inet/inet6_option.c

   1 /* Copyright (C) 2003 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 /* RFC 2292, 6.3.1
  79
  80    This function returns the number of bytes required to hold an option
  81    when it is stored as ancillary data, including the cmsghdr structure
  82    at the beginning, and any padding at the end (to make its size a
  83    multiple of 8 bytes).  The argument is the size of the structure
  84    defining the option, which must include any pad bytes at the
  85    beginning (the value y in the alignment term "xn + y"), the type
  86    byte, the length byte, and the option data.  */
  87 int
  88 inet6_option_space (nbytes)
  89      int nbytes;
  90 {
  91   /* Add room for the extension header.  */
  92   nbytes += sizeof (struct ip6_ext);
  93
  94   return CMSG_SPACE (roundup (nbytes, 8));
  95 }
  96
  97
  98 /* RFC 2292, 6.3.2
  99
 100    This function is called once per ancillary data object that will
 101    contain either Hop-by-Hop or Destination options.  It returns 0 on
 102    success or -1 on an error.  */
 103 int
 104 inet6_option_init (bp, cmsgp, type)
 105      void *bp;
 106      struct cmsghdr **cmsgp;
 107      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
 131
 132 /* RFC 2292, 6.3.3
 133
 134    This function appends a Hop-by-Hop option or a Destination option
 135    into an ancillary data object that has been initialized by
 136    inet6_option_init().  This function returns 0 if it succeeds or -1 on
 137    an error.  */
 138 int
 139 inet6_option_append (cmsg, typep, multx, plusy)
 140      struct cmsghdr *cmsg;
 141      const uint8_t *typep;
 142      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 = inet6_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
 164
 165 /* RFC 2292, 6.3.4
 166
 167    This function appends a Hop-by-Hop option or a Destination option
 168    into an ancillary data object that has been initialized by
 169    inet6_option_init().  This function returns a pointer to the 8-bit
 170    option type field that starts the option on success, or NULL on an
 171    error.  */
 172 uint8_t *
 173 inet6_option_alloc (cmsg, datalen, multx, plusy)
 174      struct cmsghdr *cmsg;
 175      int datalen;
 176      int multx;
 177      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 libc_hidden_def (inet6_option_alloc)
 218
 219
 220 /* RFC 2292, 6.3.5
 221
 222    This function processes the next Hop-by-Hop option or Destination
 223    option in an ancillary data object.  If another option remains to be
 224    processed, the return value of the function is 0 and *tptrp points to
 225    the 8-bit option type field (which is followed by the 8-bit option
 226    data length, followed by the option data).  If no more options remain
 227    to be processed, the return value is -1 and *tptrp is NULL.  If an
 228    error occurs, the return value is -1 and *tptrp is not NULL.  */
 229 int
 230 inet6_option_next (cmsg, tptrp)
 231      const struct cmsghdr *cmsg;
 232      uint8_t **tptrp;
 233 {
 234   /* Make sure it is an option of the right type.  */
 235   if (cmsg->cmsg_level != IPPROTO_IPV6
 236       || (cmsg->cmsg_type != IPV6_HOPOPTS && cmsg->cmsg_type != IPV6_DSTOPTS))
 237     return -1;
 238
 239   /* Pointer to the extension header.  We only compute the address, we
 240      don't access anything yet.  */
 241   const struct ip6_ext *ip6e = (const struct ip6_ext *) CMSG_DATA (cmsg);
 242
 243   /* Make sure the message is long enough.  */
 244   if (cmsg->cmsg_len < CMSG_LEN (sizeof (struct ip6_ext))
 245       /* Now we can access the extension header.  */
 246       || cmsg->cmsg_len < CMSG_LEN ((ip6e->ip6e_len + 1) * 8))
 247     /* Too small.  */
 248     return -1;
 249
 250   /* Determine the address of the byte past the message.  */
 251   const uint8_t *endp = CMSG_DATA (cmsg) + (ip6e->ip6e_len + 1) * 8;
 252
 253   const uint8_t *result;
 254   if (tptrp == NULL)
 255     /* This is the first call, return the first option if there is one.  */
 256     result = (const uint8_t *) (ip6e + 1);
 257   else
 258     {
 259       /* Make sure *TPTRP points to a beginning of a new option in
 260          the message.  The upper limit is checked in get_opt_end.  */
 261       if (*tptrp < (const uint8_t *) (ip6e + 1))
 262         return -1;
 263
 264       /* Get the beginning of the next option.  */
 265       if (get_opt_end (&result, *tptrp, endp) != 0)
 266         return -1;
 267     }
 268
 269   /* We know where the next option starts.  */
 270   *tptrp = (uint8_t *) result;
 271
 272   /* Check the option is fully represented in the message.  */
 273   return get_opt_end (&result, result, endp);
 274 }
 275
 276
 277 /* RFC 2292, 6.3.6
 278
 279    This function is similar to the previously described
 280    inet6_option_next() function, except this function lets the caller
 281    specify the option type to be searched for, instead of always
 282    returning the next option in the ancillary data object.  cmsg is a
 283    pointer to cmsghdr structure of which cmsg_level equals IPPROTO_IPV6
 284    and cmsg_type equals either IPV6_HOPOPTS or IPV6_DSTOPTS.  */
 285 int
 286 inet6_option_find (cmsg, tptrp, type)
 287      const struct cmsghdr *cmsg;
 288      uint8_t **tptrp;
 289      int type;
 290 {
 291   /* Make sure it is an option of the right type.  */
 292   if (cmsg->cmsg_level != IPPROTO_IPV6
 293       || (cmsg->cmsg_type != IPV6_HOPOPTS && cmsg->cmsg_type != IPV6_DSTOPTS))
 294     return -1;
 295
 296   /* Pointer to the extension header.  We only compute the address, we
 297      don't access anything yet.  */
 298   const struct ip6_ext *ip6e = (const struct ip6_ext *) CMSG_DATA (cmsg);
 299
 300   /* Make sure the message is long enough.  */
 301   if (cmsg->cmsg_len < CMSG_LEN (sizeof (struct ip6_ext))
 302       /* Now we can access the extension header.  */
 303       || cmsg->cmsg_len < CMSG_LEN ((ip6e->ip6e_len + 1) * 8))
 304     /* Too small.  */
 305     return -1;
 306
 307   /* Determine the address of the byte past the message.  */
 308   const uint8_t *endp = CMSG_DATA (cmsg) + (ip6e->ip6e_len + 1) * 8;
 309
 310   const uint8_t *next;
 311   if (tptrp == NULL)
 312     /* This is the first call, return the first option if there is one.  */
 313     next = (const uint8_t *) (ip6e + 1);
 314   else
 315     {
 316       /* Make sure *TPTRP points to a beginning of a new option in
 317          the message.  The upper limit is checked in get_opt_end.  */
 318       if (*tptrp < (const uint8_t *) (ip6e + 1))
 319         return -1;
 320
 321       /* Get the beginning of the next option.  */
 322       if (get_opt_end (&next, *tptrp, endp) != 0)
 323         return -1;
 324     }
 325
 326   /* Now search for the appropriate typed entry.  */
 327   const uint8_t *result;
 328   do
 329     {
 330       result = next;
 331
 332       /* Get the end of this entry.  */
 333       if (get_opt_end (&next, result, endp) != 0)
 334         return -1;
 335     }
 336   while (*result != type);
 337
 338   /* We know where the next option starts.  */
 339   *tptrp = (uint8_t *) result;
 340
 341   /* Success.  */
 342   return 0;
 343 }