text: // SPDX-License-Identifier: GPL-2.0
  /* Copyright (C) 2007-2019  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 "send.h"
  #include "main.h"
  
  #include <linux/atomic.h>
  #include <linux/bug.h>
  #include <linux/byteorder/generic.h>
  #include <linux/errno.h>
  #include <linux/etherdevice.h>
  #include <linux/gfp.h>
  #include <linux/if.h>
  #include <linux/if_ether.h>
  #include <linux/jiffies.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/rcupdate.h>
  #include <linux/skbuff.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/stddef.h>
  #include <linux/workqueue.h>
  
  #include "distributed-arp-table.h"
  #include "fragmentation.h"
  #include "gateway_client.h"
  #include "hard-interface.h"
  #include "log.h"
  #include "network-coding.h"
  #include "originator.h"
  #include "routing.h"
  #include "soft-interface.h"
  #include "translation-table.h"
  
  static void batadv_send_outstanding_bcast_packet(struct work_struct *work);
  
  /**
   * batadv_send_skb_packet() - send an already prepared packet
   * @skb: the packet to send
   * @hard_iface: the interface to use to send the broadcast packet
   * @dst_addr: the payload destination
   *
   * Send out an already prepared packet to the given neighbor or broadcast it
   * using the specified interface. Either hard_iface or neigh_node must be not
   * NULL.
   * If neigh_node is NULL, then the packet is broadcasted using hard_iface,
   * otherwise it is sent as unicast to the given neighbor.
   *
   * Regardless of the return value, the skb is consumed.
   *
   * Return: A negative errno code is returned on a failure. A success does not
   * guarantee the frame will be transmitted as it may be dropped due
   * to congestion or traffic shaping.
   */
  int batadv_send_skb_packet(struct sk_buff *skb,
  			   struct batadv_hard_iface *hard_iface,
  			   const u8 *dst_addr)
  {
  	struct batadv_priv *bat_priv;
  	struct ethhdr *ethhdr;
  	int ret;
  
  	bat_priv = netdev_priv(hard_iface->soft_iface);
  
  	if (hard_iface->if_status != BATADV_IF_ACTIVE)
  		goto send_skb_err;
  
  	if (unlikely(!hard_iface->net_dev))
  		goto send_skb_err;
  
  	if (!(hard_iface->net_dev->flags & IFF_UP)) {
  		pr_warn("Interface %s is not up - can't send packet via that interface!\n",
  			hard_iface->net_dev->name);
  		goto send_skb_err;
  	}
  
  	/* push to the ethernet header. */
  	if (batadv_skb_head_push(skb, ETH_HLEN) < 0)
  		goto send_skb_err;
  
  	skb_reset_mac_header(skb);
  
  	ethhdr = eth_hdr(skb);
  	ether_addr_copy(ethhdr->h_source, hard_iface->net_dev->dev_addr);
  	ether_addr_copy(ethhdr->h_dest, dst_addr);
  	ethhdr->h_proto = htons(ETH_P_BATMAN);
  
  	skb_set_network_header(skb, ETH_HLEN);
  	skb->protocol = htons(ETH_P_BATMAN);
  
  	skb->dev = hard_iface->net_dev;
  
  	/* Save a clone of the skb to use when decoding coded packets */
  	batadv_nc_skb_store_for_decoding(bat_priv, skb);
  
  	/* dev_queue_xmit() returns a negative result on error.	 However on
  	 * congestion and traffic shaping, it drops and returns NET_XMIT_DROP
  	 * (which is > 0). This will not be treated as an error.
  	 */
  	ret = dev_queue_xmit(skb);
  	return net_xmit_eval(ret);
  send_skb_err:
  	kfree_skb(skb);
  	return NET_XMIT_DROP;
  }
  
  /**
   * batadv_send_broadcast_skb() - Send broadcast packet via hard interface
   * @skb: packet to be transmitted (with batadv header and no outer eth header)
   * @hard_iface: outgoing interface
   *
   * Return: A negative errno code is returned on a failure. A success does not
   * guarantee the frame will be transmitted as it may be dropped due
   * to congestion or traffic shaping.
   */
  int batadv_send_broadcast_skb(struct sk_buff *skb,
  			      struct batadv_hard_iface *hard_iface)
  {
  	return batadv_send_skb_packet(skb, hard_iface, batadv_broadcast_addr);
  }
  
