The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/net80211/ieee80211_node.c

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    1 /*-
    2  * Copyright (c) 2001 Atsushi Onoe
    3  * Copyright (c) 2002, 2003 Sam Leffler, Errno Consulting
    4  * All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. The name of the author may not be used to endorse or promote products
   15  *    derived from this software without specific prior written permission.
   16  *
   17  * Alternatively, this software may be distributed under the terms of the
   18  * GNU General Public License ("GPL") version 2 as published by the Free
   19  * Software Foundation.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   31  */
   32 
   33 #include <sys/cdefs.h>
   34 __FBSDID("$FreeBSD: releng/5.2/sys/net80211/ieee80211_node.c 122374 2003-11-09 23:36:46Z sam $");
   35 
   36 #include "opt_inet.h"
   37 
   38 #include <sys/param.h>
   39 #include <sys/systm.h> 
   40 #include <sys/mbuf.h>   
   41 #include <sys/malloc.h>
   42 #include <sys/kernel.h>
   43 #include <sys/socket.h>
   44 #include <sys/sockio.h>
   45 #include <sys/endian.h>
   46 #include <sys/errno.h>
   47 #include <sys/bus.h>
   48 #include <sys/proc.h>
   49 #include <sys/sysctl.h>
   50 
   51 #include <machine/atomic.h>
   52  
   53 #include <net/if.h>
   54 #include <net/if_dl.h>
   55 #include <net/if_media.h>
   56 #include <net/if_arp.h>
   57 #include <net/ethernet.h>
   58 #include <net/if_llc.h>
   59 
   60 #include <net80211/ieee80211_var.h>
   61 
   62 #include <net/bpf.h>
   63 
   64 #ifdef INET
   65 #include <netinet/in.h> 
   66 #include <netinet/if_ether.h>
   67 #endif
   68 
   69 static struct ieee80211_node *ieee80211_node_alloc(struct ieee80211com *);
   70 static void ieee80211_node_free(struct ieee80211com *, struct ieee80211_node *);
   71 static void ieee80211_node_copy(struct ieee80211com *,
   72                 struct ieee80211_node *, const struct ieee80211_node *);
   73 static u_int8_t ieee80211_node_getrssi(struct ieee80211com *,
   74                 struct ieee80211_node *);
   75 
   76 static void ieee80211_setup_node(struct ieee80211com *ic,
   77                 struct ieee80211_node *ni, u_int8_t *macaddr);
   78 static void _ieee80211_free_node(struct ieee80211com *,
   79                 struct ieee80211_node *);
   80 
   81 MALLOC_DEFINE(M_80211_NODE, "node", "802.11 node state");
   82 
   83 void
   84 ieee80211_node_attach(struct ifnet *ifp)
   85 {
   86         struct ieee80211com *ic = (void *)ifp;
   87 
   88         /* XXX need unit */
   89         IEEE80211_NODE_LOCK_INIT(ic, ifp->if_xname);
   90         TAILQ_INIT(&ic->ic_node);
   91         ic->ic_node_alloc = ieee80211_node_alloc;
   92         ic->ic_node_free = ieee80211_node_free;
   93         ic->ic_node_copy = ieee80211_node_copy;
   94         ic->ic_node_getrssi = ieee80211_node_getrssi;
   95         ic->ic_scangen = 1;
   96 }
   97 
   98 void
   99 ieee80211_node_lateattach(struct ifnet *ifp)
  100 {
  101         struct ieee80211com *ic = (void *)ifp;
  102 
  103         ic->ic_bss = (*ic->ic_node_alloc)(ic);
  104         KASSERT(ic->ic_bss != NULL, ("unable to setup inital BSS node"));
  105         ic->ic_bss->ni_chan = IEEE80211_CHAN_ANYC;
  106 }
  107 
  108 void
  109 ieee80211_node_detach(struct ifnet *ifp)
  110 {
  111         struct ieee80211com *ic = (void *)ifp;
  112 
  113         if (ic->ic_bss != NULL)
  114                 (*ic->ic_node_free)(ic, ic->ic_bss);
  115         ieee80211_free_allnodes(ic);
  116         IEEE80211_NODE_LOCK_DESTROY(ic);
  117 }
  118 
  119 /*
  120  * AP scanning support.
