mac80211: fix scan races and rework scanning

There are some places marked
	/* XXX maybe racy? */
and they really are racy because there's no locking.

This patch reworks much of the scan code, and introduces proper
locking for the scan request as well as the internal scanning
(which is necessary for IBSS/managed modes). Helper functions
are added to call the scanning code whenever necessary. The
scan deferring is changed to simply queue the scanning work
instead of trying to start the scan in place, the scanning work
will then take care of the rest.

Also, currently when internal scans are requested for an interface
that is trying to associate, we reject such scans. This was not
intended, the mlme code has provisions to scan twice when it can't
find the BSS to associate with right away; this has never worked
properly. Fix this by not rejecting internal scan requests for an
interface that is associating.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 3 insertions, 19 deletions

diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
index 9fe1f937e0b..25ff583612e 100644
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -432,15 +432,7 @@ static void ieee80211_sta_merge_ibss(struct ieee80211_sub_if_data *sdata)
 	printk(KERN_DEBUG "%s: No active IBSS STAs - trying to scan for other "
 	       "IBSS networks with same SSID (merge)\n", sdata->dev->name);
 
-	/* XXX maybe racy? */
-	if (sdata->local->scan_req)
-		return;
-
-	memcpy(sdata->local->int_scan_req.ssids[0].ssid,
-	       ifibss->ssid, IEEE80211_MAX_SSID_LEN);
-	sdata->local->int_scan_req.ssids[0].ssid_len = ifibss->ssid_len;
-	if (ieee80211_request_scan(sdata, &sdata->local->int_scan_req))
-		ieee80211_scan_failed(sdata->local);
+	ieee80211_request_internal_scan(sdata, ifibss->ssid, ifibss->ssid_len);
 }
 
 static void ieee80211_sta_create_ibss(struct ieee80211_sub_if_data *sdata)
@@ -553,16 +545,8 @@ static void ieee80211_sta_find_ibss(struct ieee80211_sub_if_data *sdata)
 		printk(KERN_DEBUG "%s: Trigger new scan to find an IBSS to "
 		       "join\n", sdata->dev->name);
 
-		/* XXX maybe racy? */
-		if (local->scan_req)
-			return;
-
-		memcpy(local->int_scan_req.ssids[0].ssid,
-		       ifibss->ssid, IEEE80211_MAX_SSID_LEN);
-		local->int_scan_req.ssids[0].ssid_len =
-			ifibss->ssid_len;
-		if (ieee80211_request_scan(sdata, &local->int_scan_req))
-			ieee80211_scan_failed(local);
+		ieee80211_request_internal_scan(sdata, ifibss->ssid,
+						ifibss->ssid_len);
 	} else if (ifibss->state != IEEE80211_IBSS_MLME_JOINED) {
 		int interval = IEEE80211_SCAN_INTERVAL;