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  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 2007-2008 Sam Leffler, Errno Consulting
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   26  */
   27 
   28 #include <sys/cdefs.h>
   29 #ifdef __FreeBSD__
   30 __FBSDID("$FreeBSD: stable/12/sys/net80211/ieee80211_dfs.c 343894 2019-02-08 04:48:12Z avos $");
   31 #endif
   32 
   33 /*
   34  * IEEE 802.11 DFS/Radar support.
   35  */
   36 #include "opt_inet.h"
   37 #include "opt_wlan.h"
   38 
   39 #include <sys/param.h>
   40 #include <sys/systm.h> 
   41 #include <sys/mbuf.h>   
   42 #include <sys/malloc.h>
   43 #include <sys/kernel.h>
   44 
   45 #include <sys/socket.h>
   46 #include <sys/sockio.h>
   47 #include <sys/endian.h>
   48 #include <sys/errno.h>
   49 #include <sys/proc.h>
   50 #include <sys/sysctl.h>
   51 
   52 #include <net/if.h>
   53 #include <net/if_var.h>
   54 #include <net/if_media.h>
   55 #include <net/ethernet.h>
   56 
   57 #include <net80211/ieee80211_var.h>
   58 
   59 static MALLOC_DEFINE(M_80211_DFS, "80211dfs", "802.11 DFS state");
   60 
   61 static  int ieee80211_nol_timeout = 30*60;              /* 30 minutes */
   62 SYSCTL_INT(_net_wlan, OID_AUTO, nol_timeout, CTLFLAG_RW,
   63         &ieee80211_nol_timeout, 0, "NOL timeout (secs)");
   64 #define NOL_TIMEOUT     msecs_to_ticks(ieee80211_nol_timeout*1000)
   65 
   66 static  int ieee80211_cac_timeout = 60;         /* 60 seconds */
   67 SYSCTL_INT(_net_wlan, OID_AUTO, cac_timeout, CTLFLAG_RW,
   68         &ieee80211_cac_timeout, 0, "CAC timeout (secs)");
   69 #define CAC_TIMEOUT     msecs_to_ticks(ieee80211_cac_timeout*1000)
   70 
   71 /*
   72  DFS* In order to facilitate  debugging, a couple of operating
   73  * modes aside from the default are needed.
   74  *
   75  * 0 - default CAC/NOL behaviour - ie, start CAC, place
   76  *     channel on NOL list.
   77  * 1 - send CAC, but don't change channel or add the channel
   78  *     to the NOL list.
   79  * 2 - just match on radar, don't send CAC or place channel in
   80  *     the NOL list.
   81  */
   82 static  int ieee80211_dfs_debug = DFS_DBG_NONE;
   83 
   84 /*
   85  * This option must not be included in the default kernel
   86  * as it allows users to plainly disable CAC/NOL handling.
   87  */
   88 #ifdef  IEEE80211_DFS_DEBUG
   89 SYSCTL_INT(_net_wlan, OID_AUTO, dfs_debug, CTLFLAG_RW,
   90         &ieee80211_dfs_debug, 0, "DFS debug behaviour");
   91 #endif
   92 
   93 static int
   94 null_set_quiet(struct ieee80211_node *ni, u_int8_t *quiet_elm)
   95 {
   96         return ENOSYS;
   97 }
   98 
   99 void
  100 ieee80211_dfs_attach(struct ieee80211com *ic)
  101 {
  102         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  103 
  104         callout_init_mtx(&dfs->nol_timer, IEEE80211_LOCK_OBJ(ic), 0);
  105         callout_init_mtx(&dfs->cac_timer, IEEE80211_LOCK_OBJ(ic), 0);
  106 
  107         ic->ic_set_quiet = null_set_quiet;
  108 }
  109 
  110 void
  111 ieee80211_dfs_detach(struct ieee80211com *ic)
  112 {
  113         /* NB: we assume no locking is needed */
  114         ieee80211_dfs_reset(ic);
  115 }
  116 
  117 void
  118 ieee80211_dfs_reset(struct ieee80211com *ic)
  119 {
  120         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  121         int i;
  122 
  123         /* NB: we assume no locking is needed */
  124         /* NB: cac_timer should be cleared by the state machine */
  125         callout_drain(&dfs->nol_timer);
  126         for (i = 0; i < ic->ic_nchans; i++)
  127                 ic->ic_channels[i].ic_state = 0;
  128         dfs->lastchan = NULL;
  129 }
  130 
  131 static void
  132 cac_timeout(void *arg)
  133 {
  134         struct ieee80211vap *vap = arg;
  135         struct ieee80211com *ic = vap->iv_ic;
  136         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  137         int i;
  138 
  139         IEEE80211_LOCK_ASSERT(ic);
  140 
  141         if (vap->iv_state != IEEE80211_S_CAC)   /* NB: just in case */
  142                 return;
  143         /*
  144          * When radar is detected during a CAC we are woken
  145          * up prematurely to switch to a new channel.
