FreeBSD/Linux Kernel Cross Reference
sys/net80211/ieee80211_output.c

     /*-
      * Copyright (c) 2001 Atsushi Onoe
      * Copyright (c) 2002-2009 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.
     *
     * 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.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/11.0/sys/net80211/ieee80211_output.c 301731 2016-06-09 13:42:18Z avos $");
    
    #include "opt_inet.h"
    #include "opt_inet6.h"
    #include "opt_wlan.h"
    
    #include <sys/param.h>
    #include <sys/systm.h> 
    #include <sys/kernel.h>
    #include <sys/malloc.h>
    #include <sys/mbuf.h>   
    #include <sys/endian.h>
    
    #include <sys/socket.h>
     
    #include <net/bpf.h>
    #include <net/ethernet.h>
    #include <net/if.h>
    #include <net/if_var.h>
    #include <net/if_llc.h>
    #include <net/if_media.h>
    #include <net/if_vlan_var.h>
    
    #include <net80211/ieee80211_var.h>
    #include <net80211/ieee80211_regdomain.h>
    #ifdef IEEE80211_SUPPORT_SUPERG
    #include <net80211/ieee80211_superg.h>
    #endif
    #ifdef IEEE80211_SUPPORT_TDMA
    #include <net80211/ieee80211_tdma.h>
    #endif
    #include <net80211/ieee80211_wds.h>
    #include <net80211/ieee80211_mesh.h>
    
    #if defined(INET) || defined(INET6)
    #include <netinet/in.h> 
    #endif
    
    #ifdef INET
    #include <netinet/if_ether.h>
    #include <netinet/in_systm.h>
    #include <netinet/ip.h>
    #endif
    #ifdef INET6
    #include <netinet/ip6.h>
    #endif
    
    #include <security/mac/mac_framework.h>
    
    #define ETHER_HEADER_COPY(dst, src) \
            memcpy(dst, src, sizeof(struct ether_header))
    
    static int ieee80211_fragment(struct ieee80211vap *, struct mbuf *,
            u_int hdrsize, u_int ciphdrsize, u_int mtu);
    static  void ieee80211_tx_mgt_cb(struct ieee80211_node *, void *, int);
    
    #ifdef IEEE80211_DEBUG
    /*
     * Decide if an outbound management frame should be
     * printed when debugging is enabled.  This filters some
     * of the less interesting frames that come frequently
     * (e.g. beacons).
     */
    static __inline int
    doprint(struct ieee80211vap *vap, int subtype)
    {
            switch (subtype) {
            case IEEE80211_FC0_SUBTYPE_PROBE_RESP:
                    return (vap->iv_opmode == IEEE80211_M_IBSS);
            }
            return 1;
    }
   #endif
   
   /*
    * Transmit a frame to the given destination on the given VAP.
    *
    * It's up to the caller to figure out the details of who this
    * is going to and resolving the node.
    *
    * This routine takes care of queuing it for power save,
    * A-MPDU state stuff, fast-frames state stuff, encapsulation
    * if required, then passing it up to the driver layer.
    *
    * This routine (for now) consumes the mbuf and frees the node
    * reference; it ideally will return a TX status which reflects
    * whether the mbuf was consumed or not, so the caller can
    * free the mbuf (if appropriate) and the node reference (again,
    * if appropriate.)
    */
   int
   ieee80211_vap_pkt_send_dest(struct ieee80211vap *vap, struct mbuf *m,
       struct ieee80211_node *ni)
   {
           struct ieee80211com *ic = vap->iv_ic;
           struct ifnet *ifp = vap->iv_ifp;
   #ifdef IEEE80211_SUPPORT_SUPERG
           int mcast;
   #endif
   
           if ((ni->ni_flags & IEEE80211_NODE_PWR_MGT) &&
               (m->m_flags & M_PWR_SAV) == 0) {
                   /*
                    * Station in power save mode; pass the frame
                    * to the 802.11 layer and continue.  We'll get
                    * the frame back when the time is right.
                    * XXX lose WDS vap linkage?
                    */
                   if (ieee80211_pwrsave(ni, m) != 0)
                           if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                   ieee80211_free_node(ni);
   
                   /*
                    * We queued it fine, so tell the upper layer
                    * that we consumed it.
                    */
                   return (0);
           }
           /* calculate priority so drivers can find the tx queue */
           if (ieee80211_classify(ni, m)) {
                   IEEE80211_DISCARD_MAC(vap, IEEE80211_MSG_OUTPUT,
                       ni->ni_macaddr, NULL,
                       "%s", "classification failure");
                   vap->iv_stats.is_tx_classify++;
                   if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                   m_freem(m);
                   ieee80211_free_node(ni);
   
                   /* XXX better status? */
                   return (0);
           }
           /*
            * Stash the node pointer.  Note that we do this after
            * any call to ieee80211_dwds_mcast because that code
            * uses any existing value for rcvif to identify the
            * interface it (might have been) received on.
            */
           m->m_pkthdr.rcvif = (void *)ni;
   #ifdef IEEE80211_SUPPORT_SUPERG
           mcast = (m->m_flags & (M_MCAST | M_BCAST)) ? 1: 0;
   #endif
   
           BPF_MTAP(ifp, m);               /* 802.3 tx */
   
           /*
            * Check if A-MPDU tx aggregation is setup or if we
            * should try to enable it.  The sta must be associated
            * with HT and A-MPDU enabled for use.  When the policy
            * routine decides we should enable A-MPDU we issue an
            * ADDBA request and wait for a reply.  The frame being
            * encapsulated will go out w/o using A-MPDU, or possibly
            * it might be collected by the driver and held/retransmit.
            * The default ic_ampdu_enable routine handles staggering
            * ADDBA requests in case the receiver NAK's us or we are
            * otherwise unable to establish a BA stream.
            */
           if ((ni->ni_flags & IEEE80211_NODE_AMPDU_TX) &&
               (vap->iv_flags_ht & IEEE80211_FHT_AMPDU_TX)) {
                   if ((m->m_flags & M_EAPOL) == 0) {
                           int tid = WME_AC_TO_TID(M_WME_GETAC(m));
                           struct ieee80211_tx_ampdu *tap = &ni->ni_tx_ampdu[tid];
   
                           ieee80211_txampdu_count_packet(tap);
                           if (IEEE80211_AMPDU_RUNNING(tap)) {
                                   /*
                                    * Operational, mark frame for aggregation.
                                    *
                                    * XXX do tx aggregation here
                                    */
                                   m->m_flags |= M_AMPDU_MPDU;
                           } else if (!IEEE80211_AMPDU_REQUESTED(tap) &&
                               ic->ic_ampdu_enable(ni, tap)) {
                                   /*
                                    * Not negotiated yet, request service.
                                    */
                                   ieee80211_ampdu_request(ni, tap);
                                   /* XXX hold frame for reply? */
                           }
                   }
           }
   
   #ifdef IEEE80211_SUPPORT_SUPERG
           /*
            * Check for AMSDU/FF; queue for aggregation
            *
            * Note: we don't bother trying to do fast frames or
            * A-MSDU encapsulation for 802.3 drivers.  Now, we
            * likely could do it for FF (because it's a magic
            * atheros tunnel LLC type) but I don't think we're going
            * to really need to.  For A-MSDU we'd have to set the
            * A-MSDU QoS bit in the wifi header, so we just plain
            * can't do it.
            *
            * Strictly speaking, we could actually /do/ A-MSDU / FF
            * with A-MPDU together which for certain circumstances
            * is beneficial (eg A-MSDU of TCK ACKs.)  However,
            * I'll ignore that for now so existing behaviour is maintained.
            * Later on it would be good to make "amsdu + ampdu" configurable.
            */
           else if (__predict_true((vap->iv_caps & IEEE80211_C_8023ENCAP) == 0)) {
                   if ((! mcast) && ieee80211_amsdu_tx_ok(ni)) {
                           m = ieee80211_amsdu_check(ni, m);
                           if (m == NULL) {
                                   /* NB: any ni ref held on stageq */
                                   IEEE80211_DPRINTF(vap, IEEE80211_MSG_SUPERG,
                                       "%s: amsdu_check queued frame\n",
                                       __func__);
                                   return (0);
                           }
                   } else if ((! mcast) && IEEE80211_ATH_CAP(vap, ni,
                       IEEE80211_NODE_FF)) {
                           m = ieee80211_ff_check(ni, m);
                           if (m == NULL) {
                                   /* NB: any ni ref held on stageq */
                                   IEEE80211_DPRINTF(vap, IEEE80211_MSG_SUPERG,
                                       "%s: ff_check queued frame\n",
                                       __func__);
                                   return (0);
                           }
                   }
           }
   #endif /* IEEE80211_SUPPORT_SUPERG */
   
           /*
            * Grab the TX lock - serialise the TX process from this
            * point (where TX state is being checked/modified)
            * through to driver queue.
            */
           IEEE80211_TX_LOCK(ic);
   
           /*
            * XXX make the encap and transmit code a separate function
            * so things like the FF (and later A-MSDU) path can just call
            * it for flushed frames.
            */
           if (__predict_true((vap->iv_caps & IEEE80211_C_8023ENCAP) == 0)) {
                   /*
                    * Encapsulate the packet in prep for transmission.
                    */
                   m = ieee80211_encap(vap, ni, m);
                   if (m == NULL) {
                           /* NB: stat+msg handled in ieee80211_encap */
                           IEEE80211_TX_UNLOCK(ic);
                           ieee80211_free_node(ni);
                           if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                           return (ENOBUFS);
                   }
           }
           (void) ieee80211_parent_xmitpkt(ic, m);
   
           /*
            * Unlock at this point - no need to hold it across
            * ieee80211_free_node() (ie, the comlock)
            */
           IEEE80211_TX_UNLOCK(ic);
           ic->ic_lastdata = ticks;
   
           return (0);
   }
   
   
   
   /*
    * Send the given mbuf through the given vap.
    *
    * This consumes the mbuf regardless of whether the transmit
    * was successful or not.
    *
    * This does none of the initial checks that ieee80211_start()
    * does (eg CAC timeout, interface wakeup) - the caller must
    * do this first.
    */
   static int
   ieee80211_start_pkt(struct ieee80211vap *vap, struct mbuf *m)
   {
   #define IS_DWDS(vap) \
           (vap->iv_opmode == IEEE80211_M_WDS && \
            (vap->iv_flags_ext & IEEE80211_FEXT_WDSLEGACY) == 0)
           struct ieee80211com *ic = vap->iv_ic;
           struct ifnet *ifp = vap->iv_ifp;
           struct ieee80211_node *ni;
           struct ether_header *eh;
   
           /*
            * Cancel any background scan.
            */
           if (ic->ic_flags & IEEE80211_F_SCAN)
                   ieee80211_cancel_anyscan(vap);
           /* 
            * Find the node for the destination so we can do
            * things like power save and fast frames aggregation.
            *
            * NB: past this point various code assumes the first
            *     mbuf has the 802.3 header present (and contiguous).
            */
           ni = NULL;
           if (m->m_len < sizeof(struct ether_header) &&
              (m = m_pullup(m, sizeof(struct ether_header))) == NULL) {
                   IEEE80211_DPRINTF(vap, IEEE80211_MSG_OUTPUT,
                       "discard frame, %s\n", "m_pullup failed");
                   vap->iv_stats.is_tx_nobuf++;    /* XXX */
                   if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                   return (ENOBUFS);
           }
           eh = mtod(m, struct ether_header *);
           if (ETHER_IS_MULTICAST(eh->ether_dhost)) {
                   if (IS_DWDS(vap)) {
                           /*
                            * Only unicast frames from the above go out
                            * DWDS vaps; multicast frames are handled by
                            * dispatching the frame as it comes through
                            * the AP vap (see below).
                            */
                           IEEE80211_DISCARD_MAC(vap, IEEE80211_MSG_WDS,
                               eh->ether_dhost, "mcast", "%s", "on DWDS");
                           vap->iv_stats.is_dwds_mcast++;
                           m_freem(m);
                           if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                           /* XXX better status? */
                           return (ENOBUFS);
                   }
                   if (vap->iv_opmode == IEEE80211_M_HOSTAP) {
                           /*
                            * Spam DWDS vap's w/ multicast traffic.
                            */
                           /* XXX only if dwds in use? */
                           ieee80211_dwds_mcast(vap, m);
                   }
           }
   #ifdef IEEE80211_SUPPORT_MESH
           if (vap->iv_opmode != IEEE80211_M_MBSS) {
   #endif
                   ni = ieee80211_find_txnode(vap, eh->ether_dhost);
                   if (ni == NULL) {
                           /* NB: ieee80211_find_txnode does stat+msg */
                           if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                           m_freem(m);
                           /* XXX better status? */
                           return (ENOBUFS);
                   }
                   if (ni->ni_associd == 0 &&
                       (ni->ni_flags & IEEE80211_NODE_ASSOCID)) {
                           IEEE80211_DISCARD_MAC(vap, IEEE80211_MSG_OUTPUT,
                               eh->ether_dhost, NULL,
                               "sta not associated (type 0x%04x)",
                               htons(eh->ether_type));
                           vap->iv_stats.is_tx_notassoc++;
                           if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                           m_freem(m);
                           ieee80211_free_node(ni);
                           /* XXX better status? */
                           return (ENOBUFS);
                   }
   #ifdef IEEE80211_SUPPORT_MESH
           } else {
                   if (!IEEE80211_ADDR_EQ(eh->ether_shost, vap->iv_myaddr)) {
                           /*
                            * Proxy station only if configured.
                            */
                           if (!ieee80211_mesh_isproxyena(vap)) {
                                   IEEE80211_DISCARD_MAC(vap,
                                       IEEE80211_MSG_OUTPUT |
                                       IEEE80211_MSG_MESH,
                                       eh->ether_dhost, NULL,
                                       "%s", "proxy not enabled");
                                   vap->iv_stats.is_mesh_notproxy++;
                                   if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                                   m_freem(m);
                                   /* XXX better status? */
                                   return (ENOBUFS);
                           }
                           IEEE80211_DPRINTF(vap, IEEE80211_MSG_OUTPUT,
                               "forward frame from DS SA(%6D), DA(%6D)\n",
                               eh->ether_shost, ":",
                               eh->ether_dhost, ":");
                           ieee80211_mesh_proxy_check(vap, eh->ether_shost);
                   }
                   ni = ieee80211_mesh_discover(vap, eh->ether_dhost, m);
                   if (ni == NULL) {
                           /*
                            * NB: ieee80211_mesh_discover holds/disposes
                            * frame (e.g. queueing on path discovery).
                            */
                           if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                           /* XXX better status? */
                           return (ENOBUFS);
                   }
           }
   #endif
   
           /*
            * We've resolved the sender, so attempt to transmit it.
            */
   
           if (vap->iv_state == IEEE80211_S_SLEEP) {
                   /*
                    * In power save; queue frame and then  wakeup device
                    * for transmit.
                    */
                   ic->ic_lastdata = ticks;
                   if (ieee80211_pwrsave(ni, m) != 0)
                           if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                   ieee80211_free_node(ni);
                   ieee80211_new_state(vap, IEEE80211_S_RUN, 0);
                   return (0);
           }
   
           if (ieee80211_vap_pkt_send_dest(vap, m, ni) != 0)
                   return (ENOBUFS);
           return (0);
   #undef  IS_DWDS
   }
   
   /*
    * Start method for vap's.  All packets from the stack come
    * through here.  We handle common processing of the packets
    * before dispatching them to the underlying device.
    *
    * if_transmit() requires that the mbuf be consumed by this call
    * regardless of the return condition.
    */
   int
   ieee80211_vap_transmit(struct ifnet *ifp, struct mbuf *m)
   {
           struct ieee80211vap *vap = ifp->if_softc;
           struct ieee80211com *ic = vap->iv_ic;
   
           /*
            * No data frames go out unless we're running.
            * Note in particular this covers CAC and CSA
            * states (though maybe we should check muting
            * for CSA).
            */
           if (vap->iv_state != IEEE80211_S_RUN &&
               vap->iv_state != IEEE80211_S_SLEEP) {
                   IEEE80211_LOCK(ic);
                   /* re-check under the com lock to avoid races */
                   if (vap->iv_state != IEEE80211_S_RUN &&
                       vap->iv_state != IEEE80211_S_SLEEP) {
                           IEEE80211_DPRINTF(vap, IEEE80211_MSG_OUTPUT,
                               "%s: ignore queue, in %s state\n",
                               __func__, ieee80211_state_name[vap->iv_state]);
                           vap->iv_stats.is_tx_badstate++;
                           IEEE80211_UNLOCK(ic);
                           ifp->if_drv_flags |= IFF_DRV_OACTIVE;
                           m_freem(m);
                           if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                           return (ENETDOWN);
                   }
                   IEEE80211_UNLOCK(ic);
           }
   
           /*
            * Sanitize mbuf flags for net80211 use.  We cannot
            * clear M_PWR_SAV or M_MORE_DATA because these may
            * be set for frames that are re-submitted from the
            * power save queue.
            *
            * NB: This must be done before ieee80211_classify as
            *     it marks EAPOL in frames with M_EAPOL.
            */
           m->m_flags &= ~(M_80211_TX - M_PWR_SAV - M_MORE_DATA);
   
           /*
            * Bump to the packet transmission path.
            * The mbuf will be consumed here.
            */
           return (ieee80211_start_pkt(vap, m));
   }
   
   void
   ieee80211_vap_qflush(struct ifnet *ifp)
   {
   
           /* Empty for now */
   }
   
   /*
    * 802.11 raw output routine.
    *
    * XXX TODO: this (and other send routines) should correctly
    * XXX keep the pwr mgmt bit set if it decides to call into the
    * XXX driver to send a frame whilst the state is SLEEP.
    *
    * Otherwise the peer may decide that we're awake and flood us
    * with traffic we are still too asleep to receive!
    */
   int
   ieee80211_raw_output(struct ieee80211vap *vap, struct ieee80211_node *ni,
       struct mbuf *m, const struct ieee80211_bpf_params *params)
   {
           struct ieee80211com *ic = vap->iv_ic;
           int error;
   
