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 "radiotap_iter.h"
17#include "platform.h"
18
19/* function prototypes and related defs are in radiotap_iter.h */
20
21static const struct radiotap_align_size rtap_namespace_sizes[] = {
22	[IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, },
23	[IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, },
24	[IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, },
25	[IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, },
26	[IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, },
27	[IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, },
28	[IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, },
29	[IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, },
30	[IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, },
31	[IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, },
32	[IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, },
33	[IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, },
34	[IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, },
35	[IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, },
36	[IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, },
37	[IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, },
38	[IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, },
39	[IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, },
40	[IEEE80211_RADIOTAP_MCS] = { .align = 1, .size = 3, },
41	[IEEE80211_RADIOTAP_AMPDU_STATUS] = { .align = 4, .size = 8, },
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
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 *
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: parse.c
88 */
89
90int ieee80211_radiotap_iterator_init(
91	struct ieee80211_radiotap_iterator *iterator,
92	struct ieee80211_radiotap_header *radiotap_header,
93	int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
94{
95	/* must at least have the radiotap header */
96	if (max_length < (int)sizeof(struct ieee80211_radiotap_header))
97		return -EINVAL;
98
99	/* Linux only supports version 0 radiotap format */
100	if (radiotap_header->it_version)
101		return -EINVAL;
102
103	/* sanity check for allowed length and radiotap length field */
104	if (max_length < get_unaligned_le16(&radiotap_header->it_len))
105		return -EINVAL;
106
107	iterator->_rtheader = radiotap_header;
108	iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
109	iterator->_arg_index = 0;
110	iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
111	iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
112	iterator->_next_ns_data = NULL;
113	iterator->_reset_on_ext = 0;
114	iterator->_next_bitmap = &radiotap_header->it_present;
115	iterator->_next_bitmap++;
116	iterator->_vns = vns;
117	iterator->current_namespace = &radiotap_ns;
118	iterator->is_radiotap_ns = 1;
119#ifdef RADIOTAP_SUPPORT_OVERRIDES
120	iterator->n_overrides = 0;
121	iterator->overrides = NULL;
122#endif
123
124	/* find payload start allowing for extended bitmap(s) */
125
126	if (iterator->_bitmap_shifter & BIT(IEEE80211_RADIOTAP_EXT)) {
127		if ((unsigned long)iterator->_arg -
128		    (unsigned long)iterator->_rtheader + sizeof(uint32_t) >
129		    (unsigned long)iterator->_max_length)
130			return -EINVAL;
131		while (get_unaligned_le32(iterator->_arg) &
132		       BIT(IEEE80211_RADIOTAP_EXT)) {
133			iterator->_arg += sizeof(uint32_t);
134
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
141			if ((unsigned long)iterator->_arg -
142			    (unsigned long)iterator->_rtheader +
143			    sizeof(uint32_t) >
144			    (unsigned long)iterator->_max_length)
145				return -EINVAL;
146		}
147
148		iterator->_arg += sizeof(uint32_t);
149
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
157	iterator->this_arg = iterator->_arg;
158	iterator->this_arg_index = 0;
159	iterator->this_arg_size = 0;
160
161	/* we are all initialized happily */
162
163	return 0;
164}
165
166static void find_ns(struct ieee80211_radiotap_iterator *iterator,
167		    uint32_t oui, uint8_t subns)
168{
169	int i;
170
171	iterator->current_namespace = NULL;
172
173	if (!iterator->_vns)
174		return;
175
176	for (i = 0; i < iterator->_vns->n_ns; i++) {
177		if (iterator->_vns->ns[i].oui != oui)
178			continue;
179		if (iterator->_vns->ns[i].subns != subns)
180			continue;
181
182		iterator->current_namespace = &iterator->_vns->ns[i];
183		break;
184	}
185}
186
187#ifdef RADIOTAP_SUPPORT_OVERRIDES
188static int find_override(struct ieee80211_radiotap_iterator *iterator,
189			 int *align, int *size)
190{
191	int i;
192
193	if (!iterator->overrides)
194		return 0;
195
196	for (i = 0; i < iterator->n_overrides; i++) {
197		if (iterator->_arg_index == iterator->overrides[i].field) {
198			*align = iterator->overrides[i].align;
199			*size = iterator->overrides[i].size;
200			if (!*align) /* erroneous override */
201				return 0;
202			return 1;
203		}
204	}
205
206	return 0;
207}
208#endif
209
210
211/**
212 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
213 * @iterator: radiotap_iterator to move to next arg (if any)
214 *
215 * Returns: 0 if there is an argument to handle,
216 * -ENOENT if there are no more args or -EINVAL
217 * if there is something else wrong.
218 *
219 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
220 * in @this_arg_index and sets @this_arg to point to the
221 * payload for the field.  It takes care of alignment handling and extended
222 * present fields.  @this_arg can be changed by the caller (eg,
223 * incremented to move inside a compound argument like
224 * IEEE80211_RADIOTAP_CHANNEL).  The args pointed to are in
225 * little-endian format whatever the endianess of your CPU.
226 *
227 * Alignment Gotcha:
228 * You must take care when dereferencing iterator.this_arg
229 * for multibyte types... the pointer is not aligned.  Use
230 * get_unaligned((type *)iterator.this_arg) to dereference
231 * iterator.this_arg for type "type" safely on all arches.
