text: // SPDX-License-Identifier: GPL-2.0
  /* Copyright (C) 2007-2018  B.A.T.M.A.N. contributors:
   *
   * Marek Lindner, Simon Wunderlich
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of version 2 of the GNU General Public
   * License as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, see <http://www.gnu.org/licenses/>.
   */
  
  #include "hard-interface.h"
  #include "main.h"
  
  #include <linux/atomic.h>
  #include <linux/bug.h>
  #include <linux/byteorder/generic.h>
  #include <linux/errno.h>
  #include <linux/gfp.h>
  #include <linux/if.h>
  #include <linux/if_arp.h>
  #include <linux/if_ether.h>
  #include <linux/kernel.h>
  #include <linux/kref.h>
  #include <linux/list.h>
  #include <linux/netdevice.h>
  #include <linux/printk.h>
  #include <linux/rculist.h>
  #include <linux/rtnetlink.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <net/net_namespace.h>
  #include <net/rtnetlink.h>
  #include <uapi/linux/batadv_packet.h>
  
  #include "bat_v.h"
  #include "bridge_loop_avoidance.h"
  #include "debugfs.h"
  #include "distributed-arp-table.h"
  #include "gateway_client.h"
  #include "log.h"
  #include "originator.h"
  #include "send.h"
  #include "soft-interface.h"
  #include "sysfs.h"
  #include "translation-table.h"
  
  /**
   * batadv_hardif_release() - release hard interface from lists and queue for
   *  free after rcu grace period
   * @ref: kref pointer of the hard interface
   */
  void batadv_hardif_release(struct kref *ref)
  {
  	struct batadv_hard_iface *hard_iface;
  
  	hard_iface = container_of(ref, struct batadv_hard_iface, refcount);
  	dev_put(hard_iface->net_dev);
  
  	kfree_rcu(hard_iface, rcu);
  }
  
  /**
   * batadv_hardif_get_by_netdev() - Get hard interface object of a net_device
   * @net_dev: net_device to search for
   *
   * Return: batadv_hard_iface of net_dev (with increased refcnt), NULL on errors
   */
  struct batadv_hard_iface *
  batadv_hardif_get_by_netdev(const struct net_device *net_dev)
  {
  	struct batadv_hard_iface *hard_iface;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
  		if (hard_iface->net_dev == net_dev &&
  		    kref_get_unless_zero(&hard_iface->refcount))
  			goto out;
  	}
  
  	hard_iface = NULL;
  
  out:
  	rcu_read_unlock();
  	return hard_iface;
  }
  
  /**
   * batadv_getlink_net() - return link net namespace (of use fallback)
   * @netdev: net_device to check
   * @fallback_net: return in case get_link_net is not available for @netdev
   *
   * Return: result of rtnl_link_ops->get_link_net or @fallback_net
   */
  static struct net *batadv_getlink_net(const struct net_device *netdev,
  				      struct net *fallback_net)
  {
  	if (!netdev->rtnl_link_ops)
  		return fallback_net;
  
  	if (!netdev->rtnl_link_ops->get_link_net)
  		return fallback_net;
  
  	return netdev->rtnl_link_ops->get_link_net(netdev);
  }
  
  /**
   * batadv_mutual_parents() - check if two devices are each others parent
   * @dev1: 1st net dev
   * @net1: 1st devices netns
   * @dev2: 2nd net dev
   * @net2: 2nd devices netns
   *
   * veth devices come in pairs and each is the parent of the other!
   *
   * Return: true if the devices are each others parent, otherwise false
   */
  static bool batadv_mutual_parents(const struct net_device *dev1,
  				  struct net *net1,
  				  const struct net_device *dev2,
  				  struct net *net2)
  {
  	int dev1_parent_iflink = dev_get_iflink(dev1);
  	int dev2_parent_iflink = dev_get_iflink(dev2);
  	const struct net *dev1_parent_net;
  	const struct net *dev2_parent_net;
  
  	dev1_parent_net = batadv_getlink_net(dev1, net1);
  	dev2_parent_net = batadv_getlink_net(dev2, net2);
  
  	if (!dev1_parent_iflink || !dev2_parent_iflink)
  		return false;
  
  	return (dev1_parent_iflink == dev2->ifindex) &&
  	       (dev2_parent_iflink == dev1->ifindex) &&
  	       net_eq(dev1_parent_net, net2) &&
  	       net_eq(dev2_parent_net, net1);
  }
  
  /**
   * batadv_is_on_batman_iface() - check if a device is a batman iface descendant
   * @net_dev: the device to check
   *
   * If the user creates any virtual device on top of a batman-adv interface, it
   * is important to prevent this new interface to be used to create a new mesh
   * network (this behaviour would lead to a batman-over-batman configuration).
   * This function recursively checks all the fathers of the device passed as
   * argument looking for a batman-adv soft interface.
   *
   * Return: true if the device is descendant of a batman-adv mesh interface (or
   * if it is a batman-adv interface itself), false otherwise
   */
  static bool batadv_is_on_batman_iface(const struct net_device *net_dev)
  {
  	struct net *net = dev_net(net_dev);
  	struct net_device *parent_dev;
  	struct net *parent_net;
  	bool ret;
  
