mac80211: fix bandwidth computation for TDLS peers

Section 11.23.1 of 80211-2016 specification allows TDLS peers
to operate on wider bandwidths though they are connected to a BSS
which do not support wider bandwidth operations, provided both the
peers advertise wider bandwidth capabilities.

The existing logic considers the minimum of station's and AP's
capability for bandwidth computation. The same logic applies for
TDLS peers as well, this restricts operating on wider bandwidths
over a TDLS link when the peers are connected to legacy APs.

As an example, if 80Mhz VHT capable peers are connected to a 20Mhz
5 GHz AP, then as per the existing logic TDLS operation will be
restricted to 20Mhz.

Address this problem by not considering BSS capability in bandwidth
computation if the participating TDLS peers have wider bandwidth
capability.
Signed-off-by: Manikanta Pubbisetty <mpubbise@qti.qualcomm.com>
[lots of wording/typo fixes]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/vht.c

@@ -386,6 +386,16 @@ enum ieee80211_sta_rx_bandwidth ieee80211_sta_cur_vht_bw(struct sta_info *sta)
 
 	bw = ieee80211_sta_cap_rx_bw(sta);
 	bw = min(bw, sta->cur_max_bandwidth);
+
+	/* Don't consider AP's bandwidth for TDLS peers, section 11.23.1 of
+	 * IEEE80211-2016 specification makes higher bandwidth operation
+	 * possible on the TDLS link if the peers have wider bandwidth
+	 * capability.
+	 */
+	if (test_sta_flag(sta, WLAN_STA_TDLS_PEER) &&
+	    test_sta_flag(sta, WLAN_STA_TDLS_WIDER_BW))
+		return bw;
+
 	bw = min(bw, ieee80211_chan_width_to_rx_bw(bss_width));
 
 	return bw;