lib/libc/net/ip6opt.c

   1 /*      $NetBSD: ip6opt.c,v 1.12 2009/01/30 23:43:30 lukem Exp $        */
   2
   3 /*
   4  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the project nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 __RCSID("$NetBSD: ip6opt.c,v 1.12 2009/01/30 23:43:30 lukem Exp $");
  35 #endif /* LIBC_SCCS and not lint */
  36
  37 #include "namespace.h"
  38 #include <sys/param.h>
  39 #include <sys/types.h>
  40 #include <sys/socket.h>
  41
  42 #include <netinet/in.h>
  43 #include <netinet/ip6.h>
  44
  45 #include <assert.h>
  46 #include <string.h>
  47 #include <stdio.h>
  48
  49 #ifdef __weak_alias
  50 __weak_alias(inet6_option_alloc,_inet6_option_alloc)
  51 __weak_alias(inet6_option_append,_inet6_option_append)
  52 __weak_alias(inet6_option_find,_inet6_option_find)
  53 __weak_alias(inet6_option_init,_inet6_option_init)
  54 __weak_alias(inet6_option_next,_inet6_option_next)
  55 __weak_alias(inet6_option_space,_inet6_option_space)
  56 __weak_alias(inet6_opt_init, _inet6_opt_init)
  57 __weak_alias(inet6_opt_append, _inet6_opt_append)
  58 __weak_alias(inet6_opt_finish, _inet6_opt_finish)
  59 __weak_alias(inet6_opt_set_val, _inet6_opt_set_val)
  60 __weak_alias(inet6_opt_next, _inet6_opt_next)
  61 __weak_alias(inet6_opt_find, _inet6_opt_find)
  62 __weak_alias(inet6_opt_get_val, _inet6_opt_get_val)
  63 #endif
  64
  65 static int ip6optlen(u_int8_t *opt, u_int8_t *lim);
  66 static void inet6_insert_padopt(u_char *p, size_t len);
  67
  68 /*
  69  * This function returns the number of bytes required to hold an option
  70  * when it is stored as ancillary data, including the cmsghdr structure
  71  * at the beginning, and any padding at the end (to make its size a
  72  * multiple of 8 bytes).  The argument is the size of the structure
  73  * defining the option, which must include any pad bytes at the
  74  * beginning (the value y in the alignment term "xn + y"), the type
  75  * byte, the length byte, and the option data.
  76  */
  77 int
  78 inet6_option_space(nbytes)
  79         int nbytes;
  80 {
  81         nbytes += 2;    /* we need space for nxt-hdr and length fields */
  82         return(CMSG_SPACE((nbytes + 7) & ~7));
  83 }
  84
  85 /*
  86  * This function is called once per ancillary data object that will
  87  * contain either Hop-by-Hop or Destination options.  It returns 0 on
  88  * success or -1 on an error.
  89  */
  90 int
  91 inet6_option_init(bp, cmsgp, type)
  92         void *bp;
  93         struct cmsghdr **cmsgp;
  94         int type;
  95 {
  96         register struct cmsghdr *ch;
  97
  98         _DIAGASSERT(bp != NULL);
  99         _DIAGASSERT(cmsgp != NULL);
 100
 101         ch = (struct cmsghdr *)bp;
 102
 103         /* argument validation */
 104         if (type != IPV6_HOPOPTS && type != IPV6_DSTOPTS)
 105                 return(-1);
 106
 107         ch->cmsg_level = IPPROTO_IPV6;
 108         ch->cmsg_type = type;
 109         ch->cmsg_len = CMSG_LEN(0);
 110
 111         *cmsgp = ch;
 112         return(0);
 113 }
 114
 115 /*
 116  * This function appends a Hop-by-Hop option or a Destination option
 117  * into an ancillary data object that has been initialized by
 118  * inet6_option_init().  This function returns 0 if it succeeds or -1 on
 119  * an error.
