inet/inet6_option.c

   1 /* Copyright (C) 2003-2017 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 internal_function
  28 add_pad (struct cmsghdr *cmsg, int len)
  29 {
  30   unsigned char *p = CMSG_DATA (cmsg) + cmsg->cmsg_len - CMSG_LEN (0);
  31
  32   if (len == 1)
  33     /* Special handling for 1, a one-byte solution.  */
  34     *p++ = IP6OPT_PAD1;
  35   else if (len != 0)
  36     {
  37       /* Multibyte padding.  */
  38       *p++ = IP6OPT_PADN;
  39       *p++ = len - 2;   /* Discount the two header bytes.  */
  40       /* The rest is filled with zero.  */
  41       memset (p, '\0', len - 2);
  42       p += len - 2;
  43     }
  44
  45   /* Account for the bytes.  */
  46   cmsg->cmsg_len += len;
  47 }
  48
  49
  50 static int
  51 get_opt_end (const uint8_t **result, const uint8_t *startp,
  52              const uint8_t *endp)
  53 {
  54   if (startp >= endp)
  55     /* Out of bounds.  */
  56     return -1;
  57
  58   if (*startp == IP6OPT_PAD1)
  59     {
  60       /* Just this one byte.  */
  61       *result = startp + 1;
  62       return 0;
  63     }
  64
  65   /* Now we know there must be at least two bytes.  */
  66   if (startp + 2 > endp
  67       /* Now we can get the length byte.  */
  68       || startp + startp[1] + 2 > endp)
  69     return -1;
  70
  71   *result = startp + startp[1] + 2;
  72
  73   return 0;
  74 }
  75
  76
  77 static uint8_t *option_alloc (struct cmsghdr *cmsg, int datalen, int multx,
  78                               int plusy);
  79
  80
  81 /* RFC 2292, 6.3.1
  82
  83    This function returns the number of bytes required to hold an option
  84    when it is stored as ancillary data, including the cmsghdr structure
  85    at the beginning, and any padding at the end (to make its size a
  86    multiple of 8 bytes).  The argument is the size of the structure
  87    defining the option, which must include any pad bytes at the
  88    beginning (the value y in the alignment term "xn + y"), the type
  89    byte, the length byte, and the option data.  */
  90 int
  91 inet6_option_space (int nbytes)
  92 {
  93   /* Add room for the extension header.  */
  94   nbytes += sizeof (struct ip6_ext);
  95
  96   return CMSG_SPACE (roundup (nbytes, 8));
  97 }
  98 link_warning (inet6_option_space,
  99               "inet6_option_space is obsolete, use the RFC 3542 interfaces")
 100
 101
 102 /* RFC 2292, 6.3.2
 103
 104    This function is called once per ancillary data object that will
 105    contain either Hop-by-Hop or Destination options.  It returns 0 on
 106    success or -1 on an error.  */
 107 int
 108 inet6_option_init (void *bp, struct cmsghdr **cmsgp, int type)
 109 {
 110   /* Only Hop-by-Hop or Destination options allowed.  */
 111   if (type != IPV6_HOPOPTS && type != IPV6_DSTOPTS)
 112     return -1;
 113
 114   /* BP is a pointer to the previously allocated space.  */
 115   struct cmsghdr *newp = (struct cmsghdr *) bp;
 116
 117   /* Initialize the message header.
 118
 119      Length: No data yet, only the cmsghdr struct.  */
 120   newp->cmsg_len = CMSG_LEN (0);
 121   /* Originating protocol: obviously IPv6.  */
 122   newp->cmsg_level = IPPROTO_IPV6;
 123   /* Message type.  */
 124   newp->cmsg_type = type;
 125
 126   /* Pass up the result.  */
 127   *cmsgp = newp;
 128
 129   return 0;
 130 }
 131 link_warning (inet6_option_init,
 132               "inet6_option_init is obsolete, use the RFC 3542 interfaces")
 133
 134
 135 /* RFC 2292, 6.3.3
 136
 137    This function appends a Hop-by-Hop option or a Destination option
 138    into an ancillary data object that has been initialized by
 139    inet6_option_init().  This function returns 0 if it succeeds or -1 on
 140    an error.  */
 141 int
 142 inet6_option_append (struct cmsghdr *cmsg, const uint8_t *typep, int multx,
 143                      int plusy)
 144 {
 145   /* typep is a pointer to the 8-bit option type.  It is assumed that this
 146      field is immediately followed by the 8-bit option data length field,
 147      which is then followed immediately by the option data.
