path: root/net/mac80211/rx.c

/*
 * Copyright 2002-2005, Instant802 Networks, Inc.
 * Copyright 2005-2006, Devicescape Software, Inc.
 * Copyright 2006-2007	Jiri Benc <jbenc@suse.cz>
 * Copyright 2007	Johannes Berg <johannes@sipsolutions.net>
 *
 * 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/jiffies.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/rcupdate.h>
#include <net/mac80211.h>
#include <net/ieee80211_radiotap.h>

#include "ieee80211_i.h"
#include "led.h"
#include "mesh.h"
#include "wep.h"
#include "wpa.h"
#include "tkip.h"
#include "wme.h"

static u8 ieee80211_sta_manage_reorder_buf(struct ieee80211_hw *hw,
					   struct tid_ampdu_rx *tid_agg_rx,
					   struct sk_buff *skb,
					   u16 mpdu_seq_num,
					   int bar_req);
/*
 * monitor mode reception
 *
 * This function cleans up the SKB, i.e. it removes all the stuff
 * only useful for monitoring.
 */
static struct sk_buff *remove_monitor_info(struct ieee80211_local *local,
					   struct sk_buff *skb,
					   int rtap_len)
{
	skb_pull(skb, rtap_len);

	if (local->hw.flags & IEEE80211_HW_RX_INCLUDES_FCS) {
		if (likely(skb->len > FCS_LEN))
			skb_trim(skb, skb->len - FCS_LEN);
		else {
			/* driver bug */
			WARN_ON(1);
			dev_kfree_skb(skb);
			skb = NULL;
		}
	}

	return skb;
}

static inline int should_drop_frame(struct ieee80211_rx_status *status,
				    struct sk_buff *skb,
				    int present_fcs_len,
				    int radiotap_len)
{
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;

	if (status->flag & (RX_FLAG_FAILED_FCS_CRC | RX_FLAG_FAILED_PLCP_CRC))
		return 1;
	if (unlikely(skb->len < 16 + present_fcs_len + radiotap_len))
		return 1;
	if (ieee80211_is_ctl(hdr->frame_control) &&
	    !ieee80211_is_pspoll(hdr->frame_control) &&
	    !ieee80211_is_back_req(hdr->frame_control))
		return 1;
	return 0;
}

static int
ieee80211_rx_radiotap_len(struct ieee80211_local *local,
			  struct ieee80211_rx_status *status)
{
	int len;

	/* always present fields */
	len = sizeof(struct ieee80211_radiotap_header) + 9;

	if (status->flag & RX_FLAG_TSFT)
		len += 8;
	if (local->hw.flags & IEEE80211_HW_SIGNAL_DB ||
	    local->hw.flags & IEEE80211_HW_SIGNAL_DBM)
		len += 1;
	if (local->hw.flags & IEEE80211_HW_NOISE_DBM)
		len += 1;

	if (len & 1) /* padding for RX_FLAGS if necessary */
		len++;

	/* make sure radiotap starts at a naturally aligned address */
	if (len % 8)
		len = roundup(len, 8);

	return len;
}

/**
 * ieee80211_add_rx_radiotap_header - add radiotap header
 *
 * add a radiotap header containing all the fields which the hardware provided.
 */
static void
ieee80211_add_rx_radiotap_header(struct ieee80211_local *local,
				 struct sk_buff *skb,
				 struct ieee80211_rx_status *status,
				 struct ieee80211_rate *rate,
				 int rtap_len)
{
	struct ieee80211_radiotap_header *rthdr;
	unsigned char *pos;

	rthdr = (struct ieee80211_radiotap_header *)skb_push(skb, rtap_len);
	memset(rthdr, 0, rtap_len);

	/* radiotap header, set always present flags */
	rthdr->it_present =
		cpu_to_le32((1 << IEEE80211_RADIOTAP_FLAGS) |
			    (1 << IEEE80211_RADIOTAP_RATE) |
			    (1 << IEEE80211_RADIOTAP_CHANNEL) |
			    (1 << IEEE80211_RADIOTAP_ANTENNA) |
			    (1 << IEEE80211_RADIOTAP_RX_FLAGS));
	rthdr->it_len = cpu_to_le16(rtap_len);

	pos = (unsigned char *)(rthdr+1);

	/* the order of the following fields is important */

	/* IEEE80211_RADIOTAP_TSFT */
	if (status->flag & RX_FLAG_TSFT) {
		*(__le64 *)pos = cpu_to_le64(status->mactime);
		rthdr->it_present |=
			cpu_to_le32(1 << IEEE80211_RADIOTAP_TSFT);
		pos += 8;
	}

	/* IEEE80211_RADIOTAP_FLAGS */
	if (local->hw.flags & IEEE80211_HW_RX_INCLUDES_FCS)
		*pos |= IEEE80211_RADIOTAP_F_FCS;
	if (status->flag & RX_FLAG_SHORTPRE)
		*pos |= IEEE80211_RADIOTAP_F_SHORTPRE;
	pos++;

	/* IEEE80211_RADIOTAP_RATE */
	*pos = rate->bitrate / 5;
	pos++;

	/* IEEE80211_RADIOTAP_CHANNEL */
	*(__le16 *)pos = cpu_to_le16(status->freq);
	pos += 2;
	if (status->band == IEEE80211_BAND_5GHZ)
		*(__le16 *)pos = cpu_to_le16(IEEE80211_CHAN_OFDM |
					     IEEE80211_CHAN_5GHZ);
	else if (rate->flags & IEEE80211_RATE_ERP_G)
		*(__le16 *)pos = cpu_to_le16(IEEE80211_CHAN_OFDM |
					     IEEE80211_CHAN_2GHZ);
	else
		*(__le16 *)pos = cpu_to_le16(IEEE80211_CHAN_CCK |
					     IEEE80211_CHAN_2GHZ);
	pos += 2;

	/* IEEE80211_RADIOTAP_DBM_ANTSIGNAL */
	if (local->hw.flags & IEEE80211_HW_SIGNAL_DBM) {
		*pos = status->signal;
		rthdr->it_present |=
			cpu_to_le32(1 << IEEE80211_RADIOTAP_DBM_ANTSIGNAL);
		pos++;
	}

	/* IEEE80211_RADIOTAP_DBM_ANTNOISE */
	if (local->hw.flags & IEEE80211_HW_NOISE_DBM) {
		*pos = status->noise;
		rthdr->it_present |=
			cpu_to_le32(1 << IEEE80211_RADIOTAP_DBM_ANTNOISE);
		pos++;
	}

	/* IEEE80211_RADIOTAP_LOCK_QUALITY is missing */

	/* IEEE80211_RADIOTAP_ANTENNA */
	*pos = status->antenna;
	pos++;

	/* IEEE80211_RADIOTAP_DB_ANTSIGNAL */
	if (local->hw.flags & IEEE80211_HW_SIGNAL_DB) {
		*pos = status->signal;
		rthdr->it_present |=
			cpu_to_le32(1 << IEEE80211_RADIOTAP_DB_ANTSIGNAL);
		pos++;
	}

	/* IEEE80211_RADIOTAP_DB_ANTNOISE is not used */

	/* IEEE80211_RADIOTAP_RX_FLAGS */
	/* ensure 2 byte alignment for the 2 byte field as required */
	if ((pos - (unsigned char *)rthdr) & 1)
		pos++;
	/* FIXME: when radiotap gets a 'bad PLCP' flag use it here */
	if (status->flag & (RX_FLAG_FAILED_FCS_CRC | RX_FLAG_FAILED_PLCP_CRC))
		*(__le16 *)pos |= cpu_to_le16(IEEE80211_RADIOTAP_F_RX_BADFCS);
	pos += 2;
}

/*
 * This function copies a received frame to all monitor interfaces and
 * returns a cleaned-up SKB that no longer includes the FCS nor the
 * radiotap header the driver might have added.
 */
static struct sk_buff *
ieee80211_rx_monitor(struct ieee80211_local *local, struct sk_buff *origskb,
		     struct ieee80211_rx_status *status,
		     struct ieee80211_rate *rate)
{
	struct ieee80211_sub_if_data *sdata;
	int needed_headroom = 0;
	struct sk_buff *skb, *skb2;
	struct net_device *prev_dev = NULL;
	int present_fcs_len = 0;
	int rtap_len = 0;

	/*
	 * First, we may need to make a copy of the skb because
	 *  (1) we need to modify it for radiotap (if not present), and
	 *  (2) the other RX handlers will modify the skb we got.
	 *
	 * We don't need to, of course, if we aren't going to return
	 * the SKB because it has a bad FCS/PLCP checksum.
	 */
	if (status->flag & RX_FLAG_RADIOTAP)
		rtap_len = ieee80211_get_radiotap_len(origskb->data);
	else
		/* room for the radiotap header based on driver features */
		needed_headroom = ieee80211_rx_radiotap_len(local, status);

	if (local->hw.flags & IEEE80211_HW_RX_INCLUDES_FCS)
		present_fcs_len = FCS_LEN;

	if (!local->monitors) {
		if (should_drop_frame(status, origskb, present_fcs_len,
				      rtap_len)) {
			dev_kfree_skb(origskb);
			return NULL;
		}

		return remove_monitor_info(local, origskb, rtap_len);
	}

	if (should_drop_frame(status, origskb, present_fcs_len, rtap_len)) {
		/* only need to expand headroom if necessary */
		skb = origskb;
		origskb = NULL;

