cfg80211: allow sending vendor events unicast

Sometimes, we may want to transport higher bandwidth data
through vendor events, and in that case sending it multicast
is a bad idea. Allow vendor events to be unicast.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -5854,6 +5854,7 @@ struct sk_buff *__cfg80211_alloc_event_skb(struct wiphy *wiphy,
 					   struct wireless_dev *wdev,
 					   enum nl80211_commands cmd,
 					   enum nl80211_attrs attr,
+					   unsigned int portid,
 					   int vendor_event_idx,
 					   int approxlen, gfp_t gfp);
 
@@ -5903,6 +5904,15 @@ cfg80211_vendor_cmd_alloc_reply_skb(struct wiphy *wiphy, int approxlen)
  */
 int cfg80211_vendor_cmd_reply(struct sk_buff *skb);
 
+/**
+ * cfg80211_vendor_cmd_get_sender
+ * @wiphy: the wiphy
+ *
+ * Return the current netlink port ID in a vendor command handler.
+ * Valid to call only there.
+ */
+unsigned int cfg80211_vendor_cmd_get_sender(struct wiphy *wiphy);
+
 /**
  * cfg80211_vendor_event_alloc - allocate vendor-specific event skb
  * @wiphy: the wiphy
@@ -5930,7 +5940,42 @@ cfg80211_vendor_event_alloc(struct wiphy *wiphy, struct wireless_dev *wdev,
 {
 	return __cfg80211_alloc_event_skb(wiphy, wdev, NL80211_CMD_VENDOR,
 					  NL80211_ATTR_VENDOR_DATA,
-					  event_idx, approxlen, gfp);
+					  0, event_idx, approxlen, gfp);
+}
+
+/**
+ * cfg80211_vendor_event_alloc_ucast - alloc unicast vendor-specific event skb
+ * @wiphy: the wiphy
+ * @wdev: the wireless device
+ * @event_idx: index of the vendor event in the wiphy's vendor_events
+ * @portid: port ID of the receiver
+ * @approxlen: an upper bound of the length of the data that will
+ *	be put into the skb
+ * @gfp: allocation flags
+ *
+ * This function allocates and pre-fills an skb for an event to send to
+ * a specific (userland) socket. This socket would previously have been
+ * obtained by cfg80211_vendor_cmd_get_sender(), and the caller MUST take
+ * care to register a netlink notifier to see when the socket closes.
+ *
+ * If wdev != NULL, both the ifindex and identifier of the specified
+ * wireless device are added to the event message before the vendor data
+ * attribute.
+ *
+ * When done filling the skb, call cfg80211_vendor_event() with the
+ * skb to send the event.
+ *
+ * Return: An allocated and pre-filled skb. %NULL if any errors happen.
+ */
+static inline struct sk_buff *
+cfg80211_vendor_event_alloc_ucast(struct wiphy *wiphy,
+				  struct wireless_dev *wdev,
+				  unsigned int portid, int approxlen,
+				  int event_idx, gfp_t gfp)
+{
+	return __cfg80211_alloc_event_skb(wiphy, wdev, NL80211_CMD_VENDOR,
+					  NL80211_ATTR_VENDOR_DATA,
+					  portid, event_idx, approxlen, gfp);
 }
 
 /**
@@ -6030,7 +6075,7 @@ static inline struct sk_buff *
 cfg80211_testmode_alloc_event_skb(struct wiphy *wiphy, int approxlen, gfp_t gfp)
 {
 	return __cfg80211_alloc_event_skb(wiphy, NULL, NL80211_CMD_TESTMODE,
-					  NL80211_ATTR_TESTDATA, -1,
+					  NL80211_ATTR_TESTDATA, 0, -1,
 					  approxlen, gfp);
 }
 

net/wireless/nl80211.c

@@ -4,7 +4,7 @@
  * Copyright 2006-2010	Johannes Berg <johannes@sipsolutions.net>
  * Copyright 2013-2014  Intel Mobile Communications GmbH
  * Copyright 2015-2017	Intel Deutschland GmbH
- * Copyright (C) 2018 Intel Corporation
+ * Copyright (C) 2018-2019 Intel Corporation
  */
 
 #include <linux/if.h>
@@ -9306,6 +9306,7 @@ struct sk_buff *__cfg80211_alloc_event_skb(struct wiphy *wiphy,
 					   struct wireless_dev *wdev,
 					   enum nl80211_commands cmd,
 					   enum nl80211_attrs attr,
+					   unsigned int portid,
 					   int vendor_event_idx,
 					   int approxlen, gfp_t gfp)
 {
@@ -9329,7 +9330,7 @@ struct sk_buff *__cfg80211_alloc_event_skb(struct wiphy *wiphy,
 		return NULL;
 	}
 
-	return __cfg80211_alloc_vendor_skb(rdev, wdev, approxlen, 0, 0,
+	return __cfg80211_alloc_vendor_skb(rdev, wdev, approxlen, portid, 0,
 					   cmd, attr, info, gfp);
 }
 EXPORT_SYMBOL(__cfg80211_alloc_event_skb);
@@ -9338,6 +9339,7 @@ void __cfg80211_send_event_skb(struct sk_buff *skb, gfp_t gfp)
 {
 	struct cfg80211_registered_device *rdev = ((void **)skb->cb)[0];
 	void *hdr = ((void **)skb->cb)[1];
+	struct nlmsghdr *nlhdr = nlmsg_hdr(skb);
 	struct nlattr *data = ((void **)skb->cb)[2];
 	enum nl80211_multicast_groups mcgrp = NL80211_MCGRP_TESTMODE;
 
@@ -9347,11 +9349,16 @@ void __cfg80211_send_event_skb(struct sk_buff *skb, gfp_t gfp)
 	nla_nest_end(skb, data);
 	genlmsg_end(skb, hdr);
 
+	if (nlhdr->nlmsg_pid) {
+		genlmsg_unicast(wiphy_net(&rdev->wiphy), skb,
+				nlhdr->nlmsg_pid);
+	} else {
 		if (data->nla_type == NL80211_ATTR_VENDOR_DATA)
 			mcgrp = NL80211_MCGRP_VENDOR;
 
-	genlmsg_multicast_netns(&nl80211_fam, wiphy_net(&rdev->wiphy), skb, 0,
-				mcgrp, gfp);
+		genlmsg_multicast_netns(&nl80211_fam, wiphy_net(&rdev->wiphy),
+					skb, 0, mcgrp, gfp);
+	}
 }
 EXPORT_SYMBOL(__cfg80211_send_event_skb);
 
@@ -12736,6 +12743,17 @@ int cfg80211_vendor_cmd_reply(struct sk_buff *skb)
 }
 EXPORT_SYMBOL_GPL(cfg80211_vendor_cmd_reply);
 
+unsigned int cfg80211_vendor_cmd_get_sender(struct wiphy *wiphy)
+{
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
+
+	if (WARN_ON(!rdev->cur_cmd_info))
+		return 0;
+
+	return rdev->cur_cmd_info->snd_portid;
+}
+EXPORT_SYMBOL_GPL(cfg80211_vendor_cmd_get_sender);
+
 static int nl80211_set_qos_map(struct sk_buff *skb,
 			       struct genl_info *info)
 {