  	/* check if this is a batman-adv mesh interface */
  	if (batadv_softif_is_valid(net_dev))
  		return true;
  
  	/* no more parents..stop recursion */
  	if (dev_get_iflink(net_dev) == 0 ||
  	    dev_get_iflink(net_dev) == net_dev->ifindex)
  		return false;
  
  	parent_net = batadv_getlink_net(net_dev, net);
  
  	/* recurse over the parent device */
  	parent_dev = __dev_get_by_index((struct net *)parent_net,
  					dev_get_iflink(net_dev));
  	/* if we got a NULL parent_dev there is something broken.. */
  	if (WARN(!parent_dev, "Cannot find parent device"))
  		return false;
  
  	if (batadv_mutual_parents(net_dev, net, parent_dev, parent_net))
  		return false;
  
  	ret = batadv_is_on_batman_iface(parent_dev);
  
  	return ret;
  }
  
  static bool batadv_is_valid_iface(const struct net_device *net_dev)
  {
  	if (net_dev->flags & IFF_LOOPBACK)
  		return false;
  
  	if (net_dev->type != ARPHRD_ETHER)
  		return false;
  
  	if (net_dev->addr_len != ETH_ALEN)
  		return false;
  
  	/* no batman over batman */
  	if (batadv_is_on_batman_iface(net_dev))
  		return false;
  
  	return true;
  }
  
  /**
   * batadv_get_real_netdevice() - check if the given netdev struct is a virtual
   *  interface on top of another 'real' interface
   * @netdev: the device to check
   *
   * Callers must hold the rtnl semaphore. You may want batadv_get_real_netdev()
   * instead of this.
   *
   * Return: the 'real' net device or the original net device and NULL in case
   *  of an error.
   */
  static struct net_device *batadv_get_real_netdevice(struct net_device *netdev)
  {
  	struct batadv_hard_iface *hard_iface = NULL;
  	struct net_device *real_netdev = NULL;
  	struct net *real_net;
  	struct net *net;
  	int ifindex;
  
  	ASSERT_RTNL();
  
  	if (!netdev)
  		return NULL;
  
  	if (netdev->ifindex == dev_get_iflink(netdev)) {
  		dev_hold(netdev);
  		return netdev;
  	}
  
  	hard_iface = batadv_hardif_get_by_netdev(netdev);
  	if (!hard_iface || !hard_iface->soft_iface)
  		goto out;
  
  	net = dev_net(hard_iface->soft_iface);
  	ifindex = dev_get_iflink(netdev);
  	real_net = batadv_getlink_net(netdev, net);
  	real_netdev = dev_get_by_index(real_net, ifindex);
  
  out:
  	if (hard_iface)
  		batadv_hardif_put(hard_iface);
  	return real_netdev;
  }
  
  /**
   * batadv_get_real_netdev() - check if the given net_device struct is a virtual
   *  interface on top of another 'real' interface
   * @net_device: the device to check
   *
   * Return: the 'real' net device or the original net device and NULL in case
   *  of an error.
   */
  struct net_device *batadv_get_real_netdev(struct net_device *net_device)
  {
  	struct net_device *real_netdev;
  
  	rtnl_lock();
  	real_netdev = batadv_get_real_netdevice(net_device);
  	rtnl_unlock();
  
  	return real_netdev;
  }
  
  /**
   * batadv_is_wext_netdev() - check if the given net_device struct is a
   *  wext wifi interface
   * @net_device: the device to check
   *
   * Return: true if the net device is a wext wireless device, false
   *  otherwise.
   */
  static bool batadv_is_wext_netdev(struct net_device *net_device)
  {
  	if (!net_device)
  		return false;
  
  #ifdef CONFIG_WIRELESS_EXT
  	/* pre-cfg80211 drivers have to implement WEXT, so it is possible to
  	 * check for wireless_handlers != NULL
  	 */
  	if (net_device->wireless_handlers)
  		return true;
  #endif
  
  	return false;
  }
  
  /**
   * batadv_is_cfg80211_netdev() - check if the given net_device struct is a
   *  cfg80211 wifi interface
   * @net_device: the device to check
   *
   * Return: true if the net device is a cfg80211 wireless device, false
   *  otherwise.
   */
  static bool batadv_is_cfg80211_netdev(struct net_device *net_device)
  {
  	if (!net_device)
  		return false;
  