 120  * multx is the value x in the alignment term "xn + y" described
 121  * earlier.  It must have a value of 1, 2, 4, or 8.
 122  * plusy is the value y in the alignment term "xn + y" described
 123  * earlier.  It must have a value between 0 and 7, inclusive.
 124  */
 125 int
 126 inet6_option_append(cmsg, typep, multx, plusy)
 127         struct cmsghdr *cmsg;
 128         const u_int8_t *typep;
 129         int multx;
 130         int plusy;
 131 {
 132         size_t padlen, optlen, off;
 133         register u_char *bp;
 134         struct ip6_ext *eh;
 135
 136         _DIAGASSERT(cmsg != NULL);
 137         _DIAGASSERT(typep != NULL);
 138
 139         bp = (u_char *)(void *)cmsg + cmsg->cmsg_len;
 140         eh = (struct ip6_ext *)(void *)CMSG_DATA(cmsg);
 141
 142         /* argument validation */
 143         if (multx != 1 && multx != 2 && multx != 4 && multx != 8)
 144                 return(-1);
 145         if (plusy < 0 || plusy > 7)
 146                 return(-1);
 147
 148         /*
 149          * If this is the first option, allocate space for the
 150          * first 2 bytes(for next header and length fields) of
 151          * the option header.
 152          */
 153         if (bp == (u_char *)(void *)eh) {
 154                 bp += 2;
 155                 cmsg->cmsg_len += 2;
 156         }
 157
 158         /* calculate pad length before the option. */
 159         off = bp - (u_char *)(void *)eh;
 160         padlen = (((off % multx) + (multx - 1)) & ~(multx - 1)) -
 161                 (off % multx);
 162         padlen += plusy;
 163         padlen %= multx;        /* keep the pad as short as possible */
 164         /* insert padding */
 165         inet6_insert_padopt(bp, padlen);
 166         cmsg->cmsg_len += padlen;
 167         bp += padlen;
 168
 169         /* copy the option */
 170         if (typep[0] == IP6OPT_PAD1)
 171                 optlen = 1;
 172         else
 173                 optlen = typep[1] + 2;
 174         memcpy(bp, typep, (size_t)optlen);
 175         bp += optlen;
 176         cmsg->cmsg_len += optlen;
 177
 178         /* calculate pad length after the option and insert the padding */
 179         off = bp - (u_char *)(void *)eh;
 180         padlen = ((off + 7) & ~7) - off;
 181         inet6_insert_padopt(bp, padlen);
 182         bp += padlen;
 183         cmsg->cmsg_len += padlen;
 184
 185         /* update the length field of the ip6 option header */
 186         off = bp - (u_char *)(void *)eh;
 187         eh->ip6e_len = (off >> 3) - 1;
 188
 189         return(0);
 190 }
 191
 192 /*
 193  * This function appends a Hop-by-Hop option or a Destination option
 194  * into an ancillary data object that has been initialized by
 195  * inet6_option_init().  This function returns a pointer to the 8-bit
 196  * option type field that starts the option on success, or NULL on an
 197  * error.
 198  * The difference between this function and inet6_option_append() is
 199  * that the latter copies the contents of a previously built option into
 200  * the ancillary data object while the current function returns a
 201  * pointer to the space in the data object where the option's TLV must
 202  * then be built by the caller.
 203  *
 204  */
 205 u_int8_t *
 206 inet6_option_alloc(cmsg, datalen, multx, plusy)
 207         struct cmsghdr *cmsg;
 208         int datalen;
 209         int multx;
 210         int plusy;
 211 {
 212         size_t padlen, off;
 213         register u_int8_t *bp;
 214         u_int8_t *retval;
 215         struct ip6_ext *eh;
 216
 217         _DIAGASSERT(cmsg != NULL);
 218
 219         bp = (u_char *)(void *)cmsg + cmsg->cmsg_len;
 220         eh = (struct ip6_ext *)(void *)CMSG_DATA(cmsg);
 221
 222         /* argument validation */
 223         if (multx != 1 && multx != 2 && multx != 4 && multx != 8)
 224                 return(NULL);
 225         if (plusy < 0 || plusy > 7)
 226                 return(NULL);
 227
 228         /*
 229          * If this is the first option, allocate space for the
 230          * first 2 bytes(for next header and length fields) of
 231          * the option header.
