FreeBSD/Linux Kernel Cross Reference
sys/net80211/ieee80211_dfs.c

     /*-
      * Copyright (c) 2007-2008 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>
    #ifdef __FreeBSD__
    __FBSDID("$FreeBSD: stable/10/sys/net80211/ieee80211_dfs.c 343894 2019-02-08 04:48:12Z avos $");
    #endif
    
    /*
     * IEEE 802.11 DFS/Radar support.
     */
    #include "opt_inet.h"
    #include "opt_wlan.h"
    
    #include <sys/param.h>
    #include <sys/systm.h> 
    #include <sys/mbuf.h>   
    #include <sys/malloc.h>
    #include <sys/kernel.h>
    
    #include <sys/socket.h>
    #include <sys/sockio.h>
    #include <sys/endian.h>
    #include <sys/errno.h>
    #include <sys/proc.h>
    #include <sys/sysctl.h>
    
    #include <net/if.h>
    #include <net/if_media.h>
    
    #include <net80211/ieee80211_var.h>
    
    static MALLOC_DEFINE(M_80211_DFS, "80211dfs", "802.11 DFS state");
    
    static  int ieee80211_nol_timeout = 30*60;              /* 30 minutes */
    SYSCTL_INT(_net_wlan, OID_AUTO, nol_timeout, CTLFLAG_RW,
            &ieee80211_nol_timeout, 0, "NOL timeout (secs)");
    #define NOL_TIMEOUT     msecs_to_ticks(ieee80211_nol_timeout*1000)
    
    static  int ieee80211_cac_timeout = 60;         /* 60 seconds */
    SYSCTL_INT(_net_wlan, OID_AUTO, cac_timeout, CTLFLAG_RW,
            &ieee80211_cac_timeout, 0, "CAC timeout (secs)");
    #define CAC_TIMEOUT     msecs_to_ticks(ieee80211_cac_timeout*1000)
    
    /*
     DFS* In order to facilitate  debugging, a couple of operating
     * modes aside from the default are needed.
     *
     * 0 - default CAC/NOL behaviour - ie, start CAC, place
     *     channel on NOL list.
     * 1 - send CAC, but don't change channel or add the channel
     *     to the NOL list.
     * 2 - just match on radar, don't send CAC or place channel in
     *     the NOL list.
     */
    static  int ieee80211_dfs_debug = DFS_DBG_NONE;
    
    /*
     * This option must not be included in the default kernel
     * as it allows users to plainly disable CAC/NOL handling.
     */
    #ifdef  IEEE80211_DFS_DEBUG
    SYSCTL_INT(_net_wlan, OID_AUTO, dfs_debug, CTLFLAG_RW,
            &ieee80211_dfs_debug, 0, "DFS debug behaviour");
    #endif
    
    static int
    null_set_quiet(struct ieee80211_node *ni, u_int8_t *quiet_elm)
    {
            return ENOSYS;
    }
    
    void
    ieee80211_dfs_attach(struct ieee80211com *ic)
    {
            struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
    
           callout_init_mtx(&dfs->nol_timer, IEEE80211_LOCK_OBJ(ic), 0);
           callout_init_mtx(&dfs->cac_timer, IEEE80211_LOCK_OBJ(ic), 0);
   
           ic->ic_set_quiet = null_set_quiet;
   }
   
   void
   ieee80211_dfs_detach(struct ieee80211com *ic)
   {
           /* NB: we assume no locking is needed */
           ieee80211_dfs_reset(ic);
   }
   
   void
   ieee80211_dfs_reset(struct ieee80211com *ic)
   {
           struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
           int i;
   
           /* NB: we assume no locking is needed */
           /* NB: cac_timer should be cleared by the state machine */
           callout_drain(&dfs->nol_timer);
           for (i = 0; i < ic->ic_nchans; i++)
                   ic->ic_channels[i].ic_state = 0;
           dfs->lastchan = NULL;
   }
   
   static void
   cac_timeout(void *arg)
   {
           struct ieee80211vap *vap = arg;
           struct ieee80211com *ic = vap->iv_ic;
           struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
           int i;
   
