Fix the scan handling for 11b->11g upgrades in a world where, well,

it's not just 11b/11g.

The following was happening, and it's quite .. annoyingly grr-y.

* create vap, setup wpa_supplicant with no bgscanning, etc - there's
  no call to ieee80211_media_change, so vap->iv_des_mode is
  IEEE80211_MODE_AUTO;
* do ifconfig wlan0 scan - same thing, media_change doesn't get called,
  iv_des_mode stays as auto.
* But then, run wpa_cli and do 'scan' - it'll do a media change.
* if you're on 11ng, vap->iv_des_mode gets changed to IEEE80211_MODE_11NG
* Then makescanlist() is called.  There's a block of code that gets
  called if iv_des_mode != IEEE80211_MODE_AUTO, and it does this:

		if (vap->iv_des_mode != IEEE80211_MODE_11G ||
			    mode != IEEE80211_MODE_11B)
			continue;
		mode = IEEE80211_MODE_11G;	/* upgrade */

* .. now, iv_des_mode is not IEEE80211_MODE_11G, so it always runs
  'continue'
* .. and thus the scan list stays empty and no further channel
  scans occur. Ever.(1)

If you then disassociate and try associating to something, your
scan table has likely been purged / aged out and you'll never
see anything in the scan list.

(1) You need to do 'ifconfig wlan0 mode auto' or just destroy/re-create
    the VAP to get working wireless again.

Tested:

* iwn(4) - intel 5300 wifi; STA mode; using wpa_supplicant; bgscan
  enabled -and- wpa_supplicant scanning.

Thanks to:

* Everyone who kept poking me about this and wondering why the hell
  their wifi would eventually stop seeing scan lists.  Grr.
  I eventually snapped this evening and dug back into this code.

1 files changed, 6 insertions, 4 deletions

diff --git a/sys/net80211/ieee80211_scan_sta.c b/sys/net80211/ieee80211_scan_sta.c
index 6da06fd..1e87e35 100644
--- a/sys/net80211/ieee80211_scan_sta.c
+++ b/sys/net80211/ieee80211_scan_sta.c
@@ -600,10 +600,12 @@ makescanlist(struct ieee80211_scan_state *ss, struct ieee80211vap *vap,
 				 * so if the desired mode is 11g, then use
 				 * the 11b channel list but upgrade the mode.
 				 */
-				if (vap->iv_des_mode != IEEE80211_MODE_11G ||
-				    mode != IEEE80211_MODE_11B)
-					continue;
-				mode = IEEE80211_MODE_11G;	/* upgrade */
+				if (vap->iv_des_mode == IEEE80211_MODE_11G) {
+					if (mode == IEEE80211_MODE_11G) /* Skip the G check */
+						continue;
+					else if (mode == IEEE80211_MODE_11B)
+						mode = IEEE80211_MODE_11G;	/* upgrade */
+				}
 			}
 		} else {
 			/*