/*
 * Virtio Network Device
 *
 * Copyright IBM, Corp. 2007
 *
 * Authors:
 *  Anthony Liguori   <aliguori@us.ibm.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2.  See
 * the COPYING file in the top-level directory.
 *
 */

#include "qemu/osdep.h"
#include "qemu/atomic.h"
#include "qemu/iov.h"
#include "qemu/log.h"
#include "qemu/main-loop.h"
#include "qemu/module.h"
#include "hw/virtio/virtio.h"
#include "net/net.h"
#include "net/checksum.h"
#include "net/tap.h"
#include "qemu/error-report.h"
#include "qemu/timer.h"
#include "qemu/option.h"
#include "qemu/option_int.h"
#include "qemu/config-file.h"
#include "qapi/qmp/qdict.h"
#include "hw/virtio/virtio-net.h"
#include "net/vhost_net.h"
#include "net/announce.h"
#include "hw/virtio/virtio-bus.h"
#include "qapi/error.h"
#include "qapi/qapi-events-net.h"
#include "hw/qdev-properties.h"
#include "qapi/qapi-types-migration.h"
#include "qapi/qapi-events-migration.h"
#include "hw/virtio/virtio-access.h"
#include "migration/misc.h"
#include "standard-headers/linux/ethtool.h"
#include "sysemu/sysemu.h"
#include "trace.h"
#include "monitor/qdev.h"
#include "hw/pci/pci.h"
#include "net_rx_pkt.h"
#include "hw/virtio/vhost.h"
#include "sysemu/qtest.h"

#define VIRTIO_NET_VM_VERSION    11

#define MAX_VLAN    (1 << 12)   /* Per 802.1Q definition */

/* previously fixed value */
#define VIRTIO_NET_RX_QUEUE_DEFAULT_SIZE 256
#define VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE 256

/* for now, only allow larger queue_pairs; with virtio-1, guest can downsize */
#define VIRTIO_NET_RX_QUEUE_MIN_SIZE VIRTIO_NET_RX_QUEUE_DEFAULT_SIZE
#define VIRTIO_NET_TX_QUEUE_MIN_SIZE VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE

#define VIRTIO_NET_IP4_ADDR_SIZE   8        /* ipv4 saddr + daddr */

#define VIRTIO_NET_TCP_FLAG         0x3F
#define VIRTIO_NET_TCP_HDR_LENGTH   0xF000

/* IPv4 max payload, 16 bits in the header */
#define VIRTIO_NET_MAX_IP4_PAYLOAD (65535 - sizeof(struct ip_header))
#define VIRTIO_NET_MAX_TCP_PAYLOAD 65535

/* header length value in ip header without option */
#define VIRTIO_NET_IP4_HEADER_LENGTH 5

#define VIRTIO_NET_IP6_ADDR_SIZE   32      /* ipv6 saddr + daddr */
#define VIRTIO_NET_MAX_IP6_PAYLOAD VIRTIO_NET_MAX_TCP_PAYLOAD

/* Purge coalesced packets timer interval, This value affects the performance
   a lot, and should be tuned carefully, '300000'(300us) is the recommended
   value to pass the WHQL test, '50000' can gain 2x netperf throughput with
   tso/gso/gro 'off'. */
#define VIRTIO_NET_RSC_DEFAULT_INTERVAL 300000

#define VIRTIO_NET_RSS_SUPPORTED_HASHES (VIRTIO_NET_RSS_HASH_TYPE_IPv4 | \
                                         VIRTIO_NET_RSS_HASH_TYPE_TCPv4 | \
                                         VIRTIO_NET_RSS_HASH_TYPE_UDPv4 | \
                                         VIRTIO_NET_RSS_HASH_TYPE_IPv6 | \
                                         VIRTIO_NET_RSS_HASH_TYPE_TCPv6 | \
                                         VIRTIO_NET_RSS_HASH_TYPE_UDPv6 | \
                                         VIRTIO_NET_RSS_HASH_TYPE_IP_EX | \
                                         VIRTIO_NET_RSS_HASH_TYPE_TCP_EX | \
                                         VIRTIO_NET_RSS_HASH_TYPE_UDP_EX)

static const VirtIOFeature feature_sizes[] = {
    {.flags = 1ULL << VIRTIO_NET_F_MAC,
     .end = endof(struct virtio_net_config, mac)},
    {.flags = 1ULL << VIRTIO_NET_F_STATUS,
     .end = endof(struct virtio_net_config, status)},
    {.flags = 1ULL << VIRTIO_NET_F_MQ,
     .end = endof(struct virtio_net_config, max_virtqueue_pairs)},
    {.flags = 1ULL << VIRTIO_NET_F_MTU,
     .end = endof(struct virtio_net_config, mtu)},
    {.flags = 1ULL << VIRTIO_NET_F_SPEED_DUPLEX,
     .end = endof(struct virtio_net_config, duplex)},
    {.flags = (1ULL << VIRTIO_NET_F_RSS) | (1ULL << VIRTIO_NET_F_HASH_REPORT),
     .end = endof(struct virtio_net_config, supported_hash_types)},
    {}
};

static VirtIONetQueue *virtio_net_get_subqueue(NetClientState *nc)
{
    VirtIONet *n = qemu_get_nic_opaque(nc);

    return &n->vqs[nc->queue_index];
}

static int vq2q(int queue_index)
{
    return queue_index / 2;
}

/* TODO
 * - we could suppress RX interrupt if we were so inclined.
 */

static void virtio_net_get_config(VirtIODevice *vdev, uint8_t *config)
{
    VirtIONet *n = VIRTIO_NET(vdev);
    struct virtio_net_config netcfg;
    NetClientState *nc = qemu_get_queue(n->nic);
    static const MACAddr zero = { .a = { 0, 0, 0, 0, 0, 0 } };

    int ret = 0;
    memset(&netcfg, 0 , sizeof(struct virtio_net_config));
    virtio_stw_p(vdev, &netcfg.status, n->status);
    virtio_stw_p(vdev, &netcfg.max_virtqueue_pairs, n->max_queue_pairs);
    virtio_stw_p(vdev, &netcfg.mtu, n->net_conf.mtu);
    memcpy(netcfg.mac, n->mac, ETH_ALEN);
    virtio_stl_p(vdev, &netcfg.speed, n->net_conf.speed);
    netcfg.duplex = n->net_conf.duplex;
    netcfg.rss_max_key_size = VIRTIO_NET_RSS_MAX_KEY_SIZE;
    virtio_stw_p(vdev, &netcfg.rss_max_indirection_table_length,
                 virtio_host_has_feature(vdev, VIRTIO_NET_F_RSS) ?
                 VIRTIO_NET_RSS_MAX_TABLE_LEN : 1);
    virtio_stl_p(vdev, &netcfg.supported_hash_types,
                 VIRTIO_NET_RSS_SUPPORTED_HASHES);
    memcpy(config, &netcfg, n->config_size);

    /*
     * Is this VDPA? No peer means not VDPA: there's no way to
     * disconnect/reconnect a VDPA peer.
     */
    if (nc->peer && nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) {
        ret = vhost_net_get_config(get_vhost_net(nc->peer), (uint8_t *)&netcfg,
                                   n->config_size);
        if (ret != -1) {
            /*
             * Some NIC/kernel combinations present 0 as the mac address.  As
             * that is not a legal address, try to proceed with the
             * address from the QEMU command line in the hope that the
             * address has been configured correctly elsewhere - just not
             * reported by the device.
             */
            if (memcmp(&netcfg.mac, &zero, sizeof(zero)) == 0) {
                info_report("Zero hardware mac address detected. Ignoring.");
                memcpy(netcfg.mac, n->mac, ETH_ALEN);
            }
            memcpy(config, &netcfg, n->config_size);
        }
    }
}

static void virtio_net_set_config(VirtIODevice *vdev, const uint8_t *config)
{
    VirtIONet *n = VIRTIO_NET(vdev);
    struct virtio_net_config netcfg = {};
    NetClientState *nc = qemu_get_queue(n->nic);

    memcpy(&netcfg, config, n->config_size);

    if (!virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_MAC_ADDR) &&
        !virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1) &&
        memcmp(netcfg.mac, n->mac, ETH_ALEN)) {
        memcpy(n->mac, netcfg.mac, ETH_ALEN);
        qemu_format_nic_info_str(qemu_get_queue(n->nic), n->mac);
    }

    /*
     * Is this VDPA? No peer means not VDPA: there's no way to
     * disconnect/reconnect a VDPA peer.
     */
    if (nc->peer && nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) {
        vhost_net_set_config(get_vhost_net(nc->peer),
                             (uint8_t *)&netcfg, 0, n->config_size,
                             VHOST_SET_CONFIG_TYPE_MASTER);
      }
}

static bool virtio_net_started(VirtIONet *n, uint8_t status)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    return (status & VIRTIO_CONFIG_S_DRIVER_OK) &&
        (n->status & VIRTIO_NET_S_LINK_UP) && vdev->vm_running;
}

static void virtio_net_announce_notify(VirtIONet *net)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(net);
    trace_virtio_net_announce_notify();

    net->status |= VIRTIO_NET_S_ANNOUNCE;
    virtio_notify_config(vdev);
}

static void virtio_net_announce_timer(void *opaque)
{
    VirtIONet *n = opaque;
    trace_virtio_net_announce_timer(n->announce_timer.round);

    n->announce_timer.round--;
    virtio_net_announce_notify(n);
}

static void virtio_net_announce(NetClientState *nc)
{
    VirtIONet *n = qemu_get_nic_opaque(nc);
    VirtIODevice *vdev = VIRTIO_DEVICE(n);

    /*
     * Make sure the virtio migration announcement timer isn't running
     * If it is, let it trigger announcement so that we do not cause
     * confusion.
     */
    if (n->announce_timer.round) {
        return;
    }

    if (virtio_vdev_has_feature(vdev, VIRTIO_NET_F_GUEST_ANNOUNCE) &&
        virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) {
            virtio_net_announce_notify(n);
    }
}

static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    NetClientState *nc = qemu_get_queue(n->nic);
    int queue_pairs = n->multiqueue ? n->max_queue_pairs : 1;
    int cvq = virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ) ?
              n->max_ncs - n->max_queue_pairs : 0;

    if (!get_vhost_net(nc->peer)) {
        return;
    }

    if ((virtio_net_started(n, status) && !nc->peer->link_down) ==
        !!n->vhost_started) {
        return;
    }
    if (!n->vhost_started) {
        int r, i;

        if (n->needs_vnet_hdr_swap) {
            error_report("backend does not support %s vnet headers; "
                         "falling back on userspace virtio",
                         virtio_is_big_endian(vdev) ? "BE" : "LE");
            return;
        }

        /* Any packets outstanding? Purge them to avoid touching rings
         * when vhost is running.
         */
        for (i = 0;  i < queue_pairs; i++) {
            NetClientState *qnc = qemu_get_subqueue(n->nic, i);

            /* Purge both directions: TX and RX. */
            qemu_net_queue_purge(qnc->peer->incoming_queue, qnc);
            qemu_net_queue_purge(qnc->incoming_queue, qnc->peer);
        }

        if (virtio_has_feature(vdev->guest_features, VIRTIO_NET_F_MTU)) {
            r = vhost_net_set_mtu(get_vhost_net(nc->peer), n->net_conf.mtu);
            if (r < 0) {
                error_report("%uBytes MTU not supported by the backend",
                             n->net_conf.mtu);

                return;
            }
        }

        n->vhost_started = 1;
        r = vhost_net_start(vdev, n->nic->ncs, queue_pairs, cvq);
        if (r < 0) {
            error_report("unable to start vhost net: %d: "
                         "falling back on userspace virtio", -r);
            n->vhost_started = 0;
        }
    } else {
        vhost_net_stop(vdev, n->nic->ncs, queue_pairs, cvq);
        n->vhost_started = 0;
    }
}

static int virtio_net_set_vnet_endian_one(VirtIODevice *vdev,
                                          NetClientState *peer,
                                          bool enable)
{
    if (virtio_is_big_endian(vdev)) {
        return qemu_set_vnet_be(peer, enable);
    } else {
        return qemu_set_vnet_le(peer, enable);
    }
}

static bool virtio_net_set_vnet_endian(VirtIODevice *vdev, NetClientState *ncs,
                                       int queue_pairs, bool enable)
{
    int i;

    for (i = 0; i < queue_pairs; i++) {
        if (virtio_net_set_vnet_endian_one(vdev, ncs[i].peer, enable) < 0 &&
            enable) {
            while (--i >= 0) {
                virtio_net_set_vnet_endian_one(vdev, ncs[i].peer, false);
            }

            return true;
        }
    }

    return false;
}

static void virtio_net_vnet_endian_status(VirtIONet *n, uint8_t status)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    int queue_pairs = n->multiqueue ? n->max_queue_pairs : 1;

    if (virtio_net_started(n, status)) {
        /* Before using the device, we tell the network backend about the
         * endianness to use when parsing vnet headers. If the backend
         * can't do it, we fallback onto fixing the headers in the core
         * virtio-net code.
         */
        n->needs_vnet_hdr_swap = virtio_net_set_vnet_endian(vdev, n->nic->ncs,
                                                            queue_pairs, true);
    } else if (virtio_net_started(n, vdev->status)) {
        /* After using the device, we need to reset the network backend to
         * the default (guest native endianness), otherwise the guest may
         * lose network connectivity if it is rebooted into a different
         * endianness.
         */
        virtio_net_set_vnet_endian(vdev, n->nic->ncs, queue_pairs, false);
    }
}