  /**
   * batadv_send_unicast_skb() - Send unicast packet to neighbor
   * @skb: packet to be transmitted (with batadv header and no outer eth header)
   * @neigh: neighbor which is used as next hop to destination
   *
   * Return: A negative errno code is returned on a failure. A success does not
   * guarantee the frame will be transmitted as it may be dropped due
   * to congestion or traffic shaping.
   */
  int batadv_send_unicast_skb(struct sk_buff *skb,
  			    struct batadv_neigh_node *neigh)
  {
  #ifdef CONFIG_BATMAN_ADV_BATMAN_V
  	struct batadv_hardif_neigh_node *hardif_neigh;
  #endif
  	int ret;
  
  	ret = batadv_send_skb_packet(skb, neigh->if_incoming, neigh->addr);
  
  #ifdef CONFIG_BATMAN_ADV_BATMAN_V
  	hardif_neigh = batadv_hardif_neigh_get(neigh->if_incoming, neigh->addr);
  
  	if (hardif_neigh && ret != NET_XMIT_DROP)
  		hardif_neigh->bat_v.last_unicast_tx = jiffies;
  
  	if (hardif_neigh)
  		batadv_hardif_neigh_put(hardif_neigh);
  #endif
  
  	return ret;
  }
  
  /**
   * batadv_send_skb_to_orig() - Lookup next-hop and transmit skb.
   * @skb: Packet to be transmitted.
   * @orig_node: Final destination of the packet.
   * @recv_if: Interface used when receiving the packet (can be NULL).
   *
   * Looks up the best next-hop towards the passed originator and passes the
   * skb on for preparation of MAC header. If the packet originated from this
   * host, NULL can be passed as recv_if and no interface alternating is
   * attempted.
   *
   * Return: negative errno code on a failure, -EINPROGRESS if the skb is
   * buffered for later transmit or the NET_XMIT status returned by the
   * lower routine if the packet has been passed down.
   */
  int batadv_send_skb_to_orig(struct sk_buff *skb,
  			    struct batadv_orig_node *orig_node,
  			    struct batadv_hard_iface *recv_if)
  {
  	struct batadv_priv *bat_priv = orig_node->bat_priv;
  	struct batadv_neigh_node *neigh_node;
  	int ret;
  
  	/* batadv_find_router() increases neigh_nodes refcount if found. */
  	neigh_node = batadv_find_router(bat_priv, orig_node, recv_if);
  	if (!neigh_node) {
  		ret = -EINVAL;
  		goto free_skb;
  	}
  
  	/* Check if the skb is too large to send in one piece and fragment
  	 * it if needed.
  	 */
  	if (atomic_read(&bat_priv->fragmentation) &&
  	    skb->len > neigh_node->if_incoming->net_dev->mtu) {
  		/* Fragment and send packet. */
  		ret = batadv_frag_send_packet(skb, orig_node, neigh_node);
  		/* skb was consumed */
  		skb = NULL;
  
  		goto put_neigh_node;
  	}
  
  	/* try to network code the packet, if it is received on an interface
  	 * (i.e. being forwarded). If the packet originates from this node or if
  	 * network coding fails, then send the packet as usual.
  	 */
  	if (recv_if && batadv_nc_skb_forward(skb, neigh_node))
  		ret = -EINPROGRESS;
  	else
  		ret = batadv_send_unicast_skb(skb, neigh_node);
  
  	/* skb was consumed */
  	skb = NULL;
  
  put_neigh_node:
  	batadv_neigh_node_put(neigh_node);
  free_skb:
  	kfree_skb(skb);
  
  	return ret;
  }
  
  /**
   * batadv_send_skb_push_fill_unicast() - extend the buffer and initialize the
   *  common fields for unicast packets
   * @skb: the skb carrying the unicast header to initialize
   * @hdr_size: amount of bytes to push at the beginning of the skb
   * @orig_node: the destination node
   *
   * Return: false if the buffer extension was not possible or true otherwise.
   */
  static bool
  batadv_send_skb_push_fill_unicast(struct sk_buff *skb, int hdr_size,
  				  struct batadv_orig_node *orig_node)
  {
  	struct batadv_unicast_packet *unicast_packet;
  	u8 ttvn = (u8)atomic_read(&orig_node->last_ttvn);
  
  	if (batadv_skb_head_push(skb, hdr_size) < 0)
  		return false;
  
  	unicast_packet = (struct batadv_unicast_packet *)skb->data;
  	unicast_packet->version = BATADV_COMPAT_VERSION;
  	/* batman packet type: unicast */
  	unicast_packet->packet_type = BATADV_UNICAST;
  	/* set unicast ttl */
  	unicast_packet->ttl = BATADV_TTL;
  	/* copy the destination for faster routing */
  	ether_addr_copy(unicast_packet->dest, orig_node->orig);
  	/* set the destination tt version number */
  	unicast_packet->ttvn = ttvn;
  
