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From:   Sriram R <quic_srirrama@quicinc.com>
To:     <johannes@sipsolutions.net>
CC:     <linux-wireless@vger.kernel.org>,
        Sriram R <quic_srirrama@quicinc.com>
Subject: [PATCH 3/3] mac80211: Mesh Fast xmit support
Date:   Fri, 10 Jun 2022 16:10:39 +0530
Message-ID: <1654857639-12346-4-git-send-email-quic_srirrama@quicinc.com>
In-Reply-To: <1654857639-12346-1-git-send-email-quic_srirrama@quicinc.com>
References: <1654857639-12346-1-git-send-email-quic_srirrama@quicinc.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Support Fast xmit for mesh device type by caching the header
corresponding to the ethernet DA and reusing the cached header (mac,
mesh, llc) everytime the packet is intended for that DA.  This will
avoid multiple path table lookups during header generation for a mesh
packet tx.

Freshness of the header is verified by identifying change in mesh paths
before using the header and corresponding changes to the header and
cache entry is done on the fly.

Mutable fields of the header such as eaddr2/SA, tid, mesh SN, PN are
updated for each xmit.

Each cache entry is ~100Bytes, least used/expired entries are
periodically removed when cache gets almost full.

Signed-off-by: Sriram R <quic_srirrama@quicinc.com>
---
 net/mac80211/cfg.c            |   2 +
 net/mac80211/debugfs_netdev.c |   3 +
 net/mac80211/ieee80211_i.h    |  20 +++
 net/mac80211/mesh.c           |   2 +
 net/mac80211/mesh.h           |  45 +++++
 net/mac80211/mesh_hwmp.c      |   8 +-
 net/mac80211/mesh_pathtbl.c   | 396 ++++++++++++++++++++++++++++++++++++++++++
 net/mac80211/rx.c             |   9 +-
 net/mac80211/tx.c             |  90 ++++++++++
 9 files changed, 571 insertions(+), 4 deletions(-)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index a3d7950..38b718f 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -2383,6 +2383,8 @@ static int ieee80211_update_mesh_config(struct wiphy *wiphy,
 	if (_chg_mesh_attr(NL80211_MESHCONF_CONNECTED_TO_AS, mask))
 		conf->dot11MeshConnectedToAuthServer =
 			nconf->dot11MeshConnectedToAuthServer;
+	if (_chg_mesh_attr(NL80211_MESHCONF_HEADER_CACHE_SIZE, mask))
+		conf->hdr_cache_size = nconf->hdr_cache_size;
 	ieee80211_mbss_info_change_notify(sdata, BSS_CHANGED_BEACON);
 	return 0;
 }
diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
index cf71484..9262699 100644
--- a/net/mac80211/debugfs_netdev.c
+++ b/net/mac80211/debugfs_netdev.c
@@ -663,6 +663,8 @@ IEEE80211_IF_FILE(dot11MeshConnectedToMeshGate,
 IEEE80211_IF_FILE(dot11MeshNolearn, u.mesh.mshcfg.dot11MeshNolearn, DEC);
 IEEE80211_IF_FILE(dot11MeshConnectedToAuthServer,
 		  u.mesh.mshcfg.dot11MeshConnectedToAuthServer, DEC);
+IEEE80211_IF_FILE(hdr_cache_size,
+		  u.mesh.mshcfg.hdr_cache_size, DEC);
 #endif
 
 #define DEBUGFS_ADD_MODE(name, mode) \
@@ -786,6 +788,7 @@ static void add_mesh_config(struct ieee80211_sub_if_data *sdata)
 	MESHPARAMS_ADD(dot11MeshConnectedToMeshGate);
 	MESHPARAMS_ADD(dot11MeshNolearn);
 	MESHPARAMS_ADD(dot11MeshConnectedToAuthServer);
+	MESHPARAMS_ADD(hdr_cache_size);
 #undef MESHPARAMS_ADD
 }
 #endif
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 86ef0a4..3efb845 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -671,6 +671,25 @@ struct mesh_table {
 	atomic_t entries;		/* Up to MAX_MESH_NEIGHBOURS */
 };
 
