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>

1 files changed, 44 insertions, 10 deletions

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;