/* Copyright (C) 2011-2017  B.A.T.M.A.N. contributors:

   *
   * Linus Lüssing, Marek Lindner
   *
   * 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 "bat_v_elp.h"
  #include "main.h"
  
  #include <linux/atomic.h>

  #include <linux/bitops.h>

  #include <linux/byteorder/generic.h>
  #include <linux/errno.h>
  #include <linux/etherdevice.h>

  #include <linux/ethtool.h>

  #include <linux/fs.h>
  #include <linux/if_ether.h>
  #include <linux/jiffies.h>
  #include <linux/kernel.h>

  #include <linux/kref.h>

  #include <linux/netdevice.h>

  #include <linux/nl80211.h>

  #include <linux/random.h>
  #include <linux/rculist.h>
  #include <linux/rcupdate.h>

  #include <linux/rtnetlink.h>

  #include <linux/skbuff.h>
  #include <linux/stddef.h>
  #include <linux/string.h>
  #include <linux/types.h>
  #include <linux/workqueue.h>

  #include <net/cfg80211.h>

  
  #include "bat_algo.h"

  #include "bat_v_ogm.h"

  #include "hard-interface.h"

  #include "log.h"

  #include "originator.h"

  #include "packet.h"

  #include "routing.h"

  #include "send.h"
  
  /**
   * batadv_v_elp_start_timer - restart timer for ELP periodic work
   * @hard_iface: the interface for which the timer has to be reset
   */
  static void batadv_v_elp_start_timer(struct batadv_hard_iface *hard_iface)
  {
  	unsigned int msecs;
  
  	msecs = atomic_read(&hard_iface->bat_v.elp_interval) - BATADV_JITTER;
  	msecs += prandom_u32() % (2 * BATADV_JITTER);
  
  	queue_delayed_work(batadv_event_workqueue, &hard_iface->bat_v.elp_wq,
  			   msecs_to_jiffies(msecs));
  }
  
  /**

   * batadv_v_elp_get_throughput - get the throughput towards a neighbour
   * @neigh: the neighbour for which the throughput has to be obtained
   *
   * Return: The throughput towards the given neighbour in multiples of 100kpbs
   *         (a value of '1' equals to 0.1Mbps, '10' equals 1Mbps, etc).
   */
  static u32 batadv_v_elp_get_throughput(struct batadv_hardif_neigh_node *neigh)
  {
  	struct batadv_hard_iface *hard_iface = neigh->if_incoming;
  	struct ethtool_link_ksettings link_settings;

  	struct net_device *real_netdev;

  	struct station_info sinfo;
  	u32 throughput;
  	int ret;
  
  	/* if the user specified a customised value for this interface, then
  	 * return it directly
  	 */
  	throughput =  atomic_read(&hard_iface->bat_v.throughput_override);
  	if (throughput != 0)
  		return throughput;
  
  	/* if this is a wireless device, then ask its throughput through
  	 * cfg80211 API
  	 */

  	if (batadv_is_wifi_hardif(hard_iface)) {
  		if (!batadv_is_cfg80211_hardif(hard_iface))

  			/* unsupported WiFi driver version */
  			goto default_throughput;

  		real_netdev = batadv_get_real_netdev(hard_iface->net_dev);
  		if (!real_netdev)
  			goto default_throughput;
  
  		ret = cfg80211_get_station(real_netdev, neigh->addr, &sinfo);
  
  		dev_put(real_netdev);

  		if (ret == -ENOENT) {
  			/* Node is not associated anymore! It would be
  			 * possible to delete this neighbor. For now set
  			 * the throughput metric to 0.
  			 */
  			return 0;
  		}

  		if (ret)
  			goto default_throughput;

  		if (!(sinfo.filled & BIT(NL80211_STA_INFO_EXPECTED_THROUGHPUT)))
  			goto default_throughput;

  
  		return sinfo.expected_throughput / 100;

