mac80211: add op to configure default key id

There are hardwares which support offload of data packets
for example when auto ARP is enabled the hw will send
the ARP response. In such cases if WEP encryption is
configured the hw must know the default WEP key in order
to encrypt the packets correctly.

When hw_accel is enabled and encryption type is set to WEP,
the driver should get the default key index from mac80211.

Signed-off-by: Yoni Divinsky <[e-mail]>
[cleanups, fixes, documentation]
Signed-off-by: Johannes Berg <[e-mail]>

include/net/mac80211.h

···
  * rekeying), it will not include a valid phase 1 key. The valid phase 1 key is
  * provided by update_tkip_key only. The trigger that makes mac80211 call this
  * handler is software decryption with wrap around of iv16.
+ *
+ * The set_default_unicast_key() call updates the default WEP key index
+ * configured to the hardware for WEP encryption type. This is required
+ * for devices that support offload of data packets (e.g. ARP responses).
  */
 
 /**
···
  *	After rekeying was done it should (for example during resume) notify
  *	userspace of the new replay counter using ieee80211_gtk_rekey_notify().
  *
+ * @set_default_unicast_key: Set the default (unicast) key index, useful for
+ *	WEP when the device sends data packets autonomously, e.g. for ARP
+ *	offloading. The index can be 0-3, or -1 for unsetting it.
+ *
  * @hw_scan: Ask the hardware to service the scan request, no need to start
  *	the scan state machine in stack. The scan must honour the channel
  *	configuration done by the regulatory agent in the wiphy's
···
 	void (*set_rekey_data)(struct ieee80211_hw *hw,
 			       struct ieee80211_vif *vif,
 			       struct cfg80211_gtk_rekey_data *data);
+	void (*set_default_unicast_key)(struct ieee80211_hw *hw,
+					struct ieee80211_vif *vif, int idx);
 	int (*hw_scan)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 		       struct cfg80211_scan_request *req);
 	void (*cancel_hw_scan)(struct ieee80211_hw *hw,

net/mac80211/driver-ops.h

···
 	trace_drv_return_void(local);
 }
 
+static inline void
+drv_set_default_unicast_key(struct ieee80211_local *local,
+			    struct ieee80211_sub_if_data *sdata,
+			    int key_idx)
+{
+	check_sdata_in_driver(sdata);
+
+	WARN_ON_ONCE(key_idx < -1 || key_idx > 3);
+
+	trace_drv_set_default_unicast_key(local, sdata, key_idx);
+	if (local->ops->set_default_unicast_key)
+		local->ops->set_default_unicast_key(&local->hw, &sdata->vif,
+						    key_idx);
+	trace_drv_return_void(local);
+}
+
 #endif /* __MAC80211_DRIVER_OPS */

net/mac80211/key.c

···
 	if (idx >= 0 && idx < NUM_DEFAULT_KEYS)
 		key = key_mtx_dereference(sdata->local, sdata->keys[idx]);
 
-	if (uni)
+	if (uni) {
 		rcu_assign_pointer(sdata->default_unicast_key, key);
+		drv_set_default_unicast_key(sdata->local, sdata, idx);
+	}
+
 	if (multi)
 		rcu_assign_pointer(sdata->default_multicast_key, key);
 

net/mac80211/trace.h

···
 	)
 );
 
+TRACE_EVENT(drv_set_default_unicast_key,
+	TP_PROTO(struct ieee80211_local *local,
+		 struct ieee80211_sub_if_data *sdata,
+		 int key_idx),
+
+	TP_ARGS(local, sdata, key_idx),
+
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		VIF_ENTRY
+		__field(int, key_idx)
+	),
+
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		VIF_ASSIGN;
+		__entry->key_idx = key_idx;
+	),
+
+	TP_printk(LOCAL_PR_FMT VIF_PR_FMT " key_idx:%d",
+		  LOCAL_PR_ARG, VIF_PR_ARG, __entry->key_idx)
+);
+
 #ifdef CONFIG_MAC80211_MESSAGE_TRACING
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM mac80211_msg