drivers/net/net_failover.c

root/drivers/net/net_failover.c
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2018, Intel Corporation. */

/* This provides a net_failover interface for paravirtual drivers to
 * provide an alternate datapath by exporting APIs to create and
 * destroy a upper 'net_failover' netdev. The upper dev manages the
 * original paravirtual interface as a 'standby' netdev and uses the
 * generic failover infrastructure to register and manage a direct
 * attached VF as a 'primary' netdev. This enables live migration of
 * a VM with direct attached VF by failing over to the paravirtual
 * datapath when the VF is unplugged.
 *
 * Some of the netdev management routines are based on bond/team driver as
 * this driver provides active-backup functionality similar to those drivers.
 */

#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/ethtool.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/netpoll.h>
#include <linux/rtnetlink.h>
#include <linux/if_vlan.h>
#include <linux/pci.h>
#include <net/sch_generic.h>
#include <uapi/linux/if_arp.h>
#include <net/net_failover.h>

static bool net_failover_xmit_ready(struct net_device *dev)
{
        return netif_running(dev) && netif_carrier_ok(dev);
}

static int net_failover_open(struct net_device *dev)
{
        struct net_failover_info *nfo_info = netdev_priv(dev);
        struct net_device *primary_dev, *standby_dev;
        int err;

        primary_dev = rtnl_dereference(nfo_info->primary_dev);
        if (primary_dev) {
                err = dev_open(primary_dev, NULL);
                if (err)
                        goto err_primary_open;
        }

        standby_dev = rtnl_dereference(nfo_info->standby_dev);
        if (standby_dev) {
                err = dev_open(standby_dev, NULL);
                if (err)
                        goto err_standby_open;
        }

        if ((primary_dev && net_failover_xmit_ready(primary_dev)) ||
            (standby_dev && net_failover_xmit_ready(standby_dev))) {
                netif_carrier_on(dev);
                netif_tx_wake_all_queues(dev);
        }

        return 0;

err_standby_open:
        if (primary_dev)
                dev_close(primary_dev);
err_primary_open:
        netif_tx_disable(dev);
        return err;
}

static int net_failover_close(struct net_device *dev)
{
        struct net_failover_info *nfo_info = netdev_priv(dev);
        struct net_device *slave_dev;

        netif_tx_disable(dev);

        slave_dev = rtnl_dereference(nfo_info->primary_dev);
        if (slave_dev)
                dev_close(slave_dev);

        slave_dev = rtnl_dereference(nfo_info->standby_dev);
        if (slave_dev)
                dev_close(slave_dev);

        return 0;
}

static netdev_tx_t net_failover_drop_xmit(struct sk_buff *skb,
                                          struct net_device *dev)
{
        dev_core_stats_tx_dropped_inc(dev);
        dev_kfree_skb_any(skb);
        return NETDEV_TX_OK;
}

static netdev_tx_t net_failover_start_xmit(struct sk_buff *skb,
                                           struct net_device *dev)
{
        struct net_failover_info *nfo_info = netdev_priv(dev);
        struct net_device *xmit_dev;

        /* Try xmit via primary netdev followed by standby netdev */
        xmit_dev = rcu_dereference_bh(nfo_info->primary_dev);
        if (!xmit_dev || !net_failover_xmit_ready(xmit_dev)) {
                xmit_dev = rcu_dereference_bh(nfo_info->standby_dev);
                if (!xmit_dev || !net_failover_xmit_ready(xmit_dev))
                        return net_failover_drop_xmit(skb, dev);
        }

        skb->dev = xmit_dev;
        skb->queue_mapping = qdisc_skb_cb(skb)->slave_dev_queue_mapping;

        return dev_queue_xmit(skb);
}

static u16 net_failover_select_queue(struct net_device *dev,
                                     struct sk_buff *skb,
                                     struct net_device *sb_dev)
{
        struct net_failover_info *nfo_info = netdev_priv(dev);
        struct net_device *primary_dev;
        u16 txq;

        primary_dev = rcu_dereference(nfo_info->primary_dev);
        if (primary_dev) {
                const struct net_device_ops *ops = primary_dev->netdev_ops;

                if (ops->ndo_select_queue)
                        txq = ops->ndo_select_queue(primary_dev, skb, sb_dev);
                else
                        txq = netdev_pick_tx(primary_dev, skb, NULL);
        } else {
                txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) : 0;
        }

