/*-
 * Copyright (c) 2011, Bryan Venteicher <bryanv@FreeBSD.org>
 * 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 unmodified, 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 ``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 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.
 */

/* Driver for VirtIO network devices. */

#include "opt_ifpoll.h"

#include <sys/cdefs.h>

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/sockio.h>
#include <sys/mbuf.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/socket.h>
#include <sys/sysctl.h>
#include <sys/taskqueue.h>
#include <sys/random.h>
#include <sys/sglist.h>
#include <sys/serialize.h>
#include <sys/bus.h>
#include <sys/rman.h>

#include <machine/limits.h>

#include <net/ethernet.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <net/if_dl.h>
#include <net/if_types.h>
#include <net/if_media.h>
#include <net/vlan/if_vlan_var.h>
#include <net/vlan/if_vlan_ether.h>
#include <net/if_poll.h>
#include <net/ifq_var.h>

#include <net/bpf.h>

#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#include <netinet/udp.h>
#include <netinet/tcp.h>

#include <dev/virtual/virtio/virtio/virtio.h>
#include <dev/virtual/virtio/virtio/virtqueue.h>
#include <dev/virtual/virtio/net/virtio_net.h>
#include <dev/virtual/virtio/net/if_vtnetvar.h>

MALLOC_DEFINE(M_VTNET, "VTNET_TX", "Outgoing VTNET TX frame header");

static int      vtnet_probe(device_t);
static int      vtnet_attach(device_t);
static int      vtnet_detach(device_t);
static int      vtnet_suspend(device_t);
static int      vtnet_resume(device_t);
static int      vtnet_shutdown(device_t);

static void     vtnet_negotiate_features(struct vtnet_softc *);
#ifdef IFPOLL_ENABLE
static void     vtnet_npoll(struct ifnet *, struct ifpoll_info *);
static void     vtnet_npoll_status(struct ifnet *);
static void     vtnet_npoll_rx(struct ifnet *, void *, int);
static void     vtnet_npoll_tx(struct ifnet *, void *, int);
#endif
static void     vtnet_serialize(struct ifnet *, enum ifnet_serialize);
static void     vtnet_deserialize(struct ifnet *, enum ifnet_serialize);
static int      vtnet_tryserialize(struct ifnet *, enum ifnet_serialize);
#ifdef INVARIANTS
static void     vtnet_serialize_assert(struct ifnet *, enum ifnet_serialize,
                    boolean_t);
#endif  /* INVARIANTS */
static int      vtnet_alloc_intrs(struct vtnet_softc *);
static int      vtnet_alloc_virtqueues(struct vtnet_softc *);
static int      vtnet_bind_intrs(struct vtnet_softc *);
static void     vtnet_get_hwaddr(struct vtnet_softc *);
static void     vtnet_set_hwaddr(struct vtnet_softc *);
static int      vtnet_is_link_up(struct vtnet_softc *);
static void     vtnet_update_link_status(struct vtnet_softc *);
static void     vtnet_watchdog(struct ifaltq_subque *);
static int      vtnet_setup_interface(struct vtnet_softc *);
static int      vtnet_change_mtu(struct vtnet_softc *, int);
static int      vtnet_ioctl(struct ifnet *, u_long, caddr_t, struct ucred *);

static int      vtnet_init_rx_vq(struct vtnet_softc *);
static void     vtnet_free_rx_mbufs(struct vtnet_softc *);
static void     vtnet_free_tx_mbufs(struct vtnet_softc *);
static void     vtnet_free_ctrl_vq(struct vtnet_softc *);

static struct mbuf * vtnet_alloc_rxbuf(struct vtnet_softc *, int,
                    struct mbuf **);
static int      vtnet_replace_rxbuf(struct vtnet_softc *,
                    struct mbuf *, int);
static int      vtnet_newbuf(struct vtnet_softc *);
static void     vtnet_discard_merged_rxbuf(struct vtnet_softc *, int);
static void     vtnet_discard_rxbuf(struct vtnet_softc *, struct mbuf *);
static int      vtnet_enqueue_rxbuf(struct vtnet_softc *, struct mbuf *);
static void     vtnet_vlan_tag_remove(struct mbuf *);
static int      vtnet_rx_csum(struct vtnet_softc *, struct mbuf *,
                    struct virtio_net_hdr *);
static int      vtnet_rxeof_merged(struct vtnet_softc *, struct mbuf *, int);
static int      vtnet_rxeof(struct vtnet_softc *, int, int *);
static void     vtnet_rx_msix_intr(void *);
static void     vtnet_rx_vq_intr(void *);

static void     vtnet_enqueue_txhdr(struct vtnet_softc *,
                    struct vtnet_tx_header *);
static void     vtnet_txeof(struct vtnet_softc *);
static struct mbuf * vtnet_tx_offload(struct vtnet_softc *, struct mbuf *,
                    struct virtio_net_hdr *);
static int      vtnet_enqueue_txbuf(struct vtnet_softc *, struct mbuf **,
                    struct vtnet_tx_header *);
static int      vtnet_encap(struct vtnet_softc *, struct mbuf **);
static void     vtnet_start(struct ifnet *, struct ifaltq_subque *);

static void     vtnet_config_intr(void *);
static void     vtnet_tx_msix_intr(void *);
static void     vtnet_tx_vq_intr(void *);

static void     vtnet_stop(struct vtnet_softc *);
static int      vtnet_virtio_reinit(struct vtnet_softc *);
static void     vtnet_init(void *);

static void     vtnet_exec_ctrl_cmd(struct vtnet_softc *, void *,
                    struct sglist *, int, int);

static int      vtnet_ctrl_mac_cmd(struct vtnet_softc *, uint8_t *);
static int      vtnet_ctrl_rx_cmd(struct vtnet_softc *, int, int);
static int      vtnet_set_promisc(struct vtnet_softc *, int);
static int      vtnet_set_allmulti(struct vtnet_softc *, int);
static void     vtnet_rx_filter(struct vtnet_softc *sc);
static void     vtnet_rx_filter_mac(struct vtnet_softc *);

static int      vtnet_exec_vlan_filter(struct vtnet_softc *, int, uint16_t);
static void     vtnet_rx_filter_vlan(struct vtnet_softc *);
static void     vtnet_update_vlan_filter(struct vtnet_softc *, int, uint16_t);
static void     vtnet_register_vlan(void *, struct ifnet *, uint16_t);
static void     vtnet_unregister_vlan(void *, struct ifnet *, uint16_t);

static int      vtnet_ifmedia_upd(struct ifnet *);
static void     vtnet_ifmedia_sts(struct ifnet *, struct ifmediareq *);

static void     vtnet_add_statistics(struct vtnet_softc *);

static int      vtnet_enable_rx_intr(struct vtnet_softc *);
static int      vtnet_enable_tx_intr(struct vtnet_softc *);
static void     vtnet_disable_rx_intr(struct vtnet_softc *);
static void     vtnet_disable_tx_intr(struct vtnet_softc *);

/* Tunables. */
static int vtnet_csum_disable = 0;
TUNABLE_INT("hw.vtnet.csum_disable", &vtnet_csum_disable);
static int vtnet_tso_disable = 1;
TUNABLE_INT("hw.vtnet.tso_disable", &vtnet_tso_disable);
static int vtnet_lro_disable = 0;
TUNABLE_INT("hw.vtnet.lro_disable", &vtnet_lro_disable);

/*
 * Reducing the number of transmit completed interrupts can
 * improve performance. To do so, the define below keeps the
 * Tx vq interrupt disabled and adds calls to vtnet_txeof()
 * in the start path. The price to pay for this is the m_free'ing
 * of transmitted mbufs may be delayed.
 */
#define VTNET_TX_INTR_MODERATION

static struct virtio_feature_desc vtnet_feature_desc[] = {
        { VIRTIO_NET_F_CSUM,            "TxChecksum"    },
        { VIRTIO_NET_F_GUEST_CSUM,      "RxChecksum"    },
        { VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, "DynOffload"        },
        { VIRTIO_NET_F_MAC,             "MacAddress"    },
        { VIRTIO_NET_F_GSO,             "TxAllGSO"      },
        { VIRTIO_NET_F_GUEST_TSO4,      "RxTSOv4"       },
        { VIRTIO_NET_F_GUEST_TSO6,      "RxTSOv6"       },
        { VIRTIO_NET_F_GUEST_ECN,       "RxECN"         },
        { VIRTIO_NET_F_GUEST_UFO,       "RxUFO"         },
        { VIRTIO_NET_F_HOST_TSO4,       "TxTSOv4"       },
        { VIRTIO_NET_F_HOST_TSO6,       "TxTSOv6"       },
        { VIRTIO_NET_F_HOST_ECN,        "TxTSOECN"      },
        { VIRTIO_NET_F_HOST_UFO,        "TxUFO"         },
        { VIRTIO_NET_F_MRG_RXBUF,       "MrgRxBuf"      },
        { VIRTIO_NET_F_STATUS,          "Status"        },
        { VIRTIO_NET_F_CTRL_VQ,         "ControlVq"     },
        { VIRTIO_NET_F_CTRL_RX,         "RxMode"        },
        { VIRTIO_NET_F_CTRL_VLAN,       "VLanFilter"    },
        { VIRTIO_NET_F_CTRL_RX_EXTRA,   "RxModeExtra"   },
        { VIRTIO_NET_F_GUEST_ANNOUNCE,  "GuestAnnounce" },
        { VIRTIO_NET_F_MQ,              "Multiqueue"    },
        { VIRTIO_NET_F_CTRL_MAC_ADDR,   "SetMacAddress" },
        { 0, NULL }
};

static device_method_t vtnet_methods[] = {
        /* Device methods. */
        DEVMETHOD(device_probe,         vtnet_probe),
        DEVMETHOD(device_attach,        vtnet_attach),
        DEVMETHOD(device_detach,        vtnet_detach),
        DEVMETHOD(device_suspend,       vtnet_suspend),
        DEVMETHOD(device_resume,        vtnet_resume),
        DEVMETHOD(device_shutdown,      vtnet_shutdown),

        DEVMETHOD_END
};

static driver_t vtnet_driver = {
        "vtnet",
        vtnet_methods,
        sizeof(struct vtnet_softc)
};

static devclass_t vtnet_devclass;

DRIVER_MODULE(vtnet, virtio_pci, vtnet_driver, vtnet_devclass, NULL, NULL);
MODULE_VERSION(vtnet, 1);
MODULE_DEPEND(vtnet, virtio, 1, 1, 1);

static int
vtnet_probe(device_t dev)
{
        if (virtio_get_device_type(dev) != VIRTIO_ID_NETWORK)
                return (ENXIO);

        device_set_desc(dev, "VirtIO Networking Adapter");

        return (BUS_PROBE_DEFAULT);
}

static int
vtnet_attach(device_t dev)
{
        struct vtnet_softc *sc;
        int i, error;

        sc = device_get_softc(dev);
        sc->vtnet_dev = dev;

        lwkt_serialize_init(&sc->vtnet_slz);
        lwkt_serialize_init(&sc->vtnet_rx_slz);
        lwkt_serialize_init(&sc->vtnet_tx_slz);
        sc->serializes[0] = &sc->vtnet_slz;
        sc->serializes[1] = &sc->vtnet_rx_slz;
        sc->serializes[2] = &sc->vtnet_tx_slz;

        ifmedia_init(&sc->vtnet_media, IFM_IMASK, vtnet_ifmedia_upd,
                     vtnet_ifmedia_sts);
        ifmedia_add(&sc->vtnet_media, VTNET_MEDIATYPE, 0, NULL);
        ifmedia_set(&sc->vtnet_media, VTNET_MEDIATYPE);

        vtnet_add_statistics(sc);
        SLIST_INIT(&sc->vtnet_txhdr_free);

