/*      $OpenBSD: rthdr.c,v 1.13 2022/12/27 17:10:06 jmc Exp $  */
/*      $KAME: rthdr.c,v 1.22 2006/02/09 08:18:58 keiichi Exp $ */

/*
 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/socket.h>

#include <netinet/in.h>
#include <netinet/ip6.h>

#include <string.h>
#include <stdio.h>

/*
 * RFC3542 (2292bis) API
 */

socklen_t
inet6_rth_space(int type, int segments)
{
        switch (type) {
        case IPV6_RTHDR_TYPE_0:
                return (((segments * 2) + 1) << 3);
        default:
                return (0);     /* type not supported */
        }
}
DEF_WEAK(inet6_rth_space);

void *
inet6_rth_init(void *bp, socklen_t bp_len, int type, int segments)
{
        struct ip6_rthdr *rth = (struct ip6_rthdr *)bp;
        struct ip6_rthdr0 *rth0;

        switch (type) {
        case IPV6_RTHDR_TYPE_0:
                /* length validation */
                if (bp_len < inet6_rth_space(IPV6_RTHDR_TYPE_0, segments))
                        return (NULL);

                memset(bp, 0, bp_len);
                rth0 = (struct ip6_rthdr0 *)rth;
                rth0->ip6r0_len = segments * 2;
                rth0->ip6r0_type = IPV6_RTHDR_TYPE_0;
                rth0->ip6r0_segleft = 0;
                rth0->ip6r0_reserved = 0;
                break;
        default:
                return (NULL);  /* type not supported */
        }

        return (bp);
}

int
inet6_rth_add(void *bp, const struct in6_addr *addr)
{
        struct ip6_rthdr *rth = (struct ip6_rthdr *)bp;
        struct ip6_rthdr0 *rth0;
        struct in6_addr *nextaddr;

        switch (rth->ip6r_type) {
        case IPV6_RTHDR_TYPE_0:
                rth0 = (struct ip6_rthdr0 *)rth;
                nextaddr = (struct in6_addr *)(rth0 + 1) + rth0->ip6r0_segleft;
                *nextaddr = *addr;
                rth0->ip6r0_segleft++;
                break;
        default:
                return (-1);    /* type not supported */
        }

        return (0);
}

int
inet6_rth_reverse(const void *in, void *out)
{
        struct ip6_rthdr *rth_in = (struct ip6_rthdr *)in;
        struct ip6_rthdr0 *rth0_in, *rth0_out;
        int i, segments;

        switch (rth_in->ip6r_type) {
        case IPV6_RTHDR_TYPE_0:
                rth0_in = (struct ip6_rthdr0 *)in;
                rth0_out = (struct ip6_rthdr0 *)out;

                /* parameter validation XXX too paranoid? */
                if (rth0_in->ip6r0_len % 2)
                        return (-1);
                segments = rth0_in->ip6r0_len / 2;

                /* we can't use memcpy here, since in and out may overlap */
                memmove(rth0_out, rth0_in, ((rth0_in->ip6r0_len) + 1) << 3);
                rth0_out->ip6r0_segleft = segments;

                /* reverse the addresses */
                for (i = 0; i < segments / 2; i++) {
                        struct in6_addr addr_tmp, *addr1, *addr2;

                        addr1 = (struct in6_addr *)(rth0_out + 1) + i;
                        addr2 = (struct in6_addr *)(rth0_out + 1) +
                            (segments - i - 1);
                        addr_tmp = *addr1;
                        *addr1 = *addr2;
                        *addr2 = addr_tmp;
                }
                
                break;
        default:
                return (-1);    /* type not supported */
        }

        return (0);
}

int
inet6_rth_segments(const void *bp)
{
        struct ip6_rthdr *rh = (struct ip6_rthdr *)bp;
        struct ip6_rthdr0 *rh0;
        int addrs;

        switch (rh->ip6r_type) {
        case IPV6_RTHDR_TYPE_0:
                rh0 = (struct ip6_rthdr0 *)bp;

                /*
                 * Validation for a type-0 routing header.
                 * Is this too strict?
                 */
                if ((rh0->ip6r0_len % 2) != 0 ||
                    (addrs = (rh0->ip6r0_len >> 1)) < rh0->ip6r0_segleft)
                        return (-1);

                return (addrs);
        default:
                return (-1);    /* unknown type */
        }
}

struct in6_addr *
inet6_rth_getaddr(const void *bp, int idx)
{
        struct ip6_rthdr *rh = (struct ip6_rthdr *)bp;
        struct ip6_rthdr0 *rh0;
        int addrs;

        switch (rh->ip6r_type) {
        case IPV6_RTHDR_TYPE_0:
                 rh0 = (struct ip6_rthdr0 *)bp;
                 
                /*
                 * Validation for a type-0 routing header.
                 * Is this too strict?
                 */
                if ((rh0->ip6r0_len % 2) != 0 ||
                    (addrs = (rh0->ip6r0_len >> 1)) < rh0->ip6r0_segleft)
                        return (NULL);

                if (idx < 0 || addrs <= idx)
                        return (NULL);

                return (((struct in6_addr *)(rh0 + 1)) + idx);
        default:
                return (NULL);  /* unknown type */
                break;
        }
}