// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2008, 2009 open80211s Ltd.
 * Copyright (C) 2019, 2021-2025 Intel Corporation
 * Author:     Luis Carlos Cobo <luisca@cozybit.com>
 */
#include <linux/gfp.h>
#include <linux/kernel.h>
#include <linux/random.h>
#include <linux/rculist.h>

#include "ieee80211_i.h"
#include "rate.h"
#include "mesh.h"

#define PLINK_CNF_AID(mgmt) ((mgmt)->u.action.u.self_prot.variable + 2)
#define PLINK_GET_LLID(p) (p + 2)
#define PLINK_GET_PLID(p) (p + 4)

#define mod_plink_timer(s, t) (mod_timer(&s->mesh->plink_timer, \
                                jiffies + msecs_to_jiffies(t)))

enum plink_event {
        PLINK_UNDEFINED,
        OPN_ACPT,
        OPN_RJCT,
        OPN_IGNR,
        CNF_ACPT,
        CNF_RJCT,
        CNF_IGNR,
        CLS_ACPT,
        CLS_IGNR
};

static const char * const mplstates[] = {
        [NL80211_PLINK_LISTEN] = "LISTEN",
        [NL80211_PLINK_OPN_SNT] = "OPN-SNT",
        [NL80211_PLINK_OPN_RCVD] = "OPN-RCVD",
        [NL80211_PLINK_CNF_RCVD] = "CNF_RCVD",
        [NL80211_PLINK_ESTAB] = "ESTAB",
        [NL80211_PLINK_HOLDING] = "HOLDING",
        [NL80211_PLINK_BLOCKED] = "BLOCKED"
};

static const char * const mplevents[] = {
        [PLINK_UNDEFINED] = "NONE",
        [OPN_ACPT] = "OPN_ACPT",
        [OPN_RJCT] = "OPN_RJCT",
        [OPN_IGNR] = "OPN_IGNR",
        [CNF_ACPT] = "CNF_ACPT",
        [CNF_RJCT] = "CNF_RJCT",
        [CNF_IGNR] = "CNF_IGNR",
        [CLS_ACPT] = "CLS_ACPT",
        [CLS_IGNR] = "CLS_IGNR"
};

/* We only need a valid sta if user configured a minimum rssi_threshold. */
static bool rssi_threshold_check(struct ieee80211_sub_if_data *sdata,
                                 struct sta_info *sta)
{
        s32 rssi_threshold = sdata->u.mesh.mshcfg.rssi_threshold;
        return rssi_threshold == 0 ||
               (sta &&
                (s8)-ewma_signal_read(&sta->deflink.rx_stats_avg.signal) >
                rssi_threshold);
}

/**
 * mesh_plink_fsm_restart - restart a mesh peer link finite state machine
 *
 * @sta: mesh peer link to restart
 *
 * Locking: this function must be called holding sta->mesh->plink_lock
 */
static inline void mesh_plink_fsm_restart(struct sta_info *sta)
{
        lockdep_assert_held(&sta->mesh->plink_lock);
        sta->mesh->plink_state = NL80211_PLINK_LISTEN;
        sta->mesh->llid = sta->mesh->plid = sta->mesh->reason = 0;
        sta->mesh->plink_retries = 0;
}

/*
 * mesh_set_short_slot_time - enable / disable ERP short slot time.
 *
 * The standard indirectly mandates mesh STAs to turn off short slot time by
 * disallowing advertising this (802.11-2012 8.4.1.4), but that doesn't mean we
 * can't be sneaky about it. Enable short slot time if all mesh STAs in the
 * MBSS support ERP rates.
 *
 * Returns BSS_CHANGED_ERP_SLOT or 0 for no change.
 */
static u64 mesh_set_short_slot_time(struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_local *local = sdata->local;
        struct ieee80211_supported_band *sband;
        struct sta_info *sta;
        u32 erp_rates = 0;
        u64 changed = 0;
        int i;
        bool short_slot = false;

        sband = ieee80211_get_sband(sdata);
        if (!sband)
                return changed;

        if (sband->band == NL80211_BAND_5GHZ) {
                /* (IEEE 802.11-2012 19.4.5) */
                short_slot = true;
                goto out;
        } else if (sband->band != NL80211_BAND_2GHZ) {
                goto out;
        }

        for (i = 0; i < sband->n_bitrates; i++)
                if (sband->bitrates[i].flags & IEEE80211_RATE_ERP_G)
                        erp_rates |= BIT(i);

        if (!erp_rates)
                goto out;

        rcu_read_lock();
        list_for_each_entry_rcu(sta, &local->sta_list, list) {
                if (sdata != sta->sdata ||
                    sta->mesh->plink_state != NL80211_PLINK_ESTAB)
                        continue;

                short_slot = false;
                if (erp_rates & sta->sta.deflink.supp_rates[sband->band])
                        short_slot = true;
                 else
                        break;
        }
        rcu_read_unlock();

out:
        if (sdata->vif.bss_conf.use_short_slot != short_slot) {
                sdata->vif.bss_conf.use_short_slot = short_slot;
                changed = BSS_CHANGED_ERP_SLOT;
                mpl_dbg(sdata, "mesh_plink %pM: ERP short slot time %d\n",
                        sdata->vif.addr, short_slot);
        }
        return changed;
}