  	return true;
  }
  
  /**
   * batadv_send_skb_prepare_unicast() - encapsulate an skb with a unicast header
   * @skb: the skb containing the payload to encapsulate
   * @orig_node: the destination node
   *
   * Return: false if the payload could not be encapsulated or true otherwise.
   */
  static bool batadv_send_skb_prepare_unicast(struct sk_buff *skb,
  					    struct batadv_orig_node *orig_node)
  {
  	size_t uni_size = sizeof(struct batadv_unicast_packet);
  
  	return batadv_send_skb_push_fill_unicast(skb, uni_size, orig_node);
  }
  
  /**
   * batadv_send_skb_prepare_unicast_4addr() - encapsulate an skb with a
   *  unicast 4addr header
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: the skb containing the payload to encapsulate
   * @orig: the destination node
   * @packet_subtype: the unicast 4addr packet subtype to use
   *
   * Return: false if the payload could not be encapsulated or true otherwise.
   */
  bool batadv_send_skb_prepare_unicast_4addr(struct batadv_priv *bat_priv,
  					   struct sk_buff *skb,
  					   struct batadv_orig_node *orig,
  					   int packet_subtype)
  {
  	struct batadv_hard_iface *primary_if;
  	struct batadv_unicast_4addr_packet *uc_4addr_packet;
  	bool ret = false;
  
  	primary_if = batadv_primary_if_get_selected(bat_priv);
  	if (!primary_if)
  		goto out;
  
  	/* Pull the header space and fill the unicast_packet substructure.
  	 * We can do that because the first member of the uc_4addr_packet
  	 * is of type struct unicast_packet
  	 */
  	if (!batadv_send_skb_push_fill_unicast(skb, sizeof(*uc_4addr_packet),
  					       orig))
  		goto out;
  
  	uc_4addr_packet = (struct batadv_unicast_4addr_packet *)skb->data;
  	uc_4addr_packet->u.packet_type = BATADV_UNICAST_4ADDR;
  	ether_addr_copy(uc_4addr_packet->src, primary_if->net_dev->dev_addr);
  	uc_4addr_packet->subtype = packet_subtype;
  	uc_4addr_packet->reserved = 0;
  
  	ret = true;
  out:
  	if (primary_if)
  		batadv_hardif_put(primary_if);
  	return ret;
  }
  
  /**
   * batadv_send_skb_unicast() - encapsulate and send an skb via unicast
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: payload to send
   * @packet_type: the batman unicast packet type to use
   * @packet_subtype: the unicast 4addr packet subtype (only relevant for unicast
   *  4addr packets)
   * @orig_node: the originator to send the packet to
   * @vid: the vid to be used to search the translation table
   *
   * Wrap the given skb into a batman-adv unicast or unicast-4addr header
   * depending on whether BATADV_UNICAST or BATADV_UNICAST_4ADDR was supplied
   * as packet_type. Then send this frame to the given orig_node.
   *
   * Return: NET_XMIT_DROP in case of error or NET_XMIT_SUCCESS otherwise.
   */
  int batadv_send_skb_unicast(struct batadv_priv *bat_priv,
  			    struct sk_buff *skb, int packet_type,
  			    int packet_subtype,
  			    struct batadv_orig_node *orig_node,
  			    unsigned short vid)
  {
  	struct batadv_unicast_packet *unicast_packet;
  	struct ethhdr *ethhdr;
  	int ret = NET_XMIT_DROP;
  
  	if (!orig_node)
  		goto out;
  
  	switch (packet_type) {
  	case BATADV_UNICAST:
  		if (!batadv_send_skb_prepare_unicast(skb, orig_node))
  			goto out;
  		break;
  	case BATADV_UNICAST_4ADDR:
  		if (!batadv_send_skb_prepare_unicast_4addr(bat_priv, skb,
  							   orig_node,
  							   packet_subtype))
  			goto out;
  		break;
  	default:
  		/* this function supports UNICAST and UNICAST_4ADDR only. It
  		 * should never be invoked with any other packet type
  		 */
  		goto out;
  	}
  
  	/* skb->data might have been reallocated by
  	 * batadv_send_skb_prepare_unicast{,_4addr}()
  	 */
  	ethhdr = eth_hdr(skb);
  	unicast_packet = (struct batadv_unicast_packet *)skb->data;
  