        /* Save the original txq to restore before passing to the driver */
        qdisc_skb_cb(skb)->slave_dev_queue_mapping = skb->queue_mapping;

        if (unlikely(txq >= dev->real_num_tx_queues)) {
                do {
                        txq -= dev->real_num_tx_queues;
                } while (txq >= dev->real_num_tx_queues);
        }

        return txq;
}

/* fold stats, assuming all rtnl_link_stats64 fields are u64, but
 * that some drivers can provide 32bit values only.
 */
static void net_failover_fold_stats(struct rtnl_link_stats64 *_res,
                                    const struct rtnl_link_stats64 *_new,
                                    const struct rtnl_link_stats64 *_old)
{
        const u64 *new = (const u64 *)_new;
        const u64 *old = (const u64 *)_old;
        u64 *res = (u64 *)_res;
        int i;

        for (i = 0; i < sizeof(*_res) / sizeof(u64); i++) {
                u64 nv = new[i];
                u64 ov = old[i];
                s64 delta = nv - ov;

                /* detects if this particular field is 32bit only */
                if (((nv | ov) >> 32) == 0)
                        delta = (s64)(s32)((u32)nv - (u32)ov);

                /* filter anomalies, some drivers reset their stats
                 * at down/up events.
                 */
                if (delta > 0)
                        res[i] += delta;
        }
}

static void net_failover_get_stats(struct net_device *dev,
                                   struct rtnl_link_stats64 *stats)
{
        struct net_failover_info *nfo_info = netdev_priv(dev);
        const struct rtnl_link_stats64 *new;
        struct rtnl_link_stats64 temp;
        struct net_device *slave_dev;

        spin_lock(&nfo_info->stats_lock);
        memcpy(stats, &nfo_info->failover_stats, sizeof(*stats));

        rcu_read_lock();

        slave_dev = rcu_dereference(nfo_info->primary_dev);
        if (slave_dev) {
                new = dev_get_stats(slave_dev, &temp);
                net_failover_fold_stats(stats, new, &nfo_info->primary_stats);
                memcpy(&nfo_info->primary_stats, new, sizeof(*new));
        }

        slave_dev = rcu_dereference(nfo_info->standby_dev);
        if (slave_dev) {
                new = dev_get_stats(slave_dev, &temp);
                net_failover_fold_stats(stats, new, &nfo_info->standby_stats);
                memcpy(&nfo_info->standby_stats, new, sizeof(*new));
        }

        rcu_read_unlock();

        memcpy(&nfo_info->failover_stats, stats, sizeof(*stats));
        spin_unlock(&nfo_info->stats_lock);
}

static int net_failover_change_mtu(struct net_device *dev, int new_mtu)
{
        struct net_failover_info *nfo_info = netdev_priv(dev);
        struct net_device *primary_dev, *standby_dev;
        int ret = 0;

        primary_dev = rtnl_dereference(nfo_info->primary_dev);
        if (primary_dev) {
                ret = dev_set_mtu(primary_dev, new_mtu);
                if (ret)
                        return ret;
        }

        standby_dev = rtnl_dereference(nfo_info->standby_dev);
        if (standby_dev) {
                ret = dev_set_mtu(standby_dev, new_mtu);
                if (ret) {
                        if (primary_dev)
                                dev_set_mtu(primary_dev, dev->mtu);
                        return ret;
                }
        }

