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: releng/11.2/sys/net80211/ieee80211_dfs.c 297405 2016-03-30 00:44:10Z adrian $");
   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_var.h>
   52 #include <net/if_media.h>
   53 #include <net/ethernet.h>
   54 
   55 #include <net80211/ieee80211_var.h>
   56 
   57 static MALLOC_DEFINE(M_80211_DFS, "80211dfs", "802.11 DFS state");
   58 
   59 static  int ieee80211_nol_timeout = 30*60;              /* 30 minutes */
   60 SYSCTL_INT(_net_wlan, OID_AUTO, nol_timeout, CTLFLAG_RW,
   61         &ieee80211_nol_timeout, 0, "NOL timeout (secs)");
   62 #define NOL_TIMEOUT     msecs_to_ticks(ieee80211_nol_timeout*1000)
   63 
   64 static  int ieee80211_cac_timeout = 60;         /* 60 seconds */
   65 SYSCTL_INT(_net_wlan, OID_AUTO, cac_timeout, CTLFLAG_RW,
   66         &ieee80211_cac_timeout, 0, "CAC timeout (secs)");
   67 #define CAC_TIMEOUT     msecs_to_ticks(ieee80211_cac_timeout*1000)
   68 
   69 /*
   70  DFS* In order to facilitate  debugging, a couple of operating
   71  * modes aside from the default are needed.
   72  *
   73  * 0 - default CAC/NOL behaviour - ie, start CAC, place
   74  *     channel on NOL list.
   75  * 1 - send CAC, but don't change channel or add the channel
   76  *     to the NOL list.
   77  * 2 - just match on radar, don't send CAC or place channel in
   78  *     the NOL list.
   79  */
   80 static  int ieee80211_dfs_debug = DFS_DBG_NONE;
   81 
   82 /*
   83  * This option must not be included in the default kernel
   84  * as it allows users to plainly disable CAC/NOL handling.
   85  */
   86 #ifdef  IEEE80211_DFS_DEBUG
   87 SYSCTL_INT(_net_wlan, OID_AUTO, dfs_debug, CTLFLAG_RW,
   88         &ieee80211_dfs_debug, 0, "DFS debug behaviour");
   89 #endif
   90 
   91 static int
   92 null_set_quiet(struct ieee80211_node *ni, u_int8_t *quiet_elm)
   93 {
   94         return ENOSYS;
   95 }
   96 
   97 void
   98 ieee80211_dfs_attach(struct ieee80211com *ic)
   99 {
  100         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  101 
  102         callout_init_mtx(&dfs->nol_timer, IEEE80211_LOCK_OBJ(ic), 0);
  103         callout_init_mtx(&dfs->cac_timer, IEEE80211_LOCK_OBJ(ic), 0);
  104 
  105         ic->ic_set_quiet = null_set_quiet;
  106 }
  107 
  108 void
  109 ieee80211_dfs_detach(struct ieee80211com *ic)
  110 {
  111         /* NB: we assume no locking is needed */
  112         ieee80211_dfs_reset(ic);
  113 }
  114 
  115 void
  116 ieee80211_dfs_reset(struct ieee80211com *ic)
  117 {
  118         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  119         int i;
  120 
  121         /* NB: we assume no locking is needed */
  122         /* NB: cac_timer should be cleared by the state machine */
  123         callout_drain(&dfs->nol_timer);
  124         for (i = 0; i < ic->ic_nchans; i++)
  125                 ic->ic_channels[i].ic_state = 0;
  126         dfs->lastchan = NULL;
  127 }
  128 
  129 static void
  130 cac_timeout(void *arg)
  131 {
  132         struct ieee80211vap *vap = arg;
  133         struct ieee80211com *ic = vap->iv_ic;
  134         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  135         int i;
  136 
  137         IEEE80211_LOCK_ASSERT(ic);
  138 
  139         if (vap->iv_state != IEEE80211_S_CAC)   /* NB: just in case */
  140                 return;
  141         /*
  142          * When radar is detected during a CAC we are woken
  143          * up prematurely to switch to a new channel.
  144          * Check the channel to decide how to act.