  	/* cfg80211 drivers have to set ieee80211_ptr */
  	if (net_device->ieee80211_ptr)
  		return true;
  
  	return false;
  }
  
  /**
   * batadv_wifi_flags_evaluate() - calculate wifi flags for net_device
   * @net_device: the device to check
   *
   * Return: batadv_hard_iface_wifi_flags flags of the device
   */
  static u32 batadv_wifi_flags_evaluate(struct net_device *net_device)
  {
  	u32 wifi_flags = 0;
  	struct net_device *real_netdev;
  
  	if (batadv_is_wext_netdev(net_device))
  		wifi_flags |= BATADV_HARDIF_WIFI_WEXT_DIRECT;
  
  	if (batadv_is_cfg80211_netdev(net_device))
  		wifi_flags |= BATADV_HARDIF_WIFI_CFG80211_DIRECT;
  
  	real_netdev = batadv_get_real_netdevice(net_device);
  	if (!real_netdev)
  		return wifi_flags;
  
  	if (real_netdev == net_device)
  		goto out;
  
  	if (batadv_is_wext_netdev(real_netdev))
  		wifi_flags |= BATADV_HARDIF_WIFI_WEXT_INDIRECT;
  
  	if (batadv_is_cfg80211_netdev(real_netdev))
  		wifi_flags |= BATADV_HARDIF_WIFI_CFG80211_INDIRECT;
  
  out:
  	dev_put(real_netdev);
  	return wifi_flags;
  }
  
  /**
   * batadv_is_cfg80211_hardif() - check if the given hardif is a cfg80211 wifi
   *  interface
   * @hard_iface: the device to check
   *
   * Return: true if the net device is a cfg80211 wireless device, false
   *  otherwise.
   */
  bool batadv_is_cfg80211_hardif(struct batadv_hard_iface *hard_iface)
  {
  	u32 allowed_flags = 0;
  
  	allowed_flags |= BATADV_HARDIF_WIFI_CFG80211_DIRECT;
  	allowed_flags |= BATADV_HARDIF_WIFI_CFG80211_INDIRECT;
  
  	return !!(hard_iface->wifi_flags & allowed_flags);
  }
  
  /**
   * batadv_is_wifi_hardif() - check if the given hardif is a wifi interface
   * @hard_iface: the device to check
   *
   * Return: true if the net device is a 802.11 wireless device, false otherwise.
   */
  bool batadv_is_wifi_hardif(struct batadv_hard_iface *hard_iface)
  {
  	if (!hard_iface)
  		return false;
  
  	return hard_iface->wifi_flags != 0;
  }
  
  /**
   * batadv_hardif_no_broadcast() - check whether (re)broadcast is necessary
   * @if_outgoing: the outgoing interface checked and considered for (re)broadcast
   * @orig_addr: the originator of this packet
   * @orig_neigh: originator address of the forwarder we just got the packet from
   *  (NULL if we originated)
   *
   * Checks whether a packet needs to be (re)broadcasted on the given interface.
   *
   * Return:
   *	BATADV_HARDIF_BCAST_NORECIPIENT: No neighbor on interface
   *	BATADV_HARDIF_BCAST_DUPFWD: Just one neighbor, but it is the forwarder
   *	BATADV_HARDIF_BCAST_DUPORIG: Just one neighbor, but it is the originator
   *	BATADV_HARDIF_BCAST_OK: Several neighbors, must broadcast
   */
  int batadv_hardif_no_broadcast(struct batadv_hard_iface *if_outgoing,
  			       u8 *orig_addr, u8 *orig_neigh)
  {
  	struct batadv_hardif_neigh_node *hardif_neigh;
  	struct hlist_node *first;
  	int ret = BATADV_HARDIF_BCAST_OK;
  
  	rcu_read_lock();
  
  	/* 0 neighbors -> no (re)broadcast */
  	first = rcu_dereference(hlist_first_rcu(&if_outgoing->neigh_list));
  	if (!first) {
  		ret = BATADV_HARDIF_BCAST_NORECIPIENT;
  		goto out;
  	}
  
  	/* >1 neighbors -> (re)brodcast */
  	if (rcu_dereference(hlist_next_rcu(first)))
  		goto out;
  
  	hardif_neigh = hlist_entry(first, struct batadv_hardif_neigh_node,
  				   list);
  