  121  */
  122 
  123 /*
  124  * Initialize the active channel set based on the set
  125  * of available channels and the current PHY mode.
  126  */
  127 static void
  128 ieee80211_reset_scan(struct ifnet *ifp)
  129 {
  130         struct ieee80211com *ic = (void *)ifp;
  131 
  132         memcpy(ic->ic_chan_scan, ic->ic_chan_active,
  133                 sizeof(ic->ic_chan_active));
  134         /* NB: hack, setup so next_scan starts with the first channel */
  135         if (ic->ic_bss->ni_chan == IEEE80211_CHAN_ANYC)
  136                 ic->ic_bss->ni_chan = &ic->ic_channels[IEEE80211_CHAN_MAX];
  137 }
  138 
  139 /*
  140  * Begin an active scan.
  141  */
  142 void
  143 ieee80211_begin_scan(struct ifnet *ifp)
  144 {
  145         struct ieee80211com *ic = (void *)ifp;
  146 
  147         /*
  148          * In all but hostap mode scanning starts off in
  149          * an active mode before switching to passive.
  150          */
  151         if (ic->ic_opmode != IEEE80211_M_HOSTAP) {
  152                 ic->ic_flags |= IEEE80211_F_ASCAN;
  153                 ic->ic_stats.is_scan_active++;
  154         } else
  155                 ic->ic_stats.is_scan_passive++;
  156         if (ifp->if_flags & IFF_DEBUG)
  157                 if_printf(ifp, "begin %s scan\n",
  158                         (ic->ic_flags & IEEE80211_F_ASCAN) ?
  159                                 "active" : "passive");
  160         /*
  161          * Clear scan state and flush any previously seen
  162          * AP's.  Note that the latter assumes we don't act
  163          * as both an AP and a station, otherwise we'll
  164          * potentially flush state of stations associated
  165          * with us.
  166          */
  167         ieee80211_reset_scan(ifp);
  168         ieee80211_free_allnodes(ic);
  169 
  170         /* Scan the next channel. */
  171         ieee80211_next_scan(ifp);
  172 }
  173 
  174 /*
  175  * Switch to the next channel marked for scanning.
  176  */
  177 void
  178 ieee80211_next_scan(struct ifnet *ifp)
  179 {
  180         struct ieee80211com *ic = (void *)ifp;
  181         struct ieee80211_channel *chan;
  182 
  183         chan = ic->ic_bss->ni_chan;
  184         for (;;) {
  185                 if (++chan > &ic->ic_channels[IEEE80211_CHAN_MAX])
  186                         chan = &ic->ic_channels[0];
  187                 if (isset(ic->ic_chan_scan, ieee80211_chan2ieee(ic, chan))) {
  188                         /*
  189                          * Honor channels marked passive-only
  190                          * during an active scan.
