/*      $NetBSD: ip6opt.c,v 1.15 2014/02/07 02:36:06 christos 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/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: ip6opt.c,v 1.15 2014/02/07 02:36:06 christos Exp $");
#endif /* LIBC_SCCS and not lint */

#include "namespace.h"
#include <sys/param.h>
#include <sys/types.h>
#include <sys/socket.h>

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

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

#ifdef __weak_alias
__weak_alias(inet6_option_alloc,_inet6_option_alloc)
__weak_alias(inet6_option_append,_inet6_option_append)
__weak_alias(inet6_option_find,_inet6_option_find)
__weak_alias(inet6_option_init,_inet6_option_init)
__weak_alias(inet6_option_next,_inet6_option_next)
__weak_alias(inet6_option_space,_inet6_option_space)
__weak_alias(inet6_opt_init, _inet6_opt_init)
__weak_alias(inet6_opt_append, _inet6_opt_append)
__weak_alias(inet6_opt_finish, _inet6_opt_finish)
__weak_alias(inet6_opt_set_val, _inet6_opt_set_val)
__weak_alias(inet6_opt_next, _inet6_opt_next)
__weak_alias(inet6_opt_find, _inet6_opt_find)
__weak_alias(inet6_opt_get_val, _inet6_opt_get_val)
#endif

static int ip6optlen(uint8_t *opt, uint8_t *lim);
static void inet6_insert_padopt(uint8_t *p, size_t len);

/*
 * This function returns the number of bytes required to hold an option
 * when it is stored as ancillary data, including the cmsghdr structure
 * at the beginning, and any padding at the end (to make its size a
 * multiple of 8 bytes).  The argument is the size of the structure
 * defining the option, which must include any pad bytes at the
 * beginning (the value y in the alignment term "xn + y"), the type
 * byte, the length byte, and the option data.
 */
int
inet6_option_space(int nbytes)
{
        size_t sp;
        nbytes += 2;    /* we need space for nxt-hdr and length fields */
        sp = CMSG_SPACE((nbytes + 7) & ~7);
        _DIAGASSERT(__type_fit(int, sp));
        return (int)sp;
}

/*
 * This function is called once per ancillary data object that will
 * contain either Hop-by-Hop or Destination options.  It returns 0 on
 * success or -1 on an error.
 */
int
inet6_option_init(void *bp, struct cmsghdr **cmsgp, int type)
{
        register struct cmsghdr *ch;

        _DIAGASSERT(bp != NULL);
        _DIAGASSERT(cmsgp != NULL);

        ch = (struct cmsghdr *)bp;

        /* argument validation */
        if (type != IPV6_HOPOPTS && type != IPV6_DSTOPTS)
                return(-1);
        
        ch->cmsg_level = IPPROTO_IPV6;
        ch->cmsg_type = type;
        ch->cmsg_len = CMSG_LEN(0);

        *cmsgp = ch;
        return(0);
}

/*
 * This function appends a Hop-by-Hop option or a Destination option
 * into an ancillary data object that has been initialized by
 * inet6_option_init().  This function returns 0 if it succeeds or -1 on
 * an error.
 * multx is the value x in the alignment term "xn + y" described
 * earlier.  It must have a value of 1, 2, 4, or 8.
 * plusy is the value y in the alignment term "xn + y" described
 * earlier.  It must have a value between 0 and 7, inclusive.
 */
int
inet6_option_append(struct cmsghdr *cmsg, const uint8_t *typep, int multx,
        int plusy)
{
        size_t padlen, optlen, off;
        register uint8_t *bp;
        struct ip6_ext *eh;

        _DIAGASSERT(cmsg != NULL);
        _DIAGASSERT(typep != NULL);

        bp = (uint8_t *)(void *)cmsg + cmsg->cmsg_len;
        eh = (struct ip6_ext *)(void *)CMSG_DATA(cmsg);

        /* argument validation */
        if (multx != 1 && multx != 2 && multx != 4 && multx != 8)
                return(-1);
        if (plusy < 0 || plusy > 7)
                return(-1);

