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_dfs.c

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    1 /*-
    2  * Copyright (c) 2007-2008 Sam Leffler, Errno Consulting
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   24  */
   25 
   26 #include <sys/cdefs.h>
   27 #ifdef __FreeBSD__
   28 __FBSDID("$FreeBSD: stable/9/sys/net80211/ieee80211_dfs.c 249132 2013-04-05 08:22:11Z mav $");
   29 #endif
   30 
   31 /*
   32  * IEEE 802.11 DFS/Radar support.
   33  */
   34 #include "opt_inet.h"
   35 #include "opt_wlan.h"
   36 
   37 #include <sys/param.h>
   38 #include <sys/systm.h> 
   39 #include <sys/mbuf.h>   
   40 #include <sys/malloc.h>
   41 #include <sys/kernel.h>
   42 
   43 #include <sys/socket.h>
   44 #include <sys/sockio.h>
   45 #include <sys/endian.h>
   46 #include <sys/errno.h>
   47 #include <sys/proc.h>
   48 #include <sys/sysctl.h>
   49 
   50 #include <net/if.h>
   51 #include <net/if_media.h>
   52 
   53 #include <net80211/ieee80211_var.h>
   54 
   55 static MALLOC_DEFINE(M_80211_DFS, "80211dfs", "802.11 DFS state");
   56 
   57 static  int ieee80211_nol_timeout = 30*60;              /* 30 minutes */
   58 SYSCTL_INT(_net_wlan, OID_AUTO, nol_timeout, CTLFLAG_RW,
   59         &ieee80211_nol_timeout, 0, "NOL timeout (secs)");
   60 #define NOL_TIMEOUT     msecs_to_ticks(ieee80211_nol_timeout*1000)
   61 
   62 static  int ieee80211_cac_timeout = 60;         /* 60 seconds */
   63 SYSCTL_INT(_net_wlan, OID_AUTO, cac_timeout, CTLFLAG_RW,
   64         &ieee80211_cac_timeout, 0, "CAC timeout (secs)");
   65 #define CAC_TIMEOUT     msecs_to_ticks(ieee80211_cac_timeout*1000)
   66 
   67 void
   68 ieee80211_dfs_attach(struct ieee80211com *ic)
   69 {
   70         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
   71 
   72         callout_init_mtx(&dfs->nol_timer, IEEE80211_LOCK_OBJ(ic), 0);
   73         callout_init_mtx(&dfs->cac_timer, IEEE80211_LOCK_OBJ(ic), 0);
   74 }
   75 
   76 void
   77 ieee80211_dfs_detach(struct ieee80211com *ic)
   78 {
   79         /* NB: we assume no locking is needed */
   80         ieee80211_dfs_reset(ic);
   81 }
   82 
   83 void
   84 ieee80211_dfs_reset(struct ieee80211com *ic)
   85 {
   86         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
   87         int i;
   88 
   89         /* NB: we assume no locking is needed */
   90         /* NB: cac_timer should be cleared by the state machine */
   91         callout_drain(&dfs->nol_timer);
   92         for (i = 0; i < ic->ic_nchans; i++)
   93                 ic->ic_channels[i].ic_state = 0;
   94         dfs->lastchan = NULL;
   95 }
   96 
   97 static void
   98 cac_timeout(void *arg)
   99 {
  100         struct ieee80211vap *vap = arg;
  101         struct ieee80211com *ic = vap->iv_ic;
  102         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  103         int i;
  104 
  105         IEEE80211_LOCK_ASSERT(ic);
  106 
  107         if (vap->iv_state != IEEE80211_S_CAC)   /* NB: just in case */
  108                 return;
  109         /*
  110          * When radar is detected during a CAC we are woken
  111          * up prematurely to switch to a new channel.
  112          * Check the channel to decide how to act.
  113          */
  114         if (IEEE80211_IS_CHAN_RADAR(ic->ic_curchan)) {
  115                 ieee80211_notify_cac(ic, ic->ic_curchan,
  116                     IEEE80211_NOTIFY_CAC_RADAR);
  117 
  118                 if_printf(vap->iv_ifp,
  119                     "CAC timer on channel %u (%u MHz) stopped due to radar\n",
  120                     ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  121 
  122                 /* XXX clobbers any existing desired channel */
  123                 /* NB: dfs->newchan may be NULL, that's ok */
  124                 vap->iv_des_chan = dfs->newchan;
  125                 /* XXX recursive lock need ieee80211_new_state_locked */
  126                 ieee80211_new_state(vap, IEEE80211_S_SCAN, 0);
  127         } else {
  128                 if_printf(vap->iv_ifp,
  129                     "CAC timer on channel %u (%u MHz) expired; "
  130                     "no radar detected\n",
  131                     ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  132                 /*
  133                  * Mark all channels with the current frequency
  134                  * as having completed CAC; this keeps us from
  135                  * doing it again until we change channels.