static void virtio_net_drop_tx_queue_data(VirtIODevice *vdev, VirtQueue *vq)
{
    unsigned int dropped = virtqueue_drop_all(vq);
    if (dropped) {
        virtio_notify(vdev, vq);
    }
}

static void virtio_net_set_status(struct VirtIODevice *vdev, uint8_t status)
{
    VirtIONet *n = VIRTIO_NET(vdev);
    VirtIONetQueue *q;
    int i;
    uint8_t queue_status;

    virtio_net_vnet_endian_status(n, status);
    virtio_net_vhost_status(n, status);

    for (i = 0; i < n->max_queue_pairs; i++) {
        NetClientState *ncs = qemu_get_subqueue(n->nic, i);
        bool queue_started;
        q = &n->vqs[i];

        if ((!n->multiqueue && i != 0) || i >= n->curr_queue_pairs) {
            queue_status = 0;
        } else {
            queue_status = status;
        }
        queue_started =
            virtio_net_started(n, queue_status) && !n->vhost_started;

        if (queue_started) {
            qemu_flush_queued_packets(ncs);
        }

        if (!q->tx_waiting) {
            continue;
        }

        if (queue_started) {
            if (q->tx_timer) {
                timer_mod(q->tx_timer,
                               qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + n->tx_timeout);
            } else {
                qemu_bh_schedule(q->tx_bh);
            }
        } else {
            if (q->tx_timer) {
                timer_del(q->tx_timer);
            } else {
                qemu_bh_cancel(q->tx_bh);
            }
            if ((n->status & VIRTIO_NET_S_LINK_UP) == 0 &&
                (queue_status & VIRTIO_CONFIG_S_DRIVER_OK) &&
                vdev->vm_running) {
                /* if tx is waiting we are likely have some packets in tx queue
                 * and disabled notification */
                q->tx_waiting = 0;
                virtio_queue_set_notification(q->tx_vq, 1);
                virtio_net_drop_tx_queue_data(vdev, q->tx_vq);
            }
        }
    }
}

static void virtio_net_set_link_status(NetClientState *nc)
{
    VirtIONet *n = qemu_get_nic_opaque(nc);
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    uint16_t old_status = n->status;

    if (nc->link_down)
        n->status &= ~VIRTIO_NET_S_LINK_UP;
    else
        n->status |= VIRTIO_NET_S_LINK_UP;

    if (n->status != old_status)
        virtio_notify_config(vdev);

    virtio_net_set_status(vdev, vdev->status);
}

static void rxfilter_notify(NetClientState *nc)
{
    VirtIONet *n = qemu_get_nic_opaque(nc);

    if (nc->rxfilter_notify_enabled) {
        char *path = object_get_canonical_path(OBJECT(n->qdev));
        qapi_event_send_nic_rx_filter_changed(!!n->netclient_name,
                                              n->netclient_name, path);
        g_free(path);

        /* disable event notification to avoid events flooding */
        nc->rxfilter_notify_enabled = 0;
    }
}

static intList *get_vlan_table(VirtIONet *n)
{
    intList *list;
    int i, j;

    list = NULL;
    for (i = 0; i < MAX_VLAN >> 5; i++) {
        for (j = 0; n->vlans[i] && j <= 0x1f; j++) {
            if (n->vlans[i] & (1U << j)) {
                QAPI_LIST_PREPEND(list, (i << 5) + j);
            }
        }
    }

    return list;
}

static RxFilterInfo *virtio_net_query_rxfilter(NetClientState *nc)
{
    VirtIONet *n = qemu_get_nic_opaque(nc);
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    RxFilterInfo *info;
    strList *str_list;
    int i;

    info = g_malloc0(sizeof(*info));
    info->name = g_strdup(nc->name);
    info->promiscuous = n->promisc;

    if (n->nouni) {
        info->unicast = RX_STATE_NONE;
    } else if (n->alluni) {
        info->unicast = RX_STATE_ALL;
    } else {
        info->unicast = RX_STATE_NORMAL;
    }

    if (n->nomulti) {
        info->multicast = RX_STATE_NONE;
    } else if (n->allmulti) {
        info->multicast = RX_STATE_ALL;
    } else {
        info->multicast = RX_STATE_NORMAL;
    }

    info->broadcast_allowed = n->nobcast;
    info->multicast_overflow = n->mac_table.multi_overflow;
    info->unicast_overflow = n->mac_table.uni_overflow;

    info->main_mac = qemu_mac_strdup_printf(n->mac);

    str_list = NULL;
    for (i = 0; i < n->mac_table.first_multi; i++) {
        QAPI_LIST_PREPEND(str_list,
                      qemu_mac_strdup_printf(n->mac_table.macs + i * ETH_ALEN));
    }
    info->unicast_table = str_list;

    str_list = NULL;
    for (i = n->mac_table.first_multi; i < n->mac_table.in_use; i++) {
        QAPI_LIST_PREPEND(str_list,
                      qemu_mac_strdup_printf(n->mac_table.macs + i * ETH_ALEN));
    }
    info->multicast_table = str_list;
    info->vlan_table = get_vlan_table(n);

    if (!virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VLAN)) {
        info->vlan = RX_STATE_ALL;
    } else if (!info->vlan_table) {
        info->vlan = RX_STATE_NONE;
    } else {
        info->vlan = RX_STATE_NORMAL;
    }

    /* enable event notification after query */
    nc->rxfilter_notify_enabled = 1;

    return info;
}

static void virtio_net_reset(VirtIODevice *vdev)
{
    VirtIONet *n = VIRTIO_NET(vdev);
    int i;

    /* Reset back to compatibility mode */
    n->promisc = 1;
    n->allmulti = 0;
    n->alluni = 0;
    n->nomulti = 0;
    n->nouni = 0;
    n->nobcast = 0;
    /* multiqueue is disabled by default */
    n->curr_queue_pairs = 1;
    timer_del(n->announce_timer.tm);
    n->announce_timer.round = 0;
    n->status &= ~VIRTIO_NET_S_ANNOUNCE;

    /* Flush any MAC and VLAN filter table state */
    n->mac_table.in_use = 0;
    n->mac_table.first_multi = 0;
    n->mac_table.multi_overflow = 0;
    n->mac_table.uni_overflow = 0;
    memset(n->mac_table.macs, 0, MAC_TABLE_ENTRIES * ETH_ALEN);
    memcpy(&n->mac[0], &n->nic->conf->macaddr, sizeof(n->mac));
    qemu_format_nic_info_str(qemu_get_queue(n->nic), n->mac);
    memset(n->vlans, 0, MAX_VLAN >> 3);

    /* Flush any async TX */
    for (i = 0;  i < n->max_queue_pairs; i++) {
        NetClientState *nc = qemu_get_subqueue(n->nic, i);

        if (nc->peer) {
            qemu_flush_or_purge_queued_packets(nc->peer, true);
            assert(!virtio_net_get_subqueue(nc)->async_tx.elem);
        }
    }
}

static void peer_test_vnet_hdr(VirtIONet *n)
{
    NetClientState *nc = qemu_get_queue(n->nic);
    if (!nc->peer) {
        return;
    }

    n->has_vnet_hdr = qemu_has_vnet_hdr(nc->peer);
}

static int peer_has_vnet_hdr(VirtIONet *n)
{
    return n->has_vnet_hdr;
}

static int peer_has_ufo(VirtIONet *n)
{
    if (!peer_has_vnet_hdr(n))
        return 0;

    n->has_ufo = qemu_has_ufo(qemu_get_queue(n->nic)->peer);

    return n->has_ufo;
}

static void virtio_net_set_mrg_rx_bufs(VirtIONet *n, int mergeable_rx_bufs,
                                       int version_1, int hash_report)
{
    int i;
    NetClientState *nc;

    n->mergeable_rx_bufs = mergeable_rx_bufs;

    if (version_1) {
        n->guest_hdr_len = hash_report ?
            sizeof(struct virtio_net_hdr_v1_hash) :
            sizeof(struct virtio_net_hdr_mrg_rxbuf);
        n->rss_data.populate_hash = !!hash_report;
    } else {
        n->guest_hdr_len = n->mergeable_rx_bufs ?
            sizeof(struct virtio_net_hdr_mrg_rxbuf) :
            sizeof(struct virtio_net_hdr);
    }

    for (i = 0; i < n->max_queue_pairs; i++) {
        nc = qemu_get_subqueue(n->nic, i);

        if (peer_has_vnet_hdr(n) &&
            qemu_has_vnet_hdr_len(nc->peer, n->guest_hdr_len)) {
            qemu_set_vnet_hdr_len(nc->peer, n->guest_hdr_len);
            n->host_hdr_len = n->guest_hdr_len;
        }
    }
}

static int virtio_net_max_tx_queue_size(VirtIONet *n)
{
    NetClientState *peer = n->nic_conf.peers.ncs[0];

    /*
     * Backends other than vhost-user or vhost-vdpa don't support max queue
     * size.
     */
    if (!peer) {
        return VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE;
    }

    switch(peer->info->type) {
    case NET_CLIENT_DRIVER_VHOST_USER:
    case NET_CLIENT_DRIVER_VHOST_VDPA:
        return VIRTQUEUE_MAX_SIZE;
    default:
        return VIRTIO_NET_TX_QUEUE_DEFAULT_SIZE;
    };
}

static int peer_attach(VirtIONet *n, int index)
{
    NetClientState *nc = qemu_get_subqueue(n->nic, index);

    if (!nc->peer) {
        return 0;
    }

    if (nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_USER) {
        vhost_set_vring_enable(nc->peer, 1);
    }

    if (nc->peer->info->type != NET_CLIENT_DRIVER_TAP) {
        return 0;
    }

    if (n->max_queue_pairs == 1) {
        return 0;
    }

    return tap_enable(nc->peer);
}

static int peer_detach(VirtIONet *n, int index)
{
    NetClientState *nc = qemu_get_subqueue(n->nic, index);

    if (!nc->peer) {
        return 0;
    }

    if (nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_USER) {
        vhost_set_vring_enable(nc->peer, 0);
    }

    if (nc->peer->info->type !=  NET_CLIENT_DRIVER_TAP) {
        return 0;
    }

    return tap_disable(nc->peer);
}

static void virtio_net_set_queue_pairs(VirtIONet *n)
{
    int i;
    int r;

    if (n->nic->peer_deleted) {
        return;
    }

    for (i = 0; i < n->max_queue_pairs; i++) {
        if (i < n->curr_queue_pairs) {
            r = peer_attach(n, i);
            assert(!r);
        } else {
            r = peer_detach(n, i);
            assert(!r);
        }
    }
}

static void virtio_net_set_multiqueue(VirtIONet *n, int multiqueue);

static uint64_t virtio_net_get_features(VirtIODevice *vdev, uint64_t features,
                                        Error **errp)
{
    VirtIONet *n = VIRTIO_NET(vdev);
    NetClientState *nc = qemu_get_queue(n->nic);

    /* Firstly sync all virtio-net possible supported features */
    features |= n->host_features;

    virtio_add_feature(&features, VIRTIO_NET_F_MAC);

    if (!peer_has_vnet_hdr(n)) {
        virtio_clear_feature(&features, VIRTIO_NET_F_CSUM);
        virtio_clear_feature(&features, VIRTIO_NET_F_HOST_TSO4);
        virtio_clear_feature(&features, VIRTIO_NET_F_HOST_TSO6);
        virtio_clear_feature(&features, VIRTIO_NET_F_HOST_ECN);

        virtio_clear_feature(&features, VIRTIO_NET_F_GUEST_CSUM);
        virtio_clear_feature(&features, VIRTIO_NET_F_GUEST_TSO4);
        virtio_clear_feature(&features, VIRTIO_NET_F_GUEST_TSO6);
        virtio_clear_feature(&features, VIRTIO_NET_F_GUEST_ECN);

        virtio_clear_feature(&features, VIRTIO_NET_F_HASH_REPORT);
    }

    if (!peer_has_vnet_hdr(n) || !peer_has_ufo(n)) {
        virtio_clear_feature(&features, VIRTIO_NET_F_GUEST_UFO);
        virtio_clear_feature(&features, VIRTIO_NET_F_HOST_UFO);
    }

    if (!get_vhost_net(nc->peer)) {
        return features;
    }

    if (!ebpf_rss_is_loaded(&n->ebpf_rss)) {
        virtio_clear_feature(&features, VIRTIO_NET_F_RSS);
    }
    features = vhost_net_get_features(get_vhost_net(nc->peer), features);
    vdev->backend_features = features;

    if (n->mtu_bypass_backend &&
            (n->host_features & 1ULL << VIRTIO_NET_F_MTU)) {
        features |= (1ULL << VIRTIO_NET_F_MTU);
    }

    return features;
}

static uint64_t virtio_net_bad_features(VirtIODevice *vdev)
{
    uint64_t features = 0;