  191                          */
  192                         if ((ic->ic_flags & IEEE80211_F_ASCAN) == 0 ||
  193                             (chan->ic_flags & IEEE80211_CHAN_PASSIVE) == 0)
  194                                 break;
  195                 }
  196                 if (chan == ic->ic_bss->ni_chan) {
  197                         ieee80211_end_scan(ifp);
  198                         return;
  199                 }
  200         }
  201         clrbit(ic->ic_chan_scan, ieee80211_chan2ieee(ic, chan));
  202         IEEE80211_DPRINTF(("ieee80211_next_scan: chan %d->%d\n",
  203             ieee80211_chan2ieee(ic, ic->ic_bss->ni_chan),
  204             ieee80211_chan2ieee(ic, chan)));
  205         ic->ic_bss->ni_chan = chan;
  206         ieee80211_new_state(ic, IEEE80211_S_SCAN, -1);
  207 }
  208 
  209 void
  210 ieee80211_create_ibss(struct ieee80211com* ic, struct ieee80211_channel *chan)
  211 {
  212         struct ieee80211_node *ni;
  213         struct ifnet *ifp = &ic->ic_if;
  214 
  215         ni = ic->ic_bss;
  216         if (ifp->if_flags & IFF_DEBUG)
  217                 if_printf(ifp, "creating ibss\n");
  218         ic->ic_flags |= IEEE80211_F_SIBSS;
  219         ni->ni_chan = chan;
  220         ni->ni_rates = ic->ic_sup_rates[ieee80211_chan2mode(ic, ni->ni_chan)];
  221         IEEE80211_ADDR_COPY(ni->ni_macaddr, ic->ic_myaddr);
  222         IEEE80211_ADDR_COPY(ni->ni_bssid, ic->ic_myaddr);
  223         if (ic->ic_opmode == IEEE80211_M_IBSS)
  224                 ni->ni_bssid[0] |= 0x02;        /* local bit for IBSS */
  225         ni->ni_esslen = ic->ic_des_esslen;
  226         memcpy(ni->ni_essid, ic->ic_des_essid, ni->ni_esslen);
  227         ni->ni_rssi = 0;
  228         ni->ni_rstamp = 0;
  229         memset(ni->ni_tstamp, 0, sizeof(ni->ni_tstamp));
  230         ni->ni_intval = ic->ic_lintval;
  231         ni->ni_capinfo = IEEE80211_CAPINFO_IBSS;
  232         if (ic->ic_flags & IEEE80211_F_WEPON)
  233                 ni->ni_capinfo |= IEEE80211_CAPINFO_PRIVACY;
  234         if (ic->ic_phytype == IEEE80211_T_FH) {
  235                 ni->ni_fhdwell = 200;   /* XXX */
  236                 ni->ni_fhindex = 1;
  237         }
  238         ieee80211_new_state(ic, IEEE80211_S_RUN, -1);
  239 }
  240 
  241 /*
  242  * Complete a scan of potential channels.
  243  */
  244 void
  245 ieee80211_end_scan(struct ifnet *ifp)
  246 {
  247         struct ieee80211com *ic = (void *)ifp;
  248         struct ieee80211_node *ni, *nextbs, *selbs;
  249         u_int8_t rate;
  250         int i, fail;
  251 
  252         ic->ic_flags &= ~IEEE80211_F_ASCAN;
  253         ni = TAILQ_FIRST(&ic->ic_node);
  254 
  255         if (ic->ic_opmode == IEEE80211_M_HOSTAP) {
  256                 /* XXX off stack? */
  257                 u_char occupied[roundup(IEEE80211_CHAN_MAX, NBBY)];
  258                 /*
  259                  * The passive scan to look for existing AP's completed,
  260                  * select a channel to camp on.  Identify the channels
  261                  * that already have one or more AP's and try to locate
  262                  * an unnoccupied one.  If that fails, pick a random
  263                  * channel from the active set.
