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

/*
 * Dummynet portions related to packet handling.
 */
#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/sdt.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/if_var.h> /* NET_EPOCH_... */
#include <net/if_private.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/ip_fw_private.h>
#include <netpfil/ipfw/dn_heap.h>
#include <netpfil/ipfw/ip_dn_private.h>
#ifdef NEW_AQM
#include <netpfil/ipfw/dn_aqm.h>
#endif
#include <netpfil/ipfw/dn_sched.h>

SDT_PROVIDER_DEFINE(dummynet);
SDT_PROBE_DEFINE2(dummynet, , , drop, "struct mbuf *", "struct dn_queue *");

/*
 * We keep a private variable for the simulation time, but we could
 * probably use an existing one ("softticks" in sys/kern/kern_timeout.c)
 * instead of V_dn_cfg.curr_time
 */
VNET_DEFINE(struct dn_parms, dn_cfg);
#define V_dn_cfg VNET(dn_cfg)

/*
 * We use a heap to store entities for which we have pending timer events.
 * The heap is checked at every tick and all entities with expired events
 * are extracted.
 */
  
MALLOC_DEFINE(M_DUMMYNET, "dummynet", "dummynet heap");

extern  void (*bridge_dn_p)(struct mbuf *, struct ifnet *);

#ifdef SYSCTL_NODE

/*
 * Because of the way the SYSBEGIN/SYSEND macros work on other
 * platforms, there should not be functions between them.
 * So keep the handlers outside the block.
 */
static int
sysctl_hash_size(SYSCTL_HANDLER_ARGS)
{
        int error, value;

        value = V_dn_cfg.hash_size;
        error = sysctl_handle_int(oidp, &value, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        if (value < 16 || value > 65536)
                return (EINVAL);
        V_dn_cfg.hash_size = value;
        return (0);
}

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

        if (arg2 != 0)
                value = V_dn_cfg.slot_limit;
        else
                value = V_dn_cfg.byte_limit;
        error = sysctl_handle_long(oidp, &value, 0, req);

        if (error != 0 || req->newptr == NULL)
                return (error);
        if (arg2 != 0) {
                if (value < 1)
                        return (EINVAL);
                V_dn_cfg.slot_limit = value;
        } else {
                if (value < 1500)
                        return (EINVAL);
                V_dn_cfg.byte_limit = value;
        }
        return (0);
}

SYSBEGIN(f4)

SYSCTL_DECL(_net_inet);
SYSCTL_DECL(_net_inet_ip);
#ifdef NEW_AQM
SYSCTL_NODE(_net_inet_ip, OID_AUTO, dummynet, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "Dummynet");
#else
static SYSCTL_NODE(_net_inet_ip, OID_AUTO, dummynet,
    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "Dummynet");
#endif

/* wrapper to pass V_dn_cfg fields to SYSCTL_* */
#define DC(x)   (&(VNET_NAME(dn_cfg).x))

/* parameters */

SYSCTL_PROC(_net_inet_ip_dummynet, OID_AUTO, hash_size,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
    0, 0, sysctl_hash_size, "I",
    "Default hash table size");

SYSCTL_PROC(_net_inet_ip_dummynet, OID_AUTO, pipe_slot_limit,
    CTLTYPE_LONG | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
    0, 1, sysctl_limits, "L",
    "Upper limit in slots for pipe queue.");
SYSCTL_PROC(_net_inet_ip_dummynet, OID_AUTO, pipe_byte_limit,
    CTLTYPE_LONG | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
    0, 0, sysctl_limits, "L",
    "Upper limit in bytes for pipe queue.");
SYSCTL_INT(_net_inet_ip_dummynet, OID_AUTO, io_fast,
    CTLFLAG_RW | CTLFLAG_VNET, DC(io_fast), 0, "Enable fast dummynet io.");
SYSCTL_INT(_net_inet_ip_dummynet, OID_AUTO, debug,
    CTLFLAG_RW | CTLFLAG_VNET, DC(debug), 0, "Dummynet debug level");

/* RED parameters */
SYSCTL_INT(_net_inet_ip_dummynet, OID_AUTO, red_lookup_depth,
    CTLFLAG_RD | CTLFLAG_VNET, DC(red_lookup_depth), 0, "Depth of RED lookup table");
SYSCTL_INT(_net_inet_ip_dummynet, OID_AUTO, red_avg_pkt_size,
    CTLFLAG_RD | CTLFLAG_VNET, DC(red_avg_pkt_size), 0, "RED Medium packet size");
SYSCTL_INT(_net_inet_ip_dummynet, OID_AUTO, red_max_pkt_size,
    CTLFLAG_RD | CTLFLAG_VNET, DC(red_max_pkt_size), 0, "RED Max packet size");