        WRITE_ONCE(dev->mtu, new_mtu);

        return 0;
}

static void net_failover_set_rx_mode(struct net_device *dev)
{
        struct net_failover_info *nfo_info = netdev_priv(dev);
        struct net_device *slave_dev;

        rcu_read_lock();

        slave_dev = rcu_dereference(nfo_info->primary_dev);
        if (slave_dev) {
                dev_uc_sync_multiple(slave_dev, dev);
                dev_mc_sync_multiple(slave_dev, dev);
        }

        slave_dev = rcu_dereference(nfo_info->standby_dev);
        if (slave_dev) {
                dev_uc_sync_multiple(slave_dev, dev);
                dev_mc_sync_multiple(slave_dev, dev);
        }

        rcu_read_unlock();
}

static int net_failover_vlan_rx_add_vid(struct net_device *dev, __be16 proto,
                                        u16 vid)
{
        struct net_failover_info *nfo_info = netdev_priv(dev);
        struct net_device *primary_dev, *standby_dev;
        int ret = 0;

        primary_dev = rcu_dereference(nfo_info->primary_dev);
        if (primary_dev) {
                ret = vlan_vid_add(primary_dev, proto, vid);
                if (ret)
                        return ret;
        }

        standby_dev = rcu_dereference(nfo_info->standby_dev);
        if (standby_dev) {
                ret = vlan_vid_add(standby_dev, proto, vid);
                if (ret)
                        if (primary_dev)
                                vlan_vid_del(primary_dev, proto, vid);
        }

        return ret;
}

static int net_failover_vlan_rx_kill_vid(struct net_device *dev, __be16 proto,
                                         u16 vid)
{
        struct net_failover_info *nfo_info = netdev_priv(dev);
        struct net_device *slave_dev;

        slave_dev = rcu_dereference(nfo_info->primary_dev);
        if (slave_dev)
                vlan_vid_del(slave_dev, proto, vid);

        slave_dev = rcu_dereference(nfo_info->standby_dev);
        if (slave_dev)
                vlan_vid_del(slave_dev, proto, vid);

        return 0;
}

static const struct net_device_ops failover_dev_ops = {
        .ndo_open               = net_failover_open,
        .ndo_stop               = net_failover_close,
        .ndo_start_xmit         = net_failover_start_xmit,
        .ndo_select_queue       = net_failover_select_queue,
        .ndo_get_stats64        = net_failover_get_stats,
        .ndo_change_mtu         = net_failover_change_mtu,
        .ndo_set_rx_mode        = net_failover_set_rx_mode,
        .ndo_vlan_rx_add_vid    = net_failover_vlan_rx_add_vid,
        .ndo_vlan_rx_kill_vid   = net_failover_vlan_rx_kill_vid,
        .ndo_validate_addr      = eth_validate_addr,
        .ndo_features_check     = passthru_features_check,
};

#define FAILOVER_NAME "net_failover"
#define FAILOVER_VERSION "0.1"

static void nfo_ethtool_get_drvinfo(struct net_device *dev,
                                    struct ethtool_drvinfo *drvinfo)
{
        strscpy(drvinfo->driver, FAILOVER_NAME, sizeof(drvinfo->driver));
        strscpy(drvinfo->version, FAILOVER_VERSION, sizeof(drvinfo->version));
}

static int nfo_ethtool_get_link_ksettings(struct net_device *dev,
                                          struct ethtool_link_ksettings *cmd)
{
        struct net_failover_info *nfo_info = netdev_priv(dev);
        struct net_device *slave_dev;

        slave_dev = rtnl_dereference(nfo_info->primary_dev);
        if (!slave_dev || !net_failover_xmit_ready(slave_dev)) {
                slave_dev = rtnl_dereference(nfo_info->standby_dev);
                if (!slave_dev || !net_failover_xmit_ready(slave_dev)) {
                        cmd->base.duplex = DUPLEX_UNKNOWN;
                        cmd->base.port = PORT_OTHER;
                        cmd->base.speed = SPEED_UNKNOWN;

                        return 0;
                }
        }

        return __ethtool_get_link_ksettings(slave_dev, cmd);
}

static const struct ethtool_ops failover_ethtool_ops = {
        .get_drvinfo            = nfo_ethtool_get_drvinfo,
        .get_link               = ethtool_op_get_link,
        .get_link_ksettings     = nfo_ethtool_get_link_ksettings,
};