  264                  */
  265                 for (; ni != NULL; ni = nextbs) {
  266                         ieee80211_ref_node(ni);
  267                         nextbs = TAILQ_NEXT(ni, ni_list);
  268                         setbit(occupied, ieee80211_chan2ieee(ic, ni->ni_chan));
  269                         ieee80211_free_node(ic, ni);
  270                 }
  271                 for (i = 0; i < IEEE80211_CHAN_MAX; i++)
  272                         if (isset(ic->ic_chan_active, i) && isclr(occupied, i))
  273                                 break;
  274                 if (i == IEEE80211_CHAN_MAX) {
  275                         fail = arc4random() & 3;        /* random 0-3 */
  276                         for (i = 0; i < IEEE80211_CHAN_MAX; i++)
  277                                 if (isset(ic->ic_chan_active, i) && fail-- == 0)
  278                                         break;
  279                 }
  280                 ieee80211_create_ibss(ic, &ic->ic_channels[i]);
  281                 return;
  282         }
  283         if (ni == NULL) {
  284                 IEEE80211_DPRINTF(("%s: no scan candidate\n", __func__));
  285   notfound:
  286                 if (ic->ic_opmode == IEEE80211_M_IBSS &&
  287                     (ic->ic_flags & IEEE80211_F_IBSSON) &&
  288                     ic->ic_des_esslen != 0) {
  289                         ieee80211_create_ibss(ic, ic->ic_ibss_chan);
  290                         return;
  291                 }
  292                 /*
  293                  * Reset the list of channels to scan and start again.
  294                  */
  295                 ieee80211_reset_scan(ifp);
  296                 ieee80211_next_scan(ifp);
  297                 return;
  298         }
  299         selbs = NULL;
  300         if (ifp->if_flags & IFF_DEBUG)
  301                 if_printf(ifp, "\tmacaddr          bssid         chan  rssi rate flag  wep  essid\n");
  302         for (; ni != NULL; ni = nextbs) {
  303                 ieee80211_ref_node(ni);
  304                 nextbs = TAILQ_NEXT(ni, ni_list);
  305                 if (ni->ni_fails) {
  306                         /*
  307                          * The configuration of the access points may change
  308                          * during my scan.  So delete the entry for the AP
  309                          * and retry to associate if there is another beacon.
  310                          */
  311                         if (ni->ni_fails++ > 2)
  312                                 ieee80211_free_node(ic, ni);
  313                         continue;
  314                 }
  315                 fail = 0;
  316                 if (isclr(ic->ic_chan_active, ieee80211_chan2ieee(ic, ni->ni_chan)))
  317                         fail |= 0x01;
  318                 if (ic->ic_des_chan != IEEE80211_CHAN_ANYC &&
  319                     ni->ni_chan != ic->ic_des_chan)
  320                         fail |= 0x01;
  321                 if (ic->ic_opmode == IEEE80211_M_IBSS) {
  322                         if ((ni->ni_capinfo & IEEE80211_CAPINFO_IBSS) == 0)
  323                                 fail |= 0x02;
  324                 } else {
  325                         if ((ni->ni_capinfo & IEEE80211_CAPINFO_ESS) == 0)
  326                                 fail |= 0x02;
  327                 }
  328                 if (ic->ic_flags & IEEE80211_F_WEPON) {
  329                         if ((ni->ni_capinfo & IEEE80211_CAPINFO_PRIVACY) == 0)
  330                                 fail |= 0x04;
  331                 } else {
  332                         if (ni->ni_capinfo & IEEE80211_CAPINFO_PRIVACY)
  333                                 fail |= 0x04;
  334                 }
  335                 rate = ieee80211_fix_rate(ic, ni, IEEE80211_F_DONEGO);
  336                 if (rate & IEEE80211_RATE_BASIC)
  337                         fail |= 0x08;
  338                 if (ic->ic_des_esslen != 0 &&
  339                     (ni->ni_esslen != ic->ic_des_esslen ||
  340                      memcmp(ni->ni_essid, ic->ic_des_essid, ic->ic_des_esslen) != 0))
  341                         fail |= 0x10;
  342                 if ((ic->ic_flags & IEEE80211_F_DESBSSID) &&
  343                     !IEEE80211_ADDR_EQ(ic->ic_des_bssid, ni->ni_bssid))
  344                         fail |= 0x20;
  345                 if (ifp->if_flags & IFF_DEBUG) {
  346                         printf(" %c %s", fail ? '-' : '+',
  347                             ether_sprintf(ni->ni_macaddr));
  348                         printf(" %s%c", ether_sprintf(ni->ni_bssid),
  349                             fail & 0x20 ? '!' : ' ');
  350                         printf(" %3d%c", ieee80211_chan2ieee(ic, ni->ni_chan),
  351                                 fail & 0x01 ? '!' : ' ');
  352                         printf(" %+4d", ni->ni_rssi);
  353                         printf(" %2dM%c", (rate & IEEE80211_RATE_VAL) / 2,
  354                             fail & 0x08 ? '!' : ' ');
  355                         printf(" %4s%c",
  356                             (ni->ni_capinfo & IEEE80211_CAPINFO_ESS) ? "ess" :
  357                             (ni->ni_capinfo & IEEE80211_CAPINFO_IBSS) ? "ibss" :
  358                             "????",
  359                             fail & 0x02 ? '!' : ' ');
  360                         printf(" %3s%c ",
  361                             (ni->ni_capinfo & IEEE80211_CAPINFO_PRIVACY) ?