  	/* 1 neighbor, is the originator -> no rebroadcast */
  	if (orig_addr && batadv_compare_eth(hardif_neigh->orig, orig_addr)) {
  		ret = BATADV_HARDIF_BCAST_DUPORIG;
  	/* 1 neighbor, is the one we received from -> no rebroadcast */
  	} else if (orig_neigh &&
  		   batadv_compare_eth(hardif_neigh->orig, orig_neigh)) {
  		ret = BATADV_HARDIF_BCAST_DUPFWD;
  	}
  
  out:
  	rcu_read_unlock();
  	return ret;
  }
  
  static struct batadv_hard_iface *
  batadv_hardif_get_active(const struct net_device *soft_iface)
  {
  	struct batadv_hard_iface *hard_iface;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
  		if (hard_iface->soft_iface != soft_iface)
  			continue;
  
  		if (hard_iface->if_status == BATADV_IF_ACTIVE &&
  		    kref_get_unless_zero(&hard_iface->refcount))
  			goto out;
  	}
  
  	hard_iface = NULL;
  
  out:
  	rcu_read_unlock();
  	return hard_iface;
  }
  
  static void batadv_primary_if_update_addr(struct batadv_priv *bat_priv,
  					  struct batadv_hard_iface *oldif)
  {
  	struct batadv_hard_iface *primary_if;
  
  	primary_if = batadv_primary_if_get_selected(bat_priv);
  	if (!primary_if)
  		goto out;
  
  	batadv_dat_init_own_addr(bat_priv, primary_if);
  	batadv_bla_update_orig_address(bat_priv, primary_if, oldif);
  out:
  	if (primary_if)
  		batadv_hardif_put(primary_if);
  }
  
  static void batadv_primary_if_select(struct batadv_priv *bat_priv,
  				     struct batadv_hard_iface *new_hard_iface)
  {
  	struct batadv_hard_iface *curr_hard_iface;
  
  	ASSERT_RTNL();
  
  	if (new_hard_iface)
  		kref_get(&new_hard_iface->refcount);
  
  	curr_hard_iface = rcu_dereference_protected(bat_priv->primary_if, 1);
  	rcu_assign_pointer(bat_priv->primary_if, new_hard_iface);
  
  	if (!new_hard_iface)
  		goto out;
  
  	bat_priv->algo_ops->iface.primary_set(new_hard_iface);
  	batadv_primary_if_update_addr(bat_priv, curr_hard_iface);
  
  out:
  	if (curr_hard_iface)
  		batadv_hardif_put(curr_hard_iface);
  }
  
  static bool
  batadv_hardif_is_iface_up(const struct batadv_hard_iface *hard_iface)
  {
  	if (hard_iface->net_dev->flags & IFF_UP)
  		return true;
  
  	return false;
  }
  
  static void batadv_check_known_mac_addr(const struct net_device *net_dev)
  {
  	const struct batadv_hard_iface *hard_iface;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
  		if (hard_iface->if_status != BATADV_IF_ACTIVE &&
  		    hard_iface->if_status != BATADV_IF_TO_BE_ACTIVATED)
  			continue;
  
  		if (hard_iface->net_dev == net_dev)
  			continue;
  
  		if (!batadv_compare_eth(hard_iface->net_dev->dev_addr,
  					net_dev->dev_addr))
  			continue;
  
  		pr_warn("The newly added mac address (%pM) already exists on: %s\n",
  			net_dev->dev_addr, hard_iface->net_dev->name);
  		pr_warn("It is strongly recommended to keep mac addresses unique to avoid problems!\n");
  	}
  	rcu_read_unlock();
  }
  
  /**
   * batadv_hardif_recalc_extra_skbroom() - Recalculate skbuff extra head/tailroom
   * @soft_iface: netdev struct of the mesh interface
   */
  static void batadv_hardif_recalc_extra_skbroom(struct net_device *soft_iface)
  {
  	const struct batadv_hard_iface *hard_iface;
  	unsigned short lower_header_len = ETH_HLEN;
  	unsigned short lower_headroom = 0;
  	unsigned short lower_tailroom = 0;
  	unsigned short needed_headroom;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
  		if (hard_iface->if_status == BATADV_IF_NOT_IN_USE)
  			continue;
  
  		if (hard_iface->soft_iface != soft_iface)
  			continue;
  
  		lower_header_len = max_t(unsigned short, lower_header_len,
  					 hard_iface->net_dev->hard_header_len);
  
  		lower_headroom = max_t(unsigned short, lower_headroom,
  				       hard_iface->net_dev->needed_headroom);
  
  		lower_tailroom = max_t(unsigned short, lower_tailroom,
  				       hard_iface->net_dev->needed_tailroom);
  	}
  	rcu_read_unlock();
  
  	needed_headroom = lower_headroom + (lower_header_len - ETH_HLEN);
  	needed_headroom += batadv_max_header_len();
  
  	soft_iface->needed_headroom = needed_headroom;
  	soft_iface->needed_tailroom = lower_tailroom;
  }
  
  /**
   * batadv_hardif_min_mtu() - Calculate maximum MTU for soft interface
   * @soft_iface: netdev struct of the soft interface
   *
   * Return: MTU for the soft-interface (limited by the minimal MTU of all active
   *  slave interfaces)
   */
  int batadv_hardif_min_mtu(struct net_device *soft_iface)
  {
  	struct batadv_priv *bat_priv = netdev_priv(soft_iface);
  	const struct batadv_hard_iface *hard_iface;
  	int min_mtu = INT_MAX;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
  		if (hard_iface->if_status != BATADV_IF_ACTIVE &&
  		    hard_iface->if_status != BATADV_IF_TO_BE_ACTIVATED)
  			continue;
  
  		if (hard_iface->soft_iface != soft_iface)
  			continue;
  
  		min_mtu = min_t(int, hard_iface->net_dev->mtu, min_mtu);
  	}
  	rcu_read_unlock();
  
  	if (atomic_read(&bat_priv->fragmentation) == 0)
  		goto out;
  