  	}
  
  	/* if not a wifi interface, check if this device provides data via
  	 * ethtool (e.g. an Ethernet adapter)
  	 */
  	memset(&link_settings, 0, sizeof(link_settings));
  	rtnl_lock();
  	ret = __ethtool_get_link_ksettings(hard_iface->net_dev, &link_settings);
  	rtnl_unlock();
  	if (ret == 0) {
  		/* link characteristics might change over time */
  		if (link_settings.base.duplex == DUPLEX_FULL)
  			hard_iface->bat_v.flags |= BATADV_FULL_DUPLEX;
  		else
  			hard_iface->bat_v.flags &= ~BATADV_FULL_DUPLEX;
  
  		throughput = link_settings.base.speed;
  		if (throughput && (throughput != SPEED_UNKNOWN))
  			return throughput * 10;
  	}
  
  default_throughput:
  	if (!(hard_iface->bat_v.flags & BATADV_WARNING_DEFAULT)) {
  		batadv_info(hard_iface->soft_iface,
  			    "WiFi driver or ethtool info does not provide information about link speeds on interface %s, therefore defaulting to hardcoded throughput values of %u.%1u Mbps. Consider overriding the throughput manually or checking your driver.
  ",
  			    hard_iface->net_dev->name,
  			    BATADV_THROUGHPUT_DEFAULT_VALUE / 10,
  			    BATADV_THROUGHPUT_DEFAULT_VALUE % 10);
  		hard_iface->bat_v.flags |= BATADV_WARNING_DEFAULT;
  	}
  
  	/* if none of the above cases apply, return the base_throughput */
  	return BATADV_THROUGHPUT_DEFAULT_VALUE;
  }
  
  /**
   * batadv_v_elp_throughput_metric_update - worker updating the throughput metric
   *  of a single hop neighbour
   * @work: the work queue item
   */
  void batadv_v_elp_throughput_metric_update(struct work_struct *work)
  {
  	struct batadv_hardif_neigh_node_bat_v *neigh_bat_v;
  	struct batadv_hardif_neigh_node *neigh;
  
  	neigh_bat_v = container_of(work, struct batadv_hardif_neigh_node_bat_v,
  				   metric_work);
  	neigh = container_of(neigh_bat_v, struct batadv_hardif_neigh_node,
  			     bat_v);
  
  	ewma_throughput_add(&neigh->bat_v.throughput,
  			    batadv_v_elp_get_throughput(neigh));
  
  	/* decrement refcounter to balance increment performed before scheduling
  	 * this task
  	 */
  	batadv_hardif_neigh_put(neigh);
  }
  
  /**

   * batadv_v_elp_wifi_neigh_probe - send link probing packets to a neighbour
   * @neigh: the neighbour to probe
   *
   * Sends a predefined number of unicast wifi packets to a given neighbour in
   * order to trigger the throughput estimation on this link by the RC algorithm.
   * Packets are sent only if there there is not enough payload unicast traffic
   * towards this neighbour..
   *
   * Return: True on success and false in case of error during skb preparation.
   */
  static bool
  batadv_v_elp_wifi_neigh_probe(struct batadv_hardif_neigh_node *neigh)
  {
  	struct batadv_hard_iface *hard_iface = neigh->if_incoming;
  	struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);
  	unsigned long last_tx_diff;
  	struct sk_buff *skb;
  	int probe_len, i;
  	int elp_skb_len;
  
  	/* this probing routine is for Wifi neighbours only */

  	if (!batadv_is_wifi_hardif(hard_iface))

  		return true;
  
  	/* probe the neighbor only if no unicast packets have been sent
  	 * to it in the last 100 milliseconds: this is the rate control
  	 * algorithm sampling interval (minstrel). In this way, if not
  	 * enough traffic has been sent to the neighbor, batman-adv can
  	 * generate 2 probe packets and push the RC algorithm to perform
  	 * the sampling
  	 */
  	last_tx_diff = jiffies_to_msecs(jiffies - neigh->bat_v.last_unicast_tx);
  	if (last_tx_diff <= BATADV_ELP_PROBE_MAX_TX_DIFF)
  		return true;
  
  	probe_len = max_t(int, sizeof(struct batadv_elp_packet),
  			  BATADV_ELP_MIN_PROBE_SIZE);
  
  	for (i = 0; i < BATADV_ELP_PROBES_PER_NODE; i++) {
  		elp_skb_len = hard_iface->bat_v.elp_skb->len;
  		skb = skb_copy_expand(hard_iface->bat_v.elp_skb, 0,
  				      probe_len - elp_skb_len,
  				      GFP_ATOMIC);
  		if (!skb)
  			return false;
  