 148
 149      The option types IP6OPT_PAD1 and IP6OPT_PADN also must be handled.  */
 150   int len = typep[0] == IP6OPT_PAD1 ? 1 : typep[1] + 2;
 151
 152   /* Get the pointer to the space in the message.  */
 153   uint8_t *ptr = option_alloc (cmsg, len, multx, plusy);
 154   if (ptr == NULL)
 155     /* Some problem with the parameters.  */
 156     return -1;
 157
 158   /* Copy the content.  */
 159   memcpy (ptr, typep, len);
 160
 161   return 0;
 162 }
 163 link_warning (inet6_option_append,
 164               "inet6_option_append is obsolete, use the RFC 3542 interfaces")
 165
 166
 167 /* RFC 2292, 6.3.4
 168
 169    This function appends a Hop-by-Hop option or a Destination option
 170    into an ancillary data object that has been initialized by
 171    inet6_option_init().  This function returns a pointer to the 8-bit
 172    option type field that starts the option on success, or NULL on an
 173    error.  */
 174 static uint8_t *
 175 option_alloc (struct cmsghdr *cmsg, int datalen, int multx, int plusy)
 176 {
 177   /* The RFC limits the value of the alignment values.  */
 178   if ((multx != 1 && multx != 2 && multx != 4 && multx != 8)
 179       || ! (plusy >= 0 && plusy <= 7))
 180     return NULL;
 181
 182   /* Current data size.  */
 183   int dsize = cmsg->cmsg_len - CMSG_LEN (0);
 184
 185   /* The first two bytes of the option are for the extended header.  */
 186   if (__glibc_unlikely (dsize == 0))
 187     {
 188       cmsg->cmsg_len += sizeof (struct ip6_ext);
 189       dsize = sizeof (struct ip6_ext);
 190     }
 191
 192   /* First add padding.  */
 193   add_pad (cmsg, ((multx - (dsize & (multx - 1))) & (multx - 1)) + plusy);
 194
 195   /* Return the pointer to the start of the option space.  */
 196   uint8_t *result = CMSG_DATA (cmsg) + cmsg->cmsg_len - CMSG_LEN (0);
 197   cmsg->cmsg_len += datalen;
 198
 199   /* The extended option header length is measured in 8-byte groups.
 200      To represent the current length we might have to add padding.  */
 201   dsize = cmsg->cmsg_len - CMSG_LEN (0);
 202   add_pad (cmsg, (8 - (dsize & (8 - 1))) & (8 - 1));
 203
 204   /* Record the new length of the option.  */
 205   assert (((cmsg->cmsg_len - CMSG_LEN (0)) % 8) == 0);
 206   int len8b = (cmsg->cmsg_len - CMSG_LEN (0)) / 8 - 1;
 207   if (len8b >= 256)
 208     /* Too long.  */
 209     return NULL;
 210
 211   struct ip6_ext *ie = (void *) CMSG_DATA (cmsg);
 212   ie->ip6e_len = len8b;
 213
 214   return result;
 215 }
 216
 217
 218 uint8_t *
 219 inet6_option_alloc (struct cmsghdr *cmsg, int datalen, int multx, int plusy)
 220 {
 221   return option_alloc (cmsg, datalen, multx, plusy);
 222 }
 223 link_warning (inet6_option_alloc,
 224               "inet6_option_alloc is obsolete, use the RFC 3542 interfaces")
 225
 226
 227 /* RFC 2292, 6.3.5
 228
 229    This function processes the next Hop-by-Hop option or Destination
 230    option in an ancillary data object.  If another option remains to be
 231    processed, the return value of the function is 0 and *tptrp points to
 232    the 8-bit option type field (which is followed by the 8-bit option
 233    data length, followed by the option data).  If no more options remain
 234    to be processed, the return value is -1 and *tptrp is NULL.  If an
 235    error occurs, the return value is -1 and *tptrp is not NULL.  */
 236 int
 237 inet6_option_next (const struct cmsghdr *cmsg, uint8_t **tptrp)
 238 {
 239   /* Make sure it is an option of the right type.  */
 240   if (cmsg->cmsg_level != IPPROTO_IPV6
 241       || (cmsg->cmsg_type != IPV6_HOPOPTS && cmsg->cmsg_type != IPV6_DSTOPTS))
 242     return -1;
 243
 244   /* Pointer to the extension header.  We only compute the address, we
 245      don't access anything yet.  */
 246   const struct ip6_ext *ip6e = (const struct ip6_ext *) CMSG_DATA (cmsg);
 247
 248   /* Make sure the message is long enough.  */
