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1// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
2/*
3 * Radiotap parser
4 *
5 * Copyright 2007 Andy Green <[email protected]>
6 * Copyright 2009 Johannes Berg <[email protected]>
7 */
8
9#include <linux/kernel.h>
10#include <linux/export.h>
11#include <net/cfg80211.h>
12#include <net/ieee80211_radiotap.h>
13#include <linux/unaligned.h>
14
15/* function prototypes and related defs are in include/net/cfg80211.h */
16
17static const struct radiotap_align_size rtap_namespace_sizes[] = {
18 [IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, },
19 [IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, },
20 [IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, },
21 [IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, },
22 [IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, },
23 [IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, },
24 [IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, },
25 [IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, },
26 [IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, },
27 [IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, },
28 [IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, },
29 [IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, },
30 [IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, },
31 [IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, },
32 [IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, },
33 [IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, },
34 [IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, },
35 [IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, },
36 [IEEE80211_RADIOTAP_MCS] = { .align = 1, .size = 3, },
37 [IEEE80211_RADIOTAP_AMPDU_STATUS] = { .align = 4, .size = 8, },
38 [IEEE80211_RADIOTAP_VHT] = { .align = 2, .size = 12, },
39 /*
40 * add more here as they are defined in radiotap.h
41 */
42};
43
44static const struct ieee80211_radiotap_namespace radiotap_ns = {
45 .n_bits = ARRAY_SIZE(rtap_namespace_sizes),
46 .align_size = rtap_namespace_sizes,
47};
48
49/**
50 * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
51 * @iterator: radiotap_iterator to initialize
52 * @radiotap_header: radiotap header to parse
53 * @max_length: total length we can parse into (eg, whole packet length)
54 * @vns: vendor namespaces to parse
55 *
56 * Returns: 0 or a negative error code if there is a problem.
57 *
58 * This function initializes an opaque iterator struct which can then
59 * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
60 * argument which is present in the header. It knows about extended
61 * present headers and handles them.
62 *
63 * How to use:
64 * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
65 * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
66 * checking for a good 0 return code. Then loop calling
67 * __ieee80211_radiotap_iterator_next()... it returns either 0,
68 * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
69 * The iterator's @this_arg member points to the start of the argument
70 * associated with the current argument index that is present, which can be
71 * found in the iterator's @this_arg_index member. This arg index corresponds
72 * to the IEEE80211_RADIOTAP_... defines.
73 *
74 * Radiotap header length:
75 * You can find the CPU-endian total radiotap header length in
76 * iterator->max_length after executing ieee80211_radiotap_iterator_init()
77 * successfully.
78 *
79 * Alignment Gotcha:
80 * You must take care when dereferencing iterator.this_arg
81 * for multibyte types... the pointer is not aligned. Use
82 * get_unaligned((type *)iterator.this_arg) to dereference
83 * iterator.this_arg for type "type" safely on all arches.
84 *
85 * Example code:
86 * See Documentation/networking/radiotap-headers.rst
87 */
88
89int ieee80211_radiotap_iterator_init(
90 struct ieee80211_radiotap_iterator *iterator,
91 struct ieee80211_radiotap_header *radiotap_header,
92 int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
93{
94 /* check the radiotap header can actually be present */
95 if (max_length < sizeof(struct ieee80211_radiotap_header))
96 return -EINVAL;
97
98 /* Linux only supports version 0 radiotap format */
99 if (radiotap_header->it_version)
100 return -EINVAL;
101
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
106 iterator->_rtheader = radiotap_header;
107 iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
108 iterator->_arg_index = 0;
109 iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
110 iterator->_arg = (uint8_t *)radiotap_header->it_optional;
111 iterator->_reset_on_ext = 0;
112 iterator->_next_bitmap = radiotap_header->it_optional;
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 & (BIT(IEEE80211_RADIOTAP_EXT))) {
120 if ((unsigned long)iterator->_arg -
121 (unsigned long)iterator->_rtheader + sizeof(uint32_t) >
122 (unsigned long)iterator->_max_length)
123 return -EINVAL;
124 while (get_unaligned_le32(iterator->_arg) &
125 (BIT(IEEE80211_RADIOTAP_EXT))) {
126 iterator->_arg += sizeof(uint32_t);
127
128 /*
129 * check for insanity where the present bitmaps
130 * keep claiming to extend up to or even beyond the
131 * stated radiotap header length
132 */
133
134 if ((unsigned long)iterator->_arg -
135 (unsigned long)iterator->_rtheader +
136 sizeof(uint32_t) >
137 (unsigned long)iterator->_max_length)
138 return -EINVAL;
139 }
140
141 iterator->_arg += sizeof(uint32_t);
142
143 /*
144 * no need to check again for blowing past stated radiotap
145 * header length, because ieee80211_radiotap_iterator_next
146 * checks it before it is dereferenced
147 */
148 }
149
150 iterator->this_arg = iterator->_arg;
151
152 /* we are all initialized happily */
153
154 return 0;
155}
156EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
157
158static void find_ns(struct ieee80211_radiotap_iterator *iterator,
159 uint32_t oui, uint8_t subns)
160{
161 int i;
162
163 iterator->current_namespace = NULL;
164
165 if (!iterator->_vns)
166 return;
167
168 for (i = 0; i < iterator->_vns->n_ns; i++) {
169 if (iterator->_vns->ns[i].oui != oui)
170 continue;
171 if (iterator->_vns->ns[i].subns != subns)
172 continue;
173
174 iterator->current_namespace = &iterator->_vns->ns[i];
175 break;
176 }
177}
178
179
180
181/**
182 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
183 * @iterator: radiotap_iterator to move to next arg (if any)
184 *
185 * Returns: 0 if there is an argument to handle,
186 * -ENOENT if there are no more args or -EINVAL
187 * if there is something else wrong.
