src/utils/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 #include "platform.h"
  17 #include "radiotap_iter.h"
  18
  19 /* function prototypes and related defs are in radiotap_iter.h */
  20
  21 static const struct radiotap_align_size rtap_namespace_sizes[] = {
  22         [IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, },
  23         [IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, },
  24         [IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, },
  25         [IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, },
  26         [IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, },
  27         [IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, },
  28         [IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, },
  29         [IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, },
  30         [IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, },
  31         [IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, },
  32         [IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, },
  33         [IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, },
  34         [IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, },
  35         [IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, },
  36         [IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, },
  37         [IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, },
  38         [IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, },
  39         [IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, },
  40         [IEEE80211_RADIOTAP_MCS] = { .align = 1, .size = 3, },
  41         [IEEE80211_RADIOTAP_AMPDU_STATUS] = { .align = 4, .size = 8, },
  42         /*
  43          * add more here as they are defined in radiotap.h
  44          */
  45 };
  46
  47 static const struct ieee80211_radiotap_namespace radiotap_ns = {
  48         .n_bits = sizeof(rtap_namespace_sizes) / sizeof(rtap_namespace_sizes[0]),
  49         .align_size = rtap_namespace_sizes,
  50 };
  51
  52 /**
  53  * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
  54  * @iterator: radiotap_iterator to initialize
  55  * @radiotap_header: radiotap header to parse
  56  * @max_length: total length we can parse into (eg, whole packet length)
  57  *
  58  * Returns: 0 or a negative error code if there is a problem.
  59  *
  60  * This function initializes an opaque iterator struct which can then
  61  * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
  62  * argument which is present in the header.  It knows about extended
  63  * present headers and handles them.
  64  *
  65  * How to use:
  66  * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
  67  * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
  68  * checking for a good 0 return code.  Then loop calling
  69  * __ieee80211_radiotap_iterator_next()... it returns either 0,
  70  * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
  71  * The iterator's @this_arg member points to the start of the argument
  72  * associated with the current argument index that is present, which can be
  73  * found in the iterator's @this_arg_index member.  This arg index corresponds
  74  * to the IEEE80211_RADIOTAP_... defines.
  75  *
  76  * Radiotap header length:
  77  * You can find the CPU-endian total radiotap header length in
  78  * iterator->max_length after executing ieee80211_radiotap_iterator_init()
  79  * successfully.
  80  *
  81  * Alignment Gotcha:
  82  * You must take care when dereferencing iterator.this_arg
  83  * for multibyte types... the pointer is not aligned.  Use
  84  * get_unaligned((type *)iterator.this_arg) to dereference
  85  * iterator.this_arg for type "type" safely on all arches.
  86  *
  87  * Example code: parse.c
  88  */
  89
  90 int ieee80211_radiotap_iterator_init(
  91         struct ieee80211_radiotap_iterator *iterator,
  92         struct ieee80211_radiotap_header *radiotap_header,
  93         int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
  94 {
  95         /* must at least have the radiotap header */
  96         if (max_length < (int)sizeof(struct ieee80211_radiotap_header))
  97                 return -EINVAL;
  98
  99         /* Linux only supports version 0 radiotap format */
 100         if (radiotap_header->it_version)
 101                 return -EINVAL;
 102
 103         /* sanity check for allowed length and radiotap length field */
 104         if (max_length < get_unaligned_le16(&radiotap_header->it_len))
 105                 return -EINVAL;
 106
 107         iterator->_rtheader = radiotap_header;
 108         iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
 109         iterator->_arg_index = 0;
 110         iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
 111         iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
 112         iterator->_next_ns_data = NULL;
 113         iterator->_reset_on_ext = 0;
 114         iterator->_next_bitmap = &radiotap_header->it_present;
 115         iterator->_next_bitmap++;
 116         iterator->_vns = vns;
 117         iterator->current_namespace = &radiotap_ns;
 118         iterator->is_radiotap_ns = 1;
 119 #ifdef RADIOTAP_SUPPORT_OVERRIDES
 120         iterator->n_overrides = 0;
 121         iterator->overrides = NULL;
 122 #endif
 123
 124         /* find payload start allowing for extended bitmap(s) */
 125
 126         if (iterator->_bitmap_shifter & BIT(IEEE80211_RADIOTAP_EXT)) {
 127                 if ((unsigned long)iterator->_arg -
 128                     (unsigned long)iterator->_rtheader + sizeof(uint32_t) >
 129                     (unsigned long)iterator->_max_length)
 130                         return -EINVAL;
 131                 while (get_unaligned_le32(iterator->_arg) &
 132                        BIT(IEEE80211_RADIOTAP_EXT)) {
 133                         iterator->_arg += sizeof(uint32_t);
 134
 135                         /*
 136                          * check for insanity where the present bitmaps
 137                          * keep claiming to extend up to or even beyond the
 138                          * stated radiotap header length
 139                          */
 140
 141                         if ((unsigned long)iterator->_arg -