  	/* with fragmentation enabled the maximum size of internally generated
  	 * packets such as translation table exchanges or tvlv containers, etc
  	 * has to be calculated
  	 */
  	min_mtu = min_t(int, min_mtu, BATADV_FRAG_MAX_FRAG_SIZE);
  	min_mtu -= sizeof(struct batadv_frag_packet);
  	min_mtu *= BATADV_FRAG_MAX_FRAGMENTS;
  
  out:
  	/* report to the other components the maximum amount of bytes that
  	 * batman-adv can send over the wire (without considering the payload
  	 * overhead). For example, this value is used by TT to compute the
  	 * maximum local table table size
  	 */
  	atomic_set(&bat_priv->packet_size_max, min_mtu);
  
  	/* the real soft-interface MTU is computed by removing the payload
  	 * overhead from the maximum amount of bytes that was just computed.
  	 *
  	 * However batman-adv does not support MTUs bigger than ETH_DATA_LEN
  	 */
  	return min_t(int, min_mtu - batadv_max_header_len(), ETH_DATA_LEN);
  }
  
  /**
   * batadv_update_min_mtu() - Adjusts the MTU if a new interface with a smaller
   *  MTU appeared
   * @soft_iface: netdev struct of the soft interface
   */
  void batadv_update_min_mtu(struct net_device *soft_iface)
  {
  	soft_iface->mtu = batadv_hardif_min_mtu(soft_iface);
  
  	/* Check if the local translate table should be cleaned up to match a
  	 * new (and smaller) MTU.
  	 */
  	batadv_tt_local_resize_to_mtu(soft_iface);
  }
  
  static void
  batadv_hardif_activate_interface(struct batadv_hard_iface *hard_iface)
  {
  	struct batadv_priv *bat_priv;
  	struct batadv_hard_iface *primary_if = NULL;
  
  	if (hard_iface->if_status != BATADV_IF_INACTIVE)
  		goto out;
  
  	bat_priv = netdev_priv(hard_iface->soft_iface);
  
  	bat_priv->algo_ops->iface.update_mac(hard_iface);
  	hard_iface->if_status = BATADV_IF_TO_BE_ACTIVATED;
  
  	/* the first active interface becomes our primary interface or
  	 * the next active interface after the old primary interface was removed
  	 */
  	primary_if = batadv_primary_if_get_selected(bat_priv);
  	if (!primary_if)
  		batadv_primary_if_select(bat_priv, hard_iface);
  
  	batadv_info(hard_iface->soft_iface, "Interface activated: %s\n",
  		    hard_iface->net_dev->name);
  
  	batadv_update_min_mtu(hard_iface->soft_iface);
  
  	if (bat_priv->algo_ops->iface.activate)
  		bat_priv->algo_ops->iface.activate(hard_iface);
  
  out:
  	if (primary_if)
  		batadv_hardif_put(primary_if);
  }
  
  static void
  batadv_hardif_deactivate_interface(struct batadv_hard_iface *hard_iface)
  {
  	if (hard_iface->if_status != BATADV_IF_ACTIVE &&
  	    hard_iface->if_status != BATADV_IF_TO_BE_ACTIVATED)
  		return;
  
  	hard_iface->if_status = BATADV_IF_INACTIVE;
  
  	batadv_info(hard_iface->soft_iface, "Interface deactivated: %s\n",
  		    hard_iface->net_dev->name);
  
  	batadv_update_min_mtu(hard_iface->soft_iface);
  }
  
  /**
   * batadv_master_del_slave() - remove hard_iface from the current master iface
   * @slave: the interface enslaved in another master
   * @master: the master from which slave has to be removed
   *
   * Invoke ndo_del_slave on master passing slave as argument. In this way slave
   * is free'd and master can correctly change its internal state.
   *
   * Return: 0 on success, a negative value representing the error otherwise
   */
  static int batadv_master_del_slave(struct batadv_hard_iface *slave,
  				   struct net_device *master)
  {
  	int ret;
  
  	if (!master)
  		return 0;
  
  	ret = -EBUSY;
  	if (master->netdev_ops->ndo_del_slave)
  		ret = master->netdev_ops->ndo_del_slave(master, slave->net_dev);
  
