/*

   * 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 "mesh.h"

  #ifdef CONFIG_MAC80211_VERBOSE_MHWMP_DEBUG
  #define mhwmp_dbg(fmt, args...)   printk(KERN_DEBUG "Mesh HWMP: " fmt, ##args)
  #else
  #define mhwmp_dbg(fmt, args...)   do { (void)(0); } while (0)
  #endif

  #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)	(x + 3)

  #define PREP_IE_ORIG_SN(x)	u32_field_get(x, 9, 0);

  #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)	(AE_F_SET(x) ? x + 27 : x + 21)
  #define PREP_IE_TARGET_SN(x)	u32_field_get(x, 27, AE_F_SET(x));

  #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) ((long) (y) - (long) (x) < 0)
  #define SN_LT(x, y) ((long) (x) - (long) (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)

  
  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 = dev_alloc_skb(local->hw.extra_tx_headroom + 400);
  	struct ieee80211_mgmt *mgmt;
  	u8 *pos;
  	int ie_len;
  
  	if (!skb)
  		return -1;
  	skb_reserve(skb, local->hw.extra_tx_headroom);
  	/* 25 is the size of the common mgmt part (24) plus the size of the
  	 * common action part (1)
  	 */
  	mgmt = (struct ieee80211_mgmt *)
  		skb_put(skb, 25 + sizeof(mgmt->u.action.u.mesh_action));
  	memset(mgmt, 0, 25 + sizeof(mgmt->u.action.u.mesh_action));

  	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_PATH_SEL;

  	mgmt->u.action.u.mesh_action.action_code = MESH_PATH_SEL_ACTION;

  
  	switch (action) {
  	case MPATH_PREQ:

  		mhwmp_dbg("sending PREQ to %pM
  ", target);

  		ie_len = 37;
  		pos = skb_put(skb, 2 + ie_len);
  		*pos++ = WLAN_EID_PREQ;
  		break;
  	case MPATH_PREP:

  		mhwmp_dbg("sending PREP to %pM
  ", target);

  		ie_len = 31;
  		pos = skb_put(skb, 2 + ie_len);
  		*pos++ = WLAN_EID_PREP;
  		break;

  	case MPATH_RANN:
  		mhwmp_dbg("sending RANN from %pM
  ", 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_PREQ) {
  		memcpy(pos, &preq_id, 4);
  		pos += 4;
  	}
  	memcpy(pos, orig_addr, ETH_ALEN);
  	pos += ETH_ALEN;

  	memcpy(pos, &orig_sn, 4);

  	pos += 4;

  	if (action != MPATH_RANN) {
  		memcpy(pos, &lifetime, 4);
  		pos += 4;
  	}

  	memcpy(pos, &metric, 4);
  	pos += 4;
  	if (action == MPATH_PREQ) {
  		/* destination count */
  		*pos++ = 1;

  		*pos++ = target_flags;

  	}

  	if (action != MPATH_RANN) {

  		memcpy(pos, target, ETH_ALEN);

  		pos += ETH_ALEN;

  		memcpy(pos, &target_sn, 4);

  	}

  	ieee80211_tx_skb(sdata, skb);

  	return 0;
  }
  
  /**
   * 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
   */

  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 = dev_alloc_skb(local->hw.extra_tx_headroom + 400);
  	struct ieee80211_mgmt *mgmt;
  	u8 *pos;
  	int ie_len;
  
  	if (!skb)
  		return -1;
  	skb_reserve(skb, local->hw.extra_tx_headroom);
  	/* 25 is the size of the common mgmt part (24) plus the size of the
  	 * common action part (1)
  	 */
  	mgmt = (struct ieee80211_mgmt *)
  		skb_put(skb, 25 + sizeof(mgmt->u.action.u.mesh_action));
  	memset(mgmt, 0, 25 + sizeof(mgmt->u.action.u.mesh_action));

  	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 is left zeroed, wildcard value */

  	mgmt->u.action.category = WLAN_CATEGORY_MESH_PATH_SEL;

  	mgmt->u.action.u.mesh_action.action_code = MESH_PATH_SEL_ACTION;