  145          */
  146         if (IEEE80211_IS_CHAN_RADAR(ic->ic_curchan)) {
  147                 ieee80211_notify_cac(ic, ic->ic_curchan,
  148                     IEEE80211_NOTIFY_CAC_RADAR);
  149 
  150                 if_printf(vap->iv_ifp,
  151                     "CAC timer on channel %u (%u MHz) stopped due to radar\n",
  152                     ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  153 
  154                 /* XXX clobbers any existing desired channel */
  155                 /* NB: dfs->newchan may be NULL, that's ok */
  156                 vap->iv_des_chan = dfs->newchan;
  157                 /* XXX recursive lock need ieee80211_new_state_locked */
  158                 ieee80211_new_state(vap, IEEE80211_S_SCAN, 0);
  159         } else {
  160                 if_printf(vap->iv_ifp,
  161                     "CAC timer on channel %u (%u MHz) expired; "
  162                     "no radar detected\n",
  163                     ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  164                 /*
  165                  * Mark all channels with the current frequency
  166                  * as having completed CAC; this keeps us from
  167                  * doing it again until we change channels.
  168                  */
  169                 for (i = 0; i < ic->ic_nchans; i++) {
  170                         struct ieee80211_channel *c = &ic->ic_channels[i];
  171                         if (c->ic_freq == ic->ic_curchan->ic_freq)
  172                                 c->ic_state |= IEEE80211_CHANSTATE_CACDONE;
  173                 }
  174                 ieee80211_notify_cac(ic, ic->ic_curchan,
  175                     IEEE80211_NOTIFY_CAC_EXPIRE);
  176                 ieee80211_cac_completeswitch(vap);
  177         }
  178 }
  179 
  180 /*
  181  * Initiate the CAC timer.  The driver is responsible
  182  * for setting up the hardware to scan for radar on the
  183  * channnel, we just handle timing things out.
  184  */
  185 void
  186 ieee80211_dfs_cac_start(struct ieee80211vap *vap)
  187 {
  188         struct ieee80211com *ic = vap->iv_ic;
  189         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  190 
  191         IEEE80211_LOCK_ASSERT(ic);
  192 
  193         callout_reset(&dfs->cac_timer, CAC_TIMEOUT, cac_timeout, vap);
  194         if_printf(vap->iv_ifp, "start %d second CAC timer on channel %u (%u MHz)\n",
  195             ticks_to_secs(CAC_TIMEOUT),
  196             ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  197         ieee80211_notify_cac(ic, ic->ic_curchan, IEEE80211_NOTIFY_CAC_START);
  198 }
  199 
  200 /*
  201  * Clear the CAC timer.
  202  */
  203 void
  204 ieee80211_dfs_cac_stop(struct ieee80211vap *vap)
  205 {
  206         struct ieee80211com *ic = vap->iv_ic;
  207         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  208 
  209         IEEE80211_LOCK_ASSERT(ic);
  210 
  211         /* NB: racey but not important */
  212         if (callout_pending(&dfs->cac_timer)) {
  213                 if_printf(vap->iv_ifp, "stop CAC timer on channel %u (%u MHz)\n",
  214                     ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  215                 ieee80211_notify_cac(ic, ic->ic_curchan,
  216                     IEEE80211_NOTIFY_CAC_STOP);
  217         }
  218         callout_stop(&dfs->cac_timer);
  219 }
  220 
  221 void
  222 ieee80211_dfs_cac_clear(struct ieee80211com *ic,
  223         const struct ieee80211_channel *chan)
  224 {
  225         int i;
  226 
  227         for (i = 0; i < ic->ic_nchans; i++) {
  228                 struct ieee80211_channel *c = &ic->ic_channels[i];
  229                 if (c->ic_freq == chan->ic_freq)
  230                         c->ic_state &= ~IEEE80211_CHANSTATE_CACDONE;
  231         }
  232 }
  233 
  234 static void
  235 dfs_timeout(void *arg)
  236 {
  237         struct ieee80211com *ic = arg;
  238         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  239         struct ieee80211_channel *c;
  240         int i, oldest, now;
  241 
  242         IEEE80211_LOCK_ASSERT(ic);
  243 
  244         now = oldest = ticks;
  245         for (i = 0; i < ic->ic_nchans; i++) {
  246                 c = &ic->ic_channels[i];
  247                 if (IEEE80211_IS_CHAN_RADAR(c)) {
  248                         if (ieee80211_time_after_eq(now, dfs->nol_event[i]+NOL_TIMEOUT)) {
  249                                 c->ic_state &= ~IEEE80211_CHANSTATE_RADAR;
  250                                 if (c->ic_state & IEEE80211_CHANSTATE_NORADAR) {
  251                                         /*
  252                                          * NB: do this here so we get only one
  253                                          * msg instead of one for every channel
  254                                          * table entry.
