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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
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
Johannes Berg33e5a2f2010-02-03 10:24:30 +010023static 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
47static 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
Andy Green179f8312007-07-10 19:29:38 +020052/**
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
91int ieee80211_radiotap_iterator_init(
Johannes Berg33e5a2f2010-02-03 10:24:30 +010092 struct ieee80211_radiotap_iterator *iterator,
93 struct ieee80211_radiotap_header *radiotap_header,
94 int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
Andy Green179f8312007-07-10 19:29:38 +020095{
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 */
Harvey Harrisonae7245c2008-05-01 22:19:33 -0700101 if (max_length < get_unaligned_le16(&radiotap_header->it_len))
Andy Green179f8312007-07-10 19:29:38 +0200102 return -EINVAL;
103
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100104 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;
Andy Green179f8312007-07-10 19:29:38 +0200115
116 /* find payload start allowing for extended bitmap(s) */
117
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100118 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);
Andy Green179f8312007-07-10 19:29:38 +0200122
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
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100129 if ((unsigned long)iterator->_arg -
130 (unsigned long)iterator->_rtheader >
131 (unsigned long)iterator->_max_length)
Andy Green179f8312007-07-10 19:29:38 +0200132 return -EINVAL;
133 }
134
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100135 iterator->_arg += sizeof(uint32_t);
Andy Green179f8312007-07-10 19:29:38 +0200136
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
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100144 iterator->this_arg = iterator->_arg;
145
Andy Green179f8312007-07-10 19:29:38 +0200146 /* we are all initialized happily */
147
148 return 0;
149}
150EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
151
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100152static 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
Andy Green179f8312007-07-10 19:29:38 +0200174
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
198int ieee80211_radiotap_iterator_next(
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100199 struct ieee80211_radiotap_iterator *iterator)
Andy Green179f8312007-07-10 19:29:38 +0200200{
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100201 while (1) {
Andy Green179f8312007-07-10 19:29:38 +0200202 int hit = 0;
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100203 int pad, align, size, subns, vnslen;
204 uint32_t oui;
Andy Green179f8312007-07-10 19:29:38 +0200205
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100206 /* 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))
Andy Green179f8312007-07-10 19:29:38 +0200212 goto next_entry; /* arg not present */
213
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100214 /* 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
Andy Green179f8312007-07-10 19:29:38 +0200245 /*
246 * arg is present, account for alignment padding
Andy Green179f8312007-07-10 19:29:38 +0200247 *
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100248 * Note that these alignments are relative to the start
249 * of the radiotap header. There is no guarantee
Andy Green179f8312007-07-10 19:29:38 +0200250 * that the radiotap header itself is aligned on any
251 * kind of boundary.
252 *
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100253 * The above is why get_unaligned() is used to dereference
254 * multibyte elements from the radiotap area.
Andy Green179f8312007-07-10 19:29:38 +0200255 */
256
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100257 pad = ((unsigned long)iterator->_arg -
258 (unsigned long)iterator->_rtheader) & (align - 1);
Andy Green179f8312007-07-10 19:29:38 +0200259
260 if (pad)
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100261 iterator->_arg += align - pad;
Andy Green179f8312007-07-10 19:29:38 +0200262
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 */
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100267 iterator->this_arg_index = iterator->_arg_index;
268 iterator->this_arg = iterator->_arg;
269 iterator->this_arg_size = size;
Andy Green179f8312007-07-10 19:29:38 +0200270
271 /* internally move on the size of this arg */
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100272 iterator->_arg += size;
Andy Green179f8312007-07-10 19:29:38 +0200273
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
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100281 if ((unsigned long)iterator->_arg -
282 (unsigned long)iterator->_rtheader >
283 (unsigned long)iterator->_max_length)
Andy Green179f8312007-07-10 19:29:38 +0200284 return -EINVAL;
285
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100286 /* 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 }
Andy Green179f8312007-07-10 19:29:38 +0200344
345 /* if we found a valid arg earlier, return it now */
346 if (hit)
347 return 0;
348 }
Andy Green179f8312007-07-10 19:29:38 +0200349}
350EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);