mac80211: limit the A-MSDU Tx based on peer's capabilities

In VHT, the specification allows to limit the number of
MSDUs in an A-MSDU in the Extended Capabilities IE. There
is also a limitation on the byte size in the VHT IE.
In HT, the only limitation is on the byte size.
Parse the capabilities from the peer and make them
available to the driver.

In HT, there is another limitation when a BA agreement
is active: the byte size can't be greater than 4095.
This is not enforced here.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 166a29f..66d22de 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1131,6 +1131,34 @@ static int sta_apply_parameters(struct ieee80211_local *local,
 		sta->sta.max_sp = params->max_sp;
 	}
 
+	/* The sender might not have sent the last bit, consider it to be 0 */
+	if (params->ext_capab_len >= 8) {
+		u8 val = (params->ext_capab[7] &
+			  WLAN_EXT_CAPA8_MAX_MSDU_IN_AMSDU_LSB) >> 7;
+
+		/* we did get all the bits, take the MSB as well */
+		if (params->ext_capab_len >= 9) {
+			u8 val_msb = params->ext_capab[8] &
+				WLAN_EXT_CAPA9_MAX_MSDU_IN_AMSDU_MSB;
+			val_msb <<= 1;
+			val |= val_msb;
+		}
+
+		switch (val) {
+		case 1:
+			sta->sta.max_amsdu_subframes = 32;
+			break;
+		case 2:
+			sta->sta.max_amsdu_subframes = 16;
+			break;
+		case 3:
+			sta->sta.max_amsdu_subframes = 8;
+			break;
+		default:
+			sta->sta.max_amsdu_subframes = 0;
+		}
+	}
+
 	/*
 	 * cfg80211 validates this (1-2007) and allows setting the AID
 	 * only when creating a new station entry
@@ -1160,6 +1188,7 @@ static int sta_apply_parameters(struct ieee80211_local *local,
 		ieee80211_ht_cap_ie_to_sta_ht_cap(sdata, sband,
 						  params->ht_capa, sta);
 
+	/* VHT can override some HT caps such as the A-MSDU max length */
 	if (params->vht_capa)
 		ieee80211_vht_cap_ie_to_sta_vht_cap(sdata, sband,
 						    params->vht_capa, sta);