/* $OpenBSD: ip6opt.c,v 1.2 2005/03/25 13:24:12 otto 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 #include #include #include #include #include #include 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 (typep[0] > 255) 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; } }