mac80211: move tx crypto decision

[deliverable/linux.git] / net / mac80211 / tx.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.
 *
 *
 * Transmit and frame generation functions.
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/skbuff.h>
#include <linux/etherdevice.h>
#include <linux/bitmap.h>
#include <linux/rcupdate.h>
#include <net/net_namespace.h>
#include <net/ieee80211_radiotap.h>
#include <net/cfg80211.h>
#include <net/mac80211.h>
#include <asm/unaligned.h>

#include "ieee80211_i.h"
#include "ieee80211_led.h"
#include "wep.h"
#include "wpa.h"
#include "wme.h"
#include "ieee80211_rate.h"

#define IEEE80211_TX_OK         0
#define IEEE80211_TX_AGAIN      1
#define IEEE80211_TX_FRAG_AGAIN 2

/* misc utils */

static inline void ieee80211_include_sequence(struct ieee80211_sub_if_data *sdata,
                                              struct ieee80211_hdr *hdr)
{
        /* Set the sequence number for this frame. */
        hdr->seq_ctrl = cpu_to_le16(sdata->sequence);

        /* Increase the sequence number. */
        sdata->sequence = (sdata->sequence + 0x10) & IEEE80211_SCTL_SEQ;
}

#ifdef CONFIG_MAC80211_LOWTX_FRAME_DUMP
static void ieee80211_dump_frame(const char *ifname, const char *title,
                                 const struct sk_buff *skb)
{
        const struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
        u16 fc;
        int hdrlen;
        DECLARE_MAC_BUF(mac);

        printk(KERN_DEBUG "%s: %s (len=%d)", ifname, title, skb->len);
        if (skb->len < 4) {
                printk("\n");
                return;
        }

        fc = le16_to_cpu(hdr->frame_control);
        hdrlen = ieee80211_get_hdrlen(fc);
        if (hdrlen > skb->len)
                hdrlen = skb->len;
        if (hdrlen >= 4)
                printk(" FC=0x%04x DUR=0x%04x",
                       fc, le16_to_cpu(hdr->duration_id));
        if (hdrlen >= 10)
                printk(" A1=%s", print_mac(mac, hdr->addr1));
        if (hdrlen >= 16)
                printk(" A2=%s", print_mac(mac, hdr->addr2));
        if (hdrlen >= 24)
                printk(" A3=%s", print_mac(mac, hdr->addr3));
        if (hdrlen >= 30)
                printk(" A4=%s", print_mac(mac, hdr->addr4));
        printk("\n");
}
#else /* CONFIG_MAC80211_LOWTX_FRAME_DUMP */
static inline void ieee80211_dump_frame(const char *ifname, const char *title,
                                        struct sk_buff *skb)
{
}
#endif /* CONFIG_MAC80211_LOWTX_FRAME_DUMP */

static u16 ieee80211_duration(struct ieee80211_txrx_data *tx, int group_addr,
                              int next_frag_len)
{
        int rate, mrate, erp, dur, i;
        struct ieee80211_rate *txrate = tx->u.tx.rate;
        struct ieee80211_local *local = tx->local;
        struct ieee80211_hw_mode *mode = tx->u.tx.mode;

        erp = txrate->flags & IEEE80211_RATE_ERP;

        /*
         * data and mgmt (except PS Poll):
         * - during CFP: 32768
         * - during contention period:
         *   if addr1 is group address: 0
         *   if more fragments = 0 and addr1 is individual address: time to
         *      transmit one ACK plus SIFS
         *   if more fragments = 1 and addr1 is individual address: time to
         *      transmit next fragment plus 2 x ACK plus 3 x SIFS
         *
         * IEEE 802.11, 9.6:
         * - control response frame (CTS or ACK) shall be transmitted using the
         *   same rate as the immediately previous frame in the frame exchange
         *   sequence, if this rate belongs to the PHY mandatory rates, or else
         *   at the highest possible rate belonging to the PHY rates in the
         *   BSSBasicRateSet
         */

        if ((tx->fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_CTL) {
                /* TODO: These control frames are not currently sent by
                 * 80211.o, but should they be implemented, this function
                 * needs to be updated to support duration field calculation.
                 *
                 * RTS: time needed to transmit pending data/mgmt frame plus
                 *    one CTS frame plus one ACK frame plus 3 x SIFS
                 * CTS: duration of immediately previous RTS minus time
                 *    required to transmit CTS and its SIFS
                 * ACK: 0 if immediately previous directed data/mgmt had
                 *    more=0, with more=1 duration in ACK frame is duration
                 *    from previous frame minus time needed to transmit ACK
                 *    and its SIFS
                 * PS Poll: BIT(15) | BIT(14) | aid
                 */
                return 0;
        }

        /* data/mgmt */
        if (0 /* FIX: data/mgmt during CFP */)
                return 32768;

        if (group_addr) /* Group address as the destination - no ACK */
                return 0;

        /* Individual destination address:
         * IEEE 802.11, Ch. 9.6 (after IEEE 802.11g changes)
         * CTS and ACK frames shall be transmitted using the highest rate in
         * basic rate set that is less than or equal to the rate of the
         * immediately previous frame and that is using the same modulation
         * (CCK or OFDM). If no basic rate set matches with these requirements,
         * the highest mandatory rate of the PHY that is less than or equal to
         * the rate of the previous frame is used.
         * Mandatory rates for IEEE 802.11g PHY: 1, 2, 5.5, 11, 6, 12, 24 Mbps
         */
        rate = -1;
        mrate = 10; /* use 1 Mbps if everything fails */
        for (i = 0; i < mode->num_rates; i++) {
                struct ieee80211_rate *r = &mode->rates[i];
                if (r->rate > txrate->rate)
                        break;

                if (IEEE80211_RATE_MODULATION(txrate->flags) !=
                    IEEE80211_RATE_MODULATION(r->flags))
                        continue;

                if (r->flags & IEEE80211_RATE_BASIC)
                        rate = r->rate;
                else if (r->flags & IEEE80211_RATE_MANDATORY)
                        mrate = r->rate;
        }
        if (rate == -1) {
                /* No matching basic rate found; use highest suitable mandatory
                 * PHY rate */
                rate = mrate;
        }

        /* Time needed to transmit ACK
         * (10 bytes + 4-byte FCS = 112 bits) plus SIFS; rounded up
         * to closest integer */

        dur = ieee80211_frame_duration(local, 10, rate, erp,
                       tx->sdata->flags & IEEE80211_SDATA_SHORT_PREAMBLE);

        if (next_frag_len) {
                /* Frame is fragmented: duration increases with time needed to
                 * transmit next fragment plus ACK and 2 x SIFS. */
                dur *= 2; /* ACK + SIFS */
                /* next fragment */
                dur += ieee80211_frame_duration(local, next_frag_len,
                                txrate->rate, erp,
                                tx->sdata->flags &
                                        IEEE80211_SDATA_SHORT_PREAMBLE);
        }

        return dur;
}

static inline int __ieee80211_queue_stopped(const struct ieee80211_local *local,
                                            int queue)
{
        return test_bit(IEEE80211_LINK_STATE_XOFF, &local->state[queue]);
}

static inline int __ieee80211_queue_pending(const struct ieee80211_local *local,
                                            int queue)
{
        return test_bit(IEEE80211_LINK_STATE_PENDING, &local->state[queue]);
}

static int inline is_ieee80211_device(struct net_device *dev,
                                      struct net_device *master)
{
        return (wdev_priv(dev->ieee80211_ptr) ==
                wdev_priv(master->ieee80211_ptr));
}

/* tx handlers */

static ieee80211_txrx_result
ieee80211_tx_h_check_assoc(struct ieee80211_txrx_data *tx)
{
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
        struct sk_buff *skb = tx->skb;
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
        u32 sta_flags;

        if (unlikely(tx->flags & IEEE80211_TXRXD_TX_INJECTED))
                return TXRX_CONTINUE;

        if (unlikely(tx->local->sta_sw_scanning) &&
            ((tx->fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_MGMT ||
             (tx->fc & IEEE80211_FCTL_STYPE) != IEEE80211_STYPE_PROBE_REQ))
                return TXRX_DROP;

        if (tx->flags & IEEE80211_TXRXD_TXPS_BUFFERED)
                return TXRX_CONTINUE;

        sta_flags = tx->sta ? tx->sta->flags : 0;

        if (likely(tx->flags & IEEE80211_TXRXD_TXUNICAST)) {
                if (unlikely(!(sta_flags & WLAN_STA_ASSOC) &&
                             tx->sdata->type != IEEE80211_IF_TYPE_IBSS &&
                             (tx->fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_DATA)) {
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
                        DECLARE_MAC_BUF(mac);
                        printk(KERN_DEBUG "%s: dropped data frame to not "
                               "associated station %s\n",
                               tx->dev->name, print_mac(mac, hdr->addr1));
#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
                        I802_DEBUG_INC(tx->local->tx_handlers_drop_not_assoc);
                        return TXRX_DROP;
                }
        } else {
                if (unlikely((tx->fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_DATA &&
                             tx->local->num_sta == 0 &&
                             tx->sdata->type != IEEE80211_IF_TYPE_IBSS)) {
                        /*
                         * No associated STAs - no need to send multicast
                         * frames.
                         */
                        return TXRX_DROP;
                }
                return TXRX_CONTINUE;
        }

        return TXRX_CONTINUE;
}

static ieee80211_txrx_result
ieee80211_tx_h_sequence(struct ieee80211_txrx_data *tx)
{
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)tx->skb->data;

        if (ieee80211_get_hdrlen(le16_to_cpu(hdr->frame_control)) >= 24)
                ieee80211_include_sequence(tx->sdata, hdr);

        return TXRX_CONTINUE;
}

/* This function is called whenever the AP is about to exceed the maximum limit
 * of buffered frames for power saving STAs. This situation should not really
 * happen often during normal operation, so dropping the oldest buffered packet
 * from each queue should be OK to make some room for new frames. */
static void purge_old_ps_buffers(struct ieee80211_local *local)
{
        int total = 0, purged = 0;
        struct sk_buff *skb;
        struct ieee80211_sub_if_data *sdata;
        struct sta_info *sta;

