madwifi/net80211/ieee80211_beacon.c

/*-
 * Copyright (c) 2001 Atsushi Onoe
 * Copyright (c) 2002-2005 Sam Leffler, Errno Consulting
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * $Id$
 */
#ifndef EXPORT_SYMTAB
#define	EXPORT_SYMTAB
#endif

/*
 * IEEE 802.11 beacon handling routines
 */
#ifndef AUTOCONF_INCLUDED
#include <linux/config.h>
#endif
#include <linux/version.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/if_vlan.h>

#include "if_media.h"
#include <net80211/ieee80211_var.h>


static u_int8_t *
ieee80211_beacon_init(struct ieee80211_node *ni, struct ieee80211_beacon_offsets *bo,
	u_int8_t *frm)
{
	struct ieee80211vap *vap = ni->ni_vap;
	struct ieee80211com *ic = ni->ni_ic;
	u_int16_t capinfo;
	struct ieee80211_rateset *rs = &ni->ni_rates;

	KASSERT(ic->ic_bsschan != IEEE80211_CHAN_ANYC, ("no bss chan"));

	/* XXX timestamp is set by hardware/driver */
	memset(frm, 0, 8);
	frm += 8;

	/* beacon interval */
	*(__le16 *)frm = htole16(ni->ni_intval);
	frm += 2;

	/* capability information */
	if (vap->iv_opmode == IEEE80211_M_IBSS)
		capinfo = IEEE80211_CAPINFO_IBSS;
	else
		capinfo = IEEE80211_CAPINFO_ESS;
	if (vap->iv_flags & IEEE80211_F_PRIVACY)
		capinfo |= IEEE80211_CAPINFO_PRIVACY;
	if ((ic->ic_flags & IEEE80211_F_SHPREAMBLE) &&
	    IEEE80211_IS_CHAN_2GHZ(ic->ic_bsschan))
		capinfo |= IEEE80211_CAPINFO_SHORT_PREAMBLE;
	if (ic->ic_flags & IEEE80211_F_SHSLOT)
		capinfo |= IEEE80211_CAPINFO_SHORT_SLOTTIME;
	if (ic->ic_flags & IEEE80211_F_DOTH)
		capinfo |= IEEE80211_CAPINFO_SPECTRUM_MGMT;
	bo->bo_caps = (__le16 *)frm;
	*(__le16 *)frm = htole16(capinfo);
	frm += 2;

	/* ssid */
	*frm++ = IEEE80211_ELEMID_SSID;
	if ((vap->iv_flags & IEEE80211_F_HIDESSID) == 0) {
		*frm++ = ni->ni_esslen;
		memcpy(frm, ni->ni_essid, ni->ni_esslen);
		frm += ni->ni_esslen;
	} else
		*frm++ = 0;

	/* supported rates */
	frm = ieee80211_add_rates(frm, rs);


	/* XXX: better way to check this? */
	/* XXX: how about DS ? */
	if (!IEEE80211_IS_CHAN_FHSS(ic->ic_bsschan)) {
		*frm++ = IEEE80211_ELEMID_DSPARMS;
		*frm++ = 1;
		*frm++ = ieee80211_chan2ieee(ic, ic->ic_bsschan);
	}
	bo->bo_tim = frm;

	/* IBSS/TIM */
	if (vap->iv_opmode == IEEE80211_M_IBSS) {
		*frm++ = IEEE80211_ELEMID_IBSSPARMS;
		*frm++ = 2;
		*frm++ = 0; *frm++ = 0;		/* TODO: ATIM window */
		bo->bo_tim_len = 0;
	} else {
		struct ieee80211_tim_ie *tie = (struct ieee80211_tim_ie *)frm;

		tie->tim_ie = IEEE80211_ELEMID_TIM;
		tie->tim_len = 4;	/* length */
		tie->tim_count = 0;	/* DTIM count */
		tie->tim_period = vap->iv_dtim_period;	/* DTIM period */
		tie->tim_bitctl = 0;	/* bitmap control */
		tie->tim_bitmap[0] = 0;	/* Partial Virtual Bitmap */
		frm += sizeof(struct ieee80211_tim_ie);
		bo->bo_tim_len = 1;
	}
	bo->bo_tim_trailer = frm;

