inet/inet6_opt.c

   1 /* Copyright (C) 2006-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2006.
   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 <string.h>
  20 #include <netinet/in.h>
  21 #include <netinet/ip6.h>
  22
  23
  24 /* RFC 3542, 10.1
  25
  26    This function returns the number of bytes needed for the empty
  27    extension header i.e., without any options.  If EXTBUF is not NULL it
  28    also initializes the extension header to have the correct length
  29    field.  In that case if the EXTLEN value is not a positive (i.e.,
  30    non-zero) multiple of 8 the function fails and returns -1.  */
  31 int
  32 inet6_opt_init (void *extbuf, socklen_t extlen)
  33 {
  34   if (extbuf != NULL)
  35     {
  36       if (extlen <= 0 || (extlen % 8) != 0 || extlen > 256 * 8)
  37         return -1;
  38
  39       /* Fill in the length in units of 8 octets.  */
  40       struct ip6_hbh *extp = (struct ip6_hbh *) extbuf;
  41
  42       /* RFC 2460 requires that the header extension length is the
  43          length of the option header in 8-byte units, not including
  44          the first 8 bytes.  Hence we have to subtract one.  */
  45       extp->ip6h_len = extlen / 8 - 1;
  46     }
  47
  48   return sizeof (struct ip6_hbh);
  49 }
  50
  51
  52 static void
  53 add_padding (uint8_t *extbuf, int offset, int npad)
  54 {
  55   if (npad == 1)
  56     extbuf[offset] = IP6OPT_PAD1;
  57   else if (npad > 0)
  58     {
  59       struct ip6_opt *pad_opt = (struct ip6_opt *) (extbuf + offset);
  60
  61       pad_opt->ip6o_type = IP6OPT_PADN;
  62       pad_opt->ip6o_len = npad - sizeof (struct ip6_opt);
  63       /* Clear the memory used by the padding.  */
  64       memset (pad_opt + 1, '\0', pad_opt->ip6o_len);
  65     }
  66 }
  67
  68
  69
  70 /* RFC 3542, 10.2
  71
  72    This function returns the updated total length taking into account
  73    adding an option with length 'len' and alignment 'align'.  If
  74    EXTBUF is not NULL then, in addition to returning the length, the
  75    function inserts any needed pad option, initializes the option
  76    (setting the type and length fields) and returns a pointer to the
  77    location for the option content in databufp.  If the option does
  78    not fit in the extension header buffer the function returns -1.  */
  79 int
  80 inet6_opt_append (void *extbuf, socklen_t extlen, int offset, uint8_t type,
  81                   socklen_t len, uint8_t align, void **databufp)
  82 {
  83   /* Check minimum offset.  */
  84   if (offset < sizeof (struct ip6_hbh))
  85     return -1;
  86
  87   /* One cannot add padding options.  */
  88   if (type == IP6OPT_PAD1 || type == IP6OPT_PADN)
  89     return -1;
  90
  91   /* The option length must fit in one octet.  */
  92   if (len > 255)
  93     return -1;
  94
  95   /* The alignment can only by 1, 2, 4, or 8 and must not exceed the
  96      option length.  */
  97   if (align == 0 || align > 8 || (align & (align - 1)) != 0 || align > len)
  98     return -1;
  99
 100   /* Determine the needed padding for alignment.  Following the
 101      current content of the buffer we have the is the IPv6 option type
 102      and length, followed immediately by the data.  The data has the
 103      alignment constraints.  Therefore padding must be inserted in the
 104      form of padding options before the new option. */
 105   int data_offset = offset + sizeof (struct ip6_opt);
 106   int npad = (align - data_offset % align) & (align - 1);
 107
 108   if (extbuf != NULL)
 109     {
 110       /* Now we can check whether the buffer is large enough.  */
 111       if (data_offset + npad + len > extlen)
 112         return -1;
 113
 114       add_padding (extbuf, offset, npad);
 115
 116       offset += npad;
 117
 118       /* Now prepare the option itself.  */
 119       struct ip6_opt *opt = (struct ip6_opt *) ((uint8_t *) extbuf + offset);
 120
 121       opt->ip6o_type = type;
 122       opt->ip6o_len = len;
 123
 124       *databufp = opt + 1;
 125     }
 126   else
 127     offset += npad;
 128
 129   return offset + sizeof (struct ip6_opt) + len;
 130 }
 131
 132
 133 /* RFC 3542, 10.3
 134
 135    This function returns the updated total length taking into account
 136    the final padding of the extension header to make it a multiple of
 137    8 bytes.  If EXTBUF is not NULL the function also initializes the
 138    option by inserting a Pad1 or PadN option of the proper length.  */
 139 int
 140 inet6_opt_finish (void *extbuf, socklen_t extlen, int offset)
 141 {
 142   /* Check minimum offset.  */
 143   if (offset < sizeof (struct ip6_hbh))
 144     return -1;
 145
 146   /* Required padding at the end.  */
 147   int npad = (8 - (offset & 7)) & 7;
 148
 149   if (extbuf != NULL)
 150     {
 151       /* Make sure the buffer is large enough.  */
 152       if (offset + npad > extlen)
 153         return -1;
 154
 155       add_padding (extbuf, offset, npad);
 156     }
 157
 158   return offset + npad;
 159 }
 160
 161
 162 /* RFC 3542, 10.4
 163
 164    This function inserts data items of various sizes in the data
 165    portion of the option.  VAL should point to the data to be
 166    inserted.  OFFSET specifies where in the data portion of the option
 167    the value should be inserted; the first byte after the option type
 168    and length is accessed by specifying an offset of zero.  */
 169 int
 170 inet6_opt_set_val (void *databuf, int offset, void *val, socklen_t vallen)
 171 {
 172   memcpy ((uint8_t *) databuf + offset, val, vallen);
 173
 174   return offset + vallen;
 175 }
 176
 177
 178 /* RFC 3542, 10.5
 179
 180    This function parses received option extension headers returning
 181    the next option.  EXTBUF and EXTLEN specifies the extension header.