        /*
         * virtual interfaces are protected by RCU
         */
        rcu_read_lock();

        list_for_each_entry_rcu(sdata, &local->interfaces, list) {
                struct ieee80211_if_ap *ap;
                if (sdata->dev == local->mdev ||
                    sdata->type != IEEE80211_IF_TYPE_AP)
                        continue;
                ap = &sdata->u.ap;
                skb = skb_dequeue(&ap->ps_bc_buf);
                if (skb) {
                        purged++;
                        dev_kfree_skb(skb);
                }
                total += skb_queue_len(&ap->ps_bc_buf);
        }
        rcu_read_unlock();

        read_lock_bh(&local->sta_lock);
        list_for_each_entry(sta, &local->sta_list, list) {
                skb = skb_dequeue(&sta->ps_tx_buf);
                if (skb) {
                        purged++;
                        dev_kfree_skb(skb);
                }
                total += skb_queue_len(&sta->ps_tx_buf);
        }
        read_unlock_bh(&local->sta_lock);

        local->total_ps_buffered = total;
        printk(KERN_DEBUG "%s: PS buffers full - purged %d frames\n",
               wiphy_name(local->hw.wiphy), purged);
}

static ieee80211_txrx_result
ieee80211_tx_h_multicast_ps_buf(struct ieee80211_txrx_data *tx)
{
        /*
         * broadcast/multicast frame
         *
         * If any of the associated stations is in power save mode,
         * the frame is buffered to be sent after DTIM beacon frame.
         * This is done either by the hardware or us.
         */

        /* not AP/IBSS or ordered frame */
        if (!tx->sdata->bss || (tx->fc & IEEE80211_FCTL_ORDER))
                return TXRX_CONTINUE;

        /* no stations in PS mode */
        if (!atomic_read(&tx->sdata->bss->num_sta_ps))
                return TXRX_CONTINUE;

        /* buffered in mac80211 */
        if (tx->local->hw.flags & IEEE80211_HW_HOST_BROADCAST_PS_BUFFERING) {
                if (tx->local->total_ps_buffered >= TOTAL_MAX_TX_BUFFER)
                        purge_old_ps_buffers(tx->local);
                if (skb_queue_len(&tx->sdata->bss->ps_bc_buf) >=
                    AP_MAX_BC_BUFFER) {
                        if (net_ratelimit()) {
                                printk(KERN_DEBUG "%s: BC TX buffer full - "
                                       "dropping the oldest frame\n",
                                       tx->dev->name);
                        }
                        dev_kfree_skb(skb_dequeue(&tx->sdata->bss->ps_bc_buf));
                } else
                        tx->local->total_ps_buffered++;
                skb_queue_tail(&tx->sdata->bss->ps_bc_buf, tx->skb);
                return TXRX_QUEUED;
        }

        /* buffered in hardware */
        tx->u.tx.control->flags |= IEEE80211_TXCTL_SEND_AFTER_DTIM;

        return TXRX_CONTINUE;
}

static ieee80211_txrx_result
ieee80211_tx_h_unicast_ps_buf(struct ieee80211_txrx_data *tx)
{
        struct sta_info *sta = tx->sta;
        DECLARE_MAC_BUF(mac);

        if (unlikely(!sta ||
                     ((tx->fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_MGMT &&
                      (tx->fc & IEEE80211_FCTL_STYPE) == IEEE80211_STYPE_PROBE_RESP)))
                return TXRX_CONTINUE;

        if (unlikely((sta->flags & WLAN_STA_PS) && !sta->pspoll)) {
                struct ieee80211_tx_packet_data *pkt_data;
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
                printk(KERN_DEBUG "STA %s aid %d: PS buffer (entries "
                       "before %d)\n",
                       print_mac(mac, sta->addr), sta->aid,
                       skb_queue_len(&sta->ps_tx_buf));
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
                sta->flags |= WLAN_STA_TIM;
                if (tx->local->total_ps_buffered >= TOTAL_MAX_TX_BUFFER)
                        purge_old_ps_buffers(tx->local);
                if (skb_queue_len(&sta->ps_tx_buf) >= STA_MAX_TX_BUFFER) {
                        struct sk_buff *old = skb_dequeue(&sta->ps_tx_buf);
                        if (net_ratelimit()) {
                                printk(KERN_DEBUG "%s: STA %s TX "
                                       "buffer full - dropping oldest frame\n",
                                       tx->dev->name, print_mac(mac, sta->addr));
                        }
                        dev_kfree_skb(old);
                } else
                        tx->local->total_ps_buffered++;
                /* Queue frame to be sent after STA sends an PS Poll frame */
                if (skb_queue_empty(&sta->ps_tx_buf)) {
                        if (tx->local->ops->set_tim)
                                tx->local->ops->set_tim(local_to_hw(tx->local),
                                                       sta->aid, 1);
                        if (tx->sdata->bss)
                                bss_tim_set(tx->local, tx->sdata->bss, sta->aid);
                }
                pkt_data = (struct ieee80211_tx_packet_data *)tx->skb->cb;
                pkt_data->jiffies = jiffies;
                skb_queue_tail(&sta->ps_tx_buf, tx->skb);
                return TXRX_QUEUED;
        }
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
        else if (unlikely(sta->flags & WLAN_STA_PS)) {
                printk(KERN_DEBUG "%s: STA %s in PS mode, but pspoll "
                       "set -> send frame\n", tx->dev->name,
                       print_mac(mac, sta->addr));
        }
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
        sta->pspoll = 0;

        return TXRX_CONTINUE;
}

static ieee80211_txrx_result
ieee80211_tx_h_ps_buf(struct ieee80211_txrx_data *tx)
{
        if (unlikely(tx->flags & IEEE80211_TXRXD_TXPS_BUFFERED))
                return TXRX_CONTINUE;

        if (tx->flags & IEEE80211_TXRXD_TXUNICAST)
                return ieee80211_tx_h_unicast_ps_buf(tx);
        else
                return ieee80211_tx_h_multicast_ps_buf(tx);
}

static ieee80211_txrx_result
ieee80211_tx_h_select_key(struct ieee80211_txrx_data *tx)
{
        struct ieee80211_key *key;
        u16 fc = tx->fc;

        if (unlikely(tx->u.tx.control->flags & IEEE80211_TXCTL_DO_NOT_ENCRYPT))
                tx->key = NULL;
        else if (tx->sta && (key = rcu_dereference(tx->sta->key)))
                tx->key = key;
        else if ((key = rcu_dereference(tx->sdata->default_key)))
                tx->key = key;
        else if (tx->sdata->drop_unencrypted &&
                 !(tx->u.tx.control->flags & IEEE80211_TXCTL_EAPOL_FRAME) &&
                 !(tx->flags & IEEE80211_TXRXD_TX_INJECTED)) {
                I802_DEBUG_INC(tx->local->tx_handlers_drop_unencrypted);
                return TXRX_DROP;
        } else
                tx->key = NULL;

        if (tx->key) {
                u16 ftype, stype;

                tx->key->tx_rx_count++;
                /* TODO: add threshold stuff again */

                switch (tx->key->conf.alg) {
                case ALG_WEP:
                        ftype = fc & IEEE80211_FCTL_FTYPE;
                        stype = fc & IEEE80211_FCTL_STYPE;