        /* Register our feature descriptions. */
        virtio_set_feature_desc(dev, vtnet_feature_desc);
        vtnet_negotiate_features(sc);

        if (virtio_with_feature(dev, VIRTIO_RING_F_INDIRECT_DESC))
                sc->vtnet_flags |= VTNET_FLAG_INDIRECT;

        if (virtio_with_feature(dev, VIRTIO_NET_F_MAC)) {
                /* This feature should always be negotiated. */
                sc->vtnet_flags |= VTNET_FLAG_MAC;
        }

        if (virtio_with_feature(dev, VIRTIO_NET_F_MRG_RXBUF)) {
                sc->vtnet_flags |= VTNET_FLAG_MRG_RXBUFS;
                sc->vtnet_hdr_size = sizeof(struct virtio_net_hdr_mrg_rxbuf);
        } else {
                sc->vtnet_hdr_size = sizeof(struct virtio_net_hdr);
        }

        sc->vtnet_rx_mbuf_size = MCLBYTES;
        sc->vtnet_rx_mbuf_count = VTNET_NEEDED_RX_MBUFS(sc);

        if (virtio_with_feature(dev, VIRTIO_NET_F_CTRL_VQ)) {
                sc->vtnet_flags |= VTNET_FLAG_CTRL_VQ;

                if (virtio_with_feature(dev, VIRTIO_NET_F_CTRL_RX))
                        sc->vtnet_flags |= VTNET_FLAG_CTRL_RX;
                if (virtio_with_feature(dev, VIRTIO_NET_F_CTRL_VLAN))
                        sc->vtnet_flags |= VTNET_FLAG_VLAN_FILTER;
                if (virtio_with_feature(dev, VIRTIO_NET_F_CTRL_MAC_ADDR) &&
                    virtio_with_feature(dev, VIRTIO_NET_F_CTRL_RX))
                        sc->vtnet_flags |= VTNET_FLAG_CTRL_MAC;
        }

        error = vtnet_alloc_intrs(sc);
        if (error) {
                device_printf(dev, "cannot allocate interrupts\n");
                goto fail;
        }

        error = vtnet_alloc_virtqueues(sc);
        if (error) {
                device_printf(dev, "cannot allocate virtqueues\n");
                goto fail;
        }

        error = vtnet_bind_intrs(sc);
        if (error) {
                device_printf(dev, "cannot bind virtqueues to interrupts\n");
                goto fail;
        }

        /* Read (or generate) the MAC address for the adapter. */
        vtnet_get_hwaddr(sc);

        error = vtnet_setup_interface(sc);
        if (error) {
                device_printf(dev, "cannot setup interface\n");
                goto fail;
        }

        for (i = 0; i < sc->vtnet_nintr; i++) {
                error = virtio_setup_intr(dev, i, sc->vtnet_intr_slz[i]);
                if (error) {
                        device_printf(dev, "cannot setup virtqueue "
                            "interrupts\n");
                        ether_ifdetach(sc->vtnet_ifp);
                        goto fail;
                }
        }

        if ((sc->vtnet_flags & VTNET_FLAG_MAC) == 0) {
                ifnet_serialize_all(sc->vtnet_ifp);
                vtnet_set_hwaddr(sc);
                ifnet_deserialize_all(sc->vtnet_ifp);
        }

        /*
         * Device defaults to promiscuous mode for backwards
         * compatibility. Turn it off if possible.
         */
        if (sc->vtnet_flags & VTNET_FLAG_CTRL_RX) {
                ifnet_serialize_all(sc->vtnet_ifp);
                if (vtnet_set_promisc(sc, 0) != 0) {
                        sc->vtnet_ifp->if_flags |= IFF_PROMISC;
                        device_printf(dev,
                            "cannot disable promiscuous mode\n");
                }
                ifnet_deserialize_all(sc->vtnet_ifp);
        } else
                sc->vtnet_ifp->if_flags |= IFF_PROMISC;

fail:
        if (error)
                vtnet_detach(dev);

        return (error);
}

static int
vtnet_detach(device_t dev)
{
        struct vtnet_softc *sc;
        struct ifnet *ifp;
        int i;

        sc = device_get_softc(dev);
        ifp = sc->vtnet_ifp;

        for (i = 0; i < sc->vtnet_nintr; i++)
                virtio_teardown_intr(dev, i);

        if (device_is_attached(dev)) {
                ifnet_serialize_all(ifp);
                vtnet_stop(sc);
                lwkt_serialize_handler_disable(&sc->vtnet_slz);
                lwkt_serialize_handler_disable(&sc->vtnet_rx_slz);
                lwkt_serialize_handler_disable(&sc->vtnet_tx_slz);
                ifnet_deserialize_all(ifp);

                ether_ifdetach(ifp);
        }

        if (sc->vtnet_vlan_attach != NULL) {
                EVENTHANDLER_DEREGISTER(vlan_config, sc->vtnet_vlan_attach);
                sc->vtnet_vlan_attach = NULL;
        }
        if (sc->vtnet_vlan_detach != NULL) {
                EVENTHANDLER_DEREGISTER(vlan_unconfig, sc->vtnet_vlan_detach);
                sc->vtnet_vlan_detach = NULL;
        }

        if (ifp) {
                if_free(ifp);
                sc->vtnet_ifp = NULL;
        }

        if (sc->vtnet_rx_vq != NULL)
                vtnet_free_rx_mbufs(sc);
        if (sc->vtnet_tx_vq != NULL)
                vtnet_free_tx_mbufs(sc);
        if (sc->vtnet_ctrl_vq != NULL)
                vtnet_free_ctrl_vq(sc);

        if (sc->vtnet_txhdrarea != NULL) {
                contigfree(sc->vtnet_txhdrarea,
                    sc->vtnet_txhdrcount * sizeof(struct vtnet_tx_header),
                    M_VTNET);
                sc->vtnet_txhdrarea = NULL;
        }
        SLIST_INIT(&sc->vtnet_txhdr_free);
        if (sc->vtnet_macfilter != NULL) {
                contigfree(sc->vtnet_macfilter,
                    sizeof(struct vtnet_mac_filter), M_DEVBUF);
                sc->vtnet_macfilter = NULL;
        }

        ifmedia_removeall(&sc->vtnet_media);

        return (0);
}

static int
vtnet_suspend(device_t dev)
{
        struct vtnet_softc *sc;

        sc = device_get_softc(dev);

        ifnet_serialize_all(sc->vtnet_ifp);
        vtnet_stop(sc);
        sc->vtnet_flags |= VTNET_FLAG_SUSPENDED;
        ifnet_deserialize_all(sc->vtnet_ifp);

        return (0);
}

static int
vtnet_resume(device_t dev)
{
        struct vtnet_softc *sc;
        struct ifnet *ifp;

        sc = device_get_softc(dev);
        ifp = sc->vtnet_ifp;

        ifnet_serialize_all(ifp);
        if (ifp->if_flags & IFF_UP)
                vtnet_init(sc);
        sc->vtnet_flags &= ~VTNET_FLAG_SUSPENDED;
        ifnet_deserialize_all(ifp);

        return (0);
}

static int
vtnet_shutdown(device_t dev)
{

        /*
         * Suspend already does all of what we need to
         * do here; we just never expect to be resumed.
         */
        return (vtnet_suspend(dev));
}

static void
vtnet_negotiate_features(struct vtnet_softc *sc)
{
        device_t dev;
        uint64_t mask, features;

        dev = sc->vtnet_dev;
        mask = 0;

        if (vtnet_csum_disable)
                mask |= VIRTIO_NET_F_CSUM | VIRTIO_NET_F_GUEST_CSUM;

        /*
         * XXX DragonFly doesn't support receive checksum offload for ipv6 yet,
         *     hence always disable the virtio feature for now.
         * XXX We need to support the DynOffload feature, in order to
         *     dynamically enable/disable this feature.
         */
        mask |= VIRTIO_NET_F_GUEST_CSUM;

        /*
         * TSO is only available when the tx checksum offload feature is also
         * negotiated.
         */
        if (vtnet_csum_disable || vtnet_tso_disable)
                mask |= VIRTIO_NET_F_HOST_TSO4 | VIRTIO_NET_F_HOST_TSO6 |
                    VIRTIO_NET_F_HOST_ECN;

        if (vtnet_lro_disable)
                mask |= VTNET_LRO_FEATURES;

        features = VTNET_FEATURES & ~mask;
        features |= VIRTIO_F_NOTIFY_ON_EMPTY;
        features |= VIRTIO_F_ANY_LAYOUT;
        sc->vtnet_features = virtio_negotiate_features(dev, features);

        if (virtio_with_feature(dev, VTNET_LRO_FEATURES) &&
            virtio_with_feature(dev, VIRTIO_NET_F_MRG_RXBUF) == 0) {
                /*
                 * LRO without mergeable buffers requires special care. This
                 * is not ideal because every receive buffer must be large
                 * enough to hold the maximum TCP packet, the Ethernet header,
                 * and the header. This requires up to 34 descriptors with
                 * MCLBYTES clusters. If we do not have indirect descriptors,
                 * LRO is disabled since the virtqueue will not contain very
                 * many receive buffers.
                 */
                if (!virtio_with_feature(dev, VIRTIO_RING_F_INDIRECT_DESC)) {
                        device_printf(dev,
                            "LRO disabled due to both mergeable buffers and "
                            "indirect descriptors not negotiated\n");

                        features &= ~VTNET_LRO_FEATURES;
                        sc->vtnet_features =
                            virtio_negotiate_features(dev, features);
                } else
                        sc->vtnet_flags |= VTNET_FLAG_LRO_NOMRG;
        }
}

static void
vtnet_serialize(struct ifnet *ifp, enum ifnet_serialize slz)
{
        struct vtnet_softc *sc = ifp->if_softc;

        ifnet_serialize_array_enter(sc->serializes, 3, slz);
}

static void
vtnet_deserialize(struct ifnet *ifp, enum ifnet_serialize slz)
{
        struct vtnet_softc *sc = ifp->if_softc;

        ifnet_serialize_array_exit(sc->serializes, 3, slz);
}

static int
vtnet_tryserialize(struct ifnet *ifp, enum ifnet_serialize slz)
{
        struct vtnet_softc *sc = ifp->if_softc;

        return ifnet_serialize_array_try(sc->serializes, 3, slz);
}

#ifdef INVARIANTS

static void
vtnet_serialize_assert(struct ifnet *ifp, enum ifnet_serialize slz,
    boolean_t serialized)
{
        struct vtnet_softc *sc = ifp->if_softc;

        ifnet_serialize_array_assert(sc->serializes, 3, slz, serialized);
}

#endif  /* INVARIANTS */

static int
vtnet_alloc_intrs(struct vtnet_softc *sc)
{
        int cnt, error;
        int intrcount = virtio_intr_count(sc->vtnet_dev);
        int i;
        int use_config;

        if (virtio_with_feature(sc->vtnet_dev, VIRTIO_NET_F_STATUS)) {
                use_config = 1;
                /* We can use a maximum of 3 interrupt vectors. */
                intrcount = imin(intrcount, 3);
        } else {
                /* We can use a maximum of 2 interrupt vectors. */
                intrcount = imin(intrcount, 2);
        }

        if (intrcount < 1)
                return (ENXIO);

        for (i = 0; i < intrcount; i++)
                sc->vtnet_cpus[i] = -1;

        cnt = intrcount;
        error = virtio_intr_alloc(sc->vtnet_dev, &cnt, use_config,
            sc->vtnet_cpus);
        if (error != 0) {
                virtio_intr_release(sc->vtnet_dev);
                return (error);
        }
        sc->vtnet_nintr = cnt;

        return (0);
}

static int
vtnet_alloc_virtqueues(struct vtnet_softc *sc)
{
        device_t dev;
        struct vq_alloc_info vq_info[3];
        int nvqs;

        dev = sc->vtnet_dev;
        nvqs = 2;

        /*
         * Indirect descriptors are not needed for the Rx
         * virtqueue when mergeable buffers are negotiated.
         * The header is placed inline with the data, not
         * in a separate descriptor, and mbuf clusters are
         * always physically contiguous.
         */
        if ((sc->vtnet_flags & VTNET_FLAG_MRG_RXBUFS) == 0) {
                sc->vtnet_rx_nsegs = (sc->vtnet_flags & VTNET_FLAG_LRO_NOMRG) ?
                    VTNET_MAX_RX_SEGS : VTNET_MIN_RX_SEGS;
        } else
                sc->vtnet_rx_nsegs = VTNET_MRG_RX_SEGS;

        if (virtio_with_feature(dev, VIRTIO_NET_F_HOST_TSO4) ||
            virtio_with_feature(dev, VIRTIO_NET_F_HOST_TSO6))
                sc->vtnet_tx_nsegs = VTNET_MAX_TX_SEGS;
        else
                sc->vtnet_tx_nsegs = VTNET_MIN_TX_SEGS;

        VQ_ALLOC_INFO_INIT(&vq_info[0], sc->vtnet_rx_nsegs, &sc->vtnet_rx_vq,
            "%s receive", device_get_nameunit(dev));

        VQ_ALLOC_INFO_INIT(&vq_info[1], sc->vtnet_tx_nsegs, &sc->vtnet_tx_vq,
            "%s transmit", device_get_nameunit(dev));

        if (sc->vtnet_flags & VTNET_FLAG_CTRL_VQ) {
                nvqs++;

                VQ_ALLOC_INFO_INIT(&vq_info[2], 0, &sc->vtnet_ctrl_vq,
                    "%s control", device_get_nameunit(dev));
        }

        return (virtio_alloc_virtqueues(dev, nvqs, vq_info));
}

static int
vtnet_bind_intrs(struct vtnet_softc *sc)
{
        int error = 0;
        int i;

        for (i = 0; i < 3; i++)
                sc->vtnet_intr_slz[i] = &sc->vtnet_slz;