+/**
+ * struct mesh_hdr_cache
+ *
+ * @enabled: Flag to denote if Header caching is enabled.
+ * @rhead: the rhashtable containing struct mesh_cache_entry, keyed by addr_key which
+ *	For a 6addr format which is currently supported in the cache, the key
+ *	is the external destination address or a5
+ * @walk_head: linked list containing all mesh_cache_entry objects
+ * @walk_lock: lock protecting walk_head
+ * @size: number of entries in the cache
+ */
+struct mesh_hdr_cache {
+	bool enabled;
+	struct rhashtable rhead;
+	struct hlist_head walk_head;
+	spinlock_t walk_lock; /* protects cache entries */
+	u16 size;
+};
+
 struct ieee80211_if_mesh {
 	struct timer_list housekeeping_timer;
 	struct timer_list mesh_path_timer;
@@ -749,6 +768,7 @@ struct ieee80211_if_mesh {
 	struct mesh_table mpp_paths; /* Store paths for MPP&MAP */
 	int mesh_paths_generation;
 	int mpp_paths_generation;
+	struct mesh_hdr_cache hdr_cache;
 };
 
 #ifdef CONFIG_MAC80211_MESH
diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index 5275f4f..ba90e4a 100644
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -782,6 +782,8 @@ static void ieee80211_mesh_housekeeping(struct ieee80211_sub_if_data *sdata)
 	changed = mesh_accept_plinks_update(sdata);
 	ieee80211_mbss_info_change_notify(sdata, changed);
 
+	mesh_hdr_cache_manage(sdata);
+
 	mod_timer(&ifmsh->housekeeping_timer,
 		  round_jiffies(jiffies +
 				IEEE80211_MESH_HOUSEKEEPING_INTERVAL));
diff --git a/net/mac80211/mesh.h b/net/mac80211/mesh.h
index b2b717a..ffeef14 100644
--- a/net/mac80211/mesh.h
+++ b/net/mac80211/mesh.h
@@ -127,6 +127,44 @@ struct mesh_path {
 	u32 path_change_count;
 };
 
+#define MESH_HDR_CACHE_TIMEOUT		8000 /* msecs */
+
+#define MESH_HDR_MAX_LEN	68	/* mac+mesh+rfc1042 hdr */
+
+/**
+ * struct mhdr_cache_entry - Cached Mesh header entry
+ * @addr_key: The Ethernet DA which is the key for this entry
+ * @hdr: The cached header
+ * @machdr_len: Total length of the mac header
+ * @hdrlen: Length of this header entry
+ * @key: Key corresponding to the nexthop stored in the header
+ * @pn_offs: Offset to PN which is updated for every xmit
+ * @band:  band used for tx
+ * @walk_list: list containing all the cached header entries
+ * @rhash: rhashtable pointer
+ * @mpath: The Mesh path corresponding to the Mesh DA
+ * @mppath: The MPP entry corresponding to this DA
+ * @timestamp: Last used time of this entry
+ * @rcu: rcu to free this entry
+ * @path_change_count: Stored path change value corresponding to the mpath
+ */
+struct mhdr_cache_entry {
+	u8 addr_key[ETH_ALEN];
+	u8 hdr[MESH_HDR_MAX_LEN];
+	u16 machdr_len;
+	u16 hdrlen;
+	struct ieee80211_key *key;
+	u8 pn_offs;
+	u8 band;
+	struct hlist_node walk_list;
+	struct rhash_head rhash;
+	struct mesh_path *mpath;
+	struct mesh_path *mppath;
+	unsigned long timestamp;
+	struct rcu_head rcu;
+	u32 path_change_count;
+};
+
 /* Recent multicast cache */
 /* RMC_BUCKETS must be a power of 2, maximum 256 */
 #define RMC_BUCKETS		256
@@ -299,6 +337,13 @@ void mesh_path_tx_root_frame(struct ieee80211_sub_if_data *sdata);
 
 bool mesh_action_is_path_sel(struct ieee80211_mgmt *mgmt);
 
