mac80211: add explicit monitor interface if needed

The queue mapping redesign that I'm planning to do
will break pure injection unless we handle monitor
interfaces explicitly. One possible option would
be to have the driver tell mac80211 about monitor
mode queues etc., but that would duplicate the API
since we already need to have queue assignments
handled per virtual interface.

So in order to solve this, have a virtual monitor
interface that is added whenever all active vifs
are monitors. We could also use the state of one
of the monitor interfaces, but managing that would
be complicated, so allocate separate state.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

6 files changed, 89 insertions, 3 deletions

diff --git a/net/mac80211/driver-ops.h b/net/mac80211/driver-ops.h
index 8ad40f6..492c08c 100644
--- a/net/mac80211/driver-ops.h
+++ b/net/mac80211/driver-ops.h
@@ -101,7 +101,8 @@ static inline int drv_add_interface(struct ieee80211_local *local,
 	might_sleep();
 
 	if (WARN_ON(sdata->vif.type == NL80211_IFTYPE_AP_VLAN ||
-		    sdata->vif.type == NL80211_IFTYPE_MONITOR))
+		    (sdata->vif.type == NL80211_IFTYPE_MONITOR &&
+		     !(local->hw.flags & IEEE80211_HW_WANT_MONITOR_VIF))))
 		return -EINVAL;
 
 	trace_drv_add_interface(local, sdata);
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 41f7295..8ed074f 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1100,6 +1100,9 @@ struct ieee80211_local {
 	struct net_device napi_dev;
 
 	struct napi_struct napi;
+
+	/* virtual monitor interface */
+	struct ieee80211_sub_if_data __rcu *monitor_sdata;
 };
 
 static inline struct ieee80211_sub_if_data *
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 56a38a3..2b88cb2 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -169,6 +169,59 @@ void ieee80211_adjust_monitor_flags(struct ieee80211_sub_if_data *sdata,
 #undef ADJUST
 }
 
+static int ieee80211_add_virtual_monitor(struct ieee80211_local *local)
+{
+	struct ieee80211_sub_if_data *sdata;
+	int ret;
+
+	if (!(local->hw.flags & IEEE80211_HW_WANT_MONITOR_VIF))
+		return 0;
+
+	if (local->monitor_sdata)
+		return 0;
+
+	sdata = kzalloc(sizeof(*sdata) + local->hw.vif_data_size, GFP_KERNEL);
+	if (!sdata)
+		return -ENOMEM;
+
+	/* set up data */
+	sdata->local = local;
+	sdata->vif.type = NL80211_IFTYPE_MONITOR;
+	snprintf(sdata->name, IFNAMSIZ, "%s-monitor",
+		 wiphy_name(local->hw.wiphy));
+
+	ret = drv_add_interface(local, sdata);
+	if (WARN_ON(ret)) {
+		/* ok .. stupid driver, it asked for this! */
+		kfree(sdata);
+		return ret;
+	}
+
+	rcu_assign_pointer(local->monitor_sdata, sdata);
+
+	return 0;
+}
+
+static void ieee80211_del_virtual_monitor(struct ieee80211_local *local)
+{
+	struct ieee80211_sub_if_data *sdata;
+
+	if (!(local->hw.flags & IEEE80211_HW_WANT_MONITOR_VIF))
+		return;
+
+	sdata = rtnl_dereference(local->monitor_sdata);
+
+	if (!sdata)
+		return;
+
+	rcu_assign_pointer(local->monitor_sdata, NULL);
+	synchronize_net();
+
+	drv_remove_interface(local, sdata);
+
+	kfree(sdata);
+}
+
 /*
  * NOTE: Be very careful when changing this function, it must NOT return
  * an error on interface type changes that have been pre-checked, so most
@@ -266,6 +319,12 @@ static int ieee80211_do_open(struct net_device *dev, bool coming_up)
 			break;
 		}
 
+		if (local->monitors == 0 && local->open_count == 0) {
+			res = ieee80211_add_virtual_monitor(local);
+			if (res)
+				goto err_stop;
+		}
+
 		/* must be before the call to ieee80211_configure_filter */
 		local->monitors++;
 		if (local->monitors == 1) {
@@ -280,6 +339,8 @@ static int ieee80211_do_open(struct net_device *dev, bool coming_up)
 		break;
 	default:
 		if (coming_up) {
+			ieee80211_del_virtual_monitor(local);
+
 			res = drv_add_interface(local, sdata);
 			if (res)
 				goto err_stop;
@@ -511,6 +572,7 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
 		if (local->monitors == 0) {
 			local->hw.conf.flags &= ~IEEE80211_CONF_MONITOR;
 			hw_reconf_flags |= IEEE80211_CONF_CHANGE_MONITOR;
+			ieee80211_del_virtual_monitor(local);
 		}
 
 		ieee80211_adjust_monitor_flags(sdata, -1);
@@ -584,6 +646,9 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
 		}
 	}
 	spin_unlock_irqrestore(&local->queue_stop_reason_lock, flags);
+
+	if (local->monitors == local->open_count && local->monitors > 0)
+		ieee80211_add_virtual_monitor(local);
 }
 
 static int ieee80211_stop(struct net_device *dev)
diff --git a/net/mac80211/pm.c b/net/mac80211/pm.c
index ef8eba1..af1c4e2 100644
--- a/net/mac80211/pm.c
+++ b/net/mac80211/pm.c
@@ -127,6 +127,10 @@ int __ieee80211_suspend(struct ieee80211_hw *hw, struct cfg80211_wowlan *wowlan)
 		drv_remove_interface(local, sdata);
 	}
 
+	sdata = rtnl_dereference(local->monitor_sdata);
+	if (sdata)
+		drv_remove_interface(local, sdata);
+
 	/* stop hardware - this must stop RX */
 	if (local->open_count)
 		ieee80211_stop_device(local);
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 4109ec7..a8d0188 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1283,8 +1283,11 @@ static bool __ieee80211_tx(struct ieee80211_local *local,
 
 	switch (sdata->vif.type) {
 	case NL80211_IFTYPE_MONITOR:
-		sdata = NULL;
-		vif = NULL;
+		sdata = rcu_dereference(local->monitor_sdata);
+		if (sdata)
+			vif = &sdata->vif;
+		else
+			vif = NULL;
 		break;
 	case NL80211_IFTYPE_AP_VLAN:
 		sdata = container_of(sdata->bss,
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index a18b693..9e8f4b8 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -1223,6 +1223,16 @@ int ieee80211_reconfig(struct ieee80211_local *local)
 				   IEEE80211_TPT_LEDTRIG_FL_RADIO, 0);
 
 	/* add interfaces */
+	sdata = rtnl_dereference(local->monitor_sdata);
+	if (sdata) {
+		res = drv_add_interface(local, sdata);
+		if (WARN_ON(res)) {
+			rcu_assign_pointer(local->monitor_sdata, NULL);
+			synchronize_net();
+			kfree(sdata);
+		}
+	}
+
 	list_for_each_entry(sdata, &local->interfaces, list) {
 		if (sdata->vif.type != NL80211_IFTYPE_AP_VLAN &&
 		    sdata->vif.type != NL80211_IFTYPE_MONITOR &&