mac80211: split hardware scan by band

There's currently a very odd bug in mac80211 -- a
hardware scan that is done while the hardware is
really operating on 2.4 GHz will include CCK rates
in the probe request frame, even on 5 GHz (if the
driver uses the mac80211 IEs). Vice versa, if the
hardware is operating on 5 GHz the 2.4 GHz probe
requests will not include CCK rates even though
they should.

Fix this by splitting up cfg80211 scan requests by
band -- recalculating the IEs every time -- and
requesting only per-band scans from the driver.

Apparently this bug hasn't been a problem yet, but
it is imaginable that some older access points get
confused if confronted with such behaviour.

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

1 files changed, 71 insertions, 25 deletions

diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 1a643fe5250e..c46ac01e2a8f 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -187,6 +187,39 @@ ieee80211_scan_rx(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb)
         return RX_QUEUED;
 }
 
+/* return false if no more work */
+static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
+{
+        struct cfg80211_scan_request *req = local->scan_req;
+        enum ieee80211_band band;
+        int i, ielen, n_chans;
+
+        do {
+                if (local->hw_scan_band == IEEE80211_NUM_BANDS)
+                        return false;
+
+                band = local->hw_scan_band;
+                n_chans = 0;
+                for (i = 0; i < req->n_channels; i++) {
+                        if (req->channels[i]->band == band) {
+                                local->hw_scan_req->channels[n_chans] =
+                                                        req->channels[i];
+                                n_chans++;
+                        }
+                }
+
+                local->hw_scan_band++;
+        } while (!n_chans);
+
+        local->hw_scan_req->n_channels = n_chans;
+
+        ielen = ieee80211_build_preq_ies(local, (u8 *)local->hw_scan_req->ie,
+                                         req->ie, req->ie_len, band);
+        local->hw_scan_req->ie_len = ielen;
+
+        return true;
+}
+
 /*
  * inform AP that we will go to sleep so that it will buffer the frames
  * while we scan
@@ -247,13 +280,6 @@ static void ieee80211_scan_ps_disable(struct ieee80211_sub_if_data *sdata)
         }
 }
 
-static void ieee80211_restore_scan_ies(struct ieee80211_local *local)
-{
-        kfree(local->scan_req->ie);
-        local->scan_req->ie = local->orig_ies;
-        local->scan_req->ie_len = local->orig_ies_len;
-}
-
 void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
 {
         struct ieee80211_local *local = hw_to_local(hw);
@@ -272,15 +298,22 @@ void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
                 return;
         }
 
-        if (test_bit(SCAN_HW_SCANNING, &local->scanning))
-                ieee80211_restore_scan_ies(local);
+        was_hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
+        if (was_hw_scan && !aborted && ieee80211_prep_hw_scan(local)) {
+                ieee80211_queue_delayed_work(&local->hw,
+                                             &local->scan_work, 0);
+                mutex_unlock(&local->scan_mtx);
+                return;
+        }
+
+        kfree(local->hw_scan_req);
+        local->hw_scan_req = NULL;
 
         if (local->scan_req != local->int_scan_req)
                 cfg80211_scan_done(local->scan_req, aborted);
         local->scan_req = NULL;
         local->scan_sdata = NULL;
 
-        was_hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
         local->scanning = 0;
         local->scan_channel = NULL;
 
@@ -392,19 +425,23 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
 
         if (local->ops->hw_scan) {
                 u8 *ies;
-                int ielen;
 
-                ies = kmalloc(2 + IEEE80211_MAX_SSID_LEN +
-                              local->scan_ies_len + req->ie_len, GFP_KERNEL);
-                if (!ies)
+                local->hw_scan_req = kmalloc(
+                                sizeof(*local->hw_scan_req) +
+                                req->n_channels * sizeof(req->channels[0]) +
+                                2 + IEEE80211_MAX_SSID_LEN + local->scan_ies_len +
+                                req->ie_len, GFP_KERNEL);
+                if (!local->hw_scan_req)
                         return -ENOMEM;
 
-                ielen = ieee80211_build_preq_ies(local, ies,
-                                                 req->ie, req->ie_len);
-                local->orig_ies = req->ie;
-                local->orig_ies_len = req->ie_len;
-                req->ie = ies;
-                req->ie_len = ielen;
+                local->hw_scan_req->ssids = req->ssids;
+                local->hw_scan_req->n_ssids = req->n_ssids;
+                ies = (u8 *)local->hw_scan_req +
+                        sizeof(*local->hw_scan_req) +
+                        req->n_channels * sizeof(req->channels[0]);
+                local->hw_scan_req->ie = ies;
+
+                local->hw_scan_band = 0;
         }
 
         local->scan_req = req;
@@ -436,16 +473,17 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
         ieee80211_recalc_idle(local);
         mutex_unlock(&local->scan_mtx);
 
-        if (local->ops->hw_scan)
-                rc = drv_hw_scan(local, local->scan_req);
-        else
+        if (local->ops->hw_scan) {
+                WARN_ON(!ieee80211_prep_hw_scan(local));
+                rc = drv_hw_scan(local, local->hw_scan_req);
+        } else
                 rc = ieee80211_start_sw_scan(local);
 
         mutex_lock(&local->scan_mtx);
 
         if (rc) {
-                if (local->ops->hw_scan)
-                        ieee80211_restore_scan_ies(local);
+                kfree(local->hw_scan_req);
+                local->hw_scan_req = NULL;
                 local->scanning = 0;
 
                 ieee80211_recalc_idle(local);
@@ -654,6 +692,14 @@ void ieee80211_scan_work(struct work_struct *work)
                 return;
         }
 
+        if (local->hw_scan_req) {
+                int rc = drv_hw_scan(local, local->hw_scan_req);
+                mutex_unlock(&local->scan_mtx);
+                if (rc)
+                        ieee80211_scan_completed(&local->hw, true);
+                return;
+        }
+
         if (local->scan_req && !local->scanning) {
                 struct cfg80211_scan_request *req = local->scan_req;
                 int rc;