	/* country */
	if ((ic->ic_flags & IEEE80211_F_DOTH) ||
	    (ic->ic_flags_ext & IEEE80211_FEXT_COUNTRYIE))
		frm = ieee80211_add_country(frm, ic);

	/* power constraint */
	if (ic->ic_flags & IEEE80211_F_DOTH)
		frm = ieee80211_add_pwrcnstr(frm, ic);

	/* channel switch announcement */
	bo->bo_chanswitch = frm;

	/* ERP */
	if (IEEE80211_IS_CHAN_ANYG(ic->ic_bsschan)) {
		bo->bo_erp = frm;
		frm = ieee80211_add_erp(frm, ic);
	}

	/* Ext. Supp. Rates */
	frm = ieee80211_add_xrates(frm, rs);

	/* WME */
	if (vap->iv_flags & IEEE80211_F_WME) {
		bo->bo_wme = frm;
		frm = ieee80211_add_wme_param(frm, &ic->ic_wme, IEEE80211_VAP_UAPSD_ENABLED(vap));
		vap->iv_flags &= ~IEEE80211_F_WMEUPDATE;
	}

	/* WPA 1+2 */
	if (vap->iv_flags & IEEE80211_F_WPA)
		frm = ieee80211_add_wpa(frm, vap);

	/* athAdvCaps */
	bo->bo_ath_caps = frm;
	if (vap->iv_bss && vap->iv_bss->ni_ath_flags)
		frm = ieee80211_add_athAdvCap(frm, vap->iv_bss->ni_ath_flags,
			vap->iv_bss->ni_ath_defkeyindex);

	/* XR */
	bo->bo_xr = frm;
#ifdef ATH_SUPERG_XR
	if (vap->iv_xrvap && vap->iv_ath_cap & IEEE80211_ATHC_XR)	/* XR */
		frm = ieee80211_add_xr_param(frm, vap);
#endif
	bo->bo_appie_buf = frm;
	bo->bo_appie_buf_len = 0;

	bo->bo_tim_trailerlen = frm - bo->bo_tim_trailer;
	bo->bo_chanswitch_trailerlen = frm - bo->bo_chanswitch;

	return frm;
}


/*
 * Allocate a beacon frame and fillin the appropriate bits.
 */
struct sk_buff *
ieee80211_beacon_alloc(struct ieee80211_node *ni,
	struct ieee80211_beacon_offsets *bo)
{
	struct ieee80211vap *vap = ni->ni_vap;
	struct ieee80211com *ic = ni->ni_ic;
	struct ieee80211_frame *wh;
	struct sk_buff *skb;
	int pktlen;
	u_int8_t *frm;
	struct ieee80211_rateset *rs;

	/*
	 * beacon frame format
	 *	[8] time stamp
	 *	[2] beacon interval
	 *	[2] capability information
	 *	[tlv] ssid
	 *	[tlv] supported rates
	 *	[7] FH/DS parameter set
	 *	[tlv] IBSS/TIM parameter set
	 *	[tlv] country code 
	 *	[3] power constraint
	 *	[5] channel switch announcement
	 *	[3] extended rate phy (ERP)
	 *	[tlv] extended supported rates
	 *	[tlv] WME parameters
	 *	[tlv] WPA/RSN parameters
	 *	[tlv] Atheros Advanced Capabilities
	 *	[tlv] AtherosXR parameters
	 * XXX Vendor-specific OIDs (e.g. Atheros)
	 * NB: we allocate the max space required for the TIM bitmap.
	 */
	rs = &ni->ni_rates;
	pktlen = 8					/* time stamp */
		 + sizeof(u_int16_t)			/* beacon interval */
		 + sizeof(u_int16_t)			/* capability information */
		 + 2 + ni->ni_esslen			/* ssid */
		 + 2 + IEEE80211_RATE_SIZE		/* supported rates */
		 + 7 					/* FH/DS parameters max(7,3) */
		 + 2 + 4 + vap->iv_tim_len		/* IBSS/TIM parameter set*/
		 + ic->ic_country_ie.country_len + 2	/* country code */
		 + 3					/* power constraint */
		 + 5					/* channel switch announcement */
		 + 3					/* ERP */
		 + 2 + (IEEE80211_RATE_MAXSIZE - IEEE80211_RATE_SIZE) /* Ext. Supp. Rates */
		 + (vap->iv_caps & IEEE80211_C_WME ?	/* WME */
			sizeof(struct ieee80211_wme_param) : 0)
		 + (vap->iv_caps & IEEE80211_C_WPA ?	/* WPA 1+2 */
			2 * sizeof(struct ieee80211_ie_wpa) : 0)
		 + sizeof(struct ieee80211_ie_athAdvCap)
#ifdef ATH_SUPERG_XR
		 + (ic->ic_ath_cap & IEEE80211_ATHC_XR ?	/* XR */
			sizeof(struct ieee80211_xr_param) : 0)
#endif
		 ;
	skb = ieee80211_getmgtframe(&frm, pktlen);
	if (skb == NULL) {
		IEEE80211_NOTE(vap, IEEE80211_MSG_ANY, ni,
			"%s: cannot get buf; size %u", __func__, pktlen);
		vap->iv_stats.is_tx_nobuf++;
		return NULL;
	}

