/*
 * Copyright (c) 2008, 2009 open80211s Ltd.
 * Author:     Luis Carlos Cobo <luisca@cozybit.com>
 *
 * 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/slab.h>
#include <linux/etherdevice.h>
#include <asm/unaligned.h>
#include "wme.h"
#include "mesh.h"

#define TEST_FRAME_LEN  8192
#define MAX_METRIC      0xffffffff
#define ARITH_SHIFT     8

/* Number of frames buffered per destination for unresolved destinations */
#define MESH_FRAME_QUEUE_LEN    10
#define MAX_PREQ_QUEUE_LEN      64

/* Destination only */
#define MP_F_DO 0x1
/* Reply and forward */
#define MP_F_RF 0x2
/* Unknown Sequence Number */
#define MP_F_USN    0x01
/* Reason code Present */
#define MP_F_RCODE  0x02

static void mesh_queue_preq(struct mesh_path *, u8);

static inline u32 u32_field_get(u8 *preq_elem, int offset, bool ae)
{
        if (ae)
                offset += 6;
        return get_unaligned_le32(preq_elem + offset);
}

static inline u32 u16_field_get(u8 *preq_elem, int offset, bool ae)
{
        if (ae)
                offset += 6;
        return get_unaligned_le16(preq_elem + offset);
}

/* HWMP IE processing macros */
#define AE_F                    (1<<6)
#define AE_F_SET(x)             (*x & AE_F)
#define PREQ_IE_FLAGS(x)        (*(x))
#define PREQ_IE_HOPCOUNT(x)     (*(x + 1))
#define PREQ_IE_TTL(x)          (*(x + 2))
#define PREQ_IE_PREQ_ID(x)      u32_field_get(x, 3, 0)
#define PREQ_IE_ORIG_ADDR(x)    (x + 7)
#define PREQ_IE_ORIG_SN(x)      u32_field_get(x, 13, 0)
#define PREQ_IE_LIFETIME(x)     u32_field_get(x, 17, AE_F_SET(x))
#define PREQ_IE_METRIC(x)       u32_field_get(x, 21, AE_F_SET(x))
#define PREQ_IE_TARGET_F(x)     (*(AE_F_SET(x) ? x + 32 : x + 26))
#define PREQ_IE_TARGET_ADDR(x)  (AE_F_SET(x) ? x + 33 : x + 27)
#define PREQ_IE_TARGET_SN(x)    u32_field_get(x, 33, AE_F_SET(x))


#define PREP_IE_FLAGS(x)        PREQ_IE_FLAGS(x)
#define PREP_IE_HOPCOUNT(x)     PREQ_IE_HOPCOUNT(x)
#define PREP_IE_TTL(x)          PREQ_IE_TTL(x)
#define PREP_IE_ORIG_ADDR(x)    (AE_F_SET(x) ? x + 27 : x + 21)
#define PREP_IE_ORIG_SN(x)      u32_field_get(x, 27, AE_F_SET(x))
#define PREP_IE_LIFETIME(x)     u32_field_get(x, 13, AE_F_SET(x))
#define PREP_IE_METRIC(x)       u32_field_get(x, 17, AE_F_SET(x))
#define PREP_IE_TARGET_ADDR(x)  (x + 3)
#define PREP_IE_TARGET_SN(x)    u32_field_get(x, 9, 0)

#define PERR_IE_TTL(x)          (*(x))
#define PERR_IE_TARGET_FLAGS(x) (*(x + 2))
#define PERR_IE_TARGET_ADDR(x)  (x + 3)
#define PERR_IE_TARGET_SN(x)    u32_field_get(x, 9, 0)
#define PERR_IE_TARGET_RCODE(x) u16_field_get(x, 13, 0)

#define MSEC_TO_TU(x) (x*1000/1024)
#define SN_GT(x, y) ((s32)(y - x) < 0)
#define SN_LT(x, y) ((s32)(x - y) < 0)

#define net_traversal_jiffies(s) \
        msecs_to_jiffies(s->u.mesh.mshcfg.dot11MeshHWMPnetDiameterTraversalTime)
#define default_lifetime(s) \
        MSEC_TO_TU(s->u.mesh.mshcfg.dot11MeshHWMPactivePathTimeout)
#define min_preq_int_jiff(s) \
        (msecs_to_jiffies(s->u.mesh.mshcfg.dot11MeshHWMPpreqMinInterval))
#define max_preq_retries(s) (s->u.mesh.mshcfg.dot11MeshHWMPmaxPREQretries)
#define disc_timeout_jiff(s) \
        msecs_to_jiffies(sdata->u.mesh.mshcfg.min_discovery_timeout)
#define root_path_confirmation_jiffies(s) \
        msecs_to_jiffies(sdata->u.mesh.mshcfg.dot11MeshHWMPconfirmationInterval)

enum mpath_frame_type {
        MPATH_PREQ = 0,
        MPATH_PREP,
        MPATH_PERR,
        MPATH_RANN
};

static const u8 broadcast_addr[ETH_ALEN] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};

static int mesh_path_sel_frame_tx(enum mpath_frame_type action, u8 flags,
                u8 *orig_addr, __le32 orig_sn, u8 target_flags, u8 *target,
                __le32 target_sn, const u8 *da, u8 hop_count, u8 ttl,
                __le32 lifetime, __le32 metric, __le32 preq_id,
                struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_local *local = sdata->local;
        struct sk_buff *skb;
        struct ieee80211_mgmt *mgmt;
        u8 *pos, ie_len;
        int hdr_len = offsetof(struct ieee80211_mgmt, u.action.u.mesh_action) +
                      sizeof(mgmt->u.action.u.mesh_action);

        skb = dev_alloc_skb(local->tx_headroom +
                            hdr_len +
                            2 + 37); /* max HWMP IE */
        if (!skb)
                return -1;
        skb_reserve(skb, local->tx_headroom);
        mgmt = (struct ieee80211_mgmt *) skb_put(skb, hdr_len);
        memset(mgmt, 0, 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);
        /* BSSID == SA */
        memcpy(mgmt->bssid, sdata->vif.addr, ETH_ALEN);
        mgmt->u.action.category = WLAN_CATEGORY_MESH_ACTION;
        mgmt->u.action.u.mesh_action.action_code =
                                        WLAN_MESH_ACTION_HWMP_PATH_SELECTION;

