mac80211: code for on-demand Hybrid Wireless Mesh Protocol

This file implements the on-demand Hybrid Wireless Mesh Protocol, at this moment
using hop-count as the metric. When no mesh path exists for a given destination
or the mesh path is not active, frames addressed to that destination will be
queued and a Path Request frame will be sent. Queued frames will be sent when
the path is resolved (usually after reception of a Path Response) or discarded
if discovery times out. Path Requests will also be sent to refresh paths that
are being used and are close to expiring.

Path Errors are sent when a path discovery process triggered by the attempt to
forward a frame originated in a different mesh point times out. Path Errors are
also sent when a peer link is determined to be unreachable because of high error
rates.

Multiple destination support in Path Requests and Path Errors and precursors
have not been implemented yet.

Signed-off-by: Luis Carlos Cobo <luisca@cozybit.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/mesh_hwmp.c

@@ -0,0 +1,862 @@
+/*
+ * Copyright (c) 2008 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 "mesh.h"
+
+#define IEEE80211_FC(type, stype) cpu_to_le16(type | stype)
+
+#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
+
+/* 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) le32_to_cpu(*((u32 *) (x + 3)))
+#define PREQ_IE_ORIG_ADDR(x) (x + 7)
+#define PREQ_IE_ORIG_DSN(x) le32_to_cpu(*((u32 *) (x + 13)))
+#define PREQ_IE_LIFETIME(x) le32_to_cpu(*((u32 *) \
+			(AE_F_SET(x) ? x + 23 : x + 17)))
+#define PREQ_IE_METRIC(x) le32_to_cpu(*((u32 *) \
+			(AE_F_SET(x) ? x + 27 : x + 21)))
+#define PREQ_IE_DST_F(x) (*(AE_F_SET(x) ? x + 32 : x + 26))
+#define PREQ_IE_DST_ADDR(x) (AE_F_SET(x) ? x + 33 : x + 27)
+#define PREQ_IE_DST_DSN(x) le32_to_cpu(*((u32 *) \
+			(AE_F_SET(x) ? x + 39 : x + 33)))
+
+
+#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_DSN(x) le32_to_cpu(*((u32 *) (x + 9)))
+#define PREP_IE_LIFETIME(x) le32_to_cpu(*((u32 *) \
+			(AE_F_SET(x) ? x + 19 : x + 13)))
+#define PREP_IE_METRIC(x) le32_to_cpu(*((u32 *) \
+			(AE_F_SET(x) ? x + 23 : x + 17)))
+#define PREP_IE_DST_ADDR(x) (AE_F_SET(x) ? x + 27 : x + 21)
+#define PREP_IE_DST_DSN(x) le32_to_cpu(*((u32 *) \
+			(AE_F_SET(x) ? x + 33 : x + 27)))
+
+#define PERR_IE_DST_ADDR(x) (x + 2)
+#define PERR_IE_DST_DSN(x) le32_to_cpu(*((u32 *) (x + 8)))
+
+#define TU_TO_EXP_TIME(x) (jiffies + msecs_to_jiffies(x * 1024 / 1000))
+#define MSEC_TO_TU(x) (x*1000/1024)
+#define DSN_GT(x, y) ((long) (y) - (long) (x) < 0)
+#define DSN_LT(x, y) ((long) (x) - (long) (y) < 0)
+
+#define net_traversal_jiffies(s) \
+	msecs_to_jiffies(s->u.sta.mshcfg.dot11MeshHWMPnetDiameterTraversalTime)
+#define default_lifetime(s) \
+	MSEC_TO_TU(s->u.sta.mshcfg.dot11MeshHWMPactivePathTimeout)
+#define min_preq_int_jiff(s) \
