mac80211: connect with HT20 if HT40 is not permitted

Some changes to fix issues with HT40 APs in Korea
and follow-up changes to allow using HT40 even if
the local regulatory database disallows it caused
issues with iwlwifi (and could cause issues with
other devices); iwlwifi firmware would assert if
you tried to connect to an AP that has an invalid
configuration (e.g. using HT40- on channel 140.)

Fix this, while avoiding the "Korean AP" issue by
disabling HT40 and advertising HT20 to the AP
when connecting.

Cc: stable@vger.kernel.org [3.6]
Reported-by: Florian Reitmeir <florian@reitmeir.org>
Tested-by: Florian Reitmeir <florian@reitmeir.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index e510a33..1b7eed2 100644 (file)
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -3099,22 +3099,32 @@ static int ieee80211_prep_channel(struct ieee80211_sub_if_data *sdata,
                                   ht_cfreq, ht_oper->primary_chan,
                                   cbss->channel->band);
                        ht_oper = NULL;
+               } else {
+                       channel_type = NL80211_CHAN_HT20;
                }
        }
 
-       if (ht_oper) {
-               channel_type = NL80211_CHAN_HT20;
+       if (ht_oper && sband->ht_cap.cap & IEEE80211_HT_CAP_SUP_WIDTH_20_40) {
+               /*
+                * cfg80211 already verified that the channel itself can
+                * be used, but it didn't check that we can do the right
+                * HT type, so do that here as well. If HT40 isn't allowed
+                * on this channel, disable 40 MHz operation.
+                */
 
-               if (sband->ht_cap.cap & IEEE80211_HT_CAP_SUP_WIDTH_20_40) {
-                       switch (ht_oper->ht_param &
-                                       IEEE80211_HT_PARAM_CHA_SEC_OFFSET) {
-                       case IEEE80211_HT_PARAM_CHA_SEC_ABOVE:
+               switch (ht_oper->ht_param & IEEE80211_HT_PARAM_CHA_SEC_OFFSET) {
+               case IEEE80211_HT_PARAM_CHA_SEC_ABOVE:
+                       if (cbss->channel->flags & IEEE80211_CHAN_NO_HT40PLUS)
+                               ifmgd->flags |= IEEE80211_STA_DISABLE_40MHZ;
+                       else
                                channel_type = NL80211_CHAN_HT40PLUS;
-                               break;
-                       case IEEE80211_HT_PARAM_CHA_SEC_BELOW:
+                       break;
+               case IEEE80211_HT_PARAM_CHA_SEC_BELOW:
+                       if (cbss->channel->flags & IEEE80211_CHAN_NO_HT40MINUS)
+                               ifmgd->flags |= IEEE80211_STA_DISABLE_40MHZ;
+                       else
                                channel_type = NL80211_CHAN_HT40MINUS;
-                               break;
-                       }
+                       break;
                }
        }