    /* Linux kernel 2.6.25.  It understood MAC (as everyone must),
     * but also these: */
    virtio_add_feature(&features, VIRTIO_NET_F_MAC);
    virtio_add_feature(&features, VIRTIO_NET_F_CSUM);
    virtio_add_feature(&features, VIRTIO_NET_F_HOST_TSO4);
    virtio_add_feature(&features, VIRTIO_NET_F_HOST_TSO6);
    virtio_add_feature(&features, VIRTIO_NET_F_HOST_ECN);

    return features;
}

static void virtio_net_apply_guest_offloads(VirtIONet *n)
{
    qemu_set_offload(qemu_get_queue(n->nic)->peer,
            !!(n->curr_guest_offloads & (1ULL << VIRTIO_NET_F_GUEST_CSUM)),
            !!(n->curr_guest_offloads & (1ULL << VIRTIO_NET_F_GUEST_TSO4)),
            !!(n->curr_guest_offloads & (1ULL << VIRTIO_NET_F_GUEST_TSO6)),
            !!(n->curr_guest_offloads & (1ULL << VIRTIO_NET_F_GUEST_ECN)),
            !!(n->curr_guest_offloads & (1ULL << VIRTIO_NET_F_GUEST_UFO)));
}

static uint64_t virtio_net_guest_offloads_by_features(uint32_t features)
{
    static const uint64_t guest_offloads_mask =
        (1ULL << VIRTIO_NET_F_GUEST_CSUM) |
        (1ULL << VIRTIO_NET_F_GUEST_TSO4) |
        (1ULL << VIRTIO_NET_F_GUEST_TSO6) |
        (1ULL << VIRTIO_NET_F_GUEST_ECN)  |
        (1ULL << VIRTIO_NET_F_GUEST_UFO);

    return guest_offloads_mask & features;
}

static inline uint64_t virtio_net_supported_guest_offloads(VirtIONet *n)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    return virtio_net_guest_offloads_by_features(vdev->guest_features);
}

typedef struct {
    VirtIONet *n;
    DeviceState *dev;
} FailoverDevice;

/**
 * Set the failover primary device
 *
 * @opaque: FailoverId to setup
 * @opts: opts for device we are handling
 * @errp: returns an error if this function fails
 */
static int failover_set_primary(DeviceState *dev, void *opaque)
{
    FailoverDevice *fdev = opaque;
    PCIDevice *pci_dev = (PCIDevice *)
        object_dynamic_cast(OBJECT(dev), TYPE_PCI_DEVICE);

    if (!pci_dev) {
        return 0;
    }

    if (!g_strcmp0(pci_dev->failover_pair_id, fdev->n->netclient_name)) {
        fdev->dev = dev;
        return 1;
    }

    return 0;
}

/**
 * Find the primary device for this failover virtio-net
 *
 * @n: VirtIONet device
 * @errp: returns an error if this function fails
 */
static DeviceState *failover_find_primary_device(VirtIONet *n)
{
    FailoverDevice fdev = {
        .n = n,
    };

    qbus_walk_children(sysbus_get_default(), failover_set_primary, NULL,
                       NULL, NULL, &fdev);
    return fdev.dev;
}

static void failover_add_primary(VirtIONet *n, Error **errp)
{
    Error *err = NULL;
    DeviceState *dev = failover_find_primary_device(n);

    if (dev) {
        return;
    }

    if (!n->primary_opts) {
        error_setg(errp, "Primary device not found");
        error_append_hint(errp, "Virtio-net failover will not work. Make "
                          "sure primary device has parameter"
                          " failover_pair_id=%s\n", n->netclient_name);
        return;
    }

    dev = qdev_device_add_from_qdict(n->primary_opts,
                                     n->primary_opts_from_json,
                                     &err);
    if (err) {
        qobject_unref(n->primary_opts);
        n->primary_opts = NULL;
    } else {
        object_unref(OBJECT(dev));
    }
    error_propagate(errp, err);
}

static void virtio_net_set_features(VirtIODevice *vdev, uint64_t features)
{
    VirtIONet *n = VIRTIO_NET(vdev);
    Error *err = NULL;
    int i;

    if (n->mtu_bypass_backend &&
            !virtio_has_feature(vdev->backend_features, VIRTIO_NET_F_MTU)) {
        features &= ~(1ULL << VIRTIO_NET_F_MTU);
    }

    virtio_net_set_multiqueue(n,
                              virtio_has_feature(features, VIRTIO_NET_F_RSS) ||
                              virtio_has_feature(features, VIRTIO_NET_F_MQ));

    virtio_net_set_mrg_rx_bufs(n,
                               virtio_has_feature(features,
                                                  VIRTIO_NET_F_MRG_RXBUF),
                               virtio_has_feature(features,
                                                  VIRTIO_F_VERSION_1),
                               virtio_has_feature(features,
                                                  VIRTIO_NET_F_HASH_REPORT));

    n->rsc4_enabled = virtio_has_feature(features, VIRTIO_NET_F_RSC_EXT) &&
        virtio_has_feature(features, VIRTIO_NET_F_GUEST_TSO4);
    n->rsc6_enabled = virtio_has_feature(features, VIRTIO_NET_F_RSC_EXT) &&
        virtio_has_feature(features, VIRTIO_NET_F_GUEST_TSO6);
    n->rss_data.redirect = virtio_has_feature(features, VIRTIO_NET_F_RSS);

    if (n->has_vnet_hdr) {
        n->curr_guest_offloads =
            virtio_net_guest_offloads_by_features(features);
        virtio_net_apply_guest_offloads(n);
    }

    for (i = 0;  i < n->max_queue_pairs; i++) {
        NetClientState *nc = qemu_get_subqueue(n->nic, i);

        if (!get_vhost_net(nc->peer)) {
            continue;
        }
        vhost_net_ack_features(get_vhost_net(nc->peer), features);
    }

    if (virtio_has_feature(features, VIRTIO_NET_F_CTRL_VLAN)) {
        memset(n->vlans, 0, MAX_VLAN >> 3);
    } else {
        memset(n->vlans, 0xff, MAX_VLAN >> 3);
    }

    if (virtio_has_feature(features, VIRTIO_NET_F_STANDBY)) {
        qapi_event_send_failover_negotiated(n->netclient_name);
        qatomic_set(&n->failover_primary_hidden, false);
        failover_add_primary(n, &err);
        if (err) {
            if (!qtest_enabled()) {
                warn_report_err(err);
            } else {
                error_free(err);
            }
        }
    }
}

static int virtio_net_handle_rx_mode(VirtIONet *n, uint8_t cmd,
                                     struct iovec *iov, unsigned int iov_cnt)
{
    uint8_t on;
    size_t s;
    NetClientState *nc = qemu_get_queue(n->nic);

    s = iov_to_buf(iov, iov_cnt, 0, &on, sizeof(on));
    if (s != sizeof(on)) {
        return VIRTIO_NET_ERR;
    }

    if (cmd == VIRTIO_NET_CTRL_RX_PROMISC) {
        n->promisc = on;
    } else if (cmd == VIRTIO_NET_CTRL_RX_ALLMULTI) {
        n->allmulti = on;
    } else if (cmd == VIRTIO_NET_CTRL_RX_ALLUNI) {
        n->alluni = on;
    } else if (cmd == VIRTIO_NET_CTRL_RX_NOMULTI) {
        n->nomulti = on;
    } else if (cmd == VIRTIO_NET_CTRL_RX_NOUNI) {
        n->nouni = on;
    } else if (cmd == VIRTIO_NET_CTRL_RX_NOBCAST) {
        n->nobcast = on;
    } else {
        return VIRTIO_NET_ERR;
    }

    rxfilter_notify(nc);

    return VIRTIO_NET_OK;
}

static int virtio_net_handle_offloads(VirtIONet *n, uint8_t cmd,
                                     struct iovec *iov, unsigned int iov_cnt)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    uint64_t offloads;
    size_t s;

    if (!virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)) {
        return VIRTIO_NET_ERR;
    }

    s = iov_to_buf(iov, iov_cnt, 0, &offloads, sizeof(offloads));
    if (s != sizeof(offloads)) {
        return VIRTIO_NET_ERR;
    }

    if (cmd == VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET) {
        uint64_t supported_offloads;

        offloads = virtio_ldq_p(vdev, &offloads);

        if (!n->has_vnet_hdr) {
            return VIRTIO_NET_ERR;
        }

        n->rsc4_enabled = virtio_has_feature(offloads, VIRTIO_NET_F_RSC_EXT) &&
            virtio_has_feature(offloads, VIRTIO_NET_F_GUEST_TSO4);
        n->rsc6_enabled = virtio_has_feature(offloads, VIRTIO_NET_F_RSC_EXT) &&
            virtio_has_feature(offloads, VIRTIO_NET_F_GUEST_TSO6);
        virtio_clear_feature(&offloads, VIRTIO_NET_F_RSC_EXT);

        supported_offloads = virtio_net_supported_guest_offloads(n);
        if (offloads & ~supported_offloads) {
            return VIRTIO_NET_ERR;
        }

        n->curr_guest_offloads = offloads;
        virtio_net_apply_guest_offloads(n);

        return VIRTIO_NET_OK;
    } else {
        return VIRTIO_NET_ERR;
    }
}

static int virtio_net_handle_mac(VirtIONet *n, uint8_t cmd,
                                 struct iovec *iov, unsigned int iov_cnt)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    struct virtio_net_ctrl_mac mac_data;
    size_t s;
    NetClientState *nc = qemu_get_queue(n->nic);

    if (cmd == VIRTIO_NET_CTRL_MAC_ADDR_SET) {
        if (iov_size(iov, iov_cnt) != sizeof(n->mac)) {
            return VIRTIO_NET_ERR;
        }
        s = iov_to_buf(iov, iov_cnt, 0, &n->mac, sizeof(n->mac));
        assert(s == sizeof(n->mac));
        qemu_format_nic_info_str(qemu_get_queue(n->nic), n->mac);
        rxfilter_notify(nc);

        return VIRTIO_NET_OK;
    }

    if (cmd != VIRTIO_NET_CTRL_MAC_TABLE_SET) {
        return VIRTIO_NET_ERR;
    }

    int in_use = 0;
    int first_multi = 0;
    uint8_t uni_overflow = 0;
    uint8_t multi_overflow = 0;
    uint8_t *macs = g_malloc0(MAC_TABLE_ENTRIES * ETH_ALEN);

    s = iov_to_buf(iov, iov_cnt, 0, &mac_data.entries,
                   sizeof(mac_data.entries));
    mac_data.entries = virtio_ldl_p(vdev, &mac_data.entries);
    if (s != sizeof(mac_data.entries)) {
        goto error;
    }
    iov_discard_front(&iov, &iov_cnt, s);

    if (mac_data.entries * ETH_ALEN > iov_size(iov, iov_cnt)) {
        goto error;
    }

    if (mac_data.entries <= MAC_TABLE_ENTRIES) {
        s = iov_to_buf(iov, iov_cnt, 0, macs,
                       mac_data.entries * ETH_ALEN);
        if (s != mac_data.entries * ETH_ALEN) {
            goto error;
        }
        in_use += mac_data.entries;
    } else {
        uni_overflow = 1;
    }

    iov_discard_front(&iov, &iov_cnt, mac_data.entries * ETH_ALEN);

    first_multi = in_use;

    s = iov_to_buf(iov, iov_cnt, 0, &mac_data.entries,
                   sizeof(mac_data.entries));
    mac_data.entries = virtio_ldl_p(vdev, &mac_data.entries);
    if (s != sizeof(mac_data.entries)) {
        goto error;
    }

    iov_discard_front(&iov, &iov_cnt, s);

    if (mac_data.entries * ETH_ALEN != iov_size(iov, iov_cnt)) {
        goto error;
    }

    if (mac_data.entries <= MAC_TABLE_ENTRIES - in_use) {
        s = iov_to_buf(iov, iov_cnt, 0, &macs[in_use * ETH_ALEN],
                       mac_data.entries * ETH_ALEN);
        if (s != mac_data.entries * ETH_ALEN) {
            goto error;
        }
        in_use += mac_data.entries;
    } else {
        multi_overflow = 1;
    }

    n->mac_table.in_use = in_use;
    n->mac_table.first_multi = first_multi;
    n->mac_table.uni_overflow = uni_overflow;
    n->mac_table.multi_overflow = multi_overflow;
    memcpy(n->mac_table.macs, macs, MAC_TABLE_ENTRIES * ETH_ALEN);
    g_free(macs);
    rxfilter_notify(nc);

    return VIRTIO_NET_OK;

error:
    g_free(macs);
    return VIRTIO_NET_ERR;
}

static int virtio_net_handle_vlan_table(VirtIONet *n, uint8_t cmd,
                                        struct iovec *iov, unsigned int iov_cnt)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    uint16_t vid;
    size_t s;
    NetClientState *nc = qemu_get_queue(n->nic);

    s = iov_to_buf(iov, iov_cnt, 0, &vid, sizeof(vid));
    vid = virtio_lduw_p(vdev, &vid);
    if (s != sizeof(vid)) {
        return VIRTIO_NET_ERR;
    }

    if (vid >= MAX_VLAN)
        return VIRTIO_NET_ERR;

    if (cmd == VIRTIO_NET_CTRL_VLAN_ADD)
        n->vlans[vid >> 5] |= (1U << (vid & 0x1f));
    else if (cmd == VIRTIO_NET_CTRL_VLAN_DEL)
        n->vlans[vid >> 5] &= ~(1U << (vid & 0x1f));
    else
        return VIRTIO_NET_ERR;

    rxfilter_notify(nc);

