int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
{
	struct bonding *bond = netdev_priv(bond_dev);
	const struct net_device_ops *slave_ops = slave_dev->netdev_ops;
	struct slave *new_slave = NULL;
	struct netdev_hw_addr *ha;
	struct sockaddr addr;
	int link_reporting;
	int res = 0;

	if (!bond->params.use_carrier && slave_dev->ethtool_ops == NULL &&
		slave_ops->ndo_do_ioctl == NULL) {
		pr_warning("%s: Warning: no link monitoring support for %s\n",
			   bond_dev->name, slave_dev->name);
	}

	/* already enslaved */
	if (slave_dev->flags & IFF_SLAVE) {
		pr_debug("Error, Device was already enslaved\n");
		return -EBUSY;
	}

	/* vlan challenged mutual exclusion */
	/* no need to lock since we're protected by rtnl_lock */
	if (slave_dev->features & NETIF_F_VLAN_CHALLENGED) {
		pr_debug("%s: NETIF_F_VLAN_CHALLENGED\n", slave_dev->name);
		if (bond_vlan_used(bond)) {
			pr_err("%s: Error: cannot enslave VLAN challenged slave %s on VLAN enabled bond %s\n",
			       bond_dev->name, slave_dev->name, bond_dev->name);
			return -EPERM;
		} else {
			pr_warning("%s: Warning: enslaved VLAN challenged slave %s. Adding VLANs will be blocked as long as %s is part of bond %s\n",
				   bond_dev->name, slave_dev->name,
				   slave_dev->name, bond_dev->name);
		}
	} else {
		pr_debug("%s: ! NETIF_F_VLAN_CHALLENGED\n", slave_dev->name);
	}

	/*
	 * Old ifenslave binaries are no longer supported.  These can
	 * be identified with moderate accuracy by the state of the slave:
	 * the current ifenslave will set the interface down prior to
	 * enslaving it; the old ifenslave will not.
	 */
	if ((slave_dev->flags & IFF_UP)) {
		pr_err("%s is up. This may be due to an out of date ifenslave.\n",
		       slave_dev->name);
		res = -EPERM;
		goto err_undo_flags;
	}

	/* set bonding device ether type by slave - bonding netdevices are
	 * created with ether_setup, so when the slave type is not ARPHRD_ETHER
	 * there is a need to override some of the type dependent attribs/funcs.
	 *
	 * bond ether type mutual exclusion - don't allow slaves of dissimilar
	 * ether type (eg ARPHRD_ETHER and ARPHRD_INFINIBAND) share the same bond
	 */
	if (bond->slave_cnt == 0) {
		if (bond_dev->type != slave_dev->type) {
			pr_debug("%s: change device type from %d to %d\n",
				 bond_dev->name,
				 bond_dev->type, slave_dev->type);

			res = netdev_bonding_change(bond_dev,
						    NETDEV_PRE_TYPE_CHANGE);
			res = notifier_to_errno(res);
			if (res) {
				pr_err("%s: refused to change device type\n",
				       bond_dev->name);
				res = -EBUSY;
				goto err_undo_flags;
			}

			/* Flush unicast and multicast addresses */
			dev_uc_flush(bond_dev);
			dev_mc_flush(bond_dev);

			if (slave_dev->type != ARPHRD_ETHER)
				bond_setup_by_slave(bond_dev, slave_dev);
			else {
				ether_setup(bond_dev);
				bond_dev->priv_flags &= ~IFF_TX_SKB_SHARING;
			}

			netdev_bonding_change(bond_dev,
					      NETDEV_POST_TYPE_CHANGE);
		}
	} else if (bond_dev->type != slave_dev->type) {
		pr_err("%s ether type (%d) is different from other slaves (%d), can not enslave it.\n",
		       slave_dev->name,
		       slave_dev->type, bond_dev->type);
		res = -EINVAL;
		goto err_undo_flags;
	}

	if (slave_ops->ndo_set_mac_address == NULL) {
		if (bond->slave_cnt == 0) {
			pr_warning("%s: Warning: The first slave device specified does not support setting the MAC address. Setting fail_over_mac to active.",
				   bond_dev->name);
			bond->params.fail_over_mac = BOND_FOM_ACTIVE;
		} else if (bond->params.fail_over_mac != BOND_FOM_ACTIVE) {
			pr_err("%s: Error: The slave device specified does not support setting the MAC address, but fail_over_mac is not set to active.\n",
			       bond_dev->name);
			res = -EOPNOTSUPP;
			goto err_undo_flags;
		}
	}

	call_netdevice_notifiers(NETDEV_JOIN, slave_dev);

	/* If this is the first slave, then we need to set the master's hardware
	 * address to be the same as the slave's. */
	if (is_zero_ether_addr(bond->dev->dev_addr))
		memcpy(bond->dev->dev_addr, slave_dev->dev_addr,
		       slave_dev->addr_len);


	new_slave = kzalloc(sizeof(struct slave), GFP_KERNEL);
	if (!new_slave) {
		res = -ENOMEM;
		goto err_undo_flags;
	}

