wifi: nl80211: add MLO_LINK_ID to CMD_STOP_AP event

nl80211_send_ap_stopped() can be called multiple times on the same
netdev for each link when using Multi-Link Operation. Add the
MLO_LINK_ID attribute to the event to allow userspace to distinguish
which link the event is for.
Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Link: https://lore.kernel.org/r/20230128125844.2407135-2-alvin@pqrs.dkSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/ap.c

@@ -39,7 +39,7 @@ static int ___cfg80211_stop_ap(struct cfg80211_registered_device *rdev,
 		wdev->u.ap.ssid_len = 0;
 		rdev_set_qos_map(rdev, dev, NULL);
 		if (notify)
-			nl80211_send_ap_stopped(wdev);
+			nl80211_send_ap_stopped(wdev, link_id);
 
 		/* Should we apply the grace period during beaconing interface
 		 * shutdown also?

net/wireless/nl80211.c

@@ -19717,7 +19717,7 @@ void cfg80211_crit_proto_stopped(struct wireless_dev *wdev, gfp_t gfp)
 }
 EXPORT_SYMBOL(cfg80211_crit_proto_stopped);
 
-void nl80211_send_ap_stopped(struct wireless_dev *wdev)
+void nl80211_send_ap_stopped(struct wireless_dev *wdev, unsigned int link_id)
 {
 	struct wiphy *wiphy = wdev->wiphy;
 	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
@@ -19735,7 +19735,9 @@ void nl80211_send_ap_stopped(struct wireless_dev *wdev)
 	if (nla_put_u32(msg, NL80211_ATTR_WIPHY, rdev->wiphy_idx) ||
 	    nla_put_u32(msg, NL80211_ATTR_IFINDEX, wdev->netdev->ifindex) ||
 	    nla_put_u64_64bit(msg, NL80211_ATTR_WDEV, wdev_id(wdev),
-			      NL80211_ATTR_PAD))
+			      NL80211_ATTR_PAD) ||
+	    (wdev->valid_links &&
+	     nla_put_u8(msg, NL80211_ATTR_MLO_LINK_ID, link_id)))
 		goto out;
 
 	genlmsg_end(msg, hdr);

net/wireless/nl80211.h

@@ -114,7 +114,7 @@ nl80211_radar_notify(struct cfg80211_registered_device *rdev,
 		     enum nl80211_radar_event event,
 		     struct net_device *netdev, gfp_t gfp);
 
-void nl80211_send_ap_stopped(struct wireless_dev *wdev);
+void nl80211_send_ap_stopped(struct wireless_dev *wdev, unsigned int link_id);
 
 void cfg80211_rdev_free_coalesce(struct cfg80211_registered_device *rdev);