 232          */
 233         if (bp == (u_char *)(void *)eh) {
 234                 bp += 2;
 235                 cmsg->cmsg_len += 2;
 236         }
 237
 238         /* calculate pad length before the option. */
 239         off = bp - (u_char *)(void *)eh;
 240         padlen = (((off % multx) + (multx - 1)) & ~(multx - 1)) -
 241                 (off % multx);
 242         padlen += plusy;
 243         padlen %= multx;        /* keep the pad as short as possible */
 244         /* insert padding */
 245         inet6_insert_padopt(bp, padlen);
 246         cmsg->cmsg_len += padlen;
 247         bp += padlen;
 248
 249         /* keep space to store specified length of data */
 250         retval = bp;
 251         bp += datalen;
 252         cmsg->cmsg_len += datalen;
 253
 254         /* calculate pad length after the option and insert the padding */
 255         off = bp - (u_char *)(void *)eh;
 256         padlen = ((off + 7) & ~7) - off;
 257         inet6_insert_padopt(bp, padlen);
 258         bp += padlen;
 259         cmsg->cmsg_len += padlen;
 260
 261         /* update the length field of the ip6 option header */
 262         off = bp - (u_char *)(void *)eh;
 263         eh->ip6e_len = (off >> 3) - 1;
 264
 265         return(retval);
 266 }
 267
 268 /*
 269  * This function processes the next Hop-by-Hop option or Destination
 270  * option in an ancillary data object.  If another option remains to be
 271  * processed, the return value of the function is 0 and *tptrp points to
 272  * the 8-bit option type field (which is followed by the 8-bit option
 273  * data length, followed by the option data).  If no more options remain
 274  * to be processed, the return value is -1 and *tptrp is NULL.  If an
 275  * error occurs, the return value is -1 and *tptrp is not NULL.
 276  * (RFC 2292, 6.3.5)
 277  */
 278 int
 279 inet6_option_next(cmsg, tptrp)
 280         const struct cmsghdr *cmsg;
 281         u_int8_t **tptrp;
 282 {
 283         struct ip6_ext *ip6e;
 284         int hdrlen, optlen;
 285         u_int8_t *lim;
 286
 287         _DIAGASSERT(cmsg != NULL);
 288         _DIAGASSERT(tptrp != NULL);
 289
 290         if (cmsg->cmsg_level != IPPROTO_IPV6 ||
 291             (cmsg->cmsg_type != IPV6_HOPOPTS &&
 292              cmsg->cmsg_type != IPV6_DSTOPTS))
 293                 return(-1);
 294
 295         /* message length validation */
 296         if (cmsg->cmsg_len < CMSG_SPACE(sizeof(struct ip6_ext)))
 297                 return(-1);
 298         ip6e = __UNCONST(CCMSG_DATA(cmsg));
 299         hdrlen = (ip6e->ip6e_len + 1) << 3;
 300         if (cmsg->cmsg_len < CMSG_SPACE(hdrlen))
 301                 return(-1);
 302
 303         /*
 304          * If the caller does not specify the starting point,
 305          * simply return the 1st option.
 306          * Otherwise, search the option list for the next option.
 307          */
 308         lim = (u_int8_t *)(void *)ip6e + hdrlen;
 309         if (*tptrp == NULL)
 310                 *tptrp = (u_int8_t *)(void *)(ip6e + 1);
 311         else {
 312                 if ((optlen = ip6optlen(*tptrp, lim)) == 0)
 313                         return(-1);
 314
 315                 *tptrp = *tptrp + optlen;
 316         }
 317         if (*tptrp >= lim) {    /* there is no option */
 318                 *tptrp = NULL;
 319                 return(-1);
 320         }
 321         /*
 322          * Finally, checks if the next option is safely stored in the
 323          * cmsg data.