/* time adjustment */
SYSCTL_LONG(_net_inet_ip_dummynet, OID_AUTO, tick_delta,
    CTLFLAG_RD | CTLFLAG_VNET, DC(tick_delta), 0, "Last vs standard tick difference (usec).");
SYSCTL_LONG(_net_inet_ip_dummynet, OID_AUTO, tick_delta_sum,
    CTLFLAG_RD | CTLFLAG_VNET, DC(tick_delta_sum), 0, "Accumulated tick difference (usec).");
SYSCTL_LONG(_net_inet_ip_dummynet, OID_AUTO, tick_adjustment,
    CTLFLAG_RD | CTLFLAG_VNET, DC(tick_adjustment), 0, "Tick adjustments done.");
SYSCTL_LONG(_net_inet_ip_dummynet, OID_AUTO, tick_diff,
    CTLFLAG_RD | CTLFLAG_VNET, DC(tick_diff), 0,
    "Adjusted vs non-adjusted curr_time difference (ticks).");
SYSCTL_LONG(_net_inet_ip_dummynet, OID_AUTO, tick_lost,
    CTLFLAG_RD | CTLFLAG_VNET, DC(tick_lost), 0,
    "Number of ticks coalesced by dummynet taskqueue.");

/* Drain parameters */
SYSCTL_UINT(_net_inet_ip_dummynet, OID_AUTO, expire,
    CTLFLAG_RW | CTLFLAG_VNET, DC(expire), 0, "Expire empty queues/pipes");
SYSCTL_UINT(_net_inet_ip_dummynet, OID_AUTO, expire_cycle,
    CTLFLAG_RD | CTLFLAG_VNET, DC(expire_cycle), 0, "Expire cycle for queues/pipes");

/* statistics */
SYSCTL_INT(_net_inet_ip_dummynet, OID_AUTO, schk_count,
    CTLFLAG_RD | CTLFLAG_VNET, DC(schk_count), 0, "Number of schedulers");
SYSCTL_INT(_net_inet_ip_dummynet, OID_AUTO, si_count,
    CTLFLAG_RD | CTLFLAG_VNET, DC(si_count), 0, "Number of scheduler instances");
SYSCTL_INT(_net_inet_ip_dummynet, OID_AUTO, fsk_count,
    CTLFLAG_RD | CTLFLAG_VNET, DC(fsk_count), 0, "Number of flowsets");
SYSCTL_INT(_net_inet_ip_dummynet, OID_AUTO, queue_count,
    CTLFLAG_RD | CTLFLAG_VNET, DC(queue_count), 0, "Number of queues");
SYSCTL_ULONG(_net_inet_ip_dummynet, OID_AUTO, io_pkt,
    CTLFLAG_RD | CTLFLAG_VNET, DC(io_pkt), 0,
    "Number of packets passed to dummynet.");
SYSCTL_ULONG(_net_inet_ip_dummynet, OID_AUTO, io_pkt_fast,
    CTLFLAG_RD | CTLFLAG_VNET, DC(io_pkt_fast), 0,
    "Number of packets bypassed dummynet scheduler.");
SYSCTL_ULONG(_net_inet_ip_dummynet, OID_AUTO, io_pkt_drop,
    CTLFLAG_RD | CTLFLAG_VNET, DC(io_pkt_drop), 0,
    "Number of packets dropped by dummynet.");
#undef DC
SYSEND

#endif

static void     dummynet_send(struct mbuf *);

/*
 * Return the mbuf tag holding the dummynet state (it should
 * be the first one on the list).
 */
struct dn_pkt_tag *
dn_tag_get(struct mbuf *m)
{
        struct m_tag *mtag = m_tag_first(m);
#ifdef NEW_AQM
        /* XXX: to skip ts m_tag. For Debugging only*/
        if (mtag != NULL && mtag->m_tag_id == DN_AQM_MTAG_TS) {
                m_tag_delete(m,mtag); 
                mtag = m_tag_first(m);
                D("skip TS tag");
        }
#endif
        KASSERT(mtag != NULL &&
            mtag->m_tag_cookie == MTAG_ABI_COMPAT &&
            mtag->m_tag_id == PACKET_TAG_DUMMYNET,
            ("packet on dummynet queue w/o dummynet tag!"));
        return (struct dn_pkt_tag *)(mtag+1);
}

