radiotap.c 12 KB

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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. #include <linux/kernel.h>
  17. #include <linux/export.h>
  18. #include <net/cfg80211.h>
  19. #include <net/ieee80211_radiotap.h>
  20. #include <asm/unaligned.h>
  21. /* function prototypes and related defs are in include/net/cfg80211.h */
  22. static const struct radiotap_align_size rtap_namespace_sizes[] = {
  23. [IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, },
  24. [IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, },
  25. [IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, },
  26. [IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, },
  27. [IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, },
  28. [IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, },
  29. [IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, },
  30. [IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, },
  31. [IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, },
  32. [IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, },
  33. [IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, },
  34. [IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, },
  35. [IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, },
  36. [IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, },
  37. [IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, },
  38. [IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, },
  39. [IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, },
  40. [IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, },
  41. [IEEE80211_RADIOTAP_MCS] = { .align = 1, .size = 3, },
  42. [IEEE80211_RADIOTAP_AMPDU_STATUS] = { .align = 4, .size = 8, },
  43. [IEEE80211_RADIOTAP_VHT] = { .align = 2, .size = 12, },
  44. /*
  45. * add more here as they are defined in radiotap.h
  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. * 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. * @vns: vendor namespaces to parse
  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.rst
  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. /* check the radiotap header can actually be present */
  97. if (max_length < sizeof(struct ieee80211_radiotap_header))
  98. return -EINVAL;
  99. /* Linux only supports version 0 radiotap format */
  100. if (radiotap_header->it_version)
  101. return -EINVAL;
  102. /* sanity check for allowed length and radiotap length field */
  103. if (max_length < get_unaligned_le16(&radiotap_header->it_len))
  104. return -EINVAL;
  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. /* find payload start allowing for extended bitmap(s) */
  117. if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
  118. if ((unsigned long)iterator->_arg -
  119. (unsigned long)iterator->_rtheader + sizeof(uint32_t) >
  120. (unsigned long)iterator->_max_length)
  121. return -EINVAL;
  122. while (get_unaligned_le32(iterator->_arg) &
  123. (1 << IEEE80211_RADIOTAP_EXT)) {
  124. iterator->_arg += sizeof(uint32_t);
  125. /*
  126. * check for insanity where the present bitmaps
  127. * keep claiming to extend up to or even beyond the
  128. * stated radiotap header length
  129. */
  130. if ((unsigned long)iterator->_arg -
  131. (unsigned long)iterator->_rtheader +
  132. sizeof(uint32_t) >
  133. (unsigned long)iterator->_max_length)
  134. return -EINVAL;
  135. }
  136. iterator->_arg += sizeof(uint32_t);
  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. iterator->this_arg = iterator->_arg;
  144. /* we are all initialized happily */
  145. return 0;
  146. }
  147. EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
  148. static void find_ns(struct ieee80211_radiotap_iterator *iterator,
  149. uint32_t oui, uint8_t subns)
  150. {
  151. int i;
  152. iterator->current_namespace = NULL;
  153. if (!iterator->_vns)
  154. return;
  155. for (i = 0; i < iterator->_vns->n_ns; i++) {
  156. if (iterator->_vns->ns[i].oui != oui)
  157. continue;
  158. if (iterator->_vns->ns[i].subns != subns)
  159. continue;
  160. iterator->current_namespace = &iterator->_vns->ns[i];
  161. break;
  162. }
  163. }
  164. /**
  165. * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
  166. * @iterator: radiotap_iterator to move to next arg (if any)
  167. *
  168. * Returns: 0 if there is an argument to handle,
  169. * -ENOENT if there are no more args or -EINVAL
  170. * if there is something else wrong.
  171. *
  172. * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
  173. * in @this_arg_index and sets @this_arg to point to the
  174. * payload for the field. It takes care of alignment handling and extended
  175. * present fields. @this_arg can be changed by the caller (eg,
  176. * incremented to move inside a compound argument like
  177. * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in
  178. * little-endian format whatever the endianess of your CPU.
  179. *
  180. * Alignment Gotcha:
  181. * You must take care when dereferencing iterator.this_arg
  182. * for multibyte types... the pointer is not aligned. Use
  183. * get_unaligned((type *)iterator.this_arg) to dereference
  184. * iterator.this_arg for type "type" safely on all arches.
