wifi: cfg80211: Add support for link reconfiguration negotiation offload to driver

JIRA: https://issues.redhat.com/browse/RHEL-114891

commit 7c598c6
Author: Kavita Kavita <quic_kkavita@quicinc.com>
Date:   Wed Jun 4 16:27:57 2025 +0530

    wifi: cfg80211: Add support for link reconfiguration negotiation offload to driver
    
    In the case of SME-in-driver, the driver can internally choose to
    update the links based on the AP MLD recommendation and do link
    reconfiguration negotiation with AP MLD.
    (e.g., After the driver processing the BSS Transition Management request
    frame received from the AP MLD with Neighbor Report containing
    Multi-Link element with recommended links information chooses to do link
    reconfiguration negotiation with AP MLD).
    
    To support this, extend cfg80211_mlo_reconf_add_done() and
    NL80211_CMD_ASSOC_MLO_RECONF to indicate added links information for
    driver-initiated link reconfiguration requests. For removed links,
    the driver indicates links information using the
    NL80211_CMD_LINKS_REMOVED event for driver-initiated cases, the same as
    supplicant initiated cases.
    
    For the driver-initiated case, cfg80211 will receive link
    reconfiguration result asynchronously from driver so holding BSSes of
    the accepted add links is needed in the event path. Also, no need of
    unhold call for the rejected add link BSSes since there was no hold call
    happened previously.
    
    Once the supplicant receives the NL80211_CMD_ASSOC_MLO_RECONF event,
    it needs to process the information about newly added links and install
    per-link group keys (e.g., GTK/IGTK/BIGTK etc.).
    
    In case of the SME-in-driver, using a vendor interface etc. to notify
    the supplicant to initiate a link reconfiguration request and then
    supplicant sending command to the cfg80211 can lead to race conditions.
    The correct design to avoid this is that the driver indicates the
    cfg80211 directly with the results of the link reconfiguration
    negotiation.
    
    Signed-off-by: Kavita Kavita <quic_kkavita@quicinc.com>
    Link: https://patch.msgid.link/20250604105757.2542-3-quic_kkavita@quicinc.com
    Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm@redhat.com>

Author: jtornosm

include/net/cfg80211.h

@@ -9747,6 +9747,11 @@ void cfg80211_links_removed(struct net_device *dev, u16 link_mask);
  * struct cfg80211_mlo_reconf_done_data - MLO reconfiguration data
  * @buf: MLO Reconfiguration Response frame (header + body)
  * @len: length of the frame data
+ * @driver_initiated: Indicates whether the add links request is initiated by
+ *	driver. This is set to true when the link reconfiguration request
+ *	initiated by driver due to AP link recommendation requests
+ *	(Ex: BTM (BSS Transition Management) request) handling offloaded to
+ *	driver.
  * @added_links: BIT mask of links successfully added to the association
  * @links: per-link information indexed by link ID
  * @links.bss: the BSS that MLO reconfiguration was requested for, ownership of
@@ -9759,6 +9764,7 @@ void cfg80211_links_removed(struct net_device *dev, u16 link_mask);
 struct cfg80211_mlo_reconf_done_data {
 	const u8 *buf;
 	size_t len;
+	bool driver_initiated;
 	u16 added_links;
 	struct {
 		struct cfg80211_bss *bss;

include/uapi/linux/nl80211.h

@@ -1334,7 +1334,11 @@
  *      reconfiguration request results from the driver, this command is also
  *      used as an event to notify userspace about the added links information.
  *      For notifying the removed links information, the existing
- *      %NL80211_CMD_LINKS_REMOVED command is used.
+ *      %NL80211_CMD_LINKS_REMOVED command is used. This command is also used to
+ *      notify userspace about newly added links for the current connection in
+ *      case of AP-initiated link recommendation requests, received via
+ *      a BTM (BSS Transition Management) request or a link reconfig notify
+ *      frame, where the driver handles the link recommendation offload.
  *
  * @NL80211_CMD_EPCS_CFG: EPCS configuration for a station. Used by userland to
  *	control EPCS configuration. Used to notify userland on the current state

net/wireless/mlme.c

@@ -1331,7 +1331,8 @@ void cfg80211_mlo_reconf_add_done(struct net_device *dev,
 	lockdep_assert_wiphy(wiphy);
 
 	trace_cfg80211_mlo_reconf_add_done(dev, data->added_links,
-					   data->buf, data->len);
+					   data->buf, data->len,
+					   data->driver_initiated);
 
 	if (WARN_ON(!wdev->valid_links))
 		return;
@@ -1361,11 +1362,16 @@ void cfg80211_mlo_reconf_add_done(struct net_device *dev,
 			wdev->links[link_id].client.current_bss =
 				bss_from_pub(bss);
 
+			if (data->driver_initiated)
+				cfg80211_hold_bss(bss_from_pub(bss));
+
 			memcpy(wdev->links[link_id].addr,
 			       data->links[link_id].addr,
 			       ETH_ALEN);
 		} else {
-			cfg80211_unhold_bss(bss_from_pub(bss));
+			if (!data->driver_initiated)
+				cfg80211_unhold_bss(bss_from_pub(bss));
+
 			cfg80211_put_bss(wiphy, bss);
 		}
 	}

net/wireless/trace.h

@@ -4126,20 +4126,22 @@ TRACE_EVENT(cfg80211_links_removed,
 
 TRACE_EVENT(cfg80211_mlo_reconf_add_done,
 	TP_PROTO(struct net_device *netdev, u16 link_mask,
-		 const u8 *buf, size_t len),
-	TP_ARGS(netdev, link_mask, buf, len),
+		 const u8 *buf, size_t len, bool driver_initiated),
+	TP_ARGS(netdev, link_mask, buf, len, driver_initiated),
 	TP_STRUCT__entry(
 		NETDEV_ENTRY
 		__field(u16, link_mask)
 		__dynamic_array(u8, buf, len)
+		__field(bool, driver_initiated)
 	),
 	TP_fast_assign(
 		NETDEV_ASSIGN;
 		__entry->link_mask = link_mask;
 		memcpy(__get_dynamic_array(buf), buf, len);
+		__entry->driver_initiated = driver_initiated;
 	),
-	TP_printk(NETDEV_PR_FMT ", link_mask:0x%x",
-		  NETDEV_PR_ARG, __entry->link_mask)
+	TP_printk(NETDEV_PR_FMT ", link_mask:0x%x, driver_initiated:%d",
+		  NETDEV_PR_ARG, __entry->link_mask, __entry->driver_initiated)
 );
 
 TRACE_EVENT(rdev_assoc_ml_reconf,