		/*
		 * This shouldn't trigger often because most devices have an
		 * RX header they pull before we get here, and that should
		 * be big enough for our radiotap information. We should
		 * probably export the length to drivers so that we can have
		 * them allocate enough headroom to start with.
		 */
		if (skb_headroom(skb) < needed_headroom &&
		    pskb_expand_head(skb, needed_headroom, 0, GFP_ATOMIC)) {
			dev_kfree_skb(skb);
			return NULL;
		}
	} else {
		/*
		 * Need to make a copy and possibly remove radiotap header
		 * and FCS from the original.
		 */
		skb = skb_copy_expand(origskb, needed_headroom, 0, GFP_ATOMIC);

		origskb = remove_monitor_info(local, origskb, rtap_len);

		if (!skb)
			return origskb;
	}

	/* if necessary, prepend radiotap information */
	if (!(status->flag & RX_FLAG_RADIOTAP))
		ieee80211_add_rx_radiotap_header(local, skb, status, rate,
						 needed_headroom);

	skb_reset_mac_header(skb);
	skb->ip_summed = CHECKSUM_UNNECESSARY;
	skb->pkt_type = PACKET_OTHERHOST;
	skb->protocol = htons(ETH_P_802_2);

	list_for_each_entry_rcu(sdata, &local->interfaces, list) {
		if (!netif_running(sdata->dev))
			continue;

		if (sdata->vif.type != NL80211_IFTYPE_MONITOR)
			continue;

		if (sdata->u.mntr_flags & MONITOR_FLAG_COOK_FRAMES)
			continue;

		if (prev_dev) {
			skb2 = skb_clone(skb, GFP_ATOMIC);
			if (skb2) {
				skb2->dev = prev_dev;
				netif_rx(skb2);
			}
		}

		prev_dev = sdata->dev;
		sdata->dev->stats.rx_packets++;
		sdata->dev->stats.rx_bytes += skb->len;
	}

	if (prev_dev) {
		skb->dev = prev_dev;
		netif_rx(skb);
	} else
		dev_kfree_skb(skb);

	return origskb;
}


static void ieee80211_parse_qos(struct ieee80211_rx_data *rx)
{
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
	int tid;

	/* does the frame have a qos control field? */
	if (ieee80211_is_data_qos(hdr->frame_control)) {
		u8 *qc = ieee80211_get_qos_ctl(hdr);
		/* frame has qos control */
		tid = *qc & IEEE80211_QOS_CTL_TID_MASK;
		if (*qc & IEEE80211_QOS_CONTROL_A_MSDU_PRESENT)
			rx->flags |= IEEE80211_RX_AMSDU;
		else
			rx->flags &= ~IEEE80211_RX_AMSDU;
	} else {
		/*
		 * IEEE 802.11-2007, 7.1.3.4.1 ("Sequence Number field"):
		 *
		 *	Sequence numbers for management frames, QoS data
		 *	frames with a broadcast/multicast address in the
		 *	Address 1 field, and all non-QoS data frames sent
		 *	by QoS STAs are assigned using an additional single
		 *	modulo-4096 counter, [...]
		 *
		 * We also use that counter for non-QoS STAs.
		 */
		tid = NUM_RX_DATA_QUEUES - 1;
	}

	rx->queue = tid;
	/* Set skb->priority to 1d tag if highest order bit of TID is not set.
	 * For now, set skb->priority to 0 for other cases. */
	rx->skb->priority = (tid > 7) ? 0 : tid;
}

static void ieee80211_verify_ip_alignment(struct ieee80211_rx_data *rx)
{
#ifdef CONFIG_MAC80211_DEBUG_PACKET_ALIGNMENT
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
	int hdrlen;

	if (!ieee80211_is_data_present(hdr->frame_control))
		return;

	/*
	 * Drivers are required to align the payload data in a way that
	 * guarantees that the contained IP header is aligned to a four-
	 * byte boundary. In the case of regular frames, this simply means
	 * aligning the payload to a four-byte boundary (because either
	 * the IP header is directly contained, or IV/RFC1042 headers that
	 * have a length divisible by four are in front of it.
	 *
	 * With A-MSDU frames, however, the payload data address must
	 * yield two modulo four because there are 14-byte 802.3 headers
	 * within the A-MSDU frames that push the IP header further back
	 * to a multiple of four again. Thankfully, the specs were sane
	 * enough this time around to require padding each A-MSDU subframe
	 * to a length that is a multiple of four.
	 *
	 * Padding like atheros hardware adds which is inbetween the 802.11
	 * header and the payload is not supported, the driver is required
	 * to move the 802.11 header further back in that case.
	 */
	hdrlen = ieee80211_hdrlen(hdr->frame_control);
	if (rx->flags & IEEE80211_RX_AMSDU)
		hdrlen += ETH_HLEN;
	WARN_ON_ONCE(((unsigned long)(rx->skb->data + hdrlen)) & 3);
#endif
}


/* rx handlers */

static ieee80211_rx_result debug_noinline
ieee80211_rx_h_passive_scan(struct ieee80211_rx_data *rx)
{
	struct ieee80211_local *local = rx->local;
	struct sk_buff *skb = rx->skb;

	if (unlikely(local->hw_scanning))
		return ieee80211_scan_rx(rx->sdata, skb, rx->status);

	if (unlikely(local->sw_scanning)) {
		/* drop all the other packets during a software scan anyway */
		if (ieee80211_scan_rx(rx->sdata, skb, rx->status)
		    != RX_QUEUED)
			dev_kfree_skb(skb);
		return RX_QUEUED;
	}

	if (unlikely(rx->flags & IEEE80211_RX_IN_SCAN)) {
		/* scanning finished during invoking of handlers */
		I802_DEBUG_INC(local->rx_handlers_drop_passive_scan);
		return RX_DROP_UNUSABLE;
	}

	return RX_CONTINUE;
}

static ieee80211_rx_result
ieee80211_rx_mesh_check(struct ieee80211_rx_data *rx)
{
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
	unsigned int hdrlen = ieee80211_hdrlen(hdr->frame_control);

	if (ieee80211_is_data(hdr->frame_control)) {
		if (!ieee80211_has_a4(hdr->frame_control))
			return RX_DROP_MONITOR;
		if (memcmp(hdr->addr4, rx->dev->dev_addr, ETH_ALEN) == 0)
			return RX_DROP_MONITOR;
	}

	/* If there is not an established peer link and this is not a peer link
	 * establisment frame, beacon or probe, drop the frame.
	 */

	if (!rx->sta || sta_plink_state(rx->sta) != PLINK_ESTAB) {
		struct ieee80211_mgmt *mgmt;

		if (!ieee80211_is_mgmt(hdr->frame_control))
			return RX_DROP_MONITOR;

		if (ieee80211_is_action(hdr->frame_control)) {
			mgmt = (struct ieee80211_mgmt *)hdr;
			if (mgmt->u.action.category != PLINK_CATEGORY)
				return RX_DROP_MONITOR;
			return RX_CONTINUE;
		}

		if (ieee80211_is_probe_req(hdr->frame_control) ||
		    ieee80211_is_probe_resp(hdr->frame_control) ||
		    ieee80211_is_beacon(hdr->frame_control))
			return RX_CONTINUE;

		return RX_DROP_MONITOR;

	}

#define msh_h_get(h, l) ((struct ieee80211s_hdr *) ((u8 *)h + l))

	if (ieee80211_is_data(hdr->frame_control) &&
	    is_multicast_ether_addr(hdr->addr1) &&
	    mesh_rmc_check(hdr->addr4, msh_h_get(hdr, hdrlen), rx->sdata))
		return RX_DROP_MONITOR;
#undef msh_h_get

	return RX_CONTINUE;
}


static ieee80211_rx_result debug_noinline
ieee80211_rx_h_check(struct ieee80211_rx_data *rx)
{
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;

	/* Drop duplicate 802.11 retransmissions (IEEE 802.11 Chap. 9.2.9) */
	if (rx->sta && !is_multicast_ether_addr(hdr->addr1)) {
		if (unlikely(ieee80211_has_retry(hdr->frame_control) &&
			     rx->sta->last_seq_ctrl[rx->queue] ==
			     hdr->seq_ctrl)) {
			if (rx->flags & IEEE80211_RX_RA_MATCH) {
				rx->local->dot11FrameDuplicateCount++;
				rx->sta->num_duplicates++;
			}
			return RX_DROP_MONITOR;
		} else
			rx->sta->last_seq_ctrl[rx->queue] = hdr->seq_ctrl;
	}

	if (unlikely(rx->skb->len < 16)) {
		I802_DEBUG_INC(rx->local->rx_handlers_drop_short);
		return RX_DROP_MONITOR;
	}

	/* Drop disallowed frame classes based on STA auth/assoc state;
	 * IEEE 802.11, Chap 5.5.
	 *
	 * mac80211 filters only based on association state, i.e. it drops
	 * Class 3 frames from not associated stations. hostapd sends
	 * deauth/disassoc frames when needed. In addition, hostapd is
	 * responsible for filtering on both auth and assoc states.
	 */

	if (ieee80211_vif_is_mesh(&rx->sdata->vif))
		return ieee80211_rx_mesh_check(rx);

	if (unlikely((ieee80211_is_data(hdr->frame_control) ||
		      ieee80211_is_pspoll(hdr->frame_control)) &&
		     rx->sdata->vif.type != NL80211_IFTYPE_ADHOC &&
		     (!rx->sta || !test_sta_flags(rx->sta, WLAN_STA_ASSOC)))) {
		if ((!ieee80211_has_fromds(hdr->frame_control) &&
		     !ieee80211_has_tods(hdr->frame_control) &&
		     ieee80211_is_data(hdr->frame_control)) ||
		    !(rx->flags & IEEE80211_RX_RA_MATCH)) {
			/* Drop IBSS frames and frames for other hosts
			 * silently. */
			return RX_DROP_MONITOR;
		}

		return RX_DROP_MONITOR;
	}

	return RX_CONTINUE;
}


static ieee80211_rx_result debug_noinline
ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
{
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
	int keyidx;
	int hdrlen;
	ieee80211_rx_result result = RX_DROP_UNUSABLE;
	struct ieee80211_key *stakey = NULL;

	/*
	 * Key selection 101
	 *
	 * There are three types of keys:
	 *  - GTK (group keys)
	 *  - PTK (pairwise keys)
	 *  - STK (station-to-station pairwise keys)
	 *
	 * When selecting a key, we have to distinguish between multicast
	 * (including broadcast) and unicast frames, the latter can only
	 * use PTKs and STKs while the former always use GTKs. Unless, of
	 * course, actual WEP keys ("pre-RSNA") are used, then unicast
	 * frames can also use key indizes like GTKs. Hence, if we don't
	 * have a PTK/STK we check the key index for a WEP key.
	 *
	 * Note that in a regular BSS, multicast frames are sent by the
	 * AP only, associated stations unicast the frame to the AP first
	 * which then multicasts it on their behalf.
	 *
	 * There is also a slight problem in IBSS mode: GTKs are negotiated
	 * with each station, that is something we don't currently handle.
	 * The spec seems to expect that one negotiates the same key with
	 * every station but there's no such requirement; VLANs could be
	 * possible.
	 */

	if (!ieee80211_has_protected(hdr->frame_control))
		return RX_CONTINUE;

