ieee80211_scan.c

Linux下wifi实现

		ic->ic_flags &= ~IEEE80211_F_SCAN;
	}
	if ((flags & IEEE80211_SCAN_USECACHE) == 0)
		return ieee80211_start_scan(vap, flags, duration, nssid, ssids);
	else {
		/* If we *must* use the cache and no ap was found, return failure */
		return 0;
	}
}

/*
 * Restart a previous scan.  If the previous scan completed
 * then we start again using the existing channel list.
 */
int
ieee80211_bg_scan(struct ieee80211vap *vap)
{
	struct ieee80211com *ic = vap->iv_ic;
	struct ieee80211_scan_state *ss = ic->ic_scan;

	IEEE80211_LOCK_IRQ(ic);
	if ((ic->ic_flags & IEEE80211_F_SCAN) == 0) {
		u_int duration;
		/*
		 * Go off-channel for a fixed interval that is large
		 * enough to catch most ap's but short enough that
		 * we can return on-channel before our listen interval
		 * expires.
		 */
		duration = IEEE80211_SCAN_OFFCHANNEL;

		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
			"%s: %s scan, jiffies %lu duration %lu\n", __func__,
			ss->ss_flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive",
			jiffies, duration);

		if (ss->ss_ops != NULL) {
			ss->ss_vap = vap;
			/*
			 * A background scan does not select a new sta; it
			 * just refreshes the scan cache.  Also, indicate
			 * the scan logic should follow the beacon schedule:
			 * we go off-channel and scan for a while, then
			 * return to the bss channel to receive a beacon,
			 * then go off-channel again.  All during this time
			 * we notify the ap we're in power save mode.  When
			 * the scan is complete we leave power save mode.
			 * If any beacon indicates there are frames pending
			 *for us then we drop out of power save mode
			 * (and background scan) automatically by way of the
			 * usual sta power save logic.
			 */
			ss->ss_flags |= IEEE80211_SCAN_NOPICK |
				IEEE80211_SCAN_BGSCAN;
			/* if previous scan completed, restart */
			if (ss->ss_next >= ss->ss_last) {
				ss->ss_next = 0;
				if (ss->ss_flags & IEEE80211_SCAN_ACTIVE)
					vap->iv_stats.is_scan_active++;
				else
					vap->iv_stats.is_scan_passive++;
				ss->ss_ops->scan_restart(ss, vap);
			}
			/* NB: flush frames rx'd before 1st channel change */
			SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_DISCARD;
			ss->ss_mindwell = duration;
			if (scan_restart(SCAN_PRIVATE(ss), duration)) {
				ic->ic_flags |= IEEE80211_F_SCAN;
				ic->ic_flags_ext |= IEEE80211_FEXT_BGSCAN;
			}
		} else {
			/* XXX msg+stat */
		}
	} else {
		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
			"%s: %s scan already in progress\n", __func__,
			ss->ss_flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive");
	}
	IEEE80211_UNLOCK_IRQ(ic);

	/* NB: racey, does it matter? */
	return (ic->ic_flags & IEEE80211_F_SCAN);
}
EXPORT_SYMBOL(ieee80211_bg_scan);

/*
 * Cancel any scan currently going on.
 */
void
ieee80211_cancel_scan(struct ieee80211vap *vap)
{
	struct ieee80211com *ic = vap->iv_ic;
	struct ieee80211_scan_state *ss = ic->ic_scan;

	IEEE80211_LOCK_IRQ(ic);
	if (ic->ic_flags & IEEE80211_F_SCAN) {
		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
			"%s: cancel %s scan\n", __func__,
			ss->ss_flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive");

		/* clear bg scan NOPICK and mark cancel request */
		ss->ss_flags &= ~IEEE80211_SCAN_NOPICK;
		SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_CANCEL;
		ss->ss_ops->scan_cancel(ss, vap);
		/* force it to fire asap */
		mod_timer(&SCAN_PRIVATE(ss)->ss_scan_timer, jiffies);
	}
	IEEE80211_UNLOCK_IRQ(ic);
}

