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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 <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); |
358 |
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