        /* Possible "Virtqueue <-> IRQ" configurations */
        switch (sc->vtnet_nintr) {
        case 1:
                sc->vtnet_irqmap[0] = (struct irqmap){0, vtnet_rx_vq_intr};
                sc->vtnet_irqmap[1] = (struct irqmap){0, vtnet_tx_vq_intr};
                break;
        case 2:
                if (virtio_with_feature(sc->vtnet_dev, VIRTIO_NET_F_STATUS)) {
                        sc->vtnet_irqmap[0] =
                            (struct irqmap){1, vtnet_rx_vq_intr};
                        sc->vtnet_irqmap[1] =
                            (struct irqmap){1, vtnet_tx_vq_intr};
                } else {
                        sc->vtnet_irqmap[0] =
                            (struct irqmap){0, vtnet_rx_msix_intr};
                        sc->vtnet_irqmap[1] =
                            (struct irqmap){1, vtnet_tx_msix_intr};
                        sc->vtnet_intr_slz[0] = &sc->vtnet_rx_slz;
                        sc->vtnet_intr_slz[1] = &sc->vtnet_tx_slz;
                }
                break;
        case 3:
                sc->vtnet_irqmap[0] = (struct irqmap){1, vtnet_rx_msix_intr};
                sc->vtnet_irqmap[1] = (struct irqmap){2, vtnet_tx_msix_intr};
                sc->vtnet_intr_slz[1] = &sc->vtnet_rx_slz;
                sc->vtnet_intr_slz[2] = &sc->vtnet_tx_slz;
                break;
        default:
                device_printf(sc->vtnet_dev,
                    "Invalid interrupt vector count: %d\n", sc->vtnet_nintr);
                error = EINVAL;
                goto fail;
        }

        for (i = 0; i < 2; i++) {
                error = virtio_bind_intr(sc->vtnet_dev,
                    sc->vtnet_irqmap[i].irq, i, sc->vtnet_irqmap[i].handler,
                    sc);
                if (error) {
                        device_printf(sc->vtnet_dev,
                            "cannot bind virtqueue IRQs\n");
                        goto fail;
                }
        }
        if (virtio_with_feature(sc->vtnet_dev, VIRTIO_NET_F_STATUS)) {
                error = virtio_bind_intr(sc->vtnet_dev, 0, -1,
                    vtnet_config_intr, sc);
                if (error) {
                        device_printf(sc->vtnet_dev,
                            "cannot bind config_change IRQ\n");
                        goto fail;
                }
        }

fail:
        return (error);
}

static int
vtnet_setup_interface(struct vtnet_softc *sc)
{
        device_t dev;
        struct ifnet *ifp;
        int i;

        dev = sc->vtnet_dev;

        ifp = sc->vtnet_ifp = if_alloc(IFT_ETHER);
        if (ifp == NULL) {
                device_printf(dev, "cannot allocate ifnet structure\n");
                return (ENOSPC);
        }

        ifp->if_softc = sc;
        if_initname(ifp, device_get_name(dev), device_get_unit(dev));
        ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
        ifp->if_init = vtnet_init;
        ifp->if_start = vtnet_start;
#ifdef IFPOLL_ENABLE
        ifp->if_npoll = vtnet_npoll;
#endif
        ifp->if_serialize = vtnet_serialize;
        ifp->if_deserialize = vtnet_deserialize;
        ifp->if_tryserialize = vtnet_tryserialize;
#ifdef INVARIANTS
        ifp->if_serialize_assert = vtnet_serialize_assert;
#endif
        ifp->if_ioctl = vtnet_ioctl;

        sc->vtnet_rx_process_limit = virtqueue_size(sc->vtnet_rx_vq);
        sc->vtnet_tx_size = virtqueue_size(sc->vtnet_tx_vq);
        if (sc->vtnet_flags & VTNET_FLAG_INDIRECT)
                sc->vtnet_txhdrcount = sc->vtnet_tx_size;
        else
                sc->vtnet_txhdrcount = (sc->vtnet_tx_size / 2) + 1;
        sc->vtnet_txhdrarea = contigmalloc(
            sc->vtnet_txhdrcount * sizeof(struct vtnet_tx_header),
            M_VTNET, M_WAITOK, 0, BUS_SPACE_MAXADDR, 4, 0);
        if (sc->vtnet_txhdrarea == NULL) {
                device_printf(dev, "cannot contigmalloc the tx headers\n");
                return (ENOMEM);
        }
        for (i = 0; i < sc->vtnet_txhdrcount; i++)
                vtnet_enqueue_txhdr(sc, &sc->vtnet_txhdrarea[i]);
        sc->vtnet_macfilter = contigmalloc(
            sizeof(struct vtnet_mac_filter),
            M_DEVBUF, M_WAITOK, 0, BUS_SPACE_MAXADDR, 4, 0);
        if (sc->vtnet_macfilter == NULL) {
                device_printf(dev,
                    "cannot contigmalloc the mac filter table\n");
                return (ENOMEM);
        }
        ifq_set_maxlen(&ifp->if_snd, sc->vtnet_tx_size - 1);
        ifq_set_ready(&ifp->if_snd);

        ether_ifattach(ifp, sc->vtnet_hwaddr, NULL);

        /* The Tx IRQ is currently always the last allocated interrupt. */
        ifq_set_cpuid(&ifp->if_snd, sc->vtnet_cpus[sc->vtnet_nintr - 1]);
        ifsq_watchdog_init(&sc->vtnet_tx_watchdog,
                           ifq_get_subq_default(&ifp->if_snd),
                           vtnet_watchdog,
                           IF_WDOG_LASTTICK);
        ifq_set_hw_serialize(&ifp->if_snd, &sc->vtnet_tx_slz);

        /* Tell the upper layer(s) we support long frames. */
        ifp->if_data.ifi_hdrlen = sizeof(struct ether_vlan_header);
        ifp->if_capabilities |= IFCAP_JUMBO_MTU | IFCAP_VLAN_MTU;

        if (virtio_with_feature(dev, VIRTIO_NET_F_CSUM)) {
                ifp->if_capabilities |= IFCAP_TXCSUM;

                if (virtio_with_feature(dev, VIRTIO_NET_F_HOST_TSO4))
                        ifp->if_capabilities |= IFCAP_TSO4;
                if (virtio_with_feature(dev, VIRTIO_NET_F_HOST_TSO6))
                        ifp->if_capabilities |= IFCAP_TSO6;
                if (ifp->if_capabilities & IFCAP_TSO)
                        ifp->if_capabilities |= IFCAP_VLAN_HWTSO;

                if (virtio_with_feature(dev, VIRTIO_NET_F_HOST_ECN))
                        sc->vtnet_flags |= VTNET_FLAG_TSO_ECN;
        }

        if (virtio_with_feature(dev, VIRTIO_NET_F_GUEST_CSUM))
                ifp->if_capabilities |= IFCAP_RXCSUM;

#if 0   /* IFCAP_LRO doesn't exist in DragonFly. */
        if (virtio_with_feature(dev, VIRTIO_NET_F_GUEST_TSO4) ||
            virtio_with_feature(dev, VIRTIO_NET_F_GUEST_TSO6))
                ifp->if_capabilities |= IFCAP_LRO;
#endif

        if ((ifp->if_capabilities & IFCAP_HWCSUM) == IFCAP_HWCSUM) {
                /*
                 * VirtIO does not support VLAN tagging, but we can fake
                 * it by inserting and removing the 802.1Q header during
                 * transmit and receive. We are then able to do checksum
                 * offloading of VLAN frames.
                 */
                ifp->if_capabilities |=
                        IFCAP_VLAN_HWTAGGING | IFCAP_VLAN_HWCSUM;
        }

        ifp->if_capenable = ifp->if_capabilities;

        /*
         * Capabilities after here are not enabled by default.
         */

        if (sc->vtnet_flags & VTNET_FLAG_VLAN_FILTER) {
                ifp->if_capabilities |= IFCAP_VLAN_HWFILTER;

                sc->vtnet_vlan_attach = EVENTHANDLER_REGISTER(vlan_config,
                    vtnet_register_vlan, sc, EVENTHANDLER_PRI_FIRST);
                sc->vtnet_vlan_detach = EVENTHANDLER_REGISTER(vlan_unconfig,
                    vtnet_unregister_vlan, sc, EVENTHANDLER_PRI_FIRST);
        }

        return (0);
}

static void
vtnet_set_hwaddr(struct vtnet_softc *sc)
{
        device_t dev;

        dev = sc->vtnet_dev;

        if ((sc->vtnet_flags & VTNET_FLAG_CTRL_MAC) &&
            (sc->vtnet_flags & VTNET_FLAG_CTRL_RX)) {
                if (vtnet_ctrl_mac_cmd(sc, sc->vtnet_hwaddr) != 0)
                        device_printf(dev, "unable to set MAC address\n");
        } else if (sc->vtnet_flags & VTNET_FLAG_MAC) {
                virtio_write_device_config(dev,
                    offsetof(struct virtio_net_config, mac),
                    sc->vtnet_hwaddr, ETHER_ADDR_LEN);
        }
}

static void
vtnet_get_hwaddr(struct vtnet_softc *sc)
{
        device_t dev;

        dev = sc->vtnet_dev;

        if ((sc->vtnet_flags & VTNET_FLAG_MAC) == 0) {
                /*
                 * Generate a random locally administered unicast address.
                 *
                 * It would be nice to generate the same MAC address across
                 * reboots, but it seems all the hosts currently available
                 * support the MAC feature, so this isn't too important.
                 */
                sc->vtnet_hwaddr[0] = 0xB2;
                karc4random_buf(&sc->vtnet_hwaddr[1], ETHER_ADDR_LEN - 1);
                return;
        }

        virtio_read_device_config(dev,
            offsetof(struct virtio_net_config, mac),
            sc->vtnet_hwaddr, ETHER_ADDR_LEN);
}

static int
vtnet_is_link_up(struct vtnet_softc *sc)
{
        device_t dev;
        struct ifnet *ifp;
        uint16_t status;

        dev = sc->vtnet_dev;
        ifp = sc->vtnet_ifp;

        ASSERT_SERIALIZED(&sc->vtnet_slz);

        if (virtio_with_feature(dev, VIRTIO_NET_F_STATUS)) {
                status = virtio_read_dev_config_2(dev,
                                offsetof(struct virtio_net_config, status));
        } else {
                status = VIRTIO_NET_S_LINK_UP;
        }

        return ((status & VIRTIO_NET_S_LINK_UP) != 0);
}

static void
vtnet_update_link_status(struct vtnet_softc *sc)
{
        device_t dev;
        struct ifnet *ifp;
        struct ifaltq_subque *ifsq;
        int link;

        dev = sc->vtnet_dev;
        ifp = sc->vtnet_ifp;
        ifsq = ifq_get_subq_default(&ifp->if_snd);

        link = vtnet_is_link_up(sc);

        if (link && ((sc->vtnet_flags & VTNET_FLAG_LINK) == 0)) {
                sc->vtnet_flags |= VTNET_FLAG_LINK;
                if (bootverbose)
                        device_printf(dev, "Link is up\n");
                ifp->if_link_state = LINK_STATE_UP;
                if_link_state_change(ifp);
                if (!ifsq_is_empty(ifsq))
                        ifsq_devstart_sched(ifsq);
        } else if (!link && (sc->vtnet_flags & VTNET_FLAG_LINK)) {
                sc->vtnet_flags &= ~VTNET_FLAG_LINK;
                if (bootverbose)
                        device_printf(dev, "Link is down\n");

                ifp->if_link_state = LINK_STATE_DOWN;
                if_link_state_change(ifp);
        }
}

static void
vtnet_watchdog(struct ifaltq_subque *ifsq)
{
        struct ifnet *ifp;
        struct vtnet_softc *sc;

        ifp = ifsq_get_ifp(ifsq);
        sc = ifp->if_softc;
        ASSERT_IFNET_SERIALIZED_ALL(ifp);

        /*
         * Clean out expended tx buffers prior to terminal count.
         *
         * NOTE: vtnet_txeof() will set wd_timer to 0 if the virtqueue
         *       becomes empty, preventing further watchdog callbacks.
         */
        if (sc->vtnet_tx_watchdog.wd_timer != 0) {
                vtnet_txeof(sc);
                if (!ifq_is_empty(&ifp->if_snd))
                        if_devstart(ifp);
                return;
        }