+struct mhdr_cache_entry *mesh_fill_cached_hdr(struct ieee80211_sub_if_data *sdata,
+					      struct sk_buff *skb);
+void mesh_cache_hdr(struct ieee80211_sub_if_data *sdata,
+		    struct sk_buff *skb, struct mesh_path *mpath);
+void mesh_hdr_cache_manage(struct ieee80211_sub_if_data *sdata);
+void mesh_hdr_cache_flush(struct mesh_path *mpath, bool is_mpp);
+void mesh_queue_preq(struct mesh_path *mpath, u8 flags);
 #ifdef CONFIG_MAC80211_MESH
 static inline
 u32 mesh_plink_inc_estab_count(struct ieee80211_sub_if_data *sdata)
diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index 58ebdcd..7910ba5 100644
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -18,8 +18,6 @@
 
 #define MAX_PREQ_QUEUE_LEN	64
 
-static void mesh_queue_preq(struct mesh_path *, u8);
-
 static inline u32 u32_field_get(const u8 *preq_elem, int offset, bool ae)
 {
 	if (ae)
@@ -972,7 +970,7 @@ void mesh_rx_path_sel_frame(struct ieee80211_sub_if_data *sdata,
  * Locking: the function must be called from within a rcu read lock block.
  *
  */
-static void mesh_queue_preq(struct mesh_path *mpath, u8 flags)
+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;
@@ -1250,6 +1248,10 @@ int mesh_nexthop_lookup(struct ieee80211_sub_if_data *sdata,
 		memcpy(hdr->addr1, next_hop->sta.addr, ETH_ALEN);
 		memcpy(hdr->addr2, sdata->vif.addr, ETH_ALEN);
 		ieee80211_mps_set_frame_flags(sdata, next_hop, hdr);
+		/* Cache the whole header so as to use next time rather than resolving
+		 * and building it every time
+		 */
+		mesh_cache_hdr(sdata, skb, mpath);
 		return 0;
 	}
 
diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index acc1c29..3e79534 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -14,6 +14,7 @@
 #include "wme.h"
 #include "ieee80211_i.h"
 #include "mesh.h"
+#include <linux/rhashtable.h>
 
 static void mesh_path_free_rcu(struct mesh_table *tbl, struct mesh_path *mpath);
 
@@ -32,6 +33,56 @@ static const struct rhashtable_params mesh_rht_params = {
 	.hashfn = mesh_table_hash,
 };
 
+static const struct rhashtable_params mesh_hdr_rht_params = {
+	.nelem_hint = 10,
+	.automatic_shrinking = true,
+	.key_len =  ETH_ALEN,
+	.key_offset = offsetof(struct mhdr_cache_entry, addr_key),
+	.head_offset = offsetof(struct mhdr_cache_entry, rhash),
+	.hashfn = mesh_table_hash,
+};
+
+static void mesh_hdr_cache_entry_free(void *ptr, void *tblptr)
+{
+	struct mhdr_cache_entry *mhdr = ptr;
+
+	kfree_rcu(mhdr, rcu);
+}
+
+static void mesh_hdr_cache_deinit(struct ieee80211_sub_if_data *sdata)
+{
+	struct mesh_hdr_cache *cache;
+
+	cache = &sdata->u.mesh.hdr_cache;
+
+	if (!cache->enabled)
+		return;
+
+	rhashtable_free_and_destroy(&cache->rhead,
+				    mesh_hdr_cache_entry_free, NULL);
+
+	cache->enabled = false;
+}
+
+static void mesh_hdr_cache_init(struct ieee80211_sub_if_data *sdata)
+{
+	struct ieee80211_local *local = sdata->local;
+	struct mesh_hdr_cache *cache;
+
+	cache = &sdata->u.mesh.hdr_cache;
+
+	cache->enabled = false;
+
+	if (!ieee80211_hw_check(&local->hw, SUPPORT_FAST_XMIT))
+		return;
+
+	rhashtable_init(&cache->rhead, &mesh_hdr_rht_params);
+	INIT_HLIST_HEAD(&cache->walk_head);
+	spin_lock_init(&cache->walk_lock);
+	cache->size = 0;
+	cache->enabled = true;
+}
+
 static inline bool mpath_expired(struct mesh_path *mpath)
 {
 	return (mpath->flags & MESH_PATH_ACTIVE) &&
@@ -381,6 +432,343 @@ struct mesh_path *mesh_path_new(struct ieee80211_sub_if_data *sdata,
 	return new_mpath;
 }
 
