net/wireless/radiotap.c

   1 /*
   2  * Radiotap parser
   3  *
   4  * Copyright 2007               Andy Green <andy@warmcat.com>
   5  * Copyright 2009               Johannes Berg <johannes@sipsolutions.net>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * Alternatively, this software may be distributed under the terms of BSD
  12  * license.
  13  *
  14  * See COPYING for more details.
  15  */
  16
  17 #include <linux/kernel.h>
  18 #include <linux/export.h>
  19 #include <net/cfg80211.h>
  20 #include <net/ieee80211_radiotap.h>
  21 #include <asm/unaligned.h>
  22
  23 /* function prototypes and related defs are in include/net/cfg80211.h */
  24
  25 static const struct radiotap_align_size rtap_namespace_sizes[] = {
  26         [IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, },
  27         [IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, },
  28         [IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, },
  29         [IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, },
  30         [IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, },
  31         [IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, },
  32         [IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, },
  33         [IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, },
  34         [IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, },
  35         [IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, },
  36         [IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, },
  37         [IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, },
  38         [IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, },
  39         [IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, },
  40         [IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, },
  41         [IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, },
  42         [IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, },
  43         [IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, },
  44         /*
  45          * add more here as they are defined in radiotap.h
  46          */
  47 };
  48
  49 static const struct ieee80211_radiotap_namespace radiotap_ns = {
  50         .n_bits = ARRAY_SIZE(rtap_namespace_sizes),
  51         .align_size = rtap_namespace_sizes,
  52 };
  53
  54 /**
  55  * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
  56  * @iterator: radiotap_iterator to initialize
  57  * @radiotap_header: radiotap header to parse
  58  * @max_length: total length we can parse into (eg, whole packet length)
  59  *
  60  * Returns: 0 or a negative error code if there is a problem.
  61  *
  62  * This function initializes an opaque iterator struct which can then
  63  * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
  64  * argument which is present in the header.  It knows about extended
  65  * present headers and handles them.
  66  *
  67  * How to use:
  68  * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
  69  * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
  70  * checking for a good 0 return code.  Then loop calling
  71  * __ieee80211_radiotap_iterator_next()... it returns either 0,
  72  * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
  73  * The iterator's @this_arg member points to the start of the argument
  74  * associated with the current argument index that is present, which can be
  75  * found in the iterator's @this_arg_index member.  This arg index corresponds
  76  * to the IEEE80211_RADIOTAP_... defines.
  77  *
  78  * Radiotap header length:
  79  * You can find the CPU-endian total radiotap header length in
  80  * iterator->max_length after executing ieee80211_radiotap_iterator_init()
  81  * successfully.
  82  *
  83  * Alignment Gotcha:
  84  * You must take care when dereferencing iterator.this_arg
  85  * for multibyte types... the pointer is not aligned.  Use
  86  * get_unaligned((type *)iterator.this_arg) to dereference
  87  * iterator.this_arg for type "type" safely on all arches.