    return VIRTIO_NET_OK;
}

static int virtio_net_handle_announce(VirtIONet *n, uint8_t cmd,
                                      struct iovec *iov, unsigned int iov_cnt)
{
    trace_virtio_net_handle_announce(n->announce_timer.round);
    if (cmd == VIRTIO_NET_CTRL_ANNOUNCE_ACK &&
        n->status & VIRTIO_NET_S_ANNOUNCE) {
        n->status &= ~VIRTIO_NET_S_ANNOUNCE;
        if (n->announce_timer.round) {
            qemu_announce_timer_step(&n->announce_timer);
        }
        return VIRTIO_NET_OK;
    } else {
        return VIRTIO_NET_ERR;
    }
}

static void virtio_net_detach_epbf_rss(VirtIONet *n);

static void virtio_net_disable_rss(VirtIONet *n)
{
    if (n->rss_data.enabled) {
        trace_virtio_net_rss_disable();
    }
    n->rss_data.enabled = false;

    virtio_net_detach_epbf_rss(n);
}

static bool virtio_net_attach_ebpf_to_backend(NICState *nic, int prog_fd)
{
    NetClientState *nc = qemu_get_peer(qemu_get_queue(nic), 0);
    if (nc == NULL || nc->info->set_steering_ebpf == NULL) {
        return false;
    }

    return nc->info->set_steering_ebpf(nc, prog_fd);
}

static void rss_data_to_rss_config(struct VirtioNetRssData *data,
                                   struct EBPFRSSConfig *config)
{
    config->redirect = data->redirect;
    config->populate_hash = data->populate_hash;
    config->hash_types = data->hash_types;
    config->indirections_len = data->indirections_len;
    config->default_queue = data->default_queue;
}

static bool virtio_net_attach_epbf_rss(VirtIONet *n)
{
    struct EBPFRSSConfig config = {};

    if (!ebpf_rss_is_loaded(&n->ebpf_rss)) {
        return false;
    }

    rss_data_to_rss_config(&n->rss_data, &config);

    if (!ebpf_rss_set_all(&n->ebpf_rss, &config,
                          n->rss_data.indirections_table, n->rss_data.key)) {
        return false;
    }

    if (!virtio_net_attach_ebpf_to_backend(n->nic, n->ebpf_rss.program_fd)) {
        return false;
    }

    return true;
}

static void virtio_net_detach_epbf_rss(VirtIONet *n)
{
    virtio_net_attach_ebpf_to_backend(n->nic, -1);
}

static bool virtio_net_load_ebpf(VirtIONet *n)
{
    if (!virtio_net_attach_ebpf_to_backend(n->nic, -1)) {
        /* backend does't support steering ebpf */
        return false;
    }

    return ebpf_rss_load(&n->ebpf_rss);
}

static void virtio_net_unload_ebpf(VirtIONet *n)
{
    virtio_net_attach_ebpf_to_backend(n->nic, -1);
    ebpf_rss_unload(&n->ebpf_rss);
}

static uint16_t virtio_net_handle_rss(VirtIONet *n,
                                      struct iovec *iov,
                                      unsigned int iov_cnt,
                                      bool do_rss)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    struct virtio_net_rss_config cfg;
    size_t s, offset = 0, size_get;
    uint16_t queue_pairs, i;
    struct {
        uint16_t us;
        uint8_t b;
    } QEMU_PACKED temp;
    const char *err_msg = "";
    uint32_t err_value = 0;

    if (do_rss && !virtio_vdev_has_feature(vdev, VIRTIO_NET_F_RSS)) {
        err_msg = "RSS is not negotiated";
        goto error;
    }
    if (!do_rss && !virtio_vdev_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT)) {
        err_msg = "Hash report is not negotiated";
        goto error;
    }
    size_get = offsetof(struct virtio_net_rss_config, indirection_table);
    s = iov_to_buf(iov, iov_cnt, offset, &cfg, size_get);
    if (s != size_get) {
        err_msg = "Short command buffer";
        err_value = (uint32_t)s;
        goto error;
    }
    n->rss_data.hash_types = virtio_ldl_p(vdev, &cfg.hash_types);
    n->rss_data.indirections_len =
        virtio_lduw_p(vdev, &cfg.indirection_table_mask);
    n->rss_data.indirections_len++;
    if (!do_rss) {
        n->rss_data.indirections_len = 1;
    }
    if (!is_power_of_2(n->rss_data.indirections_len)) {
        err_msg = "Invalid size of indirection table";
        err_value = n->rss_data.indirections_len;
        goto error;
    }
    if (n->rss_data.indirections_len > VIRTIO_NET_RSS_MAX_TABLE_LEN) {
        err_msg = "Too large indirection table";
        err_value = n->rss_data.indirections_len;
        goto error;
    }
    n->rss_data.default_queue = do_rss ?
        virtio_lduw_p(vdev, &cfg.unclassified_queue) : 0;
    if (n->rss_data.default_queue >= n->max_queue_pairs) {
        err_msg = "Invalid default queue";
        err_value = n->rss_data.default_queue;
        goto error;
    }
    offset += size_get;
    size_get = sizeof(uint16_t) * n->rss_data.indirections_len;
    g_free(n->rss_data.indirections_table);
    n->rss_data.indirections_table = g_malloc(size_get);
    if (!n->rss_data.indirections_table) {
        err_msg = "Can't allocate indirections table";
        err_value = n->rss_data.indirections_len;
        goto error;
    }
    s = iov_to_buf(iov, iov_cnt, offset,
                   n->rss_data.indirections_table, size_get);
    if (s != size_get) {
        err_msg = "Short indirection table buffer";
        err_value = (uint32_t)s;
        goto error;
    }
    for (i = 0; i < n->rss_data.indirections_len; ++i) {
        uint16_t val = n->rss_data.indirections_table[i];
        n->rss_data.indirections_table[i] = virtio_lduw_p(vdev, &val);
    }
    offset += size_get;
    size_get = sizeof(temp);
    s = iov_to_buf(iov, iov_cnt, offset, &temp, size_get);
    if (s != size_get) {
        err_msg = "Can't get queue_pairs";
        err_value = (uint32_t)s;
        goto error;
    }
    queue_pairs = do_rss ? virtio_lduw_p(vdev, &temp.us) : n->curr_queue_pairs;
    if (queue_pairs == 0 || queue_pairs > n->max_queue_pairs) {
        err_msg = "Invalid number of queue_pairs";
        err_value = queue_pairs;
        goto error;
    }
    if (temp.b > VIRTIO_NET_RSS_MAX_KEY_SIZE) {
        err_msg = "Invalid key size";
        err_value = temp.b;
        goto error;
    }
    if (!temp.b && n->rss_data.hash_types) {
        err_msg = "No key provided";
        err_value = 0;
        goto error;
    }
    if (!temp.b && !n->rss_data.hash_types) {
        virtio_net_disable_rss(n);
        return queue_pairs;
    }
    offset += size_get;
    size_get = temp.b;
    s = iov_to_buf(iov, iov_cnt, offset, n->rss_data.key, size_get);
    if (s != size_get) {
        err_msg = "Can get key buffer";
        err_value = (uint32_t)s;
        goto error;
    }
    n->rss_data.enabled = true;

    if (!n->rss_data.populate_hash) {
        if (!virtio_net_attach_epbf_rss(n)) {
            /* EBPF must be loaded for vhost */
            if (get_vhost_net(qemu_get_queue(n->nic)->peer)) {
                warn_report("Can't load eBPF RSS for vhost");
                goto error;
            }
            /* fallback to software RSS */
            warn_report("Can't load eBPF RSS - fallback to software RSS");
            n->rss_data.enabled_software_rss = true;
        }
    } else {
        /* use software RSS for hash populating */
        /* and detach eBPF if was loaded before */
        virtio_net_detach_epbf_rss(n);
        n->rss_data.enabled_software_rss = true;
    }

    trace_virtio_net_rss_enable(n->rss_data.hash_types,
                                n->rss_data.indirections_len,
                                temp.b);
    return queue_pairs;
error:
    trace_virtio_net_rss_error(err_msg, err_value);
    virtio_net_disable_rss(n);
    return 0;
}

static int virtio_net_handle_mq(VirtIONet *n, uint8_t cmd,
                                struct iovec *iov, unsigned int iov_cnt)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    uint16_t queue_pairs;
    NetClientState *nc = qemu_get_queue(n->nic);

    virtio_net_disable_rss(n);
    if (cmd == VIRTIO_NET_CTRL_MQ_HASH_CONFIG) {
        queue_pairs = virtio_net_handle_rss(n, iov, iov_cnt, false);
        return queue_pairs ? VIRTIO_NET_OK : VIRTIO_NET_ERR;
    }
    if (cmd == VIRTIO_NET_CTRL_MQ_RSS_CONFIG) {
        queue_pairs = virtio_net_handle_rss(n, iov, iov_cnt, true);
    } else if (cmd == VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET) {
        struct virtio_net_ctrl_mq mq;
        size_t s;
        if (!virtio_vdev_has_feature(vdev, VIRTIO_NET_F_MQ)) {
            return VIRTIO_NET_ERR;
        }
        s = iov_to_buf(iov, iov_cnt, 0, &mq, sizeof(mq));
        if (s != sizeof(mq)) {
            return VIRTIO_NET_ERR;
        }
        queue_pairs = virtio_lduw_p(vdev, &mq.virtqueue_pairs);

    } else {
        return VIRTIO_NET_ERR;
    }

    if (queue_pairs < VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN ||
        queue_pairs > VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX ||
        queue_pairs > n->max_queue_pairs ||
        !n->multiqueue) {
        return VIRTIO_NET_ERR;
    }

    /* Avoid changing the number of queue_pairs for vdpa device in
     * userspace handler. A future fix is needed to handle the mq
     * change in userspace handler with vhost-vdpa. Let's disable
     * the mq handling from userspace for now and only allow get
     * done through the kernel. Ripples may be seen when falling
     * back to userspace, but without doing it qemu process would
     * crash on a recursive entry to virtio_net_set_status().
     */
    if (nc->peer && nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) {
        return VIRTIO_NET_ERR;
    }

    n->curr_queue_pairs = queue_pairs;
    /* stop the backend before changing the number of queue_pairs to avoid handling a
     * disabled queue */
    virtio_net_set_status(vdev, vdev->status);
    virtio_net_set_queue_pairs(n);

    return VIRTIO_NET_OK;
}

size_t virtio_net_handle_ctrl_iov(VirtIODevice *vdev,
                                  const struct iovec *in_sg, unsigned in_num,
                                  const struct iovec *out_sg,
                                  unsigned out_num)
{
    VirtIONet *n = VIRTIO_NET(vdev);
    struct virtio_net_ctrl_hdr ctrl;
    virtio_net_ctrl_ack status = VIRTIO_NET_ERR;
    size_t s;
    struct iovec *iov, *iov2;

    if (iov_size(in_sg, in_num) < sizeof(status) ||
        iov_size(out_sg, out_num) < sizeof(ctrl)) {
        virtio_error(vdev, "virtio-net ctrl missing headers");
        return 0;
    }

    iov2 = iov = g_memdup2(out_sg, sizeof(struct iovec) * out_num);
    s = iov_to_buf(iov, out_num, 0, &ctrl, sizeof(ctrl));
    iov_discard_front(&iov, &out_num, sizeof(ctrl));
    if (s != sizeof(ctrl)) {
        status = VIRTIO_NET_ERR;
    } else if (ctrl.class == VIRTIO_NET_CTRL_RX) {
        status = virtio_net_handle_rx_mode(n, ctrl.cmd, iov, out_num);
    } else if (ctrl.class == VIRTIO_NET_CTRL_MAC) {
        status = virtio_net_handle_mac(n, ctrl.cmd, iov, out_num);
    } else if (ctrl.class == VIRTIO_NET_CTRL_VLAN) {
        status = virtio_net_handle_vlan_table(n, ctrl.cmd, iov, out_num);
    } else if (ctrl.class == VIRTIO_NET_CTRL_ANNOUNCE) {
        status = virtio_net_handle_announce(n, ctrl.cmd, iov, out_num);
    } else if (ctrl.class == VIRTIO_NET_CTRL_MQ) {
        status = virtio_net_handle_mq(n, ctrl.cmd, iov, out_num);
    } else if (ctrl.class == VIRTIO_NET_CTRL_GUEST_OFFLOADS) {
        status = virtio_net_handle_offloads(n, ctrl.cmd, iov, out_num);
    }

    s = iov_from_buf(in_sg, in_num, 0, &status, sizeof(status));
    assert(s == sizeof(status));

    g_free(iov2);
    return sizeof(status);
}

static void virtio_net_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
{
    VirtQueueElement *elem;

    for (;;) {
        size_t written;
        elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
        if (!elem) {
            break;
        }

        written = virtio_net_handle_ctrl_iov(vdev, elem->in_sg, elem->in_num,
                                             elem->out_sg, elem->out_num);
        if (written > 0) {
            virtqueue_push(vq, elem, written);
            virtio_notify(vdev, vq);
            g_free(elem);
        } else {
            virtqueue_detach_element(vq, elem, 0);
            g_free(elem);
            break;
        }
    }
}