                        if (ftype == IEEE80211_FTYPE_MGMT &&
                            stype == IEEE80211_STYPE_AUTH)
                                break;
                case ALG_TKIP:
                case ALG_CCMP:
                        if (!WLAN_FC_DATA_PRESENT(fc))
                                tx->key = NULL;
                        break;
                }
        }

        if (!tx->key || !(tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE))
                tx->u.tx.control->flags |= IEEE80211_TXCTL_DO_NOT_ENCRYPT;

        return TXRX_CONTINUE;
}

static ieee80211_txrx_result
ieee80211_tx_h_fragment(struct ieee80211_txrx_data *tx)
{
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) tx->skb->data;
        size_t hdrlen, per_fragm, num_fragm, payload_len, left;
        struct sk_buff **frags, *first, *frag;
        int i;
        u16 seq;
        u8 *pos;
        int frag_threshold = tx->local->fragmentation_threshold;

        if (!(tx->flags & IEEE80211_TXRXD_FRAGMENTED))
                return TXRX_CONTINUE;

        first = tx->skb;

        hdrlen = ieee80211_get_hdrlen(tx->fc);
        payload_len = first->len - hdrlen;
        per_fragm = frag_threshold - hdrlen - FCS_LEN;
        num_fragm = DIV_ROUND_UP(payload_len, per_fragm);

        frags = kzalloc(num_fragm * sizeof(struct sk_buff *), GFP_ATOMIC);
        if (!frags)
                goto fail;

        hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_MOREFRAGS);
        seq = le16_to_cpu(hdr->seq_ctrl) & IEEE80211_SCTL_SEQ;
        pos = first->data + hdrlen + per_fragm;
        left = payload_len - per_fragm;
        for (i = 0; i < num_fragm - 1; i++) {
                struct ieee80211_hdr *fhdr;
                size_t copylen;

                if (left <= 0)
                        goto fail;

                /* reserve enough extra head and tail room for possible
                 * encryption */
                frag = frags[i] =
                        dev_alloc_skb(tx->local->tx_headroom +
                                      frag_threshold +
                                      IEEE80211_ENCRYPT_HEADROOM +
                                      IEEE80211_ENCRYPT_TAILROOM);
                if (!frag)
                        goto fail;
                /* Make sure that all fragments use the same priority so
                 * that they end up using the same TX queue */
                frag->priority = first->priority;
                skb_reserve(frag, tx->local->tx_headroom +
                                  IEEE80211_ENCRYPT_HEADROOM);
                fhdr = (struct ieee80211_hdr *) skb_put(frag, hdrlen);
                memcpy(fhdr, first->data, hdrlen);
                if (i == num_fragm - 2)
                        fhdr->frame_control &= cpu_to_le16(~IEEE80211_FCTL_MOREFRAGS);
                fhdr->seq_ctrl = cpu_to_le16(seq | ((i + 1) & IEEE80211_SCTL_FRAG));
                copylen = left > per_fragm ? per_fragm : left;
                memcpy(skb_put(frag, copylen), pos, copylen);

                pos += copylen;
                left -= copylen;
        }
        skb_trim(first, hdrlen + per_fragm);

        tx->u.tx.num_extra_frag = num_fragm - 1;
        tx->u.tx.extra_frag = frags;

        return TXRX_CONTINUE;

 fail:
        printk(KERN_DEBUG "%s: failed to fragment frame\n", tx->dev->name);
        if (frags) {
                for (i = 0; i < num_fragm - 1; i++)
                        if (frags[i])
                                dev_kfree_skb(frags[i]);
                kfree(frags);
        }
        I802_DEBUG_INC(tx->local->tx_handlers_drop_fragment);
        return TXRX_DROP;
}

static ieee80211_txrx_result
ieee80211_tx_h_encrypt(struct ieee80211_txrx_data *tx)
{
        if (!tx->key)
                return TXRX_CONTINUE;

        switch (tx->key->conf.alg) {
        case ALG_WEP:
                return ieee80211_crypto_wep_encrypt(tx);
        case ALG_TKIP:
                return ieee80211_crypto_tkip_encrypt(tx);
        case ALG_CCMP:
                return ieee80211_crypto_ccmp_encrypt(tx);
        }

        /* not reached */
        WARN_ON(1);
        return TXRX_DROP;
}

static ieee80211_txrx_result
ieee80211_tx_h_rate_ctrl(struct ieee80211_txrx_data *tx)
{
        struct rate_selection rsel;

        if (likely(!tx->u.tx.rate)) {
                rate_control_get_rate(tx->dev, tx->u.tx.mode, tx->skb, &rsel);
                tx->u.tx.rate = rsel.rate;
                if (unlikely(rsel.probe != NULL)) {
                        tx->u.tx.control->flags |=
                                IEEE80211_TXCTL_RATE_CTRL_PROBE;
                        tx->flags |= IEEE80211_TXRXD_TXPROBE_LAST_FRAG;
                        tx->u.tx.control->alt_retry_rate = tx->u.tx.rate->val;
                        tx->u.tx.rate = rsel.probe;
                } else
                        tx->u.tx.control->alt_retry_rate = -1;

                if (!tx->u.tx.rate)
                        return TXRX_DROP;
        } else
                tx->u.tx.control->alt_retry_rate = -1;

        if (tx->u.tx.mode->mode == MODE_IEEE80211G &&
            (tx->sdata->flags & IEEE80211_SDATA_USE_PROTECTION) &&
            (tx->flags & IEEE80211_TXRXD_FRAGMENTED) && rsel.nonerp) {
                tx->u.tx.last_frag_rate = tx->u.tx.rate;
                if (rsel.probe)
                        tx->flags &= ~IEEE80211_TXRXD_TXPROBE_LAST_FRAG;
                else
                        tx->flags |= IEEE80211_TXRXD_TXPROBE_LAST_FRAG;
                tx->u.tx.rate = rsel.nonerp;
                tx->u.tx.control->rate = rsel.nonerp;
                tx->u.tx.control->flags &= ~IEEE80211_TXCTL_RATE_CTRL_PROBE;
        } else {
                tx->u.tx.last_frag_rate = tx->u.tx.rate;
                tx->u.tx.control->rate = tx->u.tx.rate;
        }
        tx->u.tx.control->tx_rate = tx->u.tx.rate->val;

        return TXRX_CONTINUE;
}

static ieee80211_txrx_result
ieee80211_tx_h_misc(struct ieee80211_txrx_data *tx)
{
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) tx->skb->data;
        u16 fc = le16_to_cpu(hdr->frame_control);
        u16 dur;
        struct ieee80211_tx_control *control = tx->u.tx.control;
        struct ieee80211_hw_mode *mode = tx->u.tx.mode;

        if (!control->retry_limit) {
                if (!is_multicast_ether_addr(hdr->addr1)) {
                        if (tx->skb->len + FCS_LEN > tx->local->rts_threshold
                            && tx->local->rts_threshold <
                                        IEEE80211_MAX_RTS_THRESHOLD) {
                                control->flags |=
                                        IEEE80211_TXCTL_USE_RTS_CTS;
                                control->flags |=
                                        IEEE80211_TXCTL_LONG_RETRY_LIMIT;
                                control->retry_limit =
                                        tx->local->long_retry_limit;
                        } else {
                                control->retry_limit =
                                        tx->local->short_retry_limit;
                        }
                } else {
                        control->retry_limit = 1;
                }
        }

        if (tx->flags & IEEE80211_TXRXD_FRAGMENTED) {
                /* Do not use multiple retry rates when sending fragmented
                 * frames.
                 * TODO: The last fragment could still use multiple retry
                 * rates. */
                control->alt_retry_rate = -1;
        }

        /* Use CTS protection for unicast frames sent using extended rates if
         * there are associated non-ERP stations and RTS/CTS is not configured
         * for the frame. */
        if (mode->mode == MODE_IEEE80211G &&
            (tx->u.tx.rate->flags & IEEE80211_RATE_ERP) &&
            (tx->flags & IEEE80211_TXRXD_TXUNICAST) &&
            (tx->sdata->flags & IEEE80211_SDATA_USE_PROTECTION) &&
            !(control->flags & IEEE80211_TXCTL_USE_RTS_CTS))
                control->flags |= IEEE80211_TXCTL_USE_CTS_PROTECT;

        /* Transmit data frames using short preambles if the driver supports
         * short preambles at the selected rate and short preambles are
         * available on the network at the current point in time. */
        if (((fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_DATA) &&
            (tx->u.tx.rate->flags & IEEE80211_RATE_PREAMBLE2) &&
            (tx->sdata->flags & IEEE80211_SDATA_SHORT_PREAMBLE) &&
            (!tx->sta || (tx->sta->flags & WLAN_STA_SHORT_PREAMBLE))) {
                tx->u.tx.control->tx_rate = tx->u.tx.rate->val2;
        }