  146          * Check the channel to decide how to act.
  147          */
  148         if (IEEE80211_IS_CHAN_RADAR(ic->ic_curchan)) {
  149                 ieee80211_notify_cac(ic, ic->ic_curchan,
  150                     IEEE80211_NOTIFY_CAC_RADAR);
  151 
  152                 if_printf(vap->iv_ifp,
  153                     "CAC timer on channel %u (%u MHz) stopped due to radar\n",
  154                     ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  155 
  156                 /* XXX clobbers any existing desired channel */
  157                 /* NB: dfs->newchan may be NULL, that's ok */
  158                 vap->iv_des_chan = dfs->newchan;
  159                 ieee80211_new_state_locked(vap, IEEE80211_S_SCAN, 0);
  160         } else {
  161                 if_printf(vap->iv_ifp,
  162                     "CAC timer on channel %u (%u MHz) expired; "
  163                     "no radar detected\n",
  164                     ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  165                 /*
  166                  * Mark all channels with the current frequency
  167                  * as having completed CAC; this keeps us from
  168                  * doing it again until we change channels.
  169                  */
  170                 for (i = 0; i < ic->ic_nchans; i++) {
  171                         struct ieee80211_channel *c = &ic->ic_channels[i];
  172                         if (c->ic_freq == ic->ic_curchan->ic_freq)
  173                                 c->ic_state |= IEEE80211_CHANSTATE_CACDONE;
  174                 }
  175                 ieee80211_notify_cac(ic, ic->ic_curchan,
  176                     IEEE80211_NOTIFY_CAC_EXPIRE);
  177                 ieee80211_cac_completeswitch(vap);
  178         }
  179 }
  180 
  181 /*
  182  * Initiate the CAC timer.  The driver is responsible
  183  * for setting up the hardware to scan for radar on the
  184  * channnel, we just handle timing things out.
  185  */
  186 void
  187 ieee80211_dfs_cac_start(struct ieee80211vap *vap)
  188 {
  189         struct ieee80211com *ic = vap->iv_ic;
  190         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  191 
  192         IEEE80211_LOCK_ASSERT(ic);
  193 
  194         callout_reset(&dfs->cac_timer, CAC_TIMEOUT, cac_timeout, vap);
  195         if_printf(vap->iv_ifp, "start %d second CAC timer on channel %u (%u MHz)\n",
  196             ticks_to_secs(CAC_TIMEOUT),
  197             ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  198         ieee80211_notify_cac(ic, ic->ic_curchan, IEEE80211_NOTIFY_CAC_START);
  199 }
  200 
  201 /*
  202  * Clear the CAC timer.
  203  */
  204 void
  205 ieee80211_dfs_cac_stop(struct ieee80211vap *vap)
  206 {
  207         struct ieee80211com *ic = vap->iv_ic;
  208         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  209 
  210         IEEE80211_LOCK_ASSERT(ic);
  211 
  212         /* NB: racey but not important */
  213         if (callout_pending(&dfs->cac_timer)) {
  214                 if_printf(vap->iv_ifp, "stop CAC timer on channel %u (%u MHz)\n",
  215                     ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
  216                 ieee80211_notify_cac(ic, ic->ic_curchan,
  217                     IEEE80211_NOTIFY_CAC_STOP);
  218         }
  219         callout_stop(&dfs->cac_timer);
  220 }
  221 
  222 void
  223 ieee80211_dfs_cac_clear(struct ieee80211com *ic,
  224         const struct ieee80211_channel *chan)
  225 {
  226         int i;
  227 
  228         for (i = 0; i < ic->ic_nchans; i++) {
  229                 struct ieee80211_channel *c = &ic->ic_channels[i];
  230                 if (c->ic_freq == chan->ic_freq)
  231                         c->ic_state &= ~IEEE80211_CHANSTATE_CACDONE;
  232         }
  233 }
  234 
  235 static void
  236 dfs_timeout(void *arg)
  237 {
  238         struct ieee80211com *ic = arg;
  239         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  240         struct ieee80211_channel *c;
  241         int i, oldest, now;
  242 
  243         IEEE80211_LOCK_ASSERT(ic);
  244 
  245         now = oldest = ticks;
  246         for (i = 0; i < ic->ic_nchans; i++) {
  247                 c = &ic->ic_channels[i];
  248                 if (IEEE80211_IS_CHAN_RADAR(c)) {
  249                         if (ieee80211_time_after_eq(now, dfs->nol_event[i]+NOL_TIMEOUT)) {
  250                                 c->ic_state &= ~IEEE80211_CHANSTATE_RADAR;
  251                                 if (c->ic_state & IEEE80211_CHANSTATE_NORADAR) {
  252                                         /*
  253                                          * NB: do this here so we get only one
  254                                          * msg instead of one for every channel
  255                                          * table entry.
