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 <net/cfg80211.h>
  19 #include <net/ieee80211_radiotap.h>
  20 #include <asm/unaligned.h>
  21
  22 /* function prototypes and related defs are in include/net/cfg80211.h */
  23
  24 static const struct radiotap_align_size rtap_namespace_sizes[] = {
  25         [IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, },
  26         [IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, },
  27         [IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, },
  28         [IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, },
  29         [IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, },
  30         [IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, },
  31         [IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, },
  32         [IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, },
  33         [IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, },
  34         [IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, },
  35         [IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, },
  36         [IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, },
  37         [IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, },
  38         [IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, },
  39         [IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, },
  40         [IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, },
  41         [IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, },
  42         [IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, },
  43         /*
  44          * add more here as they are defined in radiotap.h
  45          */
  46 };
  47
  48 static const struct ieee80211_radiotap_namespace radiotap_ns = {
  49         .n_bits = ARRAY_SIZE(rtap_namespace_sizes),
  50         .align_size = rtap_namespace_sizes,
  51 };
  52
  53 /**
  54  * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
  55  * @iterator: radiotap_iterator to initialize
  56  * @radiotap_header: radiotap header to parse
  57  * @max_length: total length we can parse into (eg, whole packet length)
  58  *
  59  * Returns: 0 or a negative error code if there is a problem.
  60  *
  61  * This function initializes an opaque iterator struct which can then
  62  * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
  63  * argument which is present in the header.  It knows about extended
  64  * present headers and handles them.
  65  *
  66  * How to use:
  67  * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
  68  * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
  69  * checking for a good 0 return code.  Then loop calling
  70  * __ieee80211_radiotap_iterator_next()... it returns either 0,
  71  * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
  72  * The iterator's @this_arg member points to the start of the argument
  73  * associated with the current argument index that is present, which can be
  74  * found in the iterator's @this_arg_index member.  This arg index corresponds
  75  * to the IEEE80211_RADIOTAP_... defines.
  76  *
  77  * Radiotap header length:
  78  * You can find the CPU-endian total radiotap header length in
  79  * iterator->max_length after executing ieee80211_radiotap_iterator_init()
  80  * successfully.
  81  *
  82  * Alignment Gotcha:
  83  * You must take care when dereferencing iterator.this_arg
  84  * for multibyte types... the pointer is not aligned.  Use
  85  * get_unaligned((type *)iterator.this_arg) to dereference
  86  * iterator.this_arg for type "type" safely on all arches.
  87  *
  88  * Example code:
  89  * See Documentation/networking/radiotap-headers.txt
  90  */
  91
  92 int ieee80211_radiotap_iterator_init(
  93         struct ieee80211_radiotap_iterator *iterator,
  94         struct ieee80211_radiotap_header *radiotap_header,
  95         int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
  96 {
  97         /* Linux only supports version 0 radiotap format */
  98         if (radiotap_header->it_version)
  99                 return -EINVAL;
 100
 101         /* sanity check for allowed length and radiotap length field */
 102         if (max_length < get_unaligned_le16(&radiotap_header->it_len))
 103                 return -EINVAL;
 104
 105         iterator->_rtheader = radiotap_header;
 106         iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
 107         iterator->_arg_index = 0;
 108         iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
 109         iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
 110         iterator->_reset_on_ext = 0;
 111         iterator->_next_bitmap = &radiotap_header->it_present;
 112         iterator->_next_bitmap++;
 113         iterator->_vns = vns;
 114         iterator->current_namespace = &radiotap_ns;
 115         iterator->is_radiotap_ns = 1;
 116
 117         /* find payload start allowing for extended bitmap(s) */
 118
 119         if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
 120                 while (get_unaligned_le32(iterator->_arg) &
 121                                         (1 << IEEE80211_RADIOTAP_EXT)) {
 122                         iterator->_arg += sizeof(uint32_t);
 123
 124                         /*
 125                          * check for insanity where the present bitmaps
 126                          * keep claiming to extend up to or even beyond the
