linux/include/net/tun_proto.h

#ifndef __NET_TUN_PROTO_H
#define __NET_TUN_PROTO_H

#include <linux/if_ether.h>
#include <linux/types.h>

/* One byte protocol values as defined by VXLAN-GPE and NSH. These will
 * hopefully get a shared IANA registry.
 */
#define TUN_P_IPV4 …
#define TUN_P_IPV6 …
#define TUN_P_ETHERNET …
#define TUN_P_NSH …
#define TUN_P_MPLS_UC …

static inline __be16 tun_p_to_eth_p(u8 proto)
{ … }

static inline u8 tun_p_from_eth_p(__be16 proto)
{ … }

#endif