mac80211: use secondary channel offset IE also beacons during CSA

If we are switching from an HT40+ to an HT40- channel (or vice-versa),
we need the secondary channel offset IE to specify what is the
post-CSA offset to be used.  This applies both to beacons and to probe
responses.

In ieee80211_parse_ch_switch_ie() we were ignoring this IE from
beacons and using the *current* HT information IE instead.  This was
causing us to use the same offset as before the switch.

Fix that by using the secondary channel offset IE also for beacons and
don't ever use the pre-switch offset.  Additionally, remove the
"beacon" argument from ieee80211_parse_ch_switch_ie(), since it's not
needed anymore.

Cc: stable@vger.kernel.org
Reported-by: Jouni Malinen <j@w1.fi>
Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/ibss.c

@@ -805,7 +805,7 @@ ieee80211_ibss_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 
 	memset(&params, 0, sizeof(params));
 	memset(&csa_ie, 0, sizeof(csa_ie));
-	err = ieee80211_parse_ch_switch_ie(sdata, elems, beacon,
+	err = ieee80211_parse_ch_switch_ie(sdata, elems,
 					   ifibss->chandef.chan->band,
 					   sta_flags, ifibss->bssid, &csa_ie);
 	/* can't switch to destination channel, fail */

net/mac80211/ieee80211_i.h

@@ -1642,7 +1642,6 @@ void ieee80211_process_measurement_req(struct ieee80211_sub_if_data *sdata,
  * ieee80211_parse_ch_switch_ie - parses channel switch IEs
  * @sdata: the sdata of the interface which has received the frame
  * @elems: parsed 802.11 elements received with the frame
- * @beacon: indicates if the frame was a beacon or probe response
  * @current_band: indicates the current band
  * @sta_flags: contains information about own capabilities and restrictions
  *	to decide which channel switch announcements can be accepted. Only the
@@ -1656,7 +1655,7 @@ void ieee80211_process_measurement_req(struct ieee80211_sub_if_data *sdata,
  * Return: 0 on success, <0 on error and >0 if there is nothing to parse.
  */
 int ieee80211_parse_ch_switch_ie(struct ieee80211_sub_if_data *sdata,
-				 struct ieee802_11_elems *elems, bool beacon,
+				 struct ieee802_11_elems *elems,
 				 enum ieee80211_band current_band,
 				 u32 sta_flags, u8 *bssid,
 				 struct ieee80211_csa_ie *csa_ie);

net/mac80211/mesh.c

@@ -874,7 +874,7 @@ ieee80211_mesh_process_chnswitch(struct ieee80211_sub_if_data *sdata,
 
 	memset(&params, 0, sizeof(params));
 	memset(&csa_ie, 0, sizeof(csa_ie));
-	err = ieee80211_parse_ch_switch_ie(sdata, elems, beacon, band,
+	err = ieee80211_parse_ch_switch_ie(sdata, elems, band,
 					   sta_flags, sdata->vif.addr,
 					   &csa_ie);
 	if (err < 0)

net/mac80211/mlme.c

@@ -1072,7 +1072,7 @@ ieee80211_sta_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 
 	current_band = cbss->channel->band;
 	memset(&csa_ie, 0, sizeof(csa_ie));
-	res = ieee80211_parse_ch_switch_ie(sdata, elems, beacon, current_band,
+	res = ieee80211_parse_ch_switch_ie(sdata, elems, current_band,
 					   ifmgd->flags,
 					   ifmgd->associated->bssid, &csa_ie);
 	if (res	< 0)

net/mac80211/spectmgmt.c

@@ -22,7 +22,7 @@
 #include "wme.h"
 
 int ieee80211_parse_ch_switch_ie(struct ieee80211_sub_if_data *sdata,
-				 struct ieee802_11_elems *elems, bool beacon,
+				 struct ieee802_11_elems *elems,
 				 enum ieee80211_band current_band,
 				 u32 sta_flags, u8 *bssid,
 				 struct ieee80211_csa_ie *csa_ie)
@@ -91,18 +91,12 @@ int ieee80211_parse_ch_switch_ie(struct ieee80211_sub_if_data *sdata,
 		return -EINVAL;
 	}
 
-	if (!beacon && sec_chan_offs) {
+	if (sec_chan_offs) {
 		secondary_channel_offset = sec_chan_offs->sec_chan_offs;
-	} else if (beacon && ht_oper) {
-		secondary_channel_offset =
-			ht_oper->ht_param & IEEE80211_HT_PARAM_CHA_SEC_OFFSET;
 	} else if (!(sta_flags & IEEE80211_STA_DISABLE_HT)) {
-		/* If it's not a beacon, HT is enabled and the IE not present,
-		 * it's 20 MHz, 802.11-2012 8.5.2.6:
-		 *	This element [the Secondary Channel Offset Element] is
-		 *	present when switching to a 40 MHz channel. It may be
-		 *	present when switching to a 20 MHz channel (in which
-		 *	case the secondary channel offset is set to SCN).
+		/* If the secondary channel offset IE is not present,
+		 * we can't know what's the post-CSA offset, so the
+		 * best we can do is use 20MHz.
 		*/
 		secondary_channel_offset = IEEE80211_HT_PARAM_CHA_SEC_NONE;
 	}