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 <net/cfg80211.h>
  18 #include <net/ieee80211_radiotap.h>
  19 #include <asm/unaligned.h>
  20
  21 /* function prototypes and related defs are in include/net/cfg80211.h */
  22
  23 static const struct radiotap_align_size rtap_namespace_sizes[] = {
  24         [IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, },
  25         [IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, },
  26         [IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, },
  27         [IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, },
  28         [IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, },
  29         [IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, },
  30         [IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, },
  31         [IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, },
  32         [IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, },
  33         [IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, },
  34         [IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, },
  35         [IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, },
  36         [IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, },
  37         [IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, },
  38         [IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, },
  39         [IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, },
  40         [IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, },
  41         [IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, },
  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:
  88  * See Documentation/networking/radiotap-headers.txt
  89  */
  90
  91 int ieee80211_radiotap_iterator_init(
  92         struct ieee80211_radiotap_iterator *iterator,
  93         struct ieee80211_radiotap_header *radiotap_header,
  94         int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
  95 {
  96         /* Linux only supports version 0 radiotap format */
  97         if (radiotap_header->it_version)
  98                 return -EINVAL;
  99
 100         /* sanity check for allowed length and radiotap length field */
 101         if (max_length < get_unaligned_le16(&radiotap_header->it_len))
 102                 return -EINVAL;
 103
 104         iterator->_rtheader = radiotap_header;
 105         iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
 106         iterator->_arg_index = 0;
 107         iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
 108         iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
 109         iterator->_reset_on_ext = 0;
 110         iterator->_next_bitmap = &radiotap_header->it_present;
 111         iterator->_next_bitmap++;
 112         iterator->_vns = vns;
 113         iterator->current_namespace = &radiotap_ns;
 114         iterator->is_radiotap_ns = 1;
 115
 116         /* find payload start allowing for extended bitmap(s) */
 117
 118         if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
 119                 while (get_unaligned_le32(iterator->_arg) &
 120                                         (1 << IEEE80211_RADIOTAP_EXT)) {
 121                         iterator->_arg += sizeof(uint32_t);
 122
 123                         /*
 124                          * check for insanity where the present bitmaps
 125                          * keep claiming to extend up to or even beyond the
 126                          * stated radiotap header length
 127                          */
 128
 129                         if ((unsigned long)iterator->_arg -
 130                             (unsigned long)iterator->_rtheader >
 131                             (unsigned long)iterator->_max_length)
 132                                 return -EINVAL;
 133                 }
 134
 135                 iterator->_arg += sizeof(uint32_t);
 136
 137                 /*
 138                  * no need to check again for blowing past stated radiotap
 139                  * header length, because ieee80211_radiotap_iterator_next
 140                  * checks it before it is dereferenced
 141                  */
 142         }
 143
 144         iterator->this_arg = iterator->_arg;
 145
 146         /* we are all initialized happily */
 147
 148         return 0;
 149 }
 150 EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
 151
 152 static void find_ns(struct ieee80211_radiotap_iterator *iterator,
 153                     uint32_t oui, uint8_t subns)
 154 {
 155         int i;
 156
 157         iterator->current_namespace = NULL;
 158
 159         if (!iterator->_vns)
 160                 return;
 161
 162         for (i = 0; i < iterator->_vns->n_ns; i++) {
 163                 if (iterator->_vns->ns[i].oui != oui)
 164                         continue;
 165                 if (iterator->_vns->ns[i].subns != subns)
 166                         continue;
 167
 168                 iterator->current_namespace = &iterator->_vns->ns[i];
 169                 break;
 170         }
 171 }
 172
 173
 174
 175 /**
 176  * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
 177  * @iterator: radiotap_iterator to move to next arg (if any)
 178  *
 179  * Returns: 0 if there is an argument to handle,
 180  * -ENOENT if there are no more args or -EINVAL
 181  * if there is something else wrong.
 182  *
 183  * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
 184  * in @this_arg_index and sets @this_arg to point to the
 185  * payload for the field.  It takes care of alignment handling and extended
 186  * present fields.  @this_arg can be changed by the caller (eg,
 187  * incremented to move inside a compound argument like
 188  * IEEE80211_RADIOTAP_CHANNEL).  The args pointed to are in
 189  * little-endian format whatever the endianess of your CPU.
 190  *
 191  * Alignment Gotcha:
 192  * You must take care when dereferencing iterator.this_arg
 193  * for multibyte types... the pointer is not aligned.  Use
 194  * get_unaligned((type *)iterator.this_arg) to dereference
 195  * iterator.this_arg for type "type" safely on all arches.
