inet/inet6_option.c

   1 /* Copyright (C) 2003-2015 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 (nbytes)
  92      int nbytes;
  93 {
  94   /* Add room for the extension header.  */
  95   nbytes += sizeof (struct ip6_ext);
  96
  97   return CMSG_SPACE (roundup (nbytes, 8));
  98 }
  99 link_warning (inet6_option_space,
 100               "inet6_option_space is obsolete, use the RFC 3542 interfaces")
 101
 102
 103 /* RFC 2292, 6.3.2
 104
 105    This function is called once per ancillary data object that will
 106    contain either Hop-by-Hop or Destination options.  It returns 0 on
 107    success or -1 on an error.  */
 108 int
 109 inet6_option_init (bp, cmsgp, type)
 110      void *bp;
 111      struct cmsghdr **cmsgp;
 112      int type;
 113 {
 114   /* Only Hop-by-Hop or Destination options allowed.  */
 115   if (type != IPV6_HOPOPTS && type != IPV6_DSTOPTS)
 116     return -1;
 117
 118   /* BP is a pointer to the previously allocated space.  */
 119   struct cmsghdr *newp = (struct cmsghdr *) bp;
 120
 121   /* Initialize the message header.
 122
 123      Length: No data yet, only the cmsghdr struct.  */
 124   newp->cmsg_len = CMSG_LEN (0);
 125   /* Originating protocol: obviously IPv6.  */
 126   newp->cmsg_level = IPPROTO_IPV6;
 127   /* Message type.  */
 128   newp->cmsg_type = type;
 129
 130   /* Pass up the result.  */
 131   *cmsgp = newp;
 132
 133   return 0;
 134 }
 135 link_warning (inet6_option_init,
 136               "inet6_option_init is obsolete, use the RFC 3542 interfaces")
 137
 138
 139 /* RFC 2292, 6.3.3
 140
 141    This function appends a Hop-by-Hop option or a Destination option
 142    into an ancillary data object that has been initialized by
 143    inet6_option_init().  This function returns 0 if it succeeds or -1 on
 144    an error.  */
 145 int
 146 inet6_option_append (cmsg, typep, multx, plusy)
 147      struct cmsghdr *cmsg;
 148      const uint8_t *typep;
 149      int multx;
 150      int plusy;
 151 {
 152   /* typep is a pointer to the 8-bit option type.  It is assumed that this
 153      field is immediately followed by the 8-bit option data length field,
 154      which is then followed immediately by the option data.
 155
 156      The option types IP6OPT_PAD1 and IP6OPT_PADN also must be handled.  */
 157   int len = typep[0] == IP6OPT_PAD1 ? 1 : typep[1] + 2;
 158
 159   /* Get the pointer to the space in the message.  */
 160   uint8_t *ptr = option_alloc (cmsg, len, multx, plusy);
 161   if (ptr == NULL)
 162     /* Some problem with the parameters.  */
 163     return -1;
 164
 165   /* Copy the content.  */
 166   memcpy (ptr, typep, len);
 167
 168   return 0;
 169 }
 170 link_warning (inet6_option_append,
 171               "inet6_option_append is obsolete, use the RFC 3542 interfaces")
 172
 173
 174 /* RFC 2292, 6.3.4
 175
 176    This function appends a Hop-by-Hop option or a Destination option
 177    into an ancillary data object that has been initialized by
 178    inet6_option_init().  This function returns a pointer to the 8-bit
 179    option type field that starts the option on success, or NULL on an
 180    error.  */
 181 static uint8_t *
 182 option_alloc (struct cmsghdr *cmsg, int datalen, int multx, int plusy)
 183 {
 184   /* The RFC limits the value of the alignment values.  */
 185   if ((multx != 1 && multx != 2 && multx != 4 && multx != 8)
 186       || ! (plusy >= 0 && plusy <= 7))
 187     return NULL;
 188
 189   /* Current data size.  */
 190   int dsize = cmsg->cmsg_len - CMSG_LEN (0);
 191
 192   /* The first two bytes of the option are for the extended header.  */
 193   if (__glibc_unlikely (dsize == 0))
 194     {
 195       cmsg->cmsg_len += sizeof (struct ip6_ext);
 196       dsize = sizeof (struct ip6_ext);
 197     }
 198
 199   /* First add padding.  */
 200   add_pad (cmsg, ((multx - (dsize & (multx - 1))) & (multx - 1)) + plusy);
 201
 202   /* Return the pointer to the start of the option space.  */
 203   uint8_t *result = CMSG_DATA (cmsg) + cmsg->cmsg_len - CMSG_LEN (0);
 204   cmsg->cmsg_len += datalen;
 205
 206   /* The extended option header length is measured in 8-byte groups.