#ifndef NEW_AQM
static inline void
mq_append(struct mq *q, struct mbuf *m)
{
#ifdef USERSPACE
        // buffers from netmap need to be copied
        // XXX note that the routine is not expected to fail
        ND("append %p to %p", m, q);
        if (m->m_flags & M_STACK) {
                struct mbuf *m_new;
                void *p;
                int l, ofs;

                ofs = m->m_data - m->__m_extbuf;
                // XXX allocate
                MGETHDR(m_new, M_NOWAIT, MT_DATA);
                ND("*** WARNING, volatile buf %p ext %p %d dofs %d m_new %p",
                        m, m->__m_extbuf, m->__m_extlen, ofs, m_new);
                p = m_new->__m_extbuf;  /* new pointer */
                l = m_new->__m_extlen;  /* new len */
                if (l <= m->__m_extlen) {
                        panic("extlen too large");
                }

                *m_new = *m;    // copy
                m_new->m_flags &= ~M_STACK;
                m_new->__m_extbuf = p; // point to new buffer
                _pkt_copy(m->__m_extbuf, p, m->__m_extlen);
                m_new->m_data = p + ofs;
                m = m_new;
        }
#endif /* USERSPACE */
        if (q->head == NULL)
                q->head = m;
        else
                q->tail->m_nextpkt = m;
        q->count++;
        q->tail = m;
        m->m_nextpkt = NULL;
}
#endif

/*
 * Dispose a list of packet. Use a functions so if we need to do
 * more work, this is a central point to do it.
 */
void dn_free_pkts(struct mbuf *mnext)
{
        struct mbuf *m;
    
        while ((m = mnext) != NULL) {
                mnext = m->m_nextpkt;
                FREE_PKT(m);
        }
}

static int
red_drops (struct dn_queue *q, int len)
{
        /*
         * RED algorithm
         *
         * RED calculates the average queue size (avg) using a low-pass filter
         * with an exponential weighted (w_q) moving average:
         *      avg  <-  (1-w_q) * avg + w_q * q_size
         * where q_size is the queue length (measured in bytes or * packets).
         *
         * If q_size == 0, we compute the idle time for the link, and set
         *      avg = (1 - w_q)^(idle/s)
         * where s is the time needed for transmitting a medium-sized packet.
         *
         * Now, if avg < min_th the packet is enqueued.
         * If avg > max_th the packet is dropped. Otherwise, the packet is
         * dropped with probability P function of avg.
         */

        struct dn_fsk *fs = q->fs;
        int64_t p_b = 0;

        /* Queue in bytes or packets? */
        uint32_t q_size = (fs->fs.flags & DN_QSIZE_BYTES) ?
            q->ni.len_bytes : q->ni.length;

        /* Average queue size estimation. */
        if (q_size != 0) {
                /* Queue is not empty, avg <- avg + (q_size - avg) * w_q */
                int diff = SCALE(q_size) - q->avg;
                int64_t v = SCALE_MUL((int64_t)diff, (int64_t)fs->w_q);

                q->avg += (int)v;
        } else {
                /*
                 * Queue is empty, find for how long the queue has been
                 * empty and use a lookup table for computing
                 * (1 - * w_q)^(idle_time/s) where s is the time to send a
                 * (small) packet.
                 * XXX check wraps...
                 */
                if (q->avg) {
                        u_int t = div64((V_dn_cfg.curr_time - q->q_time), fs->lookup_step);

                        q->avg = (t < fs->lookup_depth) ?
                            SCALE_MUL(q->avg, fs->w_q_lookup[t]) : 0;
                }
        }

        /* Should i drop? */
        if (q->avg < fs->min_th) {
                q->count = -1;
                return (0);     /* accept packet */
        }
        if (q->avg >= fs->max_th) {     /* average queue >=  max threshold */
                if (fs->fs.flags & DN_IS_ECN)
                        return (1);
                if (fs->fs.flags & DN_IS_GENTLE_RED) {
                        /*
                         * According to Gentle-RED, if avg is greater than
                         * max_th the packet is dropped with a probability
                         *       p_b = c_3 * avg - c_4
                         * where c_3 = (1 - max_p) / max_th
                         *       c_4 = 1 - 2 * max_p
                         */
                        p_b = SCALE_MUL((int64_t)fs->c_3, (int64_t)q->avg) -
                            fs->c_4;
                } else {
                        q->count = -1;
                        return (1);
                }
        } else if (q->avg > fs->min_th) {
                if (fs->fs.flags & DN_IS_ECN)
                        return (1);
                /*
                 * We compute p_b using the linear dropping function
                 *       p_b = c_1 * avg - c_2
                 * where c_1 = max_p / (max_th - min_th)
                 *       c_2 = max_p * min_th / (max_th - min_th)
                 */
                p_b = SCALE_MUL((int64_t)fs->c_1, (int64_t)q->avg) - fs->c_2;
        }