        switch (action) {
        case MPATH_PREQ:
                mhwmp_dbg(sdata, "sending PREQ to %pM\n", target);
                ie_len = 37;
                pos = skb_put(skb, 2 + ie_len);
                *pos++ = WLAN_EID_PREQ;
                break;
        case MPATH_PREP:
                mhwmp_dbg(sdata, "sending PREP to %pM\n", target);
                ie_len = 31;
                pos = skb_put(skb, 2 + ie_len);
                *pos++ = WLAN_EID_PREP;
                break;
        case MPATH_RANN:
                mhwmp_dbg(sdata, "sending RANN from %pM\n", orig_addr);
                ie_len = sizeof(struct ieee80211_rann_ie);
                pos = skb_put(skb, 2 + ie_len);
                *pos++ = WLAN_EID_RANN;
                break;
        default:
                kfree_skb(skb);
                return -ENOTSUPP;
                break;
        }
        *pos++ = ie_len;
        *pos++ = flags;
        *pos++ = hop_count;
        *pos++ = ttl;
        if (action == MPATH_PREP) {
                memcpy(pos, target, ETH_ALEN);
                pos += ETH_ALEN;
                memcpy(pos, &target_sn, 4);
                pos += 4;
        } else {
                if (action == MPATH_PREQ) {
                        memcpy(pos, &preq_id, 4);
                        pos += 4;
                }
                memcpy(pos, orig_addr, ETH_ALEN);
                pos += ETH_ALEN;
                memcpy(pos, &orig_sn, 4);
                pos += 4;
        }
        memcpy(pos, &lifetime, 4);      /* interval for RANN */
        pos += 4;
        memcpy(pos, &metric, 4);
        pos += 4;
        if (action == MPATH_PREQ) {
                *pos++ = 1; /* destination count */
                *pos++ = target_flags;
                memcpy(pos, target, ETH_ALEN);
                pos += ETH_ALEN;
                memcpy(pos, &target_sn, 4);
                pos += 4;
        } else if (action == MPATH_PREP) {
                memcpy(pos, orig_addr, ETH_ALEN);
                pos += ETH_ALEN;
                memcpy(pos, &orig_sn, 4);
                pos += 4;
        }

        ieee80211_tx_skb(sdata, skb);
        return 0;
}


/*  Headroom is not adjusted.  Caller should ensure that skb has sufficient
 *  headroom in case the frame is encrypted. */
static void prepare_frame_for_deferred_tx(struct ieee80211_sub_if_data *sdata,
                struct sk_buff *skb)
{
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);

        skb_set_mac_header(skb, 0);
        skb_set_network_header(skb, 0);
        skb_set_transport_header(skb, 0);

        /* Send all internal mgmt frames on VO. Accordingly set TID to 7. */
        skb_set_queue_mapping(skb, IEEE80211_AC_VO);
        skb->priority = 7;

        info->control.vif = &sdata->vif;
        ieee80211_set_qos_hdr(sdata, skb);
}

/**
 * mesh_send_path error - Sends a PERR mesh management frame
 *
 * @target: broken destination
 * @target_sn: SN of the broken destination
 * @target_rcode: reason code for this PERR
 * @ra: node this frame is addressed to
 *
 * Note: This function may be called with driver locks taken that the driver
 * also acquires in the TX path.  To avoid a deadlock we don't transmit the
 * frame directly but add it to the pending queue instead.
 */
int mesh_path_error_tx(u8 ttl, u8 *target, __le32 target_sn,
                       __le16 target_rcode, const u8 *ra,
                       struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_local *local = sdata->local;
        struct sk_buff *skb;
        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
        struct ieee80211_mgmt *mgmt;
        u8 *pos, ie_len;
        int hdr_len = offsetof(struct ieee80211_mgmt, u.action.u.mesh_action) +
                      sizeof(mgmt->u.action.u.mesh_action);

        if (time_before(jiffies, ifmsh->next_perr))
                return -EAGAIN;

        skb = dev_alloc_skb(local->tx_headroom +
                            hdr_len +
                            2 + 15 /* PERR IE */);
        if (!skb)
                return -1;
        skb_reserve(skb, local->tx_headroom);
        mgmt = (struct ieee80211_mgmt *) skb_put(skb, hdr_len);
        memset(mgmt, 0, hdr_len);
        mgmt->frame_control = cpu_to_le16(IEEE80211_FTYPE_MGMT |
                                          IEEE80211_STYPE_ACTION);

        memcpy(mgmt->da, ra, ETH_ALEN);
        memcpy(mgmt->sa, sdata->vif.addr, ETH_ALEN);
        /* BSSID == SA */
        memcpy(mgmt->bssid, sdata->vif.addr, ETH_ALEN);
        mgmt->u.action.category = WLAN_CATEGORY_MESH_ACTION;
        mgmt->u.action.u.mesh_action.action_code =
                                        WLAN_MESH_ACTION_HWMP_PATH_SELECTION;
        ie_len = 15;
        pos = skb_put(skb, 2 + ie_len);
        *pos++ = WLAN_EID_PERR;
        *pos++ = ie_len;
        /* ttl */
        *pos++ = ttl;
        /* number of destinations */
        *pos++ = 1;
        /*
         * flags bit, bit 1 is unset if we know the sequence number and
         * bit 2 is set if we have a reason code
         */
        *pos = 0;
        if (!target_sn)
                *pos |= MP_F_USN;
        if (target_rcode)
                *pos |= MP_F_RCODE;
        pos++;
        memcpy(pos, target, ETH_ALEN);
        pos += ETH_ALEN;
        memcpy(pos, &target_sn, 4);
        pos += 4;
        memcpy(pos, &target_rcode, 2);