 142                             (unsigned long)iterator->_rtheader +
 143                             sizeof(uint32_t) >
 144                             (unsigned long)iterator->_max_length)
 145                                 return -EINVAL;
 146                 }
 147
 148                 iterator->_arg += sizeof(uint32_t);
 149
 150                 /*
 151                  * no need to check again for blowing past stated radiotap
 152                  * header length, because ieee80211_radiotap_iterator_next
 153                  * checks it before it is dereferenced
 154                  */
 155         }
 156
 157         iterator->this_arg = iterator->_arg;
 158         iterator->this_arg_index = 0;
 159         iterator->this_arg_size = 0;
 160
 161         /* we are all initialized happily */
 162
 163         return 0;
 164 }
 165
 166 static void find_ns(struct ieee80211_radiotap_iterator *iterator,
 167                     uint32_t oui, uint8_t subns)
 168 {
 169         int i;
 170
 171         iterator->current_namespace = NULL;
 172
 173         if (!iterator->_vns)
 174                 return;
 175
 176         for (i = 0; i < iterator->_vns->n_ns; i++) {
 177                 if (iterator->_vns->ns[i].oui != oui)
 178                         continue;
 179                 if (iterator->_vns->ns[i].subns != subns)
 180                         continue;
 181
 182                 iterator->current_namespace = &iterator->_vns->ns[i];
 183                 break;
 184         }
 185 }
 186
 187 #ifdef RADIOTAP_SUPPORT_OVERRIDES
 188 static int find_override(struct ieee80211_radiotap_iterator *iterator,
 189                          int *align, int *size)
 190 {
 191         int i;
 192
 193         if (!iterator->overrides)
 194                 return 0;
 195
 196         for (i = 0; i < iterator->n_overrides; i++) {
 197                 if (iterator->_arg_index == iterator->overrides[i].field) {
 198                         *align = iterator->overrides[i].align;
 199                         *size = iterator->overrides[i].size;
 200                         if (!*align) /* erroneous override */
 201                                 return 0;
 202                         return 1;
 203                 }
 204         }
 205
 206         return 0;
 207 }
 208 #endif
 209
 210
 211 /**
 212  * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
 213  * @iterator: radiotap_iterator to move to next arg (if any)
 214  *
 215  * Returns: 0 if there is an argument to handle,
 216  * -ENOENT if there are no more args or -EINVAL
 217  * if there is something else wrong.
 218  *
 219  * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
 220  * in @this_arg_index and sets @this_arg to point to the
 221  * payload for the field.  It takes care of alignment handling and extended
 222  * present fields.  @this_arg can be changed by the caller (eg,
 223  * incremented to move inside a compound argument like
 224  * IEEE80211_RADIOTAP_CHANNEL).  The args pointed to are in
 225  * little-endian format whatever the endianess of your CPU.
 226  *
 227  * Alignment Gotcha:
 228  * You must take care when dereferencing iterator.this_arg
 229  * for multibyte types... the pointer is not aligned.  Use
 230  * get_unaligned((type *)iterator.this_arg) to dereference
 231  * iterator.this_arg for type "type" safely on all arches.
 232  */
 233
 234 int ieee80211_radiotap_iterator_next(
 235         struct ieee80211_radiotap_iterator *iterator)
 236 {
 237         while (1) {
 238                 int hit = 0;
 239                 int pad, align, size, subns;
 240                 uint32_t oui;
 241
 242                 /* if no more EXT bits, that's it */
 243                 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
 244                     !(iterator->_bitmap_shifter & 1))
 245                         return -ENOENT;
 246
 247                 if (!(iterator->_bitmap_shifter & 1))
 248                         goto next_entry; /* arg not present */
 249
 250                 /* get alignment/size of data */
 251                 switch (iterator->_arg_index % 32) {
 252                 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
 253                 case IEEE80211_RADIOTAP_EXT:
 254                         align = 1;
 255                         size = 0;
 256                         break;
 257                 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
 258                         align = 2;
 259                         size = 6;
 260                         break;
 261                 default:
 262 #ifdef RADIOTAP_SUPPORT_OVERRIDES
 263                         if (find_override(iterator, &align, &size)) {
 264                                 /* all set */
 265                         } else
 266 #endif
 267                         if (!iterator->current_namespace ||
 268                             iterator->_arg_index >= iterator->current_namespace->n_bits) {
 269                                 if (iterator->current_namespace == &radiotap_ns)
 270                                         return -ENOENT;
 271                                 align = 0;
 272                         } else {
 273                                 align = iterator->current_namespace->align_size[iterator->_arg_index].align;
 274                                 size = iterator->current_namespace->align_size[iterator->_arg_index].size;
 275                         }
 276                         if (!align) {
 277                                 /* skip all subsequent data */
 278                                 iterator->_arg = iterator->_next_ns_data;
 279                                 /* give up on this namespace */
 280                                 iterator->current_namespace = NULL;
 281                                 goto next_entry;
 282                         }
 283                         break;
 284                 }
 285
 286                 /*
 287                  * arg is present, account for alignment padding
 288                  *
 289                  * Note that these alignments are relative to the start
 290                  * of the radiotap header.  There is no guarantee
 291                  * that the radiotap header itself is aligned on any
 292                  * kind of boundary.