/*
 * Switch to the next channel marked for scanning.
 */
static void
scan_next(unsigned long arg)
{
#define	ISCAN_REP	(ISCAN_MINDWELL | ISCAN_START | ISCAN_DISCARD)
	struct ieee80211_scan_state *ss = (struct ieee80211_scan_state *) arg;
	struct ieee80211vap *vap = ss->ss_vap;
	struct ieee80211com *ic = vap->iv_ic;
	struct ieee80211_channel *chan;
	unsigned long maxdwell, scanend;
	int scanning, scandone, i;

	IEEE80211_LOCK_IRQ(ic);
	scanning = (ic->ic_flags & IEEE80211_F_SCAN) != 0;
	IEEE80211_UNLOCK_IRQ(ic);
	if (!scanning)			/* canceled */
		return;

again:
	scandone = (ss->ss_next >= ss->ss_last) ||
		(SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) != 0;
	scanend = SCAN_PRIVATE(ss)->ss_scanend;
	if (!scandone &&
	    (ss->ss_flags & IEEE80211_SCAN_GOTPICK) == 0 &&
	    ((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_START) ||
	     time_before(jiffies + ss->ss_mindwell, scanend))) {
		chan = ss->ss_chans[ss->ss_next++];

		/*
		 * Watch for truncation due to the scan end time.
		 */
		if (time_after(jiffies + ss->ss_maxdwell, scanend))
			maxdwell = scanend - jiffies;
		else
			maxdwell = ss->ss_maxdwell;

		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
			"%s: chan %3d%c -> %3d%c [%s, dwell min %lu max %lu]\n",
			__func__,
			ieee80211_chan2ieee(ic, ic->ic_curchan),
		        	channel_type(ic->ic_curchan),
			ieee80211_chan2ieee(ic, chan), channel_type(chan),
			(ss->ss_flags & IEEE80211_SCAN_ACTIVE) &&
				(chan->ic_flags & IEEE80211_CHAN_PASSIVE) == 0 ?
				"active" : "passive",
			ss->ss_mindwell, maxdwell);

		/*
		 * Potentially change channel and phy mode.
		 */
		change_channel(ic, chan);

		/*
		 * If doing an active scan and the channel is not
		 * marked passive-only then send a probe request.
		 * Otherwise just listen for traffic on the channel.
		 */
		if ((ss->ss_flags & IEEE80211_SCAN_ACTIVE) &&
		    (chan->ic_flags & IEEE80211_CHAN_PASSIVE) == 0) {
			struct net_device *dev = vap->iv_dev;
			/*
			 * Send a broadcast probe request followed by
			 * any specified directed probe requests.
			 * XXX suppress broadcast probe req?
			 * XXX remove dependence on vap/vap->iv_bss
			 * XXX move to policy code?
			 */
			ieee80211_send_probereq(vap->iv_bss,
				vap->iv_myaddr, dev->broadcast,
				dev->broadcast,
				"", 0,
				vap->iv_opt_ie, vap->iv_opt_ie_len);
			for (i = 0; i < ss->ss_nssid; i++)
				ieee80211_send_probereq(vap->iv_bss,
					vap->iv_myaddr, dev->broadcast,
					dev->broadcast,
					ss->ss_ssid[i].ssid,
					ss->ss_ssid[i].len,
					vap->iv_opt_ie, vap->iv_opt_ie_len);
		}
		SCAN_PRIVATE(ss)->ss_chanmindwell = jiffies + ss->ss_mindwell;
		mod_timer(&SCAN_PRIVATE(ss)->ss_scan_timer, jiffies + maxdwell);
		/* clear mindwell lock and initial channel change flush */
		SCAN_PRIVATE(ss)->ss_iflags &= ~ISCAN_REP;
	} else {
		ic->ic_scan_end(ic);		/* notify driver */
		/*
		 * Record scan complete time.  Note that we also do
		 * this when canceled so any background scan will
		 * not be restarted for a while.
		 */
		if (scandone)
			ic->ic_lastscan = jiffies;
		/* return to the bss channel */
		if (ic->ic_bsschan != IEEE80211_CHAN_ANYC &&
		    ic->ic_curchan != ic->ic_bsschan)
			change_channel(ic, ic->ic_bsschan);
		/* clear internal flags and any indication of a pick */
		SCAN_PRIVATE(ss)->ss_iflags &= ~ISCAN_REP;
		ss->ss_flags &= ~IEEE80211_SCAN_GOTPICK;