/**
 * mesh_set_ht_prot_mode - set correct HT protection mode
 * @sdata: the (mesh) interface to handle
 *
 * Section 9.23.3.5 of IEEE 80211-2012 describes the protection rules for HT
 * mesh STA in a MBSS. Three HT protection modes are supported for now, non-HT
 * mixed mode, 20MHz-protection and no-protection mode. non-HT mixed mode is
 * selected if any non-HT peers are present in our MBSS.  20MHz-protection mode
 * is selected if all peers in our 20/40MHz MBSS support HT and at least one
 * HT20 peer is present. Otherwise no-protection mode is selected.
 *
 * Returns: BSS_CHANGED_HT or 0 for no change
 */
static u64 mesh_set_ht_prot_mode(struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_local *local = sdata->local;
        struct sta_info *sta;
        u16 ht_opmode;
        bool non_ht_sta = false, ht20_sta = false;

        switch (sdata->vif.bss_conf.chanreq.oper.width) {
        case NL80211_CHAN_WIDTH_20_NOHT:
        case NL80211_CHAN_WIDTH_5:
        case NL80211_CHAN_WIDTH_10:
                return 0;
        default:
                break;
        }

        rcu_read_lock();
        list_for_each_entry_rcu(sta, &local->sta_list, list) {
                if (sdata != sta->sdata ||
                    sta->mesh->plink_state != NL80211_PLINK_ESTAB)
                        continue;

                if (sta->sta.deflink.bandwidth > IEEE80211_STA_RX_BW_20)
                        continue;

                if (!sta->sta.deflink.ht_cap.ht_supported) {
                        mpl_dbg(sdata, "nonHT sta (%pM) is present\n",
                                       sta->sta.addr);
                        non_ht_sta = true;
                        break;
                }

                mpl_dbg(sdata, "HT20 sta (%pM) is present\n", sta->sta.addr);
                ht20_sta = true;
        }
        rcu_read_unlock();

        if (non_ht_sta)
                ht_opmode = IEEE80211_HT_OP_MODE_PROTECTION_NONHT_MIXED;
        else if (ht20_sta &&
                 sdata->vif.bss_conf.chanreq.oper.width > NL80211_CHAN_WIDTH_20)
                ht_opmode = IEEE80211_HT_OP_MODE_PROTECTION_20MHZ;
        else
                ht_opmode = IEEE80211_HT_OP_MODE_PROTECTION_NONE;

        if (sdata->vif.bss_conf.ht_operation_mode == ht_opmode)
                return 0;

        sdata->vif.bss_conf.ht_operation_mode = ht_opmode;
        sdata->u.mesh.mshcfg.ht_opmode = ht_opmode;
        mpl_dbg(sdata, "selected new HT protection mode %d\n", ht_opmode);
        return BSS_CHANGED_HT;
}

static int mesh_plink_frame_tx(struct ieee80211_sub_if_data *sdata,
                               struct sta_info *sta,
                               enum ieee80211_self_protected_actioncode action,
                               u8 *da, u16 llid, u16 plid, u16 reason)
{
        struct ieee80211_local *local = sdata->local;
        struct sk_buff *skb;
        struct ieee80211_tx_info *info;
        struct ieee80211_mgmt *mgmt;
        bool include_plid = false;
        u16 peering_proto = 0;
        u8 *pos, ie_len = 4;
        u8 ie_len_he_cap, ie_len_eht_cap;
        int hdr_len = offsetofend(struct ieee80211_mgmt, u.action.u.self_prot);
        int err = -ENOMEM;

        ie_len_he_cap = ieee80211_ie_len_he_cap(sdata);
        ie_len_eht_cap = ieee80211_ie_len_eht_cap(sdata);
        skb = dev_alloc_skb(local->tx_headroom +
                            hdr_len +
                            2 + /* capability info */
                            2 + /* AID */
                            2 + 8 + /* supported rates */
                            2 + (IEEE80211_MAX_SUPP_RATES - 8) +
                            2 + sdata->u.mesh.mesh_id_len +
                            2 + sizeof(struct ieee80211_meshconf_ie) +
                            2 + sizeof(struct ieee80211_ht_cap) +
                            2 + sizeof(struct ieee80211_ht_operation) +
                            2 + sizeof(struct ieee80211_vht_cap) +
                            2 + sizeof(struct ieee80211_vht_operation) +
                            ie_len_he_cap +
                            2 + 1 + sizeof(struct ieee80211_he_operation) +
                                    sizeof(struct ieee80211_he_6ghz_oper) +
                            2 + 1 + sizeof(struct ieee80211_he_6ghz_capa) +
                            ie_len_eht_cap +
                            2 + 1 + offsetof(struct ieee80211_eht_operation, optional) +
                                    offsetof(struct ieee80211_eht_operation_info, optional) +
                            2 + 8 + /* peering IE */
                            sdata->u.mesh.ie_len);
        if (!skb)
                return err;
        info = IEEE80211_SKB_CB(skb);
        skb_reserve(skb, local->tx_headroom);
        mgmt = skb_put_zero(skb, hdr_len);
        mgmt->frame_control = cpu_to_le16(IEEE80211_FTYPE_MGMT |
                                          IEEE80211_STYPE_ACTION);
        memcpy(mgmt->da, da, ETH_ALEN);
        memcpy(mgmt->sa, sdata->vif.addr, ETH_ALEN);
        memcpy(mgmt->bssid, sdata->vif.addr, ETH_ALEN);
        mgmt->u.action.category = WLAN_CATEGORY_SELF_PROTECTED;
        mgmt->u.action.u.self_prot.action_code = action;

        if (action != WLAN_SP_MESH_PEERING_CLOSE) {
                struct ieee80211_supported_band *sband;
                u32 basic_rates;

                sband = ieee80211_get_sband(sdata);
                if (!sband) {
                        err = -EINVAL;
                        goto free;
                }