  	return ret;
  }
  
  /**
   * batadv_hardif_enable_interface() - Enslave hard interface to soft interface
   * @hard_iface: hard interface to add to soft interface
   * @net: the applicable net namespace
   * @iface_name: name of the soft interface
   *
   * Return: 0 on success or negative error number in case of failure
   */
  int batadv_hardif_enable_interface(struct batadv_hard_iface *hard_iface,
  				   struct net *net, const char *iface_name)
  {
  	struct batadv_priv *bat_priv;
  	struct net_device *soft_iface, *master;
  	__be16 ethertype = htons(ETH_P_BATMAN);
  	int max_header_len = batadv_max_header_len();
  	int ret;
  
  	if (hard_iface->if_status != BATADV_IF_NOT_IN_USE)
  		goto out;
  
  	kref_get(&hard_iface->refcount);
  
  	soft_iface = dev_get_by_name(net, iface_name);
  
  	if (!soft_iface) {
  		soft_iface = batadv_softif_create(net, iface_name);
  
  		if (!soft_iface) {
  			ret = -ENOMEM;
  			goto err;
  		}
  
  		/* dev_get_by_name() increases the reference counter for us */
  		dev_hold(soft_iface);
  	}
  
  	if (!batadv_softif_is_valid(soft_iface)) {
  		pr_err("Can't create batman mesh interface %s: already exists as regular interface\n",
  		       soft_iface->name);
  		ret = -EINVAL;
  		goto err_dev;
  	}
  
  	/* check if the interface is enslaved in another virtual one and
  	 * in that case unlink it first
  	 */
  	master = netdev_master_upper_dev_get(hard_iface->net_dev);
  	ret = batadv_master_del_slave(hard_iface, master);
  	if (ret)
  		goto err_dev;
  
  	hard_iface->soft_iface = soft_iface;
  	bat_priv = netdev_priv(hard_iface->soft_iface);
  
  	ret = netdev_master_upper_dev_link(hard_iface->net_dev,
  					   soft_iface, NULL, NULL, NULL);
  	if (ret)
  		goto err_dev;
  
  	ret = bat_priv->algo_ops->iface.enable(hard_iface);
  	if (ret < 0)
  		goto err_upper;
  
  	hard_iface->if_status = BATADV_IF_INACTIVE;
  
  	kref_get(&hard_iface->refcount);
  	hard_iface->batman_adv_ptype.type = ethertype;
  	hard_iface->batman_adv_ptype.func = batadv_batman_skb_recv;
  	hard_iface->batman_adv_ptype.dev = hard_iface->net_dev;
  	dev_add_pack(&hard_iface->batman_adv_ptype);
  
  	batadv_info(hard_iface->soft_iface, "Adding interface: %s\n",
  		    hard_iface->net_dev->name);
  
  	if (atomic_read(&bat_priv->fragmentation) &&
  	    hard_iface->net_dev->mtu < ETH_DATA_LEN + max_header_len)
  		batadv_info(hard_iface->soft_iface,
  			    "The MTU of interface %s is too small (%i) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to %i would solve the problem.\n",
  			    hard_iface->net_dev->name, hard_iface->net_dev->mtu,
  			    ETH_DATA_LEN + max_header_len);
  
  	if (!atomic_read(&bat_priv->fragmentation) &&
  	    hard_iface->net_dev->mtu < ETH_DATA_LEN + max_header_len)
  		batadv_info(hard_iface->soft_iface,
  			    "The MTU of interface %s is too small (%i) to handle the transport of batman-adv packets. If you experience problems getting traffic through try increasing the MTU to %i.\n",
  			    hard_iface->net_dev->name, hard_iface->net_dev->mtu,
  			    ETH_DATA_LEN + max_header_len);
  
  	if (batadv_hardif_is_iface_up(hard_iface))
  		batadv_hardif_activate_interface(hard_iface);
  	else
  		batadv_err(hard_iface->soft_iface,
  			   "Not using interface %s (retrying later): interface not active\n",
  			   hard_iface->net_dev->name);
  
  	batadv_hardif_recalc_extra_skbroom(soft_iface);
  
  out:
  	return 0;
  
  err_upper:
  	netdev_upper_dev_unlink(hard_iface->net_dev, soft_iface);
  err_dev:
  	hard_iface->soft_iface = NULL;
  	dev_put(soft_iface);
  err:
  	batadv_hardif_put(hard_iface);
  	return ret;
  }
  
