms->flags & PIE_ECN_ENABLED) && pst->drop_prob <
                                        (pprms->max_ecnth << (PIE_PROB_BITS - PIE_FIX_POINT_BITS))
                                        && ecn_mark(m))
                                        t = ENQUE;
                                else
                                        t = DROP;
        }

        /* Turn PIE on when 1/3 of the queue is full */ 
        if (!(pst->sflags & PIE_ACTIVE) && qlen >= pst->one_third_q_size) {
                init_activate_pie(pst, 1);
        }

        /*  Reset burst tolerance and optinally turn PIE off*/
        if ((pst->sflags & PIE_ACTIVE) && pst->drop_prob == 0 &&
                pst->current_qdelay < (pprms->qdelay_ref >> 1) &&
                pst->qdelay_old < (pprms->qdelay_ref >> 1)) {
                        pst->burst_allowance = pprms->max_burst;
                        if ((pprms->flags & PIE_ON_OFF_MODE_ENABLED) && qlen<=0)
                                deactivate_pie(pst);
        }

        /* Timestamp the packet if Departure Rate Estimation is disabled */
        if (t != DROP && !(pprms->flags & PIE_DEPRATEEST_ENABLED)) {
                /* Add TS to mbuf as a TAG */
                struct m_tag *mtag;
                mtag = m_tag_locate(m, MTAG_ABI_COMPAT, DN_AQM_MTAG_TS, NULL);
                if (mtag == NULL)
                        mtag = m_tag_alloc(MTAG_ABI_COMPAT, DN_AQM_MTAG_TS,
                                sizeof(aqm_time_t), M_NOWAIT);
                if (mtag == NULL) {
                        t = DROP;
                } else {
                        *(aqm_time_t *)(mtag + 1) = AQM_UNOW;
                        m_tag_prepend(m, mtag);
                }
        }

        if (t != DROP) {
                mq_append(&q->mq, m);
                update_stats(q, len, 0);
                return (0);
        } else {
                update_stats(q, 0, 1);

                /* reset accu_prob after packet drop */
                pst->accu_prob = 0;
                FREE_PKT(m);
                return 1;
        }
        return 0;
}

/* 
 * initialize PIE for queue 'q' 
 * First allocate memory for PIE status.
 */
static int
aqm_pie_init(struct dn_queue *q)
{
        struct pie_status *pst;
        struct dn_aqm_pie_parms *pprms;
        int err = 0;

        pprms = q->fs->aqmcfg;

        do { /* exit with break when error occurs*/
                if (!pprms){
                        DX(2, "AQM_PIE is not configured");
                        err = EINVAL;
                        break;
                }

                q->aqm_status = malloc(sizeof(struct pie_status),
                                 M_DUMMYNET, M_NOWAIT | M_ZERO);
                if (q->aqm_status == NULL) {
                        D("cannot allocate PIE private data");
                        err =  ENOMEM ; 
                        break;
                }

                pst = q->aqm_status;
                dummynet_sched_lock();
                /* increase reference count for PIE module */
                pie_desc.ref_count++;
                dummynet_sched_unlock();
                
                pst->pq = q;
                pst->parms = pprms;
                
                /* For speed optimization, we caculate 1/3 queue size once here */
                // we can use x/3 = (x >>2) + (x >>4) + (x >>7)
                pst->one_third_q_size = q->fs->fs.qsize/3;
                
                mtx_init(&pst->lock_mtx, "mtx_pie", NULL, MTX_DEF);
                callout_init_mtx(&pst->aqm_pie_callout, &pst->lock_mtx,
                        CALLOUT_RETURNUNLOCKED);
                
                pst->current_qdelay = 0;
                init_activate_pie(pst, !(pprms->flags & PIE_ON_OFF_MODE_ENABLED));
                
                //DX(2, "aqm_PIE_init");

        } while(0);

        return err;
}

/* 
 * Callout function to destroy pie mtx and free PIE status memory
 */
static void
pie_callout_cleanup(void *x)
{
        struct pie_status *pst = (struct pie_status *) x;

        mtx_unlock(&pst->lock_mtx);
        mtx_destroy(&pst->lock_mtx);
        free(x, M_DUMMYNET);
        dummynet_sched_lock();
        pie_desc.ref_count--;
        dummynet_sched_unlock();
}

/* 
 * Clean up PIE status for queue 'q' 
 * Destroy memory allocated for PIE status.
 */
static int
aqm_pie_cleanup(struct dn_queue *q)
{

        if(!q) {
                D("q is null");
                return 0;
        }
        struct pie_status *pst  = q->aqm_status;
        if(!pst) {
                //D("queue is already cleaned up");
                return 0;
        }
        if(!q->fs || !q->fs->aqmcfg) {
                D("fs is null or no cfg");
                return 1;
        }
        if (q->fs->aqmfp && q->fs->aqmfp->type !=DN_AQM_PIE) {
                D("Not PIE fs (%d)", q->fs->fs.fs_nr);
                return 1;
        }

