/*      $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);
}

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