 127                          * stated radiotap header length
 128                          */
 129
 130                         if ((unsigned long)iterator->_arg -
 131                             (unsigned long)iterator->_rtheader >
 132                             (unsigned long)iterator->_max_length)
 133                                 return -EINVAL;
 134                 }
 135
 136                 iterator->_arg += sizeof(uint32_t);
 137
 138                 /*
 139                  * no need to check again for blowing past stated radiotap
 140                  * header length, because ieee80211_radiotap_iterator_next
 141                  * checks it before it is dereferenced
 142                  */
 143         }
 144
 145         iterator->this_arg = iterator->_arg;
 146
 147         /* we are all initialized happily */
 148
 149         return 0;
 150 }
 151 EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
 152
 153 static void find_ns(struct ieee80211_radiotap_iterator *iterator,
 154                     uint32_t oui, uint8_t subns)
 155 {
 156         int i;
 157
 158         iterator->current_namespace = NULL;
 159
 160         if (!iterator->_vns)
 161                 return;
 162
 163         for (i = 0; i < iterator->_vns->n_ns; i++) {
 164                 if (iterator->_vns->ns[i].oui != oui)
 165                         continue;
 166                 if (iterator->_vns->ns[i].subns != subns)
 167                         continue;
 168
 169                 iterator->current_namespace = &iterator->_vns->ns[i];
 170                 break;
 171         }
 172 }
 173
 174
 175
 176 /**
 177  * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
 178  * @iterator: radiotap_iterator to move to next arg (if any)
 179  *
 180  * Returns: 0 if there is an argument to handle,
 181  * -ENOENT if there are no more args or -EINVAL
 182  * if there is something else wrong.
 183  *
 184  * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
 185  * in @this_arg_index and sets @this_arg to point to the
 186  * payload for the field.  It takes care of alignment handling and extended
 187  * present fields.  @this_arg can be changed by the caller (eg,
 188  * incremented to move inside a compound argument like
 189  * IEEE80211_RADIOTAP_CHANNEL).  The args pointed to are in
 190  * little-endian format whatever the endianess of your CPU.
 191  *
 192  * Alignment Gotcha:
 193  * You must take care when dereferencing iterator.this_arg
 194  * for multibyte types... the pointer is not aligned.  Use
 195  * get_unaligned((type *)iterator.this_arg) to dereference
 196  * iterator.this_arg for type "type" safely on all arches.
 197  */
 198
 199 int ieee80211_radiotap_iterator_next(
 200         struct ieee80211_radiotap_iterator *iterator)
 201 {
 202         while (1) {
 203                 int hit = 0;
 204                 int pad, align, size, subns;
 205                 uint32_t oui;
 206
 207                 /* if no more EXT bits, that's it */
 208                 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
 209                     !(iterator->_bitmap_shifter & 1))
 210                         return -ENOENT;
 211
 212                 if (!(iterator->_bitmap_shifter & 1))
 213                         goto next_entry; /* arg not present */
 214
 215                 /* get alignment/size of data */
 216                 switch (iterator->_arg_index % 32) {
 217                 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
 218                 case IEEE80211_RADIOTAP_EXT:
 219                         align = 1;
 220                         size = 0;
 221                         break;
 222                 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
 223                         align = 2;
 224                         size = 6;
 225                         break;
 226                 default:
 227                         if (!iterator->current_namespace ||
 228                             iterator->_arg_index >= iterator->current_namespace->n_bits) {
 229                                 if (iterator->current_namespace == &radiotap_ns)
 230                                         return -ENOENT;
 231                                 align = 0;
 232                         } else {
 233                                 align = iterator->current_namespace->align_size[iterator->_arg_index].align;
 234                                 size = iterator->current_namespace->align_size[iterator->_arg_index].size;
 235                         }
 236                         if (!align) {
 237                                 /* skip all subsequent data */
 238                                 iterator->_arg = iterator->_next_ns_data;
 239                                 /* give up on this namespace */
 240                                 iterator->current_namespace = NULL;
 241                                 goto next_entry;
 242                         }
 243                         break;
 244                 }
 245
 246                 /*
 247                  * arg is present, account for alignment padding
 248                  *
 249                  * Note that these alignments are relative to the start
 250                  * of the radiotap header.  There is no guarantee
 251                  * that the radiotap header itself is aligned on any
 252                  * kind of boundary.
