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 <net/cfg80211.h> 19 #include <net/ieee80211_radiotap.h> 20 #include <asm/unaligned.h> 21 22 /* function prototypes and related defs are in include/net/cfg80211.h */ 23 24 static const struct radiotap_align_size rtap_namespace_sizes[] = { 25 [IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, }, 26 [IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, }, 27 [IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, }, 28 [IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, }, 29 [IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, }, 30 [IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, }, 31 [IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, }, 32 [IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, }, 33 [IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, }, 34 [IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, }, 35 [IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, }, 36 [IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, }, 37 [IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, }, 38 [IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, }, 39 [IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, }, 40 [IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, }, 41 [IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, }, 42 [IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, }, 43 /* 44 * add more here as they are defined in radiotap.h 45 */ 46 }; 47 48 static const struct ieee80211_radiotap_namespace radiotap_ns = { 49 .n_bits = ARRAY_SIZE(rtap_namespace_sizes), 50 .align_size = rtap_namespace_sizes, 51 }; 52 53 /** 54 * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization 55 * @iterator: radiotap_iterator to initialize 56 * @radiotap_header: radiotap header to parse 57 * @max_length: total length we can parse into (eg, whole packet length) 58 * 59 * Returns: 0 or a negative error code if there is a problem. 60 * 61 * This function initializes an opaque iterator struct which can then 62 * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap 63 * argument which is present in the header. It knows about extended 64 * present headers and handles them. 65 * 66 * How to use: 67 * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator 68 * struct ieee80211_radiotap_iterator (no need to init the struct beforehand) 69 * checking for a good 0 return code. Then loop calling 70 * __ieee80211_radiotap_iterator_next()... it returns either 0, 71 * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem. 72 * The iterator's @this_arg member points to the start of the argument 73 * associated with the current argument index that is present, which can be 74 * found in the iterator's @this_arg_index member. This arg index corresponds 75 * to the IEEE80211_RADIOTAP_... defines. 76 * 77 * Radiotap header length: 78 * You can find the CPU-endian total radiotap header length in 79 * iterator->max_length after executing ieee80211_radiotap_iterator_init() 80 * successfully. 81 * 82 * Alignment Gotcha: 83 * You must take care when dereferencing iterator.this_arg 84 * for multibyte types... the pointer is not aligned. Use 85 * get_unaligned((type *)iterator.this_arg) to dereference 86 * iterator.this_arg for type "type" safely on all arches. 87 * 88 * Example code: 89 * See Documentation/networking/radiotap-headers.txt 90 */ 91 92 int ieee80211_radiotap_iterator_init( 93 struct ieee80211_radiotap_iterator *iterator, 94 struct ieee80211_radiotap_header *radiotap_header, 95 int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns) 96 { 97 /* Linux only supports version 0 radiotap format */ 98 if (radiotap_header->it_version) 99 return -EINVAL; 100 101 /* sanity check for allowed length and radiotap length field */ 102 if (max_length < get_unaligned_le16(&radiotap_header->it_len)) 103 return -EINVAL; 104 105 iterator->_rtheader = radiotap_header; 106 iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len); 107 iterator->_arg_index = 0; 108 iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present); 109 iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header); 110 iterator->_reset_on_ext = 0; 111 iterator->_next_bitmap = &radiotap_header->it_present; 112 iterator->_next_bitmap++; 113 iterator->_vns = vns; 114 iterator->current_namespace = &radiotap_ns; 115 iterator->is_radiotap_ns = 1; 116 117 /* find payload start allowing for extended bitmap(s) */ 118 119 if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) { 120 while (get_unaligned_le32(iterator->_arg) & 121 (1 << IEEE80211_RADIOTAP_EXT)) { 122 iterator->_arg += sizeof(uint32_t); 123 124 /* 125 * check for insanity where the present bitmaps 126 * keep claiming to extend up to or even beyond the 127 * stated radiotap header length 128 */ 129 130 if ((unsigned long)iterator->_arg - 131 (unsigned long)iterator->_rtheader > 132 (unsigned long)iterator->_max_length) 133 return -EINVAL; 134 } 135 136 iterator->_arg += sizeof(uint32_t); 137 138 /* 139 * no need to check again for blowing past stated radiotap 140 * header length, because ieee80211_radiotap_iterator_next 141 * checks it before it is dereferenced 142 */ 143 } 144 145 iterator->this_arg = iterator->_arg; 146 147 /* we are all initialized happily */ 148 149 return 0; 150 } 151 EXPORT_SYMBOL(ieee80211_radiotap_iterator_init); 152 153 static void find_ns(struct ieee80211_radiotap_iterator *iterator, 154 uint32_t oui, uint8_t subns) 155 { 156 int i; 157 158 iterator->current_namespace = NULL; 159 160 if (!iterator->_vns) 161 return; 162 163 for (i = 0; i < iterator->_vns->n_ns; i++) { 164 if (iterator->_vns->ns[i].oui != oui) 165 continue; 166 if (iterator->_vns->ns[i].subns != subns) 167 continue; 168 169 iterator->current_namespace = &iterator->_vns->ns[i]; 170 break; 171 } 172 } 173 174 175 176 /** 177 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg 178 * @iterator: radiotap_iterator to move to next arg (if any) 179 * 180 * Returns: 0 if there is an argument to handle, 181 * -ENOENT if there are no more args or -EINVAL 182 * if there is something else wrong. 