                /* capability info */
                pos = skb_put_zero(skb, 2);
                if (action == WLAN_SP_MESH_PEERING_CONFIRM) {
                        /* AID */
                        pos = skb_put(skb, 2);
                        put_unaligned_le16(sta->sta.aid, pos);
                }

                basic_rates = sdata->vif.bss_conf.basic_rates;

                if (ieee80211_put_srates_elem(skb, sband, basic_rates,
                                              0, WLAN_EID_SUPP_RATES) ||
                    ieee80211_put_srates_elem(skb, sband, basic_rates,
                                              0, WLAN_EID_EXT_SUPP_RATES) ||
                    mesh_add_rsn_ie(sdata, skb) ||
                    mesh_add_meshid_ie(sdata, skb) ||
                    mesh_add_meshconf_ie(sdata, skb))
                        goto free;
        } else {        /* WLAN_SP_MESH_PEERING_CLOSE */
                info->flags |= IEEE80211_TX_CTL_NO_ACK;
                if (mesh_add_meshid_ie(sdata, skb))
                        goto free;
        }

        /* Add Mesh Peering Management element */
        switch (action) {
        case WLAN_SP_MESH_PEERING_OPEN:
                break;
        case WLAN_SP_MESH_PEERING_CONFIRM:
                ie_len += 2;
                include_plid = true;
                break;
        case WLAN_SP_MESH_PEERING_CLOSE:
                if (plid) {
                        ie_len += 2;
                        include_plid = true;
                }
                ie_len += 2;    /* reason code */
                break;
        default:
                err = -EINVAL;
                goto free;
        }

        if (WARN_ON(skb_tailroom(skb) < 2 + ie_len))
                goto free;

        pos = skb_put(skb, 2 + ie_len);
        *pos++ = WLAN_EID_PEER_MGMT;
        *pos++ = ie_len;
        memcpy(pos, &peering_proto, 2);
        pos += 2;
        put_unaligned_le16(llid, pos);
        pos += 2;
        if (include_plid) {
                put_unaligned_le16(plid, pos);
                pos += 2;
        }
        if (action == WLAN_SP_MESH_PEERING_CLOSE) {
                put_unaligned_le16(reason, pos);
                pos += 2;
        }

        if (action != WLAN_SP_MESH_PEERING_CLOSE) {
                if (mesh_add_ht_cap_ie(sdata, skb) ||
                    mesh_add_ht_oper_ie(sdata, skb) ||
                    mesh_add_vht_cap_ie(sdata, skb) ||
                    mesh_add_vht_oper_ie(sdata, skb) ||
                    mesh_add_he_cap_ie(sdata, skb, ie_len_he_cap) ||
                    mesh_add_he_oper_ie(sdata, skb) ||
                    mesh_add_he_6ghz_cap_ie(sdata, skb) ||
                    mesh_add_eht_cap_ie(sdata, skb, ie_len_eht_cap) ||
                    mesh_add_eht_oper_ie(sdata, skb))
                        goto free;
        }

        if (mesh_add_vendor_ies(sdata, skb))
                goto free;

        ieee80211_tx_skb(sdata, skb);
        return 0;
free:
        kfree_skb(skb);
        return err;
}

/**
 * __mesh_plink_deactivate - deactivate mesh peer link
 *
 * @sta: mesh peer link to deactivate
 *
 * Mesh paths with this peer as next hop should be flushed
 * by the caller outside of plink_lock.
 *
 * Returns: beacon changed flag if the beacon content changed.
 *
 * Locking: the caller must hold sta->mesh->plink_lock
 */
static u64 __mesh_plink_deactivate(struct sta_info *sta)
{
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        u64 changed = 0;

        lockdep_assert_held(&sta->mesh->plink_lock);

        if (sta->mesh->plink_state == NL80211_PLINK_ESTAB)
                changed = mesh_plink_dec_estab_count(sdata);
        sta->mesh->plink_state = NL80211_PLINK_BLOCKED;

        ieee80211_mps_sta_status_update(sta);
        changed |= ieee80211_mps_set_sta_local_pm(sta,
                        NL80211_MESH_POWER_UNKNOWN);

        return changed;
}

/**
 * mesh_plink_deactivate - deactivate mesh peer link
 *
 * @sta: mesh peer link to deactivate
 *
 * All mesh paths with this peer as next hop will be flushed
 *
 * Returns: beacon changed flag if the beacon content changed.
 */
u64 mesh_plink_deactivate(struct sta_info *sta)
{
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        u64 changed;

        spin_lock_bh(&sta->mesh->plink_lock);
        changed = __mesh_plink_deactivate(sta);

        if (!sdata->u.mesh.user_mpm) {
                sta->mesh->reason = WLAN_REASON_MESH_PEER_CANCELED;
                mesh_plink_frame_tx(sdata, sta, WLAN_SP_MESH_PEERING_CLOSE,
                                    sta->sta.addr, sta->mesh->llid,
                                    sta->mesh->plid, sta->mesh->reason);
        }
        spin_unlock_bh(&sta->mesh->plink_lock);
        if (!sdata->u.mesh.user_mpm)
                timer_delete_sync(&sta->mesh->plink_timer);
        mesh_path_flush_by_nexthop(sta);

        /* make sure no readers can access nexthop sta from here on */
        synchronize_net();

        return changed;
}

static void mesh_sta_info_init(struct ieee80211_sub_if_data *sdata,
                               struct sta_info *sta,
                               struct ieee802_11_elems *elems)
{
        struct ieee80211_local *local = sdata->local;
        struct ieee80211_supported_band *sband;
        u32 rates, changed = 0;
        enum ieee80211_sta_rx_bandwidth bw = sta->sta.deflink.bandwidth;

        sband = ieee80211_get_sband(sdata);
        if (!sband)
                return;

        rates = ieee80211_sta_get_rates(sdata, elems, sband->band, NULL);

        spin_lock_bh(&sta->mesh->plink_lock);
        sta->deflink.rx_stats.last_rx = jiffies;

