inet/inet6_option.c

   1 /* Copyright (C) 2003, 2006 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
 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 (bp, cmsgp, type)
 109      void *bp;
 110      struct cmsghdr **cmsgp;
 111      int type;
 112 {
 113   /* Only Hop-by-Hop or Destination options allowed.  */
 114   if (type != IPV6_HOPOPTS && type != IPV6_DSTOPTS)
 115     return -1;
 116
 117   /* BP is a pointer to the previously allocated space.  */
 118   struct cmsghdr *newp = (struct cmsghdr *) bp;
 119
 120   /* Initialize the message header.
 121
 122      Length: No data yet, only the cmsghdr struct.  */
 123   newp->cmsg_len = CMSG_LEN (0);
 124   /* Originating protocol: obviously IPv6.  */
 125   newp->cmsg_level = IPPROTO_IPV6;
 126   /* Message type.  */
 127   newp->cmsg_type = type;
 128
 129   /* Pass up the result.  */
 130   *cmsgp = newp;
 131
 132   return 0;
 133 }
 134
 135
 136 /* RFC 2292, 6.3.3
 137
 138    This function appends a Hop-by-Hop option or a Destination option
 139    into an ancillary data object that has been initialized by
 140    inet6_option_init().  This function returns 0 if it succeeds or -1 on
 141    an error.  */
 142 int
 143 inet6_option_append (cmsg, typep, multx, plusy)
 144      struct cmsghdr *cmsg;
 145      const uint8_t *typep;
 146      int multx;
 147      int plusy;
 148 {
 149   /* typep is a pointer to the 8-bit option type.  It is assumed that this
 150      field is immediately followed by the 8-bit option data length field,
 151      which is then followed immediately by the option data.
 152
 153      The option types IP6OPT_PAD1 and IP6OPT_PADN also must be handled.  */
 154   int len = typep[0] == IP6OPT_PAD1 ? 1 : typep[1] + 2;
 155
 156   /* Get the pointer to the space in the message.  */
 157   uint8_t *ptr = option_alloc (cmsg, len, multx, plusy);
 158   if (ptr == NULL)
 159     /* Some problem with the parameters.  */
 160     return -1;
 161
 162   /* Copy the content.  */
 163   memcpy (ptr, typep, len);
 164
 165   return 0;
 166 }
 167
 168
 169 /* RFC 2292, 6.3.4
 170
 171    This function appends a Hop-by-Hop option or a Destination option
 172    into an ancillary data object that has been initialized by
 173    inet6_option_init().  This function returns a pointer to the 8-bit
 174    option type field that starts the option on success, or NULL on an
 175    error.  */
 176 static uint8_t *
 177 option_alloc (struct cmsghdr *cmsg, int datalen, int multx, int plusy)
 178 {
 179   /* The RFC limits the value of the alignment values.  */
 180   if ((multx != 1 && multx != 2 && multx != 4 && multx != 8)
 181       || ! (plusy >= 0 && plusy <= 7))
 182     return NULL;
 183
 184   /* Current data size.  */
 185   int dsize = cmsg->cmsg_len - CMSG_LEN (0);
 186
 187   /* The first two bytes of the option are for the extended header.  */
 188   if (__builtin_expect (dsize == 0, 0))
 189     {
 190       cmsg->cmsg_len += sizeof (struct ip6_ext);
 191       dsize = sizeof (struct ip6_ext);
 192     }
 193
 194   /* First add padding.  */
 195   add_pad (cmsg, ((multx - (dsize & (multx - 1))) & (multx - 1)) + plusy);
 196
 197   /* Return the pointer to the start of the option space.  */
 198   uint8_t *result = CMSG_DATA (cmsg) + cmsg->cmsg_len - CMSG_LEN (0);
 199   cmsg->cmsg_len += datalen;
 200
 201   /* The extended option header length is measured in 8-byte groups.
