inet/inet6_option.c

   1 /* Copyright (C) 2003, 2006, 2009 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <assert.h>
  21 #include <string.h>
  22 #include <netinet/in.h>
  23 #include <netinet/ip6.h>
  24 #include <sys/param.h>
  25
  26
  27 static void
  28 internal_function
  29 add_pad (struct cmsghdr *cmsg, int len)
  30 {
  31   unsigned char *p = CMSG_DATA (cmsg) + cmsg->cmsg_len - CMSG_LEN (0);
  32
  33   if (len == 1)
  34     /* Special handling for 1, a one-byte solution.  */
  35     *p++ = IP6OPT_PAD1;
  36   else if (len != 0)
  37     {
  38       /* Multibyte padding.  */
  39       *p++ = IP6OPT_PADN;
  40       *p++ = len - 2;   /* Discount the two header bytes.  */
  41       /* The rest is filled with zero.  */
  42       memset (p, '\0', len - 2);
  43       p += len - 2;
  44     }
  45
  46   /* Account for the bytes.  */
  47   cmsg->cmsg_len += len;
  48 }
  49
  50
  51 static int
  52 get_opt_end (const uint8_t **result, const uint8_t *startp,
  53              const uint8_t *endp)
  54 {
  55   if (startp >= endp)
  56     /* Out of bounds.  */
  57     return -1;
  58
  59   if (*startp == IP6OPT_PAD1)
  60     {
  61       /* Just this one byte.  */
  62       *result = startp + 1;
  63       return 0;
  64     }
  65
  66   /* Now we know there must be at least two bytes.  */
  67   if (startp + 2 > endp
  68       /* Now we can get the length byte.  */
  69       || startp + startp[1] + 2 > endp)
  70     return -1;
  71
  72   *result = startp + startp[1] + 2;
  73
  74   return 0;
  75 }
  76
  77
  78 static uint8_t *option_alloc (struct cmsghdr *cmsg, int datalen, int multx,
  79                               int plusy);
  80
  81
  82 /* RFC 2292, 6.3.1
  83
  84    This function returns the number of bytes required to hold an option
  85    when it is stored as ancillary data, including the cmsghdr structure
  86    at the beginning, and any padding at the end (to make its size a
  87    multiple of 8 bytes).  The argument is the size of the structure
  88    defining the option, which must include any pad bytes at the
  89    beginning (the value y in the alignment term "xn + y"), the type
  90    byte, the length byte, and the option data.  */
  91 int
  92 inet6_option_space (nbytes)
  93      int nbytes;
  94 {
  95   /* Add room for the extension header.  */
  96   nbytes += sizeof (struct ip6_ext);
  97
  98   return CMSG_SPACE (roundup (nbytes, 8));
  99 }
 100 link_warning (inet6_option_space,
 101               "inet6_option_space is obsolete, use the RFC 3542 interfaces")
 102
 103
 104 /* RFC 2292, 6.3.2
 105
 106    This function is called once per ancillary data object that will
 107    contain either Hop-by-Hop or Destination options.  It returns 0 on
 108    success or -1 on an error.  */
 109 int
 110 inet6_option_init (bp, cmsgp, type)
 111      void *bp;
 112      struct cmsghdr **cmsgp;
 113      int type;
 114 {
 115   /* Only Hop-by-Hop or Destination options allowed.  */
 116   if (type != IPV6_HOPOPTS && type != IPV6_DSTOPTS)
 117     return -1;
 118
 119   /* BP is a pointer to the previously allocated space.  */
 120   struct cmsghdr *newp = (struct cmsghdr *) bp;
 121
 122   /* Initialize the message header.
 123
 124      Length: No data yet, only the cmsghdr struct.  */
 125   newp->cmsg_len = CMSG_LEN (0);
 126   /* Originating protocol: obviously IPv6.  */
 127   newp->cmsg_level = IPPROTO_IPV6;
 128   /* Message type.  */
 129   newp->cmsg_type = type;
 130
 131   /* Pass up the result.  */
 132   *cmsgp = newp;
 133
 134   return 0;
 135 }
 136 link_warning (inet6_option_init,
 137               "inet6_option_init is obsolete, use the RFC 3542 interfaces")
 138
 139
 140 /* RFC 2292, 6.3.3
 141
 142    This function appends a Hop-by-Hop option or a Destination option
 143    into an ancillary data object that has been initialized by
 144    inet6_option_init().  This function returns 0 if it succeeds or -1 on
 145    an error.  */
 146 int
 147 inet6_option_append (cmsg, typep, multx, plusy)
 148      struct cmsghdr *cmsg;
 149      const uint8_t *typep;
 150      int multx;
 151      int plusy;
 152 {
 153   /* typep is a pointer to the 8-bit option type.  It is assumed that this
 154      field is immediately followed by the 8-bit option data length field,
 155      which is then followed immediately by the option data.
 156
 157      The option types IP6OPT_PAD1 and IP6OPT_PADN also must be handled.  */
 158   int len = typep[0] == IP6OPT_PAD1 ? 1 : typep[1] + 2;
 159
 160   /* Get the pointer to the space in the message.  */
 161   uint8_t *ptr = option_alloc (cmsg, len, multx, plusy);
 162   if (ptr == NULL)
 163     /* Some problem with the parameters.  */
 164     return -1;
 165
 166   /* Copy the content.  */
 167   memcpy (ptr, typep, len);
 168
 169   return 0;
 170 }
 171 link_warning (inet6_option_append,
 172               "inet6_option_append is obsolete, use the RFC 3542 interfaces")
 173
 174
 175 /* RFC 2292, 6.3.4
 176
 177    This function appends a Hop-by-Hop option or a Destination option
 178    into an ancillary data object that has been initialized by
 179    inet6_option_init().  This function returns a pointer to the 8-bit
 180    option type field that starts the option on success, or NULL on an
 181    error.  */
 182 static uint8_t *
 183 option_alloc (struct cmsghdr *cmsg, int datalen, int multx, int plusy)
 184 {
 185   /* The RFC limits the value of the alignment values.  */
 186   if ((multx != 1 && multx != 2 && multx != 4 && multx != 8)
 187       || ! (plusy >= 0 && plusy <= 7))
 188     return NULL;
 189
 190   /* Current data size.  */
 191   int dsize = cmsg->cmsg_len - CMSG_LEN (0);
 192
 193   /* The first two bytes of the option are for the extended header.  */
 194   if (__builtin_expect (dsize == 0, 0))
 195     {
 196       cmsg->cmsg_len += sizeof (struct ip6_ext);
 197       dsize = sizeof (struct ip6_ext);
 198     }
 199
 200   /* First add padding.  */
 201   add_pad (cmsg, ((multx - (dsize & (multx - 1))) & (multx - 1)) + plusy);
 202
 203   /* Return the pointer to the start of the option space.  */
 204   uint8_t *result = CMSG_DATA (cmsg) + cmsg->cmsg_len - CMSG_LEN (0);
 205   cmsg->cmsg_len += datalen;
 206
 207   /* The extended option header length is measured in 8-byte groups.
 208      To represent the current length we might have to add padding.  */
 209   dsize = cmsg->cmsg_len - CMSG_LEN (0);
 210   add_pad (cmsg, (8 - (dsize & (8 - 1))) & (8 - 1));
 211
 212   /* Record the new length of the option.  */
 213   assert (((cmsg->cmsg_len - CMSG_LEN (0)) % 8) == 0);
 214   int len8b = (cmsg->cmsg_len - CMSG_LEN (0)) / 8 - 1;
 215   if (len8b >= 256)
 216     /* Too long.  */
 217     return NULL;
 218
 219   struct ip6_ext *ie = (void *) CMSG_DATA (cmsg);
 220   ie->ip6e_len = len8b;
 221
 222   return result;
 223 }
 224
 225
 226 uint8_t *
 227 inet6_option_alloc (cmsg, datalen, multx, plusy)
 228      struct cmsghdr *cmsg;
 229      int datalen;
 230      int multx;
 231      int plusy;
 232 {
 233   return option_alloc (cmsg, datalen, multx, plusy);
 234 }
 235 link_warning (inet6_option_alloc,
 236               "inet6_option_alloc is obsolete, use the RFC 3542 interfaces")
 237
 238
 239 /* RFC 2292, 6.3.5
 240
 241    This function processes the next Hop-by-Hop option or Destination
 242    option in an ancillary data object.  If another option remains to be
 243    processed, the return value of the function is 0 and *tptrp points to
 244    the 8-bit option type field (which is followed by the 8-bit option
 245    data length, followed by the option data).  If no more options remain
 246    to be processed, the return value is -1 and *tptrp is NULL.  If an
 247    error occurs, the return value is -1 and *tptrp is not NULL.  */
 248 int
 249 inet6_option_next (cmsg, tptrp)
 250      const struct cmsghdr *cmsg;
 251      uint8_t **tptrp;
 252 {
 253   /* Make sure it is an option of the right type.  */
 254   if (cmsg->cmsg_level != IPPROTO_IPV6
 255       || (cmsg->cmsg_type != IPV6_HOPOPTS && cmsg->cmsg_type != IPV6_DSTOPTS))
 256     return -1;
 257
 258   /* Pointer to the extension header.  We only compute the address, we
 259      don't access anything yet.  */
 260   const struct ip6_ext *ip6e = (const struct ip6_ext *) CMSG_DATA (cmsg);
 261
 262   /* Make sure the message is long enough.  */
 263   if (cmsg->cmsg_len < CMSG_LEN (sizeof (struct ip6_ext))
 264       /* Now we can access the extension header.  */
 265       || cmsg->cmsg_len < CMSG_LEN ((ip6e->ip6e_len + 1) * 8))
 266     /* Too small.  */
 267     return -1;
 268
 269   /* Determine the address of the byte past the message.  */
 270   const uint8_t *endp = CMSG_DATA (cmsg) + (ip6e->ip6e_len + 1) * 8;
 271
 272   const uint8_t *result;
 273   if (*tptrp == NULL)
 274     /* This is the first call, return the first option if there is one.  */
 275     result = (const uint8_t *) (ip6e + 1);
 276   else
 277     {
 278       /* Make sure *TPTRP points to a beginning of a new option in
 279          the message.  The upper limit is checked in get_opt_end.  */
 280       if (*tptrp < (const uint8_t *) (ip6e + 1))
 281         return -1;
 282
 283       /* Get the beginning of the next option.  */
 284       if (get_opt_end (&result, *tptrp, endp) != 0)
 285         return -1;
 286     }
 287
 288   /* We know where the next option starts.  */
 289   *tptrp = (uint8_t *) result;
 290
 291   /* Check the option is fully represented in the message.  */
 292   return get_opt_end (&result, result, endp);
 293 }
 294 link_warning (inet6_option_next,
 295               "inet6_option_next is obsolete, use the RFC 3542 interfaces")
 296
 297
 298 /* RFC 2292, 6.3.6
 299
 300    This function is similar to the previously described
 301    inet6_option_next() function, except this function lets the caller
 302    specify the option type to be searched for, instead of always
 303    returning the next option in the ancillary data object.  cmsg is a
 304    pointer to cmsghdr structure of which cmsg_level equals IPPROTO_IPV6
 305    and cmsg_type equals either IPV6_HOPOPTS or IPV6_DSTOPTS.  */
 306 int
 307 inet6_option_find (cmsg, tptrp, type)
 308      const struct cmsghdr *cmsg;
 309      uint8_t **tptrp;
 310      int type;
 311 {
 312   /* Make sure it is an option of the right type.  */
 313   if (cmsg->cmsg_level != IPPROTO_IPV6
 314       || (cmsg->cmsg_type != IPV6_HOPOPTS && cmsg->cmsg_type != IPV6_DSTOPTS))
 315     return -1;
 316
 317   /* Pointer to the extension header.  We only compute the address, we
 318      don't access anything yet.  */
 319   const struct ip6_ext *ip6e = (const struct ip6_ext *) CMSG_DATA (cmsg);
 320
 321   /* Make sure the message is long enough.  */
 322   if (cmsg->cmsg_len < CMSG_LEN (sizeof (struct ip6_ext))
 323       /* Now we can access the extension header.  */
 324       || cmsg->cmsg_len < CMSG_LEN ((ip6e->ip6e_len + 1) * 8))
 325     /* Too small.  */
 326     return -1;
 327
 328   /* Determine the address of the byte past the message.  */
 329   const uint8_t *endp = CMSG_DATA (cmsg) + (ip6e->ip6e_len + 1) * 8;
 330
 331   const uint8_t *next;
 332   if (*tptrp == NULL)
 333     /* This is the first call, return the first option if there is one.  */
 334     next = (const uint8_t *) (ip6e + 1);
 335   else
 336     {
 337       /* Make sure *TPTRP points to a beginning of a new option in
 338          the message.  The upper limit is checked in get_opt_end.  */
 339       if (*tptrp < (const uint8_t *) (ip6e + 1))
 340         return -1;
 341
 342       /* Get the beginning of the next option.  */
 343       if (get_opt_end (&next, *tptrp, endp) != 0)
 344         return -1;
 345     }
 346
 347   /* Now search for the appropriate typed entry.  */
 348   const uint8_t *result;
 349   do
 350     {
 351       result = next;
 352
 353       /* Get the end of this entry.  */
 354       if (get_opt_end (&next, result, endp) != 0)
 355         return -1;
 356     }
 357   while (*result != type);
 358
 359   /* We know where the next option starts.  */
 360   *tptrp = (uint8_t *) result;
 361
 362   /* Success.  */
 363   return 0;
 364 }
 365 link_warning (inet6_option_find,
 366               "inet6_option_find is obsolete, use the RFC 3542 interfaces")