           /*
            * Set node - the caller has taken a reference, so ensure
            * that the mbuf has the same node value that
            * it would if it were going via the normal path.
            */
           m->m_pkthdr.rcvif = (void *)ni;
   
           /*
            * Attempt to add bpf transmit parameters.
            *
            * For now it's ok to fail; the raw_xmit api still takes
            * them as an option.
            *
            * Later on when ic_raw_xmit() has params removed,
            * they'll have to be added - so fail the transmit if
            * they can't be.
            */
           if (params)
                   (void) ieee80211_add_xmit_params(m, params);
   
           error = ic->ic_raw_xmit(ni, m, params);
           if (error) {
                   if_inc_counter(vap->iv_ifp, IFCOUNTER_OERRORS, 1);
                   ieee80211_free_node(ni);
           }
           return (error);
   }
   
   /*
    * 802.11 output routine. This is (currently) used only to
    * connect bpf write calls to the 802.11 layer for injecting
    * raw 802.11 frames.
    */
   int
   ieee80211_output(struct ifnet *ifp, struct mbuf *m,
           const struct sockaddr *dst, struct route *ro)
   {
   #define senderr(e) do { error = (e); goto bad;} while (0)
           struct ieee80211_node *ni = NULL;
           struct ieee80211vap *vap;
           struct ieee80211_frame *wh;
           struct ieee80211com *ic = NULL;
           int error;
           int ret;
   
           if (ifp->if_drv_flags & IFF_DRV_OACTIVE) {
                   /*
                    * Short-circuit requests if the vap is marked OACTIVE
                    * as this can happen because a packet came down through
                    * ieee80211_start before the vap entered RUN state in
                    * which case it's ok to just drop the frame.  This
                    * should not be necessary but callers of if_output don't
                    * check OACTIVE.
                    */
                   senderr(ENETDOWN);
           }
           vap = ifp->if_softc;
           ic = vap->iv_ic;
           /*
            * Hand to the 802.3 code if not tagged as
            * a raw 802.11 frame.
            */
           if (dst->sa_family != AF_IEEE80211)
                   return vap->iv_output(ifp, m, dst, ro);
   #ifdef MAC
           error = mac_ifnet_check_transmit(ifp, m);
           if (error)
                   senderr(error);
   #endif
           if (ifp->if_flags & IFF_MONITOR)
                   senderr(ENETDOWN);
           if (!IFNET_IS_UP_RUNNING(ifp))
                   senderr(ENETDOWN);
           if (vap->iv_state == IEEE80211_S_CAC) {
                   IEEE80211_DPRINTF(vap,
                       IEEE80211_MSG_OUTPUT | IEEE80211_MSG_DOTH,
                       "block %s frame in CAC state\n", "raw data");
                   vap->iv_stats.is_tx_badstate++;
                   senderr(EIO);           /* XXX */
           } else if (vap->iv_state == IEEE80211_S_SCAN)
                   senderr(EIO);
           /* XXX bypass bridge, pfil, carp, etc. */
   
           if (m->m_pkthdr.len < sizeof(struct ieee80211_frame_ack))
                   senderr(EIO);   /* XXX */
           wh = mtod(m, struct ieee80211_frame *);
           if ((wh->i_fc[0] & IEEE80211_FC0_VERSION_MASK) !=
               IEEE80211_FC0_VERSION_0)
                   senderr(EIO);   /* XXX */
           if (m->m_pkthdr.len < ieee80211_anyhdrsize(wh))
                   senderr(EIO);   /* XXX */
   
           /* locate destination node */
           switch (wh->i_fc[1] & IEEE80211_FC1_DIR_MASK) {
           case IEEE80211_FC1_DIR_NODS:
           case IEEE80211_FC1_DIR_FROMDS:
                   ni = ieee80211_find_txnode(vap, wh->i_addr1);
                   break;
           case IEEE80211_FC1_DIR_TODS:
           case IEEE80211_FC1_DIR_DSTODS:
                   ni = ieee80211_find_txnode(vap, wh->i_addr3);
                   break;
           default:
                   senderr(EIO);   /* XXX */
           }
           if (ni == NULL) {
                   /*
                    * Permit packets w/ bpf params through regardless
                    * (see below about sa_len).
                    */
                   if (dst->sa_len == 0)
                           senderr(EHOSTUNREACH);
                   ni = ieee80211_ref_node(vap->iv_bss);
           }
   
           /*
            * Sanitize mbuf for net80211 flags leaked from above.
            *
            * NB: This must be done before ieee80211_classify as
            *     it marks EAPOL in frames with M_EAPOL.
            */
           m->m_flags &= ~M_80211_TX;
   
           /* calculate priority so drivers can find the tx queue */
           /* XXX assumes an 802.3 frame */
           if (ieee80211_classify(ni, m))
                   senderr(EIO);           /* XXX */
   
           IEEE80211_NODE_STAT(ni, tx_data);
           if (IEEE80211_IS_MULTICAST(wh->i_addr1)) {
                   IEEE80211_NODE_STAT(ni, tx_mcast);
                   m->m_flags |= M_MCAST;
           } else
                   IEEE80211_NODE_STAT(ni, tx_ucast);
           /* NB: ieee80211_encap does not include 802.11 header */
           IEEE80211_NODE_STAT_ADD(ni, tx_bytes, m->m_pkthdr.len);
   
           IEEE80211_TX_LOCK(ic);
   
           /*
            * NB: DLT_IEEE802_11_RADIO identifies the parameters are
            * present by setting the sa_len field of the sockaddr (yes,
            * this is a hack).
            * NB: we assume sa_data is suitably aligned to cast.
            */
           ret = ieee80211_raw_output(vap, ni, m,
               (const struct ieee80211_bpf_params *)(dst->sa_len ?
                   dst->sa_data : NULL));
           IEEE80211_TX_UNLOCK(ic);
           return (ret);
   bad:
           if (m != NULL)
                   m_freem(m);
           if (ni != NULL)
                   ieee80211_free_node(ni);
           if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
           return error;
   #undef senderr
   }
   
   /*
    * Set the direction field and address fields of an outgoing
    * frame.  Note this should be called early on in constructing
    * a frame as it sets i_fc[1]; other bits can then be or'd in.
    */
   void
   ieee80211_send_setup(
           struct ieee80211_node *ni,
           struct mbuf *m,
           int type, int tid,
           const uint8_t sa[IEEE80211_ADDR_LEN],
           const uint8_t da[IEEE80211_ADDR_LEN],
           const uint8_t bssid[IEEE80211_ADDR_LEN])
   {
   #define WH4(wh) ((struct ieee80211_frame_addr4 *)wh)
           struct ieee80211vap *vap = ni->ni_vap;
           struct ieee80211_tx_ampdu *tap;
           struct ieee80211_frame *wh = mtod(m, struct ieee80211_frame *);
           ieee80211_seq seqno;
   
           IEEE80211_TX_LOCK_ASSERT(ni->ni_ic);
   
           wh->i_fc[0] = IEEE80211_FC0_VERSION_0 | type;
           if ((type & IEEE80211_FC0_TYPE_MASK) == IEEE80211_FC0_TYPE_DATA) {
                   switch (vap->iv_opmode) {
                   case IEEE80211_M_STA:
                           wh->i_fc[1] = IEEE80211_FC1_DIR_TODS;
                           IEEE80211_ADDR_COPY(wh->i_addr1, bssid);
                           IEEE80211_ADDR_COPY(wh->i_addr2, sa);
                           IEEE80211_ADDR_COPY(wh->i_addr3, da);
                           break;
                   case IEEE80211_M_IBSS:
                   case IEEE80211_M_AHDEMO:
                           wh->i_fc[1] = IEEE80211_FC1_DIR_NODS;
                           IEEE80211_ADDR_COPY(wh->i_addr1, da);
                           IEEE80211_ADDR_COPY(wh->i_addr2, sa);
                           IEEE80211_ADDR_COPY(wh->i_addr3, bssid);
                           break;
                   case IEEE80211_M_HOSTAP:
                           wh->i_fc[1] = IEEE80211_FC1_DIR_FROMDS;
                           IEEE80211_ADDR_COPY(wh->i_addr1, da);
                           IEEE80211_ADDR_COPY(wh->i_addr2, bssid);
                           IEEE80211_ADDR_COPY(wh->i_addr3, sa);
                           break;
                   case IEEE80211_M_WDS:
                           wh->i_fc[1] = IEEE80211_FC1_DIR_DSTODS;
                           IEEE80211_ADDR_COPY(wh->i_addr1, da);
                           IEEE80211_ADDR_COPY(wh->i_addr2, vap->iv_myaddr);
                           IEEE80211_ADDR_COPY(wh->i_addr3, da);
                           IEEE80211_ADDR_COPY(WH4(wh)->i_addr4, sa);
                           break;
                   case IEEE80211_M_MBSS:
   #ifdef IEEE80211_SUPPORT_MESH
                           if (IEEE80211_IS_MULTICAST(da)) {
                                   wh->i_fc[1] = IEEE80211_FC1_DIR_FROMDS;
                                   /* XXX next hop */
                                   IEEE80211_ADDR_COPY(wh->i_addr1, da);
                                   IEEE80211_ADDR_COPY(wh->i_addr2,
                                       vap->iv_myaddr);
                           } else {
                                   wh->i_fc[1] = IEEE80211_FC1_DIR_DSTODS;
                                   IEEE80211_ADDR_COPY(wh->i_addr1, da);
                                   IEEE80211_ADDR_COPY(wh->i_addr2,
                                       vap->iv_myaddr);
                                   IEEE80211_ADDR_COPY(wh->i_addr3, da);
                                   IEEE80211_ADDR_COPY(WH4(wh)->i_addr4, sa);
                           }
   #endif
                           break;
                   case IEEE80211_M_MONITOR:       /* NB: to quiet compiler */
                           break;
                   }
           } else {
                   wh->i_fc[1] = IEEE80211_FC1_DIR_NODS;
                   IEEE80211_ADDR_COPY(wh->i_addr1, da);
                   IEEE80211_ADDR_COPY(wh->i_addr2, sa);
   #ifdef IEEE80211_SUPPORT_MESH
                   if (vap->iv_opmode == IEEE80211_M_MBSS)
                           IEEE80211_ADDR_COPY(wh->i_addr3, sa);
                   else
   #endif
                           IEEE80211_ADDR_COPY(wh->i_addr3, bssid);
           }
           *(uint16_t *)&wh->i_dur[0] = 0;
   
           tap = &ni->ni_tx_ampdu[tid];
           if (tid != IEEE80211_NONQOS_TID && IEEE80211_AMPDU_RUNNING(tap))
                   m->m_flags |= M_AMPDU_MPDU;
           else {
                   if (IEEE80211_HAS_SEQ(type & IEEE80211_FC0_TYPE_MASK,
                                         type & IEEE80211_FC0_SUBTYPE_MASK))
                           seqno = ni->ni_txseqs[tid]++;
                   else
                           seqno = 0;
   
                   *(uint16_t *)&wh->i_seq[0] =
                       htole16(seqno << IEEE80211_SEQ_SEQ_SHIFT);
                   M_SEQNO_SET(m, seqno);
           }
   
           if (IEEE80211_IS_MULTICAST(wh->i_addr1))
                   m->m_flags |= M_MCAST;
   #undef WH4
   }
   
   /*
    * Send a management frame to the specified node.  The node pointer
    * must have a reference as the pointer will be passed to the driver
    * and potentially held for a long time.  If the frame is successfully
    * dispatched to the driver, then it is responsible for freeing the
    * reference (and potentially free'ing up any associated storage);
    * otherwise deal with reclaiming any reference (on error).
    */
   int
   ieee80211_mgmt_output(struct ieee80211_node *ni, struct mbuf *m, int type,
           struct ieee80211_bpf_params *params)
   {
           struct ieee80211vap *vap = ni->ni_vap;
           struct ieee80211com *ic = ni->ni_ic;
           struct ieee80211_frame *wh;
           int ret;
   
           KASSERT(ni != NULL, ("null node"));
   
           if (vap->iv_state == IEEE80211_S_CAC) {
                   IEEE80211_NOTE(vap, IEEE80211_MSG_OUTPUT | IEEE80211_MSG_DOTH,
                       ni, "block %s frame in CAC state",
                           ieee80211_mgt_subtype_name(type));
                   vap->iv_stats.is_tx_badstate++;
                   ieee80211_free_node(ni);
                   m_freem(m);
                   return EIO;             /* XXX */
           }
   
           M_PREPEND(m, sizeof(struct ieee80211_frame), M_NOWAIT);
           if (m == NULL) {
                   ieee80211_free_node(ni);
                   return ENOMEM;
           }
   
           IEEE80211_TX_LOCK(ic);
   
           wh = mtod(m, struct ieee80211_frame *);
           ieee80211_send_setup(ni, m,
                IEEE80211_FC0_TYPE_MGT | type, IEEE80211_NONQOS_TID,
                vap->iv_myaddr, ni->ni_macaddr, ni->ni_bssid);
           if (params->ibp_flags & IEEE80211_BPF_CRYPTO) {
                   IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_AUTH, wh->i_addr1,
                       "encrypting frame (%s)", __func__);
                   wh->i_fc[1] |= IEEE80211_FC1_PROTECTED;
           }
           m->m_flags |= M_ENCAP;          /* mark encapsulated */
   
           KASSERT(type != IEEE80211_FC0_SUBTYPE_PROBE_RESP, ("probe response?"));
           M_WME_SETAC(m, params->ibp_pri);
   
   #ifdef IEEE80211_DEBUG
           /* avoid printing too many frames */
           if ((ieee80211_msg_debug(vap) && doprint(vap, type)) ||
               ieee80211_msg_dumppkts(vap)) {
                   printf("[%s] send %s on channel %u\n",
                       ether_sprintf(wh->i_addr1),
                       ieee80211_mgt_subtype_name(type),
                       ieee80211_chan2ieee(ic, ic->ic_curchan));
           }
   #endif
           IEEE80211_NODE_STAT(ni, tx_mgmt);
   
           ret = ieee80211_raw_output(vap, ni, m, params);
           IEEE80211_TX_UNLOCK(ic);
           return (ret);
   }
   
   static void
   ieee80211_nulldata_transmitted(struct ieee80211_node *ni, void *arg,
       int status)
   {
           struct ieee80211vap *vap = ni->ni_vap;
   
           wakeup(vap);
   }
   
   /*
    * Send a null data frame to the specified node.  If the station
    * is setup for QoS then a QoS Null Data frame is constructed.
    * If this is a WDS station then a 4-address frame is constructed.
    *
    * NB: the caller is assumed to have setup a node reference
    *     for use; this is necessary to deal with a race condition
    *     when probing for inactive stations.  Like ieee80211_mgmt_output
    *     we must cleanup any node reference on error;  however we
    *     can safely just unref it as we know it will never be the
    *     last reference to the node.
    */
   int
   ieee80211_send_nulldata(struct ieee80211_node *ni)
   {
           struct ieee80211vap *vap = ni->ni_vap;
           struct ieee80211com *ic = ni->ni_ic;
           struct mbuf *m;
           struct ieee80211_frame *wh;
           int hdrlen;
           uint8_t *frm;
           int ret;
   
           if (vap->iv_state == IEEE80211_S_CAC) {
                   IEEE80211_NOTE(vap, IEEE80211_MSG_OUTPUT | IEEE80211_MSG_DOTH,
                       ni, "block %s frame in CAC state", "null data");
                   ieee80211_unref_node(&ni);
                   vap->iv_stats.is_tx_badstate++;
                   return EIO;             /* XXX */
           }
   
           if (ni->ni_flags & (IEEE80211_NODE_QOS|IEEE80211_NODE_HT))
                   hdrlen = sizeof(struct ieee80211_qosframe);
           else
                   hdrlen = sizeof(struct ieee80211_frame);
           /* NB: only WDS vap's get 4-address frames */
           if (vap->iv_opmode == IEEE80211_M_WDS)
                   hdrlen += IEEE80211_ADDR_LEN;
           if (ic->ic_flags & IEEE80211_F_DATAPAD)
                   hdrlen = roundup(hdrlen, sizeof(uint32_t));
   
           m = ieee80211_getmgtframe(&frm, ic->ic_headroom + hdrlen, 0);
           if (m == NULL) {
                   /* XXX debug msg */
                   ieee80211_unref_node(&ni);
                   vap->iv_stats.is_tx_nobuf++;
                   return ENOMEM;
           }
           KASSERT(M_LEADINGSPACE(m) >= hdrlen,
               ("leading space %zd", M_LEADINGSPACE(m)));
           M_PREPEND(m, hdrlen, M_NOWAIT);
           if (m == NULL) {
                   /* NB: cannot happen */
                   ieee80211_free_node(ni);
                   return ENOMEM;
           }
   
           IEEE80211_TX_LOCK(ic);
   
           wh = mtod(m, struct ieee80211_frame *);         /* NB: a little lie */
           if (ni->ni_flags & IEEE80211_NODE_QOS) {
                   const int tid = WME_AC_TO_TID(WME_AC_BE);
                   uint8_t *qos;
   
                   ieee80211_send_setup(ni, m,
                       IEEE80211_FC0_TYPE_DATA | IEEE80211_FC0_SUBTYPE_QOS_NULL,
                       tid, vap->iv_myaddr, ni->ni_macaddr, ni->ni_bssid);
   
                   if (vap->iv_opmode == IEEE80211_M_WDS)
                           qos = ((struct ieee80211_qosframe_addr4 *) wh)->i_qos;
                   else
                           qos = ((struct ieee80211_qosframe *) wh)->i_qos;
                   qos[0] = tid & IEEE80211_QOS_TID;
                   if (ic->ic_wme.wme_wmeChanParams.cap_wmeParams[WME_AC_BE].wmep_noackPolicy)
                           qos[0] |= IEEE80211_QOS_ACKPOLICY_NOACK;
                   qos[1] = 0;
           } else {
                   ieee80211_send_setup(ni, m,
                       IEEE80211_FC0_TYPE_DATA | IEEE80211_FC0_SUBTYPE_NODATA,
                       IEEE80211_NONQOS_TID,
                       vap->iv_myaddr, ni->ni_macaddr, ni->ni_bssid);
           }
           if (vap->iv_opmode != IEEE80211_M_WDS) {
                   /* NB: power management bit is never sent by an AP */
                   if ((ni->ni_flags & IEEE80211_NODE_PWR_MGT) &&
                       vap->iv_opmode != IEEE80211_M_HOSTAP)
                           wh->i_fc[1] |= IEEE80211_FC1_PWR_MGT;
           }
           if ((ic->ic_flags & IEEE80211_F_SCAN) &&
               (ni->ni_flags & IEEE80211_NODE_PWR_MGT)) {
                   ieee80211_add_callback(m, ieee80211_nulldata_transmitted,
                       NULL);
           }
           m->m_len = m->m_pkthdr.len = hdrlen;
           m->m_flags |= M_ENCAP;          /* mark encapsulated */
   