/* RX */

static void virtio_net_handle_rx(VirtIODevice *vdev, VirtQueue *vq)
{
    VirtIONet *n = VIRTIO_NET(vdev);
    int queue_index = vq2q(virtio_get_queue_index(vq));

    qemu_flush_queued_packets(qemu_get_subqueue(n->nic, queue_index));
}

static bool virtio_net_can_receive(NetClientState *nc)
{
    VirtIONet *n = qemu_get_nic_opaque(nc);
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    VirtIONetQueue *q = virtio_net_get_subqueue(nc);

    if (!vdev->vm_running) {
        return false;
    }

    if (nc->queue_index >= n->curr_queue_pairs) {
        return false;
    }

    if (!virtio_queue_ready(q->rx_vq) ||
        !(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
        return false;
    }

    return true;
}

static int virtio_net_has_buffers(VirtIONetQueue *q, int bufsize)
{
    VirtIONet *n = q->n;
    if (virtio_queue_empty(q->rx_vq) ||
        (n->mergeable_rx_bufs &&
         !virtqueue_avail_bytes(q->rx_vq, bufsize, 0))) {
        virtio_queue_set_notification(q->rx_vq, 1);

        /* To avoid a race condition where the guest has made some buffers
         * available after the above check but before notification was
         * enabled, check for available buffers again.
         */
        if (virtio_queue_empty(q->rx_vq) ||
            (n->mergeable_rx_bufs &&
             !virtqueue_avail_bytes(q->rx_vq, bufsize, 0))) {
            return 0;
        }
    }

    virtio_queue_set_notification(q->rx_vq, 0);
    return 1;
}

static void virtio_net_hdr_swap(VirtIODevice *vdev, struct virtio_net_hdr *hdr)
{
    virtio_tswap16s(vdev, &hdr->hdr_len);
    virtio_tswap16s(vdev, &hdr->gso_size);
    virtio_tswap16s(vdev, &hdr->csum_start);
    virtio_tswap16s(vdev, &hdr->csum_offset);
}

/* dhclient uses AF_PACKET but doesn't pass auxdata to the kernel so
 * it never finds out that the packets don't have valid checksums.  This
 * causes dhclient to get upset.  Fedora's carried a patch for ages to
 * fix this with Xen but it hasn't appeared in an upstream release of
 * dhclient yet.
 *
 * To avoid breaking existing guests, we catch udp packets and add
 * checksums.  This is terrible but it's better than hacking the guest
 * kernels.
 *
 * N.B. if we introduce a zero-copy API, this operation is no longer free so
 * we should provide a mechanism to disable it to avoid polluting the host
 * cache.
 */
static void work_around_broken_dhclient(struct virtio_net_hdr *hdr,
                                        uint8_t *buf, size_t size)
{
    if ((hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) && /* missing csum */
        (size > 27 && size < 1500) && /* normal sized MTU */
        (buf[12] == 0x08 && buf[13] == 0x00) && /* ethertype == IPv4 */
        (buf[23] == 17) && /* ip.protocol == UDP */
        (buf[34] == 0 && buf[35] == 67)) { /* udp.srcport == bootps */
        net_checksum_calculate(buf, size, CSUM_UDP);
        hdr->flags &= ~VIRTIO_NET_HDR_F_NEEDS_CSUM;
    }
}

static void receive_header(VirtIONet *n, const struct iovec *iov, int iov_cnt,
                           const void *buf, size_t size)
{
    if (n->has_vnet_hdr) {
        /* FIXME this cast is evil */
        void *wbuf = (void *)buf;
        work_around_broken_dhclient(wbuf, wbuf + n->host_hdr_len,
                                    size - n->host_hdr_len);

        if (n->needs_vnet_hdr_swap) {
            virtio_net_hdr_swap(VIRTIO_DEVICE(n), wbuf);
        }
        iov_from_buf(iov, iov_cnt, 0, buf, sizeof(struct virtio_net_hdr));
    } else {
        struct virtio_net_hdr hdr = {
            .flags = 0,
            .gso_type = VIRTIO_NET_HDR_GSO_NONE
        };
        iov_from_buf(iov, iov_cnt, 0, &hdr, sizeof hdr);
    }
}

static int receive_filter(VirtIONet *n, const uint8_t *buf, int size)
{
    static const uint8_t bcast[] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
    static const uint8_t vlan[] = {0x81, 0x00};
    uint8_t *ptr = (uint8_t *)buf;
    int i;

    if (n->promisc)
        return 1;

    ptr += n->host_hdr_len;

    if (!memcmp(&ptr[12], vlan, sizeof(vlan))) {
        int vid = lduw_be_p(ptr + 14) & 0xfff;
        if (!(n->vlans[vid >> 5] & (1U << (vid & 0x1f))))
            return 0;
    }

    if (ptr[0] & 1) { // multicast
        if (!memcmp(ptr, bcast, sizeof(bcast))) {
            return !n->nobcast;
        } else if (n->nomulti) {
            return 0;
        } else if (n->allmulti || n->mac_table.multi_overflow) {
            return 1;
        }

        for (i = n->mac_table.first_multi; i < n->mac_table.in_use; i++) {
            if (!memcmp(ptr, &n->mac_table.macs[i * ETH_ALEN], ETH_ALEN)) {
                return 1;
            }
        }
    } else { // unicast
        if (n->nouni) {
            return 0;
        } else if (n->alluni || n->mac_table.uni_overflow) {
            return 1;
        } else if (!memcmp(ptr, n->mac, ETH_ALEN)) {
            return 1;
        }

        for (i = 0; i < n->mac_table.first_multi; i++) {
            if (!memcmp(ptr, &n->mac_table.macs[i * ETH_ALEN], ETH_ALEN)) {
                return 1;
            }
        }
    }

    return 0;
}

static uint8_t virtio_net_get_hash_type(bool isip4,
                                        bool isip6,
                                        bool isudp,
                                        bool istcp,
                                        uint32_t types)
{
    if (isip4) {
        if (istcp && (types & VIRTIO_NET_RSS_HASH_TYPE_TCPv4)) {
            return NetPktRssIpV4Tcp;
        }
        if (isudp && (types & VIRTIO_NET_RSS_HASH_TYPE_UDPv4)) {
            return NetPktRssIpV4Udp;
        }
        if (types & VIRTIO_NET_RSS_HASH_TYPE_IPv4) {
            return NetPktRssIpV4;
        }
    } else if (isip6) {
        uint32_t mask = VIRTIO_NET_RSS_HASH_TYPE_TCP_EX |
                        VIRTIO_NET_RSS_HASH_TYPE_TCPv6;

        if (istcp && (types & mask)) {
            return (types & VIRTIO_NET_RSS_HASH_TYPE_TCP_EX) ?
                NetPktRssIpV6TcpEx : NetPktRssIpV6Tcp;
        }
        mask = VIRTIO_NET_RSS_HASH_TYPE_UDP_EX | VIRTIO_NET_RSS_HASH_TYPE_UDPv6;
        if (isudp && (types & mask)) {
            return (types & VIRTIO_NET_RSS_HASH_TYPE_UDP_EX) ?
                NetPktRssIpV6UdpEx : NetPktRssIpV6Udp;
        }
        mask = VIRTIO_NET_RSS_HASH_TYPE_IP_EX | VIRTIO_NET_RSS_HASH_TYPE_IPv6;
        if (types & mask) {
            return (types & VIRTIO_NET_RSS_HASH_TYPE_IP_EX) ?
                NetPktRssIpV6Ex : NetPktRssIpV6;
        }
    }
    return 0xff;
}

static void virtio_set_packet_hash(const uint8_t *buf, uint8_t report,
                                   uint32_t hash)
{
    struct virtio_net_hdr_v1_hash *hdr = (void *)buf;
    hdr->hash_value = hash;
    hdr->hash_report = report;
}

static int virtio_net_process_rss(NetClientState *nc, const uint8_t *buf,
                                  size_t size)
{
    VirtIONet *n = qemu_get_nic_opaque(nc);
    unsigned int index = nc->queue_index, new_index = index;
    struct NetRxPkt *pkt = n->rx_pkt;
    uint8_t net_hash_type;
    uint32_t hash;
    bool isip4, isip6, isudp, istcp;
    static const uint8_t reports[NetPktRssIpV6UdpEx + 1] = {
        VIRTIO_NET_HASH_REPORT_IPv4,
        VIRTIO_NET_HASH_REPORT_TCPv4,
        VIRTIO_NET_HASH_REPORT_TCPv6,
        VIRTIO_NET_HASH_REPORT_IPv6,
        VIRTIO_NET_HASH_REPORT_IPv6_EX,
        VIRTIO_NET_HASH_REPORT_TCPv6_EX,
        VIRTIO_NET_HASH_REPORT_UDPv4,
        VIRTIO_NET_HASH_REPORT_UDPv6,
        VIRTIO_NET_HASH_REPORT_UDPv6_EX
    };

    net_rx_pkt_set_protocols(pkt, buf + n->host_hdr_len,
                             size - n->host_hdr_len);
    net_rx_pkt_get_protocols(pkt, &isip4, &isip6, &isudp, &istcp);
    if (isip4 && (net_rx_pkt_get_ip4_info(pkt)->fragment)) {
        istcp = isudp = false;
    }
    if (isip6 && (net_rx_pkt_get_ip6_info(pkt)->fragment)) {
        istcp = isudp = false;
    }
    net_hash_type = virtio_net_get_hash_type(isip4, isip6, isudp, istcp,
                                             n->rss_data.hash_types);
    if (net_hash_type > NetPktRssIpV6UdpEx) {
        if (n->rss_data.populate_hash) {
            virtio_set_packet_hash(buf, VIRTIO_NET_HASH_REPORT_NONE, 0);
        }
        return n->rss_data.redirect ? n->rss_data.default_queue : -1;
    }

    hash = net_rx_pkt_calc_rss_hash(pkt, net_hash_type, n->rss_data.key);

    if (n->rss_data.populate_hash) {
        virtio_set_packet_hash(buf, reports[net_hash_type], hash);
    }

    if (n->rss_data.redirect) {
        new_index = hash & (n->rss_data.indirections_len - 1);
        new_index = n->rss_data.indirections_table[new_index];
    }

    return (index == new_index) ? -1 : new_index;
}

static ssize_t virtio_net_receive_rcu(NetClientState *nc, const uint8_t *buf,
                                      size_t size, bool no_rss)
{
    VirtIONet *n = qemu_get_nic_opaque(nc);
    VirtIONetQueue *q = virtio_net_get_subqueue(nc);
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    VirtQueueElement *elems[VIRTQUEUE_MAX_SIZE];
    size_t lens[VIRTQUEUE_MAX_SIZE];
    struct iovec mhdr_sg[VIRTQUEUE_MAX_SIZE];
    struct virtio_net_hdr_mrg_rxbuf mhdr;
    unsigned mhdr_cnt = 0;
    size_t offset, i, guest_offset, j;
    ssize_t err;

    if (!virtio_net_can_receive(nc)) {
        return -1;
    }

    if (!no_rss && n->rss_data.enabled && n->rss_data.enabled_software_rss) {
        int index = virtio_net_process_rss(nc, buf, size);
        if (index >= 0) {
            NetClientState *nc2 = qemu_get_subqueue(n->nic, index);
            return virtio_net_receive_rcu(nc2, buf, size, true);
        }
    }

    /* hdr_len refers to the header we supply to the guest */
    if (!virtio_net_has_buffers(q, size + n->guest_hdr_len - n->host_hdr_len)) {
        return 0;
    }

    if (!receive_filter(n, buf, size))
        return size;

    offset = i = 0;

    while (offset < size) {
        VirtQueueElement *elem;
        int len, total;
        const struct iovec *sg;

        total = 0;

        if (i == VIRTQUEUE_MAX_SIZE) {
            virtio_error(vdev, "virtio-net unexpected long buffer chain");
            err = size;
            goto err;
        }

        elem = virtqueue_pop(q->rx_vq, sizeof(VirtQueueElement));
        if (!elem) {
            if (i) {
                virtio_error(vdev, "virtio-net unexpected empty queue: "
                             "i %zd mergeable %d offset %zd, size %zd, "
                             "guest hdr len %zd, host hdr len %zd "
                             "guest features 0x%" PRIx64,
                             i, n->mergeable_rx_bufs, offset, size,
                             n->guest_hdr_len, n->host_hdr_len,
                             vdev->guest_features);
            }
            err = -1;
            goto err;
        }

        if (elem->in_num < 1) {
            virtio_error(vdev,
                         "virtio-net receive queue contains no in buffers");
            virtqueue_detach_element(q->rx_vq, elem, 0);
            g_free(elem);
            err = -1;
            goto err;
        }

        sg = elem->in_sg;
        if (i == 0) {
            assert(offset == 0);
            if (n->mergeable_rx_bufs) {
                mhdr_cnt = iov_copy(mhdr_sg, ARRAY_SIZE(mhdr_sg),
                                    sg, elem->in_num,
                                    offsetof(typeof(mhdr), num_buffers),
                                    sizeof(mhdr.num_buffers));
            }

            receive_header(n, sg, elem->in_num, buf, size);
            if (n->rss_data.populate_hash) {
                offset = sizeof(mhdr);
                iov_from_buf(sg, elem->in_num, offset,
                             buf + offset, n->host_hdr_len - sizeof(mhdr));
            }
            offset = n->host_hdr_len;
            total += n->guest_hdr_len;
            guest_offset = n->guest_hdr_len;
        } else {
            guest_offset = 0;
        }