 207      To represent the current length we might have to add padding.  */
 208   dsize = cmsg->cmsg_len - CMSG_LEN (0);
 209   add_pad (cmsg, (8 - (dsize & (8 - 1))) & (8 - 1));
 210
 211   /* Record the new length of the option.  */
 212   assert (((cmsg->cmsg_len - CMSG_LEN (0)) % 8) == 0);
 213   int len8b = (cmsg->cmsg_len - CMSG_LEN (0)) / 8 - 1;
 214   if (len8b >= 256)
 215     /* Too long.  */
 216     return NULL;
 217
 218   struct ip6_ext *ie = (void *) CMSG_DATA (cmsg);
 219   ie->ip6e_len = len8b;
 220
 221   return result;
 222 }
 223
 224
 225 uint8_t *
 226 inet6_option_alloc (cmsg, datalen, multx, plusy)
 227      struct cmsghdr *cmsg;
 228      int datalen;
 229      int multx;
 230      int plusy;
 231 {
 232   return option_alloc (cmsg, datalen, multx, plusy);
 233 }
 234 link_warning (inet6_option_alloc,
 235               "inet6_option_alloc is obsolete, use the RFC 3542 interfaces")
 236
 237
 238 /* RFC 2292, 6.3.5
 239
 240    This function processes the next Hop-by-Hop option or Destination
 241    option in an ancillary data object.  If another option remains to be
 242    processed, the return value of the function is 0 and *tptrp points to
 243    the 8-bit option type field (which is followed by the 8-bit option
 244    data length, followed by the option data).  If no more options remain
 245    to be processed, the return value is -1 and *tptrp is NULL.  If an
 246    error occurs, the return value is -1 and *tptrp is not NULL.  */
 247 int
 248 inet6_option_next (cmsg, tptrp)
 249      const struct cmsghdr *cmsg;
 250      uint8_t **tptrp;
 251 {
 252   /* Make sure it is an option of the right type.  */
 253   if (cmsg->cmsg_level != IPPROTO_IPV6
 254       || (cmsg->cmsg_type != IPV6_HOPOPTS && cmsg->cmsg_type != IPV6_DSTOPTS))
 255     return -1;
 256
 257   /* Pointer to the extension header.  We only compute the address, we
 258      don't access anything yet.  */
 259   const struct ip6_ext *ip6e = (const struct ip6_ext *) CMSG_DATA (cmsg);
 260
 261   /* Make sure the message is long enough.  */
 262   if (cmsg->cmsg_len < CMSG_LEN (sizeof (struct ip6_ext))
 263       /* Now we can access the extension header.  */
 264       || cmsg->cmsg_len < CMSG_LEN ((ip6e->ip6e_len + 1) * 8))
 265     /* Too small.  */
 266     return -1;
 267
 268   /* Determine the address of the byte past the message.  */
 269   const uint8_t *endp = CMSG_DATA (cmsg) + (ip6e->ip6e_len + 1) * 8;
 270
 271   const uint8_t *result;
 272   if (*tptrp == NULL)
 273     /* This is the first call, return the first option if there is one.  */
 274     result = (const uint8_t *) (ip6e + 1);
 275   else
 276     {
 277       /* Make sure *TPTRP points to a beginning of a new option in
 278          the message.  The upper limit is checked in get_opt_end.  */
 279       if (*tptrp < (const uint8_t *) (ip6e + 1))
 280         return -1;
 281
 282       /* Get the beginning of the next option.  */
 283       if (get_opt_end (&result, *tptrp, endp) != 0)
 284         return -1;
 285     }
 286
 287   /* We know where the next option starts.  */
 288   *tptrp = (uint8_t *) result;
 289
 290   /* Check the option is fully represented in the message.  */
 291   return get_opt_end (&result, result, endp);
 292 }
 293 link_warning (inet6_option_next,
 294               "inet6_option_next is obsolete, use the RFC 3542 interfaces")
 295
 296
 297 /* RFC 2292, 6.3.6
 298
 299    This function is similar to the previously described
 300    inet6_option_next() function, except this function lets the caller
 301    specify the option type to be searched for, instead of always
 302    returning the next option in the ancillary data object.  cmsg is a
 303    pointer to cmsghdr structure of which cmsg_level equals IPPROTO_IPV6
 304    and cmsg_type equals either IPV6_HOPOPTS or IPV6_DSTOPTS.  */
 305 int
 306 inet6_option_find (cmsg, tptrp, type)
 307      const struct cmsghdr *cmsg;
 308      uint8_t **tptrp;
 309      int type;
 310 {
 311   /* Make sure it is an option of the right type.  */
 312   if (cmsg->cmsg_level != IPPROTO_IPV6
 313       || (cmsg->cmsg_type != IPV6_HOPOPTS && cmsg->cmsg_type != IPV6_DSTOPTS))
 314     return -1;
 315
 316   /* Pointer to the extension header.  We only compute the address, we
 317      don't access anything yet.  */
 318   const struct ip6_ext *ip6e = (const struct ip6_ext *) CMSG_DATA (cmsg);
 319
 320   /* Make sure the message is long enough.  */
 321   if (cmsg->cmsg_len < CMSG_LEN (sizeof (struct ip6_ext))
 322       /* Now we can access the extension header.  */
 323       || cmsg->cmsg_len < CMSG_LEN ((ip6e->ip6e_len + 1) * 8))
 324     /* Too small.  */
 325     return -1;
 326
 327   /* Determine the address of the byte past the message.  */
 328   const uint8_t *endp = CMSG_DATA (cmsg) + (ip6e->ip6e_len + 1) * 8;
 329
 330   const uint8_t *next;
 331   if (*tptrp == NULL)
 332     /* This is the first call, return the first option if there is one.  */
 333     next = (const uint8_t *) (ip6e + 1);
 334   else
 335     {
 336       /* Make sure *TPTRP points to a beginning of a new option in
 337          the message.  The upper limit is checked in get_opt_end.  */
 338       if (*tptrp < (const uint8_t *) (ip6e + 1))
 339         return -1;
 340
 341       /* Get the beginning of the next option.  */
 342       if (get_opt_end (&next, *tptrp, endp) != 0)
 343         return -1;
 344     }
 345
 346   /* Now search for the appropriate typed entry.  */
 347   const uint8_t *result;
 348   do
 349     {
 350       result = next;
 351
 352       /* Get the end of this entry.  */
 353       if (get_opt_end (&next, result, endp) != 0)
 354         return -1;
 355     }
 356   while (*result != type);
 357
 358   /* We know where the next option starts.  */
 359   *tptrp = (uint8_t *) result;
 360
 361   /* Success.  */
 362   return 0;
 363 }
 364 link_warning (inet6_option_find,
 365               "inet6_option_find is obsolete, use the RFC 3542 interfaces")