[PATCH] mac80211: validate link status before deciding on mgmt tx

[Sriram R <quic_srirrama@quicinc.com>]

Currently we check the status of bss active flag to see if the
AP is active. But in case of a MLD AP, when some of the links
are getting teardown and some are active, mgmt Tx(like deauth)
can be sent on some links before they are brought down as well.

In such cases, the bss active flag might not provide the exact
status of the MLD links, which becomes false on first link deleted.
Hence check if any of the links can be used for mgmt tx
before returning error status.

Also, use the link id passed from userspace when the link bss
address matches the mgmt SA and the chan params match the request.
This will avoid scenario where the link id from userspace
gets reset.

Signed-off-by: Sriram R <quic_srirrama@quicinc.com>
---
 net/mac80211/offchannel.c | 50 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 48 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/offchannel.c b/net/mac80211/offchannel.c
index d78c82d6b696..5e312860a976 100644
--- a/net/mac80211/offchannel.c
+++ b/net/mac80211/offchannel.c
@@ -763,6 +763,43 @@ int ieee80211_cancel_remain_on_channel(struct wiphy *wiphy,
 	return ieee80211_cancel_roc(local, cookie, false);
 }
 
+static bool ieee80211_is_link_bss_active(struct ieee80211_sub_if_data *sdata,
+					 int link_id)
+{
+	struct ieee80211_link_data *link;
+
+	if (!sdata->bss)
+		return false;
+
+	/* This is consolidated status of the MLD or non ML bss */
+	if (sdata->bss->active)
+		return true;
+
+	if (link_id < 0)
+		return false;
+
+	if (!sdata->vif.valid_links)
+		return false;
+
+	if (!(sdata->vif.valid_links & BIT(link_id)))
+		return false;
+
+	sdata_lock(sdata);
+	link = sdata_dereference(sdata->link[link_id], sdata);
+	if (!link) {
+		sdata_unlock(sdata);
+		return false;
+	}
+
+	if (sdata_dereference(link->u.ap.beacon, sdata)) {
+		sdata_unlock(sdata);
+		return true;
+	}
+
+	sdata_unlock(sdata);
+	return false;
+}
+
 int ieee80211_mgmt_tx(struct wiphy *wiphy, struct wireless_dev *wdev,
 		      struct cfg80211_mgmt_tx_params *params, u64 *cookie)
 {
@@ -804,7 +841,7 @@ int ieee80211_mgmt_tx(struct wiphy *wiphy, struct wireless_dev *wdev,
 	case NL80211_IFTYPE_P2P_GO:
 		if (sdata->vif.type != NL80211_IFTYPE_ADHOC &&
 		    !ieee80211_vif_is_mesh(&sdata->vif) &&
-		    !sdata->bss->active)
+		    !ieee80211_is_link_bss_active(sdata, params->link_id))
 			need_offchan = true;
 
 		rcu_read_lock();
@@ -883,8 +920,17 @@ int ieee80211_mgmt_tx(struct wiphy *wiphy, struct wireless_dev *wdev,
 				break;
 			}
 
-			if (ether_addr_equal(conf->addr, mgmt->sa))
+			if (ether_addr_equal(conf->addr, mgmt->sa)) {
+				/* If userspace requested Tx on a specific link
+				 * use the same link id if the link bss is matching
+				 * the requested chan.
+				 */
+				if (sdata->vif.valid_links &&
+				    params->link_id >= 0 && params->link_id == i &&
+				    params->chan == chanctx_conf->def.chan)
+					link_id = i;
 				break;
+			}
 
 			chanctx_conf = NULL;
 		}
-- 
2.17.1