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>

3 files changed, 102 insertions, 28 deletions

diff --git a/net/wireless/core.h b/net/wireless/core.h
index 4c692c7faf30..87c5889b15e3 100644
--- a/net/wireless/core.h
+++ b/net/wireless/core.h
@@ -457,6 +457,9 @@ int cfg80211_scan(struct cfg80211_registered_device *rdev);
 
 extern struct work_struct cfg80211_disconnect_work;
 
+#define NL80211_BSS_USE_FOR_ALL	(NL80211_BSS_USE_FOR_NORMAL | \
+				 NL80211_BSS_USE_FOR_MLD_LINK)
+
 void cfg80211_set_dfs_state(struct wiphy *wiphy,
 			    const struct cfg80211_chan_def *chandef,
 			    enum nl80211_dfs_state dfs_state);
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index d6a20c21f094..2820336511a2 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -818,6 +818,7 @@ static const struct nla_policy nl80211_policy[NUM_NL80211_ATTR] = {
 	[NL80211_ATTR_HW_TIMESTAMP_ENABLED] = { .type = NLA_FLAG },
 	[NL80211_ATTR_EMA_RNR_ELEMS] = { .type = NLA_NESTED },
 	[NL80211_ATTR_MLO_LINK_DISABLED] = { .type = NLA_FLAG },
+	[NL80211_ATTR_BSS_DUMP_INCLUDE_USE_DATA] = { .type = NLA_FLAG },
 };
 
 /* policy for the key attributes */
@@ -10405,6 +10406,15 @@ static int nl80211_send_bss(struct sk_buff *msg, struct netlink_callback *cb,
 		break;
 	}
 
+	if (nla_put_u32(msg, NL80211_BSS_USE_FOR, res->use_for))
+		goto nla_put_failure;
+
+	if (res->cannot_use_reasons &&
+	    nla_put_u64_64bit(msg, NL80211_BSS_CANNOT_USE_REASONS,
+			      res->cannot_use_reasons,
+			      NL80211_BSS_PAD))
+		goto nla_put_failure;
+
 	nla_nest_end(msg, bss);
 
 	genlmsg_end(msg, hdr);
@@ -10422,15 +10432,27 @@ static int nl80211_dump_scan(struct sk_buff *skb, struct netlink_callback *cb)
 	struct cfg80211_registered_device *rdev;
 	struct cfg80211_internal_bss *scan;
 	struct wireless_dev *wdev;
+	struct nlattr **attrbuf;
 	int start = cb->args[2], idx = 0;
+	bool dump_include_use_data;
 	int err;
 
-	err = nl80211_prepare_wdev_dump(cb, &rdev, &wdev, NULL);
-	if (err)
+	attrbuf = kcalloc(NUM_NL80211_ATTR, sizeof(*attrbuf), GFP_KERNEL);
+	if (!attrbuf)
+		return -ENOMEM;
+
+	err = nl80211_prepare_wdev_dump(cb, &rdev, &wdev, attrbuf);
+	if (err) {
+		kfree(attrbuf);
 		return err;
+	}
 	/* nl80211_prepare_wdev_dump acquired it in the successful case */
 	__acquire(&rdev->wiphy.mtx);
 
+	dump_include_use_data =
+		attrbuf[NL80211_ATTR_BSS_DUMP_INCLUDE_USE_DATA];
+	kfree(attrbuf);
+
 	spin_lock_bh(&rdev->bss_lock);
 
 	/*
@@ -10447,6 +10469,9 @@ static int nl80211_dump_scan(struct sk_buff *skb, struct netlink_callback *cb)
 	list_for_each_entry(scan, &rdev->bss_list, list) {
 		if (++idx <= start)
 			continue;
+		if (!dump_include_use_data &&
+		    !(scan->pub.use_for & NL80211_BSS_USE_FOR_NORMAL))
+			continue;
 		if (nl80211_send_bss(skb, cb,
 				cb->nlh->nlmsg_seq, NLM_F_MULTI,
 				rdev, wdev, scan) < 0) {
@@ -10898,12 +10923,13 @@ static int nl80211_crypto_settings(struct cfg80211_registered_device *rdev,
 