        /* Setup duration field for the first fragment of the frame. Duration
         * for remaining fragments will be updated when they are being sent
         * to low-level driver in ieee80211_tx(). */
        dur = ieee80211_duration(tx, is_multicast_ether_addr(hdr->addr1),
                                 (tx->flags & IEEE80211_TXRXD_FRAGMENTED) ?
                                 tx->u.tx.extra_frag[0]->len : 0);
        hdr->duration_id = cpu_to_le16(dur);

        if ((control->flags & IEEE80211_TXCTL_USE_RTS_CTS) ||
            (control->flags & IEEE80211_TXCTL_USE_CTS_PROTECT)) {
                struct ieee80211_rate *rate;

                /* Do not use multiple retry rates when using RTS/CTS */
                control->alt_retry_rate = -1;

                /* Use min(data rate, max base rate) as CTS/RTS rate */
                rate = tx->u.tx.rate;
                while (rate > mode->rates &&
                       !(rate->flags & IEEE80211_RATE_BASIC))
                        rate--;

                control->rts_cts_rate = rate->val;
                control->rts_rate = rate;
        }

        if (tx->sta) {
                tx->sta->tx_packets++;
                tx->sta->tx_fragments++;
                tx->sta->tx_bytes += tx->skb->len;
                if (tx->u.tx.extra_frag) {
                        int i;
                        tx->sta->tx_fragments += tx->u.tx.num_extra_frag;
                        for (i = 0; i < tx->u.tx.num_extra_frag; i++) {
                                tx->sta->tx_bytes +=
                                        tx->u.tx.extra_frag[i]->len;
                        }
                }
        }

        return TXRX_CONTINUE;
}

static ieee80211_txrx_result
ieee80211_tx_h_load_stats(struct ieee80211_txrx_data *tx)
{
        struct ieee80211_local *local = tx->local;
        struct ieee80211_hw_mode *mode = tx->u.tx.mode;
        struct sk_buff *skb = tx->skb;
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
        u32 load = 0, hdrtime;

        /* TODO: this could be part of tx_status handling, so that the number
         * of retries would be known; TX rate should in that case be stored
         * somewhere with the packet */

        /* Estimate total channel use caused by this frame */

        /* 1 bit at 1 Mbit/s takes 1 usec; in channel_use values,
         * 1 usec = 1/8 * (1080 / 10) = 13.5 */

        if (mode->mode == MODE_IEEE80211A ||
            (mode->mode == MODE_IEEE80211G &&
             tx->u.tx.rate->flags & IEEE80211_RATE_ERP))
                hdrtime = CHAN_UTIL_HDR_SHORT;
        else
                hdrtime = CHAN_UTIL_HDR_LONG;

        load = hdrtime;
        if (!is_multicast_ether_addr(hdr->addr1))
                load += hdrtime;

        if (tx->u.tx.control->flags & IEEE80211_TXCTL_USE_RTS_CTS)
                load += 2 * hdrtime;
        else if (tx->u.tx.control->flags & IEEE80211_TXCTL_USE_CTS_PROTECT)
                load += hdrtime;

        load += skb->len * tx->u.tx.rate->rate_inv;

        if (tx->u.tx.extra_frag) {
                int i;
                for (i = 0; i < tx->u.tx.num_extra_frag; i++) {
                        load += 2 * hdrtime;
                        load += tx->u.tx.extra_frag[i]->len *
                                tx->u.tx.rate->rate;
                }
        }

        /* Divide channel_use by 8 to avoid wrapping around the counter */
        load >>= CHAN_UTIL_SHIFT;
        local->channel_use_raw += load;
        if (tx->sta)
                tx->sta->channel_use_raw += load;
        tx->sdata->channel_use_raw += load;

        return TXRX_CONTINUE;
}

/* TODO: implement register/unregister functions for adding TX/RX handlers
 * into ordered list */

ieee80211_tx_handler ieee80211_tx_handlers[] =
{
        ieee80211_tx_h_check_assoc,
        ieee80211_tx_h_sequence,
        ieee80211_tx_h_ps_buf,
        ieee80211_tx_h_select_key,
        ieee80211_tx_h_michael_mic_add,
        ieee80211_tx_h_fragment,
        ieee80211_tx_h_encrypt,
        ieee80211_tx_h_rate_ctrl,
        ieee80211_tx_h_misc,
        ieee80211_tx_h_load_stats,
        NULL
};

/* actual transmit path */

/*
 * deal with packet injection down monitor interface
 * with Radiotap Header -- only called for monitor mode interface
 */
static ieee80211_txrx_result
__ieee80211_parse_tx_radiotap(struct ieee80211_txrx_data *tx,
                              struct sk_buff *skb)
{
        /*
         * this is the moment to interpret and discard the radiotap header that
         * must be at the start of the packet injected in Monitor mode
         *
         * Need to take some care with endian-ness since radiotap
         * args are little-endian
         */

        struct ieee80211_radiotap_iterator iterator;
        struct ieee80211_radiotap_header *rthdr =
                (struct ieee80211_radiotap_header *) skb->data;
        struct ieee80211_hw_mode *mode = tx->local->hw.conf.mode;
        int ret = ieee80211_radiotap_iterator_init(&iterator, rthdr, skb->len);
        struct ieee80211_tx_control *control = tx->u.tx.control;

        control->flags |= IEEE80211_TXCTL_DO_NOT_ENCRYPT;
        tx->flags |= IEEE80211_TXRXD_TX_INJECTED;
        tx->flags &= ~IEEE80211_TXRXD_FRAGMENTED;

        /*
         * for every radiotap entry that is present
         * (ieee80211_radiotap_iterator_next returns -ENOENT when no more
         * entries present, or -EINVAL on error)
         */

        while (!ret) {
                int i, target_rate;

                ret = ieee80211_radiotap_iterator_next(&iterator);

                if (ret)
                        continue;

                /* see if this argument is something we can use */
                switch (iterator.this_arg_index) {
                /*
                 * You must take care when dereferencing iterator.this_arg
                 * for multibyte types... the pointer is not aligned.  Use
                 * get_unaligned((type *)iterator.this_arg) to dereference
                 * iterator.this_arg for type "type" safely on all arches.
                */
                case IEEE80211_RADIOTAP_RATE:
                        /*
                         * radiotap rate u8 is in 500kbps units eg, 0x02=1Mbps
                         * ieee80211 rate int is in 100kbps units eg, 0x0a=1Mbps
                         */
                        target_rate = (*iterator.this_arg) * 5;
                        for (i = 0; i < mode->num_rates; i++) {
                                struct ieee80211_rate *r = &mode->rates[i];

                                if (r->rate == target_rate) {
                                        tx->u.tx.rate = r;
                                        break;
                                }
                        }
                        break;

                case IEEE80211_RADIOTAP_ANTENNA:
                        /*
                         * radiotap uses 0 for 1st ant, mac80211 is 1 for
                         * 1st ant
                         */
                        control->antenna_sel_tx = (*iterator.this_arg) + 1;
                        break;

                case IEEE80211_RADIOTAP_DBM_TX_POWER:
                        control->power_level = *iterator.this_arg;
                        break;

                case IEEE80211_RADIOTAP_FLAGS:
                        if (*iterator.this_arg & IEEE80211_RADIOTAP_F_FCS) {
                                /*
                                 * this indicates that the skb we have been
                                 * handed has the 32-bit FCS CRC at the end...
                                 * we should react to that by snipping it off
                                 * because it will be recomputed and added
                                 * on transmission
                                 */
                                if (skb->len < (iterator.max_length + FCS_LEN))
                                        return TXRX_DROP;

                                skb_trim(skb, skb->len - FCS_LEN);
                        }
                        if (*iterator.this_arg & IEEE80211_RADIOTAP_F_WEP)
                                control->flags &=
                                        ~IEEE80211_TXCTL_DO_NOT_ENCRYPT;
                        if (*iterator.this_arg & IEEE80211_RADIOTAP_F_FRAG)
                                tx->flags |= IEEE80211_TXRXD_FRAGMENTED;
                        break;

                /*
                 * Please update the file
                 * Documentation/networking/mac80211-injection.txt
                 * when parsing new fields here.
                 */

                default:
                        break;
                }
        }

        if (ret != -ENOENT) /* ie, if we didn't simply run out of fields */
                return TXRX_DROP;

        /*
         * remove the radiotap header
         * iterator->max_length was sanity-checked against
         * skb->len by iterator init
         */
        skb_pull(skb, iterator.max_length);

        return TXRX_CONTINUE;
}

/*
 * initialises @tx
 */
static ieee80211_txrx_result
__ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
                       struct sk_buff *skb,
                       struct net_device *dev,
                       struct ieee80211_tx_control *control)
{
        struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
        struct ieee80211_hdr *hdr;
        struct ieee80211_sub_if_data *sdata;
        ieee80211_txrx_result res = TXRX_CONTINUE;

        int hdrlen;

        memset(tx, 0, sizeof(*tx));
        tx->skb = skb;
        tx->dev = dev; /* use original interface */
        tx->local = local;
        tx->sdata = IEEE80211_DEV_TO_SUB_IF(dev);
        tx->u.tx.control = control;
        /*
         * Set this flag (used below to indicate "automatic fragmentation"),
         * it will be cleared/left by radiotap as desired.
         */
        tx->flags |= IEEE80211_TXRXD_FRAGMENTED;

