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