  		/* Tell the skb to get as big as the allocated space (we want
  		 * the packet to be exactly of that size to make the link
  		 * throughput estimation effective.
  		 */

  		skb_put_zero(skb, probe_len - hard_iface->bat_v.elp_skb->len);

  
  		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  			   "Sending unicast (probe) ELP packet on interface %s to %pM
  ",
  			   hard_iface->net_dev->name, neigh->addr);
  
  		batadv_send_skb_packet(skb, hard_iface, neigh->addr);
  	}
  
  	return true;
  }
  
  /**

   * batadv_v_elp_periodic_work - ELP periodic task per interface
   * @work: work queue item
   *
   * Emits broadcast ELP message in regular intervals.
   */
  static void batadv_v_elp_periodic_work(struct work_struct *work)
  {

  	struct batadv_hardif_neigh_node *hardif_neigh;

  	struct batadv_hard_iface *hard_iface;
  	struct batadv_hard_iface_bat_v *bat_v;
  	struct batadv_elp_packet *elp_packet;
  	struct batadv_priv *bat_priv;
  	struct sk_buff *skb;
  	u32 elp_interval;

  	bool ret;

  
  	bat_v = container_of(work, struct batadv_hard_iface_bat_v, elp_wq.work);
  	hard_iface = container_of(bat_v, struct batadv_hard_iface, bat_v);
  	bat_priv = netdev_priv(hard_iface->soft_iface);
  
  	if (atomic_read(&bat_priv->mesh_state) == BATADV_MESH_DEACTIVATING)
  		goto out;
  
  	/* we are in the process of shutting this interface down */
  	if ((hard_iface->if_status == BATADV_IF_NOT_IN_USE) ||
  	    (hard_iface->if_status == BATADV_IF_TO_BE_REMOVED))
  		goto out;
  
  	/* the interface was enabled but may not be ready yet */
  	if (hard_iface->if_status != BATADV_IF_ACTIVE)
  		goto restart_timer;
  
  	skb = skb_copy(hard_iface->bat_v.elp_skb, GFP_ATOMIC);
  	if (!skb)
  		goto restart_timer;
  
  	elp_packet = (struct batadv_elp_packet *)skb->data;
  	elp_packet->seqno = htonl(atomic_read(&hard_iface->bat_v.elp_seqno));
  	elp_interval = atomic_read(&hard_iface->bat_v.elp_interval);
  	elp_packet->elp_interval = htonl(elp_interval);
  
  	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  		   "Sending broadcast ELP packet on interface %s, seqno %u
  ",
  		   hard_iface->net_dev->name,
  		   atomic_read(&hard_iface->bat_v.elp_seqno));

  	batadv_send_broadcast_skb(skb, hard_iface);

  
  	atomic_inc(&hard_iface->bat_v.elp_seqno);

  	/* The throughput metric is updated on each sent packet. This way, if a
  	 * node is dead and no longer sends packets, batman-adv is still able to
  	 * react timely to its death.
  	 *
  	 * The throughput metric is updated by following these steps:
  	 * 1) if the hard_iface is wifi => send a number of unicast ELPs for
  	 *    probing/sampling to each neighbor
  	 * 2) update the throughput metric value of each neighbor (note that the
  	 *    value retrieved in this step might be 100ms old because the
  	 *    probing packets at point 1) could still be in the HW queue)
  	 */
  	rcu_read_lock();
  	hlist_for_each_entry_rcu(hardif_neigh, &hard_iface->neigh_list, list) {

  		if (!batadv_v_elp_wifi_neigh_probe(hardif_neigh))
  			/* if something goes wrong while probing, better to stop
  			 * sending packets immediately and reschedule the task
  			 */
  			break;

  		if (!kref_get_unless_zero(&hardif_neigh->refcount))
  			continue;
  
  		/* Reading the estimated throughput from cfg80211 is a task that
  		 * may sleep and that is not allowed in an rcu protected
  		 * context. Therefore schedule a task for that.
  		 */

  		ret = queue_work(batadv_event_workqueue,
  				 &hardif_neigh->bat_v.metric_work);
  
  		if (!ret)
  			batadv_hardif_neigh_put(hardif_neigh);

  	}
  	rcu_read_unlock();

  restart_timer:
  	batadv_v_elp_start_timer(hard_iface);
  out:
  	return;
  }
  
  /**
   * batadv_v_elp_iface_enable - setup the ELP interface private resources
   * @hard_iface: interface for which the data has to be prepared
   *
   * Return: 0 on success or a -ENOMEM in case of failure.
   */
  int batadv_v_elp_iface_enable(struct batadv_hard_iface *hard_iface)
  {

  	static const size_t tvlv_padding = sizeof(__be32);

  	struct batadv_elp_packet *elp_packet;
  	unsigned char *elp_buff;
  	u32 random_seqno;
  	size_t size;
  	int res = -ENOMEM;

  	size = ETH_HLEN + NET_IP_ALIGN + BATADV_ELP_HLEN + tvlv_padding;

  	hard_iface->bat_v.elp_skb = dev_alloc_skb(size);
  	if (!hard_iface->bat_v.elp_skb)
  		goto out;
  
  	skb_reserve(hard_iface->bat_v.elp_skb, ETH_HLEN + NET_IP_ALIGN);

  	elp_buff = skb_put_zero(hard_iface->bat_v.elp_skb,
  				BATADV_ELP_HLEN + tvlv_padding);

  	elp_packet = (struct batadv_elp_packet *)elp_buff;

  
  	elp_packet->packet_type = BATADV_ELP;
  	elp_packet->version = BATADV_COMPAT_VERSION;
  
  	/* randomize initial seqno to avoid collision */
  	get_random_bytes(&random_seqno, sizeof(random_seqno));
  	atomic_set(&hard_iface->bat_v.elp_seqno, random_seqno);

  	/* assume full-duplex by default */
  	hard_iface->bat_v.flags |= BATADV_FULL_DUPLEX;
  
  	/* warn the user (again) if there is no throughput data is available */
  	hard_iface->bat_v.flags &= ~BATADV_WARNING_DEFAULT;

  	if (batadv_is_wifi_hardif(hard_iface))

  		hard_iface->bat_v.flags &= ~BATADV_FULL_DUPLEX;

  	INIT_DELAYED_WORK(&hard_iface->bat_v.elp_wq,
  			  batadv_v_elp_periodic_work);
  	batadv_v_elp_start_timer(hard_iface);
  	res = 0;
  
  out:
  	return res;
  }
  
  /**
   * batadv_v_elp_iface_disable - release ELP interface private resources
   * @hard_iface: interface for which the resources have to be released
   */
  void batadv_v_elp_iface_disable(struct batadv_hard_iface *hard_iface)
  {
  	cancel_delayed_work_sync(&hard_iface->bat_v.elp_wq);
  
  	dev_kfree_skb(hard_iface->bat_v.elp_skb);
  	hard_iface->bat_v.elp_skb = NULL;
  }
  
  /**

   * batadv_v_elp_iface_activate - update the ELP buffer belonging to the given
   *  hard-interface
   * @primary_iface: the new primary interface
   * @hard_iface: interface holding the to-be-updated buffer
   */
  void batadv_v_elp_iface_activate(struct batadv_hard_iface *primary_iface,
  				 struct batadv_hard_iface *hard_iface)
  {
  	struct batadv_elp_packet *elp_packet;
  	struct sk_buff *skb;
  
  	if (!hard_iface->bat_v.elp_skb)
  		return;
  
  	skb = hard_iface->bat_v.elp_skb;
  	elp_packet = (struct batadv_elp_packet *)skb->data;
  	ether_addr_copy(elp_packet->orig,
  			primary_iface->net_dev->dev_addr);
  }
  
  /**

   * batadv_v_elp_primary_iface_set - change internal data to reflect the new
   *  primary interface
   * @primary_iface: the new primary interface
   */
  void batadv_v_elp_primary_iface_set(struct batadv_hard_iface *primary_iface)
  {
  	struct batadv_hard_iface *hard_iface;

  
  	/* update orig field of every elp iface belonging to this mesh */
  	rcu_read_lock();
  	list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
  		if (primary_iface->soft_iface != hard_iface->soft_iface)
  			continue;

  		batadv_v_elp_iface_activate(primary_iface, hard_iface);

