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 <linux/export.h>
19#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
25static 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, },
44	[IEEE80211_RADIOTAP_MCS] = { .align = 1, .size = 3, },
45	[IEEE80211_RADIOTAP_AMPDU_STATUS] = { .align = 4, .size = 8, },
46	[IEEE80211_RADIOTAP_VHT] = { .align = 2, .size = 12, },
47	/*
48	 * add more here as they are defined in radiotap.h
49	 */
50};
51
52static const struct ieee80211_radiotap_namespace radiotap_ns = {
53	.n_bits = ARRAY_SIZE(rtap_namespace_sizes),
54	.align_size = rtap_namespace_sizes,
55};
56
57/**
58 * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
59 * @iterator: radiotap_iterator to initialize
60 * @radiotap_header: radiotap header to parse
61 * @max_length: total length we can parse into (eg, whole packet length)
62 * @vns: vendor namespaces to parse
63 *
64 * Returns: 0 or a negative error code if there is a problem.
65 *
66 * This function initializes an opaque iterator struct which can then
67 * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
68 * argument which is present in the header.  It knows about extended
69 * present headers and handles them.
70 *
71 * How to use:
72 * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
73 * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
74 * checking for a good 0 return code.  Then loop calling
75 * __ieee80211_radiotap_iterator_next()... it returns either 0,
76 * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
77 * The iterator's @this_arg member points to the start of the argument
78 * associated with the current argument index that is present, which can be
79 * found in the iterator's @this_arg_index member.  This arg index corresponds
80 * to the IEEE80211_RADIOTAP_... defines.
81 *
82 * Radiotap header length:
83 * You can find the CPU-endian total radiotap header length in
84 * iterator->max_length after executing ieee80211_radiotap_iterator_init()
85 * successfully.
86 *
87 * Alignment Gotcha:
88 * You must take care when dereferencing iterator.this_arg
89 * for multibyte types... the pointer is not aligned.  Use
90 * get_unaligned((type *)iterator.this_arg) to dereference
91 * iterator.this_arg for type "type" safely on all arches.
92 *
93 * Example code:
94 * See Documentation/networking/radiotap-headers.rst
95 */
96
97int ieee80211_radiotap_iterator_init(
98	struct ieee80211_radiotap_iterator *iterator,
99	struct ieee80211_radiotap_header *radiotap_header,
100	int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
101{
102	/* check the radiotap header can actually be present */
103	if (max_length < sizeof(struct ieee80211_radiotap_header))
104		return -EINVAL;
105
106	/* Linux only supports version 0 radiotap format */
107	if (radiotap_header->it_version)
108		return -EINVAL;
109
110	/* sanity check for allowed length and radiotap length field */
111	if (max_length < get_unaligned_le16(&radiotap_header->it_len))
112		return -EINVAL;
113
114	iterator->_rtheader = radiotap_header;
115	iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
116	iterator->_arg_index = 0;
117	iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
118	iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
119	iterator->_reset_on_ext = 0;
120	iterator->_next_bitmap = &radiotap_header->it_present;
121	iterator->_next_bitmap++;
122	iterator->_vns = vns;
123	iterator->current_namespace = &radiotap_ns;
124	iterator->is_radiotap_ns = 1;
125
126	/* find payload start allowing for extended bitmap(s) */
127
128	if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
129		if ((unsigned long)iterator->_arg -
130		    (unsigned long)iterator->_rtheader + sizeof(uint32_t) >
131		    (unsigned long)iterator->_max_length)
132			return -EINVAL;
133		while (get_unaligned_le32(iterator->_arg) &
134					(1 << IEEE80211_RADIOTAP_EXT)) {
135			iterator->_arg += sizeof(uint32_t);
136
137			/*
138			 * check for insanity where the present bitmaps
139			 * keep claiming to extend up to or even beyond the
140			 * stated radiotap header length
141			 */
142
143			if ((unsigned long)iterator->_arg -
144			    (unsigned long)iterator->_rtheader +
145			    sizeof(uint32_t) >
146			    (unsigned long)iterator->_max_length)
147				return -EINVAL;
148		}
149
150		iterator->_arg += sizeof(uint32_t);
151
152		/*
153		 * no need to check again for blowing past stated radiotap
154		 * header length, because ieee80211_radiotap_iterator_next
155		 * checks it before it is dereferenced
156		 */
157	}
158
159	iterator->this_arg = iterator->_arg;
160
161	/* we are all initialized happily */
162
163	return 0;
164}
165EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
166
167static void find_ns(struct ieee80211_radiotap_iterator *iterator,
168		    uint32_t oui, uint8_t subns)
169{
170	int i;
171
172	iterator->current_namespace = NULL;
173
174	if (!iterator->_vns)
175		return;
176
177	for (i = 0; i < iterator->_vns->n_ns; i++) {
178		if (iterator->_vns->ns[i].oui != oui)
179			continue;
180		if (iterator->_vns->ns[i].subns != subns)
181			continue;
182
183		iterator->current_namespace = &iterator->_vns->ns[i];
184		break;
185	}
186}
187
188
189
190/**
191 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
192 * @iterator: radiotap_iterator to move to next arg (if any)
193 *
194 * Returns: 0 if there is an argument to handle,
195 * -ENOENT if there are no more args or -EINVAL
196 * if there is something else wrong.
197 *
198 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
199 * in @this_arg_index and sets @this_arg to point to the
200 * payload for the field.  It takes care of alignment handling and extended
201 * present fields.  @this_arg can be changed by the caller (eg,
202 * incremented to move inside a compound argument like
203 * IEEE80211_RADIOTAP_CHANNEL).  The args pointed to are in
204 * little-endian format whatever the endianess of your CPU.