  	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);

  	ieee80211_tx_skb(sdata, skb);

  	return 0;
  }

  void ieee80211s_update_metric(struct ieee80211_local *local,
  		struct sta_info *stainfo, 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 */
  	stainfo->fail_avg = ((80 * stainfo->fail_avg + 5) / 100 + 20 * failed);
  	if (stainfo->fail_avg > 95)
  		mesh_plink_broken(stainfo);
  }

  static u32 airtime_link_metric_get(struct ieee80211_local *local,
  				   struct sta_info *sta)
  {
  	struct ieee80211_supported_band *sband;
  	/* 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;
  
  	sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
  
  	if (sta->fail_avg >= 100)
  		return MAX_METRIC;

  
  	if (sta->last_tx_rate.flags & IEEE80211_TX_RC_MCS)
  		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.
  	 */

  	rate = sband->bitrates[sta->last_tx_rate.idx].bitrate;

  	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 destination in
  		 * the Path Request. The draft refers to that MP as the
  		 * destination address, even though usually it is the origin of
  		 * the PREP frame. 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_ORIG_ADDR(hwmp_ie);

  		orig_sn = PREP_IE_ORIG_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 (memcmp(orig_addr, sdata->vif.addr, ETH_ALEN) == 0) {

  		/* 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 (memcmp(orig_addr, ta, ETH_ALEN) == 0)
  		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->flags &= ~MESH_PATH_SN_VALID;

  			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;

  	u8 *target_addr, *orig_addr;
  	u8 target_flags, ttl;
  	u32 orig_sn, target_sn, lifetime;

  	bool reply = false;
  	bool forward = true;

  	/* 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);

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

  	if (memcmp(target_addr, sdata->vif.addr, ETH_ALEN) == 0) {

  		mhwmp_dbg("PREQ is for us
  ");

  		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 {
  		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("replying to the PREQ
  ");

  			mesh_path_sel_frame_tx(MPATH_PREP, 0, target_addr,
  				cpu_to_le32(target_sn), 0, orig_addr,
  				cpu_to_le32(orig_sn), mgmt->sa, 0, ttl,

  				cpu_to_le32(lifetime), cpu_to_le32(metric),

  				0, sdata);

  		} else

  			ifmsh->mshstats.dropped_frames_ttl++;

  	}
  
  	if (forward) {
  		u32 preq_id;
  		u8 hopcount, flags;
  
  		ttl = PREQ_IE_TTL(preq_elem);
  		lifetime = PREQ_IE_LIFETIME(preq_elem);
  		if (ttl <= 1) {

  			ifmsh->mshstats.dropped_frames_ttl++;

  			return;
  		}

  		mhwmp_dbg("forwarding the PREQ from %pM
  ", orig_addr);

  		--ttl;
  		flags = PREQ_IE_FLAGS(preq_elem);
  		preq_id = PREQ_IE_PREQ_ID(preq_elem);
  		hopcount = PREQ_IE_HOPCOUNT(preq_elem) + 1;
  		mesh_path_sel_frame_tx(MPATH_PREQ, flags, orig_addr,

  				cpu_to_le32(orig_sn), target_flags, target_addr,

  				cpu_to_le32(target_sn), broadcast_addr,

  				hopcount, ttl, cpu_to_le32(lifetime),
  				cpu_to_le32(metric), cpu_to_le32(preq_id),

  				sdata);

  		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 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("received PREP from %pM
  ", PREP_IE_ORIG_ADDR(prep_elem));

  	/* Note that we divert from the draft nomenclature and denominate
  	 * destination to what the draft refers to as origininator. So in this
  	 * function destnation refers to the final destination of the PREP,
  	 * which corresponds with the originator of the PREQ which this PREP
  	 * replies
  	 */

  	target_addr = PREP_IE_TARGET_ADDR(prep_elem);

  	if (memcmp(target_addr, sdata->vif.addr, ETH_ALEN) == 0)

  		/* destination, no forwarding required */
  		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(target_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;
  	orig_addr = PREP_IE_ORIG_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) {
  		spin_lock_bh(&mpath->state_lock);
  		if (mpath->flags & MESH_PATH_ACTIVE &&

  		    memcmp(ta, next_hop_deref_protected(mpath)->sta.addr,
  							ETH_ALEN) == 0 &&

  		    (!(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);