        /* rates and capabilities don't change during peering */
        if (sta->mesh->plink_state == NL80211_PLINK_ESTAB &&
            sta->mesh->processed_beacon)
                goto out;
        sta->mesh->processed_beacon = true;

        if (sta->sta.deflink.supp_rates[sband->band] != rates)
                changed |= IEEE80211_RC_SUPP_RATES_CHANGED;
        sta->sta.deflink.supp_rates[sband->band] = rates;

        if (ieee80211_ht_cap_ie_to_sta_ht_cap(sdata, sband,
                                              elems->ht_cap_elem,
                                              &sta->deflink))
                changed |= IEEE80211_RC_BW_CHANGED;

        ieee80211_vht_cap_ie_to_sta_vht_cap(sdata, sband,
                                            elems->vht_cap_elem, NULL,
                                            &sta->deflink);

        ieee80211_he_cap_ie_to_sta_he_cap(sdata, sband, elems->he_cap,
                                          elems->he_cap_len,
                                          elems->he_6ghz_capa,
                                          &sta->deflink);

        ieee80211_eht_cap_ie_to_sta_eht_cap(sdata, sband, elems->he_cap,
                                            elems->he_cap_len,
                                            elems->eht_cap, elems->eht_cap_len,
                                            &sta->deflink);

        if (bw != sta->sta.deflink.bandwidth)
                changed |= IEEE80211_RC_BW_CHANGED;

        /* HT peer is operating 20MHz-only */
        if (elems->ht_operation &&
            !(elems->ht_operation->ht_param &
              IEEE80211_HT_PARAM_CHAN_WIDTH_ANY)) {
                if (sta->sta.deflink.bandwidth != IEEE80211_STA_RX_BW_20)
                        changed |= IEEE80211_RC_BW_CHANGED;
                sta->sta.deflink.bandwidth = IEEE80211_STA_RX_BW_20;
        }

        /* FIXME: this check is wrong without SW rate control */
        if (!test_sta_flag(sta, WLAN_STA_RATE_CONTROL))
                rate_control_rate_init(&sta->deflink);
        else
                rate_control_rate_update(local, sband, &sta->deflink, changed);
out:
        spin_unlock_bh(&sta->mesh->plink_lock);
}

static int mesh_allocate_aid(struct ieee80211_sub_if_data *sdata)
{
        struct sta_info *sta;
        unsigned long *aid_map;
        int aid;

        aid_map = bitmap_zalloc(IEEE80211_MAX_AID + 1, GFP_KERNEL);
        if (!aid_map)
                return -ENOMEM;

        /* reserve aid 0 for mcast indication */
        __set_bit(0, aid_map);

        rcu_read_lock();
        list_for_each_entry_rcu(sta, &sdata->local->sta_list, list)
                __set_bit(sta->sta.aid, aid_map);
        rcu_read_unlock();

        aid = find_first_zero_bit(aid_map, IEEE80211_MAX_AID + 1);
        bitmap_free(aid_map);

        if (aid > IEEE80211_MAX_AID)
                return -ENOBUFS;

        return aid;
}

static struct sta_info *
__mesh_sta_info_alloc(struct ieee80211_sub_if_data *sdata, u8 *hw_addr)
{
        struct sta_info *sta;
        int aid;

        if (sdata->local->num_sta >= MESH_MAX_PLINKS)
                return NULL;

        aid = mesh_allocate_aid(sdata);
        if (aid < 0)
                return NULL;

        sta = sta_info_alloc(sdata, hw_addr, GFP_KERNEL);
        if (!sta)
                return NULL;

        sta->mesh->plink_state = NL80211_PLINK_LISTEN;
        sta->sta.wme = true;
        sta->sta.aid = aid;

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

        return sta;
}

static struct sta_info *
mesh_sta_info_alloc(struct ieee80211_sub_if_data *sdata, u8 *addr,
                    struct ieee802_11_elems *elems,
                    struct ieee80211_rx_status *rx_status)
{
        struct sta_info *sta = NULL;

        /* Userspace handles station allocation */
        if (sdata->u.mesh.user_mpm ||
            sdata->u.mesh.security & IEEE80211_MESH_SEC_AUTHED) {
                if (mesh_peer_accepts_plinks(elems) &&
                    mesh_plink_availables(sdata)) {
                        int sig = 0;

                        if (ieee80211_hw_check(&sdata->local->hw, SIGNAL_DBM))
                                sig = rx_status->signal;

                        cfg80211_notify_new_peer_candidate(sdata->dev, addr,
                                                           elems->ie_start,
                                                           elems->total_len,
                                                           sig, GFP_KERNEL);
                }
        } else
                sta = __mesh_sta_info_alloc(sdata, addr);

        return sta;
}

/*
 * mesh_sta_info_get - return mesh sta info entry for @addr.
 *
 * @sdata: local meshif
 * @addr: peer's address
 * @elems: IEs from beacon or mesh peering frame.
 * @rx_status: rx status for the frame for signal reporting
 *
 * Return existing or newly allocated sta_info under RCU read lock.
 * (re)initialize with given IEs.
 */
static struct sta_info *
mesh_sta_info_get(struct ieee80211_sub_if_data *sdata,
                  u8 *addr, struct ieee802_11_elems *elems,
                  struct ieee80211_rx_status *rx_status) __acquires(RCU)
{
        struct sta_info *sta = NULL;

        rcu_read_lock();
        sta = sta_info_get(sdata, addr);
        if (sta) {
                mesh_sta_info_init(sdata, sta, elems);
        } else {
                rcu_read_unlock();
                /* can't run atomic */
                sta = mesh_sta_info_alloc(sdata, addr, elems, rx_status);
                if (!sta) {
                        rcu_read_lock();
                        return NULL;
                }

                mesh_sta_info_init(sdata, sta, elems);

                if (sta_info_insert_rcu(sta))
                        return NULL;
        }

        return sta;
}

/*
 * mesh_neighbour_update - update or initialize new mesh neighbor.
 *
 * @sdata: local meshif
 * @addr: peer's address
 * @elems: IEs from beacon or mesh peering frame
 * @rx_status: rx status for the frame for signal reporting
 *
 * Initiates peering if appropriate.
 */
void mesh_neighbour_update(struct ieee80211_sub_if_data *sdata,
                           u8 *hw_addr,
                           struct ieee802_11_elems *elems,
                           struct ieee80211_rx_status *rx_status)
{
        struct sta_info *sta;
        u64 changed = 0;

