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Andy Green179f8312007-07-10 19:29:38 +02001/*
2 * Radiotap parser
3 *
4 * Copyright 2007 Andy Green <andy@warmcat.com>
Johannes Berg33e5a2f2010-02-03 10:24:30 +01005 * 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.
Andy Green179f8312007-07-10 19:29:38 +020015 */
16
Nikitas Angelinas94262312010-09-08 22:29:53 +010017#include <linux/kernel.h>
Paul Gortmakerbc3b2d72011-07-15 11:47:34 -040018#include <linux/export.h>
Andy Green179f8312007-07-10 19:29:38 +020019#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
Johannes Berg33e5a2f2010-02-03 10:24:30 +010025static 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, },
Johannes Berg48613ec2012-07-05 11:32:16 +020044 [IEEE80211_RADIOTAP_MCS] = { .align = 1, .size = 3, },
45 [IEEE80211_RADIOTAP_AMPDU_STATUS] = { .align = 4, .size = 8, },
Johannes Berg33e5a2f2010-02-03 10:24:30 +010046 /*
47 * add more here as they are defined in radiotap.h
48 */
49};
50
51static const struct ieee80211_radiotap_namespace radiotap_ns = {
Nikitas Angelinas94262312010-09-08 22:29:53 +010052 .n_bits = ARRAY_SIZE(rtap_namespace_sizes),
Johannes Berg33e5a2f2010-02-03 10:24:30 +010053 .align_size = rtap_namespace_sizes,
54};
55
Andy Green179f8312007-07-10 19:29:38 +020056/**
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(
Johannes Berg33e5a2f2010-02-03 10:24:30 +010096 struct ieee80211_radiotap_iterator *iterator,
97 struct ieee80211_radiotap_header *radiotap_header,
98 int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
Andy Green179f8312007-07-10 19:29:38 +020099{
Johannes Bergf5563312013-10-11 14:47:05 +0200100 /* check the radiotap header can actually be present */
101 if (max_length < sizeof(struct ieee80211_radiotap_header))
102 return -EINVAL;
103
Andy Green179f8312007-07-10 19:29:38 +0200104 /* Linux only supports version 0 radiotap format */
105 if (radiotap_header->it_version)
106 return -EINVAL;
107
108 /* sanity check for allowed length and radiotap length field */
Harvey Harrisonae7245c2008-05-01 22:19:33 -0700109 if (max_length < get_unaligned_le16(&radiotap_header->it_len))
Andy Green179f8312007-07-10 19:29:38 +0200110 return -EINVAL;
111
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100112 iterator->_rtheader = radiotap_header;
113 iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
114 iterator->_arg_index = 0;
115 iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
116 iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
117 iterator->_reset_on_ext = 0;
118 iterator->_next_bitmap = &radiotap_header->it_present;
119 iterator->_next_bitmap++;
120 iterator->_vns = vns;
121 iterator->current_namespace = &radiotap_ns;
122 iterator->is_radiotap_ns = 1;
Andy Green179f8312007-07-10 19:29:38 +0200123
124 /* find payload start allowing for extended bitmap(s) */
125
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100126 if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
Johannes Bergbd02cd22013-12-16 12:04:36 +0100127 if ((unsigned long)iterator->_arg -
128 (unsigned long)iterator->_rtheader + sizeof(uint32_t) >
129 (unsigned long)iterator->_max_length)
130 return -EINVAL;
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100131 while (get_unaligned_le32(iterator->_arg) &
132 (1 << IEEE80211_RADIOTAP_EXT)) {
133 iterator->_arg += sizeof(uint32_t);
Andy Green179f8312007-07-10 19:29:38 +0200134
135 /*
136 * check for insanity where the present bitmaps
137 * keep claiming to extend up to or even beyond the
138 * stated radiotap header length
139 */
140
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100141 if ((unsigned long)iterator->_arg -
Johannes Bergf5563312013-10-11 14:47:05 +0200142 (unsigned long)iterator->_rtheader +
143 sizeof(uint32_t) >
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100144 (unsigned long)iterator->_max_length)
Andy Green179f8312007-07-10 19:29:38 +0200145 return -EINVAL;
146 }
147
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100148 iterator->_arg += sizeof(uint32_t);
Andy Green179f8312007-07-10 19:29:38 +0200149
150 /*
151 * no need to check again for blowing past stated radiotap
152 * header length, because ieee80211_radiotap_iterator_next
