/*      $OpenBSD: ip6opt.c,v 1.10 2020/01/22 07:52:37 deraadt Exp $     */
/*      $KAME: ip6opt.c,v 1.18 2005/06/15 07:11:35 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>

static int ip6optlen(u_int8_t *opt, u_int8_t *lim);

/*
 * Calculate the length of a given IPv6 option. Also checks
 * if the option is safely stored in user's buffer according to the
 * calculated length and the limitation of the buffer.
 */
static int
ip6optlen(u_int8_t *opt, u_int8_t *lim)
{
        int optlen;

        if (*opt == IP6OPT_PAD1)
                optlen = 1;
        else {
                /* is there enough space to store type and len? */
                if (opt + 2 > lim)
                        return (0);
                optlen = *(opt + 1) + 2;
        }
        if (opt + optlen <= lim)
                return (optlen);

        return (0);
}

/*
 * The following functions are defined in RFC3542, which is a successor
 * of RFC2292.
 */

int
inet6_opt_init(void *extbuf, socklen_t extlen)
{
        struct ip6_ext *ext = (struct ip6_ext *)extbuf;

        if (ext) {
                if (extlen <= 0 || (extlen % 8))
                        return (-1);
                ext->ip6e_len = (extlen >> 3) - 1;
        }

        return (2);             /* sizeof the next and the length fields */
}

int
inet6_opt_append(void *extbuf, socklen_t extlen, int offset, u_int8_t type,
                 socklen_t len, u_int8_t align, void **databufp)
{
        int currentlen = offset, padlen = 0;

        /*
         * The option type must have a value from 2 to 255, inclusive.
         * (0 and 1 are reserved for the Pad1 and PadN options, respectively.)
         */
#if 0 /* always false */
        if (type < 2 || type > 255)
#else
        if (type < 2)
#endif
                return (-1);

        /*
         * The option data length must have a value between 0 and 255,
         * inclusive, and is the length of the option data that follows.
         */
        if (len > 255)
                return (-1);

        /*
         * The align parameter must have a value of 1, 2, 4, or 8.
         * The align value can not exceed the value of len.
         */
        if (align != 1 && align != 2 && align != 4 && align != 8)
                return (-1);
        if (align > len)
                return (-1);

        /* Calculate the padding length. */
        currentlen += 2 + len;  /* 2 means "type + len" */
        if (currentlen % align)
                padlen = align - (currentlen % align);

        /* The option must fit in the extension header buffer. */
        currentlen += padlen;
        if (extlen &&           /* XXX: right? */
            currentlen > extlen)
                return (-1);

        if (extbuf) {
                u_int8_t *optp = (u_int8_t *)extbuf + offset;

                if (padlen == 1) {
                        /* insert a Pad1 option */
                        *optp = IP6OPT_PAD1;
                        optp++;
                } else if (padlen > 0) {
                        /* insert a PadN option for alignment */
                        *optp++ = IP6OPT_PADN;
                        *optp++ = padlen - 2;
                        memset(optp, 0, padlen - 2);
                        optp += (padlen - 2);
                }

                *optp++ = type;
                *optp++ = len;

                *databufp = optp;
        }

        return (currentlen);
}

int
inet6_opt_finish(void *extbuf, socklen_t extlen, int offset)
{
        int updatelen = offset > 0 ? (1 + ((offset - 1) | 7)) : 0;

        if (extbuf) {
                u_int8_t *padp;
                int padlen = updatelen - offset;

                if (updatelen > extlen)
                        return (-1);

                padp = (u_int8_t *)extbuf + offset;
                if (padlen == 1)
                        *padp = IP6OPT_PAD1;
                else if (padlen > 0) {
                        *padp++ = IP6OPT_PADN;
                        *padp++ = (padlen - 2);
                        memset(padp, 0, padlen - 2);
                }
        }

        return (updatelen);
}

int
inet6_opt_set_val(void *databuf, int offset, void *val, socklen_t vallen)
{

        memcpy((u_int8_t *)databuf + offset, val, vallen);
        return (offset + vallen);
}

int
inet6_opt_next(void *extbuf, socklen_t extlen, int offset, u_int8_t *typep,
               socklen_t *lenp, void **databufp)
{
        u_int8_t *optp, *lim;
        int optlen;

        /* Validate extlen. XXX: is the variable really necessary?? */
        if (extlen == 0 || (extlen % 8))
                return (-1);
        lim = (u_int8_t *)extbuf + extlen;

        /*
         * If this is the first time this function called for this options
         * header, simply return the 1st option.
         * Otherwise, search the option list for the next option.
         */
        if (offset == 0)
                optp = (u_int8_t *)((struct ip6_hbh *)extbuf + 1);
        else
                optp = (u_int8_t *)extbuf + offset;

        /* Find the next option skipping any padding options. */
        while (optp < lim) {
                switch(*optp) {
                case IP6OPT_PAD1:
                        optp++;
                        break;
                case IP6OPT_PADN:
                        if ((optlen = ip6optlen(optp, lim)) == 0)
                                goto optend;
                        optp += optlen;
                        break;
                default:        /* found */
                        if ((optlen = ip6optlen(optp, lim)) == 0)
                                goto optend;
                        *typep = *optp;
                        *lenp = optlen - 2;
                        *databufp = optp + 2;
                        return (optp + optlen - (u_int8_t *)extbuf);
                }
        }

  optend:
        *databufp = NULL; /* for safety */
        return (-1);
}

int
inet6_opt_find(void *extbuf, socklen_t extlen, int offset, u_int8_t type,
               socklen_t *lenp, void **databufp)
{
        u_int8_t *optp, *lim;
        int optlen;

        /* Validate extlen. XXX: is the variable really necessary?? */
        if (extlen == 0 || (extlen % 8))
                return (-1);
        lim = (u_int8_t *)extbuf + extlen;

        /*
         * If this is the first time this function called for this options
         * header, simply return the 1st option.
         * Otherwise, search the option list for the next option.
         */
        if (offset == 0)
                optp = (u_int8_t *)((struct ip6_hbh *)extbuf + 1);
        else
                optp = (u_int8_t *)extbuf + offset;

        /* Find the specified option */
        while (optp < lim) {
                if ((optlen = ip6optlen(optp, lim)) == 0)
                        goto optend;

                if (*optp == type) { /* found */
                        *lenp = optlen - 2;
                        *databufp = optp + 2;
                        return (optp + optlen - (u_int8_t *)extbuf);
                }

                optp += optlen;
        }

  optend:
        *databufp = NULL; /* for safety */
        return (-1);
}

int
inet6_opt_get_val(void *databuf, int offset, void *val, socklen_t vallen)
{

        /* we can't assume alignment here */
        memcpy(val, (u_int8_t *)databuf + offset, vallen);

        return (offset + vallen);
}