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