        /* process and remove the injection radiotap header */
        sdata = IEEE80211_DEV_TO_SUB_IF(dev);
        if (unlikely(sdata->type == IEEE80211_IF_TYPE_MNTR)) {
                if (__ieee80211_parse_tx_radiotap(tx, skb) == TXRX_DROP)
                        return TXRX_DROP;

                /*
                 * __ieee80211_parse_tx_radiotap has now removed
                 * the radiotap header that was present and pre-filled
                 * 'tx' with tx control information.
                 */
        }

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

        tx->sta = sta_info_get(local, hdr->addr1);
        tx->fc = le16_to_cpu(hdr->frame_control);

        if (is_multicast_ether_addr(hdr->addr1)) {
                tx->flags &= ~IEEE80211_TXRXD_TXUNICAST;
                control->flags |= IEEE80211_TXCTL_NO_ACK;
        } else {
                tx->flags |= IEEE80211_TXRXD_TXUNICAST;
                control->flags &= ~IEEE80211_TXCTL_NO_ACK;
        }

        if (tx->flags & IEEE80211_TXRXD_FRAGMENTED) {
                if ((tx->flags & IEEE80211_TXRXD_TXUNICAST) &&
                    skb->len + FCS_LEN > local->fragmentation_threshold &&
                    !local->ops->set_frag_threshold)
                        tx->flags |= IEEE80211_TXRXD_FRAGMENTED;
                else
                        tx->flags &= ~IEEE80211_TXRXD_FRAGMENTED;
        }

        if (!tx->sta)
                control->flags |= IEEE80211_TXCTL_CLEAR_DST_MASK;
        else if (tx->sta->clear_dst_mask) {
                control->flags |= IEEE80211_TXCTL_CLEAR_DST_MASK;
                tx->sta->clear_dst_mask = 0;
        }

        hdrlen = ieee80211_get_hdrlen(tx->fc);
        if (skb->len > hdrlen + sizeof(rfc1042_header) + 2) {
                u8 *pos = &skb->data[hdrlen + sizeof(rfc1042_header)];
                tx->ethertype = (pos[0] << 8) | pos[1];
        }
        control->flags |= IEEE80211_TXCTL_FIRST_FRAGMENT;

        return res;
}

/* Device in tx->dev has a reference added; use dev_put(tx->dev) when
 * finished with it.
 *
 * NB: @tx is uninitialised when passed in here
 */
static int ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
                                struct sk_buff *skb,
                                struct net_device *mdev,
                                struct ieee80211_tx_control *control)
{
        struct ieee80211_tx_packet_data *pkt_data;
        struct net_device *dev;

        pkt_data = (struct ieee80211_tx_packet_data *)skb->cb;
        dev = dev_get_by_index(&init_net, pkt_data->ifindex);
        if (unlikely(dev && !is_ieee80211_device(dev, mdev))) {
                dev_put(dev);
                dev = NULL;
        }
        if (unlikely(!dev))
                return -ENODEV;
        /* initialises tx with control */
        __ieee80211_tx_prepare(tx, skb, dev, control);
        return 0;
}

static int __ieee80211_tx(struct ieee80211_local *local, struct sk_buff *skb,
                          struct ieee80211_txrx_data *tx)
{
        struct ieee80211_tx_control *control = tx->u.tx.control;
        int ret, i;

        if (!ieee80211_qdisc_installed(local->mdev) &&
            __ieee80211_queue_stopped(local, 0)) {
                netif_stop_queue(local->mdev);
                return IEEE80211_TX_AGAIN;
        }
        if (skb) {
                ieee80211_dump_frame(wiphy_name(local->hw.wiphy),
                                     "TX to low-level driver", skb);
                ret = local->ops->tx(local_to_hw(local), skb, control);
                if (ret)
                        return IEEE80211_TX_AGAIN;
                local->mdev->trans_start = jiffies;
                ieee80211_led_tx(local, 1);
        }
        if (tx->u.tx.extra_frag) {
                control->flags &= ~(IEEE80211_TXCTL_USE_RTS_CTS |
                                    IEEE80211_TXCTL_USE_CTS_PROTECT |
                                    IEEE80211_TXCTL_CLEAR_DST_MASK |
                                    IEEE80211_TXCTL_FIRST_FRAGMENT);
                for (i = 0; i < tx->u.tx.num_extra_frag; i++) {
                        if (!tx->u.tx.extra_frag[i])
                                continue;
                        if (__ieee80211_queue_stopped(local, control->queue))
                                return IEEE80211_TX_FRAG_AGAIN;
                        if (i == tx->u.tx.num_extra_frag) {
                                control->tx_rate = tx->u.tx.last_frag_hwrate;
                                control->rate = tx->u.tx.last_frag_rate;
                                if (tx->flags & IEEE80211_TXRXD_TXPROBE_LAST_FRAG)
                                        control->flags |=
                                                IEEE80211_TXCTL_RATE_CTRL_PROBE;
                                else
                                        control->flags &=
                                                ~IEEE80211_TXCTL_RATE_CTRL_PROBE;
                        }

                        ieee80211_dump_frame(wiphy_name(local->hw.wiphy),
                                             "TX to low-level driver",
                                             tx->u.tx.extra_frag[i]);
                        ret = local->ops->tx(local_to_hw(local),
                                            tx->u.tx.extra_frag[i],
                                            control);
                        if (ret)
                                return IEEE80211_TX_FRAG_AGAIN;
                        local->mdev->trans_start = jiffies;
                        ieee80211_led_tx(local, 1);
                        tx->u.tx.extra_frag[i] = NULL;
                }
                kfree(tx->u.tx.extra_frag);
                tx->u.tx.extra_frag = NULL;
        }
        return IEEE80211_TX_OK;
}

static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb,
                        struct ieee80211_tx_control *control)
{
        struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
        struct sta_info *sta;
        ieee80211_tx_handler *handler;
        struct ieee80211_txrx_data tx;
        ieee80211_txrx_result res = TXRX_DROP, res_prepare;
        int ret, i;

        WARN_ON(__ieee80211_queue_pending(local, control->queue));

        if (unlikely(skb->len < 10)) {
                dev_kfree_skb(skb);
                return 0;
        }

        /* initialises tx */
        res_prepare = __ieee80211_tx_prepare(&tx, skb, dev, control);

        if (res_prepare == TXRX_DROP) {
                dev_kfree_skb(skb);
                return 0;
        }

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

        sta = tx.sta;
        tx.u.tx.mode = local->hw.conf.mode;

        for (handler = local->tx_handlers; *handler != NULL;
             handler++) {
                res = (*handler)(&tx);
                if (res != TXRX_CONTINUE)
                        break;
        }

        skb = tx.skb; /* handlers are allowed to change skb */

        if (sta)
                sta_info_put(sta);

        if (unlikely(res == TXRX_DROP)) {
                I802_DEBUG_INC(local->tx_handlers_drop);
                goto drop;
        }

        if (unlikely(res == TXRX_QUEUED)) {
                I802_DEBUG_INC(local->tx_handlers_queued);
                rcu_read_unlock();
                return 0;
        }

        if (tx.u.tx.extra_frag) {
                for (i = 0; i < tx.u.tx.num_extra_frag; i++) {
                        int next_len, dur;
                        struct ieee80211_hdr *hdr =
                                (struct ieee80211_hdr *)
                                tx.u.tx.extra_frag[i]->data;

                        if (i + 1 < tx.u.tx.num_extra_frag) {
                                next_len = tx.u.tx.extra_frag[i + 1]->len;
                        } else {
                                next_len = 0;
                                tx.u.tx.rate = tx.u.tx.last_frag_rate;
                                tx.u.tx.last_frag_hwrate = tx.u.tx.rate->val;
                        }
                        dur = ieee80211_duration(&tx, 0, next_len);
                        hdr->duration_id = cpu_to_le16(dur);
                }
        }

retry:
        ret = __ieee80211_tx(local, skb, &tx);
        if (ret) {
                struct ieee80211_tx_stored_packet *store =
                        &local->pending_packet[control->queue];

                if (ret == IEEE80211_TX_FRAG_AGAIN)
                        skb = NULL;
                set_bit(IEEE80211_LINK_STATE_PENDING,
                        &local->state[control->queue]);
                smp_mb();
                /* When the driver gets out of buffers during sending of
                 * fragments and calls ieee80211_stop_queue, there is
                 * a small window between IEEE80211_LINK_STATE_XOFF and
                 * IEEE80211_LINK_STATE_PENDING flags are set. If a buffer
                 * gets available in that window (i.e. driver calls
                 * ieee80211_wake_queue), we would end up with ieee80211_tx
                 * called with IEEE80211_LINK_STATE_PENDING. Prevent this by
                 * continuing transmitting here when that situation is
                 * possible to have happened. */
                if (!__ieee80211_queue_stopped(local, control->queue)) {
                        clear_bit(IEEE80211_LINK_STATE_PENDING,
                                  &local->state[control->queue]);
                        goto retry;
                }
                memcpy(&store->control, control,
                       sizeof(struct ieee80211_tx_control));
                store->skb = skb;
                store->extra_frag = tx.u.tx.extra_frag;
                store->num_extra_frag = tx.u.tx.num_extra_frag;
                store->last_frag_hwrate = tx.u.tx.last_frag_hwrate;
                store->last_frag_rate = tx.u.tx.last_frag_rate;
                store->last_frag_rate_ctrl_probe =
                        !!(tx.flags & IEEE80211_TXRXD_TXPROBE_LAST_FRAG);
        }
        rcu_read_unlock();
        return 0;

 drop:
        if (skb)
                dev_kfree_skb(skb);
        for (i = 0; i < tx.u.tx.num_extra_frag; i++)
                if (tx.u.tx.extra_frag[i])
                        dev_kfree_skb(tx.u.tx.extra_frag[i]);
        kfree(tx.u.tx.extra_frag);
        rcu_read_unlock();
        return 0;
}