           M_WME_SETAC(m, WME_AC_BE);
   
           IEEE80211_NODE_STAT(ni, tx_data);
   
           IEEE80211_NOTE(vap, IEEE80211_MSG_DEBUG | IEEE80211_MSG_DUMPPKTS, ni,
               "send %snull data frame on channel %u, pwr mgt %s",
               ni->ni_flags & IEEE80211_NODE_QOS ? "QoS " : "",
               ieee80211_chan2ieee(ic, ic->ic_curchan),
               wh->i_fc[1] & IEEE80211_FC1_PWR_MGT ? "ena" : "dis");
   
           ret = ieee80211_raw_output(vap, ni, m, NULL);
           IEEE80211_TX_UNLOCK(ic);
           return (ret);
   }
   
   /* 
    * Assign priority to a frame based on any vlan tag assigned
    * to the station and/or any Diffserv setting in an IP header.
    * Finally, if an ACM policy is setup (in station mode) it's
    * applied.
    */
   int
   ieee80211_classify(struct ieee80211_node *ni, struct mbuf *m)
   {
           const struct ether_header *eh = mtod(m, struct ether_header *);
           int v_wme_ac, d_wme_ac, ac;
   
           /*
            * Always promote PAE/EAPOL frames to high priority.
            */
           if (eh->ether_type == htons(ETHERTYPE_PAE)) {
                   /* NB: mark so others don't need to check header */
                   m->m_flags |= M_EAPOL;
                   ac = WME_AC_VO;
                   goto done;
           }
           /*
            * Non-qos traffic goes to BE.
            */
           if ((ni->ni_flags & IEEE80211_NODE_QOS) == 0) {
                  ac = WME_AC_BE;
                  goto done;
          }
  
          /* 
           * If node has a vlan tag then all traffic
           * to it must have a matching tag.
           */
          v_wme_ac = 0;
          if (ni->ni_vlan != 0) {
                   if ((m->m_flags & M_VLANTAG) == 0) {
                          IEEE80211_NODE_STAT(ni, tx_novlantag);
                          return 1;
                  }
                  if (EVL_VLANOFTAG(m->m_pkthdr.ether_vtag) !=
                      EVL_VLANOFTAG(ni->ni_vlan)) {
                          IEEE80211_NODE_STAT(ni, tx_vlanmismatch);
                          return 1;
                  }
                  /* map vlan priority to AC */
                  v_wme_ac = TID_TO_WME_AC(EVL_PRIOFTAG(ni->ni_vlan));
          }
  
          /* XXX m_copydata may be too slow for fast path */
  #ifdef INET
          if (eh->ether_type == htons(ETHERTYPE_IP)) {
                  uint8_t tos;
                  /*
                   * IP frame, map the DSCP bits from the TOS field.
                   */
                  /* NB: ip header may not be in first mbuf */
                  m_copydata(m, sizeof(struct ether_header) +
                      offsetof(struct ip, ip_tos), sizeof(tos), &tos);
                  tos >>= 5;              /* NB: ECN + low 3 bits of DSCP */
                  d_wme_ac = TID_TO_WME_AC(tos);
          } else {
  #endif /* INET */
  #ifdef INET6
          if (eh->ether_type == htons(ETHERTYPE_IPV6)) {
                  uint32_t flow;
                  uint8_t tos;
                  /*
                   * IPv6 frame, map the DSCP bits from the traffic class field.
                   */
                  m_copydata(m, sizeof(struct ether_header) +
                      offsetof(struct ip6_hdr, ip6_flow), sizeof(flow),
                      (caddr_t) &flow);
                  tos = (uint8_t)(ntohl(flow) >> 20);
                  tos >>= 5;              /* NB: ECN + low 3 bits of DSCP */
                  d_wme_ac = TID_TO_WME_AC(tos);
          } else {
  #endif /* INET6 */
                  d_wme_ac = WME_AC_BE;
  #ifdef INET6
          }
  #endif
  #ifdef INET
          }
  #endif
          /*
           * Use highest priority AC.
           */
          if (v_wme_ac > d_wme_ac)
                  ac = v_wme_ac;
          else
                  ac = d_wme_ac;
  
          /*
           * Apply ACM policy.
           */
          if (ni->ni_vap->iv_opmode == IEEE80211_M_STA) {
                  static const int acmap[4] = {
                          WME_AC_BK,      /* WME_AC_BE */
                          WME_AC_BK,      /* WME_AC_BK */
                          WME_AC_BE,      /* WME_AC_VI */
                          WME_AC_VI,      /* WME_AC_VO */
                  };
                  struct ieee80211com *ic = ni->ni_ic;
  
                  while (ac != WME_AC_BK &&
                      ic->ic_wme.wme_wmeBssChanParams.cap_wmeParams[ac].wmep_acm)
                          ac = acmap[ac];
          }
  done:
          M_WME_SETAC(m, ac);
          return 0;
  }
  
  /*
   * Insure there is sufficient contiguous space to encapsulate the
   * 802.11 data frame.  If room isn't already there, arrange for it.
   * Drivers and cipher modules assume we have done the necessary work
   * and fail rudely if they don't find the space they need.
   */
  struct mbuf *
  ieee80211_mbuf_adjust(struct ieee80211vap *vap, int hdrsize,
          struct ieee80211_key *key, struct mbuf *m)
  {
  #define TO_BE_RECLAIMED (sizeof(struct ether_header) - sizeof(struct llc))
          int needed_space = vap->iv_ic->ic_headroom + hdrsize;
  
          if (key != NULL) {
                  /* XXX belongs in crypto code? */
                  needed_space += key->wk_cipher->ic_header;
                  /* XXX frags */
                  /*
                   * When crypto is being done in the host we must insure
                   * the data are writable for the cipher routines; clone
                   * a writable mbuf chain.
                   * XXX handle SWMIC specially
                   */
                  if (key->wk_flags & (IEEE80211_KEY_SWENCRYPT|IEEE80211_KEY_SWENMIC)) {
                          m = m_unshare(m, M_NOWAIT);
                          if (m == NULL) {
                                  IEEE80211_DPRINTF(vap, IEEE80211_MSG_OUTPUT,
                                      "%s: cannot get writable mbuf\n", __func__);
                                  vap->iv_stats.is_tx_nobuf++; /* XXX new stat */
                                  return NULL;
                          }
                  }
          }
          /*
           * We know we are called just before stripping an Ethernet
           * header and prepending an LLC header.  This means we know
           * there will be
           *      sizeof(struct ether_header) - sizeof(struct llc)
           * bytes recovered to which we need additional space for the
           * 802.11 header and any crypto header.
           */
          /* XXX check trailing space and copy instead? */
          if (M_LEADINGSPACE(m) < needed_space - TO_BE_RECLAIMED) {
                  struct mbuf *n = m_gethdr(M_NOWAIT, m->m_type);
                  if (n == NULL) {
                          IEEE80211_DPRINTF(vap, IEEE80211_MSG_OUTPUT,
                              "%s: cannot expand storage\n", __func__);
                          vap->iv_stats.is_tx_nobuf++;
                          m_freem(m);
                          return NULL;
                  }
                  KASSERT(needed_space <= MHLEN,
                      ("not enough room, need %u got %d\n", needed_space, MHLEN));
                  /*
                   * Setup new mbuf to have leading space to prepend the
                   * 802.11 header and any crypto header bits that are
                   * required (the latter are added when the driver calls
                   * back to ieee80211_crypto_encap to do crypto encapsulation).
                   */
                  /* NB: must be first 'cuz it clobbers m_data */
                  m_move_pkthdr(n, m);
                  n->m_len = 0;                   /* NB: m_gethdr does not set */
                  n->m_data += needed_space;
                  /*
                   * Pull up Ethernet header to create the expected layout.
                   * We could use m_pullup but that's overkill (i.e. we don't
                   * need the actual data) and it cannot fail so do it inline
                   * for speed.
                   */
                  /* NB: struct ether_header is known to be contiguous */
                  n->m_len += sizeof(struct ether_header);
                  m->m_len -= sizeof(struct ether_header);
                  m->m_data += sizeof(struct ether_header);
                  /*
                   * Replace the head of the chain.
                   */
                  n->m_next = m;
                  m = n;
          }
          return m;
  #undef TO_BE_RECLAIMED
  }
  
  /*
   * Return the transmit key to use in sending a unicast frame.
   * If a unicast key is set we use that.  When no unicast key is set
   * we fall back to the default transmit key.
   */ 
  static __inline struct ieee80211_key *
  ieee80211_crypto_getucastkey(struct ieee80211vap *vap,
          struct ieee80211_node *ni)
  {
          if (IEEE80211_KEY_UNDEFINED(&ni->ni_ucastkey)) {
                  if (vap->iv_def_txkey == IEEE80211_KEYIX_NONE ||
                      IEEE80211_KEY_UNDEFINED(&vap->iv_nw_keys[vap->iv_def_txkey]))
                          return NULL;
                  return &vap->iv_nw_keys[vap->iv_def_txkey];
          } else {
                  return &ni->ni_ucastkey;
          }
  }
  
  /*
   * Return the transmit key to use in sending a multicast frame.
   * Multicast traffic always uses the group key which is installed as
   * the default tx key.
   */ 
  static __inline struct ieee80211_key *
  ieee80211_crypto_getmcastkey(struct ieee80211vap *vap,
          struct ieee80211_node *ni)
  {
          if (vap->iv_def_txkey == IEEE80211_KEYIX_NONE ||
              IEEE80211_KEY_UNDEFINED(&vap->iv_nw_keys[vap->iv_def_txkey]))
                  return NULL;
          return &vap->iv_nw_keys[vap->iv_def_txkey];
  }
  
  /*
   * Encapsulate an outbound data frame.  The mbuf chain is updated.
   * If an error is encountered NULL is returned.  The caller is required
   * to provide a node reference and pullup the ethernet header in the
   * first mbuf.
   *
   * NB: Packet is assumed to be processed by ieee80211_classify which
   *     marked EAPOL frames w/ M_EAPOL.
   */
  struct mbuf *
  ieee80211_encap(struct ieee80211vap *vap, struct ieee80211_node *ni,
      struct mbuf *m)
  {
  #define WH4(wh) ((struct ieee80211_frame_addr4 *)(wh))
  #define MC01(mc)        ((struct ieee80211_meshcntl_ae01 *)mc)
          struct ieee80211com *ic = ni->ni_ic;
  #ifdef IEEE80211_SUPPORT_MESH
          struct ieee80211_mesh_state *ms = vap->iv_mesh;
          struct ieee80211_meshcntl_ae10 *mc;
          struct ieee80211_mesh_route *rt = NULL;
          int dir = -1;
  #endif
          struct ether_header eh;
          struct ieee80211_frame *wh;
          struct ieee80211_key *key;
          struct llc *llc;
          int hdrsize, hdrspace, datalen, addqos, txfrag, is4addr;
          ieee80211_seq seqno;
          int meshhdrsize, meshae;
          uint8_t *qos;
          int is_amsdu = 0;
          
          IEEE80211_TX_LOCK_ASSERT(ic);
  
          /*
           * Copy existing Ethernet header to a safe place.  The
           * rest of the code assumes it's ok to strip it when
           * reorganizing state for the final encapsulation.
           */
          KASSERT(m->m_len >= sizeof(eh), ("no ethernet header!"));
          ETHER_HEADER_COPY(&eh, mtod(m, caddr_t));
  
          /*
           * Insure space for additional headers.  First identify
           * transmit key to use in calculating any buffer adjustments
           * required.  This is also used below to do privacy
           * encapsulation work.  Then calculate the 802.11 header
           * size and any padding required by the driver.
           *
           * Note key may be NULL if we fall back to the default
           * transmit key and that is not set.  In that case the
           * buffer may not be expanded as needed by the cipher
           * routines, but they will/should discard it.
           */
          if (vap->iv_flags & IEEE80211_F_PRIVACY) {
                  if (vap->iv_opmode == IEEE80211_M_STA ||
                      !IEEE80211_IS_MULTICAST(eh.ether_dhost) ||
                      (vap->iv_opmode == IEEE80211_M_WDS &&
                       (vap->iv_flags_ext & IEEE80211_FEXT_WDSLEGACY)))
                          key = ieee80211_crypto_getucastkey(vap, ni);
                  else
                          key = ieee80211_crypto_getmcastkey(vap, ni);
                  if (key == NULL && (m->m_flags & M_EAPOL) == 0) {
                          IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO,
                              eh.ether_dhost,
                              "no default transmit key (%s) deftxkey %u",
                              __func__, vap->iv_def_txkey);
                          vap->iv_stats.is_tx_nodefkey++;
                          goto bad;
                  }
          } else
                  key = NULL;
          /*
           * XXX Some ap's don't handle QoS-encapsulated EAPOL
           * frames so suppress use.  This may be an issue if other
           * ap's require all data frames to be QoS-encapsulated
           * once negotiated in which case we'll need to make this
           * configurable.
           * NB: mesh data frames are QoS.
           */
          addqos = ((ni->ni_flags & (IEEE80211_NODE_QOS|IEEE80211_NODE_HT)) ||
              (vap->iv_opmode == IEEE80211_M_MBSS)) &&
              (m->m_flags & M_EAPOL) == 0;
          if (addqos)
                  hdrsize = sizeof(struct ieee80211_qosframe);
          else
                  hdrsize = sizeof(struct ieee80211_frame);
  #ifdef IEEE80211_SUPPORT_MESH
          if (vap->iv_opmode == IEEE80211_M_MBSS) {
                  /*
                   * Mesh data frames are encapsulated according to the
                   * rules of Section 11B.8.5 (p.139 of D3.0 spec).
                   * o Group Addressed data (aka multicast) originating
                   *   at the local sta are sent w/ 3-address format and
                   *   address extension mode 00
                   * o Individually Addressed data (aka unicast) originating
                   *   at the local sta are sent w/ 4-address format and
                   *   address extension mode 00
                   * o Group Addressed data forwarded from a non-mesh sta are
                   *   sent w/ 3-address format and address extension mode 01
                   * o Individually Address data from another sta are sent
                   *   w/ 4-address format and address extension mode 10
                   */
                  is4addr = 0;            /* NB: don't use, disable */
                  if (!IEEE80211_IS_MULTICAST(eh.ether_dhost)) {
                          rt = ieee80211_mesh_rt_find(vap, eh.ether_dhost);
                          KASSERT(rt != NULL, ("route is NULL"));
                          dir = IEEE80211_FC1_DIR_DSTODS;
                          hdrsize += IEEE80211_ADDR_LEN;
                          if (rt->rt_flags & IEEE80211_MESHRT_FLAGS_PROXY) {
                                  if (IEEE80211_ADDR_EQ(rt->rt_mesh_gate,
                                      vap->iv_myaddr)) {
                                          IEEE80211_NOTE_MAC(vap,
                                              IEEE80211_MSG_MESH,
                                              eh.ether_dhost,
                                              "%s", "trying to send to ourself");
                                          goto bad;
                                  }
                                  meshae = IEEE80211_MESH_AE_10;
                                  meshhdrsize =
                                      sizeof(struct ieee80211_meshcntl_ae10);
                          } else {
                                  meshae = IEEE80211_MESH_AE_00;
                                  meshhdrsize =
                                      sizeof(struct ieee80211_meshcntl);
                          }
                  } else {
                          dir = IEEE80211_FC1_DIR_FROMDS;
                          if (!IEEE80211_ADDR_EQ(eh.ether_shost, vap->iv_myaddr)) {
                                  /* proxy group */
                                  meshae = IEEE80211_MESH_AE_01;
                                  meshhdrsize =
                                      sizeof(struct ieee80211_meshcntl_ae01);
                          } else {
                                  /* group */
                                  meshae = IEEE80211_MESH_AE_00;
                                  meshhdrsize = sizeof(struct ieee80211_meshcntl);
                          }
                  }
          } else {
  #endif
                  /*
                   * 4-address frames need to be generated for:
                   * o packets sent through a WDS vap (IEEE80211_M_WDS)
                   * o packets sent through a vap marked for relaying
                   *   (e.g. a station operating with dynamic WDS)
                   */
                  is4addr = vap->iv_opmode == IEEE80211_M_WDS ||
                      ((vap->iv_flags_ext & IEEE80211_FEXT_4ADDR) &&
                       !IEEE80211_ADDR_EQ(eh.ether_shost, vap->iv_myaddr));
                  if (is4addr)
                          hdrsize += IEEE80211_ADDR_LEN;
                  meshhdrsize = meshae = 0;
  #ifdef IEEE80211_SUPPORT_MESH
          }
  #endif
          /*
           * Honor driver DATAPAD requirement.
           */
          if (ic->ic_flags & IEEE80211_F_DATAPAD)
                  hdrspace = roundup(hdrsize, sizeof(uint32_t));
          else
                  hdrspace = hdrsize;
  
          if (__predict_true((m->m_flags & M_FF) == 0)) {
                  /*
                   * Normal frame.
                   */
                  m = ieee80211_mbuf_adjust(vap, hdrspace + meshhdrsize, key, m);
                  if (m == NULL) {
                          /* NB: ieee80211_mbuf_adjust handles msgs+statistics */
                          goto bad;
                  }
                  /* NB: this could be optimized 'cuz of ieee80211_mbuf_adjust */
                  m_adj(m, sizeof(struct ether_header) - sizeof(struct llc));
                  llc = mtod(m, struct llc *);
                  llc->llc_dsap = llc->llc_ssap = LLC_SNAP_LSAP;
                  llc->llc_control = LLC_UI;
                  llc->llc_snap.org_code[0] = 0;
                  llc->llc_snap.org_code[1] = 0;
                  llc->llc_snap.org_code[2] = 0;
                  llc->llc_snap.ether_type = eh.ether_type;
          } else {
  #ifdef IEEE80211_SUPPORT_SUPERG
                  /*
                   * Aggregated frame.  Check if it's for AMSDU or FF.
                   *
                   * XXX TODO: IEEE80211_NODE_AMSDU* isn't implemented
                   * anywhere for some reason.  But, since 11n requires
                   * AMSDU RX, we can just assume "11n" == "AMSDU".
                   */
                  IEEE80211_DPRINTF(vap, IEEE80211_MSG_SUPERG, "%s: called; M_FF\n", __func__);
                  if (ieee80211_amsdu_tx_ok(ni)) {
                          m = ieee80211_amsdu_encap(vap, m, hdrspace + meshhdrsize, key);
                          is_amsdu = 1;
                  } else {
                          m = ieee80211_ff_encap(vap, m, hdrspace + meshhdrsize, key);
                  }
                  if (m == NULL)
  #endif
                          goto bad;
          }
          datalen = m->m_pkthdr.len;              /* NB: w/o 802.11 header */
  
