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