 324          */
 325         if (ip6optlen(*tptrp, lim) == 0)
 326                 return(-1);
 327         else
 328                 return(0);
 329 }
 330
 331 /*
 332  * This function is similar to the inet6_option_next() function,
 333  * except this function lets the caller specify the option type to be
 334  * searched for, instead of always returning the next option in the
 335  * ancillary data object.
 336  * Note: RFC 2292 says the type of tptrp is u_int8_t *, but we think
 337  *       it's a typo. The variable should be type of u_int8_t **.
 338  */
 339 int
 340 inet6_option_find(cmsg, tptrp, type)
 341         const struct cmsghdr *cmsg;
 342         u_int8_t **tptrp;
 343         int type;
 344 {
 345         struct ip6_ext *ip6e;
 346         int hdrlen, optlen;
 347         u_int8_t *optp, *lim;
 348
 349         _DIAGASSERT(cmsg != NULL);
 350         _DIAGASSERT(tptrp != NULL);
 351
 352         if (cmsg->cmsg_level != IPPROTO_IPV6 ||
 353             (cmsg->cmsg_type != IPV6_HOPOPTS &&
 354              cmsg->cmsg_type != IPV6_DSTOPTS))
 355                 return(-1);
 356
 357         /* message length validation */
 358         if (cmsg->cmsg_len < CMSG_SPACE(sizeof(struct ip6_ext)))
 359                 return(-1);
 360         ip6e = __UNCONST(CCMSG_DATA(cmsg));
 361         hdrlen = (ip6e->ip6e_len + 1) << 3;
 362         if (cmsg->cmsg_len < CMSG_SPACE(hdrlen))
 363                 return(-1);
 364
 365         /*
 366          * If the caller does not specify the starting point,
 367          * search from the beginning of the option list.
 368          * Otherwise, search from *the next option* of the specified point.
 369          */
 370         lim = (u_int8_t *)(void *)ip6e + hdrlen;
 371         if (*tptrp == NULL)
 372                 *tptrp = (u_int8_t *)(void *)(ip6e + 1);
 373         else {
 374                 if ((optlen = ip6optlen(*tptrp, lim)) == 0)
 375                         return(-1);
 376
 377                 *tptrp = *tptrp + optlen;
 378         }
 379         for (optp = *tptrp; optp < lim; optp += optlen) {
 380                 if (*optp == type) {
 381                         *tptrp = optp;
 382                         return(0);
 383                 }
 384                 if ((optlen = ip6optlen(optp, lim)) == 0)
 385                         return(-1);
 386         }
 387
 388         /* search failed */
 389         *tptrp = NULL;
 390         return(-1);
 391 }
 392
 393 /*
 394  * Calculate the length of a given IPv6 option. Also checks
 395  * if the option is safely stored in user's buffer according to the
 396  * calculated length and the limitation of the buffer.
 397  */
 398 static int
 399 ip6optlen(opt, lim)
 400         u_int8_t *opt, *lim;
 401 {
 402         int optlen;
 403
 404         _DIAGASSERT(opt != NULL);
 405         _DIAGASSERT(lim != NULL);
 406
 407         if (*opt == IP6OPT_PAD1)
 408                 optlen = 1;
 409         else {
 410                 /* is there enough space to store type and len? */
 411                 if (opt + 2 > lim)
 412                         return(0);
 413                 optlen = *(opt + 1) + 2;
 414         }
 415         if (opt + optlen <= lim)
 416                 return(optlen);
 417
 418         return(0);
 419 }
 420
 421 static void
 422 inet6_insert_padopt(u_char *p, size_t len)
 423 {
 424
 425         _DIAGASSERT(p != NULL);
 426
 427         switch(len) {
 428          case 0:
 429                  return;
 430          case 1:
 431                  p[0] = IP6OPT_PAD1;
 432                  return;
 433          default:
 434                  p[0] = IP6OPT_PADN;
 435                  p[1] = len - 2;
 436                  memset(&p[2], 0, len - 2);
 437                  return;
 438         }
 439 }
 440
 441 /*
 442  * The following functions are defined in RFC3542, which is a successor
 443  * of RFC2292.