        if (fs->fs.flags & DN_QSIZE_BYTES)
                p_b = div64((p_b * len) , fs->max_pkt_size);
        if (++q->count == 0)
                q->random = random() & 0xffff;
        else {
                /*
                 * q->count counts packets arrived since last drop, so a greater
                 * value of q->count means a greater packet drop probability.
                 */
                if (SCALE_MUL(p_b, SCALE((int64_t)q->count)) > q->random) {
                        q->count = 0;
                        /* After a drop we calculate a new random value. */
                        q->random = random() & 0xffff;
                        return (1);     /* drop */
                }
        }
        /* End of RED algorithm. */

        return (0);     /* accept */

}

/*
 * ECN/ECT Processing (partially adopted from altq)
 */
#ifndef NEW_AQM
static
#endif
int
ecn_mark(struct mbuf* m)
{
        struct ip *ip;
        ip = (struct ip *)mtodo(m, dn_tag_get(m)->iphdr_off);

        switch (ip->ip_v) {
        case IPVERSION:
        {
                uint16_t old;

                if ((ip->ip_tos & IPTOS_ECN_MASK) == IPTOS_ECN_NOTECT)
                        return (0);     /* not-ECT */
                if ((ip->ip_tos & IPTOS_ECN_MASK) == IPTOS_ECN_CE)
                        return (1);     /* already marked */

                /*
                 * ecn-capable but not marked,
                 * mark CE and update checksum
                 */
                old = *(uint16_t *)ip;
                ip->ip_tos |= IPTOS_ECN_CE;
                ip->ip_sum = cksum_adjust(ip->ip_sum, old, *(uint16_t *)ip);
                return (1);
        }
#ifdef INET6
        case (IPV6_VERSION >> 4):
        {
                struct ip6_hdr *ip6 = (struct ip6_hdr *)ip;
                u_int32_t flowlabel;

                flowlabel = ntohl(ip6->ip6_flow);
                if ((flowlabel >> 28) != 6)
                        return (0);     /* version mismatch! */
                if ((flowlabel & (IPTOS_ECN_MASK << 20)) ==
                    (IPTOS_ECN_NOTECT << 20))
                        return (0);     /* not-ECT */
                if ((flowlabel & (IPTOS_ECN_MASK << 20)) ==
                    (IPTOS_ECN_CE << 20))
                        return (1);     /* already marked */
                /*
                 * ecn-capable but not marked, mark CE
                 */
                flowlabel |= (IPTOS_ECN_CE << 20);
                ip6->ip6_flow = htonl(flowlabel);
                return (1);
        }
#endif
        }
        return (0);
}

/*
 * Enqueue a packet in q, subject to space and 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.
 */
int
dn_enqueue(struct dn_queue *q, struct mbuf* m, int drop)
{   
        struct dn_fs *f;
        struct dn_flow *ni;     /* stats for scheduler instance */
        uint64_t len;

        if (q->fs == NULL || q->_si == NULL) {
                printf("%s fs %p si %p, dropping\n",
                        __FUNCTION__, q->fs, q->_si);
                FREE_PKT(m);
                return 1;
        }
        f = &(q->fs->fs);
        ni = &q->_si->ni;
        len = m->m_pkthdr.len;
        /* Update statistics, then check reasons to drop pkt. */
        q->ni.tot_bytes += len;
        q->ni.tot_pkts++;
        ni->tot_bytes += len;
        ni->tot_pkts++;
        if (drop)
                goto drop;
        if (f->plr[0] || f->plr[1]) {
                if (__predict_true(f->plr[1] == 0)) {
                        if (random() < f->plr[0])
                                goto drop;
                } else {
                        switch (f->pl_state) {
                        case PLR_STATE_B:
                                if (random() < f->plr[3])
                                        f->pl_state = PLR_STATE_G;
                                if (random() < f->plr[2])
                                        goto drop;
                                break;
                        case PLR_STATE_G: /* FALLTHROUGH */
                        default:
                                if (random() < f->plr[1])
                                        f->pl_state = PLR_STATE_B;
                                if (random() < f->plr[0])
                                        goto drop;
                                break;
                        }
                }
        }
        if (m->m_pkthdr.rcvif != NULL)
                m_rcvif_serialize(m);
#ifdef NEW_AQM
        /* Call AQM enqueue function */
        if (q->fs->aqmfp)
                return q->fs->aqmfp->enqueue(q ,m);
#endif
        if (f->flags & DN_IS_RED && red_drops(q, m->m_pkthdr.len)) {
                if (!(f->flags & DN_IS_ECN) || !ecn_mark(m))
                        goto drop;
        }
        if (f->flags & DN_QSIZE_BYTES) {
                if (q->ni.len_bytes > f->qsize)
                        goto drop;
        } else if (q->ni.length >= f->qsize) {
                goto drop;
        }
        mq_append(&q->mq, m);
        q->ni.length++;
        q->ni.len_bytes += len;
        ni->length++;
        ni->len_bytes += len;
        return (0);