+	(msecs_to_jiffies(s->u.sta.mshcfg.dot11MeshHWMPpreqMinInterval))
+#define max_preq_retries(s) (s->u.sta.mshcfg.dot11MeshHWMPmaxPREQretries)
+#define disc_timeout_jiff(s) \
+	msecs_to_jiffies(sdata->u.sta.mshcfg.min_discovery_timeout)
+
+enum mpath_frame_type {
+	MPATH_PREQ = 0,
+	MPATH_PREP,
+	MPATH_PERR
+};
+
+static int mesh_path_sel_frame_tx(enum mpath_frame_type action, u8 flags,
+		u8 *orig_addr, __le32 orig_dsn, u8 dst_flags, u8 *dst,
+		__le32 dst_dsn, u8 *da, u8 hop_count, u8 ttl, __le32 lifetime,
+		__le32 metric, __le32 preq_id, struct net_device *dev)
+{
+	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
+	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 = IEEE80211_FC(IEEE80211_FTYPE_MGMT,
+					   IEEE80211_STYPE_ACTION);
+
+	memcpy(mgmt->da, da, ETH_ALEN);
+	memcpy(mgmt->sa, dev->dev_addr, ETH_ALEN);
+	/* BSSID is left zeroed, wildcard value */
+	mgmt->u.action.category = MESH_PATH_SEL_CATEGORY;
+	mgmt->u.action.u.mesh_action.action_code = action;
+
+	switch (action) {
+	case MPATH_PREQ:
+		ie_len = 37;
+		pos = skb_put(skb, 2 + ie_len);
+		*pos++ = WLAN_EID_PREQ;
+		break;
+	case MPATH_PREP:
+		ie_len = 31;
+		pos = skb_put(skb, 2 + ie_len);
+		*pos++ = WLAN_EID_PREP;
+		break;
+	default:
+		kfree(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_dsn, 4);
+	pos += 4;
+	memcpy(pos, &lifetime, 4);
+	pos += 4;
+	memcpy(pos, &metric, 4);
+	pos += 4;
+	if (action == MPATH_PREQ) {
+		/* destination count */
+		*pos++ = 1;
+		*pos++ = dst_flags;
+	}
+	memcpy(pos, dst, ETH_ALEN);
+	pos += ETH_ALEN;
+	memcpy(pos, &dst_dsn, 4);
+
+	ieee80211_sta_tx(dev, skb, 0);
+	return 0;
+}
+
+/**
+ * mesh_send_path error - Sends a PERR mesh management frame
+ *
+ * @dst: broken destination
+ * @dst_dsn: dsn of the broken destination
+ * @ra: node this frame is addressed to
+ */
+int mesh_path_error_tx(u8 *dst, __le32 dst_dsn, u8 *ra,
+		struct net_device *dev)
+{
+	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
+	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 = IEEE80211_FC(IEEE80211_FTYPE_MGMT,
+					   IEEE80211_STYPE_ACTION);
+
+	memcpy(mgmt->da, ra, ETH_ALEN);
+	memcpy(mgmt->sa, dev->dev_addr, ETH_ALEN);
+	/* BSSID is left zeroed, wildcard value */
+	mgmt->u.action.category = MESH_PATH_SEL_CATEGORY;
+	mgmt->u.action.u.mesh_action.action_code = MPATH_PERR;
+	ie_len = 12;
+	pos = skb_put(skb, 2 + ie_len);
+	*pos++ = WLAN_EID_PERR;
+	*pos++ = ie_len;
+	/* mode flags, reserved */
+	*pos++ = 0;
+	/* number of destinations */
+	*pos++ = 1;
+	memcpy(pos, dst, ETH_ALEN);
+	pos += ETH_ALEN;
+	memcpy(pos, &dst_dsn, 4);
+
+	ieee80211_sta_tx(dev, skb, 0);
+	return 0;
+}
+
+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;
+	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->txrate_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
+ *
+ * @dev: local mesh interface
+ * @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 fram.