        sta = mesh_sta_info_get(sdata, hw_addr, elems, rx_status);
        if (!sta)
                goto out;

        sta->mesh->connected_to_gate = elems->mesh_config->meshconf_form &
                IEEE80211_MESHCONF_FORM_CONNECTED_TO_GATE;

        if (mesh_peer_accepts_plinks(elems) &&
            sta->mesh->plink_state == NL80211_PLINK_LISTEN &&
            sdata->u.mesh.accepting_plinks &&
            sdata->u.mesh.mshcfg.auto_open_plinks &&
            rssi_threshold_check(sdata, sta))
                changed = mesh_plink_open(sta);

        ieee80211_mps_frame_release(sta, elems);
out:
        rcu_read_unlock();
        ieee80211_mbss_info_change_notify(sdata, changed);
}

void mesh_plink_timer(struct timer_list *t)
{
        struct mesh_sta *mesh = timer_container_of(mesh, t, plink_timer);
        struct sta_info *sta;
        u16 reason = 0;
        struct ieee80211_sub_if_data *sdata;
        struct mesh_config *mshcfg;
        enum ieee80211_self_protected_actioncode action = 0;

        /*
         * This STA is valid because sta_info_destroy() will
         * timer_delete_sync() this timer after having made sure
         * it cannot be re-added (by deleting the plink.)
         */
        sta = mesh->plink_sta;

        if (sta->sdata->local->quiescing)
                return;

        spin_lock_bh(&sta->mesh->plink_lock);

        /* If a timer fires just before a state transition on another CPU,
         * we may have already extended the timeout and changed state by the
         * time we've acquired the lock and arrived  here.  In that case,
         * skip this timer and wait for the new one.
         */
        if (time_before(jiffies, sta->mesh->plink_timer.expires)) {
                mpl_dbg(sta->sdata,
                        "Ignoring timer for %pM in state %s (timer adjusted)",
                        sta->sta.addr, mplstates[sta->mesh->plink_state]);
                spin_unlock_bh(&sta->mesh->plink_lock);
                return;
        }

        /* timer_delete() and handler may race when entering these states */
        if (sta->mesh->plink_state == NL80211_PLINK_LISTEN ||
            sta->mesh->plink_state == NL80211_PLINK_ESTAB) {
                mpl_dbg(sta->sdata,
                        "Ignoring timer for %pM in state %s (timer deleted)",
                        sta->sta.addr, mplstates[sta->mesh->plink_state]);
                spin_unlock_bh(&sta->mesh->plink_lock);
                return;
        }

        mpl_dbg(sta->sdata,
                "Mesh plink timer for %pM fired on state %s\n",
                sta->sta.addr, mplstates[sta->mesh->plink_state]);
        sdata = sta->sdata;
        mshcfg = &sdata->u.mesh.mshcfg;

        switch (sta->mesh->plink_state) {
        case NL80211_PLINK_OPN_RCVD:
        case NL80211_PLINK_OPN_SNT:
                /* retry timer */
                if (sta->mesh->plink_retries < mshcfg->dot11MeshMaxRetries) {
                        u32 rand;
                        mpl_dbg(sta->sdata,
                                "Mesh plink for %pM (retry, timeout): %d %d\n",
                                sta->sta.addr, sta->mesh->plink_retries,
                                sta->mesh->plink_timeout);
                        get_random_bytes(&rand, sizeof(u32));
                        sta->mesh->plink_timeout = sta->mesh->plink_timeout +
                                             rand % sta->mesh->plink_timeout;
                        ++sta->mesh->plink_retries;
                        mod_plink_timer(sta, sta->mesh->plink_timeout);
                        action = WLAN_SP_MESH_PEERING_OPEN;
                        break;
                }
                reason = WLAN_REASON_MESH_MAX_RETRIES;
                fallthrough;
        case NL80211_PLINK_CNF_RCVD:
                /* confirm timer */
                if (!reason)
                        reason = WLAN_REASON_MESH_CONFIRM_TIMEOUT;
                sta->mesh->plink_state = NL80211_PLINK_HOLDING;
                mod_plink_timer(sta, mshcfg->dot11MeshHoldingTimeout);
                action = WLAN_SP_MESH_PEERING_CLOSE;
                break;
        case NL80211_PLINK_HOLDING:
                /* holding timer */
                timer_delete(&sta->mesh->plink_timer);
                mesh_plink_fsm_restart(sta);
                break;
        default:
                break;
        }
        spin_unlock_bh(&sta->mesh->plink_lock);
        if (action)
                mesh_plink_frame_tx(sdata, sta, action, sta->sta.addr,
                                    sta->mesh->llid, sta->mesh->plid, reason);
}

static inline void mesh_plink_timer_set(struct sta_info *sta, u32 timeout)
{
        sta->mesh->plink_timeout = timeout;
        mod_timer(&sta->mesh->plink_timer, jiffies + msecs_to_jiffies(timeout));
}

static bool llid_in_use(struct ieee80211_sub_if_data *sdata,
                        u16 llid)
{
        struct ieee80211_local *local = sdata->local;
        bool in_use = false;
        struct sta_info *sta;

        rcu_read_lock();
        list_for_each_entry_rcu(sta, &local->sta_list, list) {
                if (sdata != sta->sdata)
                        continue;

                if (!memcmp(&sta->mesh->llid, &llid, sizeof(llid))) {
                        in_use = true;
                        break;
                }
        }
        rcu_read_unlock();

        return in_use;
}

static u16 mesh_get_new_llid(struct ieee80211_sub_if_data *sdata)
{
        u16 llid;