	/*
	 * No point in finding a key and decrypting if the frame is neither
	 * addressed to us nor a multicast frame.
	 */
	if (!(rx->flags & IEEE80211_RX_RA_MATCH))
		return RX_CONTINUE;

	if (rx->sta)
		stakey = rcu_dereference(rx->sta->key);

	if (!is_multicast_ether_addr(hdr->addr1) && stakey) {
		rx->key = stakey;
	} else {
		/*
		 * The device doesn't give us the IV so we won't be
		 * able to look up the key. That's ok though, we
		 * don't need to decrypt the frame, we just won't
		 * be able to keep statistics accurate.
		 * Except for key threshold notifications, should
		 * we somehow allow the driver to tell us which key
		 * the hardware used if this flag is set?
		 */
		if ((rx->status->flag & RX_FLAG_DECRYPTED) &&
		    (rx->status->flag & RX_FLAG_IV_STRIPPED))
			return RX_CONTINUE;

		hdrlen = ieee80211_hdrlen(hdr->frame_control);

		if (rx->skb->len < 8 + hdrlen)
			return RX_DROP_UNUSABLE; /* TODO: count this? */

		/*
		 * no need to call ieee80211_wep_get_keyidx,
		 * it verifies a bunch of things we've done already
		 */
		keyidx = rx->skb->data[hdrlen + 3] >> 6;

		rx->key = rcu_dereference(rx->sdata->keys[keyidx]);

		/*
		 * RSNA-protected unicast frames should always be sent with
		 * pairwise or station-to-station keys, but for WEP we allow
		 * using a key index as well.
		 */
		if (rx->key && rx->key->conf.alg != ALG_WEP &&
		    !is_multicast_ether_addr(hdr->addr1))
			rx->key = NULL;
	}

	if (rx->key) {
		rx->key->tx_rx_count++;
		/* TODO: add threshold stuff again */
	} else {
		return RX_DROP_MONITOR;
	}

	/* Check for weak IVs if possible */
	if (rx->sta && rx->key->conf.alg == ALG_WEP &&
	    ieee80211_is_data(hdr->frame_control) &&
	    (!(rx->status->flag & RX_FLAG_IV_STRIPPED) ||
	     !(rx->status->flag & RX_FLAG_DECRYPTED)) &&
	    ieee80211_wep_is_weak_iv(rx->skb, rx->key))
		rx->sta->wep_weak_iv_count++;

	switch (rx->key->conf.alg) {
	case ALG_WEP:
		result = ieee80211_crypto_wep_decrypt(rx);
		break;
	case ALG_TKIP:
		result = ieee80211_crypto_tkip_decrypt(rx);
		break;
	case ALG_CCMP:
		result = ieee80211_crypto_ccmp_decrypt(rx);
		break;
	}

	/* either the frame has been decrypted or will be dropped */
	rx->status->flag |= RX_FLAG_DECRYPTED;

	return result;
}

static void ap_sta_ps_start(struct sta_info *sta)
{
	struct ieee80211_sub_if_data *sdata = sta->sdata;

	atomic_inc(&sdata->bss->num_sta_ps);
	set_and_clear_sta_flags(sta, WLAN_STA_PS, WLAN_STA_PSPOLL);
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
	printk(KERN_DEBUG "%s: STA %pM aid %d enters power save mode\n",
	       sdata->dev->name, sta->sta.addr, sta->sta.aid);
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
}

static int ap_sta_ps_end(struct sta_info *sta)
{
	struct ieee80211_sub_if_data *sdata = sta->sdata;
	struct ieee80211_local *local = sdata->local;
	struct sk_buff *skb;
	int sent = 0;

	atomic_dec(&sdata->bss->num_sta_ps);

	clear_sta_flags(sta, WLAN_STA_PS | WLAN_STA_PSPOLL);

	if (!skb_queue_empty(&sta->ps_tx_buf))
		sta_info_clear_tim_bit(sta);

#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
	printk(KERN_DEBUG "%s: STA %pM aid %d exits power save mode\n",
	       sdata->dev->name, sta->sta.addr, sta->sta.aid);
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */

	/* Send all buffered frames to the station */
	while ((skb = skb_dequeue(&sta->tx_filtered)) != NULL) {
		sent++;
		skb->requeue = 1;
		dev_queue_xmit(skb);
	}
	while ((skb = skb_dequeue(&sta->ps_tx_buf)) != NULL) {
		local->total_ps_buffered--;
		sent++;
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
		printk(KERN_DEBUG "%s: STA %pM aid %d send PS frame "
		       "since STA not sleeping anymore\n", sdata->dev->name,
		       sta->sta.addr, sta->sta.aid);
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
		skb->requeue = 1;
		dev_queue_xmit(skb);
	}

	return sent;
}

static ieee80211_rx_result debug_noinline
ieee80211_rx_h_sta_process(struct ieee80211_rx_data *rx)
{
	struct sta_info *sta = rx->sta;
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;

	if (!sta)
		return RX_CONTINUE;

	/* Update last_rx only for IBSS packets which are for the current
	 * BSSID to avoid keeping the current IBSS network alive in cases where
	 * other STAs are using different BSSID. */
	if (rx->sdata->vif.type == NL80211_IFTYPE_ADHOC) {
		u8 *bssid = ieee80211_get_bssid(hdr, rx->skb->len,
						NL80211_IFTYPE_ADHOC);
		if (compare_ether_addr(bssid, rx->sdata->u.sta.bssid) == 0)
			sta->last_rx = jiffies;
	} else
	if (!is_multicast_ether_addr(hdr->addr1) ||
	    rx->sdata->vif.type == NL80211_IFTYPE_STATION) {
		/* Update last_rx only for unicast frames in order to prevent
		 * the Probe Request frames (the only broadcast frames from a
		 * STA in infrastructure mode) from keeping a connection alive.
		 * Mesh beacons will update last_rx when if they are found to
		 * match the current local configuration when processed.
		 */
		sta->last_rx = jiffies;
	}

	if (!(rx->flags & IEEE80211_RX_RA_MATCH))
		return RX_CONTINUE;

	sta->rx_fragments++;
	sta->rx_bytes += rx->skb->len;
	sta->last_signal = rx->status->signal;
	sta->last_qual = rx->status->qual;
	sta->last_noise = rx->status->noise;

	/*
	 * Change STA power saving mode only at the end of a frame
	 * exchange sequence.
	 */
	if (!ieee80211_has_morefrags(hdr->frame_control) &&
	    (rx->sdata->vif.type == NL80211_IFTYPE_AP ||
	     rx->sdata->vif.type == NL80211_IFTYPE_AP_VLAN)) {
		if (test_sta_flags(sta, WLAN_STA_PS)) {
			/*
			 * Ignore doze->wake transitions that are
			 * indicated by non-data frames, the standard
			 * is unclear here, but for example going to
			 * PS mode and then scanning would cause a
			 * doze->wake transition for the probe request,
			 * and that is clearly undesirable.
			 */
			if (ieee80211_is_data(hdr->frame_control) &&
			    !ieee80211_has_pm(hdr->frame_control))
				rx->sent_ps_buffered += ap_sta_ps_end(sta);
		} else {
			if (ieee80211_has_pm(hdr->frame_control))
				ap_sta_ps_start(sta);
		}
	}

	/* Drop data::nullfunc frames silently, since they are used only to
	 * control station power saving mode. */
	if (ieee80211_is_nullfunc(hdr->frame_control)) {
		I802_DEBUG_INC(rx->local->rx_handlers_drop_nullfunc);
		/* Update counter and free packet here to avoid counting this
		 * as a dropped packed. */
		sta->rx_packets++;
		dev_kfree_skb(rx->skb);
		return RX_QUEUED;
	}

	return RX_CONTINUE;
} /* ieee80211_rx_h_sta_process */

static inline struct ieee80211_fragment_entry *
ieee80211_reassemble_add(struct ieee80211_sub_if_data *sdata,
			 unsigned int frag, unsigned int seq, int rx_queue,
			 struct sk_buff **skb)
{
	struct ieee80211_fragment_entry *entry;
	int idx;

	idx = sdata->fragment_next;
	entry = &sdata->fragments[sdata->fragment_next++];
	if (sdata->fragment_next >= IEEE80211_FRAGMENT_MAX)
		sdata->fragment_next = 0;

	if (!skb_queue_empty(&entry->skb_list)) {
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
		struct ieee80211_hdr *hdr =
			(struct ieee80211_hdr *) entry->skb_list.next->data;
		printk(KERN_DEBUG "%s: RX reassembly removed oldest "
		       "fragment entry (idx=%d age=%lu seq=%d last_frag=%d "
		       "addr1=%pM addr2=%pM\n",
		       sdata->dev->name, idx,
		       jiffies - entry->first_frag_time, entry->seq,
		       entry->last_frag, hdr->addr1, hdr->addr2);
#endif
		__skb_queue_purge(&entry->skb_list);
	}

	__skb_queue_tail(&entry->skb_list, *skb); /* no need for locking */
	*skb = NULL;
	entry->first_frag_time = jiffies;
	entry->seq = seq;
	entry->rx_queue = rx_queue;
	entry->last_frag = frag;
	entry->ccmp = 0;
	entry->extra_len = 0;

	return entry;
}

static inline struct ieee80211_fragment_entry *
ieee80211_reassemble_find(struct ieee80211_sub_if_data *sdata,
			  unsigned int frag, unsigned int seq,
			  int rx_queue, struct ieee80211_hdr *hdr)
{
	struct ieee80211_fragment_entry *entry;
	int i, idx;

	idx = sdata->fragment_next;
	for (i = 0; i < IEEE80211_FRAGMENT_MAX; i++) {
		struct ieee80211_hdr *f_hdr;

		idx--;
		if (idx < 0)
			idx = IEEE80211_FRAGMENT_MAX - 1;

		entry = &sdata->fragments[idx];
		if (skb_queue_empty(&entry->skb_list) || entry->seq != seq ||
		    entry->rx_queue != rx_queue ||
		    entry->last_frag + 1 != frag)
			continue;

		f_hdr = (struct ieee80211_hdr *)entry->skb_list.next->data;