          M_PREPEND(m, hdrspace + meshhdrsize, M_NOWAIT);
          if (m == NULL) {
                  vap->iv_stats.is_tx_nobuf++;
                  goto bad;
          }
          wh = mtod(m, struct ieee80211_frame *);
          wh->i_fc[0] = IEEE80211_FC0_VERSION_0 | IEEE80211_FC0_TYPE_DATA;
          *(uint16_t *)wh->i_dur = 0;
          qos = NULL;     /* NB: quiet compiler */
          if (is4addr) {
                  wh->i_fc[1] = IEEE80211_FC1_DIR_DSTODS;
                  IEEE80211_ADDR_COPY(wh->i_addr1, ni->ni_macaddr);
                  IEEE80211_ADDR_COPY(wh->i_addr2, vap->iv_myaddr);
                  IEEE80211_ADDR_COPY(wh->i_addr3, eh.ether_dhost);
                  IEEE80211_ADDR_COPY(WH4(wh)->i_addr4, eh.ether_shost);
          } else switch (vap->iv_opmode) {
          case IEEE80211_M_STA:
                  wh->i_fc[1] = IEEE80211_FC1_DIR_TODS;
                  IEEE80211_ADDR_COPY(wh->i_addr1, ni->ni_bssid);
                  IEEE80211_ADDR_COPY(wh->i_addr2, eh.ether_shost);
                  IEEE80211_ADDR_COPY(wh->i_addr3, eh.ether_dhost);
                  break;
          case IEEE80211_M_IBSS:
          case IEEE80211_M_AHDEMO:
                  wh->i_fc[1] = IEEE80211_FC1_DIR_NODS;
                  IEEE80211_ADDR_COPY(wh->i_addr1, eh.ether_dhost);
                  IEEE80211_ADDR_COPY(wh->i_addr2, eh.ether_shost);
                  /*
                   * NB: always use the bssid from iv_bss as the
                   *     neighbor's may be stale after an ibss merge
                   */
                  IEEE80211_ADDR_COPY(wh->i_addr3, vap->iv_bss->ni_bssid);
                  break;
          case IEEE80211_M_HOSTAP:
                  wh->i_fc[1] = IEEE80211_FC1_DIR_FROMDS;
                  IEEE80211_ADDR_COPY(wh->i_addr1, eh.ether_dhost);
                  IEEE80211_ADDR_COPY(wh->i_addr2, ni->ni_bssid);
                  IEEE80211_ADDR_COPY(wh->i_addr3, eh.ether_shost);
                  break;
  #ifdef IEEE80211_SUPPORT_MESH
          case IEEE80211_M_MBSS:
                  /* NB: offset by hdrspace to deal with DATAPAD */
                  mc = (struct ieee80211_meshcntl_ae10 *)
                       (mtod(m, uint8_t *) + hdrspace);
                  wh->i_fc[1] = dir;
                  switch (meshae) {
                  case IEEE80211_MESH_AE_00:      /* no proxy */
                          mc->mc_flags = 0;
                          if (dir == IEEE80211_FC1_DIR_DSTODS) { /* ucast */
                                  IEEE80211_ADDR_COPY(wh->i_addr1,
                                      ni->ni_macaddr);
                                  IEEE80211_ADDR_COPY(wh->i_addr2,
                                      vap->iv_myaddr);
                                  IEEE80211_ADDR_COPY(wh->i_addr3,
                                      eh.ether_dhost);
                                  IEEE80211_ADDR_COPY(WH4(wh)->i_addr4,
                                      eh.ether_shost);
                                  qos =((struct ieee80211_qosframe_addr4 *)
                                      wh)->i_qos;
                          } else if (dir == IEEE80211_FC1_DIR_FROMDS) {
                                   /* mcast */
                                  IEEE80211_ADDR_COPY(wh->i_addr1,
                                      eh.ether_dhost);
                                  IEEE80211_ADDR_COPY(wh->i_addr2,
                                      vap->iv_myaddr);
                                  IEEE80211_ADDR_COPY(wh->i_addr3,
                                      eh.ether_shost);
                                  qos = ((struct ieee80211_qosframe *)
                                      wh)->i_qos;
                          }
                          break;
                  case IEEE80211_MESH_AE_01:      /* mcast, proxy */
                          wh->i_fc[1] = IEEE80211_FC1_DIR_FROMDS;
                          IEEE80211_ADDR_COPY(wh->i_addr1, eh.ether_dhost);
                          IEEE80211_ADDR_COPY(wh->i_addr2, vap->iv_myaddr);
                          IEEE80211_ADDR_COPY(wh->i_addr3, vap->iv_myaddr);
                          mc->mc_flags = 1;
                          IEEE80211_ADDR_COPY(MC01(mc)->mc_addr4,
                              eh.ether_shost);
                          qos = ((struct ieee80211_qosframe *) wh)->i_qos;
                          break;
                  case IEEE80211_MESH_AE_10:      /* ucast, proxy */
                          KASSERT(rt != NULL, ("route is NULL"));
                          IEEE80211_ADDR_COPY(wh->i_addr1, rt->rt_nexthop);
                          IEEE80211_ADDR_COPY(wh->i_addr2, vap->iv_myaddr);
                          IEEE80211_ADDR_COPY(wh->i_addr3, rt->rt_mesh_gate);
                          IEEE80211_ADDR_COPY(WH4(wh)->i_addr4, vap->iv_myaddr);
                          mc->mc_flags = IEEE80211_MESH_AE_10;
                          IEEE80211_ADDR_COPY(mc->mc_addr5, eh.ether_dhost);
                          IEEE80211_ADDR_COPY(mc->mc_addr6, eh.ether_shost);
                          qos = ((struct ieee80211_qosframe_addr4 *) wh)->i_qos;
                          break;
                  default:
                          KASSERT(0, ("meshae %d", meshae));
                          break;
                  }
                  mc->mc_ttl = ms->ms_ttl;
                  ms->ms_seq++;
                  le32enc(mc->mc_seq, ms->ms_seq);
                  break;
  #endif
          case IEEE80211_M_WDS:           /* NB: is4addr should always be true */
          default:
                  goto bad;
          }
          if (m->m_flags & M_MORE_DATA)
                  wh->i_fc[1] |= IEEE80211_FC1_MORE_DATA;
          if (addqos) {
                  int ac, tid;
  
                  if (is4addr) {
                          qos = ((struct ieee80211_qosframe_addr4 *) wh)->i_qos;
                  /* NB: mesh case handled earlier */
                  } else if (vap->iv_opmode != IEEE80211_M_MBSS)
                          qos = ((struct ieee80211_qosframe *) wh)->i_qos;
                  ac = M_WME_GETAC(m);
                  /* map from access class/queue to 11e header priorty value */
                  tid = WME_AC_TO_TID(ac);
                  qos[0] = tid & IEEE80211_QOS_TID;
                  if (ic->ic_wme.wme_wmeChanParams.cap_wmeParams[ac].wmep_noackPolicy)
                          qos[0] |= IEEE80211_QOS_ACKPOLICY_NOACK;
  #ifdef IEEE80211_SUPPORT_MESH
                  if (vap->iv_opmode == IEEE80211_M_MBSS)
                          qos[1] = IEEE80211_QOS_MC;
                  else
  #endif
                          qos[1] = 0;
                  wh->i_fc[0] |= IEEE80211_FC0_SUBTYPE_QOS;
  
                  /*
                   * If this is an A-MSDU then ensure we set the
                   * relevant field.
                   */
                  if (is_amsdu)
                          qos[0] |= IEEE80211_QOS_AMSDU;
  
                  if ((m->m_flags & M_AMPDU_MPDU) == 0) {
                          /*
                           * NB: don't assign a sequence # to potential
                           * aggregates; we expect this happens at the
                           * point the frame comes off any aggregation q
                           * as otherwise we may introduce holes in the
                           * BA sequence space and/or make window accouting
                           * more difficult.
                           *
                           * XXX may want to control this with a driver
                           * capability; this may also change when we pull
                           * aggregation up into net80211
                           */
                          seqno = ni->ni_txseqs[tid]++;
                          *(uint16_t *)wh->i_seq =
                              htole16(seqno << IEEE80211_SEQ_SEQ_SHIFT);
                          M_SEQNO_SET(m, seqno);
                  }
          } else {
                  seqno = ni->ni_txseqs[IEEE80211_NONQOS_TID]++;
                  *(uint16_t *)wh->i_seq =
                      htole16(seqno << IEEE80211_SEQ_SEQ_SHIFT);
                  M_SEQNO_SET(m, seqno);
  
                  /*
                   * XXX TODO: we shouldn't allow EAPOL, etc that would
                   * be forced to be non-QoS traffic to be A-MSDU encapsulated.
                   */
                  if (is_amsdu)
                          printf("%s: XXX ERROR: is_amsdu set; not QoS!\n",
                              __func__);
          }
  
  
          /* check if xmit fragmentation is required */
          txfrag = (m->m_pkthdr.len > vap->iv_fragthreshold &&
              !IEEE80211_IS_MULTICAST(wh->i_addr1) &&
              (vap->iv_caps & IEEE80211_C_TXFRAG) &&
              (m->m_flags & (M_FF | M_AMPDU_MPDU)) == 0);
          if (key != NULL) {
                  /*
                   * IEEE 802.1X: send EAPOL frames always in the clear.
                   * WPA/WPA2: encrypt EAPOL keys when pairwise keys are set.
                   */
                  if ((m->m_flags & M_EAPOL) == 0 ||
                      ((vap->iv_flags & IEEE80211_F_WPA) &&
                       (vap->iv_opmode == IEEE80211_M_STA ?
                        !IEEE80211_KEY_UNDEFINED(key) :
                        !IEEE80211_KEY_UNDEFINED(&ni->ni_ucastkey)))) {
                          wh->i_fc[1] |= IEEE80211_FC1_PROTECTED;
                          if (!ieee80211_crypto_enmic(vap, key, m, txfrag)) {
                                  IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_OUTPUT,
                                      eh.ether_dhost,
                                      "%s", "enmic failed, discard frame");
                                  vap->iv_stats.is_crypto_enmicfail++;
                                  goto bad;
                          }
                  }
          }
          if (txfrag && !ieee80211_fragment(vap, m, hdrsize,
              key != NULL ? key->wk_cipher->ic_header : 0, vap->iv_fragthreshold))
                  goto bad;
  
          m->m_flags |= M_ENCAP;          /* mark encapsulated */
  
          IEEE80211_NODE_STAT(ni, tx_data);
          if (IEEE80211_IS_MULTICAST(wh->i_addr1)) {
                  IEEE80211_NODE_STAT(ni, tx_mcast);
                  m->m_flags |= M_MCAST;
          } else
                  IEEE80211_NODE_STAT(ni, tx_ucast);
          IEEE80211_NODE_STAT_ADD(ni, tx_bytes, datalen);
  
          return m;
  bad:
          if (m != NULL)
                  m_freem(m);
          return NULL;
  #undef WH4
  #undef MC01
  }
  
  void
  ieee80211_free_mbuf(struct mbuf *m)
  {
          struct mbuf *next;
  
          if (m == NULL)
                  return;
  
          do {
                  next = m->m_nextpkt;
                  m->m_nextpkt = NULL;
                  m_freem(m);
          } while ((m = next) != NULL);
  }
  
  /*
   * Fragment the frame according to the specified mtu.
   * The size of the 802.11 header (w/o padding) is provided
   * so we don't need to recalculate it.  We create a new
   * mbuf for each fragment and chain it through m_nextpkt;
   * we might be able to optimize this by reusing the original
   * packet's mbufs but that is significantly more complicated.
   */
  static int
  ieee80211_fragment(struct ieee80211vap *vap, struct mbuf *m0,
          u_int hdrsize, u_int ciphdrsize, u_int mtu)
  {
          struct ieee80211com *ic = vap->iv_ic;
          struct ieee80211_frame *wh, *whf;
          struct mbuf *m, *prev;
          u_int totalhdrsize, fragno, fragsize, off, remainder, payload;
          u_int hdrspace;
  
          KASSERT(m0->m_nextpkt == NULL, ("mbuf already chained?"));
          KASSERT(m0->m_pkthdr.len > mtu,
                  ("pktlen %u mtu %u", m0->m_pkthdr.len, mtu));
  
          /*
           * Honor driver DATAPAD requirement.
           */
          if (ic->ic_flags & IEEE80211_F_DATAPAD)
                  hdrspace = roundup(hdrsize, sizeof(uint32_t));
          else
                  hdrspace = hdrsize;
  
          wh = mtod(m0, struct ieee80211_frame *);
          /* NB: mark the first frag; it will be propagated below */
          wh->i_fc[1] |= IEEE80211_FC1_MORE_FRAG;
          totalhdrsize = hdrspace + ciphdrsize;
          fragno = 1;
          off = mtu - ciphdrsize;
          remainder = m0->m_pkthdr.len - off;
          prev = m0;
          do {
                  fragsize = MIN(totalhdrsize + remainder, mtu);
                  m = m_get2(fragsize, M_NOWAIT, MT_DATA, M_PKTHDR);
                  if (m == NULL)
                          goto bad;
                  /* leave room to prepend any cipher header */
                  m_align(m, fragsize - ciphdrsize);
  
                  /*
                   * Form the header in the fragment.  Note that since
                   * we mark the first fragment with the MORE_FRAG bit
                   * it automatically is propagated to each fragment; we
                   * need only clear it on the last fragment (done below).
                   * NB: frag 1+ dont have Mesh Control field present.
                   */
                  whf = mtod(m, struct ieee80211_frame *);
                  memcpy(whf, wh, hdrsize);
  #ifdef IEEE80211_SUPPORT_MESH
                  if (vap->iv_opmode == IEEE80211_M_MBSS) {
                          if (IEEE80211_IS_DSTODS(wh))
                                  ((struct ieee80211_qosframe_addr4 *)
                                      whf)->i_qos[1] &= ~IEEE80211_QOS_MC;
                          else
                                  ((struct ieee80211_qosframe *)
                                      whf)->i_qos[1] &= ~IEEE80211_QOS_MC;
                  }
  #endif
                  *(uint16_t *)&whf->i_seq[0] |= htole16(
                          (fragno & IEEE80211_SEQ_FRAG_MASK) <<
                                  IEEE80211_SEQ_FRAG_SHIFT);
                  fragno++;
  
                  payload = fragsize - totalhdrsize;
                  /* NB: destination is known to be contiguous */
  
                  m_copydata(m0, off, payload, mtod(m, uint8_t *) + hdrspace);
                  m->m_len = hdrspace + payload;
                  m->m_pkthdr.len = hdrspace + payload;
                  m->m_flags |= M_FRAG;
  
                  /* chain up the fragment */
                  prev->m_nextpkt = m;
                  prev = m;
  
                  /* deduct fragment just formed */
                  remainder -= payload;
                  off += payload;
          } while (remainder != 0);
  
          /* set the last fragment */
          m->m_flags |= M_LASTFRAG;
          whf->i_fc[1] &= ~IEEE80211_FC1_MORE_FRAG;
  
          /* strip first mbuf now that everything has been copied */
          m_adj(m0, -(m0->m_pkthdr.len - (mtu - ciphdrsize)));
          m0->m_flags |= M_FIRSTFRAG | M_FRAG;
  
          vap->iv_stats.is_tx_fragframes++;
          vap->iv_stats.is_tx_frags += fragno-1;
  
          return 1;
  bad:
          /* reclaim fragments but leave original frame for caller to free */
          ieee80211_free_mbuf(m0->m_nextpkt);
          m0->m_nextpkt = NULL;
          return 0;
  }
  
  /*
   * Add a supported rates element id to a frame.
   */
  uint8_t *
  ieee80211_add_rates(uint8_t *frm, const struct ieee80211_rateset *rs)
  {
          int nrates;
  
          *frm++ = IEEE80211_ELEMID_RATES;
          nrates = rs->rs_nrates;
          if (nrates > IEEE80211_RATE_SIZE)
                  nrates = IEEE80211_RATE_SIZE;
          *frm++ = nrates;
          memcpy(frm, rs->rs_rates, nrates);
          return frm + nrates;
  }
  
  /*
   * Add an extended supported rates element id to a frame.
   */
  uint8_t *
  ieee80211_add_xrates(uint8_t *frm, const struct ieee80211_rateset *rs)
  {
          /*
           * Add an extended supported rates element if operating in 11g mode.
           */
          if (rs->rs_nrates > IEEE80211_RATE_SIZE) {
                  int nrates = rs->rs_nrates - IEEE80211_RATE_SIZE;
                  *frm++ = IEEE80211_ELEMID_XRATES;
                  *frm++ = nrates;
                  memcpy(frm, rs->rs_rates + IEEE80211_RATE_SIZE, nrates);
                  frm += nrates;
          }
          return frm;
  }
  