188 *
189 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
190 * in @this_arg_index and sets @this_arg to point to the
191 * payload for the field. It takes care of alignment handling and extended
192 * present fields. @this_arg can be changed by the caller (eg,
193 * incremented to move inside a compound argument like
194 * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in
195 * little-endian format whatever the endianness of your CPU.
196 *
197 * Alignment Gotcha:
198 * You must take care when dereferencing iterator.this_arg
199 * for multibyte types... the pointer is not aligned. Use
200 * get_unaligned((type *)iterator.this_arg) to dereference
201 * iterator.this_arg for type "type" safely on all arches.
202 */
203
204int ieee80211_radiotap_iterator_next(
205 struct ieee80211_radiotap_iterator *iterator)
206{
207 while (1) {
208 int hit = 0;
209 int pad, align, size, subns;
210 uint32_t oui;
211
212 /* if no more EXT bits, that's it */
213 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
214 !(iterator->_bitmap_shifter & 1))
215 return -ENOENT;
216
217 if (!(iterator->_bitmap_shifter & 1))
218 goto next_entry; /* arg not present */
219
220 /* get alignment/size of data */
221 switch (iterator->_arg_index % 32) {
222 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
223 case IEEE80211_RADIOTAP_EXT:
224 align = 1;
225 size = 0;
226 break;
227 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
228 align = 2;
229 size = 6;
230 break;
231 default:
232 if (!iterator->current_namespace ||
233 iterator->_arg_index >= iterator->current_namespace->n_bits) {
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 if (iterator->current_namespace == &radiotap_ns)
241 return -ENOENT;
242 /* skip all subsequent data */
243 iterator->_arg = iterator->_next_ns_data;
244 /* give up on this namespace */
245 iterator->current_namespace = NULL;
246 goto next_entry;
247 }
248 break;
249 }
250
251 /*
252 * arg is present, account for alignment padding
253 *
254 * Note that these alignments are relative to the start
255 * of the radiotap header. There is no guarantee
256 * that the radiotap header itself is aligned on any
257 * kind of boundary.
258 *
259 * The above is why get_unaligned() is used to dereference
260 * multibyte elements from the radiotap area.
261 */
262
263 pad = ((unsigned long)iterator->_arg -
264 (unsigned long)iterator->_rtheader) & (align - 1);
265
266 if (pad)
267 iterator->_arg += align - pad;
268
269 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
270 int vnslen;
271
272 if ((unsigned long)iterator->_arg + size -
273 (unsigned long)iterator->_rtheader >
274 (unsigned long)iterator->_max_length)
275 return -EINVAL;
276
277 oui = (*iterator->_arg << 16) |
278 (*(iterator->_arg + 1) << 8) |
279 *(iterator->_arg + 2);
280 subns = *(iterator->_arg + 3);
281
282 find_ns(iterator, oui, subns);
283
284 vnslen = get_unaligned_le16(iterator->_arg + 4);
285 iterator->_next_ns_data = iterator->_arg + size + vnslen;
286 if (!iterator->current_namespace)
287 size += vnslen;
288 }
289
290 /*
291 * this is what we will return to user, but we need to
292 * move on first so next call has something fresh to test
293 */
294 iterator->this_arg_index = iterator->_arg_index;
295 iterator->this_arg = iterator->_arg;
296 iterator->this_arg_size = size;
297
298 /* internally move on the size of this arg */
299 iterator->_arg += size;
300
301 /*
302 * check for insanity where we are given a bitmap that
303 * claims to have more arg content than the length of the
304 * radiotap section. We will normally end up equalling this
305 * max_length on the last arg, never exceeding it.
306 */
307
308 if ((unsigned long)iterator->_arg -
309 (unsigned long)iterator->_rtheader >
310 (unsigned long)iterator->_max_length)
311 return -EINVAL;
312
313 /* these special ones are valid in each bitmap word */
314 switch (iterator->_arg_index % 32) {
315 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
316 iterator->_reset_on_ext = 1;
317
318 iterator->is_radiotap_ns = 0;
319 /*
320 * If parser didn't register this vendor
321 * namespace with us, allow it to show it
322 * as 'raw. Do do that, set argument index
323 * to vendor namespace.
324 */
325 iterator->this_arg_index =
326 IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
327 if (!iterator->current_namespace)
328 hit = 1;
329 goto next_entry;
330 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
331 iterator->_reset_on_ext = 1;
332 iterator->current_namespace = &radiotap_ns;
333 iterator->is_radiotap_ns = 1;
334 goto next_entry;
335 case IEEE80211_RADIOTAP_EXT:
336 /*
337 * bit 31 was set, there is more
338 * -- move to next u32 bitmap
339 */
340 iterator->_bitmap_shifter =
341 get_unaligned_le32(iterator->_next_bitmap);
342 iterator->_next_bitmap++;
343 if (iterator->_reset_on_ext)
344 iterator->_arg_index = 0;
345 else
346 iterator->_arg_index++;
347 iterator->_reset_on_ext = 0;
348 break;
349 default:
350 /* we've got a hit! */
351 hit = 1;
352 next_entry:
353 iterator->_bitmap_shifter >>= 1;
354 iterator->_arg_index++;
355 }
356
357 /* if we found a valid arg earlier, return it now */
358 if (hit)
359 return 0;
360 }
361}
362EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);