1 /* 2 * Radiotap parser 3 * 4 * Copyright 2007 Andy Green <andy (at) warmcat.com> 5 * Copyright 2009 Johannes Berg <johannes (at) 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 21 static 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 47 static 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 90 int 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->_reset_on_ext = 0; 113 iterator->_next_bitmap = &radiotap_header->it_present; 114 iterator->_next_bitmap++; 115 iterator->_vns = vns; 116 iterator->current_namespace = &radiotap_ns; 117 iterator->is_radiotap_ns = 1; 118 #ifdef RADIOTAP_SUPPORT_OVERRIDES 119 iterator->n_overrides = 0; 120 iterator->overrides = NULL; 121 #endif 122 123 /* find payload start allowing for extended bitmap(s) */ 124 125 if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) { 126 if ((unsigned long)iterator->_arg - 127 (unsigned long)iterator->_rtheader + sizeof(uint32_t) > 128 (unsigned long)iterator->_max_length) 129 return -EINVAL; 130 while (get_unaligned_le32(iterator->_arg) & 131 (1 << IEEE80211_RADIOTAP_EXT)) { 132 iterator->_arg += sizeof(uint32_t); 133 134 /* 135 * check for insanity where the present bitmaps 136 * keep claiming to extend up to or even beyond the 137 * stated radiotap header length 138 */ 139 140 if ((unsigned long)iterator->_arg - 141 (unsigned long)iterator->_rtheader + 142 sizeof(uint32_t) > 143 (unsigned long)iterator->_max_length) 144 return -EINVAL; 145 } 146 147 iterator->_arg += sizeof(uint32_t); 148 149 /* 150 * no need to check again for blowing past stated radiotap 151 * header length, because ieee80211_radiotap_iterator_next 152 * checks it before it is dereferenced 153 */ 154 } 155 156 iterator->this_arg = iterator->_arg; 157 158 /* we are all initialized happily */ 159 160 return 0; 161 } 162 163 static void find_ns(struct ieee80211_radiotap_iterator *iterator, 164 uint32_t oui, uint8_t subns) 165 { 166 int i; 167 168 iterator->current_namespace = NULL; 169 170 if (!iterator->_vns) 171 return; 172 173 for (i = 0; i < iterator->_vns->n_ns; i++) { 174 if (iterator->_vns->ns[i].oui != oui) 175 continue; 176 if (iterator->_vns->ns[i].subns != subns) 177 continue; 178 179 iterator->current_namespace = &iterator->_vns->ns[i]; 180 break; 181 } 182 } 183 184 #ifdef RADIOTAP_SUPPORT_OVERRIDES 185 static int find_override(struct ieee80211_radiotap_iterator *iterator, 186 int *align, int *size) 187 { 188 int i; 189 190 if (!iterator->overrides) 191 return 0; 192 193 for (i = 0; i < iterator->n_overrides; i++) { 194 if (iterator->_arg_index == iterator->overrides[i].field) { 195 *align = iterator->overrides[i].align; 196 *size = iterator->overrides[i].size; 197 if (!*align) /* erroneous override */ 198 return 0; 199 return 1; 200 } 201 } 202 203 return 0; 204 } 205 #endif 206 207 208 /** 209 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg 210 * @iterator: radiotap_iterator to move to next arg (if any) 211 * 212 * Returns: 0 if there is an argument to handle, 213 * -ENOENT if there are no more args or -EINVAL 214 * if there is something else wrong. 215 * 216 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*) 217 * in @this_arg_index and sets @this_arg to point to the 218 * payload for the field. It takes care of alignment handling and extended 219 * present fields. @this_arg can be changed by the caller (eg, 220 * incremented to move inside a compound argument like 221 * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in 222 * little-endian format whatever the endianess of your CPU. 223 * 224 * Alignment Gotcha: 225 * You must take care when dereferencing iterator.this_arg 226 * for multibyte types... the pointer is not aligned. Use 227 * get_unaligned((type *)iterator.this_arg) to dereference 228 * iterator.this_arg for type "type" safely on all arches. 229 */ 230 231 int ieee80211_radiotap_iterator_next( 232 struct ieee80211_radiotap_iterator *iterator) 233 { 234 while (1) { 235 int hit = 0; 236 int pad, align, size, subns; 237 uint32_t oui; 238 239 /* if no more EXT bits, that's it */ 240 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT && 241 !(iterator->_bitmap_shifter & 1)) 242 return -ENOENT; 243 244 if (!