	/*
	 * Set the new_slave's queue_id to be zero.  Queue ID mapping
	 * is set via sysfs or module option if desired.
	 */
	new_slave->queue_id = 0;

	/* Save slave's original mtu and then set it to match the bond */
	new_slave->original_mtu = slave_dev->mtu;
	res = dev_set_mtu(slave_dev, bond->dev->mtu);
	if (res) {
		pr_debug("Error %d calling dev_set_mtu\n", res);
		goto err_free;
	}

	/*
	 * Save slave's original ("permanent") mac address for modes
	 * that need it, and for restoring it upon release, and then
	 * set it to the master's address
	 */
	memcpy(new_slave->perm_hwaddr, slave_dev->dev_addr, ETH_ALEN);

	if (!bond->params.fail_over_mac) {
		/*
		 * Set slave to master's mac address.  The application already
		 * set the master's mac address to that of the first slave
		 */
		memcpy(addr.sa_data, bond_dev->dev_addr, bond_dev->addr_len);
		addr.sa_family = slave_dev->type;
		res = dev_set_mac_address(slave_dev, &addr);
		if (res) {
			pr_debug("Error %d calling set_mac_address\n", res);
			goto err_restore_mtu;
		}
	}

	res = netdev_set_bond_master(slave_dev, bond_dev);
	if (res) {
		pr_debug("Error %d calling netdev_set_bond_master\n", res);
		goto err_restore_mac;
	}

	/* open the slave since the application closed it */
	res = dev_open(slave_dev);
	if (res) {
		pr_debug("Opening slave %s failed\n", slave_dev->name);
		goto err_unset_master;
	}

	new_slave->bond = bond;
	new_slave->dev = slave_dev;
	slave_dev->priv_flags |= IFF_BONDING;

	if (bond_is_lb(bond)) {
		/* bond_alb_init_slave() must be called before all other stages since
		 * it might fail and we do not want to have to undo everything
		 */
		res = bond_alb_init_slave(bond, new_slave);
		if (res)
			goto err_close;
	}

	/* If the mode USES_PRIMARY, then the new slave gets the
	 * master's promisc (and mc) settings only if it becomes the
	 * curr_active_slave, and that is taken care of later when calling
	 * bond_change_active()
	 */
	if (!USES_PRIMARY(bond->params.mode)) {
		/* set promiscuity level to new slave */
		if (bond_dev->flags & IFF_PROMISC) {
			res = dev_set_promiscuity(slave_dev, 1);
			if (res)
				goto err_close;
		}

		/* set allmulti level to new slave */
		if (bond_dev->flags & IFF_ALLMULTI) {
			res = dev_set_allmulti(slave_dev, 1);
			if (res)
				goto err_close;
		}

		netif_addr_lock_bh(bond_dev);
		/* upload master's mc_list to new slave */
		netdev_for_each_mc_addr(ha, bond_dev)
			dev_mc_add(slave_dev, ha->addr);
		netif_addr_unlock_bh(bond_dev);
	}

	if (bond->params.mode == BOND_MODE_8023AD) {
		/* add lacpdu mc addr to mc list */
		u8 lacpdu_multicast[ETH_ALEN] = MULTICAST_LACPDU_ADDR;

		dev_mc_add(slave_dev, lacpdu_multicast);
	}

	bond_add_vlans_on_slave(bond, slave_dev);

	write_lock_bh(&bond->lock);

	bond_attach_slave(bond, new_slave);

	new_slave->delay = 0;
	new_slave->link_failure_count = 0;

	write_unlock_bh(&bond->lock);

	bond_compute_features(bond);

	read_lock(&bond->lock);

	new_slave->last_arp_rx = jiffies;

	if (bond->params.miimon && !bond->params.use_carrier) {
		link_reporting = bond_check_dev_link(bond, slave_dev, 1);

		if ((link_reporting == -1) && !bond->params.arp_interval) {
			/*
			 * miimon is set but a bonded network driver
			 * does not support ETHTOOL/MII and
			 * arp_interval is not set.  Note: if
			 * use_carrier is enabled, we will never go
			 * here (because netif_carrier is always
			 * supported); thus, we don't need to change
			 * the messages for netif_carrier.
			 */
			pr_warning("%s: Warning: MII and ETHTOOL support not available for interface %s, and arp_interval/arp_ip_target module parameters not specified, thus bonding will not detect link failures! see bonding.txt for details.\n",
			       bond_dev->name, slave_dev->name);
		} else if (link_reporting == -1) {
			/* unable get link status using mii/ethtool */
			pr_warning("%s: Warning: can't get link status from interface %s; the network driver associated with this interface does not support MII or ETHTOOL link status reporting, thus miimon has no effect on this interface.\n",
				   bond_dev->name, slave_dev->name);
		}
	}