		/*
		 * If not canceled and scan completed, do post-processing.
		 * If the callback function returns 0, then it wants to
		 * continue/restart scanning.  Unfortunately we needed to
		 * notify the driver to end the scan above to avoid having
		 * rx frames alter the scan candidate list.
		 */
		if ((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) == 0 &&
		    !ss->ss_ops->scan_end(ss, vap, NULL, 0) &&
		    (ss->ss_flags & IEEE80211_SCAN_ONCE) == 0 &&
		    time_before(jiffies + ss->ss_mindwell, scanend)) {
			IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
				"%s: done, restart "
				"[jiffies %lu, dwell min %lu scanend %lu]\n",
				__func__,
				jiffies, ss->ss_mindwell, scanend);
			ss->ss_next = 0;	/* reset to begining */
			if (ss->ss_flags & IEEE80211_SCAN_ACTIVE)
				vap->iv_stats.is_scan_active++;
			else
				vap->iv_stats.is_scan_passive++;

			ic->ic_scan_start(ic);	/* notify driver */
			goto again;
		} else {
			/* past here, scandone is ``true'' if not in bg mode */
			if ((ss->ss_flags & IEEE80211_SCAN_BGSCAN) == 0)
				scandone = 1;

			IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
				"%s: %s, "
				"[jiffies %lu, dwell min %lu scanend %lu]\n",
				__func__, scandone ? "done" : "stopped",
				jiffies, ss->ss_mindwell, scanend);

			/*
			 * Clear the SCAN bit first in case frames are
			 * pending on the station power save queue.  If
			 * we defer this then the dispatch of the frames
			 * may generate a request to cancel scanning.
			 */
			ic->ic_flags &= ~IEEE80211_F_SCAN;
			/*
			 * Drop out of power save mode when a scan has
			 * completed.  If this scan was prematurely terminated
			 * because it is a background scan then don't notify
			 * the ap; we'll either return to scanning after we
			 * receive the beacon frame or we'll drop out of power
			 * save mode because the beacon indicates we have frames
			 * waiting for us.
			 */
			if (scandone) {
				ieee80211_sta_pwrsave(vap, 0);
				if (ss->ss_next >= ss->ss_last) {
					ieee80211_notify_scan_done(vap);
					ic->ic_flags_ext &= ~IEEE80211_FEXT_BGSCAN;
				}
			}
			SCAN_PRIVATE(ss)->ss_iflags &= ~ISCAN_CANCEL;
			ss->ss_flags &=
			    ~(IEEE80211_SCAN_ONCE | IEEE80211_SCAN_PICK1ST);
		}
	}
#undef ISCAN_REP
}