+ *
+ * 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 net_device *dev,
+			    struct ieee80211_mgmt *mgmt,
+			    u8 *hwmp_ie)
+{
+	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
+	struct mesh_path *mpath;
+	struct sta_info *sta;
+	bool fresh_info;
+	u8 *orig_addr, *ta;
+	u32 orig_dsn, orig_metric;
+	unsigned long orig_lifetime, exp_time;
+	u32 last_hop_metric, new_metric;
+	bool process = true;
+	u8 action = mgmt->u.action.u.mesh_action.action_code;
+
+	rcu_read_lock();
+	sta = sta_info_get(local, mgmt->sa);
+	if (!sta)
+		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_dsn = PREQ_IE_ORIG_DSN(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_dsn = PREP_IE_ORIG_DSN(hwmp_ie);
+		orig_lifetime = PREP_IE_LIFETIME(hwmp_ie);
+		orig_metric = PREP_IE_METRIC(hwmp_ie);
+		break;
+	default:
+		sta_info_put(sta);
+		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, dev->dev_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, dev);
+		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_DSN_VALID)) {
+				if (DSN_GT(mpath->dsn, orig_dsn) ||
+				    (mpath->dsn == orig_dsn &&
+				     action == MPATH_PREQ &&
+				     new_metric > mpath->metric)) {
+					process = false;
+					fresh_info = false;
+				}
+			}
+		} else {
+			mesh_path_add(orig_addr, dev);
+			mpath = mesh_path_lookup(orig_addr, dev);
+			if (!mpath) {
+				rcu_read_unlock();
+				sta_info_put(sta);
+				return 0;
+			}
+			spin_lock_bh(&mpath->state_lock);
+		}
+
+		if (fresh_info) {
+			mesh_path_assign_nexthop(mpath, sta);
+			mpath->flags |= MESH_PATH_DSN_VALID;
+			mpath->metric = new_metric;
+			mpath->dsn = orig_dsn;
+			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, dev);
+		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, dev);
+			mpath = mesh_path_lookup(ta, dev);
+			if (!mpath) {
+				rcu_read_unlock();
+				sta_info_put(sta);
+				return 0;
+			}
+			spin_lock_bh(&mpath->state_lock);
+		}
+
+		if (fresh_info) {
+			mesh_path_assign_nexthop(mpath, sta);
+			mpath->flags &= ~MESH_PATH_DSN_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);
+	}
+
+	sta_info_put(sta);
+	rcu_read_unlock();
+
+	return process ? new_metric : 0;
+}
+
+static void hwmp_preq_frame_process(struct net_device *dev,
+				    struct ieee80211_mgmt *mgmt,
+				    u8 *preq_elem, u32 metric) {
+	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+	struct ieee80211_if_sta *ifsta = &sdata->u.sta;
+	struct mesh_path *mpath;
+	u8 *dst_addr, *orig_addr;
+	u8 dst_flags, ttl;
+	u32 orig_dsn, dst_dsn, lifetime;
+	bool reply = false;
+	bool forward = true;
+
+	/* Update destination DSN, if present */
+	dst_addr = PREQ_IE_DST_ADDR(preq_elem);
+	orig_addr = PREQ_IE_ORIG_ADDR(preq_elem);
+	dst_dsn = PREQ_IE_DST_DSN(preq_elem);
+	orig_dsn = PREQ_IE_ORIG_DSN(preq_elem);
+	dst_flags = PREQ_IE_DST_F(preq_elem);
+
+	if (memcmp(dst_addr, dev->dev_addr, ETH_ALEN) == 0) {
+		forward = false;
+		reply = true;
+		metric = 0;
+		if (time_after(jiffies, ifsta->last_dsn_update +
+					net_traversal_jiffies(sdata)) ||
+		    time_before(jiffies, ifsta->last_dsn_update)) {
+			dst_dsn = ++ifsta->dsn;
+			ifsta->last_dsn_update = jiffies;
+		}
+	} else {
+		rcu_read_lock();
+		mpath = mesh_path_lookup(dst_addr, dev);
