mac80211: handle protection mode, RIFS and ADDBA for HT IBSS

* Follow 802.11n-2009 9.13.3.1 for protection mode and ADDBA
* Send ADDBA only to HT STAs - implement 11.5.1.1 partially

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/agg-tx.c

@@ -430,6 +430,27 @@ int ieee80211_start_tx_ba_session(struct ieee80211_sta *pubsta, u16 tid,
 		return -EINVAL;
 	}
 
+	/*
+	 * 802.11n-2009 11.5.1.1: If the initiating STA is an HT STA, is a
+	 * member of an IBSS, and has no other existing Block Ack agreement
+	 * with the recipient STA, then the initiating STA shall transmit a
+	 * Probe Request frame to the recipient STA and shall not transmit an
+	 * ADDBA Request frame unless it receives a Probe Response frame
+	 * from the recipient within dot11ADDBAFailureTimeout.
+	 *
+	 * The probe request mechanism for ADDBA is currently not implemented,
+	 * but we only build up Block Ack session with HT STAs. This information
+	 * is set when we receive a bss info from a probe response or a beacon.
+	 */
+	if (sta->sdata->vif.type == NL80211_IFTYPE_ADHOC &&
+	    !sta->sta.ht_cap.ht_supported) {
+#ifdef CONFIG_MAC80211_HT_DEBUG
+		printk(KERN_DEBUG "BA request denied - IBSS STA %pM"
+		       "does not advertise HT support\n", pubsta->addr);
+#endif /* CONFIG_MAC80211_HT_DEBUG */
+		return -EINVAL;
+	}
+
 	spin_lock_bh(&sta->lock);
 
 	/* we have tried too many times, receiver does not want A-MPDU */

net/mac80211/ibss.c

@@ -896,6 +896,7 @@ int ieee80211_ibss_join(struct ieee80211_sub_if_data *sdata,
 			struct cfg80211_ibss_params *params)
 {
 	struct sk_buff *skb;
+	u32 changed = 0;
 
 	skb = dev_alloc_skb(sdata->local->hw.extra_tx_headroom +
 			    36 /* bitrates */ +
@@ -951,6 +952,23 @@ int ieee80211_ibss_join(struct ieee80211_sub_if_data *sdata,
 	ieee80211_recalc_idle(sdata->local);
 	mutex_unlock(&sdata->local->mtx);
 
+	/*
+	 * 802.11n-2009 9.13.3.1: In an IBSS, the HT Protection field is
+	 * reserved, but an HT STA shall protect HT transmissions as though
+	 * the HT Protection field were set to non-HT mixed mode.
+	 *
+	 * In an IBSS, the RIFS Mode field of the HT Operation element is
+	 * also reserved, but an HT STA shall operate as though this field
+	 * were set to 1.
+	 */
+
+	sdata->vif.bss_conf.ht_operation_mode |=
+		  IEEE80211_HT_OP_MODE_PROTECTION_NONHT_MIXED
+		| IEEE80211_HT_PARAM_RIFS_MODE;
+
+	changed |= BSS_CHANGED_HT;
+	ieee80211_bss_info_change_notify(sdata, changed);
+
 	ieee80211_queue_work(&sdata->local->hw, &sdata->work);
 
 	return 0;

net/mac80211/util.c

@@ -1587,6 +1587,11 @@ u8 *ieee80211_ie_build_ht_info(u8 *pos,
 	}
 	if (ht_cap->cap & IEEE80211_HT_CAP_SUP_WIDTH_20_40)
 		ht_info->ht_param |= IEEE80211_HT_PARAM_CHAN_WIDTH_ANY;
+
+	/*
+	 * Note: According to 802.11n-2009 9.13.3.1, HT Protection field and
+	 * RIFS Mode are reserved in IBSS mode, therefore keep them at 0
+	 */
 	ht_info->operation_mode = 0x0000;
 	ht_info->stbc_param = 0x0000;