        /* copy in packet.  ugh */
        len = iov_from_buf(sg, elem->in_num, guest_offset,
                           buf + offset, size - offset);
        total += len;
        offset += len;
        /* If buffers can't be merged, at this point we
         * must have consumed the complete packet.
         * Otherwise, drop it. */
        if (!n->mergeable_rx_bufs && offset < size) {
            virtqueue_unpop(q->rx_vq, elem, total);
            g_free(elem);
            err = size;
            goto err;
        }

        elems[i] = elem;
        lens[i] = total;
        i++;
    }

    if (mhdr_cnt) {
        virtio_stw_p(vdev, &mhdr.num_buffers, i);
        iov_from_buf(mhdr_sg, mhdr_cnt,
                     0,
                     &mhdr.num_buffers, sizeof mhdr.num_buffers);
    }

    for (j = 0; j < i; j++) {
        /* signal other side */
        virtqueue_fill(q->rx_vq, elems[j], lens[j], j);
        g_free(elems[j]);
    }

    virtqueue_flush(q->rx_vq, i);
    virtio_notify(vdev, q->rx_vq);

    return size;

err:
    for (j = 0; j < i; j++) {
        virtqueue_detach_element(q->rx_vq, elems[j], lens[j]);
        g_free(elems[j]);
    }

    return err;
}

static ssize_t virtio_net_do_receive(NetClientState *nc, const uint8_t *buf,
                                  size_t size)
{
    RCU_READ_LOCK_GUARD();

    return virtio_net_receive_rcu(nc, buf, size, false);
}

static void virtio_net_rsc_extract_unit4(VirtioNetRscChain *chain,
                                         const uint8_t *buf,
                                         VirtioNetRscUnit *unit)
{
    uint16_t ip_hdrlen;
    struct ip_header *ip;

    ip = (struct ip_header *)(buf + chain->n->guest_hdr_len
                              + sizeof(struct eth_header));
    unit->ip = (void *)ip;
    ip_hdrlen = (ip->ip_ver_len & 0xF) << 2;
    unit->ip_plen = &ip->ip_len;
    unit->tcp = (struct tcp_header *)(((uint8_t *)unit->ip) + ip_hdrlen);
    unit->tcp_hdrlen = (htons(unit->tcp->th_offset_flags) & 0xF000) >> 10;
    unit->payload = htons(*unit->ip_plen) - ip_hdrlen - unit->tcp_hdrlen;
}

static void virtio_net_rsc_extract_unit6(VirtioNetRscChain *chain,
                                         const uint8_t *buf,
                                         VirtioNetRscUnit *unit)
{
    struct ip6_header *ip6;

    ip6 = (struct ip6_header *)(buf + chain->n->guest_hdr_len
                                 + sizeof(struct eth_header));
    unit->ip = ip6;
    unit->ip_plen = &(ip6->ip6_ctlun.ip6_un1.ip6_un1_plen);
    unit->tcp = (struct tcp_header *)(((uint8_t *)unit->ip)
                                        + sizeof(struct ip6_header));
    unit->tcp_hdrlen = (htons(unit->tcp->th_offset_flags) & 0xF000) >> 10;

    /* There is a difference between payload lenght in ipv4 and v6,
       ip header is excluded in ipv6 */
    unit->payload = htons(*unit->ip_plen) - unit->tcp_hdrlen;
}

static size_t virtio_net_rsc_drain_seg(VirtioNetRscChain *chain,
                                       VirtioNetRscSeg *seg)
{
    int ret;
    struct virtio_net_hdr_v1 *h;

    h = (struct virtio_net_hdr_v1 *)seg->buf;
    h->flags = 0;
    h->gso_type = VIRTIO_NET_HDR_GSO_NONE;

    if (seg->is_coalesced) {
        h->rsc.segments = seg->packets;
        h->rsc.dup_acks = seg->dup_ack;
        h->flags = VIRTIO_NET_HDR_F_RSC_INFO;
        if (chain->proto == ETH_P_IP) {
            h->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
        } else {
            h->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
        }
    }

    ret = virtio_net_do_receive(seg->nc, seg->buf, seg->size);
    QTAILQ_REMOVE(&chain->buffers, seg, next);
    g_free(seg->buf);
    g_free(seg);

    return ret;
}

static void virtio_net_rsc_purge(void *opq)
{
    VirtioNetRscSeg *seg, *rn;
    VirtioNetRscChain *chain = (VirtioNetRscChain *)opq;

    QTAILQ_FOREACH_SAFE(seg, &chain->buffers, next, rn) {
        if (virtio_net_rsc_drain_seg(chain, seg) == 0) {
            chain->stat.purge_failed++;
            continue;
        }
    }

    chain->stat.timer++;
    if (!QTAILQ_EMPTY(&chain->buffers)) {
        timer_mod(chain->drain_timer,
              qemu_clock_get_ns(QEMU_CLOCK_HOST) + chain->n->rsc_timeout);
    }
}

static void virtio_net_rsc_cleanup(VirtIONet *n)
{
    VirtioNetRscChain *chain, *rn_chain;
    VirtioNetRscSeg *seg, *rn_seg;

    QTAILQ_FOREACH_SAFE(chain, &n->rsc_chains, next, rn_chain) {
        QTAILQ_FOREACH_SAFE(seg, &chain->buffers, next, rn_seg) {
            QTAILQ_REMOVE(&chain->buffers, seg, next);
            g_free(seg->buf);
            g_free(seg);
        }

        timer_free(chain->drain_timer);
        QTAILQ_REMOVE(&n->rsc_chains, chain, next);
        g_free(chain);
    }
}

static void virtio_net_rsc_cache_buf(VirtioNetRscChain *chain,
                                     NetClientState *nc,
                                     const uint8_t *buf, size_t size)
{
    uint16_t hdr_len;
    VirtioNetRscSeg *seg;

    hdr_len = chain->n->guest_hdr_len;
    seg = g_new(VirtioNetRscSeg, 1);
    seg->buf = g_malloc(hdr_len + sizeof(struct eth_header)
        + sizeof(struct ip6_header) + VIRTIO_NET_MAX_TCP_PAYLOAD);
    memcpy(seg->buf, buf, size);
    seg->size = size;
    seg->packets = 1;
    seg->dup_ack = 0;
    seg->is_coalesced = 0;
    seg->nc = nc;

    QTAILQ_INSERT_TAIL(&chain->buffers, seg, next);
    chain->stat.cache++;

    switch (chain->proto) {
    case ETH_P_IP:
        virtio_net_rsc_extract_unit4(chain, seg->buf, &seg->unit);
        break;
    case ETH_P_IPV6:
        virtio_net_rsc_extract_unit6(chain, seg->buf, &seg->unit);
        break;
    default:
        g_assert_not_reached();
    }
}

static int32_t virtio_net_rsc_handle_ack(VirtioNetRscChain *chain,
                                         VirtioNetRscSeg *seg,
                                         const uint8_t *buf,
                                         struct tcp_header *n_tcp,
                                         struct tcp_header *o_tcp)
{
    uint32_t nack, oack;
    uint16_t nwin, owin;

    nack = htonl(n_tcp->th_ack);
    nwin = htons(n_tcp->th_win);
    oack = htonl(o_tcp->th_ack);
    owin = htons(o_tcp->th_win);

    if ((nack - oack) >= VIRTIO_NET_MAX_TCP_PAYLOAD) {
        chain->stat.ack_out_of_win++;
        return RSC_FINAL;
    } else if (nack == oack) {
        /* duplicated ack or window probe */
        if (nwin == owin) {
            /* duplicated ack, add dup ack count due to whql test up to 1 */
            chain->stat.dup_ack++;
            return RSC_FINAL;
        } else {
            /* Coalesce window update */
            o_tcp->th_win = n_tcp->th_win;
            chain->stat.win_update++;
            return RSC_COALESCE;
        }
    } else {
        /* pure ack, go to 'C', finalize*/
        chain->stat.pure_ack++;
        return RSC_FINAL;
    }
}

static int32_t virtio_net_rsc_coalesce_data(VirtioNetRscChain *chain,
                                            VirtioNetRscSeg *seg,
                                            const uint8_t *buf,
                                            VirtioNetRscUnit *n_unit)
{
    void *data;
    uint16_t o_ip_len;
    uint32_t nseq, oseq;
    VirtioNetRscUnit *o_unit;

    o_unit = &seg->unit;
    o_ip_len = htons(*o_unit->ip_plen);
    nseq = htonl(n_unit->tcp->th_seq);
    oseq = htonl(o_unit->tcp->th_seq);

    /* out of order or retransmitted. */
    if ((nseq - oseq) > VIRTIO_NET_MAX_TCP_PAYLOAD) {
        chain->stat.data_out_of_win++;
        return RSC_FINAL;
    }

    data = ((uint8_t *)n_unit->tcp) + n_unit->tcp_hdrlen;
    if (nseq == oseq) {
        if ((o_unit->payload == 0) && n_unit->payload) {
            /* From no payload to payload, normal case, not a dup ack or etc */
            chain->stat.data_after_pure_ack++;
            goto coalesce;
        } else {
            return virtio_net_rsc_handle_ack(chain, seg, buf,
                                             n_unit->tcp, o_unit->tcp);
        }
    } else if ((nseq - oseq) != o_unit->payload) {
        /* Not a consistent packet, out of order */
        chain->stat.data_out_of_order++;
        return RSC_FINAL;
    } else {
coalesce:
        if ((o_ip_len + n_unit->payload) > chain->max_payload) {
            chain->stat.over_size++;
            return RSC_FINAL;
        }

        /* Here comes the right data, the payload length in v4/v6 is different,
           so use the field value to update and record the new data len */
        o_unit->payload += n_unit->payload; /* update new data len */

        /* update field in ip header */
        *o_unit->ip_plen = htons(o_ip_len + n_unit->payload);

        /* Bring 'PUSH' big, the whql test guide says 'PUSH' can be coalesced
           for windows guest, while this may change the behavior for linux
           guest (only if it uses RSC feature). */
        o_unit->tcp->th_offset_flags = n_unit->tcp->th_offset_flags;

        o_unit->tcp->th_ack = n_unit->tcp->th_ack;
        o_unit->tcp->th_win = n_unit->tcp->th_win;

        memmove(seg->buf + seg->size, data, n_unit->payload);
        seg->size += n_unit->payload;
        seg->packets++;
        chain->stat.coalesced++;
        return RSC_COALESCE;
    }
}

static int32_t virtio_net_rsc_coalesce4(VirtioNetRscChain *chain,
                                        VirtioNetRscSeg *seg,
                                        const uint8_t *buf, size_t size,
                                        VirtioNetRscUnit *unit)
{
    struct ip_header *ip1, *ip2;

    ip1 = (struct ip_header *)(unit->ip);
    ip2 = (struct ip_header *)(seg->unit.ip);
    if ((ip1->ip_src ^ ip2->ip_src) || (ip1->ip_dst ^ ip2->ip_dst)
        || (unit->tcp->th_sport ^ seg->unit.tcp->th_sport)
        || (unit->tcp->th_dport ^ seg->unit.tcp->th_dport)) {
        chain->stat.no_match++;
        return RSC_NO_MATCH;
    }

    return virtio_net_rsc_coalesce_data(chain, seg, buf, unit);
}

static int32_t virtio_net_rsc_coalesce6(VirtioNetRscChain *chain,
                                        VirtioNetRscSeg *seg,
                                        const uint8_t *buf, size_t size,
                                        VirtioNetRscUnit *unit)
{
    struct ip6_header *ip1, *ip2;

    ip1 = (struct ip6_header *)(unit->ip);
    ip2 = (struct ip6_header *)(seg->unit.ip);
    if (memcmp(&ip1->ip6_src, &ip2->ip6_src, sizeof(struct in6_address))
        || memcmp(&ip1->ip6_dst, &ip2->ip6_dst, sizeof(struct in6_address))
        || (unit->tcp->th_sport ^ seg->unit.tcp->th_sport)
        || (unit->tcp->th_dport ^ seg->unit.tcp->th_dport)) {
            chain->stat.no_match++;
            return RSC_NO_MATCH;
    }

    return virtio_net_rsc_coalesce_data(chain, seg, buf, unit);
}

/* Packets with 'SYN' should bypass, other flag should be sent after drain
 * to prevent out of order */
static int virtio_net_rsc_tcp_ctrl_check(VirtioNetRscChain *chain,
                                         struct tcp_header *tcp)
{
    uint16_t tcp_hdr;
    uint16_t tcp_flag;

    tcp_flag = htons(tcp->th_offset_flags);
    tcp_hdr = (tcp_flag & VIRTIO_NET_TCP_HDR_LENGTH) >> 10;
    tcp_flag &= VIRTIO_NET_TCP_FLAG;
    if (tcp_flag & TH_SYN) {
        chain->stat.tcp_syn++;
        return RSC_BYPASS;
    }

    if (tcp_flag & (TH_FIN | TH_URG | TH_RST | TH_ECE | TH_CWR)) {
        chain->stat.tcp_ctrl_drain++;
        return RSC_FINAL;
    }

    if (tcp_hdr > sizeof(struct tcp_header)) {
        chain->stat.tcp_all_opt++;
        return RSC_FINAL;
    }

    return RSC_CANDIDATE;
}

static size_t virtio_net_rsc_do_coalesce(VirtioNetRscChain *chain,
                                         NetClientState *nc,
                                         const uint8_t *buf, size_t size,
                                         VirtioNetRscUnit *unit)
{
    int ret;
    VirtioNetRscSeg *seg, *nseg;

    if (QTAILQ_EMPTY(&chain->buffers)) {
        chain->stat.empty_cache++;
        virtio_net_rsc_cache_buf(chain, nc, buf, size);
        timer_mod(chain->drain_timer,
              qemu_clock_get_ns(QEMU_CLOCK_HOST) + chain->n->rsc_timeout);
        return size;
    }

