// 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_local = 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); static __init int net_failover_init(void) { return 0; } module_init(net_failover_init); static __exit void net_failover_exit(void) { } module_exit(net_failover_exit); MODULE_DESCRIPTION("Failover driver for Paravirtual drivers"); MODULE_LICENSE("GPL v2");