        /* 
         * Free PIE status allocated memory using pie_callout_cleanup() callout
         * function to avoid any potential race.
         * We reset aqm_pie_callout to call pie_callout_cleanup() in next 1um. This
         * stops the scheduled calculate_drop_prob() callout and call pie_callout_cleanup() 
         * which does memory freeing.
         */
        mtx_lock(&pst->lock_mtx);
        callout_reset_sbt(&pst->aqm_pie_callout,
                SBT_1US, 0, pie_callout_cleanup, pst, 0);
        q->aqm_status = NULL;
        mtx_unlock(&pst->lock_mtx);

        return 0;
}

/* 
 * Config PIE parameters
 * also allocate memory for PIE configurations
 */
static int 
aqm_pie_config(struct dn_fsk* fs, struct dn_extra_parms *ep, int len)
{ 
        struct dn_aqm_pie_parms *pcfg;

        int l = sizeof(struct dn_extra_parms);
        if (len < l) {
                D("invalid sched parms length got %d need %d", len, l);
                return EINVAL;
        }
        /* we free the old cfg because maybe the orignal allocation 
         * was used for diffirent AQM type.
         */
        if (fs->aqmcfg) {
                free(fs->aqmcfg, M_DUMMYNET);
                fs->aqmcfg = NULL;
        }

        fs->aqmcfg = malloc(sizeof(struct dn_aqm_pie_parms),
                         M_DUMMYNET, M_NOWAIT | M_ZERO);
        if (fs->aqmcfg== NULL) {
                D("cannot allocate PIE configuration parameters");
                return ENOMEM; 
        }

        /* par array contains pie configuration as follow
         * 0- qdelay_ref,1- tupdate, 2- max_burst
         * 3- max_ecnth, 4- alpha, 5- beta, 6- flags
         */

        /* configure PIE parameters */
        pcfg = fs->aqmcfg;

        if (ep->par[0] < 0)
                pcfg->qdelay_ref = pie_sysctl.qdelay_ref * AQM_TIME_1US;
        else
                pcfg->qdelay_ref = ep->par[0];
        if (ep->par[1] < 0)
                pcfg->tupdate = pie_sysctl.tupdate * AQM_TIME_1US;
        else
                pcfg->tupdate = ep->par[1];
        if (ep->par[2] < 0)
                pcfg->max_burst = pie_sysctl.max_burst * AQM_TIME_1US;
        else
                pcfg->max_burst = ep->par[2];
        if (ep->par[3] < 0)
                pcfg->max_ecnth = pie_sysctl.max_ecnth;
        else
                pcfg->max_ecnth = ep->par[3];
        if (ep->par[4] < 0)
                pcfg->alpha = pie_sysctl.alpha;
        else
                pcfg->alpha = ep->par[4];
        if (ep->par[5] < 0)
                pcfg->beta = pie_sysctl.beta;
        else
                pcfg->beta = ep->par[5];
        if (ep->par[6] < 0)
                pcfg->flags = pie_sysctl.flags;
        else
                pcfg->flags = ep->par[6];

        /* bound PIE configurations */
        pcfg->qdelay_ref = BOUND_VAR(pcfg->qdelay_ref, 1, 10 * AQM_TIME_1S);
        pcfg->tupdate = BOUND_VAR(pcfg->tupdate, 1, 10 * AQM_TIME_1S);
        pcfg->max_burst = BOUND_VAR(pcfg->max_burst, 0, 10 * AQM_TIME_1S);
        pcfg->max_ecnth = BOUND_VAR(pcfg->max_ecnth, 0, PIE_SCALE);
        pcfg->alpha = BOUND_VAR(pcfg->alpha, 0, 7 * PIE_SCALE);
        pcfg->beta = BOUND_VAR(pcfg->beta, 0 , 7 * PIE_SCALE);

        pie_desc.cfg_ref_count++;
        //D("pie cfg_ref_count=%d", pie_desc.cfg_ref_count);
        return 0;
}

/*
 * Deconfigure PIE and free memory allocation
 */
static int
aqm_pie_deconfig(struct dn_fsk* fs)
{
        if (fs && fs->aqmcfg) {
                free(fs->aqmcfg, M_DUMMYNET);
                fs->aqmcfg = NULL;
                pie_desc.cfg_ref_count--;
        }
        return 0;
}

/* 
 * Retrieve PIE configuration parameters.
 */ 
static int 
aqm_pie_getconfig (struct dn_fsk *fs, struct dn_extra_parms * ep)
{
        struct dn_aqm_pie_parms *pcfg;
        if (fs->aqmcfg) {
                strlcpy(ep->name, pie_desc.name, sizeof(ep->name));
                pcfg = fs->aqmcfg;
                ep->par[0] = pcfg->qdelay_ref / AQM_TIME_1US;
                ep->par[1] = pcfg->tupdate / AQM_TIME_1US;
                ep->par[2] = pcfg->max_burst / AQM_TIME_1US;
                ep->par[3] = pcfg->max_ecnth;
                ep->par[4] = pcfg->alpha;
                ep->par[5] = pcfg->beta;
                ep->par[6] = pcfg->flags;

                return 0;
        }
        return 1;
}

static struct dn_aqm pie_desc = {
        _SI( .type = )  DN_AQM_PIE,
        _SI( .name = )  "PIE",
        _SI( .ref_count = )  0,
        _SI( .cfg_ref_count = )  0,
        _SI( .enqueue = )  aqm_pie_enqueue,
        _SI( .dequeue = )  aqm_pie_dequeue,
        _SI( .config = )  aqm_pie_config,
        _SI( .deconfig = )  aqm_pie_deconfig,
        _SI( .getconfig = )  aqm_pie_getconfig,
        _SI( .init = )  aqm_pie_init,
        _SI( .cleanup = )  aqm_pie_cleanup,
};

DECLARE_DNAQM_MODULE(dn_aqm_pie, &pie_desc);
#endif