 444  */
 445
 446 int
 447 inet6_opt_init(void *extbuf, socklen_t extlen)
 448 {
 449         struct ip6_ext *ext = (struct ip6_ext *)extbuf;
 450
 451         if (extlen % 8)
 452                 return (-1);
 453
 454         if (ext) {
 455                 if (extlen == 0)
 456                         return (-1);
 457                 ext->ip6e_len = (extlen >> 3) - 1;
 458         }
 459
 460         return (2);             /* sizeof the next and the length fields */
 461 }
 462
 463 int
 464 inet6_opt_append(void *extbuf, socklen_t extlen, int offset, u_int8_t type,
 465                  socklen_t len, u_int8_t align, void **databufp)
 466 {
 467         int currentlen = offset;
 468         size_t padlen = 0;
 469
 470         /*
 471          * The option type must have a value from 2 to 255, inclusive.
 472          * (0 and 1 are reserved for the Pad1 and PadN options, respectively.)
 473          */
 474         if (type < 2)
 475                 return (-1);
 476
 477         /*
 478          * The option data length must have a value between 0 and 255,
 479          * inclusive, and is the length of the option data that follows.
 480          */
 481         if (len > 255)
 482                 return (-1);
 483
 484         /*
 485          * The align parameter must have a value of 1, 2, 4, or 8.
 486          * The align value can not exceed the value of len.
 487          */
 488         if (align != 1 && align != 2 && align != 4 && align != 8)
 489                 return (-1);
 490         if (align > len)
 491                 return (-1);
 492
 493         /* Calculate the padding length. */
 494         currentlen += 2 + len;  /* 2 means "type + len" */
 495         if (currentlen % align)
 496                 padlen = align - (currentlen % align);
 497
 498         /* The option must fit in the extension header buffer. */
 499         currentlen += padlen;
 500         if (extlen &&           /* XXX: right? */
 501             (socklen_t)currentlen > extlen)
 502                 return (-1);
 503
 504         if (extbuf) {
 505                 u_int8_t *optp = (u_int8_t *)extbuf + offset;
 506
 507                 if (padlen == 1) {
 508                         /* insert a Pad1 option */
 509                         *optp = IP6OPT_PAD1;
 510                         optp++;
 511                 } else if (padlen > 0) {
 512                         /* insert a PadN option for alignment */
 513                         *optp++ = IP6OPT_PADN;
 514                         *optp++ = padlen - 2;
 515                         memset(optp, 0, padlen - 2);
 516                         optp += (padlen - 2);
 517                 }
 518
 519                 *optp++ = type;
 520                 *optp++ = len;
 521
 522                 *databufp = optp;
 523         }
 524
 525         return (currentlen);
 526 }
 527
 528 int
 529 inet6_opt_finish(void *extbuf, socklen_t extlen, int offset)
 530 {
 531         int updatelen = offset > 0 ? (1 + ((offset - 1) | 7)) : 0;
 532
 533         if (extbuf) {
 534                 u_int8_t *padp;
 535                 size_t padlen = updatelen - offset;
 536
 537                 if ((socklen_t)updatelen > extlen)
 538                         return (-1);
 539
 540                 padp = (u_int8_t *)extbuf + offset;
 541                 if (padlen == 1)
 542                         *padp = IP6OPT_PAD1;
 543                 else if (padlen > 0) {
 544                         *padp++ = IP6OPT_PADN;
 545                         *padp++ = (padlen - 2);
 546                         memset(padp, 0, padlen - 2);
 547                 }
 548         }
 549
 550         return (updatelen);
 551 }
 552
 553 int
 554 inet6_opt_set_val(void *databuf, int offset, void *val, socklen_t vallen)
 555 {
 556
 557         memcpy((u_int8_t *)databuf + offset, val, vallen);
 558         return (offset + vallen);
 559 }
 560
 561 int
 562 inet6_opt_next(void *extbuf, socklen_t extlen, int offset, u_int8_t *typep,
 563                socklen_t *lenp, void **databufp)
 564 {
 565         u_int8_t *optp, *lim;
 566         int optlen;
 567
 568         /* Validate extlen. XXX: is the variable really necessary?? */
 569         if (extlen == 0 || (extlen % 8))
 570                 return (-1);
 571         lim = (u_int8_t *)extbuf + extlen;
 572
 573         /*
 574          * If this is the first time this function called for this options
 575          * header, simply return the 1st option.
