net: Add netif_is_vxlan()

Add the ability to determine whether a netdev is a VxLAN netdev by
calling the above mentioned function that checks the netdev's
rtnl_link_ops.

This will allow modules to identify netdev events involving a VxLAN
netdev and act accordingly. For example, drivers capable of VxLAN
offload will need to configure the underlying device when a VxLAN netdev
is being enslaved to an offloaded bridge.

Convert nfp to use the newly introduced helper.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Petr Machata <petrm@mellanox.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/flower/tunnel_conf.c

@@ -4,6 +4,7 @@
 #include <linux/etherdevice.h>
 #include <linux/inetdevice.h>
 #include <net/netevent.h>
+#include <net/vxlan.h>
 #include <linux/idr.h>
 #include <net/dst_metadata.h>
 #include <net/arp.h>
@@ -187,7 +188,7 @@ static bool nfp_tun_is_netdev_to_offload(struct net_device *netdev)
 		return false;
 	if (!strcmp(netdev->rtnl_link_ops->kind, "openvswitch"))
 		return true;
-	if (!strcmp(netdev->rtnl_link_ops->kind, "vxlan"))
+	if (netif_is_vxlan(netdev))
 		return true;
 
 	return false;

include/net/vxlan.h

@@ -5,6 +5,7 @@
 #include <linux/if_vlan.h>
 #include <net/udp_tunnel.h>
 #include <net/dst_metadata.h>
+#include <net/rtnetlink.h>
 
 /* VXLAN protocol (RFC 7348) header:
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
@@ -402,4 +403,10 @@ static inline bool vxlan_addr_multicast(const union vxlan_addr *ipa)
 
 #endif /* IS_ENABLED(CONFIG_IPV6) */
 
+static inline bool netif_is_vxlan(const struct net_device *dev)
+{
+	return dev->rtnl_link_ops &&
+	       !strcmp(dev->rtnl_link_ops->kind, "vxlan");
+}
+
 #endif