  /* 
   * Add an ssid element to a frame.
   */
  uint8_t *
  ieee80211_add_ssid(uint8_t *frm, const uint8_t *ssid, u_int len)
  {
          *frm++ = IEEE80211_ELEMID_SSID;
          *frm++ = len;
          memcpy(frm, ssid, len);
          return frm + len;
  }
  
  /*
   * Add an erp element to a frame.
   */
  static uint8_t *
  ieee80211_add_erp(uint8_t *frm, struct ieee80211com *ic)
  {
          uint8_t erp;
  
          *frm++ = IEEE80211_ELEMID_ERP;
          *frm++ = 1;
          erp = 0;
          if (ic->ic_nonerpsta != 0)
                  erp |= IEEE80211_ERP_NON_ERP_PRESENT;
          if (ic->ic_flags & IEEE80211_F_USEPROT)
                  erp |= IEEE80211_ERP_USE_PROTECTION;
          if (ic->ic_flags & IEEE80211_F_USEBARKER)
                  erp |= IEEE80211_ERP_LONG_PREAMBLE;
          *frm++ = erp;
          return frm;
  }
  
  /*
   * Add a CFParams element to a frame.
   */
  static uint8_t *
  ieee80211_add_cfparms(uint8_t *frm, struct ieee80211com *ic)
  {
  #define ADDSHORT(frm, v) do {   \
          le16enc(frm, v);        \
          frm += 2;               \
  } while (0)
          *frm++ = IEEE80211_ELEMID_CFPARMS;
          *frm++ = 6;
          *frm++ = 0;             /* CFP count */
          *frm++ = 2;             /* CFP period */
          ADDSHORT(frm, 0);       /* CFP MaxDuration (TU) */
          ADDSHORT(frm, 0);       /* CFP CurRemaining (TU) */
          return frm;
  #undef ADDSHORT
  }
  
  static __inline uint8_t *
  add_appie(uint8_t *frm, const struct ieee80211_appie *ie)
  {
          memcpy(frm, ie->ie_data, ie->ie_len);
          return frm + ie->ie_len;
  }
  
  static __inline uint8_t *
  add_ie(uint8_t *frm, const uint8_t *ie)
  {
          memcpy(frm, ie, 2 + ie[1]);
          return frm + 2 + ie[1];
  }
  
  #define WME_OUI_BYTES           0x00, 0x50, 0xf2
  /*
   * Add a WME information element to a frame.
   */
  uint8_t *
  ieee80211_add_wme_info(uint8_t *frm, struct ieee80211_wme_state *wme)
  {
          static const struct ieee80211_wme_info info = {
                  .wme_id         = IEEE80211_ELEMID_VENDOR,
                  .wme_len        = sizeof(struct ieee80211_wme_info) - 2,
                  .wme_oui        = { WME_OUI_BYTES },
                  .wme_type       = WME_OUI_TYPE,
                  .wme_subtype    = WME_INFO_OUI_SUBTYPE,
                  .wme_version    = WME_VERSION,
                  .wme_info       = 0,
          };
          memcpy(frm, &info, sizeof(info));
          return frm + sizeof(info); 
  }
  
  /*
   * Add a WME parameters element to a frame.
   */
  static uint8_t *
  ieee80211_add_wme_param(uint8_t *frm, struct ieee80211_wme_state *wme)
  {
  #define SM(_v, _f)      (((_v) << _f##_S) & _f)
  #define ADDSHORT(frm, v) do {   \
          le16enc(frm, v);        \
          frm += 2;               \
  } while (0)
          /* NB: this works 'cuz a param has an info at the front */
          static const struct ieee80211_wme_info param = {
                  .wme_id         = IEEE80211_ELEMID_VENDOR,
                  .wme_len        = sizeof(struct ieee80211_wme_param) - 2,
                  .wme_oui        = { WME_OUI_BYTES },
                  .wme_type       = WME_OUI_TYPE,
                  .wme_subtype    = WME_PARAM_OUI_SUBTYPE,
                  .wme_version    = WME_VERSION,
          };
          int i;
  
          memcpy(frm, &param, sizeof(param));
          frm += __offsetof(struct ieee80211_wme_info, wme_info);
          *frm++ = wme->wme_bssChanParams.cap_info;       /* AC info */
          *frm++ = 0;                                     /* reserved field */
          for (i = 0; i < WME_NUM_AC; i++) {
                  const struct wmeParams *ac =
                         &wme->wme_bssChanParams.cap_wmeParams[i];
                  *frm++ = SM(i, WME_PARAM_ACI)
                         | SM(ac->wmep_acm, WME_PARAM_ACM)
                         | SM(ac->wmep_aifsn, WME_PARAM_AIFSN)
                         ;
                  *frm++ = SM(ac->wmep_logcwmax, WME_PARAM_LOGCWMAX)
                         | SM(ac->wmep_logcwmin, WME_PARAM_LOGCWMIN)
                         ;
                  ADDSHORT(frm, ac->wmep_txopLimit);
          }
          return frm;
  #undef SM
  #undef ADDSHORT
  }
  #undef WME_OUI_BYTES
  
  /*
   * Add an 11h Power Constraint element to a frame.
   */
  static uint8_t *
  ieee80211_add_powerconstraint(uint8_t *frm, struct ieee80211vap *vap)
  {
          const struct ieee80211_channel *c = vap->iv_bss->ni_chan;
          /* XXX per-vap tx power limit? */
          int8_t limit = vap->iv_ic->ic_txpowlimit / 2;
  
          frm[0] = IEEE80211_ELEMID_PWRCNSTR;
          frm[1] = 1;
          frm[2] = c->ic_maxregpower > limit ?  c->ic_maxregpower - limit : 0;
          return frm + 3;
  }
  
  /*
   * Add an 11h Power Capability element to a frame.
   */
  static uint8_t *
  ieee80211_add_powercapability(uint8_t *frm, const struct ieee80211_channel *c)
  {
          frm[0] = IEEE80211_ELEMID_PWRCAP;
          frm[1] = 2;
          frm[2] = c->ic_minpower;
          frm[3] = c->ic_maxpower;
          return frm + 4;
  }
  
  /*
   * Add an 11h Supported Channels element to a frame.
   */
  static uint8_t *
  ieee80211_add_supportedchannels(uint8_t *frm, struct ieee80211com *ic)
  {
          static const int ielen = 26;
  
          frm[0] = IEEE80211_ELEMID_SUPPCHAN;
          frm[1] = ielen;
          /* XXX not correct */
          memcpy(frm+2, ic->ic_chan_avail, ielen);
          return frm + 2 + ielen;
  }
  
  /*
   * Add an 11h Quiet time element to a frame.
   */
  static uint8_t *
  ieee80211_add_quiet(uint8_t *frm, struct ieee80211vap *vap)
  {
          struct ieee80211_quiet_ie *quiet = (struct ieee80211_quiet_ie *) frm;
  
          quiet->quiet_ie = IEEE80211_ELEMID_QUIET;
          quiet->len = 6;
          if (vap->iv_quiet_count_value == 1)
                  vap->iv_quiet_count_value = vap->iv_quiet_count;
          else if (vap->iv_quiet_count_value > 1)
                  vap->iv_quiet_count_value--;
  
          if (vap->iv_quiet_count_value == 0) {
                  /* value 0 is reserved as per 802.11h standerd */
                  vap->iv_quiet_count_value = 1;
          }
  
          quiet->tbttcount = vap->iv_quiet_count_value;
          quiet->period = vap->iv_quiet_period;
          quiet->duration = htole16(vap->iv_quiet_duration);
          quiet->offset = htole16(vap->iv_quiet_offset);
          return frm + sizeof(*quiet);
  }
  
  /*
   * Add an 11h Channel Switch Announcement element to a frame.
   * Note that we use the per-vap CSA count to adjust the global
   * counter so we can use this routine to form probe response
   * frames and get the current count.
   */
  static uint8_t *
  ieee80211_add_csa(uint8_t *frm, struct ieee80211vap *vap)
  {
          struct ieee80211com *ic = vap->iv_ic;
          struct ieee80211_csa_ie *csa = (struct ieee80211_csa_ie *) frm;
  
          csa->csa_ie = IEEE80211_ELEMID_CSA;
          csa->csa_len = 3;
          csa->csa_mode = 1;              /* XXX force quiet on channel */
          csa->csa_newchan = ieee80211_chan2ieee(ic, ic->ic_csa_newchan);
          csa->csa_count = ic->ic_csa_count - vap->iv_csa_count;
          return frm + sizeof(*csa);
  }
  
  /*
   * Add an 11h country information element to a frame.
   */
  static uint8_t *
  ieee80211_add_countryie(uint8_t *frm, struct ieee80211com *ic)
  {
  
          if (ic->ic_countryie == NULL ||
              ic->ic_countryie_chan != ic->ic_bsschan) {
                  /*
                   * Handle lazy construction of ie.  This is done on
                   * first use and after a channel change that requires
                   * re-calculation.
                   */
                  if (ic->ic_countryie != NULL)
                          IEEE80211_FREE(ic->ic_countryie, M_80211_NODE_IE);
                  ic->ic_countryie = ieee80211_alloc_countryie(ic);
                  if (ic->ic_countryie == NULL)
                          return frm;
                  ic->ic_countryie_chan = ic->ic_bsschan;
          }
          return add_appie(frm, ic->ic_countryie);
  }
  
  uint8_t *
  ieee80211_add_wpa(uint8_t *frm, const struct ieee80211vap *vap)
  {
          if (vap->iv_flags & IEEE80211_F_WPA1 && vap->iv_wpa_ie != NULL)
                  return (add_ie(frm, vap->iv_wpa_ie));
          else {
                  /* XXX else complain? */
                  return (frm);
          }
  }
  
  uint8_t *
  ieee80211_add_rsn(uint8_t *frm, const struct ieee80211vap *vap)
  {
          if (vap->iv_flags & IEEE80211_F_WPA2 && vap->iv_rsn_ie != NULL)
                  return (add_ie(frm, vap->iv_rsn_ie));
          else {
                  /* XXX else complain? */
                  return (frm);
          }
  }
  
  uint8_t *
  ieee80211_add_qos(uint8_t *frm, const struct ieee80211_node *ni)
  {
          if (ni->ni_flags & IEEE80211_NODE_QOS) {
                  *frm++ = IEEE80211_ELEMID_QOS;
                  *frm++ = 1;
                  *frm++ = 0;
          }
  
          return (frm);
  }
  
  /*
   * Send a probe request frame with the specified ssid
   * and any optional information element data.
   */
  int
  ieee80211_send_probereq(struct ieee80211_node *ni,
          const uint8_t sa[IEEE80211_ADDR_LEN],
          const uint8_t da[IEEE80211_ADDR_LEN],
          const uint8_t bssid[IEEE80211_ADDR_LEN],
          const uint8_t *ssid, size_t ssidlen)
  {
          struct ieee80211vap *vap = ni->ni_vap;
          struct ieee80211com *ic = ni->ni_ic;
          const struct ieee80211_txparam *tp;
          struct ieee80211_bpf_params params;
          const struct ieee80211_rateset *rs;
          struct mbuf *m;
          uint8_t *frm;
          int ret;
  
          if (vap->iv_state == IEEE80211_S_CAC) {
                  IEEE80211_NOTE(vap, IEEE80211_MSG_OUTPUT, ni,
                      "block %s frame in CAC state", "probe request");
                  vap->iv_stats.is_tx_badstate++;
                  return EIO;             /* XXX */
          }
  
          /*
           * Hold a reference on the node so it doesn't go away until after
           * the xmit is complete all the way in the driver.  On error we
           * will remove our reference.
           */
          IEEE80211_DPRINTF(vap, IEEE80211_MSG_NODE,
                  "ieee80211_ref_node (%s:%u) %p<%s> refcnt %d\n",
                  __func__, __LINE__,
                  ni, ether_sprintf(ni->ni_macaddr),
                  ieee80211_node_refcnt(ni)+1);
          ieee80211_ref_node(ni);
  
          /*
           * prreq frame format
           *      [tlv] ssid
           *      [tlv] supported rates
           *      [tlv] RSN (optional)
           *      [tlv] extended supported rates
           *      [tlv] WPA (optional)
           *      [tlv] user-specified ie's
           */
          m = ieee80211_getmgtframe(&frm,
                   ic->ic_headroom + sizeof(struct ieee80211_frame),
                   2 + IEEE80211_NWID_LEN
                 + 2 + IEEE80211_RATE_SIZE
                 + sizeof(struct ieee80211_ie_wpa)
                 + 2 + (IEEE80211_RATE_MAXSIZE - IEEE80211_RATE_SIZE)
                 + sizeof(struct ieee80211_ie_wpa)
                 + (vap->iv_appie_probereq != NULL ?
                     vap->iv_appie_probereq->ie_len : 0)
          );
          if (m == NULL) {
                  vap->iv_stats.is_tx_nobuf++;
                  ieee80211_free_node(ni);
                  return ENOMEM;
          }
  
          frm = ieee80211_add_ssid(frm, ssid, ssidlen);
          rs = ieee80211_get_suprates(ic, ic->ic_curchan);
          frm = ieee80211_add_rates(frm, rs);
          frm = ieee80211_add_rsn(frm, vap);
          frm = ieee80211_add_xrates(frm, rs);
          frm = ieee80211_add_wpa(frm, vap);
          if (vap->iv_appie_probereq != NULL)
                  frm = add_appie(frm, vap->iv_appie_probereq);
          m->m_pkthdr.len = m->m_len = frm - mtod(m, uint8_t *);
  
          KASSERT(M_LEADINGSPACE(m) >= sizeof(struct ieee80211_frame),
              ("leading space %zd", M_LEADINGSPACE(m)));
          M_PREPEND(m, sizeof(struct ieee80211_frame), M_NOWAIT);
          if (m == NULL) {
                  /* NB: cannot happen */
                  ieee80211_free_node(ni);
                  return ENOMEM;
          }
  
          IEEE80211_TX_LOCK(ic);
          ieee80211_send_setup(ni, m,
               IEEE80211_FC0_TYPE_MGT | IEEE80211_FC0_SUBTYPE_PROBE_REQ,
               IEEE80211_NONQOS_TID, sa, da, bssid);
          /* XXX power management? */
          m->m_flags |= M_ENCAP;          /* mark encapsulated */
  
          M_WME_SETAC(m, WME_AC_BE);
  
          IEEE80211_NODE_STAT(ni, tx_probereq);
          IEEE80211_NODE_STAT(ni, tx_mgmt);
  
          IEEE80211_DPRINTF(vap, IEEE80211_MSG_DEBUG | IEEE80211_MSG_DUMPPKTS,
              "send probe req on channel %u bssid %s ssid \"%.*s\"\n",
              ieee80211_chan2ieee(ic, ic->ic_curchan), ether_sprintf(bssid),
              ssidlen, ssid);
  
          memset(&params, 0, sizeof(params));
          params.ibp_pri = M_WME_GETAC(m);
          tp = &vap->iv_txparms[ieee80211_chan2mode(ic->ic_curchan)];
          params.ibp_rate0 = tp->mgmtrate;
          if (IEEE80211_IS_MULTICAST(da)) {
                  params.ibp_flags |= IEEE80211_BPF_NOACK;
                  params.ibp_try0 = 1;
          } else
                  params.ibp_try0 = tp->maxretry;
          params.ibp_power = ni->ni_txpower;
          ret = ieee80211_raw_output(vap, ni, m, &params);
          IEEE80211_TX_UNLOCK(ic);
          return (ret);
  }
  
  /*
   * Calculate capability information for mgt frames.
   */
  uint16_t
  ieee80211_getcapinfo(struct ieee80211vap *vap, struct ieee80211_channel *chan)
  {
          struct ieee80211com *ic = vap->iv_ic;
          uint16_t capinfo;
  
          KASSERT(vap->iv_opmode != IEEE80211_M_STA, ("station mode"));
  
          if (vap->iv_opmode == IEEE80211_M_HOSTAP)
                  capinfo = IEEE80211_CAPINFO_ESS;
          else if (vap->iv_opmode == IEEE80211_M_IBSS)
                  capinfo = IEEE80211_CAPINFO_IBSS;
          else
                  capinfo = 0;
          if (vap->iv_flags & IEEE80211_F_PRIVACY)
                  capinfo |= IEEE80211_CAPINFO_PRIVACY;
          if ((ic->ic_flags & IEEE80211_F_SHPREAMBLE) &&
              IEEE80211_IS_CHAN_2GHZ(chan))
                  capinfo |= IEEE80211_CAPINFO_SHORT_PREAMBLE;
          if (ic->ic_flags & IEEE80211_F_SHSLOT)
                  capinfo |= IEEE80211_CAPINFO_SHORT_SLOTTIME;
          if (IEEE80211_IS_CHAN_5GHZ(chan) && (vap->iv_flags & IEEE80211_F_DOTH))
                  capinfo |= IEEE80211_CAPINFO_SPECTRUM_MGMT;
          return capinfo;
  }
  
  /*
   * Send a management frame.  The node is for the destination (or ic_bss
   * when in station mode).  Nodes other than ic_bss have their reference
   * count bumped to reflect our use for an indeterminant time.
   */
  int
  ieee80211_send_mgmt(struct ieee80211_node *ni, int type, int arg)
  {
  #define HTFLAGS (IEEE80211_NODE_HT | IEEE80211_NODE_HTCOMPAT)
  #define senderr(_x, _v) do { vap->iv_stats._v++; ret = _x; goto bad; } while (0)
          struct ieee80211vap *vap = ni->ni_vap;
          struct ieee80211com *ic = ni->ni_ic;
          struct ieee80211_node *bss = vap->iv_bss;
          struct ieee80211_bpf_params params;
          struct mbuf *m;
          uint8_t *frm;
          uint16_t capinfo;
          int has_challenge, is_shared_key, ret, status;
  
          KASSERT(ni != NULL, ("null node"));
  