           IEEE80211_LOCK_ASSERT(ic);
   
           if (vap->iv_state != IEEE80211_S_CAC)   /* NB: just in case */
                   return;
           /*
            * When radar is detected during a CAC we are woken
            * up prematurely to switch to a new channel.
            * Check the channel to decide how to act.
            */
           if (IEEE80211_IS_CHAN_RADAR(ic->ic_curchan)) {
                   ieee80211_notify_cac(ic, ic->ic_curchan,
                       IEEE80211_NOTIFY_CAC_RADAR);
   
                   if_printf(vap->iv_ifp,
                       "CAC timer on channel %u (%u MHz) stopped due to radar\n",
                       ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
   
                   /* XXX clobbers any existing desired channel */
                   /* NB: dfs->newchan may be NULL, that's ok */
                   vap->iv_des_chan = dfs->newchan;
                   ieee80211_new_state_locked(vap, IEEE80211_S_SCAN, 0);
           } else {
                   if_printf(vap->iv_ifp,
                       "CAC timer on channel %u (%u MHz) expired; "
                       "no radar detected\n",
                       ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
                   /*
                    * Mark all channels with the current frequency
                    * as having completed CAC; this keeps us from
                    * doing it again until we change channels.
                    */
                   for (i = 0; i < ic->ic_nchans; i++) {
                           struct ieee80211_channel *c = &ic->ic_channels[i];
                           if (c->ic_freq == ic->ic_curchan->ic_freq)
                                   c->ic_state |= IEEE80211_CHANSTATE_CACDONE;
                   }
                   ieee80211_notify_cac(ic, ic->ic_curchan,
                       IEEE80211_NOTIFY_CAC_EXPIRE);
                   ieee80211_cac_completeswitch(vap);
           }
   }
   
   /*
    * Initiate the CAC timer.  The driver is responsible
    * for setting up the hardware to scan for radar on the
    * channnel, we just handle timing things out.
    */
   void
   ieee80211_dfs_cac_start(struct ieee80211vap *vap)
   {
           struct ieee80211com *ic = vap->iv_ic;
           struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
   
           IEEE80211_LOCK_ASSERT(ic);
   
           callout_reset(&dfs->cac_timer, CAC_TIMEOUT, cac_timeout, vap);
           if_printf(vap->iv_ifp, "start %d second CAC timer on channel %u (%u MHz)\n",
               ticks_to_secs(CAC_TIMEOUT),
               ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
           ieee80211_notify_cac(ic, ic->ic_curchan, IEEE80211_NOTIFY_CAC_START);
   }
   
   /*
    * Clear the CAC timer.
    */
   void
   ieee80211_dfs_cac_stop(struct ieee80211vap *vap)
   {
           struct ieee80211com *ic = vap->iv_ic;
           struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
   
           IEEE80211_LOCK_ASSERT(ic);
   
           /* NB: racey but not important */
           if (callout_pending(&dfs->cac_timer)) {
                   if_printf(vap->iv_ifp, "stop CAC timer on channel %u (%u MHz)\n",
                       ic->ic_curchan->ic_ieee, ic->ic_curchan->ic_freq);
                   ieee80211_notify_cac(ic, ic->ic_curchan,
                       IEEE80211_NOTIFY_CAC_STOP);
           }
           callout_stop(&dfs->cac_timer);
   }
   
   void
   ieee80211_dfs_cac_clear(struct ieee80211com *ic,
           const struct ieee80211_channel *chan)
   {
           int i;
   
           for (i = 0; i < ic->ic_nchans; i++) {
                   struct ieee80211_channel *c = &ic->ic_channels[i];
                   if (c->ic_freq == chan->ic_freq)
                           c->ic_state &= ~IEEE80211_CHANSTATE_CACDONE;
           }
   }
   
   static void
   dfs_timeout(void *arg)
   {
           struct ieee80211com *ic = arg;
           struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
           struct ieee80211_channel *c;
           int i, oldest, now;
   