	/* check for initial state */
	if (!bond->params.miimon ||
	    (bond_check_dev_link(bond, slave_dev, 0) == BMSR_LSTATUS)) {
		if (bond->params.updelay) {
			pr_debug("Initial state of slave_dev is BOND_LINK_BACK\n");
			new_slave->link  = BOND_LINK_BACK;
			new_slave->delay = bond->params.updelay;
		} else {
			pr_debug("Initial state of slave_dev is BOND_LINK_UP\n");
			new_slave->link  = BOND_LINK_UP;
		}
		new_slave->jiffies = jiffies;
	} else {
		pr_debug("Initial state of slave_dev is BOND_LINK_DOWN\n");
		new_slave->link  = BOND_LINK_DOWN;
	}

	if (bond_update_speed_duplex(new_slave) &&
	    (new_slave->link != BOND_LINK_DOWN)) {
		pr_warning("%s: Warning: failed to get speed and duplex from %s, assumed to be 100Mb/sec and Full.\n",
			   bond_dev->name, new_slave->dev->name);

		if (bond->params.mode == BOND_MODE_8023AD) {
			pr_warning("%s: Warning: Operation of 802.3ad mode requires ETHTOOL support in base driver for proper aggregator selection.\n",
				   bond_dev->name);
		}
	}

	if (USES_PRIMARY(bond->params.mode) && bond->params.primary[0]) {
		/* if there is a primary slave, remember it */
		if (strcmp(bond->params.primary, new_slave->dev->name) == 0) {
			bond->primary_slave = new_slave;
			bond->force_primary = true;
		}
	}

	write_lock_bh(&bond->curr_slave_lock);

	switch (bond->params.mode) {
	case BOND_MODE_ACTIVEBACKUP:
		bond_set_slave_inactive_flags(new_slave);
		bond_select_active_slave(bond);
		break;
	case BOND_MODE_8023AD:
		/* in 802.3ad mode, the internal mechanism
		 * will activate the slaves in the selected
		 * aggregator
		 */
		bond_set_slave_inactive_flags(new_slave);
		/* if this is the first slave */
		if (bond->slave_cnt == 1) {
			SLAVE_AD_INFO(new_slave).id = 1;
			/* Initialize AD with the number of times that the AD timer is called in 1 second
			 * can be called only after the mac address of the bond is set
			 */
			bond_3ad_initialize(bond, 1000/AD_TIMER_INTERVAL);
		} else {
			SLAVE_AD_INFO(new_slave).id =
				SLAVE_AD_INFO(new_slave->prev).id + 1;
		}

		bond_3ad_bind_slave(new_slave);
		break;
	case BOND_MODE_TLB:
	case BOND_MODE_ALB:
		bond_set_active_slave(new_slave);
		bond_set_slave_inactive_flags(new_slave);
		bond_select_active_slave(bond);
		break;
	default:
		pr_debug("This slave is always active in trunk mode\n");

		/* always active in trunk mode */
		bond_set_active_slave(new_slave);

		/* In trunking mode there is little meaning to curr_active_slave
		 * anyway (it holds no special properties of the bond device),
		 * so we can change it without calling change_active_interface()
		 */
		if (!bond->curr_active_slave)
			bond->curr_active_slave = new_slave;

		break;
	} /* switch(bond_mode) */

	write_unlock_bh(&bond->curr_slave_lock);

	bond_set_carrier(bond);

#ifdef CONFIG_NET_POLL_CONTROLLER
	slave_dev->npinfo = bond_netpoll_info(bond);
	if (slave_dev->npinfo) {
		if (slave_enable_netpoll(new_slave)) {
			read_unlock(&bond->lock);
			pr_info("Error, %s: master_dev is using netpoll, "
				 "but new slave device does not support netpoll.\n",
				 bond_dev->name);
			res = -EBUSY;
			goto err_close;
		}
	}
#endif

	read_unlock(&bond->lock);

	res = bond_create_slave_symlinks(bond_dev, slave_dev);
	if (res)
		goto err_close;

	res = netdev_rx_handler_register(slave_dev, bond_handle_frame,
					 new_slave);
	if (res) {
		pr_debug("Error %d calling netdev_rx_handler_register\n", res);
		goto err_dest_symlinks;
	}

	pr_info("%s: enslaving %s as a%s interface with a%s link.\n",
		bond_dev->name, slave_dev->name,
		bond_is_active_slave(new_slave) ? "n active" : " backup",
		new_slave->link != BOND_LINK_DOWN ? "n up" : " down");

	/* enslave is successful */
	return 0;

/* Undo stages on error */
err_dest_symlinks:
	bond_destroy_slave_symlinks(bond_dev, slave_dev);

err_close:
	dev_close(slave_dev);

err_unset_master:
	netdev_set_bond_master(slave_dev, NULL);

err_restore_mac:
	if (!bond->params.fail_over_mac) {
		/* XXX TODO - fom follow mode needs to change master's
		 * MAC if this slave's MAC is in use by the bond, or at
		 * least print a warning.
		 */
		memcpy(addr.sa_data, new_slave->perm_hwaddr, ETH_ALEN);
		addr.sa_family = slave_dev->type;
		dev_set_mac_address(slave_dev, &addr);
	}

err_restore_mtu:
	dev_set_mtu(slave_dev, new_slave->original_mtu);

err_free:
	kfree(new_slave);

err_undo_flags:
	bond_compute_features(bond);

	return res;
}