text: #ifndef _NET_IP6_TUNNEL_H
  #define _NET_IP6_TUNNEL_H
  
  #include <linux/ipv6.h>
  #include <linux/netdevice.h>
  #include <linux/ip6_tunnel.h>
  
  /* capable of sending packets */
  #define IP6_TNL_F_CAP_XMIT 0x10000
  /* capable of receiving packets */
  #define IP6_TNL_F_CAP_RCV 0x20000
  /* determine capability on a per-packet basis */
  #define IP6_TNL_F_CAP_PER_PACKET 0x40000
  
  /* IPv6 tunnel */
  
  struct ip6_tnl {
  	struct ip6_tnl __rcu *next;	/* next tunnel in list */
  	struct net_device *dev;	/* virtual device associated with tunnel */
  	struct ip6_tnl_parm parms;	/* tunnel configuration parameters */
  	struct flowi fl;	/* flowi template for xmit */
  	struct dst_entry *dst_cache;    /* cached dst */
  	u32 dst_cookie;
  };
  
  /* Tunnel encapsulation limit destination sub-option */
  
  struct ipv6_tlv_tnl_enc_lim {
  	__u8 type;		/* type-code for option         */
  	__u8 length;		/* option length                */
  	__u8 encap_limit;	/* tunnel encapsulation limit   */
  } __packed;
  
  #endif
  