	SKB_NI(skb) = ieee80211_ref_node(ni);

	frm = ieee80211_beacon_init(ni, bo, frm);

	skb_trim(skb, frm - skb->data);

	wh = (struct ieee80211_frame *)
		skb_push(skb, sizeof(struct ieee80211_frame));
	wh->i_fc[0] = IEEE80211_FC0_VERSION_0 | IEEE80211_FC0_TYPE_MGT |
		IEEE80211_FC0_SUBTYPE_BEACON;
	wh->i_fc[1] = IEEE80211_FC1_DIR_NODS;
	wh->i_dur = 0;
	IEEE80211_ADDR_COPY(wh->i_addr1, ic->ic_dev->broadcast);
	IEEE80211_ADDR_COPY(wh->i_addr2, vap->iv_myaddr);
	IEEE80211_ADDR_COPY(wh->i_addr3, vap->iv_bssid);
	IEEE80211_DPRINTF(vap, IEEE80211_MSG_ASSOC,
			  "%s: beacon bssid:" MAC_FMT "\n",
			  __func__, MAC_ADDR(wh->i_addr3));
	*(u_int16_t *)wh->i_seq = 0;

	return skb;
}
EXPORT_SYMBOL(ieee80211_beacon_alloc);

/*
 * Update the dynamic parts of a beacon frame based on the current state.
 */
int
ieee80211_beacon_update(struct ieee80211_node *ni,
	struct ieee80211_beacon_offsets *bo, struct sk_buff *skb, 
	int mcast, int *is_dtim)
{
	struct ieee80211vap *vap = ni->ni_vap;
	struct ieee80211com *ic = ni->ni_ic;
	int len_changed = 0;
	u_int8_t *frm;
	u_int16_t capinfo;

	IEEE80211_LOCK_IRQ(ic);

	/* Check if channel switch is over, in which case we recompute beacon
	 * content */
	if ((ic->ic_flags & IEEE80211_F_DOTH) &&
	    !(ic->ic_flags & IEEE80211_F_CHANSWITCH) &&
	    (vap->iv_flags & IEEE80211_F_CHANSWITCH)) {
		IEEE80211_DPRINTF(vap, IEEE80211_MSG_DOTH,
				  "%s: reinit beacon\n", __func__);

		vap->iv_flags &= ~IEEE80211_F_CHANSWITCH;

		skb_pull(skb, sizeof(struct ieee80211_frame));
		skb_trim(skb, 0);
		frm = skb->data;
		skb_put(skb, ieee80211_beacon_init(ni, bo, frm) - frm);
		skb_push(skb, sizeof(struct ieee80211_frame));

		len_changed = 1;
	}

	/* XXX faster to recalculate entirely or just changes? */
	if (vap->iv_opmode == IEEE80211_M_IBSS)
		capinfo = IEEE80211_CAPINFO_IBSS;
	else
		capinfo = IEEE80211_CAPINFO_ESS;