 196  */
 197
 198 int ieee80211_radiotap_iterator_next(
 199         struct ieee80211_radiotap_iterator *iterator)
 200 {
 201         while (1) {
 202                 int hit = 0;
 203                 int pad, align, size, subns, vnslen;
 204                 uint32_t oui;
 205
 206                 /* if no more EXT bits, that's it */
 207                 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
 208                     !(iterator->_bitmap_shifter & 1))
 209                         return -ENOENT;
 210
 211                 if (!(iterator->_bitmap_shifter & 1))
 212                         goto next_entry; /* arg not present */
 213
 214                 /* get alignment/size of data */
 215                 switch (iterator->_arg_index % 32) {
 216                 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
 217                 case IEEE80211_RADIOTAP_EXT:
 218                         align = 1;
 219                         size = 0;
 220                         break;
 221                 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
 222                         align = 2;
 223                         size = 6;
 224                         break;
 225                 default:
 226                         if (!iterator->current_namespace ||
 227                             iterator->_arg_index >= iterator->current_namespace->n_bits) {
 228                                 if (iterator->current_namespace == &radiotap_ns)
 229                                         return -ENOENT;
 230                                 align = 0;
 231                         } else {
 232                                 align = iterator->current_namespace->align_size[iterator->_arg_index].align;
 233                                 size = iterator->current_namespace->align_size[iterator->_arg_index].size;
 234                         }
 235                         if (!align) {
 236                                 /* skip all subsequent data */
 237                                 iterator->_arg = iterator->_next_ns_data;
 238                                 /* give up on this namespace */
 239                                 iterator->current_namespace = NULL;
 240                                 goto next_entry;
 241                         }
 242                         break;
 243                 }
 244
 245                 /*
 246                  * arg is present, account for alignment padding
 247                  *
 248                  * Note that these alignments are relative to the start
 249                  * of the radiotap header.  There is no guarantee
 250                  * that the radiotap header itself is aligned on any
 251                  * kind of boundary.
 252                  *
 253                  * The above is why get_unaligned() is used to dereference
 254                  * multibyte elements from the radiotap area.
 255                  */
 256
 257                 pad = ((unsigned long)iterator->_arg -
 258                        (unsigned long)iterator->_rtheader) & (align - 1);
 259
 260                 if (pad)
 261                         iterator->_arg += align - pad;
 262
 263                 /*
 264                  * this is what we will return to user, but we need to
 265                  * move on first so next call has something fresh to test
 266                  */
 267                 iterator->this_arg_index = iterator->_arg_index;
 268                 iterator->this_arg = iterator->_arg;
 269                 iterator->this_arg_size = size;
 270
 271                 /* internally move on the size of this arg */
 272                 iterator->_arg += size;
 273
 274                 /*
 275                  * check for insanity where we are given a bitmap that
 276                  * claims to have more arg content than the length of the
 277                  * radiotap section.  We will normally end up equalling this
 278                  * max_length on the last arg, never exceeding it.
 279                  */
 280
 281                 if ((unsigned long)iterator->_arg -
 282                     (unsigned long)iterator->_rtheader >
 283                     (unsigned long)iterator->_max_length)
 284                         return -EINVAL;
 285
 286                 /* these special ones are valid in each bitmap word */
 287                 switch (iterator->_arg_index % 32) {
 288                 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
 289                         iterator->_bitmap_shifter >>= 1;
 290                         iterator->_arg_index++;
 291
 292                         iterator->_reset_on_ext = 1;
 293
 294                         vnslen = get_unaligned_le16(iterator->this_arg + 4);
 295                         iterator->_next_ns_data = iterator->_arg + vnslen;
 296                         oui = (*iterator->this_arg << 16) |
 297                                 (*(iterator->this_arg + 1) << 8) |
 298                                 *(iterator->this_arg + 2);
 299                         subns = *(iterator->this_arg + 3);
 300
 301                         find_ns(iterator, oui, subns);
 302
 303                         iterator->is_radiotap_ns = 0;
 304                         /* allow parsers to show this information */
 305                         iterator->this_arg_index =
 306                                 IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
 307                         iterator->this_arg_size += vnslen;
 308                         if ((unsigned long)iterator->this_arg +
 309                             iterator->this_arg_size -
 310                             (unsigned long)iterator->_rtheader >
 311                             (unsigned long)(unsigned long)iterator->_max_length)
 312                                 return -EINVAL;
 313                         hit = 1;
 314                         break;
 315                 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
 316                         iterator->_bitmap_shifter >>= 1;
 317                         iterator->_arg_index++;
 318
 319                         iterator->_reset_on_ext = 1;
 320                         iterator->current_namespace = &radiotap_ns;
 321                         iterator->is_radiotap_ns = 1;
 322                         break;
 323                 case IEEE80211_RADIOTAP_EXT:
 324                         /*
 325                          * bit 31 was set, there is more
 326                          * -- move to next u32 bitmap
 327                          */
 328                         iterator->_bitmap_shifter =
 329                                 get_unaligned_le32(iterator->_next_bitmap);
 330                         iterator->_next_bitmap++;
 331                         if (iterator->_reset_on_ext)
 332                                 iterator->_arg_index = 0;
 333                         else
 334                                 iterator->_arg_index++;
 335                         iterator->_reset_on_ext = 0;
 336                         break;
 337                 default:
 338                         /* we've got a hit! */
 339                         hit = 1;
 340  next_entry:
 341                         iterator->_bitmap_shifter >>= 1;
 342                         iterator->_arg_index++;
 343                 }
 344
 345                 /* if we found a valid arg earlier, return it now */
 346                 if (hit)
 347                         return 0;
 348         }
 349 }
 350 EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);