183 * 184 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*) 185 * in @this_arg_index and sets @this_arg to point to the 186 * payload for the field. It takes care of alignment handling and extended 187 * present fields. @this_arg can be changed by the caller (eg, 188 * incremented to move inside a compound argument like 189 * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in 190 * little-endian format whatever the endianess of your CPU. 191 * 192 * Alignment Gotcha: 193 * You must take care when dereferencing iterator.this_arg 194 * for multibyte types... the pointer is not aligned. Use 195 * get_unaligned((type *)iterator.this_arg) to dereference 196 * iterator.this_arg for type "type" safely on all arches. 197 */ 198 199 int ieee80211_radiotap_iterator_next( 200 struct ieee80211_radiotap_iterator *iterator) 201 { 202 while (1) { 203 int hit = 0; 204 int pad, align, size, subns; 205 uint32_t oui; 206 207 /* if no more EXT bits, that's it */ 208 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT && 209 !(iterator->_bitmap_shifter & 1)) 210 return -ENOENT; 211 212 if (!(iterator->_bitmap_shifter & 1)) 213 goto next_entry; /* arg not present */ 214 215 /* get alignment/size of data */ 216 switch (iterator->_arg_index % 32) { 217 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: 218 case IEEE80211_RADIOTAP_EXT: 219 align = 1; 220 size = 0; 221 break; 222 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: 223 align = 2; 224 size = 6; 225 break; 226 default: 227 if (!iterator->current_namespace || 228 iterator->_arg_index >= iterator->current_namespace->n_bits) { 229 if (iterator->current_namespace == &radiotap_ns) 230 return -ENOENT; 231 align = 0; 232 } else { 233 align = iterator->current_namespace->align_size[iterator->_arg_index].align; 234 size = iterator->current_namespace->align_size[iterator->_arg_index].size; 235 } 236 if (!align) { 237 /* skip all subsequent data */ 238 iterator->_arg = iterator->_next_ns_data; 239 /* give up on this namespace */ 240 iterator->current_namespace = NULL; 241 goto next_entry; 242 } 243 break; 244 } 245 246 /* 247 * arg is present, account for alignment padding 248 * 249 * Note that these alignments are relative to the start 250 * of the radiotap header. There is no guarantee 251 * that the radiotap header itself is aligned on any 252 * kind of boundary. 253 * 254 * The above is why get_unaligned() is used to dereference 255 * multibyte elements from the radiotap area. 256 */ 257 258 pad = ((unsigned long)iterator->_arg - 259 (unsigned long)iterator->_rtheader) & (align - 1); 260 261 if (pad) 262 iterator->_arg += align - pad; 263 264 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) { 265 int vnslen; 266 267 if ((unsigned long)iterator->_arg + size - 268 (unsigned long)iterator->_rtheader > 269 (unsigned long)iterator->_max_length) 270 return -EINVAL; 271 272 oui = (*iterator->_arg << 16) | 273 (*(iterator->_arg + 1) << 8) | 274 *(iterator->_arg + 2); 275 subns = *(iterator->_arg + 3); 276 277 find_ns(iterator, oui, subns); 278 279 vnslen = get_unaligned_le16(iterator->_arg + 4); 280 iterator->_next_ns_data = iterator->_arg + size + vnslen; 281 if (!iterator->current_namespace) 282 size += vnslen; 283 } 284 285 /* 286 * this is what we will return to user, but we need to 287 * move on first so next call has something fresh to test 288 */ 289 iterator->this_arg_index = iterator->_arg_index; 290 iterator->this_arg = iterator->_arg; 291 iterator->this_arg_size = size; 292 293 /* internally move on the size of this arg */ 294 iterator->_arg += size; 295 296 /* 297 * check for insanity where we are given a bitmap that 298 * claims to have more arg content than the length of the 299 * radiotap section. We will normally end up equalling this 300 * max_length on the last arg, never exceeding it. 301 */ 302 303 if ((unsigned long)iterator->_arg - 304 (unsigned long)iterator->_rtheader > 305 (unsigned long)iterator->_max_length) 306 return -EINVAL; 307 308 /* these special ones are valid in each bitmap word */ 309 switch (iterator->_arg_index % 32) { 310 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: 311 iterator->_reset_on_ext = 1; 312 313 iterator->is_radiotap_ns = 0; 314 /* 315 * If parser didn't register this vendor 316 * namespace with us, allow it to show it 317 * as 'raw. Do do that, set argument index 318 * to vendor namespace. 319 */ 320 iterator->this_arg_index = 321 IEEE80211_RADIOTAP_VENDOR_NAMESPACE; 322 if (!iterator->current_namespace) 323 hit = 1; 324 goto next_entry; 325 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: 326 iterator->_reset_on_ext = 1; 327 iterator->current_namespace = &radiotap_ns; 328 iterator->is_radiotap_ns = 1; 329 goto next_entry; 330 case IEEE80211_RADIOTAP_EXT: 331 /* 332 * bit 31 was set, there is more 333 * -- move to next u32 bitmap 334 */ 335 iterator->_bitmap_shifter = 336 get_unaligned_le32(iterator->_next_bitmap); 337 iterator->_next_bitmap++; 338 if (iterator->_reset_on_ext) 339 iterator->_arg_index = 0; 340 else 341 iterator->_arg_index++; 342 iterator->_reset_on_ext = 0; 343 break; 344 default: 345 /* we've got a hit! */ 346 hit = 1; 347 next_entry: 348 iterator->_bitmap_shifter >>= 1; 349 iterator->_arg_index++; 350 } 351 352 /* if we found a valid arg earlier, return it now */ 353 if (hit) 354 return 0; 355 } 356 } 357 EXPORT_SYMBOL(ieee80211_radiotap_iterator_next); 358