(iterator->_bitmap_shifter & 1)) 245 goto next_entry; /* arg not present */ 246 247 /* get alignment/size of data */ 248 switch (iterator->_arg_index % 32) { 249 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: 250 case IEEE80211_RADIOTAP_EXT: 251 align = 1; 252 size = 0; 253 break; 254 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: 255 align = 2; 256 size = 6; 257 break; 258 default: 259 #ifdef RADIOTAP_SUPPORT_OVERRIDES 260 if (find_override(iterator, &align, &size)) { 261 /* all set */ 262 } else 263 #endif 264 if (!iterator->current_namespace || 265 iterator->_arg_index >= iterator->current_namespace->n_bits) { 266 if (iterator->current_namespace == &radiotap_ns) 267 return -ENOENT; 268 align = 0; 269 } else { 270 align = iterator->current_namespace->align_size[iterator->_arg_index].align; 271 size = iterator->current_namespace->align_size[iterator->_arg_index].size; 272 } 273 if (!align) { 274 /* skip all subsequent data */ 275 iterator->_arg = iterator->_next_ns_data; 276 /* give up on this namespace */ 277 iterator->current_namespace = NULL; 278 goto next_entry; 279 } 280 break; 281 } 282 283 /* 284 * arg is present, account for alignment padding 285 * 286 * Note that these alignments are relative to the start 287 * of the radiotap header. There is no guarantee 288 * that the radiotap header itself is aligned on any 289 * kind of boundary. 290 * 291 * The above is why get_unaligned() is used to dereference 292 * multibyte elements from the radiotap area. 293 */ 294 295 pad = ((unsigned long)iterator->_arg - 296 (unsigned long)iterator->_rtheader) & (align - 1); 297 298 if (pad) 299 iterator->_arg += align - pad; 300 301 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) { 302 int vnslen; 303 304 if ((unsigned long)iterator->_arg + size - 305 (unsigned long)iterator->_rtheader > 306 (unsigned long)iterator->_max_length) 307 return -EINVAL; 308 309 oui = (*iterator->_arg << 16) | 310 (*(iterator->_arg + 1) << 8) | 311 *(iterator->_arg + 2); 312 subns = *(iterator->_arg + 3); 313 314 find_ns(iterator, oui, subns); 315 316 vnslen = get_unaligned_le16(iterator->_arg + 4); 317 iterator->_next_ns_data = iterator->_arg + size + vnslen; 318 if (!iterator->current_namespace) 319 size += vnslen; 320 } 321 322 /* 323 * this is what we will return to user, but we need to 324 * move on first so next call has something fresh to test 325 */ 326 iterator->this_arg_index = iterator->_arg_index; 327 iterator->this_arg = iterator->_arg; 328 iterator->this_arg_size = size; 329 330 /* internally move on the size of this arg */ 331 iterator->_arg += size; 332 333 /* 334 * check for insanity where we are given a bitmap that 335 * claims to have more arg content than the length of the 336 * radiotap section. We will normally end up equalling this 337 * max_length on the last arg, never exceeding it. 338 */ 339 340 if ((unsigned long)iterator->_arg - 341 (unsigned long)iterator->_rtheader > 342 (unsigned long)iterator->_max_length) 343 return -EINVAL; 344 345 /* these special ones are valid in each bitmap word */ 346 switch (iterator->_arg_index % 32) { 347 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: 348 iterator->_reset_on_ext = 1; 349 350 iterator->is_radiotap_ns = 0; 351 /* 352 * If parser didn't register this vendor 353 * namespace with us, allow it to show it 354 * as 'raw. Do do that, set argument index 355 * to vendor namespace. 356 */ 357 iterator->this_arg_index = 358 IEEE80211_RADIOTAP_VENDOR_NAMESPACE; 359 if (!iterator->current_namespace) 360 hit = 1; 361 goto next_entry; 362 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: 363 iterator->_reset_on_ext = 1; 364 iterator->current_namespace = &radiotap_ns; 365 iterator->is_radiotap_ns = 1; 366 goto next_entry; 367 case IEEE80211_RADIOTAP_EXT: 368 /* 369 * bit 31 was set, there is more 370 * -- move to next u32 bitmap 371 */ 372 iterator->_bitmap_shifter = 373 get_unaligned_le32(iterator->_next_bitmap); 374 iterator->_next_bitmap++; 375 if (iterator->_reset_on_ext) 376 iterator->_arg_index = 0; 377 else 378 iterator->_arg_index++; 379 iterator->_reset_on_ext = 0; 380 break; 381 default: 382 /* we've got a hit! */ 383 hit = 1; 384 next_entry: 385 iterator->_bitmap_shifter >>= 1; 386 iterator->_arg_index++; 387 } 388 389 /* if we found a valid arg earlier, return it now */ 390 if (hit) 391 return 0; 392 } 393 } 394