  	/* inform the destination node that we are still missing a correct route
  	 * for this client. The destination will receive this packet and will
  	 * try to reroute it because the ttvn contained in the header is less
  	 * than the current one
  	 */
  	if (batadv_tt_global_client_is_roaming(bat_priv, ethhdr->h_dest, vid))
  		unicast_packet->ttvn = unicast_packet->ttvn - 1;
  
  	ret = batadv_send_skb_to_orig(skb, orig_node, NULL);
  	 /* skb was consumed */
  	skb = NULL;
  
  out:
  	kfree_skb(skb);
  	return ret;
  }
  
  /**
   * batadv_send_skb_via_tt_generic() - send an skb via TT lookup
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: payload to send
   * @packet_type: the batman unicast packet type to use
   * @packet_subtype: the unicast 4addr packet subtype (only relevant for unicast
   *  4addr packets)
   * @dst_hint: can be used to override the destination contained in the skb
   * @vid: the vid to be used to search the translation table
   *
   * Look up the recipient node for the destination address in the ethernet
   * header via the translation table. Wrap the given skb into a batman-adv
   * unicast or unicast-4addr header depending on whether BATADV_UNICAST or
   * BATADV_UNICAST_4ADDR was supplied as packet_type. Then send this frame
   * to the according destination node.
   *
   * Return: NET_XMIT_DROP in case of error or NET_XMIT_SUCCESS otherwise.
   */
  int batadv_send_skb_via_tt_generic(struct batadv_priv *bat_priv,
  				   struct sk_buff *skb, int packet_type,
  				   int packet_subtype, u8 *dst_hint,
  				   unsigned short vid)
  {
  	struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
  	struct batadv_orig_node *orig_node;
  	u8 *src, *dst;
  	int ret;
  
  	src = ethhdr->h_source;
  	dst = ethhdr->h_dest;
  
  	/* if we got an hint! let's send the packet to this client (if any) */
  	if (dst_hint) {
  		src = NULL;
  		dst = dst_hint;
  	}
  	orig_node = batadv_transtable_search(bat_priv, src, dst, vid);
  
  	ret = batadv_send_skb_unicast(bat_priv, skb, packet_type,
  				      packet_subtype, orig_node, vid);
  
  	if (orig_node)
  		batadv_orig_node_put(orig_node);
  
  	return ret;
  }
  
  /**
   * batadv_send_skb_via_gw() - send an skb via gateway lookup
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: payload to send
   * @vid: the vid to be used to search the translation table
   *
   * Look up the currently selected gateway. Wrap the given skb into a batman-adv
   * unicast header and send this frame to this gateway node.
   *
   * Return: NET_XMIT_DROP in case of error or NET_XMIT_SUCCESS otherwise.
   */
  int batadv_send_skb_via_gw(struct batadv_priv *bat_priv, struct sk_buff *skb,
  			   unsigned short vid)
  {
  	struct batadv_orig_node *orig_node;
  	int ret;
  
  	orig_node = batadv_gw_get_selected_orig(bat_priv);
  	ret = batadv_send_skb_unicast(bat_priv, skb, BATADV_UNICAST_4ADDR,
  				      BATADV_P_DATA, orig_node, vid);
  
  	if (orig_node)
  		batadv_orig_node_put(orig_node);
  
  	return ret;
  }
  
  /**
   * batadv_forw_packet_free() - free a forwarding packet
   * @forw_packet: The packet to free
   * @dropped: whether the packet is freed because is is dropped
   *
   * This frees a forwarding packet and releases any resources it might
   * have claimed.
   */
  void batadv_forw_packet_free(struct batadv_forw_packet *forw_packet,
  			     bool dropped)
  {
  	if (dropped)
  		kfree_skb(forw_packet->skb);
  	else
  		consume_skb(forw_packet->skb);
  
  	if (forw_packet->if_incoming)
  		batadv_hardif_put(forw_packet->if_incoming);
  	if (forw_packet->if_outgoing)
  		batadv_hardif_put(forw_packet->if_outgoing);
  	if (forw_packet->queue_left)
  		atomic_inc(forw_packet->queue_left);
  	kfree(forw_packet);
  }
  
