bridge: add br_vlan_get_pvid_rcu()

This new function allows you to fetch bridge pvid from packet path.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>

include/linux/if_bridge.h

@@ -88,6 +88,7 @@ static inline bool br_multicast_router(const struct net_device *dev)
 #if IS_ENABLED(CONFIG_BRIDGE) && IS_ENABLED(CONFIG_BRIDGE_VLAN_FILTERING)
 bool br_vlan_enabled(const struct net_device *dev);
 int br_vlan_get_pvid(const struct net_device *dev, u16 *p_pvid);
+int br_vlan_get_pvid_rcu(const struct net_device *dev, u16 *p_pvid);
 int br_vlan_get_info(const struct net_device *dev, u16 vid,
 		     struct bridge_vlan_info *p_vinfo);
 #else
@@ -101,6 +102,11 @@ static inline int br_vlan_get_pvid(const struct net_device *dev, u16 *p_pvid)
 	return -EINVAL;
 }
 
+static inline int br_vlan_get_pvid_rcu(const struct net_device *dev, u16 *p_pvid)
+{
+	return -EINVAL;
+}
+
 static inline int br_vlan_get_info(const struct net_device *dev, u16 vid,
 				   struct bridge_vlan_info *p_vinfo)
 {

net/bridge/br_vlan.c

@@ -1227,13 +1227,11 @@ void br_vlan_get_stats(const struct net_bridge_vlan *v,
 	}
 }
 
-int br_vlan_get_pvid(const struct net_device *dev, u16 *p_pvid)
+static int __br_vlan_get_pvid(const struct net_device *dev,
+			      struct net_bridge_port *p, u16 *p_pvid)
 {
 	struct net_bridge_vlan_group *vg;
-	struct net_bridge_port *p;
 
-	ASSERT_RTNL();
-	p = br_port_get_check_rtnl(dev);
 	if (p)
 		vg = nbp_vlan_group(p);
 	else if (netif_is_bridge_master(dev))
@@ -1244,8 +1242,21 @@ int br_vlan_get_pvid(const struct net_device *dev, u16 *p_pvid)
 	*p_pvid = br_get_pvid(vg);
 	return 0;
 }
+
+int br_vlan_get_pvid(const struct net_device *dev, u16 *p_pvid)
+{
+	ASSERT_RTNL();
+
+	return __br_vlan_get_pvid(dev, br_port_get_check_rtnl(dev), p_pvid);
+}
 EXPORT_SYMBOL_GPL(br_vlan_get_pvid);
 
+int br_vlan_get_pvid_rcu(const struct net_device *dev, u16 *p_pvid)
+{
+	return __br_vlan_get_pvid(dev, br_port_get_check_rcu(dev), p_pvid);
+}
+EXPORT_SYMBOL_GPL(br_vlan_get_pvid_rcu);
+
 int br_vlan_get_info(const struct net_device *dev, u16 vid,
 		     struct bridge_vlan_info *p_vinfo)
 {