linux/net/wireless/radiotap.c
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   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
  25static 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
  51static 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
  95int 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}
 154EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
 155
 156static 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
 202int 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}
 360EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);
 361
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