+struct mhdr_cache_entry *mesh_fill_cached_hdr(struct ieee80211_sub_if_data *sdata,
+					      struct sk_buff *skb)
+{
+	struct mesh_hdr_cache *cache;
+	struct mhdr_cache_entry *entry;
+	struct mesh_path *mpath, *mppath;
+	struct ieee80211s_hdr *meshhdr;
+	struct ieee80211_hdr *hdr;
+	struct sta_info *new_nhop;
+	struct ieee80211_key *key;
+	struct ethhdr *eth;
+	u8 sa[ETH_ALEN];
+
+	u8 tid;
+
+	cache = &sdata->u.mesh.hdr_cache;
+
+	if (!cache->enabled)
+		return NULL;
+
+	entry = rhashtable_lookup(&cache->rhead, skb->data,
+				  mesh_hdr_rht_params);
+	if (!entry)
+		return NULL;
+
+	/* Avoid extra work in this path */
+	if (skb_headroom(skb) < (entry->hdrlen - ETH_HLEN + 2))
+		return NULL;
+
+	mpath = rcu_dereference(entry->mpath);
+	if (!mpath)
+		return NULL;
+
+	/* This check is with assumption that only 6addr frames are
+	 * supported currently for caching
+	 */
+	mppath = rcu_dereference(entry->mppath);
+	if (!mppath)
+		return NULL;
+
+	if (!(mpath->flags & MESH_PATH_ACTIVE))
+		return NULL;
+
+	if (mpath_expired(mpath))
+		return NULL;
+
+	/* If the skb is shared we need to obtain our own copy */
+	if (skb_shared(skb)) {
+		struct sk_buff *tmp_skb = skb;
+
+		skb = skb_clone(skb, GFP_ATOMIC);
+		kfree_skb(tmp_skb);
+
+		if (!skb)
+			return NULL;
+	}
+
+	/* In case there was a path refresh and update after we last used
+	 * update the next hop addr.
+	 */
+	spin_lock_bh(&mpath->state_lock);
+	if (entry->path_change_count != mpath->path_change_count) {
+		new_nhop = rcu_dereference(mpath->next_hop);
+		if (!new_nhop) {
+			spin_unlock_bh(&mpath->state_lock);
+			return NULL;
+		}
+		memcpy(&entry->hdr[4], new_nhop->sta.addr, ETH_ALEN);
+
+		/* update key. pn_offs will be same */
+		if (entry->key)	{
+			key = rcu_access_pointer(new_nhop->ptk[new_nhop->ptk_idx]);
+			if (!key)
+				key = rcu_access_pointer(sdata->default_unicast_key);
+			rcu_assign_pointer(entry->key, key);
+		}
+		entry->path_change_count = mpath->path_change_count;
+	}
+	spin_unlock_bh(&mpath->state_lock);
+
+	/* backup eth SA to copy as eaddr2/SA in the mesh header */
+	eth = (struct ethhdr *)skb->data;
+	ether_addr_copy(sa, eth->h_source);
+
+	/* Pull DA:SA */
+	skb_pull(skb, ETH_ALEN * 2);
+
+	memcpy(skb_push(skb, entry->hdrlen), entry->hdr, entry->hdrlen);
+
+	meshhdr = (struct ieee80211s_hdr *)(skb->data + entry->machdr_len);
+	hdr = (struct ieee80211_hdr *)skb->data;
+
+	/* Update mutables */
+	tid = skb->priority & IEEE80211_QOS_CTL_TAG1D_MASK;
+	*ieee80211_get_qos_ctl(hdr) = tid;
+
+	put_unaligned(cpu_to_le32(sdata->u.mesh.mesh_seqnum), &meshhdr->seqnum);
+	sdata->u.mesh.mesh_seqnum++;
+
+	memcpy(meshhdr->eaddr2, sa, ETH_ALEN);
+	meshhdr->ttl = sdata->u.mesh.mshcfg.dot11MeshTTL;
+
+	if (mpath->flags & (MESH_PATH_REQ_QUEUED | MESH_PATH_FIXED))
+		goto out;
+
+	/* Refresh the path, in case there is a change in nexthop after refresh
+	 * hdr will be updated on next lookup
+	 */
+	if (time_after(jiffies,
+		       mpath->exp_time -
+		       msecs_to_jiffies(sdata->u.mesh.mshcfg.path_refresh_time)) &&
+	    !(mpath->flags & MESH_PATH_RESOLVING) &&
+	    !(mpath->flags & MESH_PATH_FIXED)) {
+		mesh_queue_preq(mpath, PREQ_Q_F_START | PREQ_Q_F_REFRESH);
+	}
+
+out:
+	mppath->exp_time = jiffies;
+	entry->timestamp = jiffies;
+
+	return entry;
+}
+
+void mesh_cache_hdr(struct ieee80211_sub_if_data *sdata,
+		    struct sk_buff *skb, struct mesh_path *mpath)
+{
+	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct mesh_hdr_cache *cache;
+	struct mhdr_cache_entry *mhdr, *old_mhdr;
+	struct ieee80211s_hdr *meshhdr;
+	struct sta_info *next_hop;
+	struct ieee80211_key *key;
+	u8 band, pn_offs = 0, crypto_len = 0;
+	struct mesh_path *mppath;
+	u16 mshhdr_len;
+	int hdrlen;
+
+	if (sdata->noack_map)
+		return;
+
+	cache = &sdata->u.mesh.hdr_cache;
+
+	if (!cache->enabled)
+		return;
+
+	hdrlen = ieee80211_hdrlen(hdr->frame_control);
+
+	meshhdr = (struct ieee80211s_hdr *)(skb->data + hdrlen);
+
+	/* Currently supporting only 6addr hdr */
+	if (!(meshhdr->flags & MESH_FLAGS_AE_A5_A6))
+		return;
+
+	mshhdr_len = ieee80211_get_mesh_hdrlen(meshhdr);
+
+	spin_lock_bh(&cache->walk_lock);
+	if (cache->size > sdata->u.mesh.mshcfg.hdr_cache_size) {
+		spin_unlock_bh(&cache->walk_lock);
+		return;
+	}
+	spin_unlock_bh(&cache->walk_lock);
+
+	next_hop = rcu_dereference(mpath->next_hop);
+	if (!next_hop)
+		return;
+
+	/* This is required to keep the mppath alive */
+	mppath = mpp_path_lookup(sdata, meshhdr->eaddr1);
+
+	if (!mppath)
+		return;
+
+	band = info->band;
+
+	pn_offs = 0;
+	key = rcu_access_pointer(next_hop->ptk[next_hop->ptk_idx]);
+	if (!key)
+		key = rcu_access_pointer(sdata->default_unicast_key);
+
+	if (key) {
+		bool gen_iv, iv_spc;
+
+		gen_iv = key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV;
+		iv_spc = key->conf.flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE;
+
+		if (!(key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE))
+			return;
+
+		if (key->flags & KEY_FLAG_TAINTED)
+			return;
+
+		switch (key->conf.cipher) {
+		case WLAN_CIPHER_SUITE_CCMP:
+		case WLAN_CIPHER_SUITE_CCMP_256:
+			if (gen_iv)
+				pn_offs = hdrlen;
+			if (gen_iv || iv_spc)
+				crypto_len = IEEE80211_CCMP_HDR_LEN;
+			break;
+		default:
+			/* Limiting supported ciphers for testing */
+			return;
+		}
+		hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
+	}
+
+	if ((hdrlen + crypto_len + mshhdr_len + sizeof(rfc1042_header)) >
+		MESH_HDR_MAX_LEN) {
+		WARN_ON_ONCE(1);
+		return;
+	}
+
+	mhdr = kzalloc(sizeof(*mhdr), GFP_KERNEL);
+	if (!mhdr)
+		return;
+
+	memcpy(mhdr->addr_key, meshhdr->eaddr1, ETH_ALEN);
+
+	mhdr->machdr_len = hdrlen + crypto_len;
+	mhdr->hdrlen =  mhdr->machdr_len + mshhdr_len + sizeof(rfc1042_header);
+	rcu_assign_pointer(mhdr->mpath, mpath);
+	rcu_assign_pointer(mhdr->mppath, mppath);
+	rcu_assign_pointer(mhdr->key, key);
+	mhdr->timestamp = jiffies;
+	mhdr->band = band;
+	mhdr->pn_offs = pn_offs;
+
+	if (pn_offs) {
+		/* ignore the invalid data getting copied to pn location since it will
+		 * be overwritten during tx
+		 */
+		memcpy(mhdr->hdr, skb->data, mhdr->machdr_len);
+
+		/* copy remaining hdr */
+		memcpy(mhdr->hdr + mhdr->machdr_len,
+		       skb->data + mhdr->machdr_len - crypto_len,
+		       mhdr->hdrlen - mhdr->machdr_len);
+	} else {
+		memcpy(mhdr->hdr, skb->data, mhdr->hdrlen);
+	}
+
+	if (key) {
+		hdr = (struct ieee80211_hdr *)mhdr->hdr;
+		hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
+	}
+
+	spin_lock_bh(&cache->walk_lock);
+	old_mhdr = rhashtable_lookup_get_insert_fast(&cache->rhead,
+						     &mhdr->rhash,
+						     mesh_hdr_rht_params);
+	if (old_mhdr) {
+		spin_unlock_bh(&cache->walk_lock);
+		kfree(mhdr);
+		return;
+	}
+
+	hlist_add_head(&mhdr->walk_list, &cache->walk_head);
+
+	cache->size++;
+	spin_unlock_bh(&cache->walk_lock);
+}
+
+void mesh_hdr_cache_manage(struct ieee80211_sub_if_data *sdata)
+{
+	struct mesh_hdr_cache *cache;
+	struct mhdr_cache_entry *entry;
+	struct hlist_node *n;
+
+	cache = &sdata->u.mesh.hdr_cache;
+
+	if (!cache->enabled)
+		return;
+
+	spin_lock_bh(&cache->walk_lock);
+	if (cache->size < ((sdata->u.mesh.mshcfg.hdr_cache_size * 2) / 3)) {
+		spin_unlock_bh(&cache->walk_lock);
+		return;
+	}
+
+	hlist_for_each_entry_safe(entry, n, &cache->walk_head, walk_list) {
+		if (time_before(jiffies,
+				entry->timestamp +
+				msecs_to_jiffies(MESH_HDR_CACHE_TIMEOUT)))
+			continue;
+
+		hlist_del_rcu(&entry->walk_list);
+		rhashtable_remove_fast(&cache->rhead, &entry->rhash, mesh_hdr_rht_params);
+		kfree_rcu(entry, rcu);
+		cache->size--;
+	}
+	spin_unlock_bh(&cache->walk_lock);
+}
+
+void mesh_hdr_cache_flush(struct mesh_path *mpath, bool is_mpp)
+{
+	struct ieee80211_sub_if_data *sdata = mpath->sdata;
+	struct mesh_hdr_cache *cache;
+	struct mhdr_cache_entry *entry;
+	struct hlist_node *n;
+	struct mesh_path *entry_mpath;
+
+	cache = &sdata->u.mesh.hdr_cache;
+
+	if (!cache->enabled)
+		return;
+
+	spin_lock_bh(&cache->walk_lock);
+	/* Only one header per mpp address is expected in the header cache */
+	if (is_mpp) {
+		entry = rhashtable_lookup(&cache->rhead, mpath->dst, mesh_hdr_rht_params);
+		if (entry) {
+			hlist_del_rcu(&entry->walk_list);
+			rhashtable_remove_fast(&cache->rhead, &entry->rhash, mesh_hdr_rht_params);
+			kfree_rcu(entry, rcu);
+			cache->size--;
+		}
+		spin_unlock_bh(&cache->walk_lock);
+		return;
+	}
+
+	hlist_for_each_entry_safe(entry, n, &cache->walk_head, walk_list) {
+		entry_mpath = rcu_dereference(entry->mpath);
+
+		if (!entry_mpath)
+			continue;
+
+		if (ether_addr_equal(entry_mpath->dst, mpath->dst)) {
+			hlist_del_rcu(&entry->walk_list);
+			rhashtable_remove_fast(&cache->rhead, &entry->rhash, mesh_hdr_rht_params);
+			kfree_rcu(entry, rcu);
+			cache->size--;
+		}
+	}
+	spin_unlock_bh(&cache->walk_lock);
+}
+
 /**
  * mesh_path_add - allocate and add a new path to the mesh path table
  * @dst: destination address of the path (ETH_ALEN length)
@@ -521,6 +909,7 @@ static void mesh_path_free_rcu(struct mesh_table *tbl,
 