  255                                          */
  256                                         ic_printf(ic, "radar on channel %u "
  257                                             "(%u MHz) cleared after timeout\n",
  258                                             c->ic_ieee, c->ic_freq);
  259                                         /* notify user space */
  260                                         c->ic_state &=
  261                                             ~IEEE80211_CHANSTATE_NORADAR;
  262                                         ieee80211_notify_radar(ic, c);
  263                                 }
  264                         } else if (dfs->nol_event[i] < oldest)
  265                                 oldest = dfs->nol_event[i];
  266                 }
  267         }
  268         if (oldest != now) {
  269                 /* arrange to process next channel up for a status change */
  270                 callout_schedule(&dfs->nol_timer, oldest + NOL_TIMEOUT - now);
  271         }
  272 }
  273 
  274 static void
  275 announce_radar(struct ieee80211com *ic, const struct ieee80211_channel *curchan,
  276         const struct ieee80211_channel *newchan)
  277 {
  278         if (newchan == NULL)
  279                 ic_printf(ic, "radar detected on channel %u (%u MHz)\n",
  280                     curchan->ic_ieee, curchan->ic_freq);
  281         else
  282                 ic_printf(ic, "radar detected on channel %u (%u MHz), "
  283                     "moving to channel %u (%u MHz)\n",
  284                     curchan->ic_ieee, curchan->ic_freq,
  285                     newchan->ic_ieee, newchan->ic_freq);
  286 }
  287 
  288 /*
  289  * Handle a radar detection event on a channel. The channel is
  290  * added to the NOL list and we record the time of the event.
  291  * Entries are aged out after NOL_TIMEOUT.  If radar was
  292  * detected while doing CAC we force a state/channel change.
  293  * Otherwise radar triggers a channel switch using the CSA
  294  * mechanism (when the channel is the bss channel).
  295  */
  296 void
  297 ieee80211_dfs_notify_radar(struct ieee80211com *ic, struct ieee80211_channel *chan)
  298 {
  299         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  300         int i, now;
  301 
  302         IEEE80211_LOCK_ASSERT(ic);
  303 
  304         /*
  305          * If doing DFS debugging (mode 2), don't bother
  306          * running the rest of this function.
  307          *
  308          * Simply announce the presence of the radar and continue
  309          * along merrily.
  310          */
  311         if (ieee80211_dfs_debug == DFS_DBG_NOCSANOL) {
  312                 announce_radar(ic, chan, chan);
  313                 ieee80211_notify_radar(ic, chan);
  314                 return;
  315         }
  316 
  317         /*
  318          * Don't mark the channel and don't put it into NOL
  319          * if we're doing DFS debugging.
  320          */
  321         if (ieee80211_dfs_debug == DFS_DBG_NONE) {
  322                 /*
  323                  * Mark all entries with this frequency.  Notify user
  324                  * space and arrange for notification when the radar
  325                  * indication is cleared.  Then kick the NOL processing
  326                  * thread if not already running.