        /*
         * Check to see if there are any unexpended transmit descriptors.
         */
        if (virtqueue_empty(sc->vtnet_tx_vq)) {
                if_printf(ifp, "Spurious TX watchdog timeout -- ignoring\n");
                ifsq_watchdog_set_count(&sc->vtnet_tx_watchdog, 0);
                return;
        }

        if_printf(ifp, "TX watchdog timeout -- resetting\n");
#ifdef VTNET_DEBUG
        virtqueue_dump(sc->vtnet_tx_vq);
#endif
        ifp->if_oerrors++;
        ifp->if_flags &= ~IFF_RUNNING;
        vtnet_init(sc);
        ifsq_devstart_sched(ifsq);
}

static int
vtnet_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data,struct ucred *cr)
{
        struct vtnet_softc *sc;
        struct ifreq *ifr;
        int reinit, mask, error;

        sc = ifp->if_softc;
        ifr = (struct ifreq *) data;
        reinit = 0;
        error = 0;

        switch (cmd) {
        case SIOCSIFMTU:
                if (ifr->ifr_mtu < ETHERMIN || ifr->ifr_mtu > VTNET_MAX_MTU)
                        error = EINVAL;
                else if (ifp->if_mtu != ifr->ifr_mtu)
                        error = vtnet_change_mtu(sc, ifr->ifr_mtu);
                break;

        case SIOCSIFFLAGS:
                if ((ifp->if_flags & IFF_UP) == 0) {
                        if (ifp->if_flags & IFF_RUNNING)
                                vtnet_stop(sc);
                } else if (ifp->if_flags & IFF_RUNNING) {
                        if ((ifp->if_flags ^ sc->vtnet_if_flags) &
                            (IFF_PROMISC | IFF_ALLMULTI)) {
                                if (sc->vtnet_flags & VTNET_FLAG_CTRL_RX)
                                        vtnet_rx_filter(sc);
                                else
                                        error = ENOTSUP;
                        }
                } else {
                        vtnet_init(sc);
                }

                if (error == 0)
                        sc->vtnet_if_flags = ifp->if_flags;
                break;

        case SIOCADDMULTI:
        case SIOCDELMULTI:
                if ((sc->vtnet_flags & VTNET_FLAG_CTRL_RX) &&
                    (ifp->if_flags & IFF_RUNNING))
                        vtnet_rx_filter_mac(sc);
                break;

        case SIOCSIFMEDIA:
        case SIOCGIFMEDIA:
                error = ifmedia_ioctl(ifp, ifr, &sc->vtnet_media, cmd);
                break;

        case SIOCSIFCAP:
                mask = ifr->ifr_reqcap ^ ifp->if_capenable;


                if (mask & IFCAP_TXCSUM) {
                        ifp->if_capenable ^= IFCAP_TXCSUM;
                        if (ifp->if_capenable & IFCAP_TXCSUM)
                                ifp->if_hwassist |= VTNET_CSUM_OFFLOAD;
                        else
                                ifp->if_hwassist &= ~VTNET_CSUM_OFFLOAD;
                }

                if (mask & IFCAP_TSO4) {
                        ifp->if_capenable ^= IFCAP_TSO4;
                        if (ifp->if_capenable & IFCAP_TSO4)
                                ifp->if_hwassist |= CSUM_TSO;
                        else
                                ifp->if_hwassist &= ~CSUM_TSO;
                }

                if (mask & IFCAP_RXCSUM) {
                        ifp->if_capenable ^= IFCAP_RXCSUM;
                        reinit = 1;
                }

#if 0   /* IFCAP_LRO doesn't exist in DragonFly. */
                if (mask & IFCAP_LRO) {
                        ifp->if_capenable ^= IFCAP_LRO;
                        reinit = 1;
                }
#endif

                if (mask & IFCAP_VLAN_HWFILTER) {
                        ifp->if_capenable ^= IFCAP_VLAN_HWFILTER;
                        reinit = 1;
                }

                if (mask & IFCAP_VLAN_HWTSO)
                        ifp->if_capenable ^= IFCAP_VLAN_HWTSO;

                if (mask & IFCAP_VLAN_HWTAGGING)
                        ifp->if_capenable ^= IFCAP_VLAN_HWTAGGING;

                if (reinit && (ifp->if_flags & IFF_RUNNING)) {
                        ifp->if_flags &= ~IFF_RUNNING;
                        vtnet_init(sc);
                }
                //VLAN_CAPABILITIES(ifp);

                break;

        default:
                error = ether_ioctl(ifp, cmd, data);
                break;
        }

        return (error);
}

static int
vtnet_change_mtu(struct vtnet_softc *sc, int new_mtu)
{
        struct ifnet *ifp;
        int new_frame_size, clsize;

        ifp = sc->vtnet_ifp;

        if ((sc->vtnet_flags & VTNET_FLAG_MRG_RXBUFS) == 0) {
                new_frame_size = sizeof(struct vtnet_rx_header) +
                    sizeof(struct ether_vlan_header) + new_mtu;

                if (new_frame_size > MJUM9BYTES)
                        return (EINVAL);

                if (new_frame_size <= MCLBYTES)
                        clsize = MCLBYTES;
                else
                        clsize = MJUM9BYTES;
        } else {
                new_frame_size = sizeof(struct virtio_net_hdr_mrg_rxbuf) +
                    sizeof(struct ether_vlan_header) + new_mtu;

                if (new_frame_size <= MCLBYTES)
                        clsize = MCLBYTES;
                else
                        clsize = MJUMPAGESIZE;
        }

        sc->vtnet_rx_mbuf_size = clsize;
        sc->vtnet_rx_mbuf_count = VTNET_NEEDED_RX_MBUFS(sc);
        KASSERT(sc->vtnet_rx_mbuf_count < VTNET_MAX_RX_SEGS,
            ("too many rx mbufs: %d", sc->vtnet_rx_mbuf_count));

        ifp->if_mtu = new_mtu;

        if (ifp->if_flags & IFF_RUNNING) {
                ifp->if_flags &= ~IFF_RUNNING;
                vtnet_init(sc);
        }

        return (0);
}

static int
vtnet_init_rx_vq(struct vtnet_softc *sc)
{
        struct virtqueue *vq;
        int nbufs, error;

        vq = sc->vtnet_rx_vq;
        nbufs = 0;
        error = ENOSPC;

        while (!virtqueue_full(vq)) {
                if ((error = vtnet_newbuf(sc)) != 0)
                        break;
                nbufs++;
        }

        if (nbufs > 0) {
                virtqueue_notify(vq, NULL);

                /*
                 * EMSGSIZE signifies the virtqueue did not have enough
                 * entries available to hold the last mbuf. This is not
                 * an error. We should not get ENOSPC since we check if
                 * the virtqueue is full before attempting to add a
                 * buffer.
                 */
                if (error == EMSGSIZE)
                        error = 0;
        }

        return (error);
}

static void
vtnet_free_rx_mbufs(struct vtnet_softc *sc)
{
        struct virtqueue *vq;
        struct mbuf *m;
        int last;

        vq = sc->vtnet_rx_vq;
        last = 0;

        while ((m = virtqueue_drain(vq, &last)) != NULL)
                m_freem(m);

        KASSERT(virtqueue_empty(vq), ("mbufs remaining in Rx Vq"));
}

static void
vtnet_free_tx_mbufs(struct vtnet_softc *sc)
{
        struct virtqueue *vq;
        struct vtnet_tx_header *txhdr;
        int last;

        vq = sc->vtnet_tx_vq;
        last = 0;

        while ((txhdr = virtqueue_drain(vq, &last)) != NULL) {
                m_freem(txhdr->vth_mbuf);
                vtnet_enqueue_txhdr(sc, txhdr);
        }

        KASSERT(virtqueue_empty(vq), ("mbufs remaining in Tx Vq"));
}

static void
vtnet_free_ctrl_vq(struct vtnet_softc *sc)
{
        /*
         * The control virtqueue is only polled, therefore
         * it should already be empty.
         */
        KASSERT(virtqueue_empty(sc->vtnet_ctrl_vq),
                ("Ctrl Vq not empty"));
}

static struct mbuf *
vtnet_alloc_rxbuf(struct vtnet_softc *sc, int nbufs, struct mbuf **m_tailp)
{
        struct mbuf *m_head, *m_tail, *m;
        int i, clsize;

        clsize = sc->vtnet_rx_mbuf_size;

        /*use getcl instead of getjcl. see  if_mxge.c comment line 2398*/
        if (clsize > MCLBYTES)
                m_head = m_getjcl(M_NOWAIT, MT_DATA, M_PKTHDR, clsize);
        else
                m_head = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR );
        if (m_head == NULL)
                goto fail;

        m_head->m_len = clsize;
        m_tail = m_head;

        if (nbufs > 1) {
                KASSERT(sc->vtnet_flags & VTNET_FLAG_LRO_NOMRG,
                        ("chained Rx mbuf requested without LRO_NOMRG"));

                for (i = 0; i < nbufs - 1; i++) {
                        if (clsize > MCLBYTES)
                                m = m_getjcl(M_NOWAIT, MT_DATA, 0, clsize);
                        else
                                m = m_getcl(M_NOWAIT, MT_DATA, 0);
                        if (m == NULL)
                                goto fail;

                        m->m_len = clsize;
                        m_tail->m_next = m;
                        m_tail = m;
                }
        }

        if (m_tailp != NULL)
                *m_tailp = m_tail;

        return (m_head);

fail:
        sc->vtnet_stats.mbuf_alloc_failed++;
        m_freem(m_head);

        return (NULL);
}

static int
vtnet_replace_rxbuf(struct vtnet_softc *sc, struct mbuf *m0, int len0)
{
        struct mbuf *m, *m_prev;
        struct mbuf *m_new, *m_tail;
        int len, clsize, nreplace, error;

        m = m0;
        m_prev = NULL;
        len = len0;

        m_tail = NULL;
        clsize = sc->vtnet_rx_mbuf_size;
        nreplace = 0;

        if (m->m_next != NULL)
                KASSERT(sc->vtnet_flags & VTNET_FLAG_LRO_NOMRG,
                    ("chained Rx mbuf without LRO_NOMRG"));

        /*
         * Since LRO_NOMRG mbuf chains are so large, we want to avoid
         * allocating an entire chain for each received frame. When
         * the received frame's length is less than that of the chain,
         * the unused mbufs are reassigned to the new chain.
         */
        while (len > 0) {
                /*
                 * Something is seriously wrong if we received
                 * a frame larger than the mbuf chain. Drop it.
                 */
                if (m == NULL) {
                        sc->vtnet_stats.rx_frame_too_large++;
                        return (EMSGSIZE);
                }

                KASSERT(m->m_len == clsize,
                    ("mbuf length not expected cluster size: %d",
                    m->m_len));

                m->m_len = MIN(m->m_len, len);
                len -= m->m_len;

                m_prev = m;
                m = m->m_next;
                nreplace++;
        }

        KASSERT(m_prev != NULL, ("m_prev == NULL"));
        KASSERT(nreplace <= sc->vtnet_rx_mbuf_count,
                ("too many replacement mbufs: %d/%d", nreplace,
                sc->vtnet_rx_mbuf_count));

        m_new = vtnet_alloc_rxbuf(sc, nreplace, &m_tail);
        if (m_new == NULL) {
                m_prev->m_len = clsize;
                return (ENOBUFS);
        }

        /*
         * Move unused mbufs, if any, from the original chain
         * onto the end of the new chain.
         */
        if (m_prev->m_next != NULL) {
                m_tail->m_next = m_prev->m_next;
                m_prev->m_next = NULL;
        }

        error = vtnet_enqueue_rxbuf(sc, m_new);
        if (error) {
                /*
                 * BAD! We could not enqueue the replacement mbuf chain. We
                 * must restore the m0 chain to the original state if it was
                 * modified so we can subsequently discard it.
                 *
                 * NOTE: The replacement is suppose to be an identical copy
                 * to the one just dequeued so this is an unexpected error.
                 */
                sc->vtnet_stats.rx_enq_replacement_failed++;

                if (m_tail->m_next != NULL) {
                        m_prev->m_next = m_tail->m_next;
                        m_tail->m_next = NULL;
                }

                m_prev->m_len = clsize;
                m_freem(m_new);
        }

        return (error);
}

static int
vtnet_newbuf(struct vtnet_softc *sc)
{
        struct mbuf *m;
        int error;

        m = vtnet_alloc_rxbuf(sc, sc->vtnet_rx_mbuf_count, NULL);
        if (m == NULL)
                return (ENOBUFS);

        error = vtnet_enqueue_rxbuf(sc, m);
        if (error)
                m_freem(m);

        return (error);
}

static void
vtnet_discard_merged_rxbuf(struct vtnet_softc *sc, int nbufs)
{
        struct virtqueue *vq;
        struct mbuf *m;

        vq = sc->vtnet_rx_vq;

        while (--nbufs > 0) {
                if ((m = virtqueue_dequeue(vq, NULL)) == NULL)
                        break;
                vtnet_discard_rxbuf(sc, m);
        }
}

static void
vtnet_discard_rxbuf(struct vtnet_softc *sc, struct mbuf *m)
{
        int error;