+		if (mpath) {
+			if ((!(mpath->flags & MESH_PATH_DSN_VALID)) ||
+					DSN_LT(mpath->dsn, dst_dsn)) {
+				mpath->dsn = dst_dsn;
+				mpath->flags &= MESH_PATH_DSN_VALID;
+			} else if ((!(dst_flags & MP_F_DO)) &&
+					(mpath->flags & MESH_PATH_ACTIVE)) {
+				reply = true;
+				metric = mpath->metric;
+				dst_dsn = mpath->dsn;
+				if (dst_flags & MP_F_RF)
+					dst_flags |= MP_F_DO;
+				else
+					forward = false;
+			}
+		}
+		rcu_read_unlock();
+	}
+
+	if (reply) {
+		lifetime = PREQ_IE_LIFETIME(preq_elem);
+		ttl = ifsta->mshcfg.dot11MeshTTL;
+		if (ttl != 0)
+			mesh_path_sel_frame_tx(MPATH_PREP, 0, dst_addr,
+				__cpu_to_le32(dst_dsn), 0, orig_addr,
+				__cpu_to_le32(orig_dsn), mgmt->sa, 0, ttl,
+				__cpu_to_le32(lifetime), __cpu_to_le32(metric),
+				0, dev);
+		else
+			ifsta->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) {
+			ifsta->mshstats.dropped_frames_ttl++;
+			return;
+		}
+		--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_dsn), dst_flags, dst_addr,
+				__cpu_to_le32(dst_dsn), dev->broadcast,
+				hopcount, ttl, __cpu_to_le32(lifetime),
+				__cpu_to_le32(metric), __cpu_to_le32(preq_id),
+				dev);
+		ifsta->mshstats.fwded_frames++;
+	}
+}
+
+
+static void hwmp_prep_frame_process(struct net_device *dev,
+				    struct ieee80211_mgmt *mgmt,
+				    u8 *prep_elem, u32 metric)
+{
+	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+	struct mesh_path *mpath;
+	u8 *dst_addr, *orig_addr;
+	u8 ttl, hopcount, flags;
+	u8 next_hop[ETH_ALEN];
+	u32 dst_dsn, orig_dsn, lifetime;
+
+	/* 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
+	 */
+	dst_addr = PREP_IE_DST_ADDR(prep_elem);
+	if (memcmp(dst_addr, dev->dev_addr, ETH_ALEN) == 0)
+		/* destination, no forwarding required */
+		return;
+
+	ttl = PREP_IE_TTL(prep_elem);
+	if (ttl <= 1) {
+		sdata->u.sta.mshstats.dropped_frames_ttl++;
+		return;
+	}
+
+	rcu_read_lock();
+	mpath = mesh_path_lookup(dst_addr, dev);
+	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, mpath->next_hop->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);
+	dst_dsn = PREP_IE_DST_DSN(prep_elem);
+	orig_dsn = PREP_IE_ORIG_DSN(prep_elem);
+
+	mesh_path_sel_frame_tx(MPATH_PREP, flags, orig_addr,
+		__cpu_to_le32(orig_dsn), 0, dst_addr,
+		__cpu_to_le32(dst_dsn), mpath->next_hop->addr, hopcount, ttl,
+		__cpu_to_le32(lifetime), __cpu_to_le32(metric),
+		0, dev);
+	rcu_read_unlock();
+	sdata->u.sta.mshstats.fwded_frames++;
+	return;
+
+fail:
+	rcu_read_unlock();
+	sdata->u.sta.mshstats.dropped_frames_no_route++;
+	return;
+}
+
+static void hwmp_perr_frame_process(struct net_device *dev,
+			     struct ieee80211_mgmt *mgmt, u8 *perr_elem)
+{
+	struct mesh_path *mpath;
+	u8 *ta, *dst_addr;
+	u32 dst_dsn;
+
+	ta = mgmt->sa;
+	dst_addr = PERR_IE_DST_ADDR(perr_elem);
+	dst_dsn = PERR_IE_DST_DSN(perr_elem);
+	rcu_read_lock();
+	mpath = mesh_path_lookup(dst_addr, dev);
+	if (mpath) {
+		spin_lock_bh(&mpath->state_lock);
+		if (mpath->flags & MESH_PATH_ACTIVE &&
+		    memcmp(ta, mpath->next_hop->addr, ETH_ALEN) == 0 &&
+		    (!(mpath->flags & MESH_PATH_DSN_VALID) ||
+		    DSN_GT(dst_dsn, mpath->dsn))) {
+			mpath->flags &= ~MESH_PATH_ACTIVE;
+			mpath->dsn = dst_dsn;
+			spin_unlock_bh(&mpath->state_lock);
