iwlwifi: add test to determine if interface in monitor mode

mac80211 sets driver in monitor mode through configuring the
RX filters. We cannot trust priv->iw_mode to be accurate
regarding monitor mode as iw_mode is only set in add_interface,
which is not called by mac80211 when in monitor mode.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-core.c

@@ -698,6 +698,18 @@ static u8 iwl_count_chain_bitmap(u32 chain_bitmap)
 	return res;
 }
 
+/**
+ * iwl_is_monitor_mode - Determine if interface in monitor mode
+ *
+ * priv->iw_mode is set in add_interface, but add_interface is
+ * never called for monitor mode. The only way mac80211 informs us about
+ * monitor mode is through configuring filters (call to configure_filter).
+ */
+static bool iwl_is_monitor_mode(struct iwl_priv *priv)
+{
+	return !!(priv->staging_rxon.filter_flags & RXON_FILTER_PROMISC_MSK);
+}
+
 /**
  * iwl_set_rxon_chain - Set up Rx chain usage in "staging" RXON image
  *