/* Called when slave dev is injecting data into network stack.
 * Change the associated network device from lower dev to failover dev.
 * note: already called with rcu_read_lock
 */
static rx_handler_result_t net_failover_handle_frame(struct sk_buff **pskb)
{
        struct sk_buff *skb = *pskb;
        struct net_device *dev = rcu_dereference(skb->dev->rx_handler_data);
        struct net_failover_info *nfo_info = netdev_priv(dev);
        struct net_device *primary_dev, *standby_dev;

        primary_dev = rcu_dereference(nfo_info->primary_dev);
        standby_dev = rcu_dereference(nfo_info->standby_dev);

        if (primary_dev && skb->dev == standby_dev)
                return RX_HANDLER_EXACT;

        skb->dev = dev;

        return RX_HANDLER_ANOTHER;
}

static void net_failover_compute_features(struct net_device *dev)
{
        netdev_features_t vlan_features = FAILOVER_VLAN_FEATURES &
                                          NETIF_F_ALL_FOR_ALL;
        netdev_features_t enc_features  = FAILOVER_ENC_FEATURES;
        unsigned short max_hard_header_len = ETH_HLEN;
        unsigned int dst_release_flag = IFF_XMIT_DST_RELEASE |
                                        IFF_XMIT_DST_RELEASE_PERM;
        struct net_failover_info *nfo_info = netdev_priv(dev);
        struct net_device *primary_dev, *standby_dev;

        primary_dev = rcu_dereference(nfo_info->primary_dev);
        if (primary_dev) {
                vlan_features =
                        netdev_increment_features(vlan_features,
                                                  primary_dev->vlan_features,
                                                  FAILOVER_VLAN_FEATURES);
                enc_features =
                        netdev_increment_features(enc_features,
                                                  primary_dev->hw_enc_features,
                                                  FAILOVER_ENC_FEATURES);

                dst_release_flag &= primary_dev->priv_flags;
                if (primary_dev->hard_header_len > max_hard_header_len)
                        max_hard_header_len = primary_dev->hard_header_len;
        }

        standby_dev = rcu_dereference(nfo_info->standby_dev);
        if (standby_dev) {
                vlan_features =
                        netdev_increment_features(vlan_features,
                                                  standby_dev->vlan_features,
                                                  FAILOVER_VLAN_FEATURES);
                enc_features =
                        netdev_increment_features(enc_features,
                                                  standby_dev->hw_enc_features,
                                                  FAILOVER_ENC_FEATURES);

                dst_release_flag &= standby_dev->priv_flags;
                if (standby_dev->hard_header_len > max_hard_header_len)
                        max_hard_header_len = standby_dev->hard_header_len;
        }

        dev->vlan_features = vlan_features;
        dev->hw_enc_features = enc_features | NETIF_F_GSO_ENCAP_ALL;
        dev->hard_header_len = max_hard_header_len;

        dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
        if (dst_release_flag == (IFF_XMIT_DST_RELEASE |
                                 IFF_XMIT_DST_RELEASE_PERM))
                dev->priv_flags |= IFF_XMIT_DST_RELEASE;

        netdev_change_features(dev);
}

static void net_failover_lower_state_changed(struct net_device *slave_dev,
                                             struct net_device *primary_dev,
                                             struct net_device *standby_dev)
{
        struct netdev_lag_lower_state_info info;

        if (netif_carrier_ok(slave_dev))
                info.link_up = true;
        else
                info.link_up = false;

        if (slave_dev == primary_dev) {
                if (netif_running(primary_dev))
                        info.tx_enabled = true;
                else
                        info.tx_enabled = false;
        } else {
                if ((primary_dev && netif_running(primary_dev)) ||
                    (!netif_running(standby_dev)))
                        info.tx_enabled = false;
                else
                        info.tx_enabled = true;
        }

        netdev_lower_state_changed(slave_dev, &info);
}

static int net_failover_slave_pre_register(struct net_device *slave_dev,
                                           struct net_device *failover_dev)
{
        struct net_device *standby_dev, *primary_dev;
        struct net_failover_info *nfo_info;
        bool slave_is_standby;

        nfo_info = netdev_priv(failover_dev);
        standby_dev = rtnl_dereference(nfo_info->standby_dev);
        primary_dev = rtnl_dereference(nfo_info->primary_dev);
        slave_is_standby = slave_dev->dev.parent == failover_dev->dev.parent;
        if (slave_is_standby ? standby_dev : primary_dev) {
                netdev_err(failover_dev, "%s attempting to register as slave dev when %s already present\n",
                           slave_dev->name,
                           slave_is_standby ? "standby" : "primary");
                return -EINVAL;
        }