        /* see note in function header */
        prepare_frame_for_deferred_tx(sdata, skb);
        ifmsh->next_perr = TU_TO_EXP_TIME(
                                   ifmsh->mshcfg.dot11MeshHWMPperrMinInterval);
        ieee80211_add_pending_skb(local, skb);
        return 0;
}

void ieee80211s_update_metric(struct ieee80211_local *local,
                struct sta_info *sta, struct sk_buff *skb)
{
        struct ieee80211_tx_info *txinfo = IEEE80211_SKB_CB(skb);
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
        int failed;

        if (!ieee80211_is_data(hdr->frame_control))
                return;

        failed = !(txinfo->flags & IEEE80211_TX_STAT_ACK);

        /* moving average, scaled to 100 */
        sta->fail_avg = ((80 * sta->fail_avg + 5) / 100 + 20 * failed);
        if (sta->fail_avg > 95)
                mesh_plink_broken(sta);
}

static u32 airtime_link_metric_get(struct ieee80211_local *local,
                                   struct sta_info *sta)
{
        struct rate_info rinfo;
        /* This should be adjusted for each device */
        int device_constant = 1 << ARITH_SHIFT;
        int test_frame_len = TEST_FRAME_LEN << ARITH_SHIFT;
        int s_unit = 1 << ARITH_SHIFT;
        int rate, err;
        u32 tx_time, estimated_retx;
        u64 result;

        if (sta->fail_avg >= 100)
                return MAX_METRIC;

        sta_set_rate_info_tx(sta, &sta->last_tx_rate, &rinfo);
        rate = cfg80211_calculate_bitrate(&rinfo);
        if (WARN_ON(!rate))
                return MAX_METRIC;

        err = (sta->fail_avg << ARITH_SHIFT) / 100;

        /* bitrate is in units of 100 Kbps, while we need rate in units of
         * 1Mbps. This will be corrected on tx_time computation.
         */
        tx_time = (device_constant + 10 * test_frame_len / rate);
        estimated_retx = ((1 << (2 * ARITH_SHIFT)) / (s_unit - err));
        result = (tx_time * estimated_retx) >> (2 * ARITH_SHIFT) ;
        return (u32)result;
}

/**
 * hwmp_route_info_get - Update routing info to originator and transmitter
 *
 * @sdata: local mesh subif
 * @mgmt: mesh management frame
 * @hwmp_ie: hwmp information element (PREP or PREQ)
 *
 * This function updates the path routing information to the originator and the
 * transmitter of a HWMP PREQ or PREP frame.
 *
 * Returns: metric to frame originator or 0 if the frame should not be further
 * processed
 *
 * Notes: this function is the only place (besides user-provided info) where
 * path routing information is updated.
 */
static u32 hwmp_route_info_get(struct ieee80211_sub_if_data *sdata,
                            struct ieee80211_mgmt *mgmt,
                            u8 *hwmp_ie, enum mpath_frame_type action)
{
        struct ieee80211_local *local = sdata->local;
        struct mesh_path *mpath;
        struct sta_info *sta;
        bool fresh_info;
        u8 *orig_addr, *ta;
        u32 orig_sn, orig_metric;
        unsigned long orig_lifetime, exp_time;
        u32 last_hop_metric, new_metric;
        bool process = true;

        rcu_read_lock();
        sta = sta_info_get(sdata, mgmt->sa);
        if (!sta) {
                rcu_read_unlock();
                return 0;
        }

        last_hop_metric = airtime_link_metric_get(local, sta);
        /* Update and check originator routing info */
        fresh_info = true;

        switch (action) {
        case MPATH_PREQ:
                orig_addr = PREQ_IE_ORIG_ADDR(hwmp_ie);
                orig_sn = PREQ_IE_ORIG_SN(hwmp_ie);
                orig_lifetime = PREQ_IE_LIFETIME(hwmp_ie);
                orig_metric = PREQ_IE_METRIC(hwmp_ie);
                break;
        case MPATH_PREP:
                /* Originator here refers to the MP that was the target in the
                 * Path Request. We divert from the nomenclature in the draft
                 * so that we can easily use a single function to gather path
                 * information from both PREQ and PREP frames.
                 */
                orig_addr = PREP_IE_TARGET_ADDR(hwmp_ie);
                orig_sn = PREP_IE_TARGET_SN(hwmp_ie);
                orig_lifetime = PREP_IE_LIFETIME(hwmp_ie);
                orig_metric = PREP_IE_METRIC(hwmp_ie);
                break;
        default:
                rcu_read_unlock();
                return 0;
        }
        new_metric = orig_metric + last_hop_metric;
        if (new_metric < orig_metric)
                new_metric = MAX_METRIC;
        exp_time = TU_TO_EXP_TIME(orig_lifetime);

        if (ether_addr_equal(orig_addr, sdata->vif.addr)) {
                /* This MP is the originator, we are not interested in this
                 * frame, except for updating transmitter's path info.
                 */
                process = false;
                fresh_info = false;
        } else {
                mpath = mesh_path_lookup(orig_addr, sdata);
                if (mpath) {
                        spin_lock_bh(&mpath->state_lock);
                        if (mpath->flags & MESH_PATH_FIXED)
                                fresh_info = false;
                        else if ((mpath->flags & MESH_PATH_ACTIVE) &&
                            (mpath->flags & MESH_PATH_SN_VALID)) {
                                if (SN_GT(mpath->sn, orig_sn) ||
                                    (mpath->sn == orig_sn &&
                                     new_metric >= mpath->metric)) {
                                        process = false;
                                        fresh_info = false;
                                }
                        }
                } else {
                        mesh_path_add(orig_addr, sdata);
                        mpath = mesh_path_lookup(orig_addr, sdata);
                        if (!mpath) {
                                rcu_read_unlock();
                                return 0;
                        }
                        spin_lock_bh(&mpath->state_lock);
                }

                if (fresh_info) {
                        mesh_path_assign_nexthop(mpath, sta);
                        mpath->flags |= MESH_PATH_SN_VALID;
                        mpath->metric = new_metric;
                        mpath->sn = orig_sn;
                        mpath->exp_time = time_after(mpath->exp_time, exp_time)
                                          ?  mpath->exp_time : exp_time;
                        mesh_path_activate(mpath);
                        spin_unlock_bh(&mpath->state_lock);
                        mesh_path_tx_pending(mpath);
                        /* draft says preq_id should be saved to, but there does
                         * not seem to be any use for it, skipping by now
                         */
                } else
                        spin_unlock_bh(&mpath->state_lock);
        }

