wifi: cfg80211/nl80211: Add support to indicate STA MLD setup links removal

STA MLD setup links may get removed if AP MLD remove the corresponding
affiliated APs with Multi-Link reconfiguration as described in
P802.11be_D3.0, section 35.3.6.2.2 Removing affiliated APs. Currently,
there is no support to notify such operation to cfg80211 and userspace.

Add support for the drivers to indicate STA MLD setup links removal to
cfg80211 and notify the same to userspace. Upon receiving such
indication from the driver, clear the MLO links information of the
removed links in the WDEV.

Signed-off-by: Veerendranath Jakkam <quic_vjakkam@quicinc.com>
Link: https://lore.kernel.org/r/20230317142153.237900-1-quic_vjakkam@quicinc.com
[rename function and attribute, fix kernel-doc]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -9205,4 +9205,17 @@ static inline int cfg80211_color_change_notify(struct net_device *dev)
 bool cfg80211_valid_disable_subchannel_bitmap(u16 *bitmap,
 					      const struct cfg80211_chan_def *chandef);
 
+/**
+ * cfg80211_links_removed - Notify about removed STA MLD setup links.
+ * @dev: network device.
+ * @link_mask: BIT mask of removed STA MLD setup link IDs.
+ *
+ * Inform cfg80211 and the userspace about removed STA MLD setup links due to
+ * AP MLD removing the corresponding affiliated APs with Multi-Link
+ * reconfiguration. Note that it's not valid to remove all links, in this
+ * case disconnect instead.
+ * Also note that the wdev mutex must be held.
+ */
+void cfg80211_links_removed(struct net_device *dev, u16 link_mask);
+
 #endif /* __NET_CFG80211_H */

include/uapi/linux/nl80211.h

@@ -1309,6 +1309,11 @@
  *	The number of peers that HW timestamping can be enabled for concurrently
  *	is indicated by %NL80211_ATTR_MAX_HW_TIMESTAMP_PEERS.
  *
+ * @NL80211_CMD_LINKS_REMOVED: Notify userspace about the removal of STA MLD
+ *	setup links due to AP MLD removing the corresponding affiliated APs with
+ *	Multi-Link reconfiguration. %NL80211_ATTR_MLO_LINKS is used to provide
+ *	information about the removed STA MLD setup links.
+ *
  * @NL80211_CMD_MAX: highest used command number
  * @__NL80211_CMD_AFTER_LAST: internal use
  */
@@ -1562,6 +1567,8 @@ enum nl80211_commands {
 
 	NL80211_CMD_SET_HW_TIMESTAMP,
 
+	NL80211_CMD_LINKS_REMOVED,
+
 	/* add new commands above here */
 
 	/* used to define NL80211_CMD_MAX below */

net/wireless/core.h

@@ -576,5 +576,6 @@ void cfg80211_remove_link(struct wireless_dev *wdev, unsigned int link_id);
 void cfg80211_remove_links(struct wireless_dev *wdev);
 int cfg80211_remove_virtual_intf(struct cfg80211_registered_device *rdev,
 				 struct wireless_dev *wdev);
+void cfg80211_wdev_release_link_bsses(struct wireless_dev *wdev, u16 link_mask);
 
 #endif /* __NET_WIRELESS_CORE_H */

net/wireless/nl80211.c

@@ -18288,6 +18288,76 @@ void nl80211_send_disconnected(struct cfg80211_registered_device *rdev,
 	nlmsg_free(msg);
 }
 