  327                  */
  328                 now = ticks;
  329                 for (i = 0; i < ic->ic_nchans; i++) {
  330                         struct ieee80211_channel *c = &ic->ic_channels[i];
  331                         if (c->ic_freq == chan->ic_freq) {
  332                                 c->ic_state &= ~IEEE80211_CHANSTATE_CACDONE;
  333                                 c->ic_state |= IEEE80211_CHANSTATE_RADAR;
  334                                 dfs->nol_event[i] = now;
  335                         }
  336                 }
  337                 ieee80211_notify_radar(ic, chan);
  338                 chan->ic_state |= IEEE80211_CHANSTATE_NORADAR;
  339                 if (!callout_pending(&dfs->nol_timer))
  340                         callout_reset(&dfs->nol_timer, NOL_TIMEOUT,
  341                             dfs_timeout, ic);
  342         }
  343 
  344         /*
  345          * If radar is detected on the bss channel while
  346          * doing CAC; force a state change by scheduling the
  347          * callout to be dispatched asap.  Otherwise, if this
  348          * event is for the bss channel then we must quiet
  349          * traffic and schedule a channel switch.
  350          *
  351          * Note this allows us to receive notification about
  352          * channels other than the bss channel; not sure
  353          * that can/will happen but it's simple to support.
  354          */
  355         if (chan == ic->ic_bsschan) {
  356                 /* XXX need a way to defer to user app */
  357 
  358                 /*
  359                  * Don't flip over to a new channel if
  360                  * we are currently doing DFS debugging.
  361                  */
  362                 if (ieee80211_dfs_debug == DFS_DBG_NONE)
  363                         dfs->newchan = ieee80211_dfs_pickchannel(ic);
  364                 else
  365                         dfs->newchan = chan;
  366 
  367                 announce_radar(ic, chan, dfs->newchan);
  368 
  369                 if (callout_pending(&dfs->cac_timer))
  370                         callout_schedule(&dfs->cac_timer, 0);
  371                 else if (dfs->newchan != NULL) {
  372                         /* XXX mode 1, switch count 2 */
  373                         /* XXX calculate switch count based on max
  374                           switch time and beacon interval? */
  375                         ieee80211_csa_startswitch(ic, dfs->newchan, 1, 2);
  376                 } else {
  377                         /*
  378                          * Spec says to stop all transmissions and
  379                          * wait on the current channel for an entry
  380                          * on the NOL to expire.
  381                          */
  382                         /*XXX*/
  383                         ic_printf(ic, "%s: No free channels; waiting for entry "
  384                             "on NOL to expire\n", __func__);
  385                 }
  386         } else {
  387                 /*
  388                  * Issue rate-limited console msgs.
  389                  */
  390                 if (dfs->lastchan != chan) {
  391                         dfs->lastchan = chan;
  392                         dfs->cureps = 0;
  393                         announce_radar(ic, chan, NULL);
  394                 } else if (ppsratecheck(&dfs->lastevent, &dfs->cureps, 1)) {
  395                         announce_radar(ic, chan, NULL);
  396                 }
  397         }
  398 }
  399 
  400 struct ieee80211_channel *
  401 ieee80211_dfs_pickchannel(struct ieee80211com *ic)
  402 {
  403         struct ieee80211_channel *c;
  404         int i, flags;
  405         uint16_t v;
  406 
  407         /*
  408          * Consult the scan cache first.
  409          */
  410         flags = ic->ic_curchan->ic_flags & IEEE80211_CHAN_ALL;
  411         /*
  412          * XXX if curchan is HT this will never find a channel
  413          * XXX 'cuz we scan only legacy channels
  414          */
  415         c = ieee80211_scan_pickchannel(ic, flags);
  416         if (c != NULL)
  417                 return c;
  418         /*
  419          * No channel found in scan cache; select a compatible
  420          * one at random (skipping channels where radar has
  421          * been detected).
  422          */
  423         get_random_bytes(&v, sizeof(v));
  424         v %= ic->ic_nchans;
  425         for (i = v; i < ic->ic_nchans; i++) {
  426                 c = &ic->ic_channels[i];
  427                 if (!IEEE80211_IS_CHAN_RADAR(c) &&
  428                    (c->ic_flags & flags) == flags)
  429                         return c;
  430         }
  431         for (i = 0; i < v; i++) {
  432                 c = &ic->ic_channels[i];
  433                 if (!IEEE80211_IS_CHAN_RADAR(c) &&
  434                    (c->ic_flags & flags) == flags)
  435                         return c;
  436         }
  437         ic_printf(ic, "HELP, no channel located to switch to!\n");
  438         return NULL;
  439 }

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