 249   if (cmsg->cmsg_len < CMSG_LEN (sizeof (struct ip6_ext))
 250       /* Now we can access the extension header.  */
 251       || cmsg->cmsg_len < CMSG_LEN ((ip6e->ip6e_len + 1) * 8))
 252     /* Too small.  */
 253     return -1;
 254
 255   /* Determine the address of the byte past the message.  */
 256   const uint8_t *endp = CMSG_DATA (cmsg) + (ip6e->ip6e_len + 1) * 8;
 257
 258   const uint8_t *result;
 259   if (*tptrp == NULL)
 260     /* This is the first call, return the first option if there is one.  */
 261     result = (const uint8_t *) (ip6e + 1);
 262   else
 263     {
 264       /* Make sure *TPTRP points to a beginning of a new option in
 265          the message.  The upper limit is checked in get_opt_end.  */
 266       if (*tptrp < (const uint8_t *) (ip6e + 1))
 267         return -1;
 268
 269       /* Get the beginning of the next option.  */
 270       if (get_opt_end (&result, *tptrp, endp) != 0)
 271         return -1;
 272     }
 273
 274   /* We know where the next option starts.  */
 275   *tptrp = (uint8_t *) result;
 276
 277   /* Check the option is fully represented in the message.  */
 278   return get_opt_end (&result, result, endp);
 279 }
 280 link_warning (inet6_option_next,
 281               "inet6_option_next is obsolete, use the RFC 3542 interfaces")
 282
 283
 284 /* RFC 2292, 6.3.6
 285
 286    This function is similar to the previously described
 287    inet6_option_next() function, except this function lets the caller
 288    specify the option type to be searched for, instead of always
 289    returning the next option in the ancillary data object.  cmsg is a
 290    pointer to cmsghdr structure of which cmsg_level equals IPPROTO_IPV6
 291    and cmsg_type equals either IPV6_HOPOPTS or IPV6_DSTOPTS.  */
 292 int
 293 inet6_option_find (const struct cmsghdr *cmsg, uint8_t **tptrp, int type)
 294 {
 295   /* Make sure it is an option of the right type.  */
 296   if (cmsg->cmsg_level != IPPROTO_IPV6
 297       || (cmsg->cmsg_type != IPV6_HOPOPTS && cmsg->cmsg_type != IPV6_DSTOPTS))
 298     return -1;
 299
 300   /* Pointer to the extension header.  We only compute the address, we
 301      don't access anything yet.  */
 302   const struct ip6_ext *ip6e = (const struct ip6_ext *) CMSG_DATA (cmsg);
 303
 304   /* Make sure the message is long enough.  */
 305   if (cmsg->cmsg_len < CMSG_LEN (sizeof (struct ip6_ext))
 306       /* Now we can access the extension header.  */
 307       || cmsg->cmsg_len < CMSG_LEN ((ip6e->ip6e_len + 1) * 8))
 308     /* Too small.  */
 309     return -1;
 310
 311   /* Determine the address of the byte past the message.  */
 312   const uint8_t *endp = CMSG_DATA (cmsg) + (ip6e->ip6e_len + 1) * 8;
 313
 314   const uint8_t *next;
 315   if (*tptrp == NULL)
 316     /* This is the first call, return the first option if there is one.  */
 317     next = (const uint8_t *) (ip6e + 1);
 318   else
 319     {
 320       /* Make sure *TPTRP points to a beginning of a new option in
 321          the message.  The upper limit is checked in get_opt_end.  */
 322       if (*tptrp < (const uint8_t *) (ip6e + 1))
 323         return -1;
 324
 325       /* Get the beginning of the next option.  */
 326       if (get_opt_end (&next, *tptrp, endp) != 0)
 327         return -1;
 328     }
 329
 330   /* Now search for the appropriate typed entry.  */
 331   const uint8_t *result;
 332   do
 333     {
 334       result = next;
 335
 336       /* Get the end of this entry.  */
 337       if (get_opt_end (&next, result, endp) != 0)
 338         return -1;
 339     }
 340   while (*result != type);
 341
 342   /* We know where the next option starts.  */
 343   *tptrp = (uint8_t *) result;
 344
 345   /* Success.  */
 346   return 0;
 347 }
 348 link_warning (inet6_option_find,
 349               "inet6_option_find is obsolete, use the RFC 3542 interfaces")