  362                             "wep" : "no",
  363                             fail & 0x04 ? '!' : ' ');
  364                         ieee80211_print_essid(ni->ni_essid, ni->ni_esslen);
  365                         printf("%s\n", fail & 0x10 ? "!" : "");
  366                 }
  367                 if (!fail) {
  368                         if (selbs == NULL)
  369                                 selbs = ni;
  370                         else if (ni->ni_rssi > selbs->ni_rssi) {
  371                                 ieee80211_unref_node(&selbs);
  372                                 selbs = ni;
  373                         } else
  374                                 ieee80211_unref_node(&ni);
  375                 } else {
  376                         ieee80211_unref_node(&ni);
  377                 }
  378         }
  379         if (selbs == NULL)
  380                 goto notfound;
  381         (*ic->ic_node_copy)(ic, ic->ic_bss, selbs);
  382         if (ic->ic_opmode == IEEE80211_M_IBSS) {
  383                 ieee80211_fix_rate(ic, ic->ic_bss, IEEE80211_F_DOFRATE |
  384                     IEEE80211_F_DONEGO | IEEE80211_F_DODEL);
  385                 if (ic->ic_bss->ni_rates.rs_nrates == 0) {
  386                         selbs->ni_fails++;
  387                         ieee80211_unref_node(&selbs);
  388                         goto notfound;
  389                 }
  390                 ieee80211_unref_node(&selbs);
  391                 ieee80211_new_state(ic, IEEE80211_S_RUN, -1);
  392         } else {
  393                 ieee80211_unref_node(&selbs);
  394                 ieee80211_new_state(ic, IEEE80211_S_AUTH, -1);
  395         }
  396 }
  397 
  398 static struct ieee80211_node *
  399 ieee80211_node_alloc(struct ieee80211com *ic)
  400 {
  401         return malloc(sizeof(struct ieee80211_node), M_80211_NODE,
  402                 M_NOWAIT | M_ZERO);
  403 }
  404 
  405 static void
  406 ieee80211_node_free(struct ieee80211com *ic, struct ieee80211_node *ni)
  407 {
  408         free(ni, M_80211_NODE);
  409 }
  410 
  411 static void
  412 ieee80211_node_copy(struct ieee80211com *ic,
  413         struct ieee80211_node *dst, const struct ieee80211_node *src)
  414 {
  415         *dst = *src;
  416 }
  417 
  418 static u_int8_t
  419 ieee80211_node_getrssi(struct ieee80211com *ic, struct ieee80211_node *ni)
  420 {
  421         return ni->ni_rssi;
  422 }
  423 
  424 static void
  425 ieee80211_setup_node(struct ieee80211com *ic,
  426         struct ieee80211_node *ni, u_int8_t *macaddr)
  427 {
  428         int hash;
  429 
  430         IEEE80211_ADDR_COPY(ni->ni_macaddr, macaddr);
  431         hash = IEEE80211_NODE_HASH(macaddr);
  432         ni->ni_refcnt = 1;              /* mark referenced */
  433         IEEE80211_NODE_LOCK(ic);
  434         TAILQ_INSERT_TAIL(&ic->ic_node, ni, ni_list);
  435         LIST_INSERT_HEAD(&ic->ic_hash[hash], ni, ni_hash);
  436         /* 
  437          * Note we don't enable the inactive timer when acting
  438          * as a station.  Nodes created in this mode represent
  439          * AP's identified while scanning.  If we time them out
  440          * then several things happen: we can't return the data
  441          * to users to show the list of AP's we encountered, and
  442          * more importantly, we'll incorrectly deauthenticate
  443          * ourself because the inactivity timer will kick us off. 