  /**
   * batadv_forw_packet_alloc() - allocate a forwarding packet
   * @if_incoming: The (optional) if_incoming to be grabbed
   * @if_outgoing: The (optional) if_outgoing to be grabbed
   * @queue_left: The (optional) queue counter to decrease
   * @bat_priv: The bat_priv for the mesh of this forw_packet
   * @skb: The raw packet this forwarding packet shall contain
   *
   * Allocates a forwarding packet and tries to get a reference to the
   * (optional) if_incoming, if_outgoing and queue_left. If queue_left
   * is NULL then bat_priv is optional, too.
   *
   * Return: An allocated forwarding packet on success, NULL otherwise.
   */
  struct batadv_forw_packet *
  batadv_forw_packet_alloc(struct batadv_hard_iface *if_incoming,
  			 struct batadv_hard_iface *if_outgoing,
  			 atomic_t *queue_left,
  			 struct batadv_priv *bat_priv,
  			 struct sk_buff *skb)
  {
  	struct batadv_forw_packet *forw_packet;
  	const char *qname;
  
  	if (queue_left && !batadv_atomic_dec_not_zero(queue_left)) {
  		qname = "unknown";
  
  		if (queue_left == &bat_priv->bcast_queue_left)
  			qname = "bcast";
  
  		if (queue_left == &bat_priv->batman_queue_left)
  			qname = "batman";
  
  		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  			   "%s queue is full\n", qname);
  
  		return NULL;
  	}
  
  	forw_packet = kmalloc(sizeof(*forw_packet), GFP_ATOMIC);
  	if (!forw_packet)
  		goto err;
  
  	if (if_incoming)
  		kref_get(&if_incoming->refcount);
  
  	if (if_outgoing)
  		kref_get(&if_outgoing->refcount);
  
  	INIT_HLIST_NODE(&forw_packet->list);
  	INIT_HLIST_NODE(&forw_packet->cleanup_list);
  	forw_packet->skb = skb;
  	forw_packet->queue_left = queue_left;
  	forw_packet->if_incoming = if_incoming;
  	forw_packet->if_outgoing = if_outgoing;
  	forw_packet->num_packets = 0;
  
  	return forw_packet;
  
  err:
  	if (queue_left)
  		atomic_inc(queue_left);
  
  	return NULL;
  }
  
  /**
   * batadv_forw_packet_was_stolen() - check whether someone stole this packet
   * @forw_packet: the forwarding packet to check
   *
   * This function checks whether the given forwarding packet was claimed by
   * someone else for free().
   *
   * Return: True if someone stole it, false otherwise.
   */
  static bool
  batadv_forw_packet_was_stolen(struct batadv_forw_packet *forw_packet)
  {
  	return !hlist_unhashed(&forw_packet->cleanup_list);
  }
  
  /**
   * batadv_forw_packet_steal() - claim a forw_packet for free()
   * @forw_packet: the forwarding packet to steal
   * @lock: a key to the store to steal from (e.g. forw_{bat,bcast}_list_lock)
   *
   * This function tries to steal a specific forw_packet from global
   * visibility for the purpose of getting it for free(). That means
   * the caller is *not* allowed to requeue it afterwards.
   *
   * Return: True if stealing was successful. False if someone else stole it
   * before us.
   */
  bool batadv_forw_packet_steal(struct batadv_forw_packet *forw_packet,
  			      spinlock_t *lock)
  {
  	/* did purging routine steal it earlier? */
  	spin_lock_bh(lock);
  	if (batadv_forw_packet_was_stolen(forw_packet)) {
  		spin_unlock_bh(lock);
  		return false;
  	}
  
  	hlist_del_init(&forw_packet->list);
  
  	/* Just to spot misuse of this function */
  	hlist_add_fake(&forw_packet->cleanup_list);
  
  	spin_unlock_bh(lock);
  	return true;
  }
  
  /**
   * batadv_forw_packet_list_steal() - claim a list of forward packets for free()
   * @forw_list: the to be stolen forward packets
   * @cleanup_list: a backup pointer, to be able to dispose the packet later
   * @hard_iface: the interface to steal forward packets from
   *
   * This function claims responsibility to free any forw_packet queued on the
   * given hard_iface. If hard_iface is NULL forwarding packets on all hard
   * interfaces will be claimed.
   *
   * The packets are being moved from the forw_list to the cleanup_list and
   * by that allows already running threads to notice the claiming.
   */
  static void
  batadv_forw_packet_list_steal(struct hlist_head *forw_list,
  			      struct hlist_head *cleanup_list,
  			      const struct batadv_hard_iface *hard_iface)
  {
  	struct batadv_forw_packet *forw_packet;
  	struct hlist_node *safe_tmp_node;
  
  	hlist_for_each_entry_safe(forw_packet, safe_tmp_node,
  				  forw_list, list) {
  		/* if purge_outstanding_packets() was called with an argument
  		 * we delete only packets belonging to the given interface
  		 */
  		if (hard_iface &&
  		    forw_packet->if_incoming != hard_iface &&
  		    forw_packet->if_outgoing != hard_iface)
  			continue;
  
  		hlist_del(&forw_packet->list);
  		hlist_add_head(&forw_packet->cleanup_list, cleanup_list);
  	}
  }
  
