nl80211: allow multiple active scheduled scan requests

This patch implements the idea to have multiple scheduled scan requests
running concurrently. It mainly illustrates how to deal with the incoming
request from user-space in terms of backward compatibility. In order to
use multiple scheduled scans user-space needs to provide a flag attribute
NL80211_ATTR_SCHED_SCAN_MULTI to indicate support. If not the request is
treated as a legacy scan.

Drivers currently supporting scheduled scan are now indicating they support
a single scheduled scan request. This obsoletes WIPHY_FLAG_SUPPORTS_SCHED_SCAN.

Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
[clean up netlink destroy path to avoid allocations, code cleanups]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 96 insertions, 19 deletions

diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 6f4996c0f4df..bd9feed95c1e 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -300,6 +300,70 @@ void cfg80211_scan_done(struct cfg80211_scan_request *request,
 }
 EXPORT_SYMBOL(cfg80211_scan_done);
 
+void cfg80211_add_sched_scan_req(struct cfg80211_registered_device *rdev,
+				 struct cfg80211_sched_scan_request *req)
+{
+	ASSERT_RTNL();
+
+	list_add_rcu(&req->list, &rdev->sched_scan_req_list);
+}
+
+static void cfg80211_del_sched_scan_req(struct cfg80211_registered_device *rdev,
+					struct cfg80211_sched_scan_request *req)
+{
+	ASSERT_RTNL();
+
+	list_del_rcu(&req->list);
+	kfree_rcu(req, rcu_head);
+}
+
+static struct cfg80211_sched_scan_request *
+cfg80211_find_sched_scan_req(struct cfg80211_registered_device *rdev, u64 reqid)
+{
+	struct cfg80211_sched_scan_request *pos;
+
+	ASSERT_RTNL();
+
+	list_for_each_entry(pos, &rdev->sched_scan_req_list, list) {
+		if (pos->reqid == reqid)
+			return pos;
+	}
+	return ERR_PTR(-ENOENT);
+}
+
+/*
+ * Determines if a scheduled scan request can be handled. When a legacy
+ * scheduled scan is running no other scheduled scan is allowed regardless
+ * whether the request is for legacy or multi-support scan. When a multi-support
+ * scheduled scan is running a request for legacy scan is not allowed. In this
+ * case a request for multi-support scan can be handled if resources are
+ * available, ie. struct wiphy::max_sched_scan_reqs limit is not yet reached.
+ */
+int cfg80211_sched_scan_req_possible(struct cfg80211_registered_device *rdev,
+				     bool want_multi)
+{
+	struct cfg80211_sched_scan_request *pos;
+	int i = 0;
+
+	list_for_each_entry(pos, &rdev->sched_scan_req_list, list) {
+		/* request id zero means legacy in progress */
+		if (!i && !pos->reqid)
+			return -EINPROGRESS;
+		i++;
+	}
+
+	if (i) {
+		/* no legacy allowed when multi request(s) are active */
+		if (!want_multi)
+			return -EINPROGRESS;
+
+		/* resource limit reached */
+		if (i == rdev->wiphy.max_sched_scan_reqs)
+			return -ENOSPC;
+	}
+	return 0;
+}
+
 void __cfg80211_sched_scan_results(struct work_struct *wk)
 {
 	struct cfg80211_registered_device *rdev;
@@ -310,10 +374,10 @@ void __cfg80211_sched_scan_results(struct work_struct *wk)
 
 	rtnl_lock();
 
-	request = rtnl_dereference(rdev->sched_scan_req);
+	request = cfg80211_find_sched_scan_req(rdev, 0);
 
 	/* we don't have sched_scan_req anymore if the scan is stopping */
-	if (request) {
+	if (!IS_ERR(request)) {
 		if (request->flags & NL80211_SCAN_FLAG_FLUSH) {
 			/* flush entries from previous scans */
 			spin_lock_bh(&rdev->bss_lock);
@@ -329,10 +393,17 @@ void __cfg80211_sched_scan_results(struct work_struct *wk)
 
 void cfg80211_sched_scan_results(struct wiphy *wiphy)
 {
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
+	struct cfg80211_sched_scan_request *request;
+
 	trace_cfg80211_sched_scan_results(wiphy);
 	/* ignore if we're not scanning */
 
-	if (rcu_access_pointer(wiphy_to_rdev(wiphy)->sched_scan_req))
+	rtnl_lock();
+	request = cfg80211_find_sched_scan_req(rdev, 0);
+	rtnl_unlock();
+
+	if (!IS_ERR(request))
 		queue_work(cfg80211_wq,
 			   &wiphy_to_rdev(wiphy)->sched_scan_results_wk);
 }
@@ -346,7 +417,7 @@ void cfg80211_sched_scan_stopped_rtnl(struct wiphy *wiphy)
 
 	trace_cfg80211_sched_scan_stopped(wiphy);
 
-	__cfg80211_stop_sched_scan(rdev, true);
+	__cfg80211_stop_sched_scan(rdev, 0, true);
 }
 EXPORT_SYMBOL(cfg80211_sched_scan_stopped_rtnl);
 
@@ -358,34 +429,40 @@ void cfg80211_sched_scan_stopped(struct wiphy *wiphy)
 }
 EXPORT_SYMBOL(cfg80211_sched_scan_stopped);
 
-int __cfg80211_stop_sched_scan(struct cfg80211_registered_device *rdev,
-			       bool driver_initiated)
+int cfg80211_stop_sched_scan_req(struct cfg80211_registered_device *rdev,
+				 struct cfg80211_sched_scan_request *req,
+				 bool driver_initiated)
 {
-	struct cfg80211_sched_scan_request *sched_scan_req;
-	struct net_device *dev;
-
 	ASSERT_RTNL();
 
-	if (!rdev->sched_scan_req)
-		return -ENOENT;
-
-	sched_scan_req = rtnl_dereference(rdev->sched_scan_req);
-	dev = sched_scan_req->dev;
-
 	if (!driver_initiated) {
-		int err = rdev_sched_scan_stop(rdev, dev);
+		int err = rdev_sched_scan_stop(rdev, req->dev);
 		if (err)
 			return err;
 	}
 
-	nl80211_send_sched_scan(sched_scan_req, NL80211_CMD_SCHED_SCAN_STOPPED);
+	nl80211_send_sched_scan(req, NL80211_CMD_SCHED_SCAN_STOPPED);
 
-	RCU_INIT_POINTER(rdev->sched_scan_req, NULL);
-	kfree_rcu(sched_scan_req, rcu_head);
+	cfg80211_del_sched_scan_req(rdev, req);
 
 	return 0;
 }
 
+int __cfg80211_stop_sched_scan(struct cfg80211_registered_device *rdev,
+			       u64 reqid, bool driver_initiated)
+{
+	struct cfg80211_sched_scan_request *sched_scan_req;
+
+	ASSERT_RTNL();
+
+	sched_scan_req = cfg80211_find_sched_scan_req(rdev, reqid);
+	if (IS_ERR(sched_scan_req))
+		return PTR_ERR(sched_scan_req);
+
+	return cfg80211_stop_sched_scan_req(rdev, sched_scan_req,
+					    driver_initiated);
+}
+
 void cfg80211_bss_age(struct cfg80211_registered_device *rdev,
                       unsigned long age_secs)
 {