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         [IEEE80211_RADIOTAP_VHT] = { .align = 2, .size = 12, },
  47         /*
  48          * add more here as they are defined in radiotap.h
  49          */
  50 };
  51
  52 static const struct ieee80211_radiotap_namespace radiotap_ns = {
  53         .n_bits = ARRAY_SIZE(rtap_namespace_sizes),
  54         .align_size = rtap_namespace_sizes,
  55 };
  56
  57 /**
  58  * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
  59  * @iterator: radiotap_iterator to initialize
  60  * @radiotap_header: radiotap header to parse
  61  * @max_length: total length we can parse into (eg, whole packet length)
  62  *
  63  * Returns: 0 or a negative error code if there is a problem.
  64  *
  65  * This function initializes an opaque iterator struct which can then
  66  * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
  67  * argument which is present in the header.  It knows about extended
  68  * present headers and handles them.
  69  *
  70  * How to use:
  71  * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
  72  * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
  73  * checking for a good 0 return code.  Then loop calling
  74  * __ieee80211_radiotap_iterator_next()... it returns either 0,
  75  * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
  76  * The iterator's @this_arg member points to the start of the argument
  77  * associated with the current argument index that is present, which can be
  78  * found in the iterator's @this_arg_index member.  This arg index corresponds
  79  * to the IEEE80211_RADIOTAP_... defines.
  80  *
  81  * Radiotap header length:
  82  * You can find the CPU-endian total radiotap header length in
  83  * iterator->max_length after executing ieee80211_radiotap_iterator_init()
  84  * successfully.
  85  *
  86  * Alignment Gotcha:
  87  * You must take care when dereferencing iterator.this_arg
  88  * for multibyte types... the pointer is not aligned.  Use
  89  * get_unaligned((type *)iterator.this_arg) to dereference
  90  * iterator.this_arg for type "type" safely on all arches.
  91  *
  92  * Example code:
  93  * See Documentation/networking/radiotap-headers.txt
  94  */
  95
  96 int ieee80211_radiotap_iterator_init(
  97         struct ieee80211_radiotap_iterator *iterator,
  98         struct ieee80211_radiotap_header *radiotap_header,
  99         int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
 100 {
 101         /* check the radiotap header can actually be present */
 102         if (max_length < sizeof(struct ieee80211_radiotap_header))
 103                 return -EINVAL;
 104
 105         /* Linux only supports version 0 radiotap format */
 106         if (radiotap_header->it_version)
 107                 return -EINVAL;
 108
 109         /* sanity check for allowed length and radiotap length field */
 110         if (max_length < get_unaligned_le16(&radiotap_header->it_len))
 111                 return -EINVAL;
 112
 113         iterator->_rtheader = radiotap_header;
 114         iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
 115         iterator->_arg_index = 0;
 116         iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
 117         iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
 118         iterator->_reset_on_ext = 0;
 119         iterator->_next_bitmap = &radiotap_header->it_present;
 120         iterator->_next_bitmap++;
 121         iterator->_vns = vns;
 122         iterator->current_namespace = &radiotap_ns;
 123         iterator->is_radiotap_ns = 1;
 124
 125         /* find payload start allowing for extended bitmap(s) */
 126
 127         if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
 128                 if ((unsigned long)iterator->_arg -
 129                     (unsigned long)iterator->_rtheader + sizeof(uint32_t) >
 130                     (unsigned long)iterator->_max_length)
 131                         return -EINVAL;
 132                 while (get_unaligned_le32(iterator->_arg) &
 133                                         (1 << IEEE80211_RADIOTAP_EXT)) {
 134                         iterator->_arg += sizeof(uint32_t);
 135
 136                         /*
 137                          * check for insanity where the present bitmaps
 138                          * keep claiming to extend up to or even beyond the
 139                          * stated radiotap header length
 140                          */
 141
 142                         if ((unsigned long)iterator->_arg -
 143                             (unsigned long)iterator->_rtheader +
 144                             sizeof(uint32_t) >
 145                             (unsigned long)iterator->_max_length)
 146                                 return -EINVAL;
 147                 }
 148
 149                 iterator->_arg += sizeof(uint32_t);
 150
 151                 /*
 152                  * no need to check again for blowing past stated radiotap
 153                  * header length, because ieee80211_radiotap_iterator_next
 154                  * checks it before it is dereferenced
 155                  */
 156         }
 157
 158         iterator->this_arg = iterator->_arg;
 159
 160         /* we are all initialized happily */
 161
 162         return 0;
 163 }
 164 EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
 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
 188
 189 /**
 190  * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
 191  * @iterator: radiotap_iterator to move to next arg (if any)
 192  *
 193  * Returns: 0 if there is an argument to handle,
 194  * -ENOENT if there are no more args or -EINVAL
 195  * if there is something else wrong.
 196  *
 197  * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
 198  * in @this_arg_index and sets @this_arg to point to the
 199  * payload for the field.  It takes care of alignment handling and extended
 200  * present fields.  @this_arg can be changed by the caller (eg,
 201  * incremented to move inside a compound argument like
 202  * IEEE80211_RADIOTAP_CHANNEL).  The args pointed to are in
 203  * little-endian format whatever the endianess of your CPU.
 204  *
 205  * Alignment Gotcha:
 206  * You must take care when dereferencing iterator.this_arg
 207  * for multibyte types... the pointer is not aligned.  Use
 208  * get_unaligned((type *)iterator.this_arg) to dereference
 209  * iterator.this_arg for type "type" safely on all arches.
