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, 14 insertions, 0 deletions

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 5910085..df5698e 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1714,6 +1714,18 @@ struct ieee80211_sta_rates {
  * @tdls_initiator: indicates the STA is an initiator of the TDLS link. Only
  *	valid if the STA is a TDLS peer in the first place.
  * @mfp: indicates whether the STA uses management frame protection or not.
+ * @max_amsdu_subframes: indicates the maximal number of MSDUs in a single
+ *	A-MSDU. Taken from the Extended Capabilities element. 0 means
+ *	unlimited.
+ * @max_amsdu_len: indicates the maximal length of an A-MSDU in bytes. This
+ *	field is always valid for packets with a VHT preamble. For packets
+ *	with a HT preamble, additional limits apply:
+ *		+ If the skb is transmitted as part of a BA agreement, the
+ *		  A-MSDU maximal size is min(max_amsdu_len, 4065) bytes.
+ *		+ If the skb is not part of a BA aggreement, the A-MSDU maximal
+ *		  size is min(max_amsdu_len, 7935) bytes.
+ *	Both additional HT limits must be enforced by the low level driver.
+ *	This is defined by the spec (IEEE 802.11-2012 section 8.3.2.2 NOTE 2).
  * @txq: per-TID data TX queues (if driver uses the TXQ abstraction)
  */
 struct ieee80211_sta {
@@ -1732,6 +1744,8 @@ struct ieee80211_sta {
 	bool tdls;
 	bool tdls_initiator;
 	bool mfp;
+	u8 max_amsdu_subframes;
+	u16 max_amsdu_len;
 
 	struct ieee80211_txq *txq[IEEE80211_NUM_TIDS];