mac80211: allow disable FAT in specific configurations

This patch allows to disable FAT channel in specific configurations.

For example the configuration (8, +1), (primary channel 8, extension
channel 12) isn't permitted in U.S., but (8, -1), (primary channel 8,
extension channel 4) is. When FAT channel configuration is not
permitted, FAT channel should be reported as not supported in the
capabilities of the HT IE in association request. And sssociation is
performed on 20Mhz channel.

Signed-off-by: Emmanuel Grumbach <[e-mail]>
Signed-off-by: Tomas Winkler <[e-mail]>
Signed-off-by: John W. Linville <[e-mail]>

include/linux/ieee80211.h

···
 #define IEEE80211_HT_CAP_MCS_TX_UEQM		0x10
 /* 802.11n HT IE masks */
 #define IEEE80211_HT_IE_CHA_SEC_OFFSET		0x03
+#define IEEE80211_HT_IE_CHA_SEC_ABOVE 		0x01
+#define IEEE80211_HT_IE_CHA_SEC_BELOW 		0x03
 #define IEEE80211_HT_IE_CHA_WIDTH		0x04
 #define IEEE80211_HT_IE_HT_PROTECTION		0x0003
 #define IEEE80211_HT_IE_NON_GF_STA_PRSNT	0x0004

include/net/wireless.h

···
  *	on this channel.
  * @IEEE80211_CHAN_NO_IBSS: IBSS is not allowed on this channel.
  * @IEEE80211_CHAN_RADAR: Radar detection is required on this channel.
+ * @IEEE80211_CHAN_NO_FAT_ABOVE: extension channel above this channel
+ * 	is not permitted.
+ * @IEEE80211_CHAN_NO_FAT_BELOW: extension channel below this channel
+ * 	is not permitted.
  */
 enum ieee80211_channel_flags {
 	IEEE80211_CHAN_DISABLED		= 1<<0,
 	IEEE80211_CHAN_PASSIVE_SCAN	= 1<<1,
 	IEEE80211_CHAN_NO_IBSS		= 1<<2,
 	IEEE80211_CHAN_RADAR		= 1<<3,
+	IEEE80211_CHAN_NO_FAT_ABOVE	= 1<<4,
+	IEEE80211_CHAN_NO_FAT_BELOW	= 1<<5,
 };
 
 /**

net/mac80211/ieee80211_i.h

···
 	size_t wmm_ie_len;
 	u8 *ht_ie;
 	size_t ht_ie_len;
+	u8 *ht_add_ie;
+	size_t ht_add_ie_len;
 #ifdef CONFIG_MAC80211_MESH
 	u8 *mesh_id;
 	size_t mesh_id_len;

net/mac80211/mlme.c

···
 
 	/* wmm support is a must to HT */
 	if (wmm && (ifsta->flags & IEEE80211_STA_WMM_ENABLED) &&
-	    sband->ht_info.ht_supported) {
-		__le16 tmp = cpu_to_le16(sband->ht_info.cap);
+	    sband->ht_info.ht_supported && bss->ht_add_ie) {
+		struct ieee80211_ht_addt_info *ht_add_info =
+			(struct ieee80211_ht_addt_info *)bss->ht_add_ie;
+		u16 cap = sband->ht_info.cap;
+		__le16 tmp;
+		u32 flags = local->hw.conf.channel->flags;
+
+		switch (ht_add_info->ht_param & IEEE80211_HT_IE_CHA_SEC_OFFSET) {
+		case IEEE80211_HT_IE_CHA_SEC_ABOVE:
+			if (flags & IEEE80211_CHAN_NO_FAT_ABOVE) {
+				cap &= ~IEEE80211_HT_CAP_SUP_WIDTH;
+				cap &= ~IEEE80211_HT_CAP_SGI_40;
+			}
+			break;
+		case IEEE80211_HT_IE_CHA_SEC_BELOW:
+			if (flags & IEEE80211_CHAN_NO_FAT_BELOW) {
+				cap &= ~IEEE80211_HT_CAP_SUP_WIDTH;
+				cap &= ~IEEE80211_HT_CAP_SGI_40;
+			}
+			break;
+		}
+
+		tmp = cpu_to_le16(cap);
 		pos = skb_put(skb, sizeof(struct ieee80211_ht_cap)+2);
 		*pos++ = WLAN_EID_HT_CAPABILITY;
 		*pos++ = sizeof(struct ieee80211_ht_cap);
···
 	kfree(bss->rsn_ie);
 	kfree(bss->wmm_ie);
 	kfree(bss->ht_ie);
+	kfree(bss->ht_add_ie);
 	kfree(bss_mesh_id(bss));
 	kfree(bss_mesh_cfg(bss));
 	kfree(bss);
···
 		kfree(bss->ht_ie);
 		bss->ht_ie = NULL;
 		bss->ht_ie_len = 0;
+	}
+
+	if (elems.ht_info_elem &&
+	     (!bss->ht_add_ie ||
+	     bss->ht_add_ie_len != elems.ht_info_elem_len ||
+	     memcmp(bss->ht_add_ie, elems.ht_info_elem,
+			elems.ht_info_elem_len))) {
+		kfree(bss->ht_add_ie);
+		bss->ht_add_ie =
+			kmalloc(elems.ht_info_elem_len + 2, GFP_ATOMIC);
+		if (bss->ht_add_ie) {
+			memcpy(bss->ht_add_ie, elems.ht_info_elem - 2,
+				elems.ht_info_elem_len + 2);
+			bss->ht_add_ie_len = elems.ht_info_elem_len + 2;
+		} else
+			bss->ht_add_ie_len = 0;
+	} else if (!elems.ht_info_elem && bss->ht_add_ie) {
+		kfree(bss->ht_add_ie);
+		bss->ht_add_ie = NULL;
+		bss->ht_add_ie_len = 0;
 	}
 
 	bss->beacon_int = le16_to_cpu(mgmt->u.beacon.beacon_int);