 210  */
 211
 212 int ieee80211_radiotap_iterator_next(
 213         struct ieee80211_radiotap_iterator *iterator)
 214 {
 215         while (1) {
 216                 int hit = 0;
 217                 int pad, align, size, subns;
 218                 uint32_t oui;
 219
 220                 /* if no more EXT bits, that's it */
 221                 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
 222                     !(iterator->_bitmap_shifter & 1))
 223                         return -ENOENT;
 224
 225                 if (!(iterator->_bitmap_shifter & 1))
 226                         goto next_entry; /* arg not present */
 227
 228                 /* get alignment/size of data */
 229                 switch (iterator->_arg_index % 32) {
 230                 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
 231                 case IEEE80211_RADIOTAP_EXT:
 232                         align = 1;
 233                         size = 0;
 234                         break;
 235                 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
 236                         align = 2;
 237                         size = 6;
 238                         break;
 239                 default:
 240                         if (!iterator->current_namespace ||
 241                             iterator->_arg_index >= iterator->current_namespace->n_bits) {
 242                                 if (iterator->current_namespace == &radiotap_ns)
 243                                         return -ENOENT;
 244                                 align = 0;
 245                         } else {
 246                                 align = iterator->current_namespace->align_size[iterator->_arg_index].align;
 247                                 size = iterator->current_namespace->align_size[iterator->_arg_index].size;
 248                         }
 249                         if (!align) {
 250                                 /* skip all subsequent data */
 251                                 iterator->_arg = iterator->_next_ns_data;
 252                                 /* give up on this namespace */
 253                                 iterator->current_namespace = NULL;
 254                                 goto next_entry;
 255                         }
 256                         break;
 257                 }
 258
 259                 /*
 260                  * arg is present, account for alignment padding
 261                  *
 262                  * Note that these alignments are relative to the start
 263                  * of the radiotap header.  There is no guarantee
 264                  * that the radiotap header itself is aligned on any
 265                  * kind of boundary.
 266                  *
 267                  * The above is why get_unaligned() is used to dereference
 268                  * multibyte elements from the radiotap area.
 269                  */
 270
 271                 pad = ((unsigned long)iterator->_arg -
 272                        (unsigned long)iterator->_rtheader) & (align - 1);
 273
 274                 if (pad)
 275                         iterator->_arg += align - pad;
 276
 277                 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
 278                         int vnslen;
 279
 280                         if ((unsigned long)iterator->_arg + size -
 281                             (unsigned long)iterator->_rtheader >
 282                             (unsigned long)iterator->_max_length)
 283                                 return -EINVAL;
 284
 285                         oui = (*iterator->_arg << 16) |
 286                                 (*(iterator->_arg + 1) << 8) |
 287                                 *(iterator->_arg + 2);
 288                         subns = *(iterator->_arg + 3);
 289
 290                         find_ns(iterator, oui, subns);
 291
 292                         vnslen = get_unaligned_le16(iterator->_arg + 4);
 293                         iterator->_next_ns_data = iterator->_arg + size + vnslen;
 294                         if (!iterator->current_namespace)
 295                                 size += vnslen;
 296                 }
 297
 298                 /*
 299                  * this is what we will return to user, but we need to
 300                  * move on first so next call has something fresh to test
 301                  */
 302                 iterator->this_arg_index = iterator->_arg_index;
 303                 iterator->this_arg = iterator->_arg;
 304                 iterator->this_arg_size = size;
 305
 306                 /* internally move on the size of this arg */
 307                 iterator->_arg += size;
 308
 309                 /*
 310                  * check for insanity where we are given a bitmap that
 311                  * claims to have more arg content than the length of the
 312                  * radiotap section.  We will normally end up equalling this
 313                  * max_length on the last arg, never exceeding it.
 314                  */
 315
 316                 if ((unsigned long)iterator->_arg -
 317                     (unsigned long)iterator->_rtheader >
 318                     (unsigned long)iterator->_max_length)
 319                         return -EINVAL;
 320
 321                 /* these special ones are valid in each bitmap word */
 322                 switch (iterator->_arg_index % 32) {
 323                 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
 324                         iterator->_reset_on_ext = 1;
 325
 326                         iterator->is_radiotap_ns = 0;
 327                         /*
 328                          * If parser didn't register this vendor
 329                          * namespace with us, allow it to show it
 330                          * as 'raw. Do do that, set argument index
 331                          * to vendor namespace.
 332                          */
 333                         iterator->this_arg_index =
 334                                 IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
 335                         if (!iterator->current_namespace)
 336                                 hit = 1;
 337                         goto next_entry;
 338                 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
 339                         iterator->_reset_on_ext = 1;
 340                         iterator->current_namespace = &radiotap_ns;
 341                         iterator->is_radiotap_ns = 1;
 342                         goto next_entry;
 343                 case IEEE80211_RADIOTAP_EXT:
 344                         /*
 345                          * bit 31 was set, there is more
 346                          * -- move to next u32 bitmap
 347                          */
 348                         iterator->_bitmap_shifter =
 349                                 get_unaligned_le32(iterator->_next_bitmap);
 350                         iterator->_next_bitmap++;
 351                         if (iterator->_reset_on_ext)
 352                                 iterator->_arg_index = 0;
 353                         else
 354                                 iterator->_arg_index++;
 355                         iterator->_reset_on_ext = 0;
 356                         break;
 357                 default:
 358                         /* we've got a hit! */
 359                         hit = 1;
 360  next_entry:
 361                         iterator->_bitmap_shifter >>= 1;
 362                         iterator->_arg_index++;
 363                 }
 364
 365                 /* if we found a valid arg earlier, return it now */
 366                 if (hit)
 367                         return 0;
 368         }
 369 }
 370 EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);