 293                  *
 294                  * The above is why get_unaligned() is used to dereference
 295                  * multibyte elements from the radiotap area.
 296                  */
 297
 298                 pad = ((unsigned long)iterator->_arg -
 299                        (unsigned long)iterator->_rtheader) & (align - 1);
 300
 301                 if (pad)
 302                         iterator->_arg += align - pad;
 303
 304                 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
 305                         int vnslen;
 306
 307                         if ((unsigned long)iterator->_arg + size -
 308                             (unsigned long)iterator->_rtheader >
 309                             (unsigned long)iterator->_max_length)
 310                                 return -EINVAL;
 311
 312                         oui = (*iterator->_arg << 16) |
 313                                 (*(iterator->_arg + 1) << 8) |
 314                                 *(iterator->_arg + 2);
 315                         subns = *(iterator->_arg + 3);
 316
 317                         find_ns(iterator, oui, subns);
 318
 319                         vnslen = get_unaligned_le16(iterator->_arg + 4);
 320                         iterator->_next_ns_data = iterator->_arg + size + vnslen;
 321                         if (!iterator->current_namespace)
 322                                 size += vnslen;
 323                 }
 324
 325                 /*
 326                  * this is what we will return to user, but we need to
 327                  * move on first so next call has something fresh to test
 328                  */
 329                 iterator->this_arg_index = iterator->_arg_index;
 330                 iterator->this_arg = iterator->_arg;
 331                 iterator->this_arg_size = size;
 332
 333                 /* internally move on the size of this arg */
 334                 iterator->_arg += size;
 335
 336                 /*
 337                  * check for insanity where we are given a bitmap that
 338                  * claims to have more arg content than the length of the
 339                  * radiotap section.  We will normally end up equalling this
 340                  * max_length on the last arg, never exceeding it.
 341                  */
 342
 343                 if ((unsigned long)iterator->_arg -
 344                     (unsigned long)iterator->_rtheader >
 345                     (unsigned long)iterator->_max_length)
 346                         return -EINVAL;
 347
 348                 /* these special ones are valid in each bitmap word */
 349                 switch (iterator->_arg_index % 32) {
 350                 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
 351                         iterator->_reset_on_ext = 1;
 352
 353                         iterator->is_radiotap_ns = 0;
 354                         /*
 355                          * If parser didn't register this vendor
 356                          * namespace with us, allow it to show it
 357                          * as 'raw. Do do that, set argument index
 358                          * to vendor namespace.
 359                          */
 360                         iterator->this_arg_index =
 361                                 IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
 362                         if (!iterator->current_namespace)
 363                                 hit = 1;
 364                         goto next_entry;
 365                 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
 366                         iterator->_reset_on_ext = 1;
 367                         iterator->current_namespace = &radiotap_ns;
 368                         iterator->is_radiotap_ns = 1;
 369                         goto next_entry;
 370                 case IEEE80211_RADIOTAP_EXT:
 371                         /*
 372                          * bit 31 was set, there is more
 373                          * -- move to next u32 bitmap
 374                          */
 375                         iterator->_bitmap_shifter =
 376                                 get_unaligned_le32(iterator->_next_bitmap);
 377                         iterator->_next_bitmap++;
 378                         if (iterator->_reset_on_ext)
 379                                 iterator->_arg_index = 0;
 380                         else
 381                                 iterator->_arg_index++;
 382                         iterator->_reset_on_ext = 0;
 383                         break;
 384                 default:
 385                         /* we've got a hit! */
 386                         hit = 1;
 387  next_entry:
 388                         iterator->_bitmap_shifter >>= 1;
 389                         iterator->_arg_index++;
 390                 }
 391
 392                 /* if we found a valid arg earlier, return it now */
 393                 if (hit)
 394                         return 0;
 395         }
 396 }