        /* Update and check transmitter routing info */
        ta = mgmt->sa;
        if (ether_addr_equal(orig_addr, ta))
                fresh_info = false;
        else {
                fresh_info = true;

                mpath = mesh_path_lookup(ta, sdata);
                if (mpath) {
                        spin_lock_bh(&mpath->state_lock);
                        if ((mpath->flags & MESH_PATH_FIXED) ||
                                ((mpath->flags & MESH_PATH_ACTIVE) &&
                                        (last_hop_metric > mpath->metric)))
                                fresh_info = false;
                } else {
                        mesh_path_add(ta, sdata);
                        mpath = mesh_path_lookup(ta, sdata);
                        if (!mpath) {
                                rcu_read_unlock();
                                return 0;
                        }
                        spin_lock_bh(&mpath->state_lock);
                }

                if (fresh_info) {
                        mesh_path_assign_nexthop(mpath, sta);
                        mpath->metric = last_hop_metric;
                        mpath->exp_time = time_after(mpath->exp_time, exp_time)
                                          ?  mpath->exp_time : exp_time;
                        mesh_path_activate(mpath);
                        spin_unlock_bh(&mpath->state_lock);
                        mesh_path_tx_pending(mpath);
                } else
                        spin_unlock_bh(&mpath->state_lock);
        }

        rcu_read_unlock();

        return process ? new_metric : 0;
}

static void hwmp_preq_frame_process(struct ieee80211_sub_if_data *sdata,
                                    struct ieee80211_mgmt *mgmt,
                                    u8 *preq_elem, u32 metric)
{
        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
        struct mesh_path *mpath = NULL;
        u8 *target_addr, *orig_addr;
        const u8 *da;
        u8 target_flags, ttl, flags;
        u32 orig_sn, target_sn, lifetime, orig_metric;
        bool reply = false;
        bool forward = true;
        bool root_is_gate;

        /* Update target SN, if present */
        target_addr = PREQ_IE_TARGET_ADDR(preq_elem);
        orig_addr = PREQ_IE_ORIG_ADDR(preq_elem);
        target_sn = PREQ_IE_TARGET_SN(preq_elem);
        orig_sn = PREQ_IE_ORIG_SN(preq_elem);
        target_flags = PREQ_IE_TARGET_F(preq_elem);
        orig_metric = metric;
        /* Proactive PREQ gate announcements */
        flags = PREQ_IE_FLAGS(preq_elem);
        root_is_gate = !!(flags & RANN_FLAG_IS_GATE);

        mhwmp_dbg(sdata, "received PREQ from %pM\n", orig_addr);

        if (ether_addr_equal(target_addr, sdata->vif.addr)) {
                mhwmp_dbg(sdata, "PREQ is for us\n");
                forward = false;
                reply = true;
                metric = 0;
                if (time_after(jiffies, ifmsh->last_sn_update +
                                        net_traversal_jiffies(sdata)) ||
                    time_before(jiffies, ifmsh->last_sn_update)) {
                        target_sn = ++ifmsh->sn;
                        ifmsh->last_sn_update = jiffies;
                }
        } else if (is_broadcast_ether_addr(target_addr) &&
                   (target_flags & IEEE80211_PREQ_TO_FLAG)) {
                rcu_read_lock();
                mpath = mesh_path_lookup(orig_addr, sdata);
                if (mpath) {
                        if (flags & IEEE80211_PREQ_PROACTIVE_PREP_FLAG) {
                                reply = true;
                                target_addr = sdata->vif.addr;
                                target_sn = ++ifmsh->sn;
                                metric = 0;
                                ifmsh->last_sn_update = jiffies;
                        }
                        if (root_is_gate)
                                mesh_path_add_gate(mpath);
                }
                rcu_read_unlock();
        } else {
                rcu_read_lock();
                mpath = mesh_path_lookup(target_addr, sdata);
                if (mpath) {
                        if ((!(mpath->flags & MESH_PATH_SN_VALID)) ||
                                        SN_LT(mpath->sn, target_sn)) {
                                mpath->sn = target_sn;
                                mpath->flags |= MESH_PATH_SN_VALID;
                        } else if ((!(target_flags & MP_F_DO)) &&
                                        (mpath->flags & MESH_PATH_ACTIVE)) {
                                reply = true;
                                metric = mpath->metric;
                                target_sn = mpath->sn;
                                if (target_flags & MP_F_RF)
                                        target_flags |= MP_F_DO;
                                else
                                        forward = false;
                        }
                }
                rcu_read_unlock();
        }

        if (reply) {
                lifetime = PREQ_IE_LIFETIME(preq_elem);
                ttl = ifmsh->mshcfg.element_ttl;
                if (ttl != 0) {
                        mhwmp_dbg(sdata, "replying to the PREQ\n");
                        mesh_path_sel_frame_tx(MPATH_PREP, 0, orig_addr,
                                cpu_to_le32(orig_sn), 0, target_addr,
                                cpu_to_le32(target_sn), mgmt->sa, 0, ttl,
                                cpu_to_le32(lifetime), cpu_to_le32(metric),
                                0, sdata);
                } else {
                        ifmsh->mshstats.dropped_frames_ttl++;
                }
        }

        if (forward && ifmsh->mshcfg.dot11MeshForwarding) {
                u32 preq_id;
                u8 hopcount;