 202      To represent the current length we might have to add padding.  */
 203   dsize = cmsg->cmsg_len - CMSG_LEN (0);
 204   add_pad (cmsg, (8 - (dsize & (8 - 1))) & (8 - 1));
 205
 206   /* Record the new length of the option.  */
 207   assert (((cmsg->cmsg_len - CMSG_LEN (0)) % 8) == 0);
 208   int len8b = (cmsg->cmsg_len - CMSG_LEN (0)) / 8 - 1;
 209   if (len8b >= 256)
 210     /* Too long.  */
 211     return NULL;
 212
 213   ((struct ip6_ext *) CMSG_DATA (cmsg))->ip6e_len = len8b;
 214
 215   return result;
 216 }
 217
 218
 219 uint8_t *
 220 inet6_option_alloc (cmsg, datalen, multx, plusy)
 221      struct cmsghdr *cmsg;
 222      int datalen;
 223      int multx;
 224      int plusy;
 225 {
 226   return option_alloc (cmsg, datalen, multx, plusy);
 227 }
 228
 229
 230 /* RFC 2292, 6.3.5
 231
 232    This function processes the next Hop-by-Hop option or Destination
 233    option in an ancillary data object.  If another option remains to be
 234    processed, the return value of the function is 0 and *tptrp points to
 235    the 8-bit option type field (which is followed by the 8-bit option
 236    data length, followed by the option data).  If no more options remain
 237    to be processed, the return value is -1 and *tptrp is NULL.  If an
 238    error occurs, the return value is -1 and *tptrp is not NULL.  */
 239 int
 240 inet6_option_next (cmsg, tptrp)
 241      const struct cmsghdr *cmsg;
 242      uint8_t **tptrp;
 243 {
 244   /* Make sure it is an option of the right type.  */
 245   if (cmsg->cmsg_level != IPPROTO_IPV6
 246       || (cmsg->cmsg_type != IPV6_HOPOPTS && cmsg->cmsg_type != IPV6_DSTOPTS))
 247     return -1;
 248
 249   /* Pointer to the extension header.  We only compute the address, we
 250      don't access anything yet.  */
 251   const struct ip6_ext *ip6e = (const struct ip6_ext *) CMSG_DATA (cmsg);
 252
 253   /* Make sure the message is long enough.  */
 254   if (cmsg->cmsg_len < CMSG_LEN (sizeof (struct ip6_ext))
 255       /* Now we can access the extension header.  */
 256       || cmsg->cmsg_len < CMSG_LEN ((ip6e->ip6e_len + 1) * 8))
 257     /* Too small.  */
 258     return -1;
 259
 260   /* Determine the address of the byte past the message.  */
 261   const uint8_t *endp = CMSG_DATA (cmsg) + (ip6e->ip6e_len + 1) * 8;
 262
 263   const uint8_t *result;
 264   if (*tptrp == NULL)
 265     /* This is the first call, return the first option if there is one.  */
 266     result = (const uint8_t *) (ip6e + 1);
 267   else
 268     {
 269       /* Make sure *TPTRP points to a beginning of a new option in
 270          the message.  The upper limit is checked in get_opt_end.  */
 271       if (*tptrp < (const uint8_t *) (ip6e + 1))
 272         return -1;
 273
 274       /* Get the beginning of the next option.  */
 275       if (get_opt_end (&result, *tptrp, endp) != 0)
 276         return -1;
 277     }
 278
 279   /* We know where the next option starts.  */
 280   *tptrp = (uint8_t *) result;
 281
 282   /* Check the option is fully represented in the message.  */
 283   return get_opt_end (&result, result, endp);
 284 }
 285
 286
 287 /* RFC 2292, 6.3.6
 288
 289    This function is similar to the previously described
 290    inet6_option_next() function, except this function lets the caller
 291    specify the option type to be searched for, instead of always
 292    returning the next option in the ancillary data object.  cmsg is a
 293    pointer to cmsghdr structure of which cmsg_level equals IPPROTO_IPV6
 294    and cmsg_type equals either IPV6_HOPOPTS or IPV6_DSTOPTS.  */
 295 int
 296 inet6_option_find (cmsg, tptrp, type)
 297      const struct cmsghdr *cmsg;
 298      uint8_t **tptrp;
 299      int type;
 300 {
 301   /* Make sure it is an option of the right type.  */
 302   if (cmsg->cmsg_level != IPPROTO_IPV6
 303       || (cmsg->cmsg_type != IPV6_HOPOPTS && cmsg->cmsg_type != IPV6_DSTOPTS))
 304     return -1;
 305
 306   /* Pointer to the extension header.  We only compute the address, we
 307      don't access anything yet.  */
 308   const struct ip6_ext *ip6e = (const struct ip6_ext *) CMSG_DATA (cmsg);
 309
 310   /* Make sure the message is long enough.  */
 311   if (cmsg->cmsg_len < CMSG_LEN (sizeof (struct ip6_ext))
 312       /* Now we can access the extension header.  */
 313       || cmsg->cmsg_len < CMSG_LEN ((ip6e->ip6e_len + 1) * 8))
 314     /* Too small.  */
 315     return -1;
 316
 317   /* Determine the address of the byte past the message.  */
 318   const uint8_t *endp = CMSG_DATA (cmsg) + (ip6e->ip6e_len + 1) * 8;
 319
 320   const uint8_t *next;
 321   if (*tptrp == NULL)
 322     /* This is the first call, return the first option if there is one.  */
 323     next = (const uint8_t *) (ip6e + 1);
 324   else
 325     {
 326       /* Make sure *TPTRP points to a beginning of a new option in
 327          the message.  The upper limit is checked in get_opt_end.  */
 328       if (*tptrp < (const uint8_t *) (ip6e + 1))
 329         return -1;
 330
 331       /* Get the beginning of the next option.  */
 332       if (get_opt_end (&next, *tptrp, endp) != 0)
 333         return -1;
 334     }
 335
 336   /* Now search for the appropriate typed entry.  */
 337   const uint8_t *result;
 338   do
 339     {
 340       result = next;
 341
 342       /* Get the end of this entry.  */
 343       if (get_opt_end (&next, result, endp) != 0)
 344         return -1;
 345     }
 346   while (*result != type);
 347
 348   /* We know where the next option starts.  */
 349   *tptrp = (uint8_t *) result;
 350
 351   /* Success.  */
 352   return 0;
 353 }