/* device xmit handlers */

int ieee80211_master_start_xmit(struct sk_buff *skb,
                                struct net_device *dev)
{
        struct ieee80211_tx_control control;
        struct ieee80211_tx_packet_data *pkt_data;
        struct net_device *odev = NULL;
        struct ieee80211_sub_if_data *osdata;
        int headroom;
        int ret;

        /*
         * copy control out of the skb so other people can use skb->cb
         */
        pkt_data = (struct ieee80211_tx_packet_data *)skb->cb;
        memset(&control, 0, sizeof(struct ieee80211_tx_control));

        if (pkt_data->ifindex)
                odev = dev_get_by_index(&init_net, pkt_data->ifindex);
        if (unlikely(odev && !is_ieee80211_device(odev, dev))) {
                dev_put(odev);
                odev = NULL;
        }
        if (unlikely(!odev)) {
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
                printk(KERN_DEBUG "%s: Discarded packet with nonexistent "
                       "originating device\n", dev->name);
#endif
                dev_kfree_skb(skb);
                return 0;
        }
        osdata = IEEE80211_DEV_TO_SUB_IF(odev);

        headroom = osdata->local->tx_headroom + IEEE80211_ENCRYPT_HEADROOM;
        if (skb_headroom(skb) < headroom) {
                if (pskb_expand_head(skb, headroom, 0, GFP_ATOMIC)) {
                        dev_kfree_skb(skb);
                        dev_put(odev);
                        return 0;
                }
        }

        control.ifindex = odev->ifindex;
        control.type = osdata->type;
        if (pkt_data->flags & IEEE80211_TXPD_REQ_TX_STATUS)
                control.flags |= IEEE80211_TXCTL_REQ_TX_STATUS;
        if (pkt_data->flags & IEEE80211_TXPD_DO_NOT_ENCRYPT)
                control.flags |= IEEE80211_TXCTL_DO_NOT_ENCRYPT;
        if (pkt_data->flags & IEEE80211_TXPD_REQUEUE)
                control.flags |= IEEE80211_TXCTL_REQUEUE;
        if (pkt_data->flags & IEEE80211_TXPD_EAPOL_FRAME)
                control.flags |= IEEE80211_TXCTL_EAPOL_FRAME;
        control.queue = pkt_data->queue;

        ret = ieee80211_tx(odev, skb, &control);
        dev_put(odev);

        return ret;
}

int ieee80211_monitor_start_xmit(struct sk_buff *skb,
                                 struct net_device *dev)
{
        struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
        struct ieee80211_tx_packet_data *pkt_data;
        struct ieee80211_radiotap_header *prthdr =
                (struct ieee80211_radiotap_header *)skb->data;
        u16 len_rthdr;

        /* check for not even having the fixed radiotap header part */
        if (unlikely(skb->len < sizeof(struct ieee80211_radiotap_header)))
                goto fail; /* too short to be possibly valid */

        /* is it a header version we can trust to find length from? */
        if (unlikely(prthdr->it_version))
                goto fail; /* only version 0 is supported */

        /* then there must be a radiotap header with a length we can use */
        len_rthdr = ieee80211_get_radiotap_len(skb->data);

        /* does the skb contain enough to deliver on the alleged length? */
        if (unlikely(skb->len < len_rthdr))
                goto fail; /* skb too short for claimed rt header extent */

        skb->dev = local->mdev;

        pkt_data = (struct ieee80211_tx_packet_data *)skb->cb;
        memset(pkt_data, 0, sizeof(*pkt_data));
        /* needed because we set skb device to master */
        pkt_data->ifindex = dev->ifindex;

        pkt_data->flags |= IEEE80211_TXPD_DO_NOT_ENCRYPT;

        /*
         * fix up the pointers accounting for the radiotap
         * header still being in there.  We are being given
         * a precooked IEEE80211 header so no need for
         * normal processing
         */
        skb_set_mac_header(skb, len_rthdr);
        /*
         * these are just fixed to the end of the rt area since we
         * don't have any better information and at this point, nobody cares
         */
        skb_set_network_header(skb, len_rthdr);
        skb_set_transport_header(skb, len_rthdr);

        /* pass the radiotap header up to the next stage intact */
        dev_queue_xmit(skb);
        return NETDEV_TX_OK;

fail:
        dev_kfree_skb(skb);
        return NETDEV_TX_OK; /* meaning, we dealt with the skb */
}

/**
 * ieee80211_subif_start_xmit - netif start_xmit function for Ethernet-type
 * subinterfaces (wlan#, WDS, and VLAN interfaces)
 * @skb: packet to be sent
 * @dev: incoming interface
 *
 * Returns: 0 on success (and frees skb in this case) or 1 on failure (skb will
 * not be freed, and caller is responsible for either retrying later or freeing
 * skb).
 *
 * This function takes in an Ethernet header and encapsulates it with suitable
 * IEEE 802.11 header based on which interface the packet is coming in. The
 * encapsulated packet will then be passed to master interface, wlan#.11, for
 * transmission (through low-level driver).
 */
int ieee80211_subif_start_xmit(struct sk_buff *skb,
                               struct net_device *dev)
{
        struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
        struct ieee80211_tx_packet_data *pkt_data;
        struct ieee80211_sub_if_data *sdata;
        int ret = 1, head_need;
        u16 ethertype, hdrlen, fc;
        struct ieee80211_hdr hdr;
        const u8 *encaps_data;
        int encaps_len, skip_header_bytes;
        int nh_pos, h_pos;
        struct sta_info *sta;
        u32 sta_flags = 0;

        sdata = IEEE80211_DEV_TO_SUB_IF(dev);
        if (unlikely(skb->len < ETH_HLEN)) {
                printk(KERN_DEBUG "%s: short skb (len=%d)\n",
                       dev->name, skb->len);
                ret = 0;
                goto fail;
        }

        nh_pos = skb_network_header(skb) - skb->data;
        h_pos = skb_transport_header(skb) - skb->data;

        /* convert Ethernet header to proper 802.11 header (based on
         * operation mode) */
        ethertype = (skb->data[12] << 8) | skb->data[13];
        fc = IEEE80211_FTYPE_DATA | IEEE80211_STYPE_DATA;

        switch (sdata->type) {
        case IEEE80211_IF_TYPE_AP:
        case IEEE80211_IF_TYPE_VLAN:
                fc |= IEEE80211_FCTL_FROMDS;
                /* DA BSSID SA */
                memcpy(hdr.addr1, skb->data, ETH_ALEN);
                memcpy(hdr.addr2, dev->dev_addr, ETH_ALEN);
                memcpy(hdr.addr3, skb->data + ETH_ALEN, ETH_ALEN);
                hdrlen = 24;
                break;
        case IEEE80211_IF_TYPE_WDS:
                fc |= IEEE80211_FCTL_FROMDS | IEEE80211_FCTL_TODS;
                /* RA TA DA SA */
                memcpy(hdr.addr1, sdata->u.wds.remote_addr, ETH_ALEN);
                memcpy(hdr.addr2, dev->dev_addr, ETH_ALEN);
                memcpy(hdr.addr3, skb->data, ETH_ALEN);
                memcpy(hdr.addr4, skb->data + ETH_ALEN, ETH_ALEN);
                hdrlen = 30;
                break;
        case IEEE80211_IF_TYPE_STA:
                fc |= IEEE80211_FCTL_TODS;
                /* BSSID SA DA */
                memcpy(hdr.addr1, sdata->u.sta.bssid, ETH_ALEN);
                memcpy(hdr.addr2, skb->data + ETH_ALEN, ETH_ALEN);
                memcpy(hdr.addr3, skb->data, ETH_ALEN);
                hdrlen = 24;
                break;
        case IEEE80211_IF_TYPE_IBSS:
                /* DA SA BSSID */
                memcpy(hdr.addr1, skb->data, ETH_ALEN);
                memcpy(hdr.addr2, skb->data + ETH_ALEN, ETH_ALEN);
                memcpy(hdr.addr3, sdata->u.sta.bssid, ETH_ALEN);
                hdrlen = 24;
                break;
        default:
                ret = 0;
                goto fail;
        }

        sta = sta_info_get(local, hdr.addr1);
        if (sta) {
                sta_flags = sta->flags;
                sta_info_put(sta);
        }