        /* We want to allow only a direct attached VF device as a primary
         * netdev. As there is no easy way to check for a VF device, restrict
         * this to a pci device.
         */
        if (!slave_is_standby && (!slave_dev->dev.parent ||
                                  !dev_is_pci(slave_dev->dev.parent)))
                return -EINVAL;

        if (failover_dev->features & NETIF_F_VLAN_CHALLENGED &&
            vlan_uses_dev(failover_dev)) {
                netdev_err(failover_dev, "Device %s is VLAN challenged and failover device has VLAN set up\n",
                           failover_dev->name);
                return -EINVAL;
        }

        return 0;
}

static int net_failover_slave_register(struct net_device *slave_dev,
                                       struct net_device *failover_dev)
{
        struct net_device *standby_dev, *primary_dev;
        struct net_failover_info *nfo_info;
        bool slave_is_standby;
        u32 orig_mtu;
        int err;

        /* Align MTU of slave with failover dev */
        orig_mtu = slave_dev->mtu;
        err = dev_set_mtu(slave_dev, failover_dev->mtu);
        if (err) {
                netdev_err(failover_dev, "unable to change mtu of %s to %u register failed\n",
                           slave_dev->name, failover_dev->mtu);
                goto done;
        }

        dev_hold(slave_dev);

        if (netif_running(failover_dev)) {
                err = dev_open(slave_dev, NULL);
                if (err && (err != -EBUSY)) {
                        netdev_err(failover_dev, "Opening slave %s failed err:%d\n",
                                   slave_dev->name, err);
                        goto err_dev_open;
                }
        }

        netif_addr_lock_bh(failover_dev);
        dev_uc_sync_multiple(slave_dev, failover_dev);
        dev_mc_sync_multiple(slave_dev, failover_dev);
        netif_addr_unlock_bh(failover_dev);

        err = vlan_vids_add_by_dev(slave_dev, failover_dev);
        if (err) {
                netdev_err(failover_dev, "Failed to add vlan ids to device %s err:%d\n",
                           slave_dev->name, err);
                goto err_vlan_add;
        }

        nfo_info = netdev_priv(failover_dev);
        standby_dev = rtnl_dereference(nfo_info->standby_dev);
        primary_dev = rtnl_dereference(nfo_info->primary_dev);
        slave_is_standby = slave_dev->dev.parent == failover_dev->dev.parent;

        if (slave_is_standby) {
                rcu_assign_pointer(nfo_info->standby_dev, slave_dev);
                standby_dev = slave_dev;
                dev_get_stats(standby_dev, &nfo_info->standby_stats);
        } else {
                rcu_assign_pointer(nfo_info->primary_dev, slave_dev);
                primary_dev = slave_dev;
                dev_get_stats(primary_dev, &nfo_info->primary_stats);
                failover_dev->min_mtu = slave_dev->min_mtu;
                failover_dev->max_mtu = slave_dev->max_mtu;
        }

        net_failover_lower_state_changed(slave_dev, primary_dev, standby_dev);
        net_failover_compute_features(failover_dev);

        call_netdevice_notifiers(NETDEV_JOIN, slave_dev);

        netdev_info(failover_dev, "failover %s slave:%s registered\n",
                    slave_is_standby ? "standby" : "primary", slave_dev->name);

        return 0;

err_vlan_add:
        dev_uc_unsync(slave_dev, failover_dev);
        dev_mc_unsync(slave_dev, failover_dev);
        dev_close(slave_dev);
err_dev_open:
        dev_put(slave_dev);
        dev_set_mtu(slave_dev, orig_mtu);
done:
        return err;
}

static int net_failover_slave_pre_unregister(struct net_device *slave_dev,
                                             struct net_device *failover_dev)
{
        struct net_device *standby_dev, *primary_dev;
        struct net_failover_info *nfo_info;

        nfo_info = netdev_priv(failover_dev);
        primary_dev = rtnl_dereference(nfo_info->primary_dev);
        standby_dev = rtnl_dereference(nfo_info->standby_dev);