  /**
   * batadv_forw_packet_list_free() - free a list of forward packets
   * @head: a list of to be freed forw_packets
   *
   * This function cancels the scheduling of any packet in the provided list,
   * waits for any possibly running packet forwarding thread to finish and
   * finally, safely frees this forward packet.
   *
   * This function might sleep.
   */
  static void batadv_forw_packet_list_free(struct hlist_head *head)
  {
  	struct batadv_forw_packet *forw_packet;
  	struct hlist_node *safe_tmp_node;
  
  	hlist_for_each_entry_safe(forw_packet, safe_tmp_node, head,
  				  cleanup_list) {
  		cancel_delayed_work_sync(&forw_packet->delayed_work);
  
  		hlist_del(&forw_packet->cleanup_list);
  		batadv_forw_packet_free(forw_packet, true);
  	}
  }
  
  /**
   * batadv_forw_packet_queue() - try to queue a forwarding packet
   * @forw_packet: the forwarding packet to queue
   * @lock: a key to the store (e.g. forw_{bat,bcast}_list_lock)
   * @head: the shelve to queue it on (e.g. forw_{bat,bcast}_list)
   * @send_time: timestamp (jiffies) when the packet is to be sent
   *
   * This function tries to (re)queue a forwarding packet. Requeuing
   * is prevented if the according interface is shutting down
   * (e.g. if batadv_forw_packet_list_steal() was called for this
   * packet earlier).
   *
   * Calling batadv_forw_packet_queue() after a call to
   * batadv_forw_packet_steal() is forbidden!
   *
   * Caller needs to ensure that forw_packet->delayed_work was initialized.
   */
  static void batadv_forw_packet_queue(struct batadv_forw_packet *forw_packet,
  				     spinlock_t *lock, struct hlist_head *head,
  				     unsigned long send_time)
  {
  	spin_lock_bh(lock);
  
  	/* did purging routine steal it from us? */
  	if (batadv_forw_packet_was_stolen(forw_packet)) {
  		/* If you got it for free() without trouble, then
  		 * don't get back into the queue after stealing...
  		 */
  		WARN_ONCE(hlist_fake(&forw_packet->cleanup_list),
  			  "Requeuing after batadv_forw_packet_steal() not allowed!\n");
  
  		spin_unlock_bh(lock);
  		return;
  	}
  
  	hlist_del_init(&forw_packet->list);
  	hlist_add_head(&forw_packet->list, head);
  
  	queue_delayed_work(batadv_event_workqueue,
  			   &forw_packet->delayed_work,
  			   send_time - jiffies);
  	spin_unlock_bh(lock);
  }
  
  /**
   * batadv_forw_packet_bcast_queue() - try to queue a broadcast packet
   * @bat_priv: the bat priv with all the soft interface information
   * @forw_packet: the forwarding packet to queue
   * @send_time: timestamp (jiffies) when the packet is to be sent
   *
   * This function tries to (re)queue a broadcast packet.
   *
   * Caller needs to ensure that forw_packet->delayed_work was initialized.
   */
  static void
  batadv_forw_packet_bcast_queue(struct batadv_priv *bat_priv,
  			       struct batadv_forw_packet *forw_packet,
  			       unsigned long send_time)
  {
  	batadv_forw_packet_queue(forw_packet, &bat_priv->forw_bcast_list_lock,
  				 &bat_priv->forw_bcast_list, send_time);
  }
  
  /**
   * batadv_forw_packet_ogmv1_queue() - try to queue an OGMv1 packet
   * @bat_priv: the bat priv with all the soft interface information
   * @forw_packet: the forwarding packet to queue
   * @send_time: timestamp (jiffies) when the packet is to be sent
   *
   * This function tries to (re)queue an OGMv1 packet.
   *
   * Caller needs to ensure that forw_packet->delayed_work was initialized.
   */
  void batadv_forw_packet_ogmv1_queue(struct batadv_priv *bat_priv,
  				    struct batadv_forw_packet *forw_packet,
  				    unsigned long send_time)
  {
  	batadv_forw_packet_queue(forw_packet, &bat_priv->forw_bat_list_lock,
  				 &bat_priv->forw_bat_list, send_time);
  }
  
