mac80211: Warn users if HT fails because of freq mismatch.

I have a netgear WNDR3700 that appears to have an off-by-four
bug in how it fills out the hti->control_chan (I configure the
AP to channel 11, it reports 15 as control_chan).

Poke a message into the kernel logs to give users a
clue as to why they are not getting the expected
channel-type or rate.

Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 22 insertions, 4 deletions

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index dfa752e5520b..e059b3a6f285 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -161,6 +161,7 @@ static u32 ieee80211_enable_ht(struct ieee80211_sub_if_data *sdata,
         struct ieee80211_supported_band *sband;
         struct sta_info *sta;
         u32 changed = 0;
+        int hti_cfreq;
         u16 ht_opmode;
         bool enable_ht = true;
         enum nl80211_channel_type prev_chantype;
@@ -174,10 +175,27 @@ static u32 ieee80211_enable_ht(struct ieee80211_sub_if_data *sdata,
         if (!sband->ht_cap.ht_supported)
                 enable_ht = false;
 
-        /* check that channel matches the right operating channel */
-        if (local->hw.conf.channel->center_freq !=
-            ieee80211_channel_to_frequency(hti->control_chan, sband->band))
-                enable_ht = false;
+        if (enable_ht) {
+                hti_cfreq = ieee80211_channel_to_frequency(hti->control_chan,
+                                                           sband->band);
+                /* check that channel matches the right operating channel */
+                if (local->hw.conf.channel->center_freq != hti_cfreq) {
+                        /* Some APs mess this up, evidently.
+                         * Netgear WNDR3700 sometimes reports 4 higher than
+                         * the actual channel, for instance.
+                         */
+                        printk(KERN_DEBUG
+                               "%s: Wrong control channel in association"
+                               " response: configured center-freq: %d"
+                               " hti-cfreq: %d  hti->control_chan: %d"
+                               " band: %d.  Disabling HT.\n",
+                               sdata->name,
+                               local->hw.conf.channel->center_freq,
+                               hti_cfreq, hti->control_chan,
+                               sband->band);
+                        enable_ht = false;
+                }
+        }
 
         if (enable_ht) {
                 channel_type = NL80211_CHAN_HT20;