        /* receiver is QoS enabled, use a QoS type frame */
        if (sta_flags & WLAN_STA_WME) {
                fc |= IEEE80211_STYPE_QOS_DATA;
                hdrlen += 2;
        }

        /*
         * If port access control is enabled, drop frames to unauthorised
         * stations unless they are EAPOL frames from the local station.
         */
        if (unlikely(sdata->ieee802_1x_pac &&
                     !(sta_flags & WLAN_STA_AUTHORIZED) &&
                     !(ethertype == ETH_P_PAE &&
                       compare_ether_addr(dev->dev_addr,
                                          skb->data + ETH_ALEN) == 0))) {
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
                DECLARE_MAC_BUF(mac);

                if (net_ratelimit())
                        printk(KERN_DEBUG "%s: dropped frame to %s"
                               " (unauthorized port)\n", dev->name,
                               print_mac(mac, hdr.addr1));
#endif

                I802_DEBUG_INC(local->tx_handlers_drop_unauth_port);

                ret = 0;
                goto fail;
        }

        hdr.frame_control = cpu_to_le16(fc);
        hdr.duration_id = 0;
        hdr.seq_ctrl = 0;

        skip_header_bytes = ETH_HLEN;
        if (ethertype == ETH_P_AARP || ethertype == ETH_P_IPX) {
                encaps_data = bridge_tunnel_header;
                encaps_len = sizeof(bridge_tunnel_header);
                skip_header_bytes -= 2;
        } else if (ethertype >= 0x600) {
                encaps_data = rfc1042_header;
                encaps_len = sizeof(rfc1042_header);
                skip_header_bytes -= 2;
        } else {
                encaps_data = NULL;
                encaps_len = 0;
        }

        skb_pull(skb, skip_header_bytes);
        nh_pos -= skip_header_bytes;
        h_pos -= skip_header_bytes;

        /* TODO: implement support for fragments so that there is no need to
         * reallocate and copy payload; it might be enough to support one
         * extra fragment that would be copied in the beginning of the frame
         * data.. anyway, it would be nice to include this into skb structure
         * somehow
         *
         * There are few options for this:
         * use skb->cb as an extra space for 802.11 header
         * allocate new buffer if not enough headroom
         * make sure that there is enough headroom in every skb by increasing
         * build in headroom in __dev_alloc_skb() (linux/skbuff.h) and
         * alloc_skb() (net/core/skbuff.c)
         */
        head_need = hdrlen + encaps_len + local->tx_headroom;
        head_need -= skb_headroom(skb);

        /* We are going to modify skb data, so make a copy of it if happens to
         * be cloned. This could happen, e.g., with Linux bridge code passing
         * us broadcast frames. */

        if (head_need > 0 || skb_cloned(skb)) {
#if 0
                printk(KERN_DEBUG "%s: need to reallocate buffer for %d bytes "
                       "of headroom\n", dev->name, head_need);
#endif

                if (skb_cloned(skb))
                        I802_DEBUG_INC(local->tx_expand_skb_head_cloned);
                else
                        I802_DEBUG_INC(local->tx_expand_skb_head);
                /* Since we have to reallocate the buffer, make sure that there
                 * is enough room for possible WEP IV/ICV and TKIP (8 bytes
                 * before payload and 12 after). */
                if (pskb_expand_head(skb, (head_need > 0 ? head_need + 8 : 8),
                                     12, GFP_ATOMIC)) {
                        printk(KERN_DEBUG "%s: failed to reallocate TX buffer"
                               "\n", dev->name);
                        goto fail;
                }
        }

        if (encaps_data) {
                memcpy(skb_push(skb, encaps_len), encaps_data, encaps_len);
                nh_pos += encaps_len;
                h_pos += encaps_len;
        }

        if (fc & IEEE80211_STYPE_QOS_DATA) {
                __le16 *qos_control;

                qos_control = (__le16*) skb_push(skb, 2);
                memcpy(skb_push(skb, hdrlen - 2), &hdr, hdrlen - 2);
                /*
                 * Maybe we could actually set some fields here, for now just
                 * initialise to zero to indicate no special operation.
                 */
                *qos_control = 0;
        } else
                memcpy(skb_push(skb, hdrlen), &hdr, hdrlen);

        nh_pos += hdrlen;
        h_pos += hdrlen;

        pkt_data = (struct ieee80211_tx_packet_data *)skb->cb;
        memset(pkt_data, 0, sizeof(struct ieee80211_tx_packet_data));
        pkt_data->ifindex = dev->ifindex;
        if (ethertype == ETH_P_PAE)
                pkt_data->flags |= IEEE80211_TXPD_EAPOL_FRAME;

        skb->dev = local->mdev;
        dev->stats.tx_packets++;
        dev->stats.tx_bytes += skb->len;

        /* Update skb pointers to various headers since this modified frame
         * is going to go through Linux networking code that may potentially
         * need things like pointer to IP header. */
        skb_set_mac_header(skb, 0);
        skb_set_network_header(skb, nh_pos);
        skb_set_transport_header(skb, h_pos);

        dev->trans_start = jiffies;
        dev_queue_xmit(skb);

        return 0;

 fail:
        if (!ret)
                dev_kfree_skb(skb);

        return ret;
}

/* helper functions for pending packets for when queues are stopped */

void ieee80211_clear_tx_pending(struct ieee80211_local *local)
{
        int i, j;
        struct ieee80211_tx_stored_packet *store;

        for (i = 0; i < local->hw.queues; i++) {
                if (!__ieee80211_queue_pending(local, i))
                        continue;
                store = &local->pending_packet[i];
                kfree_skb(store->skb);
                for (j = 0; j < store->num_extra_frag; j++)
                        kfree_skb(store->extra_frag[j]);
                kfree(store->extra_frag);
                clear_bit(IEEE80211_LINK_STATE_PENDING, &local->state[i]);
        }
}

void ieee80211_tx_pending(unsigned long data)
{
        struct ieee80211_local *local = (struct ieee80211_local *)data;
        struct net_device *dev = local->mdev;
        struct ieee80211_tx_stored_packet *store;
        struct ieee80211_txrx_data tx;
        int i, ret, reschedule = 0;

        netif_tx_lock_bh(dev);
        for (i = 0; i < local->hw.queues; i++) {
                if (__ieee80211_queue_stopped(local, i))
                        continue;
                if (!__ieee80211_queue_pending(local, i)) {
                        reschedule = 1;
                        continue;
                }
                store = &local->pending_packet[i];
                tx.u.tx.control = &store->control;
                tx.u.tx.extra_frag = store->extra_frag;
                tx.u.tx.num_extra_frag = store->num_extra_frag;
                tx.u.tx.last_frag_hwrate = store->last_frag_hwrate;
                tx.u.tx.last_frag_rate = store->last_frag_rate;
                tx.flags = 0;
                if (store->last_frag_rate_ctrl_probe)
                        tx.flags |= IEEE80211_TXRXD_TXPROBE_LAST_FRAG;
                ret = __ieee80211_tx(local, store->skb, &tx);
                if (ret) {
                        if (ret == IEEE80211_TX_FRAG_AGAIN)
                                store->skb = NULL;
                } else {
                        clear_bit(IEEE80211_LINK_STATE_PENDING,
                                  &local->state[i]);
                        reschedule = 1;
                }
        }
        netif_tx_unlock_bh(dev);
        if (reschedule) {
                if (!ieee80211_qdisc_installed(dev)) {
                        if (!__ieee80211_queue_stopped(local, 0))
                                netif_wake_queue(dev);
                } else
                        netif_schedule(dev);
        }
}

/* functions for drivers to get certain frames */

static void ieee80211_beacon_add_tim(struct ieee80211_local *local,
                                     struct ieee80211_if_ap *bss,
                                     struct sk_buff *skb)
{
        u8 *pos, *tim;
        int aid0 = 0;
        int i, have_bits = 0, n1, n2;