        /*
         * If this is the first option, allocate space for the
         * first 2 bytes(for next header and length fields) of
         * the option header.
         */
        if (bp == (uint8_t *)(void *)eh) {
                bp += 2;
                cmsg->cmsg_len += 2;
        }

        /* calculate pad length before the option. */
        off = bp - (uint8_t *)(void *)eh;
        padlen = (((off % multx) + (multx - 1)) & ~(multx - 1)) -
                (off % multx);
        padlen += plusy;
        padlen %= multx;        /* keep the pad as short as possible */
        /* insert padding */
        inet6_insert_padopt(bp, padlen);
        _DIAGASSERT(__type_fit(socklen_t, padlen + cmsg->cmsg_len));
        cmsg->cmsg_len += (socklen_t)padlen;
        bp += padlen;

        /* copy the option */
        if (typep[0] == IP6OPT_PAD1)
                optlen = 1;
        else
                optlen = typep[1] + 2;
        memcpy(bp, typep, (size_t)optlen);
        bp += optlen;
        _DIAGASSERT(__type_fit(socklen_t, optlen + cmsg->cmsg_len));
        cmsg->cmsg_len += (socklen_t)optlen;

        /* calculate pad length after the option and insert the padding */
        off = bp - (uint8_t *)(void *)eh;
        padlen = ((off + 7) & ~7) - off;
        inet6_insert_padopt(bp, padlen);
        bp += padlen;
        _DIAGASSERT(__type_fit(socklen_t, padlen + cmsg->cmsg_len));
        cmsg->cmsg_len += (socklen_t)padlen;

        /* update the length field of the ip6 option header */
        off = bp - (uint8_t *)(void *)eh;
        _DIAGASSERT(__type_fit(uint8_t, (off >> 3) - 1));
        eh->ip6e_len = (uint8_t)((off >> 3) - 1);

        return(0);
}

/*
 * This function appends a Hop-by-Hop option or a Destination option
 * into an ancillary data object that has been initialized by
 * inet6_option_init().  This function returns a pointer to the 8-bit
 * option type field that starts the option on success, or NULL on an
 * error.
 * The difference between this function and inet6_option_append() is
 * that the latter copies the contents of a previously built option into
 * the ancillary data object while the current function returns a
 * pointer to the space in the data object where the option's TLV must
 * then be built by the caller.
 * 
 */
uint8_t *
inet6_option_alloc(struct cmsghdr *cmsg, int datalen, int multx, int plusy)
{
        size_t padlen, off;
        register uint8_t *bp;
        uint8_t *retval;
        struct ip6_ext *eh;

        _DIAGASSERT(cmsg != NULL);

        bp = (uint8_t *)(void *)cmsg + cmsg->cmsg_len;
        eh = (struct ip6_ext *)(void *)CMSG_DATA(cmsg);

        /* argument validation */
        if (multx != 1 && multx != 2 && multx != 4 && multx != 8)
                return(NULL);
        if (plusy < 0 || plusy > 7)
                return(NULL);

        /*
         * If this is the first option, allocate space for the
         * first 2 bytes(for next header and length fields) of
         * the option header.
         */
        if (bp == (uint8_t *)(void *)eh) {
                bp += 2;
                cmsg->cmsg_len += 2;
        }

        /* calculate pad length before the option. */
        off = bp - (uint8_t *)(void *)eh;
        padlen = (((off % multx) + (multx - 1)) & ~(multx - 1)) -
                (off % multx);
        padlen += plusy;
        padlen %= multx;        /* keep the pad as short as possible */
        /* insert padding */
        inet6_insert_padopt(bp, padlen);
        cmsg->cmsg_len += (socklen_t)padlen;
        bp += padlen;

        /* keep space to store specified length of data */
        retval = bp;
        bp += datalen;
        cmsg->cmsg_len += datalen;

        /* calculate pad length after the option and insert the padding */
        off = bp - (uint8_t *)(void *)eh;
        padlen = ((off + 7) & ~7) - off;
        inet6_insert_padopt(bp, padlen);
        bp += padlen;
        _DIAGASSERT(__type_fit(socklen_t, padlen + cmsg->cmsg_len));
        cmsg->cmsg_len += (socklen_t)padlen;