                ttl = PREQ_IE_TTL(preq_elem);
                lifetime = PREQ_IE_LIFETIME(preq_elem);
                if (ttl <= 1) {
                        ifmsh->mshstats.dropped_frames_ttl++;
                        return;
                }
                mhwmp_dbg(sdata, "forwarding the PREQ from %pM\n", orig_addr);
                --ttl;
                preq_id = PREQ_IE_PREQ_ID(preq_elem);
                hopcount = PREQ_IE_HOPCOUNT(preq_elem) + 1;
                da = (mpath && mpath->is_root) ?
                        mpath->rann_snd_addr : broadcast_addr;

                if (flags & IEEE80211_PREQ_PROACTIVE_PREP_FLAG) {
                        target_addr = PREQ_IE_TARGET_ADDR(preq_elem);
                        target_sn = PREQ_IE_TARGET_SN(preq_elem);
                        metric = orig_metric;
                }

                mesh_path_sel_frame_tx(MPATH_PREQ, flags, orig_addr,
                                cpu_to_le32(orig_sn), target_flags, target_addr,
                                cpu_to_le32(target_sn), da,
                                hopcount, ttl, cpu_to_le32(lifetime),
                                cpu_to_le32(metric), cpu_to_le32(preq_id),
                                sdata);
                if (!is_multicast_ether_addr(da))
                        ifmsh->mshstats.fwded_unicast++;
                else
                        ifmsh->mshstats.fwded_mcast++;
                ifmsh->mshstats.fwded_frames++;
        }
}


static inline struct sta_info *
next_hop_deref_protected(struct mesh_path *mpath)
{
        return rcu_dereference_protected(mpath->next_hop,
                                         lockdep_is_held(&mpath->state_lock));
}


static void hwmp_prep_frame_process(struct ieee80211_sub_if_data *sdata,
                                    struct ieee80211_mgmt *mgmt,
                                    u8 *prep_elem, u32 metric)
{
        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
        struct mesh_path *mpath;
        u8 *target_addr, *orig_addr;
        u8 ttl, hopcount, flags;
        u8 next_hop[ETH_ALEN];
        u32 target_sn, orig_sn, lifetime;

        mhwmp_dbg(sdata, "received PREP from %pM\n",
                  PREP_IE_ORIG_ADDR(prep_elem));

        orig_addr = PREP_IE_ORIG_ADDR(prep_elem);
        if (ether_addr_equal(orig_addr, sdata->vif.addr))
                /* destination, no forwarding required */
                return;

        if (!ifmsh->mshcfg.dot11MeshForwarding)
                return;

        ttl = PREP_IE_TTL(prep_elem);
        if (ttl <= 1) {
                sdata->u.mesh.mshstats.dropped_frames_ttl++;
                return;
        }

        rcu_read_lock();
        mpath = mesh_path_lookup(orig_addr, sdata);
        if (mpath)
                spin_lock_bh(&mpath->state_lock);
        else
                goto fail;
        if (!(mpath->flags & MESH_PATH_ACTIVE)) {
                spin_unlock_bh(&mpath->state_lock);
                goto fail;
        }
        memcpy(next_hop, next_hop_deref_protected(mpath)->sta.addr, ETH_ALEN);
        spin_unlock_bh(&mpath->state_lock);
        --ttl;
        flags = PREP_IE_FLAGS(prep_elem);
        lifetime = PREP_IE_LIFETIME(prep_elem);
        hopcount = PREP_IE_HOPCOUNT(prep_elem) + 1;
        target_addr = PREP_IE_TARGET_ADDR(prep_elem);
        target_sn = PREP_IE_TARGET_SN(prep_elem);
        orig_sn = PREP_IE_ORIG_SN(prep_elem);

        mesh_path_sel_frame_tx(MPATH_PREP, flags, orig_addr,
                cpu_to_le32(orig_sn), 0, target_addr,
                cpu_to_le32(target_sn), next_hop, hopcount,
                ttl, cpu_to_le32(lifetime), cpu_to_le32(metric),
                0, sdata);
        rcu_read_unlock();

        sdata->u.mesh.mshstats.fwded_unicast++;
        sdata->u.mesh.mshstats.fwded_frames++;
        return;

fail:
        rcu_read_unlock();
        sdata->u.mesh.mshstats.dropped_frames_no_route++;
}

static void hwmp_perr_frame_process(struct ieee80211_sub_if_data *sdata,
                             struct ieee80211_mgmt *mgmt, u8 *perr_elem)
{
        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
        struct mesh_path *mpath;
        u8 ttl;
        u8 *ta, *target_addr;
        u32 target_sn;
        u16 target_rcode;

        ta = mgmt->sa;
        ttl = PERR_IE_TTL(perr_elem);
        if (ttl <= 1) {
                ifmsh->mshstats.dropped_frames_ttl++;
                return;
        }
        ttl--;
        target_addr = PERR_IE_TARGET_ADDR(perr_elem);
        target_sn = PERR_IE_TARGET_SN(perr_elem);
        target_rcode = PERR_IE_TARGET_RCODE(perr_elem);

        rcu_read_lock();
        mpath = mesh_path_lookup(target_addr, sdata);
        if (mpath) {
                struct sta_info *sta;

                spin_lock_bh(&mpath->state_lock);
                sta = next_hop_deref_protected(mpath);
                if (mpath->flags & MESH_PATH_ACTIVE &&
                    ether_addr_equal(ta, sta->sta.addr) &&
                    (!(mpath->flags & MESH_PATH_SN_VALID) ||
                    SN_GT(target_sn, mpath->sn))) {
                        mpath->flags &= ~MESH_PATH_ACTIVE;
                        mpath->sn = target_sn;
                        spin_unlock_bh(&mpath->state_lock);
                        if (!ifmsh->mshcfg.dot11MeshForwarding)
                                goto endperr;
                        mesh_path_error_tx(ttl, target_addr, cpu_to_le32(target_sn),
                                           cpu_to_le16(target_rcode),
                                           broadcast_addr, sdata);
                } else
                        spin_unlock_bh(&mpath->state_lock);
        }
endperr:
        rcu_read_unlock();
}

static void hwmp_rann_frame_process(struct ieee80211_sub_if_data *sdata,
                                struct ieee80211_mgmt *mgmt,
                                struct ieee80211_rann_ie *rann)
{
        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
        struct ieee80211_local *local = sdata->local;
        struct sta_info *sta;
        struct mesh_path *mpath;
        u8 ttl, flags, hopcount;
        u8 *orig_addr;
        u32 orig_sn, metric, metric_txsta, interval;
        bool root_is_gate;

        ttl = rann->rann_ttl;
        flags = rann->rann_flags;
        root_is_gate = !!(flags & RANN_FLAG_IS_GATE);
        orig_addr = rann->rann_addr;
        orig_sn = le32_to_cpu(rann->rann_seq);
        interval = le32_to_cpu(rann->rann_interval);
        hopcount = rann->rann_hopcount;
        hopcount++;
        metric = le32_to_cpu(rann->rann_metric);

        /*  Ignore our own RANNs */
        if (ether_addr_equal(orig_addr, sdata->vif.addr))
                return;

        mhwmp_dbg(sdata,
                  "received RANN from %pM via neighbour %pM (is_gate=%d)\n",
                  orig_addr, mgmt->sa, root_is_gate);

        rcu_read_lock();
        sta = sta_info_get(sdata, mgmt->sa);
        if (!sta) {
                rcu_read_unlock();
                return;
        }

        metric_txsta = airtime_link_metric_get(local, sta);

        mpath = mesh_path_lookup(orig_addr, sdata);
        if (!mpath) {
                mesh_path_add(orig_addr, sdata);
                mpath = mesh_path_lookup(orig_addr, sdata);
                if (!mpath) {
                        rcu_read_unlock();
                        sdata->u.mesh.mshstats.dropped_frames_no_route++;
                        return;
                }
        }

        if (!(SN_LT(mpath->sn, orig_sn)) &&
            !(mpath->sn == orig_sn && metric < mpath->rann_metric)) {
                rcu_read_unlock();
                return;
        }

        if ((!(mpath->flags & (MESH_PATH_ACTIVE | MESH_PATH_RESOLVING)) ||
             (time_after(jiffies, mpath->last_preq_to_root +
                                  root_path_confirmation_jiffies(sdata)) ||
             time_before(jiffies, mpath->last_preq_to_root))) &&
             !(mpath->flags & MESH_PATH_FIXED) && (ttl != 0)) {
                mhwmp_dbg(sdata,
                          "time to refresh root mpath %pM\n",
                          orig_addr);
                mesh_queue_preq(mpath, PREQ_Q_F_START | PREQ_Q_F_REFRESH);
                mpath->last_preq_to_root = jiffies;
        }

        mpath->sn = orig_sn;
        mpath->rann_metric = metric + metric_txsta;
        mpath->is_root = true;
        /* Recording RANNs sender address to send individually
         * addressed PREQs destined for root mesh STA */
        memcpy(mpath->rann_snd_addr, mgmt->sa, ETH_ALEN);

        if (root_is_gate)
                mesh_path_add_gate(mpath);

        if (ttl <= 1) {
                ifmsh->mshstats.dropped_frames_ttl++;
                rcu_read_unlock();
                return;
        }
        ttl--;

        if (ifmsh->mshcfg.dot11MeshForwarding) {
                mesh_path_sel_frame_tx(MPATH_RANN, flags, orig_addr,
                                       cpu_to_le32(orig_sn),
                                       0, NULL, 0, broadcast_addr,
                                       hopcount, ttl, cpu_to_le32(interval),
                                       cpu_to_le32(metric + metric_txsta),
                                       0, sdata);
        }

        rcu_read_unlock();
}


void mesh_rx_path_sel_frame(struct ieee80211_sub_if_data *sdata,
                            struct ieee80211_mgmt *mgmt,
                            size_t len)
{
        struct ieee802_11_elems elems;
        size_t baselen;
        u32 last_hop_metric;
        struct sta_info *sta;

        /* need action_code */
        if (len < IEEE80211_MIN_ACTION_SIZE + 1)
                return;

        rcu_read_lock();
        sta = sta_info_get(sdata, mgmt->sa);
        if (!sta || sta->plink_state != NL80211_PLINK_ESTAB) {
                rcu_read_unlock();
                return;
        }
        rcu_read_unlock();

        baselen = (u8 *) mgmt->u.action.u.mesh_action.variable - (u8 *) mgmt;
        ieee802_11_parse_elems(mgmt->u.action.u.mesh_action.variable,
                        len - baselen, &elems);

        if (elems.preq) {
                if (elems.preq_len != 37)
                        /* Right now we support just 1 destination and no AE */
                        return;
                last_hop_metric = hwmp_route_info_get(sdata, mgmt, elems.preq,
                                                      MPATH_PREQ);
                if (last_hop_metric)
                        hwmp_preq_frame_process(sdata, mgmt, elems.preq,
                                                last_hop_metric);
        }
        if (elems.prep) {
                if (elems.prep_len != 31)
                        /* Right now we support no AE */
                        return;
                last_hop_metric = hwmp_route_info_get(sdata, mgmt, elems.prep,
                                                      MPATH_PREP);
                if (last_hop_metric)
                        hwmp_prep_frame_process(sdata, mgmt, elems.prep,
                                                last_hop_metric);
        }
        if (elems.perr) {
                if (elems.perr_len != 15)
                        /* Right now we support only one destination per PERR */
                        return;
                hwmp_perr_frame_process(sdata, mgmt, elems.perr);
        }
        if (elems.rann)
                hwmp_rann_frame_process(sdata, mgmt, elems.rann);
}