  /**
   * batadv_add_bcast_packet_to_list() - queue broadcast packet for multiple sends
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: broadcast packet to add
   * @delay: number of jiffies to wait before sending
   * @own_packet: true if it is a self-generated broadcast packet
   *
   * add a broadcast packet to the queue and setup timers. broadcast packets
   * are sent multiple times to increase probability for being received.
   *
   * The skb is not consumed, so the caller should make sure that the
   * skb is freed.
   *
   * Return: NETDEV_TX_OK on success and NETDEV_TX_BUSY on errors.
   */
  int batadv_add_bcast_packet_to_list(struct batadv_priv *bat_priv,
  				    const struct sk_buff *skb,
  				    unsigned long delay,
  				    bool own_packet)
  {
  	struct batadv_hard_iface *primary_if;
  	struct batadv_forw_packet *forw_packet;
  	struct batadv_bcast_packet *bcast_packet;
  	struct sk_buff *newskb;
  
  	primary_if = batadv_primary_if_get_selected(bat_priv);
  	if (!primary_if)
  		goto err;
  
  	newskb = skb_copy(skb, GFP_ATOMIC);
  	if (!newskb) {
  		batadv_hardif_put(primary_if);
  		goto err;
  	}
  
  	forw_packet = batadv_forw_packet_alloc(primary_if, NULL,
  					       &bat_priv->bcast_queue_left,
  					       bat_priv, newskb);
  	batadv_hardif_put(primary_if);
  	if (!forw_packet)
  		goto err_packet_free;
  
  	/* as we have a copy now, it is safe to decrease the TTL */
  	bcast_packet = (struct batadv_bcast_packet *)newskb->data;
  	bcast_packet->ttl--;
  
  	forw_packet->own = own_packet;
  
  	INIT_DELAYED_WORK(&forw_packet->delayed_work,
  			  batadv_send_outstanding_bcast_packet);
  
  	batadv_forw_packet_bcast_queue(bat_priv, forw_packet, jiffies + delay);
  	return NETDEV_TX_OK;
  
  err_packet_free:
  	kfree_skb(newskb);
  err:
  	return NETDEV_TX_BUSY;
  }
  
  /**
   * batadv_forw_packet_bcasts_left() - check if a retransmission is necessary
   * @forw_packet: the forwarding packet to check
   * @hard_iface: the interface to check on
   *
   * Checks whether a given packet has any (re)transmissions left on the provided
   * interface.
   *
   * hard_iface may be NULL: In that case the number of transmissions this skb had
   * so far is compared with the maximum amount of retransmissions independent of
   * any interface instead.
   *
   * Return: True if (re)transmissions are left, false otherwise.
   */
  static bool
  batadv_forw_packet_bcasts_left(struct batadv_forw_packet *forw_packet,
  			       struct batadv_hard_iface *hard_iface)
  {
  	unsigned int max;
  
  	if (hard_iface)
  		max = hard_iface->num_bcasts;
  	else
  		max = BATADV_NUM_BCASTS_MAX;
  
  	return BATADV_SKB_CB(forw_packet->skb)->num_bcasts < max;
  }
  
  /**
   * batadv_forw_packet_bcasts_inc() - increment retransmission counter of a
   *  packet
   * @forw_packet: the packet to increase the counter for
   */
  static void
  batadv_forw_packet_bcasts_inc(struct batadv_forw_packet *forw_packet)
  {
  	BATADV_SKB_CB(forw_packet->skb)->num_bcasts++;
  }
  
  /**
   * batadv_forw_packet_is_rebroadcast() - check packet for previous transmissions
   * @forw_packet: the packet to check
   *
   * Return: True if this packet was transmitted before, false otherwise.
   */
  bool batadv_forw_packet_is_rebroadcast(struct batadv_forw_packet *forw_packet)
  {
  	return BATADV_SKB_CB(forw_packet->skb)->num_bcasts > 0;
  }
  
  static void batadv_send_outstanding_bcast_packet(struct work_struct *work)
  {
  	struct batadv_hard_iface *hard_iface;
  	struct batadv_hardif_neigh_node *neigh_node;
  	struct delayed_work *delayed_work;
  	struct batadv_forw_packet *forw_packet;
  	struct batadv_bcast_packet *bcast_packet;
  	struct sk_buff *skb1;
  	struct net_device *soft_iface;
  	struct batadv_priv *bat_priv;
  	unsigned long send_time = jiffies + msecs_to_jiffies(5);
  	bool dropped = false;
  	u8 *neigh_addr;
  	u8 *orig_neigh;
  	int ret = 0;
  
  	delayed_work = to_delayed_work(work);
  	forw_packet = container_of(delayed_work, struct batadv_forw_packet,
  				   delayed_work);
  	soft_iface = forw_packet->if_incoming->soft_iface;
  	bat_priv = netdev_priv(soft_iface);
  
  	if (atomic_read(&bat_priv->mesh_state) == BATADV_MESH_DEACTIVATING) {
  		dropped = true;
  		goto out;
  	}
  
  	if (batadv_dat_drop_broadcast_packet(bat_priv, forw_packet)) {
  		dropped = true;
  		goto out;
  	}
  
  	bcast_packet = (struct batadv_bcast_packet *)forw_packet->skb->data;
  