232 */
233
234int ieee80211_radiotap_iterator_next(
235	struct ieee80211_radiotap_iterator *iterator)
236{
237	while (1) {
238		int hit = 0;
239		int pad, align, size, subns;
240		uint32_t oui;
241
242		/* if no more EXT bits, that's it */
243		if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
244		    !(iterator->_bitmap_shifter & 1))
245			return -ENOENT;
246
247		if (!(iterator->_bitmap_shifter & 1))
248			goto next_entry; /* arg not present */
249
250		/* get alignment/size of data */
251		switch (iterator->_arg_index % 32) {
252		case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
253		case IEEE80211_RADIOTAP_EXT:
254			align = 1;
255			size = 0;
256			break;
257		case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
258			align = 2;
259			size = 6;
260			break;
261		default:
262#ifdef RADIOTAP_SUPPORT_OVERRIDES
263			if (find_override(iterator, &align, &size)) {
264				/* all set */
265			} else
266#endif
267			if (!iterator->current_namespace ||
268			    iterator->_arg_index >= iterator->current_namespace->n_bits) {
269				if (iterator->current_namespace == &radiotap_ns)
270					return -ENOENT;
271				align = 0;
272			} else {
273				align = iterator->current_namespace->align_size[iterator->_arg_index].align;
274				size = iterator->current_namespace->align_size[iterator->_arg_index].size;
275			}
276			if (!align) {
277				/* skip all subsequent data */
278				iterator->_arg = iterator->_next_ns_data;
279				/* give up on this namespace */
280				iterator->current_namespace = NULL;
281				goto next_entry;
282			}
283			break;
284		}
285
286		/*
287		 * arg is present, account for alignment padding
288		 *
289		 * Note that these alignments are relative to the start
290		 * of the radiotap header.  There is no guarantee
291		 * that the radiotap header itself is aligned on any
292		 * kind of boundary.
293		 *
294		 * The above is why get_unaligned() is used to dereference
295		 * multibyte elements from the radiotap area.
296		 */
297
298		pad = ((unsigned long)iterator->_arg -
299		       (unsigned long)iterator->_rtheader) & (align - 1);
300
301		if (pad)
302			iterator->_arg += align - pad;
303
304		if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
305			int vnslen;
306
307			if ((unsigned long)iterator->_arg + size -
308			    (unsigned long)iterator->_rtheader >
309			    (unsigned long)iterator->_max_length)
310				return -EINVAL;
311
312			oui = (*iterator->_arg << 16) |
313				(*(iterator->_arg + 1) << 8) |
314				*(iterator->_arg + 2);
315			subns = *(iterator->_arg + 3);
316
317			find_ns(iterator, oui, subns);
318
319			vnslen = get_unaligned_le16(iterator->_arg + 4);
320			iterator->_next_ns_data = iterator->_arg + size + vnslen;
321			if (!iterator->current_namespace)
322				size += vnslen;
323		}
324
325		/*
326		 * this is what we will return to user, but we need to
327		 * move on first so next call has something fresh to test
328		 */
329		iterator->this_arg_index = iterator->_arg_index;
330		iterator->this_arg = iterator->_arg;
331		iterator->this_arg_size = size;
332
333		/* internally move on the size of this arg */
334		iterator->_arg += size;
335
336		/*
337		 * check for insanity where we are given a bitmap that
338		 * claims to have more arg content than the length of the
339		 * radiotap section.  We will normally end up equalling this
340		 * max_length on the last arg, never exceeding it.
341		 */
342
343		if ((unsigned long)iterator->_arg -
344		    (unsigned long)iterator->_rtheader >
345		    (unsigned long)iterator->_max_length)
346			return -EINVAL;
347
348		/* these special ones are valid in each bitmap word */
349		switch (iterator->_arg_index % 32) {
350		case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
351			iterator->_reset_on_ext = 1;
352
353			iterator->is_radiotap_ns = 0;
354			/*
355			 * If parser didn't register this vendor
356			 * namespace with us, allow it to show it
357			 * as 'raw. Do do that, set argument index
358			 * to vendor namespace.
359			 */
360			iterator->this_arg_index =
361				IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
362			if (!iterator->current_namespace)
363				hit = 1;
364			goto next_entry;
365		case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
366			iterator->_reset_on_ext = 1;
367			iterator->current_namespace = &radiotap_ns;
368			iterator->is_radiotap_ns = 1;
369			goto next_entry;
370		case IEEE80211_RADIOTAP_EXT:
371			/*
372			 * bit 31 was set, there is more
373			 * -- move to next u32 bitmap
374			 */
375			iterator->_bitmap_shifter =
376				get_unaligned_le32(iterator->_next_bitmap);
377			iterator->_next_bitmap++;
378			if (iterator->_reset_on_ext)
379				iterator->_arg_index = 0;
380			else
381				iterator->_arg_index++;
382			iterator->_reset_on_ext = 0;
383			break;
384		default:
385			/* we've got a hit! */
386			hit = 1;
387 next_entry:
388			iterator->_bitmap_shifter >>= 1;
389			iterator->_arg_index++;
390		}
391
392		/* if we found a valid arg earlier, return it now */
393		if (hit)
394			return 0;
395	}
396}
397