          /*
           * Hold a reference on the node so it doesn't go away until after
           * the xmit is complete all the way in the driver.  On error we
           * will remove our reference.
           */
          IEEE80211_DPRINTF(vap, IEEE80211_MSG_NODE,
                  "ieee80211_ref_node (%s:%u) %p<%s> refcnt %d\n",
                  __func__, __LINE__,
                  ni, ether_sprintf(ni->ni_macaddr),
                  ieee80211_node_refcnt(ni)+1);
          ieee80211_ref_node(ni);
  
          memset(&params, 0, sizeof(params));
          switch (type) {
  
          case IEEE80211_FC0_SUBTYPE_AUTH:
                  status = arg >> 16;
                  arg &= 0xffff;
                  has_challenge = ((arg == IEEE80211_AUTH_SHARED_CHALLENGE ||
                      arg == IEEE80211_AUTH_SHARED_RESPONSE) &&
                      ni->ni_challenge != NULL);
  
                  /*
                   * Deduce whether we're doing open authentication or
                   * shared key authentication.  We do the latter if
                   * we're in the middle of a shared key authentication
                   * handshake or if we're initiating an authentication
                   * request and configured to use shared key.
                   */
                  is_shared_key = has_challenge ||
                       arg >= IEEE80211_AUTH_SHARED_RESPONSE ||
                       (arg == IEEE80211_AUTH_SHARED_REQUEST &&
                        bss->ni_authmode == IEEE80211_AUTH_SHARED);
  
                  m = ieee80211_getmgtframe(&frm,
                            ic->ic_headroom + sizeof(struct ieee80211_frame),
                            3 * sizeof(uint16_t)
                          + (has_challenge && status == IEEE80211_STATUS_SUCCESS ?
                                  sizeof(uint16_t)+IEEE80211_CHALLENGE_LEN : 0)
                  );
                  if (m == NULL)
                          senderr(ENOMEM, is_tx_nobuf);
  
                  ((uint16_t *)frm)[0] =
                      (is_shared_key) ? htole16(IEEE80211_AUTH_ALG_SHARED)
                                      : htole16(IEEE80211_AUTH_ALG_OPEN);
                  ((uint16_t *)frm)[1] = htole16(arg);    /* sequence number */
                  ((uint16_t *)frm)[2] = htole16(status);/* status */
  
                  if (has_challenge && status == IEEE80211_STATUS_SUCCESS) {
                          ((uint16_t *)frm)[3] =
                              htole16((IEEE80211_CHALLENGE_LEN << 8) |
                              IEEE80211_ELEMID_CHALLENGE);
                          memcpy(&((uint16_t *)frm)[4], ni->ni_challenge,
                              IEEE80211_CHALLENGE_LEN);
                          m->m_pkthdr.len = m->m_len =
                                  4 * sizeof(uint16_t) + IEEE80211_CHALLENGE_LEN;
                          if (arg == IEEE80211_AUTH_SHARED_RESPONSE) {
                                  IEEE80211_NOTE(vap, IEEE80211_MSG_AUTH, ni,
                                      "request encrypt frame (%s)", __func__);
                                  /* mark frame for encryption */
                                  params.ibp_flags |= IEEE80211_BPF_CRYPTO;
                          }
                  } else
                          m->m_pkthdr.len = m->m_len = 3 * sizeof(uint16_t);
  
                  /* XXX not right for shared key */
                  if (status == IEEE80211_STATUS_SUCCESS)
                          IEEE80211_NODE_STAT(ni, tx_auth);
                  else
                          IEEE80211_NODE_STAT(ni, tx_auth_fail);
  
                  if (vap->iv_opmode == IEEE80211_M_STA)
                          ieee80211_add_callback(m, ieee80211_tx_mgt_cb,
                                  (void *) vap->iv_state);
                  break;
  
          case IEEE80211_FC0_SUBTYPE_DEAUTH:
                  IEEE80211_NOTE(vap, IEEE80211_MSG_AUTH, ni,
                      "send station deauthenticate (reason: %d (%s))", arg,
                      ieee80211_reason_to_string(arg));
                  m = ieee80211_getmgtframe(&frm,
                          ic->ic_headroom + sizeof(struct ieee80211_frame),
                          sizeof(uint16_t));
                  if (m == NULL)
                          senderr(ENOMEM, is_tx_nobuf);
                  *(uint16_t *)frm = htole16(arg);        /* reason */
                  m->m_pkthdr.len = m->m_len = sizeof(uint16_t);
  
                  IEEE80211_NODE_STAT(ni, tx_deauth);
                  IEEE80211_NODE_STAT_SET(ni, tx_deauth_code, arg);
  
                  ieee80211_node_unauthorize(ni);         /* port closed */
                  break;
  
          case IEEE80211_FC0_SUBTYPE_ASSOC_REQ:
          case IEEE80211_FC0_SUBTYPE_REASSOC_REQ:
                  /*
                   * asreq frame format
                   *      [2] capability information
                   *      [2] listen interval
                   *      [6*] current AP address (reassoc only)
                   *      [tlv] ssid
                   *      [tlv] supported rates
                   *      [tlv] extended supported rates
                   *      [4] power capability (optional)
                   *      [28] supported channels (optional)
                   *      [tlv] HT capabilities
                   *      [tlv] WME (optional)
                   *      [tlv] Vendor OUI HT capabilities (optional)
                   *      [tlv] Atheros capabilities (if negotiated)
                   *      [tlv] AppIE's (optional)
                   */
                  m = ieee80211_getmgtframe(&frm,
                           ic->ic_headroom + sizeof(struct ieee80211_frame),
                           sizeof(uint16_t)
                         + sizeof(uint16_t)
                         + IEEE80211_ADDR_LEN
                         + 2 + IEEE80211_NWID_LEN
                         + 2 + IEEE80211_RATE_SIZE
                         + 2 + (IEEE80211_RATE_MAXSIZE - IEEE80211_RATE_SIZE)
                         + 4
                         + 2 + 26
                         + sizeof(struct ieee80211_wme_info)
                         + sizeof(struct ieee80211_ie_htcap)
                         + 4 + sizeof(struct ieee80211_ie_htcap)
  #ifdef IEEE80211_SUPPORT_SUPERG
                         + sizeof(struct ieee80211_ath_ie)
  #endif
                         + (vap->iv_appie_wpa != NULL ?
                                  vap->iv_appie_wpa->ie_len : 0)
                         + (vap->iv_appie_assocreq != NULL ?
                                  vap->iv_appie_assocreq->ie_len : 0)
                  );
                  if (m == NULL)
                          senderr(ENOMEM, is_tx_nobuf);
  
                  KASSERT(vap->iv_opmode == IEEE80211_M_STA,
                      ("wrong mode %u", vap->iv_opmode));
                  capinfo = IEEE80211_CAPINFO_ESS;
                  if (vap->iv_flags & IEEE80211_F_PRIVACY)
                          capinfo |= IEEE80211_CAPINFO_PRIVACY;
                  /*
                   * NB: Some 11a AP's reject the request when
                   *     short premable is set.
                   */
                  if ((ic->ic_flags & IEEE80211_F_SHPREAMBLE) &&
                      IEEE80211_IS_CHAN_2GHZ(ic->ic_curchan))
                          capinfo |= IEEE80211_CAPINFO_SHORT_PREAMBLE;
                  if (IEEE80211_IS_CHAN_ANYG(ic->ic_curchan) &&
                      (ic->ic_caps & IEEE80211_C_SHSLOT))
                          capinfo |= IEEE80211_CAPINFO_SHORT_SLOTTIME;
                  if ((ni->ni_capinfo & IEEE80211_CAPINFO_SPECTRUM_MGMT) &&
                      (vap->iv_flags & IEEE80211_F_DOTH))
                          capinfo |= IEEE80211_CAPINFO_SPECTRUM_MGMT;
                  *(uint16_t *)frm = htole16(capinfo);
                  frm += 2;
  
                  KASSERT(bss->ni_intval != 0, ("beacon interval is zero!"));
                  *(uint16_t *)frm = htole16(howmany(ic->ic_lintval,
                                                      bss->ni_intval));
                  frm += 2;
  
                  if (type == IEEE80211_FC0_SUBTYPE_REASSOC_REQ) {
                          IEEE80211_ADDR_COPY(frm, bss->ni_bssid);
                          frm += IEEE80211_ADDR_LEN;
                  }
  
                  frm = ieee80211_add_ssid(frm, ni->ni_essid, ni->ni_esslen);
                  frm = ieee80211_add_rates(frm, &ni->ni_rates);
                  frm = ieee80211_add_rsn(frm, vap);
                  frm = ieee80211_add_xrates(frm, &ni->ni_rates);
                  if (capinfo & IEEE80211_CAPINFO_SPECTRUM_MGMT) {
                          frm = ieee80211_add_powercapability(frm,
                              ic->ic_curchan);
                          frm = ieee80211_add_supportedchannels(frm, ic);
                  }
  
                  /*
                   * Check the channel - we may be using an 11n NIC with an
                   * 11n capable station, but we're configured to be an 11b
                   * channel.
                   */
                  if ((vap->iv_flags_ht & IEEE80211_FHT_HT) &&
                      IEEE80211_IS_CHAN_HT(ni->ni_chan) &&
                      ni->ni_ies.htcap_ie != NULL &&
                      ni->ni_ies.htcap_ie[0] == IEEE80211_ELEMID_HTCAP) {
                          frm = ieee80211_add_htcap(frm, ni);
                  }
                  frm = ieee80211_add_wpa(frm, vap);
                  if ((ic->ic_flags & IEEE80211_F_WME) &&
                      ni->ni_ies.wme_ie != NULL)
                          frm = ieee80211_add_wme_info(frm, &ic->ic_wme);
  
                  /*
                   * Same deal - only send HT info if we're on an 11n
                   * capable channel.
                   */
                  if ((vap->iv_flags_ht & IEEE80211_FHT_HT) &&
                      IEEE80211_IS_CHAN_HT(ni->ni_chan) &&
                      ni->ni_ies.htcap_ie != NULL &&
                      ni->ni_ies.htcap_ie[0] == IEEE80211_ELEMID_VENDOR) {
                          frm = ieee80211_add_htcap_vendor(frm, ni);
                  }
  #ifdef IEEE80211_SUPPORT_SUPERG
                  if (IEEE80211_ATH_CAP(vap, ni, IEEE80211_F_ATHEROS)) {
                          frm = ieee80211_add_ath(frm, 
                                  IEEE80211_ATH_CAP(vap, ni, IEEE80211_F_ATHEROS),
                                  ((vap->iv_flags & IEEE80211_F_WPA) == 0 &&
                                   ni->ni_authmode != IEEE80211_AUTH_8021X) ?
                                  vap->iv_def_txkey : IEEE80211_KEYIX_NONE);
                  }
  #endif /* IEEE80211_SUPPORT_SUPERG */
                  if (vap->iv_appie_assocreq != NULL)
                          frm = add_appie(frm, vap->iv_appie_assocreq);
                  m->m_pkthdr.len = m->m_len = frm - mtod(m, uint8_t *);
  
                  ieee80211_add_callback(m, ieee80211_tx_mgt_cb,
                          (void *) vap->iv_state);
                  break;
  
          case IEEE80211_FC0_SUBTYPE_ASSOC_RESP:
          case IEEE80211_FC0_SUBTYPE_REASSOC_RESP:
                  /*
                   * asresp frame format
                   *      [2] capability information
                   *      [2] status
                   *      [2] association ID
                   *      [tlv] supported rates
                   *      [tlv] extended supported rates
                   *      [tlv] HT capabilities (standard, if STA enabled)
                   *      [tlv] HT information (standard, if STA enabled)
                   *      [tlv] WME (if configured and STA enabled)
                   *      [tlv] HT capabilities (vendor OUI, if STA enabled)
                   *      [tlv] HT information (vendor OUI, if STA enabled)
                   *      [tlv] Atheros capabilities (if STA enabled)
                   *      [tlv] AppIE's (optional)
                   */
                  m = ieee80211_getmgtframe(&frm,
                           ic->ic_headroom + sizeof(struct ieee80211_frame),
                           sizeof(uint16_t)
                         + sizeof(uint16_t)
                         + sizeof(uint16_t)
                         + 2 + IEEE80211_RATE_SIZE
                         + 2 + (IEEE80211_RATE_MAXSIZE - IEEE80211_RATE_SIZE)
                         + sizeof(struct ieee80211_ie_htcap) + 4
                         + sizeof(struct ieee80211_ie_htinfo) + 4
                         + sizeof(struct ieee80211_wme_param)
  #ifdef IEEE80211_SUPPORT_SUPERG
                         + sizeof(struct ieee80211_ath_ie)
  #endif
                         + (vap->iv_appie_assocresp != NULL ?
                                  vap->iv_appie_assocresp->ie_len : 0)
                  );
                  if (m == NULL)
                          senderr(ENOMEM, is_tx_nobuf);
  
                  capinfo = ieee80211_getcapinfo(vap, bss->ni_chan);
                  *(uint16_t *)frm = htole16(capinfo);
                  frm += 2;
  
                  *(uint16_t *)frm = htole16(arg);        /* status */
                  frm += 2;
  
                  if (arg == IEEE80211_STATUS_SUCCESS) {
                          *(uint16_t *)frm = htole16(ni->ni_associd);
                          IEEE80211_NODE_STAT(ni, tx_assoc);
                  } else
                          IEEE80211_NODE_STAT(ni, tx_assoc_fail);
                  frm += 2;
  
                  frm = ieee80211_add_rates(frm, &ni->ni_rates);
                  frm = ieee80211_add_xrates(frm, &ni->ni_rates);
                  /* NB: respond according to what we received */
                  if ((ni->ni_flags & HTFLAGS) == IEEE80211_NODE_HT) {
                          frm = ieee80211_add_htcap(frm, ni);
                          frm = ieee80211_add_htinfo(frm, ni);
                  }
                  if ((vap->iv_flags & IEEE80211_F_WME) &&
                      ni->ni_ies.wme_ie != NULL)
                          frm = ieee80211_add_wme_param(frm, &ic->ic_wme);
                  if ((ni->ni_flags & HTFLAGS) == HTFLAGS) {
                          frm = ieee80211_add_htcap_vendor(frm, ni);
                          frm = ieee80211_add_htinfo_vendor(frm, ni);
                  }
  #ifdef IEEE80211_SUPPORT_SUPERG
                  if (IEEE80211_ATH_CAP(vap, ni, IEEE80211_F_ATHEROS))
                          frm = ieee80211_add_ath(frm, 
                                  IEEE80211_ATH_CAP(vap, ni, IEEE80211_F_ATHEROS),
                                  ((vap->iv_flags & IEEE80211_F_WPA) == 0 &&
                                   ni->ni_authmode != IEEE80211_AUTH_8021X) ?
                                  vap->iv_def_txkey : IEEE80211_KEYIX_NONE);
  #endif /* IEEE80211_SUPPORT_SUPERG */
                  if (vap->iv_appie_assocresp != NULL)
                          frm = add_appie(frm, vap->iv_appie_assocresp);
                  m->m_pkthdr.len = m->m_len = frm - mtod(m, uint8_t *);
                  break;
  
          case IEEE80211_FC0_SUBTYPE_DISASSOC:
                  IEEE80211_NOTE(vap, IEEE80211_MSG_ASSOC, ni,
                      "send station disassociate (reason: %d (%s))", arg,
                      ieee80211_reason_to_string(arg));
                  m = ieee80211_getmgtframe(&frm,
                          ic->ic_headroom + sizeof(struct ieee80211_frame),
                          sizeof(uint16_t));
                  if (m == NULL)
                          senderr(ENOMEM, is_tx_nobuf);
                  *(uint16_t *)frm = htole16(arg);        /* reason */
                  m->m_pkthdr.len = m->m_len = sizeof(uint16_t);
  
                  IEEE80211_NODE_STAT(ni, tx_disassoc);
                  IEEE80211_NODE_STAT_SET(ni, tx_disassoc_code, arg);
                  break;
  
          default:
                  IEEE80211_NOTE(vap, IEEE80211_MSG_ANY, ni,
                      "invalid mgmt frame type %u", type);
                  senderr(EINVAL, is_tx_unknownmgt);
                  /* NOTREACHED */
          }
  
          /* NB: force non-ProbeResp frames to the highest queue */
          params.ibp_pri = WME_AC_VO;
          params.ibp_rate0 = bss->ni_txparms->mgmtrate;
          /* NB: we know all frames are unicast */
          params.ibp_try0 = bss->ni_txparms->maxretry;
          params.ibp_power = bss->ni_txpower;
          return ieee80211_mgmt_output(ni, m, type, &params);
  bad:
          ieee80211_free_node(ni);
          return ret;
  #undef senderr
  #undef HTFLAGS
  }
  
  /*
   * Return an mbuf with a probe response frame in it.
   * Space is left to prepend and 802.11 header at the
   * front but it's left to the caller to fill in.
   */
  struct mbuf *
  ieee80211_alloc_proberesp(struct ieee80211_node *bss, int legacy)
  {
          struct ieee80211vap *vap = bss->ni_vap;
          struct ieee80211com *ic = bss->ni_ic;
          const struct ieee80211_rateset *rs;
          struct mbuf *m;
          uint16_t capinfo;
          uint8_t *frm;
  