 static void __mesh_path_del(struct mesh_table *tbl, struct mesh_path *mpath)
 {
+	mesh_hdr_cache_flush(mpath, tbl == &mpath->sdata->u.mesh.mpp_paths);
 	hlist_del_rcu(&mpath->walk_list);
 	rhashtable_remove_fast(&tbl->rhead, &mpath->rhash, mesh_rht_params);
 	mesh_path_free_rcu(tbl, mpath);
@@ -739,7 +1128,10 @@ void mesh_path_flush_pending(struct mesh_path *mpath)
  */
 void mesh_path_fix_nexthop(struct mesh_path *mpath, struct sta_info *next_hop)
 {
+	struct sta_info *old_next_hop;
+
 	spin_lock_bh(&mpath->state_lock);
+	old_next_hop = rcu_dereference(mpath->next_hop);
 	mesh_path_assign_nexthop(mpath, next_hop);
 	mpath->sn = 0xffff;
 	mpath->metric = 0;
@@ -747,6 +1139,8 @@ void mesh_path_fix_nexthop(struct mesh_path *mpath, struct sta_info *next_hop)
 	mpath->exp_time = 0;
 	mpath->flags = MESH_PATH_FIXED | MESH_PATH_SN_VALID;
 	mesh_path_activate(mpath);
+	if (!old_next_hop || !ether_addr_equal(old_next_hop->addr, next_hop->addr))
+		mpath->path_change_count++;
 	spin_unlock_bh(&mpath->state_lock);
 	ewma_mesh_fail_avg_init(&next_hop->mesh->fail_avg);
 	/* init it at a low value - 0 start is tricky */
@@ -758,6 +1152,7 @@ void mesh_pathtbl_init(struct ieee80211_sub_if_data *sdata)
 {
 	mesh_table_init(&sdata->u.mesh.mesh_paths);
 	mesh_table_init(&sdata->u.mesh.mpp_paths);
+	mesh_hdr_cache_init(sdata);
 }
 