205 *
206 * Alignment Gotcha:
207 * You must take care when dereferencing iterator.this_arg
208 * for multibyte types... the pointer is not aligned.  Use
209 * get_unaligned((type *)iterator.this_arg) to dereference
210 * iterator.this_arg for type "type" safely on all arches.
211 */
212
213int ieee80211_radiotap_iterator_next(
214	struct ieee80211_radiotap_iterator *iterator)
215{
216	while (1) {
217		int hit = 0;
218		int pad, align, size, subns;
219		uint32_t oui;
220
221		/* if no more EXT bits, that's it */
222		if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
223		    !(iterator->_bitmap_shifter & 1))
224			return -ENOENT;
225
226		if (!(iterator->_bitmap_shifter & 1))
227			goto next_entry; /* arg not present */
228
229		/* get alignment/size of data */
230		switch (iterator->_arg_index % 32) {
231		case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
232		case IEEE80211_RADIOTAP_EXT:
233			align = 1;
234			size = 0;
235			break;
236		case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
237			align = 2;
238			size = 6;
239			break;
240		default:
241			if (!iterator->current_namespace ||
242			    iterator->_arg_index >= iterator->current_namespace->n_bits) {
243				if (iterator->current_namespace == &radiotap_ns)
244					return -ENOENT;
245				align = 0;
246			} else {
247				align = iterator->current_namespace->align_size[iterator->_arg_index].align;
248				size = iterator->current_namespace->align_size[iterator->_arg_index].size;
249			}
250			if (!align) {
251				/* skip all subsequent data */
252				iterator->_arg = iterator->_next_ns_data;
253				/* give up on this namespace */
254				iterator->current_namespace = NULL;
255				goto next_entry;
256			}
257			break;
258		}
259
260		/*
261		 * arg is present, account for alignment padding
262		 *
263		 * Note that these alignments are relative to the start
264		 * of the radiotap header.  There is no guarantee
265		 * that the radiotap header itself is aligned on any
266		 * kind of boundary.
267		 *
268		 * The above is why get_unaligned() is used to dereference
269		 * multibyte elements from the radiotap area.
270		 */
271
272		pad = ((unsigned long)iterator->_arg -
273		       (unsigned long)iterator->_rtheader) & (align - 1);
274
275		if (pad)
276			iterator->_arg += align - pad;
277
278		if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
279			int vnslen;
280
281			if ((unsigned long)iterator->_arg + size -
282			    (unsigned long)iterator->_rtheader >
283			    (unsigned long)iterator->_max_length)
284				return -EINVAL;
285
286			oui = (*iterator->_arg << 16) |
287				(*(iterator->_arg + 1) << 8) |
288				*(iterator->_arg + 2);
289			subns = *(iterator->_arg + 3);
290
291			find_ns(iterator, oui, subns);
292
293			vnslen = get_unaligned_le16(iterator->_arg + 4);
294			iterator->_next_ns_data = iterator->_arg + size + vnslen;
295			if (!iterator->current_namespace)
296				size += vnslen;
297		}
298
299		/*
300		 * this is what we will return to user, but we need to
301		 * move on first so next call has something fresh to test
302		 */
303		iterator->this_arg_index = iterator->_arg_index;
304		iterator->this_arg = iterator->_arg;
305		iterator->this_arg_size = size;
306
307		/* internally move on the size of this arg */
308		iterator->_arg += size;
309
310		/*
311		 * check for insanity where we are given a bitmap that
312		 * claims to have more arg content than the length of the
313		 * radiotap section.  We will normally end up equalling this
314		 * max_length on the last arg, never exceeding it.
315		 */
316
317		if ((unsigned long)iterator->_arg -
318		    (unsigned long)iterator->_rtheader >
319		    (unsigned long)iterator->_max_length)
320			return -EINVAL;
321
322		/* these special ones are valid in each bitmap word */
323		switch (iterator->_arg_index % 32) {
324		case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
325			iterator->_reset_on_ext = 1;
326
327			iterator->is_radiotap_ns = 0;
328			/*
329			 * If parser didn't register this vendor
330			 * namespace with us, allow it to show it
331			 * as 'raw. Do do that, set argument index
332			 * to vendor namespace.
333			 */
334			iterator->this_arg_index =
335				IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
336			if (!iterator->current_namespace)
337				hit = 1;
338			goto next_entry;
339		case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
340			iterator->_reset_on_ext = 1;
341			iterator->current_namespace = &radiotap_ns;
342			iterator->is_radiotap_ns = 1;
343			goto next_entry;
344		case IEEE80211_RADIOTAP_EXT:
345			/*
346			 * bit 31 was set, there is more
347			 * -- move to next u32 bitmap
348			 */
349			iterator->_bitmap_shifter =
350				get_unaligned_le32(iterator->_next_bitmap);
351			iterator->_next_bitmap++;
352			if (iterator->_reset_on_ext)
353				iterator->_arg_index = 0;
354			else
355				iterator->_arg_index++;
356			iterator->_reset_on_ext = 0;
357			break;
358		default:
359			/* we've got a hit! */
360			hit = 1;
361 next_entry:
362			iterator->_bitmap_shifter >>= 1;
363			iterator->_arg_index++;
364		}
365
366		/* if we found a valid arg earlier, return it now */
367		if (hit)
368			return 0;
369	}
370}
371EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);
372