		/*
		 * Check ftype and addresses are equal, else check next fragment
		 */
		if (((hdr->frame_control ^ f_hdr->frame_control) &
		     cpu_to_le16(IEEE80211_FCTL_FTYPE)) ||
		    compare_ether_addr(hdr->addr1, f_hdr->addr1) != 0 ||
		    compare_ether_addr(hdr->addr2, f_hdr->addr2) != 0)
			continue;

		if (time_after(jiffies, entry->first_frag_time + 2 * HZ)) {
			__skb_queue_purge(&entry->skb_list);
			continue;
		}
		return entry;
	}

	return NULL;
}

static ieee80211_rx_result debug_noinline
ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx)
{
	struct ieee80211_hdr *hdr;
	u16 sc;
	__le16 fc;
	unsigned int frag, seq;
	struct ieee80211_fragment_entry *entry;
	struct sk_buff *skb;

	hdr = (struct ieee80211_hdr *)rx->skb->data;
	fc = hdr->frame_control;
	sc = le16_to_cpu(hdr->seq_ctrl);
	frag = sc & IEEE80211_SCTL_FRAG;

	if (likely((!ieee80211_has_morefrags(fc) && frag == 0) ||
		   (rx->skb)->len < 24 ||
		   is_multicast_ether_addr(hdr->addr1))) {
		/* not fragmented */
		goto out;
	}
	I802_DEBUG_INC(rx->local->rx_handlers_fragments);

	seq = (sc & IEEE80211_SCTL_SEQ) >> 4;

	if (frag == 0) {
		/* This is the first fragment of a new frame. */
		entry = ieee80211_reassemble_add(rx->sdata, frag, seq,
						 rx->queue, &(rx->skb));
		if (rx->key && rx->key->conf.alg == ALG_CCMP &&
		    ieee80211_has_protected(fc)) {
			/* Store CCMP PN so that we can verify that the next
			 * fragment has a sequential PN value. */
			entry->ccmp = 1;
			memcpy(entry->last_pn,
			       rx->key->u.ccmp.rx_pn[rx->queue],
			       CCMP_PN_LEN);
		}
		return RX_QUEUED;
	}

	/* This is a fragment for a frame that should already be pending in
	 * fragment cache. Add this fragment to the end of the pending entry.
	 */
	entry = ieee80211_reassemble_find(rx->sdata, frag, seq, rx->queue, hdr);
	if (!entry) {
		I802_DEBUG_INC(rx->local->rx_handlers_drop_defrag);
		return RX_DROP_MONITOR;
	}

	/* Verify that MPDUs within one MSDU have sequential PN values.
	 * (IEEE 802.11i, 8.3.3.4.5) */
	if (entry->ccmp) {
		int i;
		u8 pn[CCMP_PN_LEN], *rpn;
		if (!rx->key || rx->key->conf.alg != ALG_CCMP)
			return RX_DROP_UNUSABLE;
		memcpy(pn, entry->last_pn, CCMP_PN_LEN);
		for (i = CCMP_PN_LEN - 1; i >= 0; i--) {
			pn[i]++;
			if (pn[i])
				break;
		}
		rpn = rx->key->u.ccmp.rx_pn[rx->queue];
		if (memcmp(pn, rpn, CCMP_PN_LEN))
			return RX_DROP_UNUSABLE;
		memcpy(entry->last_pn, pn, CCMP_PN_LEN);
	}

	skb_pull(rx->skb, ieee80211_hdrlen(fc));
	__skb_queue_tail(&entry->skb_list, rx->skb);
	entry->last_frag = frag;
	entry->extra_len += rx->skb->len;
	if (ieee80211_has_morefrags(fc)) {
		rx->skb = NULL;
		return RX_QUEUED;
	}

	rx->skb = __skb_dequeue(&entry->skb_list);
	if (skb_tailroom(rx->skb) < entry->extra_len) {
		I802_DEBUG_INC(rx->local->rx_expand_skb_head2);
		if (unlikely(pskb_expand_head(rx->skb, 0, entry->extra_len,
					      GFP_ATOMIC))) {
			I802_DEBUG_INC(rx->local->rx_handlers_drop_defrag);
			__skb_queue_purge(&entry->skb_list);
			return RX_DROP_UNUSABLE;
		}
	}
	while ((skb = __skb_dequeue(&entry->skb_list))) {
		memcpy(skb_put(rx->skb, skb->len), skb->data, skb->len);
		dev_kfree_skb(skb);
	}

	/* Complete frame has been reassembled - process it now */
	rx->flags |= IEEE80211_RX_FRAGMENTED;

 out:
	if (rx->sta)
		rx->sta->rx_packets++;
	if (is_multicast_ether_addr(hdr->addr1))
		rx->local->dot11MulticastReceivedFrameCount++;
	else
		ieee80211_led_rx(rx->local);
	return RX_CONTINUE;
}

static ieee80211_rx_result debug_noinline
ieee80211_rx_h_ps_poll(struct ieee80211_rx_data *rx)
{
	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(rx->dev);
	struct sk_buff *skb;
	int no_pending_pkts;
	__le16 fc = ((struct ieee80211_hdr *)rx->skb->data)->frame_control;

	if (likely(!rx->sta || !ieee80211_is_pspoll(fc) ||
		   !(rx->flags & IEEE80211_RX_RA_MATCH)))
		return RX_CONTINUE;

	if ((sdata->vif.type != NL80211_IFTYPE_AP) &&
	    (sdata->vif.type != NL80211_IFTYPE_AP_VLAN))
		return RX_DROP_UNUSABLE;

	skb = skb_dequeue(&rx->sta->tx_filtered);
	if (!skb) {
		skb = skb_dequeue(&rx->sta->ps_tx_buf);
		if (skb)
			rx->local->total_ps_buffered--;
	}
	no_pending_pkts = skb_queue_empty(&rx->sta->tx_filtered) &&
		skb_queue_empty(&rx->sta->ps_tx_buf);

	if (skb) {
		struct ieee80211_hdr *hdr =
			(struct ieee80211_hdr *) skb->data;

		/*
		 * Tell TX path to send one frame even though the STA may
		 * still remain is PS mode after this frame exchange.
		 */
		set_sta_flags(rx->sta, WLAN_STA_PSPOLL);

#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
		printk(KERN_DEBUG "STA %pM aid %d: PS Poll (entries after %d)\n",
		       rx->sta->sta.addr, rx->sta->sta.aid,
		       skb_queue_len(&rx->sta->ps_tx_buf));
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */

		/* Use MoreData flag to indicate whether there are more
		 * buffered frames for this STA */
		if (no_pending_pkts)
			hdr->frame_control &= cpu_to_le16(~IEEE80211_FCTL_MOREDATA);
		else
			hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_MOREDATA);

		dev_queue_xmit(skb);

		if (no_pending_pkts)
			sta_info_clear_tim_bit(rx->sta);
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
	} else if (!rx->sent_ps_buffered) {
		/*
		 * FIXME: This can be the result of a race condition between
		 *	  us expiring a frame and the station polling for it.
		 *	  Should we send it a null-func frame indicating we
		 *	  have nothing buffered for it?
		 */
		printk(KERN_DEBUG "%s: STA %pM sent PS Poll even "
		       "though there are no buffered frames for it\n",
		       rx->dev->name, rx->sta->sta.addr);
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
	}

	/* Free PS Poll skb here instead of returning RX_DROP that would
	 * count as an dropped frame. */
	dev_kfree_skb(rx->skb);

	return RX_QUEUED;
}

static ieee80211_rx_result debug_noinline
ieee80211_rx_h_remove_qos_control(struct ieee80211_rx_data *rx)
{
	u8 *data = rx->skb->data;
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)data;

	if (!ieee80211_is_data_qos(hdr->frame_control))
		return RX_CONTINUE;

	/* remove the qos control field, update frame type and meta-data */
	memmove(data + IEEE80211_QOS_CTL_LEN, data,
		ieee80211_hdrlen(hdr->frame_control) - IEEE80211_QOS_CTL_LEN);
	hdr = (struct ieee80211_hdr *)skb_pull(rx->skb, IEEE80211_QOS_CTL_LEN);
	/* change frame type to non QOS */
	hdr->frame_control &= ~cpu_to_le16(IEEE80211_STYPE_QOS_DATA);

	return RX_CONTINUE;
}

static int
ieee80211_802_1x_port_control(struct ieee80211_rx_data *rx)
{
	if (unlikely(!rx->sta ||
	    !test_sta_flags(rx->sta, WLAN_STA_AUTHORIZED)))
		return -EACCES;

	return 0;
}

static int
ieee80211_drop_unencrypted(struct ieee80211_rx_data *rx, __le16 fc)
{
	/*
	 * Pass through unencrypted frames if the hardware has
	 * decrypted them already.
	 */
	if (rx->status->flag & RX_FLAG_DECRYPTED)
		return 0;

	/* Drop unencrypted frames if key is set. */
	if (unlikely(!ieee80211_has_protected(fc) &&
		     !ieee80211_is_nullfunc(fc) &&
		     (rx->key || rx->sdata->drop_unencrypted)))
		return -EACCES;

	return 0;
}

static int
ieee80211_data_to_8023(struct ieee80211_rx_data *rx)
{
	struct net_device *dev = rx->dev;
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) rx->skb->data;
	u16 hdrlen, ethertype;
	u8 *payload;
	u8 dst[ETH_ALEN];
	u8 src[ETH_ALEN] __aligned(2);
	struct sk_buff *skb = rx->skb;
	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);

	if (unlikely(!ieee80211_is_data_present(hdr->frame_control)))
		return -1;

	hdrlen = ieee80211_hdrlen(hdr->frame_control);

