wifi: cfg80211: add BSS usage reporting

Sometimes there may be reasons for which a BSS that's
actually found in scan cannot be used to connect to,
for example a nonprimary link of an NSTR mobile AP MLD
cannot be used for normal direct connections to it.

Not indicating these to userspace as we do now of course
avoids being able to connect to them, but it's better if
they're shown to userspace and it can make an appropriate
decision, without e.g. doing an additional ML probe.

Thus add an indication of what a BSS can be used for,
currently "normal" and "MLD link", including a reason
bitmap for it being not usable.

The latter can be extended later for certain BSSes if there
are other reasons they cannot be used.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Ilan Peer <ilan.peer@intel.com>
Reviewed-by: Gregory Greenman <gregory.greenman@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20231211085121.0464f25e0b1d.I9f70ca9f1440565ad9a5207d0f4d00a20cca67e7@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

2 files changed, 93 insertions, 7 deletions

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 324a5f710ad3..cabe57a00eaf 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -2828,6 +2828,13 @@ enum cfg80211_signal_type {
  *	the BSS that requested the scan in which the beacon/probe was received.
  * @chains: bitmask for filled values in @chain_signal.
  * @chain_signal: per-chain signal strength of last received BSS in dBm.
+ * @restrict_use: restrict usage, if not set, assume @use_for is
+ *	%NL80211_BSS_USE_FOR_NORMAL.
+ * @use_for: bitmap of possible usage for this BSS, see
+ *	&enum nl80211_bss_use_for
+ * @cannot_use_reasons: the reasons (bitmap) for not being able to connect,
+ *	if @restrict_use is set and @use_for is zero (empty); may be 0 for
+ *	unspecified reasons; see &enum nl80211_bss_cannot_use_reasons
  * @drv_data: Data to be passed through to @inform_bss
  */
 struct cfg80211_inform_bss {
@@ -2839,6 +2846,9 @@ struct cfg80211_inform_bss {
 	u8 chains;
 	s8 chain_signal[IEEE80211_MAX_CHAINS];
 
+	u8 restrict_use:1, use_for:7;
+	u8 cannot_use_reasons;
+
 	void *drv_data;
 };
 
@@ -2890,6 +2900,11 @@ struct cfg80211_bss_ies {
  * @chain_signal: per-chain signal strength of last received BSS in dBm.
  * @bssid_index: index in the multiple BSS set
  * @max_bssid_indicator: max number of members in the BSS set
+ * @use_for: bitmap of possible usage for this BSS, see
+ *	&enum nl80211_bss_use_for
+ * @cannot_use_reasons: the reasons (bitmap) for not being able to connect,
+ *	if @restrict_use is set and @use_for is zero (empty); may be 0 for
+ *	unspecified reasons; see &enum nl80211_bss_cannot_use_reasons
  * @priv: private area for driver use, has at least wiphy->bss_priv_size bytes
  */
 struct cfg80211_bss {
@@ -2915,6 +2930,9 @@ struct cfg80211_bss {
 	u8 bssid_index;
 	u8 max_bssid_indicator;
 
+	u8 use_for;
+	u8 cannot_use_reasons;
+
 	u8 priv[] __aligned(sizeof(void *));
 };
 
@@ -4922,6 +4940,8 @@ struct cfg80211_ops {
  *	NL80211_REGDOM_SET_BY_DRIVER.
  * @WIPHY_FLAG_CHANNEL_CHANGE_ON_BEACON: reg_call_notifier() is called if driver
  *	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.
  */
 enum wiphy_flags {
 	WIPHY_FLAG_SUPPORTS_EXT_KEK_KCK		= BIT(0),
@@ -4935,7 +4955,7 @@ enum wiphy_flags {
 	WIPHY_FLAG_IBSS_RSN			= BIT(8),
 	WIPHY_FLAG_MESH_AUTH			= BIT(10),
 	WIPHY_FLAG_SUPPORTS_EXT_KCK_32          = BIT(11),
-	/* use hole at 12 */
+	WIPHY_FLAG_SUPPORTS_NSTR_NONPRIMARY	= BIT(12),
 	WIPHY_FLAG_SUPPORTS_FW_ROAM		= BIT(13),
 	WIPHY_FLAG_AP_UAPSD			= BIT(14),
 	WIPHY_FLAG_SUPPORTS_TDLS		= BIT(15),
@@ -7174,6 +7194,25 @@ cfg80211_inform_bss(struct wiphy *wiphy,
 }
 
