/* 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.\n",
                            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(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\n",
                           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;

        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\n",
                   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.
                 */
                queue_work(batadv_event_workqueue,
                           &hardif_neigh->bat_v.metric_work);
        }
        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)
{
        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;
        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);
        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\n",
                   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;
}