          /*
           * probe response frame format
           *      [8] time stamp
           *      [2] beacon interval
           *      [2] cabability information
           *      [tlv] ssid
           *      [tlv] supported rates
           *      [tlv] parameter set (FH/DS)
           *      [tlv] parameter set (IBSS)
           *      [tlv] country (optional)
           *      [3] power control (optional)
           *      [5] channel switch announcement (CSA) (optional)
           *      [tlv] extended rate phy (ERP)
           *      [tlv] extended supported rates
           *      [tlv] RSN (optional)
           *      [tlv] HT capabilities
           *      [tlv] HT information
           *      [tlv] WPA (optional)
           *      [tlv] WME (optional)
           *      [tlv] Vendor OUI HT capabilities (optional)
           *      [tlv] Vendor OUI HT information (optional)
           *      [tlv] Atheros capabilities
           *      [tlv] AppIE's (optional)
           *      [tlv] Mesh ID (MBSS)
           *      [tlv] Mesh Conf (MBSS)
           */
          m = ieee80211_getmgtframe(&frm,
                   ic->ic_headroom + sizeof(struct ieee80211_frame),
                   8
                 + sizeof(uint16_t)
                 + sizeof(uint16_t)
                 + 2 + IEEE80211_NWID_LEN
                 + 2 + IEEE80211_RATE_SIZE
                 + 7      /* max(7,3) */
                 + IEEE80211_COUNTRY_MAX_SIZE
                 + 3
                 + sizeof(struct ieee80211_csa_ie)
                 + sizeof(struct ieee80211_quiet_ie)
                 + 3
                 + 2 + (IEEE80211_RATE_MAXSIZE - IEEE80211_RATE_SIZE)
                 + sizeof(struct ieee80211_ie_wpa)
                 + sizeof(struct ieee80211_ie_htcap)
                 + sizeof(struct ieee80211_ie_htinfo)
                 + sizeof(struct ieee80211_ie_wpa)
                 + sizeof(struct ieee80211_wme_param)
                 + 4 + sizeof(struct ieee80211_ie_htcap)
                 + 4 + sizeof(struct ieee80211_ie_htinfo)
  #ifdef IEEE80211_SUPPORT_SUPERG
                 + sizeof(struct ieee80211_ath_ie)
  #endif
  #ifdef IEEE80211_SUPPORT_MESH
                 + 2 + IEEE80211_MESHID_LEN
                 + sizeof(struct ieee80211_meshconf_ie)
  #endif
                 + (vap->iv_appie_proberesp != NULL ?
                          vap->iv_appie_proberesp->ie_len : 0)
          );
          if (m == NULL) {
                  vap->iv_stats.is_tx_nobuf++;
                  return NULL;
          }
  
          memset(frm, 0, 8);      /* timestamp should be filled later */
          frm += 8;
          *(uint16_t *)frm = htole16(bss->ni_intval);
          frm += 2;
          capinfo = ieee80211_getcapinfo(vap, bss->ni_chan);
          *(uint16_t *)frm = htole16(capinfo);
          frm += 2;
  
          frm = ieee80211_add_ssid(frm, bss->ni_essid, bss->ni_esslen);
          rs = ieee80211_get_suprates(ic, bss->ni_chan);
          frm = ieee80211_add_rates(frm, rs);
  
          if (IEEE80211_IS_CHAN_FHSS(bss->ni_chan)) {
                  *frm++ = IEEE80211_ELEMID_FHPARMS;
                  *frm++ = 5;
                  *frm++ = bss->ni_fhdwell & 0x00ff;
                  *frm++ = (bss->ni_fhdwell >> 8) & 0x00ff;
                  *frm++ = IEEE80211_FH_CHANSET(
                      ieee80211_chan2ieee(ic, bss->ni_chan));
                  *frm++ = IEEE80211_FH_CHANPAT(
                      ieee80211_chan2ieee(ic, bss->ni_chan));
                  *frm++ = bss->ni_fhindex;
          } else {
                  *frm++ = IEEE80211_ELEMID_DSPARMS;
                  *frm++ = 1;
                  *frm++ = ieee80211_chan2ieee(ic, bss->ni_chan);
          }
  
          if (vap->iv_opmode == IEEE80211_M_IBSS) {
                  *frm++ = IEEE80211_ELEMID_IBSSPARMS;
                  *frm++ = 2;
                  *frm++ = 0; *frm++ = 0;         /* TODO: ATIM window */
          }
          if ((vap->iv_flags & IEEE80211_F_DOTH) ||
              (vap->iv_flags_ext & IEEE80211_FEXT_DOTD))
                  frm = ieee80211_add_countryie(frm, ic);
          if (vap->iv_flags & IEEE80211_F_DOTH) {
                  if (IEEE80211_IS_CHAN_5GHZ(bss->ni_chan))
                          frm = ieee80211_add_powerconstraint(frm, vap);
                  if (ic->ic_flags & IEEE80211_F_CSAPENDING)
                          frm = ieee80211_add_csa(frm, vap);
          }
          if (vap->iv_flags & IEEE80211_F_DOTH) {
                  if (IEEE80211_IS_CHAN_DFS(ic->ic_bsschan) &&
                      (vap->iv_flags_ext & IEEE80211_FEXT_DFS)) {
                          if (vap->iv_quiet)
                                  frm = ieee80211_add_quiet(frm, vap);
                  }
          }
          if (IEEE80211_IS_CHAN_ANYG(bss->ni_chan))
                  frm = ieee80211_add_erp(frm, ic);
          frm = ieee80211_add_xrates(frm, rs);
          frm = ieee80211_add_rsn(frm, vap);
          /*
           * NB: legacy 11b clients do not get certain ie's.
           *     The caller identifies such clients by passing
           *     a token in legacy to us.  Could expand this to be
           *     any legacy client for stuff like HT ie's.
           */
          if (IEEE80211_IS_CHAN_HT(bss->ni_chan) &&
              legacy != IEEE80211_SEND_LEGACY_11B) {
                  frm = ieee80211_add_htcap(frm, bss);
                  frm = ieee80211_add_htinfo(frm, bss);
          }
          frm = ieee80211_add_wpa(frm, vap);
          if (vap->iv_flags & IEEE80211_F_WME)
                  frm = ieee80211_add_wme_param(frm, &ic->ic_wme);
          if (IEEE80211_IS_CHAN_HT(bss->ni_chan) &&
              (vap->iv_flags_ht & IEEE80211_FHT_HTCOMPAT) &&
              legacy != IEEE80211_SEND_LEGACY_11B) {
                  frm = ieee80211_add_htcap_vendor(frm, bss);
                  frm = ieee80211_add_htinfo_vendor(frm, bss);
          }
  #ifdef IEEE80211_SUPPORT_SUPERG
          if ((vap->iv_flags & IEEE80211_F_ATHEROS) &&
              legacy != IEEE80211_SEND_LEGACY_11B)
                  frm = ieee80211_add_athcaps(frm, bss);
  #endif
          if (vap->iv_appie_proberesp != NULL)
                  frm = add_appie(frm, vap->iv_appie_proberesp);
  #ifdef IEEE80211_SUPPORT_MESH
          if (vap->iv_opmode == IEEE80211_M_MBSS) {
                  frm = ieee80211_add_meshid(frm, vap);
                  frm = ieee80211_add_meshconf(frm, vap);
          }
  #endif
          m->m_pkthdr.len = m->m_len = frm - mtod(m, uint8_t *);
  
          return m;
  }
  
  /*
   * Send a probe response frame to the specified mac address.
   * This does not go through the normal mgt frame api so we
   * can specify the destination address and re-use the bss node
   * for the sta reference.
   */
  int
  ieee80211_send_proberesp(struct ieee80211vap *vap,
          const uint8_t da[IEEE80211_ADDR_LEN], int legacy)
  {
          struct ieee80211_node *bss = vap->iv_bss;
          struct ieee80211com *ic = vap->iv_ic;
          struct mbuf *m;
          int ret;
  
          if (vap->iv_state == IEEE80211_S_CAC) {
                  IEEE80211_NOTE(vap, IEEE80211_MSG_OUTPUT, bss,
                      "block %s frame in CAC state", "probe response");
                  vap->iv_stats.is_tx_badstate++;
                  return EIO;             /* XXX */
          }
  
          /*
           * Hold a reference on the node so it doesn't go away until after
           * the xmit is complete all the way in the driver.  On error we
           * will remove our reference.
           */
          IEEE80211_DPRINTF(vap, IEEE80211_MSG_NODE,
              "ieee80211_ref_node (%s:%u) %p<%s> refcnt %d\n",
              __func__, __LINE__, bss, ether_sprintf(bss->ni_macaddr),
              ieee80211_node_refcnt(bss)+1);
          ieee80211_ref_node(bss);
  
          m = ieee80211_alloc_proberesp(bss, legacy);
          if (m == NULL) {
                  ieee80211_free_node(bss);
                  return ENOMEM;
          }
  
          M_PREPEND(m, sizeof(struct ieee80211_frame), M_NOWAIT);
          KASSERT(m != NULL, ("no room for header"));
  
          IEEE80211_TX_LOCK(ic);
          ieee80211_send_setup(bss, m,
               IEEE80211_FC0_TYPE_MGT | IEEE80211_FC0_SUBTYPE_PROBE_RESP,
               IEEE80211_NONQOS_TID, vap->iv_myaddr, da, bss->ni_bssid);
          /* XXX power management? */
          m->m_flags |= M_ENCAP;          /* mark encapsulated */
  
          M_WME_SETAC(m, WME_AC_BE);
  
          IEEE80211_DPRINTF(vap, IEEE80211_MSG_DEBUG | IEEE80211_MSG_DUMPPKTS,
              "send probe resp on channel %u to %s%s\n",
              ieee80211_chan2ieee(ic, ic->ic_curchan), ether_sprintf(da),
              legacy ? " <legacy>" : "");
          IEEE80211_NODE_STAT(bss, tx_mgmt);
  
          ret = ieee80211_raw_output(vap, bss, m, NULL);
          IEEE80211_TX_UNLOCK(ic);
          return (ret);
  }
  
  /*
   * Allocate and build a RTS (Request To Send) control frame.
   */
  struct mbuf *
  ieee80211_alloc_rts(struct ieee80211com *ic,
          const uint8_t ra[IEEE80211_ADDR_LEN],
          const uint8_t ta[IEEE80211_ADDR_LEN],
          uint16_t dur)
  {
          struct ieee80211_frame_rts *rts;
          struct mbuf *m;
  
          /* XXX honor ic_headroom */
          m = m_gethdr(M_NOWAIT, MT_DATA);
          if (m != NULL) {
                  rts = mtod(m, struct ieee80211_frame_rts *);
                  rts->i_fc[0] = IEEE80211_FC0_VERSION_0 |
                          IEEE80211_FC0_TYPE_CTL | IEEE80211_FC0_SUBTYPE_RTS;
                  rts->i_fc[1] = IEEE80211_FC1_DIR_NODS;
                  *(u_int16_t *)rts->i_dur = htole16(dur);
                  IEEE80211_ADDR_COPY(rts->i_ra, ra);
                  IEEE80211_ADDR_COPY(rts->i_ta, ta);
  
                  m->m_pkthdr.len = m->m_len = sizeof(struct ieee80211_frame_rts);
          }
          return m;
  }
  
  /*
   * Allocate and build a CTS (Clear To Send) control frame.
   */
  struct mbuf *
  ieee80211_alloc_cts(struct ieee80211com *ic,
          const uint8_t ra[IEEE80211_ADDR_LEN], uint16_t dur)
  {
          struct ieee80211_frame_cts *cts;
          struct mbuf *m;
  
          /* XXX honor ic_headroom */
          m = m_gethdr(M_NOWAIT, MT_DATA);
          if (m != NULL) {
                  cts = mtod(m, struct ieee80211_frame_cts *);
                  cts->i_fc[0] = IEEE80211_FC0_VERSION_0 |
                          IEEE80211_FC0_TYPE_CTL | IEEE80211_FC0_SUBTYPE_CTS;
                  cts->i_fc[1] = IEEE80211_FC1_DIR_NODS;
                  *(u_int16_t *)cts->i_dur = htole16(dur);
                  IEEE80211_ADDR_COPY(cts->i_ra, ra);
  
                  m->m_pkthdr.len = m->m_len = sizeof(struct ieee80211_frame_cts);
          }
          return m;
  }
  
  static void
  ieee80211_tx_mgt_timeout(void *arg)
  {
          struct ieee80211vap *vap = arg;
  
          IEEE80211_LOCK(vap->iv_ic);
          if (vap->iv_state != IEEE80211_S_INIT &&
              (vap->iv_ic->ic_flags & IEEE80211_F_SCAN) == 0) {
                  /*
                   * NB: it's safe to specify a timeout as the reason here;
                   *     it'll only be used in the right state.
                   */
                  ieee80211_new_state_locked(vap, IEEE80211_S_SCAN,
                          IEEE80211_SCAN_FAIL_TIMEOUT);
          }
          IEEE80211_UNLOCK(vap->iv_ic);
  }
  
  /*
   * This is the callback set on net80211-sourced transmitted
   * authentication request frames.
   *
   * This does a couple of things:
   *
   * + If the frame transmitted was a success, it schedules a future
   *   event which will transition the interface to scan.
   *   If a state transition _then_ occurs before that event occurs,
   *   said state transition will cancel this callout.
   *
   * + If the frame transmit was a failure, it immediately schedules
   *   the transition back to scan.
   */
  static void
  ieee80211_tx_mgt_cb(struct ieee80211_node *ni, void *arg, int status)
  {
          struct ieee80211vap *vap = ni->ni_vap;
          enum ieee80211_state ostate = (enum ieee80211_state) arg;
  
          /*
           * Frame transmit completed; arrange timer callback.  If
           * transmit was successfully we wait for response.  Otherwise
           * we arrange an immediate callback instead of doing the
           * callback directly since we don't know what state the driver
           * is in (e.g. what locks it is holding).  This work should
           * not be too time-critical and not happen too often so the
           * added overhead is acceptable.
           *
           * XXX what happens if !acked but response shows up before callback?
           */
          if (vap->iv_state == ostate) {
                  callout_reset(&vap->iv_mgtsend,
                          status == 0 ? IEEE80211_TRANS_WAIT*hz : 0,
                          ieee80211_tx_mgt_timeout, vap);
          }
  }
  
  static void
  ieee80211_beacon_construct(struct mbuf *m, uint8_t *frm,
          struct ieee80211_node *ni)
  {
          struct ieee80211vap *vap = ni->ni_vap;
          struct ieee80211_beacon_offsets *bo = &vap->iv_bcn_off;
          struct ieee80211com *ic = ni->ni_ic;
          struct ieee80211_rateset *rs = &ni->ni_rates;
          uint16_t capinfo;
  
          /*
           * beacon frame format
           *      [8] time stamp
           *      [2] beacon interval
           *      [2] cabability information
           *      [tlv] ssid
           *      [tlv] supported rates
           *      [3] parameter set (DS)
           *      [8] CF parameter set (optional)
           *      [tlv] parameter set (IBSS/TIM)
           *      [tlv] country (optional)
           *      [3] power control (optional)
           *      [5] channel switch announcement (CSA) (optional)
           *      [tlv] extended rate phy (ERP)
           *      [tlv] extended supported rates
           *      [tlv] RSN parameters
           *      [tlv] HT capabilities
           *      [tlv] HT information
           * XXX Vendor-specific OIDs (e.g. Atheros)
           *      [tlv] WPA parameters
           *      [tlv] WME parameters
           *      [tlv] Vendor OUI HT capabilities (optional)
           *      [tlv] Vendor OUI HT information (optional)
           *      [tlv] Atheros capabilities (optional)
           *      [tlv] TDMA parameters (optional)
           *      [tlv] Mesh ID (MBSS)
           *      [tlv] Mesh Conf (MBSS)
           *      [tlv] application data (optional)
           */
  
          memset(bo, 0, sizeof(*bo));
  
          memset(frm, 0, 8);      /* XXX timestamp is set by hardware/driver */
          frm += 8;
          *(uint16_t *)frm = htole16(ni->ni_intval);
          frm += 2;
          capinfo = ieee80211_getcapinfo(vap, ni->ni_chan);
          bo->bo_caps = (uint16_t *)frm;
          *(uint16_t *)frm = htole16(capinfo);
          frm += 2;
          *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;
          frm = ieee80211_add_rates(frm, rs);
          if (!IEEE80211_IS_CHAN_FHSS(ni->ni_chan)) {
                  *frm++ = IEEE80211_ELEMID_DSPARMS;
                  *frm++ = 1;
                  *frm++ = ieee80211_chan2ieee(ic, ni->ni_chan);
          }
          if (ic->ic_flags & IEEE80211_F_PCF) {
                  bo->bo_cfp = frm;
                  frm = ieee80211_add_cfparms(frm, ic);
          }
          bo->bo_tim = frm;
          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 if (vap->iv_opmode == IEEE80211_M_HOSTAP ||
              vap->iv_opmode == IEEE80211_M_MBSS) {
                  /* TIM IE is the same for Mesh and Hostap */
                  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;
          if ((vap->iv_flags & IEEE80211_F_DOTH) ||
              (vap->iv_flags_ext & IEEE80211_FEXT_DOTD))
                  frm = ieee80211_add_countryie(frm, ic);
          if (vap->iv_flags & IEEE80211_F_DOTH) {
                  if (IEEE80211_IS_CHAN_5GHZ(ni->ni_chan))
                          frm = ieee80211_add_powerconstraint(frm, vap);
                  bo->bo_csa = frm;
                  if (ic->ic_flags & IEEE80211_F_CSAPENDING)
                          frm = ieee80211_add_csa(frm, vap);      
          } else
                  bo->bo_csa = frm;
  
          if (vap->iv_flags & IEEE80211_F_DOTH) {
                  bo->bo_quiet = frm;
                  if (IEEE80211_IS_CHAN_DFS(ic->ic_bsschan) &&
                      (vap->iv_flags_ext & IEEE80211_FEXT_DFS)) {
                          if (vap->iv_quiet)
                                  frm = ieee80211_add_quiet(frm,vap);
                  }
          } else
                  bo->bo_quiet = frm;
  
          if (IEEE80211_IS_CHAN_ANYG(ni->ni_chan)) {
                  bo->bo_erp = frm;
                  frm = ieee80211_add_erp(frm, ic);
          }
          frm = ieee80211_add_xrates(frm, rs);
          frm = ieee80211_add_rsn(frm, vap);
          if (IEEE80211_IS_CHAN_HT(ni->ni_chan)) {
                  frm = ieee80211_add_htcap(frm, ni);
                  bo->bo_htinfo = frm;
                  frm = ieee80211_add_htinfo(frm, ni);
          }
          frm = ieee80211_add_wpa(frm, vap);
          if (vap->iv_flags & IEEE80211_F_WME) {
                  bo->bo_wme = frm;
                  frm = ieee80211_add_wme_param(frm, &ic->ic_wme);
          }
          if (IEEE80211_IS_CHAN_HT(ni->ni_chan) &&
              (vap->iv_flags_ht & IEEE80211_FHT_HTCOMPAT)) {
                  frm = ieee80211_add_htcap_vendor(frm, ni);
                  frm = ieee80211_add_htinfo_vendor(frm, ni);
          }
  #ifdef IEEE80211_SUPPORT_SUPERG
          if (vap->iv_flags & IEEE80211_F_ATHEROS) {
                  bo->bo_ath = frm;
                  frm = ieee80211_add_athcaps(frm, ni);
          }
  #endif
  #ifdef IEEE80211_SUPPORT_TDMA
          if (vap->iv_caps & IEEE80211_C_TDMA) {
                  bo->bo_tdma = frm;
                  frm = ieee80211_add_tdma(frm, vap);
          }
  #endif
          if (vap->iv_appie_beacon != NULL) {
                  bo->bo_appie = frm;
                  bo->bo_appie_len = vap->iv_appie_beacon->ie_len;
                  frm = add_appie(frm, vap->iv_appie_beacon);
          }
  #ifdef IEEE80211_SUPPORT_MESH
          if (vap->iv_opmode == IEEE80211_M_MBSS) {
                  frm = ieee80211_add_meshid(frm, vap);
                  bo->bo_meshconf = frm;
                  frm = ieee80211_add_meshconf(frm, vap);
          }
  #endif
          bo->bo_tim_trailer_len = frm - bo->bo_tim_trailer;
          bo->bo_csa_trailer_len = frm - bo->bo_csa;
          m->m_pkthdr.len = m->m_len = frm - mtod(m, uint8_t *);
  }
  