 /**
+ * __cfg80211_get_bss - get a BSS reference
+ * @wiphy: the wiphy this BSS struct belongs to
+ * @channel: the channel to search on (or %NULL)
+ * @bssid: the desired BSSID (or %NULL)
+ * @ssid: the desired SSID (or %NULL)
+ * @ssid_len: length of the SSID (or 0)
+ * @bss_type: type of BSS, see &enum ieee80211_bss_type
+ * @privacy: privacy filter, see &enum ieee80211_privacy
+ * @use_for: indicates which use is intended
+ */
+struct cfg80211_bss *__cfg80211_get_bss(struct wiphy *wiphy,
+					struct ieee80211_channel *channel,
+					const u8 *bssid,
+					const u8 *ssid, size_t ssid_len,
+					enum ieee80211_bss_type bss_type,
+					enum ieee80211_privacy privacy,
+					u32 use_for);
+
+/**
  * cfg80211_get_bss - get a BSS reference
  * @wiphy: the wiphy this BSS struct belongs to
  * @channel: the channel to search on (or %NULL)
@@ -7182,13 +7221,20 @@ cfg80211_inform_bss(struct wiphy *wiphy,
  * @ssid_len: length of the SSID (or 0)
  * @bss_type: type of BSS, see &enum ieee80211_bss_type
  * @privacy: privacy filter, see &enum ieee80211_privacy
+ *
+ * This version implies regular usage, %NL80211_BSS_USE_FOR_NORMAL.
  */
-struct cfg80211_bss *cfg80211_get_bss(struct wiphy *wiphy,
-				      struct ieee80211_channel *channel,
-				      const u8 *bssid,
-				      const u8 *ssid, size_t ssid_len,
-				      enum ieee80211_bss_type bss_type,
-				      enum ieee80211_privacy privacy);
+static inline struct cfg80211_bss *
+cfg80211_get_bss(struct wiphy *wiphy, struct ieee80211_channel *channel,
+		 const u8 *bssid, const u8 *ssid, size_t ssid_len,
+		 enum ieee80211_bss_type bss_type,
+		 enum ieee80211_privacy privacy)
+{
+	return __cfg80211_get_bss(wiphy, channel, bssid, ssid, ssid_len,
+				  bss_type, privacy,
+				  NL80211_BSS_USE_FOR_NORMAL);
+}
+
 static inline struct cfg80211_bss *
 cfg80211_get_ibss(struct wiphy *wiphy,
 		  struct ieee80211_channel *channel,
diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
index 8f42d598e285..07fc1fec4b12 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -2831,6 +2831,10 @@ enum nl80211_commands {
  * @NL80211_ATTR_MLO_LINK_DISABLED: Flag attribute indicating that the link is
  *	disabled.
  *
+ * @NL80211_ATTR_BSS_DUMP_INCLUDE_USE_DATA: Include BSS usage data, i.e.
+ *	include BSSes that can only be used in restricted scenarios and/or
+ *	cannot be used at all.
+ *
  * @NUM_NL80211_ATTR: total number of nl80211_attrs available
  * @NL80211_ATTR_MAX: highest attribute number currently defined
  * @__NL80211_ATTR_AFTER_LAST: internal use
@@ -3369,6 +3373,8 @@ enum nl80211_attrs {
 
 	NL80211_ATTR_MLO_LINK_DISABLED,
 
+	NL80211_ATTR_BSS_DUMP_INCLUDE_USE_DATA,
+
 	/* add attributes here, update the policy in nl80211.c */
 
 	__NL80211_ATTR_AFTER_LAST,
@@ -5033,6 +5039,30 @@ enum nl80211_bss_scan_width {
 };
 
 /**
+ * enum nl80211_bss_use_for - bitmap indicating possible BSS use
+ * @NL80211_BSS_USE_FOR_NORMAL: Use this BSS for normal "connection",
+ *	including IBSS/MBSS depending on the type.
+ * @NL80211_BSS_USE_FOR_MLD_LINK: This BSS can be used as a link in an
+ *	MLO connection. Note that for an MLO connection, all links including
+ *	the assoc link must have this flag set, and the assoc link must
+ *	additionally have %NL80211_BSS_USE_FOR_NORMAL set.
+ */
+enum nl80211_bss_use_for {
+	NL80211_BSS_USE_FOR_NORMAL = 1 << 0,
+	NL80211_BSS_USE_FOR_MLD_LINK = 1 << 1,
+};
+
+/**
+ * enum nl80211_bss_cannot_use_reasons - reason(s) connection to a
+ *	BSS isn't possible
+ * @NL80211_BSS_CANNOT_USE_NSTR_NONPRIMARY: NSTR nonprimary links aren't
+ *	supported by the device, and this BSS entry represents one.
+ */
+enum nl80211_bss_cannot_use_reasons {
+	NL80211_BSS_CANNOT_USE_NSTR_NONPRIMARY	= 1 << 0,
+};
+
+/**
  * enum nl80211_bss - netlink attributes for a BSS
  *
  * @__NL80211_BSS_INVALID: invalid
@@ -5084,6 +5114,14 @@ enum nl80211_bss_scan_width {
  * @NL80211_BSS_FREQUENCY_OFFSET: frequency offset in KHz
  * @NL80211_BSS_MLO_LINK_ID: MLO link ID of the BSS (u8).
  * @NL80211_BSS_MLD_ADDR: MLD address of this BSS if connected to it.
+ * @NL80211_BSS_USE_FOR: u32 bitmap attribute indicating what the BSS can be
+ *	used for, see &enum nl80211_bss_use_for.
+ * @NL80211_BSS_CANNOT_USE_REASONS: Indicates the reason that this BSS cannot
+ *	be used for all or some of the possible uses by the device reporting it,
+ *	even though its presence was detected.
+ *	This is a u64 attribute containing a bitmap of values from
+ *	&enum nl80211_cannot_use_reasons, note that the attribute may be missing
+ *	if no reasons are specified.
  * @__NL80211_BSS_AFTER_LAST: internal
  * @NL80211_BSS_MAX: highest BSS attribute
  */
@@ -5111,6 +5149,8 @@ enum nl80211_bss {
 	NL80211_BSS_FREQUENCY_OFFSET,
 	NL80211_BSS_MLO_LINK_ID,
 	NL80211_BSS_MLD_ADDR,
+	NL80211_BSS_USE_FOR,
+	NL80211_BSS_CANNOT_USE_REASONS,
 
 	/* keep last */
 	__NL80211_BSS_AFTER_LAST,