wifi: cfg80211: add a flag to disable wireless extensions

Wireless extensions are already disabled if MLO is enabled,
given that we cannot support MLO there with all the hard-
coded assumptions about BSSID etc.

However, the WiFi7 ecosystem is still stabilizing, and some
devices may need MLO disabled while that happens. In that
case, we might end up with a device that supports wext (but
not MLO) in one kernel, and then breaks wext in the future
(by enabling MLO), which is not desirable.

Add a flag to let such drivers/devices disable wext even if
MLO isn't yet enabled.

Cc: stable@vger.kernel.org
Link: https://msgid.link/20240314110951.b50f1dc4ec21.I656ddd8178eedb49dc5c6c0e70f8ce5807afb54f@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -4991,6 +4991,7 @@ struct cfg80211_ops {
  *	set this flag to update channels on beacon hints.
  * @WIPHY_FLAG_SUPPORTS_NSTR_NONPRIMARY: support connection to non-primary link
  *	of an NSTR mobile AP MLD.
+ * @WIPHY_FLAG_DISABLE_WEXT: disable wireless extensions for this device
  */
 enum wiphy_flags {
 	WIPHY_FLAG_SUPPORTS_EXT_KEK_KCK		= BIT(0),
@@ -5002,6 +5003,7 @@ enum wiphy_flags {
 	WIPHY_FLAG_4ADDR_STATION		= BIT(6),
 	WIPHY_FLAG_CONTROL_PORT_PROTOCOL	= BIT(7),
 	WIPHY_FLAG_IBSS_RSN			= BIT(8),
+	WIPHY_FLAG_DISABLE_WEXT			= BIT(9),
 	WIPHY_FLAG_MESH_AUTH			= BIT(10),
 	WIPHY_FLAG_SUPPORTS_EXT_KCK_32          = BIT(11),
 	WIPHY_FLAG_SUPPORTS_NSTR_NONPRIMARY	= BIT(12),

net/wireless/wext-core.c

@@ -4,6 +4,7 @@
  * Authors :	Jean Tourrilhes - HPL - <jt@hpl.hp.com>
  * Copyright (c) 1997-2007 Jean Tourrilhes, All Rights Reserved.
  * Copyright	2009 Johannes Berg <johannes@sipsolutions.net>
+ * Copyright (C) 2024 Intel Corporation
  *
  * (As all part of the Linux kernel, this file is GPL)
  */
@@ -662,7 +663,8 @@ struct iw_statistics *get_wireless_stats(struct net_device *dev)
 	    dev->ieee80211_ptr->wiphy->wext &&
 	    dev->ieee80211_ptr->wiphy->wext->get_wireless_stats) {
 		wireless_warn_cfg80211_wext();
-		if (dev->ieee80211_ptr->wiphy->flags & WIPHY_FLAG_SUPPORTS_MLO)
+		if (dev->ieee80211_ptr->wiphy->flags & (WIPHY_FLAG_SUPPORTS_MLO |
+							WIPHY_FLAG_DISABLE_WEXT))
 			return NULL;
 		return dev->ieee80211_ptr->wiphy->wext->get_wireless_stats(dev);
 	}
@@ -704,7 +706,8 @@ static iw_handler get_handler(struct net_device *dev, unsigned int cmd)
 #ifdef CONFIG_CFG80211_WEXT
 	if (dev->ieee80211_ptr && dev->ieee80211_ptr->wiphy) {
 		wireless_warn_cfg80211_wext();
-		if (dev->ieee80211_ptr->wiphy->flags & WIPHY_FLAG_SUPPORTS_MLO)
+		if (dev->ieee80211_ptr->wiphy->flags & (WIPHY_FLAG_SUPPORTS_MLO |
+							WIPHY_FLAG_DISABLE_WEXT))
 			return NULL;
 		handlers = dev->ieee80211_ptr->wiphy->wext;
 	}