/**
 * mesh_queue_preq - queue a PREQ to a given destination
 *
 * @mpath: mesh path to discover
 * @flags: special attributes of the PREQ to be sent
 *
 * Locking: the function must be called from within a rcu read lock block.
 *
 */
static void mesh_queue_preq(struct mesh_path *mpath, u8 flags)
{
        struct ieee80211_sub_if_data *sdata = mpath->sdata;
        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
        struct mesh_preq_queue *preq_node;

        preq_node = kmalloc(sizeof(struct mesh_preq_queue), GFP_ATOMIC);
        if (!preq_node) {
                mhwmp_dbg(sdata, "could not allocate PREQ node\n");
                return;
        }

        spin_lock_bh(&ifmsh->mesh_preq_queue_lock);
        if (ifmsh->preq_queue_len == MAX_PREQ_QUEUE_LEN) {
                spin_unlock_bh(&ifmsh->mesh_preq_queue_lock);
                kfree(preq_node);
                if (printk_ratelimit())
                        mhwmp_dbg(sdata, "PREQ node queue full\n");
                return;
        }

        spin_lock(&mpath->state_lock);
        if (mpath->flags & MESH_PATH_REQ_QUEUED) {
                spin_unlock(&mpath->state_lock);
                spin_unlock_bh(&ifmsh->mesh_preq_queue_lock);
                kfree(preq_node);
                return;
        }

        memcpy(preq_node->dst, mpath->dst, ETH_ALEN);
        preq_node->flags = flags;

        mpath->flags |= MESH_PATH_REQ_QUEUED;
        spin_unlock(&mpath->state_lock);

        list_add_tail(&preq_node->list, &ifmsh->preq_queue.list);
        ++ifmsh->preq_queue_len;
        spin_unlock_bh(&ifmsh->mesh_preq_queue_lock);

        if (time_after(jiffies, ifmsh->last_preq + min_preq_int_jiff(sdata)))
                ieee80211_queue_work(&sdata->local->hw, &sdata->work);

        else if (time_before(jiffies, ifmsh->last_preq)) {
                /* avoid long wait if did not send preqs for a long time
                 * and jiffies wrapped around
                 */
                ifmsh->last_preq = jiffies - min_preq_int_jiff(sdata) - 1;
                ieee80211_queue_work(&sdata->local->hw, &sdata->work);
        } else
                mod_timer(&ifmsh->mesh_path_timer, ifmsh->last_preq +
                                                min_preq_int_jiff(sdata));
}

/**
 * mesh_path_start_discovery - launch a path discovery from the PREQ queue
 *
 * @sdata: local mesh subif
 */
void mesh_path_start_discovery(struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
        struct mesh_preq_queue *preq_node;
        struct mesh_path *mpath;
        u8 ttl, target_flags;
        const u8 *da;
        u32 lifetime;

        spin_lock_bh(&ifmsh->mesh_preq_queue_lock);
        if (!ifmsh->preq_queue_len ||
                time_before(jiffies, ifmsh->last_preq +
                                min_preq_int_jiff(sdata))) {
                spin_unlock_bh(&ifmsh->mesh_preq_queue_lock);
                return;
        }

        preq_node = list_first_entry(&ifmsh->preq_queue.list,
                        struct mesh_preq_queue, list);
        list_del(&preq_node->list);
        --ifmsh->preq_queue_len;
        spin_unlock_bh(&ifmsh->mesh_preq_queue_lock);

        rcu_read_lock();
        mpath = mesh_path_lookup(preq_node->dst, sdata);
        if (!mpath)

                goto enddiscovery;

        spin_lock_bh(&mpath->state_lock);
        mpath->flags &= ~MESH_PATH_REQ_QUEUED;
        if (preq_node->flags & PREQ_Q_F_START) {
                if (mpath->flags & MESH_PATH_RESOLVING) {
                        spin_unlock_bh(&mpath->state_lock);
                        goto enddiscovery;
                } else {
                        mpath->flags &= ~MESH_PATH_RESOLVED;
                        mpath->flags |= MESH_PATH_RESOLVING;
                        mpath->discovery_retries = 0;
                        mpath->discovery_timeout = disc_timeout_jiff(sdata);
                }
        } else if (!(mpath->flags & MESH_PATH_RESOLVING) ||
                        mpath->flags & MESH_PATH_RESOLVED) {
                mpath->flags &= ~MESH_PATH_RESOLVING;
                spin_unlock_bh(&mpath->state_lock);
                goto enddiscovery;
        }

        ifmsh->last_preq = jiffies;

        if (time_after(jiffies, ifmsh->last_sn_update +
                                net_traversal_jiffies(sdata)) ||
            time_before(jiffies, ifmsh->last_sn_update)) {
                ++ifmsh->sn;
                sdata->u.mesh.last_sn_update = jiffies;
        }
        lifetime = default_lifetime(sdata);
        ttl = sdata->u.mesh.mshcfg.element_ttl;
        if (ttl == 0) {
                sdata->u.mesh.mshstats.dropped_frames_ttl++;
                spin_unlock_bh(&mpath->state_lock);
                goto enddiscovery;
        }

        if (preq_node->flags & PREQ_Q_F_REFRESH)
                target_flags = MP_F_DO;
        else
                target_flags = MP_F_RF;

        spin_unlock_bh(&mpath->state_lock);
        da = (mpath->is_root) ? mpath->rann_snd_addr : broadcast_addr;
        mesh_path_sel_frame_tx(MPATH_PREQ, 0, sdata->vif.addr,
                        cpu_to_le32(ifmsh->sn), target_flags, mpath->dst,
                        cpu_to_le32(mpath->sn), da, 0,
                        ttl, cpu_to_le32(lifetime), 0,
                        cpu_to_le32(ifmsh->preq_id++), sdata);
        mod_timer(&mpath->timer, jiffies + mpath->discovery_timeout);

enddiscovery:
        rcu_read_unlock();
        kfree(preq_node);
}

/**
 * mesh_nexthop_resolve - lookup next hop; conditionally start path discovery
 *
 * @skb: 802.11 frame to be sent
 * @sdata: network subif the frame will be sent through
 *
 * Lookup next hop for given skb and start path discovery if no
 * forwarding information is found.
 *
 * Returns: 0 if the next hop was found and -ENOENT if the frame was queued.
 * skb is freeed here if no mpath could be allocated.
 */
int mesh_nexthop_resolve(struct sk_buff *skb,
                         struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
        struct mesh_path *mpath;
        struct sk_buff *skb_to_free = NULL;
        u8 *target_addr = hdr->addr3;
        int err = 0;

        rcu_read_lock();
        err = mesh_nexthop_lookup(skb, sdata);
        if (!err)
                goto endlookup;