drop:
        V_dn_cfg.io_pkt_drop++;
        SDT_PROBE2(dummynet, , , drop, m, q);
        q->ni.drops++;
        ni->drops++;
        FREE_PKT(m);
        return (1);
}

/*
 * Fetch packets from the delay line which are due now. If there are
 * leftover packets, reinsert the delay line in the heap.
 * Runs under scheduler lock.
 */
static void
transmit_event(struct mq *q, struct delay_line *dline, uint64_t now)
{
        struct mbuf *m;
        struct dn_pkt_tag *pkt = NULL;

        dline->oid.subtype = 0; /* not in heap */
        while ((m = dline->mq.head) != NULL) {
                pkt = dn_tag_get(m);
                if (!DN_KEY_LEQ(pkt->output_time, now))
                        break;
                dline->mq.head = m->m_nextpkt;
                dline->mq.count--;
                if (m->m_pkthdr.rcvif != NULL &&
                  __predict_false(m_rcvif_restore(m) == NULL))
                        m_freem(m);
                else
                        mq_append(q, m);
        }
        if (m != NULL) {
                dline->oid.subtype = 1; /* in heap */
                heap_insert(&V_dn_cfg.evheap, pkt->output_time, dline);
        }
}

/*
 * Convert the additional MAC overheads/delays into an equivalent
 * number of bits for the given data rate. The samples are
 * in milliseconds so we need to divide by 1000.
 */
static uint64_t
extra_bits(struct mbuf *m, struct dn_schk *s)
{
        int index;
        uint64_t bits;
        struct dn_profile *pf = s->profile;

        if (!pf || pf->samples_no == 0)
                return 0;
        index  = random() % pf->samples_no;
        bits = div64((uint64_t)pf->samples[index] * s->link.bandwidth, 1000);
        if (index >= pf->loss_level) {
                struct dn_pkt_tag *dt = dn_tag_get(m);
                if (dt)
                        dt->dn_dir = DIR_DROP;
        }
        return bits;
}

/*
 * Send traffic from a scheduler instance due by 'now'.
 * Return a pointer to the head of the queue.
 */
static struct mbuf *
serve_sched(struct mq *q, struct dn_sch_inst *si, uint64_t now)
{
        struct mq def_q;
        struct dn_schk *s = si->sched;
        struct mbuf *m = NULL;
        int delay_line_idle = (si->dline.mq.head == NULL);
        int done;
        uint32_t bw;

        if (q == NULL) {
                q = &def_q;
                q->head = NULL;
        }

        bw = s->link.bandwidth;
        si->kflags &= ~DN_ACTIVE;

        if (bw > 0)
                si->credit += (now - si->sched_time) * bw;
        else
                si->credit = 0;
        si->sched_time = now;
        done = 0;
        while (si->credit >= 0 && (m = s->fp->dequeue(si)) != NULL) {
                uint64_t len_scaled;

                done++;
                len_scaled = (bw == 0) ? 0 : hz *
                        (m->m_pkthdr.len * 8 + extra_bits(m, s));
                si->credit -= len_scaled;
                /* Move packet in the delay line */
                dn_tag_get(m)->output_time = V_dn_cfg.curr_time + s->link.delay ;
                if (m->m_pkthdr.rcvif != NULL)
                        m_rcvif_serialize(m);
                mq_append(&si->dline.mq, m);
        }