        /* update the length field of the ip6 option header */
        off = bp - (uint8_t *)(void *)eh;
        _DIAGASSERT(__type_fit(uint8_t, (off >> 3) - 1));
        eh->ip6e_len = (uint8_t)((off >> 3) - 1);

        return(retval);
}

/*
 * This function processes the next Hop-by-Hop option or Destination
 * option in an ancillary data object.  If another option remains to be
 * processed, the return value of the function is 0 and *tptrp points to
 * the 8-bit option type field (which is followed by the 8-bit option
 * data length, followed by the option data).  If no more options remain
 * to be processed, the return value is -1 and *tptrp is NULL.  If an
 * error occurs, the return value is -1 and *tptrp is not NULL.
 * (RFC 2292, 6.3.5)
 */
int
inet6_option_next(const struct cmsghdr *cmsg, uint8_t **tptrp)
{
        struct ip6_ext *ip6e;
        int hdrlen, optlen;
        uint8_t *lim;

        _DIAGASSERT(cmsg != NULL);
        _DIAGASSERT(tptrp != NULL);

        if (cmsg->cmsg_level != IPPROTO_IPV6 ||
            (cmsg->cmsg_type != IPV6_HOPOPTS &&
             cmsg->cmsg_type != IPV6_DSTOPTS))
                return(-1);

        /* message length validation */
        if (cmsg->cmsg_len < CMSG_SPACE(sizeof(struct ip6_ext)))
                return(-1);
        ip6e = __UNCONST(CCMSG_DATA(cmsg));
        hdrlen = (ip6e->ip6e_len + 1) << 3;
        if (cmsg->cmsg_len < CMSG_SPACE(hdrlen))
                return(-1);

        /*
         * If the caller does not specify the starting point,
         * simply return the 1st option.
         * Otherwise, search the option list for the next option.
         */
        lim = (uint8_t *)(void *)ip6e + hdrlen;
        if (*tptrp == NULL)
                *tptrp = (uint8_t *)(void *)(ip6e + 1);
        else {
                if ((optlen = ip6optlen(*tptrp, lim)) == 0)
                        return(-1);

                *tptrp = *tptrp + optlen;
        }
        if (*tptrp >= lim) {    /* there is no option */
                *tptrp = NULL;
                return(-1);
        }
        /*
         * Finally, checks if the next option is safely stored in the
         * cmsg data.
         */
        if (ip6optlen(*tptrp, lim) == 0)
                return(-1);
        else
                return(0);
}

/*
 * This function is similar to the inet6_option_next() function,
 * except this function lets the caller specify the option type to be
 * searched for, instead of always returning the next option in the
 * ancillary data object.
 * Note: RFC 2292 says the type of tptrp is uint8_t *, but we think
 *       it's a typo. The variable should be type of uint8_t **.
 */
int
inet6_option_find(const struct cmsghdr *cmsg, uint8_t **tptrp, int type)
{
        struct ip6_ext *ip6e;
        int hdrlen, optlen;
        uint8_t *optp, *lim;

        _DIAGASSERT(cmsg != NULL);
        _DIAGASSERT(tptrp != NULL);

        if (cmsg->cmsg_level != IPPROTO_IPV6 ||
            (cmsg->cmsg_type != IPV6_HOPOPTS &&
             cmsg->cmsg_type != IPV6_DSTOPTS))
                return(-1);

        /* message length validation */
        if (cmsg->cmsg_len < CMSG_SPACE(sizeof(struct ip6_ext)))
                return(-1);
        ip6e = __UNCONST(CCMSG_DATA(cmsg));
        hdrlen = (ip6e->ip6e_len + 1) << 3;
        if (cmsg->cmsg_len < CMSG_SPACE(hdrlen))
                return(-1);     

        /*
         * If the caller does not specify the starting point,
         * search from the beginning of the option list.
         * Otherwise, search from *the next option* of the specified point.
         */
        lim = (uint8_t *)(void *)ip6e + hdrlen;
        if (*tptrp == NULL)
                *tptrp = (uint8_t *)(void *)(ip6e + 1);
        else {
                if ((optlen = ip6optlen(*tptrp, lim)) == 0)
                        return(-1);