  /*
   * Allocate a beacon frame and fillin the appropriate bits.
   */
  struct mbuf *
  ieee80211_beacon_alloc(struct ieee80211_node *ni)
  {
          struct ieee80211vap *vap = ni->ni_vap;
          struct ieee80211com *ic = ni->ni_ic;
          struct ifnet *ifp = vap->iv_ifp;
          struct ieee80211_frame *wh;
          struct mbuf *m;
          int pktlen;
          uint8_t *frm;
  
          /*
           * beacon frame format
           *      [8] time stamp
           *      [2] beacon interval
           *      [2] cabability information
           *      [tlv] ssid
           *      [tlv] supported rates
           *      [3] parameter set (DS)
           *      [8] CF parameter set (optional)
           *      [tlv] parameter set (IBSS/TIM)
           *      [tlv] country (optional)
           *      [3] power control (optional)
           *      [5] channel switch announcement (CSA) (optional)
           *      [tlv] extended rate phy (ERP)
           *      [tlv] extended supported rates
           *      [tlv] RSN parameters
           *      [tlv] HT capabilities
           *      [tlv] HT information
           *      [tlv] Vendor OUI HT capabilities (optional)
           *      [tlv] Vendor OUI HT information (optional)
           * XXX Vendor-specific OIDs (e.g. Atheros)
           *      [tlv] WPA parameters
           *      [tlv] WME parameters
           *      [tlv] TDMA parameters (optional)
           *      [tlv] Mesh ID (MBSS)
           *      [tlv] Mesh Conf (MBSS)
           *      [tlv] application data (optional)
           * NB: we allocate the max space required for the TIM bitmap.
           * XXX how big is this?
           */
          pktlen =   8                                    /* time stamp */
                   + sizeof(uint16_t)                     /* beacon interval */
                   + sizeof(uint16_t)                     /* capabilities */
                   + 2 + ni->ni_esslen                    /* ssid */
                   + 2 + IEEE80211_RATE_SIZE              /* supported rates */
                   + 2 + 1                                /* DS parameters */
                   + 2 + 6                                /* CF parameters */
                   + 2 + 4 + vap->iv_tim_len              /* DTIM/IBSSPARMS */
                   + IEEE80211_COUNTRY_MAX_SIZE           /* country */
                   + 2 + 1                                /* power control */
                   + sizeof(struct ieee80211_csa_ie)      /* CSA */
                   + sizeof(struct ieee80211_quiet_ie)    /* Quiet */
                   + 2 + 1                                /* ERP */
                   + 2 + (IEEE80211_RATE_MAXSIZE - IEEE80211_RATE_SIZE)
                   + (vap->iv_caps & IEEE80211_C_WPA ?    /* WPA 1+2 */
                          2*sizeof(struct ieee80211_ie_wpa) : 0)
                   /* XXX conditional? */
                   + 4+2*sizeof(struct ieee80211_ie_htcap)/* HT caps */
                   + 4+2*sizeof(struct ieee80211_ie_htinfo)/* HT info */
                   + (vap->iv_caps & IEEE80211_C_WME ?    /* WME */
                          sizeof(struct ieee80211_wme_param) : 0)
  #ifdef IEEE80211_SUPPORT_SUPERG
                   + sizeof(struct ieee80211_ath_ie)      /* ATH */
  #endif
  #ifdef IEEE80211_SUPPORT_TDMA
                   + (vap->iv_caps & IEEE80211_C_TDMA ?   /* TDMA */
                          sizeof(struct ieee80211_tdma_param) : 0)
  #endif
  #ifdef IEEE80211_SUPPORT_MESH
                   + 2 + ni->ni_meshidlen
                   + sizeof(struct ieee80211_meshconf_ie)
  #endif
                   + IEEE80211_MAX_APPIE
                   ;
          m = ieee80211_getmgtframe(&frm,
                  ic->ic_headroom + sizeof(struct ieee80211_frame), pktlen);
          if (m == NULL) {
                  IEEE80211_DPRINTF(vap, IEEE80211_MSG_ANY,
                          "%s: cannot get buf; size %u\n", __func__, pktlen);
                  vap->iv_stats.is_tx_nobuf++;
                  return NULL;
          }
          ieee80211_beacon_construct(m, frm, ni);
  
          M_PREPEND(m, sizeof(struct ieee80211_frame), M_NOWAIT);
          KASSERT(m != NULL, ("no space for 802.11 header?"));
          wh = mtod(m, 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;
          *(uint16_t *)wh->i_dur = 0;
          IEEE80211_ADDR_COPY(wh->i_addr1, ifp->if_broadcastaddr);
          IEEE80211_ADDR_COPY(wh->i_addr2, vap->iv_myaddr);
          IEEE80211_ADDR_COPY(wh->i_addr3, ni->ni_bssid);
          *(uint16_t *)wh->i_seq = 0;
  
          return m;
  }
  
  /*
   * Update the dynamic parts of a beacon frame based on the current state.
   */
  int
  ieee80211_beacon_update(struct ieee80211_node *ni, struct mbuf *m, int mcast)
  {
          struct ieee80211vap *vap = ni->ni_vap;
          struct ieee80211_beacon_offsets *bo = &vap->iv_bcn_off;
          struct ieee80211com *ic = ni->ni_ic;
          int len_changed = 0;
          uint16_t capinfo;
          struct ieee80211_frame *wh;
          ieee80211_seq seqno;
  
          IEEE80211_LOCK(ic);
          /*
           * Handle 11h channel change when we've reached the count.
           * We must recalculate the beacon frame contents to account
           * for the new channel.  Note we do this only for the first
           * vap that reaches this point; subsequent vaps just update
           * their beacon state to reflect the recalculated channel.
           */
          if (isset(bo->bo_flags, IEEE80211_BEACON_CSA) &&
              vap->iv_csa_count == ic->ic_csa_count) {
                  vap->iv_csa_count = 0;
                  /*
                   * Effect channel change before reconstructing the beacon
                   * frame contents as many places reference ni_chan.
                   */
                  if (ic->ic_csa_newchan != NULL)
                          ieee80211_csa_completeswitch(ic);
                  /*
                   * NB: ieee80211_beacon_construct clears all pending
                   * updates in bo_flags so we don't need to explicitly
                   * clear IEEE80211_BEACON_CSA.
                   */
                  ieee80211_beacon_construct(m,
                      mtod(m, uint8_t*) + sizeof(struct ieee80211_frame), ni);
  
                  /* XXX do WME aggressive mode processing? */
                  IEEE80211_UNLOCK(ic);
                  return 1;               /* just assume length changed */
          }
  
          wh = mtod(m, struct ieee80211_frame *);
          seqno = ni->ni_txseqs[IEEE80211_NONQOS_TID]++;
          *(uint16_t *)&wh->i_seq[0] =
                  htole16(seqno << IEEE80211_SEQ_SEQ_SHIFT);
          M_SEQNO_SET(m, seqno);
  
          /* XXX faster to recalculate entirely or just changes? */
          capinfo = ieee80211_getcapinfo(vap, ni->ni_chan);
          *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_DPRINTF(vap, IEEE80211_MSG_WME,
                                      "%s: traffic %u, disable aggressive mode\n",
                                      __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_DPRINTF(vap, IEEE80211_MSG_WME,
                                      "%s: traffic %u, enable aggressive mode\n",
                                      __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;
                  }
                  if (isset(bo->bo_flags, IEEE80211_BEACON_WME)) {
                          (void) ieee80211_add_wme_param(bo->bo_wme, wme);
                          clrbit(bo->bo_flags, IEEE80211_BEACON_WME);
                  }
          }
  
          if (isset(bo->bo_flags,  IEEE80211_BEACON_HTINFO)) {
                  ieee80211_ht_update_beacon(vap, bo);
                  clrbit(bo->bo_flags, IEEE80211_BEACON_HTINFO);
          }
  #ifdef IEEE80211_SUPPORT_TDMA
          if (vap->iv_caps & IEEE80211_C_TDMA) {
                  /*
                   * NB: the beacon is potentially updated every TBTT.
                   */
                  ieee80211_tdma_update_beacon(vap, bo);
          }
  #endif
  #ifdef IEEE80211_SUPPORT_MESH
          if (vap->iv_opmode == IEEE80211_M_MBSS)
                  ieee80211_mesh_update_beacon(vap, bo);
  #endif
  
          if (vap->iv_opmode == IEEE80211_M_HOSTAP ||
              vap->iv_opmode == IEEE80211_M_MBSS) {       /* NB: no IBSS support*/
                  struct ieee80211_tim_ie *tie =
                          (struct ieee80211_tim_ie *) bo->bo_tim;
                  if (isset(bo->bo_flags, IEEE80211_BEACON_TIM)) {
                          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
                           * insures there is space in the mbuf to write a
                           * maximal-size virtual bitmap (based on iv_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 &~ 1;
                                                  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 adjust = tie->tim_bitmap+timlen
                                             - bo->bo_tim_trailer;
                                  ovbcopy(bo->bo_tim_trailer,
                                      bo->bo_tim_trailer+adjust,
                                      bo->bo_tim_trailer_len);
                                  bo->bo_tim_trailer += adjust;
                                  bo->bo_erp += adjust;
                                  bo->bo_htinfo += adjust;
  #ifdef IEEE80211_SUPPORT_SUPERG
                                  bo->bo_ath += adjust;
  #endif
  #ifdef IEEE80211_SUPPORT_TDMA
                                  bo->bo_tdma += adjust;
  #endif
  #ifdef IEEE80211_SUPPORT_MESH
                                  bo->bo_meshconf += adjust;
  #endif
                                  bo->bo_appie += adjust;
                                  bo->bo_wme += adjust;
                                  bo->bo_csa += adjust;
                                  bo->bo_quiet += adjust;
                                  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);
  
                          clrbit(bo->bo_flags, IEEE80211_BEACON_TIM);
  
                          IEEE80211_DPRINTF(vap, IEEE80211_MSG_POWER,
                                  "%s: TIM updated, pending %u, off %u, len %u\n",
                                  __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 |= 1;
                  else
                          tie->tim_bitctl &= ~1;
                  if (isset(bo->bo_flags, IEEE80211_BEACON_CSA)) {
                          struct ieee80211_csa_ie *csa =
                              (struct ieee80211_csa_ie *) bo->bo_csa;
  
                          /*
                           * Insert or update CSA ie.  If we're just starting
                           * to count down to the channel switch then we need
                           * to insert the CSA ie.  Otherwise we just need to
                           * drop the count.  The actual change happens above
                           * when the vap's count reaches the target count.
                           */
                          if (vap->iv_csa_count == 0) {
                                  memmove(&csa[1], csa, bo->bo_csa_trailer_len);
                                  bo->bo_erp += sizeof(*csa);
                                  bo->bo_htinfo += sizeof(*csa);
                                  bo->bo_wme += sizeof(*csa);
  #ifdef IEEE80211_SUPPORT_SUPERG
                                  bo->bo_ath += sizeof(*csa);
  #endif
  #ifdef IEEE80211_SUPPORT_TDMA
                                  bo->bo_tdma += sizeof(*csa);
  #endif
  #ifdef IEEE80211_SUPPORT_MESH
                                  bo->bo_meshconf += sizeof(*csa);
  #endif
                                  bo->bo_appie += sizeof(*csa);
                                  bo->bo_csa_trailer_len += sizeof(*csa);
                                  bo->bo_quiet += sizeof(*csa);
                                  bo->bo_tim_trailer_len += sizeof(*csa);
                                  m->m_len += sizeof(*csa);
                                  m->m_pkthdr.len += sizeof(*csa);
  
                                  ieee80211_add_csa(bo->bo_csa, vap);
                          } else
                                  csa->csa_count--;
                          vap->iv_csa_count++;
                          /* NB: don't clear IEEE80211_BEACON_CSA */
                  }
                  if (IEEE80211_IS_CHAN_DFS(ic->ic_bsschan) &&
                      (vap->iv_flags_ext & IEEE80211_FEXT_DFS) ){
                          if (vap->iv_quiet)
                                  ieee80211_add_quiet(bo->bo_quiet, vap);
                  }
                  if (isset(bo->bo_flags, IEEE80211_BEACON_ERP)) {
                          /*
                           * ERP element needs updating.
                           */
                          (void) ieee80211_add_erp(bo->bo_erp, ic);
                          clrbit(bo->bo_flags, IEEE80211_BEACON_ERP);
                  }
  #ifdef IEEE80211_SUPPORT_SUPERG
                  if (isset(bo->bo_flags,  IEEE80211_BEACON_ATH)) {
                          ieee80211_add_athcaps(bo->bo_ath, ni);
                          clrbit(bo->bo_flags, IEEE80211_BEACON_ATH);
                  }
  #endif
          }
          if (isset(bo->bo_flags, IEEE80211_BEACON_APPIE)) {
                  const struct ieee80211_appie *aie = vap->iv_appie_beacon;
                  int aielen;
                  uint8_t *frm;
  
                  aielen = 0;
                  if (aie != NULL)
                          aielen += aie->ie_len;
                  if (aielen != bo->bo_appie_len) {
                          /* copy up/down trailer */
                          int adjust = aielen - bo->bo_appie_len;
                          ovbcopy(bo->bo_tim_trailer, bo->bo_tim_trailer+adjust,
                                  bo->bo_tim_trailer_len);
                          bo->bo_tim_trailer += adjust;
                          bo->bo_appie += adjust;
                          bo->bo_appie_len = aielen;
  
                          len_changed = 1;
                  }
                  frm = bo->bo_appie;
                  if (aie != NULL)
                          frm  = add_appie(frm, aie);
                  clrbit(bo->bo_flags, IEEE80211_BEACON_APPIE);
          }
          IEEE80211_UNLOCK(ic);
  
          return len_changed;
  }
  
  /*
   * Do Ethernet-LLC encapsulation for each payload in a fast frame
   * tunnel encapsulation.  The frame is assumed to have an Ethernet
   * header at the front that must be stripped before prepending the
   * LLC followed by the Ethernet header passed in (with an Ethernet
   * type that specifies the payload size).
   */
  struct mbuf *
  ieee80211_ff_encap1(struct ieee80211vap *vap, struct mbuf *m,
          const struct ether_header *eh)
  {
          struct llc *llc;
          uint16_t payload;
  
          /* XXX optimize by combining m_adj+M_PREPEND */
          m_adj(m, sizeof(struct ether_header) - sizeof(struct llc));
          llc = mtod(m, struct llc *);
          llc->llc_dsap = llc->llc_ssap = LLC_SNAP_LSAP;
          llc->llc_control = LLC_UI;
          llc->llc_snap.org_code[0] = 0;
          llc->llc_snap.org_code[1] = 0;
          llc->llc_snap.org_code[2] = 0;
          llc->llc_snap.ether_type = eh->ether_type;
          payload = m->m_pkthdr.len;              /* NB: w/o Ethernet header */
  
          M_PREPEND(m, sizeof(struct ether_header), M_NOWAIT);
          if (m == NULL) {                /* XXX cannot happen */
                  IEEE80211_DPRINTF(vap, IEEE80211_MSG_SUPERG,
                          "%s: no space for ether_header\n", __func__);
                  vap->iv_stats.is_tx_nobuf++;
                  return NULL;
          }
          ETHER_HEADER_COPY(mtod(m, void *), eh);
          mtod(m, struct ether_header *)->ether_type = htons(payload);
          return m;
  }
  
  /*
   * Complete an mbuf transmission.
   *
   * For now, this simply processes a completed frame after the
   * driver has completed it's transmission and/or retransmission.
   * It assumes the frame is an 802.11 encapsulated frame.
   *
   * Later on it will grow to become the exit path for a given frame
   * from the driver and, depending upon how it's been encapsulated
   * and already transmitted, it may end up doing A-MPDU retransmission,
   * power save requeuing, etc.
   *
   * In order for the above to work, the driver entry point to this
   * must not hold any driver locks.  Thus, the driver needs to delay
   * any actual mbuf completion until it can release said locks.
   *
   * This frees the mbuf and if the mbuf has a node reference,
   * the node reference will be freed.
   */
  void
  ieee80211_tx_complete(struct ieee80211_node *ni, struct mbuf *m, int status)
  {
  
          if (ni != NULL) {
                  struct ifnet *ifp = ni->ni_vap->iv_ifp;
  
                  if (status == 0) {
                          if_inc_counter(ifp, IFCOUNTER_OBYTES, m->m_pkthdr.len);
                          if_inc_counter(ifp, IFCOUNTER_OPACKETS, 1);
                          if (m->m_flags & M_MCAST)
                                  if_inc_counter(ifp, IFCOUNTER_OMCASTS, 1);
                  } else
                          if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
                  if (m->m_flags & M_TXCB)
                          ieee80211_process_callback(ni, m, status);
                  ieee80211_free_node(ni);
          }
          m_freem(m);
  }