/*
 * OCB mode implementation
 *
 * Copyright: (c) 2014 Czech Technical University in Prague
 *            (c) 2014 Volkswagen Group Research
 * Author:    Rostislav Lisovy <rostislav.lisovy@fel.cvut.cz>
 * Funded by: Volkswagen Group Research
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/delay.h>
#include <linux/if_ether.h>
#include <linux/skbuff.h>
#include <linux/if_arp.h>
#include <linux/etherdevice.h>
#include <linux/rtnetlink.h>
#include <net/mac80211.h>
#include <asm/unaligned.h>

#include "ieee80211_i.h"
#include "driver-ops.h"
#include "rate.h"

#define IEEE80211_OCB_HOUSEKEEPING_INTERVAL             (60 * HZ)
#define IEEE80211_OCB_PEER_INACTIVITY_LIMIT             (240 * HZ)
#define IEEE80211_OCB_MAX_STA_ENTRIES                   128

/**
 * enum ocb_deferred_task_flags - mac80211 OCB deferred tasks
 * @OCB_WORK_HOUSEKEEPING: run the periodic OCB housekeeping tasks
 *
 * These flags are used in @wrkq_flags field of &struct ieee80211_if_ocb
 */
enum ocb_deferred_task_flags {
        OCB_WORK_HOUSEKEEPING,
};

void ieee80211_ocb_rx_no_sta(struct ieee80211_sub_if_data *sdata,
                             const u8 *bssid, const u8 *addr,
                             u32 supp_rates)
{
        struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;
        struct ieee80211_local *local = sdata->local;
        struct ieee80211_chanctx_conf *chanctx_conf;
        struct ieee80211_supported_band *sband;
        enum nl80211_bss_scan_width scan_width;
        struct sta_info *sta;
        int band;

        /* XXX: Consider removing the least recently used entry and
         *      allow new one to be added.
         */
        if (local->num_sta >= IEEE80211_OCB_MAX_STA_ENTRIES) {
                net_info_ratelimited("%s: No room for a new OCB STA entry %pM\n",
                                     sdata->name, addr);
                return;
        }

        ocb_dbg(sdata, "Adding new OCB station %pM\n", addr);

        rcu_read_lock();
        chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf);
        if (WARN_ON_ONCE(!chanctx_conf)) {
                rcu_read_unlock();
                return;
        }
        band = chanctx_conf->def.chan->band;
        scan_width = cfg80211_chandef_to_scan_width(&chanctx_conf->def);
        rcu_read_unlock();

        sta = sta_info_alloc(sdata, addr, GFP_ATOMIC);
        if (!sta)
                return;

        /* Add only mandatory rates for now */
        sband = local->hw.wiphy->bands[band];
        sta->sta.supp_rates[band] =
                ieee80211_mandatory_rates(sband, scan_width);

        spin_lock(&ifocb->incomplete_lock);
        list_add(&sta->list, &ifocb->incomplete_stations);
        spin_unlock(&ifocb->incomplete_lock);
        ieee80211_queue_work(&local->hw, &sdata->work);
}

static struct sta_info *ieee80211_ocb_finish_sta(struct sta_info *sta)
        __acquires(RCU)
{
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        u8 addr[ETH_ALEN];

        memcpy(addr, sta->sta.addr, ETH_ALEN);

        ocb_dbg(sdata, "Adding new IBSS station %pM (dev=%s)\n",
                addr, sdata->name);

        sta_info_move_state(sta, IEEE80211_STA_AUTH);
        sta_info_move_state(sta, IEEE80211_STA_ASSOC);
        sta_info_move_state(sta, IEEE80211_STA_AUTHORIZED);

        rate_control_rate_init(sta);