  	/* rebroadcast packet */
  	rcu_read_lock();
  	list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
  		if (hard_iface->soft_iface != soft_iface)
  			continue;
  
  		if (!batadv_forw_packet_bcasts_left(forw_packet, hard_iface))
  			continue;
  
  		if (forw_packet->own) {
  			neigh_node = NULL;
  		} else {
  			neigh_addr = eth_hdr(forw_packet->skb)->h_source;
  			neigh_node = batadv_hardif_neigh_get(hard_iface,
  							     neigh_addr);
  		}
  
  		orig_neigh = neigh_node ? neigh_node->orig : NULL;
  
  		ret = batadv_hardif_no_broadcast(hard_iface, bcast_packet->orig,
  						 orig_neigh);
  
  		if (ret) {
  			char *type;
  
  			switch (ret) {
  			case BATADV_HARDIF_BCAST_NORECIPIENT:
  				type = "no neighbor";
  				break;
  			case BATADV_HARDIF_BCAST_DUPFWD:
  				type = "single neighbor is source";
  				break;
  			case BATADV_HARDIF_BCAST_DUPORIG:
  				type = "single neighbor is originator";
  				break;
  			default:
  				type = "unknown";
  			}
  
  			batadv_dbg(BATADV_DBG_BATMAN, bat_priv, "BCAST packet from orig %pM on %s suppressed: %s\n",
  				   bcast_packet->orig,
  				   hard_iface->net_dev->name, type);
  
  			if (neigh_node)
  				batadv_hardif_neigh_put(neigh_node);
  
  			continue;
  		}
  
  		if (neigh_node)
  			batadv_hardif_neigh_put(neigh_node);
  
  		if (!kref_get_unless_zero(&hard_iface->refcount))
  			continue;
  
  		/* send a copy of the saved skb */
  		skb1 = skb_clone(forw_packet->skb, GFP_ATOMIC);
  		if (skb1)
  			batadv_send_broadcast_skb(skb1, hard_iface);
  
  		batadv_hardif_put(hard_iface);
  	}
  	rcu_read_unlock();
  
  	batadv_forw_packet_bcasts_inc(forw_packet);
  
  	/* if we still have some more bcasts to send */
  	if (batadv_forw_packet_bcasts_left(forw_packet, NULL)) {
  		batadv_forw_packet_bcast_queue(bat_priv, forw_packet,
  					       send_time);
  		return;
  	}
  
  out:
  	/* do we get something for free()? */
  	if (batadv_forw_packet_steal(forw_packet,
  				     &bat_priv->forw_bcast_list_lock))
  		batadv_forw_packet_free(forw_packet, dropped);
  }
  
  /**
   * batadv_purge_outstanding_packets() - stop/purge scheduled bcast/OGMv1 packets
   * @bat_priv: the bat priv with all the soft interface information
   * @hard_iface: the hard interface to cancel and purge bcast/ogm packets on
   *
   * This method cancels and purges any broadcast and OGMv1 packet on the given
   * hard_iface. If hard_iface is NULL, broadcast and OGMv1 packets on all hard
   * interfaces will be canceled and purged.
   *
   * This function might sleep.
   */
  void
  batadv_purge_outstanding_packets(struct batadv_priv *bat_priv,
  				 const struct batadv_hard_iface *hard_iface)
  {
  	struct hlist_head head = HLIST_HEAD_INIT;
  
  	if (hard_iface)
  		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  			   "%s(): %s\n",
  			   __func__, hard_iface->net_dev->name);
  	else
  		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  			   "%s()\n", __func__);
  
  	/* claim bcast list for free() */
  	spin_lock_bh(&bat_priv->forw_bcast_list_lock);
  	batadv_forw_packet_list_steal(&bat_priv->forw_bcast_list, &head,
  				      hard_iface);
  	spin_unlock_bh(&bat_priv->forw_bcast_list_lock);
  
  	/* claim batman packet list for free() */
  	spin_lock_bh(&bat_priv->forw_bat_list_lock);
  	batadv_forw_packet_list_steal(&bat_priv->forw_bat_list, &head,
  				      hard_iface);
  	spin_unlock_bh(&bat_priv->forw_bat_list_lock);
  
  	/* then cancel or wait for packet workers to finish and free */
  	batadv_forw_packet_list_free(&head);
  }
  