        /*
         * If credit >= 0 the instance is idle, mark time.
         * Otherwise put back in the heap, and adjust the output
         * time of the last inserted packet, m, which was too early.
         */
        if (si->credit >= 0) {
                si->idle_time = now;
        } else {
                uint64_t t;
                KASSERT (bw > 0, ("bw=0 and credit<0 ?"));
                t = div64(bw - 1 - si->credit, bw);
                if (m)
                        dn_tag_get(m)->output_time += t;
                si->kflags |= DN_ACTIVE;
                heap_insert(&V_dn_cfg.evheap, now + t, si);
        }
        if (delay_line_idle && done)
                transmit_event(q, &si->dline, now);
        return q->head;
}

/*
 * The timer handler for dummynet. Time is computed in ticks, but
 * but the code is tolerant to the actual rate at which this is called.
 * Once complete, the function reschedules itself for the next tick.
 */
void
dummynet_task(void *context, int pending)
{
        struct timeval t;
        struct mq q = { NULL, NULL }; /* queue to accumulate results */
        struct epoch_tracker et;

        VNET_ITERATOR_DECL(vnet_iter);
        VNET_LIST_RLOCK();
        NET_EPOCH_ENTER(et);

        VNET_FOREACH(vnet_iter) {
                memset(&q, 0, sizeof(struct mq));
                CURVNET_SET(vnet_iter);

                if (! V_dn_cfg.init_done) {
                        CURVNET_RESTORE();
                        continue;
                }

                DN_BH_WLOCK();

                /* Update number of lost(coalesced) ticks. */
                V_dn_cfg.tick_lost += pending - 1;

                getmicrouptime(&t);
                /* Last tick duration (usec). */
                V_dn_cfg.tick_last = (t.tv_sec - V_dn_cfg.prev_t.tv_sec) * 1000000 +
                (t.tv_usec - V_dn_cfg.prev_t.tv_usec);
                /* Last tick vs standard tick difference (usec). */
                V_dn_cfg.tick_delta = (V_dn_cfg.tick_last * hz - 1000000) / hz;
                /* Accumulated tick difference (usec). */
                V_dn_cfg.tick_delta_sum += V_dn_cfg.tick_delta;

                V_dn_cfg.prev_t = t;

                /*
                * Adjust curr_time if the accumulated tick difference is
                * greater than the 'standard' tick. Since curr_time should
                * be monotonically increasing, we do positive adjustments
                * as required, and throttle curr_time in case of negative
                * adjustment.
                */
                V_dn_cfg.curr_time++;
                if (V_dn_cfg.tick_delta_sum - tick >= 0) {
                        int diff = V_dn_cfg.tick_delta_sum / tick;

                        V_dn_cfg.curr_time += diff;
                        V_dn_cfg.tick_diff += diff;
                        V_dn_cfg.tick_delta_sum %= tick;
                        V_dn_cfg.tick_adjustment++;
                } else if (V_dn_cfg.tick_delta_sum + tick <= 0) {
                        V_dn_cfg.curr_time--;
                        V_dn_cfg.tick_diff--;
                        V_dn_cfg.tick_delta_sum += tick;
                        V_dn_cfg.tick_adjustment++;
                }

                /* serve pending events, accumulate in q */
                for (;;) {
                        struct dn_id *p;    /* generic parameter to handler */

                        if (V_dn_cfg.evheap.elements == 0 ||
                            DN_KEY_LT(V_dn_cfg.curr_time, HEAP_TOP(&V_dn_cfg.evheap)->key))
                                break;
                        p = HEAP_TOP(&V_dn_cfg.evheap)->object;
                        heap_extract(&V_dn_cfg.evheap, NULL);
                        if (p->type == DN_SCH_I) {
                                serve_sched(&q, (struct dn_sch_inst *)p, V_dn_cfg.curr_time);
                        } else { /* extracted a delay line */
                                transmit_event(&q, (struct delay_line *)p, V_dn_cfg.curr_time);
                        }
                }
                if (V_dn_cfg.expire && ++V_dn_cfg.expire_cycle >= V_dn_cfg.expire) {
                        V_dn_cfg.expire_cycle = 0;
                        dn_drain_scheduler();
                        dn_drain_queue();
                }
                DN_BH_WUNLOCK();
                if (q.head != NULL)
                        dummynet_send(q.head);

                CURVNET_RESTORE();
        }
        NET_EPOCH_EXIT(et);
        VNET_LIST_RUNLOCK();

        /* Schedule our next run. */
        dn_reschedule();
}

/*
 * forward a chain of packets to the proper destination.
 * This runs outside the dummynet lock.
 */
static void
dummynet_send(struct mbuf *m)
{
        struct mbuf *n;

