mac80211: allow low-level drivers to set netdev feature bits

Low level drivers can now set certain netdev feature bits in
netdev_features member of the ieee80211_hw struct. These will be
propagated to every netdev created from this HW.

The white-listed features currently include only ones related to HW
checksumming.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/net/mac80211.h

@@ -1297,6 +1297,10 @@ enum ieee80211_hw_flags {
  *	reports, by default it is set to _MCS, _GI and _BW but doesn't
  *	include _FMT. Use %IEEE80211_RADIOTAP_MCS_HAVE_* values, only
  *	adding _BW is supported today.
+ *
+ * @netdev_features: netdev features to be set in each netdev created
+ *	from this HW. Note only HW checksum features are currently
+ *	compatible with mac80211. Other feature bits will be rejected.
  */
 struct ieee80211_hw {
 	struct ieee80211_conf conf;
@@ -1319,6 +1323,7 @@ struct ieee80211_hw {
 	u8 max_tx_aggregation_subframes;
 	u8 offchannel_tx_hw_queue;
 	u8 radiotap_mcs_details;
+	netdev_features_t netdev_features;
 };
 
 /**

net/mac80211/iface.c

@@ -1352,6 +1352,8 @@ int ieee80211_if_add(struct ieee80211_local *local, const char *name,
 			sdata->u.mgd.use_4addr = params->use_4addr;
 	}
 
+	ndev->features |= local->hw.netdev_features;
+
 	ret = register_netdevice(ndev);
 	if (ret)
 		goto fail;

net/mac80211/main.c

@@ -682,6 +682,7 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 	enum ieee80211_band band;
 	int channels, max_bitrates;
 	bool supp_ht;
+	netdev_features_t feature_whitelist;
 	static const u32 cipher_suites[] = {
 		/* keep WEP first, it may be removed below */
 		WLAN_CIPHER_SUITE_WEP40,
@@ -708,6 +709,12 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 	if ((hw->flags & IEEE80211_HW_SCAN_WHILE_IDLE) && !local->ops->hw_scan)
 		return -EINVAL;
 
+	/* Only HW csum features are currently compatible with mac80211 */
+	feature_whitelist = NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
+			    NETIF_F_HW_CSUM;
+	if (WARN_ON(hw->netdev_features & ~feature_whitelist))
+		return -EINVAL;
+
 	if (hw->max_report_rates == 0)
 		hw->max_report_rates = hw->max_rates;