 253                  *
 254                  * The above is why get_unaligned() is used to dereference
 255                  * multibyte elements from the radiotap area.
 256                  */
 257
 258                 pad = ((unsigned long)iterator->_arg -
 259                        (unsigned long)iterator->_rtheader) & (align - 1);
 260
 261                 if (pad)
 262                         iterator->_arg += align - pad;
 263
 264                 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
 265                         int vnslen;
 266
 267                         if ((unsigned long)iterator->_arg + size -
 268                             (unsigned long)iterator->_rtheader >
 269                             (unsigned long)iterator->_max_length)
 270                                 return -EINVAL;
 271
 272                         oui = (*iterator->_arg << 16) |
 273                                 (*(iterator->_arg + 1) << 8) |
 274                                 *(iterator->_arg + 2);
 275                         subns = *(iterator->_arg + 3);
 276
 277                         find_ns(iterator, oui, subns);
 278
 279                         vnslen = get_unaligned_le16(iterator->_arg + 4);
 280                         iterator->_next_ns_data = iterator->_arg + size + vnslen;
 281                         if (!iterator->current_namespace)
 282                                 size += vnslen;
 283                 }
 284
 285                 /*
 286                  * this is what we will return to user, but we need to
 287                  * move on first so next call has something fresh to test
 288                  */
 289                 iterator->this_arg_index = iterator->_arg_index;
 290                 iterator->this_arg = iterator->_arg;
 291                 iterator->this_arg_size = size;
 292
 293                 /* internally move on the size of this arg */
 294                 iterator->_arg += size;
 295
 296                 /*
 297                  * check for insanity where we are given a bitmap that
 298                  * claims to have more arg content than the length of the
 299                  * radiotap section.  We will normally end up equalling this
 300                  * max_length on the last arg, never exceeding it.
 301                  */
 302
 303                 if ((unsigned long)iterator->_arg -
 304                     (unsigned long)iterator->_rtheader >
 305                     (unsigned long)iterator->_max_length)
 306                         return -EINVAL;
 307
 308                 /* these special ones are valid in each bitmap word */
 309                 switch (iterator->_arg_index % 32) {
 310                 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
 311                         iterator->_reset_on_ext = 1;
 312
 313                         iterator->is_radiotap_ns = 0;
 314                         /*
 315                          * If parser didn't register this vendor
 316                          * namespace with us, allow it to show it
 317                          * as 'raw. Do do that, set argument index
 318                          * to vendor namespace.
 319                          */
 320                         iterator->this_arg_index =
 321                                 IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
 322                         if (!iterator->current_namespace)
 323                                 hit = 1;
 324                         goto next_entry;
 325                 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
 326                         iterator->_reset_on_ext = 1;
 327                         iterator->current_namespace = &radiotap_ns;
 328                         iterator->is_radiotap_ns = 1;
 329                         goto next_entry;
 330                 case IEEE80211_RADIOTAP_EXT:
 331                         /*
 332                          * bit 31 was set, there is more
 333                          * -- move to next u32 bitmap
 334                          */
 335                         iterator->_bitmap_shifter =
 336                                 get_unaligned_le32(iterator->_next_bitmap);
 337                         iterator->_next_bitmap++;
 338                         if (iterator->_reset_on_ext)
 339                                 iterator->_arg_index = 0;
 340                         else
 341                                 iterator->_arg_index++;
 342                         iterator->_reset_on_ext = 0;
 343                         break;
 344                 default:
 345                         /* we've got a hit! */
 346                         hit = 1;
 347  next_entry:
 348                         iterator->_bitmap_shifter >>= 1;
 349                         iterator->_arg_index++;
 350                 }
 351
 352                 /* if we found a valid arg earlier, return it now */
 353                 if (hit)
 354                         return 0;
 355         }
 356 }
 357 EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);