        if (slave_dev != primary_dev && slave_dev != standby_dev)
                return -ENODEV;

        return 0;
}

static int net_failover_slave_unregister(struct net_device *slave_dev,
                                         struct net_device *failover_dev)
{
        struct net_device *standby_dev, *primary_dev;
        struct net_failover_info *nfo_info;
        bool slave_is_standby;

        nfo_info = netdev_priv(failover_dev);
        primary_dev = rtnl_dereference(nfo_info->primary_dev);
        standby_dev = rtnl_dereference(nfo_info->standby_dev);

        if (WARN_ON_ONCE(slave_dev != primary_dev && slave_dev != standby_dev))
                return -ENODEV;

        vlan_vids_del_by_dev(slave_dev, failover_dev);
        dev_uc_unsync(slave_dev, failover_dev);
        dev_mc_unsync(slave_dev, failover_dev);
        dev_close(slave_dev);

        nfo_info = netdev_priv(failover_dev);
        dev_get_stats(failover_dev, &nfo_info->failover_stats);

        slave_is_standby = slave_dev->dev.parent == failover_dev->dev.parent;
        if (slave_is_standby) {
                RCU_INIT_POINTER(nfo_info->standby_dev, NULL);
        } else {
                RCU_INIT_POINTER(nfo_info->primary_dev, NULL);
                if (standby_dev) {
                        failover_dev->min_mtu = standby_dev->min_mtu;
                        failover_dev->max_mtu = standby_dev->max_mtu;
                }
        }

        dev_put(slave_dev);

        net_failover_compute_features(failover_dev);

        netdev_info(failover_dev, "failover %s slave:%s unregistered\n",
                    slave_is_standby ? "standby" : "primary", slave_dev->name);

        return 0;
}

static int net_failover_slave_link_change(struct net_device *slave_dev,
                                          struct net_device *failover_dev)
{
        struct net_device *primary_dev, *standby_dev;
        struct net_failover_info *nfo_info;

        nfo_info = netdev_priv(failover_dev);

        primary_dev = rtnl_dereference(nfo_info->primary_dev);
        standby_dev = rtnl_dereference(nfo_info->standby_dev);

        if (slave_dev != primary_dev && slave_dev != standby_dev)
                return -ENODEV;

        if ((primary_dev && net_failover_xmit_ready(primary_dev)) ||
            (standby_dev && net_failover_xmit_ready(standby_dev))) {
                netif_carrier_on(failover_dev);
                netif_tx_wake_all_queues(failover_dev);
        } else {
                dev_get_stats(failover_dev, &nfo_info->failover_stats);
                netif_carrier_off(failover_dev);
                netif_tx_stop_all_queues(failover_dev);
        }

        net_failover_lower_state_changed(slave_dev, primary_dev, standby_dev);

        return 0;
}

static int net_failover_slave_name_change(struct net_device *slave_dev,
                                          struct net_device *failover_dev)
{
        struct net_device *primary_dev, *standby_dev;
        struct net_failover_info *nfo_info;

        nfo_info = netdev_priv(failover_dev);

        primary_dev = rtnl_dereference(nfo_info->primary_dev);
        standby_dev = rtnl_dereference(nfo_info->standby_dev);

        if (slave_dev != primary_dev && slave_dev != standby_dev)
                return -ENODEV;

        /* We need to bring up the slave after the rename by udev in case
         * open failed with EBUSY when it was registered.
         */
        dev_open(slave_dev, NULL);

        return 0;
}

static struct failover_ops net_failover_ops = {
        .slave_pre_register     = net_failover_slave_pre_register,
        .slave_register         = net_failover_slave_register,
        .slave_pre_unregister   = net_failover_slave_pre_unregister,
        .slave_unregister       = net_failover_slave_unregister,
        .slave_link_change      = net_failover_slave_link_change,
        .slave_name_change      = net_failover_slave_name_change,
        .slave_handle_frame     = net_failover_handle_frame,
};