  136                  */
  137                 for (i = 0; i < ic->ic_nchans; i++) {
  138                         struct ieee80211_channel *c = &ic->ic_channels[i];
  139                         if (c->ic_freq == ic->ic_curchan->ic_freq)
  140                                 c->ic_state |= IEEE80211_CHANSTATE_CACDONE;
  141                 }
  142                 ieee80211_notify_cac(ic, ic->ic_curchan,
  143                     IEEE80211_NOTIFY_CAC_EXPIRE);
  144                 ieee80211_cac_completeswitch(vap);
  145         }
  146 }
  147 
  148 /*
  149  * Initiate the CAC timer.  The driver is responsible
  150  * for setting up the hardware to scan for radar on the
  151  * channnel, we just handle timing things out.
  152  */
  153 void
  154 ieee80211_dfs_cac_start(struct ieee80211vap *vap)
  155 {
  156         struct ieee80211com *ic = vap->iv_ic;
  157         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  158 
  159         IEEE80211_LOCK_ASSERT(ic);
  160 
  161         callout_reset(&dfs->cac_timer, CAC_TIMEOUT, cac_timeout, vap);
  162         if_printf(vap->iv_ifp, "start %d second CAC timer on channel %u (%u MHz)\n",
  163             ticks_to_secs(CAC_TIMEOUT),
  164             ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  165         ieee80211_notify_cac(ic, ic->ic_curchan, IEEE80211_NOTIFY_CAC_START);
  166 }
  167 
  168 /*
  169  * Clear the CAC timer.
  170  */
  171 void
  172 ieee80211_dfs_cac_stop(struct ieee80211vap *vap)
  173 {
  174         struct ieee80211com *ic = vap->iv_ic;
  175         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  176 
  177         IEEE80211_LOCK_ASSERT(ic);
  178 
  179         /* NB: racey but not important */
  180         if (callout_pending(&dfs->cac_timer)) {
  181                 if_printf(vap->iv_ifp, "stop CAC timer on channel %u (%u MHz)\n",
  182                     ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  183                 ieee80211_notify_cac(ic, ic->ic_curchan,
  184                     IEEE80211_NOTIFY_CAC_STOP);
  185         }
  186         callout_stop(&dfs->cac_timer);
  187 }
  188 
  189 void
  190 ieee80211_dfs_cac_clear(struct ieee80211com *ic,
  191         const struct ieee80211_channel *chan)
  192 {
  193         int i;
  194 
  195         for (i = 0; i < ic->ic_nchans; i++) {
  196                 struct ieee80211_channel *c = &ic->ic_channels[i];
  197                 if (c->ic_freq == chan->ic_freq)
  198                         c->ic_state &= ~IEEE80211_CHANSTATE_CACDONE;
  199         }
  200 }
  201 
  202 static void
  203 dfs_timeout(void *arg)
  204 {
  205         struct ieee80211com *ic = arg;
  206         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  207         struct ieee80211_channel *c;
  208         int i, oldest, now;
  209 
  210         IEEE80211_LOCK_ASSERT(ic);
  211 
  212         now = oldest = ticks;
  213         for (i = 0; i < ic->ic_nchans; i++) {
  214                 c = &ic->ic_channels[i];
  215                 if (IEEE80211_IS_CHAN_RADAR(c)) {
  216                         if (time_after_eq(now, dfs->nol_event[i]+NOL_TIMEOUT)) {
  217                                 c->ic_state &= ~IEEE80211_CHANSTATE_RADAR;
  218                                 if (c->ic_state & IEEE80211_CHANSTATE_NORADAR) {
  219                                         /*
  220                                          * NB: do this here so we get only one
  221                                          * msg instead of one for every channel
  222                                          * table entry.
  223                                          */
  224                                         if_printf(ic->ic_ifp, "radar on channel"
  225                                             " %u (%u MHz) cleared after timeout\n",
  226                                             c->ic_ieee, c->ic_freq);
  227                                         /* notify user space */
  228                                         c->ic_state &=
  229                                             ~IEEE80211_CHANSTATE_NORADAR;
  230                                         ieee80211_notify_radar(ic, c);
  231                                 }
  232                         } else if (dfs->nol_event[i] < oldest)
  233                                 oldest = dfs->nol_event[i];
  234                 }
  235         }
  236         if (oldest != now) {
  237                 /* arrange to process next channel up for a status change */
  238                 callout_schedule(&dfs->nol_timer, oldest + NOL_TIMEOUT - now);
  239         }
  240 }
  241 
  242 static void
  243 announce_radar(struct ifnet *ifp, const struct ieee80211_channel *curchan,
  244         const struct ieee80211_channel *newchan)
  245 {
  246         if (newchan == NULL)
  247                 if_printf(ifp, "radar detected on channel %u (%u MHz)\n",
  248                     curchan->ic_ieee, curchan->ic_freq);
  249         else
  250                 if_printf(ifp, "radar detected on channel %u (%u MHz), "
  251                     "moving to channel %u (%u MHz)\n",
  252                     curchan->ic_ieee, curchan->ic_freq,
  253                     newchan->ic_ieee, newchan->ic_freq);
  254 }
  255 
  256 /*
  257  * Handle a radar detection event on a channel. The channel is
  258  * added to the NOL list and we record the time of the event.
  259  * Entries are aged out after NOL_TIMEOUT.  If radar was
  260  * detected while doing CAC we force a state/channel change.