    QTAILQ_FOREACH_SAFE(seg, &chain->buffers, next, nseg) {
        if (chain->proto == ETH_P_IP) {
            ret = virtio_net_rsc_coalesce4(chain, seg, buf, size, unit);
        } else {
            ret = virtio_net_rsc_coalesce6(chain, seg, buf, size, unit);
        }

        if (ret == RSC_FINAL) {
            if (virtio_net_rsc_drain_seg(chain, seg) == 0) {
                /* Send failed */
                chain->stat.final_failed++;
                return 0;
            }

            /* Send current packet */
            return virtio_net_do_receive(nc, buf, size);
        } else if (ret == RSC_NO_MATCH) {
            continue;
        } else {
            /* Coalesced, mark coalesced flag to tell calc cksum for ipv4 */
            seg->is_coalesced = 1;
            return size;
        }
    }

    chain->stat.no_match_cache++;
    virtio_net_rsc_cache_buf(chain, nc, buf, size);
    return size;
}

/* Drain a connection data, this is to avoid out of order segments */
static size_t virtio_net_rsc_drain_flow(VirtioNetRscChain *chain,
                                        NetClientState *nc,
                                        const uint8_t *buf, size_t size,
                                        uint16_t ip_start, uint16_t ip_size,
                                        uint16_t tcp_port)
{
    VirtioNetRscSeg *seg, *nseg;
    uint32_t ppair1, ppair2;

    ppair1 = *(uint32_t *)(buf + tcp_port);
    QTAILQ_FOREACH_SAFE(seg, &chain->buffers, next, nseg) {
        ppair2 = *(uint32_t *)(seg->buf + tcp_port);
        if (memcmp(buf + ip_start, seg->buf + ip_start, ip_size)
            || (ppair1 != ppair2)) {
            continue;
        }
        if (virtio_net_rsc_drain_seg(chain, seg) == 0) {
            chain->stat.drain_failed++;
        }

        break;
    }

    return virtio_net_do_receive(nc, buf, size);
}

static int32_t virtio_net_rsc_sanity_check4(VirtioNetRscChain *chain,
                                            struct ip_header *ip,
                                            const uint8_t *buf, size_t size)
{
    uint16_t ip_len;

    /* Not an ipv4 packet */
    if (((ip->ip_ver_len & 0xF0) >> 4) != IP_HEADER_VERSION_4) {
        chain->stat.ip_option++;
        return RSC_BYPASS;
    }

    /* Don't handle packets with ip option */
    if ((ip->ip_ver_len & 0xF) != VIRTIO_NET_IP4_HEADER_LENGTH) {
        chain->stat.ip_option++;
        return RSC_BYPASS;
    }

    if (ip->ip_p != IPPROTO_TCP) {
        chain->stat.bypass_not_tcp++;
        return RSC_BYPASS;
    }

    /* Don't handle packets with ip fragment */
    if (!(htons(ip->ip_off) & IP_DF)) {
        chain->stat.ip_frag++;
        return RSC_BYPASS;
    }

    /* Don't handle packets with ecn flag */
    if (IPTOS_ECN(ip->ip_tos)) {
        chain->stat.ip_ecn++;
        return RSC_BYPASS;
    }

    ip_len = htons(ip->ip_len);
    if (ip_len < (sizeof(struct ip_header) + sizeof(struct tcp_header))
        || ip_len > (size - chain->n->guest_hdr_len -
                     sizeof(struct eth_header))) {
        chain->stat.ip_hacked++;
        return RSC_BYPASS;
    }

    return RSC_CANDIDATE;
}

static size_t virtio_net_rsc_receive4(VirtioNetRscChain *chain,
                                      NetClientState *nc,
                                      const uint8_t *buf, size_t size)
{
    int32_t ret;
    uint16_t hdr_len;
    VirtioNetRscUnit unit;

    hdr_len = ((VirtIONet *)(chain->n))->guest_hdr_len;

    if (size < (hdr_len + sizeof(struct eth_header) + sizeof(struct ip_header)
        + sizeof(struct tcp_header))) {
        chain->stat.bypass_not_tcp++;
        return virtio_net_do_receive(nc, buf, size);
    }

    virtio_net_rsc_extract_unit4(chain, buf, &unit);
    if (virtio_net_rsc_sanity_check4(chain, unit.ip, buf, size)
        != RSC_CANDIDATE) {
        return virtio_net_do_receive(nc, buf, size);
    }

    ret = virtio_net_rsc_tcp_ctrl_check(chain, unit.tcp);
    if (ret == RSC_BYPASS) {
        return virtio_net_do_receive(nc, buf, size);
    } else if (ret == RSC_FINAL) {
        return virtio_net_rsc_drain_flow(chain, nc, buf, size,
                ((hdr_len + sizeof(struct eth_header)) + 12),
                VIRTIO_NET_IP4_ADDR_SIZE,
                hdr_len + sizeof(struct eth_header) + sizeof(struct ip_header));
    }

    return virtio_net_rsc_do_coalesce(chain, nc, buf, size, &unit);
}

static int32_t virtio_net_rsc_sanity_check6(VirtioNetRscChain *chain,
                                            struct ip6_header *ip6,
                                            const uint8_t *buf, size_t size)
{
    uint16_t ip_len;

    if (((ip6->ip6_ctlun.ip6_un1.ip6_un1_flow & 0xF0) >> 4)
        != IP_HEADER_VERSION_6) {
        return RSC_BYPASS;
    }

    /* Both option and protocol is checked in this */
    if (ip6->ip6_ctlun.ip6_un1.ip6_un1_nxt != IPPROTO_TCP) {
        chain->stat.bypass_not_tcp++;
        return RSC_BYPASS;
    }

    ip_len = htons(ip6->ip6_ctlun.ip6_un1.ip6_un1_plen);
    if (ip_len < sizeof(struct tcp_header) ||
        ip_len > (size - chain->n->guest_hdr_len - sizeof(struct eth_header)
                  - sizeof(struct ip6_header))) {
        chain->stat.ip_hacked++;
        return RSC_BYPASS;
    }

    /* Don't handle packets with ecn flag */
    if (IP6_ECN(ip6->ip6_ctlun.ip6_un3.ip6_un3_ecn)) {
        chain->stat.ip_ecn++;
        return RSC_BYPASS;
    }

    return RSC_CANDIDATE;
}

static size_t virtio_net_rsc_receive6(void *opq, NetClientState *nc,
                                      const uint8_t *buf, size_t size)
{
    int32_t ret;
    uint16_t hdr_len;
    VirtioNetRscChain *chain;
    VirtioNetRscUnit unit;

    chain = (VirtioNetRscChain *)opq;
    hdr_len = ((VirtIONet *)(chain->n))->guest_hdr_len;

    if (size < (hdr_len + sizeof(struct eth_header) + sizeof(struct ip6_header)
        + sizeof(tcp_header))) {
        return virtio_net_do_receive(nc, buf, size);
    }

    virtio_net_rsc_extract_unit6(chain, buf, &unit);
    if (RSC_CANDIDATE != virtio_net_rsc_sanity_check6(chain,
                                                 unit.ip, buf, size)) {
        return virtio_net_do_receive(nc, buf, size);
    }

    ret = virtio_net_rsc_tcp_ctrl_check(chain, unit.tcp);
    if (ret == RSC_BYPASS) {
        return virtio_net_do_receive(nc, buf, size);
    } else if (ret == RSC_FINAL) {
        return virtio_net_rsc_drain_flow(chain, nc, buf, size,
                ((hdr_len + sizeof(struct eth_header)) + 8),
                VIRTIO_NET_IP6_ADDR_SIZE,
                hdr_len + sizeof(struct eth_header)
                + sizeof(struct ip6_header));
    }

    return virtio_net_rsc_do_coalesce(chain, nc, buf, size, &unit);
}

static VirtioNetRscChain *virtio_net_rsc_lookup_chain(VirtIONet *n,
                                                      NetClientState *nc,
                                                      uint16_t proto)
{
    VirtioNetRscChain *chain;

    if ((proto != (uint16_t)ETH_P_IP) && (proto != (uint16_t)ETH_P_IPV6)) {
        return NULL;
    }

    QTAILQ_FOREACH(chain, &n->rsc_chains, next) {
        if (chain->proto == proto) {
            return chain;
        }
    }

    chain = g_malloc(sizeof(*chain));
    chain->n = n;
    chain->proto = proto;
    if (proto == (uint16_t)ETH_P_IP) {
        chain->max_payload = VIRTIO_NET_MAX_IP4_PAYLOAD;
        chain->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
    } else {
        chain->max_payload = VIRTIO_NET_MAX_IP6_PAYLOAD;
        chain->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
    }
    chain->drain_timer = timer_new_ns(QEMU_CLOCK_HOST,
                                      virtio_net_rsc_purge, chain);
    memset(&chain->stat, 0, sizeof(chain->stat));

    QTAILQ_INIT(&chain->buffers);
    QTAILQ_INSERT_TAIL(&n->rsc_chains, chain, next);

    return chain;
}

static ssize_t virtio_net_rsc_receive(NetClientState *nc,
                                      const uint8_t *buf,
                                      size_t size)
{
    uint16_t proto;
    VirtioNetRscChain *chain;
    struct eth_header *eth;
    VirtIONet *n;

    n = qemu_get_nic_opaque(nc);
    if (size < (n->host_hdr_len + sizeof(struct eth_header))) {
        return virtio_net_do_receive(nc, buf, size);
    }

    eth = (struct eth_header *)(buf + n->guest_hdr_len);
    proto = htons(eth->h_proto);

    chain = virtio_net_rsc_lookup_chain(n, nc, proto);
    if (chain) {
        chain->stat.received++;
        if (proto == (uint16_t)ETH_P_IP && n->rsc4_enabled) {
            return virtio_net_rsc_receive4(chain, nc, buf, size);
        } else if (proto == (uint16_t)ETH_P_IPV6 && n->rsc6_enabled) {
            return virtio_net_rsc_receive6(chain, nc, buf, size);
        }
    }
    return virtio_net_do_receive(nc, buf, size);
}

static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf,
                                  size_t size)
{
    VirtIONet *n = qemu_get_nic_opaque(nc);
    if ((n->rsc4_enabled || n->rsc6_enabled)) {
        return virtio_net_rsc_receive(nc, buf, size);
    } else {
        return virtio_net_do_receive(nc, buf, size);
    }
}

static int32_t virtio_net_flush_tx(VirtIONetQueue *q);

static void virtio_net_tx_complete(NetClientState *nc, ssize_t len)
{
    VirtIONet *n = qemu_get_nic_opaque(nc);
    VirtIONetQueue *q = virtio_net_get_subqueue(nc);
    VirtIODevice *vdev = VIRTIO_DEVICE(n);

    virtqueue_push(q->tx_vq, q->async_tx.elem, 0);
    virtio_notify(vdev, q->tx_vq);

    g_free(q->async_tx.elem);
    q->async_tx.elem = NULL;

    virtio_queue_set_notification(q->tx_vq, 1);
    virtio_net_flush_tx(q);
}

/* TX */
static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
{
    VirtIONet *n = q->n;
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    VirtQueueElement *elem;
    int32_t num_packets = 0;
    int queue_index = vq2q(virtio_get_queue_index(q->tx_vq));
    if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
        return num_packets;
    }

    if (q->async_tx.elem) {
        virtio_queue_set_notification(q->tx_vq, 0);
        return num_packets;
    }

    for (;;) {
        ssize_t ret;
        unsigned int out_num;
        struct iovec sg[VIRTQUEUE_MAX_SIZE], sg2[VIRTQUEUE_MAX_SIZE + 1], *out_sg;
        struct virtio_net_hdr_mrg_rxbuf mhdr;

        elem = virtqueue_pop(q->tx_vq, sizeof(VirtQueueElement));
        if (!elem) {
            break;
        }

        out_num = elem->out_num;
        out_sg = elem->out_sg;
        if (out_num < 1) {
            virtio_error(vdev, "virtio-net header not in first element");
            virtqueue_detach_element(q->tx_vq, elem, 0);
            g_free(elem);
            return -EINVAL;
        }

        if (n->has_vnet_hdr) {
            if (iov_to_buf(out_sg, out_num, 0, &mhdr, n->guest_hdr_len) <
                n->guest_hdr_len) {
                virtio_error(vdev, "virtio-net header incorrect");
                virtqueue_detach_element(q->tx_vq, elem, 0);
                g_free(elem);
                return -EINVAL;
            }
            if (n->needs_vnet_hdr_swap) {
                virtio_net_hdr_swap(vdev, (void *) &mhdr);
                sg2[0].iov_base = &mhdr;
                sg2[0].iov_len = n->guest_hdr_len;
                out_num = iov_copy(&sg2[1], ARRAY_SIZE(sg2) - 1,
                                   out_sg, out_num,
                                   n->guest_hdr_len, -1);
                if (out_num == VIRTQUEUE_MAX_SIZE) {
                    goto drop;
                }
                out_num += 1;
                out_sg = sg2;
            }
        }
        /*
         * If host wants to see the guest header as is, we can
         * pass it on unchanged. Otherwise, copy just the parts
         * that host is interested in.
         */
        assert(n->host_hdr_len <= n->guest_hdr_len);
        if (n->host_hdr_len != n->guest_hdr_len) {
            unsigned sg_num = iov_copy(sg, ARRAY_SIZE(sg),
                                       out_sg, out_num,
                                       0, n->host_hdr_len);
            sg_num += iov_copy(sg + sg_num, ARRAY_SIZE(sg) - sg_num,
                             out_sg, out_num,
                             n->guest_hdr_len, -1);
            out_num = sg_num;
            out_sg = sg;
        }

        ret = qemu_sendv_packet_async(qemu_get_subqueue(n->nic, queue_index),
                                      out_sg, out_num, virtio_net_tx_complete);
        if (ret == 0) {
            virtio_queue_set_notification(q->tx_vq, 0);
            q->async_tx.elem = elem;
            return -EBUSY;
        }

drop:
        virtqueue_push(q->tx_vq, elem, 0);
        virtio_notify(vdev, q->tx_vq);
        g_free(elem);

        if (++num_packets >= n->tx_burst) {
            break;
        }
    }
    return num_packets;
}

static void virtio_net_handle_tx_timer(VirtIODevice *vdev, VirtQueue *vq)
{
    VirtIONet *n = VIRTIO_NET(vdev);
    VirtIONetQueue *q = &n->vqs[vq2q(virtio_get_queue_index(vq))];

    if (unlikely((n->status & VIRTIO_NET_S_LINK_UP) == 0)) {
        virtio_net_drop_tx_queue_data(vdev, vq);
        return;
    }