 static struct cfg80211_bss *nl80211_assoc_bss(struct cfg80211_registered_device *rdev,
 					      const u8 *ssid, int ssid_len,
-					      struct nlattr **attrs)
+					      struct nlattr **attrs,
+					      int assoc_link_id, int link_id)
 {
 	struct ieee80211_channel *chan;
 	struct cfg80211_bss *bss;
 	const u8 *bssid;
-	u32 freq;
+	u32 freq, use_for = 0;
 
 	if (!attrs[NL80211_ATTR_MAC] || !attrs[NL80211_ATTR_WIPHY_FREQ])
 		return ERR_PTR(-EINVAL);
@@ -10918,10 +10944,16 @@ static struct cfg80211_bss *nl80211_assoc_bss(struct cfg80211_registered_device
 	if (!chan)
 		return ERR_PTR(-EINVAL);
 
-	bss = cfg80211_get_bss(&rdev->wiphy, chan, bssid,
-			       ssid, ssid_len,
-			       IEEE80211_BSS_TYPE_ESS,
-			       IEEE80211_PRIVACY_ANY);
+	if (assoc_link_id >= 0)
+		use_for = NL80211_BSS_USE_FOR_MLD_LINK;
+	if (assoc_link_id == link_id)
+		use_for |= NL80211_BSS_USE_FOR_NORMAL;
+
+	bss = __cfg80211_get_bss(&rdev->wiphy, chan, bssid,
+				 ssid, ssid_len,
+				 IEEE80211_BSS_TYPE_ESS,
+				 IEEE80211_PRIVACY_ANY,
+				 use_for);
 	if (!bss)
 		return ERR_PTR(-ENOENT);
 
@@ -11100,7 +11132,8 @@ static int nl80211_associate(struct sk_buff *skb, struct genl_info *info)
 				goto free;
 			}
 			req.links[link_id].bss =
-				nl80211_assoc_bss(rdev, ssid, ssid_len, attrs);
+				nl80211_assoc_bss(rdev, ssid, ssid_len, attrs,
+						  req.link_id, link_id);
 			if (IS_ERR(req.links[link_id].bss)) {
 				err = PTR_ERR(req.links[link_id].bss);
 				req.links[link_id].bss = NULL;
@@ -11165,7 +11198,8 @@ static int nl80211_associate(struct sk_buff *skb, struct genl_info *info)
 		if (req.link_id >= 0)
 			return -EINVAL;
 
-		req.bss = nl80211_assoc_bss(rdev, ssid, ssid_len, info->attrs);
+		req.bss = nl80211_assoc_bss(rdev, ssid, ssid_len, info->attrs,
+					    -1, -1);
 		if (IS_ERR(req.bss))
 			return PTR_ERR(req.bss);
 		ap_addr = req.bss->bssid;
diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 9e5ccffd6868..2f8c9b6f7ebc 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -1535,12 +1535,13 @@ static bool cfg80211_bss_type_match(u16 capability,
 }
 
 /* Returned bss is reference counted and must be cleaned up appropriately. */
-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)
+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)
 {
 	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
 	struct cfg80211_internal_bss *bss, *res = NULL;
@@ -1565,6 +1566,8 @@ struct cfg80211_bss *cfg80211_get_bss(struct wiphy *wiphy,
 			continue;
 		if (!is_valid_ether_addr(bss->pub.bssid))
 			continue;
+		if ((bss->pub.use_for & use_for) != use_for)
+			continue;
 		/* Don't get expired BSS structs */
 		if (time_after(now, bss->ts + IEEE80211_SCAN_RESULT_EXPIRE) &&
 		    !atomic_read(&bss->hold))
@@ -1582,7 +1585,7 @@ struct cfg80211_bss *cfg80211_get_bss(struct wiphy *wiphy,
 	trace_cfg80211_return_bss(&res->pub);
 	return &res->pub;
 }
-EXPORT_SYMBOL(cfg80211_get_bss);
+EXPORT_SYMBOL(__cfg80211_get_bss);
 