  /**
   * batadv_hardif_cnt() - get number of interfaces enslaved to soft interface
   * @soft_iface: soft interface to check
   *
   * This function is only using RCU for locking - the result can therefore be
   * off when another functions is modifying the list at the same time. The
   * caller can use the rtnl_lock to make sure that the count is accurate.
   *
   * Return: number of connected/enslaved hard interfaces
   */
  static size_t batadv_hardif_cnt(const struct net_device *soft_iface)
  {
  	struct batadv_hard_iface *hard_iface;
  	size_t count = 0;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
  		if (hard_iface->soft_iface != soft_iface)
  			continue;
  
  		count++;
  	}
  	rcu_read_unlock();
  
  	return count;
  }
  
  /**
   * batadv_hardif_disable_interface() - Remove hard interface from soft interface
   * @hard_iface: hard interface to be removed
   * @autodel: whether to delete soft interface when it doesn't contain any other
   *  slave interfaces
   */
  void batadv_hardif_disable_interface(struct batadv_hard_iface *hard_iface,
  				     enum batadv_hard_if_cleanup autodel)
  {
  	struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);
  	struct batadv_hard_iface *primary_if = NULL;
  
  	batadv_hardif_deactivate_interface(hard_iface);
  
  	if (hard_iface->if_status != BATADV_IF_INACTIVE)
  		goto out;
  
  	batadv_info(hard_iface->soft_iface, "Removing interface: %s\n",
  		    hard_iface->net_dev->name);
  	dev_remove_pack(&hard_iface->batman_adv_ptype);
  	batadv_hardif_put(hard_iface);
  
  	primary_if = batadv_primary_if_get_selected(bat_priv);
  	if (hard_iface == primary_if) {
  		struct batadv_hard_iface *new_if;
  
  		new_if = batadv_hardif_get_active(hard_iface->soft_iface);
  		batadv_primary_if_select(bat_priv, new_if);
  
  		if (new_if)
  			batadv_hardif_put(new_if);
  	}
  
  	bat_priv->algo_ops->iface.disable(hard_iface);
  	hard_iface->if_status = BATADV_IF_NOT_IN_USE;
  
  	/* delete all references to this hard_iface */
  	batadv_purge_orig_ref(bat_priv);
  	batadv_purge_outstanding_packets(bat_priv, hard_iface);
  	dev_put(hard_iface->soft_iface);
  
  	netdev_upper_dev_unlink(hard_iface->net_dev, hard_iface->soft_iface);
  	batadv_hardif_recalc_extra_skbroom(hard_iface->soft_iface);
  
  	/* nobody uses this interface anymore */
  	if (batadv_hardif_cnt(hard_iface->soft_iface) <= 1) {
  		batadv_gw_check_client_stop(bat_priv);
  
  		if (autodel == BATADV_IF_CLEANUP_AUTO)
  			batadv_softif_destroy_sysfs(hard_iface->soft_iface);
  	}
  
  	hard_iface->soft_iface = NULL;
  	batadv_hardif_put(hard_iface);
  
  out:
  	if (primary_if)
  		batadv_hardif_put(primary_if);
  }
  
  static struct batadv_hard_iface *
  batadv_hardif_add_interface(struct net_device *net_dev)
  {
  	struct batadv_hard_iface *hard_iface;
  	int ret;
  
  	ASSERT_RTNL();
  
  	if (!batadv_is_valid_iface(net_dev))
  		goto out;
  
  	dev_hold(net_dev);
  
  	hard_iface = kzalloc(sizeof(*hard_iface), GFP_ATOMIC);
  	if (!hard_iface)
  		goto release_dev;
  
  	ret = batadv_sysfs_add_hardif(&hard_iface->hardif_obj, net_dev);
  	if (ret)
  		goto free_if;
  
  	hard_iface->net_dev = net_dev;
  	hard_iface->soft_iface = NULL;
  	hard_iface->if_status = BATADV_IF_NOT_IN_USE;
  
  	ret = batadv_debugfs_add_hardif(hard_iface);
  	if (ret)
  		goto free_sysfs;
  
  	INIT_LIST_HEAD(&hard_iface->list);
  	INIT_HLIST_HEAD(&hard_iface->neigh_list);
  
  	spin_lock_init(&hard_iface->neigh_list_lock);
  	kref_init(&hard_iface->refcount);
  
  	hard_iface->num_bcasts = BATADV_NUM_BCASTS_DEFAULT;
  	hard_iface->wifi_flags = batadv_wifi_flags_evaluate(net_dev);
  	if (batadv_is_wifi_hardif(hard_iface))
  		hard_iface->num_bcasts = BATADV_NUM_BCASTS_WIRELESS;
  
  	batadv_v_hardif_init(hard_iface);
  
  	batadv_check_known_mac_addr(hard_iface->net_dev);
  	kref_get(&hard_iface->refcount);
  	list_add_tail_rcu(&hard_iface->list, &batadv_hardif_list);
  
  	return hard_iface;
  
  free_sysfs:
  	batadv_sysfs_del_hardif(&hard_iface->hardif_obj);
  free_if:
  	kfree(hard_iface);
  release_dev:
  	dev_put(net_dev);
  out:
  	return NULL;
  }
  
  static void batadv_hardif_remove_interface(struct batadv_hard_iface *hard_iface)
  {
  	ASSERT_RTNL();
  