        /* If it fails, maybe we raced another insertion? */
        if (sta_info_insert_rcu(sta))
                return sta_info_get(sdata, addr);
        return sta;
}

static void ieee80211_ocb_housekeeping(struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;

        ocb_dbg(sdata, "Running ocb housekeeping\n");

        ieee80211_sta_expire(sdata, IEEE80211_OCB_PEER_INACTIVITY_LIMIT);

        mod_timer(&ifocb->housekeeping_timer,
                  round_jiffies(jiffies + IEEE80211_OCB_HOUSEKEEPING_INTERVAL));
}

void ieee80211_ocb_work(struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;
        struct sta_info *sta;

        if (ifocb->joined != true)
                return;

        sdata_lock(sdata);

        spin_lock_bh(&ifocb->incomplete_lock);
        while (!list_empty(&ifocb->incomplete_stations)) {
                sta = list_first_entry(&ifocb->incomplete_stations,
                                       struct sta_info, list);
                list_del(&sta->list);
                spin_unlock_bh(&ifocb->incomplete_lock);

                ieee80211_ocb_finish_sta(sta);
                rcu_read_unlock();
                spin_lock_bh(&ifocb->incomplete_lock);
        }
        spin_unlock_bh(&ifocb->incomplete_lock);

        if (test_and_clear_bit(OCB_WORK_HOUSEKEEPING, &ifocb->wrkq_flags))
                ieee80211_ocb_housekeeping(sdata);

        sdata_unlock(sdata);
}

static void ieee80211_ocb_housekeeping_timer(struct timer_list *t)
{
        struct ieee80211_sub_if_data *sdata =
                from_timer(sdata, t, u.ocb.housekeeping_timer);
        struct ieee80211_local *local = sdata->local;
        struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;

        set_bit(OCB_WORK_HOUSEKEEPING, &ifocb->wrkq_flags);

        ieee80211_queue_work(&local->hw, &sdata->work);
}

void ieee80211_ocb_setup_sdata(struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;

        timer_setup(&ifocb->housekeeping_timer,
                    ieee80211_ocb_housekeeping_timer, 0);
        INIT_LIST_HEAD(&ifocb->incomplete_stations);
        spin_lock_init(&ifocb->incomplete_lock);
}

int ieee80211_ocb_join(struct ieee80211_sub_if_data *sdata,
                       struct ocb_setup *setup)
{
        struct ieee80211_local *local = sdata->local;
        struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;
        u32 changed = BSS_CHANGED_OCB | BSS_CHANGED_BSSID;
        int err;

        if (ifocb->joined == true)
                return -EINVAL;

        sdata->flags |= IEEE80211_SDATA_OPERATING_GMODE;
        sdata->smps_mode = IEEE80211_SMPS_OFF;
        sdata->needed_rx_chains = sdata->local->rx_chains;

        mutex_lock(&sdata->local->mtx);
        err = ieee80211_vif_use_channel(sdata, &setup->chandef,
                                        IEEE80211_CHANCTX_SHARED);
        mutex_unlock(&sdata->local->mtx);
        if (err)
                return err;

        ieee80211_bss_info_change_notify(sdata, changed);

        ifocb->joined = true;

        set_bit(OCB_WORK_HOUSEKEEPING, &ifocb->wrkq_flags);
        ieee80211_queue_work(&local->hw, &sdata->work);

        netif_carrier_on(sdata->dev);
        return 0;
}

int ieee80211_ocb_leave(struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;
        struct ieee80211_local *local = sdata->local;
        struct sta_info *sta;

        ifocb->joined = false;
        sta_info_flush(sdata);

        spin_lock_bh(&ifocb->incomplete_lock);
        while (!list_empty(&ifocb->incomplete_stations)) {
                sta = list_first_entry(&ifocb->incomplete_stations,
                                       struct sta_info, list);
                list_del(&sta->list);
                spin_unlock_bh(&ifocb->incomplete_lock);

                sta_info_free(local, sta);
                spin_lock_bh(&ifocb->incomplete_lock);
        }
        spin_unlock_bh(&ifocb->incomplete_lock);

        netif_carrier_off(sdata->dev);
        clear_bit(SDATA_STATE_OFFCHANNEL, &sdata->state);
        ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_OCB);

        mutex_lock(&sdata->local->mtx);
        ieee80211_vif_release_channel(sdata);
        mutex_unlock(&sdata->local->mtx);

        skb_queue_purge(&sdata->skb_queue);

        del_timer_sync(&sdata->u.ocb.housekeeping_timer);
        /* If the timer fired while we waited for it, it will have
         * requeued the work. Now the work will be running again
         * but will not rearm the timer again because it checks
         * whether we are connected to the network or not -- at this
         * point we shouldn't be anymore.
         */

        return 0;
}