text: /*	$KAME: ip6opt.c,v 1.13 2003/06/06 10:08:20 suz 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.
   *
   * $FreeBSD: src/lib/libc/net/ip6opt.c,v 1.8 2005/07/19 18:13:58 ume Exp $
   * $DragonFly: src/lib/libc/net/ip6opt.c,v 1.6 2007/05/29 10:58:11 hasso Exp $
   */
  
  #include <sys/param.h>
  #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);
  static void inet6_insert_padopt(u_char *p, int 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)
  {
  	nbytes += 2;	/* we need space for nxt-hdr and length fields */
  	return(CMSG_SPACE((nbytes + 7) & ~7));
  }
  
  /*
   * 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)
  {
  	struct cmsghdr *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 u_int8_t *typep, int multx,
  		    int plusy)
  {
  	int padlen, optlen, off;
  	u_char *bp = (u_char *)cmsg + cmsg->cmsg_len;
  	struct ip6_ext *eh = (struct ip6_ext *)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 == (u_char *)eh) {
  		bp += 2;
  		cmsg->cmsg_len += 2;
  	}
  
  	/* calculate pad length before the option. */
  	off = bp - (u_char *)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 += padlen;
  	bp += padlen;
  
  	/* copy the option */
  	if (typep[0] == IP6OPT_PAD1)
  		optlen = 1;
  	else
  		optlen = typep[1] + 2;
  	memcpy(bp, typep, optlen);
  	bp += optlen;
  	cmsg->cmsg_len += optlen;
  
  	/* calculate pad length after the option and insert the padding */
  	off = bp - (u_char *)eh;
  	padlen = ((off + 7) & ~7) - off;
  	inet6_insert_padopt(bp, padlen);
  	bp += padlen;
  	cmsg->cmsg_len += padlen;
  
  	/* update the length field of the ip6 option header */
  	eh->ip6e_len = ((bp - (u_char *)eh) >> 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.
   * 
   */
  u_int8_t *
  inet6_option_alloc(struct cmsghdr *cmsg, int datalen, int multx, int plusy)
  {
  	int padlen, off;
  	u_int8_t *bp = (u_char *)cmsg + cmsg->cmsg_len;
  	u_int8_t *retval;
  	struct ip6_ext *eh = (struct ip6_ext *)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 == (u_char *)eh) {
  		bp += 2;
  		cmsg->cmsg_len += 2;
  	}
  
  	/* calculate pad length before the option. */
  	off = bp - (u_char *)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 += 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 - (u_char *)eh;
  	padlen = ((off + 7) & ~7) - off;
  	inet6_insert_padopt(bp, padlen);
  	bp += padlen;
  	cmsg->cmsg_len += padlen;
  
  	/* update the length field of the ip6 option header */
  	eh->ip6e_len = ((bp - (u_char *)eh) >> 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, u_int8_t **tptrp)
  {
  	struct ip6_ext *ip6e;
  	int hdrlen, optlen;
  	u_int8_t *lim;
  
  	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 = (struct ip6_ext *)CMSG_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 = (u_int8_t *)ip6e + hdrlen;
  	if (*tptrp == NULL)
  		*tptrp = (u_int8_t *)(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 u_int8_t *, but we think
   *       it's a typo. The variable should be type of u_int8_t **.
   */
  int
  inet6_option_find(const struct cmsghdr *cmsg, u_int8_t **tptrp, int type)
  {
  	struct ip6_ext *ip6e;
  	int hdrlen, optlen;
  	u_int8_t *optp, *lim;
  
  	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 = (struct ip6_ext *)CMSG_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 = (u_int8_t *)ip6e + hdrlen;
  	if (*tptrp == NULL)
  		*tptrp = (u_int8_t *)(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(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);
  }
  
  static void
  inet6_insert_padopt(u_char *p, int len)
  {
  	switch(len) {
  	case 0:
  		return;
  	case 1:
  		p[0] = IP6OPT_PAD1;
  		return;
  	default:
  		p[0] = IP6OPT_PADN;
  		p[1] = 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 (extlen < 0 || (extlen % 8))
  		return(-1);
  
  	if (ext) {
  		if (extlen == 0)
  			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 (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 < 0 || 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);
  }
  