        /*
         * Requeue the discarded mbuf. This should always be
         * successful since it was just dequeued.
         */
        error = vtnet_enqueue_rxbuf(sc, m);
        KASSERT(error == 0, ("cannot requeue discarded mbuf"));
}

static int
vtnet_enqueue_rxbuf(struct vtnet_softc *sc, struct mbuf *m)
{
        struct sglist sg;
        struct sglist_seg segs[VTNET_MAX_RX_SEGS];
        struct vtnet_rx_header *rxhdr;
        struct virtio_net_hdr *hdr;
        uint8_t *mdata;
        int offset, error;

        ASSERT_SERIALIZED(&sc->vtnet_rx_slz);
        if ((sc->vtnet_flags & VTNET_FLAG_LRO_NOMRG) == 0)
                KASSERT(m->m_next == NULL, ("chained Rx mbuf"));

        sglist_init(&sg, sc->vtnet_rx_nsegs, segs);

        mdata = mtod(m, uint8_t *);
        offset = 0;

        if ((sc->vtnet_flags & VTNET_FLAG_MRG_RXBUFS) == 0) {
                rxhdr = (struct vtnet_rx_header *) mdata;
                hdr = &rxhdr->vrh_hdr;
                offset += sizeof(struct vtnet_rx_header);

                error = sglist_append(&sg, hdr, sc->vtnet_hdr_size);
                KASSERT(error == 0, ("cannot add header to sglist"));
        }

        error = sglist_append(&sg, mdata + offset, m->m_len - offset);
        if (error)
                return (error);

        if (m->m_next != NULL) {
                error = sglist_append_mbuf(&sg, m->m_next);
                if (error)
                        return (error);
        }

        return (virtqueue_enqueue(sc->vtnet_rx_vq, m, &sg, 0, sg.sg_nseg));
}

#ifdef IFPOLL_ENABLE

static void
vtnet_npoll_status(struct ifnet *ifp)
{
        struct vtnet_softc *sc = ifp->if_softc;

        ASSERT_SERIALIZED(&sc->vtnet_slz);

        vtnet_update_link_status(sc);
}

static void
vtnet_npoll_rx(struct ifnet *ifp, void *arg __unused, int cycle)
{
        struct vtnet_softc *sc = ifp->if_softc;

        vtnet_rxeof(sc, cycle, NULL);
}

static void
vtnet_npoll_tx(struct ifnet *ifp, void *arg __unused, int cycle __unused)
{
        struct vtnet_softc *sc = ifp->if_softc;

        ASSERT_SERIALIZED(&sc->vtnet_tx_slz);

        vtnet_txeof(sc);
        if (!ifq_is_empty(&ifp->if_snd))
                if_devstart(ifp);
}

static void
vtnet_npoll(struct ifnet *ifp, struct ifpoll_info *info)
{
        struct vtnet_softc *sc = ifp->if_softc;
        int i;

        ASSERT_IFNET_SERIALIZED_ALL(ifp);

        if (info) {
                int cpu;

                info->ifpi_status.status_func = vtnet_npoll_status;
                info->ifpi_status.serializer = &sc->vtnet_slz;

                /* Use the same cpu for rx and tx. */
                cpu = device_get_unit(device_get_parent(sc->vtnet_dev));
                /* Shuffle a bit. */
                cpu = (cpu * 61) % netisr_ncpus;
                KKASSERT(cpu < netisr_ncpus);
                info->ifpi_tx[cpu].poll_func = vtnet_npoll_tx;
                info->ifpi_tx[cpu].arg = NULL;
                info->ifpi_tx[cpu].serializer = &sc->vtnet_tx_slz;
                ifq_set_cpuid(&ifp->if_snd, cpu);

                info->ifpi_rx[cpu].poll_func = vtnet_npoll_rx;
                info->ifpi_rx[cpu].arg = NULL;
                info->ifpi_rx[cpu].serializer = &sc->vtnet_rx_slz;

                for (i = 0; i < 3; i++)
                        lwkt_serialize_handler_disable(sc->serializes[i]);
                vtnet_disable_rx_intr(sc);
                vtnet_disable_tx_intr(sc);
                for (i = 0; i < sc->vtnet_nintr; i++)
                        virtio_teardown_intr(sc->vtnet_dev, i);
                if (virtio_with_feature(sc->vtnet_dev, VIRTIO_NET_F_STATUS))
                        virtio_unbind_intr(sc->vtnet_dev, -1);
                for (i = 0; i < 2; i++)
                        virtio_unbind_intr(sc->vtnet_dev, i);
        } else {
                int error;

                ifq_set_cpuid(&ifp->if_snd,
                    sc->vtnet_cpus[sc->vtnet_nintr - 1]);
                for (i = 0; i < 3; i++)
                        lwkt_serialize_handler_enable(sc->serializes[i]);
                for (i = 0; i < 2; i++) {
                        error = virtio_bind_intr(sc->vtnet_dev,
                            sc->vtnet_irqmap[i].irq, i,
                            sc->vtnet_irqmap[i].handler, sc);
                        if (error) {
                                device_printf(sc->vtnet_dev,
                                    "cannot re-bind virtqueue IRQs\n");
                        }
                }
                if (virtio_with_feature(sc->vtnet_dev, VIRTIO_NET_F_STATUS)) {
                        error = virtio_bind_intr(sc->vtnet_dev, 0, -1,
                            vtnet_config_intr, sc);
                        if (error) {
                                device_printf(sc->vtnet_dev,
                                    "cannot re-bind config_change IRQ\n");
                        }
                }
                for (i = 0; i < sc->vtnet_nintr; i++) {
                        error = virtio_setup_intr(sc->vtnet_dev, i,
                            sc->vtnet_intr_slz[i]);
                        if (error) {
                                device_printf(sc->vtnet_dev,
                                    "cannot setup virtqueue interrupts\n");
                        }
                }
                vtnet_enable_rx_intr(sc);
                vtnet_enable_tx_intr(sc);
        }
}

#endif  /* IFPOLL_ENABLE */

static void
vtnet_vlan_tag_remove(struct mbuf *m)
{
        struct ether_vlan_header *evl;

        evl = mtod(m, struct ether_vlan_header *);

        m->m_pkthdr.ether_vlantag = ntohs(evl->evl_tag);
        m->m_flags |= M_VLANTAG;

        /* Strip the 802.1Q header. */
        bcopy((char *) evl, (char *) evl + ETHER_VLAN_ENCAP_LEN,
            ETHER_HDR_LEN - ETHER_TYPE_LEN);
        m_adj(m, ETHER_VLAN_ENCAP_LEN);
}

/*
 * Alternative method of doing receive checksum offloading. Rather
 * than parsing the received frame down to the IP header, use the
 * csum_offset to determine which CSUM_* flags are appropriate. We
 * can get by with doing this only because the checksum offsets are
 * unique for the things we care about.
 */
static int
vtnet_rx_csum(struct vtnet_softc *sc, struct mbuf *m,
    struct virtio_net_hdr *hdr)
{
        struct ether_header *eh;
        struct ether_vlan_header *evh;
        struct udphdr *udp;
        int csum_len;
        uint16_t eth_type;

        csum_len = hdr->csum_start + hdr->csum_offset;

        if (csum_len < sizeof(struct ether_header) + sizeof(struct ip))
                return (1);
        if (m->m_len < csum_len)
                return (1);

        eh = mtod(m, struct ether_header *);
        eth_type = ntohs(eh->ether_type);
        if (eth_type == ETHERTYPE_VLAN) {
                evh = mtod(m, struct ether_vlan_header *);
                eth_type = ntohs(evh->evl_proto);
        }

        if (eth_type != ETHERTYPE_IP && eth_type != ETHERTYPE_IPV6) {
                sc->vtnet_stats.rx_csum_bad_ethtype++;
                return (1);
        }

        /* Use the offset to determine the appropriate CSUM_* flags. */
        switch (hdr->csum_offset) {
        case offsetof(struct udphdr, uh_sum):
                if (m->m_len < hdr->csum_start + sizeof(struct udphdr))
                        return (1);
                udp = (struct udphdr *)(mtod(m, uint8_t *) + hdr->csum_start);
                if (udp->uh_sum == 0)
                        return (0);

                /* FALLTHROUGH */

        case offsetof(struct tcphdr, th_sum):
                m->m_pkthdr.csum_flags |= CSUM_DATA_VALID | CSUM_PSEUDO_HDR;
                m->m_pkthdr.csum_data = 0xFFFF;
                break;

        default:
                sc->vtnet_stats.rx_csum_bad_offset++;
                return (1);
        }

        sc->vtnet_stats.rx_csum_offloaded++;

        return (0);
}

static int
vtnet_rxeof_merged(struct vtnet_softc *sc, struct mbuf *m_head, int nbufs)
{
        struct ifnet *ifp;
        struct virtqueue *vq;
        struct mbuf *m, *m_tail;
        int len;

        ifp = sc->vtnet_ifp;
        vq = sc->vtnet_rx_vq;
        m_tail = m_head;

        while (--nbufs > 0) {
                m = virtqueue_dequeue(vq, &len);
                if (m == NULL) {
                        ifp->if_ierrors++;
                        goto fail;
                }

                if (vtnet_newbuf(sc) != 0) {
                        ifp->if_iqdrops++;
                        vtnet_discard_rxbuf(sc, m);
                        if (nbufs > 1)
                                vtnet_discard_merged_rxbuf(sc, nbufs);
                        goto fail;
                }

                if (m->m_len < len)
                        len = m->m_len;

                m->m_len = len;
                m->m_flags &= ~M_PKTHDR;

                m_head->m_pkthdr.len += len;
                m_tail->m_next = m;
                m_tail = m;
        }

        return (0);

fail:
        sc->vtnet_stats.rx_mergeable_failed++;
        m_freem(m_head);

        return (1);
}

static int
vtnet_rxeof(struct vtnet_softc *sc, int count, int *rx_npktsp)
{
        struct virtio_net_hdr lhdr;
        struct ifnet *ifp;
        struct virtqueue *vq;
        struct mbuf *m;
        struct ether_header *eh;
        struct virtio_net_hdr *hdr;
        struct virtio_net_hdr_mrg_rxbuf *mhdr;
        int len, deq, nbufs, adjsz, rx_npkts;

        ifp = sc->vtnet_ifp;
        vq = sc->vtnet_rx_vq;
        hdr = &lhdr;
        deq = 0;
        rx_npkts = 0;

        while (--count >= 0) {
                m = virtqueue_dequeue(vq, &len);
                if (m == NULL)
                        break;
                deq++;

                if (len < sc->vtnet_hdr_size + ETHER_HDR_LEN) {
                        ifp->if_ierrors++;
                        vtnet_discard_rxbuf(sc, m);
                        continue;
                }

                if ((sc->vtnet_flags & VTNET_FLAG_MRG_RXBUFS) == 0) {
                        nbufs = 1;
                        adjsz = sizeof(struct vtnet_rx_header);
                        /*
                         * Account for our pad between the header and
                         * the actual start of the frame.
                         */
                        len += VTNET_RX_HEADER_PAD;
                } else {
                        mhdr = mtod(m, struct virtio_net_hdr_mrg_rxbuf *);
                        nbufs = mhdr->num_buffers;
                        adjsz = sizeof(struct virtio_net_hdr_mrg_rxbuf);
                }

                if (vtnet_replace_rxbuf(sc, m, len) != 0) {
                        ifp->if_iqdrops++;
                        vtnet_discard_rxbuf(sc, m);
                        if (nbufs > 1)
                                vtnet_discard_merged_rxbuf(sc, nbufs);
                        continue;
                }

                m->m_pkthdr.len = len;
                m->m_pkthdr.rcvif = ifp;
                m->m_pkthdr.csum_flags = 0;

                if (nbufs > 1) {
                        if (vtnet_rxeof_merged(sc, m, nbufs) != 0)
                                continue;
                }

                ifp->if_ipackets++;

                /*
                 * Save copy of header before we strip it. For both mergeable
                 * and non-mergeable, the VirtIO header is placed first in the
                 * mbuf's data. We no longer need num_buffers, so always use a
                 * virtio_net_hdr.
                 */
                memcpy(hdr, mtod(m, void *), sizeof(struct virtio_net_hdr));
                m_adj(m, adjsz);

                if (ifp->if_capenable & IFCAP_VLAN_HWTAGGING) {
                        eh = mtod(m, struct ether_header *);
                        if (eh->ether_type == htons(ETHERTYPE_VLAN)) {
                                vtnet_vlan_tag_remove(m);