+			mesh_path_error_tx(dst_addr, dst_dsn, dev->broadcast,
+					dev);
+		} else
+			spin_unlock_bh(&mpath->state_lock);
+	}
+	rcu_read_unlock();
+}
+
+
+
+void mesh_rx_path_sel_frame(struct net_device *dev,
+			    struct ieee80211_mgmt *mgmt,
+			    size_t len)
+{
+	struct ieee802_11_elems elems;
+	size_t baselen;
+	u32 last_hop_metric;
+
+	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);
+
+	switch (mgmt->u.action.u.mesh_action.action_code) {
+	case MPATH_PREQ:
+		if (!elems.preq || elems.preq_len != 37)
+			/* Right now we support just 1 destination and no AE */
+			return;
+		last_hop_metric = hwmp_route_info_get(dev, mgmt, elems.preq);
+		if (!last_hop_metric)
+			return;
+		hwmp_preq_frame_process(dev, mgmt, elems.preq, last_hop_metric);
+		break;
+	case MPATH_PREP:
+		if (!elems.prep || elems.prep_len != 31)
+			/* Right now we support no AE */
+			return;
+		last_hop_metric = hwmp_route_info_get(dev, mgmt, elems.prep);
+		if (!last_hop_metric)
+			return;
+		hwmp_prep_frame_process(dev, mgmt, elems.prep, last_hop_metric);
+		break;
+	case MPATH_PERR:
+		if (!elems.perr || elems.perr_len != 12)
+			/* Right now we support only one destination per PERR */
+			return;
+		hwmp_perr_frame_process(dev, mgmt, elems.perr);
+	default:
+		return;
+	}
+
+}
+
+/**
+ * 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 =
+		IEEE80211_DEV_TO_SUB_IF(mpath->dev);
+	struct ieee80211_if_sta *ifsta = &sdata->u.sta;
+	struct mesh_preq_queue *preq_node;
+
+	preq_node = kmalloc(sizeof(struct mesh_preq_queue), GFP_KERNEL);
+	if (!preq_node) {
+		printk(KERN_DEBUG "Mesh HWMP: could not allocate PREQ node\n");
+		return;
+	}
+
+	spin_lock(&ifsta->mesh_preq_queue_lock);
+	if (ifsta->preq_queue_len == MAX_PREQ_QUEUE_LEN) {
+		spin_unlock(&ifsta->mesh_preq_queue_lock);
+		kfree(preq_node);
+		if (printk_ratelimit())
+			printk(KERN_DEBUG "Mesh HWMP: PREQ node queue full\n");
+		return;
+	}
+
+	memcpy(preq_node->dst, mpath->dst, ETH_ALEN);
+	preq_node->flags = flags;
+
+	list_add_tail(&preq_node->list, &ifsta->preq_queue.list);
+	++ifsta->preq_queue_len;
+	spin_unlock(&ifsta->mesh_preq_queue_lock);
+
+	if (time_after(jiffies, ifsta->last_preq + min_preq_int_jiff(sdata)))
+		queue_work(sdata->local->hw.workqueue, &ifsta->work);
+
+	else if (time_before(jiffies, ifsta->last_preq)) {
+		/* avoid long wait if did not send preqs for a long time
+		 * and jiffies wrapped around
+		 */
+		ifsta->last_preq = jiffies - min_preq_int_jiff(sdata) - 1;
+		queue_work(sdata->local->hw.workqueue, &ifsta->work);
+	} else
+		mod_timer(&ifsta->mesh_path_timer, ifsta->last_preq +
+						min_preq_int_jiff(sdata));
+}
+
+/**
+ * mesh_path_start_discovery - launch a path discovery from the PREQ queue
+ *
+ * @dev: local mesh interface
+ */
+void mesh_path_start_discovery(struct net_device *dev)
+{
+	struct ieee80211_sub_if_data *sdata =
+		IEEE80211_DEV_TO_SUB_IF(dev);
+	struct ieee80211_if_sta *ifsta = &sdata->u.sta;
+	struct mesh_preq_queue *preq_node;
+	struct mesh_path *mpath;
+	u8 ttl, dst_flags;
+	u32 lifetime;
+
+	spin_lock(&ifsta->mesh_preq_queue_lock);
+	if (!ifsta->preq_queue_len ||
+		time_before(jiffies, ifsta->last_preq +
+				min_preq_int_jiff(sdata))) {
+		spin_unlock(&ifsta->mesh_preq_queue_lock);