	/* convert IEEE 802.11 header + possible LLC headers into Ethernet
	 * header
	 * IEEE 802.11 address fields:
	 * ToDS FromDS Addr1 Addr2 Addr3 Addr4
	 *   0     0   DA    SA    BSSID n/a
	 *   0     1   DA    BSSID SA    n/a
	 *   1     0   BSSID SA    DA    n/a
	 *   1     1   RA    TA    DA    SA
	 */
	memcpy(dst, ieee80211_get_DA(hdr), ETH_ALEN);
	memcpy(src, ieee80211_get_SA(hdr), ETH_ALEN);

	switch (hdr->frame_control &
		cpu_to_le16(IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS)) {
	case __constant_cpu_to_le16(IEEE80211_FCTL_TODS):
		if (unlikely(sdata->vif.type != NL80211_IFTYPE_AP &&
			     sdata->vif.type != NL80211_IFTYPE_AP_VLAN))
			return -1;
		break;
	case __constant_cpu_to_le16(IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS):
		if (unlikely(sdata->vif.type != NL80211_IFTYPE_WDS &&
			     sdata->vif.type != NL80211_IFTYPE_MESH_POINT))
			return -1;
		if (ieee80211_vif_is_mesh(&sdata->vif)) {
			struct ieee80211s_hdr *meshdr = (struct ieee80211s_hdr *)
				(skb->data + hdrlen);
			hdrlen += ieee80211_get_mesh_hdrlen(meshdr);
			if (meshdr->flags & MESH_FLAGS_AE_A5_A6) {
				memcpy(dst, meshdr->eaddr1, ETH_ALEN);
				memcpy(src, meshdr->eaddr2, ETH_ALEN);
			}
		}
		break;
	case __constant_cpu_to_le16(IEEE80211_FCTL_FROMDS):
		if (sdata->vif.type != NL80211_IFTYPE_STATION ||
		    (is_multicast_ether_addr(dst) &&
		     !compare_ether_addr(src, dev->dev_addr)))
			return -1;
		break;
	case __constant_cpu_to_le16(0):
		if (sdata->vif.type != NL80211_IFTYPE_ADHOC)
			return -1;
		break;
	}

	if (unlikely(skb->len - hdrlen < 8))
		return -1;

	payload = skb->data + hdrlen;
	ethertype = (payload[6] << 8) | payload[7];

	if (likely((compare_ether_addr(payload, rfc1042_header) == 0 &&
		    ethertype != ETH_P_AARP && ethertype != ETH_P_IPX) ||
		   compare_ether_addr(payload, bridge_tunnel_header) == 0)) {
		/* remove RFC1042 or Bridge-Tunnel encapsulation and
		 * replace EtherType */
		skb_pull(skb, hdrlen + 6);
		memcpy(skb_push(skb, ETH_ALEN), src, ETH_ALEN);
		memcpy(skb_push(skb, ETH_ALEN), dst, ETH_ALEN);
	} else {
		struct ethhdr *ehdr;
		__be16 len;

		skb_pull(skb, hdrlen);
		len = htons(skb->len);
		ehdr = (struct ethhdr *) skb_push(skb, sizeof(struct ethhdr));
		memcpy(ehdr->h_dest, dst, ETH_ALEN);
		memcpy(ehdr->h_source, src, ETH_ALEN);
		ehdr->h_proto = len;
	}
	return 0;
}

/*
 * requires that rx->skb is a frame with ethernet header
 */
static bool ieee80211_frame_allowed(struct ieee80211_rx_data *rx, __le16 fc)
{
	static const u8 pae_group_addr[ETH_ALEN] __aligned(2)
		= { 0x01, 0x80, 0xC2, 0x00, 0x00, 0x03 };
	struct ethhdr *ehdr = (struct ethhdr *) rx->skb->data;

	/*
	 * Allow EAPOL frames to us/the PAE group address regardless
	 * of whether the frame was encrypted or not.
	 */
	if (ehdr->h_proto == htons(ETH_P_PAE) &&
	    (compare_ether_addr(ehdr->h_dest, rx->dev->dev_addr) == 0 ||
	     compare_ether_addr(ehdr->h_dest, pae_group_addr) == 0))
		return true;

	if (ieee80211_802_1x_port_control(rx) ||
	    ieee80211_drop_unencrypted(rx, fc))
		return false;

	return true;
}

/*
 * requires that rx->skb is a frame with ethernet header
 */
static void
ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
{
	struct net_device *dev = rx->dev;
	struct ieee80211_local *local = rx->local;
	struct sk_buff *skb, *xmit_skb;
	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
	struct ethhdr *ehdr = (struct ethhdr *) rx->skb->data;
	struct sta_info *dsta;

	skb = rx->skb;
	xmit_skb = NULL;

	if ((sdata->vif.type == NL80211_IFTYPE_AP ||
	     sdata->vif.type == NL80211_IFTYPE_AP_VLAN) &&
	    !(sdata->flags & IEEE80211_SDATA_DONT_BRIDGE_PACKETS) &&
	    (rx->flags & IEEE80211_RX_RA_MATCH)) {
		if (is_multicast_ether_addr(ehdr->h_dest)) {
			/*
			 * send multicast frames both to higher layers in
			 * local net stack and back to the wireless medium
			 */
			xmit_skb = skb_copy(skb, GFP_ATOMIC);
			if (!xmit_skb && net_ratelimit())
				printk(KERN_DEBUG "%s: failed to clone "
				       "multicast frame\n", dev->name);
		} else {
			dsta = sta_info_get(local, skb->data);
			if (dsta && dsta->sdata->dev == dev) {
				/*
				 * The destination station is associated to
				 * this AP (in this VLAN), so send the frame
				 * directly to it and do not pass it to local
				 * net stack.
				 */
				xmit_skb = skb;
				skb = NULL;
			}
		}
	}

	if (skb) {
		/* deliver to local stack */
		skb->protocol = eth_type_trans(skb, dev);
		memset(skb->cb, 0, sizeof(skb->cb));
		netif_rx(skb);
	}

	if (xmit_skb) {
		/* send to wireless media */
		xmit_skb->protocol = htons(ETH_P_802_3);
		skb_reset_network_header(xmit_skb);
		skb_reset_mac_header(xmit_skb);
		dev_queue_xmit(xmit_skb);
	}
}

static ieee80211_rx_result debug_noinline
ieee80211_rx_h_amsdu(struct ieee80211_rx_data *rx)
{
	struct net_device *dev = rx->dev;
	struct ieee80211_local *local = rx->local;
	u16 ethertype;
	u8 *payload;
	struct sk_buff *skb = rx->skb, *frame = NULL;
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
	__le16 fc = hdr->frame_control;
	const struct ethhdr *eth;
	int remaining, err;
	u8 dst[ETH_ALEN];
	u8 src[ETH_ALEN];

	if (unlikely(!ieee80211_is_data(fc)))
		return RX_CONTINUE;

	if (unlikely(!ieee80211_is_data_present(fc)))
		return RX_DROP_MONITOR;

	if (!(rx->flags & IEEE80211_RX_AMSDU))
		return RX_CONTINUE;

	err = ieee80211_data_to_8023(rx);
	if (unlikely(err))
		return RX_DROP_UNUSABLE;

	skb->dev = dev;

	dev->stats.rx_packets++;
	dev->stats.rx_bytes += skb->len;

	/* skip the wrapping header */
	eth = (struct ethhdr *) skb_pull(skb, sizeof(struct ethhdr));
	if (!eth)
		return RX_DROP_UNUSABLE;

	while (skb != frame) {
		u8 padding;
		__be16 len = eth->h_proto;
		unsigned int subframe_len = sizeof(struct ethhdr) + ntohs(len);

		remaining = skb->len;
		memcpy(dst, eth->h_dest, ETH_ALEN);
		memcpy(src, eth->h_source, ETH_ALEN);

		padding = ((4 - subframe_len) & 0x3);
		/* the last MSDU has no padding */
		if (subframe_len > remaining)
			return RX_DROP_UNUSABLE;

		skb_pull(skb, sizeof(struct ethhdr));
		/* if last subframe reuse skb */
		if (remaining <= subframe_len + padding)
			frame = skb;
		else {
			frame = dev_alloc_skb(local->hw.extra_tx_headroom +
					      subframe_len);

			if (frame == NULL)
				return RX_DROP_UNUSABLE;

			skb_reserve(frame, local->hw.extra_tx_headroom +
				    sizeof(struct ethhdr));
			memcpy(skb_put(frame, ntohs(len)), skb->data,
				ntohs(len));

			eth = (struct ethhdr *) skb_pull(skb, ntohs(len) +
							padding);
			if (!eth) {
				dev_kfree_skb(frame);
				return RX_DROP_UNUSABLE;
			}
		}

		skb_reset_network_header(frame);
		frame->dev = dev;
		frame->priority = skb->priority;
		rx->skb = frame;

		payload = frame->data;
		ethertype = (payload[6] << 8) | payload[7];

		if (likely((compare_ether_addr(payload, rfc1042_header) == 0 &&
			    ethertype != ETH_P_AARP && ethertype != ETH_P_IPX) ||
			   compare_ether_addr(payload,
					      bridge_tunnel_header) == 0)) {
			/* remove RFC1042 or Bridge-Tunnel
			 * encapsulation and replace EtherType */
			skb_pull(frame, 6);
			memcpy(skb_push(frame, ETH_ALEN), src, ETH_ALEN);
			memcpy(skb_push(frame, ETH_ALEN), dst, ETH_ALEN);
		} else {
			memcpy(skb_push(frame, sizeof(__be16)),
			       &len, sizeof(__be16));
			memcpy(skb_push(frame, ETH_ALEN), src, ETH_ALEN);
			memcpy(skb_push(frame, ETH_ALEN), dst, ETH_ALEN);
		}

		if (!ieee80211_frame_allowed(rx, fc)) {
			if (skb == frame) /* last frame */
				return RX_DROP_UNUSABLE;
			dev_kfree_skb(frame);
			continue;
		}

		ieee80211_deliver_skb(rx);
	}

	return RX_QUEUED;
}

#ifdef CONFIG_MAC80211_MESH
static ieee80211_rx_result
ieee80211_rx_h_mesh_fwding(struct ieee80211_rx_data *rx)
{
	struct ieee80211_hdr *hdr;
	struct ieee80211s_hdr *mesh_hdr;
	unsigned int hdrlen;
	struct sk_buff *skb = rx->skb, *fwd_skb;

	hdr = (struct ieee80211_hdr *) skb->data;
	hdrlen = ieee80211_hdrlen(hdr->frame_control);
	mesh_hdr = (struct ieee80211s_hdr *) (skb->data + hdrlen);