  	/* first deactivate interface */
  	if (hard_iface->if_status != BATADV_IF_NOT_IN_USE)
  		batadv_hardif_disable_interface(hard_iface,
  						BATADV_IF_CLEANUP_KEEP);
  
  	if (hard_iface->if_status != BATADV_IF_NOT_IN_USE)
  		return;
  
  	hard_iface->if_status = BATADV_IF_TO_BE_REMOVED;
  	batadv_debugfs_del_hardif(hard_iface);
  	batadv_sysfs_del_hardif(&hard_iface->hardif_obj);
  	batadv_hardif_put(hard_iface);
  }
  
  /**
   * batadv_hardif_remove_interfaces() - Remove all hard interfaces
   */
  void batadv_hardif_remove_interfaces(void)
  {
  	struct batadv_hard_iface *hard_iface, *hard_iface_tmp;
  
  	rtnl_lock();
  	list_for_each_entry_safe(hard_iface, hard_iface_tmp,
  				 &batadv_hardif_list, list) {
  		list_del_rcu(&hard_iface->list);
  		batadv_hardif_remove_interface(hard_iface);
  	}
  	rtnl_unlock();
  }
  
  /**
   * batadv_hard_if_event_softif() - Handle events for soft interfaces
   * @event: NETDEV_* event to handle
   * @net_dev: net_device which generated an event
   *
   * Return: NOTIFY_* result
   */
  static int batadv_hard_if_event_softif(unsigned long event,
  				       struct net_device *net_dev)
  {
  	struct batadv_priv *bat_priv;
  
  	switch (event) {
  	case NETDEV_REGISTER:
  		batadv_sysfs_add_meshif(net_dev);
  		bat_priv = netdev_priv(net_dev);
  		batadv_softif_create_vlan(bat_priv, BATADV_NO_FLAGS);
  		break;
  	case NETDEV_CHANGENAME:
  		batadv_debugfs_rename_meshif(net_dev);
  		break;
  	}
  
  	return NOTIFY_DONE;
  }
  
  static int batadv_hard_if_event(struct notifier_block *this,
  				unsigned long event, void *ptr)
  {
  	struct net_device *net_dev = netdev_notifier_info_to_dev(ptr);
  	struct batadv_hard_iface *hard_iface;
  	struct batadv_hard_iface *primary_if = NULL;
  	struct batadv_priv *bat_priv;
  
  	if (batadv_softif_is_valid(net_dev))
  		return batadv_hard_if_event_softif(event, net_dev);
  
  	hard_iface = batadv_hardif_get_by_netdev(net_dev);
  	if (!hard_iface && (event == NETDEV_REGISTER ||
  			    event == NETDEV_POST_TYPE_CHANGE))
  		hard_iface = batadv_hardif_add_interface(net_dev);
  
  	if (!hard_iface)
  		goto out;
  
  	switch (event) {
  	case NETDEV_UP:
  		batadv_hardif_activate_interface(hard_iface);
  		break;
  	case NETDEV_GOING_DOWN:
  	case NETDEV_DOWN:
  		batadv_hardif_deactivate_interface(hard_iface);
  		break;
  	case NETDEV_UNREGISTER:
  	case NETDEV_PRE_TYPE_CHANGE:
  		list_del_rcu(&hard_iface->list);
  
  		batadv_hardif_remove_interface(hard_iface);
  		break;
  	case NETDEV_CHANGEMTU:
  		if (hard_iface->soft_iface)
  			batadv_update_min_mtu(hard_iface->soft_iface);
  		break;
  	case NETDEV_CHANGEADDR:
  		if (hard_iface->if_status == BATADV_IF_NOT_IN_USE)
  			goto hardif_put;
  
  		batadv_check_known_mac_addr(hard_iface->net_dev);
  
  		bat_priv = netdev_priv(hard_iface->soft_iface);
  		bat_priv->algo_ops->iface.update_mac(hard_iface);
  
  		primary_if = batadv_primary_if_get_selected(bat_priv);
  		if (!primary_if)
  			goto hardif_put;
  
  		if (hard_iface == primary_if)
  			batadv_primary_if_update_addr(bat_priv, NULL);
  		break;
  	case NETDEV_CHANGEUPPER:
  		hard_iface->wifi_flags = batadv_wifi_flags_evaluate(net_dev);
  		if (batadv_is_wifi_hardif(hard_iface))
  			hard_iface->num_bcasts = BATADV_NUM_BCASTS_WIRELESS;
  		break;
  	case NETDEV_CHANGENAME:
  		batadv_debugfs_rename_hardif(hard_iface);
  		break;
  	default:
  		break;
  	}
  
  hardif_put:
  	batadv_hardif_put(hard_iface);
  out:
  	if (primary_if)
  		batadv_hardif_put(primary_if);
  	return NOTIFY_DONE;
  }
  
  struct notifier_block batadv_hard_if_notifier = {
  	.notifier_call = batadv_hard_if_event,
  };
  