  			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);
  	}
  	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 mesh_path *mpath;

  	u8 ttl, flags, hopcount;
  	u8 *orig_addr;

  	u32 orig_sn, metric;

  	ttl = rann->rann_ttl;
  	if (ttl <= 1) {
  		ifmsh->mshstats.dropped_frames_ttl++;
  		return;
  	}
  	ttl--;
  	flags = rann->rann_flags;
  	orig_addr = rann->rann_addr;

  	orig_sn = rann->rann_seq;

  	hopcount = rann->rann_hopcount;

  	hopcount++;

  	metric = rann->rann_metric;
  	mhwmp_dbg("received RANN from %pM
  ", orig_addr);
  
  	rcu_read_lock();
  	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;
  		}
  		mesh_queue_preq(mpath,
  				PREQ_Q_F_START | PREQ_Q_F_REFRESH);
  	}

  	if (mpath->sn < orig_sn) {

  		mesh_path_sel_frame_tx(MPATH_RANN, flags, orig_addr,

  				       cpu_to_le32(orig_sn),

  				       0, NULL, 0, broadcast_addr,

  				       hopcount, ttl, 0,
  				       cpu_to_le32(metric + mpath->metric),

  				       0, sdata);

  		mpath->sn = orig_sn;

  	}
  	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;

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

  	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("could not allocate PREQ node
  ");

  		return;
  	}

  	spin_lock(&ifmsh->mesh_preq_queue_lock);
  	if (ifmsh->preq_queue_len == MAX_PREQ_QUEUE_LEN) {
  		spin_unlock(&ifmsh->mesh_preq_queue_lock);

  		kfree(preq_node);
  		if (printk_ratelimit())

  			mhwmp_dbg("PREQ node queue full
  ");

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

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

  	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);
  	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);

  	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), broadcast_addr, 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_lookup - put the appropriate next hop on a mesh frame

   *

   * @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. If no next hop is
   * found, the function will start a path discovery and queue the frame so it is
   * sent when the path is resolved. This means the caller must not free the skb
   * in this case.
   */

  int mesh_nexthop_lookup(struct sk_buff *skb,
  			struct ieee80211_sub_if_data *sdata)

  {

  	struct sk_buff *skb_to_free = NULL;
  	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 = 0;
  
  	rcu_read_lock();

  	mpath = mesh_path_lookup(target_addr, sdata);

  
  	if (!mpath) {

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

  		if (!mpath) {

  			sdata->u.mesh.mshstats.dropped_frames_no_route++;

  			err = -ENOSPC;
  			goto endlookup;
  		}
  	}
  
  	if (mpath->flags & MESH_PATH_ACTIVE) {

  		if (time_after(jiffies,

  			       mpath->exp_time -

  			       msecs_to_jiffies(sdata->u.mesh.mshcfg.path_refresh_time)) &&

  		    !memcmp(sdata->vif.addr, hdr->addr4, ETH_ALEN) &&

  		    !(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);
  		else
  			err = -ENOENT;

  	} else {

  		struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);

  		if (!(mpath->flags & MESH_PATH_RESOLVING)) {
  			/* Start discovery only if it is not running yet */
  			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;

  		skb_queue_tail(&mpath->frame_queue, skb);
  		if (skb_to_free)

  			mesh_path_discard_frame(skb_to_free, sdata);

  		err = -ENOENT;
  	}
  
  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;

  	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);
  	else if (mpath->discovery_retries < max_preq_retries(sdata)) {
  		++mpath->discovery_retries;
  		mpath->discovery_timeout *= 2;
  		mesh_queue_preq(mpath, 0);
  	} else {
  		mpath->flags = 0;
  		mpath->exp_time = jiffies;
  		mesh_path_flush_pending(mpath);
  	}
  
  	spin_unlock_bh(&mpath->state_lock);

  }

  
  void
  mesh_path_tx_root_frame(struct ieee80211_sub_if_data *sdata)
  {
  	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;

  	mesh_path_sel_frame_tx(MPATH_RANN, 0, sdata->vif.addr,

  			       cpu_to_le32(++ifmsh->sn),

  			       0, NULL, 0, broadcast_addr,

  			       0, sdata->u.mesh.mshcfg.element_ttl,
  			       0, 0, 0, sdata);

  }