+void cfg80211_links_removed(struct net_device *dev, u16 link_mask)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct wiphy *wiphy = wdev->wiphy;
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
+	struct sk_buff *msg;
+	struct nlattr *links;
+	void *hdr;
+
+	ASSERT_WDEV_LOCK(wdev);
+	trace_cfg80211_links_removed(dev, link_mask);
+
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_STATION &&
+		    wdev->iftype != NL80211_IFTYPE_P2P_CLIENT))
+		return;
+
+	if (WARN_ON(!wdev->valid_links || !link_mask ||
+		    (wdev->valid_links & link_mask) != link_mask ||
+		    wdev->valid_links == link_mask))
+		return;
+
+	cfg80211_wdev_release_link_bsses(wdev, link_mask);
+	wdev->valid_links &= ~link_mask;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return;
+
+	hdr = nl80211hdr_put(msg, 0, 0, 0, NL80211_CMD_LINKS_REMOVED);
+	if (!hdr) {
+		nlmsg_free(msg);
+		return;
+	}
+
+	if (nla_put_u32(msg, NL80211_ATTR_WIPHY, rdev->wiphy_idx) ||
+	    nla_put_u32(msg, NL80211_ATTR_IFINDEX, dev->ifindex))
+		goto nla_put_failure;
+
+	links = nla_nest_start(msg, NL80211_ATTR_MLO_LINKS);
+	if (!links)
+		goto nla_put_failure;
+
+	while (link_mask) {
+		struct nlattr *link;
+		int link_id = __ffs(link_mask);
+
+		link = nla_nest_start(msg, link_id + 1);
+		if (!link)
+			goto nla_put_failure;
+
+		if (nla_put_u8(msg, NL80211_ATTR_MLO_LINK_ID, link_id))
+			goto nla_put_failure;
+
+		nla_nest_end(msg, link);
+		link_mask &= ~(1 << link_id);
+	}
+
+	nla_nest_end(msg, links);
+
+	genlmsg_end(msg, hdr);
+
+	genlmsg_multicast_netns(&nl80211_fam, wiphy_net(&rdev->wiphy), msg, 0,
+				NL80211_MCGRP_MLME, GFP_KERNEL);
+	return;
+
+ nla_put_failure:
+	nlmsg_free(msg);
+}
+EXPORT_SYMBOL(cfg80211_links_removed);
+
 void nl80211_send_ibss_bssid(struct cfg80211_registered_device *rdev,
 			     struct net_device *netdev, const u8 *bssid,
 			     gfp_t gfp)

net/wireless/sme.c

@@ -491,6 +491,21 @@ static void cfg80211_wdev_release_bsses(struct wireless_dev *wdev)
 	}
 }
 
+void cfg80211_wdev_release_link_bsses(struct wireless_dev *wdev, u16 link_mask)
+{
+	unsigned int link;
+
+	for_each_valid_link(wdev, link) {
+		if (!wdev->links[link].client.current_bss ||
+		    !(link_mask & BIT(link)))
+			continue;
+		cfg80211_unhold_bss(wdev->links[link].client.current_bss);
+		cfg80211_put_bss(wdev->wiphy,
+				 &wdev->links[link].client.current_bss->pub);
+		wdev->links[link].client.current_bss = NULL;
+	}
+}
+
 static int cfg80211_sme_get_conn_ies(struct wireless_dev *wdev,
 				     const u8 *ies, size_t ies_len,
 				     const u8 **out_ies, size_t *out_ies_len)

net/wireless/trace.h

@@ -3966,6 +3966,21 @@ TRACE_EVENT(rdev_set_hw_timestamp,
 		  __entry->enable)
 );
 
+TRACE_EVENT(cfg80211_links_removed,
+	TP_PROTO(struct net_device *netdev, u16 link_mask),
+	TP_ARGS(netdev, link_mask),
+	TP_STRUCT__entry(
+		NETDEV_ENTRY
+		__field(u16, link_mask)
+	),
+	TP_fast_assign(
+		NETDEV_ASSIGN;
+		__entry->link_mask = link_mask;
+	),
+	TP_printk(NETDEV_PR_FMT ", link_mask:%u", NETDEV_PR_ARG,
+		  __entry->link_mask)
+);
+
 #endif /* !__RDEV_OPS_TRACE || TRACE_HEADER_MULTI_READ */
 
 #undef TRACE_INCLUDE_PATH