cfg80211: allow registering more than one beacon listener

The commit:

commit 5e760230e4
Author: Johannes Berg <johannes.berg@intel.com>
Date:   Fri Nov 4 11:18:17 2011 +0100

    cfg80211: allow registering to beacons

allowed only a single process to register for beacon events
per wiphy.  This breaks cases where a user may want two or
more VIFs on a wiphy and run a seperate hostapd process on
each vif.

This patch allows multiple beacon listeners, fixing the
regression.

Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/nl80211.c

@@ -6934,16 +6934,35 @@ static int nl80211_probe_client(struct sk_buff *skb,
 static int nl80211_register_beacons(struct sk_buff *skb, struct genl_info *info)
 {
 	struct cfg80211_registered_device *rdev = info->user_ptr[0];
+	struct cfg80211_beacon_registration *reg, *nreg;
+	int rv;
 
 	if (!(rdev->wiphy.flags & WIPHY_FLAG_REPORTS_OBSS))
 		return -EOPNOTSUPP;
 
-	if (rdev->ap_beacons_nlportid)
-		return -EBUSY;
+	nreg = kzalloc(sizeof(*nreg), GFP_KERNEL);
+	if (!nreg)
+		return -ENOMEM;
 
-	rdev->ap_beacons_nlportid = info->snd_portid;
+	/* First, check if already registered. */
+	spin_lock_bh(&rdev->beacon_registrations_lock);
+	list_for_each_entry(reg, &rdev->beacon_registrations, list) {
+		if (reg->nlportid == info->snd_portid) {
+			rv = -EALREADY;
+			goto out_err;
+		}
+	}
+	/* Add it to the list */
+	nreg->nlportid = info->snd_portid;
+	list_add(&nreg->list, &rdev->beacon_registrations);
+
+	spin_unlock_bh(&rdev->beacon_registrations_lock);
 
 	return 0;
+out_err:
+	spin_unlock_bh(&rdev->beacon_registrations_lock);
+	kfree(nreg);
+	return rv;
 }
 
 static int nl80211_start_p2p_device(struct sk_buff *skb, struct genl_info *info)
@@ -8957,43 +8976,46 @@ EXPORT_SYMBOL(cfg80211_probe_status);
 
 void cfg80211_report_obss_beacon(struct wiphy *wiphy,
 				 const u8 *frame, size_t len,
-				 int freq, int sig_dbm, gfp_t gfp)
+				 int freq, int sig_dbm)
 {
 	struct cfg80211_registered_device *rdev = wiphy_to_dev(wiphy);
 	struct sk_buff *msg;
 	void *hdr;
-	u32 nlportid = ACCESS_ONCE(rdev->ap_beacons_nlportid);
+	struct cfg80211_beacon_registration *reg;
 
 	trace_cfg80211_report_obss_beacon(wiphy, frame, len, freq, sig_dbm);
 
-	if (!nlportid)
-		return;
+	spin_lock_bh(&rdev->beacon_registrations_lock);
+	list_for_each_entry(reg, &rdev->beacon_registrations, list) {
+		msg = nlmsg_new(len + 100, GFP_ATOMIC);
+		if (!msg) {
+			spin_unlock_bh(&rdev->beacon_registrations_lock);
+			return;
+		}
 
-	msg = nlmsg_new(len + 100, gfp);
-	if (!msg)
-		return;
+		hdr = nl80211hdr_put(msg, 0, 0, 0, NL80211_CMD_FRAME);
+		if (!hdr)
+			goto nla_put_failure;
 
-	hdr = nl80211hdr_put(msg, 0, 0, 0, NL80211_CMD_FRAME);
-	if (!hdr) {
-		nlmsg_free(msg);
-		return;
+		if (nla_put_u32(msg, NL80211_ATTR_WIPHY, rdev->wiphy_idx) ||
+		    (freq &&
+		     nla_put_u32(msg, NL80211_ATTR_WIPHY_FREQ, freq)) ||
+		    (sig_dbm &&
+		     nla_put_u32(msg, NL80211_ATTR_RX_SIGNAL_DBM, sig_dbm)) ||
+		    nla_put(msg, NL80211_ATTR_FRAME, len, frame))
+			goto nla_put_failure;
+
+		genlmsg_end(msg, hdr);
+
+		genlmsg_unicast(wiphy_net(&rdev->wiphy), msg, reg->nlportid);
 	}
-
-	if (nla_put_u32(msg, NL80211_ATTR_WIPHY, rdev->wiphy_idx) ||
-	    (freq &&
-	     nla_put_u32(msg, NL80211_ATTR_WIPHY_FREQ, freq)) ||
-	    (sig_dbm &&
-	     nla_put_u32(msg, NL80211_ATTR_RX_SIGNAL_DBM, sig_dbm)) ||
-	    nla_put(msg, NL80211_ATTR_FRAME, len, frame))
-		goto nla_put_failure;
-
-	genlmsg_end(msg, hdr);
-
-	genlmsg_unicast(wiphy_net(&rdev->wiphy), msg, nlportid);
+	spin_unlock_bh(&rdev->beacon_registrations_lock);
 	return;
 
  nla_put_failure:
-	genlmsg_cancel(msg, hdr);
+	spin_unlock_bh(&rdev->beacon_registrations_lock);
+	if (hdr)
+		genlmsg_cancel(msg, hdr);
 	nlmsg_free(msg);
 }
 EXPORT_SYMBOL(cfg80211_report_obss_beacon);
@@ -9005,6 +9027,7 @@ static int nl80211_netlink_notify(struct notifier_block * nb,
 	struct netlink_notify *notify = _notify;
 	struct cfg80211_registered_device *rdev;
 	struct wireless_dev *wdev;
+	struct cfg80211_beacon_registration *reg, *tmp;
 
 	if (state != NETLINK_URELEASE)
 		return NOTIFY_DONE;
@@ -9014,8 +9037,17 @@ static int nl80211_netlink_notify(struct notifier_block * nb,
 	list_for_each_entry_rcu(rdev, &cfg80211_rdev_list, list) {
 		list_for_each_entry_rcu(wdev, &rdev->wdev_list, list)
 			cfg80211_mlme_unregister_socket(wdev, notify->portid);
-		if (rdev->ap_beacons_nlportid == notify->portid)
-			rdev->ap_beacons_nlportid = 0;
+
+		spin_lock_bh(&rdev->beacon_registrations_lock);
+		list_for_each_entry_safe(reg, tmp, &rdev->beacon_registrations,
+					 list) {
+			if (reg->nlportid == notify->portid) {
+				list_del(&reg->list);
+				kfree(reg);
+				break;
+			}
+		}
+		spin_unlock_bh(&rdev->beacon_registrations_lock);
 	}
 
 	rcu_read_unlock();