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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_scanning != 0) &&
          ((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;
      }

      if (unlikely(/* !injected && */ tx->sdata->ieee802_1x &&
                 !(sta_flags & WLAN_STA_AUTHORIZED))) {
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
            DECLARE_MAC_BUF(mac);
            printk(KERN_DEBUG "%s: dropped frame to %s"
                   " (unauthorized port)\n", tx->dev->name,
                   print_mac(mac, hdr->addr1));
#endif
            I802_DEBUG_INC(tx->local->tx_handlers_drop_unauth_port);
            return TXRX_DROP;
      }

      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 inline 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 */
      if ((tx->local->hw.flags & IEEE80211_HW_HOST_BROADCAST_PS_BUFFERING) &&
          tx->sdata->type != IEEE80211_IF_TYPE_WDS &&
          tx->sdata->bss && atomic_read(&tx->sdata->bss->num_sta_ps) &&
          !(tx->fc & IEEE80211_FCTL_ORDER)) {
            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;
      }

      return TXRX_CONTINUE;
}

static inline 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;

      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->sdata->eapol && ieee80211_is_eapol(tx->skb))) {
            I802_DEBUG_INC(tx->local->tx_handlers_drop_unencrypted);
            return TXRX_DROP;
      } else {
            tx->key = NULL;
            tx->u.tx.control->flags |= IEEE80211_TXCTL_DO_NOT_ENCRYPT;
      }

      if (tx->key) {
            tx->key->tx_rx_count++;
            /* TODO: add threshold stuff again */
      }

      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_control_extra extra;

      if (likely(!tx->u.tx.rate)) {
            memset(&extra, 0, sizeof(extra));
            extra.mode = tx->u.tx.mode;
            extra.ethertype = tx->ethertype;

            tx->u.tx.rate = rate_control_get_rate(tx->local, tx->dev,
                                          tx->skb, &extra);
            if (unlikely(extra.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 = extra.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) && extra.nonerp) {
            tx->u.tx.last_frag_rate = tx->u.tx.rate;
            if (extra.probe)
                  tx->flags &= ~IEEE80211_TXRXD_TXPROBE_LAST_FRAG;
            else
                  tx->flags |= IEEE80211_TXRXD_TXPROBE_LAST_FRAG;
            tx->u.tx.rate = extra.nonerp;
            tx->u.tx.control->rate = extra.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;
                  }
            }
      }

      /*
       * Tell hardware to not encrypt when we had sw crypto.
       * Because we use the same flag to internally indicate that
       * no (software) encryption should be done, we have to set it
       * after all crypto handlers.
       */
      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_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;
      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;

      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];
      /* TODO: handling for 802.1x authorized/unauthorized port */
      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;
      }

      /* receiver is QoS enabled, use a QoS type frame */
      sta = sta_info_get(local, hdr.addr1);
      if (sta) {
            if (sta->flags & WLAN_STA_WME) {
                  fc |= IEEE80211_STYPE_QOS_DATA;
                  hdrlen += 2;
            }
            sta_info_put(sta);
      }

      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;

      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;
}

/*
 * This is the transmit routine for the 802.11 type interfaces
 * called by upper layers of the linux networking
 * stack when it has a frame to transmit
 */
int ieee80211_mgmt_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
      struct ieee80211_sub_if_data *sdata;
      struct ieee80211_tx_packet_data *pkt_data;
      struct ieee80211_hdr *hdr;
      u16 fc;

      sdata = IEEE80211_DEV_TO_SUB_IF(dev);

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

      if (skb_headroom(skb) < sdata->local->tx_headroom) {
            if (pskb_expand_head(skb, sdata->local->tx_headroom,
                             0, GFP_ATOMIC)) {
                  dev_kfree_skb(skb);
                  return 0;
            }
      }

      hdr = (struct ieee80211_hdr *) skb->data;
      fc = le16_to_cpu(hdr->frame_control);

      pkt_data = (struct ieee80211_tx_packet_data *) skb->cb;
      memset(pkt_data, 0, sizeof(struct ieee80211_tx_packet_data));
      pkt_data->ifindex = sdata->dev->ifindex;

      skb->priority = 20; /* use hardcoded priority for mgmt TX queue */
      skb->dev = sdata->local->mdev;

      /*
       * We're using the protocol field of the the frame control header
       * to request TX callback for hostapd. BIT(1) is checked.
       */
      if ((fc & BIT(1)) == BIT(1)) {
            pkt_data->flags |= IEEE80211_TXPD_REQ_TX_STATUS;
            fc &= ~BIT(1);
            hdr->frame_control = cpu_to_le16(fc);
      }

      if (!(fc & IEEE80211_FCTL_PROTECTED))
            pkt_data->flags |= IEEE80211_TXPD_DO_NOT_ENCRYPT;

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

      dev_queue_xmit(skb);

      return 0;
}

/* 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 ieee80211_rate *rate;
      struct rate_control_extra extra;
      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) {
            memset(&extra, 0, sizeof(extra));
            extra.mode = local->oper_hw_mode;

            rate = rate_control_get_rate(local, local->mdev, skb, &extra);
            if (!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) &&
                  (rate->flags & IEEE80211_RATE_PREAMBLE2)) ?
                  rate->val2 : 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);

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