                *tptrp = *tptrp + optlen;
        }
        for (optp = *tptrp; optp < lim; optp += optlen) {
                if (*optp == type) {
                        *tptrp = optp;
                        return(0);
                }
                if ((optlen = ip6optlen(optp, lim)) == 0)
                        return(-1);
        }

        /* search failed */
        *tptrp = NULL;
        return(-1);
}

/*
 * 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(uint8_t *opt, uint8_t *lim)
{
        int optlen;

        _DIAGASSERT(opt != NULL);
        _DIAGASSERT(lim != NULL);

        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);
}

static void
inet6_insert_padopt(uint8_t *p, size_t len)
{

        _DIAGASSERT(p != NULL);

        switch(len) {
         case 0:
                 return;
         case 1:
                 p[0] = IP6OPT_PAD1;
                 return;
         default:
                 p[0] = IP6OPT_PADN;
                 _DIAGASSERT(__type_fit(uint8_t, len - 2));
                 p[1] = (uint8_t)(len - 2); 
                 memset(&p[2], 0, len - 2);
                 return;
        }
}

/*
 * 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, uint8_t type,
                 socklen_t len, uint8_t align, void **databufp)
{
        int currentlen = offset;
        size_t 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 (type < 2)
                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. */
        _DIAGASSERT(__type_fit(int, currentlen + padlen));
        currentlen += (int)padlen;
        if (extlen &&           /* XXX: right? */
            (socklen_t)currentlen > extlen)
                return (-1);

        if (extbuf) {
                uint8_t *optp = (uint8_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;
                        _DIAGASSERT(__type_fit(uint8_t, padlen - 2));
                        *optp++ = (uint8_t)(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) {
                uint8_t *padp;
                size_t padlen = updatelen - offset;

                if ((socklen_t)updatelen > extlen || padlen >= 256 + 2)
                        return (-1);

                padp = (uint8_t *)extbuf + offset;
                if (padlen == 1)
                        *padp = IP6OPT_PAD1;
                else if (padlen > 0) {
                        *padp++ = IP6OPT_PADN;
                        *padp++ = (uint8_t)(padlen - 2);
                        memset(padp, 0, padlen - 2);
                }
        }

        return (updatelen);
}

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

        memcpy((uint8_t *)databuf + offset, val, vallen);
        return (offset + vallen);
}

int
inet6_opt_next(void *extbuf, socklen_t extlen, int offset, uint8_t *typep,
               socklen_t *lenp, void **databufp)
{
        uint8_t *optp, *lim;
        int optlen;

        /* Validate extlen. XXX: is the variable really necessary?? */
        if (extlen == 0 || (extlen % 8))
                return (-1);
        lim = (uint8_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 = (uint8_t *)(void *)((struct ip6_hbh *)extbuf + 1);
        else
                optp = (uint8_t *)extbuf + offset;

        /* Find the next option skipping any padding options. */
        while (optp < lim) {
                ptrdiff_t rv;
                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;
                        rv = optp + optlen - (uint8_t *)extbuf;
                        _DIAGASSERT(__type_fit(int, rv));
                        return (int)rv;
                }
        }

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

int
inet6_opt_find(void *extbuf, socklen_t extlen, int offset, uint8_t type,
               socklen_t *lenp, void **databufp)
{
        uint8_t *optp, *lim;
        int optlen;

        /* Validate extlen. XXX: is the variable really necessary?? */
        if (extlen == 0 || (extlen % 8))
                return (-1);
        lim = (uint8_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 = (uint8_t *)(void *)((struct ip6_hbh *)extbuf + 1);
        else
                optp = (uint8_t *)extbuf + offset;

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

                if (*optp == type) { /* found */
                        ptrdiff_t td;
                        *lenp = optlen - 2;
                        *databufp = optp + 2;
                        td = optp + optlen - (uint8_t *)extbuf;
                        _DIAGASSERT(__type_fit(int, td));
                        return (int)td;
                }

                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, (uint8_t *)databuf + offset, vallen);

        return (offset + vallen);
}