  444          */
  445         if (ic->ic_opmode != IEEE80211_M_STA)
  446                 ic->ic_inact_timer = IEEE80211_INACT_WAIT;
  447         IEEE80211_NODE_UNLOCK(ic);
  448 }
  449 
  450 struct ieee80211_node *
  451 ieee80211_alloc_node(struct ieee80211com *ic, u_int8_t *macaddr)
  452 {
  453         struct ieee80211_node *ni = (*ic->ic_node_alloc)(ic);
  454         if (ni != NULL)
  455                 ieee80211_setup_node(ic, ni, macaddr);
  456         return ni;
  457 }
  458 
  459 struct ieee80211_node *
  460 ieee80211_dup_bss(struct ieee80211com *ic, u_int8_t *macaddr)
  461 {
  462         struct ieee80211_node *ni = (*ic->ic_node_alloc)(ic);
  463         if (ni != NULL) {
  464                 memcpy(ni, ic->ic_bss, sizeof(struct ieee80211_node));
  465                 ieee80211_setup_node(ic, ni, macaddr);
  466         }
  467         return ni;
  468 }
  469 
  470 struct ieee80211_node *
  471 ieee80211_find_node(struct ieee80211com *ic, u_int8_t *macaddr)
  472 {
  473         struct ieee80211_node *ni;
  474         int hash;
  475 
  476         hash = IEEE80211_NODE_HASH(macaddr);
  477         IEEE80211_NODE_LOCK(ic);
  478         LIST_FOREACH(ni, &ic->ic_hash[hash], ni_hash) {
  479                 if (IEEE80211_ADDR_EQ(ni->ni_macaddr, macaddr)) {
  480                         atomic_add_int(&ni->ni_refcnt, 1); /* mark referenced */
  481                         break;
  482                 }
  483         }
  484         IEEE80211_NODE_UNLOCK(ic);
  485         return ni;
  486 }
  487 
  488 /*
  489  * Like find but search based on the channel too.
  490  */
  491 struct ieee80211_node *
  492 ieee80211_lookup_node(struct ieee80211com *ic,
  493         u_int8_t *macaddr, struct ieee80211_channel *chan)
  494 {
  495         struct ieee80211_node *ni;
  496         int hash;
  497 
  498         hash = IEEE80211_NODE_HASH(macaddr);
  499         IEEE80211_NODE_LOCK(ic);
  500         LIST_FOREACH(ni, &ic->ic_hash[hash], ni_hash) {
  501                 if (IEEE80211_ADDR_EQ(ni->ni_macaddr, macaddr) && ni->ni_chan == chan) {
  502                         atomic_add_int(&ni->ni_refcnt, 1);/* mark referenced */
  503                         break;
  504                 }
  505         }
  506         IEEE80211_NODE_UNLOCK(ic);
  507         return ni;
  508 }
  509 
  510 static void
  511 _ieee80211_free_node(struct ieee80211com *ic, struct ieee80211_node *ni)
  512 {
  513         KASSERT(ni != ic->ic_bss, ("freeing bss node"));
  514 
  515         TAILQ_REMOVE(&ic->ic_node, ni, ni_list);
  516         LIST_REMOVE(ni, ni_hash);
  517         if (TAILQ_EMPTY(&ic->ic_node))
  518                 ic->ic_inact_timer = 0;
  519         (*ic->ic_node_free)(ic, ni);
  520 }
  521 
  522 void
  523 ieee80211_free_node(struct ieee80211com *ic, struct ieee80211_node *ni)
  524 {
  525         KASSERT(ni != ic->ic_bss, ("freeing ic_bss"));
  526 
  527         /* XXX need equivalent of atomic_dec_and_test */
  528         atomic_subtract_int(&ni->ni_refcnt, 1);
  529         if (atomic_cmpset_int(&ni->ni_refcnt, 0, 1)) {
  530                 IEEE80211_NODE_LOCK(ic);
  531                 _ieee80211_free_node(ic, ni);