 static void rb_insert_bss(struct cfg80211_registered_device *rdev,
 			  struct cfg80211_internal_bss *bss)
@@ -1800,6 +1803,8 @@ cfg80211_update_known_bss(struct cfg80211_registered_device *rdev,
 	ether_addr_copy(known->parent_bssid, new->parent_bssid);
 	known->pub.max_bssid_indicator = new->pub.max_bssid_indicator;
 	known->pub.bssid_index = new->pub.bssid_index;
+	known->pub.use_for &= new->pub.use_for;
+	known->pub.cannot_use_reasons = new->pub.cannot_use_reasons;
 
 	return true;
 }
@@ -2044,6 +2049,9 @@ struct cfg80211_inform_single_bss_data {
 	struct cfg80211_bss *source_bss;
 	u8 max_bssid_indicator;
 	u8 bssid_index;
+
+	u8 use_for;
+	u64 cannot_use_reasons;
 };
 
 /* Returned bss is reference counted and must be cleaned up appropriately. */
@@ -2089,6 +2097,8 @@ cfg80211_inform_single_bss_data(struct wiphy *wiphy,
 	tmp.ts_boottime = drv_data->boottime_ns;
 	tmp.parent_tsf = drv_data->parent_tsf;
 	ether_addr_copy(tmp.parent_bssid, drv_data->parent_bssid);
+	tmp.pub.use_for = data->use_for;
+	tmp.pub.cannot_use_reasons = data->cannot_use_reasons;
 
 	if (data->bss_source != BSS_SOURCE_DIRECT) {
 		tmp.pub.transmitted_bss = data->source_bss;
@@ -2259,6 +2269,8 @@ cfg80211_parse_mbssid_data(struct wiphy *wiphy,
 		.beacon_interval = tx_data->beacon_interval,
 		.source_bss = source_bss,
 		.bss_source = BSS_SOURCE_MBSSID,
+		.use_for = tx_data->use_for,
+		.cannot_use_reasons = tx_data->cannot_use_reasons,
 	};
 	const u8 *mbssid_index_ie;
 	const struct element *elem, *sub;
@@ -2521,7 +2533,7 @@ error:
 	return NULL;
 }
 
-static bool
+static u8
 cfg80211_tbtt_info_for_mld_ap(const u8 *ie, size_t ielen, u8 mld_id, u8 link_id,
 			      const struct ieee80211_neighbor_ap_info **ap_info,
 			      const u8 **tbtt_info)
@@ -2540,6 +2552,7 @@ cfg80211_tbtt_info_for_mld_ap(const u8 *ie, size_t ielen, u8 mld_id, u8 link_id,
 			u16 params;
 			u8 length, i, count, mld_params_offset;
 			u8 type, lid;
+			u32 use_for;
 
 			info = (void *)pos;
 			count = u8_get_bits(info->tbtt_info_hdr,
@@ -2549,20 +2562,22 @@ cfg80211_tbtt_info_for_mld_ap(const u8 *ie, size_t ielen, u8 mld_id, u8 link_id,
 			pos += sizeof(*info);
 
 			if (count * length > end - pos)
-				return false;
+				return 0;
 
 			type = u8_get_bits(info->tbtt_info_hdr,
 					   IEEE80211_AP_INFO_TBTT_HDR_TYPE);
 
-			/* Only accept full TBTT information. NSTR mobile APs
-			 * use the shortened version, but we ignore them here.
-			 */
 			if (type == IEEE80211_TBTT_INFO_TYPE_TBTT &&
 			    length >=
 			    offsetofend(struct ieee80211_tbtt_info_ge_11,
 					mld_params)) {
 				mld_params_offset =
 					offsetof(struct ieee80211_tbtt_info_ge_11, mld_params);
+				use_for = NL80211_BSS_USE_FOR_ALL;
+			} else if (type == IEEE80211_TBTT_INFO_TYPE_MLD &&
+				   length >= sizeof(struct ieee80211_rnr_mld_params)) {
+				mld_params_offset = 0;
+				use_for = NL80211_BSS_USE_FOR_MLD_LINK;
 			} else {
 				pos += count * length;
 				continue;
@@ -2580,7 +2595,7 @@ cfg80211_tbtt_info_for_mld_ap(const u8 *ie, size_t ielen, u8 mld_id, u8 link_id,
 					*ap_info = info;
 					*tbtt_info = pos;
 