                                /*
                                 * With the 802.1Q header removed, update the
                                 * checksum starting location accordingly.
                                 */
                                if (hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM)
                                        hdr->csum_start -=
                                            ETHER_VLAN_ENCAP_LEN;
                        }
                }

                if (ifp->if_capenable & IFCAP_RXCSUM &&
                    hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
                        if (vtnet_rx_csum(sc, m, hdr) != 0)
                                sc->vtnet_stats.rx_csum_failed++;
                }

                rx_npkts++;
                ifp->if_input(ifp, m, NULL, mycpuid);

                /*
                 * The interface may have been stopped while we were
                 * passing the packet up the network stack.
                 */
                if ((ifp->if_flags & IFF_RUNNING) == 0)
                        break;
        }

        if (deq > 0)
                virtqueue_notify(vq, NULL);

        if (rx_npktsp != NULL)
                *rx_npktsp = rx_npkts;

        return (count > 0 ? 0 : EAGAIN);
}

static void
vtnet_rx_msix_intr(void *xsc)
{
        struct vtnet_softc *sc;
        struct ifnet *ifp;
        int more;

        sc = xsc;
        ifp = sc->vtnet_ifp;

        if (!virtqueue_pending(sc->vtnet_rx_vq))
                return;

        vtnet_disable_rx_intr(sc);
next:
        if ((ifp->if_flags & IFF_RUNNING) == 0) {
                vtnet_enable_rx_intr(sc);
                return;
        }

        more = vtnet_rxeof(sc, sc->vtnet_rx_process_limit, NULL);
        if (!more && vtnet_enable_rx_intr(sc) != 0) {
                vtnet_disable_rx_intr(sc);
                more = 1;
        }

        if (more) {
                sc->vtnet_stats.rx_task_rescheduled++;
                goto next;
        }
}

static void
vtnet_rx_vq_intr(void *xsc)
{
        struct vtnet_softc *sc = xsc;

        lwkt_serialize_enter(&sc->vtnet_rx_slz);
        vtnet_rx_msix_intr(xsc);
        lwkt_serialize_exit(&sc->vtnet_rx_slz);
}

static void
vtnet_enqueue_txhdr(struct vtnet_softc *sc, struct vtnet_tx_header *txhdr)
{
        bzero(txhdr, sizeof(*txhdr));
        SLIST_INSERT_HEAD(&sc->vtnet_txhdr_free, txhdr, link);
}

static void
vtnet_txeof(struct vtnet_softc *sc)
{
        struct virtqueue *vq;
        struct ifnet *ifp;
        struct vtnet_tx_header *txhdr;
        int deq;

        vq = sc->vtnet_tx_vq;
        ifp = sc->vtnet_ifp;
        deq = 0;

        while ((txhdr = virtqueue_dequeue(vq, NULL)) != NULL) {
                deq++;
                ifp->if_opackets++;
                m_freem(txhdr->vth_mbuf);
                vtnet_enqueue_txhdr(sc, txhdr);
        }

        if (deq > 0) {
                ifq_clr_oactive(&ifp->if_snd);
                if (virtqueue_empty(vq))
                        ifsq_watchdog_set_count(&sc->vtnet_tx_watchdog, 0);
                else
                        ifsq_watchdog_set_count(&sc->vtnet_tx_watchdog,
                                                VTNET_WATCHDOG_TIMEOUT);
        }
}

static struct mbuf *
vtnet_tx_offload(struct vtnet_softc *sc, struct mbuf *m,
    struct virtio_net_hdr *hdr)
{
        struct ifnet *ifp;
        struct ether_header *eh;
        struct ether_vlan_header *evh;
        struct ip *ip;
        struct ip6_hdr *ip6;
        struct tcphdr *tcp;
        int ip_offset;
        uint16_t eth_type, csum_start;
        uint8_t ip_proto, gso_type;

        ifp = sc->vtnet_ifp;
        M_ASSERTPKTHDR(m);

        ip_offset = sizeof(struct ether_header);
        if (m->m_len < ip_offset) {
                if ((m = m_pullup(m, ip_offset)) == NULL)
                        return (NULL);
        }

        eh = mtod(m, struct ether_header *);
        eth_type = ntohs(eh->ether_type);
        if (eth_type == ETHERTYPE_VLAN) {
                ip_offset = sizeof(struct ether_vlan_header);
                if (m->m_len < ip_offset) {
                        if ((m = m_pullup(m, ip_offset)) == NULL)
                                return (NULL);
                }
                evh = mtod(m, struct ether_vlan_header *);
                eth_type = ntohs(evh->evl_proto);
        }

        switch (eth_type) {
        case ETHERTYPE_IP:
                if (m->m_len < ip_offset + sizeof(struct ip)) {
                        m = m_pullup(m, ip_offset + sizeof(struct ip));
                        if (m == NULL)
                                return (NULL);
                }

                ip = (struct ip *)(mtod(m, uint8_t *) + ip_offset);
                ip_proto = ip->ip_p;
                csum_start = ip_offset + (ip->ip_hl << 2);
                gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
                break;

        case ETHERTYPE_IPV6:
                if (m->m_len < ip_offset + sizeof(struct ip6_hdr)) {
                        m = m_pullup(m, ip_offset + sizeof(struct ip6_hdr));
                        if (m == NULL)
                                return (NULL);
                }

                ip6 = (struct ip6_hdr *)(mtod(m, uint8_t *) + ip_offset);
                /*
                 * XXX Assume no extension headers are present. Presently,
                 * this will always be true in the case of TSO, and FreeBSD
                 * does not perform checksum offloading of IPv6 yet.
                 */
                ip_proto = ip6->ip6_nxt;
                csum_start = ip_offset + sizeof(struct ip6_hdr);
                gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
                break;

        default:
                return (m);
        }

        if (m->m_pkthdr.csum_flags & VTNET_CSUM_OFFLOAD) {
                hdr->flags |= VIRTIO_NET_HDR_F_NEEDS_CSUM;
                hdr->csum_start = csum_start;
                hdr->csum_offset = m->m_pkthdr.csum_data;

                sc->vtnet_stats.tx_csum_offloaded++;
        }

        if (m->m_pkthdr.csum_flags & CSUM_TSO) {
                if (ip_proto != IPPROTO_TCP)
                        return (m);

                if (m->m_len < csum_start + sizeof(struct tcphdr)) {
                        m = m_pullup(m, csum_start + sizeof(struct tcphdr));
                        if (m == NULL)
                                return (NULL);
                }

                tcp = (struct tcphdr *)(mtod(m, uint8_t *) + csum_start);
                hdr->gso_type = gso_type;
                hdr->hdr_len = csum_start + (tcp->th_off << 2);
                hdr->gso_size = m->m_pkthdr.tso_segsz;

                if (tcp->th_flags & TH_CWR) {
                        /*
                         * Drop if we did not negotiate VIRTIO_NET_F_HOST_ECN.
                         * ECN support is only configurable globally with the
                         * net.inet.tcp.ecn.enable sysctl knob.
                         */
                        if ((sc->vtnet_flags & VTNET_FLAG_TSO_ECN) == 0) {
                                if_printf(ifp, "TSO with ECN not supported "
                                    "by host\n");
                                m_freem(m);
                                return (NULL);
                        }

                        hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN;
                }

                sc->vtnet_stats.tx_tso_offloaded++;
        }

        return (m);
}

static int
vtnet_enqueue_txbuf(struct vtnet_softc *sc, struct mbuf **m_head,
    struct vtnet_tx_header *txhdr)
{
        struct sglist sg;
        struct sglist_seg segs[VTNET_MAX_TX_SEGS];
        struct virtqueue *vq;
        struct mbuf *m;
        int error;

        vq = sc->vtnet_tx_vq;
        m = *m_head;

        sglist_init(&sg, sc->vtnet_tx_nsegs, segs);
        error = sglist_append(&sg, &txhdr->vth_uhdr, sc->vtnet_hdr_size);
        KASSERT(error == 0 && sg.sg_nseg == 1,
            ("%s: error %d adding header to sglist", __func__, error));

        error = sglist_append_mbuf(&sg, m);
        if (error) {
                m = m_defrag(m, M_NOWAIT);
                if (m == NULL)
                        goto fail;

                *m_head = m;
                sc->vtnet_stats.tx_defragged++;

                error = sglist_append_mbuf(&sg, m);
                if (error)
                        goto fail;
        }

        txhdr->vth_mbuf = m;
        error = virtqueue_enqueue(vq, txhdr, &sg, sg.sg_nseg, 0);

        return (error);

fail:
        sc->vtnet_stats.tx_defrag_failed++;
        m_freem(*m_head);
        *m_head = NULL;

        return (ENOBUFS);
}

static struct mbuf *
vtnet_vlan_tag_insert(struct mbuf *m)
{
        struct mbuf *n;
        struct ether_vlan_header *evl;

        if (M_WRITABLE(m) == 0) {
                n = m_dup(m, M_NOWAIT);
                m_freem(m);
                if ((m = n) == NULL)
                        return (NULL);
        }

        M_PREPEND(m, ETHER_VLAN_ENCAP_LEN, M_NOWAIT);
        if (m == NULL)
                return (NULL);
        if (m->m_len < sizeof(struct ether_vlan_header)) {
                m = m_pullup(m, sizeof(struct ether_vlan_header));
                if (m == NULL)
                        return (NULL);
        }

        /* Insert 802.1Q header into the existing Ethernet header. */
        evl = mtod(m, struct ether_vlan_header *);
        bcopy((char *) evl + ETHER_VLAN_ENCAP_LEN,
              (char *) evl, ETHER_HDR_LEN - ETHER_TYPE_LEN);
        evl->evl_encap_proto = htons(ETHERTYPE_VLAN);
        evl->evl_tag = htons(m->m_pkthdr.ether_vlantag);
        m->m_flags &= ~M_VLANTAG;

        return (m);
}

static int
vtnet_encap(struct vtnet_softc *sc, struct mbuf **m_head)
{
        struct vtnet_tx_header *txhdr;
        struct virtio_net_hdr *hdr;
        struct mbuf *m;
        int error;

        txhdr = SLIST_FIRST(&sc->vtnet_txhdr_free);
        if (txhdr == NULL)
                return (ENOBUFS);
        SLIST_REMOVE_HEAD(&sc->vtnet_txhdr_free, link);

        /*
         * Always use the non-mergeable header to simplify things. When
         * the mergeable feature is negotiated, the num_buffers field
         * must be set to zero. We use vtnet_hdr_size later to enqueue
         * the correct header size to the host.
         */
        hdr = &txhdr->vth_uhdr.hdr;
        m = *m_head;

        error = ENOBUFS;

        if (m->m_flags & M_VLANTAG) {
                //m = ether_vlanencap(m, m->m_pkthdr.ether_vtag);
                m = vtnet_vlan_tag_insert(m);
                if ((*m_head = m) == NULL)
                        goto fail;
                m->m_flags &= ~M_VLANTAG;
        }

        if (m->m_pkthdr.csum_flags != 0) {
                m = vtnet_tx_offload(sc, m, hdr);
                if ((*m_head = m) == NULL)
                        goto fail;
        }

        error = vtnet_enqueue_txbuf(sc, m_head, txhdr);
fail:
        if (error != 0)
                vtnet_enqueue_txhdr(sc, txhdr);
        return (error);
}

static void
vtnet_start(struct ifnet *ifp, struct ifaltq_subque *ifsq)
{
        struct vtnet_softc *sc;
        struct virtqueue *vq;
        struct mbuf *m0;
        int enq;

        sc = ifp->if_softc;
        vq = sc->vtnet_tx_vq;
        enq = 0;

        ASSERT_ALTQ_SQ_DEFAULT(ifp, ifsq);
        ASSERT_SERIALIZED(&sc->vtnet_tx_slz);

        if ((ifp->if_flags & (IFF_RUNNING)) !=
            IFF_RUNNING || ((sc->vtnet_flags & VTNET_FLAG_LINK) == 0))
                return;

#ifdef VTNET_TX_INTR_MODERATION
        if (virtqueue_nused(vq) >= sc->vtnet_tx_size / 2)
                vtnet_txeof(sc);
#endif

        while (!ifsq_is_empty(ifsq)) {
                if (virtqueue_full(vq)) {
                        ifsq_set_oactive(ifsq);
                        break;
                }

                m0 = ifsq_dequeue(ifsq);
                if (m0 == NULL)
                        break;

                if (vtnet_encap(sc, &m0) != 0) {
                        if (m0 == NULL)
                                break;
                        ifsq_prepend(ifsq, m0);
                        ifsq_set_oactive(ifsq);
                        break;
                }

                enq++;
                ETHER_BPF_MTAP(ifp, m0);
        }

        if (enq > 0) {
                virtqueue_notify(vq, NULL);
                ifsq_watchdog_set_count(&sc->vtnet_tx_watchdog,
                                        VTNET_WATCHDOG_TIMEOUT);
        }
}

static void
vtnet_tx_msix_intr(void *xsc)
{
        struct vtnet_softc *sc;
        struct ifnet *ifp;
        struct ifaltq_subque *ifsq;

        sc = xsc;
        ifp = sc->vtnet_ifp;
        ifsq = ifq_get_subq_default(&ifp->if_snd);

        if (!virtqueue_pending(sc->vtnet_tx_vq))
                return;

        vtnet_disable_tx_intr(sc);
next:
        if ((ifp->if_flags & IFF_RUNNING) == 0) {
                vtnet_enable_tx_intr(sc);
                return;
        }

        vtnet_txeof(sc);

        if (!ifsq_is_empty(ifsq))
                ifsq_devstart(ifsq);

        if (vtnet_enable_tx_intr(sc) != 0) {
                vtnet_disable_tx_intr(sc);
                sc->vtnet_stats.tx_task_rescheduled++;
                goto next;
        }
}

static void
vtnet_tx_vq_intr(void *xsc)
{
        struct vtnet_softc *sc = xsc;

        lwkt_serialize_enter(&sc->vtnet_tx_slz);
        vtnet_tx_msix_intr(xsc);
        lwkt_serialize_exit(&sc->vtnet_tx_slz);
}

static void
vtnet_config_intr(void *arg)
{
        struct vtnet_softc *sc;

        sc = arg;

        vtnet_update_link_status(sc);
}

static void
vtnet_stop(struct vtnet_softc *sc)
{
        device_t dev;
        struct ifnet *ifp;

        dev = sc->vtnet_dev;
        ifp = sc->vtnet_ifp;

        ASSERT_IFNET_SERIALIZED_ALL(ifp);

        ifq_clr_oactive(&ifp->if_snd);
        ifsq_watchdog_stop(&sc->vtnet_tx_watchdog);
        ifp->if_flags &= ~(IFF_RUNNING);

        vtnet_disable_rx_intr(sc);
        vtnet_disable_tx_intr(sc);

        /*
         * Stop the host VirtIO adapter. Note this will reset the host
         * adapter's state back to the pre-initialized state, so in
         * order to make the device usable again, we must drive it
         * through virtio_reinit() and virtio_reinit_complete().
         */
        virtio_stop(dev);

        sc->vtnet_flags &= ~VTNET_FLAG_LINK;

        vtnet_free_rx_mbufs(sc);
        vtnet_free_tx_mbufs(sc);
}

static int
vtnet_virtio_reinit(struct vtnet_softc *sc)
{
        device_t dev;
        struct ifnet *ifp;
        uint64_t features;
        int error;

        dev = sc->vtnet_dev;
        ifp = sc->vtnet_ifp;
        features = sc->vtnet_features;

        /*
         * Re-negotiate with the host, removing any disabled receive
         * features. Transmit features are disabled only on our side
         * via if_capenable and if_hwassist.
         */

        if (ifp->if_capabilities & IFCAP_RXCSUM) {
                if ((ifp->if_capenable & IFCAP_RXCSUM) == 0)
                        features &= ~VIRTIO_NET_F_GUEST_CSUM;
        }

#if 0   /* IFCAP_LRO doesn't exist in DragonFly. */
        if (ifp->if_capabilities & IFCAP_LRO) {
                if ((ifp->if_capenable & IFCAP_LRO) == 0)
                        features &= ~VTNET_LRO_FEATURES;
        }
#endif

        if (ifp->if_capabilities & IFCAP_VLAN_HWFILTER) {
                if ((ifp->if_capenable & IFCAP_VLAN_HWFILTER) == 0)
                        features &= ~VIRTIO_NET_F_CTRL_VLAN;
        }

        error = virtio_reinit(dev, features);
        if (error)
                device_printf(dev, "virtio reinit error %d\n", error);

        return (error);
}

static void
vtnet_init(void *xsc)
{
        struct vtnet_softc *sc;
        device_t dev;
        struct ifnet *ifp;
        int error;

        sc = xsc;
        dev = sc->vtnet_dev;
        ifp = sc->vtnet_ifp;

        ASSERT_IFNET_SERIALIZED_ALL(ifp);

        if (ifp->if_flags & IFF_RUNNING)
                return;

        /* Stop host's adapter, cancel any pending I/O. */
        vtnet_stop(sc);

        /* Reinitialize the host device. */
        error = vtnet_virtio_reinit(sc);
        if (error) {
                device_printf(dev,
                    "reinitialization failed, stopping device...\n");
                vtnet_stop(sc);
                return;
        }

        /* Update host with assigned MAC address. */
        bcopy(IF_LLADDR(ifp), sc->vtnet_hwaddr, ETHER_ADDR_LEN);
        vtnet_set_hwaddr(sc);

        ifp->if_hwassist = 0;
        if (ifp->if_capenable & IFCAP_TXCSUM)
                ifp->if_hwassist |= VTNET_CSUM_OFFLOAD;
        if (ifp->if_capenable & IFCAP_TSO4)
                ifp->if_hwassist |= CSUM_TSO;

        error = vtnet_init_rx_vq(sc);
        if (error) {
                device_printf(dev,
                    "cannot allocate mbufs for Rx virtqueue\n");
                vtnet_stop(sc);
                return;
        }

        if (sc->vtnet_flags & VTNET_FLAG_CTRL_VQ) {
                if (sc->vtnet_flags & VTNET_FLAG_CTRL_RX) {
                        /* Restore promiscuous and all-multicast modes. */
                        vtnet_rx_filter(sc);

                        /* Restore filtered MAC addresses. */
                        vtnet_rx_filter_mac(sc);
                }

                /* Restore VLAN filters. */
                if (ifp->if_capenable & IFCAP_VLAN_HWFILTER)
                        vtnet_rx_filter_vlan(sc);
        }

#ifdef IFPOLL_ENABLE
        if (!(ifp->if_flags & IFF_NPOLLING))
#endif
        {
                vtnet_enable_rx_intr(sc);
                vtnet_enable_tx_intr(sc);
        }

        ifp->if_flags |= IFF_RUNNING;
        ifq_clr_oactive(&ifp->if_snd);
        ifsq_watchdog_start(&sc->vtnet_tx_watchdog);

        virtio_reinit_complete(dev);

        vtnet_update_link_status(sc);
}

static void
vtnet_exec_ctrl_cmd(struct vtnet_softc *sc, void *cookie,
    struct sglist *sg, int readable, int writable)
{
        struct virtqueue *vq;
        void *c;

        vq = sc->vtnet_ctrl_vq;

        ASSERT_IFNET_SERIALIZED_ALL(sc->vtnet_ifp);
        KASSERT(sc->vtnet_flags & VTNET_FLAG_CTRL_VQ,
            ("no control virtqueue"));
        KASSERT(virtqueue_empty(vq),
            ("control command already enqueued"));

        if (virtqueue_enqueue(vq, cookie, sg, readable, writable) != 0)
                return;

        /*
         * XXX We can safely drop the serializer between here, and the end of
         *     the function, when we can correctly sleep for this command to
         *     be finished.
         */
        virtqueue_notify(vq, NULL);

        /*
         * Poll until the command is complete. Previously, we would
         * sleep until the control virtqueue interrupt handler woke
         * us up, but dropping the VTNET_MTX leads to serialization
         * difficulties.
         *
         * Furthermore, it appears QEMU/KVM only allocates three MSIX
         * vectors. Two of those vectors are needed for the Rx and Tx
         * virtqueues. We do not support sharing both a Vq and config
         * changed notification on the same MSIX vector.
         */
        c = virtqueue_poll(vq, NULL);
        KASSERT(c == cookie, ("unexpected control command response"));
}

static int
vtnet_ctrl_mac_cmd(struct vtnet_softc *sc, uint8_t *hwaddr)
{
        struct {
                struct virtio_net_ctrl_hdr hdr __aligned(2);
                uint8_t pad1;
                char aligned_hwaddr[ETHER_ADDR_LEN] __aligned(8);
                uint8_t pad2;
                uint8_t ack;
        } s;
        struct sglist_seg segs[3];
        struct sglist sg;
        int error;

        s.hdr.class = VIRTIO_NET_CTRL_MAC;
        s.hdr.cmd = VIRTIO_NET_CTRL_MAC_ADDR_SET;
        s.ack = VIRTIO_NET_ERR;

        /* Copy the mac address into physically contiguous memory */
        memcpy(s.aligned_hwaddr, hwaddr, ETHER_ADDR_LEN);

        sglist_init(&sg, 3, segs);
        error = 0;
        error |= sglist_append(&sg, &s.hdr,
            sizeof(struct virtio_net_ctrl_hdr));
        error |= sglist_append(&sg, s.aligned_hwaddr, ETHER_ADDR_LEN);
        error |= sglist_append(&sg, &s.ack, sizeof(uint8_t));
        KASSERT(error == 0 && sg.sg_nseg == 3,
            ("%s: error %d adding set MAC msg to sglist", __func__, error));

        vtnet_exec_ctrl_cmd(sc, &s.ack, &sg, sg.sg_nseg - 1, 1);

        return (s.ack == VIRTIO_NET_OK ? 0 : EIO);
}

static void
vtnet_rx_filter(struct vtnet_softc *sc)
{
        device_t dev;
        struct ifnet *ifp;

        dev = sc->vtnet_dev;
        ifp = sc->vtnet_ifp;

        ASSERT_IFNET_SERIALIZED_ALL(ifp);
        KASSERT(sc->vtnet_flags & VTNET_FLAG_CTRL_RX,
            ("CTRL_RX feature not negotiated"));

        if (vtnet_set_promisc(sc, ifp->if_flags & IFF_PROMISC) != 0)
                device_printf(dev, "cannot %s promiscuous mode\n",
                    (ifp->if_flags & IFF_PROMISC) ? "enable" : "disable");

        if (vtnet_set_allmulti(sc, ifp->if_flags & IFF_ALLMULTI) != 0)
                device_printf(dev, "cannot %s all-multicast mode\n",
                    (ifp->if_flags & IFF_ALLMULTI) ? "enable" : "disable");
}

static int
vtnet_ctrl_rx_cmd(struct vtnet_softc *sc, int cmd, int on)
{
        struct sglist_seg segs[3];
        struct sglist sg;
        struct {
                struct virtio_net_ctrl_hdr hdr __aligned(2);
                uint8_t pad1;
                uint8_t onoff;
                uint8_t pad2;
                uint8_t ack;
        } s;
        int error;

        KASSERT(sc->vtnet_flags & VTNET_FLAG_CTRL_RX,
            ("%s: CTRL_RX feature not negotiated", __func__));

        s.hdr.class = VIRTIO_NET_CTRL_RX;
        s.hdr.cmd = cmd;
        s.onoff = !!on;
        s.ack = VIRTIO_NET_ERR;

        sglist_init(&sg, 3, segs);
        error = 0;
        error |= sglist_append(&sg, &s.hdr, sizeof(struct virtio_net_ctrl_hdr));
        error |= sglist_append(&sg, &s.onoff, sizeof(uint8_t));
        error |= sglist_append(&sg, &s.ack, sizeof(uint8_t));
        KASSERT(error == 0 && sg.sg_nseg == 3,
            ("%s: error %d adding Rx message to sglist", __func__, error));

        vtnet_exec_ctrl_cmd(sc, &s.ack, &sg, sg.sg_nseg - 1, 1);

        return (s.ack == VIRTIO_NET_OK ? 0 : EIO);
}

static int
vtnet_set_promisc(struct vtnet_softc *sc, int on)
{

        return (vtnet_ctrl_rx_cmd(sc, VIRTIO_NET_CTRL_RX_PROMISC, on));
}

static int
vtnet_set_allmulti(struct vtnet_softc *sc, int on)
{

        return (vtnet_ctrl_rx_cmd(sc, VIRTIO_NET_CTRL_RX_ALLMULTI, on));
}

static void
vtnet_rx_filter_mac(struct vtnet_softc *sc)
{
        struct virtio_net_ctrl_hdr hdr __aligned(2);
        struct vtnet_mac_filter *filter;
        struct sglist_seg segs[4];
        struct sglist sg;
        struct ifnet *ifp;
        struct ifaddr *ifa;
        struct ifaddr_container *ifac;
        struct ifmultiaddr *ifma;
        int ucnt, mcnt, promisc, allmulti, error;
        uint8_t ack;

        ifp = sc->vtnet_ifp;
        ucnt = 0;
        mcnt = 0;
        promisc = 0;
        allmulti = 0;

        ASSERT_IFNET_SERIALIZED_ALL(ifp);
        KASSERT(sc->vtnet_flags & VTNET_FLAG_CTRL_RX,
            ("%s: CTRL_RX feature not negotiated", __func__));