        do {
                get_random_bytes(&llid, sizeof(llid));
        } while (llid_in_use(sdata, llid));

        return llid;
}

u64 mesh_plink_open(struct sta_info *sta)
{
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        u64 changed;

        if (!test_sta_flag(sta, WLAN_STA_AUTH))
                return 0;

        spin_lock_bh(&sta->mesh->plink_lock);
        sta->mesh->llid = mesh_get_new_llid(sdata);
        if (sta->mesh->plink_state != NL80211_PLINK_LISTEN &&
            sta->mesh->plink_state != NL80211_PLINK_BLOCKED) {
                spin_unlock_bh(&sta->mesh->plink_lock);
                return 0;
        }
        sta->mesh->plink_state = NL80211_PLINK_OPN_SNT;
        mesh_plink_timer_set(sta, sdata->u.mesh.mshcfg.dot11MeshRetryTimeout);
        spin_unlock_bh(&sta->mesh->plink_lock);
        mpl_dbg(sdata,
                "Mesh plink: starting establishment with %pM\n",
                sta->sta.addr);

        /* set the non-peer mode to active during peering */
        changed = ieee80211_mps_local_status_update(sdata);

        mesh_plink_frame_tx(sdata, sta, WLAN_SP_MESH_PEERING_OPEN,
                            sta->sta.addr, sta->mesh->llid, 0, 0);
        return changed;
}

u64 mesh_plink_block(struct sta_info *sta)
{
        u64 changed;

        spin_lock_bh(&sta->mesh->plink_lock);
        changed = __mesh_plink_deactivate(sta);
        sta->mesh->plink_state = NL80211_PLINK_BLOCKED;
        spin_unlock_bh(&sta->mesh->plink_lock);
        mesh_path_flush_by_nexthop(sta);

        return changed;
}

static void mesh_plink_close(struct ieee80211_sub_if_data *sdata,
                             struct sta_info *sta,
                             enum plink_event event)
{
        struct mesh_config *mshcfg = &sdata->u.mesh.mshcfg;
        u16 reason = (event == CLS_ACPT) ?
                     WLAN_REASON_MESH_CLOSE : WLAN_REASON_MESH_CONFIG;

        sta->mesh->reason = reason;
        sta->mesh->plink_state = NL80211_PLINK_HOLDING;
        mod_plink_timer(sta, mshcfg->dot11MeshHoldingTimeout);
}

static u64 mesh_plink_establish(struct ieee80211_sub_if_data *sdata,
                                struct sta_info *sta)
{
        struct mesh_config *mshcfg = &sdata->u.mesh.mshcfg;
        u64 changed = 0;

        timer_delete(&sta->mesh->plink_timer);
        sta->mesh->plink_state = NL80211_PLINK_ESTAB;
        changed |= mesh_plink_inc_estab_count(sdata);
        changed |= mesh_set_ht_prot_mode(sdata);
        changed |= mesh_set_short_slot_time(sdata);
        mpl_dbg(sdata, "Mesh plink with %pM ESTABLISHED\n", sta->sta.addr);
        ieee80211_mps_sta_status_update(sta);
        changed |= ieee80211_mps_set_sta_local_pm(sta, mshcfg->power_mode);
        return changed;
}

/**
 * mesh_plink_fsm - step @sta MPM based on @event
 *
 * @sdata: interface
 * @sta: mesh neighbor
 * @event: peering event
 *
 * Return: changed MBSS flags
 */
static u64 mesh_plink_fsm(struct ieee80211_sub_if_data *sdata,
                          struct sta_info *sta, enum plink_event event)
{
        struct mesh_config *mshcfg = &sdata->u.mesh.mshcfg;
        enum ieee80211_self_protected_actioncode action = 0;
        u64 changed = 0;
        bool flush = false;

        mpl_dbg(sdata, "peer %pM in state %s got event %s\n", sta->sta.addr,
                mplstates[sta->mesh->plink_state], mplevents[event]);

        spin_lock_bh(&sta->mesh->plink_lock);
        switch (sta->mesh->plink_state) {
        case NL80211_PLINK_LISTEN:
                switch (event) {
                case CLS_ACPT:
                        mesh_plink_fsm_restart(sta);
                        break;
                case OPN_ACPT:
                        sta->mesh->plink_state = NL80211_PLINK_OPN_RCVD;
                        sta->mesh->llid = mesh_get_new_llid(sdata);
                        mesh_plink_timer_set(sta,
                                             mshcfg->dot11MeshRetryTimeout);