-					return true;
+					return use_for;
 				}
 
 				pos += length;
@@ -2588,7 +2603,7 @@ cfg80211_tbtt_info_for_mld_ap(const u8 *ie, size_t ielen, u8 mld_id, u8 link_id,
 		}
 	}
 
-	return false;
+	return 0;
 }
 
 static void cfg80211_parse_ml_sta_data(struct wiphy *wiphy,
@@ -2676,7 +2691,7 @@ static void cfg80211_parse_ml_sta_data(struct wiphy *wiphy,
 		const u8 *profile;
 		const u8 *tbtt_info;
 		ssize_t profile_len;
-		u8 link_id;
+		u8 link_id, use_for;
 
 		if (!ieee80211_mle_basic_sta_prof_size_ok((u8 *)mle->sta_prof[i],
 							  mle->sta_prof_len[i]))
@@ -2718,9 +2733,11 @@ static void cfg80211_parse_ml_sta_data(struct wiphy *wiphy,
 		profile_len -= 2;
 
 		/* Find in RNR to look up channel information */
-		if (!cfg80211_tbtt_info_for_mld_ap(tx_data->ie, tx_data->ielen,
-						   mld_id, link_id,
-						   &ap_info, &tbtt_info))
+		use_for = cfg80211_tbtt_info_for_mld_ap(tx_data->ie,
+							tx_data->ielen,
+							mld_id, link_id,
+							&ap_info, &tbtt_info);
+		if (!use_for)
 			continue;
 
 		/* We could sanity check the BSSID is included */
@@ -2732,6 +2749,14 @@ static void cfg80211_parse_ml_sta_data(struct wiphy *wiphy,
 		freq = ieee80211_channel_to_freq_khz(ap_info->channel, band);
 		data.channel = ieee80211_get_channel_khz(wiphy, freq);
 
+		if (use_for == NL80211_BSS_USE_FOR_MLD_LINK &&
+		    !(wiphy->flags & WIPHY_FLAG_SUPPORTS_NSTR_NONPRIMARY)) {
+			use_for = 0;
+			data.cannot_use_reasons =
+				NL80211_BSS_CANNOT_USE_NSTR_NONPRIMARY;
+		}
+		data.use_for = use_for;
+
 		/* Generate new elements */
 		memset(new_ie, 0, IEEE80211_MAX_DATA_LEN);
 		data.ie = new_ie;
@@ -2769,6 +2794,10 @@ cfg80211_inform_bss_data(struct wiphy *wiphy,
 		.beacon_interval = beacon_interval,
 		.ie = ie,
 		.ielen = ielen,
+		.use_for = data->restrict_use ?
+				data->use_for :
+				NL80211_BSS_USE_FOR_ALL,
+		.cannot_use_reasons = data->cannot_use_reasons,
 	};
 	struct cfg80211_bss *res;
 
@@ -2899,6 +2928,10 @@ cfg80211_inform_single_bss_frame_data(struct wiphy *wiphy,
 	tmp.pub.chains = data->chains;
 	memcpy(tmp.pub.chain_signal, data->chain_signal, IEEE80211_MAX_CHAINS);
 	ether_addr_copy(tmp.parent_bssid, data->parent_bssid);
+	tmp.pub.use_for = data->restrict_use ?
+				data->use_for :
+				NL80211_BSS_USE_FOR_ALL;
+	tmp.pub.cannot_use_reasons = data->cannot_use_reasons;
 
 	signal_valid = data->chan == channel;
 	spin_lock_bh(&rdev->bss_lock);
@@ -2930,6 +2963,10 @@ cfg80211_inform_bss_frame_data(struct wiphy *wiphy,
 		.ie = mgmt->u.probe_resp.variable,
 		.ielen = len - offsetof(struct ieee80211_mgmt,
 					u.probe_resp.variable),
+		.use_for = data->restrict_use ?
+				data->use_for :
+				NL80211_BSS_USE_FOR_ALL,
+		.cannot_use_reasons = data->cannot_use_reasons,
 	};
 	struct cfg80211_bss *res;