cfg80211: advertise extended capabilities to userspace

In many cases, userspace may need to know which of the
802.11 extended capabilities ("Extended Capabilities
element") are implemented in the driver or device, to
include them e.g. in beacons, assoc request/response
or other frames. Add a new nl80211 attribute to hold
the extended capabilities bitmap for this.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -2480,6 +2480,14 @@ struct wiphy_wowlan_support {
  *
  * @max_acl_mac_addrs: Maximum number of MAC addresses that the device
  *	supports for ACL.
+ *
+ * @extended_capabilities: extended capabilities supported by the driver,
+ *	additional capabilities might be supported by userspace; these are
+ *	the 802.11 extended capabilities ("Extended Capabilities element")
+ *	and are in the same format as in the information element. See
+ *	802.11-2012 8.4.2.29 for the defined fields.
+ * @extended_capabilities_mask: mask of the valid values
+ * @extended_capabilities_len: length of the extended capabilities
  */
 struct wiphy {
 	/* assign these fields before you register the wiphy */
@@ -2546,6 +2554,9 @@ struct wiphy {
 	 */
 	u32 probe_resp_offload;
 
+	const u8 *extended_capabilities, *extended_capabilities_mask;
+	u8 extended_capabilities_len;
+
 	/* If multiple wiphys are registered and you're handed e.g.
 	 * a regular netdev with assigned ieee80211_ptr, you won't
 	 * know whether it points to a wiphy your driver has registered

include/uapi/linux/nl80211.h

@@ -1355,6 +1355,12 @@ enum nl80211_commands {
  * @NL80211_ATTR_RADAR_EVENT: Type of radar event for notification to userspace,
  *	contains a value of enum nl80211_radar_event (u32).
  *
+ * @NL80211_ATTR_EXT_CAPA: 802.11 extended capabilities that the kernel driver
+ *	has and handles. The format is the same as the IE contents. See
+ *	802.11-2012 8.4.2.29 for more information.
+ * @NL80211_ATTR_EXT_CAPA_MASK: Extended capabilities that the kernel driver
+ *	has set in the %NL80211_ATTR_EXT_CAPA value, for multibit fields.
+ *
  * @NL80211_ATTR_MAX: highest attribute number currently defined
  * @__NL80211_ATTR_AFTER_LAST: internal use
  */
@@ -1635,6 +1641,9 @@ enum nl80211_attrs {
 
 	NL80211_ATTR_RADAR_EVENT,
 
+	NL80211_ATTR_EXT_CAPA,
+	NL80211_ATTR_EXT_CAPA_MASK,
+
 	/* add attributes here, update the policy in nl80211.c */
 
 	__NL80211_ATTR_AFTER_LAST,

net/wireless/nl80211.c

@@ -1363,6 +1363,15 @@ static int nl80211_send_wiphy(struct sk_buff *msg, u32 portid, u32 seq, int flag
 			dev->wiphy.max_acl_mac_addrs))
 		goto nla_put_failure;
 
+	if (dev->wiphy.extended_capabilities &&
+	    (nla_put(msg, NL80211_ATTR_EXT_CAPA,
+		     dev->wiphy.extended_capabilities_len,
+		     dev->wiphy.extended_capabilities) ||
+	     nla_put(msg, NL80211_ATTR_EXT_CAPA_MASK,
+		     dev->wiphy.extended_capabilities_len,
+		     dev->wiphy.extended_capabilities_mask)))
+		goto nla_put_failure;
+
 	return genlmsg_end(msg, hdr);
 
  nla_put_failure: