inet/inet6_option.c

   1 /* Copyright (C) 2003-2019 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <string.h>
  21 #include <netinet/in.h>
  22 #include <netinet/ip6.h>
  23 #include <sys/param.h>
  24
  25
  26 static void
  27 add_pad (struct cmsghdr *cmsg, int len)
  28 {
  29   unsigned char *p = CMSG_DATA (cmsg) + cmsg->cmsg_len - CMSG_LEN (0);
  30
  31   if (len == 1)
  32     /* Special handling for 1, a one-byte solution.  */
  33     *p++ = IP6OPT_PAD1;
  34   else if (len != 0)
  35     {
  36       /* Multibyte padding.  */
  37       *p++ = IP6OPT_PADN;
  38       *p++ = len - 2;   /* Discount the two header bytes.  */
  39       /* The rest is filled with zero.  */
  40       memset (p, '\0', len - 2);
  41       p += len - 2;
  42     }
  43
  44   /* Account for the bytes.  */
  45   cmsg->cmsg_len += len;
  46 }
  47
  48
  49 static int
  50 get_opt_end (const uint8_t **result, const uint8_t *startp,
  51              const uint8_t *endp)
  52 {
  53   if (startp >= endp)
  54     /* Out of bounds.  */
  55     return -1;
  56
  57   if (*startp == IP6OPT_PAD1)
  58     {
  59       /* Just this one byte.  */
  60       *result = startp + 1;
  61       return 0;
  62     }
  63
  64   /* Now we know there must be at least two bytes.  */
  65   if (startp + 2 > endp
  66       /* Now we can get the length byte.  */
  67       || startp + startp[1] + 2 > endp)
  68     return -1;
  69
  70   *result = startp + startp[1] + 2;
  71
  72   return 0;
  73 }
  74
  75
  76 static uint8_t *option_alloc (struct cmsghdr *cmsg, int datalen, int multx,
  77                               int plusy);
  78
  79
  80 /* RFC 2292, 6.3.1
  81
  82    This function returns the number of bytes required to hold an option
  83    when it is stored as ancillary data, including the cmsghdr structure
  84    at the beginning, and any padding at the end (to make its size a
  85    multiple of 8 bytes).  The argument is the size of the structure
  86    defining the option, which must include any pad bytes at the
  87    beginning (the value y in the alignment term "xn + y"), the type
  88    byte, the length byte, and the option data.  */
  89 int
  90 inet6_option_space (int nbytes)
  91 {
  92   /* Add room for the extension header.  */
  93   nbytes += sizeof (struct ip6_ext);
  94
  95   return CMSG_SPACE (roundup (nbytes, 8));
  96 }
  97 link_warning (inet6_option_space,
  98               "inet6_option_space is obsolete, use the RFC 3542 interfaces")
  99
 100
 101 /* RFC 2292, 6.3.2
 102
 103    This function is called once per ancillary data object that will
 104    contain either Hop-by-Hop or Destination options.  It returns 0 on
 105    success or -1 on an error.  */
 106 int
 107 inet6_option_init (void *bp, struct cmsghdr **cmsgp, int type)
 108 {
 109   /* Only Hop-by-Hop or Destination options allowed.  */
 110   if (type != IPV6_HOPOPTS && type != IPV6_DSTOPTS)
 111     return -1;
 112
 113   /* BP is a pointer to the previously allocated space.  */
 114   struct cmsghdr *newp = (struct cmsghdr *) bp;
 115
 116   /* Initialize the message header.
 117
 118      Length: No data yet, only the cmsghdr struct.  */
 119   newp->cmsg_len = CMSG_LEN (0);
 120   /* Originating protocol: obviously IPv6.  */
 121   newp->cmsg_level = IPPROTO_IPV6;
 122   /* Message type.  */
 123   newp->cmsg_type = type;
 124
 125   /* Pass up the result.  */
 126   *cmsgp = newp;
 127
 128   return 0;
 129 }
 130 link_warning (inet6_option_init,
 131               "inet6_option_init is obsolete, use the RFC 3542 interfaces")
 132
 133
 134 /* RFC 2292, 6.3.3
 135
 136    This function appends a Hop-by-Hop option or a Destination option
 137    into an ancillary data object that has been initialized by
 138    inet6_option_init().  This function returns 0 if it succeeds or -1 on
 139    an error.  */
 140 int
 141 inet6_option_append (struct cmsghdr *cmsg, const uint8_t *typep, int multx,
 142                      int plusy)
 143 {
 144   /* typep is a pointer to the 8-bit option type.  It is assumed that this
 145      field is immediately followed by the 8-bit option data length field,
 146      which is then followed immediately by the option data.
 147
 148      The option types IP6OPT_PAD1 and IP6OPT_PADN also must be handled.  */
 149   int len = typep[0] == IP6OPT_PAD1 ? 1 : typep[1] + 2;
 150
 151   /* Get the pointer to the space in the message.  */
 152   uint8_t *ptr = option_alloc (cmsg, len, multx, plusy);
 153   if (ptr == NULL)
 154     /* Some problem with the parameters.  */
 155     return -1;
 156
 157   /* Copy the content.  */
 158   memcpy (ptr, typep, len);
 159
 160   return 0;
 161 }
 162 link_warning (inet6_option_append,
 163               "inet6_option_append is obsolete, use the RFC 3542 interfaces")
 164
 165
 166 /* RFC 2292, 6.3.4
 167
 168    This function appends a Hop-by-Hop option or a Destination option
 169    into an ancillary data object that has been initialized by
 170    inet6_option_init().  This function returns a pointer to the 8-bit
 171    option type field that starts the option on success, or NULL on an
 172    error.  */
 173 static uint8_t *
 174 option_alloc (struct cmsghdr *cmsg, int datalen, int multx, int plusy)
 175 {
 176   /* The RFC limits the value of the alignment values.  */
 177   if ((multx != 1 && multx != 2 && multx != 4 && multx != 8)
 178       || ! (plusy >= 0 && plusy <= 7))
 179     return NULL;
 180
 181   /* Current data size.  */
 182   int dsize = cmsg->cmsg_len - CMSG_LEN (0);
 183
 184   /* The first two bytes of the option are for the extended header.  */
 185   if (__glibc_unlikely (dsize == 0))
 186     {
 187       cmsg->cmsg_len += sizeof (struct ip6_ext);
 188       dsize = sizeof (struct ip6_ext);
 189     }
 190
 191   /* First add padding.  */
 192   add_pad (cmsg, ((multx - (dsize & (multx - 1))) & (multx - 1)) + plusy);
 193
 194   /* Return the pointer to the start of the option space.  */
 195   uint8_t *result = CMSG_DATA (cmsg) + cmsg->cmsg_len - CMSG_LEN (0);
 196   cmsg->cmsg_len += datalen;
 197
 198   /* The extended option header length is measured in 8-byte groups.
 199      To represent the current length we might have to add padding.  */
 200   dsize = cmsg->cmsg_len - CMSG_LEN (0);
 201   add_pad (cmsg, (8 - (dsize & (8 - 1))) & (8 - 1));
 202
 203   /* Record the new length of the option.  */
 204   assert (((cmsg->cmsg_len - CMSG_LEN (0)) % 8) == 0);
 205   int len8b = (cmsg->cmsg_len - CMSG_LEN (0)) / 8 - 1;
 206   if (len8b >= 256)
 207     /* Too long.  */
 208     return NULL;
 209
 210   struct ip6_ext *ie = (void *) CMSG_DATA (cmsg);
 211   ie->ip6e_len = len8b;
 212
 213   return result;
 214 }
 215
 216
 217 uint8_t *
 218 inet6_option_alloc (struct cmsghdr *cmsg, int datalen, int multx, int plusy)
 219 {
 220   return option_alloc (cmsg, datalen, multx, plusy);
 221 }
 222 link_warning (inet6_option_alloc,
 223               "inet6_option_alloc is obsolete, use the RFC 3542 interfaces")
 224
 225
 226 /* RFC 2292, 6.3.5
 227
 228    This function processes the next Hop-by-Hop option or Destination
 229    option in an ancillary data object.  If another option remains to be
 230    processed, the return value of the function is 0 and *tptrp points to
 231    the 8-bit option type field (which is followed by the 8-bit option
 232    data length, followed by the option data).  If no more options remain
 233    to be processed, the return value is -1 and *tptrp is NULL.  If an
 234    error occurs, the return value is -1 and *tptrp is not NULL.  */
 235 int
 236 inet6_option_next (const struct cmsghdr *cmsg, uint8_t **tptrp)
 237 {
 238   /* Make sure it is an option of the right type.  */
 239   if (cmsg->cmsg_level != IPPROTO_IPV6
 240       || (cmsg->cmsg_type != IPV6_HOPOPTS && cmsg->cmsg_type != IPV6_DSTOPTS))
 241     return -1;
 242
 243   /* Pointer to the extension header.  We only compute the address, we
 244      don't access anything yet.  */
 245   const struct ip6_ext *ip6e = (const struct ip6_ext *) CMSG_DATA (cmsg);
 246
 247   /* Make sure the message is long enough.  */
 248   if (cmsg->cmsg_len < CMSG_LEN (sizeof (struct ip6_ext))
 249       /* Now we can access the extension header.  */
 250       || cmsg->cmsg_len < CMSG_LEN ((ip6e->ip6e_len + 1) * 8))
 251     /* Too small.  */
 252     return -1;
 253
 254   /* Determine the address of the byte past the message.  */
 255   const uint8_t *endp = CMSG_DATA (cmsg) + (ip6e->ip6e_len + 1) * 8;
 256
 257   const uint8_t *result;
 258   if (*tptrp == NULL)
 259     /* This is the first call, return the first option if there is one.  */
 260     result = (const uint8_t *) (ip6e + 1);
 261   else
 262     {
 263       /* Make sure *TPTRP points to a beginning of a new option in
 264          the message.  The upper limit is checked in get_opt_end.  */
 265       if (*tptrp < (const uint8_t *) (ip6e + 1))
 266         return -1;
 267
 268       /* Get the beginning of the next option.  */
 269       if (get_opt_end (&result, *tptrp, endp) != 0)
 270         return -1;
 271     }
 272
 273   /* We know where the next option starts.  */
 274   *tptrp = (uint8_t *) result;
 275
 276   /* Check the option is fully represented in the message.  */
 277   return get_opt_end (&result, result, endp);
 278 }
 279 link_warning (inet6_option_next,
 280               "inet6_option_next is obsolete, use the RFC 3542 interfaces")
 281
 282
 283 /* RFC 2292, 6.3.6
 284
 285    This function is similar to the previously described
 286    inet6_option_next() function, except this function lets the caller
 287    specify the option type to be searched for, instead of always
 288    returning the next option in the ancillary data object.  cmsg is a
 289    pointer to cmsghdr structure of which cmsg_level equals IPPROTO_IPV6
 290    and cmsg_type equals either IPV6_HOPOPTS or IPV6_DSTOPTS.  */
 291 int
 292 inet6_option_find (const struct cmsghdr *cmsg, uint8_t **tptrp, int type)
 293 {
 294   /* Make sure it is an option of the right type.  */
 295   if (cmsg->cmsg_level != IPPROTO_IPV6
 296       || (cmsg->cmsg_type != IPV6_HOPOPTS && cmsg->cmsg_type != IPV6_DSTOPTS))
 297     return -1;
 298
 299   /* Pointer to the extension header.  We only compute the address, we
 300      don't access anything yet.  */
 301   const struct ip6_ext *ip6e = (const struct ip6_ext *) CMSG_DATA (cmsg);
 302
 303   /* Make sure the message is long enough.  */
 304   if (cmsg->cmsg_len < CMSG_LEN (sizeof (struct ip6_ext))
 305       /* Now we can access the extension header.  */
 306       || cmsg->cmsg_len < CMSG_LEN ((ip6e->ip6e_len + 1) * 8))
 307     /* Too small.  */
 308     return -1;
 309
 310   /* Determine the address of the byte past the message.  */
 311   const uint8_t *endp = CMSG_DATA (cmsg) + (ip6e->ip6e_len + 1) * 8;
 312
 313   const uint8_t *next;
 314   if (*tptrp == NULL)
 315     /* This is the first call, return the first option if there is one.  */
 316     next = (const uint8_t *) (ip6e + 1);
 317   else
 318     {
 319       /* Make sure *TPTRP points to a beginning of a new option in
 320          the message.  The upper limit is checked in get_opt_end.  */
 321       if (*tptrp < (const uint8_t *) (ip6e + 1))
 322         return -1;
 323
 324       /* Get the beginning of the next option.  */
 325       if (get_opt_end (&next, *tptrp, endp) != 0)
 326         return -1;
 327     }
 328
 329   /* Now search for the appropriate typed entry.  */
 330   const uint8_t *result;
 331   do
 332     {
 333       result = next;
 334
 335       /* Get the end of this entry.  */
 336       if (get_opt_end (&next, result, endp) != 0)
 337         return -1;
 338     }
 339   while (*result != type);
 340
 341   /* We know where the next option starts.  */
 342   *tptrp = (uint8_t *) result;
 343
 344   /* Success.  */
 345   return 0;
 346 }
 347 link_warning (inet6_option_find,
 348               "inet6_option_find is obsolete, use the RFC 3542 interfaces")