#ifdef IEEE80211_DEBUG
static void
dump_probe_beacon(u_int8_t subtype, int isnew,
	const u_int8_t mac[IEEE80211_ADDR_LEN],
	const struct ieee80211_scanparams *sp)
{

	printf("[%s] %s%s on chan %u (bss chan %u) ",
		ether_sprintf(mac), isnew ? "new " : "",
		ieee80211_mgt_subtype_name[subtype >> IEEE80211_FC0_SUBTYPE_SHIFT],
		sp->chan, sp->bchan);
	ieee80211_print_essid(sp->ssid + 2, sp->ssid[1]);
	printf("\n");

	if (isnew) {
		printf("[%s] caps 0x%x bintval %u erp 0x%x", 
			ether_sprintf(mac), sp->capinfo, sp->bintval, sp->erp);
		if (sp->country != NULL) {
#ifdef __FreeBSD__
			printf(" country info %*D",
				sp->country[1], sp->country + 2, " ");
#else
			int i;
			printf(" country info");
			for (i = 0; i < sp->country[1]; i++)
				printf(" %02x", sp->country[i + 2]);
#endif
		}
		printf("\n");
	}
}
#endif /* IEEE80211_DEBUG */

/*
 * Process a beacon or probe response frame.
 */
void
ieee80211_add_scan(struct ieee80211vap *vap,
	const struct ieee80211_scanparams *sp,
	const struct ieee80211_frame *wh,
	int subtype, int rssi, int rstamp)
{
	struct ieee80211com *ic = vap->iv_ic;
	struct ieee80211_scan_state *ss = ic->ic_scan;

	/*
	 * Frames received during startup are discarded to avoid
	 * using scan state setup on the initial entry to the timer
	 * callback.  This can occur because the device may enable
	 * rx prior to our doing the initial channel change in the
	 * timer routine (we defer the channel change to the timer
	 * code to simplify locking on linux).
	 */
	if (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_DISCARD)
		return;
#ifdef IEEE80211_DEBUG
	if (ieee80211_msg_scan(vap) && (ic->ic_flags & IEEE80211_F_SCAN))
		dump_probe_beacon(subtype, 1, wh->i_addr2, sp);
#endif
	if (ss->ss_ops != NULL &&
	    ss->ss_ops->scan_add(ss, sp, wh, subtype, rssi, rstamp)) {
		/*
		 * If we've reached the min dwell time terminate
		 * the timer so we'll switch to the next channel.
		 */
		if ((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_MINDWELL) == 0 &&
		    time_after_eq(jiffies, SCAN_PRIVATE(ss)->ss_chanmindwell)) {
			IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
				"%s: chan %3d%c min dwell met (%lu > %lu)\n",
				__func__,
				ieee80211_chan2ieee(ic, ic->ic_curchan),
					channel_type(ic->ic_curchan),
				jiffies, SCAN_PRIVATE(ss)->ss_chanmindwell);
			/*
			 * XXX
			 * We want to just kick the timer and still
			 * process frames until it fires but linux
			 * will livelock unless we discard frames.
			 */
#if 0
			SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_MINDWELL;
#else
			SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_DISCARD;
#endif
			/* NB: trigger at next clock tick */
			mod_timer(&SCAN_PRIVATE(ss)->ss_scan_timer, jiffies);
		}
	}
}

/*
 * Timeout/age scan cache entries; called from sta timeout
 * timer (XXX should be self-contained).
 */
void
ieee80211_scan_timeout(struct ieee80211com *ic)
{
	struct ieee80211_scan_state *ss = ic->ic_scan;

	if (ss->ss_ops != NULL)
		ss->ss_ops->scan_age(ss);
}

/*
 * Mark a scan cache entry after a successful associate.
 */
void
ieee80211_scan_assoc_success(struct ieee80211com *ic, const u_int8_t mac[])
{
	struct ieee80211_scan_state *ss = ic->ic_scan;

	if (ss->ss_ops != NULL) {
		IEEE80211_NOTE_MAC(ss->ss_vap, IEEE80211_MSG_SCAN,
			mac, "%s",  __func__);
		ss->ss_ops->scan_assoc_success(ss, mac);
	}
}