 576          * Otherwise, search the option list for the next option.
 577          */
 578         if (offset == 0)
 579                 optp = (u_int8_t *)(void *)((struct ip6_hbh *)extbuf + 1);
 580         else
 581                 optp = (u_int8_t *)extbuf + offset;
 582
 583         /* Find the next option skipping any padding options. */
 584         while (optp < lim) {
 585                 switch(*optp) {
 586                 case IP6OPT_PAD1:
 587                         optp++;
 588                         break;
 589                 case IP6OPT_PADN:
 590                         if ((optlen = ip6optlen(optp, lim)) == 0)
 591                                 goto optend;
 592                         optp += optlen;
 593                         break;
 594                 default:        /* found */
 595                         if ((optlen = ip6optlen(optp, lim)) == 0)
 596                                 goto optend;
 597                         *typep = *optp;
 598                         *lenp = optlen - 2;
 599                         *databufp = optp + 2;
 600                         return (optp + optlen - (u_int8_t *)extbuf);
 601                 }
 602         }
 603
 604   optend:
 605         *databufp = NULL; /* for safety */
 606         return (-1);
 607 }
 608
 609 int
 610 inet6_opt_find(void *extbuf, socklen_t extlen, int offset, u_int8_t type,
 611                socklen_t *lenp, void **databufp)
 612 {
 613         u_int8_t *optp, *lim;
 614         int optlen;
 615
 616         /* Validate extlen. XXX: is the variable really necessary?? */
 617         if (extlen == 0 || (extlen % 8))
 618                 return (-1);
 619         lim = (u_int8_t *)extbuf + extlen;
 620
 621         /*
 622          * If this is the first time this function called for this options
 623          * header, simply return the 1st option.
 624          * Otherwise, search the option list for the next option.
 625          */
 626         if (offset == 0)
 627                 optp = (u_int8_t *)(void *)((struct ip6_hbh *)extbuf + 1);
 628         else
 629                 optp = (u_int8_t *)extbuf + offset;
 630
 631         /* Find the specified option */
 632         while (optp < lim) {
 633                 if ((optlen = ip6optlen(optp, lim)) == 0)
 634                         goto optend;
 635
 636                 if (*optp == type) { /* found */
 637                         *lenp = optlen - 2;
 638                         *databufp = optp + 2;
 639                         return (optp + optlen - (u_int8_t *)extbuf);
 640                 }
 641
 642                 optp += optlen;
 643         }
 644
 645   optend:
 646         *databufp = NULL; /* for safety */
 647         return (-1);
 648 }
 649
 650 int
 651 inet6_opt_get_val(void *databuf, int offset, void *val, socklen_t vallen)
 652 {
 653
 654         /* we can't assume alignment here */
 655         memcpy(val, (u_int8_t *)databuf + offset, vallen);
 656
 657         return (offset + vallen);
 658 }