                        /* set the non-peer mode to active during peering */
                        changed |= ieee80211_mps_local_status_update(sdata);
                        action = WLAN_SP_MESH_PEERING_OPEN;
                        break;
                default:
                        break;
                }
                break;
        case NL80211_PLINK_OPN_SNT:
                switch (event) {
                case OPN_RJCT:
                case CNF_RJCT:
                case CLS_ACPT:
                        mesh_plink_close(sdata, sta, event);
                        action = WLAN_SP_MESH_PEERING_CLOSE;
                        break;
                case OPN_ACPT:
                        /* retry timer is left untouched */
                        sta->mesh->plink_state = NL80211_PLINK_OPN_RCVD;
                        action = WLAN_SP_MESH_PEERING_CONFIRM;
                        break;
                case CNF_ACPT:
                        sta->mesh->plink_state = NL80211_PLINK_CNF_RCVD;
                        mod_plink_timer(sta, mshcfg->dot11MeshConfirmTimeout);
                        break;
                default:
                        break;
                }
                break;
        case NL80211_PLINK_OPN_RCVD:
                switch (event) {
                case OPN_RJCT:
                case CNF_RJCT:
                case CLS_ACPT:
                        mesh_plink_close(sdata, sta, event);
                        action = WLAN_SP_MESH_PEERING_CLOSE;
                        break;
                case OPN_ACPT:
                        action = WLAN_SP_MESH_PEERING_CONFIRM;
                        break;
                case CNF_ACPT:
                        changed |= mesh_plink_establish(sdata, sta);
                        break;
                default:
                        break;
                }
                break;
        case NL80211_PLINK_CNF_RCVD:
                switch (event) {
                case OPN_RJCT:
                case CNF_RJCT:
                case CLS_ACPT:
                        mesh_plink_close(sdata, sta, event);
                        action = WLAN_SP_MESH_PEERING_CLOSE;
                        break;
                case OPN_ACPT:
                        changed |= mesh_plink_establish(sdata, sta);
                        action = WLAN_SP_MESH_PEERING_CONFIRM;
                        break;
                default:
                        break;
                }
                break;
        case NL80211_PLINK_ESTAB:
                switch (event) {
                case CLS_ACPT:
                        changed |= __mesh_plink_deactivate(sta);
                        changed |= mesh_set_ht_prot_mode(sdata);
                        changed |= mesh_set_short_slot_time(sdata);
                        mesh_plink_close(sdata, sta, event);
                        action = WLAN_SP_MESH_PEERING_CLOSE;
                        flush = true;
                        break;
                case OPN_ACPT:
                        action = WLAN_SP_MESH_PEERING_CONFIRM;
                        break;
                default:
                        break;
                }
                break;
        case NL80211_PLINK_HOLDING:
                switch (event) {
                case CLS_ACPT:
                        timer_delete(&sta->mesh->plink_timer);
                        mesh_plink_fsm_restart(sta);
                        break;
                case OPN_ACPT:
                case CNF_ACPT:
                case OPN_RJCT:
                case CNF_RJCT:
                        action = WLAN_SP_MESH_PEERING_CLOSE;
                        break;
                default:
                        break;
                }
                break;
        default:
                /* should not get here, PLINK_BLOCKED is dealt with at the
                 * beginning of the function
                 */
                break;
        }
        spin_unlock_bh(&sta->mesh->plink_lock);
        if (flush)
                mesh_path_flush_by_nexthop(sta);
        if (action) {
                mesh_plink_frame_tx(sdata, sta, action, sta->sta.addr,
                                    sta->mesh->llid, sta->mesh->plid,
                                    sta->mesh->reason);

                /* also send confirm in open case */
                if (action == WLAN_SP_MESH_PEERING_OPEN) {
                        mesh_plink_frame_tx(sdata, sta,
                                            WLAN_SP_MESH_PEERING_CONFIRM,
                                            sta->sta.addr, sta->mesh->llid,
                                            sta->mesh->plid, 0);
                }
        }

        return changed;
}

/*
 * mesh_plink_get_event - get correct MPM event
 *
 * @sdata: interface
 * @sta: peer, leave NULL if processing a frame from a new suitable peer
 * @elems: peering management IEs
 * @ftype: frame type
 * @llid: peer's peer link ID
 * @plid: peer's local link ID
 *
 * Return: new peering event for @sta, but PLINK_UNDEFINED should be treated as
 * an error.
 */
static enum plink_event
mesh_plink_get_event(struct ieee80211_sub_if_data *sdata,
                     struct sta_info *sta,
                     struct ieee802_11_elems *elems,
                     enum ieee80211_self_protected_actioncode ftype,
                     u16 llid, u16 plid)
{
        enum plink_event event = PLINK_UNDEFINED;
        u8 ie_len = elems->peering_len;
        bool matches_local;

        matches_local = (ftype == WLAN_SP_MESH_PEERING_CLOSE ||
                         mesh_matches_local(sdata, elems));

        /* deny open request from non-matching peer */
        if (!matches_local && !sta) {
                event = OPN_RJCT;
                goto out;
        }

        if (!sta) {
                if (ftype != WLAN_SP_MESH_PEERING_OPEN) {
                        mpl_dbg(sdata, "Mesh plink: cls or cnf from unknown peer\n");
                        goto out;
                }
                /* ftype == WLAN_SP_MESH_PEERING_OPEN */
                if (!mesh_plink_free_count(sdata)) {
                        mpl_dbg(sdata, "Mesh plink error: no more free plinks\n");
                        goto out;
                }

                /* new matching peer */
                event = OPN_ACPT;
                goto out;
        } else {
                if (!test_sta_flag(sta, WLAN_STA_AUTH)) {
                        mpl_dbg(sdata, "Mesh plink: Action frame from non-authed peer\n");
                        goto out;
                }
                if (sta->mesh->plink_state == NL80211_PLINK_BLOCKED)
                        goto out;
        }

        switch (ftype) {
        case WLAN_SP_MESH_PEERING_OPEN:
                if (!matches_local)
                        event = OPN_RJCT;
                else if (!mesh_plink_free_count(sdata) ||
                         (sta->mesh->plid && sta->mesh->plid != plid))
                        event = OPN_IGNR;
                else
                        event = OPN_ACPT;
                break;
        case WLAN_SP_MESH_PEERING_CONFIRM:
                if (!matches_local)
                        event = CNF_RJCT;
                else if (!mesh_plink_free_count(sdata) ||
                         sta->mesh->llid != llid ||
                         (sta->mesh->plid && sta->mesh->plid != plid))
                        event = CNF_IGNR;
                else
                        event = CNF_ACPT;
                break;
        case WLAN_SP_MESH_PEERING_CLOSE:
                if (sta->mesh->plink_state == NL80211_PLINK_ESTAB)
                        /* Do not check for llid or plid. This does not
                         * follow the standard but since multiple plinks
                         * per sta are not supported, it is necessary in
                         * order to avoid a livelock when MP A sees an
                         * establish peer link to MP B but MP B does not
                         * see it. This can be caused by a timeout in
                         * B's peer link establishment or B beign
                         * restarted.
                         */
                        event = CLS_ACPT;
                else if (sta->mesh->plid != plid)
                        event = CLS_IGNR;
                else if (ie_len == 8 && sta->mesh->llid != llid)
                        event = CLS_IGNR;
                else
                        event = CLS_ACPT;
                break;
        default:
                mpl_dbg(sdata, "Mesh plink: unknown frame subtype\n");
                break;
        }