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

	if (!mesh_hdr->ttl)
		/* illegal frame */
		return RX_DROP_MONITOR;

	if (mesh_hdr->flags & MESH_FLAGS_AE_A5_A6){
		struct ieee80211_sub_if_data *sdata;
		struct mesh_path *mppath;

		sdata = IEEE80211_DEV_TO_SUB_IF(rx->dev);
		rcu_read_lock();
		mppath = mpp_path_lookup(mesh_hdr->eaddr2, sdata);
		if (!mppath) {
			mpp_path_add(mesh_hdr->eaddr2, hdr->addr4, sdata);
		} else {
			spin_lock_bh(&mppath->state_lock);
			mppath->exp_time = jiffies;
			if (compare_ether_addr(mppath->mpp, hdr->addr4) != 0)
				memcpy(mppath->mpp, hdr->addr4, ETH_ALEN);
			spin_unlock_bh(&mppath->state_lock);
		}
		rcu_read_unlock();
	}

	if (compare_ether_addr(rx->dev->dev_addr, hdr->addr3) == 0)
		return RX_CONTINUE;

	mesh_hdr->ttl--;

	if (rx->flags & IEEE80211_RX_RA_MATCH) {
		if (!mesh_hdr->ttl)
			IEEE80211_IFSTA_MESH_CTR_INC(&rx->sdata->u.mesh,
						     dropped_frames_ttl);
		else {
			struct ieee80211_hdr *fwd_hdr;
			fwd_skb = skb_copy(skb, GFP_ATOMIC);

			if (!fwd_skb && net_ratelimit())
				printk(KERN_DEBUG "%s: failed to clone mesh frame\n",
						   rx->dev->name);

			fwd_hdr =  (struct ieee80211_hdr *) fwd_skb->data;
			/*
			 * Save TA to addr1 to send TA a path error if a
			 * suitable next hop is not found
			 */
			memcpy(fwd_hdr->addr1, fwd_hdr->addr2, ETH_ALEN);
			memcpy(fwd_hdr->addr2, rx->dev->dev_addr, ETH_ALEN);
			fwd_skb->dev = rx->local->mdev;
			fwd_skb->iif = rx->dev->ifindex;
			dev_queue_xmit(fwd_skb);
		}
	}

	if (is_multicast_ether_addr(hdr->addr3) ||
	    rx->dev->flags & IFF_PROMISC)
		return RX_CONTINUE;
	else
		return RX_DROP_MONITOR;
}
#endif

static ieee80211_rx_result debug_noinline
ieee80211_rx_h_data(struct ieee80211_rx_data *rx)
{
	struct net_device *dev = rx->dev;
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
	__le16 fc = hdr->frame_control;
	int err;

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

	if (unlikely(!ieee80211_is_data_present(hdr->frame_control)))
		return RX_DROP_MONITOR;

	err = ieee80211_data_to_8023(rx);
	if (unlikely(err))
		return RX_DROP_UNUSABLE;

	if (!ieee80211_frame_allowed(rx, fc))
		return RX_DROP_MONITOR;

	rx->skb->dev = dev;

	dev->stats.rx_packets++;
	dev->stats.rx_bytes += rx->skb->len;

	ieee80211_deliver_skb(rx);

	return RX_QUEUED;
}

static ieee80211_rx_result debug_noinline
ieee80211_rx_h_ctrl(struct ieee80211_rx_data *rx)
{
	struct ieee80211_local *local = rx->local;
	struct ieee80211_hw *hw = &local->hw;
	struct sk_buff *skb = rx->skb;
	struct ieee80211_bar *bar = (struct ieee80211_bar *)skb->data;
	struct tid_ampdu_rx *tid_agg_rx;
	u16 start_seq_num;
	u16 tid;

	if (likely(!ieee80211_is_ctl(bar->frame_control)))
		return RX_CONTINUE;

	if (ieee80211_is_back_req(bar->frame_control)) {
		if (!rx->sta)
			return RX_CONTINUE;
		tid = le16_to_cpu(bar->control) >> 12;
		if (rx->sta->ampdu_mlme.tid_state_rx[tid]
					!= HT_AGG_STATE_OPERATIONAL)
			return RX_CONTINUE;
		tid_agg_rx = rx->sta->ampdu_mlme.tid_rx[tid];

		start_seq_num = le16_to_cpu(bar->start_seq_num) >> 4;

		/* reset session timer */
		if (tid_agg_rx->timeout) {
			unsigned long expires =
				jiffies + (tid_agg_rx->timeout / 1000) * HZ;
			mod_timer(&tid_agg_rx->session_timer, expires);
		}

		/* manage reordering buffer according to requested */
		/* sequence number */
		rcu_read_lock();
		ieee80211_sta_manage_reorder_buf(hw, tid_agg_rx, NULL,
						 start_seq_num, 1);
		rcu_read_unlock();
		return RX_DROP_UNUSABLE;
	}

	return RX_CONTINUE;
}

static ieee80211_rx_result debug_noinline
ieee80211_rx_h_action(struct ieee80211_rx_data *rx)
{
	struct ieee80211_local *local = rx->local;
	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(rx->dev);
	struct ieee80211_mgmt *mgmt = (struct ieee80211_mgmt *) rx->skb->data;
	int len = rx->skb->len;

	if (!ieee80211_is_action(mgmt->frame_control))
		return RX_CONTINUE;

	if (!rx->sta)
		return RX_DROP_MONITOR;

	if (!(rx->flags & IEEE80211_RX_RA_MATCH))
		return RX_DROP_MONITOR;

	/* all categories we currently handle have action_code */
	if (len < IEEE80211_MIN_ACTION_SIZE + 1)
		return RX_DROP_MONITOR;

	switch (mgmt->u.action.category) {
	case WLAN_CATEGORY_BACK:
		switch (mgmt->u.action.u.addba_req.action_code) {
		case WLAN_ACTION_ADDBA_REQ:
			if (len < (IEEE80211_MIN_ACTION_SIZE +
				   sizeof(mgmt->u.action.u.addba_req)))
				return RX_DROP_MONITOR;
			ieee80211_process_addba_request(local, rx->sta, mgmt, len);
			break;
		case WLAN_ACTION_ADDBA_RESP:
			if (len < (IEEE80211_MIN_ACTION_SIZE +
				   sizeof(mgmt->u.action.u.addba_resp)))
				return RX_DROP_MONITOR;
			ieee80211_process_addba_resp(local, rx->sta, mgmt, len);
			break;
		case WLAN_ACTION_DELBA:
			if (len < (IEEE80211_MIN_ACTION_SIZE +
				   sizeof(mgmt->u.action.u.delba)))
				return RX_DROP_MONITOR;
			ieee80211_process_delba(sdata, rx->sta, mgmt, len);
			break;
		}
		break;
	case WLAN_CATEGORY_SPECTRUM_MGMT:
		if (local->hw.conf.channel->band != IEEE80211_BAND_5GHZ)
			return RX_DROP_MONITOR;
		switch (mgmt->u.action.u.measurement.action_code) {
		case WLAN_ACTION_SPCT_MSR_REQ:
			if (len < (IEEE80211_MIN_ACTION_SIZE +
				   sizeof(mgmt->u.action.u.measurement)))
				return RX_DROP_MONITOR;
			ieee80211_process_measurement_req(sdata, mgmt, len);
			break;
		}
		break;
	default:
		return RX_CONTINUE;
	}

	rx->sta->rx_packets++;
	dev_kfree_skb(rx->skb);
	return RX_QUEUED;
}

static ieee80211_rx_result debug_noinline
ieee80211_rx_h_mgmt(struct ieee80211_rx_data *rx)
{
	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(rx->dev);

	if (!(rx->flags & IEEE80211_RX_RA_MATCH))
		return RX_DROP_MONITOR;

	if (ieee80211_vif_is_mesh(&sdata->vif))
		return ieee80211_mesh_rx_mgmt(sdata, rx->skb, rx->status);

	if (sdata->vif.type != NL80211_IFTYPE_STATION &&
	    sdata->vif.type != NL80211_IFTYPE_ADHOC)
		return RX_DROP_MONITOR;

	if (sdata->flags & IEEE80211_SDATA_USERSPACE_MLME)
		return RX_DROP_MONITOR;

	ieee80211_sta_rx_mgmt(sdata, rx->skb, rx->status);
	return RX_QUEUED;
}

static void ieee80211_rx_michael_mic_report(struct net_device *dev,
					    struct ieee80211_hdr *hdr,
					    struct ieee80211_rx_data *rx)
{
	int keyidx;
	unsigned int hdrlen;

	hdrlen = ieee80211_hdrlen(hdr->frame_control);
	if (rx->skb->len >= hdrlen + 4)
		keyidx = rx->skb->data[hdrlen + 3] >> 6;
	else
		keyidx = -1;

	if (!rx->sta) {
		/*
		 * Some hardware seem to generate incorrect Michael MIC
		 * reports; ignore them to avoid triggering countermeasures.
		 */
		goto ignore;
	}

	if (!ieee80211_has_protected(hdr->frame_control))
		goto ignore;

	if (rx->sdata->vif.type == NL80211_IFTYPE_AP && keyidx) {
		/*
		 * APs with pairwise keys should never receive Michael MIC
		 * errors for non-zero keyidx because these are reserved for
		 * group keys and only the AP is sending real multicast
		 * frames in the BSS.
		 */
		goto ignore;
	}

	if (!ieee80211_is_data(hdr->frame_control) &&
	    !ieee80211_is_auth(hdr->frame_control))
		goto ignore;

	mac80211_ev_michael_mic_failure(rx->sdata, keyidx, hdr);
 ignore:
	dev_kfree_skb(rx->skb);
	rx->skb = NULL;
}

