text: #ifndef _IPV6_H
  #define _IPV6_H
  
  #include <linux/in6.h>
  #include <asm/byteorder.h>
  
  /* The latest drafts declared increase in minimal mtu up to 1280. */
  
  #define IPV6_MIN_MTU	1280
  
  /*
   *	Advanced API
   *	source interface/address selection, source routing, etc...
   *	*under construction*
   */
  
  
  struct in6_pktinfo {
  	struct in6_addr	ipi6_addr;
  	int		ipi6_ifindex;
  };
  
  
  struct in6_ifreq {
  	struct in6_addr	ifr6_addr;
  	__u32		ifr6_prefixlen;
  	int		ifr6_ifindex; 
  };
  
  #define IPV6_SRCRT_STRICT	0x01	/* this hop must be a neighbor	*/
  #define IPV6_SRCRT_TYPE_0	0	/* IPv6 type 0 Routing Header	*/
  
  /*
   *	routing header
   */
  struct ipv6_rt_hdr {
  	__u8		nexthdr;
  	__u8		hdrlen;
  	__u8		type;
  	__u8		segments_left;
  
  	/*
  	 *	type specific data
  	 *	variable length field
  	 */
  };
  
  
  struct ipv6_opt_hdr {
  	__u8 		nexthdr;
  	__u8 		hdrlen;
  	/* 
  	 * TLV encoded option data follows.
  	 */
  };
  
  #define ipv6_destopt_hdr ipv6_opt_hdr
  #define ipv6_hopopt_hdr  ipv6_opt_hdr
  
  #ifdef __KERNEL__
  #define ipv6_optlen(p)  (((p)->hdrlen+1) << 3)
  #endif
  
  /*
   *	routing header type 0 (used in cmsghdr struct)
   */
  
  struct rt0_hdr {
  	struct ipv6_rt_hdr	rt_hdr;
  	__u32			bitmap;		/* strict/loose bit map */
  	struct in6_addr		addr[0];
  
  #define rt0_type		rt_hdr.type
  };
  
  /*
   *	IPv6 fixed header
   *
   *	BEWARE, it is incorrect. The first 4 bits of flow_lbl
   *	are glued to priority now, forming "class".
   */
  
  struct ipv6hdr {
  #if defined(__LITTLE_ENDIAN_BITFIELD)
  	__u8			priority:4,
  				version:4;
  #elif defined(__BIG_ENDIAN_BITFIELD)
  	__u8			version:4,
  				priority:4;
  #else
  #error	"Please fix <asm/byteorder.h>"
  #endif
  	__u8			flow_lbl[3];
  
  	__u16			payload_len;
  	__u8			nexthdr;
  	__u8			hop_limit;
  
  	struct	in6_addr	saddr;
  	struct	in6_addr	daddr;
  };
  
  /*
   * This structure contains configuration options per IPv6 link.
   */
  struct ipv6_devconf {
  	__s32		forwarding;
  	__s32		hop_limit;
  	__s32		mtu6;
  	__s32		accept_ra;
  	__s32		accept_redirects;
  	__s32		autoconf;
  	__s32		dad_transmits;
  	__s32		rtr_solicits;
  	__s32		rtr_solicit_interval;
  	__s32		rtr_solicit_delay;
  #ifdef CONFIG_IPV6_PRIVACY
  	__s32		use_tempaddr;
  	__s32		temp_valid_lft;
  	__s32		temp_prefered_lft;
  	__s32		regen_max_retry;
  	__s32		max_desync_factor;
  #endif
  	void		*sysctl;
  };
  
  /* index values for the variables in ipv6_devconf */
  enum {
  	DEVCONF_FORWARDING = 0,
  	DEVCONF_HOPLIMIT,
  	DEVCONF_MTU6,
  	DEVCONF_ACCEPT_RA,
  	DEVCONF_ACCEPT_REDIRECTS,
  	DEVCONF_AUTOCONF,
  	DEVCONF_DAD_TRANSMITS,
  	DEVCONF_RTR_SOLICITS,
  	DEVCONF_RTR_SOLICIT_INTERVAL,
  	DEVCONF_RTR_SOLICIT_DELAY,
  #ifdef CONFIG_IPV6_PRIVACY
  	DEVCONF_USE_TEMPADDR,
  	DEVCONF_TEMP_VALID_LFT,
  	DEVCONF_TEMP_PREFERED_LFT,
  	DEVCONF_REGEN_MAX_RETRY,
  	DEVCONF_MAX_DESYNC_FACTOR,
  #endif
  	DEVCONF_MAX
  };
  
  #ifdef __KERNEL__
  
  /* 
     This structure contains results of exthdrs parsing
     as offsets from skb->nh.
   */
  
  struct inet6_skb_parm
  {
  	int			iif;
  	__u16			ra;
  	__u16			hop;
  	__u16			auth;
  	__u16			dst0;
  	__u16			srcrt;
  	__u16			dst1;
  };
  
  #endif
  
  #endif
  