        /* Generate bitmap for TIM only if there are any STAs in power save
         * mode. */
        read_lock_bh(&local->sta_lock);
        if (atomic_read(&bss->num_sta_ps) > 0)
                /* in the hope that this is faster than
                 * checking byte-for-byte */
                have_bits = !bitmap_empty((unsigned long*)bss->tim,
                                          IEEE80211_MAX_AID+1);

        if (bss->dtim_count == 0)
                bss->dtim_count = bss->dtim_period - 1;
        else
                bss->dtim_count--;

        tim = pos = (u8 *) skb_put(skb, 6);
        *pos++ = WLAN_EID_TIM;
        *pos++ = 4;
        *pos++ = bss->dtim_count;
        *pos++ = bss->dtim_period;

        if (bss->dtim_count == 0 && !skb_queue_empty(&bss->ps_bc_buf))
                aid0 = 1;

        if (have_bits) {
                /* Find largest even number N1 so that bits numbered 1 through
                 * (N1 x 8) - 1 in the bitmap are 0 and number N2 so that bits
                 * (N2 + 1) x 8 through 2007 are 0. */
                n1 = 0;
                for (i = 0; i < IEEE80211_MAX_TIM_LEN; i++) {
                        if (bss->tim[i]) {
                                n1 = i & 0xfe;
                                break;
                        }
                }
                n2 = n1;
                for (i = IEEE80211_MAX_TIM_LEN - 1; i >= n1; i--) {
                        if (bss->tim[i]) {
                                n2 = i;
                                break;
                        }
                }

                /* Bitmap control */
                *pos++ = n1 | aid0;
                /* Part Virt Bitmap */
                memcpy(pos, bss->tim + n1, n2 - n1 + 1);

                tim[1] = n2 - n1 + 4;
                skb_put(skb, n2 - n1);
        } else {
                *pos++ = aid0; /* Bitmap control */
                *pos++ = 0; /* Part Virt Bitmap */
        }
        read_unlock_bh(&local->sta_lock);
}

struct sk_buff *ieee80211_beacon_get(struct ieee80211_hw *hw, int if_id,
                                     struct ieee80211_tx_control *control)
{
        struct ieee80211_local *local = hw_to_local(hw);
        struct sk_buff *skb;
        struct net_device *bdev;
        struct ieee80211_sub_if_data *sdata = NULL;
        struct ieee80211_if_ap *ap = NULL;
        struct rate_selection rsel;
        u8 *b_head, *b_tail;
        int bh_len, bt_len;

        bdev = dev_get_by_index(&init_net, if_id);
        if (bdev) {
                sdata = IEEE80211_DEV_TO_SUB_IF(bdev);
                ap = &sdata->u.ap;
                dev_put(bdev);
        }

        if (!ap || sdata->type != IEEE80211_IF_TYPE_AP ||
            !ap->beacon_head) {
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
                if (net_ratelimit())
                        printk(KERN_DEBUG "no beacon data avail for idx=%d "
                               "(%s)\n", if_id, bdev ? bdev->name : "N/A");
#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
                return NULL;
        }

        /* Assume we are generating the normal beacon locally */
        b_head = ap->beacon_head;
        b_tail = ap->beacon_tail;
        bh_len = ap->beacon_head_len;
        bt_len = ap->beacon_tail_len;

        skb = dev_alloc_skb(local->tx_headroom +
                bh_len + bt_len + 256 /* maximum TIM len */);
        if (!skb)
                return NULL;

        skb_reserve(skb, local->tx_headroom);
        memcpy(skb_put(skb, bh_len), b_head, bh_len);

        ieee80211_include_sequence(sdata, (struct ieee80211_hdr *)skb->data);

        ieee80211_beacon_add_tim(local, ap, skb);

        if (b_tail) {
                memcpy(skb_put(skb, bt_len), b_tail, bt_len);
        }

        if (control) {
                rate_control_get_rate(local->mdev, local->oper_hw_mode, skb,
                                      &rsel);
                if (!rsel.rate) {
                        if (net_ratelimit()) {
                                printk(KERN_DEBUG "%s: ieee80211_beacon_get: "
                                       "no rate found\n",
                                       wiphy_name(local->hw.wiphy));
                        }
                        dev_kfree_skb(skb);
                        return NULL;
                }

                control->tx_rate =
                        ((sdata->flags & IEEE80211_SDATA_SHORT_PREAMBLE) &&
                        (rsel.rate->flags & IEEE80211_RATE_PREAMBLE2)) ?
                        rsel.rate->val2 : rsel.rate->val;
                control->antenna_sel_tx = local->hw.conf.antenna_sel_tx;
                control->power_level = local->hw.conf.power_level;
                control->flags |= IEEE80211_TXCTL_NO_ACK;
                control->retry_limit = 1;
                control->flags |= IEEE80211_TXCTL_CLEAR_DST_MASK;
        }

        ap->num_beacons++;
        return skb;
}
EXPORT_SYMBOL(ieee80211_beacon_get);

void ieee80211_rts_get(struct ieee80211_hw *hw, int if_id,
                       const void *frame, size_t frame_len,
                       const struct ieee80211_tx_control *frame_txctl,
                       struct ieee80211_rts *rts)
{
        const struct ieee80211_hdr *hdr = frame;
        u16 fctl;

        fctl = IEEE80211_FTYPE_CTL | IEEE80211_STYPE_RTS;
        rts->frame_control = cpu_to_le16(fctl);
        rts->duration = ieee80211_rts_duration(hw, if_id, frame_len, frame_txctl);
        memcpy(rts->ra, hdr->addr1, sizeof(rts->ra));
        memcpy(rts->ta, hdr->addr2, sizeof(rts->ta));
}
EXPORT_SYMBOL(ieee80211_rts_get);

void ieee80211_ctstoself_get(struct ieee80211_hw *hw, int if_id,
                             const void *frame, size_t frame_len,
                             const struct ieee80211_tx_control *frame_txctl,
                             struct ieee80211_cts *cts)
{
        const struct ieee80211_hdr *hdr = frame;
        u16 fctl;

        fctl = IEEE80211_FTYPE_CTL | IEEE80211_STYPE_CTS;
        cts->frame_control = cpu_to_le16(fctl);
        cts->duration = ieee80211_ctstoself_duration(hw, if_id, frame_len, frame_txctl);
        memcpy(cts->ra, hdr->addr1, sizeof(cts->ra));
}
EXPORT_SYMBOL(ieee80211_ctstoself_get);

struct sk_buff *
ieee80211_get_buffered_bc(struct ieee80211_hw *hw, int if_id,
                          struct ieee80211_tx_control *control)
{
        struct ieee80211_local *local = hw_to_local(hw);
        struct sk_buff *skb;
        struct sta_info *sta;
        ieee80211_tx_handler *handler;
        struct ieee80211_txrx_data tx;
        ieee80211_txrx_result res = TXRX_DROP;
        struct net_device *bdev;
        struct ieee80211_sub_if_data *sdata;
        struct ieee80211_if_ap *bss = NULL;

        bdev = dev_get_by_index(&init_net, if_id);
        if (bdev) {
                sdata = IEEE80211_DEV_TO_SUB_IF(bdev);
                bss = &sdata->u.ap;
                dev_put(bdev);
        }
        if (!bss || sdata->type != IEEE80211_IF_TYPE_AP || !bss->beacon_head)
                return NULL;

        if (bss->dtim_count != 0)
                return NULL; /* send buffered bc/mc only after DTIM beacon */
        memset(control, 0, sizeof(*control));
        while (1) {
                skb = skb_dequeue(&bss->ps_bc_buf);
                if (!skb)
                        return NULL;
                local->total_ps_buffered--;

                if (!skb_queue_empty(&bss->ps_bc_buf) && skb->len >= 2) {
                        struct ieee80211_hdr *hdr =
                                (struct ieee80211_hdr *) skb->data;
                        /* more buffered multicast/broadcast frames ==> set
                         * MoreData flag in IEEE 802.11 header to inform PS
                         * STAs */
                        hdr->frame_control |=
                                cpu_to_le16(IEEE80211_FCTL_MOREDATA);
                }

                if (!ieee80211_tx_prepare(&tx, skb, local->mdev, control))
                        break;
                dev_kfree_skb_any(skb);
        }
        sta = tx.sta;
        tx.flags |= IEEE80211_TXRXD_TXPS_BUFFERED;
        tx.u.tx.mode = local->hw.conf.mode;

        for (handler = local->tx_handlers; *handler != NULL; handler++) {
                res = (*handler)(&tx);
                if (res == TXRX_DROP || res == TXRX_QUEUED)
                        break;
        }
        dev_put(tx.dev);
        skb = tx.skb; /* handlers are allowed to change skb */

        if (res == TXRX_DROP) {
                I802_DEBUG_INC(local->tx_handlers_drop);
                dev_kfree_skb(skb);
                skb = NULL;
        } else if (res == TXRX_QUEUED) {
                I802_DEBUG_INC(local->tx_handlers_queued);
                skb = NULL;
        }

        if (sta)
                sta_info_put(sta);

        return skb;
}
EXPORT_SYMBOL(ieee80211_get_buffered_bc);