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