  	}
  	rcu_read_unlock();
  }

  
  /**

   * batadv_v_elp_neigh_update - update an ELP neighbour node
   * @bat_priv: the bat priv with all the soft interface information
   * @neigh_addr: the neighbour interface address
   * @if_incoming: the interface the packet was received through
   * @elp_packet: the received ELP packet
   *
   * Updates the ELP neighbour node state with the data received within the new
   * ELP packet.
   */
  static void batadv_v_elp_neigh_update(struct batadv_priv *bat_priv,
  				      u8 *neigh_addr,
  				      struct batadv_hard_iface *if_incoming,
  				      struct batadv_elp_packet *elp_packet)
  
  {
  	struct batadv_neigh_node *neigh;
  	struct batadv_orig_node *orig_neigh;
  	struct batadv_hardif_neigh_node *hardif_neigh;
  	s32 seqno_diff;
  	s32 elp_latest_seqno;
  
  	orig_neigh = batadv_v_ogm_orig_get(bat_priv, elp_packet->orig);
  	if (!orig_neigh)
  		return;

  	neigh = batadv_neigh_node_get_or_create(orig_neigh,
  						if_incoming, neigh_addr);

  	if (!neigh)
  		goto orig_free;
  
  	hardif_neigh = batadv_hardif_neigh_get(if_incoming, neigh_addr);
  	if (!hardif_neigh)
  		goto neigh_free;
  
  	elp_latest_seqno = hardif_neigh->bat_v.elp_latest_seqno;
  	seqno_diff = ntohl(elp_packet->seqno) - elp_latest_seqno;
  
  	/* known or older sequence numbers are ignored. However always adopt
  	 * if the router seems to have been restarted.
  	 */
  	if (seqno_diff < 1 && seqno_diff > -BATADV_ELP_MAX_AGE)
  		goto hardif_free;
  
  	neigh->last_seen = jiffies;
  	hardif_neigh->last_seen = jiffies;
  	hardif_neigh->bat_v.elp_latest_seqno = ntohl(elp_packet->seqno);
  	hardif_neigh->bat_v.elp_interval = ntohl(elp_packet->elp_interval);
  
  hardif_free:
  	if (hardif_neigh)
  		batadv_hardif_neigh_put(hardif_neigh);
  neigh_free:
  	if (neigh)
  		batadv_neigh_node_put(neigh);
  orig_free:
  	if (orig_neigh)
  		batadv_orig_node_put(orig_neigh);
  }
  
  /**
   * batadv_v_elp_packet_recv - main ELP packet handler
   * @skb: the received packet
   * @if_incoming: the interface this packet was received through
   *
   * Return: NET_RX_SUCCESS and consumes the skb if the packet was peoperly
   * processed or NET_RX_DROP in case of failure.
   */
  int batadv_v_elp_packet_recv(struct sk_buff *skb,
  			     struct batadv_hard_iface *if_incoming)
  {
  	struct batadv_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
  	struct batadv_elp_packet *elp_packet;
  	struct batadv_hard_iface *primary_if;
  	struct ethhdr *ethhdr = (struct ethhdr *)skb_mac_header(skb);

  	bool res;
  	int ret = NET_RX_DROP;

  	res = batadv_check_management_packet(skb, if_incoming, BATADV_ELP_HLEN);
  	if (!res)
  		goto free_skb;

  
  	if (batadv_is_my_mac(bat_priv, ethhdr->h_source))

  		goto free_skb;

  
  	/* did we receive a B.A.T.M.A.N. V ELP packet on an interface
  	 * that does not have B.A.T.M.A.N. V ELP enabled ?
  	 */

  	if (strcmp(bat_priv->algo_ops->name, "BATMAN_V") != 0)

  		goto free_skb;

  
  	elp_packet = (struct batadv_elp_packet *)skb->data;
  
  	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  		   "Received ELP packet from %pM seqno %u ORIG: %pM
  ",
  		   ethhdr->h_source, ntohl(elp_packet->seqno),
  		   elp_packet->orig);
  
  	primary_if = batadv_primary_if_get_selected(bat_priv);
  	if (!primary_if)

  		goto free_skb;

  
  	batadv_v_elp_neigh_update(bat_priv, ethhdr->h_source, if_incoming,
  				  elp_packet);

  	ret = NET_RX_SUCCESS;
  	batadv_hardif_put(primary_if);
  
  free_skb:
  	if (ret == NET_RX_SUCCESS)
  		consume_skb(skb);
  	else
  		kfree_skb(skb);
  
  	return ret;

  }