  256                                          */
  257                                         ic_printf(ic, "radar on channel %u "
  258                                             "(%u MHz) cleared after timeout\n",
  259                                             c->ic_ieee, c->ic_freq);
  260                                         /* notify user space */
  261                                         c->ic_state &=
  262                                             ~IEEE80211_CHANSTATE_NORADAR;
  263                                         ieee80211_notify_radar(ic, c);
  264                                 }
  265                         } else if (dfs->nol_event[i] < oldest)
  266                                 oldest = dfs->nol_event[i];
  267                 }
  268         }
  269         if (oldest != now) {
  270                 /* arrange to process next channel up for a status change */
  271                 callout_schedule(&dfs->nol_timer, oldest + NOL_TIMEOUT - now);
  272         }
  273 }
  274 
  275 static void
  276 announce_radar(struct ieee80211com *ic, const struct ieee80211_channel *curchan,
  277         const struct ieee80211_channel *newchan)
  278 {
  279         if (newchan == NULL)
  280                 ic_printf(ic, "radar detected on channel %u (%u MHz)\n",
  281                     curchan->ic_ieee, curchan->ic_freq);
  282         else
  283                 ic_printf(ic, "radar detected on channel %u (%u MHz), "
  284                     "moving to channel %u (%u MHz)\n",
  285                     curchan->ic_ieee, curchan->ic_freq,
  286                     newchan->ic_ieee, newchan->ic_freq);
  287 }
  288 
  289 /*
  290  * Handle a radar detection event on a channel. The channel is
  291  * added to the NOL list and we record the time of the event.
  292  * Entries are aged out after NOL_TIMEOUT.  If radar was
  293  * detected while doing CAC we force a state/channel change.
  294  * Otherwise radar triggers a channel switch using the CSA
  295  * mechanism (when the channel is the bss channel).
  296  */
  297 void
  298 ieee80211_dfs_notify_radar(struct ieee80211com *ic, struct ieee80211_channel *chan)
  299 {
  300         struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
  301         int i, now;
  302 
  303         IEEE80211_LOCK_ASSERT(ic);
  304 
  305         /*
  306          * If doing DFS debugging (mode 2), don't bother
  307          * running the rest of this function.
  308          *
  309          * Simply announce the presence of the radar and continue
  310          * along merrily.
  311          */
  312         if (ieee80211_dfs_debug == DFS_DBG_NOCSANOL) {
  313                 announce_radar(ic, chan, chan);
  314                 ieee80211_notify_radar(ic, chan);
  315                 return;
  316         }
  317 
  318         /*
  319          * Don't mark the channel and don't put it into NOL
  320          * if we're doing DFS debugging.
  321          */
  322         if (ieee80211_dfs_debug == DFS_DBG_NONE) {
  323                 /*
  324                  * Mark all entries with this frequency.  Notify user
  325                  * space and arrange for notification when the radar
  326                  * indication is cleared.  Then kick the NOL processing
  327                  * thread if not already running.
