cfg80211: Add support for notifying association comeback

Thought the underline driver MLME can handle association temporal
rejection with comeback, it is still useful to notify this to
user space, as user space might want to handle the temporal
rejection differently. For example, in case the comeback time
is too long, user space can deauthenticate immediately and try
to associate with a different AP.

Signed-off-by: Ilan Peer <[e-mail]>
Signed-off-by: Luca Coelho <[e-mail]>
Link: https://lore.kernel.org/r/iwlwifi.20211129152938.2467809e8cb3.I45574185b582666bc78eef0c29a4c36b478e5382@changeid
Signed-off-by: Johannes Berg <[e-mail]>

include/net/cfg80211.h

···
 			     bool is_4addr, u8 check_swif);
 
 
+/**
+ * cfg80211_assoc_comeback - notification of association that was
+ * temporarly rejected with a comeback
+ * @netdev: network device
+ * @bss: the bss entry with which association is in progress.
+ * @timeout: timeout interval value TUs.
+ *
+ * this function may sleep. the caller must hold the corresponding wdev's mutex.
+ */
+void cfg80211_assoc_comeback(struct net_device *netdev,
+			     struct cfg80211_bss *bss, u32 timeout);
+
 /* Logging, debugging and troubleshooting/diagnostic helpers. */
 
 /* wiphy_printk helpers, similar to dev_printk */

include/uapi/linux/nl80211.h

···
  *	&NL80211_ATTR_FILS_NONCES - for FILS Nonces
  *		(STA Nonce 16 bytes followed by AP Nonce 16 bytes)
  *
+ * @NL80211_CMD_ASSOC_COMEBACK: notification about an association
+ *      temporal rejection with comeback. The event includes %NL80211_ATTR_MAC
+ *      to describe the BSSID address of the AP and %NL80211_ATTR_TIMEOUT to
+ *      specify the timeout value.
+ *
  * @NL80211_CMD_MAX: highest used command number
  * @__NL80211_CMD_AFTER_LAST: internal use
  */
···
 	NL80211_CMD_COLOR_CHANGE_COMPLETED,
 
 	NL80211_CMD_SET_FILS_AAD,
+
+	NL80211_CMD_ASSOC_COMEBACK,
 
 	/* add new commands above here */
 

net/wireless/nl80211.c

···
 	nlmsg_free(msg);
 }
 
+void cfg80211_assoc_comeback(struct net_device *netdev,
+			     struct cfg80211_bss *bss, u32 timeout)
+{
+	struct wireless_dev *wdev = netdev->ieee80211_ptr;
+	struct wiphy *wiphy = wdev->wiphy;
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
+	struct sk_buff *msg;
+	void *hdr;
+
+	trace_cfg80211_assoc_comeback(wdev, bss->bssid, timeout);
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return;
+
+	hdr = nl80211hdr_put(msg, 0, 0, 0, NL80211_CMD_ASSOC_COMEBACK);
+	if (!hdr) {
+		nlmsg_free(msg);
+		return;
+	}
+
+	if (nla_put_u32(msg, NL80211_ATTR_WIPHY, rdev->wiphy_idx) ||
+	    nla_put_u32(msg, NL80211_ATTR_IFINDEX, netdev->ifindex) ||
+	    nla_put(msg, NL80211_ATTR_MAC, ETH_ALEN, bss->bssid) ||
+	    nla_put_u32(msg, NL80211_ATTR_TIMEOUT, timeout))
+		goto nla_put_failure;
+
+	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_assoc_comeback);
+
 void cfg80211_ready_on_channel(struct wireless_dev *wdev, u64 cookie,
 			       struct ieee80211_channel *chan,
 			       unsigned int duration, gfp_t gfp)

net/wireless/trace.h

···
 		  WIPHY_PR_ARG, CHAN_DEF_PR_ARG)
 );
 
+TRACE_EVENT(cfg80211_assoc_comeback,
+	TP_PROTO(struct wireless_dev *wdev, const u8 *bssid, u32 timeout),
+	TP_ARGS(wdev, bssid, timeout),
+	TP_STRUCT__entry(
+		WDEV_ENTRY
+		MAC_ENTRY(bssid)
+		__field(u32, timeout)
+	),
+	TP_fast_assign(
+		WDEV_ASSIGN;
+		MAC_ASSIGN(bssid, bssid);
+		__entry->timeout = timeout;
+	),
+	TP_printk(WDEV_PR_FMT ", " MAC_PR_FMT ", timeout: %u TUs",
+		  WDEV_PR_ARG, MAC_PR_ARG(bssid), __entry->timeout)
+);
+
 #endif /* !__RDEV_OPS_TRACE || TRACE_HEADER_MULTI_READ */
 
 #undef TRACE_INCLUDE_PATH