  185. */
  186. int ieee80211_radiotap_iterator_next(
  187. struct ieee80211_radiotap_iterator *iterator)
  188. {
  189. while (1) {
  190. int hit = 0;
  191. int pad, align, size, subns;
  192. uint32_t oui;
  193. /* if no more EXT bits, that's it */
  194. if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
  195. !(iterator->_bitmap_shifter & 1))
  196. return -ENOENT;
  197. if (!(iterator->_bitmap_shifter & 1))
  198. goto next_entry; /* arg not present */
  199. /* get alignment/size of data */
  200. switch (iterator->_arg_index % 32) {
  201. case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
  202. case IEEE80211_RADIOTAP_EXT:
  203. align = 1;
  204. size = 0;
  205. break;
  206. case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
  207. align = 2;
  208. size = 6;
  209. break;
  210. default:
  211. if (!iterator->current_namespace ||
  212. iterator->_arg_index >= iterator->current_namespace->n_bits) {
  213. if (iterator->current_namespace == &radiotap_ns)
  214. return -ENOENT;
  215. align = 0;
  216. } else {
  217. align = iterator->current_namespace->align_size[iterator->_arg_index].align;
  218. size = iterator->current_namespace->align_size[iterator->_arg_index].size;
  219. }
  220. if (!align) {
  221. /* skip all subsequent data */
  222. iterator->_arg = iterator->_next_ns_data;
  223. /* give up on this namespace */
  224. iterator->current_namespace = NULL;
  225. goto next_entry;
  226. }
  227. break;
  228. }
  229. /*
  230. * arg is present, account for alignment padding
  231. *
  232. * Note that these alignments are relative to the start
  233. * of the radiotap header. There is no guarantee
  234. * that the radiotap header itself is aligned on any
  235. * kind of boundary.
  236. *
  237. * The above is why get_unaligned() is used to dereference
  238. * multibyte elements from the radiotap area.
  239. */
  240. pad = ((unsigned long)iterator->_arg -
  241. (unsigned long)iterator->_rtheader) & (align - 1);
  242. if (pad)
  243. iterator->_arg += align - pad;
  244. if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
  245. int vnslen;
  246. if ((unsigned long)iterator->_arg + size -
  247. (unsigned long)iterator->_rtheader >
  248. (unsigned long)iterator->_max_length)
  249. return -EINVAL;
  250. oui = (*iterator->_arg << 16) |
  251. (*(iterator->_arg + 1) << 8) |
  252. *(iterator->_arg + 2);
  253. subns = *(iterator->_arg + 3);
  254. find_ns(iterator, oui, subns);
  255. vnslen = get_unaligned_le16(iterator->_arg + 4);
  256. iterator->_next_ns_data = iterator->_arg + size + vnslen;
  257. if (!iterator->current_namespace)
  258. size += vnslen;
  259. }
  260. /*
  261. * this is what we will return to user, but we need to
  262. * move on first so next call has something fresh to test
  263. */
  264. iterator->this_arg_index = iterator->_arg_index;
  265. iterator->this_arg = iterator->_arg;
  266. iterator->this_arg_size = size;
  267. /* internally move on the size of this arg */
  268. iterator->_arg += size;
  269. /*
  270. * check for insanity where we are given a bitmap that
  271. * claims to have more arg content than the length of the
  272. * radiotap section. We will normally end up equalling this
  273. * max_length on the last arg, never exceeding it.
  274. */
  275. if ((unsigned long)iterator->_arg -
  276. (unsigned long)iterator->_rtheader >
  277. (unsigned long)iterator->_max_length)
  278. return -EINVAL;
  279. /* these special ones are valid in each bitmap word */
  280. switch (iterator->_arg_index % 32) {
  281. case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
  282. iterator->_reset_on_ext = 1;
  283. iterator->is_radiotap_ns = 0;
  284. /*
  285. * If parser didn't register this vendor
  286. * namespace with us, allow it to show it
  287. * as 'raw. Do do that, set argument index
  288. * to vendor namespace.
  289. */
  290. iterator->this_arg_index =
  291. IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
  292. if (!iterator->current_namespace)
  293. hit = 1;
  294. goto next_entry;
  295. case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
  296. iterator->_reset_on_ext = 1;
  297. iterator->current_namespace = &radiotap_ns;
  298. iterator->is_radiotap_ns = 1;
  299. goto next_entry;
  300. case IEEE80211_RADIOTAP_EXT:
  301. /*
  302. * bit 31 was set, there is more
  303. * -- move to next u32 bitmap
  304. */
  305. iterator->_bitmap_shifter =
  306. get_unaligned_le32(iterator->_next_bitmap);
  307. iterator->_next_bitmap++;
  308. if (iterator->_reset_on_ext)
  309. iterator->_arg_index = 0;
  310. else
  311. iterator->_arg_index++;
  312. iterator->_reset_on_ext = 0;
  313. break;
  314. default:
  315. /* we've got a hit! */
  316. hit = 1;
  317. next_entry:
  318. iterator->_bitmap_shifter >>= 1;
  319. iterator->_arg_index++;
  320. }
  321. /* if we found a valid arg earlier, return it now */
  322. if (hit)
  323. return 0;
  324. }
  325. }
  326. EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);