153 * checks it before it is dereferenced
154 */
155 }
156
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100157 iterator->this_arg = iterator->_arg;
158
Andy Green179f8312007-07-10 19:29:38 +0200159 /* we are all initialized happily */
160
161 return 0;
162}
163EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
164
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100165static void find_ns(struct ieee80211_radiotap_iterator *iterator,
166 uint32_t oui, uint8_t subns)
167{
168 int i;
169
170 iterator->current_namespace = NULL;
171
172 if (!iterator->_vns)
173 return;
174
175 for (i = 0; i < iterator->_vns->n_ns; i++) {
176 if (iterator->_vns->ns[i].oui != oui)
177 continue;
178 if (iterator->_vns->ns[i].subns != subns)
179 continue;
180
181 iterator->current_namespace = &iterator->_vns->ns[i];
182 break;
183 }
184}
185
186
Andy Green179f8312007-07-10 19:29:38 +0200187
188/**
189 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
190 * @iterator: radiotap_iterator to move to next arg (if any)
191 *
192 * Returns: 0 if there is an argument to handle,
193 * -ENOENT if there are no more args or -EINVAL
194 * if there is something else wrong.
195 *
196 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
197 * in @this_arg_index and sets @this_arg to point to the
198 * payload for the field. It takes care of alignment handling and extended
199 * present fields. @this_arg can be changed by the caller (eg,
200 * incremented to move inside a compound argument like
201 * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in
202 * little-endian format whatever the endianess of your CPU.
203 *
204 * Alignment Gotcha:
205 * You must take care when dereferencing iterator.this_arg
206 * for multibyte types... the pointer is not aligned. Use
207 * get_unaligned((type *)iterator.this_arg) to dereference
208 * iterator.this_arg for type "type" safely on all arches.
209 */
210
211int ieee80211_radiotap_iterator_next(
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100212 struct ieee80211_radiotap_iterator *iterator)
Andy Green179f8312007-07-10 19:29:38 +0200213{
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100214 while (1) {
Andy Green179f8312007-07-10 19:29:38 +0200215 int hit = 0;
Johannes Berg9ebad4a2010-10-14 13:41:35 +0200216 int pad, align, size, subns;
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100217 uint32_t oui;
Andy Green179f8312007-07-10 19:29:38 +0200218
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100219 /* if no more EXT bits, that's it */
220 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
221 !(iterator->_bitmap_shifter & 1))
222 return -ENOENT;
223
224 if (!(iterator->_bitmap_shifter & 1))
Andy Green179f8312007-07-10 19:29:38 +0200225 goto next_entry; /* arg not present */
226
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100227 /* get alignment/size of data */
228 switch (iterator->_arg_index % 32) {
229 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
230 case IEEE80211_RADIOTAP_EXT:
231 align = 1;
232 size = 0;
233 break;
234 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
235 align = 2;
236 size = 6;
237 break;
238 default:
239 if (!iterator->current_namespace ||
240 iterator->_arg_index >= iterator->current_namespace->n_bits) {
241 if (iterator->current_namespace == &radiotap_ns)
242 return -ENOENT;
243 align = 0;
244 } else {
245 align = iterator->current_namespace->align_size[iterator->_arg_index].align;
246 size = iterator->current_namespace->align_size[iterator->_arg_index].size;
247 }
248 if (!align) {
249 /* skip all subsequent data */
250 iterator->_arg = iterator->_next_ns_data;
251 /* give up on this namespace */
252 iterator->current_namespace = NULL;
253 goto next_entry;
254 }
255 break;
256 }
257
Andy Green179f8312007-07-10 19:29:38 +0200258 /*
259 * arg is present, account for alignment padding
Andy Green179f8312007-07-10 19:29:38 +0200260 *
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100261 * Note that these alignments are relative to the start
262 * of the radiotap header. There is no guarantee
Andy Green179f8312007-07-10 19:29:38 +0200263 * that the radiotap header itself is aligned on any
264 * kind of boundary.
