wireless: deprecate WDS and disable by default

The old WDS 4-addr frame support is very limited, e.g.
 * no encryption is possible on such links
 * it cannot support rate/HT/VHT negotiation
 * management APIs are very restricted

These make the WDS legacy mode useless in practice.

All of these are resolved by the 4-addr AP/client support,
so there's also no reason to improve WDS in the future.

Therefore, add a Kconfig option to disable legacy WDS.
This gives people an "emergency valve" while they migrate
to the better-supported 4-addr AP/client option; we plan
to remove it (and the associated cfg80211/mac80211 code,
which is the ultimate goal) in the future.

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

net/wireless/core.c

@@ -571,6 +571,11 @@ static int wiphy_verify_combinations(struct wiphy *wiphy)
 				return -EINVAL;
 		}
 
+#ifndef CONFIG_WIRELESS_WDS
+		if (WARN_ON(all_iftypes & BIT(NL80211_IFTYPE_WDS)))
+			return -EINVAL;
+#endif
+
 		/* You can't even choose that many! */
 		if (WARN_ON(cnt < c->max_interfaces))
 			return -EINVAL;
@@ -609,6 +614,11 @@ int wiphy_register(struct wiphy *wiphy)
 		     !rdev->ops->add_nan_func || !rdev->ops->del_nan_func)))
 		return -EINVAL;
 
+#ifndef CONFIG_WIRELESS_WDS
+	if (WARN_ON(wiphy->interface_modes & BIT(NL80211_IFTYPE_WDS)))
+		return -EINVAL;
+#endif
+
 	/*
 	 * if a wiphy has unsupported modes for regulatory channel enforcement,
 	 * opt-out of enforcement checking