/* TODO: use IEEE80211_RX_FRAGMENTED */
static void ieee80211_rx_cooked_monitor(struct ieee80211_rx_data *rx)
{
	struct ieee80211_sub_if_data *sdata;
	struct ieee80211_local *local = rx->local;
	struct ieee80211_rtap_hdr {
		struct ieee80211_radiotap_header hdr;
		u8 flags;
		u8 rate;
		__le16 chan_freq;
		__le16 chan_flags;
	} __attribute__ ((packed)) *rthdr;
	struct sk_buff *skb = rx->skb, *skb2;
	struct net_device *prev_dev = NULL;
	struct ieee80211_rx_status *status = rx->status;

	if (rx->flags & IEEE80211_RX_CMNTR_REPORTED)
		goto out_free_skb;

	if (skb_headroom(skb) < sizeof(*rthdr) &&
	    pskb_expand_head(skb, sizeof(*rthdr), 0, GFP_ATOMIC))
		goto out_free_skb;

	rthdr = (void *)skb_push(skb, sizeof(*rthdr));
	memset(rthdr, 0, sizeof(*rthdr));
	rthdr->hdr.it_len = cpu_to_le16(sizeof(*rthdr));
	rthdr->hdr.it_present =
		cpu_to_le32((1 << IEEE80211_RADIOTAP_FLAGS) |
			    (1 << IEEE80211_RADIOTAP_RATE) |
			    (1 << IEEE80211_RADIOTAP_CHANNEL));

	rthdr->rate = rx->rate->bitrate / 5;
	rthdr->chan_freq = cpu_to_le16(status->freq);

	if (status->band == IEEE80211_BAND_5GHZ)
		rthdr->chan_flags = cpu_to_le16(IEEE80211_CHAN_OFDM |
						IEEE80211_CHAN_5GHZ);
	else
		rthdr->chan_flags = cpu_to_le16(IEEE80211_CHAN_DYN |
						IEEE80211_CHAN_2GHZ);

	skb_set_mac_header(skb, 0);
	skb->ip_summed = CHECKSUM_UNNECESSARY;
	skb->pkt_type = PACKET_OTHERHOST;
	skb->protocol = htons(ETH_P_802_2);

	list_for_each_entry_rcu(sdata, &local->interfaces, list) {
		if (!netif_running(sdata->dev))
			continue;

		if (sdata->vif.type != NL80211_IFTYPE_MONITOR ||
		    !(sdata->u.mntr_flags & MONITOR_FLAG_COOK_FRAMES))
			continue;

		if (prev_dev) {
			skb2 = skb_clone(skb, GFP_ATOMIC);
			if (skb2) {
				skb2->dev = prev_dev;
				netif_rx(skb2);
			}
		}

		prev_dev = sdata->dev;
		sdata->dev->stats.rx_packets++;
		sdata->dev->stats.rx_bytes += skb->len;
	}

	if (prev_dev) {
		skb->dev = prev_dev;
		netif_rx(skb);
		skb = NULL;
	} else
		goto out_free_skb;

	rx->flags |= IEEE80211_RX_CMNTR_REPORTED;
	return;

 out_free_skb:
	dev_kfree_skb(skb);
}


static void ieee80211_invoke_rx_handlers(struct ieee80211_sub_if_data *sdata,
					 struct ieee80211_rx_data *rx,
					 struct sk_buff *skb)
{
	ieee80211_rx_result res = RX_DROP_MONITOR;

	rx->skb = skb;
	rx->sdata = sdata;
	rx->dev = sdata->dev;

#define CALL_RXH(rxh)			\
	do {				\
		res = rxh(rx);		\
		if (res != RX_CONTINUE)	\
			goto rxh_done;  \
	} while (0);

	CALL_RXH(ieee80211_rx_h_passive_scan)
	CALL_RXH(ieee80211_rx_h_check)
	CALL_RXH(ieee80211_rx_h_decrypt)
	CALL_RXH(ieee80211_rx_h_sta_process)
	CALL_RXH(ieee80211_rx_h_defragment)
	CALL_RXH(ieee80211_rx_h_ps_poll)
	CALL_RXH(ieee80211_rx_h_michael_mic_verify)
	/* must be after MMIC verify so header is counted in MPDU mic */
	CALL_RXH(ieee80211_rx_h_remove_qos_control)
	CALL_RXH(ieee80211_rx_h_amsdu)
#ifdef CONFIG_MAC80211_MESH
	if (ieee80211_vif_is_mesh(&sdata->vif))
		CALL_RXH(ieee80211_rx_h_mesh_fwding);
#endif
	CALL_RXH(ieee80211_rx_h_data)
	CALL_RXH(ieee80211_rx_h_ctrl)
	CALL_RXH(ieee80211_rx_h_action)
	CALL_RXH(ieee80211_rx_h_mgmt)

#undef CALL_RXH

 rxh_done:
	switch (res) {
	case RX_DROP_MONITOR:
		I802_DEBUG_INC(sdata->local->rx_handlers_drop);
		if (rx->sta)
			rx->sta->rx_dropped++;
		/* fall through */
	case RX_CONTINUE:
		ieee80211_rx_cooked_monitor(rx);
		break;
	case RX_DROP_UNUSABLE:
		I802_DEBUG_INC(sdata->local->rx_handlers_drop);
		if (rx->sta)
			rx->sta->rx_dropped++;
		dev_kfree_skb(rx->skb);
		break;
	case RX_QUEUED:
		I802_DEBUG_INC(sdata->local->rx_handlers_queued);
		break;
	}
}

/* main receive path */

static int prepare_for_handlers(struct ieee80211_sub_if_data *sdata,
				u8 *bssid, struct ieee80211_rx_data *rx,
				struct ieee80211_hdr *hdr)
{
	int multicast = is_multicast_ether_addr(hdr->addr1);

	switch (sdata->vif.type) {
	case NL80211_IFTYPE_STATION:
		if (!bssid)
			return 0;
		if (!ieee80211_bssid_match(bssid, sdata->u.sta.bssid)) {
			if (!(rx->flags & IEEE80211_RX_IN_SCAN))
				return 0;
			rx->flags &= ~IEEE80211_RX_RA_MATCH;
		} else if (!multicast &&
			   compare_ether_addr(sdata->dev->dev_addr,
					      hdr->addr1) != 0) {
			if (!(sdata->dev->flags & IFF_PROMISC))
				return 0;
			rx->flags &= ~IEEE80211_RX_RA_MATCH;
		}
		break;
	case NL80211_IFTYPE_ADHOC:
		if (!bssid)
			return 0;
		if (ieee80211_is_beacon(hdr->frame_control)) {
			return 1;
		}
		else if (!ieee80211_bssid_match(bssid, sdata->u.sta.bssid)) {
			if (!(rx->flags & IEEE80211_RX_IN_SCAN))
				return 0;
			rx->flags &= ~IEEE80211_RX_RA_MATCH;
		} else if (!multicast &&
			   compare_ether_addr(sdata->dev->dev_addr,
					      hdr->addr1) != 0) {
			if (!(sdata->dev->flags & IFF_PROMISC))
				return 0;
			rx->flags &= ~IEEE80211_RX_RA_MATCH;
		} else if (!rx->sta)
			rx->sta = ieee80211_ibss_add_sta(sdata, rx->skb,
						bssid, hdr->addr2,
						BIT(rx->status->rate_idx));
		break;
	case NL80211_IFTYPE_MESH_POINT:
		if (!multicast &&
		    compare_ether_addr(sdata->dev->dev_addr,
				       hdr->addr1) != 0) {
			if (!(sdata->dev->flags & IFF_PROMISC))
				return 0;

			rx->flags &= ~IEEE80211_RX_RA_MATCH;
		}
		break;
	case NL80211_IFTYPE_AP_VLAN:
	case NL80211_IFTYPE_AP:
		if (!bssid) {
			if (compare_ether_addr(sdata->dev->dev_addr,
					       hdr->addr1))
				return 0;
		} else if (!ieee80211_bssid_match(bssid,
					sdata->dev->dev_addr)) {
			if (!(rx->flags & IEEE80211_RX_IN_SCAN))
				return 0;
			rx->flags &= ~IEEE80211_RX_RA_MATCH;
		}
		break;
	case NL80211_IFTYPE_WDS:
		if (bssid || !ieee80211_is_data(hdr->frame_control))
			return 0;
		if (compare_ether_addr(sdata->u.wds.remote_addr, hdr->addr2))
			return 0;
		break;
	case NL80211_IFTYPE_MONITOR:
		/* take everything */
		break;
	case NL80211_IFTYPE_UNSPECIFIED:
	case __NL80211_IFTYPE_AFTER_LAST:
		/* should never get here */
		WARN_ON(1);
		break;
	}

	return 1;
}

/*
 * This is the actual Rx frames handler. as it blongs to Rx path it must
 * be called with rcu_read_lock protection.
 */
static void __ieee80211_rx_handle_packet(struct ieee80211_hw *hw,
					 struct sk_buff *skb,
					 struct ieee80211_rx_status *status,
					 struct ieee80211_rate *rate)
{
	struct ieee80211_local *local = hw_to_local(hw);
	struct ieee80211_sub_if_data *sdata;
	struct ieee80211_hdr *hdr;
	struct ieee80211_rx_data rx;
	int prepares;
	struct ieee80211_sub_if_data *prev = NULL;
	struct sk_buff *skb_new;
	u8 *bssid;

	hdr = (struct ieee80211_hdr *)skb->data;
	memset(&rx, 0, sizeof(rx));
	rx.skb = skb;
	rx.local = local;

	rx.status = status;
	rx.rate = rate;

	if (ieee80211_is_data(hdr->frame_control) || ieee80211_is_mgmt(hdr->frame_control))
		local->dot11ReceivedFragmentCount++;

	rx.sta = sta_info_get(local, hdr->addr2);
	if (rx.sta) {
		rx.sdata = rx.sta->sdata;
		rx.dev = rx.sta->sdata->dev;
	}

	if ((status->flag & RX_FLAG_MMIC_ERROR)) {
		ieee80211_rx_michael_mic_report(local->mdev, hdr, &rx);
		return;
	}

	if (unlikely(local->sw_scanning || local->hw_scanning))
		rx.flags |= IEEE80211_RX_IN_SCAN;

	ieee80211_parse_qos(&rx);
	ieee80211_verify_ip_alignment(&rx);

	skb = rx.skb;

	list_for_each_entry_rcu(sdata, &local->interfaces, list) {
		if (!netif_running(sdata->dev))
			continue;

		if (sdata->vif.type == NL80211_IFTYPE_MONITOR)
			continue;

		bssid = ieee80211_get_bssid(hdr, skb->len, sdata->vif.type);
		rx.flags |= IEEE80211_RX_RA_MATCH;
		prepares = prepare_for_handlers(sdata, bssid, &rx, hdr);

		if (!prepares)
			continue;

		/*
		 * frame is destined for this interface, but if it's not
		 * also for the previous one we handle that after the
		 * loop to avoid copying the SKB once too much
		 */

		if (!prev) {
			prev = sdata;
			continue;
		}

		/*
		 * frame was destined for the previous interface
		 * so invoke RX handlers for it
		 */

		skb_new = skb_copy(skb, GFP_ATOMIC);
		if (!skb_new) {
			if (net_ratelimit())
				printk(KERN_DEBUG "%s: failed to copy "
				       "multicast frame for %s\n",
				       wiphy_name(local->hw.wiphy),
				       prev->dev->name);
			continue;
		}
		ieee80211_invoke_rx_handlers(prev, &rx, skb_new);
		prev = sdata;
	}
	if (prev)
		ieee80211_invoke_rx_handlers(prev, &rx, skb);
	else
		dev_kfree_skb(skb);
}

#define SEQ_MODULO 0x1000
#define SEQ_MASK   0xfff

static inline int seq_less(u16 sq1, u16 sq2)
{
	return ((sq1 - sq2) & SEQ_MASK) > (SEQ_MODULO >> 1);
}

static inline u16 seq_inc(u16 sq)
{
	return (sq + 1) & SEQ_MASK;
}

static inline u16 seq_sub(u16 sq1, u16 sq2)
{
	return (sq1 - sq2) & SEQ_MASK;
}


/*
 * As it function blongs to Rx path it must be called with
 * the proper rcu_read_lock protection for its flow.
 */
static u8 ieee80211_sta_manage_reorder_buf(struct ieee80211_hw *hw,
					   struct tid_ampdu_rx *tid_agg_rx,
					   struct sk_buff *skb,
					   u16 mpdu_seq_num,
					   int bar_req)
{
	struct ieee80211_local *local = hw_to_local(hw);
	struct ieee80211_rx_status status;
	u16 head_seq_num, buf_size;
	int index;
	struct ieee80211_supported_band *sband;
	struct ieee80211_rate *rate;

	buf_size = tid_agg_rx->buf_size;
	head_seq_num = tid_agg_rx->head_seq_num;

	/* frame with out of date sequence number */
	if (seq_less(mpdu_seq_num, head_seq_num)) {
		dev_kfree_skb(skb);
		return 1;
	}

	/* if frame sequence number exceeds our buffering window size or
	 * block Ack Request arrived - release stored frames */
	if ((!seq_less(mpdu_seq_num, head_seq_num + buf_size)) || (bar_req)) {
		/* new head to the ordering buffer */
		if (bar_req)
			head_seq_num = mpdu_seq_num;
		else
			head_seq_num =
				seq_inc(seq_sub(mpdu_seq_num, buf_size));
		/* release stored frames up to new head to stack */
		while (seq_less(tid_agg_rx->head_seq_num, head_seq_num)) {
			index = seq_sub(tid_agg_rx->head_seq_num,
				tid_agg_rx->ssn)
				% tid_agg_rx->buf_size;

			if (tid_agg_rx->reorder_buf[index]) {
				/* release the reordered frames to stack */
				memcpy(&status,
					tid_agg_rx->reorder_buf[index]->cb,
					sizeof(status));
				sband = local->hw.wiphy->bands[status.band];
				rate = &sband->bitrates[status.rate_idx];
				__ieee80211_rx_handle_packet(hw,
					tid_agg_rx->reorder_buf[index],
					&status, rate);
				tid_agg_rx->stored_mpdu_num--;
				tid_agg_rx->reorder_buf[index] = NULL;
			}
			tid_agg_rx->head_seq_num =
				seq_inc(tid_agg_rx->head_seq_num);
		}
		if (bar_req)
			return 1;
	}

	/* now the new frame is always in the range of the reordering */
	/* buffer window */
	index = seq_sub(mpdu_seq_num, tid_agg_rx->ssn)
				% tid_agg_rx->buf_size;
	/* check if we already stored this frame */
	if (tid_agg_rx->reorder_buf[index]) {
		dev_kfree_skb(skb);
		return 1;
	}

	/* if arrived mpdu is in the right order and nothing else stored */
	/* release it immediately */
	if (mpdu_seq_num == tid_agg_rx->head_seq_num &&
			tid_agg_rx->stored_mpdu_num == 0) {
		tid_agg_rx->head_seq_num =
			seq_inc(tid_agg_rx->head_seq_num);
		return 0;
	}

	/* put the frame in the reordering buffer */
	tid_agg_rx->reorder_buf[index] = skb;
	tid_agg_rx->stored_mpdu_num++;
	/* release the buffer until next missing frame */
	index = seq_sub(tid_agg_rx->head_seq_num, tid_agg_rx->ssn)
						% tid_agg_rx->buf_size;
	while (tid_agg_rx->reorder_buf[index]) {
		/* release the reordered frame back to stack */
		memcpy(&status, tid_agg_rx->reorder_buf[index]->cb,
			sizeof(status));
		sband = local->hw.wiphy->bands[status.band];
		rate = &sband->bitrates[status.rate_idx];
		__ieee80211_rx_handle_packet(hw, tid_agg_rx->reorder_buf[index],
					     &status, rate);
		tid_agg_rx->stored_mpdu_num--;
		tid_agg_rx->reorder_buf[index] = NULL;
		tid_agg_rx->head_seq_num = seq_inc(tid_agg_rx->head_seq_num);
		index =	seq_sub(tid_agg_rx->head_seq_num,
			tid_agg_rx->ssn) % tid_agg_rx->buf_size;
	}
	return 1;
}

static u8 ieee80211_rx_reorder_ampdu(struct ieee80211_local *local,
				     struct sk_buff *skb)
{
	struct ieee80211_hw *hw = &local->hw;
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
	struct sta_info *sta;
	struct tid_ampdu_rx *tid_agg_rx;
	u16 sc;
	u16 mpdu_seq_num;
	u8 ret = 0;
	int tid;

	sta = sta_info_get(local, hdr->addr2);
	if (!sta)
		return ret;

	/* filter the QoS data rx stream according to
	 * STA/TID and check if this STA/TID is on aggregation */
	if (!ieee80211_is_data_qos(hdr->frame_control))
		goto end_reorder;

	tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;

	if (sta->ampdu_mlme.tid_state_rx[tid] != HT_AGG_STATE_OPERATIONAL)
		goto end_reorder;

	tid_agg_rx = sta->ampdu_mlme.tid_rx[tid];

	/* qos null data frames are excluded */
	if (unlikely(hdr->frame_control & cpu_to_le16(IEEE80211_STYPE_NULLFUNC)))
		goto end_reorder;

	/* new un-ordered ampdu frame - process it */

	/* reset session timer */
	if (tid_agg_rx->timeout) {
		unsigned long expires =
			jiffies + (tid_agg_rx->timeout / 1000) * HZ;
		mod_timer(&tid_agg_rx->session_timer, expires);
	}

	/* if this mpdu is fragmented - terminate rx aggregation session */
	sc = le16_to_cpu(hdr->seq_ctrl);
	if (sc & IEEE80211_SCTL_FRAG) {
		ieee80211_sta_stop_rx_ba_session(sta->sdata, sta->sta.addr,
			tid, 0, WLAN_REASON_QSTA_REQUIRE_SETUP);
		ret = 1;
		goto end_reorder;
	}

	/* according to mpdu sequence number deal with reordering buffer */
	mpdu_seq_num = (sc & IEEE80211_SCTL_SEQ) >> 4;
	ret = ieee80211_sta_manage_reorder_buf(hw, tid_agg_rx, skb,
						mpdu_seq_num, 0);
 end_reorder:
	return ret;
}

/*
 * This is the receive path handler. It is called by a low level driver when an
 * 802.11 MPDU is received from the hardware.
 */
void __ieee80211_rx(struct ieee80211_hw *hw, struct sk_buff *skb,
		    struct ieee80211_rx_status *status)
{
	struct ieee80211_local *local = hw_to_local(hw);
	struct ieee80211_rate *rate = NULL;
	struct ieee80211_supported_band *sband;

	if (status->band < 0 ||
	    status->band >= IEEE80211_NUM_BANDS) {
		WARN_ON(1);
		return;
	}

	sband = local->hw.wiphy->bands[status->band];

	if (!sband ||
	    status->rate_idx < 0 ||
	    status->rate_idx >= sband->n_bitrates) {
		WARN_ON(1);
		return;
	}

	rate = &sband->bitrates[status->rate_idx];

	/*
	 * key references and virtual interfaces are protected using RCU
	 * and this requires that we are in a read-side RCU section during
	 * receive processing
	 */
	rcu_read_lock();

	/*
	 * Frames with failed FCS/PLCP checksum are not returned,
	 * all other frames are returned without radiotap header
	 * if it was previously present.
	 * Also, frames with less than 16 bytes are dropped.
	 */
	skb = ieee80211_rx_monitor(local, skb, status, rate);
	if (!skb) {
		rcu_read_unlock();
		return;
	}

	if (!ieee80211_rx_reorder_ampdu(local, skb))
		__ieee80211_rx_handle_packet(hw, skb, status, rate);

	rcu_read_unlock();
}
EXPORT_SYMBOL(__ieee80211_rx);

/* This is a version of the rx handler that can be called from hard irq
 * context. Post the skb on the queue and schedule the tasklet */
void ieee80211_rx_irqsafe(struct ieee80211_hw *hw, struct sk_buff *skb,
			  struct ieee80211_rx_status *status)
{
	struct ieee80211_local *local = hw_to_local(hw);

	BUILD_BUG_ON(sizeof(struct ieee80211_rx_status) > sizeof(skb->cb));

	skb->dev = local->mdev;
	/* copy status into skb->cb for use by tasklet */
	memcpy(skb->cb, status, sizeof(*status));
	skb->pkt_type = IEEE80211_RX_MSG;
	skb_queue_tail(&local->skb_queue, skb);
	tasklet_schedule(&local->tasklet);
}
EXPORT_SYMBOL(ieee80211_rx_irqsafe);