 182    OFFSET should either be zero (for the first option) or the length
 183    returned by a previous call to 'inet6_opt_next' or
 184    'inet6_opt_find'.  It specifies the position where to continue
 185    scanning the extension buffer.  */
 186 int
 187 inet6_opt_next (void *extbuf, socklen_t extlen, int offset, uint8_t *typep,
 188                 socklen_t *lenp, void **databufp)
 189 {
 190   if (offset == 0)
 191     offset = sizeof (struct ip6_hbh);
 192   else if (offset < sizeof (struct ip6_hbh))
 193     return -1;
 194
 195   while (offset < extlen)
 196     {
 197       struct ip6_opt *opt = (struct ip6_opt *) ((uint8_t *) extbuf + offset);
 198
 199       if (opt->ip6o_type == IP6OPT_PAD1)
 200         /* Single byte padding.  */
 201         ++offset;
 202       else if (opt->ip6o_type == IP6OPT_PADN)
 203         offset += sizeof (struct ip6_opt) + opt->ip6o_len;
 204       else
 205         {
 206           /* Check whether the option is valid.  */
 207           offset += sizeof (struct ip6_opt) + opt->ip6o_len;
 208           if (offset > extlen)
 209             return -1;
 210
 211           *typep = opt->ip6o_type;
 212           *lenp = opt->ip6o_len;
 213           *databufp = opt + 1;
 214           return offset;
 215         }
 216     }
 217
 218   return -1;
 219 }
 220
 221
 222 /* RFC 3542, 10.6
 223
 224    This function is similar to the previously described
 225    'inet6_opt_next' function, except this function lets the caller
 226    specify the option type to be searched for, instead of always
 227    returning the next option in the extension header.  */
 228 int
 229 inet6_opt_find (void *extbuf, socklen_t extlen, int offset, uint8_t type,
 230                 socklen_t *lenp, void **databufp)
 231 {
 232   if (offset == 0)
 233     offset = sizeof (struct ip6_hbh);
 234   else if (offset < sizeof (struct ip6_hbh))
 235     return -1;
 236
 237   while (offset < extlen)
 238     {
 239       struct ip6_opt *opt = (struct ip6_opt *) ((uint8_t *) extbuf + offset);
 240
 241       if (opt->ip6o_type == IP6OPT_PAD1)
 242         {
 243           /* Single byte padding.  */
 244           ++offset;
 245           if (type == IP6OPT_PAD1)
 246             {
 247               *lenp = 0;
 248               *databufp = (uint8_t *) extbuf + offset;
 249               return offset;
 250             }
 251         }
 252       else if (opt->ip6o_type != type)
 253         offset += sizeof (struct ip6_opt) + opt->ip6o_len;
 254       else
 255         {
 256           /* Check whether the option is valid.  */
 257           offset += sizeof (struct ip6_opt) + opt->ip6o_len;
 258           if (offset > extlen)
 259             return -1;
 260
 261           *lenp = opt->ip6o_len;
 262           *databufp = opt + 1;
 263           return offset;
 264         }
 265     }
 266
 267   return -1;
 268 }
 269
 270
 271 /* RFC 3542, 10.7
 272
 273    This function extracts data items of various sizes in the data
 274    portion of the option.  */
 275 int
 276 inet6_opt_get_val (void *databuf, int offset, void *val, socklen_t vallen)
 277 {
 278   memcpy (val, (uint8_t *) databuf + offset, vallen);
 279
 280   return offset + vallen;
 281 }