 static
@@ -785,6 +1180,7 @@ void mesh_path_expire(struct ieee80211_sub_if_data *sdata)
 
 void mesh_pathtbl_unregister(struct ieee80211_sub_if_data *sdata)
 {
+	mesh_hdr_cache_deinit(sdata);
 	mesh_table_free(&sdata->u.mesh.mesh_paths);
 	mesh_table_free(&sdata->u.mesh.mpp_paths);
 }
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 3c08ae04..65557a9 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -2891,6 +2891,7 @@ ieee80211_rx_h_mesh_fwding(struct ieee80211_rx_data *rx)
 		struct mesh_path *mppath;
 		char *proxied_addr;
 		char *mpp_addr;
+		bool update = false;
 
 		if (is_multicast_ether_addr(hdr->addr1)) {
 			mpp_addr = hdr->addr3;
@@ -2910,12 +2911,18 @@ ieee80211_rx_h_mesh_fwding(struct ieee80211_rx_data *rx)
 			mpp_path_add(sdata, proxied_addr, mpp_addr);
 		} else {
 			spin_lock_bh(&mppath->state_lock);
-			if (!ether_addr_equal(mppath->mpp, mpp_addr))
+			if (!ether_addr_equal(mppath->mpp, mpp_addr)) {
+				update = true;
 				memcpy(mppath->mpp, mpp_addr, ETH_ALEN);
+			}
 			mppath->exp_time = jiffies;
 			spin_unlock_bh(&mppath->state_lock);
 		}
 		rcu_read_unlock();
+
+		/* Flush any hdr, if external device moved to a new gate */
+		if (update)
+			mesh_hdr_cache_flush(mppath, true);
 	}
 
 	/* Frame has reached destination.  Don't forward */
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 0e4efc0..98b5a1d 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2691,6 +2691,7 @@ static struct sk_buff *ieee80211_build_hdr(struct ieee80211_sub_if_data *sdata,
 						skb->data + ETH_ALEN);
 
