mac80211: add fast-rx path

The regular RX path has a lot of code, but with a few
assumptions on the hardware it's possible to reduce the
amount of code significantly. Currently the assumptions
on the driver are the following:
 * hardware/driver reordering buffer (if supporting aggregation)
 * hardware/driver decryption & PN checking (if using encryption)
 * hardware/driver did de-duplication
 * hardware/driver did A-MSDU deaggregation
 * AP_LINK_PS is used (in AP mode)
 * no client powersave handling in mac80211 (in client mode)

of which some are actually checked per packet:
 * de-duplication
 * PN checking
 * decryption
and additionally packets must
 * not be A-MSDU (have been deaggregated by driver/device)
 * be data packets
 * not be fragmented
 * be unicast
 * have RFC 1042 header

Additionally dynamically we assume:
 * no encryption or CCMP/GCMP, TKIP/WEP/other not allowed
 * station must be authorized
 * 4-addr format not enabled

Some data needed for the RX path is cached in a new per-station
"fast_rx" structure, so that we only need to look at this and
the packet, no other memory when processing packets on the fast
RX path.

After doing the above per-packet checks, the data path collapses
down to a pretty simple conversion function taking advantage of
the data cached in the small fast_rx struct.

This should speed up the RX processing, and will make it easier
to reason about parallelizing RX (for which statistics will need
to be per-CPU still.)

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 7c23b575672e..a0a06609338d 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -286,6 +286,38 @@ struct ieee80211_fast_tx {
 };
 
 /**
+ * struct ieee80211_fast_rx - RX fastpath information
+ * @dev: netdevice for reporting the SKB
+ * @vif_type: (P2P-less) interface type of the original sdata (sdata->vif.type)
+ * @vif_addr: interface address
+ * @rfc1042_hdr: copy of the RFC 1042 SNAP header (to have in cache)
+ * @control_port_protocol: control port protocol copied from sdata
+ * @expected_ds_bits: from/to DS bits expected
+ * @icv_len: length of the MIC if present
+ * @key: bool indicating encryption is expected (key is set)
+ * @sta_notify: notify the MLME code (once)
+ * @internal_forward: forward froms internally on AP/VLAN type interfaces
+ * @da_offs: offset of the DA in the header (for header conversion)
+ * @sa_offs: offset of the SA in the header (for header conversion)
+ * @rcu_head: RCU head for freeing this structure
+ */
+struct ieee80211_fast_rx {
+	struct net_device *dev;
+	enum nl80211_iftype vif_type;
+	u8 vif_addr[ETH_ALEN] __aligned(2);
+	u8 rfc1042_hdr[6] __aligned(2);
+	__be16 control_port_protocol;
+	__le16 expected_ds_bits;
+	u8 icv_len;
+	u8 key:1,
+	   sta_notify:1,
+	   internal_forward:1;
+	u8 da_offs, sa_offs;
+
+	struct rcu_head rcu_head;
+};
+
+/**
  * struct mesh_sta - mesh STA information
  * @plink_lock: serialize access to plink fields
  * @llid: Local link ID
@@ -391,6 +423,7 @@ DECLARE_EWMA(signal, 1024, 8)
  * @cipher_scheme: optional cipher scheme for this station
  * @reserved_tid: reserved TID (if any, otherwise IEEE80211_TID_UNRESERVED)
  * @fast_tx: TX fastpath information
+ * @fast_rx: RX fastpath information
  * @tdls_chandef: a TDLS peer can have a wider chandef that is compatible to
  *	the BSS one.
  * @tx_stats: TX statistics
@@ -414,6 +447,7 @@ struct sta_info {
 	spinlock_t lock;
 
 	struct ieee80211_fast_tx __rcu *fast_tx;
+	struct ieee80211_fast_rx __rcu *fast_rx;
 
 #ifdef CONFIG_MAC80211_MESH
 	struct mesh_sta *mesh;