	if (vap->iv_flags & IEEE80211_F_PRIVACY)
		capinfo |= IEEE80211_CAPINFO_PRIVACY;
	if ((ic->ic_flags & IEEE80211_F_SHPREAMBLE) &&
	    IEEE80211_IS_CHAN_2GHZ(ic->ic_bsschan))
		capinfo |= IEEE80211_CAPINFO_SHORT_PREAMBLE;
	if (ic->ic_flags & IEEE80211_F_SHSLOT)
		capinfo |= IEEE80211_CAPINFO_SHORT_SLOTTIME;
	if (ic->ic_flags & IEEE80211_F_DOTH)
		capinfo |= IEEE80211_CAPINFO_SPECTRUM_MGMT;

	*bo->bo_caps = htole16(capinfo);

	if (vap->iv_flags & IEEE80211_F_WME) {
		struct ieee80211_wme_state *wme = &ic->ic_wme;

		/*
		 * Check for aggressive mode change.  When there is
		 * significant high priority traffic in the BSS
		 * throttle back BE traffic by using conservative
		 * parameters.  Otherwise BE uses aggressive params
		 * to optimize performance of legacy/non-QoS traffic.
		 */
		if (wme->wme_flags & WME_F_AGGRMODE) {
			if (wme->wme_hipri_traffic >
			    wme->wme_hipri_switch_thresh) {
				IEEE80211_NOTE(vap, IEEE80211_MSG_WME, ni,
					"%s: traffic %u, disable aggressive mode",
					__func__, wme->wme_hipri_traffic);
				wme->wme_flags &= ~WME_F_AGGRMODE;
				ieee80211_wme_updateparams_locked(vap);
				wme->wme_hipri_traffic =
					wme->wme_hipri_switch_hysteresis;
			} else
				wme->wme_hipri_traffic = 0;
		} else {
			if (wme->wme_hipri_traffic <=
			    wme->wme_hipri_switch_thresh) {
				IEEE80211_NOTE(vap, IEEE80211_MSG_WME, ni,
					"%s: traffic %u, enable aggressive mode",
					__func__, wme->wme_hipri_traffic);
				wme->wme_flags |= WME_F_AGGRMODE;
				ieee80211_wme_updateparams_locked(vap);
				wme->wme_hipri_traffic = 0;
			} else
				wme->wme_hipri_traffic =
					wme->wme_hipri_switch_hysteresis;
		}
		/* XXX multi-bss */
		if (vap->iv_flags & IEEE80211_F_WMEUPDATE) {
			(void) ieee80211_add_wme_param(bo->bo_wme, wme, IEEE80211_VAP_UAPSD_ENABLED(vap));
			vap->iv_flags &= ~IEEE80211_F_WMEUPDATE;
		}
	}

	if (vap->iv_opmode == IEEE80211_M_HOSTAP) {	/* NB: no IBSS support*/
		struct ieee80211_tim_ie *tie =
			(struct ieee80211_tim_ie *)bo->bo_tim;
		if (vap->iv_flags & IEEE80211_F_TIMUPDATE) {
			u_int timlen, timoff, i;
			/*
			 * ATIM/DTIM needs updating.  If it fits in the
			 * current space allocated then just copy in the
			 * new bits.  Otherwise we need to move any trailing
			 * data to make room.  Note that we know there is
			 * contiguous space because ieee80211_beacon_allocate
			 * ensures there is space in the mbuf to write a
			 * maximal-size virtual bitmap (based on ic_max_aid).
			 */
			/*
			 * Calculate the bitmap size and offset, copy any
			 * trailer out of the way, and then copy in the
			 * new bitmap and update the information element.
			 * Note that the tim bitmap must contain at least
			 * one byte and any offset must be even.
			 */
			if (vap->iv_ps_pending != 0) {
				timoff = 128;		/* impossibly large */
				for (i = 0; i < vap->iv_tim_len; i++)
					if (vap->iv_tim_bitmap[i]) {
						timoff = i & BITCTL_BUFD_UCAST_AID_MASK;
						break;
					}
				KASSERT(timoff != 128, ("tim bitmap empty!"));
				for (i = vap->iv_tim_len-1; i >= timoff; i--)
					if (vap->iv_tim_bitmap[i])
						break;
				timlen = 1 + (i - timoff);
			} else {
				timoff = 0;
				timlen = 1;
			}
			if (timlen != bo->bo_tim_len) {
				/* copy up/down trailer */
				int trailer_adjust =
					(tie->tim_bitmap+timlen) - (bo->bo_tim_trailer);
				memmove(tie->tim_bitmap+timlen, bo->bo_tim_trailer,
					bo->bo_tim_trailerlen);
				bo->bo_tim_trailer = tie->tim_bitmap+timlen;
				bo->bo_chanswitch += trailer_adjust;
				bo->bo_wme += trailer_adjust;
				bo->bo_erp += trailer_adjust;
				bo->bo_ath_caps += trailer_adjust;
				bo->bo_xr += trailer_adjust;
				if (timlen > bo->bo_tim_len)
					skb_put(skb, timlen - bo->bo_tim_len);
				else
					skb_trim(skb, skb->len - (bo->bo_tim_len - timlen));
				bo->bo_tim_len = timlen;