        /* no nexthop found, start resolving */
        mpath = mesh_path_lookup(target_addr, sdata);
        if (!mpath) {
                mesh_path_add(target_addr, sdata);
                mpath = mesh_path_lookup(target_addr, sdata);
                if (!mpath) {
                        mesh_path_discard_frame(skb, sdata);
                        err = -ENOSPC;
                        goto endlookup;
                }
        }

        if (!(mpath->flags & MESH_PATH_RESOLVING))
                mesh_queue_preq(mpath, PREQ_Q_F_START);

        if (skb_queue_len(&mpath->frame_queue) >= MESH_FRAME_QUEUE_LEN)
                skb_to_free = skb_dequeue(&mpath->frame_queue);

        info->flags |= IEEE80211_TX_INTFL_NEED_TXPROCESSING;
        ieee80211_set_qos_hdr(sdata, skb);
        skb_queue_tail(&mpath->frame_queue, skb);
        err = -ENOENT;
        if (skb_to_free)
                mesh_path_discard_frame(skb_to_free, sdata);

endlookup:
        rcu_read_unlock();
        return err;
}
/**
 * mesh_nexthop_lookup - put the appropriate next hop on a mesh frame. Calling
 * this function is considered "using" the associated mpath, so preempt a path
 * refresh if this mpath expires soon.
 *
 * @skb: 802.11 frame to be sent
 * @sdata: network subif the frame will be sent through
 *
 * Returns: 0 if the next hop was found. Nonzero otherwise.
 */
int mesh_nexthop_lookup(struct sk_buff *skb,
                        struct ieee80211_sub_if_data *sdata)
{
        struct mesh_path *mpath;
        struct sta_info *next_hop;
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
        u8 *target_addr = hdr->addr3;
        int err = -ENOENT;

        rcu_read_lock();
        mpath = mesh_path_lookup(target_addr, sdata);

        if (!mpath || !(mpath->flags & MESH_PATH_ACTIVE))
                goto endlookup;

        if (time_after(jiffies,
                       mpath->exp_time -
                       msecs_to_jiffies(sdata->u.mesh.mshcfg.path_refresh_time)) &&
            ether_addr_equal(sdata->vif.addr, hdr->addr4) &&
            !(mpath->flags & MESH_PATH_RESOLVING) &&
            !(mpath->flags & MESH_PATH_FIXED))
                mesh_queue_preq(mpath, PREQ_Q_F_START | PREQ_Q_F_REFRESH);

        next_hop = rcu_dereference(mpath->next_hop);
        if (next_hop) {
                memcpy(hdr->addr1, next_hop->sta.addr, ETH_ALEN);
                memcpy(hdr->addr2, sdata->vif.addr, ETH_ALEN);
                err = 0;
        }

endlookup:
        rcu_read_unlock();
        return err;
}

void mesh_path_timer(unsigned long data)
{
        struct mesh_path *mpath = (void *) data;
        struct ieee80211_sub_if_data *sdata = mpath->sdata;
        int ret;

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

        spin_lock_bh(&mpath->state_lock);
        if (mpath->flags & MESH_PATH_RESOLVED ||
                        (!(mpath->flags & MESH_PATH_RESOLVING))) {
                mpath->flags &= ~(MESH_PATH_RESOLVING | MESH_PATH_RESOLVED);
                spin_unlock_bh(&mpath->state_lock);
        } else if (mpath->discovery_retries < max_preq_retries(sdata)) {
                ++mpath->discovery_retries;
                mpath->discovery_timeout *= 2;
                mpath->flags &= ~MESH_PATH_REQ_QUEUED;
                spin_unlock_bh(&mpath->state_lock);
                mesh_queue_preq(mpath, 0);
        } else {
                mpath->flags = 0;
                mpath->exp_time = jiffies;
                spin_unlock_bh(&mpath->state_lock);
                if (!mpath->is_gate && mesh_gate_num(sdata) > 0) {
                        ret = mesh_path_send_to_gates(mpath);
                        if (ret)
                                mhwmp_dbg(sdata, "no gate was reachable\n");
                } else
                        mesh_path_flush_pending(mpath);
        }
}

void
mesh_path_tx_root_frame(struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
        u32 interval = ifmsh->mshcfg.dot11MeshHWMPRannInterval;
        u8 flags, target_flags = 0;

        flags = (ifmsh->mshcfg.dot11MeshGateAnnouncementProtocol)
                        ? RANN_FLAG_IS_GATE : 0;

        switch (ifmsh->mshcfg.dot11MeshHWMPRootMode) {
        case IEEE80211_PROACTIVE_RANN:
                mesh_path_sel_frame_tx(MPATH_RANN, flags, sdata->vif.addr,
                               cpu_to_le32(++ifmsh->sn),
                               0, NULL, 0, broadcast_addr,
                               0, ifmsh->mshcfg.element_ttl,
                               cpu_to_le32(interval), 0, 0, sdata);
                break;
        case IEEE80211_PROACTIVE_PREQ_WITH_PREP:
                flags |= IEEE80211_PREQ_PROACTIVE_PREP_FLAG;
        case IEEE80211_PROACTIVE_PREQ_NO_PREP:
                interval = ifmsh->mshcfg.dot11MeshHWMPactivePathToRootTimeout;
                target_flags |= IEEE80211_PREQ_TO_FLAG |
                                IEEE80211_PREQ_USN_FLAG;
                mesh_path_sel_frame_tx(MPATH_PREQ, flags, sdata->vif.addr,
                                cpu_to_le32(++ifmsh->sn), target_flags,
                                (u8 *) broadcast_addr, 0, broadcast_addr,
                                0, ifmsh->mshcfg.element_ttl,
                                cpu_to_le32(interval),
                                0, cpu_to_le32(ifmsh->preq_id++), sdata);
                break;
        default:
                mhwmp_dbg(sdata, "Proactive mechanism not supported\n");
                return;
        }
}