 		}
+
 		chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf);
 		if (!chanctx_conf) {
 			ret = -ENOTCONN;
@@ -3497,6 +3498,91 @@ ieee80211_xmit_fast_finish(struct ieee80211_sub_if_data *sdata,
 	return TX_CONTINUE;
 }
 
+static bool ieee80211_mesh_xmit_fast(struct ieee80211_sub_if_data *sdata,
+				     struct sk_buff *skb, u32 ctrl_flags)
+{
+	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
+	struct ieee80211_tx_data tx;
+	struct ieee80211_tx_info *info;
+	struct mhdr_cache_entry *entry;
+	u16 ethertype;
+	struct ieee80211_key *key;
+	struct sta_info *sta;
+
+	if (ctrl_flags & IEEE80211_TX_CTRL_SKIP_MPATH_LOOKUP)
+		return false;
+
+	if (ifmsh->mshcfg.dot11MeshNolearn)
+		return false;
+
+	if (!ieee80211_hw_check(&local->hw, SUPPORT_FAST_XMIT))
+		return false;
+
+	/* Add support for these cases later */
+	if (ifmsh->ps_peers_light_sleep || ifmsh->ps_peers_deep_sleep)
+		return false;
+
+	if (is_multicast_ether_addr(skb->data))
+		return false;
+
+	ethertype = (skb->data[12] << 8) | skb->data[13];
+
+	if (ethertype < ETH_P_802_3_MIN)
+		return false;
+
+	if (skb->sk && skb_shinfo(skb)->tx_flags & SKBTX_WIFI_STATUS)
+		return false;
+
+	if (skb->ip_summed == CHECKSUM_PARTIAL) {
+		skb_set_transport_header(skb,
+					 skb_checksum_start_offset(skb));
+		if (skb_checksum_help(skb))
+			return false;
+	}
+
+	/* Fill cached header for this eth data */
+	entry = mesh_fill_cached_hdr(sdata, skb);
+
+	if (!entry)
+		return false;
+
+	sk_pacing_shift_update(skb->sk, sdata->local->hw.tx_sk_pacing_shift);
+
+	info = IEEE80211_SKB_CB(skb);
+	memset(info, 0, sizeof(*info));
+	info->band = entry->band;
+	info->control.vif = &sdata->vif;
+	info->flags = IEEE80211_TX_CTL_FIRST_FRAGMENT |
+		      IEEE80211_TX_CTL_DONTFRAG;
+
+	info->control.flags = IEEE80211_TX_CTRL_FAST_XMIT;
+
+#ifdef CONFIG_MAC80211_DEBUGFS
+	if (local->force_tx_status)
+		info->flags |= IEEE80211_TX_CTL_REQ_TX_STATUS;
+#endif
+
+	sta = entry->mpath->next_hop;
+	key = entry->key;
+
+	__skb_queue_head_init(&tx.skbs);
+
+	tx.flags = IEEE80211_TX_UNICAST;
+	tx.local = local;
+	tx.sdata = sdata;
+	tx.sta = sta;
+	tx.key = key;
+	tx.skb = skb;
+
+	ieee80211_xmit_fast_finish(sdata, sta, entry->pn_offs,
+				   key, &tx);
+
+	__skb_queue_tail(&tx.skbs, skb);
+	ieee80211_tx_frags(local, &sdata->vif, sta, &tx.skbs, false);
+	return true;
+}
+
 static bool ieee80211_xmit_fast(struct ieee80211_sub_if_data *sdata,
 				struct sta_info *sta,
 				struct ieee80211_fast_tx *fast_tx,
@@ -4175,6 +4261,10 @@ void __ieee80211_subif_start_xmit(struct sk_buff *skb,
 
 	rcu_read_lock();
 
+	if (ieee80211_vif_is_mesh(&sdata->vif) &&
+	    ieee80211_mesh_xmit_fast(sdata, skb, ctrl_flags))
+		goto out;
+
 	if (ieee80211_lookup_ra_sta(sdata, skb, &sta))
 		goto out_free;
 
-- 
2.7.4