/*
 * Demerit a scan cache entry after failing to associate.
 */
void
ieee80211_scan_assoc_fail(struct ieee80211com *ic,
	const u_int8_t mac[], int reason)
{
	struct ieee80211_scan_state *ss = ic->ic_scan;

	if (ss->ss_ops != NULL) {
		IEEE80211_NOTE_MAC(ss->ss_vap, IEEE80211_MSG_SCAN, mac,
			"%s: reason %u", __func__, reason);
		ss->ss_ops->scan_assoc_fail(ss, mac, reason);
	}
}

/*
 * Iterate over the contents of the scan cache.
 */
void
ieee80211_scan_iterate(struct ieee80211com *ic,
	ieee80211_scan_iter_func *f, void *arg)
{
	struct ieee80211_scan_state *ss = ic->ic_scan;

	if (ss->ss_ops != NULL)
		ss->ss_ops->scan_iterate(ss, f, arg);
}

/*
 * Flush the contents of the scan cache.
 */
void
ieee80211_scan_flush(struct ieee80211com *ic)
{
	struct ieee80211_scan_state *ss = ic->ic_scan;

	if (ss->ss_ops != NULL) {
		IEEE80211_DPRINTF(ss->ss_vap, IEEE80211_MSG_SCAN,
			"%s\n",  __func__);
		ss->ss_ops->scan_flush(ss);
	}
}

/*
 * Execute radar channel change. This is called when a radar/dfs
 * signal is detected.  AP mode only.  Return 1 on success, 0 on
 * failure
 */
int
ieee80211_scan_dfs_action(struct ieee80211vap *vap,
			  const struct ieee80211_scan_entry *se)
{
	struct ieee80211com *ic = vap->iv_ic;
	struct net_device *dev = ic->ic_dev;

	if (vap->iv_opmode != IEEE80211_M_HOSTAP)
		return 0;
	if (se != NULL) {
		/* A suitable scan entry was found, so change channels */
		if_printf(dev,"Changing to channel %d (%d MHz)\n",
			  se->se_chan->ic_ieee,
			  se->se_chan->ic_freq);
		if (vap->iv_state == IEEE80211_S_RUN) {
			ic->ic_chanchange_chan = se->se_chan->ic_ieee;
			ic->ic_chanchange_tbtt = IEEE80211_RADAR_11HCOUNT;
			ic->ic_flags |= IEEE80211_F_CHANSWITCH;
		} else {
			/* 
			 * vap is not in run state yet. so
			 * change the channel here.
			 */
			change_channel(ic,se->se_chan);
			ic->ic_bsschan = se->se_chan;
			if (vap->iv_bss)
				vap->iv_bss->ni_chan = se->se_chan;
		}
	} else {
		/* No channel wa found via scan module, means no good scanlist
		   was found */
		int chanStart, n = 0;
		u_int32_t curChanFlags;

		/* Only pick a random channel if we're in RUN state.  In scan 
		 * state, we don't need to pick a channel
		 */
		if (vap->iv_state == IEEE80211_S_RUN) {
			/* Pick a random channel */
			chanStart = jiffies % ic->ic_nchans;
			curChanFlags = (ic->ic_curchan->ic_flags) & ~(IEEE80211_CHAN_RADAR);
			while (ic->ic_channels[chanStart].ic_flags != curChanFlags) {
				if (++n >= ic->ic_nchans)
					break;
				chanStart++;
				if (chanStart == ic->ic_nchans)
					chanStart = 0;
			}
			if (n < ic->ic_nchans) {
				if_printf(dev,"Changing to channel %d (%d MHz)\n",
					  ic->ic_channels[chanStart].ic_ieee,
					  ic->ic_channels[chanStart].ic_freq);
				ic->ic_chanchange_chan = ic->ic_channels[chanStart].ic_ieee;
				ic->ic_chanchange_tbtt = IEEE80211_RADAR_11HCOUNT;
				ic->ic_flags |= IEEE80211_F_CHANSWITCH;
			}
		}
	}
	return 1;
}
EXPORT_SYMBOL(ieee80211_scan_dfs_action);