text: /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
  #ifndef _IPV6_H
  #define _IPV6_H
  
  #include <linux/libc-compat.h>
  #include <linux/types.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*
   */
  
  #if __UAPI_DEF_IN6_PKTINFO
  struct in6_pktinfo {
  	struct in6_addr	ipi6_addr;
  	int		ipi6_ifindex;
  };
  #endif
  
  #if __UAPI_DEF_IP6_MTUINFO
  struct ip6_mtuinfo {
  	struct sockaddr_in6	ip6m_addr;
  	__u32			ip6m_mtu;
  };
  #endif
  
  struct in6_ifreq {
  	struct in6_addr	ifr6_addr;
  	__u32		ifr6_prefixlen;
  	int		ifr6_ifindex; 
  };
  
  #define IPV6_SRCRT_STRICT	0x01	/* Deprecated; will be removed */
  #define IPV6_SRCRT_TYPE_0	0	/* Deprecated; will be removed */
  #define IPV6_SRCRT_TYPE_2	2	/* IPv6 type 2 Routing Header	*/
  #define IPV6_SRCRT_TYPE_4	4	/* Segment Routing with IPv6 */
  
  /*
   *	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.
  	 */
  } __attribute__((packed));	/* required for some archs */
  
  #define ipv6_destopt_hdr ipv6_opt_hdr
  #define ipv6_hopopt_hdr  ipv6_opt_hdr
  
  /* Router Alert option values (RFC2711) */
  #define IPV6_OPT_ROUTERALERT_MLD	0x0000	/* MLD(RFC2710) */
  
  /*
   *	routing header type 0 (used in cmsghdr struct)
   */
  
  struct rt0_hdr {
  	struct ipv6_rt_hdr	rt_hdr;
  	__u32			reserved;
  	struct in6_addr		addr[0];
  
  #define rt0_type		rt_hdr.type
  };
  
  /*
   *	routing header type 2
   */
  
  struct rt2_hdr {
  	struct ipv6_rt_hdr	rt_hdr;
  	__u32			reserved;
  	struct in6_addr		addr;
  
  #define rt2_type		rt_hdr.type
  };
  
  /*
   *	home address option in destination options header
   */
  
  struct ipv6_destopt_hao {
  	__u8			type;
  	__u8			length;
  	struct in6_addr		addr;
  } __attribute__((packed));
  
  /*
   *	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];
  
  	__be16			payload_len;
  	__u8			nexthdr;
  	__u8			hop_limit;
  
  	struct	in6_addr	saddr;
  	struct	in6_addr	daddr;
  };
  
  
  /* 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,
  	DEVCONF_USE_TEMPADDR,
  	DEVCONF_TEMP_VALID_LFT,
  	DEVCONF_TEMP_PREFERED_LFT,
  	DEVCONF_REGEN_MAX_RETRY,
  	DEVCONF_MAX_DESYNC_FACTOR,
  	DEVCONF_MAX_ADDRESSES,
  	DEVCONF_FORCE_MLD_VERSION,
  	DEVCONF_ACCEPT_RA_DEFRTR,
  	DEVCONF_ACCEPT_RA_PINFO,
  	DEVCONF_ACCEPT_RA_RTR_PREF,
  	DEVCONF_RTR_PROBE_INTERVAL,
  	DEVCONF_ACCEPT_RA_RT_INFO_MAX_PLEN,
  	DEVCONF_PROXY_NDP,
  	DEVCONF_OPTIMISTIC_DAD,
  	DEVCONF_ACCEPT_SOURCE_ROUTE,
  	DEVCONF_MC_FORWARDING,
  	DEVCONF_DISABLE_IPV6,
  	DEVCONF_ACCEPT_DAD,
  	DEVCONF_FORCE_TLLAO,
  	DEVCONF_NDISC_NOTIFY,
  	DEVCONF_MLDV1_UNSOLICITED_REPORT_INTERVAL,
  	DEVCONF_MLDV2_UNSOLICITED_REPORT_INTERVAL,
  	DEVCONF_SUPPRESS_FRAG_NDISC,
  	DEVCONF_ACCEPT_RA_FROM_LOCAL,
  	DEVCONF_USE_OPTIMISTIC,
  	DEVCONF_ACCEPT_RA_MTU,
  	DEVCONF_STABLE_SECRET,
  	DEVCONF_USE_OIF_ADDRS_ONLY,
  	DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT,
  	DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN,
  	DEVCONF_DROP_UNICAST_IN_L2_MULTICAST,
  	DEVCONF_DROP_UNSOLICITED_NA,
  	DEVCONF_KEEP_ADDR_ON_DOWN,
  	DEVCONF_RTR_SOLICIT_MAX_INTERVAL,
  	DEVCONF_SEG6_ENABLED,
  	DEVCONF_SEG6_REQUIRE_HMAC,
  	DEVCONF_ENHANCED_DAD,
  	DEVCONF_ADDR_GEN_MODE,
  	DEVCONF_DISABLE_POLICY,
  	DEVCONF_ACCEPT_RA_RT_INFO_MIN_PLEN,
  	DEVCONF_NDISC_TCLASS,
  	DEVCONF_MAX
  };
  
  
  #endif /* _IPV6_H */