           IEEE80211_LOCK_ASSERT(ic);
   
           now = oldest = ticks;
           for (i = 0; i < ic->ic_nchans; i++) {
                   c = &ic->ic_channels[i];
                   if (IEEE80211_IS_CHAN_RADAR(c)) {
                           if (time_after_eq(now, dfs->nol_event[i]+NOL_TIMEOUT)) {
                                   c->ic_state &= ~IEEE80211_CHANSTATE_RADAR;
                                   if (c->ic_state & IEEE80211_CHANSTATE_NORADAR) {
                                           /*
                                            * NB: do this here so we get only one
                                            * msg instead of one for every channel
                                            * table entry.
                                            */
                                           if_printf(ic->ic_ifp, "radar on channel"
                                               " %u (%u MHz) cleared after timeout\n",
                                               c->ic_ieee, c->ic_freq);
                                           /* notify user space */
                                           c->ic_state &=
                                               ~IEEE80211_CHANSTATE_NORADAR;
                                           ieee80211_notify_radar(ic, c);
                                   }
                           } else if (dfs->nol_event[i] < oldest)
                                   oldest = dfs->nol_event[i];
                   }
           }
           if (oldest != now) {
                   /* arrange to process next channel up for a status change */
                   callout_schedule(&dfs->nol_timer, oldest + NOL_TIMEOUT - now);
           }
   }
   
   static void
   announce_radar(struct ifnet *ifp, const struct ieee80211_channel *curchan,
           const struct ieee80211_channel *newchan)
   {
           if (newchan == NULL)
                   if_printf(ifp, "radar detected on channel %u (%u MHz)\n",
                       curchan->ic_ieee, curchan->ic_freq);
           else
                   if_printf(ifp, "radar detected on channel %u (%u MHz), "
                       "moving to channel %u (%u MHz)\n",
                       curchan->ic_ieee, curchan->ic_freq,
                       newchan->ic_ieee, newchan->ic_freq);
   }
   
   /*
    * Handle a radar detection event on a channel. The channel is
    * added to the NOL list and we record the time of the event.
    * Entries are aged out after NOL_TIMEOUT.  If radar was
    * detected while doing CAC we force a state/channel change.
    * Otherwise radar triggers a channel switch using the CSA
    * mechanism (when the channel is the bss channel).
    */
   void
   ieee80211_dfs_notify_radar(struct ieee80211com *ic, struct ieee80211_channel *chan)
   {
           struct ieee80211_dfs_state *dfs = &ic->ic_dfs;
           int i, now;
   
           IEEE80211_LOCK_ASSERT(ic);
   
           /*
            * If doing DFS debugging (mode 2), don't bother
            * running the rest of this function.
            *
            * Simply announce the presence of the radar and continue
            * along merrily.
            */
           if (ieee80211_dfs_debug == DFS_DBG_NOCSANOL) {
                   announce_radar(ic->ic_ifp, chan, chan);
                   ieee80211_notify_radar(ic, chan);
                   return;
           }
   
           /*
            * Don't mark the channel and don't put it into NOL
            * if we're doing DFS debugging.
            */
           if (ieee80211_dfs_debug == DFS_DBG_NONE) {
                   /*
                    * Mark all entries with this frequency.  Notify user
                    * space and arrange for notification when the radar
                    * indication is cleared.  Then kick the NOL processing
                    * thread if not already running.
                    */
                   now = ticks;
                   for (i = 0; i < ic->ic_nchans; i++) {
                           struct ieee80211_channel *c = &ic->ic_channels[i];
                           if (c->ic_freq == chan->ic_freq) {
                                   c->ic_state &= ~IEEE80211_CHANSTATE_CACDONE;
                                   c->ic_state |= IEEE80211_CHANSTATE_RADAR;
                                   dfs->nol_event[i] = now;
                           }
                   }
                   ieee80211_notify_radar(ic, chan);
                   chan->ic_state |= IEEE80211_CHANSTATE_NORADAR;
                   if (!callout_pending(&dfs->nol_timer))
                           callout_reset(&dfs->nol_timer, NOL_TIMEOUT,
                               dfs_timeout, ic);
           }
   