    /* This happens when device was stopped but VCPU wasn't. */
    if (!vdev->vm_running) {
        q->tx_waiting = 1;
        return;
    }

    if (q->tx_waiting) {
        virtio_queue_set_notification(vq, 1);
        timer_del(q->tx_timer);
        q->tx_waiting = 0;
        if (virtio_net_flush_tx(q) == -EINVAL) {
            return;
        }
    } else {
        timer_mod(q->tx_timer,
                       qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + n->tx_timeout);
        q->tx_waiting = 1;
        virtio_queue_set_notification(vq, 0);
    }
}

static void virtio_net_handle_tx_bh(VirtIODevice *vdev, VirtQueue *vq)
{
    VirtIONet *n = VIRTIO_NET(vdev);
    VirtIONetQueue *q = &n->vqs[vq2q(virtio_get_queue_index(vq))];

    if (unlikely((n->status & VIRTIO_NET_S_LINK_UP) == 0)) {
        virtio_net_drop_tx_queue_data(vdev, vq);
        return;
    }

    if (unlikely(q->tx_waiting)) {
        return;
    }
    q->tx_waiting = 1;
    /* This happens when device was stopped but VCPU wasn't. */
    if (!vdev->vm_running) {
        return;
    }
    virtio_queue_set_notification(vq, 0);
    qemu_bh_schedule(q->tx_bh);
}

static void virtio_net_tx_timer(void *opaque)
{
    VirtIONetQueue *q = opaque;
    VirtIONet *n = q->n;
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    /* This happens when device was stopped but BH wasn't. */
    if (!vdev->vm_running) {
        /* Make sure tx waiting is set, so we'll run when restarted. */
        assert(q->tx_waiting);
        return;
    }

    q->tx_waiting = 0;

    /* Just in case the driver is not ready on more */
    if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
        return;
    }

    virtio_queue_set_notification(q->tx_vq, 1);
    virtio_net_flush_tx(q);
}

static void virtio_net_tx_bh(void *opaque)
{
    VirtIONetQueue *q = opaque;
    VirtIONet *n = q->n;
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    int32_t ret;

    /* This happens when device was stopped but BH wasn't. */
    if (!vdev->vm_running) {
        /* Make sure tx waiting is set, so we'll run when restarted. */
        assert(q->tx_waiting);
        return;
    }

    q->tx_waiting = 0;

    /* Just in case the driver is not ready on more */
    if (unlikely(!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK))) {
        return;
    }

    ret = virtio_net_flush_tx(q);
    if (ret == -EBUSY || ret == -EINVAL) {
        return; /* Notification re-enable handled by tx_complete or device
                 * broken */
    }

    /* If we flush a full burst of packets, assume there are
     * more coming and immediately reschedule */
    if (ret >= n->tx_burst) {
        qemu_bh_schedule(q->tx_bh);
        q->tx_waiting = 1;
        return;
    }

    /* If less than a full burst, re-enable notification and flush
     * anything that may have come in while we weren't looking.  If
     * we find something, assume the guest is still active and reschedule */
    virtio_queue_set_notification(q->tx_vq, 1);
    ret = virtio_net_flush_tx(q);
    if (ret == -EINVAL) {
        return;
    } else if (ret > 0) {
        virtio_queue_set_notification(q->tx_vq, 0);
        qemu_bh_schedule(q->tx_bh);
        q->tx_waiting = 1;
    }
}

static void virtio_net_add_queue(VirtIONet *n, int index)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(n);

    n->vqs[index].rx_vq = virtio_add_queue(vdev, n->net_conf.rx_queue_size,
                                           virtio_net_handle_rx);

    if (n->net_conf.tx && !strcmp(n->net_conf.tx, "timer")) {
        n->vqs[index].tx_vq =
            virtio_add_queue(vdev, n->net_conf.tx_queue_size,
                             virtio_net_handle_tx_timer);
        n->vqs[index].tx_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
                                              virtio_net_tx_timer,
                                              &n->vqs[index]);
    } else {
        n->vqs[index].tx_vq =
            virtio_add_queue(vdev, n->net_conf.tx_queue_size,
                             virtio_net_handle_tx_bh);
        n->vqs[index].tx_bh = qemu_bh_new(virtio_net_tx_bh, &n->vqs[index]);
    }

    n->vqs[index].tx_waiting = 0;
    n->vqs[index].n = n;
}

static void virtio_net_del_queue(VirtIONet *n, int index)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    VirtIONetQueue *q = &n->vqs[index];
    NetClientState *nc = qemu_get_subqueue(n->nic, index);

    qemu_purge_queued_packets(nc);

    virtio_del_queue(vdev, index * 2);
    if (q->tx_timer) {
        timer_free(q->tx_timer);
        q->tx_timer = NULL;
    } else {
        qemu_bh_delete(q->tx_bh);
        q->tx_bh = NULL;
    }
    q->tx_waiting = 0;
    virtio_del_queue(vdev, index * 2 + 1);
}

static void virtio_net_change_num_queue_pairs(VirtIONet *n, int new_max_queue_pairs)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    int old_num_queues = virtio_get_num_queues(vdev);
    int new_num_queues = new_max_queue_pairs * 2 + 1;
    int i;

    assert(old_num_queues >= 3);
    assert(old_num_queues % 2 == 1);

    if (old_num_queues == new_num_queues) {
        return;
    }

    /*
     * We always need to remove and add ctrl vq if
     * old_num_queues != new_num_queues. Remove ctrl_vq first,
     * and then we only enter one of the following two loops.
     */
    virtio_del_queue(vdev, old_num_queues - 1);

    for (i = new_num_queues - 1; i < old_num_queues - 1; i += 2) {
        /* new_num_queues < old_num_queues */
        virtio_net_del_queue(n, i / 2);
    }

    for (i = old_num_queues - 1; i < new_num_queues - 1; i += 2) {
        /* new_num_queues > old_num_queues */
        virtio_net_add_queue(n, i / 2);
    }

    /* add ctrl_vq last */
    n->ctrl_vq = virtio_add_queue(vdev, 64, virtio_net_handle_ctrl);
}

static void virtio_net_set_multiqueue(VirtIONet *n, int multiqueue)
{
    int max = multiqueue ? n->max_queue_pairs : 1;

    n->multiqueue = multiqueue;
    virtio_net_change_num_queue_pairs(n, max);

    virtio_net_set_queue_pairs(n);
}

static int virtio_net_post_load_device(void *opaque, int version_id)
{
    VirtIONet *n = opaque;
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    int i, link_down;

    trace_virtio_net_post_load_device();
    virtio_net_set_mrg_rx_bufs(n, n->mergeable_rx_bufs,
                               virtio_vdev_has_feature(vdev,
                                                       VIRTIO_F_VERSION_1),
                               virtio_vdev_has_feature(vdev,
                                                       VIRTIO_NET_F_HASH_REPORT));

    /* MAC_TABLE_ENTRIES may be different from the saved image */
    if (n->mac_table.in_use > MAC_TABLE_ENTRIES) {
        n->mac_table.in_use = 0;
    }

    if (!virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)) {
        n->curr_guest_offloads = virtio_net_supported_guest_offloads(n);
    }

    /*
     * curr_guest_offloads will be later overwritten by the
     * virtio_set_features_nocheck call done from the virtio_load.
     * Here we make sure it is preserved and restored accordingly
     * in the virtio_net_post_load_virtio callback.
     */
    n->saved_guest_offloads = n->curr_guest_offloads;

    virtio_net_set_queue_pairs(n);

    /* Find the first multicast entry in the saved MAC filter */
    for (i = 0; i < n->mac_table.in_use; i++) {
        if (n->mac_table.macs[i * ETH_ALEN] & 1) {
            break;
        }
    }
    n->mac_table.first_multi = i;

    /* nc.link_down can't be migrated, so infer link_down according
     * to link status bit in n->status */
    link_down = (n->status & VIRTIO_NET_S_LINK_UP) == 0;
    for (i = 0; i < n->max_queue_pairs; i++) {
        qemu_get_subqueue(n->nic, i)->link_down = link_down;
    }

    if (virtio_vdev_has_feature(vdev, VIRTIO_NET_F_GUEST_ANNOUNCE) &&
        virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) {
        qemu_announce_timer_reset(&n->announce_timer, migrate_announce_params(),
                                  QEMU_CLOCK_VIRTUAL,
                                  virtio_net_announce_timer, n);
        if (n->announce_timer.round) {
            timer_mod(n->announce_timer.tm,
                      qemu_clock_get_ms(n->announce_timer.type));
        } else {
            qemu_announce_timer_del(&n->announce_timer, false);
        }
    }

    if (n->rss_data.enabled) {
        n->rss_data.enabled_software_rss = n->rss_data.populate_hash;
        if (!n->rss_data.populate_hash) {
            if (!virtio_net_attach_epbf_rss(n)) {
                if (get_vhost_net(qemu_get_queue(n->nic)->peer)) {
                    warn_report("Can't post-load eBPF RSS for vhost");
                } else {
                    warn_report("Can't post-load eBPF RSS - "
                                "fallback to software RSS");
                    n->rss_data.enabled_software_rss = true;
                }
            }
        }

        trace_virtio_net_rss_enable(n->rss_data.hash_types,
                                    n->rss_data.indirections_len,
                                    sizeof(n->rss_data.key));
    } else {
        trace_virtio_net_rss_disable();
    }
    return 0;
}

static int virtio_net_post_load_virtio(VirtIODevice *vdev)
{
    VirtIONet *n = VIRTIO_NET(vdev);
    /*
     * The actual needed state is now in saved_guest_offloads,
     * see virtio_net_post_load_device for detail.
     * Restore it back and apply the desired offloads.
     */
    n->curr_guest_offloads = n->saved_guest_offloads;
    if (peer_has_vnet_hdr(n)) {
        virtio_net_apply_guest_offloads(n);
    }

    return 0;
}

/* tx_waiting field of a VirtIONetQueue */
static const VMStateDescription vmstate_virtio_net_queue_tx_waiting = {
    .name = "virtio-net-queue-tx_waiting",
    .fields = (VMStateField[]) {
        VMSTATE_UINT32(tx_waiting, VirtIONetQueue),
        VMSTATE_END_OF_LIST()
   },
};

static bool max_queue_pairs_gt_1(void *opaque, int version_id)
{
    return VIRTIO_NET(opaque)->max_queue_pairs > 1;
}

static bool has_ctrl_guest_offloads(void *opaque, int version_id)
{
    return virtio_vdev_has_feature(VIRTIO_DEVICE(opaque),
                                   VIRTIO_NET_F_CTRL_GUEST_OFFLOADS);
}

static bool mac_table_fits(void *opaque, int version_id)
{
    return VIRTIO_NET(opaque)->mac_table.in_use <= MAC_TABLE_ENTRIES;
}

static bool mac_table_doesnt_fit(void *opaque, int version_id)
{
    return !mac_table_fits(opaque, version_id);
}

/* This temporary type is shared by all the WITH_TMP methods
 * although only some fields are used by each.
 */
struct VirtIONetMigTmp {
    VirtIONet      *parent;
    VirtIONetQueue *vqs_1;
    uint16_t        curr_queue_pairs_1;
    uint8_t         has_ufo;
    uint32_t        has_vnet_hdr;
};

/* The 2nd and subsequent tx_waiting flags are loaded later than
 * the 1st entry in the queue_pairs and only if there's more than one
 * entry.  We use the tmp mechanism to calculate a temporary
 * pointer and count and also validate the count.
 */

static int virtio_net_tx_waiting_pre_save(void *opaque)
{
    struct VirtIONetMigTmp *tmp = opaque;

    tmp->vqs_1 = tmp->parent->vqs + 1;