265 *
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100266 * The above is why get_unaligned() is used to dereference
267 * multibyte elements from the radiotap area.
Andy Green179f8312007-07-10 19:29:38 +0200268 */
269
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100270 pad = ((unsigned long)iterator->_arg -
271 (unsigned long)iterator->_rtheader) & (align - 1);
Andy Green179f8312007-07-10 19:29:38 +0200272
273 if (pad)
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100274 iterator->_arg += align - pad;
Andy Green179f8312007-07-10 19:29:38 +0200275
Johannes Berg9ebad4a2010-10-14 13:41:35 +0200276 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
277 int vnslen;
278
279 if ((unsigned long)iterator->_arg + size -
280 (unsigned long)iterator->_rtheader >
281 (unsigned long)iterator->_max_length)
282 return -EINVAL;
283
284 oui = (*iterator->_arg << 16) |
285 (*(iterator->_arg + 1) << 8) |
286 *(iterator->_arg + 2);
287 subns = *(iterator->_arg + 3);
288
289 find_ns(iterator, oui, subns);
290
291 vnslen = get_unaligned_le16(iterator->_arg + 4);
292 iterator->_next_ns_data = iterator->_arg + size + vnslen;
293 if (!iterator->current_namespace)
294 size += vnslen;
295 }
296
Andy Green179f8312007-07-10 19:29:38 +0200297 /*
298 * this is what we will return to user, but we need to
299 * move on first so next call has something fresh to test
300 */
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100301 iterator->this_arg_index = iterator->_arg_index;
302 iterator->this_arg = iterator->_arg;
303 iterator->this_arg_size = size;
Andy Green179f8312007-07-10 19:29:38 +0200304
305 /* internally move on the size of this arg */
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100306 iterator->_arg += size;
Andy Green179f8312007-07-10 19:29:38 +0200307
308 /*
309 * check for insanity where we are given a bitmap that
310 * claims to have more arg content than the length of the
311 * radiotap section. We will normally end up equalling this
312 * max_length on the last arg, never exceeding it.
313 */
314
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100315 if ((unsigned long)iterator->_arg -
316 (unsigned long)iterator->_rtheader >
317 (unsigned long)iterator->_max_length)
Andy Green179f8312007-07-10 19:29:38 +0200318 return -EINVAL;
319
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100320 /* these special ones are valid in each bitmap word */
321 switch (iterator->_arg_index % 32) {
322 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100323 iterator->_reset_on_ext = 1;
324
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100325 iterator->is_radiotap_ns = 0;
Johannes Berg9ebad4a2010-10-14 13:41:35 +0200326 /*
327 * If parser didn't register this vendor
328 * namespace with us, allow it to show it
329 * as 'raw. Do do that, set argument index
330 * to vendor namespace.
331 */
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100332 iterator->this_arg_index =
333 IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
Johannes Berg9ebad4a2010-10-14 13:41:35 +0200334 if (!iterator->current_namespace)
335 hit = 1;
336 goto next_entry;
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100337 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100338 iterator->_reset_on_ext = 1;
339 iterator->current_namespace = &radiotap_ns;
340 iterator->is_radiotap_ns = 1;
Johannes Berg9ebad4a2010-10-14 13:41:35 +0200341 goto next_entry;
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100342 case IEEE80211_RADIOTAP_EXT:
343 /*
344 * bit 31 was set, there is more
345 * -- move to next u32 bitmap
346 */
347 iterator->_bitmap_shifter =
348 get_unaligned_le32(iterator->_next_bitmap);
349 iterator->_next_bitmap++;
350 if (iterator->_reset_on_ext)
351 iterator->_arg_index = 0;
352 else
353 iterator->_arg_index++;
354 iterator->_reset_on_ext = 0;
355 break;
356 default:
357 /* we've got a hit! */
358 hit = 1;
359 next_entry:
360 iterator->_bitmap_shifter >>= 1;
361 iterator->_arg_index++;
362 }
Andy Green179f8312007-07-10 19:29:38 +0200363
364 /* if we found a valid arg earlier, return it now */
365 if (hit)
366 return 0;
367 }
Andy Green179f8312007-07-10 19:29:38 +0200368}
369EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);