        NET_EPOCH_ASSERT();

        for (; m != NULL; m = n) {
                struct ifnet *ifp = NULL;       /* gcc 3.4.6 complains */
                struct m_tag *tag;
                int dst;

                n = m->m_nextpkt;
                m->m_nextpkt = NULL;
                tag = m_tag_first(m);
                if (tag == NULL) { /* should not happen */
                        dst = DIR_DROP;
                } else {
                        struct dn_pkt_tag *pkt = dn_tag_get(m);
                        /* extract the dummynet info, rename the tag
                         * to carry reinject info.
                         */
                        ifp = ifnet_byindexgen(pkt->if_index, pkt->if_idxgen);
                        if (((pkt->dn_dir == (DIR_OUT | PROTO_LAYER2)) ||
                            (pkt->dn_dir == (DIR_OUT | PROTO_LAYER2 | PROTO_IPV6))) &&
                                ifp == NULL) {
                                dst = DIR_DROP;
                        } else {
                                dst = pkt->dn_dir;
                                tag->m_tag_cookie = MTAG_IPFW_RULE;
                                tag->m_tag_id = 0;
                        }
                }

                switch (dst) {
                case DIR_OUT:
                        ip_output(m, NULL, NULL, IP_FORWARDING, NULL, NULL);
                        break ;

                case DIR_IN :
                        netisr_dispatch(NETISR_IP, m);
                        break;

#ifdef INET6
                case DIR_IN | PROTO_IPV6:
                        netisr_dispatch(NETISR_IPV6, m);
                        break;

                case DIR_OUT | PROTO_IPV6:
                        ip6_output(m, NULL, NULL, IPV6_FORWARDING, NULL, NULL, NULL);
                        break;
#endif

                case DIR_FWD | PROTO_IFB: /* DN_TO_IFB_FWD: */
                        if (bridge_dn_p != NULL)
                                ((*bridge_dn_p)(m, ifp));
                        else
                                printf("dummynet: if_bridge not loaded\n");

                        break;

                case DIR_IN | PROTO_LAYER2 | PROTO_IPV6:
                case DIR_IN | PROTO_LAYER2: /* DN_TO_ETH_DEMUX: */
                        /*
                         * The Ethernet code assumes the Ethernet header is
                         * contiguous in the first mbuf header.
                         * Insure this is true.
                         */
                        if (m->m_len < ETHER_HDR_LEN &&
                            (m = m_pullup(m, ETHER_HDR_LEN)) == NULL) {
                                printf("dummynet/ether: pullup failed, "
                                    "dropping packet\n");
                                break;
                        }
                        ether_demux(m->m_pkthdr.rcvif, m);
                        break;

                case DIR_OUT | PROTO_LAYER2 | PROTO_IPV6:
                case DIR_OUT | PROTO_LAYER2: /* DN_TO_ETH_OUT: */
                        MPASS(ifp != NULL);
                        ether_output_frame(ifp, m);
                        break;

                case DIR_DROP:
                        /* drop the packet after some time */
                        FREE_PKT(m);
                        break;

                default:
                        printf("dummynet: bad switch %d!\n", dst);
                        FREE_PKT(m);
                        break;
                }
        }
}

static inline int
tag_mbuf(struct mbuf *m, int dir, struct ip_fw_args *fwa)
{
        struct dn_pkt_tag *dt;
        struct m_tag *mtag;

        mtag = m_tag_get(PACKET_TAG_DUMMYNET,
                    sizeof(*dt), M_NOWAIT | M_ZERO);
        if (mtag == NULL)
                return 1;               /* Cannot allocate packet header. */
        m_tag_prepend(m, mtag);         /* Attach to mbuf chain. */
        dt = (struct dn_pkt_tag *)(mtag + 1);
        dt->rule = fwa->rule;
        /* only keep this info */
        dt->rule.info &= (IPFW_ONEPASS | IPFW_IS_DUMMYNET);
        dt->dn_dir = dir;
        if (fwa->flags & IPFW_ARGS_OUT && fwa->ifp != NULL) {
                NET_EPOCH_ASSERT();
                dt->if_index = fwa->ifp->if_index;
                dt->if_idxgen = fwa->ifp->if_idxgen;
        }
        /* dt->output_time is updated as we move through */
        dt->output_time = V_dn_cfg.curr_time;
        dt->iphdr_off = (dir & PROTO_LAYER2) ? ETHER_HDR_LEN : 0;
        return 0;
}

