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 25 static 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 52 static 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 97 int 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 } 165 EXPORT_SYMBOL(ieee80211_radiotap_iterator_init); 166 167 static 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 */ 212 213 int 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 } 371 EXPORT_SYMBOL(ieee80211_radiotap_iterator_next); 372