        /* Use the MAC filtering table allocated in vtnet_attach. */
        filter = sc->vtnet_macfilter;
        memset(filter, 0, sizeof(struct vtnet_mac_filter));

        /* Unicast MAC addresses: */
        //if_addr_rlock(ifp);
        TAILQ_FOREACH(ifac, &ifp->if_addrheads[mycpuid], ifa_link) {
                ifa = ifac->ifa;
                if (ifa->ifa_addr->sa_family != AF_LINK)
                        continue;
                else if (memcmp(LLADDR((struct sockaddr_dl *)ifa->ifa_addr),
                    sc->vtnet_hwaddr, ETHER_ADDR_LEN) == 0)
                        continue;
                else if (ucnt == VTNET_MAX_MAC_ENTRIES) {
                        promisc = 1;
                        break;
                }

                bcopy(LLADDR((struct sockaddr_dl *)ifa->ifa_addr),
                    &filter->vmf_unicast.macs[ucnt], ETHER_ADDR_LEN);
                ucnt++;
        }
        //if_addr_runlock(ifp);

        if (promisc != 0) {
                filter->vmf_unicast.nentries = 0;
                if_printf(ifp, "more than %d MAC addresses assigned, "
                    "falling back to promiscuous mode\n",
                    VTNET_MAX_MAC_ENTRIES);
        } else
                filter->vmf_unicast.nentries = ucnt;

        /* Multicast MAC addresses: */
        //if_maddr_rlock(ifp);
        TAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                if (ifma->ifma_addr->sa_family != AF_LINK)
                        continue;
                else if (mcnt == VTNET_MAX_MAC_ENTRIES) {
                        allmulti = 1;
                        break;
                }

                bcopy(LLADDR((struct sockaddr_dl *)ifma->ifma_addr),
                    &filter->vmf_multicast.macs[mcnt], ETHER_ADDR_LEN);
                mcnt++;
        }
        //if_maddr_runlock(ifp);

        if (allmulti != 0) {
                filter->vmf_multicast.nentries = 0;
                if_printf(ifp, "more than %d multicast MAC addresses "
                    "assigned, falling back to all-multicast mode\n",
                    VTNET_MAX_MAC_ENTRIES);
        } else
                filter->vmf_multicast.nentries = mcnt;

        if (promisc != 0 && allmulti != 0)
                goto out;

        hdr.class = VIRTIO_NET_CTRL_MAC;
        hdr.cmd = VIRTIO_NET_CTRL_MAC_TABLE_SET;
        ack = VIRTIO_NET_ERR;

        sglist_init(&sg, 4, segs);
        error = 0;
        error |= sglist_append(&sg, &hdr, sizeof(struct virtio_net_ctrl_hdr));
        error |= sglist_append(&sg, &filter->vmf_unicast,
            sizeof(uint32_t) + filter->vmf_unicast.nentries * ETHER_ADDR_LEN);
        error |= sglist_append(&sg, &filter->vmf_multicast,
            sizeof(uint32_t) + filter->vmf_multicast.nentries * ETHER_ADDR_LEN);
        error |= sglist_append(&sg, &ack, sizeof(uint8_t));
        KASSERT(error == 0 && sg.sg_nseg == 4,
            ("%s: error %d adding MAC filter msg to sglist", __func__, error));

        vtnet_exec_ctrl_cmd(sc, &ack, &sg, sg.sg_nseg - 1, 1);

        if (ack != VIRTIO_NET_OK)
                if_printf(ifp, "error setting host MAC filter table\n");

out:
        if (promisc != 0 && vtnet_set_promisc(sc, 1) != 0)
                if_printf(ifp, "cannot enable promiscuous mode\n");
        if (allmulti != 0 && vtnet_set_allmulti(sc, 1) != 0)
                if_printf(ifp, "cannot enable all-multicast mode\n");
}

static int
vtnet_exec_vlan_filter(struct vtnet_softc *sc, int add, uint16_t tag)
{
        struct sglist_seg segs[3];
        struct sglist sg;
        struct {
                struct virtio_net_ctrl_hdr hdr __aligned(2);
                uint8_t pad1;
                uint16_t tag;
                uint8_t pad2;
                uint8_t ack;
        } s;
        int error;

        s.hdr.class = VIRTIO_NET_CTRL_VLAN;
        s.hdr.cmd = add ? VIRTIO_NET_CTRL_VLAN_ADD : VIRTIO_NET_CTRL_VLAN_DEL;
        s.tag = tag;
        s.ack = VIRTIO_NET_ERR;

        sglist_init(&sg, 3, segs);
        error = 0;
        error |= sglist_append(&sg, &s.hdr, sizeof(struct virtio_net_ctrl_hdr));
        error |= sglist_append(&sg, &s.tag, sizeof(uint16_t));
        error |= sglist_append(&sg, &s.ack, sizeof(uint8_t));
        KASSERT(error == 0 && sg.sg_nseg == 3,
            ("%s: error %d adding VLAN message to sglist", __func__, error));

        vtnet_exec_ctrl_cmd(sc, &s.ack, &sg, sg.sg_nseg - 1, 1);

        return (s.ack == VIRTIO_NET_OK ? 0 : EIO);
}

static void
vtnet_rx_filter_vlan(struct vtnet_softc *sc)
{
        uint32_t w;
        uint16_t tag;
        int i, bit, nvlans;

        ASSERT_IFNET_SERIALIZED_ALL(sc->vtnet_ifp);
        KASSERT(sc->vtnet_flags & VTNET_FLAG_VLAN_FILTER,
            ("%s: VLAN_FILTER feature not negotiated", __func__));

        nvlans = sc->vtnet_nvlans;

        /* Enable the filter for each configured VLAN. */
        for (i = 0; i < VTNET_VLAN_SHADOW_SIZE && nvlans > 0; i++) {
                w = sc->vtnet_vlan_shadow[i];
                while ((bit = ffs(w) - 1) != -1) {
                        w &= ~(1 << bit);
                        tag = sizeof(w) * CHAR_BIT * i + bit;
                        nvlans--;

                        if (vtnet_exec_vlan_filter(sc, 1, tag) != 0) {
                                device_printf(sc->vtnet_dev,
                                    "cannot enable VLAN %d filter\n", tag);
                        }
                }
        }

        KASSERT(nvlans == 0, ("VLAN count incorrect"));
}

static void
vtnet_update_vlan_filter(struct vtnet_softc *sc, int add, uint16_t tag)
{
        struct ifnet *ifp;
        int idx, bit;

        ifp = sc->vtnet_ifp;
        idx = (tag >> 5) & 0x7F;
        bit = tag & 0x1F;

        if (tag == 0 || tag > 4095)
                return;

        ifnet_serialize_all(ifp);

        /* Update shadow VLAN table. */
        if (add) {
                sc->vtnet_nvlans++;
                sc->vtnet_vlan_shadow[idx] |= (1 << bit);
        } else {
                sc->vtnet_nvlans--;
                sc->vtnet_vlan_shadow[idx] &= ~(1 << bit);
        }

        if (ifp->if_capenable & IFCAP_VLAN_HWFILTER &&
            vtnet_exec_vlan_filter(sc, add, tag) != 0) {
                device_printf(sc->vtnet_dev,
                    "cannot %s VLAN %d %s the host filter table\n",
                    add ? "add" : "remove", tag, add ? "to" : "from");
        }

        ifnet_deserialize_all(ifp);
}

static void
vtnet_register_vlan(void *arg, struct ifnet *ifp, uint16_t tag)
{

        if (ifp->if_softc != arg)
                return;

        vtnet_update_vlan_filter(arg, 1, tag);
}

static void
vtnet_unregister_vlan(void *arg, struct ifnet *ifp, uint16_t tag)
{

        if (ifp->if_softc != arg)
                return;

        vtnet_update_vlan_filter(arg, 0, tag);
}

static int
vtnet_ifmedia_upd(struct ifnet *ifp)
{
        struct vtnet_softc *sc;
        struct ifmedia *ifm;

        sc = ifp->if_softc;
        ifm = &sc->vtnet_media;

        if (IFM_TYPE(ifm->ifm_media) != IFM_ETHER)
                return (EINVAL);

        return (0);
}

static void
vtnet_ifmedia_sts(struct ifnet *ifp, struct ifmediareq *ifmr)
{
        struct vtnet_softc *sc;

        sc = ifp->if_softc;

        ifmr->ifm_status = IFM_AVALID;
        ifmr->ifm_active = IFM_ETHER;

        if (vtnet_is_link_up(sc) != 0) {
                ifmr->ifm_status |= IFM_ACTIVE;
                ifmr->ifm_active |= VTNET_MEDIATYPE;
        } else
                ifmr->ifm_active |= IFM_NONE;
}

static void
vtnet_add_statistics(struct vtnet_softc *sc)
{
        device_t dev;
        struct vtnet_statistics *stats;
        struct sysctl_ctx_list *ctx;
        struct sysctl_oid *tree;
        struct sysctl_oid_list *child;

        dev = sc->vtnet_dev;
        stats = &sc->vtnet_stats;
        ctx = device_get_sysctl_ctx(dev);
        tree = device_get_sysctl_tree(dev);
        child = SYSCTL_CHILDREN(tree);

        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "mbuf_alloc_failed",
            CTLFLAG_RD, &stats->mbuf_alloc_failed, 0,
            "Mbuf cluster allocation failures");

        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "rx_frame_too_large",
            CTLFLAG_RD, &stats->rx_frame_too_large, 0,
            "Received frame larger than the mbuf chain");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "rx_enq_replacement_failed",
            CTLFLAG_RD, &stats->rx_enq_replacement_failed, 0,
            "Enqueuing the replacement receive mbuf failed");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "rx_mergeable_failed",
            CTLFLAG_RD, &stats->rx_mergeable_failed, 0,
            "Mergeable buffers receive failures");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "rx_csum_bad_ethtype",
            CTLFLAG_RD, &stats->rx_csum_bad_ethtype, 0,
            "Received checksum offloaded buffer with unsupported "
            "Ethernet type");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "rx_csum_bad_ipproto",
            CTLFLAG_RD, &stats->rx_csum_bad_ipproto, 0,
            "Received checksum offloaded buffer with incorrect IP protocol");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "rx_csum_bad_offset",
            CTLFLAG_RD, &stats->rx_csum_bad_offset, 0,
            "Received checksum offloaded buffer with incorrect offset");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "rx_csum_failed",
            CTLFLAG_RD, &stats->rx_csum_failed, 0,
            "Received buffer checksum offload failed");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "rx_csum_offloaded",
            CTLFLAG_RD, &stats->rx_csum_offloaded, 0,
            "Received buffer checksum offload succeeded");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "rx_task_rescheduled",
            CTLFLAG_RD, &stats->rx_task_rescheduled, 0,
            "Times the receive interrupt task rescheduled itself");

        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "tx_csum_bad_ethtype",
            CTLFLAG_RD, &stats->tx_csum_bad_ethtype, 0,
            "Aborted transmit of checksum offloaded buffer with unknown "
            "Ethernet type");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "tx_tso_bad_ethtype",
            CTLFLAG_RD, &stats->tx_tso_bad_ethtype, 0,
            "Aborted transmit of TSO buffer with unknown Ethernet type");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "tx_defragged",
            CTLFLAG_RD, &stats->tx_defragged, 0,
            "Transmit mbufs defragged");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "tx_defrag_failed",
            CTLFLAG_RD, &stats->tx_defrag_failed, 0,
            "Aborted transmit of buffer because defrag failed");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "tx_csum_offloaded",
            CTLFLAG_RD, &stats->tx_csum_offloaded, 0,
            "Offloaded checksum of transmitted buffer");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "tx_tso_offloaded",
            CTLFLAG_RD, &stats->tx_tso_offloaded, 0,
            "Segmentation offload of transmitted buffer");
        SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "tx_task_rescheduled",
            CTLFLAG_RD, &stats->tx_task_rescheduled, 0,
            "Times the transmit interrupt task rescheduled itself");
}

static int
vtnet_enable_rx_intr(struct vtnet_softc *sc)
{

        return (virtqueue_enable_intr(sc->vtnet_rx_vq));
}

static void
vtnet_disable_rx_intr(struct vtnet_softc *sc)
{

        virtqueue_disable_intr(sc->vtnet_rx_vq);
}

static int
vtnet_enable_tx_intr(struct vtnet_softc *sc)
{

#ifdef VTNET_TX_INTR_MODERATION
        return (0);
#else
        return (virtqueue_enable_intr(sc->vtnet_tx_vq));
#endif
}

static void
vtnet_disable_tx_intr(struct vtnet_softc *sc)
{

        virtqueue_disable_intr(sc->vtnet_tx_vq);
}