/*
 * dummynet hook for packets.
 * We use the argument to locate the flowset fs and the sched_set sch
 * associated to it. The we apply flow_mask and sched_mask to
 * determine the queue and scheduler instances.
 */
int
dummynet_io(struct mbuf **m0, struct ip_fw_args *fwa)
{
        struct mbuf *m = *m0;
        struct dn_fsk *fs = NULL;
        struct dn_sch_inst *si;
        struct dn_queue *q = NULL;      /* default */
        int fs_id, dir;

        fs_id = (fwa->rule.info & IPFW_INFO_MASK) +
                ((fwa->rule.info & IPFW_IS_PIPE) ? 2*DN_MAX_ID : 0);
        /* XXXGL: convert args to dir */
        if (fwa->flags & IPFW_ARGS_IN)
                dir = DIR_IN;
        else
                dir = DIR_OUT;
        if (fwa->flags & IPFW_ARGS_ETHER)
                dir |= PROTO_LAYER2;
        else if (fwa->flags & IPFW_ARGS_IP6)
                dir |= PROTO_IPV6;
        DN_BH_WLOCK();
        V_dn_cfg.io_pkt++;
        /* we could actually tag outside the lock, but who cares... */
        if (tag_mbuf(m, dir, fwa))
                goto dropit;
        /* XXX locate_flowset could be optimised with a direct ref. */
        fs = dn_ht_find(V_dn_cfg.fshash, fs_id, 0, NULL);
        if (fs == NULL)
                goto dropit;    /* This queue/pipe does not exist! */
        if (fs->sched == NULL)  /* should not happen */
                goto dropit;
        /* find scheduler instance, possibly applying sched_mask */
        si = ipdn_si_find(fs->sched, &(fwa->f_id));
        if (si == NULL)
                goto dropit;
        /*
         * If the scheduler supports multiple queues, find the right one
         * (otherwise it will be ignored by enqueue).
         */
        if (fs->sched->fp->flags & DN_MULTIQUEUE) {
                q = ipdn_q_find(fs, si, &(fwa->f_id));
                if (q == NULL)
                        goto dropit;
        }
        if (fs->sched->fp->enqueue(si, q, m)) {
                /* packet was dropped by enqueue() */
                m = *m0 = NULL;

                /* dn_enqueue already increases io_pkt_drop */
                V_dn_cfg.io_pkt_drop--;

                goto dropit;
        }

        if (si->kflags & DN_ACTIVE) {
                m = *m0 = NULL; /* consumed */
                goto done; /* already active, nothing to do */
        }

        /* compute the initial allowance */
        if (si->idle_time < V_dn_cfg.curr_time) {
            /* Do this only on the first packet on an idle pipe */
            struct dn_link *p = &fs->sched->link;

            si->sched_time = V_dn_cfg.curr_time;
            si->credit = V_dn_cfg.io_fast ? p->bandwidth : 0;
            if (p->burst) {
                uint64_t burst = (V_dn_cfg.curr_time - si->idle_time) * p->bandwidth;
                if (burst > p->burst)
                        burst = p->burst;
                si->credit += burst;
            }
        }
        /* pass through scheduler and delay line */
        m = serve_sched(NULL, si, V_dn_cfg.curr_time);

        /* optimization -- pass it back to ipfw for immediate send */
        /* XXX Don't call dummynet_send() if scheduler return the packet
         *     just enqueued. This avoid a lock order reversal.
         *     
         */
        if (/*V_dn_cfg.io_fast &&*/ m == *m0 && (dir & PROTO_LAYER2) == 0 ) {
                /* fast io, rename the tag * to carry reinject info. */
                struct m_tag *tag = m_tag_first(m);

                tag->m_tag_cookie = MTAG_IPFW_RULE;
                tag->m_tag_id = 0;
                V_dn_cfg.io_pkt_fast++;
                if (m->m_nextpkt != NULL) {
                        printf("dummynet: fast io: pkt chain detected!\n");
                        m->m_nextpkt = NULL;
                }
                m = NULL;
        } else {
                *m0 = NULL;
        }
done:
        DN_BH_WUNLOCK();
        if (m)
                dummynet_send(m);
        return 0;

dropit:
        V_dn_cfg.io_pkt_drop++;
        SDT_PROBE2(dummynet, , , drop, m, q);
        DN_BH_WUNLOCK();
        if (m)
                FREE_PKT(m);
        *m0 = NULL;
        return (fs && (fs->fs.flags & DN_NOERROR)) ? 0 : ENOBUFS;
}