  328                  */
  329                 now = ticks;
  330                 for (i = 0; i < ic->ic_nchans; i++) {
  331                         struct ieee80211_channel *c = &ic->ic_channels[i];
  332                         if (c->ic_freq == chan->ic_freq) {
  333                                 c->ic_state &= ~IEEE80211_CHANSTATE_CACDONE;
  334                                 c->ic_state |= IEEE80211_CHANSTATE_RADAR;
  335                                 dfs->nol_event[i] = now;
  336                         }
  337                 }
  338                 ieee80211_notify_radar(ic, chan);
  339                 chan->ic_state |= IEEE80211_CHANSTATE_NORADAR;
  340                 if (!callout_pending(&dfs->nol_timer))
  341                         callout_reset(&dfs->nol_timer, NOL_TIMEOUT,
  342                             dfs_timeout, ic);
  343         }
  344 
  345         /*
  346          * If radar is detected on the bss channel while
  347          * doing CAC; force a state change by scheduling the
  348          * callout to be dispatched asap.  Otherwise, if this
  349          * event is for the bss channel then we must quiet
  350          * traffic and schedule a channel switch.
  351          *
  352          * Note this allows us to receive notification about
  353          * channels other than the bss channel; not sure
  354          * that can/will happen but it's simple to support.
  355          */
  356         if (chan == ic->ic_bsschan) {
  357                 /* XXX need a way to defer to user app */
  358 
  359                 /*
  360                  * Don't flip over to a new channel if
  361                  * we are currently doing DFS debugging.
  362                  */
  363                 if (ieee80211_dfs_debug == DFS_DBG_NONE)
  364                         dfs->newchan = ieee80211_dfs_pickchannel(ic);
  365                 else
  366                         dfs->newchan = chan;
  367 
  368                 announce_radar(ic, chan, dfs->newchan);
  369 
  370                 if (callout_pending(&dfs->cac_timer))
  371                         callout_schedule(&dfs->cac_timer, 0);
  372                 else if (dfs->newchan != NULL) {
  373                         /* XXX mode 1, switch count 2 */
  374                         /* XXX calculate switch count based on max
  375                           switch time and beacon interval? */
  376                         ieee80211_csa_startswitch(ic, dfs->newchan, 1, 2);
  377                 } else {
  378                         /*
  379                          * Spec says to stop all transmissions and
  380                          * wait on the current channel for an entry
  381                          * on the NOL to expire.
  382                          */
  383                         /*XXX*/
  384                         ic_printf(ic, "%s: No free channels; waiting for entry "
  385                             "on NOL to expire\n", __func__);
  386                 }
  387         } else {
  388                 /*
  389                  * Issue rate-limited console msgs.
  390                  */
  391                 if (dfs->lastchan != chan) {
  392                         dfs->lastchan = chan;
  393                         dfs->cureps = 0;
  394                         announce_radar(ic, chan, NULL);
  395                 } else if (ppsratecheck(&dfs->lastevent, &dfs->cureps, 1)) {
  396                         announce_radar(ic, chan, NULL);
  397                 }
  398         }
  399 }
  400 
  401 struct ieee80211_channel *
  402 ieee80211_dfs_pickchannel(struct ieee80211com *ic)
  403 {
  404         struct ieee80211_channel *c;
  405         int i, flags;
  406         uint16_t v;
  407 
  408         /*
  409          * Consult the scan cache first.
  410          */
  411         flags = ic->ic_curchan->ic_flags & IEEE80211_CHAN_ALL;
  412         /*
  413          * XXX if curchan is HT this will never find a channel
  414          * XXX 'cuz we scan only legacy channels
  415          */
  416         c = ieee80211_scan_pickchannel(ic, flags);
  417         if (c != NULL)
  418                 return c;
  419         /*
  420          * No channel found in scan cache; select a compatible
  421          * one at random (skipping channels where radar has
  422          * been detected).
  423          */
  424         get_random_bytes(&v, sizeof(v));
  425         v %= ic->ic_nchans;
  426         for (i = v; i < ic->ic_nchans; i++) {
  427                 c = &ic->ic_channels[i];
  428                 if (!IEEE80211_IS_CHAN_RADAR(c) &&
  429                    (c->ic_flags & flags) == flags)
  430                         return c;
  431         }
  432         for (i = 0; i < v; i++) {
  433                 c = &ic->ic_channels[i];
  434                 if (!IEEE80211_IS_CHAN_RADAR(c) &&
  435                    (c->ic_flags & flags) == flags)
  436                         return c;
  437         }
  438         ic_printf(ic, "HELP, no channel located to switch to!\n");
  439         return NULL;
  440 }

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