           /*
            * If radar is detected on the bss channel while
            * doing CAC; force a state change by scheduling the
            * callout to be dispatched asap.  Otherwise, if this
            * event is for the bss channel then we must quiet
            * traffic and schedule a channel switch.
            *
            * Note this allows us to receive notification about
            * channels other than the bss channel; not sure
            * that can/will happen but it's simple to support.
            */
           if (chan == ic->ic_bsschan) {
                   /* XXX need a way to defer to user app */
   
                   /*
                    * Don't flip over to a new channel if
                    * we are currently doing DFS debugging.
                    */
                   if (ieee80211_dfs_debug == DFS_DBG_NONE)
                           dfs->newchan = ieee80211_dfs_pickchannel(ic);
                   else
                           dfs->newchan = chan;
   
                   announce_radar(ic->ic_ifp, chan, dfs->newchan);
   
                   if (callout_pending(&dfs->cac_timer))
                           callout_schedule(&dfs->cac_timer, 0);
                   else if (dfs->newchan != NULL) {
                           /* XXX mode 1, switch count 2 */
                           /* XXX calculate switch count based on max
                             switch time and beacon interval? */
                           ieee80211_csa_startswitch(ic, dfs->newchan, 1, 2);
                   } else {
                           /*
                            * Spec says to stop all transmissions and
                            * wait on the current channel for an entry
                            * on the NOL to expire.
                            */
                           /*XXX*/
                           if_printf(ic->ic_ifp, "%s: No free channels; waiting for entry "
                               "on NOL to expire\n", __func__);
                   }
           } else {
                   /*
                    * Issue rate-limited console msgs.
                    */
                   if (dfs->lastchan != chan) {
                           dfs->lastchan = chan;
                           dfs->cureps = 0;
                           announce_radar(ic->ic_ifp, chan, NULL);
                   } else if (ppsratecheck(&dfs->lastevent, &dfs->cureps, 1)) {
                           announce_radar(ic->ic_ifp, chan, NULL);
                   }
           }
   }
   
   struct ieee80211_channel *
   ieee80211_dfs_pickchannel(struct ieee80211com *ic)
   {
           struct ieee80211_channel *c;
           int i, flags;
           uint16_t v;
   
           /*
            * Consult the scan cache first.
            */
           flags = ic->ic_curchan->ic_flags & IEEE80211_CHAN_ALL;
           /*
            * XXX if curchan is HT this will never find a channel
            * XXX 'cuz we scan only legacy channels
            */
           c = ieee80211_scan_pickchannel(ic, flags);
           if (c != NULL)
                   return c;
           /*
            * No channel found in scan cache; select a compatible
            * one at random (skipping channels where radar has
            * been detected).
            */
           get_random_bytes(&v, sizeof(v));
           v %= ic->ic_nchans;
           for (i = v; i < ic->ic_nchans; i++) {
                   c = &ic->ic_channels[i];
                   if (!IEEE80211_IS_CHAN_RADAR(c) &&
                      (c->ic_flags & flags) == flags)
                           return c;
           }
           for (i = 0; i < v; i++) {
                   c = &ic->ic_channels[i];
                   if (!IEEE80211_IS_CHAN_RADAR(c) &&
                      (c->ic_flags & flags) == flags)
                           return c;
           }
           if_printf(ic->ic_ifp, "HELP, no channel located to switch to!\n");
           return NULL;
   }

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