out:
        return event;
}

static void
mesh_process_plink_frame(struct ieee80211_sub_if_data *sdata,
                         struct ieee80211_mgmt *mgmt,
                         struct ieee802_11_elems *elems,
                         struct ieee80211_rx_status *rx_status)
{

        struct sta_info *sta;
        enum plink_event event;
        enum ieee80211_self_protected_actioncode ftype;
        u64 changed = 0;
        u8 ie_len = elems->peering_len;
        u16 plid, llid = 0;

        if (!elems->peering) {
                mpl_dbg(sdata,
                        "Mesh plink: missing necessary peer link ie\n");
                return;
        }

        if (elems->rsn_len &&
            sdata->u.mesh.security == IEEE80211_MESH_SEC_NONE) {
                mpl_dbg(sdata,
                        "Mesh plink: can't establish link with secure peer\n");
                return;
        }

        ftype = mgmt->u.action.u.self_prot.action_code;
        if ((ftype == WLAN_SP_MESH_PEERING_OPEN && ie_len != 4) ||
            (ftype == WLAN_SP_MESH_PEERING_CONFIRM && ie_len != 6) ||
            (ftype == WLAN_SP_MESH_PEERING_CLOSE && ie_len != 6
                                                        && ie_len != 8)) {
                mpl_dbg(sdata,
                        "Mesh plink: incorrect plink ie length %d %d\n",
                        ftype, ie_len);
                return;
        }

        if (ftype != WLAN_SP_MESH_PEERING_CLOSE &&
            (!elems->mesh_id || !elems->mesh_config)) {
                mpl_dbg(sdata, "Mesh plink: missing necessary ie\n");
                return;
        }
        /* Note the lines below are correct, the llid in the frame is the plid
         * from the point of view of this host.
         */
        plid = get_unaligned_le16(PLINK_GET_LLID(elems->peering));
        if (ftype == WLAN_SP_MESH_PEERING_CONFIRM ||
            (ftype == WLAN_SP_MESH_PEERING_CLOSE && ie_len == 8))
                llid = get_unaligned_le16(PLINK_GET_PLID(elems->peering));

        /* WARNING: Only for sta pointer, is dropped & re-acquired */
        rcu_read_lock();

        sta = sta_info_get(sdata, mgmt->sa);

        if (ftype == WLAN_SP_MESH_PEERING_OPEN &&
            !rssi_threshold_check(sdata, sta)) {
                mpl_dbg(sdata, "Mesh plink: %pM does not meet rssi threshold\n",
                        mgmt->sa);
                goto unlock_rcu;
        }

        /* Now we will figure out the appropriate event... */
        event = mesh_plink_get_event(sdata, sta, elems, ftype, llid, plid);

        if (event == OPN_ACPT) {
                rcu_read_unlock();
                /* allocate sta entry if necessary and update info */
                sta = mesh_sta_info_get(sdata, mgmt->sa, elems, rx_status);
                if (!sta) {
                        mpl_dbg(sdata, "Mesh plink: failed to init peer!\n");
                        goto unlock_rcu;
                }
                sta->mesh->plid = plid;
        } else if (!sta && event == OPN_RJCT) {
                mesh_plink_frame_tx(sdata, NULL, WLAN_SP_MESH_PEERING_CLOSE,
                                    mgmt->sa, 0, plid,
                                    WLAN_REASON_MESH_CONFIG);
                goto unlock_rcu;
        } else if (!sta || event == PLINK_UNDEFINED) {
                /* something went wrong */
                goto unlock_rcu;
        }

        if (event == CNF_ACPT) {
                /* 802.11-2012 13.3.7.2 - update plid on CNF if not set */
                if (!sta->mesh->plid)
                        sta->mesh->plid = plid;

                sta->mesh->aid = get_unaligned_le16(PLINK_CNF_AID(mgmt));
        }

        changed |= mesh_plink_fsm(sdata, sta, event);

unlock_rcu:
        rcu_read_unlock();

        if (changed)
                ieee80211_mbss_info_change_notify(sdata, changed);
}

void mesh_rx_plink_frame(struct ieee80211_sub_if_data *sdata,
                         struct ieee80211_mgmt *mgmt, size_t len,
                         struct ieee80211_rx_status *rx_status)
{
        struct ieee802_11_elems *elems;
        size_t baselen;
        u8 *baseaddr;

        /* need action_code, aux */
        if (len < IEEE80211_MIN_ACTION_SIZE + 3)
                return;

        if (sdata->u.mesh.user_mpm)
                /* userspace must register for these */
                return;

        if (is_multicast_ether_addr(mgmt->da)) {
                mpl_dbg(sdata,
                        "Mesh plink: ignore frame from multicast address\n");
                return;
        }

        baseaddr = mgmt->u.action.u.self_prot.variable;
        baselen = (u8 *) mgmt->u.action.u.self_prot.variable - (u8 *) mgmt;
        if (mgmt->u.action.u.self_prot.action_code ==
                                                WLAN_SP_MESH_PEERING_CONFIRM) {
                baseaddr += 4;
                baselen += 4;

                if (baselen > len)
                        return;
        }
        elems = ieee802_11_parse_elems(baseaddr, len - baselen,
                                       IEEE80211_FTYPE_MGMT |
                                       IEEE80211_STYPE_ACTION,
                                       NULL);
        if (elems) {
                mesh_process_plink_frame(sdata, mgmt, elems, rx_status);
                kfree(elems);
        }
}