  88  *
  89  * Example code:
  90  * See Documentation/networking/radiotap-headers.txt
  91  */
  92
  93 int ieee80211_radiotap_iterator_init(
  94         struct ieee80211_radiotap_iterator *iterator,
  95         struct ieee80211_radiotap_header *radiotap_header,
  96         int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
  97 {
  98         /* Linux only supports version 0 radiotap format */
  99         if (radiotap_header->it_version)
 100                 return -EINVAL;
 101
 102         /* sanity check for allowed length and radiotap length field */
 103         if (max_length < get_unaligned_le16(&radiotap_header->it_len))
 104                 return -EINVAL;
 105
 106         iterator->_rtheader = radiotap_header;
 107         iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
 108         iterator->_arg_index = 0;
 109         iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
 110         iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
 111         iterator->_reset_on_ext = 0;
 112         iterator->_next_bitmap = &radiotap_header->it_present;
 113         iterator->_next_bitmap++;
 114         iterator->_vns = vns;
 115         iterator->current_namespace = &radiotap_ns;
 116         iterator->is_radiotap_ns = 1;
 117
 118         /* find payload start allowing for extended bitmap(s) */
 119
 120         if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
 121                 while (get_unaligned_le32(iterator->_arg) &
 122                                         (1 << IEEE80211_RADIOTAP_EXT)) {
 123                         iterator->_arg += sizeof(uint32_t);
 124
 125                         /*
 126                          * check for insanity where the present bitmaps
 127                          * keep claiming to extend up to or even beyond the
 128                          * stated radiotap header length
 129                          */
 130
 131                         if ((unsigned long)iterator->_arg -
 132                             (unsigned long)iterator->_rtheader >
 133                             (unsigned long)iterator->_max_length)
 134                                 return -EINVAL;
 135                 }
 136
 137                 iterator->_arg += sizeof(uint32_t);
 138
 139                 /*
 140                  * no need to check again for blowing past stated radiotap
 141                  * header length, because ieee80211_radiotap_iterator_next
 142                  * checks it before it is dereferenced
 143                  */
 144         }
 145
 146         iterator->this_arg = iterator->_arg;
 147
 148         /* we are all initialized happily */
 149
 150         return 0;
 151 }
 152 EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
 153
 154 static void find_ns(struct ieee80211_radiotap_iterator *iterator,
 155                     uint32_t oui, uint8_t subns)
 156 {
 157         int i;
 158
 159         iterator->current_namespace = NULL;
 160
 161         if (!iterator->_vns)
 162                 return;
 163
 164         for (i = 0; i < iterator->_vns->n_ns; i++) {
 165                 if (iterator->_vns->ns[i].oui != oui)
 166                         continue;
 167                 if (iterator->_vns->ns[i].subns != subns)
 168                         continue;
 169
 170                 iterator->current_namespace = &iterator->_vns->ns[i];
 171                 break;
 172         }
 173 }
 174
 175
 176
 177 /**
 178  * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
 179  * @iterator: radiotap_iterator to move to next arg (if any)
 180  *
 181  * Returns: 0 if there is an argument to handle,
 182  * -ENOENT if there are no more args or -EINVAL
 183  * if there is something else wrong.
 184  *
 185  * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
 186  * in @this_arg_index and sets @this_arg to point to the
 187  * payload for the field.  It takes care of alignment handling and extended
 188  * present fields.  @this_arg can be changed by the caller (eg,
 189  * incremented to move inside a compound argument like
 190  * IEEE80211_RADIOTAP_CHANNEL).  The args pointed to are in
 191  * little-endian format whatever the endianess of your CPU.
 192  *
 193  * Alignment Gotcha:
 194  * You must take care when dereferencing iterator.this_arg
 195  * for multibyte types... the pointer is not aligned.  Use
 196  * get_unaligned((type *)iterator.this_arg) to dereference
 197  * iterator.this_arg for type "type" safely on all arches.
 198  */
 199
 200 int ieee80211_radiotap_iterator_next(
 201         struct ieee80211_radiotap_iterator *iterator)
 202 {
 203         while (1) {
 204                 int hit = 0;
 205                 int pad, align, size, subns;
 206                 uint32_t oui;
 207
 208                 /* if no more EXT bits, that's it */
 209                 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
 210                     !(iterator->_bitmap_shifter & 1))
 211                         return -ENOENT;
 212
 213                 if (!(iterator->_bitmap_shifter & 1))
 214                         goto next_entry; /* arg not present */
 215
 216                 /* get alignment/size of data */
 217                 switch (iterator->_arg_index % 32) {
 218                 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
 219                 case IEEE80211_RADIOTAP_EXT:
 220                         align = 1;
 221                         size = 0;
 222                         break;
 223                 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
 224                         align = 2;
 225                         size = 6;
 226                         break;
 227                 default:
 228                         if (!iterator->current_namespace ||
 229                             iterator->_arg_index >= iterator->current_namespace->n_bits) {
 230                                 if (iterator->current_namespace == &radiotap_ns)
 231                                         return -ENOENT;
 232                                 align = 0;
 233                         } else {
 234                                 align = iterator->current_namespace->align_size[iterator->_arg_index].align;
 235                                 size = iterator->current_namespace->align_size[iterator->_arg_index].size;
 236                         }
 237                         if (!align) {
 238                                 /* skip all subsequent data */
 239                                 iterator->_arg = iterator->_next_ns_data;
 240                                 /* give up on this namespace */
 241                                 iterator->current_namespace = NULL;
 242                                 goto next_entry;
 243                         }
 244                         break;
 245                 }
 246
 247                 /*
 248                  * arg is present, account for alignment padding
 249                  *
 250                  * Note that these alignments are relative to the start
 251                  * of the radiotap header.  There is no guarantee
 252                  * that the radiotap header itself is aligned on any
 253                  * kind of boundary.