				/* update information element */
				tie->tim_len = 3 + timlen;
				tie->tim_bitctl = timoff;
				len_changed = 1;
			}
			memcpy(tie->tim_bitmap, vap->iv_tim_bitmap + timoff,
				bo->bo_tim_len);

			vap->iv_flags &= ~IEEE80211_F_TIMUPDATE;

			IEEE80211_NOTE(vap, IEEE80211_MSG_POWER, ni,
				"%s: TIM updated, pending %u, off %u, len %u",
				__func__, vap->iv_ps_pending, timoff, timlen);
		}
		/* count down DTIM period */
		if (tie->tim_count == 0)
			tie->tim_count = tie->tim_period - 1;
		else
			tie->tim_count--;
		/* update state for buffered multicast frames on DTIM */
		if (mcast && (tie->tim_count == 0))
			tie->tim_bitctl |= BITCTL_BUFD_MCAST;
		else
			tie->tim_bitctl &= ~BITCTL_BUFD_MCAST;
		*is_dtim = (tie->tim_count == 0);
	}

	/* Whenever we want to switch to a new channel, we just need to call
	 * ieee80211_start_new_csa() which will set :
	 *
	 * - ic_csa_mode = IEEE80211_CSA_{CAN|MUST}_STOP_TX
	 * - ic_csa_chan = pointer to struct ieee80211_channel
	 * - ic_csa_expires_tu = switch time in TU
	 * - mod_timer(&ic_csa_timer, expires) = switch time in jiffies
	 * - ic_flags |= IEEE80211_F_CHANSWITCH */

	if (IEEE80211_IS_MODE_BEACON(vap->iv_opmode)) {

		if ((ic->ic_flags & IEEE80211_F_DOTH) &&
		    (ic->ic_flags & IEEE80211_F_CHANSWITCH)) {
			struct ieee80211_ie_csa *csa_ie =
				(struct ieee80211_ie_csa *)bo->bo_chanswitch;
			u_int32_t now_tu, nexttbtt;

			if (!(vap->iv_flags & IEEE80211_F_CHANSWITCH)) {
				vap->iv_flags |= IEEE80211_F_CHANSWITCH;

				/* copy out trailer to open up a slot */
				memmove(bo->bo_chanswitch + sizeof(*csa_ie),
					bo->bo_chanswitch, 
					bo->bo_chanswitch_trailerlen);

				/* add ie in opened slot */
				csa_ie->csa_id = IEEE80211_ELEMID_CHANSWITCHANN;
				/* fixed length */
				csa_ie->csa_len = sizeof(*csa_ie) - 2;

				/* update the trailer lens */
				bo->bo_chanswitch_trailerlen += sizeof(*csa_ie);
				bo->bo_tim_trailerlen += sizeof(*csa_ie);
				bo->bo_wme += sizeof(*csa_ie);
				bo->bo_erp += sizeof(*csa_ie);
				bo->bo_ath_caps += sizeof(*csa_ie);
				bo->bo_xr += sizeof(*csa_ie);