  532                 IEEE80211_NODE_UNLOCK(ic);
  533         }
  534 }
  535 
  536 void
  537 ieee80211_free_allnodes(struct ieee80211com *ic)
  538 {
  539         struct ieee80211_node *ni;
  540 
  541         IEEE80211_NODE_LOCK(ic);
  542         while ((ni = TAILQ_FIRST(&ic->ic_node)) != NULL)
  543                 _ieee80211_free_node(ic, ni);  
  544         IEEE80211_NODE_UNLOCK(ic);
  545 }
  546 
  547 /*
  548  * Timeout inactive nodes.  Note that we cannot hold the node
  549  * lock while sending a frame as this would lead to a LOR.
  550  * Instead we use a generation number to mark nodes that we've
  551  * scanned and drop the lock and restart a scan if we have to
  552  * time out a node.  Since we are single-threaded by virtue of
  553  * controlling the inactivity timer we can be sure this will
  554  * process each node only once.
  555  */
  556 void
  557 ieee80211_timeout_nodes(struct ieee80211com *ic)
  558 {
  559         struct ieee80211_node *ni;
  560         u_int gen = ic->ic_scangen++;           /* NB: ok 'cuz single-threaded*/
  561 
  562 restart:
  563         IEEE80211_NODE_LOCK(ic);
  564         TAILQ_FOREACH(ni, &ic->ic_node, ni_list) {
  565                 if (ni->ni_scangen == gen)      /* previously handled */
  566                         continue;
  567                 ni->ni_scangen = gen;
  568                 if (++ni->ni_inact > IEEE80211_INACT_MAX) {
  569                         IEEE80211_DPRINTF(("station %s timed out "
  570                             "due to inactivity (%u secs)\n",
  571                             ether_sprintf(ni->ni_macaddr),
  572                             ni->ni_inact));
  573                         /*
  574                          * Send a deauthenticate frame.
  575                          *
  576                          * Drop the node lock before sending the
  577                          * deauthentication frame in case the driver takes     
  578                          * a lock, as this will result in a LOR between the     
  579                          * node lock and the driver lock.
  580                          */
  581                         IEEE80211_NODE_UNLOCK(ic);
  582                         IEEE80211_SEND_MGMT(ic, ni,
  583                             IEEE80211_FC0_SUBTYPE_DEAUTH,
  584                             IEEE80211_REASON_AUTH_EXPIRE);
  585                         ieee80211_free_node(ic, ni);
  586                         ic->ic_stats.is_node_timeout++;
  587                         goto restart;
  588                 }
  589         }
  590         if (!TAILQ_EMPTY(&ic->ic_node))
  591                 ic->ic_inact_timer = IEEE80211_INACT_WAIT;
  592         IEEE80211_NODE_UNLOCK(ic);
  593 }
  594 
  595 void
  596 ieee80211_iterate_nodes(struct ieee80211com *ic, ieee80211_iter_func *f, void *arg)
  597 {
  598         struct ieee80211_node *ni;
  599 
  600         IEEE80211_NODE_LOCK(ic);
  601         TAILQ_FOREACH(ni, &ic->ic_node, ni_list)
  602                 (*f)(arg, ni);
  603         IEEE80211_NODE_UNLOCK(ic);
  604 }

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