 254                  *
 255                  * The above is why get_unaligned() is used to dereference
 256                  * multibyte elements from the radiotap area.
 257                  */
 258
 259                 pad = ((unsigned long)iterator->_arg -
 260                        (unsigned long)iterator->_rtheader) & (align - 1);
 261
 262                 if (pad)
 263                         iterator->_arg += align - pad;
 264
 265                 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
 266                         int vnslen;
 267
 268                         if ((unsigned long)iterator->_arg + size -
 269                             (unsigned long)iterator->_rtheader >
 270                             (unsigned long)iterator->_max_length)
 271                                 return -EINVAL;
 272
 273                         oui = (*iterator->_arg << 16) |
 274                                 (*(iterator->_arg + 1) << 8) |
 275                                 *(iterator->_arg + 2);
 276                         subns = *(iterator->_arg + 3);
 277
 278                         find_ns(iterator, oui, subns);
 279
 280                         vnslen = get_unaligned_le16(iterator->_arg + 4);
 281                         iterator->_next_ns_data = iterator->_arg + size + vnslen;
 282                         if (!iterator->current_namespace)
 283                                 size += vnslen;
 284                 }
 285
 286                 /*
 287                  * this is what we will return to user, but we need to
 288                  * move on first so next call has something fresh to test
 289                  */
 290                 iterator->this_arg_index = iterator->_arg_index;
 291                 iterator->this_arg = iterator->_arg;
 292                 iterator->this_arg_size = size;
 293
 294                 /* internally move on the size of this arg */
 295                 iterator->_arg += size;
 296
 297                 /*
 298                  * check for insanity where we are given a bitmap that
 299                  * claims to have more arg content than the length of the
 300                  * radiotap section.  We will normally end up equalling this
 301                  * max_length on the last arg, never exceeding it.
 302                  */
 303
 304                 if ((unsigned long)iterator->_arg -
 305                     (unsigned long)iterator->_rtheader >
 306                     (unsigned long)iterator->_max_length)
 307                         return -EINVAL;
 308
 309                 /* these special ones are valid in each bitmap word */
 310                 switch (iterator->_arg_index % 32) {
 311                 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
 312                         iterator->_reset_on_ext = 1;
 313
 314                         iterator->is_radiotap_ns = 0;
 315                         /*
 316                          * If parser didn't register this vendor
 317                          * namespace with us, allow it to show it
 318                          * as 'raw. Do do that, set argument index
 319                          * to vendor namespace.
 320                          */
 321                         iterator->this_arg_index =
 322                                 IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
 323                         if (!iterator->current_namespace)
 324                                 hit = 1;
 325                         goto next_entry;
 326                 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
 327                         iterator->_reset_on_ext = 1;
 328                         iterator->current_namespace = &radiotap_ns;
 329                         iterator->is_radiotap_ns = 1;
 330                         goto next_entry;
 331                 case IEEE80211_RADIOTAP_EXT:
 332                         /*
 333                          * bit 31 was set, there is more
 334                          * -- move to next u32 bitmap
 335                          */
 336                         iterator->_bitmap_shifter =
 337                                 get_unaligned_le32(iterator->_next_bitmap);
 338                         iterator->_next_bitmap++;
 339                         if (iterator->_reset_on_ext)
 340                                 iterator->_arg_index = 0;
 341                         else
 342                                 iterator->_arg_index++;
 343                         iterator->_reset_on_ext = 0;
 344                         break;
 345                 default:
 346                         /* we've got a hit! */
 347                         hit = 1;
 348  next_entry:
 349                         iterator->_bitmap_shifter >>= 1;
 350                         iterator->_arg_index++;
 351                 }
 352
 353                 /* if we found a valid arg earlier, return it now */
 354                 if (hit)
 355                         return 0;
 356         }
 357 }
 358 EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);