				/* indicate new beacon length so other layers
				 * may manage memory */
				skb_put(skb, sizeof(*csa_ie));
				len_changed = 1;
			}

			now_tu   = IEEE80211_TSF_TO_TU(vap->iv_get_tsf(vap));
			nexttbtt = vap->iv_get_nexttbtt(vap);

			csa_ie->csa_mode = ic->ic_csa_mode;
			csa_ie->csa_chan = ic->ic_csa_chan->ic_ieee;

			IEEE80211_DPRINTF(vap, IEEE80211_MSG_DOTH,
					  "%s: now_tu:%ld nexttbtt_tu:%ld "
					  "=> expires_tu:%ld\n",
					  __func__, now_tu, nexttbtt,
					  ic->ic_csa_expires_tu);

			if (ic->ic_csa_expires_tu > nexttbtt) {
				csa_ie->csa_count =
					(ic->ic_csa_expires_tu - nexttbtt)
					/ vap->iv_bss->ni_intval;
			} else {
				csa_ie->csa_count = 0;
			}

			/* Since beaconing is a shared process in IBSS mode,
			 * we send Action frames as well. */
			if (vap->iv_opmode == IEEE80211_M_IBSS) {
				ieee80211_send_csa_frame(vap,
							 csa_ie->csa_mode,
							 csa_ie->csa_chan,
							 csa_ie->csa_count);
			}

			IEEE80211_DPRINTF(vap, IEEE80211_MSG_DOTH,
					  "%s: Sending beacon frame with "
					  "CSA IE: %u/%u/%u\n", __func__,
					  csa_ie->csa_mode,
					  csa_ie->csa_chan,
					  csa_ie->csa_count);
		}
#ifdef ATH_SUPERG_XR
		if (vap->iv_flags & IEEE80211_F_XRUPDATE) {
			if (vap->iv_xrvap)
				(void)ieee80211_add_xr_param(bo->bo_xr, vap);
			vap->iv_flags &= ~IEEE80211_F_XRUPDATE;
		}
#endif
		if ((ic->ic_flags_ext & IEEE80211_FEXT_ERPUPDATE) && 
				(bo->bo_erp != NULL)) {
			(void)ieee80211_add_erp(bo->bo_erp, ic);
			ic->ic_flags_ext &= ~IEEE80211_FEXT_ERPUPDATE;
		}
	}
	/* if it is a mode change beacon for dynamic turbo case */
	if (((ic->ic_ath_cap & IEEE80211_ATHC_BOOST) != 0) ^
	    IEEE80211_IS_CHAN_TURBO(ic->ic_curchan))
		ieee80211_add_athAdvCap(bo->bo_ath_caps, 
				vap->iv_bss->ni_ath_flags,
				vap->iv_bss->ni_ath_defkeyindex);
	/* add APP_IE buffer if app updated it */
	if (vap->iv_flags_ext & IEEE80211_FEXT_APPIE_UPDATE) {
		/* adjust the buffer size if the size is changed */
		if (vap->app_ie[IEEE80211_APPIE_FRAME_BEACON].length != 
				bo->bo_appie_buf_len) {
			int diff_len;
			diff_len = 
				vap->app_ie[IEEE80211_APPIE_FRAME_BEACON].
					length - 
				bo->bo_appie_buf_len;

			if (diff_len > 0)
				skb_put(skb, diff_len);
			else
				skb_trim(skb, skb->len + diff_len);

			bo->bo_appie_buf_len = 
				vap->app_ie[IEEE80211_APPIE_FRAME_BEACON].
					length;
			/* update the trailer lens */
			bo->bo_chanswitch_trailerlen += diff_len;
			bo->bo_tim_trailerlen += diff_len;

			len_changed = 1;
		}
		memcpy(bo->bo_appie_buf, 
			vap->app_ie[IEEE80211_APPIE_FRAME_BEACON].ie,
			vap->app_ie[IEEE80211_APPIE_FRAME_BEACON].length);

		vap->iv_flags_ext &= ~IEEE80211_FEXT_APPIE_UPDATE;
	}

	IEEE80211_UNLOCK_IRQ(ic);

	return len_changed;
}
EXPORT_SYMBOL(ieee80211_beacon_update);