/* Copyright (C) 1991-2025 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#ifndef _NETINET_IP6_H
#define _NETINET_IP6_H 1

#include <inttypes.h>
#include <netinet/in.h>

struct ip6_hdr
  {
    union
      {
	struct ip6_hdrctl
	  {
	    uint32_t ip6_un1_flow;   /* 4 bits version, 8 bits TC,
					20 bits flow-ID */
	    uint16_t ip6_un1_plen;   /* payload length */
	    uint8_t  ip6_un1_nxt;    /* next header */
	    uint8_t  ip6_un1_hlim;   /* hop limit */
	  } ip6_un1;
	uint8_t ip6_un2_vfc;       /* 4 bits version, top 4 bits tclass */
      } ip6_ctlun;
    struct in6_addr ip6_src;      /* source address */
    struct in6_addr ip6_dst;      /* destination address */
  };

#define ip6_vfc   ip6_ctlun.ip6_un2_vfc
#define ip6_flow  ip6_ctlun.ip6_un1.ip6_un1_flow
#define ip6_plen  ip6_ctlun.ip6_un1.ip6_un1_plen
#define ip6_nxt   ip6_ctlun.ip6_un1.ip6_un1_nxt
#define ip6_hlim  ip6_ctlun.ip6_un1.ip6_un1_hlim
#define ip6_hops  ip6_ctlun.ip6_un1.ip6_un1_hlim

#define IPV6_VERSION       0x60
#define IPV6_VERSION_MASK  0xf0

#if __BYTE_ORDER == __BIG_ENDIAN
#define IPV6_FLOWINFO_MASK   0x0fffffff  /* flow info (28 bits) */
#define IPV6_FLOWLABEL_MASK  0x000fffff  /* flow label (20 bits) */
#else   /* __BYTE_ORDER == __LITTLE_ENDIAN */
#define IPV6_FLOWINFO_MASK   0xffffff0f  /* flow info (28 bits) */
#define IPV6_FLOWLABEL_MASK  0xffff0f00  /* flow label (20 bits) */
#endif

/* Generic extension header.  */
struct ip6_ext
  {
    uint8_t  ip6e_nxt;		/* next header.  */
    uint8_t  ip6e_len;		/* length in units of 8 octets.  */
  };

/* Hop-by-Hop options header.  */
struct ip6_hbh
  {
    uint8_t  ip6h_nxt;		/* next header.  */
    uint8_t  ip6h_len;		/* length in units of 8 octets.  */
    /* followed by options */
  };

/* Destination options header */
struct ip6_dest
  {
    uint8_t  ip6d_nxt;		/* next header */
    uint8_t  ip6d_len;		/* length in units of 8 octets */
    /* followed by options */
  };

/* Routing header */
struct ip6_rthdr
  {
    uint8_t  ip6r_nxt;		/* next header */
    uint8_t  ip6r_len;		/* length in units of 8 octets */
    uint8_t  ip6r_type;		/* routing type */
    uint8_t  ip6r_segleft;	/* segments left */
    /* followed by routing type specific data */
  };

/* Type 0 Routing header */
struct ip6_rthdr0
  {
    uint8_t  ip6r0_nxt;		/* next header */
    uint8_t  ip6r0_len;		/* length in units of 8 octets */
    uint8_t  ip6r0_type;	/* always zero */
    uint8_t  ip6r0_segleft;	/* segments left */
    uint8_t  ip6r0_reserved;	/* reserved field */
    uint8_t  ip6r0_slmap[3];	/* strict/loose bit map */
    /* followed by up to 127 struct in6_addr */
    struct in6_addr ip6r0_addr[0];
  };

/* Fragment header */
struct ip6_frag
  {
    uint8_t   ip6f_nxt;		/* next header */
    uint8_t   ip6f_reserved;	/* reserved field */
    uint16_t  ip6f_offlg;	/* offset, reserved, and flag */
    uint32_t  ip6f_ident;	/* identification */
  };

#if __BYTE_ORDER == __BIG_ENDIAN
# define IP6F_OFF_MASK       0xfff8  /* mask out offset from _offlg */
# define IP6F_RESERVED_MASK  0x0006  /* reserved bits in ip6f_offlg */
# define IP6F_MORE_FRAG      0x0001  /* more-fragments flag */
#else   /* __BYTE_ORDER == __LITTLE_ENDIAN */
# define IP6F_OFF_MASK       0xf8ff  /* mask out offset from _offlg */
# define IP6F_RESERVED_MASK  0x0600  /* reserved bits in ip6f_offlg */
# define IP6F_MORE_FRAG      0x0100  /* more-fragments flag */
#endif

/* IPv6 options */
struct ip6_opt
  {
    uint8_t  ip6o_type;
    uint8_t  ip6o_len;
  };

/* The high-order 3 bits of the option type define the behavior
 * when processing an unknown option and whether or not the option
 * content changes in flight.
 */
#define IP6OPT_TYPE(o)		((o) & 0xc0)
#define IP6OPT_TYPE_SKIP	0x00
#define IP6OPT_TYPE_DISCARD	0x40
#define IP6OPT_TYPE_FORCEICMP	0x80
#define IP6OPT_TYPE_ICMP	0xc0
#define IP6OPT_TYPE_MUTABLE	0x20

/* Special option types for padding.  */
#define IP6OPT_PAD1	0
#define IP6OPT_PADN	1

#define IP6OPT_JUMBO		0xc2
#define IP6OPT_NSAP_ADDR	0xc3
#define IP6OPT_TUNNEL_LIMIT	0x04
#define IP6OPT_ROUTER_ALERT	0x05

/* Jumbo Payload Option */
struct ip6_opt_jumbo
  {
    uint8_t  ip6oj_type;
    uint8_t  ip6oj_len;
    uint8_t  ip6oj_jumbo_len[4];
  };
#define IP6OPT_JUMBO_LEN	6

/* NSAP Address Option */
struct ip6_opt_nsap
  {
    uint8_t  ip6on_type;
    uint8_t  ip6on_len;
    uint8_t  ip6on_src_nsap_len;
    uint8_t  ip6on_dst_nsap_len;
      /* followed by source NSAP */
      /* followed by destination NSAP */
  };

/* Tunnel Limit Option */
struct ip6_opt_tunnel
  {
    uint8_t  ip6ot_type;
    uint8_t  ip6ot_len;
    uint8_t  ip6ot_encap_limit;
  };

/* Router Alert Option */
struct ip6_opt_router
  {
    uint8_t  ip6or_type;
    uint8_t  ip6or_len;
    uint8_t  ip6or_value[2];
  };

/* Router alert values (in network byte order) */
#if __BYTE_ORDER == __BIG_ENDIAN
# define IP6_ALERT_MLD	0x0000
# define IP6_ALERT_RSVP	0x0001
# define IP6_ALERT_AN	0x0002
#else /* __BYTE_ORDER == __LITTLE_ENDIAN */
# define IP6_ALERT_MLD	0x0000
# define IP6_ALERT_RSVP	0x0100
# define IP6_ALERT_AN	0x0200
#endif

#endif /* netinet/ip6.h */