+		return;
+	}
+
+	preq_node = list_first_entry(&ifsta->preq_queue.list,
+			struct mesh_preq_queue, list);
+	list_del(&preq_node->list);
+	--ifsta->preq_queue_len;
+	spin_unlock(&ifsta->mesh_preq_queue_lock);
+
+	rcu_read_lock();
+	mpath = mesh_path_lookup(preq_node->dst, dev);
+	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;
+	}
+
+	ifsta->last_preq = jiffies;
+
+	if (time_after(jiffies, ifsta->last_dsn_update +
+				net_traversal_jiffies(sdata)) ||
+	    time_before(jiffies, ifsta->last_dsn_update)) {
+		++ifsta->dsn;
+		sdata->u.sta.last_dsn_update = jiffies;
+	}
+	lifetime = default_lifetime(sdata);
+	ttl = sdata->u.sta.mshcfg.dot11MeshTTL;
+	if (ttl == 0) {
+		sdata->u.sta.mshstats.dropped_frames_ttl++;
+		spin_unlock_bh(&mpath->state_lock);
+		goto enddiscovery;
+	}
+
+	if (preq_node->flags & PREQ_Q_F_REFRESH)
+		dst_flags = MP_F_DO;
+	else
+		dst_flags = MP_F_RF;
+
+	spin_unlock_bh(&mpath->state_lock);
+	mesh_path_sel_frame_tx(MPATH_PREQ, 0, dev->dev_addr,
+			__cpu_to_le32(ifsta->dsn), dst_flags, mpath->dst,
+			__cpu_to_le32(mpath->dsn), dev->broadcast, 0,
+			ttl, __cpu_to_le32(lifetime), 0,
+			__cpu_to_le32(ifsta->preq_id++), dev);
+	mod_timer(&mpath->timer, jiffies + mpath->discovery_timeout);
+
+enddiscovery:
+	rcu_read_unlock();
+	kfree(preq_node);
+}
+
+/**
+ * ieee80211s_lookup_nexthop - put the appropriate next hop on a mesh frame
+ *
+ * @next_hop: output argument for next hop address
+ * @skb: frame to be sent
+ * @dev: network device 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(u8 *next_hop, struct sk_buff *skb,
+		struct net_device *dev)
+{
+	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+	struct sk_buff *skb_to_free = NULL;
+	struct mesh_path *mpath;
+	int err = 0;
+
+	rcu_read_lock();
+	mpath = mesh_path_lookup(skb->data, dev);
+
+	if (!mpath) {
+		mesh_path_add(skb->data, dev);
+		mpath = mesh_path_lookup(skb->data, dev);
+		if (!mpath) {
+			dev_kfree_skb(skb);
+			sdata->u.sta.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.sta.mshcfg.path_refresh_time))
+				&& skb->pkt_type != PACKET_OTHERHOST
+				&& !(mpath->flags & MESH_PATH_RESOLVING)
+				&& !(mpath->flags & MESH_PATH_FIXED)) {
+			mesh_queue_preq(mpath,
+					PREQ_Q_F_START | PREQ_Q_F_REFRESH);
+		}
+		memcpy(next_hop, mpath->next_hop->addr,
+				ETH_ALEN);
+	} else {
+		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 = mpath->frame_queue.next;
+			skb_unlink(skb_to_free, &mpath->frame_queue);
+		}
+
+		skb_queue_tail(&mpath->frame_queue, skb);
+		if (skb_to_free)
+			mesh_path_discard_frame(skb_to_free, dev);
+		err = -ENOENT;
+	}
+
+endlookup:
+	rcu_read_unlock();
+	return err;
+}
+
+void mesh_path_timer(unsigned long data)
+{
+	struct ieee80211_sub_if_data *sdata;
+	struct mesh_path *mpath;
+	bool delete = false;
+
+	rcu_read_lock();
+	mpath = (struct mesh_path *) data;
+	mpath = rcu_dereference(mpath);
+	if (!mpath)
+		goto endmpathtimer;
+	spin_lock_bh(&mpath->state_lock);
+	sdata = IEEE80211_DEV_TO_SUB_IF(mpath->dev);
+	if (mpath->flags & MESH_PATH_DELETE) {
+		mpath->flags = 0;
+		delete = true;
+	} else 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);
+endmpathtimer:
+	rcu_read_unlock();
+	if (delete)
+		mesh_path_del(mpath->dst, mpath->dev);
+}