/**
 * net_failover_create - Create and register a failover instance
 *
 * @standby_dev: standby netdev
 *
 * Creates a failover netdev and registers a failover instance for a standby
 * netdev. Used by paravirtual drivers that use 3-netdev model.
 * The failover netdev acts as a master device and controls 2 slave devices -
 * the original standby netdev and a VF netdev with the same MAC gets
 * registered as primary netdev.
 *
 * Return: pointer to failover instance
 */
struct failover *net_failover_create(struct net_device *standby_dev)
{
        struct device *dev = standby_dev->dev.parent;
        struct net_device *failover_dev;
        struct failover *failover;
        int err;

        /* Alloc at least 2 queues, for now we are going with 16 assuming
         * that VF devices being enslaved won't have too many queues.
         */
        failover_dev = alloc_etherdev_mq(sizeof(struct net_failover_info), 16);
        if (!failover_dev) {
                dev_err(dev, "Unable to allocate failover_netdev!\n");
                return ERR_PTR(-ENOMEM);
        }

        dev_net_set(failover_dev, dev_net(standby_dev));
        SET_NETDEV_DEV(failover_dev, dev);

        failover_dev->netdev_ops = &failover_dev_ops;
        failover_dev->ethtool_ops = &failover_ethtool_ops;

        /* Initialize the device options */
        failover_dev->priv_flags |= IFF_UNICAST_FLT | IFF_NO_QUEUE;
        failover_dev->priv_flags &= ~(IFF_XMIT_DST_RELEASE |
                                       IFF_TX_SKB_SHARING);

        /* don't acquire failover netdev's netif_tx_lock when transmitting */
        failover_dev->lltx = true;

        /* Don't allow failover devices to change network namespaces. */
        failover_dev->netns_immutable = true;

        failover_dev->hw_features = FAILOVER_VLAN_FEATURES |
                                    NETIF_F_HW_VLAN_CTAG_TX |
                                    NETIF_F_HW_VLAN_CTAG_RX |
                                    NETIF_F_HW_VLAN_CTAG_FILTER;

        failover_dev->hw_features |= NETIF_F_GSO_ENCAP_ALL;
        failover_dev->features |= failover_dev->hw_features;

        dev_addr_set(failover_dev, standby_dev->dev_addr);

        failover_dev->min_mtu = standby_dev->min_mtu;
        failover_dev->max_mtu = standby_dev->max_mtu;

        err = register_netdev(failover_dev);
        if (err) {
                dev_err(dev, "Unable to register failover_dev!\n");
                goto err_register_netdev;
        }

        netif_carrier_off(failover_dev);

        failover = failover_register(failover_dev, &net_failover_ops);
        if (IS_ERR(failover)) {
                err = PTR_ERR(failover);
                goto err_failover_register;
        }

        return failover;

err_failover_register:
        unregister_netdev(failover_dev);
err_register_netdev:
        free_netdev(failover_dev);

        return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(net_failover_create);

/**
 * net_failover_destroy - Destroy a failover instance
 *
 * @failover: pointer to failover instance
 *
 * Unregisters any slave netdevs associated with the failover instance by
 * calling failover_slave_unregister().
 * unregisters the failover instance itself and finally frees the failover
 * netdev. Used by paravirtual drivers that use 3-netdev model.
 *
 */
void net_failover_destroy(struct failover *failover)
{
        struct net_failover_info *nfo_info;
        struct net_device *failover_dev;
        struct net_device *slave_dev;

        if (!failover)
                return;

        failover_dev = rcu_dereference(failover->failover_dev);
        nfo_info = netdev_priv(failover_dev);

        netif_device_detach(failover_dev);

        rtnl_lock();

        slave_dev = rtnl_dereference(nfo_info->primary_dev);
        if (slave_dev)
                failover_slave_unregister(slave_dev);

        slave_dev = rtnl_dereference(nfo_info->standby_dev);
        if (slave_dev)
                failover_slave_unregister(slave_dev);

        failover_unregister(failover);

        unregister_netdevice(failover_dev);

        rtnl_unlock();

        free_netdev(failover_dev);
}
EXPORT_SYMBOL_GPL(net_failover_destroy);

MODULE_DESCRIPTION("Failover driver for Paravirtual drivers");
MODULE_LICENSE("GPL v2");
Linux