  261  * Otherwise radar triggers a channel switch using the CSA
  262  * mechanism (when the channel is the bss channel).
  263  */
  264 void
  265 ieee80211_dfs_notify_radar(struct ieee80211com *ic, struct ieee80211_channel *chan)
  266 {
  267         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  268         int i, now;
  269 
  270         IEEE80211_LOCK_ASSERT(ic);
  271 
  272         /*
  273          * Mark all entries with this frequency.  Notify user
  274          * space and arrange for notification when the radar
  275          * indication is cleared.  Then kick the NOL processing
  276          * thread if not already running.
  277          */
  278         now = ticks;
  279         for (i = 0; i < ic->ic_nchans; i++) {
  280                 struct ieee80211_channel *c = &ic->ic_channels[i];
  281                 if (c->ic_freq == chan->ic_freq) {
  282                         c->ic_state &= ~IEEE80211_CHANSTATE_CACDONE;
  283                         c->ic_state |= IEEE80211_CHANSTATE_RADAR;
  284                         dfs->nol_event[i] = now;
  285                 }
  286         }
  287         ieee80211_notify_radar(ic, chan);
  288         chan->ic_state |= IEEE80211_CHANSTATE_NORADAR;
  289         if (!callout_pending(&dfs->nol_timer))
  290                 callout_reset(&dfs->nol_timer, NOL_TIMEOUT, dfs_timeout, ic);
  291 
  292         /*
  293          * If radar is detected on the bss channel while
  294          * doing CAC; force a state change by scheduling the
  295          * callout to be dispatched asap.  Otherwise, if this
  296          * event is for the bss channel then we must quiet
  297          * traffic and schedule a channel switch.
  298          *
  299          * Note this allows us to receive notification about
  300          * channels other than the bss channel; not sure
  301          * that can/will happen but it's simple to support.
  302          */
  303         if (chan == ic->ic_bsschan) {
  304                 /* XXX need a way to defer to user app */
  305                 dfs->newchan = ieee80211_dfs_pickchannel(ic);
  306 
  307                 announce_radar(ic->ic_ifp, chan, dfs->newchan);
  308 
  309                 if (callout_pending(&dfs->cac_timer))
  310                         callout_schedule(&dfs->cac_timer, 0);
  311                 else if (dfs->newchan != NULL) {
  312                         /* XXX mode 1, switch count 2 */
  313                         /* XXX calculate switch count based on max
  314                           switch time and beacon interval? */
  315                         ieee80211_csa_startswitch(ic, dfs->newchan, 1, 2);
  316                 } else {
  317                         /*
  318                          * Spec says to stop all transmissions and
  319                          * wait on the current channel for an entry
  320                          * on the NOL to expire.
  321                          */
  322                         /*XXX*/
  323                         if_printf(ic->ic_ifp, "%s: No free channels; waiting for entry "
  324                             "on NOL to expire\n", __func__);
  325                 }
  326         } else {
  327                 /*
  328                  * Issue rate-limited console msgs.
  329                  */
  330                 if (dfs->lastchan != chan) {
  331                         dfs->lastchan = chan;
  332                         dfs->cureps = 0;
  333                         announce_radar(ic->ic_ifp, chan, NULL);
  334                 } else if (ppsratecheck(&dfs->lastevent, &dfs->cureps, 1)) {
  335                         announce_radar(ic->ic_ifp, chan, NULL);
  336                 }
  337         }
  338 }
  339 
  340 struct ieee80211_channel *
  341 ieee80211_dfs_pickchannel(struct ieee80211com *ic)
  342 {
  343         struct ieee80211_channel *c;
  344         int i, flags;
  345         uint16_t v;
  346 
  347         /*
  348          * Consult the scan cache first.
  349          */
  350         flags = ic->ic_curchan->ic_flags & IEEE80211_CHAN_ALL;
  351         /*
  352          * XXX if curchan is HT this will never find a channel
  353          * XXX 'cuz we scan only legacy channels
  354          */
  355         c = ieee80211_scan_pickchannel(ic, flags);
  356         if (c != NULL)
  357                 return c;
  358         /*
  359          * No channel found in scan cache; select a compatible
  360          * one at random (skipping channels where radar has
  361          * been detected).
  362          */
  363         get_random_bytes(&v, sizeof(v));
  364         v %= ic->ic_nchans;
  365         for (i = v; i < ic->ic_nchans; i++) {
  366                 c = &ic->ic_channels[i];
  367                 if (!IEEE80211_IS_CHAN_RADAR(c) &&
  368                    (c->ic_flags & flags) == flags)
  369                         return c;
  370         }
  371         for (i = 0; i < v; i++) {
  372                 c = &ic->ic_channels[i];
  373                 if (!IEEE80211_IS_CHAN_RADAR(c) &&
  374                    (c->ic_flags & flags) == flags)
  375                         return c;
  376         }
  377         if_printf(ic->ic_ifp, "HELP, no channel located to switch to!\n");
  378         return NULL;
  379 }

Cache object: e5951bcbc947ee9920422ea2052ecf35


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